jit

name	jit
description	Generate ephemeral catching tests on the current diff, run them, and report behavior regressions. Tests are never committed. Works across Java, Kotlin, Scala, Python, and Node.js stacks.

You are running the JIT Catching Test skill. The user invoked /jit. Your job is to find bugs introduced by the user's pending diff, without writing any test that lands in the repo.

Pipeline

1. Detect the language target:

   ~/.claude/jit/bin/jit detect
   

2. Decide the comparison mode. The pipeline auto-detects:
   • Snapshot mode (default if .parent/ exists in the cwd): compares the current files against .parent/. No git history required. Used by sample projects and any directory that ships a parent snapshot.
   • Git mode (otherwise): compares HEAD~1..HEAD (or a user-supplied range).
3. Honor --diff <range>, --target <name>, --workflow {dodgy|intent|both}, --mode {auto|git|snapshot}, --parent-dir <dir> if the user passed them.
4. Run the pipeline:

   ~/.claude/jit/bin/jit run --repo . [--diff <range>] [--target X] [--workflow Y] [--mode Z]
   

5. The pipeline writes its output to .jit-testing/runs/<run_id>/. Read report.md from that directory.
6. Present the top three catches as sense-check questions. Do not show test code first. Example:

   On the parent, qualifiesForFreeShipping($49.99 delivery) returned false. On your change, it returns true. Is this expected?

7. For each catch, offer three actions: Confirm bug, Expected change, Show test code.
8. If the user picks Show test code, print the relevant section of the report.
9. On a verdict, persist it:

   ~/.claude/jit/bin/jit verdict <run_id> <catch_id> {confirmed|expected|deferred}
   

Supported targets

java8, java25, scala3-sbt, scala2-bazel, kotlin, python3, python3-django, nodejs.

If detection fails, stop and ask the user to pass --target explicitly.

Hard rules

• Never commit anything from .jit-testing/.
• Never write tests outside .jit-testing/runs/<run_id>/tests/.
• Keep dismissals fast: do not lecture the user when they say a change is expected.

After the run

Tell the user they can open the dashboard with /jit-dashboard.