LZH-1-G

MigrationGuard Harness — Development skill for Claude Code

Development community

An Evidence-Driven Agent Harness for Safe Dependency Migration, featuring Claude-powered code repair, differential verification, secure sandboxing, and checkpoint recovery.

How to install MigrationGuard Harness

This entry records only its repository, not the path inside it, so there is no exact command to give. Open LZH-1-G/MigrationGuard-Harness and copy the folder into ~/.claude/skills/, or the file into ~/.claude/agents/.

What MigrationGuard Harness does

An Evidence-Driven Agent Harness for Safe Dependency Migration, featuring Claude-powered code repair, differential verification, secure sandboxing, and checkpoint recovery.

Alternatives in Development

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Zeroshot — Runs coding agents as a graph: one agent implements, independent agents review, failures go to repair, and not 1.9k ★
Vibekit — A simple SDK for safely running Codex, Gemini CLI, and Claude Code in a secure sandbox 1.7k ★

README

MigrationGuard

**An evidence-driven agent harness for safe dependency migration.** MigrationGuard migrates Python projects from Pydantic v1 to v2 with deterministic codemods and Claude agents, and accepts the result only when sandboxed, differential evidence proves it is safe. It never trusts an agent's self-reported success.

$ migrationguard run ./billing --agent claude          # real run, abridged
  verify ✔ tests.pass: PASS — 7 passed
  verify ✔ tests.differential: PASS — all 7 baseline-passing tests pass
  verify ✘ behavior.probes: FAIL — 13 behavioural difference(s)     ← codemods alone: tests green, behaviour changed
▶ verify -> repair
  repair repair attempt 1: finished; 6 tool call(s), 0 denied; $0.2223, ...
  verify ✔ tests.integrity: PASS — 0 protected file(s) changed, all re-derivable from the audited codemod
  verify ✔ behavior.probes: PASS — 16 probes agree
  review ✔ review.independent: PASS — The migration is faithful to v1 behaviour. ...
ACCEPTED: all blocking gates passed at iteration 2

Why

Coding agents are good at making a migration *look* done. The common shortcuts — a green test suite, an agent saying "all tests pass" — miss exactly the failures that matter in dependency upgrades:

silent behaviour changes: Pydantic v2 stops coercing 123 to "123", rejects 42.7 for an int, serialises Decimal as a string and UTC as Z. Typical test suites stay green.
reward hacking: deleting, skipping or weakening failing tests, adding a conftest.py that deselects them, pinning back to v1, or importing pydantic.v1.
fragile execution: long agent runs die halfway (crash, rate limit, budget) and start over from scratch.

MigrationGuard combines four things to address that:

Autonomous migration — deterministic libcst codemods for everything mechanical, a Claude Agent SDK repair agent for what needs judgement.
Differential behavioural verification — the original project (pydantic 1.x) and t