fix(providers): fall back to public Code Suggestions endpoint on GitLab Duo direct_access 401 (#10365)

changelog.d/fixes/10365-gitlab-duo-401-fallback.md

@@ -0,0 +1 @@
+- fix(providers): GitLab Duo falls back to the public Code Suggestions endpoint when direct_access returns 401 (#10365)

open-sse/executors/gitlab.ts

@@ -583,10 +583,20 @@ export class GitlabExecutor extends BaseExecutor {
       }
 
       if (response.status === 401) {
+        if (input.log) {
+          input.log.warn(
+            "GITLAB-DUO",
+            "direct_access exchange rejected (401); falling back to public completions endpoint"
+          );
+        }
         return {
-          target: null,
+          target: {
+            mode: "monolith",
+            url: endpoints.publicCompletionsUrl,
+            headers: buildMonolithHeaders(credentials.accessToken || null),
+          },
           credentials,
-          errorResponse: toOpenAIError(401, "GitLab Duo direct access token request was rejected"),
+          errorResponse: null,
         };
       }
 

tests/unit/executor-gitlab.test.ts

@@ -261,3 +261,54 @@ test("GitlabExecutor falls back to the public Code Suggestions endpoint when dir
     globalThis.fetch = originalFetch;
   }
 });
+
+// #10365: a 401 from the direct_access exchange must ALSO fall back to the public
+// Code Suggestions completions endpoint (same resilience as the 403-disabled case
+// above), instead of surfacing an opaque 401 token error with no fallback.
+test("GitlabExecutor falls back to the public Code Suggestions endpoint when direct_access returns 401", async () => {
+  const executor = getExecutor("gitlab-duo") as GitlabExecutor;
+  const originalFetch = globalThis.fetch;
+  const calls: string[] = [];
+
+  globalThis.fetch = async (url) => {
+    calls.push(String(url));
+
+    if (String(url) === "https://gitlab.example.com/api/v4/code_suggestions/direct_access") {
+      return jsonResponse({ error: "invalid_token" }, 401);
+    }
+
+    return jsonResponse({
+      model: { name: "code-gecko" },
+      choices: [{ text: "monolith fallback works" }],
+    });
+  };
+
+  try {
+    const result = await executor.execute({
+      model: "gitlab-duo-code-suggestions",
+      body: {
+        messages: [{ role: "user", content: "Say hello" }],
+      },
+      stream: false,
+      credentials: {
+        accessToken: "oauth-access",
+        providerSpecificData: {
+          baseUrl: "https://gitlab.example.com",
+        },
+      },
+      signal: AbortSignal.timeout(10_000),
+      log: null,
+    });
+
+    assert.deepEqual(calls, [
+      "https://gitlab.example.com/api/v4/code_suggestions/direct_access",
+      "https://gitlab.example.com/api/v4/code_suggestions/completions",
+    ]);
+
+    const body = (await result.response.json()) as any;
+    assert.equal(body.model, "code-gecko");
+    assert.match(body.choices[0].message.content, /monolith fallback works/i);
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});