diff --git a/docs/REMEDIATION_PLAN.md b/docs/REMEDIATION_PLAN.md
index addc9b3..da4a9b0 100644
--- a/docs/REMEDIATION_PLAN.md
+++ b/docs/REMEDIATION_PLAN.md
@@ -20,7 +20,7 @@ Key: `S` ≤ half day · `M` ~1–3 days · `L` ~1 week+ · 🔴 launch-blocker
 - [x] **0.1 🔴 S — Verify amount received ≥ expected before confirming.** ✅ Gate on `status.complete` in `paymentHandlers.js`; underpaid → stay pending + `payment_underpaid` warning (once). `received_amount` now recorded for single-game + credits. Regression test added (`payment_flow.integration.test.js`). _113 tests green._
 - [x] **0.2 🔴 M — Make provably-fair real.** ✅ Per-game seeded RNG (`seedToInt`) threaded through `dungeon.js` (Digger reseed + all `Math.random()` → `rng`), `monster.js` (`seededShuffle`), `game.js` (chase + generation). `DungeonGenerator.regenerateFromSeed` + `layoutFingerprint`; `/api/verify` regenerates & returns fingerprint. Determinism test suite added (`provablyFair.test.js`). _Verifier can now reproduce the exact dungeon from the seed._
 - [x] **0.3 🔴 M — Fix batch-payout `tx_hash` collision + double-pay.** ✅ Migration 015 drops the payouts `tx_hash` unique index (batches legitimately share a tx_hash) and extends the one-per-game guard to cover `processing`. Batch completion now happens in ONE transaction via `id = ANY` (no row stranded mid-batch); BIGINT stat math (no float). Ambiguous batch failures → `needs_review` (retry service won't re-send) + operator alert. New `batchPayout.test.js` covers both paths.
-- [ ] **0.4 🔴 S — Harden identity transport.** Move `anon_token` from query string to handshake `auth` (`src/network/sessionManager.js:24`); call `rotateToken` on resume.
+- [x] **0.4 🔴 S — Harden identity transport.** ✅ Client sends `anon_token` in handshake `auth` (not the URL query → no proxy/referer/access-log leakage); server reads `auth` first with a query-string fallback for older clients. Token is now **rotated on every resume** (`rotateToken`), so a leaked token is invalidated when the real owner reconnects; client already persists the returned token. Rotation + old-token-replay-rejection test added to `security.test.js`.
 - [ ] **0.5 🟠 S — Single-game disconnect recovery.** Extend `recoverPendingPayments` (`src/network/sessionManager.js:158`) to handle `single_game`; stop silently deleting in-progress paid games (`src/network/socketHandlers.js:787`).
 - [ ] **0.6 🟠 S — Client + admin XSS and CSP.** Escape chat/admin fields (`html/js/network/socketHandlers.js:291,323`; `html/admin.html`); add CSP headers.
 
diff --git a/html/index.html b/html/index.html
index 77d0ee9..96d9d03 100644
--- a/html/index.html
+++ b/html/index.html
@@ -20,7 +20,11 @@
                 window._localStorageAvailable = true;
                 const existing = localStorage.getItem('wownerogue_token');
                 if (existing) {
-                    opts.query = { resumeToken: existing };
+                    // Send the session token in the handshake `auth` payload, NOT the URL
+                    // query string. Query strings leak into proxy/access/referer logs;
+                    // auth is carried in the connection body. (Server keeps a query-string
+                    // fallback for older clients during rollout.)
+                    opts.auth = { resumeToken: existing };
                 }
             } catch(_) {
                 window._localStorageAvailable = false;
diff --git a/src/network/connectionHandler.js b/src/network/connectionHandler.js
index 81027ed..0d2a491 100644
--- a/src/network/connectionHandler.js
+++ b/src/network/connectionHandler.js
@@ -172,7 +172,11 @@ class ConnectionHandler {
 
     _getResumeToken(socket) {
         try {
-            return socket.handshake.query?.resumeToken || null;
+            // Prefer the handshake `auth` payload (not logged by proxies); fall back to the
+            // query string for backward compatibility with older clients during rollout.
+            return socket.handshake.auth?.resumeToken
+                || socket.handshake.query?.resumeToken
+                || null;
         } catch (_) {
             return null;
         }
diff --git a/src/network/sessionManager.js b/src/network/sessionManager.js
index 19c4b58..647cb9c 100644
--- a/src/network/sessionManager.js
+++ b/src/network/sessionManager.js
@@ -53,10 +53,24 @@ class SessionManager {
             }
           }
 
+          // SECURITY: Rotate the token on every resume. The session token is a bearer
+          // credential — rotating it limits the window in which a leaked/observed token is
+          // usable (a leaked token is invalidated the next time the real owner reconnects).
+          // The client persists the returned token from the `session_resumed` event.
+          let issuedToken = resumeToken;
+          try {
+            issuedToken = await this.rotateToken(user.id);
+            user.anon_token = issuedToken;
+            this.sessions.set(socketId, user);
+          } catch (rotErr) {
+            // If rotation fails, keep the existing token rather than locking the user out.
+            console.error('[SessionManager] Token rotation failed, keeping existing token:', rotErr.message);
+          }
+
           if (this.debugManager.CONSOLE_LOGGING) console.log(`[SessionManager] Resumed session for user ${user.id}`);
           return {
             resumed: true,
-            token: resumeToken,
+            token: issuedToken,
             user: {
               ...user,
               socket_id: socketId
diff --git a/test/security.test.js b/test/security.test.js
index d5ddf68..633a736 100644
--- a/test/security.test.js
+++ b/test/security.test.js
@@ -71,6 +71,9 @@ function createMockDb() {
                         const addrIdx = params.findIndex((_, i) => text.includes(`payout_address = $${i + 1}`));
                         if (addrIdx >= 0) user.payout_address = params[addrIdx];
                     }
+                    if (text.includes('anon_token =')) {
+                        user.anon_token = params[0];
+                    }
                 }
                 return { rows: user ? [user] : [] };
             }
@@ -239,6 +242,36 @@ describe('SQL Injection Prevention', () => {
             }
         });
 
+        test('should rotate the session token on resume (bearer-token replay protection)', async () => {
+            // Create a session to obtain a real token.
+            const created = await sessionManager.resumeOrCreate({
+                socketId: 'rotate-socket-1',
+                ipAddress: '127.0.0.1',
+                resumeToken: null
+            });
+            expect(created.resumed).toBe(false);
+            const firstToken = created.token;
+            expect(firstToken).toBeTruthy();
+
+            // Resume with that token — should succeed and hand back a DIFFERENT token.
+            const resumed = await sessionManager.resumeOrCreate({
+                socketId: 'rotate-socket-2',
+                ipAddress: '127.0.0.1',
+                resumeToken: firstToken
+            });
+            expect(resumed.resumed).toBe(true);
+            expect(resumed.token).toBeTruthy();
+            expect(resumed.token).not.toBe(firstToken); // rotated
+
+            // The OLD token must no longer resume (it was invalidated).
+            const replay = await sessionManager.resumeOrCreate({
+                socketId: 'rotate-socket-3',
+                ipAddress: '127.0.0.1',
+                resumeToken: firstToken
+            });
+            expect(replay.resumed).toBe(false);
+        });
+
         test('should safely handle malicious socket ID', async () => {
             const maliciousSocketId = "'; DROP TABLE users; --";