Kyushu

Open source toolServerless

A Self-Hostable Wasm Sandbox for JavaScript Workers — run a Cloudflare Workers-style handler on a VPS or anywhere, without Node.js, Bun, or even Docker.

Homepage Docs Repository

Scanned 14 Oct 2026 · Schema v5 · features v21

Licence: MIT
Self-hosted; you pay for the infrastructure.
Free tier: Free to run
Isolation: WebAssembly
shares the host process
Regions: —
Not disclosed on the public surface.
Capabilities: 3 / 61
6 partial · 44 fail · 0 not assessed
Agent readiness: 5/10 · 1/8
read · drive, pre-login surface

Advertised for

Self hosted JS/TS HTTP fetch handlers · Static websites/assets embedded into a Wasm worker · Experimental sandboxing of user defined or third party logic; production untrusted input explicitly cautioned against

Built for

Developers

· Terminal-first: `curl install | bash`, `kyu build`, `kyu run`
· Low-level vocabulary: WebAssembly, wasm32-wasip2, QuickJS, Wizer, Wasmtime, Rust
· 'without Node.js, Bun, or even Docker' — a deliberately minimal dev tool

01 Website design Desktop public website · assessed 14 Oct 2026

Complete assessment.

The desktop landing and getting-started documentation share a restrained white, text-led presentation with fine dividers, dark command panels and a small illustrated logo. Documentation adds persistent side navigation and colored instructional callouts; hosted pricing is not applicable to this MIT-licensed self-hosted CLI.

Editorial minimalism

Landing page: captured
Pricing: not applicable
Docs: captured

02 Runtime Each fact carries its source; dots show confidence. Open a row for the evidence.

Isolation & lifecycle

Isolation primitive

WebAssemblyshares the host process

Persistence

JavaScript module state is reset between requests. Explicit host filesystem mounts may be writable and retain operator-owned files; no managed persistent volume service.

Snapshots / forks

Wizer freezes pre-initialized JavaScript memory into the build artifact. No user-facing checkpoint/fork of a live serving instance documented.

Resources & limits

Storage

Explicit host/guest filesystem mounts, read-only by default with writable opt-in; static assets can be embedded in the worker or served from filesystem. No managed database/object store.

Limits & quotas

No documented operator-facing memory/fuel/concurrency quotas in the current run configuration. Experimental, unaudited runtime.

GPU

Access

Deploy interface

cli

SDK languages

JavaScriptTypeScript

Network & secrets

Egress controls

Outbound DNS name lookup, TCP and UDP are individually disabled by default and enabled with worker.network.ip_name_lookup/tcp/udp. No per-destination allowlist documented. Outbound fetch uses wasi:http separately; do not interpret these raw socket flags as a verified HTTP deny policy.

Secrets

Explicit worker.env key/value injection into the worker; no dedicated secret vault or rotation documented.

Bring your own cloud

Placement & use

Jurisdiction

Advertised workloads

Self hosted JS/TS HTTP fetch handlersStatic websites/assets embedded into a Wasm workerExperimental sandboxing of user defined or third party logic; production untrusted input explicitly cautioned against

03 Capabilities 3 pass · 6 partial · 44 fail · 61 of 61 assessed

Supported — Documented on the public surface and verified.
Partially supported — Exists with caveats: gated, thin, or enterprise-only.
Not supported — Checked and not offered.
Not assessed — Scanned before this capability was tracked. Not a lack.

Compute & storage 1/11

Persistent diskStorage that survives restart/stop (not ephemeral-only).

Partially supported

Object storageManaged S3-compatible / blob object store the platform PROVIDES to a user's workloads (buckets, presigned URLs). DISTINCT from persistent-disk (block/volume attached to an instance) and from a self-host dependency (source.self_host.deps[]=["object-storage"] is an infra dep to RUN an OSS tool — the opposite direction). SCOPE varies and matters: native first-class (Railway Buckets, Cloudflare R2) vs a sibling SKU / extension (Fly Tigris, Bunny Storage, DigitalOcean Spaces) — record which in the evidence quote / note. Admitted v15.

Not supported

Snapshots / forkingSnapshot or copy-on-write fork of a running instance (filesystem-only counts). Whether the snapshot also restores memory + running processes is recorded separately by memory-snapshot (v19).

