feat(favicons): one server route for every site icon, with parent-domain fallback by waleedlatif1 · Pull Request #9494 · simstudioai/sim

waleedlatif1 · 2026-10-31T02:52:10Z

Summary

Every site icon in the app now comes from one place, and a site Google can't see no longer renders Google's grey placeholder globe.

Why: icons were <img src="https://www.google.com/s2/favicons?..."> in the browser. For a host Google has no icon for (a private tenant such as <tenant>.atlassian.net, an internal host), it answers 404 with a 16px globe image, which the browser treats as a successful load, so onError never fired and every such row showed the placeholder. One surface also fetched <site>/favicon.ico straight from the destination.

Resolution (lib/favicon)

GET /api/favicon?host= asks Google, then DuckDuckGo, server-side, where the 404 is visible (the approach Bitwarden's and Linkwarden's icon services use); the second provider only learns a host the first had no icon for
A host with no icon walks up to its parent domain, stopping before the ICANN public suffix (via tldts), so x.gitlab.io → gitlab.io and x.atlassian.net → atlassian.net, never io or co.uk; at most 3 parents
Internal hosts (IP literals, single labels, names outside public DNS, .arpa) and names DNS can't hold (punctuation that could reshape a provider URL, empty labels) never leave the server; the destination itself is never contacted
Hits are sniffed from their bytes (shared sniffImageContentType plus ICO), never SVG, capped at 256 KB, and served nosniff
Only a provider 404/410 is "no icon"; any other failure is unavailable. Redis cache per host: 30 days for an icon, 1 day for none, 5 minutes after an outage; a parent resolved for one subdomain is reused by its siblings; concurrent lookups share one resolution
No icon is an ordinary answer: 204 (an <img> still reports it as failed and renders the fallback), not an error status

Route and client

Session-only operation (favicons.get, capability: 'none') through defineInternalBinaryRoute, with a per-user rate limit. Binary internal routes now accept the same user rate-limit policy JSON routes do, and may declare several success statuses (validation shared with the JSON builder) and present a 204
<Favicon host fallback> and faviconSrc(host) replace faviconUrl (deleted) in chat source icons, browser tab / suggestion / agent icons, table URL cells, and Sim Links; browser-imported icons stay local, with their link fallback restored on error

Type of Change

New feature

Testing

lib/favicon/{hosts,probe}.test.ts (49), written red-first from the failure modes: internal hosts never offered, tenant → platform walk, never a bare suffix, 3-parent cap, normalization and IDN, URL-reshaping punctuation and empty labels rejected (verified to fail with tldts hostname validation off); 404-with-placeholder, HTML, SVG, empty, and oversized bodies are misses; 403/408/429/5xx are unavailable
Route builder suite, source-icon lookalike tests, and the browser-agent icon test (398 total)
End-to-end against the running app with made-up hosts (12/12): signed-out 401; public site 200 with nosniff and private caching; made-up Atlassian and GitLab tenants get their platform's icon (~0.6 s cold); unknown site, internal hosts, and a URL-injection host answer 204 fast; malformed host 400; repeat lookup served from cache in ~20 ms. Not committed, since it depends on live third-party providers
Headless browser QA of Sim Links: tenant rows show the platform icon, unknown hosts the app's globe, no page errors
biome, check:api-validation:strict, check:source-conventions, check:client-boundary, check:boundaries, check:application-graph, check:permission-group-enforcement, check:route-verbs, check:file-names, check:comment-hygiene, check:utils, check:test-patterns, check:source-text

Checklist

Code follows project style guidelines
Self-reviewed my changes
Tests added/updated and passing (new tests pass the test-audit authoring gate)
No new warnings introduced
I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

… parent-domain fallback Icons were requested straight from Google in the browser, which shows Google's placeholder globe for any host it can't see (a 404 with an image body that an <img> treats as success), so private tenants and internal hosts rendered a generic placeholder. GET /api/favicon asks Google and DuckDuckGo server-side, where the 404 is visible, walks up to the parent domain so a tenant shows its platform's icon, never sends internal hosts or the destination itself anything, and caches results in Redis. Every surface now uses the shared <Favicon> or faviconSrc, and binary internal routes accept a user rate limit.

vercel · 2026-10-31T02:52:15Z

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Project	Deployment	Actions	Updated
docs	Skipped		Oct 31, 2026 3:25am UTC

cubic-dev-ai

All reported issues were addressed across 20 files

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greptile-apps · 2026-10-31T02:57:01Z

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no new actionable issues were found.

