synapse-rmcp

MCP server and CLI for host and container operations: Docker and Compose control, SSH, host inspection, logs, ZFS, and safe file transfer.

Synapse is a full-parity Rust port of synapse-mcp, built with the rmcp framework.

The server exposes two MCP tools (flux and scout) plus equivalent CLI commands, covering all 59 production actions from the original TypeScript server.

Contents

• Naming
• Capabilities And Boundaries
• Install
• Quickstart
• Client Configuration
• Plugin Packages
• Runtime Surfaces
• MCP Tool Reference
• CLI Reference
• Authentication
• Safety And Trust Model
• Distribution Contract
• Verification
• Deployment
• Troubleshooting
• Tools and Actions
• Known Parity Gaps
• Configuration
• Run
• Architecture
• Development
• Documentation
• Related Servers
• License

Naming

The repository is synapse-rmcp, the Rust crate is synapse, the MCP server identity is synapse, and the installed binary is synapse. The npm launcher package is synapse-rmcp.

Across most of the RMCP family, naming follows repo=<service>-rmcp, npm=<service>-rmcp, and CLI=r<service>. Synapse is an exception because it is a Rust port of the older TypeScript synapse-mcp project and keeps the operator-facing synapse binary.

Capabilities And Boundaries

Synapse provides local Docker, Compose, host, SSH, log, ZFS, and file-operation workflows through two MCP tools and the equivalent CLI:

• flux manages Docker infrastructure, containers, Compose projects, and host inspection.
• scout handles SSH/local host inspection, safe file reads, allowlisted command execution, bounded descriptor-confined file transfer, ZFS introspection, and log retrieval.
• REST exists only as a compatibility shim for a subset of actions.
• The web surface is a lightweight static admin shell, not a full dashboard.

Not for: arbitrary shell access, unaudited remote mutation, or bypassing host SSH trust. Destructive Docker/Compose/exec/file-transfer actions require explicit host targets and confirmation policy.

MCP callers never provide credentials, tokens, keys, or secrets as action arguments. Tokens, OAuth settings, host topology, SSH trust, and allowlists live in server-side configuration or the local SSH environment.

Install

Use the npm launcher for stdio MCP or CLI access without a manual binary install:

npx -y @dinglebear/synapse --help
npx -y @dinglebear/synapse mcp

For a permanent command:

npm i -g @dinglebear/synapse
synapse --version

The npm package downloads the synapse binary from GitHub Releases during postinstall, keeping the release tag aligned with packages/synapse-rmcp/package.json.

From source:

cargo build --release

The production image includes Python 3 plus the official Docker CLI/Compose plugin because Scout's remote descriptor wrappers and Flux Compose operations invoke those runtime tools. The image does not contain a Docker daemon; Flux uses the mounted socket or SSH-forwarded remote socket. Persistent appdata lives at ~/.synapse on the host and /data in the container.

Quickstart

The first-screen 30-second path is:

npx -y @dinglebear/synapse mcp

Then configure an MCP client with stdio:

{
  "mcpServers": {
    "synapse": {
      "command": "npx",
      "args": ["-y", "synapse-rmcp", "mcp"]
    }
  }
}

Start with a read-only call:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "scout",
    "arguments": {
      "action": "nodes"
    }
  }
}

Client Configuration

stdio is preferred for local MCP clients:

{
  "mcpServers": {
    "synapse": {
      "command": "synapse",
      "args": ["mcp"]
    }
  }
}

Streamable HTTP uses /mcp on the configured host and port:

{
  "mcpServers": {
    "synapse": {
      "url": "http://127.0.0.1:40080/mcp",
      "headers": {
        "Authorization": "Bearer ${SYNAPSE_MCP_TOKEN}"
      }
    }
  }
}

Plugin Packages

plugins/synapse/ ships Claude Code, Codex, and Gemini CLI manifests that all point at the same HTTP MCP endpoint and the same shared skill.