Not supported

Live-state (memory) snapshotsA snapshot / checkpoint / pause captures a running instance's MEMORY and PROCESS state and restores it, so running processes continue where they left off instead of a freshly booted instance with the same files. Counts whether user-triggered (snapshot, checkpoint, pause-to-storage) or used to restore pre-initialised state (memory snapshots for fast cold starts). Distinct from snapshots-forks (any snapshot or fork, including filesystem-only; a product passing that key may still fail this one) and from scale-to-zero (an idle-cost property; suspension may or may not keep memory). Actor multiplexing (see scale-to-zero) records its live-state half here — only when the suspended actor's MEMORY/process state is what comes back, not a freshly booted worker with the actor's files.

Supported

Scale to zeroIdle instances suspend at no / negligible cost. ACTOR MULTIPLEXING (many suspended stateful actors sharing a small pool of pre-warmed workers, woken on request — Agent Substrate, AX, kagent; Rivet's hibernating actors) has NO key of its own (proposal REJECTED v20) — score the idle-cost half HERE and the live-state half under memory-snapshot; the oversubscription ratio / density is a performance characteristic the registry does not key.

Not supported

GPU computeGPU-backed instances available.

Not supported

Multi-regionCompute placeable in more than one geographic region.

Not supported

Sandbox templates / custom imagesBuild reusable sandbox/VM images from an OCI image or Dockerfile (a base you fork instances from).

Not supported

Cloud-init / ignition configCustomise a VM / microVM / instance at boot via cloud-init (or ignition) user-data — the same boot-metadata interface as AWS/Azure/GCP. Inject packages, users, SSH keys, files, and run-commands declaratively at launch. Distinct from sandbox-templates (a PREBUILT image you fork instances from) — this is PER-LAUNCH declarative customisation, not a baked image.

Not supported

Desktop / computer-use sandboxA virtual desktop (GUI) for LLM computer-use — browser + desktop automation, often via noVNC/VNC.

Not supported

Selectable isolation runtimeThe user chooses the isolation runtime per workload / environment / sandbox from more than one option (e.g. microVM vs gVisor vs plain container, native namespaces vs gVisor, gVisor vs VM). Records the CHOICE; the isolation_primitive facet still records the best-evidenced primary. A platform that switches runtime automatically without a user choice (e.g. gVisor forced for GPU) does not pass on that alone.

Not supported

Networking & delivery 0/8

Automatic HTTPSTLS endpoints provisioned automatically per workload.

Not supported

Built-in reverse proxyPlatform routes external traffic to workload services.

Not supported

Custom domainsBring-your-own domain via CNAME/DNS.

Not supported

Public preview URLsShareable per-deploy / per-branch URLs.

Not supported

Direct public IPv6Per-instance stable public IPv6 for raw TCP/UDP (beyond a managed HTTPS proxy) — e.g. mosh / raw sockets.

Not supported

Egress controlsConfigurable OUTBOUND network policy — egress firewall / allowlist / egress proxy on traffic LEAVING a workload. Scoped to OUTBOUND only (v15): private-network REACHABILITY between a user's own services is private-networking, not this. Static-egress-IP belongs here (an outbound concept).

Partially supported

Private networkingA platform-internal private network between a user's OWN services — service-to-service connectivity, VPC, service mesh, and/or service discovery, not exposed to the public internet. DISTINCT from egress-controls (OUTBOUND firewall/allowlist), reverse-proxy (PUBLIC inbound ingress), and direct-ipv6 (per-instance PUBLIC addressing). Admitted v15.

Not supported

Email send / receiveSend and/or receive email from the workload.

Not supported

Edge KV storeA globally-replicated key-value store read from WITHIN an edge runtime at the PoP (low-latency, eventually-consistent) — Cloudflare Workers KV, Deno KV, Fastly KV Store, Akamai EdgeKV, Vercel Edge Config. Distinct from first-party-db (a managed DATABASE service you provision and connect to) and from http-query-api (HTTP access to an external store) — edge-kv is colocated with the edge compute and read at the edge.

Not applicable

Developer access 1/9

Public APIDocumented programmatic API.

Not supported

OpenAPI specMachine-readable OpenAPI / Swagger spec published.

Not supported

CLIOfficial command-line tool.

Supported

SDKOfficial client library/libraries.

