diff --git a/open-sse/config/codexClient.ts b/open-sse/config/codexClient.ts
index 5c71e931a5..e824f2b68b 100644
--- a/open-sse/config/codexClient.ts
+++ b/open-sse/config/codexClient.ts
@@ -33,13 +33,67 @@ export function getCodexClientVersion(): string {
   );
 }
 
-export function getCodexUserAgent(): string {
+/**
+ * Extract the Codex client version the CALLER actually reported, so OmniRoute
+ * forwards it upstream instead of substituting a pinned default. The official
+ * CLI sends it in User-Agent, e.g.
+ *   codex_cli_rs/0.154.0 (Mac OS 26.6.2; arm64) ...
+ *   codex_exec/0.154.0 (Mac OS 26.6.2; arm64) xterm-256color (codex_exec; 0.154.0)
+ * Some clients also send a `version` header.
+ *
+ * Why this matters: the ChatGPT backend gates newer models on the client
+ * version ("The 'gpt-6-astra' model requires a newer version of Codex").
+ * A pinned default silently rots every time the user upgrades their CLI.
+ *
+ * Returns null when the caller sent nothing usable, so callers can fall back
+ * to getCodexClientVersion().
+ */
+const CODEX_CLIENT_VERSION_IN_UA_PATTERN = /(?:codex[-_][A-Za-z0-9_]*|codex-cli)\/(\d+\.\d+\.\d+)/i;
+
+export function getCodexClientVersionFromHeaders(
+  clientHeaders?: Record<string, string> | null
+): string | null {
+  if (!clientHeaders) return null;
+
+  const pick = (name: string): string | null => {
+    const direct = clientHeaders[name];
+    if (typeof direct === "string" && direct.trim()) return direct.trim();
+    const lower = name.toLowerCase();
+    for (const [k, v] of Object.entries(clientHeaders)) {
+      if (k.toLowerCase() === lower && typeof v === "string" && v.trim()) {
+        return v.trim();
+      }
+    }
+    return null;
+  };
+
+  const fromVersionHeader = pick("version");
+  if (fromVersionHeader && SAFE_HEADER_TOKEN_PATTERN.test(fromVersionHeader)) {
+    return fromVersionHeader;
+  }
+
+  const userAgent = pick("user-agent");
+  if (!userAgent) return null;
+
+  const match = CODEX_CLIENT_VERSION_IN_UA_PATTERN.exec(userAgent);
+  if (!match) return null;
+
+  const version = match[1];
+  return SAFE_HEADER_TOKEN_PATTERN.test(version) ? version : null;
+}
+
+export function getCodexUserAgent(versionOverride?: string | null): string {
   const override = getSafeEnvValue(CODEX_USER_AGENT_OVERRIDE_ENV, SAFE_HEADER_VALUE_PATTERN);
   if (override) {
     return override;
   }
 
-  return `codex-cli/${getCodexClientVersion()} (${DEFAULT_CODEX_USER_AGENT_PLATFORM}; ${DEFAULT_CODEX_USER_AGENT_ARCH})`;
+  const version =
+    versionOverride && SAFE_HEADER_TOKEN_PATTERN.test(versionOverride)
+      ? versionOverride
+      : getCodexClientVersion();
+
+  return `codex-cli/${version} (${DEFAULT_CODEX_USER_AGENT_PLATFORM}; ${DEFAULT_CODEX_USER_AGENT_ARCH})`;
 }
 
 export function getCodexDefaultHeaders(): Record<string, string> {
diff --git a/open-sse/executors/codex.ts b/open-sse/executors/codex.ts
index 6940ee89f5..5e6c4175ac 100644
--- a/open-sse/executors/codex.ts
+++ b/open-sse/executors/codex.ts
@@ -23,9 +23,11 @@ import { stripCodexPassthroughRejectedParams } from "./codex/stripPassthroughRej
 import {
   CODEX_CLI_RS_ORIGINATOR,
   getCodexClientVersion,
+  getCodexClientVersionFromHeaders,
   getCodexUserAgent,
   normalizeCodexSessionId,
 } from "../config/codexClient.ts";
+import type { KeyHealth } from "../services/apiKeyRotator.ts";
 import {
   applyCodexClientIdentityHeaders,
   applyCodexClientMetadata,
@@ -1117,11 +1119,30 @@ export class CodexExecutor extends BaseExecutor {
    * Always request event-stream from upstream, even when client requested stream=false.
