# Remote Sessions (SSH) Codeman can run a session's agent on a **remote host over SSH** instead of the local machine. The agent (Claude, OpenCode, Codex, Antigravity, Gemini, Pi, Grok, or a plain shell) runs inside a `tmux` server **on the remote host**, so it survives the SSH connection dropping; Codeman attaches to it the same way it attaches to a local managed session. This document covers the data model, the shell-safe SSH command construction (COD-107), the durable-launch design (COD-104), and the operational caveats. For the local session/mux machinery this builds on, see the **Mux** and **Session** entries in `CLAUDE.md` → Architecture. ## Why it exists A developer box (`AA-DESKTOP`) often needs to drive an agent on another machine — a NAS, a build server, a host reachable only through a jump box or a cloudflared SOCKS5 proxy. Rather than wrap `ssh` by hand per host, Codeman stores reusable **remote hosts** + **remote cases** and reproduces the exact connection the operator already uses (`ssh-aa-desktop`-style configs: custom port, identity file, `-J` jump host, `-o ProxyCommand`). ## Data model Types live in `src/types/session.ts`; persistence in `src/remote-hosts.ts`. | Type | Role | | -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | `RemoteSshOptions` | The **HOW-to-reach** fields, shared by host + session: `identityFile`, `socksProxy` (`host:port`), `jumpHost` (`[user@]host[:port]`), `extraSshOptions` (`KEY=VALUE[]`). Every field optional — all-absent reproduces port-22, default-identity, directly-SSH-able behavior. | | `RemoteHost` (extends `RemoteSshOptions`) | A saved host: `id`, `label`, `host`, `username`, `port?`, `commands?` (per-mode launch command override). | | `RemoteCase` | A working directory on a host: `name`, `type: 'remote'`, `hostId`, `remotePath`. | | `SessionRemote` (extends `RemoteSshOptions`) | The resolved bundle stamped onto a live session: host coordinates + `remotePath` + `commands`, plus **`owned?`** and **`remoteSessionName?`** (COD-105 — see [Ownership](#ownership-launched-vs-discovered-and-attached-cod-105)). Built by `toSessionRemote(host, case)` (sets `owned: true`) for the launch path, or `toAttachedSessionRemote(host, name, path)` (sets `owned: false`) for the attach path. Both copy the advanced SSH options through so every connection is identical. | | `RemoteCommandMode` | `Extract` — the modes that can run remotely. | | `RemoteSessionInfo` (COD-105) | One discovered remote tmux session: `name` (always `codeman-*`), `attached` (a client is connected), `created` (epoch s), `windows`. Returned by `listRemoteCodemanSessions()`. | Persistence is two flat JSON arrays in the instance data dir: - `~/.codeman/remote-hosts.json` — `readRemoteHosts()` / `writeRemoteHosts()` - `~/.codeman/remote-cases.json` — `readRemoteCases()` / `writeRemoteCases()` (Paths via `remoteHostsPath()` / `remoteCasesPath()`; both honor `CODEMAN_INSTANCE` because the config dir is the instance data dir.) On the live `Session`, the remote rides as `_remote?: SessionRemote`. When attaching, `resolveMuxAttachCwd()` forces the cwd to `/tmp` for remote sessions — the local working directory is meaningless on the remote box. ## SSH command construction (COD-107 — the injection surface) **All** SSH command lines flow through one function so user-controlled fields are escaped once and the launch + prereq probe can never drift apart: ```ts // src/remote-hosts.ts buildSshConnectionArgs(remote: RemoteSshOptions & Pick): string[] ``` It returns the **ordered leading tokens** of an ssh command line (no `-t`, no target, no remote command): ``` ssh -o BatchMode=yes [-p ] [-i ] # ~ / $HOME expanded, then shellescaped [-J ] # shellescaped, single token [-o ProxyCommand=nc -X 5 -x %h %p] # ONE shellescaped -o token [-o ] … # each extra option, shellescaped ``` Rules that keep this safe — **do not bypass them by hand-building an ssh line elsewhere:** - **Every** user-controlled value (`-i`, `-J`, `-o`, ProxyCommand) is POSIX