Ca Preview Agent Skill

$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

• Collect the diff. Call the thin entry hook preview.py in diff mode, which wraps

collect_diff from ${CLAUDE_PLUGIN_ROOT}/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:

   python3 "${CLAUDE_PLUGIN_ROOT}/hooks/preview.py" diff || python "${CLAUDE_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.

• Predict reviewers by path. Read the reviewer-to-path matrix at

${CLAUDE_PLUGIN_ROOT}/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.

• Run the state-free secret scan. Call the thin entry hook preview.py in secrets mode,

which wraps scan_secrets from ${CLAUDE_PLUGIN_ROOT}/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:

   python3 "${CLAUDE_PLUGIN_ROOT}/hooks/preview.py" secrets || python "${CLAUDE_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.