Rebaseplan MCP Server

rebaseplan

Rebasing a branch is easy to start and hard to undo, especially once other people have the old history. The risky parts are rarely visible in the branch name: merge commits that a plain rebase will flatten, squash-merge markers whose original commits may also live upstream, an upstream that has moved far ahead, and a published history that a rewrite will orphan. rebaseplan reads that shape before you start and returns a plan instead of a surprise.

You hand it the branch's own commits, oldest first, each with a hash, a subject, and optionally a flag saying it is a merge commit. You may also hand it the commits upstream has that this branch does not, and say whether the branch has been pushed or shared. Nothing is fetched, rebased, or pushed — the tool only counts and advises.

A commit counts as a squash marker in exactly two ways: its subject starts with Squashed commit, or it ends with a GitHub squash-merge suffix such as (#123) — the pinned test is the regular expression /\(#\d+\)$/. Upstream commits are never counted as markers, however their subjects read.

Force-push risk follows a fixed table. An unpublished branch is low. A published branch with no merge commits and no squash markers is medium. A published branch with either is high.

The recommended strategy is chosen by first match: any merge commits means rebase_with_merge_preservation; otherwise any squash markers means interactive_squash_cleanup; otherwise linear_rebase. Merge history therefore beats squash markers when both are present.

The plan's steps always start with fetching upstream and end with running the test suite on the rebased head and a push instruction: --force-with-lease, never plain --force, for a published branch, with a backup branch created first; or a normal push when the branch was never published. Warnings, in order, flag merge commits, squash markers, an upstream ten or more commits ahead (the warning text is fixed regardless of the exact count), and the published-history rewrite.

Malformed input — a missing, empty, or non-array commits, an entry with a missing, empty, or non-string hash or subject or a non-boolean merge, a badly typed upstream_commits entry, or a non-boolean published — is a validation error naming the offending path, with no partial result. Unknown extra fields are ignored.

CLI

npx @reneturcios/rebaseplan plan --input args.json
npx @reneturcios/rebaseplan --version

args.json contains the full arguments object:

{
  "commits": [
    { "hash": "a1b2c3", "subject": "Add login form" },
    { "hash": "d4e5f6", "subject": "Merge branch 'main'", "merge": true }
  ],
  "upstream_commits": [
    { "hash": "f7a8b9", "subject": "Bump dependencies" }
  ],
  "published": true
}

upstream_commits defaults to [], published defaults to false, and each commit's merge defaults to false. The result is printed as JSON:

{
  "commit_count": 2,
  "merge_commits": 1,
  "squash_markers": 0,
  "upstream_new_commits": 1,
  "published": true,
  "force_push_risk": "high",
  "recommended_strategy": "rebase_with_merge_preservation",
  "steps": [
    "fetch upstream before planning the final rebase",
    "create a backup branch pointing at the current head",
    "rebase onto upstream preserving merge commits",
    "run the test suite on the rebased head",
    "push with --force-with-lease, never plain --force"
  ],
  "warnings": [
    "history contains merge commits; a plain rebase will flatten them",
    "branch is published; rewriting it rewrites history others may have based work on"
  ]
}

Exit codes: 0 on success, 1 on a runtime error (including an unreadable or invalid input file, or invalid input), 2 on a usage error.

MCP server

npx -y @reneturcios/rebaseplan mcp

MCP client config:

{
  "mcpServers": {
    "rebaseplan": {
      "command": "npx",
      "args": ["-y", "@reneturcios/rebaseplan", "mcp"]
    }
  }
}

Tools

• plan_rebase — Plan a safe rebase before you start.

  • commits (array, required, non-empty) — the branch's own commits, oldest first: {hash, subject, merge}
  • upstream_commits (array, optional, default []) — commits the upstream branch has that this branch does not: {hash, subject}
  • published (boolean, optional, default false) — whether the branch has been pushed or shared

  Returns {commit_count, merge_commits, squash_markers, upstream_new_commits, published, force_push_risk, recommended_strategy, steps, warnings}.

Docker

docker run -i ghcr.io/cloudcorprecords/rebaseplan
docker run --rm -v "$PWD:/w" ghcr.io/cloudcorprecords/rebaseplan plan --input /w/args.json

Development

npm install
npm run build   # tsc -> dist/
npm test        # tsx --test test/*.test.ts (pure local, no network)
npm run dev     # run the CLI from source

License

MIT — Copyright (c) 2026 Rene Turcios