Cross-Review — a second-vendor set of eyes on your diff

A different vendor's model has different blind spots. Claude reviewing Claude's diff shares those
blind spots; a DeepSeek (or GLM, or any OpenAI-compatible) reviewer catches a different class of
issue. This skill runs that second reviewer over the current changes and acts on its verdict.

When to use

• After a phase is green, before you commit or merge.
• On a risky diff (auth, crypto, data-touching, concurrency) where a second opinion is cheap insurance.
• NOT a replacement for the in-repo /caddis:code-review — this is the cross-vendor complement.

Check the key FIRST, and ask if it is missing

python "$TOOL" --check-config

Exit 0 prints which providers have a key. Exit 3 means nothing is configured — stop and ask the
user before reading any diff. Do not proceed, and do not silently skip the review.

Ask with AskUserQuestion which provider to set up, then write the key to ~/.caddis/keys.env as
DEEPSEEK_API_KEY=<key> (or the matching variable). That file sits outside every git repo, so it
cannot be committed by accident. Never put a key in the repo, in a command, or in a reply.

This used to fail mid-task with a commit pending — the worst moment to go hunting for a credential.
A command that fails once at an inconvenient moment does not get retried, so the safety check is
quietly lost and nothing records the loss. The script stays non-interactive because it also runs
headless, where a stdin prompt hangs instead of asking; the asking is the agent's job.

If a key exists for a different provider than the one requested, the error names it and gives the
exact flag (--provider glm). Read the message before concluding anything is missing.

Prerequisites (one-time)

Only the key is mandatory — the tool ships provider presets (default deepseek, the cheapest + most
architecturally distinct-from-Claude option; a review costs well under a cent):

REVIEW_API_KEY   = <your provider key>     # REQUIRED (exit 3 without it)
REVIEW_PROVIDER  = deepseek                 # optional: deepseek | glm | openrouter (default deepseek)
REVIEW_BASE_URL  = ...                      # optional: overrides the preset's URL
REVIEW_MODEL     = ...                      # optional: overrides the preset's model id

Switch provider with one flag: --provider glm (or REVIEW_PROVIDER=glm). Future-proofing: model ids
churn — the preset table in oss_review.py is the one place to edit a rename, and REVIEW_MODEL /
REVIEW_BASE_URL always win, so you can point at any new id without touching code.

How to run

From the repo root. Resolve the tool path deterministically — check only these two exact
locations, in order, and never search the filesystem for it (see Rules below):

# THE PLUGIN COPY WINS. It is the one `caddis update` refreshes; a vendored copy is a snapshot
# of whatever caddis shipped the day someone copied it, and it never updates again.
if [ -f "${CLAUDE_PLUGIN_ROOT}/scripts/oss_review.py" ]; then
  TOOL="${CLAUDE_PLUGIN_ROOT}/scripts/oss_review.py"
  # A vendored copy that DIFFERS is a live hazard, not a curiosity — say so, do not stay silent.
  if [ -f ".github/tools/oss_review.py" ]      && ! diff -q ".github/tools/oss_review.py" "$TOOL" >/dev/null 2>&1; then
    echo "[cross-review] WARNING: .github/tools/oss_review.py differs from the caddis copy and is"
    echo "               being IGNORED. Delete it, or keep the local change deliberately."
  fi
elif [ -f ".github/tools/oss_review.py" ]; then
  TOOL=".github/tools/oss_review.py"   # no plugin present — the vendored copy is all there is
else
  echo "oss_review.py not found at either known location — report this and stop. Do NOT search for it."
  exit 3
fi

Why the plugin copy is first. It used to be second. On 2026-08-10 a repo ran a stale vendored
oss_review.py and got REVIEW: CLEAN on a database write path that was never reviewed. The bug
had been fixed on 2026-08-01 — the fix just never reached the caller, because a file someone
copied weeks earlier silently won. caddis_gate.py vendor-drift now fails on the same condition.

python "$TOOL"                                             # review the working tree (staged+unstaged)
python "$TOOL" --range origin/main..HEAD                   # review a branch's commits

Optional flags: --cwd <repo>, --base-url <url>, --model <id> (override the env).

Diff-size ceiling. A diff over REVIEW_MAX_DIFF_CHARS (default 60,000 chars) is split into batches on whole-file boundaries and each batch reviewed separately (verdict is CLEAN only if every batch is). Exit 2 now means a single unsplittable file over the ceiling, or too many batches — not an ordinary large diff. Previously it was refused with exit 2
before any LLM call — an oversized diff has been observed to come back either an empty response, or
worse, a REVIEW: CLEAN with zero real engagement. If you hit this, narrow --range or review in
smaller chunks; don't just raise --max-diff-chars without knowing the endpoint's real limit.

Interpret the exit code

• 0 — REVIEW: CLEAN → no blocking issues. Proceed.
• 1 — REVIEW: BLOCKING → the reviewer found blocking issues. Read the printed findings, then FIX
  each blocking item (or, if you judge one a false positive, state explicitly why it's safe to ignore).
  Re-run until CLEAN.
• 2 — error → no verdict parsed, a git failure, or an endpoint/parse failure. Read stderr; do not
  treat this as CLEAN — investigate.
• 3 — misconfigured → REVIEW_API_KEY is unset. Set it (see Prerequisites) and re-run.

Rules

• This is a read-only second opinion — the tool never edits, commits, or pushes. YOU apply fixes in
  the main thread after reading the findings.
• Treat exit 2/3 as blocking-unknown, never as approval (the tool is fail-closed by design).
• Different vendor ⇒ different style; weigh its findings on merit, don't cargo-cult them.
• Never use find, Get-ChildItem -Recurse, or any other filesystem-wide search to locate
  oss_review.py. Check only the two paths above. On Git Bash under Windows, find / (or any
  search rooted at /) walks every mounted drive, not just the repo — it can hang or take minutes.
  If neither path exists, stop and report it; don't go hunting for the file.