Mitos

Isolated, forkable computers for your AI agents.
Millisecond microVM sandbox forking on Kubernetes: fork a running VM into parallel attempts and restore from memory in tens of milliseconds.

Quickstart . Documentation . Features . Comparison . Contributing . Community

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What is Mitos

Mitos gives every AI agent its own isolated computer: a hardware-isolated Firecracker microVM that runs untrusted code safely and that you can fork while it is running. A live copy-on-write fork branches one warm VM into N independent siblings in tens of milliseconds, so an agent can explore many attempts in parallel from a shared, ready state, and you pay only for the pages each sibling changes.

Run it on your own Kubernetes cluster today, where your agents' code, data, and credentials never leave your infrastructure, or on the hosted API with no nodes to manage. As far as we know, it is the only runtime that is open source, self-hostable, Kubernetes-native, and able to live-fork a running VM, all at once.

Quickstart

1. Install and authenticate

pip install mitos-run
export MITOS_API_KEY=sk-...   # a key from https://mitos.run; no Kubernetes required

The SDK defaults to the hosted endpoint. The same code runs against your own cluster or a standalone sandbox-server by setting MITOS_BASE_URL. The key is resolved from the argument or MITOS_API_KEY and is never logged.

2. Create a sandbox and run code

import mitos

sb = mitos.create("python")                  # Ready microVM sandbox (~27 ms warm-claim)
print(sb.exec("echo hello").stdout)          # hello

# Files and a stateful code interpreter hang off the same flat handle.
sb.files.write("/workspace/plan.txt", "draft")
print(sb.run_code("import math; math.sqrt(144)").text)   # 12.0

Full reference: mitos.run/docs/quickstart.

3. Fork into parallel attempts

# N-way copy-on-write fork of the live VM: each sibling lands warm and independent.
a, b = sb.fork(2)
a.exec("echo conservative > /workspace/plan.txt")
b.exec("echo aggressive  > /workspace/plan.txt")

sb.terminate()

The async client mirrors the same surface: await mitos.aio.create("python") returns an AsyncDirectSandbox with the same exec / run_code / files / create_pty / fork / terminate.

Blocking exec and run_code work on the husk default. Streaming exec (sb.exec(..., on_stdout=...)), background processes (sb.exec_background(...)), and the interactive PTY (sb.create_pty()) run on the engine path today and are being brought to the husk default; run_code returns a fail-closed KernelUnavailable until the kernel ships in the husk base image.

Run it your way

Same engine, same API, more on-ramps. Depth is one click into the docs.

Every language, two modes. Each SDK speaks the same sandbox-server REST API in direct mode (standalone or hosted), and each also has cluster mode (an AgentRun that drives the mitos.run/v1 CRDs through the Kubernetes API). Default-pool naming is byte-for-byte identical across all six.

Language	Install	Direct	Cluster	SDK docs
Python	pip install mitos-run	sync + async	AgentRun	sdk/python
TypeScript	npm i @mitos/sdk	yes	AgentRun	sdk/typescript
Go	go get github.com/mitos-run/mitos/sdk/go	typed, errors.Is-friendly	AgentRun	sdk/go
Ruby	gem (stdlib only)	yes	AgentRun	sdk/ruby
Rust	crate (blocking)	yes	AgentRun	sdk/rust
Java	JDK 17 (stdlib only)	yes	AgentRun	sdk/java

The Go SDK ships in its own nested module (github.com/mitos-run/mitos/sdk/go), so importing it never pulls the controller into your build.

Self-hosting? Same code. The Helm chart deploys the same gateway the hosted service runs, so the quickstart above works unchanged against your own cluster: point MITOS_BASE_URL at your gateway and keep everything else. Hosted and self-hosted are one experience; only the URL and who operates it differ.

Kubernetes-native control, when you want it. For platform teams that manage pools declaratively (GitOps, RBAC-scoped automation, operators), the two-tier AgentRun path skips the gateway and drives the mitos.run/v1 CRDs through the Kubernetes API directly:

from mitos import AgentRun

c = AgentRun()                                   # kubeconfig or in-cluster; autodetected
sb = c.sandbox("python", ready=True)             # claims a warm sandbox, waits Ready
print(sb.exec("python -c 'print(40 + 2)'").stdout)   # 42

fork_a, fork_b = sb.fork(2)                       # fork against shared warmed state
sb.terminate()

c.sandbox("python") lazily creates a default pool if you have none; pass pool="my-pool" to use an existing one. Errors raise AgentRunError(code, cause, remediation). AsyncAgentRun mirrors the hot paths and adds create_pty() over WebSocket.

