Refactor constructor parameter for clarity in LeakyBucketLimiter

.gitea/workflows/ci.yml

@@ -8,7 +8,6 @@ on:
 jobs:
   run-tests:
     runs-on: java26
-
     steps:
       - name: Checkout Code
         run: |
@@ -42,67 +41,8 @@ jobs:
             ls -la build/test-results/test || true
           fi
 
-  check-and-publish:
-    runs-on: java26
-    # Publish to the Maven repo after the Gitea release has been created
-    needs: create-release
-    env:
-      MAVEN_REPO_URL: ${{ secrets.MAVEN_REPO_URL }}
-      MAVEN_REPO_USER: ${{ secrets.MAVEN_REPO_USER }}
-      MAVEN_REPO_PASS: ${{ secrets.MAVEN_REPO_PASS }}
-
-    steps:
-      - name: Checkout Code
-        run: |
-          SERVER_DOMAIN=$(echo "${{ github.server_url }}" | sed 's/https:\/\///')
-          rm -rf "$GITHUB_WORKSPACE"/*
-          git clone "https://${{ github.actor }}:${{ secrets.GITHUB_TOKEN }}@${SERVER_DOMAIN}/${{ github.repository }}.git" "$GITHUB_WORKSPACE"
-          cd "$GITHUB_WORKSPACE"
-          git checkout ${{ github.sha }}
-
-      - name: Read version from Gradle
-        id: get_version
-        run: |
-          cd "$GITHUB_WORKSPACE"
-          chmod +x ./gradlew
-          VERSION=$(./gradlew properties | grep "^version:" | awk '{print $2}')
-          echo "Found local project version: $VERSION"
-          echo "version=$VERSION" >> $GITHUB_OUTPUT
-
-      - name: Check if version exists on repository
-        id: check_repo
-        run: |
-          cd "$GITHUB_WORKSPACE"
-          RAW_GROUP=$(./gradlew properties | grep "^group:" | awk '{print $2}')
-          GROUP_PATH=$(echo "$RAW_GROUP" | tr '.' '/')
-          ARTIFACT_ID=$(./gradlew properties | grep "^name:" | awk '{print $2}')
-
-          LOCAL_VERSION="${{ steps.get_version.outputs.version }}"
-
-          echo "Detected project: $RAW_GROUP:$ARTIFACT_ID:$LOCAL_VERSION"
-
-          CHECK_URL="${{ env.MAVEN_REPO_URL }}/${GROUP_PATH}/${ARTIFACT_ID}/${LOCAL_VERSION}/${ARTIFACT_ID}-${LOCAL_VERSION}.pom"
-          echo "Check url: $CHECK_URL"
-
-          STATUS=$(curl -o /dev/null -s -w "%{http_code}" -u "${{ env.MAVEN_REPO_USER }}:${{ env.MAVEN_REPO_PASS }}" "$CHECK_URL")
-          if [ "$STATUS" = "200" ]; then
-            echo "Version $LOCAL_VERSION already exists in repository. Skipping publishing."
-            echo "is_new=false" >> $GITHUB_OUTPUT
-          else
-            echo "Version $LOCAL_VERSION not found (Status $STATUS). Start deployment..."
-            echo "is_new=true" >> $GITHUB_OUTPUT
-          fi
-
-      - name: Push to Maven Repository
-        if: steps.check_repo.outputs.is_new == 'true'
-        run: |
-          cd "$GITHUB_WORKSPACE"
-          echo "Publishing version ${{ steps.get_version.outputs.version }} zu Repository..."
-          ./gradlew publish
-
   create-release:
     runs-on: java26
-    # Create the Gitea tag/release after tests pass, before publishing
     needs: run-tests
     env:
       API_BASE: ${{ github.server_url }}/api/v1/repos/${{ github.repository }}
@@ -236,3 +176,61 @@ jobs:
           fi
 
           echo "JAR $JAR_NAME attached to release successfully."
+
+  check-and-publish:
+    runs-on: java26
+    needs: run-tests
+    env:
+      MAVEN_REPO_URL: ${{ secrets.MAVEN_REPO_URL }}
+      MAVEN_REPO_USER: ${{ secrets.MAVEN_REPO_USER }}
+      MAVEN_REPO_PASS: ${{ secrets.MAVEN_REPO_PASS }}
+
+    steps:
+      - name: Checkout Code
+        run: |
+          SERVER_DOMAIN=$(echo "${{ github.server_url }}" | sed 's/https:\/\///')
+          rm -rf "$GITHUB_WORKSPACE"/*
+          git clone "https://${{ github.actor }}:${{ secrets.GITHUB_TOKEN }}@${SERVER_DOMAIN}/${{ github.repository }}.git" "$GITHUB_WORKSPACE"
+          cd "$GITHUB_WORKSPACE"
+          git checkout ${{ github.sha }}
+
+      - name: Read version from Gradle
+        id: get_version
+        run: |
+          cd "$GITHUB_WORKSPACE"
+          chmod +x ./gradlew
+          VERSION=$(./gradlew properties | grep "^version:" | awk '{print $2}')
+          echo "Found local project version: $VERSION"
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+
+      - name: Check if version exists on repository
+        id: check_repo
+        run: |
+          cd "$GITHUB_WORKSPACE"
+          RAW_GROUP=$(./gradlew properties | grep "^group:" | awk '{print $2}')
+          GROUP_PATH=$(echo "$RAW_GROUP" | tr '.' '/')
+          ARTIFACT_ID=$(./gradlew properties | grep "^name:" | awk '{print $2}')
+
+          LOCAL_VERSION="${{ steps.get_version.outputs.version }}"
+
+          echo "Detected project: $RAW_GROUP:$ARTIFACT_ID:$LOCAL_VERSION"
+
+          CHECK_URL="${{ env.MAVEN_REPO_URL }}/${GROUP_PATH}/${ARTIFACT_ID}/${LOCAL_VERSION}/${ARTIFACT_ID}-${LOCAL_VERSION}.pom"
+          echo "Check url: $CHECK_URL"
+
+          STATUS=$(curl -o /dev/null -s -w "%{http_code}" -u "${{ env.MAVEN_REPO_USER }}:${{ env.MAVEN_REPO_PASS }}" "$CHECK_URL")
+          if [ "$STATUS" = "200" ]; then
+            echo "Version $LOCAL_VERSION already exists in repository. Skipping publishing."
+            echo "is_new=false" >> $GITHUB_OUTPUT
+          else
+            echo "Version $LOCAL_VERSION not found (Status $STATUS). Start deployment..."
+            echo "is_new=true" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Push to Maven Repository
+        if: steps.check_repo.outputs.is_new == 'true'
+        run: |
+          cd "$GITHUB_WORKSPACE"
+          echo "Publishing version ${{ steps.get_version.outputs.version }} zu Repository..."
+          ./gradlew publish
+

.idea/misc.xml

@@ -4,7 +4,7 @@
   <component name="FrameworkDetectionExcludesConfiguration">
     <file type="web" url="file://$PROJECT_DIR$" />
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_26" default="true" project-jdk-name="openjdk-26" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_26" default="true" project-jdk-name="26" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>

.idea/vcs.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+    <mapping directory="" vcs="Git" />
   </component>
 </project>

README.md

@@ -5,13 +5,17 @@ A lightweight, high-performance HTTP server library built on top of Netty. Nexus
 ## Features
 
 - **Netty-based** — uses epoll/kqueue/NIO automatically based on the platform
-- **Virtual thread dispatch** — each request is handled on a Java 21 virtual thread
+- **Virtual thread dispatch** — each request is handled on a Java virtual thread, with per-connection read backpressure and HTTP keep-alive
+- **TLS / HTTPS** — enable encryption with a single `withTls(...)` call (PEM files or a custom `SslContext`)
+- **Pluggable authentication** — insert an auth layer that protects selected paths; API key, cookie, HTTP Basic, bearer or any custom scheme (not tied to bearer tokens)
 - **Trie-based router** — supports static paths, path parameters (`{id}`), and wildcards (`*`)
 - **Annotation-based controllers** — define routes declaratively with `@Controller`, `@GET`, `@POST`, etc.
 - **Middleware chain** — attach cross-cutting logic to all routes
 - **CORS support** — configurable origins, methods, headers, credentials, and preflight caching
-- **Rate limiting** — four algorithm implementations with per-IP, per-token, or custom key strategies
-- **WebSockets** — path-routed handlers with origin validation, idle timeout, frame size limits and permessage-deflate
+- **Security headers** — opt-in `nosniff`, `X-Frame-Options`, `Referrer-Policy`, CSP and HTTPS-only HSTS, applied to every response
+- **Rate limiting** — four algorithm implementations with per-IP, per-header, per-cookie, per-principal or custom key strategies, with automatic eviction of idle state
+- **Spoofing-safe client IP** — `X-Forwarded-For` is honoured only behind configured trusted proxies
+- **WebSockets** — path-routed handlers with origin validation, optional authentication, ordered per-connection delivery, backpressure, idle timeout, frame size limits and permessage-deflate
 - **JSON I/O** — built-in Jackson integration for request parsing and response serialization
 
 ---
@@ -166,11 +170,17 @@ req.pathParam("id")           // path parameter, e.g. from /users/{id}
 req.queryParam("search")      // first value of ?search=
 req.queryParams("tag")        // all values of ?tag= as List<String>
 req.header("Authorization")   // raw header value
+req.cookie("sid")             // value of a named cookie
 req.body()                    // raw body as UTF-8 String
 req.json()                    // body parsed as Jackson JsonNode
 req.jsonAs(MyDto.class)       // body deserialized into a POJO
 req.method()                  // HttpMethod
 req.path()                    // decoded path without query string
+req.clientIp()                // resolved client IP (honours trusted proxies)
+req.principal()               // authenticated principal, or null (see Authentication)
+req.isAuthenticated()         // whether a principal is attached
+req.attribute("k", value)     // attach per-request state
+req.<T>attribute("k")         // read it back
 ```
 
 `json()` and `jsonAs()` throw `BadRequestException` (→ `400`) on malformed JSON.
@@ -214,6 +224,167 @@ Use `CorsConfig.permissive()` for a development preset that allows any origin wi
 
 ---
 
+## TLS / HTTPS
+
+Enable encryption by attaching a `TlsConfig`. The TLS handler becomes the first element of every connection's pipeline, so both HTTP and WebSocket traffic are served over TLS (HTTPS / WSS).
+
+```java
+import dev.coph.nextusweb.server.tls.TlsConfig;
+
+HttpServer.builder(443, router)
+        .withTls(TlsConfig.fromPem(
+                new File("fullchain.pem"),   // PEM certificate chain
+                new File("privkey.pem")))    // PKCS#8 private key
+        .start();
+```
+
+| Factory | Use |
+|---|---|
+| `TlsConfig.fromPem(cert, key)` | PEM certificate chain + unencrypted PKCS#8 key |
+| `TlsConfig.fromPem(cert, key, password)` | …with a password-protected key |
+| `TlsConfig.fromPem(certStream, keyStream, password)` | Load PEM material from the classpath or another stream |
+| `TlsConfig.fromSslContext(ctx)` | Full control — supply a Netty `SslContext` (custom ciphers, mutual TLS, …) |
+
+Any initialisation failure (missing/invalid material) is reported as an `IllegalStateException`.
+
+---
+
+## Authentication
+
+The auth layer authenticates **selected paths** before they reach handlers and attaches a `Principal` to the request (visible to rate limiting, middleware and handlers). It is deliberately **not** tied to bearer tokens — choose any credential scheme.
+
+```java
+import dev.coph.nextusweb.server.auth.*;
+
+// 1. An authenticator turns a credential into a Principal (or null if invalid).
+Authenticator auth = Authenticator.apiKey("X-API-Key", key ->
+        key.equals(System.getenv("API_KEY")) ? Principal.of("service", Set.of("admin")) : null);
+
+// 2. Decide which paths it protects.
+AuthConfig authConfig = AuthConfig.builder(auth)
+        .protectPrefix("/api/")        // required: 401 if missing/invalid
+        .optional("/feed")             // attach principal if present, never reject
+        .challenge("ApiKey realm=\"api\"")
+        .build();
+
+HttpServer.builder(8080, router)
+        .withAuth(new AuthGate(authConfig))
+        .start();
+```
+
+In a handler:
+
+```java
+router.get("/api/me", (req, res) -> {
+    Principal p = req.principal();              // never null on a protected path
+    if (!p.hasRole("admin")) { res.status(403); return; }
+    res.json(Map.of("id", p.id()));
+});
+```
+
+### Authenticators
+
+| Factory | Credential |
+|---|---|
+| `Authenticator.apiKey(header, validator)` | An API key in a request header (e.g. `X-API-Key`) |
+| `Authenticator.cookie(name, validator)` | A session (or other) cookie |
+| `Authenticator.basic(validator)` | HTTP Basic `username` / `password` |
+| `Authenticator.bearer(validator)` | A bearer token (provided for completeness; never required) |
+| `Authenticator.anyOf(a, b, …)` | Tries each in order, first match wins |
+| Custom | Implement `Authenticator` — e.g. mutual-TLS cert, HMAC-signed request |
+
+`validator` returns the resolved `Principal`, or `null` for missing/invalid credentials (→ `401` on a `REQUIRED` path). A thrown exception is treated as an internal error (→ generic `500`); details are logged, never sent to the client. Rate limiting runs **before** authentication, so an unauthenticated flood is shed before reaching a (potentially expensive) authenticator.
+
+When a validator compares a presented secret (API key, token, password) against an expected value, use `Authenticator.constantTimeEquals(presented, expected)` instead of `String.equals` to avoid leaking how many characters matched through a timing side channel:
+
+```java
+Authenticator auth = Authenticator.apiKey("X-API-Key",
+        key -> Authenticator.constantTimeEquals(key, EXPECTED_KEY) ? Principal.of("svc") : null);
+```
+
+WebSocket upgrades on protected paths are authenticated the same way; the resolved principal is available via `session.principal()`.
+
+---
+
+## Trusted proxies & client IP
+
+`req.clientIp()` and `KeyResolver.clientIp()` return a spoofing-safe client address. By default (`TrustedProxies.none()`) the transport peer address is used and `X-Forwarded-For` is ignored — a directly connected client cannot forge its IP. When running behind a reverse proxy, declare it trusted so the forwarded header is honoured:
+
+```java
+import dev.coph.nextusweb.server.net.TrustedProxies;
+
+HttpServer.builder(8080, router)
+        .withTrustedProxies(TrustedProxies.of("10.0.0.0/8", "127.0.0.1", "::1"))
+        .start();
+```
+
+The resolver walks `X-Forwarded-For` from right to left and returns the first hop that is **not** a trusted proxy, so forged left-most entries are ignored. Use `TrustedProxies.all()` only when the server can never be reached except through a trusted proxy.
+
+---
+
+## Hardening & limits
+
+| Concern | How it's handled |
+|---|---|
+| Connection reuse | HTTP keep-alive is honoured; connections close only on `Connection: close` or error |
+| Slow-client / Slowloris | A per-connection read timeout (`httpReadTimeout`, default 30s) closes stalled/idle connections |
+| Request memory | Auto-read is disabled while a request is in flight (one buffered body per connection); `maxHttpContentLength` (default 1 MiB) caps the body, returning `413` |
+| Error disclosure | Handler exceptions return a generic `500`; the detail is logged server-side, never sent to the client |
+
+```java
+HttpServer.builder(8080, router)
+        .maxHttpContentLength(2 * 1024 * 1024)      // 2 MiB body cap
+        .httpReadTimeout(Duration.ofSeconds(20))    // null/zero disables
+        .start();
+```
+
+---
+
+## Security headers
+
+`withSecurityHeaders(...)` adds standard browser-hardening response headers to **every** response (handler responses, errors, CORS preflights and rejections alike). It is opt-in; without the call no security headers are sent.
+
+```java
+import dev.coph.nextusweb.server.security.SecurityHeaders;
+
+HttpServer.builder(443, router)
+        .withTls(TlsConfig.fromPem(cert, key))
+        .withSecurityHeaders(SecurityHeaders.defaults())
+        .start();
+```
+
+`SecurityHeaders.defaults()` emits a conservative baseline:
+
+| Header | Value | Notes |
+|---|---|---|
+| `X-Content-Type-Options` | `nosniff` | Blocks MIME sniffing |
+| `X-Frame-Options` | `DENY` | Click-jacking defence |
+| `Referrer-Policy` | `no-referrer` | No referrer leakage |
+| `Strict-Transport-Security` | `max-age=31536000` | **Only sent over HTTPS** (when `withTls(...)` is set); pins HTTPS for a year |
+
+Two safety rules keep it from breaking anything: **HSTS is emitted only on TLS connections** (a browser ignores it on plain HTTP), and a header a handler has **already set is never overwritten** — so per-route choices win.
+
+For full control use the builder. Passing `null`/blank to a setter omits that header:
+
+```java
+SecurityHeaders headers = SecurityHeaders.builder()
+        .frameOptions("SAMEORIGIN")                       // or null to omit
+        .referrerPolicy("strict-origin-when-cross-origin")
+        .contentSecurityPolicy("default-src 'self'")      // off by default (app-specific)
+        .hsts(Duration.ofDays(365), true, false)          // maxAge, includeSubDomains, preload
+        .header("Permissions-Policy", "geolocation=()")   // any extra header
+        .build();
+
+HttpServer.builder(443, router)
+        .withTls(TlsConfig.fromPem(cert, key))
+        .withSecurityHeaders(headers)
+        .start();
+```
+
+> `includeSubDomains` and `preload` are hard to roll back — enable them only once every subdomain is reliably served over HTTPS.
+
+---
+
 ## Rate Limiting
 
 ### Algorithms
@@ -233,8 +404,8 @@ RateLimitConfig config = RateLimitConfig.builder()
         .global(new TokenBucketLimiter(100, 200), KeyResolver.clientIp())
         // Stricter rule for a specific path
         .forPath("/login", new FixedWindowLimiter(5, 60_000), KeyResolver.clientIp())
-        // Rule for an entire path prefix
-        .forPrefix("/api/", new SlidingWindowLimiter(1000, 1000), KeyResolver.userOrIp())
+        // Per-API-key rule for an entire path prefix (no bearer token required)
+        .forPrefix("/api/", new SlidingWindowLimiter(1000, 1000), KeyResolver.header("X-API-Key"))
         .build();
 
 RateLimitGate gate = new RateLimitGate(config);
@@ -246,6 +417,8 @@ HttpServer.builder(8080, router)
 
 When the limit is exceeded the server responds with `429 Too Many Requests` and a `Retry-After` header.
 
+Per-key limiter state is evicted automatically by a background task (every 5 minutes, entries idle for >10 minutes), so a high-cardinality key (many distinct IPs/API keys) cannot grow the limiter maps without bound. Call `gate.shutdown()` when stopping the server.
+
 ### Response headers
 
 Every response automatically includes:
@@ -260,9 +433,13 @@ Every response automatically includes:
 
 | Factory | Behaviour |
 |---|---|
-| `KeyResolver.clientIp()` | Uses `X-Forwarded-For` if present, otherwise the remote IP |
-| `KeyResolver.userOrIp()` | Uses the Bearer token if present (`u:<token>`), otherwise the client IP (`ip:<addr>`) |
-| Custom lambda | `(req, remoteAddr) -> myKey(req)` |
+| `KeyResolver.clientIp()` | The resolved client IP (honours trusted proxies — `X-Forwarded-For` is **not** trusted from a direct client) |
+| `KeyResolver.header(name)` | Header value (e.g. an API key in `X-API-Key`); falls back to `ip:<addr>` when absent |
+| `KeyResolver.cookie(name)` | Cookie value (e.g. a session id); falls back to `ip:<addr>` when absent |
+| `KeyResolver.principal()` | The authenticated principal id (`p:<id>`); falls back to `ip:<addr>` when anonymous (requires the auth layer to run for the path) |
+| Custom lambda | `(req, clientIp) -> myKey(req)` — `req` is the framework `Request`, `clientIp` the resolved IP |
+
+> The old `KeyResolver.userOrIp()` (which trusted any client's `X-Forwarded-For` and keyed on a raw bearer token) has been removed. It allowed trivial rate-limit bypass and unbounded key growth; use `header(...)`, `cookie(...)` or `principal()` instead.
 
 ---
 
@@ -307,7 +484,8 @@ WebSocketRouter wsRouter = new WebSocketRouter()
 WebSocketConfig wsConfig = WebSocketConfig.builder()
         .allowedOrigins("https://app.example.com")
         .maxFramePayloadLength(64 * 1024)         // 64 KiB per frame
-        .maxAggregatedMessageSize(1024 * 1024)    // 1 MiB upgrade body cap
+        .maxAggregatedMessageSize(1024 * 1024)    // 1 MiB cap on a reassembled (fragmented) message
+        .maxQueuedMessages(1024)                  // per-connection backlog before backpressure
         .idleTimeout(Duration.ofSeconds(60))      // close idle peers
         .subprotocols("chat.v1")
         .compression(true)                        // permessage-deflate
@@ -327,6 +505,7 @@ session.id();                       // stable UUID for this connection
 session.path();                     // matched path
 session.pathParam("room");          // path parameter, e.g. from /ws/rooms/{room}
 session.remoteAddress();            // client IP
+session.principal();                // authenticated principal, or null
 session.attribute("userId", id);    // attach state to the session
 session.attribute("userId");        // read it back
 
@@ -357,7 +536,9 @@ group.broadcastExcept(sessionA, "everyone but A");
 | Concern | How it's handled |
 |---|---|
 | Cross-origin upgrades | `Origin` header validated against `WebSocketConfig.allowedOrigins(...)`; mismatched origins are rejected with `403` |
-| Memory exhaustion | `maxFramePayloadLength` caps a single frame; `maxAggregatedMessageSize` caps the upgrade request body |
+| Authentication | When an `AuthGate` is configured, protected upgrade paths are authenticated and the principal is exposed via `session.principal()` |
+| Memory exhaustion | `maxFramePayloadLength` caps a single frame; `maxQueuedMessages` (default 1024) bounds the per-connection callback backlog and pauses reads (backpressure) when exceeded |
+| Message ordering | Callbacks for a single connection run **strictly in arrival order** on a per-connection serial drainer (still on virtual threads, so handlers may block) |
 | Idle / zombie connections | `idleTimeout` triggers a server-side close when no read **and** no write happen within the window |
 | User code isolation | All callbacks dispatch onto Java virtual threads, never the Netty event loop |
 | Subprotocol negotiation | Server advertises the configured `subprotocols(...)` list; clients that ask for an unsupported subprotocol fail the handshake |
@@ -415,6 +596,7 @@ WebSocketConfig wsConfig = WebSocketConfig.builder()
 HttpServer.builder(8080, router)
         .withCorsHandler(cors)
         .withRateLimitGate(gate)
+        .withSecurityHeaders(SecurityHeaders.defaults())
         .withWebSockets(wsRouter, wsConfig)
         .start();
 ```

build.gradle

@@ -4,7 +4,7 @@ plugins {
 }
 
 group = 'dev.coph'
-version = '0.0.4'
+version = '0.0.5'
 
 repositories {
     mavenCentral()

src/main/java/dev/coph/nextusweb/server/HttpRequestHandler.java

@@ -1,12 +1,17 @@
 package dev.coph.nextusweb.server;
 
+import dev.coph.nextusweb.server.auth.AuthGate;
+import dev.coph.nextusweb.server.auth.Principal;
 import dev.coph.nextusweb.server.cores.CorsHandler;
+import dev.coph.nextusweb.server.net.ClientIp;
+import dev.coph.nextusweb.server.net.TrustedProxies;
 import dev.coph.nextusweb.server.ratelimit.RateLimitGate;
 import dev.coph.nextusweb.server.ratelimit.RateLimiter;
 import dev.coph.nextusweb.server.router.Request;
 import dev.coph.nextusweb.server.router.Response;
 import dev.coph.nextusweb.server.router.Router;
 import dev.coph.nextusweb.server.router.exception.BadRequestException;
+import dev.coph.nextusweb.server.security.SecurityHeaders;
 import dev.coph.nextusweb.server.websocket.WebSocketConfig;
 import dev.coph.nextusweb.server.websocket.WebSocketFrameHandlerFactory;
 import dev.coph.nextusweb.server.websocket.WebSocketRouter;
@@ -16,12 +21,17 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.handler.codec.http.*;
+import io.netty.handler.codec.http.websocketx.WebSocketFrameAggregator;
 import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolConfig;
 import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
 import io.netty.handler.codec.http.websocketx.extensions.compression.WebSocketServerCompressionHandler;
 import io.netty.handler.timeout.IdleStateHandler;
 
+import java.lang.System.Logger;
+import java.lang.System.Logger.Level;
 import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.util.Map;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
@@ -31,31 +41,66 @@ import java.util.stream.Collectors;
  * The core inbound channel handler that processes every aggregated HTTP request.
  *
  * <p>For each request it, in order: detects and performs WebSocket upgrades (when a WebSocket
- * router is configured), answers CORS preflight requests, enforces rate limits, resolves the
- * route via the {@link Router}, runs middlewares and the matched handler, and finally writes the
- * response with CORS and rate-limit headers applied.</p>
+ * router is configured), answers CORS preflight requests, enforces rate limits, runs the
+ * authentication layer, resolves the route via the {@link Router}, runs middlewares and the
+ * matched handler, and finally writes the response with security, CORS and rate-limit headers
+ * applied.</p>
  *
  * <p>Blocking handler logic runs on a virtual-thread executor rather than on the Netty event
- * loop, so handlers may perform blocking work without stalling I/O. WebSocket upgrades, by
- * contrast, mutate the pipeline and are handled inline on the event loop.</p>
+ * loop, so handlers may perform blocking work without stalling I/O. To keep memory bounded the
+ * connection's auto-read is disabled while a request is in flight and re-enabled once the response
+ * has been flushed, so at most one request per connection is buffered at a time. Persistent
+ * (keep-alive) connections are honoured; the connection is closed only when the client requested
+ * {@code Connection: close} or an unrecoverable error occurred.</p>
  */
 public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
 
-    /** Executor running one virtual thread per task, used to offload blocking handler work. */
-    private static final Executor VT_EXECUTOR =
-            Executors.newVirtualThreadPerTaskExecutor();
+    /**
+     * Logger used for server-side error diagnostics (never leaked to clients).
+     */
+    private static final Logger LOG = System.getLogger(HttpRequestHandler.class.getName());
 
-    /** Router resolving requests to handlers. */
+    /**
+     * Executor running one virtual thread per task, used to offload blocking handler work.
+     */
+    private static final Executor VT_EXECUTOR = Executors.newVirtualThreadPerTaskExecutor();
+
+    /**
+     * Router resolving requests to handlers.
+     */
     private final Router router;
-    /** CORS handler, or {@code null} if CORS is disabled. */
+    /**
+     * CORS handler, or {@code null} if CORS is disabled.
+     */
     private final CorsHandler cors;
-    /** Rate-limit gate, or {@code null} if rate limiting is disabled. */
+    /**
+     * Rate-limit gate, or {@code null} if rate limiting is disabled.
+     */
     private final RateLimitGate rateLimit;
-    /** WebSocket router, or {@code null} if WebSocket support is disabled. */
+    /**
+     * Authentication gate, or {@code null} if the auth layer is disabled.
+     */
+    private final AuthGate authGate;
+    /**
+     * Trusted-proxy policy used to resolve the client IP; never {@code null}.
+     */
+    private final TrustedProxies trustedProxies;
+    /**
+     * WebSocket router, or {@code null} if WebSocket support is disabled.
+     */
     private final WebSocketRouter wsRouter;
-    /** WebSocket configuration; only consulted when {@link #wsRouter} is non-null. */
+    /**
+     * WebSocket configuration; only consulted when {@link #wsRouter} is non-null.
+     */
     private final WebSocketConfig wsConfig;
-
+    /**
+     * Security-header policy applied to every response, or {@code null} if disabled.
+     */
+    private final SecurityHeaders securityHeaders;
+    /**
+     * Whether this server's connections are secured by TLS (gates HSTS emission).
+     */
+    private final boolean secure;
 
