MergeForge

A JetBrains/WebStorm-style three-pane visual merge conflict resolver for VS Code and Cursor — with an AI assistant that actually reads your repository.

VS Code's built-in merge editor stacks Incoming and Current above the result. MergeForge uses the layout JetBrains users know instead: your version, the result, and theirs, side by side and scrolled together. Left is your local version, center is the editable result seeded from the common ancestor, right is the incoming branch.

The merge editor

• » / « to accept, × to ignore — per-chunk controls in the gutter strips, with connector bands linking each change to its place in the result. On a conflict, take one side or both in the order you click them.
• Apply All Non-Conflicting Changes (the wand) resolves everything only one side touched, leaving the real decisions to you. Also available per side.
• Magic Resolve settles conflicts where both sides simply added lines by keeping both — and deliberately refuses genuine rewrites, where guessing would drop someone's work.
• Edit the result freely — hand-write a blend of both sides; an edited chunk counts as decided. Everything is undoable with ordinary Cmd/Ctrl+Z.
• JetBrains colours — blue modified, green added, gray deleted, red conflict — plus word-level diff emphasis, base line numbers in the result margin, and your editor's own font in all three panes.
• Apply writes the result and runs git add; applying with conflicts still open asks first. Abort leaves the conflicted file untouched.
• Line endings, BOMs, and missing trailing newlines round-trip; CRLF/LF disagreements surface a choice. Binary and 10 MB+ files are refused with honest guidance instead of garbage panes.

The AI assistant

Works out of the box in VS Code with GitHub Copilot (via the Language Model API), or with your own API key for Anthropic, OpenAI, DeepSeek, Kimi/Moonshot, or any OpenAI-compatible endpoint (OpenRouter, local Ollama, proxies). Set up once with Merge Forge: Set AI Provider & API Key; keys live in VS Code's secret storage and are used only for these requests.

• ✦ Explain conflicts — a streamed, per-conflict analysis of what each branch changed, why they collide, and a suggested resolution.
• ✦ Resolve with AI — writes merged code into the result pane as ordinary resolved chunks: review it in the three panes, undo per conflict, nothing touches git until you Apply. Unparseable answers get one automatic retry; whatever fails stays open for you.
• ▶ Fix all — non-conflicting changes are applied mechanically (deterministic, no tokens spent), only the red conflicts go to the model, one combined report.
• The model reads your repo, not just the conflict. Every request carries the surrounding file and each branch's commit intent, and the model can call read-only tools — read files, search code, inspect git history, look up symbols — with live ⚙ activity lines in the drawer so you see exactly what it consulted.
• Ask follow-ups in the drawer's chat box, with full conversation context.
• A per-conflict ✦ menu on every red chunk scopes any of this to a single conflict.

Who wrote this, and how did we get here?

• Authorship chips — each conflict side shows the engineer who last shaped it (GitHub avatars when derivable, colored initials otherwise, fully offline-safe). Click for the commit, date, subject, and links to the commit and profile on GitHub.
• ⟲ History timeline — one toggle swaps the panes for a chronological two-lane view of the commits that produced this merge, yours vs theirs, merge base marked. Esc returns with all state intact.

The workflow around the editor

• Conflicts dialog — every conflicted file with Yours/Theirs status columns, Accept-side bulk actions, and "2 of 5 resolved" progress. Opens automatically when a merge, rebase, or cherry-pick hits conflicts (configurable).
• Status bar cluster — "⚠ Merging main → feature" with one-click access to the dialog and a guarded abort.
• Next-file loop — after Apply, jump straight to the next conflicted file via the toast, or set mergeForge.autoAdvance and never stop.
• Crash safety — half-done merges are snapshotted as you work; reopening the same merge offers "Restore / Discard". Never silent, never stale.
• Rebase & cherry-pick aware — git swaps its stages mid-rebase; MergeForge swaps them back so the left pane is always your work — in the panes, the blame chips, and the timeline alike.
• Delete/modify conflicts get a clear keep-or-delete choice instead of empty panes.

Getting started

Open a file with conflicts and use any of:

• the editor title bar button, or the Resolve in Merge Forge CodeLens above a conflict
• right-click the file in the Explorer or Source Control view
• Merge Forge: Resolve Conflicts in File… from the command palette

Keyboard

Settings

Notes for Cursor users

Cursor does not expose its built-in models to extensions, so the AI features use your configured provider key — any of the five above; a local Ollama endpoint via the Custom provider works too. Everything else is identical.

Correctness

The chunking engine is checked against real git merge-file output: on generated conflict cases it must agree with git about what conflicts, and where git merges cleanly its auto-merge output must match git byte for byte. Line endings, BOMs, and missing trailing newlines are covered by tests against real conflicted repositories. The AI pipeline ships with a replay eval (dev/eval) that re-runs real historical merges and scores the model against the human resolution.

Development

pnpm install
pnpm run watch     # extension host + webview + Monaco worker
# press F5 to launch the Extension Development Host

pnpm test          # unit, git-parity, and end-to-end tests
pnpm run check     # format + lint + typecheck + test
pnpm run package   # build a .vsix

node scripts/make-conflict-repo.mjs            # throwaway repo with every conflict shape
node scripts/make-conflict-repo.mjs --rebase   # ...stopped mid-rebase instead

To iterate on the UI without launching an editor, serve the repo and open dev/harness.html — it drives the real webview bundle in a plain browser with a stubbed host, including ?scenario=hero|ai|history|light self-driving states.

License

MIT