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fix(server): Antigravity Google sign-in shows its URL on Windows - #26115
On Windows, Antigravity Google sign-in never shows the sign-in page or the Open browser / Copy sign-in link controls; the provider stays in sign-in until it times out. T3 learns the URL from a BROWSER helper that writes it to stderr, but CPython's webbrowser on Windows starts that helper with subprocess.Popen(cmdline), no std redirection and close_fds=True, so the helper never inherits the agent's stderr pipe. Node writes into a discarded handle, exits 0, and the agent believes a browser opened. The agent's own stdout copy of the URL stays block-buffered.
Reproduced on Linux with main's exact helper and quoting: when the helper inherits stderr (POSIX) the URL reaches T3; with the stdio state Windows gives it, the helper exits 0 and T3 receives nothing.
Change
Each sign-in runtime (the driver runtime that has an onAuthorizationUrl) starts a loopback listener on 127.0.0.1 with a random path token, scoped to that runtime, and passes its address to the agent in T3_ANTIGRAVITY_AUTH_SINK. The listener validates the body with the existing parseAntigravityAuthorizationUrl (16 KiB cap) and hands it to the same onAuthorizationUrl.
The browser helper POSTs the URL there with node:http and agent: false (so NODE_USE_ENV_PROXY proxies are bypassed) and exits 0 after a 204. Without the variable, or on any failure or a 5 s timeout, it writes the existing stderr marker as before, still exiting 0.
T3_ANTIGRAVITY_AUTH_SINK is stripped from inherited environments, so turn, refresh and preflight launches never carry it. If the listener cannot start, sign-in logs a warning and keeps the stderr path.
AntigravityDriver > shows the Google sign-in URL when the agent opens BROWSER without sharing its stderr: the fake agent splits $BROWSER like CPython and runs T3's real helper with stdin, stdout and stderr on /dev/null. Fails on main (the sign-in flow never received the URL the agent handed to BROWSER: expected undefined to be 'https://accounts.google.com/…'), passes here.
posts the sign-in URL to the listener directly when an environment proxy is set: fails with a fetch-based helper (URL went to the proxy, then stderr), passes here.
falls back to stderr when the sign-in listener rejects the URL or is gone: exit 0 and the marker on stderr in both cases.
Server-only change with no rendered surface changed, so no screenshots.
cannot-verify windows: not run on a Windows desktop with the packaged agent, Electron-as-Node, or a real Google account. Windows argv quoting of the helper was checked by modelling shlex → list2cmdline → CRT parsing.
Built with Claude Opus 5.5 (lead, tests, implementation, review) and Codex gpt-6.1-sol (review) in Claude Code through T3 Code.
…SER has no stderr
Adds a failing driver test that reproduces #9624. A fake agent runs the
configured BROWSER the way CPython's webbrowser does on Windows
(shlex-split, %s substituted, stdio not inherited). The helper's marker
goes nowhere, so the sign-in flow never shows the Google URL.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
On Windows, CPython's webbrowser starts BROWSER without the agent's
stdio, so the helper's stderr marker never reached T3 and sign-in
waited with no URL.
Sign-in runtimes now serve a scoped 127.0.0.1 listener with a random
path token and pass its URL to the agent in T3_ANTIGRAVITY_AUTH_SINK.
The helper POSTs the URL there and exits once it is accepted, and it
falls back to the stderr marker when the variable is absent or delivery
fails. The listener validates with parseAntigravityAuthorizationUrl and
hands off to the same onAuthorizationUrl. Inherited copies of the
variable are stripped from every launch.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The browser helper posts to the loopback listener with node:http and
agent: false, so NODE_USE_ENV_PROXY with HTTP_PROXY no longer routes it
to a proxy and back to the lost stderr path.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Macroscope's review found this PR requires human approval — The change delivers Antigravity sign-in URLs through a token-protected loopback listener, retaining stderr fallback. It also adds a static-analysis suppression for the node:http import, which requires human review under the configured policy.
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Walkthrough
The Antigravity authentication flow now sends authorization URLs through a loopback HTTP sink when available. The browser helper falls back to an stderr marker if delivery fails. Driver and helper tests cover URL delivery, fallback behavior, and sign-in state.
Changes: Antigravity authorization URL handoff
Layer / File(s)
Summary
Authorization URL sink and helper transport apps/server/src/provider/antigravityAuthSupport.ts, apps/server/src/provider/antigravityAuthSupport.test.ts
The browser helper posts the authorization URL to the configured sink without using proxy settings. If delivery fails, it writes the URL marker to stderr. The loopback listener accepts tokenized POST requests, limits request bodies, and invokes the supplied callback. Tests cover delivery failure, a closed sink, and delivery with proxy settings.
Driver integration and sign-in validation apps/server/src/provider/Drivers/AntigravityDriver.ts, apps/server/src/provider/Drivers/AntigravityDriver.test.ts
The driver starts the sink when an authorization callback is present and passes its URL to the ACP process. A test verifies that sign-in reaches the waiting state with the URL when the browser process does not share its standard streams.
33032 — Reports Antigravity sign-in failures with a proxy and browser-helper stderr output; this change updates the helper’s sink delivery and stderr fallback.
17508 — Reports rejected redirect URLs during sign-in; this change validates URLs received by the listener and handles callback rejection.
Suggested reviewers:maria-rcks
Merge Risk: Minimal · up to cb580
No concrete issue remains that would block merging. A real Windows sign-in check would provide additional confidence in the intended fix.
Pre-merge checks: 4
Check name
Status
Explanation
Title check
The title is concise, conventional, and clearly identifies the main change: fixing the Antigravity Google sign-in URL handoff on Windows.