     /**
      * Creates a handler without WebSocket support.
@@ -63,9 +108,36 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
      * @param router         the router resolving requests
      * @param cors           the CORS handler, or {@code null} to disable CORS
      * @param rateLimit      the rate-limit gate, or {@code null} to disable rate limiting
+     * @param authGate       the auth gate, or {@code null} to disable the auth layer
+     * @param trustedProxies the trusted-proxy policy, or {@code null} for {@link TrustedProxies#none()}
      */
-    public HttpRequestHandler(Router router, CorsHandler cors, RateLimitGate rateLimit) {
-        this(router, cors, rateLimit, null, null);
+    public HttpRequestHandler(Router router, CorsHandler cors, RateLimitGate rateLimit, AuthGate authGate, TrustedProxies trustedProxies) {
+        this(router, cors, rateLimit, authGate, trustedProxies, null, null, null, false);
+    }
+
+    /**
+     * Creates a handler with WebSocket support and a security-header policy.
+     *
+     * @param router          the router resolving requests
+     * @param cors            the CORS handler, or {@code null} to disable CORS
+     * @param rateLimit       the rate-limit gate, or {@code null} to disable rate limiting
+     * @param authGate        the auth gate, or {@code null} to disable the auth layer
+     * @param trustedProxies  the trusted-proxy policy, or {@code null} for {@link TrustedProxies#none()}
+     * @param wsRouter        the WebSocket router, or {@code null} to disable WebSocket support
+     * @param wsConfig        the WebSocket configuration, used only when {@code wsRouter} is non-null
+     * @param securityHeaders the security-header policy, or {@code null} to add no security headers
+     * @param secure          whether the server's connections are secured by TLS (gates HSTS)
+     */
+    public HttpRequestHandler(Router router, CorsHandler cors, RateLimitGate rateLimit, AuthGate authGate, TrustedProxies trustedProxies, WebSocketRouter wsRouter, WebSocketConfig wsConfig, SecurityHeaders securityHeaders, boolean secure) {
+        this.router = router;
+        this.cors = cors;
+        this.rateLimit = rateLimit;
+        this.authGate = authGate;
+        this.trustedProxies = trustedProxies == null ? TrustedProxies.none() : trustedProxies;
+        this.wsRouter = wsRouter;
+        this.wsConfig = wsConfig;
+        this.securityHeaders = securityHeaders;
+        this.secure = secure;
     }
 
     /**
@@ -74,22 +146,20 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
      * @param router         the router resolving requests
      * @param cors           the CORS handler, or {@code null} to disable CORS
      * @param rateLimit      the rate-limit gate, or {@code null} to disable rate limiting
+     * @param authGate       the auth gate, or {@code null} to disable the auth layer
+     * @param trustedProxies the trusted-proxy policy, or {@code null} for {@link TrustedProxies#none()}
      * @param wsRouter       the WebSocket router, or {@code null} to disable WebSocket support
      * @param wsConfig       the WebSocket configuration, used only when {@code wsRouter} is non-null
      */
-    public HttpRequestHandler(Router router, CorsHandler cors, RateLimitGate rateLimit,
-                              WebSocketRouter wsRouter, WebSocketConfig wsConfig) {
-        this.router = router;
-        this.cors = cors;
-        this.rateLimit = rateLimit;
-        this.wsRouter = wsRouter;
-        this.wsConfig = wsConfig;
+    public HttpRequestHandler(Router router, CorsHandler cors, RateLimitGate rateLimit, AuthGate authGate, TrustedProxies trustedProxies, WebSocketRouter wsRouter, WebSocketConfig wsConfig) {
+        this(router, cors, rateLimit, authGate, trustedProxies, wsRouter, wsConfig, null, false);
     }
 
     /**
      * Entry point invoked by Netty for each fully aggregated request. WebSocket upgrade requests
-     * are handled inline; all other requests are retained and dispatched to a virtual thread for
-     * processing, with the request released once handling completes.
+     * are handled inline; all other requests disable the connection's auto-read (one in-flight
+     * request per connection) and are retained and dispatched to a virtual thread for processing,
+     * with the request released once handling completes.
      *
      * @param ctx the channel context
      * @param req the aggregated HTTP request
@@ -100,6 +170,8 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
             if (handleWebSocketUpgrade(ctx, req)) return;
         }
 
+        ctx.channel().config().setAutoRead(false);
+
         req.retain();
         VT_EXECUTOR.execute(() -> {
             try {
@@ -121,7 +193,7 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
     private static boolean isWebSocketUpgrade(FullHttpRequest req) {
         if (req.method() != HttpMethod.GET) return false;
         String upgrade = req.headers().get(HttpHeaderNames.UPGRADE);
-        if (upgrade == null || !"websocket".equalsIgnoreCase(upgrade)) return false;
+        if (!"websocket".equalsIgnoreCase(upgrade)) return false;
         String connection = req.headers().get(HttpHeaderNames.CONNECTION);
         if (connection == null) return false;
         for (String token : connection.split(",")) {
@@ -134,15 +206,15 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
      * Attempts to upgrade the connection to WebSocket for the request's path.
      *
      * <p>Resolves the path against the WebSocket router; if no handler matches the upgrade is
-     * declined. Otherwise the origin is validated, the WebSocket protocol/compression/idle
-     * handlers and the application frame handler are inserted into the pipeline, and the request
-     * is re-fired so Netty performs the handshake.</p>
+     * declined. Otherwise the origin is validated, the auth layer (if configured) authenticates
+     * the upgrade and may reject it, and then the WebSocket protocol/compression/idle handlers and
+     * the application frame handler are inserted into the pipeline and the request is re-fired so
+     * Netty performs the handshake. The resolved principal (if any) is handed to the session.</p>
      *
      * @param ctx the channel context
      * @param req the upgrade request
      * @return {@code true} if the request was consumed (handshake started or rejected),
-     *         {@code false} if no WebSocket route matched and normal HTTP handling should
-     *         continue
+     * {@code false} if no WebSocket route matched and normal HTTP handling should continue
      */
     private boolean handleWebSocketUpgrade(ChannelHandlerContext ctx, FullHttpRequest req) {
         String path = new QueryStringDecoder(req.uri()).path();
@@ -151,13 +223,23 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
 
         String origin = req.headers().get(HttpHeaderNames.ORIGIN);
         if (!wsConfig.isOriginAllowed(origin)) {
-            FullHttpResponse forbidden = new DefaultFullHttpResponse(
-                    HttpVersion.HTTP_1_1, HttpResponseStatus.FORBIDDEN);
-            forbidden.headers().setInt(HttpHeaderNames.CONTENT_LENGTH, 0);
-            ctx.writeAndFlush(forbidden).addListener(ChannelFutureListener.CLOSE);
+            sendStatusAndClose(ctx, HttpResponseStatus.FORBIDDEN);
             return true;
         }
 
+
+        Principal principal = null;
+        if (authGate != null) {
+            Request upgradeReq = new Request(req, resolution.pathParams());
+            upgradeReq.clientIp(resolveClientIp(ctx, req));
+            Response rejection = authGate.authenticate(upgradeReq, path);
+            if (rejection != null) {
+                sendStatusAndClose(ctx, HttpResponseStatus.valueOf(rejection.status()));
+                return true;
+            }
+            principal = upgradeReq.principal();
+        }
+
         WebSocketServerProtocolConfig protoCfg = WebSocketServerProtocolConfig.newBuilder()
                 .websocketPath(path)
                 .checkStartsWith(false)
@@ -169,19 +251,21 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
         ChannelPipeline pipeline = ctx.pipeline();
         String myName = ctx.name();
 
+        if (pipeline.get("read-timeout") != null) {
+            pipeline.remove("read-timeout");
+        }
+
         if (wsConfig.idleTimeout() != null) {
             long secs = Math.max(1, wsConfig.idleTimeout().toSeconds());
-            pipeline.addBefore(myName, "ws-idle",
-                    new IdleStateHandler(0, 0, secs, TimeUnit.SECONDS));
+            pipeline.addBefore(myName, "ws-idle", new IdleStateHandler(0, 0, secs, TimeUnit.SECONDS));
         }
         if (wsConfig.compression()) {
-            pipeline.addBefore(myName, "ws-deflate",
-                    new WebSocketServerCompressionHandler());
+            pipeline.addBefore(myName, "ws-deflate", new WebSocketServerCompressionHandler());
         }
-        pipeline.addBefore(myName, "ws-proto",
-                new WebSocketServerProtocolHandler(protoCfg));
-        pipeline.addBefore(myName, "ws-frames",
-                WebSocketFrameHandlerFactory.create(resolution.handler(), path, resolution.pathParams()));
+        pipeline.addBefore(myName, "ws-proto", new WebSocketServerProtocolHandler(protoCfg));
+
+        pipeline.addBefore(myName, "ws-aggregator", new WebSocketFrameAggregator(wsConfig.maxAggregatedMessageSize()));
+        pipeline.addBefore(myName, "ws-frames", WebSocketFrameHandlerFactory.create(resolution.handler(), path, resolution.pathParams(), principal, wsConfig.maxQueuedMessages()));
 
         ChannelHandlerContext anchor = pipeline.context(HttpObjectAggregator.class);
         if (anchor == null) anchor = pipeline.firstContext();
@@ -190,55 +274,72 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
     }
 
     /**
-     * Processes a normal (non-WebSocket) HTTP request: applies CORS preflight handling and rate
-     * limiting, resolves the route, runs middlewares and the handler, and sends the response.
+     * Processes a normal (non-WebSocket) HTTP request: applies CORS preflight handling, rate
+     * limiting and authentication, resolves the route, runs middlewares and the handler, and sends
+     * the response.
      *
-     * <p>Exceptions from the handler are mapped to responses: a {@link BadRequestException}
-     * becomes a {@code 400}, any other exception a {@code 500}. Routing misses become
-     * {@code 404}, and method mismatches a {@code 405} with an {@code Allow} header. CORS and
-     * rate-limit headers are applied to the final response in all cases.</p>
+     * <p>The whole method is guarded so that <em>some</em> response is always produced — even an
+     * unexpected failure in the pre-handler stages yields a generic {@code 500} rather than a
+     * leaked, hung connection. Handler exceptions are mapped to responses: a
+     * {@link BadRequestException} becomes a {@code 400}, any other exception a {@code 500} whose
+     * details are logged server-side but never sent to the client. Routing misses become
+     * {@code 404}, method mismatches a {@code 405} with an {@code Allow} header.</p>
      *
      * @param ctx the channel context
      * @param raw the aggregated request being handled
      */
     private void handle(ChannelHandlerContext ctx, FullHttpRequest raw) {
-        String origin = raw.headers().get("Origin");
+        boolean keepAlive = HttpUtil.isKeepAlive(raw);
+        try {
+            String origin = raw.headers().get(HttpHeaderNames.ORIGIN);
 
             if (cors != null && cors.isPreflight(raw.method(), raw.headers())) {
-            send(ctx, cors.handlePreflight(origin, raw.headers()));
+                send(ctx, cors.handlePreflight(origin, raw.headers()), keepAlive);
                 return;
             }
 
             String path = new QueryStringDecoder(raw.uri()).path();
+            String clientIp = resolveClientIp(ctx, raw);
+
+            Router.Resolution resolution = router.resolve(raw.method(), path);
+            Map<String, String> params = resolution instanceof Router.Resolution.Match m ? m.pathParams() : Map.of();
+            Request request = new Request(raw, params);
+            request.clientIp(clientIp);
 
             RateLimiter.Result rlResult = null;
             if (rateLimit != null) {
-            String remote = ((InetSocketAddress) ctx.channel().remoteAddress()).getAddress().getHostAddress();
-            rlResult = rateLimit.check(raw, path, remote);
+                rlResult = rateLimit.check(request, path, clientIp);
                 if (rlResult != null && !rlResult.allowed()) {
                     Response res = new Response().status(429).json("{\"error\":\"Too Many Requests\"}");
                     RateLimitGate.applyHeaders(rlResult, res);
                     if (cors != null) cors.applyHeaders(origin, res);
-                send(ctx, res);
+                    send(ctx, res, keepAlive);
                     return;
                 }
             }
 
-
-        Router.Resolution resolution = router.resolve(raw.method(), path);
+            if (authGate != null) {
+                Response rejection = authGate.authenticate(request, path);
+                if (rejection != null) {
+                    RateLimitGate.applyHeaders(rlResult, rejection);
+                    if (cors != null) cors.applyHeaders(origin, rejection);
+                    send(ctx, rejection, keepAlive);
+                    return;
+                }
+            }
 
             Response res = new Response();
-
             switch (resolution) {
                 case Router.Resolution.Match m -> {
-                Request request = new Request(raw, m.pathParams());
                     try {
-                    for (var mw : router.middlewares()) mw.accept(request, res);
+                        for (var mw : router.middlewares())
+                            mw.accept(request, res);
                         m.handler().handle(request, res);
                     } catch (BadRequestException e) {
-                    res.status(400).json("{\"error\":\"" + e.getMessage() + "\"}");
+                        res.status(400).json(Map.of("error", e.getMessage() == null ? "Bad Request" : e.getMessage()));
                     } catch (Exception e) {
-                    res.status(500).text("Internal Server Error: " + e.getMessage());
+                        LOG.log(Level.ERROR, "Handler failed for " + raw.method() + " " + path, e);
+                        res.status(500).json("{\"error\":\"Internal Server Error\"}");
                     }
                 }
                 case Router.Resolution.MethodNotAllowed mna -> {
@@ -248,24 +349,65 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
                             .collect(Collectors.joining(", "));
                     res.status(405)
                             .header(HttpHeaderNames.ALLOW.toString(), allow)
-                        .json("{\"error\":\"Method Not Allowed\",\"allowed\":\"" + allow + "\"}");
+                            .json(Map.of("error", "Method Not Allowed", "allowed", allow));
                 }
                 case Router.Resolution.NotFound nf -> res.status(404).json("{\"error\":\"Not Found\"}");
             }
 
             RateLimitGate.applyHeaders(rlResult, res);
             if (cors != null) cors.applyHeaders(origin, res);
-        send(ctx, res);
+            send(ctx, res, keepAlive);
+        } catch (Throwable t) {
+            LOG.log(Level.ERROR, "Unexpected failure while handling request", t);
+            try {
+                send(ctx, new Response().status(500).json("{\"error\":\"Internal Server Error\"}"), false);
+            } catch (Throwable ignored) {
+                ctx.close();
+            }
+        }
+    }
+
+    /**
+     * Writes an empty-bodied response with the given status and closes the connection, used for
+     * rejected WebSocket upgrades.
+     *
+     * @param ctx    the channel context
+     * @param status the HTTP status to send
+     */
+    private static void sendStatusAndClose(ChannelHandlerContext ctx, HttpResponseStatus status) {
+        FullHttpResponse res = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, status);
+        res.headers().setInt(HttpHeaderNames.CONTENT_LENGTH, 0);
+        ctx.writeAndFlush(res).addListener(ChannelFutureListener.CLOSE);
+    }
+
+    /**
+     * Resolves the effective client IP for a request, honouring the configured trusted proxies.
+     *
+     * @param ctx the channel context
+     * @param raw the request (for the forwarded-for header)
+     * @return the resolved client IP, or {@code "unknown"} if the peer address is unavailable
+     */
+    private String resolveClientIp(ChannelHandlerContext ctx, FullHttpRequest raw) {
+        SocketAddress addr = ctx.channel().remoteAddress();
+        String socketIp = (addr instanceof InetSocketAddress isa && isa.getAddress() != null) ? isa.getAddress().getHostAddress() : "unknown";
+        String forwarded = raw.headers().get(ClientIp.FORWARDED_FOR_HEADER);
+        return ClientIp.resolve(socketIp, forwarded, trustedProxies);
     }
 
     /**
      * Converts the framework {@link Response} into a Netty {@link FullHttpResponse}, sets the
-     * {@code Content-Length}, writes it and closes the connection afterwards.
+     * {@code Content-Length} and {@code Connection} headers and writes it. For keep-alive
+     * connections the connection is kept open and reading resumes for the next request; otherwise
+     * the connection is closed after the write.
      *
      * @param ctx       the channel context
      * @param res       the response to send
+     * @param keepAlive whether the client requested a persistent connection
      */
-    private void send(ChannelHandlerContext ctx, Response res) {
+    private void send(ChannelHandlerContext ctx, Response res, boolean keepAlive) {
+        if (securityHeaders != null) {
+            securityHeaders.apply(res, secure);
+        }
         var nettyRes = new DefaultFullHttpResponse(
                 HttpVersion.HTTP_1_1,
                 HttpResponseStatus.valueOf(res.status()),
@@ -273,11 +415,31 @@ public final class HttpRequestHandler extends SimpleChannelInboundHandler<FullHt
         );
         nettyRes.headers().add(res.headers());
         nettyRes.headers().setInt(HttpHeaderNames.CONTENT_LENGTH, res.body().length);
+
+        if (keepAlive) {
+            nettyRes.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
+            ctx.writeAndFlush(nettyRes).addListener(future -> resumeReading(ctx));
+        } else {
+            nettyRes.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE);
             ctx.writeAndFlush(nettyRes).addListener(ChannelFutureListener.CLOSE);
         }
+    }
 
     /**
-     * Closes the channel on any unhandled pipeline exception.
+     * Re-enables auto-read and requests the next message, resuming intake on a persistent
+     * connection after its in-flight request has been answered.
+     *
+     * @param ctx the channel context
+     */
+    private static void resumeReading(ChannelHandlerContext ctx) {
+        if (ctx.channel().isActive()) {
+            ctx.channel().config().setAutoRead(true);
+            ctx.read();
+        }
+    }
+
+    /**
+     * Closes the channel on any unhandled pipeline exception (including read timeouts).
      *
      * @param ctx   the channel context
      * @param cause the exception that propagated up the pipeline

src/main/java/dev/coph/nextusweb/server/HttpServer.java

@@ -1,8 +1,12 @@
 package dev.coph.nextusweb.server;
 
+import dev.coph.nextusweb.server.auth.AuthGate;
 import dev.coph.nextusweb.server.cores.CorsHandler;
+import dev.coph.nextusweb.server.net.TrustedProxies;
 import dev.coph.nextusweb.server.ratelimit.RateLimitGate;
 import dev.coph.nextusweb.server.router.Router;
+import dev.coph.nextusweb.server.security.SecurityHeaders;
+import dev.coph.nextusweb.server.tls.TlsConfig;
 import dev.coph.nextusweb.server.websocket.WebSocketConfig;
 import dev.coph.nextusweb.server.websocket.WebSocketRouter;
 import io.netty.bootstrap.ServerBootstrap;
@@ -18,44 +22,89 @@ import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.handler.codec.http.HttpObjectAggregator;
 import io.netty.handler.codec.http.HttpServerCodec;
+import io.netty.handler.timeout.ReadTimeoutHandler;
+
+import java.time.Duration;
+import java.util.Objects;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Bootstraps and runs the Netty-based HTTP (and optionally WebSocket) server.
  *
  * <p>The class doubles as a small fluent builder: {@link #builder(int, Router)} creates an
- * instance bound to a port and {@link Router}, and the {@code withXxx} methods attach optional
- * features (CORS, rate limiting, WebSockets) before {@link #start()} launches the server.</p>
+ * instance bound to a port and {@link Router}, and the {@code withXxx}/setter methods attach
+ * optional features (TLS, CORS, rate limiting, authentication, WebSockets, trusted proxies,
+ * limits and timeouts) before {@link #start()} launches the server.</p>
  *
  * <p>At start-up it selects the most efficient available transport &mdash; {@code epoll} on
  * Linux, {@code kqueue} on macOS/BSD, or the portable NIO transport otherwise &mdash; and wires
- * up the Netty channel pipeline (codec, aggregator and the {@link HttpRequestHandler}). The
- * {@link #start()} call blocks until the server channel is closed.</p>
+ * up the Netty channel pipeline (optional TLS, a read timeout that defeats slow-client attacks,
+ * the HTTP codec, aggregator and the {@link HttpRequestHandler}). The {@link #start()} call
+ * blocks until the server channel is closed.</p>
  */
 public final class HttpServer {
 
-    /** TCP port the server binds to. */
-    private final int port;
-    /** Router resolving requests to handlers. */
-    private final Router router;
-    /** Optional CORS handler; {@code null} disables CORS handling. */
-    private CorsHandler cors;
-    /** Optional rate-limit gate; {@code null} disables rate limiting. */
-    private RateLimitGate gate;
-    /** Optional WebSocket router; {@code null} disables WebSocket support. */
-    private WebSocketRouter wsRouter;
-    /** WebSocket configuration; only used when {@link #wsRouter} is set. */
-    private WebSocketConfig wsConfig;
+    /**
+     * Default cap on aggregated HTTP request bodies: 1&nbsp;MiB.
+     */
+    private static final int DEFAULT_MAX_HTTP_CONTENT_LENGTH = 1_048_576;
+    /**
+     * Default per-connection read timeout that reaps slow/idle clients.
+     */
+    private static final Duration DEFAULT_HTTP_READ_TIMEOUT = Duration.ofSeconds(30);
 
     /**
-     * Creates a server bound to a port and router. Use {@link #builder(int, Router)} instead of
-     * calling this directly.
-     *
-     * @param port   the TCP port to bind
-     * @param router the router resolving requests
+     * TCP port the server binds to.
      */
+    private final int port;
+    /**
+     * Router resolving requests to handlers.
+     */
+    private final Router router;
+    /**
+     * Optional TLS configuration; {@code null} serves plain HTTP.
+     */
+    private TlsConfig tls;
+    /**
+     * Optional CORS handler; {@code null} disables CORS handling.
+     */
+    private CorsHandler cors;
+    /**
+     * Optional rate-limit gate; {@code null} disables rate limiting.
+     */
+    private RateLimitGate gate;
+    /**
+     * Optional authentication gate; {@code null} disables the auth layer.
+     */
+    private AuthGate authGate;
+    /**
+     * Optional security-header policy; {@code null} adds no security headers.
+     */
+    private SecurityHeaders securityHeaders;
+    /**
+     * Optional WebSocket router; {@code null} disables WebSocket support.
+     */
+    private WebSocketRouter wsRouter;
+    /**
+     * WebSocket configuration; only used when {@link #wsRouter} is set.
+     */
+    private WebSocketConfig wsConfig;
+    /**
+     * Trusted-proxy policy for resolving the client IP; never {@code null}.
+     */
+    private TrustedProxies trustedProxies = TrustedProxies.none();
+    /**
+     * Maximum aggregated HTTP request body size in bytes.
+     */
+    private int maxHttpContentLength = DEFAULT_MAX_HTTP_CONTENT_LENGTH;
+    /**
+     * Per-connection HTTP read timeout; {@code null} or non-positive disables it.
+     */
+    private Duration httpReadTimeout = DEFAULT_HTTP_READ_TIMEOUT;
+
     private HttpServer(int port, Router router) {
         this.port = port;
-        this.router = router;
+        this.router = Objects.requireNonNull(router, "router");
     }
 
     /**
@@ -69,6 +118,18 @@ public final class HttpServer {
         return new HttpServer(port, router);
     }
 
+    /**
+     * Enables TLS (HTTPS / WSS). The TLS handler becomes the first element of every connection's
+     * pipeline.
+     *
+     * @param tls the TLS configuration
+     * @return this instance, for fluent chaining
+     */
+    public HttpServer withTls(TlsConfig tls) {
+        this.tls = tls;
+        return this;
+    }
+
     /**
      * Attaches a CORS handler that decorates responses and answers preflight requests.
      *
@@ -91,6 +152,72 @@ public final class HttpServer {
         return this;
     }
 
+    /**
+     * Attaches an authentication gate that authenticates configured requests before they reach
+     * handlers and attaches the resolved principal to the request.
+     *
+     * @param authGate the auth gate to use
+     * @return this instance, for fluent chaining
+     */
+    public HttpServer withAuth(AuthGate authGate) {
+        this.authGate = authGate;
+        return this;
+    }
+
+    /**
+     * Attaches a security-header policy whose headers are added to every response. HSTS, if
+     * configured, is emitted only when TLS is enabled on this server. Existing headers set by a
+     * handler are preserved.
+     *
+     * @param securityHeaders the security-header policy to apply
+     * @return this instance, for fluent chaining
+     * @see SecurityHeaders#defaults()
+     */
+    public HttpServer withSecurityHeaders(SecurityHeaders securityHeaders) {
+        this.securityHeaders = securityHeaders;
+        return this;
+    }
+
+    /**
+     * Configures which transport peers are trusted reverse proxies, controlling whether
+     * {@code X-Forwarded-For} is honoured when resolving the client IP. Defaults to
+     * {@link TrustedProxies#none()} (forwarded headers ignored).
+     *
+     * @param trustedProxies the trusted-proxy policy
+     * @return this instance, for fluent chaining
+     */
+    public HttpServer withTrustedProxies(TrustedProxies trustedProxies) {
+        this.trustedProxies = Objects.requireNonNull(trustedProxies, "trustedProxies");
+        return this;
+    }
+
+    /**
+     * Sets the maximum aggregated HTTP request body size in bytes. Requests exceeding it are
+     * rejected by the aggregator with {@code 413 Request Entity Too Large}.
+     *
+     * @param bytes the limit in bytes; must be positive
+     * @return this instance, for fluent chaining
+     */
+    public HttpServer maxHttpContentLength(int bytes) {
+        if (bytes <= 0)
+            throw new IllegalArgumentException("maxHttpContentLength must be > 0");
+        this.maxHttpContentLength = bytes;
+        return this;
+    }
+
+    /**
+     * Sets the per-connection HTTP read timeout. A connection that sends no data for this long is
+     * closed, which both reaps idle keep-alive connections and defeats slow-client (Slowloris)
+     * attacks. Pass {@code null} or a non-positive duration to disable it.
+     *
+     * @param timeout the read timeout, or {@code null}/non-positive to disable
+     * @return this instance, for fluent chaining
+     */
+    public HttpServer httpReadTimeout(Duration timeout) {
+        this.httpReadTimeout = timeout;
+        return this;
+    }
+
     /**
      * Enables WebSocket support with default configuration.
      *
@@ -116,46 +243,12 @@ public final class HttpServer {
     }
 
