diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1be3ab30d..78ba13cbe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,8 @@ parallel copies under `docs/` or `scripts/notes/`. At cut time: rename
   cycles through a closed live-activity set (`working`, `warping`,
   `buzzing`, `grinding`, `thinking`, `doing`, `cooking`, `creating`,
   `imagining`, `inventing`) instead of going blank.
+- OpenCode Go routes Muse Spark 1.2 Contributor and Muse Spark 1.3
+  Contributor through the Responses API instead of chat completions.
 
 
 ## [0.3.19] - 2026-09-10
diff --git a/packages/opencode-go/src/endpoint.test.ts b/packages/opencode-go/src/endpoint.test.ts
index 0db852f06..645a0d3fb 100644
--- a/packages/opencode-go/src/endpoint.test.ts
+++ b/packages/opencode-go/src/endpoint.test.ts
@@ -14,6 +14,8 @@ describe("protocolForGoModel", () => {
   test("returns protocol for known models", () => {
     expect(protocolForGoModel("kimi-k2.7-code")).toBe("chat-completions");
     expect(protocolForGoModel("gpt-5.6-luna")).toBe("responses");
+    expect(protocolForGoModel("muse-spark-1.3-contributor")).toBe("responses");
+    expect(protocolForGoModel("muse-spark-1.2-contributor")).toBe("responses");
     expect(protocolForGoModel("minimax-m3")).toBe("messages");
   });
 
@@ -48,6 +50,18 @@ describe("resolveGoEndpoint", () => {
     expect(ep.baseURL).toContain("/zen/go/v1");
   });
 
+  test("routes Muse Spark Contributor models to openai-responses adapter", () => {
+    for (const id of [
+      "muse-spark-1.3-contributor",
+      "muse-spark-1.2-contributor",
+    ]) {
+      const ep = resolveGoEndpoint(id);
+      expect(ep.adapter).toBe("openai-responses");
+      expect(ep.protocol).toBe("responses");
+      expect(ep.baseURL).toContain("/zen/go/v1");
+    }
+  });
+
   test("routes messages models to anthropic base", () => {
     const ep = resolveGoEndpoint("minimax-m3");
     expect(ep.adapter).toBe("anthropic");
diff --git a/packages/opencode-go/src/models.ts b/packages/opencode-go/src/models.ts
index bf6618df6..723dda5b5 100644
--- a/packages/opencode-go/src/models.ts
+++ b/packages/opencode-go/src/models.ts
@@ -14,6 +14,16 @@ export interface GoModel {
 export const OPENCODE_GO_MODELS = [
   { id: "grok-4.5", name: "Grok 4.5", protocol: "chat-completions" },
   { id: "gpt-5.6-luna", name: "GPT 5.6 Luna", protocol: "responses" },
+  {
+    id: "muse-spark-1.3-contributor",
+    name: "Muse Spark 1.3 Contributor",
+    protocol: "responses",
+  },
+  {
+    id: "muse-spark-1.2-contributor",
+    name: "Muse Spark 1.2 Contributor",
+    protocol: "responses",
+  },
   { id: "glm-5.2", name: "GLM-5.2", protocol: "chat-completions" },
   { id: "glm-5.1", name: "GLM-5.1", protocol: "chat-completions" },
   { id: "kimi-k3", name: "Kimi K3", protocol: "chat-completions" },
diff --git a/src/config.test.ts b/src/config.test.ts
index 143da7876..be1a0b7eb 100644
--- a/src/config.test.ts
+++ b/src/config.test.ts
@@ -1986,13 +1986,13 @@ describe("refreshLiveProviderCatalog", () => {
 
     globalThis.fetch = (async () =>
       Response.json({
-        data: [{ id: "grok-4.5" }, { id: "muse-spark-1.2-contributor" }],
+        data: [{ id: "grok-4.5" }, { id: "live-only-fixture-model" }],
       })) as unknown as typeof fetch;
     await prefetchGoModels();
 
     const warm = await refreshLiveProviderCatalog(settings, resolved);
     const warmGo = warm.find((c) => c.name === "go");
-    expect(warmGo?.models).toContain("muse-spark-1.2-contributor");
+    expect(warmGo?.models).toContain("live-only-fixture-model");
     expect(warm.find((c) => c.name === "fp")?.models).toEqual(["fp-large"]);
     expect(
       buildProviderCatalog(settings, resolved).find((c) => c.name === "go")
diff --git a/src/provider/billing-product.test.ts b/src/provider/billing-product.test.ts
index d824ca24c..a8de3b5f7 100644
--- a/src/provider/billing-product.test.ts
+++ b/src/provider/billing-product.test.ts
@@ -102,12 +102,21 @@ describe("isGoModelOnZenPath", () => {
     ).toBe(false);
   });
 
-  test("false for a live-only Go id on Zen (protocol map, not picker membership)", () => {
+  test("true when a packaged Muse Spark model sits on a Zen-billed provider", () => {
     expect(
       isGoModelOnZenPath("muse-spark-1.2-contributor", {
         name: "zen",
         baseURL: "https://opencode.ai/zen/v1",
       }),
+    ).toBe(true);
+  });
+
+  test("false for a live-only Go id on Zen (protocol map, not picker membership)", () => {
+    expect(
+      isGoModelOnZenPath("live-only-fixture-model", {
+        name: "zen",
+        baseURL: "https://opencode.ai/zen/v1",
+      }),
     ).toBe(false);
   });
 
diff --git a/src/provider/opencode-go-models.test.ts b/src/provider/opencode-go-models.test.ts
index c0f2c7377..5785601b5 100644
--- a/src/provider/opencode-go-models.test.ts
+++ b/src/provider/opencode-go-models.test.ts
@@ -12,7 +12,7 @@ import {
 } from "./opencode-go-models.js";
 
 const originalFetch = globalThis.fetch;
-const LIVE_ONLY_ID = "muse-spark-1.2-contributor";
+const LIVE_ONLY_ID = "live-only-fixture-model";
 const GO_MODELS_URL = "https://opencode.ai/zen/go/v1/models";
 
 beforeEach(() => {
diff --git a/src/tui/provider-setup.test.ts b/src/tui/provider-setup.test.ts
index c0563e486..defc79860 100644
--- a/src/tui/provider-setup.test.ts
+++ b/src/tui/provider-setup.test.ts
@@ -751,7 +751,7 @@ describe("runProviderSetup Ollama discovery", () => {
 });
 
 describe("runProviderSetup Go models", () => {
-  const LIVE_ONLY_ID = "muse-spark-1.2-contributor";
+  const LIVE_ONLY_ID = "live-only-fixture-model";
 
   test("choiceFromDef lists selectable Go ids", () => {
     const go = providerChoiceById("opencode-go");