fix: normalize stale openai completions transport

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

@@ -54,9 +54,33 @@ function normalizeOpenAICodexTransport(params: {
   } as Model<Api>;
 }
 
+function normalizeOpenAITransport(params: { provider: string; model: Model<Api> }): Model<Api> {
+  if (normalizeProviderId(params.provider) !== "openai") {
+    return params.model;
+  }
+
+  const useResponsesTransport =
+    params.model.api === "openai-completions" &&
+    (!params.model.baseUrl || isOpenAIApiBaseUrl(params.model.baseUrl));
+
+  if (!useResponsesTransport) {
+    return params.model;
+  }
+
+  return {
+    ...params.model,
+    api: "openai-responses",
+  } as Model<Api>;
+}
+
 export function normalizeResolvedProviderModel(params: {
   provider: string;
   model: Model<Api>;
 }): Model<Api> {
-  return normalizeModelCompat(normalizeOpenAICodexTransport(params));
+  const normalizedOpenAI = normalizeOpenAITransport(params);
+  const normalizedCodex = normalizeOpenAICodexTransport({
+    provider: params.provider,
+    model: normalizedOpenAI,
+  });
+  return normalizeModelCompat(normalizedCodex);
 }

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

@@ -518,6 +518,54 @@ describe("resolveModel", () => {
     });
   });
 
+  it("normalizes stale native openai gpt-5.4 completions transport to responses", () => {
+    mockDiscoveredModel({
+      provider: "openai",
+      modelId: "gpt-5.4",
+      templateModel: buildForwardCompatTemplate({
+        id: "gpt-5.4",
+        name: "GPT-5.4",
+        provider: "openai",
+        api: "openai-completions",
+        baseUrl: "https://api.openai.com/v1",
+      }),
+    });
+
+    const result = resolveModel("openai", "gpt-5.4", "/tmp/agent");
+
+    expect(result.error).toBeUndefined();
+    expect(result.model).toMatchObject({
+      provider: "openai",
+      id: "gpt-5.4",
+      api: "openai-responses",
+      baseUrl: "https://api.openai.com/v1",
+    });
+  });
+
+  it("keeps proxied openai completions transport untouched", () => {
+    mockDiscoveredModel({
+      provider: "openai",
+      modelId: "gpt-5.4",
+      templateModel: buildForwardCompatTemplate({
+        id: "gpt-5.4",
+        name: "GPT-5.4",
+        provider: "openai",
+        api: "openai-completions",
+        baseUrl: "https://proxy.example.com/v1",
+      }),
+    });
+
+    const result = resolveModel("openai", "gpt-5.4", "/tmp/agent");
+
+    expect(result.error).toBeUndefined();
+    expect(result.model).toMatchObject({
+      provider: "openai",
+      id: "gpt-5.4",
+      api: "openai-completions",
+      baseUrl: "https://proxy.example.com/v1",
+    });
+  });
+
   it("builds an anthropic forward-compat fallback for claude-opus-4-6", () => {
     mockDiscoveredModel({
       provider: "anthropic",