diff --git a/src/agents/btw.test.ts b/src/agents/btw.test.ts
index e37227f0336..9f64d956c13 100644
--- a/src/agents/btw.test.ts
+++ b/src/agents/btw.test.ts
@@ -17,6 +17,7 @@ const getActiveEmbeddedRunSnapshotMock = vi.fn();
 const resolveSessionAgentIdMock = vi.fn();
 const resolveAgentWorkspaceDirMock = vi.fn();
 const prepareProviderRuntimeAuthMock = vi.fn();
+const registerProviderStreamForModelMock = vi.fn();
 const diagDebugMock = vi.fn();
 
 vi.mock("@mariozechner/pi-ai", async () => {
@@ -71,6 +72,11 @@ vi.mock("../plugins/provider-runtime.js", () => ({
   prepareProviderRuntimeAuth: (...args: unknown[]) => prepareProviderRuntimeAuthMock(...args),
 }));
 
+vi.mock("./provider-stream.js", () => ({
+  registerProviderStreamForModel: (...args: unknown[]) =>
+    registerProviderStreamForModelMock(...args),
+}));
+
 vi.mock("./auth-profiles/session-override.js", () => ({
   resolveSessionAuthProfileOverride: (...args: unknown[]) =>
     resolveSessionAuthProfileOverrideMock(...args),
@@ -275,6 +281,7 @@ describe("runBtwSideQuestion", () => {
     resolveSessionAgentIdMock.mockReset();
     resolveAgentWorkspaceDirMock.mockReset();
     prepareProviderRuntimeAuthMock.mockReset();
+    registerProviderStreamForModelMock.mockReset();
     diagDebugMock.mockReset();
 
     buildSessionContextMock.mockReturnValue({
@@ -293,6 +300,7 @@ describe("runBtwSideQuestion", () => {
     resolveSessionAgentIdMock.mockReturnValue("main");
     resolveAgentWorkspaceDirMock.mockReturnValue("/tmp/workspace");
     prepareProviderRuntimeAuthMock.mockResolvedValue(undefined);
+    registerProviderStreamForModelMock.mockReturnValue(undefined);
   });
 
   it("streams blocks without persisting BTW data to disk", async () => {
@@ -432,6 +440,48 @@ describe("runBtwSideQuestion", () => {
     );
   });
 
+  it("uses the provider's stream fn when registered so provider URL construction runs (#68336)", async () => {
+    // Regression: before this fix, /btw called streamSimple directly and
+    // bypassed the provider's createStreamFn/wrapStreamFn hooks. That caused
+    // Ollama Cloud (api: "openai-completions", baseUrl: "https://ollama.com/")
+    // to hit the marketing site instead of /v1/chat/completions.
+    resolveModelWithRegistryMock.mockReturnValue({
+      provider: "ollama",
+      id: "glm-5.1",
+      api: "openai-completions",
+      baseUrl: "https://ollama.com/",
+    });
+    const providerStreamFn = vi
+      .fn()
+      .mockReturnValue(makeAsyncEvents([createDoneEvent("Ollama Cloud answer.")]));
+    registerProviderStreamForModelMock.mockReturnValue(providerStreamFn);
+
+    const result = await runSideQuestion({ provider: "ollama", model: "glm-5.1" });
+
+    expect(result).toEqual({ text: "Ollama Cloud answer." });
+    expect(registerProviderStreamForModelMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        model: expect.objectContaining({
+          provider: "ollama",
+          api: "openai-completions",
+          baseUrl: "https://ollama.com/",
+        }),
+      }),
+    );
+    expect(providerStreamFn).toHaveBeenCalledTimes(1);
+    expect(streamSimpleMock).not.toHaveBeenCalled();
+  });
+
+  it("falls back to streamSimple when no provider stream fn is registered", async () => {
+    registerProviderStreamForModelMock.mockReturnValue(undefined);
+    mockDoneAnswer("Fallback answer.");
+
+    const result = await runSideQuestion();
+
+    expect(result).toEqual({ text: "Fallback answer." });
+    expect(streamSimpleMock).toHaveBeenCalledTimes(1);
+  });
+
   it("strips injected empty tools arrays from BTW payloads before sending", async () => {
     mockDoneAnswer("Final answer.");
 
diff --git a/src/agents/btw.ts b/src/agents/btw.ts
index ab71d9e9b22..0530a2d748a 100644
--- a/src/agents/btw.ts
+++ b/src/agents/btw.ts
@@ -33,6 +33,7 @@ import { resolveModelWithRegistry } from "./pi-embedded-runner/model.js";
 import { getActiveEmbeddedRunSnapshot } from "./pi-embedded-runner/runs.js";
 import { streamWithPayloadPatch } from "./pi-embedded-runner/stream-payload-utils.js";
 import { discoverAuthStorage, discoverModels } from "./pi-model-discovery.js";
+import { registerProviderStreamForModel } from "./provider-stream.js";
 import { stripToolResultDetails } from "./session-transcript-repair.js";
 import { sanitizeImageBlocks } from "./tool-images.js";
 
@@ -432,6 +433,17 @@ export async function runBtwSideQuestion(
     }
   }
 
+  // Use the provider's own stream fn so providers like Ollama (which build
+  // `/api/chat` or `/v1/chat/completions` paths based on api mode) construct
+  // URLs correctly. Without this, streamSimple hits the provider's baseUrl
+  // directly and 404s on endpoints like Ollama Cloud (#68336).
+  const providerStreamFn = registerProviderStreamForModel({
+    model: runtimeModel,
+    cfg: params.cfg,
+    agentDir: params.agentDir,
+    env: process.env,
+  });
+
   const chunker =
     params.opts?.onBlockReply && params.blockReplyChunking
       ? new EmbeddedBlockChunker(params.blockReplyChunking)
@@ -459,7 +471,7 @@ export async function runBtwSideQuestion(
   };
 
   const stream = await streamWithPayloadPatch(
-    streamSimple,
+    providerStreamFn ?? streamSimple,
     runtimeModel,
     {
       systemPrompt: buildBtwSystemPrompt(),