single-quote `shellescape`d (`'…'` with embedded `'\''`). The helper mirrors the one in `tmux-manager.ts`. - **`~`/`$HOME` in `identityFile` is expanded at build time** (`expandIdentityPath`), _before_ escaping — ssh does not expand `~` inside `-i`, and the escaped value never reaches a shell that would. - **The ProxyCommand is one shellescaped `-o KEY=VALUE` token**, so its spaces and the `%h`/`%p` placeholders reach ssh as a single argument. `%h %p` survive verbatim — **ssh** expands them to the real host/port, not the shell. - **Empty options ⇒ `['ssh', '-o BatchMode=yes']`** (+ `-p` only when set) — byte-identical to the historical behavior. Token construction is unit-tested independently of any live connection (see `test/` for `buildSshConnectionArgs` / `buildRemoteTmuxCheckCommand` cases). ## Durable launch (COD-104) `buildRemoteLaunchCommand({ mode, remote, sessionId })` in `tmux-manager.ts` builds the command that launches (or **reattaches** to) the remote session: ``` ssh -o BatchMode=yes -t user@host \ 'tmux -L codeman-remote new-session -A -s codeman-ssh- -c "cd && exec " \; \ set -t codeman-ssh- status off \; set -t codeman-ssh- mouse off \; \ set -t codeman-ssh- prefix C-q \; set -s escape-time 0 \; \ set -t codeman-ssh- window-size latest' ``` Key points: - **`new-session -A -s codeman-ssh-`** = attach-if-exists-else-create, so a reconnect (same deterministic `remoteTmuxSessionName(sessionId)` — `codeman-ssh-` + the first 8 chars of the session id) lands back in the **same** remote session rather than spawning a duplicate. This is what makes the remote agent survive an SSH drop. The name deliberately fails `SAFE_MUX_NAME_PATTERN` so a Codeman running ON the remote host never adopts it. - **`-L codeman-remote`** = a DEDICATED socket for sessions launched by remote Codemans, NOT the canonical `-L codeman` socket the remote host's own Codeman uses. Options are set per-session (`set -t`), never `-g`, so a shared remote tmux server's other sessions are untouched (#145 hardening). Note the asymmetry: **discovery/attach (COD-105) target the canonical `-L codeman` socket** — they join sessions the remote's own Codeman manages, while owned durable launches live on `-L codeman-remote`. - **`exec `** replaces the pane shell with the agent, so the pane PID _is_ the agent. The per-mode command comes from `remote.commands?.[mode]` or `defaultRemoteCommandForMode(mode)` (`exec claude` / `exec opencode` / `exec codex` / `exec gemini` / `exec agy` / `exec bash -l`). - The **whole tmux invocation is a single shell-quoted ssh argument**, and the pane command is independently quoted, so a `remotePath` with spaces is safe. - Connection options come from the **same `buildSshConnectionArgs(remote)`** as the prereq probe; `-t` is inserted right after `ssh -o BatchMode=yes`, preserving historical token order. ### tmux prerequisite probe Because durable remote sessions require tmux on the remote host, `checkRemoteTmuxAvailable(host)` runs `command -v tmux` over SSH **before** creating a remote case/session and returns a structured, never-throwing result: - empty stdout / non-zero exit → _"remote host `` needs tmux installed for durable remote sessions"_ - stderr present → _"could not verify tmux on remote host ``: ``"_ (a real connection failure, surfaced to the operator) - success → `{ ok: true, tmuxPath }` It connects with the **identical** options as the launch (`buildRemoteTmuxCheckCommand` reuses `buildSshConnectionArgs` and inserts `-o ConnectTimeout=10`), so a proxied/custom-port/identity host that the launch can reach also passes the probe (and vice-versa). **Test-mode short-circuit:** under `VITEST` the probe returns `{ ok: true, tmuxPath: '(test-mode)' }` without opening a socket — mirroring `TmuxManager`'s no-op-shell-under-VITEST (`IS_TEST_MODE`). Without it, remote-case create-path tests would hit a real ~10s ssh timeout. Only the live probe is skipped; command construction is still asserted by unit tests. ## Ownership: