Why Tessera?

Git assumes one person is editing one branch in one folder at a time. Every terminal tab and editor window in your project reads from the same .git/HEAD and writes to the same working tree on disk.

That works fine when you write code by hand in a single editor, but it breaks down when you run two or three AI coding agents in parallel.

If two agents edit src/App.vue at the same time, the second agent to save overwrites the first agent's lines, or sees unfamiliar code and reverts it. If one agent runs git checkout feat/pricing to test its work, it switches the branch underneath your editor, your running dev server, and every other agent in the folder.

The usual workaround is git worktree: creating a separate copy of the repository in another folder for every agent. That requires duplicating node_modules or target directories, waiting on fresh builds, configuring different ports by hand so dev servers do not collide on localhost:3000, and jumping between separate editor windows.

One Folder, Multiple Branches and Dev Servers

Tessera lets multiple agents and terminal tabs work in the same repository folder at the same time, either on separate branches or on the same branch.

Parallel Agents in One Repository

Prompt in One Repo

Agent 1: "Add Pricing"

Agent 2: "Add FAQ"

1 Folder (~/acme-web)

Own Branches

Same ~/acme-web folder

✓ Isolated in Place

Branch Dev Servers

✓ View Both Live

Merge into main

Updated

✓ Preserved & Merged

One repo folder·Per-agent branches·Live branch dev servers·AST merge into main

When an agent claims a branch like feat/pricing, Tessera isolates that session inside .git/tessera/ without changing .git/HEAD for the rest of your workspace. Both agents can edit src/App.vue on their own branches in ~/acme-web at the same time without touching each other's uncommitted files.

When you want to preview or test a branch, tes exec -b feat/pricing -- npm run dev starts the dev server inside a copy-on-write sandbox. It clones your existing node_modules, target, or .venv directory in milliseconds using filesystem reflinks and assigns each branch its own port (localhost:4100, localhost:4200) so you can open both branches side by side in your browser.

Merging by Syntax Tree

Line-based Git merges fail whenever two branches touch adjacent lines, like when two agents add imports at the top of src/App.vue or register two new components in the same template.

When you run tes merge feat/pricing feat/faq --into main, Tessera parses each file into a syntax tree with Tree-sitter and merges functions, imports, JSX/Vue templates, and lockfiles structurally. Compatible edits merge without manual conflict resolution.

Editing on the Same Branch

You do not always want separate branches. When two agents work directly on main at the same time, Tessera runs a 3-way AST merge on disk every time an agent saves a file.

Same-Branch AST Merging on main

Prompt on main

Agent 1: "Add locale"

Agent 2: "Add decimals"

1 File (currency.ts)

Concurrent Edits

Both save on main

✓ No File Locks

Tree-sitter AST

✓ Structural AST

Unified on Disk

Both Kept

✓ Zero Overwrites

Two agents on main·Concurrent saves·Tree-sitter AST merge·Both edits preserved

If one agent updates formatCurrency() while another adds formatCompact() in src/currency.ts, both edits are preserved on disk. In VS Code and Cursor, the Tessera extension highlights each agent's lines so you can see which session owns each change.

Built on Top of Git, Not a Replacement

Tessera is not a replacement for Git and does not use a hosted server. Instead, it gives each AI agent and terminal session its own isolated state in .git/tessera/ so concurrent sessions can use Git branches, diffs, and commits safely in the same working directory.

Every tes commit or tes merge writes standard Git blobs, trees, and commits directly into .git/objects/ and refs/heads/*. Your existing git push, GitHub pull requests, and CI pipelines work without changes.

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