These packages contain no lifecycle hooks. Connecting to a server that is already running needs no setup — the manifests substitute your server_url and api_token directly. If this machine also runs the server, bootstrap it once by hand:

synapse setup install                  # put/refresh the binary on PATH
synapse setup plugin-hook              # check, then repair on blocking failures
synapse setup plugin-hook --no-repair  # audit only; never mutates appdata

Export the relevant SYNAPSE_* variables (or write them to ~/.synapse/.env) first; plugins/README.md maps each plugin option to its variable. Re-run synapse setup install after a plugin update.

Runtime Surfaces

| Surface | Status | Purpose | |---|---:|---| | MCP | Required | Agent-facing flux and scout tools | | CLI | Required | Scriptable parity surface for operators | | REST | Compatibility | Thin local action endpoint for 14 of 59 actions | | Web | Present | Lightweight static admin shell |

MCP Tool Reference

Synapse exposes two MCP tools:

• flux: Docker daemon, container, host, and Compose operations.
• scout: SSH/local host inspection, filesystem reads, allowlisted exec, multi-host emit, file beam, ZFS, and logs.

Both tools use an action-dispatched JSON shape:

{"name":"flux","arguments":{"action":"docker","subaction":"info"}}
{"name":"scout","arguments":{"action":"nodes"}}

The detailed action tables below are curated README reference material. The generated runtime MCP schema and the Rust action definitions are the source of truth for the live tool contract.

CLI Reference

Common commands:

synapse flux docker info
synapse flux container list
synapse flux compose list --host myhost
synapse scout nodes
synapse scout exec --host myhost --command hostname
synapse scout zfs pools --host myhost
synapse scout logs journal --host myhost --unit docker

Authentication

Mounted HTTP supports bearer and Google OAuth modes. Loopback stdio/local dev can run without mounted HTTP auth. Important variables:

SYNAPSE_MCP_HOST=127.0.0.1
SYNAPSE_MCP_PORT=40080
SYNAPSE_MCP_TOKEN=change-me
SYNAPSE_MCP_AUTH_MODE=bearer

See Configuration and docs/CONFIG.md for the full auth matrix.

Safety And Trust Model

Synapse separates read and write scopes (synapse:read, synapse:write) and uses confirmation gates for destructive operations. SYNAPSE_MCP_ALLOW_DESTRUCTIVE can skip prompts only in loopback-safe contexts. Host protocol is authoritative and defaults to SSH when omitted; local execution requires the explicit built-in local host or protocol: "local". SSH host trust is delegated to OpenSSH known-hosts behavior, and command execution uses execvp/argv semantics without shell interpolation. scout beam enforces both endpoints' configured read roots, blocks sensitive and symlinked paths, and caps each transfer at 64 MiB.

scout exec and scout emit accept only these 18 typed commands (ALLOWED_READ_COMMANDS in src/synapse/command_policy.rs):

cat, head, tail, grep, rg, ls, tree, wc, uniq, diff, stat, file, du, df, pwd, hostname, uptime, whoami

git is deliberately excluded, as are shells, interpreters, network clients, and mutating tools (EXEC_DENYLIST). There is no find or sort in the allowlist — use the dedicated scout find action for filesystem search. Per-host custom commands may be enabled via execAllowlist, but receive a zero-argument policy until a typed argument policy is registered.

Distribution Contract

The source of truth for release identity is the version shared by Cargo.toml, .release-please-manifest.json, packages/synapse-rmcp/package.json, release artifacts, and server.json.

Distribution/version invariants:

• The npm package downloads the matching GitHub Release binary.
• The installed binary remains synapse.
• server.json must point at ghcr.io/dinglebear-ai/synapse:<version>.
• Plugin manifests stay versionless where marketplaces derive identity from git state.
• Generated docs and schemas must come from source-controlled generation inputs; curated README/docs should point at source-of-truth files for details.

Verification

just validate-plugin          # plugin manifests, MCP config, monitors, skills
npm --prefix packages/synapse-rmcp run check
cargo fmt --check
cargo check
cargo test
git diff --check

Deployment

For a persistent mounted HTTP server:

SYNAPSE_MCP_HOST=0.0.0.0 \
SYNAPSE_MCP_PORT=40080 \
SYNAPSE_MCP_TOKEN=change-me \
synapse serve

Use bearer or OAuth before exposing the endpoint beyond loopback. Production Docker/Compose notes live in docs/DEPLOYMENT.md and docs/DOCKER.md when present; local operator usage can stay on stdio.

