Handover.tools README

handover.tools

One agent writes it, another agent reads it. You only carry an 8-letter link between them.

handover.tools moves a piece of work from one AI agent to another: across devices, across vendors, or to another person. Brainstorm with the agent on your phone, then say "hand this over with handover.tools". Paste the link it gives you (handover.tools/kvmtrhxp) into Claude Code on your laptop, and that agent picks the work up where your documents already are.

Bring the idea to your context, not your context to the idea.

There is no account and nothing to install. Any agent that can open a web page can use it.

Two modes

	One-shot	Channel
Use it for	Handing over one piece of text	Several rounds between two agents
Encryption	None. The server can read it, so don't put secrets in it	End-to-end (SPAKE2 + ChaCha20-Poly1305). The server only ever stores ciphertext
Lifetime	Gone after the first read, or after 60 minutes (24 h max)	Until either side closes it
What the agent needs	Can open a URL, or has MCP	Can run a Python script (`uv run`)
Who decides	The person carries the link	The person approves every send and starts every fetch

One-shot

Terminal

curl -X POST https://handover.tools/api/handoff/put \
     -H 'Content-Type: application/json' \
     -d '{"content":"...","label":"notes"}'          # → {"code":"kvmtrhxp", "revoke_key":"...", ...}
curl "https://handover.tools/api/handoff/get?code=kvmtrhxp"

Opening handover.tools/<code> doesn't use up the code. That URL returns instructions, and the actual read is a second request. Link previews in Slack or iMessage therefore don't burn the content before the recipient sees it.

Channel

Terminal

curl -so ~/.handoff/channel.py --create-dirs https://handover.tools/client/channel.py
uv run ~/.handoff/channel.py open --name study --brief "..."   # machine A: prints a code
uv run ~/.handoff/channel.py join kvmtrhxp --name study        # machine B
uv run ~/.handoff/channel.py send --name study --kind question --file q.md
uv run ~/.handoff/channel.py fetch --name study

The 8 letters are a 3-letter nameplate, which the server sees and uses to find the channel, plus a 5-letter password that is generated on machine A and never uploaded. The password goes into SPAKE2, the same construction magic-wormhole uses. The server never learns the password, so it cannot impersonate either side. /client/channel.py is served from client/channel.py, and its sha256 is published at /api/discover, so you can check that the client you downloaded matches this repository.

The threat model, including what we don't claim, is at handover.tools/security.

For agents

MCP endpoint: https://handover.tools/mcp. It serves both the 2026-07-28 (modern) and 2025-11-25 and earlier (legacy) protocol eras.
Plain text instructions: /llms.txt, /guide.md, /security.md
Full REST schema: /api/discover

How it's built

Cloudflare Python Workers + D1. One Worker, no other infrastructure. The routes, the MCP tools/list and /api/discover are all derived from a single tool registry (src/registry.py), so they can't drift apart.
Limits are layered: 10 writes and 200 calls per caller per day, plus a global daily cap. The site runs on the Workers Free plan, which makes $0 the hard spending ceiling.
Fonts are self-hosted and embedded in the Worker, so no visitor IP goes to a third party. Caller IPs are erased after 30 days.

Code

src/
  entry.py        routing, MCP (dual-era), content negotiation
  registry.py     @tool decorator — one source for REST, MCP and discover
  tools/handoff.py, tools/channel.py   the two tools
  guard.py        quotas and the operator blocklist
  meter.py        per-call metering
  page.py, docs.py, style.py   the website and docs pages
client/channel.py   the local E2EE client, run on the user's machine
tests/              end-to-end, channel and quota test suites
scripts/            dev, deploy, repository checks, operator tools

Documentation

Document	What it covers
docs/system-design.md	Architecture: components, request pipeline, data model, flows, trust boundaries, limits and capacity, failure modes, known gaps
docs/spec/handoff.md	The one-shot contract: operations, code format and normalization, atomicity, code links, limits
docs/spec/channel.md	The channel protocol: pairing, SPAKE2 parameters, key schedule, wire format, receiver rules, server API, lifecycle. Detailed enough to write a second client
docs/decisions.md	Why it is built this way: what was tried, what was rejected, and what broke
CHANGELOG.md	What changed, newest first. Also at handover.tools/changelog

The specs are the contract. A behavior change starts in the spec, then the code and tests follow.

Run it locally

Requires Node ≥ 22 and Python 3.12.

Terminal

npm install
scripts/dev.sh      # generates src/*_src.py and public/, then runs wrangler dev on :8787
tests/e2e.sh        # end-to-end tests against the local server
tests/channel.sh    # two isolated clients: pairing, tampering, replay
tests/quota.sh      # quota gates (local only: edits counters directly)
scripts/check.sh    # repository rules: English only, every Dxx reference resolves

CI runs the check and the three suites on every push.

Deploy your own

npx wrangler d1 create <name>, then put the name and id into wrangler.toml.
Change the routes pattern to your domain.
CLOUDFLARE_API_TOKEN=… scripts/deploy.sh

Tables are created on the first request. scripts/block.sh has the operator tools for abuse reports: block writes from an IP or a range, look up or delete a handoff by its link.

Contributing and security

Issues and pull requests are welcome. AGENTS.md has the working rules, for people and coding agents alike: a change in behavior starts with the spec in docs/spec/, then the code and the tests. Report vulnerabilities privately: see SECURITY.md.

License

MIT. Fonts: Atkinson Hyperlegible, SIL OFL 1.1 (see assets/fonts/LICENSE.txt).