diff --git a/changelog.d/fixes/7548-claude-web-ua.md b/changelog.d/fixes/7548-claude-web-ua.md
new file mode 100644
index 0000000000..c5f2d5f623
--- /dev/null
+++ b/changelog.d/fixes/7548-claude-web-ua.md
@@ -0,0 +1 @@
+- fix(claude-web): unify Turnstile solver, executor and httpBackedChat fast-path User-Agents behind one shared fingerprint module so `cf_clearance` is never solved under a different UA than the one that replays it (#7548)
diff --git a/open-sse/config/claudeWebFingerprint.ts b/open-sse/config/claudeWebFingerprint.ts
new file mode 100644
index 0000000000..1e8d996d8f
--- /dev/null
+++ b/open-sse/config/claudeWebFingerprint.ts
@@ -0,0 +1,30 @@
+/**
+ * Claude Web — shared browser fingerprint source of truth
+ *
+ * Cloudflare binds the `cf_clearance` cookie minted by the Turnstile solver
+ * to the User-Agent (+ TLS/JA3 fingerprint + IP) that solved the challenge.
+ * If the completion request later replays that cookie under a *different*
+ * User-Agent, Cloudflare rejects it and the executor surfaces a persistent
+ * 429 (see #7548).
+ *
+ * Every part of the claude-web pipeline that talks to claude.ai — the
+ * Turnstile solver, the direct-fetch executor, and the httpBackedChat
+ * fast path — MUST derive its User-Agent / Client-Hints headers from this
+ * single constant so they can never drift apart again.
+ *
+ * Platform choice: Linux, matching the `chrome_146` TLS/JA3 profile used by
+ * `claudeTlsClient.ts` and the browser-pool default (`browserPool.ts`).
+ */
+export const CLAUDE_WEB_FINGERPRINT = {
+  userAgent:
+    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36",
+  secChUa: '"Chromium";v="149", "Not-A.Brand";v="24", "Google Chrome";v="149"',
+  secChUaPlatform: '"Linux"',
+} as const;
+
+/**
+ * Bump this whenever `CLAUDE_WEB_FINGERPRINT` changes so any previously
+ * cached `cf_clearance` token (minted under the old fingerprint) is treated
+ * as stale rather than replayed under the new one.
+ */
+export const CLAUDE_WEB_FINGERPRINT_VERSION = "v2-linux-unified";
diff --git a/open-sse/executors/claude-web.ts b/open-sse/executors/claude-web.ts
index 7e26777339..b28f585078 100644
--- a/open-sse/executors/claude-web.ts
+++ b/open-sse/executors/claude-web.ts
@@ -23,6 +23,7 @@ import { BaseExecutor, mergeAbortSignals, type ExecuteInput } from "./base.ts";
 import { FETCH_TIMEOUT_MS } from "../config/constants.ts";
 import { tlsFetchClaude } from "../services/claudeTlsClient.ts";
 import { getCfClearanceToken } from "../services/claudeTurnstileSolver.ts";
+import { CLAUDE_WEB_FINGERPRINT } from "../config/claudeWebFingerprint.ts";
 import { normalizeSessionCookieHeader } from "@/lib/providers/webCookieAuth";
 import { randomUUID } from "crypto";
 import { sanitizeErrorMessage } from "../utils/error.ts";
@@ -37,8 +38,7 @@ import {
 const CLAUDE_WEB_API_BASE = "https://claude.ai/api";
 const CLAUDE_WEB_ORGS_URL = `${CLAUDE_WEB_API_BASE}/organizations`;
 
-const CLAUDE_USER_AGENT =
-  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36";
+const CLAUDE_USER_AGENT = CLAUDE_WEB_FINGERPRINT.userAgent;
 
 // Session cookie constants
 const CLAUDE_SESSION_COOKIE_NAME = "sessionKey";
@@ -108,9 +108,9 @@ function getBrowserHeaders(deviceId?: string): Record<string, string> {
     Pragma: "no-cache",
     Priority: "u=1, i",
     Referer: "https://claude.ai/new",
-    "Sec-Ch-Ua": '"Chromium";v="149", "Not-A.Brand";v="24", "Google Chrome";v="149"',
+    "Sec-Ch-Ua": CLAUDE_WEB_FINGERPRINT.secChUa,
     "Sec-Ch-Ua-Mobile": "?0",
-    "Sec-Ch-Ua-Platform": '"Linux"',
+    "Sec-Ch-Ua-Platform": CLAUDE_WEB_FINGERPRINT.secChUaPlatform,
     "Sec-Fetch-Dest": "empty",
     "Sec-Fetch-Mode": "cors",
     "Sec-Fetch-Site": "same-origin",
diff --git a/open-sse/services/browserBackedChat.ts b/open-sse/services/browserBackedChat.ts
index 71e63b46d3..567e22338a 100644
--- a/open-sse/services/browserBackedChat.ts
+++ b/open-sse/services/browserBackedChat.ts
@@ -26,6 +26,7 @@ import {
 } from "./browserPool.ts";
 import tlsClient from "../utils/tlsClient.ts";
 import { sanitizeErrorMessage } from "../utils/error.ts";
+import { resolveHttpBackedChatFingerprint } from "./httpBackedChatFingerprint.ts";
 
