fix(openai-codex): normalize legacy copilot transport

extensions/openai/openai-codex-provider.test.ts

@@ -521,6 +521,32 @@ describe("openai codex provider", () => {
     });
   });
 
+  it("normalizes legacy GitHub Copilot Codex metadata to the codex transport", () => {
+    const provider = buildOpenAICodexProviderPlugin();
+
+    const model = provider.normalizeResolvedModel?.({
+      provider: "openai-codex",
+      model: {
+        id: "gpt-5.4",
+        name: "gpt-5.4",
+        provider: "openai-codex",
+        api: "openai-completions",
+        baseUrl: "https://api.githubcopilot.com",
+        reasoning: true,
+        input: ["text", "image"],
+        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+        contextWindow: 1_050_000,
+        contextTokens: 272_000,
+        maxTokens: 128_000,
+      },
+    } as never);
+
+    expect(model).toMatchObject({
+      api: "openai-codex-responses",
+      baseUrl: "https://chatgpt.com/backend-api/codex",
+    });
+  });
+
   it("normalizes transport metadata for stale /backend-api/v1 codex routes", () => {
     const provider = buildOpenAICodexProviderPlugin();
 
@@ -551,6 +577,21 @@ describe("openai codex provider", () => {
     });
   });
 
+  it("normalizes transport metadata for legacy GitHub Copilot Codex routes", () => {
+    const provider = buildOpenAICodexProviderPlugin();
+
+    expect(
+      provider.normalizeTransport?.({
+        provider: "openai-codex",
+        api: "openai-completions",
+        baseUrl: "https://api.githubcopilot.com/v1",
+      } as never),
+    ).toEqual({
+      api: "openai-codex-responses",
+      baseUrl: "https://chatgpt.com/backend-api/codex",
+    });
+  });
+
   it("leaves custom proxy completions transport metadata unchanged", () => {
     const provider = buildOpenAICodexProviderPlugin();
 

extensions/openai/openai-codex-provider.ts

@@ -96,6 +96,11 @@ const OPENAI_CODEX_MODERN_MODEL_IDS = [
   OPENAI_CODEX_GPT_53_SPARK_MODEL_ID,
 ] as const;
 
+function isLegacyCodexCompatBaseUrl(baseUrl?: string): boolean {
+  const trimmed = baseUrl?.trim();
+  return !!trimmed && /^https?:\/\/api\.githubcopilot\.com(?:\/v1)?\/?$/iu.test(trimmed);
+}
+
 function normalizeCodexTransportFields(params: {
   api?: ProviderRuntimeModel["api"] | null;
   baseUrl?: string;
@@ -104,7 +109,10 @@ function normalizeCodexTransportFields(params: {
   baseUrl?: string;
 } {
   const useCodexTransport =
-    !params.baseUrl || isOpenAIApiBaseUrl(params.baseUrl) || isOpenAICodexBaseUrl(params.baseUrl);
+    !params.baseUrl ||
+    isOpenAIApiBaseUrl(params.baseUrl) ||
+    isOpenAICodexBaseUrl(params.baseUrl) ||
+    isLegacyCodexCompatBaseUrl(params.baseUrl);
   const api =
     useCodexTransport &&
     (!params.api || params.api === "openai-responses" || params.api === "openai-completions")