fix(markdown): repair unclosed local file links in assistant messages

apps/mobile/src/features/threads/ThreadFeed.tsx

@@ -36,6 +36,7 @@ import {
   classifyMarkdownImageSource,
   markdownImageSourceFragment,
 } from "@t3tools/client-runtime/markdown-images";
+import { repairMarkdownFileLinks } from "@t3tools/client-runtime/repair-markdown-file-links";
 import { resolveViewedImageAsset } from "@t3tools/client-runtime/work-log/presentation";
 import {
   renderCodexFileCitationsAsMarkdown,
@@ -788,7 +789,7 @@ const AssistantMarkdownContent = memo(function AssistantMarkdownContent(props: {
   readonly skills?: ReadonlyArray<SelectableMarkdownSkill> | undefined;
 }) {
   const segments = useMemo(
-    () => splitCodexArtifactTemplateMarkdown(props.markdown),
+    () => splitCodexArtifactTemplateMarkdown(repairMarkdownFileLinks(props.markdown)),
     [props.markdown],
   );
 

apps/web/src/components/chat/MessagesTimeline.tsx

@@ -23,6 +23,7 @@ import {
   type TurnId,
   type WorktreeSetupSnapshot,
 } from "@t3tools/contracts";
+import { repairMarkdownFileLinks } from "@t3tools/client-runtime/repair-markdown-file-links";
 import { parseScopedThreadKey } from "@t3tools/client-runtime/environment";
 import { replaceComposerContextReferences } from "@t3tools/shared/composerContextReferences";
 import type { CodexArtifactTemplate } from "@t3tools/client-runtime/codex-artifact-templates";
@@ -2380,7 +2381,8 @@ function TurnFoldTimelineRow({ row }: { row: Extract<TimelineRow, { kind: "turn-
 
 function AssistantTimelineRow({ row }: { row: Extract<TimelineRow, { kind: "message" }> }) {
   const ctx = use(TimelineRowCtx);
-  const messageText = row.message.text || (row.message.streaming ? "" : "(empty response)");
+  const messageText =
+    repairMarkdownFileLinks(row.message.text) || (row.message.streaming ? "" : "(empty response)");
 
   return (
     <>

packages/client-runtime/package.json

@@ -15,6 +15,10 @@
       "types": "./src/worktreeSetup.ts",
       "default": "./src/worktreeSetup.ts"
     },
+    "./repair-markdown-file-links": {
+      "types": "./src/repairMarkdownFileLinks.ts",
+      "default": "./src/repairMarkdownFileLinks.ts"
+    },
     "./load-balancing": {
       "types": "./src/load-balancing.ts",
       "default": "./src/load-balancing.ts"