 // Safety constants
 const MAX_RESPONSE_BYTES = 10 * 1024 * 1024; // 10 MB
@@ -441,11 +442,10 @@ export async function httpBackedChat(
   const t0 = Date.now();
 
   const { chatUrl, userMessage, cookieString, cookieDomain, chatUrlMatchDomain, signal } = req;
-
+  const fingerprint = resolveHttpBackedChatFingerprint(chatUrlMatchDomain); // #7548
   // Build browser-emulated headers
   const headers: Record<string, string> = {
-    "User-Agent":
-      "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36",
+    "User-Agent": fingerprint.userAgent,
     Accept: "text/event-stream, application/json, text/plain, */*",
     "Accept-Language": "en-US,en;q=0.9",
     "Content-Type": "application/json",
@@ -460,9 +460,9 @@ export async function httpBackedChat(
     "Sec-Fetch-Dest": "empty",
     "Sec-Fetch-Mode": "cors",
     "Sec-Fetch-Site": "same-origin",
-    "Sec-Ch-Ua": '"Chromium";v="149", "Google Chrome";v="149", "Not-A.Brand";v="99"',
+    "Sec-Ch-Ua": fingerprint.secChUa,
     "Sec-Ch-Ua-Mobile": "?0",
-    "Sec-Ch-Ua-Platform": '"macOS"',
+    "Sec-Ch-Ua-Platform": fingerprint.secChUaPlatform,
     Priority: "u=1, i",
   };
 
diff --git a/open-sse/services/claudeTurnstileSolver.ts b/open-sse/services/claudeTurnstileSolver.ts
index 2f3af01fa3..a9164839a3 100644
--- a/open-sse/services/claudeTurnstileSolver.ts
+++ b/open-sse/services/claudeTurnstileSolver.ts
@@ -11,6 +11,10 @@
  */
 
 import type { Browser, Page } from "playwright";
+import {
+  CLAUDE_WEB_FINGERPRINT,
+  CLAUDE_WEB_FINGERPRINT_VERSION,
+} from "../config/claudeWebFingerprint.ts";
 
 const CLAUDE_WEB_URL = "https://claude.ai";
 const CHALLENGE_TIMEOUT = 60000; // 60s to solve challenge
@@ -85,8 +89,7 @@ export async function solveTurnstile(options?: {
     const { chromium } = await import("playwright");
     browser = await chromium.launch({ headless });
     const context = await browser.newContext({
-      userAgent:
-        "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36",
+      userAgent: CLAUDE_WEB_FINGERPRINT.userAgent,
       viewport: { width: 1280, height: 720 },
       ignoreHTTPSErrors: process.env.OMNIROUTE_TURNSTILE_IGNORE_TLS_ERRORS === "true",
     });
@@ -149,7 +152,7 @@ export async function getCfClearanceToken(options?: {
   force?: boolean;
   headless?: boolean;
 }): Promise<string> {
-  const cacheKey = "claude-cf-clearance";
+  const cacheKey = `claude-cf-clearance-${CLAUDE_WEB_FINGERPRINT_VERSION}`;
   const cached = tokenCache.get(cacheKey);
 
   if (cfClearanceTokenOverride) {
@@ -193,7 +196,7 @@ export function getCacheStatus(): {
   hasCached: boolean;
   expiresIn?: number;
 } {
-  const cacheKey = "claude-cf-clearance";
+  const cacheKey = `claude-cf-clearance-${CLAUDE_WEB_FINGERPRINT_VERSION}`;
   const cached = tokenCache.get(cacheKey);
 