     /**
-     * Starts the server using the configuration accumulated on this instance and blocks until
-     * the server channel closes.
+     * Starts the server using the configuration accumulated on this instance and blocks until the
+     * server channel closes.
      *
      * @throws InterruptedException if the binding or close-future wait is interrupted
      */
     public void start() throws InterruptedException {
-        start(port, router, cors, gate, wsRouter, wsConfig);
-    }
-
-    /**
-     * Starts a server without WebSocket support. Convenience overload of
-     * {@link #start(int, Router, CorsHandler, RateLimitGate, WebSocketRouter, WebSocketConfig)}.
-     *
-     * @param port   the TCP port to bind
-     * @param router the router resolving requests
-     * @param cors   the CORS handler, or {@code null} to disable CORS
-     * @param gate   the rate-limit gate, or {@code null} to disable rate limiting
-     * @throws InterruptedException if the binding or close-future wait is interrupted
-     */
-    public static void start(int port, Router router, CorsHandler cors, RateLimitGate gate)
-            throws InterruptedException {
-        start(port, router, cors, gate, null, null);
-    }
-
-    /**
-     * Starts the server, selecting the best transport for the platform, configuring the Netty
-     * channel pipeline and binding the port. The call blocks until the server channel is closed,
-     * after which the event-loop groups are shut down gracefully.
-     *
-     * @param port     the TCP port to bind
-     * @param router   the router resolving requests
-     * @param cors     the CORS handler, or {@code null} to disable CORS
-     * @param gate     the rate-limit gate, or {@code null} to disable rate limiting
-     * @param wsRouter the WebSocket router, or {@code null} to disable WebSocket support
-     * @param wsConfig the WebSocket configuration, used only when {@code wsRouter} is non-null
-     * @throws InterruptedException if the binding or close-future wait is interrupted
-     */
-    public static void start(int port, Router router, CorsHandler cors, RateLimitGate gate,
-                             WebSocketRouter wsRouter, WebSocketConfig wsConfig)
-            throws InterruptedException {
         EventLoopGroup boss, worker;
         Class<? extends ServerChannel> channelClass;
 
@@ -173,9 +266,17 @@ public final class HttpServer {
             channelClass = NioServerSocketChannel.class;
         }
 
-        int maxAggregated = wsConfig != null
-                ? Math.max(1024 * 1024, wsConfig.maxAggregatedMessageSize())
-                : 1024 * 1024;
+        final TlsConfig tlsCfg = this.tls;
+        final CorsHandler corsHandler = this.cors;
+        final RateLimitGate rateLimitGate = this.gate;
+        final AuthGate auth = this.authGate;
+        final WebSocketRouter websocketRouter = this.wsRouter;
+        final WebSocketConfig websocketConfig = this.wsConfig;
+        final SecurityHeaders secHeaders = this.securityHeaders;
+        final boolean tlsEnabled = tlsCfg != null;
+        final TrustedProxies proxies = this.trustedProxies;
+        final int maxContent = this.maxHttpContentLength;
+        final long readTimeoutSeconds = (httpReadTimeout != null && !httpReadTimeout.isZero() && !httpReadTimeout.isNegative()) ? Math.max(1, httpReadTimeout.toSeconds()) : 0;
 
         try {
             new ServerBootstrap()
@@ -187,10 +288,16 @@ public final class HttpServer {
                     .childHandler(new ChannelInitializer<SocketChannel>() {
                         @Override
                         protected void initChannel(SocketChannel ch) {
-                            ch.pipeline()
-                                    .addLast(new HttpServerCodec())
-                                    .addLast(new HttpObjectAggregator(maxAggregated))
-                                    .addLast(new HttpRequestHandler(router, cors, gate, wsRouter, wsConfig));
+                            ChannelPipeline pipeline = ch.pipeline();
+                            if (tlsCfg != null) {
+                                pipeline.addLast("ssl", tlsCfg.newHandler(ch.alloc()));
+                            }
+                            if (readTimeoutSeconds > 0) {
+                                pipeline.addLast("read-timeout", new ReadTimeoutHandler(readTimeoutSeconds, TimeUnit.SECONDS));
+                            }
+                            pipeline.addLast(new HttpServerCodec())
+                                    .addLast(new HttpObjectAggregator(maxContent))
+                                    .addLast(new HttpRequestHandler(router, corsHandler, rateLimitGate, auth, proxies, websocketRouter, websocketConfig, secHeaders, tlsEnabled));
                         }
                     })
                     .bind(port).sync().channel().closeFuture().sync();

src/main/java/dev/coph/nextusweb/server/annotation/AnnotationScanner.java

@@ -4,6 +4,7 @@ import dev.coph.nextusweb.server.router.Request;
 import dev.coph.nextusweb.server.router.Response;
 import dev.coph.nextusweb.server.router.Router;
 import io.netty.handler.codec.http.HttpMethod;
+
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;

src/main/java/dev/coph/nextusweb/server/auth/AuthConfig.java

@@ -0,0 +1,242 @@
+package dev.coph.nextusweb.server.auth;
+
+import java.util.*;
+
+/**
+ * Immutable mapping from request paths to the authentication requirement that applies to them,
+ * consumed by {@link AuthGate}.
+ *
+ * <p>The model mirrors {@code RateLimitConfig}: a path resolves to at most one rule, chosen with
+ * the precedence</p>
+ * <ol>
+ *     <li><strong>exact-path</strong> rules (matched by exact equality);</li>
+ *     <li><strong>prefix</strong> rules (longest matching prefix wins);</li>
+ *     <li>an optional <strong>global</strong> rule applied to every other path.</li>
+ * </ol>
+ *
+ * <p>Each rule pairs an {@link Authenticator} with a {@link Mode}: {@link Mode#REQUIRED} rejects
+ * the request with {@code 401} when authentication fails, while {@link Mode#OPTIONAL} attaches the
+ * principal when present but never rejects (useful for endpoints that behave differently for
+ * signed-in callers). Paths with no matching rule are not authenticated at all.</p>
+ */
+public final class AuthConfig {
+
+    /**
+     * Rule applied to every path with no more specific match, or {@code null} if none.
+     */
+    private final Rule globalRule;
+    /**
+     * Rules matched by exact path equality.
+     */
+    private final Map<String, Rule> exactPathRules;
+    /**
+     * Prefix rules, pre-sorted longest-prefix-first.
+     */
+    private final List<PrefixRule> prefixRules;
+    /**
+     * Optional {@code WWW-Authenticate} challenge sent with {@code 401} responses.
+     */
+    private final String challenge;
+
+    private AuthConfig(Builder b) {
+        this.globalRule = b.globalRule;
+        this.exactPathRules = Map.copyOf(b.exactPathRules);
+        this.prefixRules = b.prefixRules.stream()
+                .sorted((a, c) -> Integer.compare(c.prefix.length(), a.prefix.length()))
+                .toList();
+        this.challenge = b.challenge;
+    }
+
+    /**
+     * Creates a builder using the given authenticator as the default for rules that do not specify
+     * their own.
+     *
+     * @param defaultAuthenticator the authenticator used by rules added without an explicit one
+     * @return a fresh builder
+     */
+    public static Builder builder(Authenticator defaultAuthenticator) {
+        return new Builder(defaultAuthenticator);
+    }
+
+    /**
+     * Returns the rule that applies to the given path, or {@code null} if the path requires no
+     * authentication.
+     *
+     * @param path the request path
+     * @return the applicable rule, or {@code null}
+     */
+    public Rule ruleFor(String path) {
+        Rule exact = exactPathRules.get(path);
+        if (exact != null) return exact;
+        for (PrefixRule pr : prefixRules) {
+            if (path.startsWith(pr.prefix)) return pr.rule;
+        }
+        return globalRule;
+    }
+
+    /**
+     * Returns the configured {@code WWW-Authenticate} challenge sent with {@code 401} responses.
+     *
+     * @return the challenge string, or {@code null} if none is configured
+     */
+    public String challenge() {
+        return challenge;
+    }
+
+    /**
+     * Whether a matched rule rejects unauthenticated requests or merely annotates them.
+     */
+    public enum Mode {
+        /**
+         * Authentication is mandatory; failure yields {@code 401 Unauthorized}.
+         */
+        REQUIRED,
+        /**
+         * Authentication is best-effort; the principal is attached if present, never rejected.
+         */
+        OPTIONAL
+    }
+
+    /**
+     * An authentication rule: which authenticator to use and whether it is mandatory.
+     *
+     * @param authenticator the authenticator to apply
+     * @param mode          whether authentication is required or optional
+     */
+    public record Rule(Authenticator authenticator, Mode mode) {
+    }
+
+    /**
+     * Internal pairing of a path prefix with its rule.
+     */
+    private record PrefixRule(String prefix, Rule rule) {
+    }
+
+    /**
+     * Fluent builder for {@link AuthConfig}.
+     */
+    public static final class Builder {
+        private final Authenticator defaultAuthenticator;
+        private final Map<String, Rule> exactPathRules = new HashMap<>();
+        private final List<PrefixRule> prefixRules = new ArrayList<>();
+        private Rule globalRule;
+        private String challenge;
+
+        private Builder(Authenticator defaultAuthenticator) {
+            this.defaultAuthenticator = Objects.requireNonNull(defaultAuthenticator,
+                    "defaultAuthenticator");
+        }
+
+        /**
+         * Requires authentication for an exact path, using the default authenticator.
+         *
+         * @param path the exact path to protect
+         * @return this builder
+         */
+        public Builder protect(String path) {
+            return protect(path, defaultAuthenticator);
+        }
+
+        /**
+         * Requires authentication for an exact path, using a specific authenticator.
+         *
+         * @param path          the exact path to protect
+         * @param authenticator the authenticator to apply on that path
+         * @return this builder
+         */
+        public Builder protect(String path, Authenticator authenticator) {
+            exactPathRules.put(path, new Rule(authenticator, Mode.REQUIRED));
+            return this;
+        }
+
+        /**
+         * Requires authentication for every path starting with the given prefix, using the default
+         * authenticator.
+         *
+         * @param prefix the path prefix to protect
+         * @return this builder
+         */
+        public Builder protectPrefix(String prefix) {
+            return protectPrefix(prefix, defaultAuthenticator);
+        }
+
+        /**
+         * Requires authentication for every path starting with the given prefix, using a specific
+         * authenticator.
+         *
+         * @param prefix        the path prefix to protect
+         * @param authenticator the authenticator to apply on that prefix
+         * @return this builder
+         */
+        public Builder protectPrefix(String prefix, Authenticator authenticator) {
+            prefixRules.add(new PrefixRule(prefix, new Rule(authenticator, Mode.REQUIRED)));
+            return this;
+        }
+
+        /**
+         * Optionally authenticates an exact path: the principal is attached when credentials are
+         * valid, but the request is never rejected.
+         *
+         * @param path the exact path
+         * @return this builder
+         */
+        public Builder optional(String path) {
+            exactPathRules.put(path, new Rule(defaultAuthenticator, Mode.OPTIONAL));
+            return this;
+        }
+
+        /**
+         * Optionally authenticates a path prefix (attach-if-present, never reject).
+         *
+         * @param prefix the path prefix
+         * @return this builder
+         */
+        public Builder optionalPrefix(String prefix) {
+            prefixRules.add(new PrefixRule(prefix, new Rule(defaultAuthenticator, Mode.OPTIONAL)));
+            return this;
+        }
+
+        /**
+         * Optionally authenticates every path that has no more specific rule (attach-if-present,
+         * never reject). Handy for attaching a principal everywhere while protecting only selected
+         * routes with {@link #protect(String)}.
+         *
+         * @return this builder
+         */
+        public Builder optionalEverywhere() {
+            this.globalRule = new Rule(defaultAuthenticator, Mode.OPTIONAL);
+            return this;
+        }
+
+        /**
+         * Requires authentication for every path that has no more specific rule.
+         *
+         * @return this builder
+         */
+        public Builder requireEverywhere() {
+            this.globalRule = new Rule(defaultAuthenticator, Mode.REQUIRED);
+            return this;
+        }
+
+        /**
+         * Sets the {@code WWW-Authenticate} challenge header value sent with {@code 401}
+         * responses (for example {@code "Basic realm=\"api\""}).
+         *
+         * @param challenge the challenge value
+         * @return this builder
+         */
+        public Builder challenge(String challenge) {
+            this.challenge = challenge;
+            return this;
+        }
+
+        /**
+         * Builds the immutable configuration.
+         *
+         * @return the configured instance
+         */
+        public AuthConfig build() {
+            return new AuthConfig(this);
+        }
+    }
+}

src/main/java/dev/coph/nextusweb/server/auth/AuthGate.java

@@ -0,0 +1,71 @@
+package dev.coph.nextusweb.server.auth;
+
+import dev.coph.nextusweb.server.router.Request;
+import dev.coph.nextusweb.server.router.Response;
+
+/**
+ * Request-pipeline entry point for the authentication layer. Given a request and its path it
+ * consults the {@link AuthConfig}, runs the applicable {@link Authenticator}, and decides whether
+ * the request may proceed.
+ *
+ * <p>On success the resolved {@link Principal} is attached to the {@link Request} (visible to
+ * downstream rate limiting, middlewares and handlers via {@link Request#principal()}). The gate is
+ * stateless and may be shared across all connections.</p>
+ */
+public final class AuthGate {
+
+    /**
+     * The policy this gate enforces.
+     */
+    private final AuthConfig config;
+
+    /**
+     * Creates a gate for the given configuration.
+     *
+     * @param config the authentication policy to enforce
+     */
+    public AuthGate(AuthConfig config) {
+        this.config = config;
+    }
+
+    /**
+     * Applies the authentication policy to a request.
+     *
+     * <p>Returns {@code null} when the request may proceed — either because the path requires no
+     * authentication, because a principal was resolved (and has been attached to {@code req}), or
+     * because the path is only optionally authenticated. Returns a populated rejection response
+     * ({@code 401} when a required credential is missing/invalid, {@code 500} when the
+     * authenticator itself errors) that the caller should send instead of invoking the handler.
+     * Error details are never leaked to the client.</p>
+     *
+     * @param req  the incoming request
+     * @param path the resolved request path
+     * @return {@code null} to proceed, or the rejection response to send
+     */
+    public Response authenticate(Request req, String path) {
+        AuthConfig.Rule rule = config.ruleFor(path);
+        if (rule == null) return null;
+
+        Principal principal;
+        try {
+            principal = rule.authenticator().authenticate(req);
+        } catch (Exception e) {
+            return new Response().status(500).json("{\"error\":\"Authentication error\"}");
+        }
+
+        if (principal != null) {
+            req.principal(principal);
+            return null;
+        }
+
+        if (rule.mode() == AuthConfig.Mode.OPTIONAL) {
+            return null;
+        }
+
+        Response res = new Response().status(401).json("{\"error\":\"Unauthorized\"}");
+        if (config.challenge() != null) {
+            res.header("WWW-Authenticate", config.challenge());
+        }
+        return res;
+    }
+}

src/main/java/dev/coph/nextusweb/server/auth/Authenticator.java

@@ -0,0 +1,153 @@
+package dev.coph.nextusweb.server.auth;
+
+import dev.coph.nextusweb.server.router.Request;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.util.Base64;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * Establishes the {@link Principal} behind a request from whatever credential the application
+ * uses. The framework is deliberately scheme-agnostic: ready-made factories cover API keys,
+ * session cookies, HTTP Basic and bearer tokens, and {@code Authenticator} is a functional
+ * interface so any custom scheme (mutual-TLS client certs, HMAC-signed requests, opaque session
+ * stores, ...) can be plugged in directly.
+ *
+ * <p>An authenticator returns the resolved {@link Principal} on success, or {@code null} when the
+ * request carries no usable or no valid credential. It must not throw for the ordinary
+ * "no/invalid credential" case (return {@code null} instead); a thrown exception is treated by
+ * {@link AuthGate} as an internal error, not an authentication failure.</p>
+ */
+@FunctionalInterface
+public interface Authenticator {
+
+    /**
+     * Authenticates via an API key carried in a request header (for example {@code X-API-Key}).
+     * The validator maps a presented key to a {@link Principal}, or to {@code null} if the key is
+     * unknown/revoked. Prefer a constant-time lookup in the validator to avoid timing oracles.
+     *
+     * @param headerName the header carrying the API key
+     * @param validator  maps a presented key to a principal, or {@code null} if invalid
+     * @return an API-key authenticator
+     * @see #constantTimeEquals(String, String)
+     */
+    static Authenticator apiKey(String headerName, Function<String, Principal> validator) {
+        return request -> {
+            String key = request.header(headerName);
+            if (key == null || key.isEmpty()) return null;
+            return validator.apply(key);
+        };
+    }
+
+    /**
+     * Authenticates via a session (or other) cookie. The validator maps a presented cookie value
+     * to a {@link Principal}, or to {@code null} if the session is unknown/expired.
+     *
+     * @param cookieName the cookie carrying the credential
+     * @param validator  maps a presented cookie value to a principal, or {@code null} if invalid
+     * @return a cookie authenticator
+     */
+    static Authenticator cookie(String cookieName, Function<String, Principal> validator) {
+        return request -> {
+            String value = request.cookie(cookieName);
+            if (value == null || value.isEmpty()) return null;
+            return validator.apply(value);
+        };
+    }
+
+    /**
+     * Authenticates via HTTP Basic credentials from the {@code Authorization} header. The
+     * validator receives the decoded username and password and returns a {@link Principal} or
+     * {@code null}. Malformed headers resolve to {@code null} rather than an error.
+     *
+     * @param validator maps {@code (username, password)} to a principal, or {@code null} if invalid
+     * @return a Basic-auth authenticator
+     * @see #constantTimeEquals(String, String)
+     */
+    static Authenticator basic(BiFunction<String, String, Principal> validator) {
+        return request -> {
+            String header = request.header("Authorization");
+            if (header == null || !header.regionMatches(true, 0, "Basic ", 0, 6)) return null;
+            String encoded = header.substring(6).trim();
+            byte[] decoded;
+            try {
+                decoded = Base64.getDecoder().decode(encoded);
+            } catch (IllegalArgumentException e) {
+                return null;
+            }
+            String creds = new String(decoded, StandardCharsets.UTF_8);
+            int colon = creds.indexOf(':');
+            if (colon < 0) return null;
+            return validator.apply(creds.substring(0, colon), creds.substring(colon + 1));
+        };
+    }
+
+    /**
+     * Authenticates via a bearer token from the {@code Authorization} header. Provided for
+     * completeness; the rest of the framework never requires bearer tokens.
+     *
+     * @param validator maps a presented token to a principal, or {@code null} if invalid
+     * @return a bearer-token authenticator
+     */
+    static Authenticator bearer(Function<String, Principal> validator) {
+        return request -> {
+            String header = request.header("Authorization");
+            if (header == null || !header.regionMatches(true, 0, "Bearer ", 0, 7)) return null;
+            String token = header.substring(7).trim();
+            if (token.isEmpty()) return null;
+            return validator.apply(token);
+        };
+    }
+
+    /**
+     * Combines several authenticators, trying each in order and returning the first principal one
+     * of them produces. Lets an endpoint accept, say, either an API key or a session cookie.
+     *
+     * @param authenticators the authenticators to try, in order
+     * @return a composite authenticator
+     */
+    static Authenticator anyOf(Authenticator... authenticators) {
+        Authenticator[] copy = authenticators.clone();
+        return request -> {
+            for (Authenticator a : copy) {
+                Principal p = a.authenticate(request);
+                if (p != null) return p;
+            }
+            return null;
+        };
+    }
+
+    /**
+     * Attempts to authenticate a request.
+     *
+     * @param request the incoming request
+     * @return the authenticated principal, or {@code null} if the request is unauthenticated
+     * @throws Exception if an unexpected error occurs while validating the credential (treated as
+     *                   an internal error, not an authentication failure)
+     */
+    Principal authenticate(Request request) throws Exception;
+
+    /**
+     * Compares two secrets (API keys, tokens, passwords, ...) in length-constant time, so the
+     * time taken does not reveal how many leading characters matched. Use this inside a validator
+     * instead of {@link String#equals(Object)} whenever the comparison guards a credential, to
+     * deny attackers a timing oracle for guessing the secret byte by byte.
+     *
+     * <p>The comparison is performed on the UTF-8 bytes of the inputs via
+     * {@link MessageDigest#isEqual(byte[], byte[])}. A {@code null} on either side yields
+     * {@code false}. Note that the <em>length</em> of the presented value is not hidden; keep
+     * secrets of a fixed length if even that must not leak.</p>
+     *
+     * @param a the first value (for example the presented credential), may be {@code null}
+     * @param b the second value (for example the expected secret), may be {@code null}
+     * @return {@code true} if both are non-{@code null} and byte-for-byte equal
+     */
+    static boolean constantTimeEquals(String a, String b) {
+        if (a == null || b == null) return false;
+        return MessageDigest.isEqual(
+                a.getBytes(StandardCharsets.UTF_8),
+                b.getBytes(StandardCharsets.UTF_8));
+    }
+}

src/main/java/dev/coph/nextusweb/server/auth/Principal.java

@@ -0,0 +1,96 @@
+package dev.coph.nextusweb.server.auth;
+
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * The authenticated identity attached to a request by the {@link AuthGate auth layer}.
+ *
+ * <p>The framework deliberately does not prescribe <em>how</em> an identity is established —
+ * it may come from an API key, a session cookie, HTTP Basic credentials, a mutual-TLS client
+ * certificate or any custom scheme implemented by an {@link Authenticator}. All the rest of the
+ * pipeline needs is a stable {@link #id() identifier} (used, for example, as a rate-limit key
+ * via {@link dev.coph.nextusweb.server.ratelimit.KeyResolver#principal()}) plus optional
+ * {@link #roles() roles} for authorization and free-form {@link #claims() claims}.</p>
+ *
+ * <p>A ready-made immutable implementation is available via {@link #of(String)} and
+ * {@link #of(String, Set)}; applications may also implement this interface to carry richer
+ * domain objects.</p>
+ */
+public interface Principal {
+
+    /**
+     * Creates a simple immutable principal with no roles.
+     *
+     * @param id the principal identifier
+     * @return a principal carrying only the given id
+     */
+    static Principal of(String id) {
+        return of(id, Set.of());
+    }
+
+    /**
+     * Creates a simple immutable principal with the given id and roles.
+     *
+     * @param id    the principal identifier
+     * @param roles the roles granted to the principal
+     * @return an immutable principal
+     */
+    static Principal of(String id, Set<String> roles) {
+        Set<String> copy = Set.copyOf(roles);
+        return new Principal() {
+            @Override
+            public String id() {
+                return id;
+            }
+
+            @Override
+            public Set<String> roles() {
+                return copy;
+            }
+
+            @Override
+            public String toString() {
+                return "Principal[id=" + id + ", roles=" + copy + "]";
+            }
+        };
+    }
+
+    /**
+     * Returns the stable, unique identifier of this principal (for example a user id, an account
+     * name or an API-key id). Used wherever the identity must be reduced to a single string, such
+     * as principal-based rate limiting.
+     *
+     * @return the principal identifier; never {@code null}
+     */
+    String id();
+
+    /**
+     * Indicates whether this principal holds the given role.
+     *
+     * @param role the role to test for
+     * @return {@code true} if {@link #roles()} contains {@code role}
+     */
+    default boolean hasRole(String role) {
+        return roles().contains(role);
+    }
+
+    /**
+     * Returns the roles granted to this principal, for coarse-grained authorization checks.
+     *
+     * @return the (possibly empty) set of roles; never {@code null}
+     */
+    default Set<String> roles() {
+        return Set.of();
+    }
+
+    /**
+     * Returns arbitrary additional attributes describing this principal (for example token
+     * scopes, an email address or tenant information).
+     *
+     * @return the (possibly empty) claim map; never {@code null}
+     */
+    default Map<String, Object> claims() {
+        return Map.of();
+    }
+}

src/main/java/dev/coph/nextusweb/server/cores/CorsConfig.java

@@ -19,19 +19,33 @@ import java.util.Set;
  */
 public final class CorsConfig {
 
-    /** Explicit set of allowed origins; ignored when {@link #allowAnyOrigin} is {@code true}. */
+    /**
+     * Explicit set of allowed origins; ignored when {@link #allowAnyOrigin} is {@code true}.
+     */
     private final Set<String> allowedOrigins;
-    /** HTTP methods advertised as allowed in preflight responses. */
+    /**
+     * HTTP methods advertised as allowed in preflight responses.
+     */
     private final Set<HttpMethod> allowedMethods;
-    /** Request headers advertised as allowed in preflight responses. */
+    /**
+     * Request headers advertised as allowed in preflight responses.
+     */
     private final Set<String> allowedHeaders;
-    /** Response headers exposed to the browser via {@code Access-Control-Expose-Headers}. */
+    /**
+     * Response headers exposed to the browser via {@code Access-Control-Expose-Headers}.
+     */
     private final Set<String> exposedHeaders;
-    /** Whether credentialed (cookie/authorization) requests are permitted. */
+    /**
+     * Whether credentialed (cookie/authorization) requests are permitted.
+     */
     private final boolean allowCredentials;
-    /** How long (in seconds) a preflight response may be cached by the browser. */
+    /**
+     * How long (in seconds) a preflight response may be cached by the browser.
+     */
     private final long maxAgeSeconds;
-    /** Whether any origin is allowed (the {@code *} wildcard). */
+    /**
+     * Whether any origin is allowed (the {@code *} wildcard).
+     */
     private final boolean allowAnyOrigin;
 
     /**
@@ -157,19 +171,33 @@ public final class CorsConfig {
      * be called multiple times to accumulate values.
      */
     public static final class Builder {
-        /** Accumulated explicit origins. */
+        /**
+         * Accumulated explicit origins.
+         */
         private final Set<String> allowedOrigins = new HashSet<>();
-        /** Accumulated allowed methods. */
+        /**
+         * Accumulated allowed methods.
+         */
         private final Set<HttpMethod> allowedMethods = new HashSet<>();
-        /** Accumulated allowed request headers. */
+        /**
+         * Accumulated allowed request headers.
+         */
         private final Set<String> allowedHeaders = new HashSet<>();
-        /** Accumulated exposed response headers. */
+        /**
+         * Accumulated exposed response headers.
+         */
         private final Set<String> exposedHeaders = new HashSet<>();
-        /** Whether credentialed requests are permitted; defaults to {@code false}. */
+        /**
+         * Whether credentialed requests are permitted; defaults to {@code false}.
+         */
         private boolean allowCredentials = false;
-        /** Preflight cache lifetime in seconds; defaults to {@code 0} (disabled). */
+        /**
+         * Preflight cache lifetime in seconds; defaults to {@code 0} (disabled).
+         */
         private long maxAgeSeconds = 0;
-        /** Whether any origin is permitted; defaults to {@code false}. */
+        /**
+         * Whether any origin is permitted; defaults to {@code false}.
+         */
         private boolean allowAnyOrigin = false;
 
         /**

src/main/java/dev/coph/nextusweb/server/cores/CorsHandler.java

@@ -1,7 +1,8 @@
 package dev.coph.nextusweb.server.cores;
 
 import dev.coph.nextusweb.server.router.Response;
-import io.netty.handler.codec.http.*;
+import io.netty.handler.codec.http.HttpHeaders;
+import io.netty.handler.codec.http.HttpMethod;
 
 import java.util.stream.Collectors;
 
@@ -22,13 +23,21 @@ import java.util.stream.Collectors;
  */
 public final class CorsHandler {
 
-    /** The policy this handler enforces. */
+    /**
+     * The policy this handler enforces.
+     */
     private final CorsConfig config;
-    /** Pre-joined {@code Access-Control-Allow-Methods} value. */
+    /**
+     * Pre-joined {@code Access-Control-Allow-Methods} value.
+     */
     private final String allowedMethodsHeader;
-    /** Pre-joined {@code Access-Control-Allow-Headers} value. */
+    /**
+     * Pre-joined {@code Access-Control-Allow-Headers} value.
+     */
     private final String allowedHeadersHeader;
-    /** Pre-joined {@code Access-Control-Expose-Headers} value. */
+    /**
+     * Pre-joined {@code Access-Control-Expose-Headers} value.
+     */
     private final String exposedHeadersHeader;
 
     /**
@@ -44,6 +53,55 @@ public final class CorsHandler {
         this.exposedHeadersHeader = String.join(", ", config.exposedHeaders());
     }
 