CLI and MCP.

The mitos CLI works against the hosted gateway (no cluster needed) or your own Kubernetes cluster:

go install mitos.run/mitos/cmd/mitos@latest      # requires a Go toolchain

# Hosted mode: set MITOS_API_KEY, no kubeconfig required.
export MITOS_API_KEY=sk-...
mitos sandbox create --pool python               # create from the python template
mitos sandbox exec <id> "python3 -c 'print(42)'"
mitos fork <id> --count 2                        # fork into 2 independent siblings
mitos sandbox ls
mitos sandbox terminate <id>

# Cluster mode (kubeconfig): target your own Kubernetes nodes.
mitos sandbox create --pool dev-default
mitos run echo hello --pool dev-default

mitos dev up brings up a one-command local control plane on a mock engine for cluster-mode development. An MCP server (mitos-mcp) exposes sandboxes as MCP tools for any MCP-speaking agent, and an Agent Skill teaches skill-aware agents the workflow. The full install matrix (script, Homebrew, deb/rpm, scoop/winget, checksums) is in mitos.run/docs/install.

Drop into the agent you already use. Each adapter is a thin shim over the same native ops (exec, run_code, files, fork), with no hard dependency on the framework package: Claude Code and opencode (MCP server + agent skill), the OpenAI Agents SDK, the Claude Agent SDK, LangChain / deepagents, Vercel AI SDK / Pydantic AI / AutoGen / LlamaIndex (standard MCP), and "change one import" migration shims for teams leaving the E2B or Daytona clouds. The integrations hub indexes every path.

Install the operator.

kubectl apply -k deploy/

The self-contained kustomize base installs the CRDs, the controller (husk mode), the forkd DaemonSet, the /dev/kvm device plugin, and the PKI bootstrap, and applies on a real KVM node with no manual patches. Nodes need /dev/kvm and the label mitos.run/kvm=true. The Helm chart is published at https://mitos.run/charts (helm repo add mitos https://mitos.run/charts); see deploy/charts/mitos. Then declare a warm pool, and fork from it with a Sandbox whose source.fromSandbox points at a live session (templates):

apiVersion: mitos.run/v1
kind: SandboxPool
metadata:
  name: python-agent-pool
spec:
  template:
    image: python:3.12-slim
    init: ["pip install numpy pandas requests"]
    resources: { cpu: "1", memory: "512Mi" }
    volumes:
      - { name: workspace, size: 5Gi, forkPolicy: Snapshot }
  warm: { min: 10 }

Why Mitos

Agent harnesses need fast, isolated environments where agents read and write files, install packages, and run untrusted code. Every existing option forces a trade: speed without ownership, isolation without forking, Kubernetes-native without warm starts, or durability locked inside someone else's cloud.

• Live-fork a running VM. N-way copy-on-write fork of a live microVM: daughters share the parent's memory pages until they write, so each fork lands in a warm, ready environment. Branch one agent into many parallel attempts.
• ~27 ms warm-claim activate. Firecracker microVMs restore from a memory snapshot in the tens-of-milliseconds class: P50 ~27 ms on the bare-metal reference node, reproducible from bench/husk-activate-latency.sh.
• Open source, self-hostable, Kubernetes-native. As far as we know, the only runtime that does all three. You drive the whole lifecycle through declarative CRDs (mitos.run).

Two ways to run it:

• Self-hosted (today): any Kubernetes cluster with KVM nodes. Your data never leaves your infrastructure. Bare metal (Talos + Hetzner) is the first-class reference platform.
• Hosted (in progress): the same engine and API operated by us, for teams that want milliseconds without managing nodes.

Two engine paths exist. The husk pod-native path is the default: each VM runs in its own unprivileged pod, and the source husk pod snapshots its running VM so N child pods restore it via CoW. The raw-forkd path runs forks in forkd's in-process engine. Everything here runs on the husk default unless explicitly marked engine path.