Partially supported

SSH accessDirect SSH into workloads.

Not supported

Filesystem APIRemote file operations over the API (list/read/write/watch/copy/upload) without SSH.

Not supported

Git deployDeploy from a Git repo / push-to-deploy.

Partially supported

Private container registryHosted private image registry.

Not supported

E2B-compatible APIDrop-in compatibility with the E2B sandbox API/SDKs — existing E2B client code runs against this product by changing the endpoint/domain + key, with no business-code changes. E2B itself passes as the reference implementation. Distinct from public-api / sdk (the product has its own API — this key says it also speaks another vendor's) and from self-host-oss (a self-hosted E2B-compatible server is scored on both).

Not supported

HTTP data APIQuery / read / write the stored DATA over plain HTTP/REST (or GraphQL) WITHOUT the native protocol driver (Postgres wire / Redis RESP) — agent- and edge-friendly data access via fetch(). The DATA plane; distinct from public-api (a control-plane / management API). Auto-generated-from-schema REST/GraphQL (PostgREST, pg_graphql) is a flavour of this.

Not applicable

AI & agents 0/11

Built-in coding agentShips a first-party AI coding agent in the product.

Not supported

Agent skillsInstallable / declarable agent skills or tools.

Not supported

AI app builderPrompt-to-app / vibe-coding generation surface.

Not supported

MCP serverExposes a Model Context Protocol server for agents.

Not supported

MCP clientActs as an MCP client / consumes MCP tools.

Not supported

MCP-server hostingRun/host MCP servers as a workload on the platform (distinct from exposing a first-party MCP control server — that is mcp-server).

Not supported

LLM gatewayRoutes LLM API calls through the platform (multi-provider).

Not supported

BYOK for LLMsBring-your-own LLM provider keys.

Not supported

Model inference API (first-party)A FIRST-PARTY hosted LLM/model inference API — the provider serves its OWN catalogue of (usually open-weight) models behind a (typically OpenAI-compatible) endpoint, billed per token. Distinct from llm-gateway (a multi-PROVIDER proxy/router for YOUR calls to external providers like OpenAI/Anthropic) and from byok-llm (bring your own provider keys) — here the platform IS the inference provider, serving its own models.

Not applicable

Autonomous QA agentA first-party AUTONOMOUS AI agent that QA-TESTS a running app / implementation — exercising it like a real user (clicking through flows, checking behaviour) and reporting bugs/defects (often back to a coding agent, or before a human review). Distinct from built-in-agent (a code-AUTHORING agent — this one VERIFIES the result, it does not write the feature; a product can ship both), from ai-guided-code-review (organises a diff for a HUMAN to review — not an autonomous tester), and from observability (runtime metrics/logs, not active testing).

Not supported

Credential-injection proxyThe platform holds real secrets OUTSIDE the workload and injects them on the wire (an egress / broker proxy swaps a placeholder or phantom token for the real credential on matching outbound requests), so code running in the sandbox — e.g. an untrusted agent — never sees or can exfiltrate the real key. Distinct from secrets-management (storage + injection INTO the workload as env vars/files — the workload holds the secret) and from egress-controls (outbound allow/deny POLICY; a product can have an allowlist without injecting credentials, and vice versa).

Not supported

Preinstalled coding agentThe platform installs and launches a THIRD-PARTY coding agent (a harnesses.yml entry — Claude Code, Codex, OpenCode, Pi ...) inside a workspace/sandbox it provisions, with the agent's auth wired in (your own account or API key), so you start an agent session rather than an empty box. Distinct from built-in-agent (a FIRST-PARTY agent the vendor ships) and from harnesses[] (which records that a harness CAN target the product, not that the product runs it for you).

Not supported

Data 0/1

First-party databasePlatform-provided managed database.

Not supported

Database branchingCopy-on-write branch of a DATABASE (schema + data) as a dev-lifecycle primitive — branch your data like code, usually instant via a metadata operation. Distinct from snapshots-forks (forks a running compute INSTANCE / VM state) and from preview-environments (a full per-PR environment that may USE a DB branch). For a data product a CoW branch maps HERE, not to snapshots-forks.

Not applicable

Vector searchFirst-class storage, indexing, and similarity search of vector embeddings — a native vector type/index or a managed vector DB. The data-layer primitive for RAG / semantic retrieval.

