fix chat

packages/coding-agent/src/core/agent-session.ts

@@ -913,6 +913,14 @@ export class AgentSession {
     await this._memoryDisposePromise;
   }
 
+  private async _awaitAgentEventProcessing(): Promise<void> {
+    try {
+      await this._agentEventQueue;
+    } catch {
+      // Agent event failures are surfaced through normal listener paths.
+    }
+  }
+
   private _enqueueMemoryPromotion(messages: AgentMessage[]): void {
     this._memoryWriteQueue = this._memoryWriteQueue
       .catch(() => undefined)
@@ -1161,6 +1169,7 @@ export class AgentSession {
 
     await this.agent.prompt(messages);
     await this.waitForRetry();
+    await this._awaitAgentEventProcessing();
   }
 
   /**
@@ -1369,6 +1378,8 @@ export class AgentSession {
       }
     } else if (options?.triggerTurn) {
       await this.agent.prompt(appMessage);
+      await this.waitForRetry();
+      await this._awaitAgentEventProcessing();
     } else {
       this.agent.appendMessage(appMessage);
       this.sessionManager.appendCustomMessageEntry(

packages/coding-agent/src/core/gateway/vercel-ai-stream.ts

@@ -2,6 +2,43 @@ import { randomUUID } from "node:crypto";
 import type { ServerResponse } from "node:http";
 import type { AgentSessionEvent } from "../agent-session.js";
 
+type TextStreamState = {
+  started: boolean;
+  ended: boolean;
+  streamedText: string;
+};
+
+function isTextContent(
+  value: unknown,
+): value is { type: "text"; text: string } {
+  return (
+    typeof value === "object" &&
+    value !== null &&
+    "type" in value &&
+    "text" in value &&
+    (value as { type: unknown }).type === "text" &&
+    typeof (value as { text: unknown }).text === "string"
+  );
+}
+
+function getAssistantTextParts(
+  event: Extract<AgentSessionEvent, { type: "message_end" }>,
+): Array<{ contentIndex: number; text: string }> {
+  if (event.message.role !== "assistant" || !Array.isArray(event.message.content)) {
+    return [];
+  }
+
+  const textParts: Array<{ contentIndex: number; text: string }> = [];
+  for (const [contentIndex, content] of event.message.content.entries()) {
+    if (!isTextContent(content) || content.text.length === 0) {
+      continue;
+    }
+    textParts.push({ contentIndex, text: content.text });
+  }
+
+  return textParts;
+}
+
 /**
  * Write a single Vercel AI SDK v5+ SSE chunk to the response.
  * Format: `data: <JSON>\n\n`
@@ -63,6 +100,76 @@ export function createVercelStreamListener(
   // so these guards only need to bound the stream to that prompt's event span.
   let active = false;
   const msgId = messageId ?? randomUUID();
+  let textStates = new Map<number, TextStreamState>();
+
+  const getTextState = (contentIndex: number): TextStreamState => {
+    const existing = textStates.get(contentIndex);
+    if (existing) {
+      return existing;
+    }
+    const initial: TextStreamState = {
+      started: false,
+      ended: false,
+      streamedText: "",
+    };
+    textStates.set(contentIndex, initial);
+    return initial;
+  };
+
+  const emitTextStart = (contentIndex: number): void => {
+    const state = getTextState(contentIndex);
+    if (state.started) {
+      return;
+    }
+    writeChunk(response, {
+      type: "text-start",
+      id: `text_${contentIndex}`,
+    });
+    state.started = true;
+  };
+
+  const emitTextDelta = (contentIndex: number, delta: string): void => {
+    if (delta.length === 0) {
+      return;
+    }
+    emitTextStart(contentIndex);
+    writeChunk(response, {
+      type: "text-delta",
+      id: `text_${contentIndex}`,
+      delta,
+    });
+    getTextState(contentIndex).streamedText += delta;
+  };
+
+  const emitTextEnd = (contentIndex: number): void => {
+    const state = getTextState(contentIndex);
+    if (state.ended) {
+      return;
+    }
+    emitTextStart(contentIndex);
+    writeChunk(response, {
+      type: "text-end",
+      id: `text_${contentIndex}`,
+    });
+    state.ended = true;
+  };
+
+  const flushAssistantMessageText = (
+    event: Extract<AgentSessionEvent, { type: "message_end" }>,
+  ): void => {
+    for (const part of getAssistantTextParts(event)) {
+      const state = getTextState(part.contentIndex);
+      if (!part.text.startsWith(state.streamedText)) {
+        continue;
+      }
+
+      const suffix = part.text.slice(state.streamedText.length);
+      if (suffix.length > 0) {
+        emitTextDelta(part.contentIndex, suffix);
+      }
+      emitTextEnd(part.contentIndex);
+    }
+  };
 
   return (event: AgentSessionEvent) => {
     if (response.writableEnded) return;
@@ -85,6 +192,7 @@ export function createVercelStreamListener(
 
     switch (event.type) {
       case "turn_start":
+        textStates = new Map();
         writeChunk(response, { type: "start-step" });
         return;
 