Troubleshooting

• 401 or 403 from /mcp: check bearer/OAuth settings and gateway headers.
• no hosts appear: check SYNAPSE_HOSTS_CONFIG, SYNAPSE_CONFIG_FILE, and ~/.ssh/config.
• destructive actions are refused: confirm the host target and confirmation policy.
• SSH errors: verify OpenSSH known_hosts, mux/socket availability, and host reachability outside Synapse first.

Tools and Actions

flux — Docker infrastructure management

flux docker — Docker daemon operations (9 actions)

| Subaction | Scope | Description | |---|---|---| | info | synapse:read | Docker daemon information | | df | synapse:read | Docker disk usage | | images | synapse:read | List Docker images; dangling_only to filter untagged | | networks | synapse:read | List Docker networks | | volumes | synapse:read | List Docker volumes | | pull | synapse:write | Pull a Docker image; requires host, image | | build | synapse:write | Build a Docker image; requires host, context, tag; optional dockerfile, no_cache | | rmi | synapse:write | Remove a Docker image; requires host, image, force=true | | prune | synapse:write | Remove unused resources; requires host, prune_target, force=true |

flux container — Container lifecycle + inspection (14 actions)

| Subaction | Scope | Description | |---|---|---| | list | synapse:read | List containers; optional state, name_filter, image_filter, label_filter | | inspect | synapse:read | Detailed container info; requires container_id; optional summary | | logs | synapse:read | Container logs; requires container_id; optional lines, since, until, grep, stream | | stats | synapse:read | Resource usage stats; optional container_id | | top | synapse:read | Show running processes; requires container_id | | search | synapse:read | Full-text search by name/image/labels; requires query | | start | synapse:write | Start a stopped container; requires host, container_id | | stop | synapse:write | Stop a running container (destructive); requires host, container_id | | restart | synapse:write | Restart a container; requires host, container_id | | pause | synapse:write | Pause a running container; requires host, container_id | | resume | synapse:write | Resume a paused container; requires host, container_id | | pull | synapse:write | Pull latest image for a container; requires host, container_id | | recreate | synapse:write | Recreate container with image pull (destructive); requires host, container_id; optional pull (default true) | | exec | synapse:write | Execute command inside container (destructive, execvp); requires host, container_id, command array |

flux host — Host inspection (9 actions)

| Subaction | Scope | Description | |---|---|---| | status | synapse:read | Check Docker connectivity on a host | | info | synapse:read | OS, kernel, architecture | | uptime | synapse:read | System uptime | | resources | synapse:read | CPU, memory, disk usage | | services | synapse:read | Systemd service status; requires host; optional state, service | | network | synapse:read | Network interfaces | | mounts | synapse:read | Mounted filesystems; requires host | | ports | synapse:read | Port mappings; requires host; optional protocol, limit, offset | | doctor | synapse:read | Diagnostic checks; requires host; optional checks (comma-separated) |

flux compose — Docker Compose project management (10 actions)

| Subaction | Scope | Description | |---|---|---| | list | synapse:read | List all Docker Compose projects; requires host | | status | synapse:read | Get project service status; requires host, project; optional service | | up | synapse:write | Start a compose project; requires host, project | | down | synapse:write | Stop a compose project (destructive); requires host, project; optional remove_volumes, force | | restart | synapse:write | Restart a compose project (destructive); requires host, project | | recreate | synapse:write | Recreate compose containers (destructive); requires host, project | | logs | synapse:read | Get project logs; requires host, project; optional service, lines, since | | build | synapse:write | Build compose project images; requires host, project; optional service | | pull | synapse:write | Pull compose project images; requires host, project; optional service | | refresh | synapse:read | Refresh compose project cache; requires host |

flux help — Auto-generated flux docs

| Action | Scope | Description | |---|---|---| | help | public | Return flux action reference; optional topic (e.g. "container:list"), format (markdown|json) |

