fix: send only final answer with reasoning

When reasoning is enabled on non‑block providers, we now ignore interim streaming chunks and send only the final assistant answer at completion, so replies aren’t partial or duplicated.

src/agents/pi-embedded-subscribe.test.ts

@@ -347,6 +347,53 @@ describe("subscribeEmbeddedPiSession", () => {
     expect(combined).toBe("Final answer");
   });
 
+  it("keeps assistantTexts to the final answer when block replies are disabled", () => {
+    let handler: ((evt: unknown) => void) | undefined;
+    const session: StubSession = {
+      subscribe: (fn) => {
+        handler = fn;
+        return () => {};
+      },
+    };
+
+    const subscription = subscribeEmbeddedPiSession({
+      session: session as unknown as Parameters<
+        typeof subscribeEmbeddedPiSession
+      >[0]["session"],
+      runId: "run",
+      reasoningMode: "on",
+    });
+
+    handler?.({ type: "message_start", message: { role: "assistant" } });
+    handler?.({
+      type: "message_update",
+      message: { role: "assistant" },
+      assistantMessageEvent: {
+        type: "text_delta",
+        delta: "Final answer",
+      },
+    });
+    handler?.({
+      type: "message_update",
+      message: { role: "assistant" },
+      assistantMessageEvent: {
+        type: "text_end",
+      },
+    });
+
+    const assistantMessage = {
+      role: "assistant",
+      content: [
+        { type: "thinking", thinking: "Because it helps" },
+        { type: "text", text: "Final answer" },
+      ],
+    } as AssistantMessage;
+
+    handler?.({ type: "message_end", message: assistantMessage });
+
+    expect(subscription.assistantTexts).toEqual(["Final answer"]);
+  });
+
   it("emits block replies on text_end and does not duplicate on message_end", () => {
     let handler: ((evt: unknown) => void) | undefined;
     const session: StubSession = {
@@ -580,6 +627,37 @@ describe("subscribeEmbeddedPiSession", () => {
     expect(subscription.assistantTexts).toEqual(["Hello world"]);
   });
 
+  it("does not duplicate assistantTexts when message_end repeats with reasoning blocks", () => {
+    let handler: SessionEventHandler | undefined;
+    const session: StubSession = {
+      subscribe: (fn) => {
+        handler = fn;
+        return () => {};
+      },
+    };
+
+    const subscription = subscribeEmbeddedPiSession({
+      session: session as unknown as Parameters<
+        typeof subscribeEmbeddedPiSession
+      >[0]["session"],
+      runId: "run",
+      reasoningMode: "on",
+    });
+
+    const assistantMessage = {
+      role: "assistant",
+      content: [
+        { type: "thinking", thinking: "Because" },
+        { type: "text", text: "Hello world" },
+      ],
+    } as AssistantMessage;
+
+    handler?.({ type: "message_end", message: assistantMessage });
+    handler?.({ type: "message_end", message: assistantMessage });
+
+    expect(subscription.assistantTexts).toEqual(["Hello world"]);
+  });
+
   it("populates assistantTexts for non-streaming models with chunking enabled", () => {
     // Non-streaming models (e.g. zai/glm-4.7): no text_delta events; message_end
     // must still populate assistantTexts so providers can deliver a final reply.

src/agents/pi-embedded-subscribe.ts

@@ -294,6 +294,7 @@ export function subscribeEmbeddedPiSession(params: {
   let lastStreamedReasoning: string | undefined;
   let lastBlockReplyText: string | undefined;
   let assistantTextBaseline = 0;
+  let suppressBlockChunks = false; // Avoid late chunk inserts after final text merge.
   let compactionInFlight = false;
   let pendingCompactionRetry = 0;
   let compactionRetryResolve: (() => void) | undefined;
@@ -419,6 +420,7 @@ export function subscribeEmbeddedPiSession(params: {
   };
 
   const emitBlockChunk = (text: string) => {
+    if (suppressBlockChunks) return;
     // Strip <think> blocks across chunk boundaries to avoid leaking reasoning.
     const strippedText = stripBlockThinkingSegments(text);
     const chunk = strippedText.trimEnd();
@@ -476,6 +478,7 @@ export function subscribeEmbeddedPiSession(params: {
     lastStreamedAssistant = undefined;
     lastStreamedReasoning = undefined;
     lastBlockReplyText = undefined;
+    suppressBlockChunks = false;
     assistantTextBaseline = 0;
   };
 
@@ -497,6 +500,7 @@ export function subscribeEmbeddedPiSession(params: {
           lastBlockReplyText = undefined;
           lastStreamedReasoning = undefined;
           lastReasoningSent = undefined;
+          suppressBlockChunks = false;
           assistantTextBaseline = assistantTexts.length;
         }
       }
@@ -818,9 +822,23 @@ export function subscribeEmbeddedPiSession(params: {
           const addedDuringMessage =
             assistantTexts.length > assistantTextBaseline;
           const chunkerHasBuffered = blockChunker?.hasBuffered() ?? false;
-          // Non-streaming models (no text_delta): ensure assistantTexts gets the
+          // If we're not streaming block replies, ensure the final payload
-          // final text when the chunker has nothing buffered to drain.
+          // includes the final text even when deltas already populated assistantTexts.
-          if (!addedDuringMessage && !chunkerHasBuffered && text) {
+          if (includeReasoning && text && !params.onBlockReply) {
+            if (assistantTexts.length > assistantTextBaseline) {
+              assistantTexts.splice(
+                assistantTextBaseline,
+                assistantTexts.length - assistantTextBaseline,
+                text,
+              );
+            } else {
+              const last = assistantTexts.at(-1);
+              if (!last || last !== text) assistantTexts.push(text);
+            }
+            suppressBlockChunks = true;
+          } else if (!addedDuringMessage && !chunkerHasBuffered && text) {
+            // Non-streaming models (no text_delta): ensure assistantTexts gets the
+            // final text when the chunker has nothing buffered to drain.
             const last = assistantTexts.at(-1);
             if (!last || last !== text) assistantTexts.push(text);
           }