+    /**
+     * Determines whether a request is a CORS preflight request, i.e. an {@code OPTIONS}
+     * request carrying an {@code Access-Control-Request-Method} header.
+     *
+     * @param method  the request method
+     * @param headers the request headers
+     * @return {@code true} if the request is a preflight request
+     */
+    public boolean isPreflight(HttpMethod method, HttpHeaders headers) {
+        return method.equals(HttpMethod.OPTIONS)
+                && headers.contains("Access-Control-Request-Method");
+    }
+
+    /**
+     * Builds the response to a CORS preflight request.
+     *
+     * <p>If the origin is missing or disallowed the response is a {@code 403 Forbidden};
+     * otherwise it is a {@code 204 No Content} carrying the allowed methods and headers, the
+     * requested headers echoed back when no explicit allow-list is configured, and the
+     * {@code Access-Control-Max-Age} cache hint when configured.</p>
+     *
+     * @param origin         the request's {@code Origin} header, may be {@code null}
+     * @param requestHeaders the request's headers (used to read
+     *                       {@code Access-Control-Request-Headers})
+     * @return the fully populated preflight response
+     */
+    public Response handlePreflight(String origin, HttpHeaders requestHeaders) {
+        Response res = new Response().status(204);
+
+        if (!config.isOriginAllowed(origin)) {
+            return res.status(403);
+        }
+
+        applyHeaders(origin, res);
+        res.header("Access-Control-Allow-Methods", allowedMethodsHeader);
+
+        String requestedHeaders = requestHeaders.get("Access-Control-Request-Headers");
+        if (!allowedHeadersHeader.isEmpty()) {
+            res.header("Access-Control-Allow-Headers", allowedHeadersHeader);
+        } else if (requestedHeaders != null) {
+            res.header("Access-Control-Allow-Headers", requestedHeaders);
+        }
+
+        if (config.maxAgeSeconds() > 0) {
+            res.header("Access-Control-Max-Age", String.valueOf(config.maxAgeSeconds()));
+        }
+
+        return res;
+    }
 
     /**
      * Adds the {@code Access-Control-Allow-Origin} (and related) headers to a response, if and
@@ -77,54 +135,4 @@ public final class CorsHandler {
             res.header("Access-Control-Expose-Headers", exposedHeadersHeader);
         }
     }
-
-    /**
-     * Determines whether a request is a CORS preflight request, i.e. an {@code OPTIONS}
-     * request carrying an {@code Access-Control-Request-Method} header.
-     *
-     * @param method  the request method
-     * @param headers the request headers
-     * @return {@code true} if the request is a preflight request
-     */
-    public boolean isPreflight(HttpMethod method, HttpHeaders headers) {
-        return method.equals(HttpMethod.OPTIONS)
-                && headers.contains("Access-Control-Request-Method");
-    }
-
-    /**
-     * Builds the response to a CORS preflight request.
-     *
-     * <p>If the origin is missing or disallowed the response is a {@code 403 Forbidden};
-     * otherwise it is a {@code 204 No Content} carrying the allowed methods and headers, the
-     * requested headers echoed back when no explicit allow-list is configured, and the
-     * {@code Access-Control-Max-Age} cache hint when configured.</p>
-     *
-     * @param origin         the request's {@code Origin} header, may be {@code null}
-     * @param requestHeaders the request's headers (used to read
-     *                       {@code Access-Control-Request-Headers})
-     * @return the fully populated preflight response
-     */
-    public Response handlePreflight(String origin, HttpHeaders requestHeaders) {
-        Response res = new Response().status(204);
-
-        if (origin == null || !config.isOriginAllowed(origin)) {
-            return res.status(403);
-        }
-
-        applyHeaders(origin, res);
-        res.header("Access-Control-Allow-Methods", allowedMethodsHeader);
-
-        String requestedHeaders = requestHeaders.get("Access-Control-Request-Headers");
-        if (!allowedHeadersHeader.isEmpty()) {
-            res.header("Access-Control-Allow-Headers", allowedHeadersHeader);
-        } else if (requestedHeaders != null) {
-            res.header("Access-Control-Allow-Headers", requestedHeaders);
-        }
-
-        if (config.maxAgeSeconds() > 0) {
-            res.header("Access-Control-Max-Age", String.valueOf(config.maxAgeSeconds()));
-        }
-
-        return res;
-    }
 }

src/main/java/dev/coph/nextusweb/server/json/JsonMapper.java

@@ -26,5 +26,6 @@ public final class JsonMapper {
     /**
      * Private constructor preventing instantiation of this static holder class.
      */
-    private JsonMapper() {}
+    private JsonMapper() {
+    }
 }

src/main/java/dev/coph/nextusweb/server/net/ClientIp.java

@@ -0,0 +1,52 @@
+package dev.coph.nextusweb.server.net;
+
+/**
+ * Resolves the effective client IP of a request from the transport-level peer address and an
+ * optional {@code X-Forwarded-For} header, according to a {@link TrustedProxies} policy.
+ *
+ * <p>This is the single place where forwarded headers are interpreted, so the spoofing-resistant
+ * logic lives in one spot and is reused by rate limiting, the auth layer and logging.</p>
+ */
+public final class ClientIp {
+
+    /**
+     * The de-facto standard header proxies use to record the originating client chain.
+     */
+    public static final String FORWARDED_FOR_HEADER = "X-Forwarded-For";
+
+    private ClientIp() {
+    }
+
+    /**
+     * Resolves the client IP.
+     *
+     * <p>If the immediate peer is not a trusted proxy (or no forwarded header is present), the
+     * transport-level {@code socketIp} is returned unchanged — a directly connected client cannot
+     * influence its own apparent address. Otherwise the comma-separated forwarded chain is walked
+     * from right to left and the first address that is <em>not</em> itself a trusted proxy is
+     * returned: that is the closest hop the trusted infrastructure actually observed and which the
+     * real client cannot forge. If every listed hop is trusted, the left-most entry is used.</p>
+     *
+     * @param socketIp           the transport-level peer IP (never {@code null} in practice)
+     * @param forwardedForHeader the {@code X-Forwarded-For} header value, may be {@code null}
+     * @param trusted            the trusted-proxy policy
+     * @return the resolved client IP
+     */
+    public static String resolve(String socketIp, String forwardedForHeader, TrustedProxies trusted) {
+        if (forwardedForHeader == null || forwardedForHeader.isBlank() || !trusted.isTrusted(socketIp)) {
+            return socketIp;
+        }
+
+        String[] hops = forwardedForHeader.split(",");
+        for (int i = hops.length - 1; i >= 0; i--) {
+            String hop = hops[i].trim();
+            if (hop.isEmpty()) continue;
+            if (!trusted.isTrusted(hop)) {
+                return hop;
+            }
+        }
+
+        String first = hops[0].trim();
+        return first.isEmpty() ? socketIp : first;
+    }
+}

src/main/java/dev/coph/nextusweb/server/net/TrustedProxies.java

@@ -0,0 +1,168 @@
+package dev.coph.nextusweb.server.net;
+
+import io.netty.util.NetUtil;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Describes which transport-level peers are trusted reverse proxies, and is the basis for safely
+ * honouring {@code X-Forwarded-For} (and similar) headers.
+ *
+ * <p>Forwarded-for headers are client-supplied and therefore trivially spoofable: a client that
+ * talks to the server directly can claim any IP it likes. Trusting them unconditionally lets an
+ * attacker forge a fresh client IP on every request, which defeats IP-based rate limiting and
+ * pollutes logs. To avoid that, {@link ClientIp} only consults the forwarded header when the
+ * immediate peer is a trusted proxy, and then walks the header from right to left skipping
+ * further trusted hops — so the value returned is the address of the first <em>untrusted</em>
+ * hop, which cannot be spoofed by the real client.</p>
+ *
+ * <p>Both IPv4 and IPv6 CIDR ranges are supported. Instances are immutable and thread-safe.</p>
+ */
+public final class TrustedProxies {
+
+    /**
+     * Shared instance that trusts no peer; forwarded headers are always ignored.
+     */
+    private static final TrustedProxies NONE = new TrustedProxies(List.of(), false);
+    /**
+     * Shared instance that trusts every peer; forwarded headers are always honoured.
+     */
+    private static final TrustedProxies ALL = new TrustedProxies(List.of(), true);
+
+    /**
+     * Parsed CIDR ranges of trusted proxies.
+     */
+    private final List<Cidr> cidrs;
+    /**
+     * When {@code true}, every peer is trusted regardless of {@link #cidrs}.
+     */
+    private final boolean trustAll;
+
+    private TrustedProxies(List<Cidr> cidrs, boolean trustAll) {
+        this.cidrs = cidrs;
+        this.trustAll = trustAll;
+    }
+
+    /**
+     * Returns a policy that trusts no peer. Forwarded headers are ignored and the transport-level
+     * peer address is always used. This is the safe default for servers exposed directly to
+     * clients.
+     *
+     * @return a never-trust policy
+     */
+    public static TrustedProxies none() {
+        return NONE;
+    }
+
+    /**
+     * Returns a policy that trusts every peer and therefore always honours the forwarded header.
+     *
+     * <p>Only use this when the server can <em>never</em> be reached except through a trusted
+     * proxy that overwrites the forwarded header (for example a private network behind a load
+     * balancer), otherwise it reintroduces the spoofing problem.</p>
+     *
+     * @return a trust-all policy
+     */
+    public static TrustedProxies all() {
+        return ALL;
+    }
+
+    /**
+     * Returns a policy that trusts peers whose address falls inside any of the given CIDR ranges.
+     * A bare address (without {@code /prefix}) is treated as a single host ({@code /32} for IPv4,
+     * {@code /128} for IPv6).
+     *
+     * @param cidrs the trusted ranges, e.g. {@code "10.0.0.0/8"}, {@code "127.0.0.1"},
+     *              {@code "::1"}, {@code "fd00::/8"}
+     * @return a policy trusting the given ranges
+     * @throws IllegalArgumentException if a range cannot be parsed
+     */
+    public static TrustedProxies of(String... cidrs) {
+        List<Cidr> parsed = new ArrayList<>(cidrs.length);
+        for (String c : cidrs) parsed.add(Cidr.parse(c));
+        return new TrustedProxies(List.copyOf(parsed), false);
+    }
+
+    /**
+     * Tests whether the given IP address belongs to a trusted proxy.
+     *
+     * @param ip the literal IP address to test (no DNS resolution is performed)
+     * @return {@code true} if the address is trusted
+     */
+    public boolean isTrusted(String ip) {
+        if (trustAll) return true;
+        if (ip == null || cidrs.isEmpty()) return false;
+        byte[] addr = NetUtil.createByteArrayFromIpAddressString(ip);
+        if (addr == null) return false;
+        for (Cidr c : cidrs) {
+            if (c.contains(addr)) return true;
+        }
+        return false;
+    }
+
+    /**
+     * An IP range expressed as a base address and a prefix length, matching either IPv4 or IPv6.
+     *
+     * @param base       the network base address bytes (4 for IPv4, 16 for IPv6)
+     * @param prefixBits the number of leading bits that must match
+     */
+    private record Cidr(byte[] base, int prefixBits) {
+
+        static Cidr parse(String spec) {
+            if (spec == null || spec.isBlank()) {
+                throw new IllegalArgumentException("Empty CIDR specification");
+            }
+            String trimmed = spec.trim();
+            int slash = trimmed.indexOf('/');
+            String ipPart = slash >= 0 ? trimmed.substring(0, slash) : trimmed;
+            byte[] base = NetUtil.createByteArrayFromIpAddressString(ipPart);
+            if (base == null) {
+                throw new IllegalArgumentException("Not a valid IP address: " + ipPart);
+            }
+            int maxBits = base.length * 8;
+            int prefixBits = maxBits;
+            if (slash >= 0) {
+                try {
+                    prefixBits = Integer.parseInt(trimmed.substring(slash + 1).trim());
+                } catch (NumberFormatException e) {
+                    throw new IllegalArgumentException("Invalid CIDR prefix in: " + spec, e);
+                }
+                if (prefixBits < 0 || prefixBits > maxBits) {
+                    throw new IllegalArgumentException("CIDR prefix out of range in: " + spec);
+                }
+            }
+            return new Cidr(base, prefixBits);
+        }
+
+        boolean contains(byte[] addr) {
+            if (addr.length != base.length) return false;
+            int fullBytes = prefixBits / 8;
+            for (int i = 0; i < fullBytes; i++) {
+                if (addr[i] != base[i]) return false;
+            }
+            int remainingBits = prefixBits % 8;
+            if (remainingBits != 0) {
+                int mask = 0xFF << (8 - remainingBits) & 0xFF;
+                return (addr[fullBytes] & mask) == (base[fullBytes] & mask);
+            }
+            return true;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            return o instanceof Cidr(byte[] base1, int bits) && prefixBits == bits && Arrays.equals(base, base1);
+        }
+
+        @Override
+        public int hashCode() {
+            return 31 * Arrays.hashCode(base) + prefixBits;
+        }
+
+        @Override
+        public String toString() {
+            return "Cidr[base=" + Arrays.toString(base) + ", prefixBits=" + prefixBits + "]";
+        }
+    }
+}

src/main/java/dev/coph/nextusweb/server/ratelimit/FixedWindowLimiter.java

@@ -17,11 +17,17 @@ import java.util.concurrent.atomic.AtomicLong;
  */
 public final class FixedWindowLimiter implements RateLimiter {
 
-    /** Maximum number of requests permitted per window. */
+    /**
+     * Maximum number of requests permitted per window.
+     */
     private final long limit;
-    /** Window length in nanoseconds. */
+    /**
+     * Window length in nanoseconds.
+     */
     private final long windowNanos;
-    /** Per-key windows, created on demand. */
+    /**
+     * Per-key windows, created on demand.
+     */
     private final ConcurrentHashMap<String, Window> windows = new ConcurrentHashMap<>();
 
     /**
@@ -51,6 +57,7 @@ public final class FixedWindowLimiter implements RateLimiter {
      *
      * @param olderThanNanos maximum age in nanoseconds before a window is removed
      */
+    @Override
     public void cleanup(long olderThanNanos) {
         long now = System.nanoTime();
         windows.entrySet().removeIf(e -> now - e.getValue().windowStart.get() > olderThanNanos);
@@ -61,9 +68,13 @@ public final class FixedWindowLimiter implements RateLimiter {
      * within it.
      */
     private static final class Window {
-        /** Start timestamp of the current window, in nanoseconds. */
+        /**
+         * Start timestamp of the current window, in nanoseconds.
+         */
         final AtomicLong windowStart;
-        /** Number of requests counted in the current window. */
+        /**
+         * Number of requests counted in the current window.
+         */
         final AtomicLong count;
 
         /**
@@ -80,23 +91,30 @@ public final class FixedWindowLimiter implements RateLimiter {
          * Rolls the window over if it has expired, then counts this request and decides whether
          * it stays within the limit.
          *
+         * <p>The roll-over (resetting {@code windowStart} and {@code count}) and the subsequent
+         * increment must happen atomically together: the previous lock-free version reset the
+         * count in one thread while another was incrementing it, so increments were silently lost
+         * and the window admitted more than {@code limit} requests around a boundary. Guarding the
+         * whole operation with the window's monitor keeps the count exact; contention is per key
+         * only, so throughput is unaffected in practice.</p>
+         *
          * @param now         the current time in nanoseconds
          * @param limit       the per-window request limit
          * @param windowNanos the window length in nanoseconds
          * @return an allow result with the remaining quota, or a deny result with the time until
          * the window resets
          */
-        Result tryAcquire(long now, long limit, long windowNanos) {
+        synchronized Result tryAcquire(long now, long limit, long windowNanos) {
             long start = windowStart.get();
             if (now - start >= windowNanos) {
-                if (windowStart.compareAndSet(start, now)) {
+                windowStart.set(now);
                 count.set(0);
-                }
+                start = now;
             }
 
             long current = count.incrementAndGet();
             if (current > limit) {
-                long retryMs = (windowNanos - (now - windowStart.get())) / 1_000_000L;
+                long retryMs = (windowNanos - (now - start)) / 1_000_000L;
                 return Result.deny(limit, Math.max(1, retryMs));
             }
             return Result.allow(limit - current, limit);

src/main/java/dev/coph/nextusweb/server/ratelimit/KeyResolver.java

@@ -1,60 +1,88 @@
 package dev.coph.nextusweb.server.ratelimit;
 
-import io.netty.handler.codec.http.HttpRequest;
+import dev.coph.nextusweb.server.auth.Principal;
+import dev.coph.nextusweb.server.router.Request;
 
 /**
  * Strategy for deriving the logical key under which a request is rate limited. The key
- * determines which bucket a request counts against — for example one bucket per client IP, or
- * one per authenticated user.
+ * determines which bucket a request counts against — for example one bucket per client IP, one
+ * per API key, one per session cookie, or one per authenticated user.
  *
- * <p>Two ready-made resolvers are provided as factory methods: {@link #clientIp()} and
- * {@link #userOrIp()}.</p>
+ * <p>Resolvers receive the framework {@link Request} together with the already-resolved client
+ * IP (the pipeline computes it once, honouring the configured trusted proxies — see
+ * {@link dev.coph.nextusweb.server.net.ClientIp}). They are therefore <strong>not</strong> tied
+ * to bearer tokens: pick whichever request facet identifies the caller for your API.</p>
+ *
+ * <p>Built-in resolvers: {@link #clientIp()}, {@link #header(String)}, {@link #cookie(String)}
+ * and {@link #principal()}. The header/cookie/principal resolvers fall back to the client IP when
+ * their facet is absent, so an anonymous caller is still bucketed rather than sharing one global
+ * bucket. Each key is additionally namespaced by the rule, so different rules never collide.</p>
  */
 @FunctionalInterface
 public interface KeyResolver {
 
     /**
-     * Resolves the rate-limit key for a request.
-     *
-     * @param req           the incoming HTTP request, used to inspect headers
-     * @param remoteAddress the transport-level remote address, used as a fallback
-     * @return the key the request should be counted against
-     */
-    String resolve(HttpRequest req, String remoteAddress);
-
-    /**
-     * Returns a resolver that keys on the client IP address. It prefers the first entry of the
-     * {@code X-Forwarded-For} header (so it works behind a reverse proxy) and falls back to the
-     * transport-level remote address when that header is absent.
+     * Returns a resolver that keys purely on the resolved client IP. This is the spoofing-safe
+     * replacement for the old header-trusting behaviour: the IP has already been derived through
+     * the trusted-proxy policy, so a directly connected client cannot forge it.
      *
      * @return a client-IP key resolver
      */
     static KeyResolver clientIp() {
-        return (req, remote) -> {
-            String forwarded = req.headers().get("X-Forwarded-For");
-            if (forwarded != null && !forwarded.isEmpty()) {
-                int comma = forwarded.indexOf(',');
-                return comma > 0 ? forwarded.substring(0, comma).trim() : forwarded.trim();
+        return (request, clientIp) -> clientIp;
     }
-            return remote;
+
+    /**
+     * Returns a resolver that keys on the value of a request header (for example an API key in
+     * {@code X-API-Key}), falling back to the client IP when the header is absent.
+     *
+     * @param headerName the header to key on
+     * @return a header-value key resolver
+     */
+    static KeyResolver header(String headerName) {
+        return (request, clientIp) -> {
+            String value = request.header(headerName);
+            return (value != null && !value.isEmpty()) ? "h:" + value : "ip:" + clientIp;
         };
     }
 
     /**
-     * Returns a resolver that keys on the authenticated user when possible, falling back to the
-     * client IP otherwise. A {@code Bearer} token from the {@code Authorization} header yields a
-     * {@code "u:<token>"} key; otherwise the {@code "ip:<address>"} key from {@link #clientIp()}
-     * is used.
+     * Returns a resolver that keys on the value of a request cookie (for example a session id),
+     * falling back to the client IP when the cookie is absent.
      *
-     * @return a user-or-IP key resolver
+     * @param cookieName the cookie to key on
+     * @return a cookie-value key resolver
      */
-    static KeyResolver userOrIp() {
-        return (req, remote) -> {
-            String auth = req.headers().get("Authorization");
-            if (auth != null && auth.startsWith("Bearer ")) {
-                return "u:" + auth.substring(7);
-            }
-            return "ip:" + clientIp().resolve(req, remote);
+    static KeyResolver cookie(String cookieName) {
+        return (request, clientIp) -> {
+            String value = request.cookie(cookieName);
+            return (value != null && !value.isEmpty()) ? "c:" + value : "ip:" + clientIp;
         };
     }
+
+    /**
+     * Returns a resolver that keys on the authenticated {@link Principal} attached to the request,
+     * falling back to the client IP for unauthenticated requests.
+     *
+     * <p>For this to key on the principal, the {@link dev.coph.nextusweb.server.auth.AuthGate auth
+     * layer} must have run before rate limiting (configure it to authenticate the relevant paths).
+     * When no principal is present the resolver degrades gracefully to per-IP limiting.</p>
+     *
+     * @return a principal-or-IP key resolver
+     */
+    static KeyResolver principal() {
+        return (request, clientIp) -> {
+            Principal p = request.principal();
+            return p != null ? "p:" + p.id() : "ip:" + clientIp;
+        };
+    }
+
+    /**
+     * Resolves the rate-limit key for a request.
+     *
+     * @param request  the incoming request (headers, cookies, attached principal, ...)
+     * @param clientIp the resolved client IP, honouring trusted proxies
+     * @return the key the request should be counted against; never {@code null}
+     */
+    String resolve(Request request, String clientIp);
 }

src/main/java/dev/coph/nextusweb/server/ratelimit/LeakyBucketLimiter.java

@@ -1,7 +1,7 @@
 package dev.coph.nextusweb.server.ratelimit;
 
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * A {@link RateLimiter} implementing the <em>leaky bucket</em> algorithm.
@@ -12,16 +12,24 @@ import java.util.concurrent.atomic.AtomicLong;
  * enough has leaked away. Compared to the token bucket this smooths bursts into a steady
  * outflow rather than allowing them through up front.</p>
  *
- * <p>State is held in {@link AtomicLong}s and updated with a lock-free compare-and-set loop, so
- * the limiter is safe for concurrent use.</p>
+ * <p>Each bucket's water level and last-leak timestamp are held together in a single immutable
+ * {@link LeakyBucket.State} behind one {@link AtomicReference} and advanced with a lock-free
+ * compare-and-set loop, so the level and the timestamp it was leaked to are always published
+ * together and the limiter is safe for concurrent use.</p>
  */
 public final class LeakyBucketLimiter implements RateLimiter {
 
-    /** Maximum water level (number of queued units) the bucket tolerates. */
+    /**
+     * Maximum water level (number of queued units) the bucket tolerates.
+     */
     private final long capacity;
-    /** Nanoseconds it takes for exactly one unit to leak out. */
+    /**
+     * Nanoseconds it takes for exactly one unit to leak out.
+     */
     private final long leakIntervalNanos;
-    /** Per-key buckets, created on demand. */
+    /**
+     * Per-key buckets, created on demand.
+     */
     private final ConcurrentHashMap<String, LeakyBucket> buckets = new ConcurrentHashMap<>();
 
     /**
@@ -51,33 +59,42 @@ public final class LeakyBucketLimiter implements RateLimiter {
      *
      * @param olderThanNanos maximum idle age in nanoseconds before a bucket is removed
      */
+    @Override
     public void cleanup(long olderThanNanos) {
         long now = System.nanoTime();
-        buckets.entrySet().removeIf(e -> now - e.getValue().lastLeakNanos.get() > olderThanNanos);
+        buckets.entrySet().removeIf(e -> now - e.getValue().lastLeak() > olderThanNanos);
     }
 
     /**
      * A single client's leaky bucket, tracking the current water level and the timestamp up to
-     * which leakage has been accounted for.
+     * which leakage has been accounted for as one atomic unit.
+     *
+     * @param state Holds the current {@code (waterLevel, lastLeakNanos)} pair as one atomic unit.
      */
-    private static final class LeakyBucket {
-        /** Current water level (number of units in the bucket). */
-        final AtomicLong waterLevel;
-        /** Timestamp, in nanoseconds, up to which leakage has been applied. */
-        final AtomicLong lastLeakNanos;
-
+    private record LeakyBucket(AtomicReference<State> state) {
         /**
          * Creates an empty bucket.
          *
-         * @param now the creation timestamp in nanoseconds
+         * @param nowNanos the creation timestamp in nanoseconds
          */
-        LeakyBucket(long now) {
-            this.waterLevel = new AtomicLong(0);
-            this.lastLeakNanos = new AtomicLong(now);
+        private LeakyBucket(long nowNanos) {
+            this(new AtomicReference<>(new State(0, nowNanos)));
         }
 
         /**
-         * Applies elapsed leakage and, if there is room, adds one unit of water.
+         * Returns the timestamp leakage was last accounted to, used by {@link #cleanup(long)}.
+         *
+         * @return the last-leak timestamp in nanoseconds
+         */
+        long lastLeak() {
+            return state.get().lastLeakNanos();
+        }
+
+        /**
+         * Applies elapsed leakage and, if there is room, adds one unit of water. The new level and
+         * the timestamp it was leaked to are swapped in together, so the previous race where the
+         * level advanced but the timestamp update was lost (drifting the leak accounting) can no
+         * longer occur.
          *
          * @param now               the current time in nanoseconds
          * @param capacity          the bucket capacity
@@ -87,24 +104,33 @@ public final class LeakyBucketLimiter implements RateLimiter {
          */
         Result tryAcquire(long now, long capacity, long leakIntervalNanos) {
             while (true) {
-                long lastLeak = lastLeakNanos.get();
-                long current = waterLevel.get();
+                State current = state.get();
 
-                long leaked = (now - lastLeak) / leakIntervalNanos;
-                long newLevel = Math.max(0, current - leaked);
+                long leaked = (now - current.lastLeakNanos()) / leakIntervalNanos;
+                long newLevel = Math.max(0, current.waterLevel() - leaked);
 
                 if (newLevel >= capacity) {
                     long retryMs = leakIntervalNanos / 1_000_000L;
                     return Result.deny(capacity, retryMs);
                 }
 
-                long newLastLeak = leaked > 0 ? lastLeak + leaked * leakIntervalNanos : lastLeak;
+                long newLastLeak = leaked > 0
+                        ? current.lastLeakNanos() + leaked * leakIntervalNanos
+                        : current.lastLeakNanos();
 
-                if (waterLevel.compareAndSet(current, newLevel + 1)) {
-                    lastLeakNanos.compareAndSet(lastLeak, newLastLeak);
+                if (state.compareAndSet(current, new State(newLevel + 1, newLastLeak))) {
                     return Result.allow(capacity - newLevel - 1, capacity);
                 }
             }
         }
+
+        /**
+         * Immutable snapshot of a bucket's mutable state.
+         *
+         * @param waterLevel    current water level (number of units in the bucket)
+         * @param lastLeakNanos timestamp leakage has been applied up to, in nanoseconds
+         */
+        private record State(long waterLevel, long lastLeakNanos) {
+        }
     }
 }

src/main/java/dev/coph/nextusweb/server/ratelimit/RateLimitConfig.java

@@ -1,9 +1,6 @@
 package dev.coph.nextusweb.server.ratelimit;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 /**
  * Immutable mapping from request paths to the {@link Rule rate-limit rules} that apply to them.
@@ -21,12 +18,22 @@ import java.util.Map;
  */
 public final class RateLimitConfig {
 
