feat(browser): give the embedded browser a faithful Chrome user-agent

[Astro-Han]

Summary

Give the embedded browser a faithful Chrome user-agent. Electron's default UA carries an Electron/<ver> token and the app's own product token (opencode/<ver> after index.ts's rewrite, PawWork .../<ver> before it) exactly where a real Chrome UA has nothing — both are obvious "not a normal browser" tells. We strip them and pin the Chrome token to the reduced Chrome/<major>.0.0.0 form real Chrome reports, deriving the major from process.versions.chrome so it tracks the embedded Chromium and never drifts. The clean UA is set on the persist:pawwork-browser partition, so it applies to both manual browsing and CDP-driven automation.

This is the first stealth-fidelity change after a real Xiaohongshu "suspected automation" warning. It is legitimate fingerprint fidelity: the view IS real Chromium (Electron), and we present it as the Chromium it actually is — for users operating their own accounts — rather than leaking Electron/app tokens that look like a bot.

Why this shape (Client Hints left at Chromium defaults — deliberate)

Codex consult + Electron/Chromium source confirmed:

• Electron does not invent its own UA Client Hints; it delegates to Chromium's embedder_support::GetUserAgentMetadata(). So default navigator.userAgentData brands as Chromium (+ a GREASE brand) and does not leak "Electron" or the app name.
• session.setUserAgent sets only the UA string + Accept-Language. The only way to set Client Hints for manual browsing would be a permanent CDP debugger attach, which is itself a detectable signal and is explicitly not worth it.

So the chosen identity is faithful, consistent Chromium, not impersonated Google Chrome:

• A real Chromium build reports UA Chrome/<major>.0.0.0 and CH brand Chromium — exactly what we now produce. Internally consistent, nothing faked.
• The rejected alternative (add a "Google Chrome" brand via CDP on the automation path only) would make the same profile present as Chromium when browsed manually and Google Chrome when the agent drives — an intra-profile identity flip a real browser never does, i.e. a new tell. Consistency is the better stealth.
• Verified opencli's automation path does not override UA or touch navigator.userAgentData (only Emulation.setDeviceMetricsOverride + Network.enable), so automation inherits the same consistent identity; its stealth script handles the automation-specific JS tells (webdriver, chrome, plugins, languages).

Honest ceiling: this fixes the fingerprint layer only. It does not make automation "safe" on a mature behavioral risk-control platform (speed/rhythm/trajectory still matter). It removes the loud UA tell that this browser is not a normal one.

Related Issue

None — follow-up from a maintainer report; no tracking issue yet.

Human Review Status

Pending

Review Focus

• toChromeUserAgent in user-agent.ts: token stripping is robust to both the opencode/ (post-rewrite) and PawWork .../ (pre-rewrite, app name with a space) forms, preserves the OS platform token (macOS vs Windows), and is idempotent.
• Placement/scope in controller.ts: partition-scoped (app renderer UA untouched), once-guarded, set before the first view's first request.
• The Client-Hints decision above — is "faithful Chromium, consistent across manual+auto" the identity we want, vs. impersonating Google Chrome?

Risk Notes

• Scope is the persist:pawwork-browser partition only; app.userAgentFallback (app renderer) is intentionally left as-is.
• Client Hints are unchanged (Chromium defaults). If a site compares UA string vs CH it sees a consistent real-Chromium browser.
• No visible UI/copy changed; this is network-level identity.

How To Verify

Verified by me (CI-checkable):

packages/desktop-electron:
typecheck (tsgo -b): clean
test src/main/browser/: 58 pass (incl. user-agent.test.ts 10 pass — Electron/opencode/PawWork tokens stripped, Chrome version pinned, macOS+Windows shapes, idempotent, unparseable-version fallback, and the configurePartitionUserAgent seam applies the cleaned UA to the partition session)

Runtime check (needs the desktop GUI — your machine), using the fingerprint probe I sent separately:

1. Run dev:desktop, open the embedded browser, load the probe HTML.
2. Confirm navigator.userAgent = ...Chrome/<major>.0.0.0 Safari/537.36 with no Electron / opencode / PawWork (probe flags these red).
3. Confirm navigator.userAgentData.brands shows Chromium (+ GREASE), no Electron/app leak.
4. Compare against an external Chrome — UA string and CH should both read as a coherent Chromium/Chrome browser.

