swarm-migrate

swarm-migrate — Cross-Repo Migration Swarm

One command, N repos, one coordinator, one ledger.

When to use

Use when the same transformation needs to land in 3 or more repos with the same shape (workflow bump, dependency upgrade, codemod, lint-rule introduction, secret rotation, runbook header). Don't use for one-repo work — that's implement. Don't use for novel exploration — that's brainstorm.

This skill exists because the 275-session insights showed 25 sessions burned coordinating PR cascades manually (M164 deploy-migration, M17 yg-mcp-core extraction, @v1 reusable workflow rollout across 14 repos). The pattern was always: pick a repo, branch, apply, push, watch CI, repeat. This automates the repeat.

vs CC /workflows (2.1.154): CC's dynamic workflows orchestrate tens-to-hundreds of agents in the background and report via /workflows. swarm-migrate is different on purpose: it's a coordinator-led, foreground DAG with CI gates, conflict auto-rebase, and stop-on-novel-failure — you watch it and it stops on the first unexpected failure. Reach for CC /workflows when you want large-scale fire-and-forget background fan-out; reach for swarm-migrate when each step needs a CI gate and a human-visible ledger. CC 2.1.202 adds a Dynamic workflow size setting in /config (small / medium / large agent counts) that advises /workflows on how many agents to spawn — it's a hint, not an enforced cap, so check it before hand-capping fan-out.

Inputs

A YAML spec at swarm-specs/<name>.yaml:

name: bump-actions-checkout-v4
description: "Pin @actions/checkout to v4 across all repos"

# Topology — repos in dependency order. Coordinator only proceeds
# to a downstream repo after every upstream parent has merged green.
repos:
  - path: ~/coding/yonatan-hq/platform
    upstream: []
  - path: ~/coding/yonatan-hq/ventures/jobscraper
    upstream: [platform]   # waits for platform to merge first

# Transformation — applied identically per repo. The agent runs this
# inside the isolated worktree, then verifies with the next field.
transform:
  type: codemod              # codemod | regex | command
  command: |
    grep -rl 'actions/checkout@v3' .github/workflows | \
      xargs sed -i '' 's|actions/checkout@v3|actions/checkout@v4|g'

# Verification — must pass before PR opens. Coordinator skips the repo
# if it fails locally (records skip-reason in ledger).
verify:
  - command: "git diff --quiet"
    expect: nonzero            # must have changes
  - command: "grep -r 'actions/checkout@v3' .github/workflows"
    expect: nonzero            # zero matches = clean

# PR shape — title, body, base branch
pr:
  branch_prefix: chore/bump-checkout-v4
  title: "chore(ci): pin @actions/checkout to v4"
  body_file: swarm-specs/bump-actions-checkout-v4.pr.md
  base: main
  labels: [chore, ci]

# CI gate — coordinator waits for required checks to pass before
# moving downstream. Set to false for dry-run, or in repos without CI.
ci_gate:
  required_checks: ["build", "test"]
  timeout_minutes: 20
  on_failure: pause            # pause | skip | abort

# Limits
max_parallel: 4
abort_on_novel_failure: true