fix(chat): trim padding around internal thread links

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

@@ -62,7 +62,11 @@ import {
 import type { ToolCallVisibility } from "@t3tools/contracts/settings";
 import { renderAssistantCitationsAsText } from "@t3tools/shared/assistantCitations";
 import { encodeComposerContextFragment } from "@t3tools/shared/composerContextClipboard";
-import { hostedThreadLink, parseThreadLinkHref } from "@t3tools/shared/threadLinks";
+import {
+  hostedThreadLink,
+  parseThreadLinkHref,
+  trimThreadAutolinkPadding,
+} from "@t3tools/shared/threadLinks";
 import { PROMPT_LINK_MAX_PROMPT_LENGTH } from "@t3tools/shared/promptLinks";
 import {
   parseComposerContextHref,
@@ -1202,7 +1206,10 @@ const AssistantMarkdownContent = memo(function AssistantMarkdownContent(props: {
   readonly skills?: ReadonlyArray<SelectableMarkdownSkill> | undefined;
 }) {
   const models = useModelMentions(props.environmentId, props.markdown);
-  const liveMarkdown = useLiveThreadLinkLabels(props.markdown, props.environmentId);
+  const liveMarkdown = useLiveThreadLinkLabels(
+    trimThreadAutolinkPadding(props.markdown),
+    props.environmentId,
+  );
   const threadIcons = useThreadChipIcons(props.environmentId, liveMarkdown);
   const linkHandlers: MarkdownLinkHandlers = {
     ...props.linkHandlers,

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

@@ -1,4 +1,5 @@
 import { shouldPreserveAssistantLineBreaks } from "@t3tools/shared/markdownPipeline";
+import { trimThreadAutolinkPadding } from "@t3tools/shared/threadLinks";
 import { type RunId } from "@t3tools/contracts";
 import { canForkProjectedAssistantItem } from "@t3tools/client-runtime/state/thread-workflows";
 import { memo, use, useState } from "react";
@@ -33,7 +34,8 @@ export function AssistantTimelineRow({ row }: { row: Extract<TimelineRow, { kind
     row.projectedItem?.item.id,
   );
   const text = liveText ?? row.message.text;
-  const messageText = text || (row.message.streaming ? "" : "(empty response)");
+  const messageText =
+    trimThreadAutolinkPadding(text) || (row.message.streaming ? "" : "(empty response)");
 
   return (
     <>

packages/shared/src/threadLinks.test.ts

@@ -10,6 +10,7 @@ import {
   relabelThreadLinks,
   threadLinkCandidates,
   threadLinkRefs,
+  trimThreadAutolinkPadding,
 } from "./threadLinks.ts";
 
 const ref = (environmentId: string, threadId = "chat-1") => ({
@@ -151,6 +152,35 @@ describe("thread links", () => {
     );
   });
 
+  it("trims the whitespace a model writes inside a thread autolink's brackets, and nothing else", () => {
+    const delegated =
+      "t3-thread://v2/ffa70b7f-bbd5-47ff-9f01-bdad03fba727/thread:delegated-task:command%3Amcp%3A14ece488-0be2-4b67-bb57-7c2ee9190309%3Adelegate-task%3Azack-settings-ui-opus-20261107-2144";
+    expect(trimThreadAutolinkPadding(`Opened < ${delegated}>.`)).toBe(`Opened <${delegated}>.`);
+    expect(
+      trimThreadAutolinkPadding("<\tt3-thread://v1/t1 \t> and <\n  t3-thread://v2/local/t2\n>"),
+    ).toBe("<t3-thread://v1/t1> and <t3-thread://v2/local/t2>");
+    expect(
+      trimThreadAutolinkPadding("[Settings](< t3-thread://v1/t1 >)\r\n<\r\nt3-thread://v1/t2\r\n>"),
+    ).toBe("[Settings](<t3-thread://v1/t1>)\r\n<t3-thread://v1/t2>");
+    const untouched = [
+      "<t3-thread://v2/local/t1> [a](<t3-thread://v2/local/t1>)",
+      "< t3 > < t3-thread://v2/env > < t3-thread://v2/<env>/<thread> > < t3-thread://v1/ >",
+      "< t3-thread://v2/local/thr ead > <\n\nt3-thread://v1/t1>",
+      '< https://example.com/t3-thread > <a href="t3-thread://v2/local/t1">x</a>',
+      "Literal `< t3-thread://v2/local/t1 >`",
+      "Literal `code\n< t3-thread://v2/local/t1 >\ncode`",
+      "    < t3-thread://v2/local/t1 >",
+      "\t< t3-thread://v2/local/t1 >",
+      "```md",
+      "< t3-thread://v2/local/t1 >",
+      "```",
+    ].join("\n");
+    expect(trimThreadAutolinkPadding(untouched)).toBe(untouched);
+    expect(
+      relabelThreadLinks(trimThreadAutolinkPadding(`< ${delegated} >`), local, () => "Settings UI"),
+    ).toBe(`[Settings UI](${delegated})`);
+  });
+
   it("lists the threads a message's links can name, outside code", () => {
     expect(
       threadLinkRefs(

