fix(agents): let forward-compat resolve api when inline model omits it

When a user configures `models.providers.openai-codex` with a models
array but omits the `api` field, `buildInlineProviderModels` produces
an entry with `api: undefined`.  The inline-match early return then
hands this incomplete model straight to the caller, skipping the
forward-compat resolver that would supply the correct
`openai-codex-responses` api — causing a crash loop.

Let the inline match fall through to forward-compat when `api` is
absent so the resolver chain can fill it in.

Fixes #39682

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

@@ -638,6 +638,32 @@ describe("resolveModel", () => {
     });
   });
 
+  it("uses codex fallback when inline model omits api (#39682)", () => {
+    mockOpenAICodexTemplateModel();
+
+    // When a user lists gpt-5.4 under openai-codex models without specifying
+    // an api, the inline match must not shadow the forward-compat resolver
+    // that supplies "openai-codex-responses".
+    const cfg: OpenClawConfig = {
+      models: {
+        providers: {
+          "openai-codex": {
+            baseUrl: "https://custom.example.com",
+            models: [{ id: "gpt-5.4" }],
+          },
+        },
+      },
+    } as unknown as OpenClawConfig;
+
+    const result = resolveModel("openai-codex", "gpt-5.4", "/tmp/agent", cfg);
+    expect(result.error).toBeUndefined();
+    expect(result.model).toMatchObject({
+      api: "openai-codex-responses",
+      id: "gpt-5.4",
+      provider: "openai-codex",
+    });
+  });
+
   it("includes auth hint for unknown ollama models (#17328)", () => {
     // resetMockDiscoverModels() in beforeEach already sets find → null
     const result = resolveModel("ollama", "gemma3:4b", "/tmp/agent");

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

@@ -161,7 +161,12 @@ export function resolveModelWithRegistry(params: {
     (entry) => normalizeProviderId(entry.provider) === normalizedProvider && entry.id === modelId,
   );
   if (inlineMatch) {
-    return normalizeModelCompat(inlineMatch as Model<Api>);
+    // When the inline model already carries a concrete api, use it as-is.
+    // Otherwise fall through so forward-compat resolvers can supply the
+    // correct api (e.g. "openai-codex-responses" for gpt-5.4).  #39682
+    if (inlineMatch.api) {
+      return normalizeModelCompat(inlineMatch as Model<Api>);
+    }
   }
 
   // Forward-compat fallbacks must be checked BEFORE the generic providerCfg fallback.