launched vs. discovered-and-attached (COD-105) COD-104 (above) was Phase 1 — Codeman _launches_ a remote session and owns it. COD-105 is Phase 2 — Codeman can also **discover** `codeman-*` tmux sessions already running on a remote host (created by the remote's own Codeman or another instance) and **attach** to one it didn't launch. Ownership decides what happens when the tab closes. `SessionRemote.owned` carries this: - **`owned: true`** (or absent — legacy/COD-104 sessions persisted before this field) — we launched it via `buildRemoteLaunchCommand` and may explicitly kill it. - **`owned: false`** — discovered + attached; another Codeman owns the remote session. `remoteSessionName` holds its existing tmux name. Closing the tab **detaches**, never kills. ### Discovery `listRemoteCodemanSessions(host)` lists the remote's `codeman-*` sessions: - `buildRemoteListSessionsCommand()` runs `tmux -L codeman list-sessions -F "…"` over SSH (connection args from the shared `buildSshConnectionArgs`, so discovery connects identically to launch/probe). `2>/dev/null` swallows tmux's "no server running" stderr. - `parseRemoteSessionList()` is a **pure, unit-tested** parser. ⚠️ Quirk: the remote tmux's `-F "…\t…"` format emits the **literal two-character `\t`**, not a real tab (verified on tmux next-3.7), so the parser splits on `/\\t|\t/` (literal backslash-t **or** a real tab, for builds that do expand it). It keeps only `codeman-*` names, coerces types, and skips malformed lines. - `listRemoteCodemanSessions()` **never throws** — unreachable host / no tmux / no sessions all map to `[]`. Like the prereq probe, it **no-ops to `[]` under `VITEST`** so a request path never opens a real ssh connection. Discovery is **explicit** — the UI has a "Discover existing sessions" button per host; Codeman never auto-discovers on host select. ### Attach vs. launch selection `buildRemoteSessionCommand(mode, remote, sessionId)` in `tmux-manager.ts` picks the remote command line by ownership: - **`owned === false`** → `buildRemoteAttachCommand(remote, name)` — emits `ssh … -t … 'tmux -L codeman attach -t '`. It uses **`attach`, NOT `new-session -A`**, so it only _joins_ an existing session and never creates one. - **owned (default)** → `buildRemoteLaunchCommand` (the COD-104 path above). ### Detach-not-kill `TmuxManager.killSession()` has an **early return for non-owned remote sessions**: it tears down **only the LOCAL pane** holding the ssh client (`tmux -L codeman kill-session` on _this_ host's socket). Killing the local ssh sends SIGHUP to the remote `tmux attach`, which **detaches** — the durable remote session survives. The early return is a structural guarantee that **no code path can ever issue a remote `kill-session` for a session we don't own** — the only `kill-session` run is on the local socket, which never reaches the remote socket. ## Respawn / reattach continuation A dropped connection or a dead pane must reconnect to the **same conversation**, not launch a fresh one — the whole point of a durable remote session. - **Claude**: the launch command is idempotent — `claude --session-id || claude --resume ` (see `buildRemoteLaunchCommand`'s claude branch). The first run creates the conversation under the deterministic session id; every later reattach/respawn re-runs the same line, `--session-id` fails ("already in use"), and the `||` fallback resumes it. - **OMP**: `omp` has no equivalent idempotent single-line form, so `Session._pinOmpRespawnId()` resolves and pins an explicit `--resume ` before a respawn (mirroring the local/docker builders, rendered through the same `buildSpawnCommandFromRegistry` engine — not a hand-rolled command and not `appendResumeFlag()`, which is docker-only and cannot work here: appending a flag after the quoted `-c 'omp'` hands the id to the login shell as `$0` instead of to `omp`). ⚠️ **The resolver only ever reads THIS host's local `~/.omp/agent/sessions/`**, which is meaningless for a remote session — the conversation