-    /** Rule applied to every request, or {@code null} if no global rule is configured. */
+    /**
+     * Rule applied to every request, or {@code null} if no global rule is configured.
+     */
     private final Rule globalRule;
-    /** Rules matched by exact path equality, keyed by path. */
+    /**
+     * Rules matched by exact path equality, keyed by path.
+     */
     private final Map<String, Rule> exactPathRules;
-    /** Prefix rules, pre-sorted longest-prefix-first so the most specific match wins. */
+    /**
+     * Prefix rules, pre-sorted longest-prefix-first so the most specific match wins.
+     */
     private final List<PrefixRule> prefixRules;
+    /**
+     * Every distinct limiter referenced by any rule, by identity; used for periodic cleanup.
+     */
+    private final Set<RateLimiter> allLimiters;
 
     /**
      * Builds an immutable configuration from a {@link Builder}, copying the exact-path rules
@@ -40,6 +47,12 @@ public final class RateLimitConfig {
         this.prefixRules = b.prefixRules.stream()
                 .sorted((a, c) -> Integer.compare(c.prefix.length(), a.prefix.length()))
                 .toList();
+
+        Set<RateLimiter> limiters = Collections.newSetFromMap(new IdentityHashMap<>());
+        if (globalRule != null) limiters.add(globalRule.limiter());
+        for (Rule r : exactPathRules.values()) limiters.add(r.limiter());
+        for (PrefixRule pr : prefixRules) limiters.add(pr.rule.limiter());
+        this.allLimiters = Collections.unmodifiableSet(limiters);
     }
 
     /**
@@ -79,6 +92,16 @@ public final class RateLimitConfig {
         return rules;
     }
 
+    /**
+     * Returns every distinct limiter referenced by this configuration, for periodic state
+     * eviction by {@link RateLimitGate}.
+     *
+     * @return the immutable set of distinct limiters (de-duplicated by identity)
+     */
+    public Set<RateLimiter> allLimiters() {
+        return allLimiters;
+    }
+
     /**
      * A single rate-limit rule: a limiter, the key resolver feeding it, and a name used to
      * namespace keys and aid diagnostics.
@@ -103,11 +126,17 @@ public final class RateLimitConfig {
      * Fluent builder for {@link RateLimitConfig}.
      */
     public static final class Builder {
-        /** Accumulated exact-path rules, keyed by path. */
+        /**
+         * Accumulated exact-path rules, keyed by path.
+         */
         private final Map<String, Rule> exactPathRules = new HashMap<>();
-        /** Accumulated prefix rules. */
+        /**
+         * Accumulated prefix rules.
+         */
         private final List<PrefixRule> prefixRules = new ArrayList<>();
-        /** The global rule, if configured. */
+        /**
+         * The global rule, if configured.
+         */
         private Rule globalRule;
 
         /**

src/main/java/dev/coph/nextusweb/server/ratelimit/RateLimitGate.java

@@ -1,7 +1,7 @@
 package dev.coph.nextusweb.server.ratelimit;
 
+import dev.coph.nextusweb.server.router.Request;
 import dev.coph.nextusweb.server.router.Response;
-import io.netty.handler.codec.http.HttpRequest;
 
 import java.util.List;
 import java.util.concurrent.Executors;
@@ -22,19 +22,46 @@ import java.util.concurrent.TimeUnit;
  */
 public final class RateLimitGate {
 
-    /** The rule set this gate enforces. */
+    /**
+     * Default idle age after which per-key limiter state is eligible for eviction.
+     */
+    private static final long DEFAULT_STALE_AFTER_NANOS = 10L * 60 * 1_000_000_000L;
+
+    /**
+     * The rule set this gate enforces.
+     */
     private final RateLimitConfig config;
-    /** Single-threaded scheduler driving periodic cleanup of stale buckets. */
+    /**
+     * Idle age (nanoseconds) after which a limiter's per-key state may be evicted.
+     */
+    private final long staleAfterNanos;
+    /**
+     * Single-threaded scheduler driving periodic cleanup of stale buckets.
+     */
     private final ScheduledExecutorService cleanup;
 
     /**
      * Creates a gate for the given configuration and starts a background cleanup task that runs
-     * every five minutes on a daemon thread.
+     * every five minutes on a daemon thread, evicting per-key state idle for more than ten
+     * minutes.
      *
      * @param config the rate-limit rules to enforce
      */
     public RateLimitGate(RateLimitConfig config) {
+        this(config, DEFAULT_STALE_AFTER_NANOS);
+    }
+
+    /**
+     * Creates a gate with an explicit idle age before per-key limiter state is evicted.
+     *
+     * @param config          the rate-limit rules to enforce
+     * @param staleAfterNanos idle age in nanoseconds after which per-key state is evicted; must
+     *                        be positive
+     */
+    public RateLimitGate(RateLimitConfig config, long staleAfterNanos) {
+        if (staleAfterNanos <= 0) throw new IllegalArgumentException("staleAfterNanos must be > 0");
         this.config = config;
+        this.staleAfterNanos = staleAfterNanos;
         this.cleanup = Executors.newSingleThreadScheduledExecutor(r -> {
             Thread t = new Thread(r, "ratelimit-cleanup");
             t.setDaemon(true);
@@ -43,38 +70,18 @@ public final class RateLimitGate {
         cleanup.scheduleAtFixedRate(this::doCleanup, 5, 5, TimeUnit.MINUTES);
     }
 
-
     /**
-     * Evaluates all rules applicable to the given path and decides whether the request may
-     * proceed.
-     *
-     * <p>Each rule's key is namespaced with the rule name to keep buckets from different rules
-     * independent. The first denial short-circuits and is returned immediately; if every rule
-     * allows the request, the result with the least remaining quota is returned.</p>
-     *
-     * @param req           the incoming request, used by key resolvers
-     * @param path          the request path used to select rules
-     * @param remoteAddress the client's remote address, used as a key-resolver fallback
-     * @return the limiting result, or {@code null} if no rule applies to the path
+     * Periodic cleanup hook invoked by the background scheduler. Asks every configured limiter to
+     * evict per-key state idle for longer than {@link #staleAfterNanos}. A failure cleaning one
+     * limiter must not abort the others or kill the scheduler, so each call is guarded.
      */
-    public RateLimiter.Result check(HttpRequest req, String path, String remoteAddress) {
-        List<RateLimitConfig.Rule> rules = config.rulesFor(path);
-        if (rules.isEmpty()) return null;
-
-        long now = System.nanoTime();
-        RateLimiter.Result strictest = null;
-
-        for (var rule : rules) {
-            String key = rule.name() + ":" + rule.keyResolver().resolve(req, remoteAddress);
-            RateLimiter.Result result = rule.limiter().tryAcquire(key, now);
-
-            if (!result.allowed()) return result;
-
-            if (strictest == null || result.remaining() < strictest.remaining()) {
-                strictest = result;
+    private void doCleanup() {
+        for (RateLimiter limiter : config.allLimiters()) {
+            try {
+                limiter.cleanup(staleAfterNanos);
+            } catch (RuntimeException ignored) {
             }
         }
-        return strictest;
     }
 
     /**
@@ -97,15 +104,43 @@ public final class RateLimitGate {
     }
 
     /**
-     * Periodic cleanup hook invoked by the background scheduler to evict limiter state that has
-     * not been touched recently (older than roughly ten minutes).
+     * Evaluates all rules applicable to the given path and decides whether the request may
+     * proceed.
+     *
+     * <p>Each rule's key is namespaced with the rule name to keep buckets from different rules
+     * independent. The first denial short-circuits and is returned immediately; if every rule
+     * allows the request, the result with the least remaining quota is returned.</p>
+     *
+     * @param req      the incoming request, used by key resolvers
+     * @param path     the request path used to select rules
+     * @param clientIp the resolved client IP (honouring trusted proxies), used as a key-resolver
+     *                 fallback
+     * @return the limiting result, or {@code null} if no rule applies to the path
      */
-    private void doCleanup() {
-        long threshold = 10L * 60 * 1_000_000_000L;
+    public RateLimiter.Result check(Request req, String path, String clientIp) {
+        List<RateLimitConfig.Rule> rules = config.rulesFor(path);
+        if (rules.isEmpty()) return null;
+
+        long now = System.nanoTime();
+        RateLimiter.Result strictest = null;
+
+        for (var rule : rules) {
+            String key = rule.name() + ":" + rule.keyResolver().resolve(req, clientIp);
+            RateLimiter.Result result = rule.limiter().tryAcquire(key, now);
+
+            if (!result.allowed()) return result;
+
+            if (strictest == null || result.remaining() < strictest.remaining()) {
+                strictest = result;
+            }
+        }
+        return strictest;
     }
 
     /**
      * Stops the background cleanup scheduler. Should be called when the server shuts down.
      */
-    public void shutdown() { cleanup.shutdown(); }
+    public void shutdown() {
+        cleanup.shutdown();
+    }
 }

src/main/java/dev/coph/nextusweb/server/ratelimit/RateLimiter.java

@@ -8,6 +8,10 @@ package dev.coph.nextusweb.server.ratelimit;
  * {@link LeakyBucketLimiter}, {@link FixedWindowLimiter} and {@link SlidingWindowLimiter}.
  * Implementations are expected to be thread-safe, since the same limiter is shared across all
  * request-handling threads.</p>
+ *
+ * <p>The interface remains effectively functional ({@link #tryAcquire} is its single abstract
+ * method), so simple stateless limiters can still be written as a lambda; stateful limiters that
+ * keep one entry per key should additionally override {@link #cleanup(long)}.</p>
  */
 public interface RateLimiter {
 
@@ -21,6 +25,24 @@ public interface RateLimiter {
      */
     Result tryAcquire(String key, long nowNanos);
 
+    /**
+     * Evicts per-key state that has not been accessed within the given age, bounding the memory
+     * a limiter consumes when it has seen many distinct keys.
+     *
+     * <p>Implementations keep one entry per key seen ({@code clientIp}, API key, ...). Without
+     * periodic eviction those maps grow without bound, which is both a memory leak and a denial
+     * of service vector (an attacker that varies the key on every request can exhaust the heap).
+     * {@link RateLimitGate} calls this periodically for every configured limiter.</p>
+     *
+     * <p>The default implementation does nothing, which is correct for stateless limiters; any
+     * limiter that retains per-key state <strong>must</strong> override it to evict stale
+     * entries.</p>
+     *
+     * @param olderThanNanos maximum idle age in nanoseconds before an entry is removed
+     */
+    default void cleanup(long olderThanNanos) {
+    }
+
     /**
      * Immutable outcome of a {@link #tryAcquire(String, long)} call.
      *

src/main/java/dev/coph/nextusweb/server/ratelimit/SlidingWindowLimiter.java

@@ -18,11 +18,17 @@ import java.util.concurrent.atomic.AtomicLong;
  */
 public final class SlidingWindowLimiter implements RateLimiter {
 
-    /** Maximum effective (weighted) number of requests per window. */
+    /**
+     * Maximum effective (weighted) number of requests per window.
+     */
     private final long limit;
-    /** Window length in nanoseconds. */
+    /**
+     * Window length in nanoseconds.
+     */
     private final long windowNanos;
-    /** Per-key sliding windows, created on demand. */
+    /**
+     * Per-key sliding windows, created on demand.
+     */
     private final ConcurrentHashMap<String, SlidingWindow> windows = new ConcurrentHashMap<>();
 
     /**
@@ -53,6 +59,7 @@ public final class SlidingWindowLimiter implements RateLimiter {
      *
      * @param olderThanNanos maximum age in nanoseconds before a window is removed
      */
+    @Override
     public void cleanup(long olderThanNanos) {
         long now = System.nanoTime();
         windows.entrySet().removeIf(e -> now - e.getValue().windowStart.get() > olderThanNanos);
@@ -63,11 +70,17 @@ public final class SlidingWindowLimiter implements RateLimiter {
      * previous window counts.
      */
     private static final class SlidingWindow {
-        /** Start timestamp of the current window, in nanoseconds. */
+        /**
+         * Start timestamp of the current window, in nanoseconds.
+         */
         final AtomicLong windowStart;
-        /** Request count accumulated in the current window. */
+        /**
+         * Request count accumulated in the current window.
+         */
         final AtomicLong currentCount;
-        /** Request count carried over from the immediately preceding window. */
+        /**
+         * Request count carried over from the immediately preceding window.
+         */
         final AtomicLong previousCount;
 
         /**

src/main/java/dev/coph/nextusweb/server/ratelimit/TokenBucketLimiter.java

@@ -1,7 +1,7 @@
 package dev.coph.nextusweb.server.ratelimit;
 
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * A {@link RateLimiter} implementing the <em>token bucket</em> algorithm.
@@ -12,18 +12,29 @@ import java.util.concurrent.atomic.AtomicLong;
  * with a retry hint computed from the refill rate. This permits short bursts (up to the bucket
  * capacity) while bounding the sustained rate.</p>
  *
- * <p>Token counts are stored in fixed-point form (scaled by 1e9) inside {@link AtomicLong}s and
- * updated with a lock-free compare-and-set loop, so the limiter is safe for concurrent use.</p>
+ * <p>Token counts are stored in fixed-point form (scaled by 1e9). Each bucket's token count and
+ * last-refill timestamp are held together in a single immutable {@link Bucket.State} behind one
+ * {@link AtomicReference} and advanced with a lock-free compare-and-set loop, so a refill and the
+ * timestamp it is based on are always published as one atomic unit and the limiter is safe for
+ * concurrent use.</p>
  */
 public final class TokenBucketLimiter implements RateLimiter {
 
-    /** Maximum number of tokens a bucket can hold (the burst allowance). */
+    /**
+     * Maximum number of tokens a bucket can hold (the burst allowance).
+     */
     private final long capacity;
-    /** Refill rate expressed as tokens added per nanosecond. */
+    /**
+     * Refill rate expressed as tokens added per nanosecond.
+     */
     private final double tokensPerNano;
-    /** Approximate nanoseconds between single-token refills, used for retry hints. */
+    /**
+     * Approximate nanoseconds between single-token refills, used for retry hints.
+     */
     private final long refillIntervalNs;
-    /** Per-key buckets, created on demand. */
+    /**
+     * Per-key buckets, created on demand.
+     */
     private final ConcurrentHashMap<String, Bucket> buckets = new ConcurrentHashMap<>();
 
     /**
@@ -55,6 +66,7 @@ public final class TokenBucketLimiter implements RateLimiter {
      *
      * @param olderThanNanos maximum idle age in nanoseconds before a bucket is removed
      */
+    @Override
     public void cleanup(long olderThanNanos) {
         long now = System.nanoTime();
         buckets.entrySet().removeIf(e -> now - e.getValue().lastAccess() > olderThanNanos);
@@ -63,20 +75,23 @@ public final class TokenBucketLimiter implements RateLimiter {
 
     /**
      * A single client's token bucket. Tokens are stored in fixed-point form (multiplied by
-     * 1e9) to retain sub-token precision while using integer atomics.
-     *
-     * @param tokensFixed      current token count in fixed-point (tokens &times; 1e9)
-     * @param lastRefillNanos  timestamp of the last refill/consume, in nanoseconds
+     * 1e9) to retain sub-token precision; the mutable pair {@code (tokens, timestamp)} lives in a
+     * single {@link AtomicReference} so updates are atomic as a unit.
      */
-    private record Bucket(AtomicLong tokensFixed, AtomicLong lastRefillNanos) {
+    private static final class Bucket {
+        /**
+         * Holds the current {@code (tokensFixed, lastRefillNanos)} pair as one atomic unit.
+         */
+        private final AtomicReference<State> state;
+
         /**
          * Creates a full bucket.
          *
-             * @param tokensFixed     initial token count (in whole tokens, scaled internally)
+         * @param tokens          initial token count in whole tokens (scaled internally)
          * @param lastRefillNanos the creation timestamp in nanoseconds
          */
-            private Bucket(long tokensFixed, long lastRefillNanos) {
-                this(new AtomicLong(tokensFixed * 1_000_000_000L), new AtomicLong(lastRefillNanos));
+        Bucket(long tokens, long lastRefillNanos) {
+            this.state = new AtomicReference<>(new State(tokens * 1_000_000_000L, lastRefillNanos));
         }
 
         /**
@@ -85,34 +100,34 @@ public final class TokenBucketLimiter implements RateLimiter {
          * @return the last-refill timestamp in nanoseconds
          */
         long lastAccess() {
-                return lastRefillNanos.get();
+            return state.get().lastRefillNanos();
         }
 
         /**
          * Refills the bucket according to elapsed time and attempts to consume one token,
-             * retrying via compare-and-set on contention.
+         * retrying via compare-and-set on contention. The token count and the timestamp it was
+         * computed from are swapped in together, so no thread can ever observe refilled tokens
+         * paired with a stale timestamp (or vice versa).
          *
          * @param now              the current time in nanoseconds
          * @param capacity         the bucket capacity in whole tokens
          * @param tokensPerNano    the refill rate in tokens per nanosecond
-             * @param refillIntervalNs the nominal nanoseconds per token (unused in the hot path
-             *                         but kept for symmetry/retry computation)
+         * @param refillIntervalNs the nominal nanoseconds per token (kept for retry computation)
          * @return an allow result with the remaining tokens, or a deny result with a retry
          * hint when fewer than one token is available
          */
         Result tryAcquire(long now, long capacity, double tokensPerNano, long refillIntervalNs) {
+            long oneTokenFixed = 1_000_000_000L;
             while (true) {
-                    long lastRefill = lastRefillNanos.get();
-                    long currentTokens = tokensFixed.get();
+                State current = state.get();
 
-                    long elapsed = now - lastRefill;
-                    long refilled = currentTokens;
+                long elapsed = now - current.lastRefillNanos();
+                long refilled = current.tokensFixed();
                 if (elapsed > 0) {
                     long addedFixed = (long) (elapsed * tokensPerNano * 1_000_000_000.0);
-                        refilled = Math.min(currentTokens + addedFixed, capacity * 1_000_000_000L);
+                    refilled = Math.min(current.tokensFixed() + addedFixed, capacity * 1_000_000_000L);
                 }
 
-                    long oneTokenFixed = 1_000_000_000L;
                 if (refilled < oneTokenFixed) {
                     long deficitFixed = oneTokenFixed - refilled;
                     long retryNs = (long) (deficitFixed / (tokensPerNano * 1_000_000_000.0));
@@ -120,11 +135,19 @@ public final class TokenBucketLimiter implements RateLimiter {
                 }
 
                 long newTokens = refilled - oneTokenFixed;
-                    if (tokensFixed.compareAndSet(currentTokens, newTokens)) {
-                        lastRefillNanos.set(now);
+                if (state.compareAndSet(current, new State(newTokens, now))) {
                     return Result.allow(newTokens / 1_000_000_000L, capacity);
                 }
             }
         }
+
+        /**
+         * Immutable snapshot of a bucket's mutable state.
+         *
+         * @param tokensFixed     current token count in fixed-point (tokens &times; 1e9)
+         * @param lastRefillNanos timestamp the token count was last advanced to, in nanoseconds
+         */
+        private record State(long tokensFixed, long lastRefillNanos) {
+        }
     }
 }

src/main/java/dev/coph/nextusweb/server/router/Request.java

@@ -1,13 +1,21 @@
 package dev.coph.nextusweb.server.router;
 
+import dev.coph.nextusweb.server.auth.Principal;
 import dev.coph.nextusweb.server.json.JsonMapper;
 import dev.coph.nextusweb.server.router.exception.BadRequestException;
-import io.netty.handler.codec.http.*;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.QueryStringDecoder;
+import io.netty.handler.codec.http.cookie.Cookie;
+import io.netty.handler.codec.http.cookie.ServerCookieDecoder;
 import io.netty.util.CharsetUtil;
 import tools.jackson.core.JacksonException;
 import tools.jackson.databind.JsonNode;
 
-import java.util.*;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 /**
  * A convenience wrapper around a Netty {@link FullHttpRequest} that exposes the parts of an
@@ -20,18 +28,46 @@ import java.util.*;
  */
 public final class Request {
 
-    /** The underlying Netty request this wrapper delegates to. */
+    /**
+     * The underlying Netty request this wrapper delegates to.
+     */
     private final FullHttpRequest raw;
 
-    /** Path parameters captured by the router while matching, keyed by name. */
+    /**
+     * Path parameters captured by the router while matching, keyed by name.
+     */
     private final Map<String, String> pathParams;
 
-    /** Lazily decoded query-string parameters; {@code null} until first accessed. */
+    /**
+     * Lazily decoded query-string parameters; {@code null} until first accessed.
+     */
     private Map<String, List<String>> queryParams;
 
-    /** Lazily parsed JSON body; {@code null} until {@link #json()} is first called. */
+    /**
+     * Lazily parsed JSON body; {@code null} until {@link #json()} is first called.
+     */
     private JsonNode jsonCache;
 
+    /**
+     * Lazily decoded request cookies, keyed by name; {@code null} until first accessed.
+     */
+    private Map<String, String> cookies;
+
+    /**
+     * Lazily created bag of per-request attributes set by middlewares/handlers.
+     */
+    private Map<String, Object> attributes;
+
+    /**
+     * Resolved client IP (honouring trusted proxies); {@code null} until set by the pipeline.
+     */
+    private String clientIp;
+
+    /**
+     * Authenticated principal attached by the auth layer, or {@code null} if unauthenticated.
+     */
+    private Principal principal;
+
     /**
      * Creates a request wrapper.
      *
@@ -147,6 +183,106 @@ public final class Request {
         }
     }
 
+    /**
+     * Returns the value of a request cookie, decoding the {@code Cookie} header on first access.
+     *
+     * @param name the cookie name
+     * @return the cookie value, or {@code null} if no such cookie is present
+     */
+    public String cookie(String name) {
+        if (cookies == null) {
+            String header = raw.headers().get(HttpHeaderNames.COOKIE);
+            if (header == null || header.isEmpty()) {
+                cookies = Map.of();
+            } else {
+                Map<String, String> parsed = new HashMap<>();
+                for (Cookie c : ServerCookieDecoder.STRICT.decode(header)) {
+                    parsed.putIfAbsent(c.name(), c.value());
+                }
+                cookies = parsed;
+            }
+        }
+        return cookies.get(name);
+    }
+
+    /**
+     * Stores a per-request attribute, or removes it when {@code value} is {@code null}. Useful for
+     * passing state from middlewares or the auth layer to handlers.
+     *
+     * @param name  the attribute name
+     * @param value the value to store, or {@code null} to remove it
+     * @return this request, for fluent chaining
+     */
+    public Request attribute(String name, Object value) {
+        if (value == null) {
+            if (attributes != null) attributes.remove(name);
+        } else {
+            if (attributes == null) attributes = new HashMap<>(8);
+            attributes.put(name, value);
+        }
+        return this;
+    }
+
+    /**
+     * Retrieves a previously stored attribute, cast to the caller's expected type.
+     *
+     * @param name the attribute name
+     * @param <T>  the expected attribute type
+     * @return the stored value, or {@code null} if absent
+     */
+    @SuppressWarnings("unchecked")
+    public <T> T attribute(String name) {
+        return attributes == null ? null : (T) attributes.get(name);
+    }
+
+    /**
+     * Returns the resolved client IP address for this request. Unlike the raw socket address this
+     * honours the server's trusted-proxy configuration, so it reflects the originating client
+     * when the server sits behind a trusted reverse proxy and the socket peer otherwise.
+     *
+     * @return the resolved client IP, or {@code null} if the pipeline has not set one
+     */
+    public String clientIp() {
+        return clientIp;
+    }
+
+    /**
+     * Sets the resolved client IP. Called by the request pipeline; not intended for handler use.
+     *
+     * @param clientIp the resolved client IP
+     */
+    public void clientIp(String clientIp) {
+        this.clientIp = clientIp;
+    }
+
+    /**
+     * Returns the authenticated principal attached to this request by the auth layer.
+     *
+     * @return the principal, or {@code null} if the request was not authenticated
+     */
+    public Principal principal() {
+        return principal;
+    }
+
+    /**
+     * Attaches an authenticated principal to this request. Called by the auth layer; not intended
+     * for handler use.
+     *
+     * @param principal the authenticated principal
+     */
+    public void principal(Principal principal) {
+        this.principal = principal;
+    }
+
+    /**
+     * Returns whether this request carries an authenticated principal.
+     *
+     * @return {@code true} if a principal is attached
+     */
+    public boolean isAuthenticated() {
+        return principal != null;
+    }
+
     /**
      * Returns the request's HTTP method.
      *

src/main/java/dev/coph/nextusweb/server/router/Response.java

@@ -1,7 +1,9 @@
 package dev.coph.nextusweb.server.router;
 
 import dev.coph.nextusweb.server.json.JsonMapper;
-import io.netty.handler.codec.http.*;
+import io.netty.handler.codec.http.DefaultHttpHeaders;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.util.CharsetUtil;
 import tools.jackson.core.JacksonException;
 
@@ -16,13 +18,17 @@ import tools.jackson.core.JacksonException;
  */
 public final class Response {
 
-    /** HTTP status code; defaults to {@code 200}. */
-    private int status = 200;
-
-    /** Response headers accumulated by the handler. */
+    /**
+     * Response headers accumulated by the handler.
+     */
     private final HttpHeaders headers = new DefaultHttpHeaders();
-
-    /** Response body bytes; defaults to an empty array. */
+    /**
+     * HTTP status code; defaults to {@code 200}.
+     */
+    private int status = 200;
+    /**
+     * Response body bytes; defaults to an empty array.
+     */
     private byte[] body = new byte[0];
 
     /**
@@ -38,7 +44,10 @@ public final class Response {
      * @param s the status code
      * @return this response, for fluent chaining
      */
-    public Response status(int s) { this.status = s; return this; }
+    public Response status(int s) {
+        this.status = s;
+        return this;
+    }
 
     /**
      * Sets a response header, replacing any existing value for the same name.
@@ -101,19 +110,25 @@ public final class Response {
      *
      * @return the status code
      */
-    public int status() { return status; }
+    public int status() {
+        return status;
+    }
 
     /**
      * Returns the accumulated response headers.
      *
      * @return the headers
      */
-    public HttpHeaders headers() { return headers; }
+    public HttpHeaders headers() {
+        return headers;
+    }
 
     /**
      * Returns the response body bytes.
      *
      * @return the body bytes
      */
-    public byte[] body() { return body; }
+    public byte[] body() {
+        return body;
+    }
 }

src/main/java/dev/coph/nextusweb/server/router/Router.java

@@ -28,10 +28,14 @@ import java.util.function.BiConsumer;
  */
 public final class Router {
 
-    /** Root of the routing trie; every registered path descends from here. */
+    /**
+     * Root of the routing trie; every registered path descends from here.
+     */
     private final Node root = new Node();
 
-    /** Middlewares executed in insertion order for every matched request. */
+    /**
+     * Middlewares executed in insertion order for every matched request.
+     */
     private final List<BiConsumer<Request, Response>> middlewares = new ArrayList<>();
 
     /**
@@ -159,13 +163,14 @@ public final class Router {
      * @return the resolution outcome, never {@code null}
      */
     public Resolution resolve(HttpMethod method, String path) {
-        Map<String, String> params = new HashMap<>(4);
+        Map<String, String> params = null;
         Node node = root;
         for (String segment : split(path)) {
             Node next = node.children.get(segment);
             if (next != null) {
                 node = next;
             } else if (node.paramChild != null) {
+                if (params == null) params = new HashMap<>(4);
                 params.put(node.paramName, segment);
                 node = node.paramChild;
             } else if (node.wildcardChild != null) {
@@ -177,7 +182,7 @@ public final class Router {
 
