A Three-Pass Hygiene Check for Free Coding Model Diffs

Cheap model access does not remove code review; it moves review from "what did it write" to "what did it touch".

Free model endpoints make it easy to generate many small patches. The failure mode worth watching is not bad code. It is scope creep: one requested function turns into a dependency update, a new file, and a network call.

Disclosure: This article was prepared as part of MonkeyCode's product outreach.

The checklist

Review every generated diff with three questions:

• Scope — Did it only touch the files you asked for?
• Side effects — Did it add dependencies, network calls, or new files?
• Reversibility — Can you revert it with one command?

Pass all three before you read the code line by line. Fail one, send it back.

Why diff-level checks first

Semantic review is slow. Hygiene checks are fast. A model can write plausible code that still changes the wrong file. If the diff is not contained, code-quality arguments are moot.

This matters more with free model access because another patch is cheap. Low cost invites large, exploratory diffs. The harness below is a gate, not a judge.

Harness: review_patch.sh

Save this as review_patch.sh:

#!/usr/bin/env bash
set -euo pipefail

PATCH="${1:?usage: review_patch.sh <file.patch> 'src/*'}"
PATTERN="${2:-src/*}"

echo '== files touched =='
grep '^+++ ' "$PATCH" | sed 's|^+++ b/||' || true

echo '== out-of-scope files =='
grep '^+++ ' "$PATCH" | sed 's|^+++ b/||' |
  while read -r f; do
      case "$f" in
        $PATTERN) : ;;
        *) echo "OUT_OF_SCOPE: $f" ;;
      esac
    done

echo '== dependency edits =='
grep '^+' "$PATCH" |
  grep -Ei 'import |from |require|pip install|npm install|go get|cargo add|gem ' || true

echo '== network-ish strings =='
grep '^+' "$PATCH" |
  grep -Eio 'https?://[^ ]+|curl|wget|socket|fetch' || true

echo '== new or deleted files =='
grep -E '^(new file mode|deleted file mode)' "$PATCH" || true

echo '== patch size =='
wc -l "$PATCH"

Run it on a unified diff, not on raw model output. Most endpoints can be prompted to return a patch; apply it only after this script passes.

A reproducible test plan

Use three small fixture patches to confirm the harness works.

Patch	Expected signal
One source file plus one test, no dependencies	Files touched only; no flags
Adds package.json and opens https://example.com	Dependency edit + network string
Adds .github/workflows/deploy.yml outside src/*	OUT_OF_SCOPE
Empty patch	Zero lines; no files

Keep the fixtures in fixtures/. The same three patches become a smoke test for any new free endpoint you try.

Where MonkeyCode fits

Keep generation and review separate. If you have MonkeyCode free model access and a free server option, use that as the patch generator; the harness still only reads the resulting diff. That keeps the review gate independent of the endpoint.

The same loop works with any local or hosted model that can emit a unified diff.

Limitations

• This checks change hygiene, not semantic correctness.
• It misses copied vulnerable code, broken tests, and subtle logic bugs.
• A passing patch can still break the build; combine this with a real test run.
• The script flags strings, so it over-reports network matches. That is deliberate for a first pass.

Who should skip this

• You already have mandatory code review and branch protection.
• You work in an air-gapped or regulated repo where generated patches are not allowed.
• You cannot justify fixture creation time.

For everyone else, it is a cheap first gate. You can make it stricter later: require test files in every diff, ban executable bits, or block lockfile changes.

One next step: add a second pass that runs the repo's own test command before model output gets near main.