Not applicable

Ephemeral instant DB (no-signup)Provision a working, usable instance via a single command / HTTP call with NO account, signup, or card — typically time-boxed (expires unless claimed). A zero-onboarding path an agent can hit directly.

Not applicable

Platform & operations 0/5

Scheduled tasksCron / scheduled job primitive.

Not supported

Durable workflowsDurable execution / long-running workflow primitive.

Not supported

Preview environmentsA full EPHEMERAL environment spun up per PR / branch — compute + addons + (often) a DB branch — torn down on merge. More than preview-urls (which is just a shareable URL for one deploy).

Not supported

Built-in observabilityFirst-party metrics / logs / tracing / APM / profiling included in the platform (no third-party stack required to see what a workload is doing).

Partially supported

Managed CI/CD runnersPlatform-hosted, drop-in CI/CD runner VMs (GitHub Actions / GitLab), typically faster and cheaper than the CI vendor's own hosted runners, billed per runner-minute; isolated + ephemeral per job. Distinct from git-deploy (push-to-deploy of an APP) and scheduled-tasks (cron) — this is managed CI COMPUTE you point your existing pipelines at.

Not applicable

Project template marketplaceA marketplace / gallery of prebuilt PROJECT STARTER templates (apps or websites) a user clones or launches a new project from and then customises — the "start from a template" surface of a builder / PaaS. Distinct from sandbox-templates (a COMPUTE base IMAGE you fork runtime INSTANCES from — Dockerfile / OCI), from app-builder (the prompt-to-app GENERATION surface — a product can have both), and from one-click OSS-app catalogues / helm-addon-marketplace (deploy a FINISHED app as-is, not a starter you build on).

Not supported

Organisation & security 1/8

Built-in authPlatform-provided authentication / IAM for workloads.

Not supported

SSO / SAMLEnterprise single sign-on.

Not supported

Secrets managementFirst-class secrets storage / injection.

Partially supported

TeamsMulti-user team accounts.

Not supported

SharingShare a running workload/resource via link (optionally gated).

Not supported

BYOCRuns inside the customer's own cloud account.

Not applicable

Deploy into customers' VPCsA SaaS vendor uses the platform to deploy and operate ITS software inside ITS CUSTOMERS' cloud accounts / VPCs (nested or "customer BYOC"), managed from the vendor's control plane. Distinct from byoc (your own workloads in your own cloud account).

Not supported

Workload identityThe platform gives each workload its own verifiable identity (OIDC token, SPIFFE SVID, cloud IAM federation) that it exchanges for short-lived credentials, so no long-lived static secret is stored or injected. Distinct from secrets-management (stores / injects static secrets) and credential-injection-proxy (swaps real secrets in on the wire).

Not supported

Self-host / OSS coreOpen-source core that can be self-hosted.

Supported

Proposed, not verified

Capabilities the scan saw but the registry does not track yet. A key is admitted only once two distinct products exhibit it. These are not scored.

Embedded static assetsembedded-static-assets
“Kyushu supports bundling static files (HTML, CSS, JS, images) directly into your worker.” kyushu.dev

04 Agent readiness Pre-login surface · counts, not a grade

Can an agent read it?

parse-ability · docs, metadata, machine-readable surfaces

5/10

4 full · 2 partial · 50% of applicable checks

llms.txt
Not supported
“/llms.txt + /.well-known/llms.txt both 404.”
llms-full.txt
Not supported
“/llms-full.txt 404.”
robots.txt AI policy
Partially supported
“/robots.txt 404 = default-allow (nothing disallowed) = half per rubric v3.”
JSON-LD
Not supported
“0 <script type=application/ld+json> on the homepage.”
Sitemap
Supported
“https://kyushu.dev/sitemap-index.xml links sitemap-0.xml with 19 official page URLs, both retained.”
Meta tags
Supported
“Complete title + description + OG (title/description/image/type) + Twitter summary_large_image; descriptive.”
Markdown negotiation
Not supported
“Accept: text/markdown returned HTML; .md probe returned 404. Retained homepage-markdown.txt and probe manifest.”
Content efficiency
Partially supported
“Retained homepage.html: 1084 readable UTF-8 text bytes / 24308 HTML bytes = 4.46% after excluding script/style text; within 1–5% half-credit band.”
Docs discoverable
Supported
“Homepage hero links 'Get started' / 'Read docs' -> /getting-started, first-class without JS.”
Machine-readable pricing
Not applicable
“oss-tool — no pricing (/pricing 404).”
No anti-bot wall
Supported
“Fresh anonymous browser and retained homepage/docs/raw well-known fetches did not show a public bot challenge.”

