test(mv3): prove ephemeral Agent Task profile isolation

[seonghobae]

Buyer-visible gap

Partial implementation of #28. The pinned real-Chromium compatibility lane must prove that every Agent Task trial starts from an empty profile, reuses only that trial-local profile across the controlled restart pair, removes it afterwards, and does not leave inherited Chromium descendants alive after ChromeDriver exits.

Repaired live stack

Current exact prerequisite PR #43 head: c5e33b47b7a2ade47ecf962a41220b62c96a88db.
Current exact child head: 4344b2d22e945a6ceddf0667faf6ad6f60534a42.

The prior child head 3dc0cfd1fc6636ab3b258e00e01715f96c7ca535 had diverged from the moved prerequisite. The child was reconstructed non-destructively from the exact current #43 tree and advanced by a two-parent commit whose first parent is the previous child and whose second parent is the current prerequisite. Fresh comparison reports behind 0, merge base exactly c5e33b47b7a2ade47ecf962a41220b62c96a88db, and a remaining semantic delta of exactly three child-owned files:

• scripts/ci/run_mv3_compatibility.py;
• tests/test_mv3_ephemeral_profile_contract.py; and
• tests/test_mv3_process_group_cleanup_contract.py.

No prerequisite/predecessor check or review is transferred.

Implemented boundary

The current head preserves all prerequisite download/diagnostic/cleanup hardening and adds:

• one fresh temporary Chromium profile per compatibility trial;
• reuse of only that trial-local profile across the controlled initial/restart pair;
• profile deletion after the pair, with the profile path absent from returned evidence;
• ChromeDriver launch in a fresh operating-system session;
• process-group SIGTERM with bounded SIGKILL recovery so inherited Chromium descendants do not retain the supposedly ephemeral profile;
• bounded fallback behavior for already-gone or failing process-group signals without catch-all suppression; and
• causal error preservation: a primary browser-pass failure remains primary if session cleanup/process teardown also fail; a reviewed session-delete failure remains the cause of typed WebDriverSessionCleanupError when teardown also fails.

The process-group behavior is controlled Linux CI evidence, not a claim of a complete cross-platform production process supervisor.

Exact-current verification

On unchanged exact head 4344b2d22e945a6ceddf0667faf6ad6f60534a42 against exact prerequisite c5e33b47b7a2ade47ecf962a41220b62c96a88db:

• ancestry: ahead, behind 0, merge base exactly the live prerequisite;
• Manifest V3 Compatibility run 31979916749: success;
• CI run 31979916762: success;
• Rust contracts job 95244934137: repository contracts, formatting, workspace checks, full tests, strict Clippy and rustdoc success;
• Production coverage job 95244934130: exact production coverage enforcement success;
• the exact-head check-run set contains only the successful Rust-contract, production-coverage and pinned-Chromium fixture checks; and
• GitHub freshly reports the Draft mergeable.

Feature-base organization security/review workflows that did not execute on this exact head are absent evidence and are not represented as passing.

Scope / governance

This remains compatibility evidence, not a production browser adapter. It adds no default-profile access, raw credential handling, persistent profile storage, extension grant widening, general browser-protocol authority, model call, workflow mutation, or release claim. Keep Draft while #43 remains active. Protected-main AGENTS.md forbids this scheduled actor from merging, self-approving, altering workflows, adding secrets, weakening checks, tagging, or publishing.

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: e0c194d7-d9dd-4f1f-b2cc-3b230f11107d

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}