Sandboxes are not pods. Pod-scoped Kubernetes mechanisms (NetworkPolicy, ResourceQuota, PSA) govern the husk pod, not the workload inside the microVM; the sandbox is the VM, not the husk pod, and where we provide an equivalent it is documented as ours. The full claim and exec data paths and the component diagram are at mitos.run/docs/architecture.

Features

The husk pod-native path is the default. A few capabilities run today only on the raw-forkd engine path and are marked, with a link to the tracking issue.

Speed

Capability	What you get	Docs
Warm-claim activate	P50 ~27 ms on the bare-metal reference node (snapshot load + fork-correctness handshake + guest-ready); ~6-16 ms snapshot restore; ~3 MiB marginal memory per fork via CoW page sharing	BENCHMARKS.md
Pre-snapshotted pools	OCI images flattened to ext4 rootfs and warmed with your init steps before snapshotting, so there is no cold start on claim	docs/templates.md
CoW memory sharing	You pay for unique pages across forks, not for copies	mitos.run/docs/metering
Content-addressed distribution	Forks pull only the missing sha256 chunks from a holder over mTLS; rebuilds ship deltas under a version-compatibility contract	docs/snapshot-distribution.md

Isolation

Capability	What you get	Docs
Hardware isolation per session	A dedicated kernel per sandbox (KVM/Firecracker); on the husk default each VM runs in its own unprivileged, PSA-restricted pod, which is the per-VM boundary	mitos.run/docs/threat-model
No silent secret inheritance	Live forks of secret-holding sandboxes are rejected unless explicitly opted in; credentials are injected at claim time over vsock, never baked into snapshots	mitos.run/docs/threat-model
Default-deny egress	An in-pod nftables default-deny filter in the pod's own netns (CNI-independent), with an unconditional cloud-metadata (169.254.169.254) block and a per-template allowlist by IP:port and by name through an in-pod DNS proxy. Verified end to end on a real KVM cluster; the guest cannot influence enforcement	mitos.run/docs/networking
Encryption at rest	Per-scope LUKS2 containers with crypto-shredding and KMS envelope wrapping (behind --enable-encryption, fail-closed); HSM-backed keys and per-workspace scope are follow-ups	docs/encryption.md

Agent DX

Capability	What you get	Docs
Blocking exec	Correct stdout and exit code over the sandbox API	mitos.run/docs/cli
Streaming exec and PTY	Incremental stdout/stderr, background processes, and a token-gated interactive WebSocket terminal (engine path)	mitos.run/docs/cli
Code interpreter	run_code with a stateful kernel and rich multi-MIME results, in every SDK and the MCP server; fail-closed KernelUnavailable until the kernel ships in the husk base image	mitos.run/docs/mcp
LLM-legible errors	Every failure carries {code, cause, remediation}, parsed by the SDKs into a structured AgentRunError	docs/api/errors.md

Kubernetes-native

Capability	What you get	Docs
Declarative CRDs	SandboxPool, Sandbox (poolRef/fromSandbox/fromRevision source), Workspace/WorkspaceRevision in mitos.run/v1 with volume topology and fork behavior	docs/templates.md
Pod-native execution	Each per-sandbox VM runs in an unprivileged pod (/dev/kvm from a device plugin, not privileged), so CPU/memory requests are scheduler truth and PSA governs the pod	mitos.run/docs/threat-model
Capacity-aware scheduling	CoW bin-packing onto warm holders, a CoW-aware overcommit budget, a MaxSandboxes host-DoS ceiling with atomic slot reservation, and typed NoCapacity backpressure instead of OOMing a node	docs/scheduling.md
Demand-driven autoscaling	SandboxPool.spec.autoscale scales the dormant husk-pod count to clamp(inUse + targetSpare, minWarm, maxWarm) with an anti-thrash cooldown; a fixed pool is just minWarm == replicas	docs/scheduling.md
Failure and GC semantics	Claim TTLs, orphan-VM sweeps, controller-restart reconciliation, forkd crash reaping via an on-disk journal, node-loss handling, and saturation backpressure, all CI-proven	docs/failure-gc.md

