docs(gemini-task): Gemini reviews its finished work with a fresh subagent

.claude/skills/gemini-task/SKILL.md

@@ -273,7 +273,7 @@ This section is for the Gemini agent in the owner's agy session.
      to take.
 
    Reading GitHub is fine. Your only writes are your own branch and your own
-   draft PR (step 7); never create, edit, comment on, label, or close anything
+   draft PR (step 8); never create, edit, comment on, label, or close anything
    else.
 
    **Scale out when there is work for several agents (owner, 2026-10-30).**
@@ -313,18 +313,20 @@ This section is for the Gemini agent in the owner's agy session.
      gates and test commands on the merged result; its path checks (which
      files may change) hold per package, so run those on its package branch
      (`git diff --name-only origin/main...origin/gemini/<slug>-<k>`). Add one
-     changelog fragment for the task, push, and open one draft PR (step 7)
-     whose `## Plan` lists each package with its merge commit. A package that
-     failed stays out; name it under open steps.
+     changelog fragment for the task, push, have the whole task reviewed
+     (step 7), and open one draft PR (step 8) whose `## Plan` lists each
+     package with its merge commit. A package that failed stays out; name it
+     under open steps.
    - **A review round** is an owner's comment on the draft PR that lists
      packages the way briefs do (section 3, step 4). Work it as above, with
      these differences: round `<n>`'s packages branch from
      `origin/gemini/<slug>` as `gemini/<slug>-r<n>-<k>` and merge back into
      `gemini/<slug>` the same way; path checks diff against
      `origin/gemini/<slug>` instead of `origin/main`; and the fragment and the
      draft PR exist already, so update the fragment only if the round changes
-     what it says. After the push, comment on the PR with each package's merge
-     commit and the result of every mutation-table row.
+     what it says. After the push, have the round reviewed (step 7), then
+     comment on the PR with each package's merge commit, the result of every
+     mutation-table row, and the self-review's findings.
    - Do not use `/teamwork` for this repository: it builds in its own folder
      (`~/teamwork_projects/<project>`) without branches or PRs.
 2. **Work in the dedicated clone on your own branch.** That clone is
@@ -401,7 +403,34 @@ This section is for the Gemini agent in the owner's agy session.
    Co-Authored-By: Antigravity (<your current model name>) <noreply@google.com>
    ```
 
-7. **Hand over** when you finish or stop, whether on a blocker or at the end of
+7. **Have the finished work reviewed before you hand it over** (owner,
+   2026-10-30: code quality comes before saving tokens). This holds for every
+   task, a single brief as much as one in packages. When every step is done
+   (for packages: after the integration in step 1) and the gates pass, push
+   the branch and start one fresh subagent as the reviewer, in its own
+   worktree (the `branch` mode) on a detached checkout of
+   `origin/gemini/<id>`. Its prompt names only:
+   - the Constraints and Acceptance sections of each brief, to `cat` itself,
+     or of the issue;
+   - the diff: `git diff origin/main...origin/gemini/<id>`, or for a review
+     round only the round's changes,
+     `git diff <tip before the round>...origin/gemini/<id>`;
+   - its job: read the whole diff for defects (bugs, missed edge cases,
+     changes outside the Constraints, broken conventions, tests that
+     would stay green against a broken implementation); run the mutation
+     table, if Acceptance has one, and add two or three breaks of its own in
+     the code the change claims to cover; report each finding with
+     `path:line`, severity, and a concrete fix; commit and push nothing.
+
+   Leave out your plan and your notes, so the reviewer judges the code and
+   not your intent. Fix the findings that hold up, in commits of their own,
+   run the gates again, and push. The PR body lists every finding under
+   `## Self-review`, fixed with its commit or declined with the reason. A
+   hand-over on a blocker skips this step. The self-review does not replace
+   Claude's review (section 3, step 3): a reviewer of the same model shares
+   the author's blind spots, so Claude's stays the independent one.
+
+8. **Hand over** when you finish or stop, whether on a blocker or at the end of
    the session. Push your branch and open a draft PR, or update the one you
    opened before. Write the body into a temp file first, in the repository's
    PR format, so Claude can ship it without rewriting it:
@@ -426,6 +455,11 @@ This section is for the Gemini agent in the owner's agy session.
    ## Decisions
    - The choices the task left to you, and what you chose.
 
+   ## Self-review
+   - Each finding of the review subagent (step 7): fixed in <commit>, or
+     declined and why. On a blocker hand-over: "Not run: hand-over on a
+     blocker."
+
    ## Open steps and questions
    - The steps still open and your questions, or "None".
    ```
@@ -496,7 +530,9 @@ This section is for the Gemini agent in the owner's agy session.
    package that drifted stands out.
    - Add Fable for high-risk diffs: security, production data, sandboxing,
      privacy.
-   - Gemini never reviews its own work.
+   - Gemini's self-review (section 2, step 7) does not replace this one, and
+     the subagent never sees it. Afterwards, judge each finding the
+     self-review declined in the PR body yourself.
    - **New tests need their mutation table run** by the subagent: apply each
      row to the real code, check that a test turns red, and revert; add a
      break or two of its own in the logic the tests claim to cover. On
@@ -550,7 +586,7 @@ This section is for the Gemini agent in the owner's agy session.
    branch, never by rebasing a pushed branch.
 5. **Ship.** Run the open-pr gates, add the PR number to the changelog
    fragment, and add one Summary bullet to the PR body, which Gemini wrote in
-   the repository's format (section 2, step 7): the change was implemented by
+   the repository's format (section 2, step 8): the change was implemented by
    Gemini 4 Argon in the owner's interactive agy session and reviewed by
    Claude, with the defects the review found and the commits that fixed them.
    This is provenance for the reviewer, not a "Generated with" footer. Then

changelog.d/gemini-self-review.md

@@ -0,0 +1,12 @@
+### Changed
+
+- **Gemini reviews its own finished work before it hands over.** In the
+  `gemini-task` skill, Gemini starts one fresh subagent as a reviewer once a
+  task, single or in packages, or a review round is done. The reviewer sees
+  only the brief's Constraints and Acceptance and the diff, reads the whole
+  diff for defects, and runs the mutation table plus
+  breaks of its own. Gemini fixes the findings that hold up and lists every
+  finding in a new `## Self-review` section of the PR body, as fixed or
+  declined. Claude's independent Opus review stays, because a reviewer of
+  the same model shares the author's blind spots. The owner's reason: code
+  quality comes before saving tokens. (#12476)