         Handler h = node.handlers.get(method);
         if (h != null) {
-            return new Resolution.Match(h, params);
+            return new Resolution.Match(h, params == null ? Map.of() : params);
         }
 
         if (!node.handlers.isEmpty()) {
@@ -247,15 +252,25 @@ public final class Router {
      * registered at this node, and optional parameter/wildcard children.
      */
     private static final class Node {
-        /** Static child nodes keyed by their literal path segment. */
+        /**
+         * Static child nodes keyed by their literal path segment.
+         */
         final Map<String, Node> children = new ConcurrentHashMap<>();
-        /** Handlers registered directly at this node, keyed by HTTP method. */
+        /**
+         * Handlers registered directly at this node, keyed by HTTP method.
+         */
         final Map<HttpMethod, Handler> handlers = new ConcurrentHashMap<>();
-        /** Child matching any single segment as a path parameter, or {@code null} if none. */
+        /**
+         * Child matching any single segment as a path parameter, or {@code null} if none.
+         */
         Node paramChild;
-        /** Name under which {@link #paramChild} captures the matched segment. */
+        /**
+         * Name under which {@link #paramChild} captures the matched segment.
+         */
         String paramName;
-        /** Child matching any single segment as a wildcard, or {@code null} if none. */
+        /**
+         * Child matching any single segment as a wildcard, or {@code null} if none.
+         */
         Node wildcardChild;
     }
 }

src/main/java/dev/coph/nextusweb/server/router/exception/BadRequestException.java

@@ -16,5 +16,7 @@ public final class BadRequestException extends RuntimeException {
      *
      * @param message the detail message describing why the request is invalid
      */
-    public BadRequestException(String message) { super(message); }
+    public BadRequestException(String message) {
+        super(message);
+    }
 }

src/main/java/dev/coph/nextusweb/server/security/SecurityHeaders.java

@@ -0,0 +1,249 @@
+package dev.coph.nextusweb.server.security;
+
+import dev.coph.nextusweb.server.router.Response;
+import io.netty.handler.codec.http.HttpHeaders;
+
+import java.time.Duration;
+import java.util.*;
+
+/**
+ * A small, immutable policy of standard HTTP security response headers that the server adds to
+ * every response. It complements the transport- and authentication-level protections (TLS, CORS,
+ * the auth gate, rate limiting) with the browser-facing hardening headers that mitigate
+ * MIME-sniffing, click-jacking, referrer leakage and protocol-downgrade attacks.
+ *
+ * <p>Like {@code CorsHandler} the header strings are computed once at construction time and then
+ * reused for every response, so applying them is cheap. Attach an instance with
+ * {@code HttpServer.withSecurityHeaders(...)} and the request pipeline applies it to all
+ * responses.</p>
+ *
+ * <p>Two design choices keep the feature safe to switch on:</p>
+ * <ul>
+ *     <li><strong>Existing headers are never overwritten.</strong> If a handler has already set a
+ *     given header (say a route-specific {@code Content-Security-Policy}), that value is kept and
+ *     the policy default is skipped — so enabling security headers cannot silently clobber
+ *     deliberate per-route choices.</li>
+ *     <li><strong>HSTS is emitted only over HTTPS.</strong> {@code Strict-Transport-Security} is
+ *     added only when the connection is actually secured by TLS, because a browser ignores it on
+ *     plain HTTP and sending it there is meaningless (and a footgun behind a misconfigured
+ *     proxy).</li>
+ * </ul>
+ */
+public final class SecurityHeaders {
+
+    /**
+     * The {@code Strict-Transport-Security} header name, gated on a secure connection.
+     */
+    private static final String HSTS = "Strict-Transport-Security";
+
+    /**
+     * Headers added to every response (subject to not already being present).
+     */
+    private final List<Map.Entry<String, String>> always;
+    /**
+     * Pre-rendered HSTS header value, or {@code null} if HSTS is disabled.
+     */
+    private final String hstsValue;
+
+    private SecurityHeaders(Builder b) {
+        List<Map.Entry<String, String>> list = new ArrayList<>();
+        if (b.contentTypeOptions) {
+            list.add(Map.entry("X-Content-Type-Options", "nosniff"));
+        }
+        if (notBlank(b.frameOptions)) {
+            list.add(Map.entry("X-Frame-Options", b.frameOptions));
+        }
+        if (notBlank(b.referrerPolicy)) {
+            list.add(Map.entry("Referrer-Policy", b.referrerPolicy));
+        }
+        if (notBlank(b.contentSecurityPolicy)) {
+            list.add(Map.entry("Content-Security-Policy", b.contentSecurityPolicy));
+        }
+        for (var e : b.custom.entrySet()) {
+            list.add(Map.entry(e.getKey(), e.getValue()));
+        }
+        this.always = List.copyOf(list);
+
+        if (b.hstsMaxAge != null && !b.hstsMaxAge.isZero() && !b.hstsMaxAge.isNegative()) {
+            StringBuilder sb = new StringBuilder("max-age=").append(b.hstsMaxAge.toSeconds());
+            if (b.hstsIncludeSubDomains) sb.append("; includeSubDomains");
+            if (b.hstsPreload) sb.append("; preload");
+            this.hstsValue = sb.toString();
+        } else {
+            this.hstsValue = null;
+        }
+    }
+
+    private static boolean notBlank(String s) {
+        return s != null && !s.isBlank();
+    }
+
+    /**
+     * A sensible, conservative default policy: {@code X-Content-Type-Options: nosniff},
+     * {@code X-Frame-Options: DENY}, {@code Referrer-Policy: no-referrer} and, on HTTPS
+     * connections, a one-year {@code Strict-Transport-Security} header (without
+     * {@code includeSubDomains}/{@code preload}, which are opt-in because of their wide blast
+     * radius). No {@code Content-Security-Policy} is set, since a useful CSP is application
+     * specific.
+     *
+     * @return the default security-header policy
+     */
+    public static SecurityHeaders defaults() {
+        return builder()
+                .hsts(Duration.ofDays(365), false, false)
+                .build();
+    }
+
+    /**
+     * Creates a builder pre-populated with the conservative defaults (see {@link #defaults()}),
+     * except that HSTS is disabled until configured with {@link Builder#hsts}.
+     *
+     * @return a fresh builder
+     */
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    /**
+     * Adds the configured security headers to a response, skipping any header the handler has
+     * already set, and adding {@code Strict-Transport-Security} only when {@code secure} is
+     * {@code true}.
+     *
+     * @param res    the response to decorate
+     * @param secure whether the underlying connection is secured by TLS
+     */
+    public void apply(Response res, boolean secure) {
+        HttpHeaders headers = res.headers();
+        for (Map.Entry<String, String> e : always) {
+            if (!headers.contains(e.getKey())) {
+                headers.set(e.getKey(), e.getValue());
+            }
+        }
+        if (secure && hstsValue != null && !headers.contains(HSTS)) {
+            headers.set(HSTS, hstsValue);
+        }
+    }
+
+    /**
+     * Fluent builder for {@link SecurityHeaders}. Sensible defaults are pre-set; call the setters
+     * only to override them. Passing {@code null} (or a blank string) to a setter disables that
+     * particular header.
+     */
+    public static final class Builder {
+        private final Map<String, String> custom = new LinkedHashMap<>();
+        private boolean contentTypeOptions = true;
+        private String frameOptions = "DENY";
+        private String referrerPolicy = "no-referrer";
+        private String contentSecurityPolicy;
+        private Duration hstsMaxAge;
+        private boolean hstsIncludeSubDomains;
+        private boolean hstsPreload;
+
+        private Builder() {
+        }
+
+        /**
+         * Enables or disables {@code X-Content-Type-Options: nosniff} (defends against MIME
+         * sniffing). Enabled by default.
+         *
+         * @param enabled {@code true} to emit the header
+         * @return this builder, for fluent chaining
+         */
+        public Builder contentTypeOptions(boolean enabled) {
+            this.contentTypeOptions = enabled;
+            return this;
+        }
+
+        /**
+         * Sets the {@code X-Frame-Options} value (click-jacking defence); typical values are
+         * {@code "DENY"} (the default) or {@code "SAMEORIGIN"}. Pass {@code null} or a blank string
+         * to omit the header.
+         *
+         * @param value the header value, or {@code null}/blank to disable
+         * @return this builder, for fluent chaining
+         */
+        public Builder frameOptions(String value) {
+            this.frameOptions = value;
+            return this;
+        }
+
+        /**
+         * Sets the {@code Referrer-Policy} value (defaults to {@code "no-referrer"}). Pass
+         * {@code null} or a blank string to omit the header.
+         *
+         * @param value the header value, or {@code null}/blank to disable
+         * @return this builder, for fluent chaining
+         */
+        public Builder referrerPolicy(String value) {
+            this.referrerPolicy = value;
+            return this;
+        }
+
+        /**
+         * Sets a {@code Content-Security-Policy}. Disabled by default because a useful CSP is
+         * application specific; supply one tailored to your app. Pass {@code null} or a blank
+         * string to omit the header.
+         *
+         * @param value the policy string, or {@code null}/blank to disable
+         * @return this builder, for fluent chaining
+         */
+        public Builder contentSecurityPolicy(String value) {
+            this.contentSecurityPolicy = value;
+            return this;
+        }
+
+        /**
+         * Enables {@code Strict-Transport-Security} (HSTS), which is emitted only on HTTPS
+         * connections. Be deliberate with {@code includeSubDomains} and {@code preload}: they are
+         * hard to roll back, so enable them only once every subdomain is reliably served over
+         * HTTPS.
+         *
+         * @param maxAge            how long browsers should pin HTTPS; {@code null}/zero/negative
+         *                          disables HSTS
+         * @param includeSubDomains whether the policy also covers every subdomain
+         * @param preload           whether to request inclusion in browser preload lists
+         * @return this builder, for fluent chaining
+         */
+        public Builder hsts(Duration maxAge, boolean includeSubDomains, boolean preload) {
+            this.hstsMaxAge = maxAge;
+            this.hstsIncludeSubDomains = includeSubDomains;
+            this.hstsPreload = preload;
+            return this;
+        }
+
+        /**
+         * Disables {@code Strict-Transport-Security}.
+         *
+         * @return this builder, for fluent chaining
+         */
+        public Builder noHsts() {
+            this.hstsMaxAge = null;
+            return this;
+        }
+
+        /**
+         * Adds an arbitrary additional response header (for example {@code Permissions-Policy} or
+         * {@code Cross-Origin-Opener-Policy}). Like the built-in headers it is only applied when the
+         * handler has not already set it.
+         *
+         * @param name  the header name
+         * @param value the header value
+         * @return this builder, for fluent chaining
+         */
+        public Builder header(String name, String value) {
+            Objects.requireNonNull(name, "name");
+            Objects.requireNonNull(value, "value");
+            this.custom.put(name, value);
+            return this;
+        }
+
+        /**
+         * Builds the immutable {@link SecurityHeaders}.
+         *
+         * @return the configured instance
+         */
+        public SecurityHeaders build() {
+            return new SecurityHeaders(this);
+        }
+    }
+}

src/main/java/dev/coph/nextusweb/server/tls/TlsConfig.java

@@ -0,0 +1,124 @@
+package dev.coph.nextusweb.server.tls;
+
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslContextBuilder;
+import io.netty.handler.ssl.SslHandler;
+
+import javax.net.ssl.SSLException;
+import java.io.File;
+import java.io.InputStream;
+import java.util.Objects;
+
+/**
+ * Configuration that enables TLS (HTTPS / WSS) on the server. Holds a ready-built Netty
+ * {@link SslContext} and produces the per-connection {@link SslHandler} the pipeline installs as
+ * its first handler.
+ *
+ * <p>Enabling TLS is meant to be a one-liner — point the factory at a PEM certificate chain and
+ * private key and pass the result to {@code HttpServer.withTls(...)}:</p>
+ * <pre>{@code
+ * HttpServer.builder(443, router)
+ *           .withTls(TlsConfig.fromPem(new File("fullchain.pem"), new File("privkey.pem")))
+ *           .start();
+ * }</pre>
+ *
+ * <p>For full control (custom cipher suites, client-auth / mutual TLS, a non-default provider)
+ * build a Netty {@link SslContext} yourself and wrap it with {@link #fromSslContext(SslContext)}.
+ * The {@code SslContext} is built once and reused for every connection, so it is cheap per
+ * request.</p>
+ */
+public final class TlsConfig {
+
+    /**
+     * The pre-built, shareable server SSL context.
+     */
+    private final SslContext sslContext;
+
+    private TlsConfig(SslContext sslContext) {
+        this.sslContext = Objects.requireNonNull(sslContext, "sslContext");
+    }
+
+    /**
+     * Builds a TLS configuration from a PEM-encoded certificate chain and an unencrypted
+     * PKCS#8 private key.
+     *
+     * @param certificateChain the PEM file containing the certificate (chain)
+     * @param privateKey       the PEM file containing the PKCS#8 private key
+     * @return a TLS configuration
+     * @throws IllegalStateException if the certificate/key cannot be loaded
+     */
+    public static TlsConfig fromPem(File certificateChain, File privateKey) {
+        return fromPem(certificateChain, privateKey, null);
+    }
+
+    /**
+     * Builds a TLS configuration from a PEM-encoded certificate chain and a (optionally
+     * password-protected) PKCS#8 private key.
+     *
+     * @param certificateChain the PEM file containing the certificate (chain)
+     * @param privateKey       the PEM file containing the PKCS#8 private key
+     * @param keyPassword      the password protecting {@code privateKey}, or {@code null} if none
+     * @return a TLS configuration
+     * @throws IllegalStateException if the certificate/key cannot be loaded
+     */
+    public static TlsConfig fromPem(File certificateChain, File privateKey, String keyPassword) {
+        Objects.requireNonNull(certificateChain, "certificateChain");
+        Objects.requireNonNull(privateKey, "privateKey");
+        try {
+            return new TlsConfig(SslContextBuilder.forServer(certificateChain, privateKey, keyPassword).build());
+        } catch (SSLException | RuntimeException e) {
+            throw new IllegalStateException("Failed to initialise TLS from PEM files", e);
+        }
+    }
+
+    /**
+     * Builds a TLS configuration from PEM-encoded streams, for certificates/keys loaded from the
+     * classpath or another non-file source. The caller retains ownership of the streams.
+     *
+     * @param certificateChain a stream of the PEM certificate (chain)
+     * @param privateKey       a stream of the PEM PKCS#8 private key
+     * @param keyPassword      the password protecting {@code privateKey}, or {@code null} if none
+     * @return a TLS configuration
+     * @throws IllegalStateException if the certificate/key cannot be loaded
+     */
+    public static TlsConfig fromPem(InputStream certificateChain, InputStream privateKey, String keyPassword) {
+        Objects.requireNonNull(certificateChain, "certificateChain");
+        Objects.requireNonNull(privateKey, "privateKey");
+        try {
+            return new TlsConfig(SslContextBuilder.forServer(certificateChain, privateKey, keyPassword).build());
+        } catch (SSLException | RuntimeException e) {
+            throw new IllegalStateException("Failed to initialise TLS from PEM streams", e);
+        }
+    }
+
+    /**
+     * Wraps a fully configured Netty {@link SslContext}, for advanced setups such as custom cipher
+     * suites or mutual TLS.
+     *
+     * @param sslContext a server-mode SSL context
+     * @return a TLS configuration backed by the given context
+     */
+    public static TlsConfig fromSslContext(SslContext sslContext) {
+        return new TlsConfig(sslContext);
+    }
+
+    /**
+     * Creates a new per-connection {@link SslHandler} from the shared context.
+     *
+     * @param alloc the channel's buffer allocator
+     * @return a fresh TLS handler for one connection
+     */
+    public SslHandler newHandler(ByteBufAllocator alloc) {
+        return sslContext.newHandler(alloc);
+    }
+
+    /**
+     * Returns the underlying Netty SSL context.
+     *
+     * @return the shared server SSL context
+     */
+    public SslContext sslContext() {
+        return sslContext;
+    }
+}

src/main/java/dev/coph/nextusweb/server/websocket/WebSocketConfig.java

@@ -15,22 +15,42 @@ import java.util.Set;
  */
 public final class WebSocketConfig {
 
-    /** Maximum size, in bytes, of a single WebSocket frame payload. */
+    /**
+     * Maximum size, in bytes, of a single WebSocket frame payload.
+     */
     private final int maxFramePayloadLength;
-    /** Maximum size, in bytes, of an aggregated (multi-frame) message. */
+    /**
+     * Maximum size, in bytes, of an aggregated (multi-frame) message.
+     */
     private final int maxAggregatedMessageSize;
-    /** Idle timeout after which an inactive connection is closed; {@code null} disables it. */
+    /**
+     * Idle timeout after which an inactive connection is closed; {@code null} disables it.
+     */
     private final Duration idleTimeout;
-    /** Explicit set of allowed origins; ignored when {@link #allowAnyOrigin} is {@code true}. */
+    /**
+     * Explicit set of allowed origins; ignored when {@link #allowAnyOrigin} is {@code true}.
+     */
     private final Set<String> allowedOrigins;
-    /** Whether connections from any origin are accepted. */
+    /**
+     * Whether connections from any origin are accepted.
+     */
     private final boolean allowAnyOrigin;
-    /** Subprotocols offered during negotiation. */
+    /**
+     * Subprotocols offered during negotiation.
+     */
     private final Set<String> subprotocols;
-    /** Whether per-message deflate compression is enabled. */
+    /**
+     * Whether per-message deflate compression is enabled.
+     */
     private final boolean compression;
-    /** Whether the protocol handler matches the path by prefix rather than exact equality. */
+    /**
+     * Whether the protocol handler matches the path by prefix rather than exact equality.
+     */
     private final boolean checkStartsWith;
+    /**
+     * Max in-flight callbacks queued per connection before read backpressure kicks in.
+     */
+    private final int maxQueuedMessages;
 
     /**
      * Builds an immutable configuration from a {@link Builder}, defensively copying its sets.
@@ -46,6 +66,7 @@ public final class WebSocketConfig {
         this.subprotocols = Set.copyOf(b.subprotocols);
         this.compression = b.compression;
         this.checkStartsWith = b.checkStartsWith;
+        this.maxQueuedMessages = b.maxQueuedMessages;
     }
 
     /**
@@ -153,28 +174,59 @@ public final class WebSocketConfig {
         return checkStartsWith;
     }
 
+    /**
+     * Returns the maximum number of in-flight callbacks that may be queued per connection before
+     * the framework stops reading further frames (backpressure), protecting the server from a
+     * client that floods messages faster than the handler consumes them.
+     *
+     * @return the per-connection queued-message high-watermark
+     */
+    public int maxQueuedMessages() {
+        return maxQueuedMessages;
+    }
+
     /**
      * Fluent builder for {@link WebSocketConfig}, pre-populated with sensible defaults: 64&nbsp;KiB
      * frames, 1&nbsp;MiB aggregated messages, a 60-second idle timeout, no origin restriction
      * list, compression enabled, and exact path matching.
      */
     public static final class Builder {
-        /** Maximum single-frame payload size in bytes; defaults to 64&nbsp;KiB. */
-        private int maxFramePayloadLength = 65_536;
-        /** Maximum aggregated message size in bytes; defaults to 1&nbsp;MiB. */
-        private int maxAggregatedMessageSize = 1_048_576;
-        /** Idle timeout; defaults to 60 seconds. */
-        private Duration idleTimeout = Duration.ofSeconds(60);
-        /** Accumulated allowed origins (insertion-ordered). */
+        /**
+         * Accumulated allowed origins (insertion-ordered).
+         */
         private final Set<String> allowedOrigins = new LinkedHashSet<>();
-        /** Whether any origin is allowed; defaults to {@code false}. */
-        private boolean allowAnyOrigin = false;
-        /** Accumulated subprotocols (insertion-ordered). */
+        /**
+         * Accumulated subprotocols (insertion-ordered).
+         */
         private final Set<String> subprotocols = new LinkedHashSet<>();
-        /** Whether compression is enabled; defaults to {@code true}. */
+        /**
+         * Maximum single-frame payload size in bytes; defaults to 64&nbsp;KiB.
+         */
+        private int maxFramePayloadLength = 65_536;
+        /**
+         * Maximum aggregated message size in bytes; defaults to 1&nbsp;MiB.
+         */
+        private int maxAggregatedMessageSize = 1_048_576;
+        /**
+         * Idle timeout; defaults to 60 seconds.
+         */
+        private Duration idleTimeout = Duration.ofSeconds(60);
+        /**
+         * Whether any origin is allowed; defaults to {@code false}.
+         */
+        private boolean allowAnyOrigin = false;
+        /**
+         * Whether compression is enabled; defaults to {@code true}.
+         */
         private boolean compression = true;
-        /** Whether path matching uses a prefix check; defaults to {@code false}. */
+        /**
+         * Whether path matching uses a prefix check; defaults to {@code false}.
+         */
         private boolean checkStartsWith = false;
+        /**
+         * Per-connection queued-message high-watermark; defaults to 1024.
+         */
+        private int maxQueuedMessages = 1024;
 
         /**
          * Creates a builder pre-populated with the default configuration values described
@@ -284,6 +336,19 @@ public final class WebSocketConfig {
             return this;
         }
 
+        /**
+         * Sets the per-connection queued-message high-watermark for backpressure.
+         *
+         * @param messages the maximum queued callbacks before reads are paused; must be positive
+         * @return this builder, for fluent chaining
+         * @throws IllegalArgumentException if {@code messages <= 0}
+         */
+        public Builder maxQueuedMessages(int messages) {
+            if (messages <= 0) throw new IllegalArgumentException("maxQueuedMessages must be > 0");
+            this.maxQueuedMessages = messages;
+            return this;
+        }
+
         /**
          * Builds the immutable {@link WebSocketConfig}.
          *

src/main/java/dev/coph/nextusweb/server/websocket/WebSocketFrameHandler.java

@@ -1,18 +1,18 @@
 package dev.coph.nextusweb.server.websocket;
 
+import dev.coph.nextusweb.server.auth.Principal;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.SimpleChannelInboundHandler;
-import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
-import io.netty.handler.codec.http.websocketx.WebSocketFrame;
-import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
-import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
-import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
+import io.netty.handler.codec.http.websocketx.*;
 import io.netty.handler.timeout.IdleStateEvent;
-import io.netty.util.CharsetUtil;
 
 import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * Netty channel handler that bridges low-level WebSocket frames to the high-level
@@ -20,24 +20,68 @@ import java.util.concurrent.Executors;
  *
  * <p>It creates a {@link WebSocketSession} when the handshake completes, then translates each
  * incoming frame into the matching callback ({@code onMessage}, {@code onBinary},
- * {@code onClose}). Callbacks are dispatched on a virtual-thread executor so application code
- * may block without stalling the Netty event loop, and any exception they throw is funneled to
- * {@link WebSocketHandler#onError}. Idle-timeout events close the channel.</p>
+ * {@code onClose}). Callbacks run on virtual threads so application code may block without
+ * stalling the Netty event loop, but, crucially, all callbacks for a single connection are
+ * executed <strong>strictly in arrival order</strong> by a per-connection serial drainer rather
+ * than each on its own thread — message ordering within a connection is therefore guaranteed.</p>
+ *
+ * <p>The drainer's pending queue is bounded: once it reaches the configured high-watermark the
+ * handler disables the channel's auto-read (backpressure), so a client that floods messages faster
+ * than the handler consumes them cannot exhaust memory or spawn unbounded work; reading resumes
+ * once the backlog drains. Each handler instance serves exactly one connection, so this state is
+ * per-connection.</p>
  *
  * <p>This class is package-private; instances are created via
  * {@link WebSocketFrameHandlerFactory}.</p>
  */
 final class WebSocketFrameHandler extends SimpleChannelInboundHandler<WebSocketFrame> {
 
-    /** Executor running one virtual thread per task, used to dispatch handler callbacks. */
+    /**
+     * Executor running one virtual thread per drain task.
+     */
     private static final Executor VT_EXECUTOR = Executors.newVirtualThreadPerTaskExecutor();
 
-    /** The application handler receiving lifecycle callbacks. */
+    /**
+     * The application handler receiving lifecycle callbacks.
+     */
     private final WebSocketHandler handler;
-    /** The path the connection was established on. */
+    /**
+     * The path the connection was established on.
+     */
     private final String path;
-    /** Path parameters captured during routing, keyed by name. */
+    /**
+     * Path parameters captured during routing, keyed by name.
+     */
     private final Map<String, String> pathParams;
+    /**
+     * Authenticated principal for the connection, or {@code null} if anonymous.
+     */
+    private final Principal principal;
+    /**
+     * Queued-callback high-watermark at which reads are paused.
+     */
+    private final int maxQueued;
+    /**
+     * Watermark at which reads resume after having been paused.
+     */
+    private final int resumeQueued;
+
+    /**
+     * FIFO of pending callbacks for this connection; drained by a single virtual thread.
+     */
+    private final Queue<Runnable> tasks = new ConcurrentLinkedQueue<>();
+    /**
+     * Number of callbacks currently queued (drives the backpressure watermarks).
+     */
+    private final AtomicInteger queued = new AtomicInteger();
+    /**
+     * Guards that at most one drainer runs at a time, preserving ordering.
+     */
+    private final AtomicBoolean draining = new AtomicBoolean(false);
+    /**
+     * Whether reads are currently paused for backpressure.
+     */
+    private volatile boolean readsPaused = false;
 
