fix: merge provider config api into registry model

Fixes #1695

src/agents/pi-embedded-runner/model.test.ts

@@ -127,4 +127,40 @@ describe("resolveModel", () => {
     expect(result.model?.provider).toBe("custom");
     expect(result.model?.id).toBe("missing-model");
   });
+
+  it("inherits provider api when registry model has no api (issue #1695)", async () => {
+    const { discoverModels } = await import("@mariozechner/pi-coding-agent");
+    const mockModel = {
+      id: "test-model",
+      name: "test-model",
+      provider: "lmstudio",
+      reasoning: false,
+      input: ["text"],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: 4096,
+      maxTokens: 4096,
+      // No api field set
+    };
+
+    vi.mocked(discoverModels).mockReturnValue({
+      find: vi.fn(() => mockModel),
+    } as any);
+
+    const cfg = {
+      models: {
+        providers: {
+          lmstudio: {
+            api: "openai-responses",
+            baseUrl: "http://localhost:1234",
+          },
+        },
+      },
+    } as MoltbotConfig;
+
+    const result = resolveModel("lmstudio", "test-model", "/tmp/agent", cfg);
+
+    expect(result.model?.api).toBe("openai-responses");
+    expect(result.model?.id).toBe("test-model");
+    expect(result.model?.provider).toBe("lmstudio");
+  });
 });

src/agents/pi-embedded-runner/model.ts

@@ -97,5 +97,7 @@ export function resolveModel(
       modelRegistry,
     };
   }
-  return { model: normalizeModelCompat(model), authStorage, modelRegistry };
+  const providerCfg = cfg?.models?.providers?.[provider];
+  const merged = { ...model, api: model.api ?? providerCfg?.api };
+  return { model: normalizeModelCompat(merged), authStorage, modelRegistry };
 }