    * Includes chatgpt-account-id header for strict workspace binding.
    */
-  buildHeaders(credentials: ProviderCredentials, stream = true) {
+  buildHeaders(
+    credentials: ProviderCredentials,
+    stream = true,
+    clientHeaders?: Record<string, string> | null,
+    model?: string,
+    health?: Record<string, KeyHealth>
+  ) {
     const isCompactRequest = isCompactResponsesEndpoint(credentials?.requestEndpointPath);
-    const headers = super.buildHeaders(credentials, isCompactRequest ? false : true);
-    headers.Version = getCodexClientVersion();
-    setUserAgentHeader(headers, getCodexUserAgent());
+    const headers = super.buildHeaders(
+      credentials,
+      isCompactRequest ? false : true,
+      clientHeaders,
+      model,
+      health
+    );
+
+    // Forward the CALLER's own Codex client version upstream instead of a pinned
+    // default. The ChatGPT backend gates newer models on the reported client
+    // version (e.g. "The 'gpt-6-astra' model requires a newer version of Codex"),
+    // so a hardcoded value silently rots whenever the user upgrades their CLI.
+    // Falls back to the configured/default version when the caller sends none.
+    const clientVersion = getCodexClientVersionFromHeaders(clientHeaders);
+    headers.Version = clientVersion ?? getCodexClientVersion();
+    setUserAgentHeader(headers, getCodexUserAgent(clientVersion));
 
     // Add workspace binding header if workspaceId is persisted
     const workspaceId = credentials?.providerSpecificData?.workspaceId;
diff --git a/tests/unit/codex-client-headers.test.ts b/tests/unit/codex-client-headers.test.ts
new file mode 100644
index 0000000000..02db806724
--- /dev/null
+++ b/tests/unit/codex-client-headers.test.ts
@@ -0,0 +1,113 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+import { getCodexClientVersionFromHeaders } from "../../open-sse/config/codexClient.ts";
+import { CodexExecutor } from "../../open-sse/executors/codex.ts";
+
+test("getCodexClientVersionFromHeaders: extracts the version from a real Codex CLI User-Agent", () => {
+  assert.equal(
+    getCodexClientVersionFromHeaders({
+      "user-agent": "codex_cli_rs/0.154.0 (Mac OS 26.6.2; arm64)",
+    }),
+    "0.154.0"
+  );
+  assert.equal(
+    getCodexClientVersionFromHeaders({
+      "user-agent":
+        "codex_exec/0.154.0 (Mac OS 26.6.2; arm64) xterm-256color (codex_exec; 0.154.0)",
+    }),
+    "0.154.0"
+  );
+});
+
+test("getCodexClientVersionFromHeaders: prefers a valid generic version header over User-Agent", () => {
+  assert.equal(
+    getCodexClientVersionFromHeaders({
+      version: "9.9.9",
+      "user-agent": "codex_cli_rs/0.154.0 (Mac OS 26.6.2; arm64)",
+    }),
+    "9.9.9"
+  );
+});
+
+test("getCodexClientVersionFromHeaders: returns null when headers are absent or empty", () => {
+  assert.equal(getCodexClientVersionFromHeaders(null), null);
+  assert.equal(getCodexClientVersionFromHeaders(undefined), null);
+  assert.equal(getCodexClientVersionFromHeaders({}), null);
+});
+
+test("getCodexClientVersionFromHeaders: returns null for a non-Codex User-Agent with no version header", () => {