     /**
      * Creates a frame handler bound to an application handler and connection metadata.
@@ -45,11 +89,136 @@ final class WebSocketFrameHandler extends SimpleChannelInboundHandler<WebSocketF
      * @param handler    the application handler to dispatch to
      * @param path       the connection path
      * @param pathParams the captured path parameters
+     * @param principal  the authenticated principal, or {@code null} if the connection is anonymous
+     * @param maxQueued  the per-connection queued-callback high-watermark for backpressure
      */
-    WebSocketFrameHandler(WebSocketHandler handler, String path, Map<String, String> pathParams) {
+    WebSocketFrameHandler(WebSocketHandler handler, String path, Map<String, String> pathParams,
+                          Principal principal, int maxQueued) {
         this.handler = handler;
         this.path = path;
         this.pathParams = pathParams;
+        this.principal = principal;
+        this.maxQueued = Math.max(1, maxQueued);
+        this.resumeQueued = Math.max(1, this.maxQueued / 4);
+    }
+
+    /**
+     * Dispatches an incoming frame to the appropriate handler callback. Text, binary and close
+     * frames are forwarded to {@code onMessage}, {@code onBinary} and {@code onClose}
+     * respectively, in arrival order via the per-connection serial drainer. Frame payloads are
+     * copied eagerly here (on the event loop) before the frame buffer is recycled. Frames arriving
+     * before the session exists are ignored.
+     *
+     * @param ctx   the channel context
+     * @param frame the received WebSocket frame
+     */
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx, WebSocketFrame frame) {
+        WebSocketSession session = ctx.channel().attr(WebSocketSession.SESSION_KEY).get();
+        if (session == null) return;
+
+        if (frame instanceof TextWebSocketFrame text) {
+            String content = text.text();
+            submit(ctx, () -> {
+                try {
+                    handler.onMessage(session, content);
+                } catch (Throwable t) {
+                    safeError(session, t);
+                }
+            });
+        } else if (frame instanceof BinaryWebSocketFrame bin) {
+            int readable = bin.content().readableBytes();
+            byte[] data = new byte[readable];
+            bin.content().getBytes(bin.content().readerIndex(), data);
+            submit(ctx, () -> {
+                try {
+                    handler.onBinary(session, data);
+                } catch (Throwable t) {
+                    safeError(session, t);
+                }
+            });
+        } else if (frame instanceof CloseWebSocketFrame close) {
+            int code = close.statusCode();
+            String reason = close.reasonText() == null ? "" : close.reasonText();
+            submit(ctx, () -> {
+                try {
+                    handler.onClose(session, code, reason);
+                } catch (Throwable t) {
+                    safeError(session, t);
+                }
+            });
+        }
+    }
+
+    /**
+     * Enqueues a callback for ordered execution and ensures a drainer is running. Applies read
+     * backpressure when the queue reaches its high-watermark.
+     *
+     * @param ctx  the channel context
+     * @param task the callback to run in order
+     */
+    private void submit(ChannelHandlerContext ctx, Runnable task) {
+        tasks.add(task);
+        if (queued.incrementAndGet() >= maxQueued && !readsPaused) {
+            readsPaused = true;
+            ctx.channel().config().setAutoRead(false);
+        }
+        if (draining.compareAndSet(false, true)) {
+            VT_EXECUTOR.execute(() -> drain(ctx));
+        }
+    }
+
+    /**
+     * Drains and runs queued callbacks one at a time (preserving order) until the queue is empty,
+     * resuming reads once the backlog falls back below the low-watermark. The single-drainer
+     * invariant is upheld by {@link #draining}; a final re-check avoids a lost wake-up if a task
+     * was enqueued just as the drainer was finishing.
+     *
+     * @param ctx the channel context
+     */
+    private void drain(ChannelHandlerContext ctx) {
+        try {
+            Runnable task;
+            while ((task = tasks.poll()) != null) {
+                try {
+                    task.run();
+                } finally {
+                    int remaining = queued.decrementAndGet();
+                    if (readsPaused && remaining <= resumeQueued) {
+                        readsPaused = false;
+                        if (ctx.channel().isActive()) {
+                            ctx.channel().config().setAutoRead(true);
+                            ctx.read();
+                        }
+                    }
+                }
+            }
+        } finally {
+            draining.set(false);
+            if (!tasks.isEmpty() && draining.compareAndSet(false, true)) {
+                VT_EXECUTOR.execute(() -> drain(ctx));
+            }
+        }
+    }
+
+    /**
+     * Invoked when the channel goes inactive (the connection dropped without a clean close
+     * handshake). Clears the stored session and dispatches {@link WebSocketHandler#onClose} with
+     * the abnormal-closure code {@code 1006}, ordered after any still-queued callbacks.
+     *
+     * @param ctx the channel context
+     */
+    @Override
+    public void channelInactive(ChannelHandlerContext ctx) {
+        WebSocketSession session = ctx.channel().attr(WebSocketSession.SESSION_KEY).getAndSet(null);
+        if (session == null) return;
+        submit(ctx, () -> {
+            try {
+                handler.onClose(session, 1006, "Connection closed");
+            } catch (Throwable t) {
+                safeError(session, t);
+            }
+        });
     }
 
     /**
@@ -64,9 +233,9 @@ final class WebSocketFrameHandler extends SimpleChannelInboundHandler<WebSocketF
     @Override
     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
         if (evt instanceof WebSocketServerProtocolHandler.HandshakeComplete) {
-            WebSocketSession session = new WebSocketSession(ctx.channel(), path, pathParams);
+            WebSocketSession session = new WebSocketSession(ctx.channel(), path, pathParams, principal);
             ctx.channel().attr(WebSocketSession.SESSION_KEY).set(session);
-            VT_EXECUTOR.execute(() -> {
+            submit(ctx, () -> {
                 try {
                     handler.onOpen(session);
                 } catch (Throwable t) {
@@ -82,73 +251,6 @@ final class WebSocketFrameHandler extends SimpleChannelInboundHandler<WebSocketF
         super.userEventTriggered(ctx, evt);
     }
 
-    /**
-     * Dispatches an incoming frame to the appropriate handler callback. Text, binary and close
-     * frames are forwarded to {@code onMessage}, {@code onBinary} and {@code onClose}
-     * respectively, each on a virtual thread. Frames arriving before the session exists are
-     * ignored.
-     *
-     * @param ctx   the channel context
-     * @param frame the received WebSocket frame
-     */
-    @Override
-    protected void channelRead0(ChannelHandlerContext ctx, WebSocketFrame frame) {
-        WebSocketSession session = ctx.channel().attr(WebSocketSession.SESSION_KEY).get();
-        if (session == null) return;
-
-        if (frame instanceof TextWebSocketFrame text) {
-            String content = text.text();
-            VT_EXECUTOR.execute(() -> {
-                try {
-                    handler.onMessage(session, content);
-                } catch (Throwable t) {
-                    safeError(session, t);
-                }
-            });
-        } else if (frame instanceof BinaryWebSocketFrame bin) {
-            int readable = bin.content().readableBytes();
-            byte[] data = new byte[readable];
-            bin.content().getBytes(bin.content().readerIndex(), data);
-            VT_EXECUTOR.execute(() -> {
-                try {
-                    handler.onBinary(session, data);
-                } catch (Throwable t) {
-                    safeError(session, t);
-                }
-            });
-        } else if (frame instanceof CloseWebSocketFrame close) {
-            int code = close.statusCode();
-            String reason = close.reasonText() == null ? "" : close.reasonText();
-            VT_EXECUTOR.execute(() -> {
-                try {
-                    handler.onClose(session, code, reason);
-                } catch (Throwable t) {
-                    safeError(session, t);
-                }
-            });
-        }
-    }
-
-    /**
-     * Invoked when the channel goes inactive (the connection dropped without a clean close
-     * handshake). Clears the stored session and dispatches {@link WebSocketHandler#onClose} with
-     * the abnormal-closure code {@code 1006}.
-     *
-     * @param ctx the channel context
-     */
-    @Override
-    public void channelInactive(ChannelHandlerContext ctx) {
-        WebSocketSession session = ctx.channel().attr(WebSocketSession.SESSION_KEY).getAndSet(null);
-        if (session == null) return;
-        VT_EXECUTOR.execute(() -> {
-            try {
-                handler.onClose(session, 1006, "Connection closed");
-            } catch (Throwable t) {
-                safeError(session, t);
-            }
-        });
-    }
-
     /**
      * Routes a pipeline exception to {@link WebSocketHandler#onError} (when a session exists)
      * and then closes the channel.

src/main/java/dev/coph/nextusweb/server/websocket/WebSocketFrameHandlerFactory.java

@@ -1,5 +1,6 @@
 package dev.coph.nextusweb.server.websocket;
 
+import dev.coph.nextusweb.server.auth.Principal;
 import io.netty.channel.ChannelHandler;
 
 import java.util.Map;
@@ -13,6 +14,11 @@ import java.util.Map;
  */
 public final class WebSocketFrameHandlerFactory {
 
+    /**
+     * Default per-connection queued-message high-watermark when none is supplied.
+     */
+    private static final int DEFAULT_MAX_QUEUED = 1024;
+
     /**
      * Private constructor preventing instantiation of this stateless utility class.
      */
@@ -21,7 +27,7 @@ public final class WebSocketFrameHandlerFactory {
 
     /**
      * Creates a channel handler that bridges Netty WebSocket frames to the given application
-     * {@link WebSocketHandler}.
+     * {@link WebSocketHandler}, using the default backpressure watermark and no principal.
      *
      * @param handler    the application handler to dispatch lifecycle events to
      * @param path       the path the connection was established on
@@ -30,6 +36,38 @@ public final class WebSocketFrameHandlerFactory {
      */
     public static ChannelHandler create(WebSocketHandler handler, String path,
                                         Map<String, String> pathParams) {
-        return new WebSocketFrameHandler(handler, path, pathParams);
+        return create(handler, path, pathParams, null, DEFAULT_MAX_QUEUED);
+    }
+
+    /**
+     * Creates a channel handler with an authenticated principal and an explicit backpressure
+     * watermark.
+     *
+     * @param handler    the application handler to dispatch lifecycle events to
+     * @param path       the path the connection was established on
+     * @param pathParams the path parameters captured during routing
+     * @param principal  the authenticated principal, or {@code null} if the connection is anonymous
+     * @param maxQueued  the per-connection queued-message high-watermark before reads are paused
+     * @return a new channel handler ready to be inserted into the pipeline
+     */
+    public static ChannelHandler create(WebSocketHandler handler, String path,
+                                        Map<String, String> pathParams, Principal principal,
+                                        int maxQueued) {
+        return new WebSocketFrameHandler(handler, path, pathParams, principal, maxQueued);
+    }
+
+    /**
+     * Creates a channel handler with an authenticated principal and the default backpressure
+     * watermark.
+     *
+     * @param handler    the application handler to dispatch lifecycle events to
+     * @param path       the path the connection was established on
+     * @param pathParams the path parameters captured during routing
+     * @param principal  the authenticated principal, or {@code null} if the connection is anonymous
+     * @return a new channel handler ready to be inserted into the pipeline
+     */
+    public static ChannelHandler create(WebSocketHandler handler, String path,
+                                        Map<String, String> pathParams, Principal principal) {
+        return create(handler, path, pathParams, principal, DEFAULT_MAX_QUEUED);
     }
 }

src/main/java/dev/coph/nextusweb/server/websocket/WebSocketGroup.java

@@ -1,6 +1,7 @@
 package dev.coph.nextusweb.server.websocket;
 
 import dev.coph.nextusweb.server.json.JsonMapper;
+import io.netty.buffer.Unpooled;
 import io.netty.channel.group.ChannelGroup;
 import io.netty.channel.group.DefaultChannelGroup;
 import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
@@ -19,9 +20,13 @@ import tools.jackson.core.JacksonException;
  */
 public final class WebSocketGroup {
 
-    /** Underlying Netty channel group holding the member connections. */
+    /**
+     * Underlying Netty channel group holding the member connections.
+     */
     private final ChannelGroup channels;
-    /** Human-readable name of this group. */
+    /**
+     * Human-readable name of this group.
+     */
     private final String name;
 
     /**
@@ -102,8 +107,7 @@ public final class WebSocketGroup {
     public WebSocketGroup broadcastJson(Object value) {
         try {
             byte[] bytes = JsonMapper.MAPPER.writeValueAsBytes(value);
-            String text = new String(bytes, java.nio.charset.StandardCharsets.UTF_8);
-            channels.writeAndFlush(new TextWebSocketFrame(text));
+            channels.writeAndFlush(new TextWebSocketFrame(Unpooled.wrappedBuffer(bytes)));
         } catch (JacksonException e) {
             throw new RuntimeException("JSON serialization failed", e);
         }

src/main/java/dev/coph/nextusweb/server/websocket/WebSocketRouter.java

@@ -16,7 +16,9 @@ import java.util.concurrent.ConcurrentHashMap;
  */
 public final class WebSocketRouter {
 
-    /** Root of the routing trie. */
+    /**
+     * Root of the routing trie.
+     */
     private final Node root = new Node();
 
     /**
@@ -50,6 +52,26 @@ public final class WebSocketRouter {
         return this;
     }
 
+    /**
+     * Splits a path into its non-empty segments, ignoring leading and collapsing internal
+     * slashes.
+     *
+     * @param path the raw path
+     * @return the ordered list of path segments
+     */
+    private static List<String> split(String path) {
+        List<String> out = new ArrayList<>();
+        int start = path.startsWith("/") ? 1 : 0;
+        for (int i = start; i < path.length(); i++) {
+            if (path.charAt(i) == '/') {
+                if (i > start) out.add(path.substring(start, i));
+                start = i + 1;
+            }
+        }
+        if (start < path.length()) out.add(path.substring(start));
+        return out;
+    }
+
     /**
      * Resolves a path to its handler, capturing any path parameters along the way.
      *
@@ -75,26 +97,6 @@ public final class WebSocketRouter {
         return new Resolution(node.handler, params);
     }
 
-    /**
-     * Splits a path into its non-empty segments, ignoring leading and collapsing internal
-     * slashes.
-     *
-     * @param path the raw path
-     * @return the ordered list of path segments
-     */
-    private static List<String> split(String path) {
-        List<String> out = new ArrayList<>();
-        int start = path.startsWith("/") ? 1 : 0;
-        for (int i = start; i < path.length(); i++) {
-            if (path.charAt(i) == '/') {
-                if (i > start) out.add(path.substring(start, i));
-                start = i + 1;
-            }
-        }
-        if (start < path.length()) out.add(path.substring(start));
-        return out;
-    }
-
     /**
      * A successful path resolution.
      *
@@ -109,13 +111,21 @@ public final class WebSocketRouter {
      * optional path-parameter child, and the handler (if any) registered at this node.
      */
     private static final class Node {
-        /** Static child nodes keyed by their literal path segment. */
+        /**
+         * Static child nodes keyed by their literal path segment.
+         */
         final Map<String, Node> children = new ConcurrentHashMap<>();
-        /** Child matching any single segment as a path parameter, or {@code null} if none. */
+        /**
+         * Child matching any single segment as a path parameter, or {@code null} if none.
+         */
         Node paramChild;
-        /** Name under which {@link #paramChild} captures the matched segment. */
+        /**
+         * Name under which {@link #paramChild} captures the matched segment.
+         */
         String paramName;
-        /** Handler registered at this node, or {@code null} if the path is only a prefix. */
+        /**
+         * Handler registered at this node, or {@code null} if the path is only a prefix.
+         */
         WebSocketHandler handler;
     }
 }

src/main/java/dev/coph/nextusweb/server/websocket/WebSocketSession.java

@@ -1,5 +1,6 @@
 package dev.coph.nextusweb.server.websocket;
 
+import dev.coph.nextusweb.server.auth.Principal;
 import dev.coph.nextusweb.server.json.JsonMapper;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
@@ -35,19 +36,35 @@ import java.util.concurrent.ConcurrentHashMap;
  */
 public final class WebSocketSession {
 
-    /** Channel attribute key under which the session is stored on its Netty channel. */
+    /**
+     * Channel attribute key under which the session is stored on its Netty channel.
+     */
     static final AttributeKey<WebSocketSession> SESSION_KEY =
             AttributeKey.valueOf("nexusweb.ws.session");
 
-    /** The underlying Netty channel for this connection. */
+    /**
+     * The underlying Netty channel for this connection.
+     */
     private final Channel channel;
-    /** Unique identifier generated for this session. */
+    /**
+     * Unique identifier generated for this session.
+     */
     private final String id;
-    /** The path the connection was established on. */
+    /**
+     * The path the connection was established on.
+     */
     private final String path;
-    /** Path parameters captured during routing, keyed by name. */
+    /**
+     * Path parameters captured during routing, keyed by name.
+     */
     private final Map<String, String> pathParams;
-    /** Thread-safe bag of user-defined attributes attached to the session. */
+    /**
+     * Authenticated principal for this connection, or {@code null} if anonymous.
+     */
+    private final Principal principal;
+    /**
+     * Thread-safe bag of user-defined attributes attached to the session.
+     */
     private final Map<String, Object> attributes = new ConcurrentHashMap<>();
 
     /**
@@ -57,12 +74,44 @@ public final class WebSocketSession {
      * @param channel    the underlying Netty channel
      * @param path       the connection path
      * @param pathParams the path parameters captured during routing
+     * @param principal  the authenticated principal, or {@code null} if the connection is anonymous
      */
-    WebSocketSession(Channel channel, String path, Map<String, String> pathParams) {
+    WebSocketSession(Channel channel, String path, Map<String, String> pathParams, Principal principal) {
         this.channel = channel;
         this.id = UUID.randomUUID().toString();
         this.path = path;
         this.pathParams = pathParams;
+        this.principal = principal;
+    }
+
+    /**
+     * Low-level helper that writes a text payload directly to a channel, allocating the buffer
+     * from the channel's allocator. Used by collaborators that hold a channel but not a session.
+     *
+     * @param channel the channel to write to
+     * @param text    the text to send
+     * @return a future completing when the write finishes; an already-succeeded future if the
+     * channel is no longer active
+     */
+    static ChannelFuture sendRaw(Channel channel, String text) {
+        if (!channel.isActive()) return channel.newSucceededFuture();
+        ByteBuf buf = channel.alloc().buffer();
+        buf.writeCharSequence(text, CharsetUtil.UTF_8);
+        return channel.writeAndFlush(new TextWebSocketFrame(true, 0, buf));
+    }
+
+    /**
+     * Low-level helper that writes a binary payload directly to a channel.
+     *
+     * @param channel the channel to write to
+     * @param data    the bytes to send
+     * @return a future completing when the write finishes; an already-succeeded future if the
+     * channel is no longer active
+     */
+    static ChannelFuture sendRawBinary(Channel channel, byte[] data) {
+        if (!channel.isActive()) return channel.newSucceededFuture();
+        ByteBuf buf = channel.alloc().buffer(data.length).writeBytes(Unpooled.wrappedBuffer(data));
+        return channel.writeAndFlush(new BinaryWebSocketFrame(buf));
     }
 
     /**
@@ -93,6 +142,16 @@ public final class WebSocketSession {
         return pathParams.get(name);
     }
 
+    /**
+     * Returns the authenticated principal associated with this connection, established by the auth
+     * layer during the upgrade handshake.
+     *
+     * @return the principal, or {@code null} if the connection is anonymous
+     */
+    public Principal principal() {
+        return principal;
+    }
+
     /**
      * Indicates whether the connection is still open.
      *
@@ -229,34 +288,4 @@ public final class WebSocketSession {
         return channel.writeAndFlush(new CloseWebSocketFrame(code, reason))
                 .addListener(ChannelFutureListener.CLOSE);
     }
-
-    /**
-     * Low-level helper that writes a text payload directly to a channel, allocating the buffer
-     * from the channel's allocator. Used by collaborators that hold a channel but not a session.
-     *
-     * @param channel the channel to write to
-     * @param text    the text to send
-     * @return a future completing when the write finishes; an already-succeeded future if the
-     *         channel is no longer active
-     */
-    static ChannelFuture sendRaw(Channel channel, String text) {
-        if (!channel.isActive()) return channel.newSucceededFuture();
-        ByteBuf buf = channel.alloc().buffer();
-        buf.writeCharSequence(text, CharsetUtil.UTF_8);
-        return channel.writeAndFlush(new TextWebSocketFrame(true, 0, buf));
-    }
-
-    /**
-     * Low-level helper that writes a binary payload directly to a channel.
-     *
-     * @param channel the channel to write to
-     * @param data    the bytes to send
-     * @return a future completing when the write finishes; an already-succeeded future if the
-     *         channel is no longer active
-     */
-    static ChannelFuture sendRawBinary(Channel channel, byte[] data) {
-        if (!channel.isActive()) return channel.newSucceededFuture();
-        ByteBuf buf = channel.alloc().buffer(data.length).writeBytes(Unpooled.wrappedBuffer(data));
-        return channel.writeAndFlush(new BinaryWebSocketFrame(buf));
-    }
 }

src/test/java/dev/coph/nextusweb/server/auth/AuthConfigTest.java

@@ -0,0 +1,126 @@
+package dev.coph.nextusweb.server.auth;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class AuthConfigTest {
+
+    /** A distinct authenticator instance, identifiable by reference, that authenticates nobody. */
+    private Authenticator marker() {
+        return req -> null;
+    }
+
+    @Test
+    void ruleForReturnsNullWhenUnprotected() {
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .protect("/admin")
+                .build();
+        assertNull(cfg.ruleFor("/public"));
+    }
+
+    @Test
+    void exactPathBeatsPrefix() {
+        Authenticator exactAuth = marker();
+        Authenticator prefixAuth = marker();
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .protect("/api/health", exactAuth)
+                .protectPrefix("/api/", prefixAuth)
+                .build();
+
+        AuthConfig.Rule rule = cfg.ruleFor("/api/health");
+        assertNotNull(rule);
+        assertSame(exactAuth, rule.authenticator());
+    }
+
+    @Test
+    void longerPrefixWins() {
+        Authenticator shortAuth = marker();
+        Authenticator longAuth = marker();
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .protectPrefix("/api/", shortAuth)
+                .protectPrefix("/api/v2/", longAuth)
+                .build();
+
+        assertSame(longAuth, cfg.ruleFor("/api/v2/users").authenticator());
+        assertSame(shortAuth, cfg.ruleFor("/api/v1/users").authenticator());
+    }
+
+    @Test
+    void protectUsesRequiredMode() {
+        AuthConfig cfg = AuthConfig.builder(marker()).protect("/admin").build();
+        assertEquals(AuthConfig.Mode.REQUIRED, cfg.ruleFor("/admin").mode());
+    }
+
+    @Test
+    void optionalUsesOptionalMode() {
+        AuthConfig cfg = AuthConfig.builder(marker()).optional("/feed").build();
+        assertEquals(AuthConfig.Mode.OPTIONAL, cfg.ruleFor("/feed").mode());
+    }
+
+    @Test
+    void requireEverywhereAppliesGlobalRequiredRule() {
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .requireEverywhere()
+                .build();
+        AuthConfig.Rule rule = cfg.ruleFor("/anything");
+        assertNotNull(rule);
+        assertEquals(AuthConfig.Mode.REQUIRED, rule.mode());
+    }
+
+    @Test
+    void optionalEverywhereAppliesGlobalOptionalRule() {
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .optionalEverywhere()
+                .build();
+        AuthConfig.Rule rule = cfg.ruleFor("/anything");
+        assertNotNull(rule);
+        assertEquals(AuthConfig.Mode.OPTIONAL, rule.mode());
+    }
+
+    @Test
+    void specificRuleBeatsGlobal() {
+        Authenticator specific = marker();
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .optionalEverywhere()
+                .protect("/admin", specific)
+                .build();
+
+        AuthConfig.Rule adminRule = cfg.ruleFor("/admin");
+        assertEquals(AuthConfig.Mode.REQUIRED, adminRule.mode());
+        assertSame(specific, adminRule.authenticator());
+        // Everything else still falls through to the optional global rule.
+        assertEquals(AuthConfig.Mode.OPTIONAL, cfg.ruleFor("/other").mode());
+    }
+
+    @Test
+    void defaultAuthenticatorUsedWhenNotOverridden() {
+        Authenticator def = marker();
+        AuthConfig cfg = AuthConfig.builder(def)
+                .protect("/admin")
+                .protectPrefix("/api/")
+                .build();
+        assertSame(def, cfg.ruleFor("/admin").authenticator());
+        assertSame(def, cfg.ruleFor("/api/x").authenticator());
+    }
+
+    @Test
+    void challengeIsStored() {
+        AuthConfig cfg = AuthConfig.builder(marker())
+                .protect("/admin")
+                .challenge("Basic realm=\"api\"")
+                .build();
+        assertEquals("Basic realm=\"api\"", cfg.challenge());
+    }
+
+    @Test
+    void challengeDefaultsToNull() {
+        AuthConfig cfg = AuthConfig.builder(marker()).build();
+        assertNull(cfg.challenge());
+    }
+
+    @Test
+    void builderRejectsNullDefaultAuthenticator() {
+        assertThrows(NullPointerException.class, () -> AuthConfig.builder(null));
+    }
+}

src/test/java/dev/coph/nextusweb/server/auth/AuthGateTest.java

@@ -0,0 +1,147 @@
+package dev.coph.nextusweb.server.auth;
+
+import dev.coph.nextusweb.server.router.Request;
+import dev.coph.nextusweb.server.router.Response;
+import io.netty.buffer.Unpooled;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.HttpVersion;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class AuthGateTest {
+
+    private Request request(String apiKey) {
+        FullHttpRequest raw = new DefaultFullHttpRequest(
+                HttpVersion.HTTP_1_1, HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);
+        if (apiKey != null) raw.headers().set("X-API-Key", apiKey);
+        return new Request(raw, Map.of());
+    }
+
+    private Authenticator apiKeyAuth() {
+        return Authenticator.apiKey("X-API-Key",
+                key -> key.equals("valid") ? Principal.of("user-1") : null);
+    }
+
+    @Test
+    void unprotectedPathProceedsWithoutPrincipal() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .protectPrefix("/admin")
+                .build());
+        Request req = request(null);
+        assertNull(gate.authenticate(req, "/public"));
+        assertNull(req.principal());
+    }
+
+    @Test
+    void protectedPathRejectsMissingCredentials() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .protectPrefix("/admin")
+                .build());
+        Response rejection = gate.authenticate(request(null), "/admin/users");
+        assertNotNull(rejection);
+        assertEquals(401, rejection.status());
+    }
+
+    @Test
+    void protectedPathRejectsInvalidCredentials() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .protect("/admin")
+                .build());
+        Response rejection = gate.authenticate(request("wrong"), "/admin");
+        assertNotNull(rejection);
+        assertEquals(401, rejection.status());
+    }
+
+    @Test
+    void protectedPathAttachesPrincipalOnSuccess() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .protect("/admin")
+                .build());
+        Request req = request("valid");
+        assertNull(gate.authenticate(req, "/admin"));
+        assertNotNull(req.principal());
+        assertEquals("user-1", req.principal().id());
+    }
+
+    @Test
+    void optionalPathProceedsAnonymouslyButAttachesWhenPresent() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .optionalPrefix("/feed")
+                .build());
+
+        Request anon = request(null);
+        assertNull(gate.authenticate(anon, "/feed"));
+        assertNull(anon.principal());
+
+        Request authed = request("valid");
+        assertNull(gate.authenticate(authed, "/feed"));
+        assertEquals("user-1", authed.principal().id());
+    }
+
+    @Test
+    void challengeHeaderAddedToUnauthorized() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .protect("/admin")
+                .challenge("ApiKey realm=\"api\"")
+                .build());
+        Response rejection = gate.authenticate(request(null), "/admin");
+        assertEquals("ApiKey realm=\"api\"", rejection.headers().get("WWW-Authenticate"));
+    }
+
+    @Test
+    void authenticatorErrorYields500() {
+        Authenticator boom = req -> {
+            throw new IllegalStateException("db down");
+        };
+        AuthGate gate = new AuthGate(AuthConfig.builder(boom).protect("/admin").build());
+        Response rejection = gate.authenticate(request(null), "/admin");
+        assertNotNull(rejection);
+        assertEquals(500, rejection.status());
+    }
+
+    @Test
+    void exactPathAuthenticatorIsUsedOverPrefix() {
+        // The prefix authenticator never authenticates; the exact-path one accepts the "valid"
+        // key. The exact rule must win so the request on the exact path can succeed.
+        Authenticator prefixDeny = req -> null;
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .protect("/api/health", apiKeyAuth())
+                .protectPrefix("/api/", prefixDeny)
+                .build());
+
+        Request exact = request("valid");
+        assertNull(gate.authenticate(exact, "/api/health"));
+        assertEquals("user-1", exact.principal().id());
+
+        // A sibling path under the prefix uses the (always-denying) prefix authenticator.
+        Response rejection = gate.authenticate(request("valid"), "/api/other");
+        assertNotNull(rejection);
+        assertEquals(401, rejection.status());
+    }
+
+    @Test
+    void requireEverywhereRejectsAnyPathWithoutCredentials() {
+        AuthGate gate = new AuthGate(AuthConfig.builder(apiKeyAuth())
+                .requireEverywhere()
+                .build());
+        assertEquals(401, gate.authenticate(request(null), "/whatever").status());
+        assertNull(gate.authenticate(request("valid"), "/whatever"));
+    }
+
+    @Test
+    void anyOfAuthenticatorAcceptsEitherCredential() {
+        Authenticator combined = Authenticator.anyOf(
+                apiKeyAuth(),
+                Authenticator.cookie("sid", s -> s.equals("sess") ? Principal.of("cookie-user") : null));
+        AuthGate gate = new AuthGate(AuthConfig.builder(combined).protect("/admin").build());
+
+        Request viaKey = request("valid");
+        assertNull(gate.authenticate(viaKey, "/admin"));
+        assertEquals("user-1", viaKey.principal().id());
+    }
+}