   if (!cached) {
diff --git a/open-sse/services/httpBackedChatFingerprint.ts b/open-sse/services/httpBackedChatFingerprint.ts
new file mode 100644
index 0000000000..ea2cb408b3
--- /dev/null
+++ b/open-sse/services/httpBackedChatFingerprint.ts
@@ -0,0 +1,29 @@
+/**
+ * Header fingerprint resolution for `httpBackedChat()`.
+ *
+ * claude.ai MUST reuse the exact fingerprint the Turnstile solver used to
+ * mint `cf_clearance` (see `open-sse/config/claudeWebFingerprint.ts`) —
+ * otherwise Cloudflare rejects the replayed cookie and every request 429s
+ * (#7548). Other `httpBackedChat` callers (e.g. duckduckgo-web) keep their
+ * own independent fingerprint, which never needs to match a solved cookie.
+ */
+import { CLAUDE_WEB_FINGERPRINT } from "../config/claudeWebFingerprint.ts";
+
+export interface HttpBackedChatFingerprint {
+  userAgent: string;
+  secChUa: string;
+  secChUaPlatform: string;
+}
+
+const DUCKDUCKGO_FALLBACK_FINGERPRINT: HttpBackedChatFingerprint = {
+  userAgent:
+    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36",
+  secChUa: '"Chromium";v="149", "Google Chrome";v="149", "Not-A.Brand";v="99"',
+  secChUaPlatform: '"macOS"',
+};
+
+export function resolveHttpBackedChatFingerprint(
+  chatUrlMatchDomain: string
+): HttpBackedChatFingerprint {
+  return chatUrlMatchDomain === "claude.ai" ? CLAUDE_WEB_FINGERPRINT : DUCKDUCKGO_FALLBACK_FINGERPRINT;
+}
diff --git a/tests/unit/claude-web-turnstile-ua-mismatch-7548.test.ts b/tests/unit/claude-web-turnstile-ua-mismatch-7548.test.ts
new file mode 100644
index 0000000000..ad732ec507
--- /dev/null
+++ b/tests/unit/claude-web-turnstile-ua-mismatch-7548.test.ts
@@ -0,0 +1,70 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { dirname, join } from "node:path";
+import { CLAUDE_WEB_FINGERPRINT } from "../../open-sse/config/claudeWebFingerprint.ts";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const REPO_ROOT = join(__dirname, "..", "..");
+const readSource = (rel: string) => readFileSync(join(REPO_ROOT, rel), "utf8");
+
+function detectPlatform(ua: string): string {
+  if (/Windows/i.test(ua)) return "Windows";
+  if (/Macintosh|Mac OS X/i.test(ua)) return "macOS";
+  if (/X11; Linux/i.test(ua)) return "Linux";
+  return "unknown";
+}
+
+const IMPORT_PATTERN = /import\s*\{\s*CLAUDE_WEB_FINGERPRINT[^}]*\}\s*from\s*"[^"]*config\/claudeWebFingerprint\.ts"/;
+
+test("claude-web: Turnstile solver derives its UA from the shared fingerprint module (#7548)", () => {
+  const solverSrc = readSource("open-sse/services/claudeTurnstileSolver.ts");
+
+  assert.ok(
+    IMPORT_PATTERN.test(solverSrc),
+    "claudeTurnstileSolver.ts must import CLAUDE_WEB_FINGERPRINT from the shared module"
+  );
+  assert.match(solverSrc, /userAgent:\s*CLAUDE_WEB_FINGERPRINT\.userAgent/);
+  // No stray hardcoded UA literal left behind (that's exactly how #7548 regressed).
+  assert.ok(
+    !/Mozilla\/5\.0[^"]*"/.test(solverSrc),
+    "solver must not hardcode a UA literal anymore — it must come from CLAUDE_WEB_FINGERPRINT"
+  );
+});
+
+test("claude-web: executor CLAUDE_USER_AGENT and Sec-Ch-Ua-Platform derive from the shared fingerprint (#7548)", () => {
+  const executorSrc = readSource("open-sse/executors/claude-web.ts");
+
+  assert.ok(
+    IMPORT_PATTERN.test(executorSrc),
+    "claude-web.ts must import CLAUDE_WEB_FINGERPRINT from the shared module"
+  );
+  assert.match(executorSrc, /const CLAUDE_USER_AGENT = CLAUDE_WEB_FINGERPRINT\.userAgent;/);
+  assert.match(executorSrc, /"Sec-Ch-Ua-Platform":\s*CLAUDE_WEB_FINGERPRINT\.secChUaPlatform/);
+});
+
+test("claude-web: httpBackedChat fast path uses the shared fingerprint for the claude.ai branch (#7548)", () => {
+  const fastPathSrc = readSource("open-sse/services/browserBackedChat.ts");
+  const resolverSrc = readSource("open-sse/services/httpBackedChatFingerprint.ts");
+
+  assert.match(
+    fastPathSrc,
+    /resolveHttpBackedChatFingerprint/,
+    "browserBackedChat.ts must resolve headers via resolveHttpBackedChatFingerprint()"
+  );
+  assert.ok(
+    IMPORT_PATTERN.test(resolverSrc),
+    "httpBackedChatFingerprint.ts must import CLAUDE_WEB_FINGERPRINT from the shared module"
+  );
+  assert.match(resolverSrc, /chatUrlMatchDomain === "claude\.ai" \? CLAUDE_WEB_FINGERPRINT/);
+});
+
+test("claude-web: solver, executor and fast-path UAs are all the same value at runtime, platform Linux (#7548)", () => {
+  // This is the actual regression: before the fix these three literals were
+  // "Windows", "Linux" and "macOS" respectively — a cf_clearance token minted
+  // under one UA got replayed under a different one and Cloudflare rejected
+  // it, surfacing as a persistent 429 on every claude-web request.
+  assert.equal(detectPlatform(CLAUDE_WEB_FINGERPRINT.userAgent), "Linux");
+  assert.equal(CLAUDE_WEB_FINGERPRINT.secChUaPlatform, '"Linux"');
+});