scout — SSH/local host inspection

Scout simple actions (9 actions)

| Action | Scope | Description | |---|---|---| | nodes | synapse:read | List all configured SSH hosts | | peek | synapse:read | Read a file or directory listing; requires host, path; optional tree, depth | | find | synapse:read | Find files by glob; requires host, path, pattern; optional depth, limit | | ps | synapse:read | List processes; requires host; optional sort (cpu|mem|pid|time), grep, user, limit | | df | synapse:read | Disk usage; requires host; optional path | | delta | synapse:read | Compare files or content; requires source_host, source_path; then either target_host+target_path or content | | exec | synapse:write | Execute allowlisted command (destructive, execvp); requires host, command; optional path, args, timeout_secs | | emit | synapse:write | Multi-host execution (destructive); requires targets array, command; optional args, timeout_secs | | beam | synapse:write | Bounded root-confined file transfer (destructive); requires source_host, source_path, dest_host, dest_path; both paths must be under configured Scout/Compose roots |

scout zfs — ZFS introspection (3 subactions)

| Subaction | Scope | Description | |---|---|---| | pools | synapse:read | List ZFS pools; requires host; optional pool name filter | | datasets | synapse:read | List ZFS datasets; requires host; optional pool, dataset_type, recursive | | snapshots | synapse:read | List ZFS snapshots; requires host; optional pool, dataset, limit |

scout logs — Log retrieval (4 subactions)

| Subaction | Scope | Description | |---|---|---| | syslog | synapse:read | Read /var/log/syslog (falls back to /var/log/messages); requires host; optional lines, grep | | journal | synapse:read | Read systemd journal; requires host; optional lines, unit, priority, since, until, grep | | dmesg | synapse:read | Read kernel ring buffer; requires host; optional lines, grep | | auth | synapse:read | Read /var/log/auth.log (falls back to /var/log/secure); requires host; optional lines, grep |

scout help — Auto-generated scout docs

| Action | Scope | Description | |---|---|---| | help | public | Return scout action reference; optional topic (e.g. "zfs:pools"), format (markdown|json) |

Known Parity Gaps

synapse achieves action-level parity with synapse-mcp — all 59 production actions from synapse-mcp/docs/INVENTORY.md are implemented. However, the following features from the original TypeScript server are not yet ported:

Not ported

| Feature | Description | |---|---| | claude/channel notifications | Original forwards Docker events and log tails as notifications/claude/channel MCP notifications. No equivalent exists in Rust. | | Templated MCP resources | Original exposes synapse://hosts/{host}, synapse://hosts/{host}/stacks, synapse://stacks, synapse://stacks/{host}/{stack}, synapse://stacks/{host}/{stack}/env, synapse://containers/{host}, synapse://containers/{host}/{id}. Rust exposes tool-specific schema and help resources plus read-scoped synapse://hosts, synapse://compose/projects, synapse://status, and synapse://activity. | | Root SSH login gate | Original gates sshUser=root through elicitation unless SYNAPSE_ALLOW_ROOT_LOGIN=true. Rust has destructive-operation elicitation but no root-login gate. | | TOFU fingerprint store | Original persists fingerprints to ~/.config/synapse/known_hosts.json and rejects changed fingerprints. Rust uses strict OpenSSH known_hosts with wildcard warnings — different operator behavior. | | SYNAPSE_EXCLUDE_HOSTS | Original env var to exclude hosts from fleet discovery is absent in Rust. | | SYNAPSE_MCP_ALLOW_YOLO | Original "skip all confirmation gates" mode. Rust has SYNAPSE_MCP_ALLOW_DESTRUCTIVE (per-restart override, loopback-only), which is not identical. | | SYNAPSE_DEBUG_ERRORS | Original opt-in mode that returns full internal error detail. Rust always sanitizes internal tool errors. | | git in exec allowlist | Original includes git in ALLOWED_READ_COMMANDS with flag guards. Rust deliberately excludes git. |

