mountable.io

Mountable CLI

mountable mounts a Mountable filesystem, a shared POSIX filesystem for agents and teams, on any Linux machine or agent sandbox and on a Mac (macOS 26, Apple Silicon), and manages filesystems, mount tickets and sessions. It is also an MCP server.

npx -y mountable-cli login                          # npm
uvx mountable login                                 # PyPI
curl -fsSL https://mountable.io/install.sh | sh     # standalone binary

The CLI is one self-contained binary: it downloads nothing at mount time and keeps the session's credentials in memory. Mounting needs FUSE (/dev/fuse) on Linux; on macOS it needs nothing else installed and no sudo (see macOS).

Authentication

• People: mountable login signs this machine in with a device flow.
• Backends and agents: set MOUNTABLE_API_KEY=mtbl_…. An API key belongs to one organisation, and the commands use it.
• Sandboxes: need no credentials, only a one-time ticket on stdin.

Commands that work inside an organisation take --org ORG_ID, then MOUNTABLE_ORG, then the only organisation the caller has; with several, they fail with org_required.

Commands

Command	Does
mountable orgs list	the caller's organisations
mountable fs list	filesystems
mountable fs create NAME	create a filesystem; prints its ID
mountable fs usage FS_ID	stored bytes and files against quotas, 30-day traffic
mountable ticket create FS_ID [--ro] [--idempotency-key KEY] [--max-duration D]	a one-time mount ticket for a sandbox; the session lasts D (such as 12h or 720h; default 12 hours, at most the API key's or login's expiry)
mountable sessions list FS_ID	live mount sessions
mountable sessions revoke SESSION_ID	revoke a session; its mount stops
mountable mount [--ro] FS_ID DIR	mount with your login
mountable mount --ticket-stdin DIR	mount with a ticket read from stdin
mountable unmount DIR	unmount; on Linux, pending writes are committed
mountable mcp	MCP server over stdio
mountable login, logout, version, licenses

Deleting a filesystem is done in the console.

Output, errors and exit codes

• --json on every command writes one JSON document to stdout, with the API's field names (help --json writes {"usage": …}). Diagnostics go to stderr. Nothing ever prompts. The exception is mountable mcp, whose stdout is the MCP protocol.
• mountable mount --json writes JSON lines as the mount progresses: {"event":"mounted","path":…,"filesystem_id":…,"mode":…} once the mount is usable, and {"event":"unmounted","reason":"signal|unmount|revoked|expired|error","detail":…} when it ends. Wait for mounted before using the directory.
• Exit codes: 0 success; 1 an error from the API, network, mount or credentials; 2 wrong usage.
• Errors carry a stable code and a next step: on stderr, or with --json as {"error":{"code":…,"message":…,"hint":…}} on stdout. For example, unauthenticated (run mountable login or set MOUNTABLE_API_KEY), org_required (pass --org), not_found (check the ID with mountable fs list), payment_required (the hint is the console's billing link), rate_limited (wait retry_after seconds).
• The one-time ticket appears only in the result of ticket create. API keys, login tokens, certificates and tickets never appear in errors or logs.

Retries

• Reads (list, usage) are safe to retry.
• ticket create sends an idempotency key: the one given with --idempotency-key, or a random one it prints to stderr before sending. Retry with the same key after a timeout. When the outcome is unknown (network_error or outcome_unknown), the error's idempotency_key is the key that request was sent with: retry with exactly that key. A replay returns the existing session without a ticket:
  • still requested: its ticket was lost. The CLI revokes that session, creates a new one with a fresh key and reports both session IDs (replaced_session_id).
  • active or later: the ticket was used. The CLI revokes nothing and fails with ticket_already_used; use a new key for another mount.
• fs create has no idempotency key, and names need not be unique. After a timeout, run fs list and look for the name before creating again.
• sessions revoke is idempotent.
• On HTTP 429 (rate_limited), wait retry_after seconds.

Agent workflow

The backend holds the API key; the sandbox gets only a ticket.

# Backend
export MOUNTABLE_API_KEY=mtbl_…
FS_ID=$(mountable fs create agent-workspace)
mountable ticket create "$FS_ID" --idempotency-key job-42 --json   # → {"ticket": "mtbltk_…", …}

# Sandbox, with the ticket in MOUNTABLE_TICKET
mkdir -p /mnt/work
printf '%s\n' "$MOUNTABLE_TICKET" | mountable mount --ticket-stdin --json /mnt/work &
# wait for {"event":"mounted",…}, use /mnt/work, then:
mountable unmount /mnt/work

Any existing, writable directory works as the mount point; mount checks it before it uses the ticket. The ticket is read from stdin, so it never appears in an argument list.

macOS

On macOS 26 (Apple Silicon) there is nothing else to install: no macFUSE, no kernel extension and no sudo. The CLI serves your filesystem to macOS's own NFS client, so it works like any other folder:

FS_ID=$(mountable fs list --json | jq -r '.[0].id')   # or the ID from `mountable fs list`
mkdir -p ~/mnt/work
mountable mount "$FS_ID" ~/mnt/work                   # add --ro for read-only

mountable mount stays running while the folder is mounted; use the folder from another terminal or any app, and stop with Ctrl-C or mountable unmount ~/mnt/work.

Your mount is private to your account: the CLI serves it over a socket only you can open and checks your user ID on every request. Revoking the session, or letting it expire, takes the mount away. Every write the Mac sends is saved by the service before macOS hears OK, so a crash of the CLI never loses a write macOS was told succeeded. Changes from other machines show up within moments.

