/ca-preview

name: ca-preview
description: Zero-onboarding, read-only dry-run of the reviewer fleet against the current uncommitted diff. Predicts reviewers, runs the state-free secret scan, writes nothing.
argument-hint: (none)

$ca-preview — reviewer-fleet dry-run

See what codeArbiter would do to your real code before paying any onboarding cost. This is a read-only dry-run against the current uncommitted diff: it predicts which reviewers the change would dispatch, runs the checks that need no project rules, and reports. It never writes state.

It requires no `$ca-init`, no `.codearbiter/` directory, and no decompose or create-context interview. It functions in a repo that never opted in, and it modifies nothing: not the worktree, not the index, not `.codearbiter/`. `git status` is unchanged by a run.

Flow

1. **Collect the diff.** Call the thin entry hook `preview.py` in `diff` mode, which wraps `collect_diff` from [hooks/_previewlib.py](../../hooks/_previewlib.py). It unions HEAD-vs-worktree changes, staged changes, and untracked files (forward-slash paths). Run it from the project root so `_previewlib`/`_hooklib` resolve on the same `sys.path`. Resolve the interpreter once by presence — `PY=python3; { command -v python3 >/dev/null 2>&1 && python3 --version >/dev/null 2>&1; } || PY=python` — never `python3 X || python X`, which reruns X on any nonzero exit (#577):

   "$PY" "${PLUGIN_ROOT}/hooks/preview.py" diff

If the result is empty (clean tree, or not a git repo), print a friendly **"Nothing to preview"** line and STOP. This is a clean exit, not an error: no stack trace, no failure.

2. **Predict reviewers by path.** Read the reviewer-to-path matrix at [includes/review-matrix.md](../../includes/review-matrix.md). That include is the single source of truth for which reviewer is dispatched when scope touches a given path: do NOT restate, fork, or inline a second copy of the table here. For each changed path, list the reviewers that WOULD dispatch and name the triggering path for each. This is the same mapping `$ca-review` uses, so the predicted set matches what a real review would dispatch.

3. **Run the state-free secret scan.** Call the thin entry hook `preview.py` in `secrets` mode, which wraps `scan_secrets` from [hooks/_previewlib.py](../../hooks/_previewlib.py). It reads each changed file's current content and returns `SecretFinding(path, line_no, snippet)` for every credential line, with the secret VALUE already masked to `****` in `snippet`:

   "$PY" "${PLUGIN_ROOT}/hooks/preview.py" secrets

Report each finding by `path:line_no` with its redacted snippet. The snippet arrives already masked: never reconstruct or print a raw secret value.

Report

Emit one clear report with these parts:

• **Changed files** — the reviewed-file set from step 1, each with its change kind(s) (unstaged,

staged, untracked).

• **Predicted reviewers** — per the matrix, which reviewers would dispatch and the triggering path

for each. These are predicted (would-dispatch), not run here.

• **Secret findings** — the results of the real scan from step 3, by `path:line_no` with the

redacted snippet, marked as found (ran locally), at BLOCK severity. State "none found" when the scan is clean.

• **Onboarding nudge** — close with one line: the full gated review comes via `$ca-init` then

`$ca-review`.

Distinct from $ca-doctor

This reports reviewer and gate behavior on the current diff. It makes NO hook-probe claims and says nothing about whether the install's hooks fire: that is `$ca-doctor`. Do not blend the two.

When NOT to use

• An onboarded repo wanting the full gated verdict → `$ca-init` then `$ca-review`.
• Proving the install's hooks actually fire → `$ca-doctor`.
• A question about the code → `$ca-btw`.

Hard gate

• Read-only. MUST NOT write, create, or modify any file, including anything under `.codearbiter/`;

MUST NOT stage or commit. `git status` MUST be unchanged after a run.

• MUST NOT require, trigger, or error on missing `$ca-init`, `.codearbiter/` state, or the

decompose / create-context interview.

• MUST NOT print a raw secret value: the lib returns the snippet already redacted, and the report

carries only that masked form.

• An empty diff or a non-git directory MUST yield the "Nothing to preview" message and a clean

exit, never a stack trace.

• MUST treat the reviewer prediction as predicted (would-dispatch) and the secret scan as found

(ran locally): it MUST NOT attribute fabricated findings to any predicted reviewer.