# Review by a second model Audience: an adopter or contributor who wants to know what reviews a change, what a finding can stop, and how to answer one. > **Where it runs:** the merge gate's reviewer check and CodeRabbit run in your > own project. The `/pr-check` review runs from your himmel checkout: its > scripts can review a branch of your project, but the command itself is not > installed into your project. Details in [Where it runs](#where-it-runs). Every change is reviewed twice. `/pr-check` reviews the branch before its pull request opens, and the merge gate checks the reviewers again at the pull request's head before `gh pr merge` goes through. A second model family (OpenAI GPT through Codex) is what makes the review a cross-check rather than Claude grading its own work. ## What reviews your change The reviewers are the rows of `scripts/cr/critics.json`. As shipped: - **codex**: an OpenAI GPT model through the Codex CLI (the row's `model` field pins which one). Mode `hard`, `required`. This is the second model family and, as shipped, the only one. - **claude**: a Claude model through the Claude API lane. Mode `hard`, but absent while that lane is off, so it leaves the set. It is the same model family as the author, so it never counts as cross-model evidence. - **coderabbit**: the CodeRabbit GitHub app on your repo. It reviews the pull request once it opens and posts threads and a commit status. Mode `best-effort`. The critic tier, `CR_PROFILE`, picks which rows `/pr-check` dispatches: - `none`: Claude only, no external spend. - `free` (the default when unset): the free rows. The shipped file has none, so the panel falls back to the paid codex critic, which spends on your OpenAI account. - `paid`: the paid rows, codex and claude. If every critic fails, `/pr-check` falls back to a Claude-only review. ## What a finding does A finding has a severity: Critical, Important or Suggestion. Critical and Important findings block; a Suggestion is a note. A reviewer that cannot run blocks or is a note depending on its mode. **Before the pull request opens** (`/pr-check`, in a himmel checkout): - A push leaves a review-owed marker on the branch, and `gh pr create` is refused while it is there. - The marker clears only when a critic actually responded at the branch tip; zero responders is a missing review, not a clean one. - A Critical or Important finding blocks the clear until it is ruled `disproved`, or `deferred` with a ticket key and a reason. - Every finding, a Suggestion too, needs a ruling before the marker clears. - With `CR_REQUIRE_CROSS_MODEL=1`, at least one responder must be a non-Claude critic. - A branch gets three full review rounds, then one delta round over only what changed since the last review. A fourth full round is refused. **At the merge** (in your project and in a himmel checkout): - A `hard` reviewer must pass at the pull request's head. Anything else (in progress, not yet run, rate limited, unavailable, an open finding) holds the merge. - A `best-effort` reviewer holds only on an open finding. Otherwise it prints a NOTE and the merge goes on. - A reviewer set with no `hard` reviewer left is a config error and blocks, unless the repo says `"review": "no_code_review"`; then CI alone decides. - Every review thread on the pull request, CodeRabbit's included, must be resolved: `check-ci.sh` does not pass while one is open. ## Answering a finding Each finding gets one of three answers: 1. **Fix it.** Change the code and push. The fix is reviewed in the next round, at the new head. The finding is ruled `fixed`. 2. **Dispute it.** Rule it `disproved` with a written reason, when the finding is wrong. 3. **Defer it.** Rule it `deferred` with a ticket key and a reason, when it is real but belongs in a follow-up. A `deferred` ruling with no ticket key still blocks. `/pr-check` records each ruling in the review ledger for you. A CodeRabbit thread is answered on the pull request: fix it, or reply with why, then resolve the thread. When a `hard` reviewer is unavailable (out of credit, rate limited), the merge holds until it can review. Re-run it, or change its mode in your `critics.local.json` overlay. ## Settings The settings that change the review are in the [Review by a second model](../configuration.md#review-by-a-second-model) group of the configuration page: - `CR_PROFILE`: the critic tier. - `CR_REQUIRE_CROSS_MODEL`: require a non-Claude critic. - `critics.local.json`: add, change or drop a reviewer on your machine. Its field rules are in [Reviewer modes](../configuration.md#reviewer-modes). `bash scripts/cr/critic-panel.sh --check` prints every reviewer with its mode and state. ## Where it runs - **In your own project.** The install copies in the merge gate's reviewer check and the reviewer list, so `gh pr merge` holds there on the same rules. CodeRabbit reviews pull requests on your repo once you add the app. - **From your himmel checkout.** The `/pr-check` command ships with the himmel checkout, not your project. Its scripts take the repo from the working directory and the himmel scripts from the checkout that `HIMMEL_REPO` names, so they can review a branch of your project. Your project has no review-owed marker, so nothing there refuses `gh pr create` before a review.