Limits

• Writes are write-through, at about 7 MiB/s; each write macOS sends, up to 1 MiB, uses one unit of the filesystem's metadata rate.
• Files reach about 9.76 GiB written sequentially, less when written in many small append-and-fsync cycles.
• A file takes about 9,999 writes that change existing bytes or append small pieces; after that, writes to it fail with "file too large". Keep databases (SQLite and the like) and other files rewritten in place on local disk, or copy them in and out. Editors save by writing a fresh file (or truncating first), so they are unaffected.
• A failed write is reported once per file, to the first write, fsync or close of it by any program.
• Writes through mmap can fail without an error.
• Other mounts are coordinated per write, not for the whole time a file is open.
• Finish writing (close or fsync your files) before you unmount: a forced unmount of a busy mount can drop writes still in flight.
• macOS creates ._ files beside most files; to keep them out of git, run mkdir -p ~/.config/git && echo '._*' >> ~/.config/git/ignore (or append ._* to the file git config --global core.excludesFile names, if set).
• No Spotlight indexing, and locks (flock, fcntl) are local to the mount.

Skill

A skill teaches coding agents this workflow, the error codes and the retry rules:

npx skills add writeitai/mountable

It lives in skills/mountable/SKILL.md.

MCP server

mountable mcp serves the tools list_organizations, list_filesystems, create_filesystem, filesystem_usage, create_mount_ticket, list_mount_sessions and revoke_mount_session over stdio (create_mount_ticket takes an optional max_duration_seconds). It authenticates like the CLI. Results are the API's JSON; errors return the code and hint. Mounting stays a process in the sandbox: create_mount_ticket returns the ticket and the command that mounts with it.

Give the server MOUNTABLE_API_KEY through its environment: inherited from the environment the MCP client starts in, or set in the client's MCP configuration under env. Never pass the key as a command-line argument, where it would end up in process listings and shell history.

Claude Code (.mcp.json in the project; ${MOUNTABLE_API_KEY} is taken from the environment Claude Code runs in, so the key stays out of the file):

{
  "mcpServers": {
    "mountable": {
      "command": "npx",
      "args": ["-y", "mountable-cli", "mcp"],
      "env": { "MOUNTABLE_API_KEY": "${MOUNTABLE_API_KEY}" }
    }
  }
}

Claude Desktop (claude_desktop_config.json) and Cursor (~/.cursor/mcp.json); keep these files private, since they hold the key:

{
  "mcpServers": {
    "mountable": {
      "command": "npx",
      "args": ["-y", "mountable-cli", "mcp"],
      "env": { "MOUNTABLE_API_KEY": "mtbl_…" }
    }
  }
}

SDKs

Backends that read and write files without mounting use the files API through the SDKs, which create and refresh their own short token sessions from an API key.

Both are published as mountable-sdk, Python 3.10+ on PyPI and TypeScript on npm (Node 18+, Bun, or Deno):

pip install mountable-sdk      # import mountable_sdk
npm install mountable-sdk      # import { Mountable } from "mountable-sdk"

from mountable_sdk import Mountable

fs = Mountable().filesystem("fs_…", mode="rw")   # MOUNTABLE_API_KEY
info = fs.write("notes/a.md", "hello")
fs.write("notes/a.md", "hello again", if_match=info.etag)
print(fs.read("notes/a.md").data)

They live in sdk/python and sdk/typescript, behave the same way (the shared cases are in sdk/contract.md), and will be released together on tags sdk-vX.Y.Z.

LLM provider starters

examples/llm-providers has stdlib-only tools for the OpenAI Agents SDK and Responses API, Anthropic Messages API and Claude Code, Gemini ADK, and xAI Grok. The orchestrator holds MOUNTABLE_API_KEY and the sandbox receives the one-time ticket on stdin. The guide is https://mountable.io/docs/integrations.

Showcase demos

examples/showcase runs two demos: a planner sandbox and a coder sandbox sharing one directory, then a read-only laptop mount; and a revocation kill switch. python3 examples/showcase/relay.py --dry-run prints the sequence without calling the API. The same illustrations play at https://mountable.io/showcase and do not create a filesystem.

Notebook starters

examples/notebooks has a Jupyter notebook for Colab, Kaggle, Deepnote and Hugging Face Spaces and a Marimo notebook. They keep datasets, feature caches and checkpoints in a Mountable folder with mountable-sdk, so the files stay when the kernel restarts.

Multi-agent coding harness

examples/research-showcases/multi-agent-harness runs a planner, coder and verifier on one shared folder. A signed file-change webhook triggers a read-only verifier mount. Run harness.py offline by default, or use --live to create a filesystem with a monthly spend cap and rate limit.

Licenses

mountable licenses prints the licenses and notices of the third-party code compiled into the CLI, which also ship as THIRD_PARTY_NOTICES with every package and release archive.

Documentation: https://mountable.io/docs.

Development

go test ./...
go run ./tools/notices > THIRD_PARTY_NOTICES   # after changing dependencies
packaging/build.sh 0.0.0    # binaries, release archives, npm tarball and wheel in dist/

# SDKs
(cd sdk/python && uv run ruff format --check . && uv run ruff check . && uv run pyright && uv run pytest)
(cd sdk/typescript && npm ci && npm run typecheck && npm test && npm run build)

Releases are cut by pushing a tag vX.Y.Z (CLI) or sdk-vX.Y.Z (SDKs); see packaging/README.md. The Mountable service itself is operated by WriteIt.ai s.r.o.; this repository contains the open-source client only.

License

Apache-2.0.