# Show HN: Concord – let Claude Code, Codex and Cursor talk to each other > Source: > Published: 2026-08-27 13:34:54+00:00 **Let Claude Code, Codex, Cursor, Gemini CLI, and Grok Build talk to each other.** The open-source, local-first communication and coordination layer for AI coding agents. Send live messages across harnesses, detect overlapping work before agents edit, share decisions, and hand off tasks with evidence - through one MCP server. [Demo](#see-it-work) · [Quick start](#quick-start) · [Supported agents](#supported-agents) · [Website](https://getconcord.ai) · [Contributing](/Get-Concord-AI/concord-mcp/blob/main/CONTRIBUTING.md) Two agents in different harnesses can discover each other, exchange messages, and divide work without a human relaying context between them: ``` Claude Code → Concord Claim src/app/page.tsx Codex → Concord Claim src/app/page.tsx Concord → Codex Overlap: Claude Code already owns this file Codex → Claude I'll take src/app/api instead. Does that work? Claude → Codex Yes. I'll keep the page and use your API contract. ``` Run the [real Claude Code ↔ Codex demo](/Get-Concord-AI/concord-mcp/blob/main/examples/whack-a-mole) to watch both agents resolve an overlapping claim through a live prompt/reply, build a playable app, transfer ownership, and hand the result to an independent reviewer. ``` npm install -g @concord-ai/concord-mcp cd /path/to/your/repository concord setup ``` Restart your agent clients, then ask two of them to work in the same repository. Concord gives them a shared workspace and makes reachable sessions available for direct prompts and replies. ## What `concord setup` changes `concord setup` creates the local `.concord/` workspace, registers the MCP server for Claude, Cursor, Gemini, Grok, and Codex (`.mcp.json` , `.cursor/mcp.json` , `.gemini/settings.json` , `.grok/config.toml` , and `~/.codex/config.toml` ) and writes Concord's tool instructions into your client configs (`CLAUDE.md` , `AGENTS.md` , `.codex/` , `.cursor/rules/` ). It merges into existing config rather than replacing it and is safe to re-run. Setup also detects supported clients and attempts to install their global Concord adapters independently. Use `--no-adapters` to skip that step or `--require-adapters` in managed installs that should fail on degraded support. Pass `--no-mcp` to write only the workspace and instructions while managing MCP registration yourself. | Agent | Integration guide | |---|---| | Claude Code | | [Setup and delivery](/Get-Concord-AI/concord-mcp/blob/main/docs/codex.md)[Setup and delivery](/Get-Concord-AI/concord-mcp/blob/main/docs/cursor.md)[Setup and delivery](/Get-Concord-AI/concord-mcp/blob/main/docs/gemini-cli.md)[Setup and delivery](/Get-Concord-AI/concord-mcp/blob/main/docs/grok-build.md)There is no universal `/concord` slash command — commands are client-specific. Concord works through MCP tools plus the installed instructions on any MCP-capable client. Live delivery depends on the receiving harness and session state. Run `concord adapters status` to see which installed agents are reachable and how messages will be delivered. Messaging gets agents talking. Concord's shared work-state keeps the resulting collaboration reliable after the message is delivered. | Without Concord | With Concord | |---|---| | Agents cannot contact peers in another harness | Agents send direct, replyable prompts across supported clients | | Agents discover collisions after editing | Agents claim files and modules before work begins | | Context disappears when a session ends | Decisions, assumptions, and findings stay attached to the task | | Ownership is implied by chat history | Assignments and handoffs are explicit and acknowledged | | Humans reconstruct progress from branches and diffs | Review packets arrive with scope, tests, risks, and provenance | Concord is not another autonomous agent or orchestrator. It is the shared layer around your agents: presence, messaging, task memory, ownership, handoffs, and review state through one small MCP server. | Tool | Purpose | |---|---| `start_work` | registers presence, claims or accepts one task, and reports scope overlaps before editing | `inspect_work` | reads workspace/task state, an agent inbox/outbox, or a durable prompt/reply thread | `update_work` | records task context or immediately prompts/replies to another promptable workspace agent | `transfer_work` | assigns, accepts, declines, releases, reassigns, offers handoffs, or reopens versioned work | `finish_work` | records evidence and optionally marks a task review-ready, complete, or closed | Writes accept an `agent_id` , which keeps presence live just by working. `inspect_work` shows **who is here** and flags **stale claims** — an active claim whose owning agent has gone away without handing off. For live agent-to-agent communication, run `concord setup` , then restart existing client sessions once. A prompt uses `update_work` with `operation: "prompt"` , the target `to_agent_id` , content, and an `idempotency_key` ; a reply uses `operation: "reply"` and `reply_to_message_id` . A receipt-bearing adapter steers a busy turn or starts an idle turn. Hook-only integrations leave a durable pull message and state that limitation in the result. Delivery fails immediately when the named agent has no reachable endpoint; Concord does not silently reroute it. `concord adapters status` reports each harness separately, including its monitor/controller kind, verified