packages/client-runtime/src/repairMarkdownFileLinks.test.ts

@@ -0,0 +1,80 @@
+import remarkParse from "remark-parse";
+import { unified } from "unified";
+import { describe, expect, it } from "vite-plus/test";
+
+import { repairMarkdownFileLinks } from "./repairMarkdownFileLinks.ts";
+
+describe("repairMarkdownFileLinks", () => {
+  it.each([
+    "local/path/file.md",
+    "./Release Notes.md",
+    "/Users/demo/My Project/report.md",
+    "C:/Users/demo/My Project/report.md",
+    String.raw`C:\Users\demo\My Project\report.md`,
+    "./output/",
+    "/tmp/output/",
+    "src/main.ts:12:3",
+  ])("makes an unclosed destination clickable: %s", (path) => {
+    const source = `[file](<${path})`;
+    const repaired = repairMarkdownFileLinks(source);
+    expect(repaired).toBe(`[file](<${path}>)`);
+    const paragraph = unified().use(remarkParse).parse(repaired).children[0];
+    expect(paragraph).toMatchObject({
+      type: "paragraph",
+      children: [{ type: "link", url: path }],
+    });
+    expect(repairMarkdownFileLinks(repaired)).toBe(repaired);
+  });
+
+  it("repairs multiple list items and formatted labels without changing surrounding text", () => {
+    expect(
+      repairMarkdownFileLinks("Files:\n\n- [**one**](<./one.md)\n- [two](<./two.md)\n\nDone."),
+    ).toBe("Files:\n\n- [**one**](<./one.md>)\n- [two](<./two.md>)\n\nDone.");
+  });
+
+  it.each([
+    ["", true],
+    ["\\", false],
+    ["\\\\", true],
+    ["\\\\\\", false],
+    ["!", false],
+    ["\\!", true],
+    ["\\\\!", false],
+    ["\\\\\\!", true],
+  ])("respects CommonMark escape parity after %j", (prefix, isLink) => {
+    const source = `${prefix}[file](<./file.md)`;
+    const repaired = repairMarkdownFileLinks(source);
+    expect(repaired).toBe(isLink ? `${prefix}[file](<./file.md>)` : source);
+    const paragraph = unified().use(remarkParse).parse(repaired).children[0];
+    expect(
+      paragraph?.type === "paragraph" && paragraph.children.some((node) => node.type === "link"),
+    ).toBe(isLink);
+  });
+
+  it.each([
+    "[file](<local/path/file.md>)",
+    "[file](local/path/file.md)",
+    "[web](<https://example.com/file.md)",
+    "[route](</chat/settings)",
+    "![image](<./image.png)",
+    "`[file](<./file.md)`",
+    "```md\n[file](<./file.md)\n```",
+    "~~~md\n[file](<./file.md)\n~~~",
+    "    [file](<./file.md)",
+    '<div title="[file](<./file.md)">HTML</div>',
+    '<span title="[file](<./file.md)">HTML</span>',
+    String.raw`\[file](<./file.md)`,
+    "[file](<./file.md",
+    "[file](<./report (1).md)",
+    '[file](<./file.md "title")',
+    "![outer [file](<./file.md)][image]\n\n[image]: ./image.png",
+    "[outer [file](<./file.md)](https://example.com)",
+  ])("preserves other Markdown: %s", (source) => {
+    expect(repairMarkdownFileLinks(source)).toBe(source);
+  });
+
+  it("preserves code examples while repairing a following link", () => {
+    const source = "`[file](<./file.md)`\n\n[file](<./file.md)";
+    expect(repairMarkdownFileLinks(source)).toBe("`[file](<./file.md)`\n\n[file](<./file.md>)");
+  });
+});

packages/client-runtime/src/repairMarkdownFileLinks.ts

@@ -0,0 +1,66 @@
+import remarkParse from "remark-parse";
+import { unified } from "unified";
+
+import { parseMarkdownFileLink } from "./markdownLinks.ts";
+
+const parser = unified().use(remarkParse).freeze();
+type MarkdownNode = ReturnType<typeof parser.parse>["children"][number];
+
+// ponytail: leave parentheses in malformed paths alone; use a tokenizer if those need repair.
+const UNCLOSED_FILE_LINK = /\[[^[\]\\\r\n]*\]\([ \t]*<([^<>()[\]\r\n"']+)\)/g;
+
+export function repairMarkdownFileLinks(markdown: string): string {
+  if (!markdown.includes("](")) return markdown;
+
+  function isEscaped(index: number): boolean {
+    let start = index;
+    while (markdown[start - 1] === "\\") start -= 1;
+    return (index - start) % 2 === 1;
+  }
+
+  const matches = Array.from(markdown.matchAll(UNCLOSED_FILE_LINK)).filter((match) => {
+    const previous = markdown[match.index - 1];
+    return (
+      !isEscaped(match.index) &&
+      (previous !== "!" || isEscaped(match.index - 1)) &&
+      parseMarkdownFileLink(match[1] ?? "")
+    );
+  });
+  if (matches.length === 0) return markdown;
+
+  const protectedRanges: Array<{ start: number; end: number }> = [];
+  function visit(node: MarkdownNode): void {
+    if (
+      node.type === "code" ||
+      node.type === "inlineCode" ||
+      node.type === "html" ||
+      node.type === "link" ||
+      node.type === "linkReference" ||
+      node.type === "image" ||
+      node.type === "imageReference" ||
+      node.type === "definition"
+    ) {
+      const start = node.position?.start.offset;
+      const end = node.position?.end.offset;
+      if (start !== undefined && end !== undefined) protectedRanges.push({ start, end });
+      return;
+    }
+    if ("children" in node) node.children.forEach(visit);
+  }
+  parser.parse(markdown).children.forEach(visit);
+
+  const parts: string[] = [];
+  let cursor = 0;
+  let rangeIndex = 0;
+  for (const match of matches) {
+    const end = match.index + match[0].length;
+    while ((protectedRanges[rangeIndex]?.end ?? Infinity) <= match.index) {
+      rangeIndex += 1;
+    }
+    if ((protectedRanges[rangeIndex]?.start ?? Infinity) < end) continue;
+    parts.push(markdown.slice(cursor, end - 1), ">");
+    cursor = end - 1;
+  }
+  parts.push(markdown.slice(cursor));
+  return parts.join("");
+}