and its session file live on the remote host, under the remote user's home. For a remote session, `_pinOmpRespawnId()` therefore skips local resolution entirely and falls back to `omp`'s own ambiguous `--continue` (`ompConfig.continueSession`), which the remote pane command already renders. This is a known, accepted degradation versus the local/docker paths' exact `--resume` pin — safe in practice because each remote respawn talks to exactly one remote pane's own omp history, so "most recent" is normally correct, but it can drift the same way `--continue` always could if two remote sessions ever share one remote directory. ## Auto-reconnect vs. a clean agent exit `remoteAutoReconnect` (default ON) watches for a dropped SSH connection and reconnects with bounded backoff. It must **never** revive a session whose agent exited cleanly (Ctrl-C, Ctrl-D, `exit`) — that tears down the durable remote tmux session itself, and a transport-level `isPaneDead()` cannot tell that apart from a plain network drop. `remoteTmuxSessionAlive()` (#355) resolves this by probing the remote host directly: `tmux -L codeman-remote has-session -t codeman-ssh-` over the same `buildSshConnectionArgs` as launch, classified by **exit status alone** (`classifyRemoteAliveExit`: `0` = alive, ssh's `255` or a timeout = unknown, anything else = gone) — `has-session` prints nothing on success, so reading stdout would misclassify every live session as gone. An unreachable host answers "unknown", which also means do not revive. The answer is cached per session and cleared whenever the pane is next seen alive, so a stale `true` from one transport drop can never revive the NEXT clean exit. ## API Routes are registered in `src/web/routes/case-routes.ts`: | Method | Path | Purpose | | -------- | ------------------------------------ | ---------------------------------------------------------------------------------------------- | | `GET` | `/api/remote-hosts` | List saved hosts | | `POST` | `/api/remote-hosts` | Create a host | | `PUT` | `/api/remote-hosts/:id` | Update a host | | `DELETE` | `/api/remote-hosts/:id` | Delete a host | | `GET` | `/api/remote-hosts/:hostId/sessions` | Discover `codeman-*` sessions on the host (COD-105; `listRemoteCodemanSessions`, never errors) | | `POST` | `/api/cases/remote-link` | Link a case to a remote host (creates the `RemoteCase`) | Attaching to a discovered session is a **session-create** path, not a host route: `POST /api/sessions` accepts `attachRemoteSession: { hostId, remoteSessionName }` (schema in `schemas.ts`; `remoteSessionName` must match `^codeman-[a-zA-Z0-9._-]+$`), which `session-routes.ts` turns into a non-owned (`owned: false`) session. Frontend touchpoints: the remote-host management UI is in `session-ui.js` / `panels-ui.js`; a remote session is created by picking a remote host/case in the session-create flow, or via the per-host **"Discover existing sessions"** button → **Attach** action (creates an `owned: false` session). ## Security notes - **`identityFile` is a path only — never key bytes.** Codeman stores the path and passes it to `ssh -i`; the key never enters Codeman's state or the wire. - The injection surface is the SSH option fields. The single-source `buildSshConnectionArgs` + `shellescape` discipline (COD-107) is the control — audit any new code path that constructs an ssh command to route through it rather than concatenating options inline. - `BatchMode=yes` means **no interactive password/passphrase prompts** — remote hosts must be reachable with key-based or agent auth (or an unencrypted key the agent has loaded). A host needing a passphrase will fail the probe with an ssh diagnostic rather than hang. ## Related - `CLAUDE.md` → Architecture → **Remote** row, and the **Remote sessions (SSH)** Key Pattern. - `docs/security-architecture.md` — overall network/auth model. - COD-104 (tmux prereq + durable launch), COD-105 (discover + attach, detach-not-kill ownership), COD-107 (shell-safe connection args).