fix: stop favicon requests for private chat-link hosts

[leoisadev1]

What Changed

Private, reserved, Tailscale, and special-purpose hosts no longer get a Google favicon request from chat markdown or the mobile feed. The host classifier lives in @t3tools/shared so web preview tabs and chat links use the same rule. Public links still show the favicon.

Why

A link to http://192.168.1.10 or http://localhost:3000 was leaking that hostname to a public favicon provider.

Adapted from pingdotgg/t3code#5838.

UI Changes

Private-host links in bot/group markdown use the globe fallback. Public hosts are unchanged.

Checklist

• This PR is small and focused
• I explained what changed and why
• I linked the accepted plugin or provider proposal in Why, or this PR does not add one
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Verification

• vp test run packages/shared/src/favicon.test.ts packages/shared/src/hostClassification.test.ts apps/web/src/browser/browserTargetResolver.test.ts (53 tests)
• targeted lint/format
• Live ChatMarkdown path is the bot/group renderer. Native mobile was not run on a device.

Implemented and verified by Grok 4.6 High in Grok Build via Orca.

[vercel]

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Project	Deployment	Actions	Updated
akeru-bot-landing	Building	Preview	Sep 10, 2026 6:22pm UTC

[greptile-apps]

Greptile Summary

Summary

• Host classification and favicon URL generation are now shared across applications.
• Web markdown links use a globe fallback for private, reserved, local, and Tailscale hosts instead of loading a public favicon URL; public links retain favicon rendering.
• Repository identity resolution now prioritizes origin and falls back to upstream.

T-Rex validation blocked

• A sequential runtime capture for the repository-identity harness could not be completed because the command-execution connection closed before valid output was captured.

Confidence Score: 5/5

Safe to merge: no actionable defects were established.

The final finding set is empty. Rendered markdown-link checks confirmed safe favicon behavior for private and public hosts.

Files Needing Attention: No files require follow-up changes.

T-Rex Logs

What T-Rex did

• Validated favicon rendering across six web markdown-link cases, confirming globe fallback for private IPv4, reserved, local, Tailscale hostname, and Tailscale CGNAT links, while a public GitHub link correctly used a Google favicon URL without the fallback.
• Authored a focused repository-identity harness to verify origin preference and the upstream-only fallback, but the required sequential runtime capture could not complete because the command-execution connection closed before valid output was captured.
• Referenced the harness script trex-artifacts/repository-identity-origin-contract.sh as the harness reference, and noted that prior logs could not be used because concurrent execution invalidated them.

_{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "fix: stop favicon requests for private c..." | Re-trigger Greptile}