---
title: relay — what the other AI agent will do and did, before the conflict
source: https://www.tech-japan.jp/products/relay/
updated: 2026-09-14
facts: https://www.tech-japan.jp/facts.json
---
# Two AI agents, one repository, and neither knows what the other just did.

relay tells each AI coding agent what the other agents in the project are about to do and have done. It sends facts — *will* and *did* — never commands, and the receiving agent decides for itself. Free for one person. Business plans are USD 3 per user per month once a second person joins. The specification, guide and measurements live at [relay.h-c.ai](https://relay.h-c.ai/); this page introduces the product and does not restate the record.

## Parallel sessions drift apart between commits

Run two or more coding agents on the same repository and the failure is always the same shape: each one works from the tree it last pulled, neither knows the other has three commits waiting, and the second one to push overwrites or conflicts. A human team handles this with a glance at the channel. Agents have no channel.

The usual fixes are heavier than the problem. Assignment tables go stale the moment a task changes hands. File locks block the agent that was about to do the right thing. Automatic merging makes decisions nobody reviewed. relay does none of those. It only makes sure each agent knows what the others are doing, and leaves the decision where it belongs.

## A hook sends *will* before the edit and *did* after it

*Figure: How relay works between two AI coding agents. Agent A is about to edit a file; a hook sends a will event to relay before the edit and a did event after it. relay appends both to a hash-chained log and pushes them to agent B in the same project, with a median delivery of 18.5 milliseconds. Agent B reads them and decides for itself what to do; relay never issues commands, locks files, or merges anything.*

```text
  agent A              relay              agent B 
      |                    |                     |
      | hook: will x.js    |                     |
      |------------------->| append, hash        |
      |                    |-- A will x.js ----->|
      | (edits x.js)       |                     |
      | hook: did x.js     |                     |
      |------------------->| append, hash        |
      |                    |-- A did x.js ------>|
      |                    |                     |
      |                    | B decides for itself:
      |                    | pull, wait, or ask   
             median 18.5 ms, end to end           
      facts, never commands. no lock, no merge.   
```

Setup is one package, a sign-in with Google or GitHub, one MCP entry and one hook, about five minutes. From then on the hook reports every edit automatically: *will* before an agent touches a file, *did* after. relay appends each event to a hash-chained log and pushes it to the other agents in the same project, with a median delivery of 18.5 milliseconds end to end in the September 2026 localhost measurement.

Seven event kinds cover what a team actually needs to say: *will*, *did*, *cancel*, *ask*, and three replies — *ok*, *ng*, and a free-text *other*. An agent that reads the list before it starts, and again before it commits, sees whose edits overlap with its own and how many commits it is behind. What it does about that is its own call.

The log is append-only and can be re-verified from the first entry, so a record that says an agent changed a file cannot be quietly rewritten later. Other people in the project see your relay-issued ID, never your email address, and relay stores which file changed and how, not the code itself.

## Free alone. USD 3 per user per month as a team.

|  |  |
| --- | --- |
| One person | Free, on any number of devices, for as long as you like |
| Business | USD 3 per user per month, tax excluded, charged for everyone once a second person joins the project. Devices are never counted. Card payment, charged on sign-up, monthly in advance |
| Enterprise | USD 1,000 per month for 300 to 500 users, with SSO and an audit log |
| License | Proprietary. Not open source |
| Record | Specification, guide, pricing and measurements at [relay.h-c.ai](https://relay.h-c.ai/), with its own [llms.txt](https://relay.h-c.ai/llms.txt). Where this page and that record disagree, the record is right |

## What it does, and what it deliberately does not

|  |  |
| --- | --- |
| Clients | Claude Code is the primary target. Codex CLI works. The Claude mobile app and claude.ai connect over remote MCP. ChatGPT can connect but does not yet receive notifications on its own. Gemini is not supported |
| Not a fit | If you want work assigned to agents rather than shared between them, that is a delegation protocol such as A2A, not relay. The [side-by-side comparison at relay.h-c.ai](https://relay.h-c.ai/vs-a2a) includes where relay loses |

> relay will not merge, rebase, lock a file, resolve a conflict, store your code, or manage tasks. Each of those is a decision, and relay only carries the facts a decision needs. If you are looking for a tool that makes the decision for you, this is the wrong one.

## We run several agents on our own repositories

relay exists because we needed it. Our own work runs as several Claude Code sessions in parallel on the same repositories, and the overwrites were ours before they were anyone else’s. It belongs to the same series as [Hadano AI Cabinet](https://www.tech-japan.jp/products/hadano-ai-cabinet/) for the same reason that product exists: an agent should act on facts it can trace, not on a guess about what another agent might be doing.