+  assert.equal(getCodexClientVersionFromHeaders({ "user-agent": "curl/8.4.0" }), null);
+});
+
+test("getCodexClientVersionFromHeaders: rejects a CRLF injection attempt in the version header", () => {
+  assert.equal(getCodexClientVersionFromHeaders({ version: "1.0.0\r\nX-Injected: evil" }), null);
+});
+
+test("getCodexClientVersionFromHeaders: rejects a version header longer than the 32-char safe token limit", () => {
+  const overlong = "1.0.0-" + "a".repeat(30);
+  assert.ok(overlong.length > 32);
+  assert.equal(getCodexClientVersionFromHeaders({ version: overlong }), null);
+});
+
+test("getCodexClientVersionFromHeaders: a CRLF/oversized User-Agent injection only ever yields the captured digits", () => {
+  assert.equal(
+    getCodexClientVersionFromHeaders({
+      "user-agent": "codex_cli_rs/1.0.0\r\nX-Evil: 1",
+    }),
+    "1.0.0"
+  );
+});
+
+test("CodexExecutor.buildHeaders forwards the caller's Codex client version from clientHeaders", () => {
+  const executor = new CodexExecutor();
+
+  const fromUserAgent = executor.buildHeaders({ accessToken: "codex-token" }, true, {
+    "user-agent": "codex_cli_rs/0.160.2 (Mac OS 26.6.2; arm64)",
+  });
+  assert.equal(fromUserAgent.Version, "0.160.2");
+  assert.equal(fromUserAgent["User-Agent"], "codex-cli/0.160.2 (Windows 10.0.26200; x64)");
+
+  const fromVersionHeader = executor.buildHeaders({ accessToken: "codex-token" }, true, {
+    version: "9.9.9",
+  });
+  assert.equal(fromVersionHeader.Version, "9.9.9");
+  assert.equal(fromVersionHeader["User-Agent"], "codex-cli/9.9.9 (Windows 10.0.26200; x64)");
+});
+
+test("CodexExecutor.buildHeaders falls back to the default client version when clientHeaders is absent, empty, or unusable", () => {
+  const executor = new CodexExecutor();
+
+  const noHeaders = executor.buildHeaders({ accessToken: "codex-token" }, true);
+  assert.equal(noHeaders.Version, "0.153.4");
+
+  const emptyHeaders = executor.buildHeaders({ accessToken: "codex-token" }, true, {});
+  assert.equal(emptyHeaders.Version, "0.153.4");
+
+  const nonCodexUserAgent = executor.buildHeaders({ accessToken: "codex-token" }, true, {
+    "user-agent": "curl/8.4.0",
+  });
+  assert.equal(nonCodexUserAgent.Version, "0.153.4");
+});
+
+test("CodexExecutor.buildHeaders rejects injection attempts in the caller's version/User-Agent headers", () => {
+  const executor = new CodexExecutor();
+
+  const crlfVersion = executor.buildHeaders({ accessToken: "codex-token" }, true, {
+    version: "1.0.0\r\nX-Injected: evil",
+  });
+  assert.equal(crlfVersion.Version, "0.153.4");
+  assert.equal(crlfVersion["User-Agent"].includes("\r\n"), false);
+
+  const overlongVersion = executor.buildHeaders({ accessToken: "codex-token" }, true, {
+    version: "1.0.0-" + "a".repeat(30),
+  });
+  assert.equal(overlongVersion.Version, "0.153.4");
+
+  const injectedUserAgent = executor.buildHeaders({ accessToken: "codex-token" }, true, {
+    "user-agent": "codex_cli_rs/1.0.0\r\nX-Evil: 1",
+  });
+  assert.equal(injectedUserAgent.Version, "1.0.0");
+  assert.equal(injectedUserAgent["User-Agent"].includes("\r\n"), false);
+  assert.equal(injectedUserAgent["User-Agent"], "codex-cli/1.0.0 (Windows 10.0.26200; x64)");
+});