fix(validation): strip trailing /models in Gemini validator to avoid /models/models 404 (#2545)

src/lib/providers/validation.ts

@@ -741,11 +741,15 @@ async function validateGeminiLikeProvider({
       return { valid: false, error: "Missing base URL" };
     }
 
+    // Strip a trailing /models before appending — the default Gemini registry baseUrl is
+    // `.../v1beta/models` (for the chat urlBuilder), so naively appending /models produced
+    // `.../v1beta/models/models` → upstream 404 on connection validation (#2545).
+    const baseForModels = baseUrl.replace(/\/models\/?$/, "");
     const requestUrl =
       typeof providerSpecificData?.modelsUrl === "string" &&
       providerSpecificData.modelsUrl.trim() !== ""
         ? providerSpecificData.modelsUrl.trim()
-        : `${baseUrl}/models`;
+        : `${baseForModels}/models`;
 
     const urlWithKey =
       authType === "query" ? `${requestUrl}?key=${encodeURIComponent(apiKey)}` : requestUrl;

tests/unit/provider-validation-hardening.test.ts

@@ -163,3 +163,28 @@ test("#2463 openai-compatible validation does not throw on non-string modelsUrl"
   });
   assert.equal(typeof result.valid, "boolean");
 });
+
+// Regression for #2545: the default Gemini (AI Studio) base URL ends in /v1beta/models,
+// so the validator must not append a second /models (which produced /models/models → 404).
+test("#2545 gemini validation does not produce /models/models", async () => {
+  const calls: string[] = [];
+  globalThis.fetch = async (url: any) => {
+    calls.push(String(url));
+    return new Response(JSON.stringify({ models: [] }), { status: 200 });
+  };
+  const result = await validateProviderApiKey({
+    provider: "gemini",
+    apiKey: "AIzaTestKey",
+    providerSpecificData: {},
+  });
+  assert.equal(typeof result.valid, "boolean");
+  assert.ok(calls.length > 0, "validator must make a request");
+  assert.ok(
+    !calls.some((u) => u.includes("/models/models")),
+    `outbound URL must not contain /models/models — got ${calls.join(", ")}`
+  );
+  assert.ok(
+    calls.some((u) => /\/v1beta\/models(\?|$)/.test(u)),
+    `outbound URL must hit a single /models segment — got ${calls.join(", ")}`
+  );
+});