Description check
The description includes complete Problem, Change, Scope and approval, and Verification sections. It explains the failure, implementation, linked issue, targeted tests, observed results, and unverifie…
Linked Issues check
Issue [#9624] requires the Antigravity sign-in URL to reach T3 when the Windows browser helper does not share stderr. AntigravityDriver starts a runtime-scoped loopback sink when `onAuthorizationUrl…
Out of Scope Changes check
The changes stay within issue [#9624]. Production changes modify Antigravity sign-in URL transport, child-environment isolation, and browser-helper fallback. The tests cover these authentication paths…
Full details: Description check
Explanation
The description includes complete Problem, Change, Scope and approval, and Verification sections. It explains the failure, implementation, linked issue, targeted tests, observed results, and unverified Windows conditions.
Full details: Linked Issues check
Explanation
Issue [#9624] requires the Antigravity sign-in URL to reach T3 when the Windows browser helper does not share stderr. AntigravityDriver starts a runtime-scoped loopback sink when onAuthorizationUrl exists and passes its address through T3_ANTIGRAVITY_AUTH_SINK. The helper posts with node:http and agent: false, validates the URL through the existing parser, and falls back to the existing stderr marker on failure. The tests cover the Windows-style no-stdio handoff, proxy bypass, and fallback paths. The driver logs a warning and retains the stderr path when listener startup fails.
Full details: Out of Scope Changes check
Explanation
The changes stay within issue [#9624]. Production changes modify Antigravity sign-in URL transport, child-environment isolation, and browser-helper fallback. The tests cover these authentication paths. No unrelated product area or user-facing surface is changed.
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Actionable comments posted: 1
🪄 Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix review comments
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Inline comments:
Review comments at @apps/server/src/provider/antigravityAuthSupport.ts:
- Line 512: Update the Effect.mapError handler in the Antigravity sign-in URL
listener startup flow to preserve the original bind or crypto failure as the
AcpTransportError cause. Construct the transport error with the existing
startup-failure detail and the caught error as cause instead of using
authSupportError, which drops it.
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The automated pipeline stopped on this pull request and will not merge it:
the proof has no capture anyone can open:
Permanent blocker: Antigravity is explicitly unavailable on this VM, preventing the real Google sign-in flow on both commits.
The Windows-specific browser-helper launch behavior could not be exercised on this Linux VM.
Authorization URL delivery, Open browser and Copy sign-in link controls, and continued Google authentication remain unverified.
No capture uploads were attempted because no valid captures were produced; there is no ghdrop failure output.
It stays open for a person to finish or close.
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bugfixFix PR opened by an issue lead; enters the PR looppr:needs-juliusNeeds Julius: route gate, unverifiable surface, or blockedsize:M30-99 changed lines (additions + deletions).vouch:trustedPR author is trusted by repo permissions or the VOUCHED list.
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Problem
On Windows, Antigravity Google sign-in never shows the sign-in page or the Open browser / Copy sign-in link controls; the provider stays in sign-in until it times out. T3 learns the URL from a
BROWSERhelper that writes it to stderr, but CPython'swebbrowseron Windows starts that helper withsubprocess.Popen(cmdline), no std redirection andclose_fds=True, so the helper never inherits the agent's stderr pipe. Node writes into a discarded handle, exits 0, and the agent believes a browser opened. The agent's own stdout copy of the URL stays block-buffered.Reproduced on Linux with main's exact helper and quoting: when the helper inherits stderr (POSIX) the URL reaches T3; with the stdio state Windows gives it, the helper exits 0 and T3 receives nothing.
Change
onAuthorizationUrl) starts a loopback listener on127.0.0.1with a random path token, scoped to that runtime, and passes its address to the agent inT3_ANTIGRAVITY_AUTH_SINK. The listener validates the body with the existingparseAntigravityAuthorizationUrl(16 KiB cap) and hands it to the sameonAuthorizationUrl.node:httpandagent: false(soNODE_USE_ENV_PROXYproxies are bypassed) and exits 0 after a 204. Without the variable, or on any failure or a 5 s timeout, it writes the existing stderr marker as before, still exiting 0.T3_ANTIGRAVITY_AUTH_SINKis stripped from inherited environments, so turn, refresh and preflight launches never carry it. If the listener cannot start, sign-in logs a warning and keeps the stderr path.Scope and approval
Fixes #9624
Triaged via the automated issue flow.
Verification
AntigravityDriver > shows the Google sign-in URL when the agent opens BROWSER without sharing its stderr: the fake agent splits$BROWSERlike CPython and runs T3's real helper with stdin, stdout and stderr on/dev/null. Fails on main (the sign-in flow never received the URL the agent handed to BROWSER: expected undefined to be 'https://accounts.google.com/…'), passes here.posts the sign-in URL to the listener directly when an environment proxy is set: fails with afetch-based helper (URL went to the proxy, then stderr), passes here.falls back to stderr when the sign-in listener rejects the URL or is gone: exit 0 and the marker on stderr in both cases.antigravityAuthSupport,AntigravityDriver,AntigravityAuth,AntigravityAcpSupport,AntigravityProvider): 101 passed.vp run check:changedpasses.%ssubstitution, helper stdio not inherited):onAuthorizationUrlreceived the URL — issue-9624-after-head.txt, driver issue-9624-after-driver.tscannot-verify windows: not run on a Windows desktop with the packaged agent, Electron-as-Node, or a real Google account. Windows argv quoting of the helper was checked by modellingshlex→list2cmdline→ CRT parsing.Built with Claude Opus 5.5 (lead, tests, implementation, review) and Codex gpt-6.1-sol (review) in Claude Code through T3 Code.
🤖 Generated with Claude Code