Durable state

Capability	What you get	Docs
Durable forkable workspaces	Workspace/WorkspaceRevision CRDs: durable, versioned, forkable agent state independent of any sandbox. /workspace hydrates on start and a committed revision dehydrates on terminate over the content-addressed store. Verified create -> commit -> fork on a real KVM cluster	mitos.run/docs/workspaces
Outputs and diff	spec.lifetime.onTerminate.outputs narrows the dehydrate to listed subtrees; {diff: true} records a content-hash diff against the parent head	mitos.run/docs/workspaces
Git rendezvous	A {git} output pushes per-attempt branches to a rendezvous remote (the engine pushes; a human or CI merges). Best-effort on husk today	mitos.run/docs/workspaces
Dev-environment URL	mitos workspace serve <ws> --pool P warm-claims a forked sandbox bound to the workspace and returns a ready https://<label>.<expose-domain>/ URL; each forked session gets its own URL	docs/recipes/dev-environment.md

Operable

Capability	What you get	Docs
Metrics and tracing	Node and controller Prometheus metrics, a per-claim OpenTelemetry trace (--otlp-endpoint), and a toggleable structured audit log (--audit-log) recording command/path and byte counts, never content or secrets	mitos.run/docs/observability
CoW-aware metering	The shared template page set is counted once, not once per fork, so billing and scheduling reflect the honest physical footprint	mitos.run/docs/metering
Operator tooling	kubectl mitos plugin (ls / ps) and the operational GET /v1/metering report	mitos.run/docs/observability
Bare metal first-class	Talos + Hetzner is the reference platform	docs/platforms/talos-hetzner.md
Single-user first run	k3s quickstart with a one-user login gate (QA only, not production)	docs/platforms/k3s-quickstart.md

Comparison

A head-to-head numbers table belongs here only when our harness can regenerate it against the actual competitors on the same hardware, with scripts in this repo. That harness is #15. The figures below are other vendors' published numbers, for different operations, on different hardware, with different methodology: they are not measured by us and are not a head-to-head claim.

Runtime	Published figure (theirs, not ours)	Operation they describe
Mitos (ours, measured)	~27 ms P50	warm-claim activate on the bare-metal reference node
E2B	~150 ms	sandbox create
Daytona	sub-90 ms	create from snapshot
Modal	sub-second	sandbox create
CodeSandbox SDK	~863 ms / ~495 ms	live fork / memory-resume
Fly Machines	< 1 s	machine start

What is comparable and real today is the qualitative pareto map: the combination of open source, self-hostable, k8s-native, and live snapshot fork is the axis where Mitos is alone.

	Mitos	E2B	Modal	Daytona	Morph	Cloudflare	Box	Agent Sandbox	Kata/KubeVirt	raw Firecracker
Hardware isolation per session	KVM microVM	microVM	gVisor	container/VM	microVM	V8 isolate	VM	Kata option	KVM	KVM
Snapshot fork of running state	yes, core primitive	snapshot/resume	memory snapshots	no	yes (Infinibranch)	no	disk fork	no	no	DIY
Warm-pool millisecond claims	yes (design center)	warm pools	warm pools	workspaces	yes	instant isolates	not published	1-3s cold	seconds	DIY
Durable forkable workspaces	Workspace CRD	no	volumes	workspaces	yes, proprietary	yes (disk)	no	PVCs	PVCs	no
Kubernetes-native API	CRDs	SaaS API	SaaS API	SaaS/OSS	SaaS API	SaaS API	agent-native CLI	CRDs	CRDs	no
Self-hostable	yes, any KVM cluster	partial OSS	no	OSS core	no	no	no	yes	yes	yes
Hosted option	planned (same engine)	yes	yes	yes	yes	yes	yes (only)	no	no	no
Your data stays on your infra	yes (self-hosted)	no	no	partial	no	no	no	yes	yes	yes
Open source	Apache 2.0	partial	no	partial	no	no	no	Apache 2.0	Apache 2.0	Apache 2.0

SaaS runtimes (E2B, Modal, Daytona, Cloudflare) are fast, but your agents' code, data, and credentials run on someone else's infrastructure with no self-host path at equivalent capability. Morph built the right state model (branch/restore) as a proprietary cloud; our Workspace primitive targets the same semantics, open source, at fork(2) speeds. Agent Sandbox (k8s-sigs) is winning the Kubernetes API standard without a snapshot-fork engine, which is why we ship a conformance facade (cmd/facade) to be its fastest backend rather than fight it (docs/facade-conformance.md). Kata, KubeVirt, and raw Firecracker give you the isolation primitive and leave the pool, fork, distribution, and agent-API layers as your problem.