reachability, required action, and version probe result. `concord adapters install` , `doctor` , and `uninstall` provide the same global lifecycle outside repository setup. Concord resolves the repository workspace automatically. Operations return its `workspace_id` and repository root so a client can detect a misrouted call; the id can be passed explicitly when one server is coordinating multiple roots. Lifecycle-changing operations use the task's monotonic `version` as `expected_version` . If two agents act on the same version, only the first transition succeeds. Assignment leaves work in `assigned` until the named agent uses `transfer_work` with `action: "accept"` ; a handoff offer likewise keeps ownership with the sender until the recipient accepts. Every ownership change is retained in an append-only audit history. SQLite is the local source of truth, kept in the `.concord/` at the **root of the repo** the work is happening in. The MCP server resolves that root from `CONCORD_REPO_ROOT` if set, then Claude Code's `CLAUDE_PROJECT_DIR` (which Claude Code sets automatically, even for a user-scoped server), then its working directory — so every agent in one repo shares one store. Set `CONCORD_REPO_ROOT` when running the server somewhere its working directory is not inside the repo. Linked Git worktrees follow Git's `commondir` metadata to the primary checkout, so the main checkout and all linked worktrees intentionally share one Concord database and workspace id. To restrict explicit workspace selection, set `CONCORD_ALLOWED_ROOTS` to a path-delimited list of allowed repository roots. Without an allowlist, decoded roots must still exist and be directories. `concord setup` adds `.concord/` to the repository's `.gitignore` , so the generated workspace stays local by default. Teams that want selected artifacts in PRs can remove that rule or force-add the human-readable files: ``` .concord/ ├── concord.db local source of truth ├── HANDOFF.md human-readable handoff ├── REVIEW_PACKET.md review-ready evidence └── WORK_STATE.json generated export (optional) ``` Concord supports both typed MCP tools and a regular CLI. MCP-capable agents can call the tools directly; humans and CLI-oriented agents can work with the same shared workspace through `concord` commands. ``` concord setup # set up local state, instructions, and MCP clients concord status # roster, active work, overlaps, stale claims, review-ready concord dashboard # live, keyboard-driven view of agents, tasks, alerts, and activity concord who # which agents are present and what they are working on concord tasks # list all tracked tasks concord handoff # print the latest handoff concord review-packet # print the latest review packet concord export markdown # regenerate .concord/ artifacts concord doctor # workspace checks + per-task tool adoption concord adapters status # global harness delivery capability matrix concord --repo ../project status # select by repository path from anywhere concord --workspace ws_... status # select an id returned by a Concord operation ``` `--repo` and `--workspace` are global, mutually exclusive options. The CLI uses the same `CONCORD_REPO_ROOT` → `CLAUDE_PROJECT_DIR` → working-directory priority and the same linked-worktree canonicalization as MCP. `concord dashboard` is a read-only, full-screen local TUI. It refreshes from the shared SQLite workspace every second while keeping agents, tasks, alerts, context, and timeline inside a fixed terminal viewport. Use `Tab` to change panes, `j` /`k` or the arrow keys to select work, `/` to filter, `?` for help, and `q` to quit. ``` npm install -g @concord-ai/concord-mcp@latest concord --version ``` Concord checks daily and surfaces available updates in the CLI, MCP tools, and dashboard; `concord setup` can install one with confirmation, and `CONCORD_NO_UPDATE_CHECK=1` disables checks. Shared work-state and task memory for coding agents using the same local checkout. **Not** an orchestrator, code reviewer, hosted sync service, memory vector DB, or autonomous coding agent. See also: [Why not just use markdown?](/Get-Concord-AI/concord-mcp/blob/main/docs/why-not-markdown.md) See [ CONTRIBUTING.md](/Get-Concord-AI/concord-mcp/blob/main/CONTRIBUTING.md) and [. This repo is strictly typed (no](/Get-Concord-AI/concord-mcp/blob/main/CLAUDE.md) `CLAUDE.md` `any` , no typecasts) and modular. Good first issues are labelled [.](https://github.com/Get-Concord-AI/concord-mcp/labels/good%20first%20issue) `good first issue` Concord sends product and coordination telemetry to `getconcord.ai` . It includes random installation/invocation identifiers; irreversible per-install workspace and task-flow pseudonyms; Concord/Node/platform versions; normalized client metadata; operation names, outcomes, and durations; aggregate overlap/edit-guard results; message delivery stages and latencies; task lifecycle transitions and elapsed time; and explicitly reported acceptance, integration, human-intervention, and rework outcomes. Concord never sends code, raw file or repository paths, remotes, usernames, raw task or agent identifiers, message identifiers or content, command arguments, tool inputs/outputs, or task content. The receiving server stores the request IP address and derives/stores a country code. Those server-side fields currently have no automatic expiry. Set `CONCORD_TELEMETRY_DISABLED=1` (or `DO_NOT_TRACK=1` ) to disable telemetry. Delivery is best effort and can never make a Concord operation fail.