cosyncingDeepSeek Harness plugin

From CLI to GUI, live and in sync

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Synchronize and control your agents — from CLI to GUI, from desktop to phone. Pick up right where you left off, anywhere. cosyncing keeps your coding agents in sync across your own network.

The broker runs on the machine where your agents work. It watches their sessions and serves a client that shows each one — grouped by project, with its transcript, diffs, commands, and any prompt waiting on you. Read a session, answer a prompt, or take over. No account to create, no hosted service between the client and the broker.

Supported agents

One protocol covers all seven. Per-agent control differs, and Claude Code sessions open read-only until you take over. See supported-agent setup for versions and installation, and adapter support for the capability matrix.

Foreground clients can join the same broker-owned Codex or Pi Drive session without starting a second native Resume. Claude Code keeps its Observe/Take-over flow on another client, while OpenCode keeps its shared-live behavior. Background Observe connections stay read-only.

Experimental: Three provisional adapters are available to source contributors. Kimi Code observes every session on a kimi web server read-only, drives the ones cosyncing created — prompts, approvals, model selection — and takes over the ones it did not, explicitly. DeepSeek Harness connects to a dsh web host and gives active foreground clients a shared transcript and control surface, with model and reasoning-effort selection, permission presets, the host's own slash commands, and image attachments. General file attachments are not supported — the host accepts image content only — and background resident subscriptions and some message presentation remain follow-up work. Antigravity reads the Antigravity CLI's own conversation store — no server involved — replays every conversation read-only, and drives one through a broker-owned agy child; two clients can share a Drive, and a write from a terminal hands the session back.

None needs a rollout flag. Neither server-backed adapter needs a terminal left open: an installed cosyncing service starts a host when none is running, restarts one that crashes, and stops the one it started. A host you started yourself is never stopped, replaced, or reconfigured, and setup names both hosts before you agree to manage them. Install DeepSeek Harness globally with npm install -g @deepseek-ai/dsh — cosyncing looks for dsh on your PATH, so an npx-only install can be talked to but never started or version-checked. See supported-agent setup for both hosts.

Prerequisites

The server requires Bun 1.3.8 or newer to run cosyncing and Node.js/npm to install and update it. The broker is local-only by default. Cross-device use requires a proxy, tunnel, VPN, mesh network, or another operator-owned connectivity method. For a simple private route, see Tailscale Serve; for a self-managed overlay, see WireGuard or EasyTier. After cosyncing setup, you can also copy https://github.com/cosyncing/cosyncing/tree/main/docs/connectivity to a coding agent and ask it to configure your chosen method while keeping the broker bound to loopback. Tokdash is optional but strongly recommended for quota tracking and warnings.

See installation prerequisites for Linux and macOS commands, WSL notes, and Tokdash setup.

Install

The package contains one JavaScript application bundle and the web client. Supported broker hosts are Linux x64, Linux arm64, Apple Silicon macOS, and Windows x64. Windows ARM64 is not qualified yet, and the broker refuses it — including an x64 process running under ARM64 emulation.

Before setup, install only the agents you use; see agent setup and PATH preflight.

Install the current release:

bash
npm install --global cosyncing

Open a new login shell, then configure the service:

bash
cosyncing setup

# After setup, use cosy as the shorthand for cosyncing
cosy restart
cosy doctor
cosy status
cosy pair

setup inspects the machine, shows exactly what it will change, and applies the whole plan or none of it. It copies the broker to ~/.cosyncing/bin/cosyncing, installs a user service that runs that copy with your Bun, and prints your broker URL. The broker refuses to start until setup has committed.

To update, let npm replace the global package, then re-run setup so cosyncing copies the new application into its managed service and reconciles the installation:

bash
npm update --global cosyncing
cosy setup

cosy update reports this package-manager-owned update path; it does not run npm or modify the global package.

cosy pair --broker-url https://cosy.example.com includes that client-reachable origin in a five-minute, one-use QR code. The URL is not persisted or probed. Omit the flag for an authentication-only offer when the client already knows its broker URL. See the connectivity chooser. Scan the QR from a client to grant access; cosy devices list lists paired devices, and cosy devices revoke <id> revokes one.

After setup, cosy doctor diagnoses the machine without changing it, and cosy status summarizes install, service, agents, and sessions.

Client

The packaged Flutter web app is served by your own broker at /cosy/; it does not fetch application code from a third-party host at runtime. Setup prints the URL; open it in any browser that can reach the broker. Android and desktop clients are available from GitHub Releases. The iOS client will follow later through TestFlight.

Server — the broker runs on:

Clients — the source tree and CI cover six platforms:

Windows x64 hosts the broker natively in this release. Windows ARM64 does not: it is not qualified yet, and the broker refuses it rather than running unverified — including an x64 process under ARM64 emulation, which reports itself as x64 and is detected by asking Windows what the machine is. Intel macOS server hosting remains unsupported. WSL also remains supported, as a Linux host; connectivity software that forwards broker loopback must run where it can reach that broker, so see the method-specific guides if you stay on WSL.

Privacy and security

The broker runs on your machine, under your account. Broker state is stored there; session content is sent only to authenticated clients over the network you choose. cosyncing operates no hosted service in that connection path and includes no analytics or advertising telemetry. Optional features contact only the services they name, such as local Tokdash quota data. cosyncing does not configure or contact connectivity providers; any proxy, tunnel, VPN, or mesh is operator-owned. The npm-installed broker does not silently replace itself: npm owns package updates, and cosy setup reconciles the installed service after an update.

Report vulnerabilities through GitHub private vulnerability reporting, per SECURITY.md.

Repository layout

• packages/typescript/ — broker, wire-contract owner, agent adapters, transport, and crypto.
• packages/dart/ — client contract, transport, Flutter adapter, and crypto.
• apps/client/ — the Flutter application, including every platform runner, test suite, integration driver, and developer tool.
• contracts/generated/ — broker-owned, flattened client contract snapshot.
• apps/poc-ui/ — non-production proof-of-concept UI retained for deterministic broker tests.

Development

The repository pins Flutter 3.44.3 in .fvmrc and Bun 1.3.8 in package.json. Run commands from the repository root.

bash
bun install --frozen-lockfile
bun run client:pub-get
bun run typecheck
bun run client:analyze
bun run client:test

Regenerate broker-owned client contracts with bun run contract:generate. CI runs bun run contract:check and fails on a stale snapshot.

Start with docs/README.md and build and test. Read CONTRIBUTING.md and CODE_OF_CONDUCT.md before opening a change; contributions use fork-and-pull-request and require a signed-off commit. Usage questions go to GitHub Discussions and reproducible defects to GitHub Issues — see SUPPORT.md. Installs from a predecessor client start fresh; see local data and upgrades.

License

First-party source is licensed under the Apache License 2.0. See LICENSE and NOTICE.