Can an agent drive it?

act-ability · APIs, SDKs, MCP, credentials, webhooks

1/8

1 full · 0 partial · 13% of applicable checks

Public API
Not supported
“No programmatic HTTP control API — the interface is the `kyu` CLI.”
OpenAPI spec
Not supported
“No OpenAPI spec.”
MCP server
Not supported
“No MCP server.”
SDK packages
Not supported
“Official kyushu-types is an authoring types package, not a functional API client SDK; no client SDK documented.”
Auth documented
Not applicable
“Self-hosted CLI — no hosted API to authenticate.”
Self-serve credentials
Not applicable
“No hosted signup/credential issuance (self-host).”
Webhooks
Not supported
“No webhooks.”
CLI tool
Supported
“https://kyushu.dev/reference/cli documents kyu build, run, dev and --version.”
Error model
Not supported
“No documented JSON error model (worker responses are user-defined).”
Rate limits documented
Not applicable
“Self-hosted — no hosted API rate limiting.”
Agent config files
Not supported
“No agents.md / /.well-known/agent / skills listing.”

05 Coding harnesses Which agents and IDEs are documented to run here

Advertised integrations 0

The public surface names no coding harness as supported or documented-to-run-here.

Plausible compatibility 0

Derived, not stored: the product passes SSH access, so any CLI coding agent is installable inside it. This is plausible compatibility, not a supported integration.

No general shell access documented, so nothing is derived. Absence is not unsupported.

06 Compliance & regions Standards held, with ordinal rigor; never a score

Certifications held 0

No attestations found on the public surface. Empty means nothing is advertised, after checking, not that nothing was checked.

Regions —

No region list captured.

07 Open source MIT · fetched by machine, not quoted from marketing

Licence & repository

Licence: MITOSI
Primary language: JavaScript
Stars: 193
Forks: 4
Created: 29 May 2026
Archived: No

Activity

Last commit: 23 Sep 2026
Latest release: docs/v0.1.9 · 23 Sep 2026
Issues open / closed: 1 / 5 · 83% closed

Component-tagged releases; latest docs/v0.1.9, cli/v0.4.0 and worker/v0.3.0 were published September 23, 2026. Recent retained releases cluster in August–September; no stable cadence asserted.

Fetched via gh on 14 Oct 2026.

Self-hosting

Methods: binarysource-build
You operate: —

MIT-licensed, free software plus operator infrastructure cost. Prebuilt binary or Rust source build; no external service dependencies. Experimental and unaudited: README says not recommended for production and warns against exposing untrusted input without review. Host filesystem mounts and environment variables require explicit grants. Plain HTTP runner; documented Caddy/systemd deployment leaves TLS, lifecycle and infrastructure to the operator.

Documentation signals 6/8

SupportedQuickstart
SupportedAPI reference
SupportedSelf-host guide
SupportedChangelog
Not supportedOpenAPI
Not supportedllms.txt
SupportedExamples
SupportedArchitecture doc

08 Company & presence Facts only, not scored

Company

Headquarters: Not disclosed
Founded: 29 May 2026
Team size: Not disclosed
Hiring: Unknown

Activity

Last release: docs/v0.1.9; cli/v0.4.0; worker/v0.3.0 — 2026-09-23 github.com
Last blog post: — kyushu.dev

Presence 2

Links found on the public surface scanned; not an exhaustive search.

09 Sources & method How this entry was produced

Public surface only

Everything here was read from kyushu.dev's unauthenticated pages, docs, pricing and repository on 14 Oct 2026. Nothing behind a login was used.

Statuses, not scores

Capabilities are pass, partial or fail against a written rubric (features v21). “Not assessed” means the scan predates the key.

Confidence is separate

Each fact carries its own confidence. Low-confidence facts are shown, never hidden, so you can weigh them.

Schema: scan v5
Features registry: v21
Keys tracked today: 61
Assessed on this entry: 61

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