openclaw · vincentkoc · Jun 26, 2026 · Jun 25, 2026 · Jun 26, 2026
diff --git a/packages/markdown-core/src/fences.test.ts b/packages/markdown-core/src/fences.test.ts
@@ -0,0 +1,45 @@
+// Tests fenced-code-block span scanning used to keep chunk breaks out of code blocks.
+import { describe, expect, it } from "vitest";
+import { isSafeFenceBreak, parseFenceSpans } from "./fences.js";
+
+describe("parseFenceSpans closing-fence rules", () => {
+  it("treats a marker line with trailing text as code content, not a closing fence", () => {
+    // CommonMark: a closing fence may be followed only by whitespace, so "``` not a close" is code
+    // content and the block stays open until the real closing fence. Reporting an interior offset
+    // as a safe break would let a chunker split inside the code block.
+    const text = "```\ncode\n``` not a close\nmore code\n```\n";
+    const spans = parseFenceSpans(text);
+
+    expect(spans).toHaveLength(1);
+    expect(isSafeFenceBreak(spans, text.indexOf("more code") + 1)).toBe(false);
+  });
+
+  it("does not close on non-space/tab whitespace", () => {
+    for (const suffix of ["\u00a0", "\v", "\f"]) {
+      const text = `\`\`\`\ncode\n\`\`\`${suffix}\nmore code\n`;
+      const spans = parseFenceSpans(text);
+
+      expect(spans).toHaveLength(1);
+      expect(spans[0]?.end).toBe(text.length);
+      expect(isSafeFenceBreak(spans, text.indexOf("more code") + 1)).toBe(false);
+    }
+  });
+
+  it("closes fences with CRLF line endings", () => {
+    const text = "```\r\ncode\r\n```\r\nafter\r\n";
+    const spans = parseFenceSpans(text);
+
+    expect(spans).toHaveLength(1);
+    expect(isSafeFenceBreak(spans, text.indexOf("after") + 1)).toBe(true);
+  });
+
+  it("still closes on a bare fence, a longer same-marker fence, and keeps an opener info string", () => {
+    expect(parseFenceSpans("```\ncode\n```\nafter\n")).toHaveLength(1);
+    expect(parseFenceSpans("```\ncode\n`````  \nafter\n")).toHaveLength(1);
+    expect(parseFenceSpans("```python\nx = 1\n```\n")).toHaveLength(1);
+
+    const closed = "```\ncode\n```\nafter\n";
+    const spans = parseFenceSpans(closed);
+    expect(isSafeFenceBreak(spans, closed.indexOf("after") + 1)).toBe(true);
+  });
+});
diff --git a/packages/markdown-core/src/fences.ts b/packages/markdown-core/src/fences.ts
@@ -41,7 +41,7 @@ export function scanFenceSpans(
   while (offset <= buffer.length) {
     const nextNewline = buffer.indexOf("\n", offset);
     const lineEnd = nextNewline === -1 ? buffer.length : nextNewline;
-    const line = buffer.slice(offset, lineEnd);
+    const line = buffer.slice(offset, lineEnd).replace(/\r$/, "");
 
     const match = line.match(/^( {0,3})(`{3,}|~{3,})(.*)$/);
     if (match && (offset > 0 || startsAtLineStart)) {
@@ -58,9 +58,13 @@ export function scanFenceSpans(
           marker,
           indent,
         };
-      } else if (open.markerChar === markerChar && markerLen >= open.markerLen) {
-        // CommonMark allows a closing fence to be longer than the opener, but
-        // it must use the same marker character to avoid crossing fence kinds.
+      } else if (
+        open.markerChar === markerChar &&
+        markerLen >= open.markerLen &&
+        /^[ \t]*$/.test(match[3])
+      ) {
+        // CommonMark permits only spaces or tabs after a closing fence. A marker line carrying
+        // other trailing text is code content, not a close, so it must not end the block.
         const end = lineEnd;
         spans.push({
           start: open.start,