diff --git a/src/integrations/pi.ts b/src/integrations/pi.ts
index ab63869..40f23a7 100644
--- a/src/integrations/pi.ts
+++ b/src/integrations/pi.ts
@@ -18,6 +18,7 @@ export type ThinkingLevelMap = Partial<Record<PiThinkingLevel, string | null>>;
 
 export type PiModelEntry = {
   id: string;
+  api?: string;
   contextWindow?: number;
   name?: string;
   input?: string[];
@@ -90,6 +91,7 @@ export function deriveThinkingFields(
 }
 
 const isDeepSeekModel = (id: string): boolean => id.startsWith("deepseek");
+const isGptModel = (id: string): boolean => id.startsWith("gpt-");
 
 /** Project one daemon model onto a pi config entry. */
 export function buildPiModelEntry(
@@ -113,6 +115,15 @@ export function buildPiModelEntry(
   if (mods.includes("image")) input.push("image");
   entry.input = input;
 
+  // gpt-* models are served through OpenAI's Responses API; the provider-level
+  // `api: "openai-completions"` stays the default for everything else. For
+  // non-gpt models keep whatever per-model api the user curated.
+  if (isGptModel(model.id)) {
+    entry.api = "openai-responses";
+  } else if (previous?.api !== undefined) {
+    entry.api = previous.api;
+  }
+
   const derived = deriveThinkingFields(model);
   if (derived) {
     entry.reasoning = derived.reasoning;
diff --git a/tests/integrations/pi.test.ts b/tests/integrations/pi.test.ts
index abbc673..88495e8 100644
--- a/tests/integrations/pi.test.ts
+++ b/tests/integrations/pi.test.ts
@@ -246,6 +246,7 @@ describe("buildPiModelEntry", () => {
 
     expect(entry).toEqual({
       id: "gpt-5.6-sol",
+      api: "openai-responses",
       name: "OpenAI: GPT-5.6 Sol",
       contextWindow: 1050000,
       input: ["text", "image"],
@@ -313,4 +314,23 @@ describe("buildPiModelEntry", () => {
     expect("reasoning" in entry).toBe(false);
     expect("thinkingLevelMap" in entry).toBe(false);
   });
+
+  it("pins api=openai-responses for gpt-* models, overriding any curated value", () => {
+    const previous: PiModelEntry = { id: "gpt-5.6-sol", api: "openai-completions" };
+
+    const entry = buildPiModelEntry(model({ id: "gpt-5.6-sol" }), previous);
+
+    expect(entry.api).toBe("openai-responses");
+  });
+
+  it("preserves a user-curated api on non-gpt models and omits it otherwise", () => {
+    const curated = buildPiModelEntry(
+      model({ id: "glm-5.3" }),
+      { id: "glm-5.3", api: "openai-responses" },
+    );
+    expect(curated.api).toBe("openai-responses");
+
+    const plain = buildPiModelEntry(model({ id: "glm-5.3" }));
+    expect("api" in plain).toBe(false);
+  });
 });