Screenshots or Recordings

N/A — no visible UI change (network-level UA).

Checklist

• Type label — exactly one of bug, enhancement, task, documentation.
• Routing labels — at least one of app, ui, platform, harness, ci.
• Priority label — exactly one of P0, P1, P2, P3.
• Human Review Status above is set to Pending.
• I linked the related issue, or stated in Summary why there is no issue.
• I described the review focus and any meaningful risks.
• I replaced the example block in How To Verify with the real verification steps and the key result for each.
• I did not introduce unrelated refactors, dependencies, generated files, or file changes beyond the stated scope.
• (conditional) I manually checked visible UI or copy changes when needed. Left unticked: no visible UI/copy changed.
• (conditional) I considered macOS and Windows impact — the UA platform token differs per OS; toChromeUserAgent preserves Electron's frozen per-OS token and is tested for both macOS and Windows shapes.
• (conditional) docs/release notes/deps/permissions/credentials/deletion/generated content/local files — none touched.
• I reviewed the final diff for unrelated changes and suspicious dependency changes.
• I am targeting dev, and my PR title and commit messages use Conventional Commits in English.

Summary by CodeRabbit

• New Features

  • Browser now automatically identifies itself to web servers using Chrome user agent format instead of Electron
  • Browser initialization updated to apply the correct user agent from the first request onward

• Tests

  • Added tests validating user agent string normalization, Chrome version extraction, and proper format conversion

[github-actions]

Suggested priority: P2 (includes user-path files (packages/desktop-electron/src/main/browser/controller.ts, packages/desktop-electron/src/main/browser/user-agent.test.ts, packages/desktop-electron/src/main/browser/user-agent.ts)).

P1/P0 are reserved for maintainer confirmation. Please relabel manually if this is a release blocker, security issue, data-loss risk, or updater/runtime failure.

[coderabbitai]

📝 Walkthrough

Walkthrough

A new user-agent.ts module exports chromeMajorVersion and toChromeUserAgent, which rewrite Electron's default UA into a Chrome-only UA by stripping Electron and app-specific tokens and pinning the Chrome version. A one-time guarded helper in controller.ts applies this rewrite to the shared browser partition session before the first WebContentsView is instantiated. Tests validate all normalization cases.

Changes

Electron Partition User-Agent Normalization

Layer / File(s)	Summary
UA normalization module and tests packages/desktop-electron/src/main/browser/user-agent.ts, packages/desktop-electron/src/main/browser/user-agent.test.ts	Introduces chromeMajorVersion (extracts leading numeric major from a version string) and toChromeUserAgent (strips Electron/app tokens, pins Chrome/ to <major>.0.0.0, normalizes whitespace). Tests cover token stripping, version pinning, idempotence, Windows platform preservation, double-space removal, and unparseable version fallback.
Controller partition UA wiring packages/desktop-electron/src/main/browser/controller.ts	Adds ensureBrowserPartitionUserAgent, a once-per-process guard that fetches the partition session via session.fromPartition(BROWSER_PARTITION) and sets its UA using toChromeUserAgent. Calls the guard at the top of BrowserViewController construction. Replaces the browserViewWebPreferences import with toChromeUserAgent.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

enhancement, desktop, P2

Poem

🐇 A browser once said "I'm Electron, you see!"
But websites just frowned and turned it away with glee.
Now Chrome is the mask that the partition shall wear,
No Electron tokens left lurking in there.
One guard, one rewrite — the UA is clean!
The web sees plain Chrome where Electron had been. 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly describes the main change: configuring the embedded browser with a Chrome-style user-agent that removes Electron/app tokens.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description comprehensively covers all required template sections including summary, rationale, related issues, human review status, review focus, risk notes, verification steps, and a complete checklist.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/browser-ua

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[gemini-code-assist]

Code Review

This pull request introduces a mechanism to rewrite the default Electron user-agent string into a clean, standard Chrome user-agent for the embedded browser's shared partition. This is achieved by stripping out Electron-specific and application-specific tokens and pinning the Chrome version to the reduced major.0.0.0 format, reducing the risk of anti-automation detection. Unit tests have been added to verify the parsing and rewriting logic. I have no feedback to provide as there are no review comments.

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