@@ -92,23 +200,13 @@ export function createVercelStreamListener(
         const inner = event.assistantMessageEvent;
         switch (inner.type) {
           case "text_start":
-            writeChunk(response, {
-              type: "text-start",
-              id: `text_${inner.contentIndex}`,
-            });
+            emitTextStart(inner.contentIndex);
             return;
           case "text_delta":
-            writeChunk(response, {
-              type: "text-delta",
-              id: `text_${inner.contentIndex}`,
-              delta: inner.delta,
-            });
+            emitTextDelta(inner.contentIndex, inner.delta);
             return;
           case "text_end":
-            writeChunk(response, {
-              type: "text-end",
-              id: `text_${inner.contentIndex}`,
-            });
+            emitTextEnd(inner.contentIndex);
             return;
           case "toolcall_start": {
             const content = inner.partial.content[inner.contentIndex];
@@ -163,6 +261,12 @@ export function createVercelStreamListener(
         return;
       }
 
+      case "message_end":
+        if (event.message.role === "assistant") {
+          flushAssistantMessageText(event);
+        }
+        return;
+
       case "turn_end":
         writeChunk(response, { type: "finish-step" });
         return;

packages/coding-agent/test/vercel-ai-stream.test.ts

@@ -1,3 +1,5 @@
+import type { IncomingMessage, ServerResponse } from "node:http";
+import type { AssistantMessage } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
 import type { AgentSessionEvent } from "../src/core/agent-session.js";
 import {
@@ -5,6 +7,24 @@ import {
   extractUserText,
 } from "../src/core/gateway/vercel-ai-stream.js";
 
+type MessageUpdateSessionEvent = Extract<
+  AgentSessionEvent,
+  { type: "message_update" }
+>;
+type MessageEndSessionEvent = Extract<
+  AgentSessionEvent,
+  { type: "message_end" }
+>;
+type TurnEndSessionEvent = Extract<AgentSessionEvent, { type: "turn_end" }>;
+type TextAssistantMessageEvent = Extract<
+  MessageUpdateSessionEvent["assistantMessageEvent"],
+  { type: "text_start" | "text_delta" | "text_end" }
+>;
+type MockResponse = ServerResponse<IncomingMessage> & {
+  chunks: string[];
+  ended: boolean;
+};
+
 describe("extractUserText", () => {
   it("extracts text from useChat v5+ format with parts", () => {
     const body = {
@@ -61,24 +81,73 @@ describe("extractUserText", () => {
 });
 
 describe("createVercelStreamListener", () => {
-  function createMockResponse() {
+  function createAssistantMessage(text: string): AssistantMessage {
+    return {
+      role: "assistant",
+      content: [{ type: "text", text }],
+      api: "anthropic-messages",
+      provider: "anthropic",
+      model: "mock",
+      usage: {
+        input: 0,
+        output: 0,
+        cacheRead: 0,
+        cacheWrite: 0,
+        totalTokens: 0,
+        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+      },
+      stopReason: "stop",
+      timestamp: Date.now(),
+    };
+  }
+
+  function createMockResponse(): MockResponse {
     const chunks: string[] = [];
     let ended = false;
-    return {
-      writableEnded: false,
+    const response = {
+      get writableEnded() {
+        return ended;
+      },
       write(data: string) {
         chunks.push(data);
         return true;
       },
       end() {
         ended = true;
-        this.writableEnded = true;
       },
       chunks,
       get ended() {
         return ended;
       },
-    } as any;
+    } as unknown as MockResponse;
+    return response;
+  }
+
+  function createMessageUpdateEvent(
+    assistantMessageEvent: TextAssistantMessageEvent,
+  ): MessageUpdateSessionEvent {
+    return {
+      type: "message_update",
+      message: createAssistantMessage(""),
+      assistantMessageEvent,
+    };
+  }
+
+  function createAssistantMessageEndEvent(
+    text: string,
+  ): MessageEndSessionEvent {
+    return {
+      type: "message_end",
+      message: createAssistantMessage(text),
+    };
+  }
+
+  function createTurnEndEvent(): TurnEndSessionEvent {
+    return {
+      type: "turn_end",
+      message: createAssistantMessage(""),
+      toolResults: [],
+    };
   }
 