Configuration

SYNAPSE_MCP_HOST=127.0.0.1
SYNAPSE_MCP_PORT=40080
SYNAPSE_MCP_TOKEN=change-me

Key environment variables:

| Variable | Default | Description | |---|---:|---| | SYNAPSE_MCP_HOST | 127.0.0.1 | Bind host for HTTP transport. | | SYNAPSE_MCP_PORT | 40080 | Bind port for HTTP transport. | | SYNAPSE_MCP_TOKEN | unset | Static bearer token for auth. | | SYNAPSE_MCP_NO_AUTH | false | Disable auth for loopback development only. | | SYNAPSE_NOAUTH | false | Delegate auth/authz to an isolated trusted upstream gateway. | | SYNAPSE_MCP_ALLOW_DESTRUCTIVE | false | Skip destructive-operation confirmation prompts (loopback only). | | SYNAPSE_MCP_MAX_CONCURRENCY | 50 | Maximum simultaneous in-flight operational requests. Excess requests receive HTTP 429 with Retry-After. Set to 0 to disable. Public probes, OAuth discovery, and static assets are exempt from concurrency shedding. | | SYNAPSE_MCP_PUBLIC_URL | unset | OAuth public URL; HTTPS required except loopback development. | | SYNAPSE_HOSTS_CONFIG | unset | Inline host topology. Omitted host protocols default to SSH; local execution requires protocol: "local". |

See .env.example for the full list of variables, docs/CONFIG.md for configuration details, and docs/SECURITY.md for transport, path, transfer, container, and CI runner trust boundaries.

Run

# Start MCP server (stdio transport)
cargo run -- mcp

# Start HTTP server
cargo run -- serve

# CLI examples
cargo run -- flux docker info
cargo run -- flux container list
cargo run -- flux compose list --host myhost
cargo run -- scout nodes
cargo run -- scout exec --host myhost --command hostname
cargo run -- scout zfs pools --host myhost
cargo run -- scout logs journal --host myhost --unit docker

MCP examples:

{"name":"flux","arguments":{"action":"docker","subaction":"info"}}
{"name":"flux","arguments":{"action":"container","subaction":"list","state":"running"}}
{"name":"flux","arguments":{"action":"compose","subaction":"status","host":"myhost","project":"mystack"}}
{"name":"scout","arguments":{"action":"nodes"}}
{"name":"scout","arguments":{"action":"exec","host":"myhost","command":"hostname"}}
{"name":"scout","arguments":{"action":"zfs","subaction":"pools","host":"myhost"}}
{"name":"scout","arguments":{"action":"logs","subaction":"journal","host":"myhost","unit":"docker"}}

Architecture

FluxService   (src/flux_service/)  Docker/container/compose/host ops
ScoutService  (src/scout_service/) SSH/exec/fs/zfs/logs ops
      ↓ via SynapseService facade (src/app.rs)
MCP shims     (src/mcp/tools.rs)  tool args → service → Value
CLI shim      (src/cli.rs)        argv → service → stdout
REST layer    (src/api.rs)        POST /v1/synapse → service → JSON

Development

cargo fmt --check
cargo test
cargo clippy -- -D warnings
cargo build --release

just dev     # serve with no auth (loopback, dev mode)
just test    # cargo test
just lint    # clippy
just fmt     # cargo fmt

Useful docs:

• docs/API.md for full tool contracts
• docs/CONFIG.md for environment and auth
• docs/QUICKSTART.md for local smoke tests
• plugins/synapse/skills/synapse/SKILL.md for agent usage guidance
• tests/parity.rs for automated parity verification against synapse-mcp INVENTORY

Documentation

This README is curated for first-run orientation and high-level action discovery. Source-of-truth docs and code are split as follows:

• docs/API.md for the curated action contract reference.
• docs/MCP_SCHEMA.md for MCP schema shape and drift expectations.
• docs/CONFIG.md for environment and auth policy.
• docs/QUICKSTART.md for local smoke tests.
• docs/PLUGINS.md and plugins/synapse/skills/synapse/SKILL.md for agent and marketplace usage.
• docs/generated/openapi.json for generated OpenAPI output.
• src/flux_service/, src/scout_service/, and src/mcp/ for runtime source of truth.

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License

MIT