If an alternative beats us on an axis you care about and we have no roadmap line that closes it, that is a bug in our strategy: open an issue.

Architecture

Mitos boots Firecracker microVMs, forks them through copy-on-write snapshots, and exposes the whole lifecycle through declarative CRDs (SandboxPool, Sandbox, Workspace) in the mitos.run/v1 API group. A sandbox is a microVM, not a pod: it gets hardware isolation through KVM, and pod-scoped mechanisms (NetworkPolicy, ResourceQuota, PSA) do not govern it.

The pieces:

• controller (Deployment): reconciles the CRDs, selects a node, and drives forkd. It tracks the available fork nodes through a registry fed by per-node capacity heartbeats.
• forkd (DaemonSet): the per-node daemon that owns the VMs. It serves gRPC on :9090 for the controller (fork, prepare-pool, heartbeat) and an HTTP sandbox API on :9091 for exec and file traffic. It needs /dev/kvm, so it runs only on KVM-capable nodes.
• guest agent: PID 1 inside each microVM. It speaks a vsock protocol for exec, files, environment, and fork notifications.
• sandbox-server: the same fork engine behind a plain REST API, with no Kubernetes required, for local loops and single-host use.
• SDKs (sdk/python, sdk/typescript, sdk/go, and more): clients for the hosted service, a cluster, or sandbox-server.

Two hot paths carry the system:

• Claim path: the controller picks a warm node from the registry and calls forkd Fork over gRPC; the resulting sandbox reports Ready through forkd's HTTP API on that node.
• Exec path: the SDK or CLI talks to forkd on :9091, which bridges over vsock to the guest agent inside the VM.

Fork is the core primitive: a source VM is snapshotted once and N children restore from that snapshot through copy-on-write, so each sibling lands warm and independent while the shared template pages are stored and metered once. Because Firecracker needs hardware virtualization, bare metal (Talos on Hetzner is the reference platform) is a first-class target; the cloud control plane stays on ordinary nodes while execution lands on KVM-capable machines.

Project status

Early development, pre-1.0 (latest release v0.3.0). Do not run untrusted code in production yet: there has been no external security review and some isolation controls remain open (see the threat model for the exact per-boundary status). The control plane is real end to end, proven in CI against mock engines and real Firecracker VMs, and exercised on a single-node Talos KVM cluster.

Verified on a real KVM cluster (husk default): warm-claim activate, blocking exec, run_code failing closed with KernelUnavailable, self-heal / re-pend, pool warming plus demand autoscaling, live sandbox fork (the source husk pod snapshots its VM and N child pods restore it via CoW, each an independent Ready child), durable forkable workspaces (create -> commit -> fork), and pod egress isolation (default-deny, cloud-metadata block, per-template allowlist).

Tracked tails not yet on the husk default: streaming exec and the interactive PTY; live-VM memory snapshot hooks for resumable workspace heads; S3/encryption live store-selection; the husk {git} workspace push; and multi-node N>1 (designed, single-node-verified).

ROADMAP.md is the single source for what is done, in progress, and gated. The operating rule: this repository never describes a system that does not exist.

Local development (no KVM required)

mitos dev up brings up a local kind cluster on a mock control plane and the mitos CLI drives the full claim path; the mock engine reconciles claims to Ready and exercises control-plane dispatch, but a real in-VM exec needs a node with /dev/kvm. For the no-cluster REST loop, run go run ./cmd/sandbox-server --mock --addr :8080 and point the Python SDK at it. The full kind walkthrough is at mitos.run/docs/cli.

Documentation

Full documentation lives at mitos.run/docs: quickstart, architecture, SDK and CLI reference, sandbox lifecycle, workspaces, networking, and the threat model, all rendered from this repository.

The complete long tail (templates, snapshot format and distribution, encryption and secrets, scheduling and density, failure and GC, fork-engine correctness, recipes, and the target v2 API spec) lives in docs/ in this repo. Benchmark methodology is in BENCHMARKS.md.

Contributing

Contributions welcome. See CONTRIBUTING.md and CLAUDE.md for conventions, and the issues page for work tracked against ROADMAP.md.

Security

The threat model with per-boundary status lives at mitos.run/docs/threat-model; no external security review has happened yet, and the document says exactly what is open. To report a vulnerability, see SECURITY.md.

License

Apache 2.0.