fix(server): favicon resolution no longer pins the event loop

[murenovich]

What Changed

LINK_ICON_OBJ_RE is gone. Object icon metadata is now found by scanning brace-free runs instead of by one combined pattern:

-const LINK_ICON_OBJ_RE =
-  /(?=[^}]*\brel\s*:\s*["'](?:icon|shortcut icon)["'])(?=[^}]*\bhref\s*:\s*["']([^"'?]+))[^}]*/i;
+const ICON_REL_RE = /\brel\s*:\s*["'](?:icon|shortcut icon)["']/i;
+const ICON_HREF_RE = /\bhref\s*:\s*["']([^"'?]+)/i;

 function extractIconHref(source: string): string | null {
   const htmlMatch = source.match(LINK_ICON_HTML_RE);
   if (htmlMatch?.[1]) return htmlMatch[1];
-  const objMatch = source.match(LINK_ICON_OBJ_RE);
-  if (objMatch?.[1]) return objMatch[1];
+  for (const run of source.split("}")) {
+    if (!ICON_REL_RE.test(run)) continue;
+    const hrefMatch = run.match(ICON_HREF_RE);
+    if (hrefMatch?.[1]) return hrefMatch[1];
+  }
   return null;
 }

Five tests come with it. The object branch had no coverage at all — every existing case exercises the <link> branch — so this adds both key orders, a nested-object case, a no-href-then-valid case, and a large brace-sparse source that hangs the suite without the fix.

LINK_ICON_HTML_RE is untouched. It is already anchored on <link\b, so it was never part of the problem.

Why

Fixes #5537.

The old pattern began with a lookahead and no literal anchor, so the engine retried at every offset and rescanned forward with [^}]* from each one. On a brace-sparse file that is quadratic.

That turns one file into a full environment outage. A project with no icon and a large index.html lacking <link rel="icon"> — the shape of a generated single-file build — made resolvePath spin for minutes on the server's only thread. Every endpoint stopped answering, including /.well-known/t3/environment; the desktop client timed out at 10s, respawned the server, and it re-scanned and re-wedged. The environment never recovered on its own.

	before	after
1.6 MB icon source, no icon metadata	killed at 30s, never completed	2 ms
200 KB	~4s	<1 ms

Why runs rather than an anchored pattern

Anchoring the existing pattern on { is the obvious fix and it is not equivalent. It breaks two cases the current code handles:

source	current	anchored \{…\}	this PR
{ attributes: {}, rel: "icon", href: "/x.svg" }	/x.svg	null	/x.svg
[{ rel: "icon" }, { rel: "icon", href: "/x.svg" }]	/x.svg	null	/x.svg

The old pattern accepted any position from which both rel and href were visible before the next } — which is exactly "both live in the same brace-free run". Walking those runs reproduces that rule directly: a run holding rel but no href falls through to the next candidate, and metadata beside a nested object still resolves because the run boundary sits at }, not at the enclosing object.

I checked this against the old pattern across both key orders, shortcut icon, query stripping, rel: "stylesheet", a TanStack head() block, and the two rows above: same result on every one.

UI Changes

None.

Verification

• vp test run src/project/ProjectFaviconResolver.test.ts — 17 passed (12 existing + 5 new), 445 ms.
• Reverting only the source change and keeping the new tests: the run was still going at 100s and had to be killed, confirming the regression test actually catches this.
• vp lint on both changed files: clean.
• tsgo --noEmit for apps/server: exit 0, no diagnostics in the changed files.

Branched off main @ e4abc31f.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (N/A, no UI change)
• I included a video for animation/interaction changes (N/A)

Model: Claude Opus 5 · Harness: Claude Code

---

Note

Medium Risk
Touches server-side favicon discovery on every workspace scan; behavior is intended to be equivalent for object metadata but the parsing path changed, so edge-case regressions are possible despite new tests.

Overview
Fixes event-loop wedging when ProjectFaviconResolver scans large project sources that have no icon metadata (e.g. generated single-file index.html).

Object-literal icon detection no longer uses the unanchored LINK_ICON_OBJ_RE regex (which retried at every offset and could run for minutes). extractIconHref now splits the source on } and, within each brace-free run, looks for rel: "icon" / shortcut icon and a matching href—same semantics as before for TanStack-style head() blocks, arbitrary key order, nested objects, and “icon without href then valid entry” cases. HTML <link rel="icon"> matching is unchanged.

Adds five tests covering object metadata cases plus a large-file timing guard (< 5s, expects null).

^{Reviewed by Cursor Bugbot for commit 6ba92f5. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix extractIconHref to resolve object-literal favicons without pinning the event loop

• Replaces the single unanchored LINK_ICON_OBJ_RE regex with a segment-based scan in ProjectFaviconResolver.ts: the source is split on } into brace-free runs, each checked for rel: "icon" then href.
• Fixes correctness issues where href before rel, extra nested properties, or rel-only segments caused resolution to fail.
• Behavioral Change: scanning large sources without icon metadata now runs in linear time instead of quadratic time, preventing the event loop from stalling.

^{Macroscope summarized 6ba92f5.}

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[macroscopeapp]

Approvability

Verdict: Approved 6ba92f5

Straightforward performance fix replacing a quadratic regex pattern with a linear split-and-scan approach for favicon resolution. The change is isolated, well-documented, and includes comprehensive test coverage including a performance regression test.

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