From 3adec3563278cdd215a989da0a300cd5bd8a3fd8 Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Fri, 9 Jan 2026 21:52:47 +0000
Subject: [PATCH] fix: make forced block chunking fence-safe

---
 src/agents/pi-embedded-block-chunker.ts      | 9 ++++++---
 src/auto-reply/reply.block-streaming.test.ts | 4 ++++
 src/markdown/fences.ts                       | 2 +-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/agents/pi-embedded-block-chunker.ts b/src/agents/pi-embedded-block-chunker.ts
index 53e933273..4236eb53d 100644
--- a/src/agents/pi-embedded-block-chunker.ts
+++ b/src/agents/pi-embedded-block-chunker.ts
@@ -68,7 +68,7 @@ export class EmbeddedBlockChunker {
       const breakResult =
         force && this.#buffer.length <= maxChars
           ? this.#pickSoftBreakIndex(this.#buffer, 1)
-          : this.#pickBreakIndex(this.#buffer);
+          : this.#pickBreakIndex(this.#buffer, force ? 1 : undefined);
       if (breakResult.index <= 0) {
         if (force) {
           emit(this.#buffer);
@@ -169,8 +169,11 @@ export class EmbeddedBlockChunker {
     return { index: -1 };
   }
 
-  #pickBreakIndex(buffer: string): BreakResult {
-    const minChars = Math.max(1, Math.floor(this.#chunking.minChars));
+  #pickBreakIndex(buffer: string, minCharsOverride?: number): BreakResult {
+    const minChars = Math.max(
+      1,
+      Math.floor(minCharsOverride ?? this.#chunking.minChars),
+    );
     const maxChars = Math.max(minChars, Math.floor(this.#chunking.maxChars));
     if (buffer.length < minChars) return { index: -1 };
     const window = buffer.slice(0, Math.min(maxChars, buffer.length));
diff --git a/src/auto-reply/reply.block-streaming.test.ts b/src/auto-reply/reply.block-streaming.test.ts
index 1aa142470..a2d592f2c 100644
--- a/src/auto-reply/reply.block-streaming.test.ts
+++ b/src/auto-reply/reply.block-streaming.test.ts
@@ -74,6 +74,7 @@ describe("block streaming", () => {
         {
           onReplyStart,
           onBlockReply,
+          disableBlockStreaming: false,
         },
         {
           agents: {
@@ -131,6 +132,7 @@ describe("block streaming", () => {
         {
           onReplyStart,
           onBlockReply,
+          disableBlockStreaming: false,
         },
         {
           agents: {
@@ -178,6 +180,7 @@ describe("block streaming", () => {
         },
         {
           onBlockReply,
+          disableBlockStreaming: false,
         },
         {
           agents: {
@@ -234,6 +237,7 @@ describe("block streaming", () => {
         {
           onBlockReply,
           blockReplyTimeoutMs: 10,
+          disableBlockStreaming: false,
         },
         {
           agents: {
diff --git a/src/markdown/fences.ts b/src/markdown/fences.ts
index efd31da99..975e5405b 100644
--- a/src/markdown/fences.ts
+++ b/src/markdown/fences.ts
@@ -44,7 +44,7 @@ export function parseFenceSpans(buffer: string): FenceSpan[] {
         open.markerChar === markerChar &&
         markerLen >= open.markerLen
       ) {
-        const end = nextNewline === -1 ? buffer.length : nextNewline + 1;
+        const end = lineEnd;
         spans.push({
           start: open.start,
           end,