   function parseChunks(chunks: string[]): Array<object | string> {
@@ -104,41 +173,30 @@ describe("createVercelStreamListener", () => {
       turnIndex: 0,
       timestamp: Date.now(),
     } as AgentSessionEvent);
-    listener({
-      type: "message_update",
-      message: {} as any,
-      assistantMessageEvent: {
+    listener(
+      createMessageUpdateEvent({
         type: "text_start",
         contentIndex: 0,
-        partial: {} as any,
-      },
-    } as AgentSessionEvent);
-    listener({
-      type: "message_update",
-      message: {} as any,
-      assistantMessageEvent: {
+        partial: createAssistantMessage(""),
+      }),
+    );
+    listener(
+      createMessageUpdateEvent({
         type: "text_delta",
         contentIndex: 0,
         delta: "hello",
-        partial: {} as any,
-      },
-    } as AgentSessionEvent);
-    listener({
-      type: "message_update",
-      message: {} as any,
-      assistantMessageEvent: {
+        partial: createAssistantMessage("hello"),
+      }),
+    );
+    listener(
+      createMessageUpdateEvent({
         type: "text_end",
         contentIndex: 0,
         content: "hello",
-        partial: {} as any,
-      },
-    } as AgentSessionEvent);
-    listener({
-      type: "turn_end",
-      turnIndex: 0,
-      message: {} as any,
-      toolResults: [],
-    } as AgentSessionEvent);
+        partial: createAssistantMessage("hello"),
+      }),
+    );
+    listener(createTurnEndEvent());
 
     const parsed = parseChunks(response.chunks);
     expect(parsed).toEqual([
@@ -151,6 +209,70 @@ describe("createVercelStreamListener", () => {
     ]);
   });
 
+  it("flushes final assistant text from message_end when no deltas streamed", () => {
+    const response = createMockResponse();
+    const listener = createVercelStreamListener(response, "test-msg-id");
+
+    listener({ type: "agent_start" } as AgentSessionEvent);
+    listener({
+      type: "turn_start",
+      turnIndex: 0,
+      timestamp: Date.now(),
+    } as AgentSessionEvent);
+    listener(createAssistantMessageEndEvent("final answer"));
+    listener(createTurnEndEvent());
+
+    const parsed = parseChunks(response.chunks);
+    expect(parsed).toEqual([
+      { type: "start", messageId: "test-msg-id" },
+      { type: "start-step" },
+      { type: "text-start", id: "text_0" },
+      { type: "text-delta", id: "text_0", delta: "final answer" },
+      { type: "text-end", id: "text_0" },
+      { type: "finish-step" },
+    ]);
+  });
+
+  it("flushes the missing text suffix on message_end", () => {
+    const response = createMockResponse();
+    const listener = createVercelStreamListener(response, "test-msg-id");
+
+    listener({ type: "agent_start" } as AgentSessionEvent);
+    listener({
+      type: "turn_start",
+      turnIndex: 0,
+      timestamp: Date.now(),
+    } as AgentSessionEvent);
+    listener(
+      createMessageUpdateEvent({
+        type: "text_start",
+        contentIndex: 0,
+        partial: createAssistantMessage(""),
+      }),
+    );
+    listener(
+      createMessageUpdateEvent({
+        type: "text_delta",
+        contentIndex: 0,
+        delta: "hel",
+        partial: createAssistantMessage("hel"),
+      }),
+    );
+    listener(createAssistantMessageEndEvent("hello"));
+    listener(createTurnEndEvent());
+
+    const parsed = parseChunks(response.chunks);
+    expect(parsed).toEqual([
+      { type: "start", messageId: "test-msg-id" },
+      { type: "start-step" },
+      { type: "text-start", id: "text_0" },
+      { type: "text-delta", id: "text_0", delta: "hel" },
+      { type: "text-delta", id: "text_0", delta: "lo" },
+      { type: "text-end", id: "text_0" },
+      { type: "finish-step" },
+    ]);
+  });
+
   it("does not write after response has ended", () => {
     const response = createMockResponse();
     const listener = createVercelStreamListener(response, "test-msg-id");