fix: handle fence-close paragraph breaks

src/agents/pi-embedded-block-chunker.ts

@@ -129,11 +129,13 @@ export class EmbeddedBlockChunker {
     if (preference === "paragraph") {
       let paragraphIdx = buffer.indexOf("\n\n");
       while (paragraphIdx !== -1) {
-        if (
+        const candidates = [paragraphIdx, paragraphIdx + 1];
-          paragraphIdx >= minChars &&
+        for (const candidate of candidates) {
-          isSafeFenceBreak(fenceSpans, paragraphIdx)
+          if (candidate < minChars) continue;
-        ) {
+          if (candidate < 0 || candidate >= buffer.length) continue;
-          return { index: paragraphIdx };
+          if (isSafeFenceBreak(fenceSpans, candidate)) {
+            return { index: candidate };
+          }
         }
         paragraphIdx = buffer.indexOf("\n\n", paragraphIdx + 2);
       }
@@ -183,8 +185,13 @@ export class EmbeddedBlockChunker {
     if (preference === "paragraph") {
       let paragraphIdx = window.lastIndexOf("\n\n");
       while (paragraphIdx >= minChars) {
-        if (isSafeFenceBreak(fenceSpans, paragraphIdx)) {
+        const candidates = [paragraphIdx, paragraphIdx + 1];
-          return { index: paragraphIdx };
+        for (const candidate of candidates) {
+          if (candidate < minChars) continue;
+          if (candidate < 0 || candidate >= buffer.length) continue;
+          if (isSafeFenceBreak(fenceSpans, candidate)) {
+            return { index: candidate };
+          }
         }
         paragraphIdx = window.lastIndexOf("\n\n", paragraphIdx - 1);
       }

src/auto-reply/reply.block-streaming.test.ts

@@ -2,11 +2,21 @@ import path from "node:path";
 
 import { beforeEach, describe, expect, it, vi } from "vitest";
 
+import { runEmbeddedPiAgent as runEmbeddedPiAgentRunner } from "/src/agents/pi-embedded.js";
 import { withTempHome as withTempHomeBase } from "../../test/helpers/temp-home.js";
 import { loadModelCatalog } from "../agents/model-catalog.js";
-import { runEmbeddedPiAgent } from "../agents/pi-embedded.js";
+import { runEmbeddedPiAgent as runEmbeddedPiAgentAutoReply } from "../agents/pi-embedded.js";
 import { getReplyFromConfig } from "./reply.js";
 
+vi.mock("/src/agents/pi-embedded.js", () => ({
+  abortEmbeddedPiRun: vi.fn().mockReturnValue(false),
+  runEmbeddedPiAgent: vi.fn(),
+  queueEmbeddedPiMessage: vi.fn().mockReturnValue(false),
+  resolveEmbeddedSessionLane: (key: string) =>
+    `session:${key.trim() || "main"}`,
+  isEmbeddedPiRunActive: vi.fn().mockReturnValue(false),
+  isEmbeddedPiRunStreaming: vi.fn().mockReturnValue(false),
+}));
 vi.mock("../agents/pi-embedded.js", () => ({
   abortEmbeddedPiRun: vi.fn().mockReturnValue(false),
   runEmbeddedPiAgent: vi.fn(),
@@ -26,7 +36,8 @@ async function withTempHome<T>(fn: (home: string) => Promise<T>): Promise<T> {
 
 describe("block streaming", () => {
   beforeEach(() => {
-    vi.mocked(runEmbeddedPiAgent).mockReset();
+    vi.mocked(runEmbeddedPiAgentAutoReply).mockReset();
+    vi.mocked(runEmbeddedPiAgentRunner).mockReset();
     vi.mocked(loadModelCatalog).mockResolvedValue([
       { id: "claude-opus-4-5", name: "Opus 4.5", provider: "anthropic" },
       { id: "gpt-4.1-mini", name: "GPT-4.1 Mini", provider: "openai" },
@@ -52,7 +63,9 @@ describe("block streaming", () => {
       const onReplyStart = vi.fn(() => typingGate);
       const onBlockReply = vi.fn().mockResolvedValue(undefined);
 
-      vi.mocked(runEmbeddedPiAgent).mockImplementation(async (params) => {
+      const impl = async (
+        params: Parameters<typeof runEmbeddedPiAgentRunner>[0],
+      ) => {
         void params.onBlockReply?.({ text: "hello" });
         return {
           payloads: [{ text: "hello" }],
@@ -61,7 +74,9 @@ describe("block streaming", () => {
             agentMeta: { sessionId: "s", provider: "p", model: "m" },
           },
         };
-      });
+      };
+      vi.mocked(runEmbeddedPiAgentAutoReply).mockImplementation(impl);
+      vi.mocked(runEmbeddedPiAgentRunner).mockImplementation(impl);
 
       const replyPromise = getReplyFromConfig(
         {
@@ -109,7 +124,9 @@ describe("block streaming", () => {
         seen.push(payload.text ?? "");
       });
 
-      vi.mocked(runEmbeddedPiAgent).mockImplementation(async (params) => {
+      const impl = async (
+        params: Parameters<typeof runEmbeddedPiAgentRunner>[0],
+      ) => {
         void params.onBlockReply?.({ text: "first" });
         void params.onBlockReply?.({ text: "second" });
         return {
@@ -119,7 +136,9 @@ describe("block streaming", () => {
             agentMeta: { sessionId: "s", provider: "p", model: "m" },
           },
         };
-      });
+      };
+      vi.mocked(runEmbeddedPiAgentAutoReply).mockImplementation(impl);
+      vi.mocked(runEmbeddedPiAgentRunner).mockImplementation(impl);
 
       const replyPromise = getReplyFromConfig(
         {
@@ -159,7 +178,9 @@ describe("block streaming", () => {
     await withTempHome(async (home) => {
       const onBlockReply = vi.fn().mockResolvedValue(undefined);
 
-      vi.mocked(runEmbeddedPiAgent).mockImplementation(async (params) => {
+      const impl = async (
+        params: Parameters<typeof runEmbeddedPiAgentRunner>[0],
+      ) => {
         void params.onBlockReply?.({ text: "chunk-1" });
         return {
           payloads: [{ text: "chunk-1\nchunk-2" }],
@@ -168,7 +189,9 @@ describe("block streaming", () => {
             agentMeta: { sessionId: "s", provider: "p", model: "m" },
           },
         };
-      });
+      };
+      vi.mocked(runEmbeddedPiAgentAutoReply).mockImplementation(impl);
+      vi.mocked(runEmbeddedPiAgentRunner).mockImplementation(impl);
 
       const res = await getReplyFromConfig(
         {
@@ -215,7 +238,9 @@ describe("block streaming", () => {
         });
       });
 
-      vi.mocked(runEmbeddedPiAgent).mockImplementation(async (params) => {
+      const impl = async (
+        params: Parameters<typeof runEmbeddedPiAgentRunner>[0],
+      ) => {
         void params.onBlockReply?.({ text: "streamed" });
         return {
           payloads: [{ text: "final" }],
@@ -224,7 +249,9 @@ describe("block streaming", () => {
             agentMeta: { sessionId: "s", provider: "p", model: "m" },
           },
         };
-      });
+      };
+      vi.mocked(runEmbeddedPiAgentAutoReply).mockImplementation(impl);
+      vi.mocked(runEmbeddedPiAgentRunner).mockImplementation(impl);
 
       const replyPromise = getReplyFromConfig(
         {