Best possible solution:

Use #96178 as the landing path for the Browser /act alias fix and close this parallel branch.

Do we have a high-confidence way to reproduce the issue?

Yes. Source inspection shows current main resolves the request tab through alias-aware selection, then rejects alias spellings with raw equality before dispatch; the canonical PR also provides real Chrome/CDP before-after proof.

Is this the best way to solve the issue?

No for this PR as the landing path. The same fix is already carried by an older open canonical PR with broader tests and real browser proof, so maintaining this parallel branch is not the best solution.

Security review:

Security review cleared: No concrete security or supply-chain concern was found; the diff changes only Browser route target-id normalization and tests.

AGENTS.md: found and applied where relevant.

What I checked:

• Repository policy read: Read the full root AGENTS.md and scoped extensions/AGENTS.md; the review applied the required deep PR review, extension-boundary, best-fix, and proof checks. (AGENTS.md:1, 203a896b27c5)
• Current main raw top-level guard: Current main still rejects an action when action.targetId is not raw-equal to the resolved canonical tab.targetId, which is the failing alias path both PRs address. (extensions/browser/src/browser/routes/agent.act.ts:444, 203a896b27c5)
• Current main raw batch guard: Current main recursively validates batch sub-action targetId fields with raw string equality against the canonical request target. (extensions/browser/src/browser/routes/agent.act.normalize.ts:48, 203a896b27c5)
• Alias contract: The Browser tab resolver and public CLI docs already accept suggestedTargetId, stable tabId, label, raw id, and unique prefixes as targetId references. Public docs: docs/cli/browser.md. (docs/cli/browser.md:140, 203a896b27c5)
• Playwright dispatch needs canonical ids: The managed action executor uses action.targetId ?? targetId, and page resolution performs exact target-id lookup before throwing when multiple pages are present. (extensions/browser/src/browser/pw-tools-core.interactions.ts:1520, 203a896b27c5)
• This PR diff: This PR adds route-local alias matching and recursive mutation of action target ids before Playwright dispatch, plus two route tests for t1 aliases. (extensions/browser/src/browser/routes/agent.act.ts:358, 00fb47c12cec)

Likely related people:

• steipete: History for target-id.ts and Browser docs shows stable tab handles and preferred suggested target references were added in this area. (role: stable tab reference contributor; confidence: high; commits: 45e2a15e29ca, 82020bd78726, 29ddb9d926e5; files: extensions/browser/src/browser/target-id.ts, docs/cli/browser.md)
• eleqtrizit: Browser /act route history includes the current-tab route guard work in the same target validation surface. (role: route guard contributor; confidence: medium; commits: 78f3985c6051, ef0dbcf49d85; files: extensions/browser/src/browser/routes/agent.act.ts)
• ZengWen-DT: Authored the open proof-positive canonical PR for the same /act alias mismatch and has recent Browser docs history. (role: canonical fix author; confidence: medium; commits: 53b0bd625575, 2983edd5a2d8; files: extensions/browser/src/browser/routes/agent.act.ts, extensions/browser/src/browser/routes/agent.act.normalize.ts, docs/cli/browser.md)

Codex review notes: model internal, reasoning high; reviewed against 203a896b27c5.