Summary

Site icons now use one signed-in server route with provider fallback, parent-domain lookup, and caching.

Sim serves site icons through one route with parent-domain fallback.
App icon surfaces use Sim's shared route and their own fallbacks.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Site icon] --> B[Signed-in favicon route]
  B --> C[Check host]
  C -->|Internal or invalid| D[204: show fallback]
  C -->|Public| E[Check cache]
  E -->|Cached| F[Return saved result]
  E -->|Not cached| G[Try Google, then DuckDuckGo]
  G -->|Icon found| H[Cache and return image]
  G -->|No usable icon| I[Try allowed parent domains]
  I -->|Icon found| H
  I -->|None available| D

_{Reviews (4) · Last reviewed commit: "fix(favicons): annotate the presenter so..." · Reviewed by Greptile}

…mpty labels and non-DNS hostnames A miss is an ordinary answer, so it returns 204 (which an img still reports as failed) instead of an error status; binary internal routes may now declare several success statuses and present a no-content response, sharing the JSON builder's status validation. Providers are asked one at a time so a second only learns a host the first had no icon for, a non-200 body is never read, and anything but 404/410 counts as unavailable rather than a cached miss.

waleedlatif1 · 2026-10-31T03:02:23Z

@greptile

waleedlatif1 · 2026-10-31T03:02:24Z

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cubic-dev-ai · 2026-10-31T03:02:30Z

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cubic-dev-ai

All reported issues were addressed across 23 files

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…ody before one classification

waleedlatif1 · 2026-10-31T03:13:38Z

@greptile

waleedlatif1 · 2026-10-31T03:13:40Z

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cubic-dev-ai · 2026-10-31T03:13:45Z

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

cubic-dev-ai

No issues found across 23 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

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…st its own descriptor

waleedlatif1 · 2026-10-31T03:25:21Z

@greptile

waleedlatif1 · 2026-10-31T03:25:22Z

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cubic-dev-ai · 2026-10-31T03:25:27Z

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

cubic-dev-ai

No issues found across 23 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

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cubic-dev-ai Bot reviewed Oct 31, 2026

View reviewed changes

Comment thread ...rkspace/[workspaceId]/home/components/message-content/components/source-chip/source-icon.tsx Resolved

Comment thread apps/sim/lib/favicon/probe.ts Resolved

Comment thread apps/sim/lib/favicon/hosts.ts Resolved

greptile-apps Bot reviewed Oct 31, 2026

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Comment thread apps/sim/lib/favicon/resolve.server.ts Resolved

vercel Bot temporarily deployed to Preview October 31, 2026 03:01 Inactive

cubic-dev-ai Bot reviewed Oct 31, 2026

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Comment thread apps/sim/lib/favicon/hosts.ts Resolved

fix(favicons): keep the presenter's 204 literal and read only a 200 b…

9109940

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vercel Bot temporarily deployed to Preview October 31, 2026 03:13 Inactive

cubic-dev-ai Bot reviewed Oct 31, 2026

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fix(favicons): annotate the presenter so each branch is checked again…

ddc6806

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cubic-dev-ai Bot reviewed Oct 31, 2026

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waleedlatif1 merged commit 17389db into staging Oct 31, 2026
75 checks passed

waleedlatif1 deleted the feat/favicon-service branch October 31, 2026 03:43

waleedlatif1 mentioned this pull request Oct 31, 2026

v0.9.38: favicon service, docs improvements #9500

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