src/test/java/dev/coph/nextusweb/server/auth/AuthenticatorTest.java

@@ -0,0 +1,133 @@
+package dev.coph.nextusweb.server.auth;
+
+import dev.coph.nextusweb.server.router.Request;
+import io.netty.buffer.Unpooled;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.HttpVersion;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class AuthenticatorTest {
+
+    private Request request(String header, String value) {
+        FullHttpRequest raw = new DefaultFullHttpRequest(
+                HttpVersion.HTTP_1_1, HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);
+        if (header != null) raw.headers().set(header, value);
+        return new Request(raw, Map.of());
+    }
+
+    @Test
+    void apiKeyResolvesViaValidator() throws Exception {
+        Authenticator auth = Authenticator.apiKey("X-API-Key",
+                key -> key.equals("good") ? Principal.of("svc") : null);
+
+        assertEquals("svc", auth.authenticate(request("X-API-Key", "good")).id());
+        assertNull(auth.authenticate(request("X-API-Key", "bad")));
+        assertNull(auth.authenticate(request(null, null)));
+    }
+
+    @Test
+    void cookieResolvesViaValidator() throws Exception {
+        Authenticator auth = Authenticator.cookie("sid",
+                sid -> sid.equals("abc") ? Principal.of("u1") : null);
+
+        assertEquals("u1", auth.authenticate(request("Cookie", "sid=abc")).id());
+        assertNull(auth.authenticate(request("Cookie", "sid=zzz")));
+        assertNull(auth.authenticate(request(null, null)));
+    }
+
+    @Test
+    void basicDecodesCredentials() throws Exception {
+        Authenticator auth = Authenticator.basic(
+                (user, pass) -> user.equals("alice") && pass.equals("s3cret") ? Principal.of(user) : null);
+
+        String header = "Basic " + Base64.getEncoder()
+                .encodeToString("alice:s3cret".getBytes(StandardCharsets.UTF_8));
+        assertEquals("alice", auth.authenticate(request("Authorization", header)).id());
+
+        String wrong = "Basic " + Base64.getEncoder()
+                .encodeToString("alice:nope".getBytes(StandardCharsets.UTF_8));
+        assertNull(auth.authenticate(request("Authorization", wrong)));
+        assertNull(auth.authenticate(request("Authorization", "Basic not-base64!!")));
+        assertNull(auth.authenticate(request(null, null)));
+    }
+
+    @Test
+    void anyOfReturnsFirstMatch() throws Exception {
+        Authenticator key = Authenticator.apiKey("X-API-Key",
+                k -> k.equals("k") ? Principal.of("byKey") : null);
+        Authenticator cookie = Authenticator.cookie("sid",
+                s -> Principal.of("byCookie"));
+        Authenticator combined = Authenticator.anyOf(key, cookie);
+
+        assertEquals("byKey", combined.authenticate(request("X-API-Key", "k")).id());
+        assertEquals("byCookie", combined.authenticate(request("Cookie", "sid=x")).id());
+        assertNull(combined.authenticate(request(null, null)));
+    }
+
+    @Test
+    void bearerDecodesToken() throws Exception {
+        Authenticator auth = Authenticator.bearer(
+                token -> token.equals("tok123") ? Principal.of("u") : null);
+
+        assertEquals("u", auth.authenticate(request("Authorization", "Bearer tok123")).id());
+        assertNull(auth.authenticate(request("Authorization", "Bearer wrong")));
+        assertNull(auth.authenticate(request("Authorization", "Bearer ")));
+        assertNull(auth.authenticate(request("Authorization", "Basic abc")));
+        assertNull(auth.authenticate(request(null, null)));
+    }
+
+    @Test
+    void authSchemesAreCaseInsensitive() throws Exception {
+        Authenticator bearer = Authenticator.bearer(t -> Principal.of("b"));
+        assertEquals("b", bearer.authenticate(request("Authorization", "bearer tok")).id());
+
+        Authenticator basic = Authenticator.basic((u, p) -> Principal.of(u));
+        String header = "basic " + Base64.getEncoder()
+                .encodeToString("alice:pw".getBytes(StandardCharsets.UTF_8));
+        assertEquals("alice", basic.authenticate(request("Authorization", header)).id());
+    }
+
+    @Test
+    void basicReturnsNullWhenNoColon() throws Exception {
+        Authenticator auth = Authenticator.basic((u, p) -> Principal.of(u));
+        String header = "Basic " + Base64.getEncoder()
+                .encodeToString("nocolon".getBytes(StandardCharsets.UTF_8));
+        assertNull(auth.authenticate(request("Authorization", header)));
+    }
+
+    @Test
+    void basicAllowsEmptyPassword() throws Exception {
+        Authenticator auth = Authenticator.basic((u, p) -> Principal.of(u + ":" + p));
+        String header = "Basic " + Base64.getEncoder()
+                .encodeToString("user:".getBytes(StandardCharsets.UTF_8));
+        assertEquals("user:", auth.authenticate(request("Authorization", header)).id());
+    }
+
+    @Test
+    void apiKeyEmptyHeaderTreatedAsAbsent() throws Exception {
+        Authenticator auth = Authenticator.apiKey("X-API-Key", k -> Principal.of("never"));
+        assertNull(auth.authenticate(request("X-API-Key", "")));
+    }
+
+    @Test
+    void constantTimeEqualsMatchesIdenticalValues() {
+        assertTrue(Authenticator.constantTimeEquals("s3cr3t", "s3cr3t"));
+    }
+
+    @Test
+    void constantTimeEqualsRejectsDifferentValuesAndNulls() {
+        assertFalse(Authenticator.constantTimeEquals("s3cr3t", "s3cr3T"));
+        assertFalse(Authenticator.constantTimeEquals("short", "longer-value"));
+        assertFalse(Authenticator.constantTimeEquals(null, "x"));
+        assertFalse(Authenticator.constantTimeEquals("x", null));
+        assertFalse(Authenticator.constantTimeEquals(null, null));
+    }
+}

src/test/java/dev/coph/nextusweb/server/auth/PrincipalTest.java

@@ -0,0 +1,61 @@
+package dev.coph.nextusweb.server.auth;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PrincipalTest {
+
+    @Test
+    void ofIdOnlyHasNoRolesOrClaims() {
+        Principal p = Principal.of("user-1");
+        assertEquals("user-1", p.id());
+        assertTrue(p.roles().isEmpty());
+        assertTrue(p.claims().isEmpty());
+        assertFalse(p.hasRole("admin"));
+    }
+
+    @Test
+    void ofWithRolesExposesRolesAndHasRole() {
+        Principal p = Principal.of("user-2", Set.of("admin", "ops"));
+        assertEquals("user-2", p.id());
+        assertEquals(Set.of("admin", "ops"), p.roles());
+        assertTrue(p.hasRole("admin"));
+        assertTrue(p.hasRole("ops"));
+        assertFalse(p.hasRole("guest"));
+    }
+
+    @Test
+    void rolesAreDefensivelyCopiedAndImmutable() {
+        Set<String> source = new HashSet<>(Set.of("admin"));
+        Principal p = Principal.of("user-3", source);
+
+        // Mutating the source after construction must not affect the principal.
+        source.add("sneaky");
+        assertEquals(Set.of("admin"), p.roles());
+
+        // The exposed set must be unmodifiable.
+        assertThrows(UnsupportedOperationException.class, () -> p.roles().add("x"));
+    }
+
+    @Test
+    void customImplementationIsSupported() {
+        Principal custom = new Principal() {
+            @Override
+            public String id() {
+                return "svc";
+            }
+
+            @Override
+            public Set<String> roles() {
+                return Set.of("service");
+            }
+        };
+        assertEquals("svc", custom.id());
+        assertTrue(custom.hasRole("service"));
+        assertTrue(custom.claims().isEmpty());
+    }
+}

src/test/java/dev/coph/nextusweb/server/net/ClientIpTest.java

@@ -0,0 +1,56 @@
+package dev.coph.nextusweb.server.net;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ClientIpTest {
+
+    @Test
+    void usesSocketIpWhenNoForwardedHeader() {
+        assertEquals("203.0.113.5",
+                ClientIp.resolve("203.0.113.5", null, TrustedProxies.all()));
+    }
+
+    @Test
+    void ignoresForwardedHeaderWhenPeerNotTrusted() {
+        // A direct (untrusted) client cannot spoof its IP via X-Forwarded-For.
+        assertEquals("203.0.113.5",
+                ClientIp.resolve("203.0.113.5", "1.2.3.4", TrustedProxies.none()));
+    }
+
+    @Test
+    void usesForwardedHeaderWhenPeerTrusted() {
+        TrustedProxies trusted = TrustedProxies.of("10.0.0.0/8");
+        assertEquals("1.2.3.4",
+                ClientIp.resolve("10.0.0.1", "1.2.3.4", trusted));
+    }
+
+    @Test
+    void returnsFirstUntrustedHopFromTheRight() {
+        // Chain: realClient, edgeProxy, internalProxy(=peer). Both proxies are trusted, so the
+        // resolved client is the first untrusted entry walking from the right.
+        TrustedProxies trusted = TrustedProxies.of("10.0.0.0/8");
+        String xff = "9.9.9.9, 10.0.0.9, 10.0.0.8";
+        assertEquals("9.9.9.9",
+                ClientIp.resolve("10.0.0.8", xff, trusted));
+    }
+
+    @Test
+    void spoofedLeadingEntriesAreIgnored() {
+        // Attacker prepends a fake hop; since the genuine client hop (8.8.8.8) is the first
+        // untrusted from the right, the forged "1.1.1.1" is never returned.
+        TrustedProxies trusted = TrustedProxies.of("10.0.0.0/8");
+        String xff = "1.1.1.1, 8.8.8.8, 10.0.0.8";
+        assertEquals("8.8.8.8",
+                ClientIp.resolve("10.0.0.8", xff, trusted));
+    }
+
+    @Test
+    void allHopsTrustedFallsBackToLeftmost() {
+        TrustedProxies trusted = TrustedProxies.of("10.0.0.0/8");
+        String xff = "10.0.0.7, 10.0.0.8";
+        assertEquals("10.0.0.7",
+                ClientIp.resolve("10.0.0.8", xff, trusted));
+    }
+}

src/test/java/dev/coph/nextusweb/server/net/TrustedProxiesTest.java

@@ -0,0 +1,64 @@
+package dev.coph.nextusweb.server.net;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class TrustedProxiesTest {
+
+    @Test
+    void noneTrustsNothing() {
+        TrustedProxies tp = TrustedProxies.none();
+        assertFalse(tp.isTrusted("127.0.0.1"));
+        assertFalse(tp.isTrusted("10.0.0.1"));
+    }
+
+    @Test
+    void allTrustsEverything() {
+        TrustedProxies tp = TrustedProxies.all();
+        assertTrue(tp.isTrusted("8.8.8.8"));
+        assertTrue(tp.isTrusted("::1"));
+    }
+
+    @Test
+    void matchesIpv4Cidr() {
+        TrustedProxies tp = TrustedProxies.of("10.0.0.0/8");
+        assertTrue(tp.isTrusted("10.1.2.3"));
+        assertTrue(tp.isTrusted("10.255.255.255"));
+        assertFalse(tp.isTrusted("11.0.0.1"));
+        assertFalse(tp.isTrusted("192.168.0.1"));
+    }
+
+    @Test
+    void matchesBareHostAsSingleAddress() {
+        TrustedProxies tp = TrustedProxies.of("127.0.0.1");
+        assertTrue(tp.isTrusted("127.0.0.1"));
+        assertFalse(tp.isTrusted("127.0.0.2"));
+    }
+
+    @Test
+    void matchesIpv6Cidr() {
+        TrustedProxies tp = TrustedProxies.of("fd00::/8");
+        assertTrue(tp.isTrusted("fd12:3456::1"));
+        assertFalse(tp.isTrusted("fe80::1"));
+    }
+
+    @Test
+    void differentFamilyDoesNotMatch() {
+        TrustedProxies tp = TrustedProxies.of("10.0.0.0/8");
+        assertFalse(tp.isTrusted("::1"));
+    }
+
+    @Test
+    void invalidAddressIsNotTrusted() {
+        TrustedProxies tp = TrustedProxies.of("10.0.0.0/8");
+        assertFalse(tp.isTrusted("not-an-ip"));
+        assertFalse(tp.isTrusted(null));
+    }
+
+    @Test
+    void rejectsInvalidCidr() {
+        assertThrows(IllegalArgumentException.class, () -> TrustedProxies.of("10.0.0.0/40"));
+        assertThrows(IllegalArgumentException.class, () -> TrustedProxies.of("garbage"));
+    }
+}

src/test/java/dev/coph/nextusweb/server/ratelimit/KeyResolverTest.java

@@ -1,53 +1,70 @@
 package dev.coph.nextusweb.server.ratelimit;
 
-import io.netty.handler.codec.http.DefaultHttpRequest;
+import dev.coph.nextusweb.server.auth.Principal;
+import dev.coph.nextusweb.server.router.Request;
+import io.netty.buffer.Unpooled;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
 import io.netty.handler.codec.http.HttpMethod;
-import io.netty.handler.codec.http.HttpRequest;
 import io.netty.handler.codec.http.HttpVersion;
 import org.junit.jupiter.api.Test;
 
+import java.util.Map;
+import java.util.Set;
+
 import static org.junit.jupiter.api.Assertions.*;
 
 class KeyResolverTest {
 
-    private HttpRequest req(String header, String value) {
-        HttpRequest r = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/");
-        if (header != null) r.headers().set(header, value);
-        return r;
+    private Request request() {
+        FullHttpRequest raw = new DefaultFullHttpRequest(
+                HttpVersion.HTTP_1_1, HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);
+        return new Request(raw, Map.of());
+    }
+
+    private Request requestWith(String header, String value) {
+        FullHttpRequest raw = new DefaultFullHttpRequest(
+                HttpVersion.HTTP_1_1, HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);
+        raw.headers().set(header, value);
+        return new Request(raw, Map.of());
     }
 
     @Test
-    void clientIpUsesRemoteWhenNoForwardedHeader() {
-        assertEquals("10.0.0.1", KeyResolver.clientIp().resolve(req(null, null), "10.0.0.1"));
+    void clientIpReturnsResolvedIpVerbatim() {
+        assertEquals("10.0.0.1", KeyResolver.clientIp().resolve(request(), "10.0.0.1"));
     }
 
     @Test
-    void clientIpUsesForwardedHeaderFirstValue() {
-        HttpRequest r = req("X-Forwarded-For", "1.1.1.1, 2.2.2.2");
-        assertEquals("1.1.1.1", KeyResolver.clientIp().resolve(r, "10.0.0.1"));
+    void headerResolverUsesHeaderValue() {
+        Request r = requestWith("X-API-Key", "secret123");
+        assertEquals("h:secret123", KeyResolver.header("X-API-Key").resolve(r, "10.0.0.1"));
     }
 
     @Test
-    void clientIpHandlesSingleForwardedValue() {
-        HttpRequest r = req("X-Forwarded-For", "3.3.3.3");
-        assertEquals("3.3.3.3", KeyResolver.clientIp().resolve(r, "10.0.0.1"));
+    void headerResolverFallsBackToClientIp() {
+        assertEquals("ip:10.0.0.1", KeyResolver.header("X-API-Key").resolve(request(), "10.0.0.1"));
     }
 
     @Test
-    void userOrIpReturnsBearerToken() {
-        HttpRequest r = req("Authorization", "Bearer abc123");
-        assertEquals("u:abc123", KeyResolver.userOrIp().resolve(r, "10.0.0.1"));
+    void cookieResolverUsesCookieValue() {
+        Request r = requestWith("Cookie", "sid=abc; other=x");
+        assertEquals("c:abc", KeyResolver.cookie("sid").resolve(r, "10.0.0.1"));
     }
 
     @Test
-    void userOrIpFallsBackToClientIp() {
-        HttpRequest r = req(null, null);
-        assertEquals("ip:10.0.0.1", KeyResolver.userOrIp().resolve(r, "10.0.0.1"));
+    void cookieResolverFallsBackToClientIp() {
+        assertEquals("ip:10.0.0.1", KeyResolver.cookie("sid").resolve(request(), "10.0.0.1"));
     }
 
     @Test
-    void userOrIpIgnoresNonBearerAuth() {
-        HttpRequest r = req("Authorization", "Basic xyz");
-        assertEquals("ip:10.0.0.1", KeyResolver.userOrIp().resolve(r, "10.0.0.1"));
+    void principalResolverUsesPrincipalId() {
+        Request r = request();
+        r.principal(Principal.of("user-42", Set.of("admin")));
+        assertEquals("p:user-42", KeyResolver.principal().resolve(r, "10.0.0.1"));
+    }
+
+    @Test
+    void principalResolverFallsBackToClientIpWhenAnonymous() {
+        assertEquals("ip:10.0.0.1", KeyResolver.principal().resolve(request(), "10.0.0.1"));
     }
 }

src/test/java/dev/coph/nextusweb/server/ratelimit/RateLimitConfigTest.java

@@ -75,4 +75,30 @@ class RateLimitConfigTest {
         assertEquals("global", rules.get(0).name());
         assertEquals("/x", rules.get(1).name());
     }
+
+    @Test
+    void allLimitersCollectsEveryDistinctLimiter() {
+        // Distinct concrete instances (non-capturing lambdas would be the same JVM singleton).
+        RateLimiter a = new FixedWindowLimiter(1, 1000);
+        RateLimiter b = new FixedWindowLimiter(1, 1000);
+        RateLimiter c = new FixedWindowLimiter(1, 1000);
+        RateLimitConfig cfg = RateLimitConfig.builder()
+                .global(a, keyer())
+                .forPath("/x", b, keyer())
+                .forPrefix("/api/", c, keyer())
+                .build();
+        assertEquals(3, cfg.allLimiters().size());
+        assertTrue(cfg.allLimiters().containsAll(List.of(a, b, c)));
+    }
+
+    @Test
+    void allLimitersDeduplicatesSharedInstance() {
+        RateLimiter shared = alwaysAllow();
+        RateLimitConfig cfg = RateLimitConfig.builder()
+                .global(shared, keyer())
+                .forPath("/x", shared, keyer())
+                .forPrefix("/api/", shared, keyer())
+                .build();
+        assertEquals(1, cfg.allLimiters().size());
+    }
 }

src/test/java/dev/coph/nextusweb/server/ratelimit/RateLimitGateTest.java

@@ -1,18 +1,24 @@
 package dev.coph.nextusweb.server.ratelimit;
 
+import dev.coph.nextusweb.server.router.Request;
 import dev.coph.nextusweb.server.router.Response;
-import io.netty.handler.codec.http.DefaultHttpRequest;
+import io.netty.buffer.Unpooled;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
 import io.netty.handler.codec.http.HttpMethod;
-import io.netty.handler.codec.http.HttpRequest;
 import io.netty.handler.codec.http.HttpVersion;
 import org.junit.jupiter.api.Test;
 
+import java.util.Map;
+
 import static org.junit.jupiter.api.Assertions.*;
 
 class RateLimitGateTest {
 
-    private HttpRequest req() {
-        return new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/");
+    private Request req() {
+        FullHttpRequest raw = new DefaultFullHttpRequest(
+                HttpVersion.HTTP_1_1, HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);
+        return new Request(raw, Map.of());
     }
 
     @Test

src/test/java/dev/coph/nextusweb/server/router/RequestTest.java

@@ -1,5 +1,6 @@
 package dev.coph.nextusweb.server.router;
 
+import dev.coph.nextusweb.server.auth.Principal;
 import dev.coph.nextusweb.server.router.exception.BadRequestException;
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.http.DefaultFullHttpRequest;
@@ -101,4 +102,48 @@ class RequestTest {
         Request req = new Request(build(HttpMethod.POST, "/", "not-json"), Map.of());
         assertThrows(BadRequestException.class, () -> req.jsonAs(Payload.class));
     }
+
+    @Test
+    void cookieParsesNamedCookie() {
+        FullHttpRequest raw = build(HttpMethod.GET, "/", null);
+        raw.headers().set("Cookie", "sid=abc123; theme=dark");
+        Request req = new Request(raw, Map.of());
+        assertEquals("abc123", req.cookie("sid"));
+        assertEquals("dark", req.cookie("theme"));
+        assertNull(req.cookie("missing"));
+    }
+
+    @Test
+    void cookieReturnsNullWhenNoCookieHeader() {
+        Request req = new Request(build(HttpMethod.GET, "/", null), Map.of());
+        assertNull(req.cookie("sid"));
+    }
+
+    @Test
+    void attributesSetGetAndRemove() {
+        Request req = new Request(build(HttpMethod.GET, "/", null), Map.of());
+        assertNull(req.attribute("k"));
+        req.attribute("k", "v");
+        assertEquals("v", req.<String>attribute("k"));
+        req.attribute("k", null);
+        assertNull(req.attribute("k"));
+    }
+
+    @Test
+    void clientIpRoundTrips() {
+        Request req = new Request(build(HttpMethod.GET, "/", null), Map.of());
+        assertNull(req.clientIp());
+        req.clientIp("203.0.113.9");
+        assertEquals("203.0.113.9", req.clientIp());
+    }
+
+    @Test
+    void principalRoundTripsAndDrivesIsAuthenticated() {
+        Request req = new Request(build(HttpMethod.GET, "/", null), Map.of());
+        assertFalse(req.isAuthenticated());
+        assertNull(req.principal());
+        req.principal(Principal.of("user-7"));
+        assertTrue(req.isAuthenticated());
+        assertEquals("user-7", req.principal().id());
+    }
 }

src/test/java/dev/coph/nextusweb/server/security/SecurityHeadersTest.java

@@ -0,0 +1,105 @@
+package dev.coph.nextusweb.server.security;
+
+import dev.coph.nextusweb.server.router.Response;
+import org.junit.jupiter.api.Test;
+
+import java.time.Duration;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class SecurityHeadersTest {
+
+    @Test
+    void defaultsApplyConservativeHeaders() {
+        Response res = new Response();
+        SecurityHeaders.defaults().apply(res, false);
+
+        assertEquals("nosniff", res.headers().get("X-Content-Type-Options"));
+        assertEquals("DENY", res.headers().get("X-Frame-Options"));
+        assertEquals("no-referrer", res.headers().get("Referrer-Policy"));
+        assertNull(res.headers().get("Content-Security-Policy"));
+    }
+
+    @Test
+    void hstsIsOmittedOnInsecureConnections() {
+        Response res = new Response();
+        SecurityHeaders.defaults().apply(res, false);
+        assertNull(res.headers().get("Strict-Transport-Security"));
+    }
+
+    @Test
+    void hstsIsEmittedOnSecureConnections() {
+        Response res = new Response();
+        SecurityHeaders.defaults().apply(res, true);
+        assertEquals("max-age=31536000", res.headers().get("Strict-Transport-Security"));
+    }
+
+    @Test
+    void hstsRendersIncludeSubDomainsAndPreload() {
+        SecurityHeaders sh = SecurityHeaders.builder()
+                .hsts(Duration.ofDays(365), true, true)
+                .build();
+        Response res = new Response();
+        sh.apply(res, true);
+        assertEquals("max-age=31536000; includeSubDomains; preload",
+                res.headers().get("Strict-Transport-Security"));
+    }
+
+    @Test
+    void noHstsDisablesTheHeaderEvenWhenSecure() {
+        SecurityHeaders sh = SecurityHeaders.builder().noHsts().build();
+        Response res = new Response();
+        sh.apply(res, true);
+        assertNull(res.headers().get("Strict-Transport-Security"));
+    }
+
+    @Test
+    void existingHandlerHeadersAreNotOverwritten() {
+        Response res = new Response();
+        res.header("X-Frame-Options", "SAMEORIGIN");
+
+        SecurityHeaders.defaults().apply(res, true);
+
+        assertEquals("SAMEORIGIN", res.headers().get("X-Frame-Options"));
+        // Other headers the handler did not set are still added.
+        assertEquals("nosniff", res.headers().get("X-Content-Type-Options"));
+    }
+
+    @Test
+    void existingHstsHeaderIsNotOverwritten() {
+        Response res = new Response();
+        res.header("Strict-Transport-Security", "max-age=60");
+        SecurityHeaders.defaults().apply(res, true);
+        assertEquals("max-age=60", res.headers().get("Strict-Transport-Security"));
+    }
+
+    @Test
+    void disabledHeadersAreOmitted() {
+        SecurityHeaders sh = SecurityHeaders.builder()
+                .contentTypeOptions(false)
+                .frameOptions(null)
+                .referrerPolicy("  ")
+                .noHsts()
+                .build();
+        Response res = new Response();
+        sh.apply(res, true);
+
+        assertNull(res.headers().get("X-Content-Type-Options"));
+        assertNull(res.headers().get("X-Frame-Options"));
+        assertNull(res.headers().get("Referrer-Policy"));
+        assertNull(res.headers().get("Strict-Transport-Security"));
+    }
+
+    @Test
+    void contentSecurityPolicyAndCustomHeaderAreApplied() {
+        SecurityHeaders sh = SecurityHeaders.builder()
+                .contentSecurityPolicy("default-src 'self'")
+                .header("Permissions-Policy", "geolocation=()")
+                .build();
+        Response res = new Response();
+        sh.apply(res, false);
+
+        assertEquals("default-src 'self'", res.headers().get("Content-Security-Policy"));
+        assertEquals("geolocation=()", res.headers().get("Permissions-Policy"));
+    }
+}

src/test/java/dev/coph/nextusweb/server/tls/TlsConfigTest.java

@@ -0,0 +1,22 @@
+package dev.coph.nextusweb.server.tls;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class TlsConfigTest {
+
+    @Test
+    void fromPemWithMissingFilesThrowsIllegalState() {
+        File missingCert = new File("does-not-exist-cert.pem");
+        File missingKey = new File("does-not-exist-key.pem");
+        assertThrows(IllegalStateException.class, () -> TlsConfig.fromPem(missingCert, missingKey));
+    }
+
+    @Test
+    void fromSslContextRejectsNull() {
+        assertThrows(NullPointerException.class, () -> TlsConfig.fromSslContext(null));
+    }
+}

src/test/java/dev/coph/nextusweb/server/websocket/WebSocketGroupTest.java

@@ -17,7 +17,7 @@ class WebSocketGroupTest {
     }
 
     private WebSocketSession session(EmbeddedChannel ch) {
-        return new WebSocketSession(ch, "/ws", Map.of());
+        return new WebSocketSession(ch, "/ws", Map.of(), null);
     }
 
     @Test

src/test/java/dev/coph/nextusweb/server/websocket/WebSocketHandlerTest.java

@@ -13,7 +13,7 @@ class WebSocketHandlerTest {
     void defaultMethodsDoNotThrow() {
         WebSocketHandler handler = new WebSocketHandler() {};
         EmbeddedChannel ch = new EmbeddedChannel();
-        WebSocketSession session = new WebSocketSession(ch, "/ws", Map.of());
+        WebSocketSession session = new WebSocketSession(ch, "/ws", Map.of(), null);
         assertDoesNotThrow(() -> handler.onOpen(session));
         assertDoesNotThrow(() -> handler.onMessage(session, "msg"));
         assertDoesNotThrow(() -> handler.onBinary(session, new byte[]{1}));

src/test/java/dev/coph/nextusweb/server/websocket/WebSocketSessionTest.java

@@ -15,7 +15,7 @@ import static org.junit.jupiter.api.Assertions.*;
 class WebSocketSessionTest {
 
     private WebSocketSession session(EmbeddedChannel ch) {
-        return new WebSocketSession(ch, "/ws/{id}", Map.of("id", "42"));
+        return new WebSocketSession(ch, "/ws/{id}", Map.of("id", "42"), null);
     }
 
     @Test