packages/shared/src/threadLinks.ts

@@ -10,9 +10,10 @@ const V2_PREFIX = `${THREAD_LINK_PROTOCOL}://v2/`;
 const HOSTED_PREFIX = `${DEFAULT_HOSTED_APP_URL}/threads/`;
 const HOSTED_SEGMENT = "[A-Za-z0-9_%-]+";
 const HOSTED_LINK = `${HOSTED_PREFIX.replace(/[.*+?^${}()|[\]\\/]/g, "\\$&")}${HOSTED_SEGMENT}/${HOSTED_SEGMENT}`;
-// Code comes first in the alternation so a link written inside a code span or fence is skipped.
+// Code comes first in an alternation so a link written inside a code span or fence is skipped.
+const CODE = String.raw`(?<fence>(\`{3,}|~{3,})[\s\S]*?(?:\2|(?![\s\S])))|(?<span>(\`+)[\s\S]*?\4)`;
 const THREAD_LINK_OUTSIDE_CODE = new RegExp(
-  String.raw`(?<fence>(\`{3,}|~{3,})[\s\S]*?(?:\2|$))|(?<span>(\`+)[^\n]*?\4)|\[(?<label>[^\]\n]*)\]\(<?(?<href>t3-thread:\/\/v[12]\/[^\s>)]+|${HOSTED_LINK})>?\)|<(?<autolink>t3-thread:\/\/v[12]\/[^\s<>]+|${HOSTED_LINK})>|(?<bare>${HOSTED_LINK})(?![\w%/?#-])`,
+  String.raw`${CODE}|\[(?<label>[^\]\n]*)\]\(<?(?<href>t3-thread:\/\/v[12]\/[^\s>)]+|${HOSTED_LINK})>?\)|<(?<autolink>t3-thread:\/\/v[12]\/[^\s<>]+|${HOSTED_LINK})>|(?<bare>${HOSTED_LINK})(?![\w%/?#-])`,
   "g",
 );
 
@@ -139,6 +140,21 @@ export function formatHostedThreadLink(
   return cleaned ? `[${cleaned}](${href})` : href;
 }
 
+// At most one line break on a side, so a blank line never joins two paragraphs.
+const PADDED_THREAD_AUTOLINK = new RegExp(
+  String.raw`${CODE}|^(?: {4}|\t)[^\n]*|<[ \t]*\r?\n?[ \t]*(?<autolink>t3-thread:\/\/v[12]\/[^\s<>]+)[ \t]*\r?\n?[ \t]*>`,
+  "gm",
+);
+
+/** Models sometimes pad an autolink, as in `< t3-thread://… >`, which Markdown leaves as text. */
+export function trimThreadAutolinkPadding(markdown: string): string {
+  if (!markdown.includes(`${THREAD_LINK_PROTOCOL}://v`)) return markdown;
+  return markdown.replace(PADDED_THREAD_AUTOLINK, (source, ...args) => {
+    const href = (args.at(-1) as { autolink?: string }).autolink;
+    return href !== undefined && parseThreadLinkHref(href) ? `<${href}>` : source;
+  });
+}
+
 export function hasThreadLinks(markdown: string): boolean {
   return markdown.includes(`${THREAD_LINK_PROTOCOL}://v`) || markdown.includes(HOSTED_PREFIX);
 }