The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Asynthetic listing page.
Ground truth for AI coding agents.
Your agent's knowledge froze on a date. Asynthetic tells it exactly what changed — every breaking change between library versions, cited and tested.
Every coding agent ships with a knowledge freeze date. The libraries it writes against don't.
So agents do what the training data taught them: they write maxTokens into AI SDK 5 (removed), synchronous params into Next.js 15 (now a Promise), LangChainAdapter imports from a package that no longer exports them. The code looks right. The agent is confident. The build breaks — or worse, it doesn't, and the bug ships.
Tools that fetch current documentation tell agents what the API looks like today. That's half the problem. An upgrade needs the diff: what changed, what replaced it, and what silently behaves differently. No amount of "current docs" contains that.
Asynthetic is that missing half. Ask it about an upgrade, and it returns a hand-curated migration map: ordered breaking changes with before/after code, deprecation timelines, peer-version requirements, and a citation for every claim. Retrieval, never generation — the same question gets the same verified answer every time.
Without Asynthetic — the agent "upgrades" your AI SDK app from memory: keeps result.usage for billing (now silently counts only the final step), leaves temperature unset (v5 removed the implicit 0 — output turns nondeterministic), renames nothing because v4 syntax was correct when the model trained.
With Asynthetic — one tool call returns all 23 breaking changes for that exact version window, including the three above, each with the fix and the official source. The agent applies facts. You review a diff instead of debugging a regression.
That's the product: the difference between an agent that remembers and an agent that knows.
| Migration Maps | Hand-curated upgrade intelligence per version window: 40 breaking changes across 2 live maps (next 14→15, ai 4→5) |
| Citations | Every map cites official sources and carries a last_verified date. Maps are never LLM-generated. |
| Verification Levels | Every response self-reports confidence: high (empirically tested on real builds), medium, low — derived, never self-declared |
| Field Notes | Where reality diverges from docs, maps say so — e.g. Turbopack doesn't actually enforce the @next/font removal that Webpack does; Next 15's React 19 "requirement" isn't build-enforced. Found by running the upgrades, not reading about them. |
| SemVer Resolution | Ask with ranges (^14.2.0 → ^15.0.0); resolution method is always disclosed |
| Peer Checks | Static compatibility answers (next@15 + react@18.2 → false, with the cited reason) |
| Honest Misses | No data means found: false and an explicit instruction not to guess — never a plausible fabrication |
The next 14→15 map is Asynthetic's first verification_level: high: every entry tested against real builds on 14.2.35 and 15.5.20, across Turbopack and Webpack, dev and production.
Hosted (nothing to install):
Local (offline, bundled data):
Any MCP client works — Cursor, Claude Code, Windsurf, or your own agent:
Then upgrade something. The agent calls get_migration before it edits.
| Tool | Answers |
|---|---|
get_migration(package, from, to) | "What breaks between these versions, and how do I fix each one?" |
get_breaking_changes(package, version) | "What does this version break?" |
check_peer_compatibility(a, va, b, vb) | "Do these two versions work together?" — true / false / unknown, cited |
list_available_maps() | "What does Asynthetic know?" |
Full response shape, transports (Streamable HTTP + stdio + legacy SSE), and self-hosting: see docs below.
Asynthetic's founding rule: a wrong map is worse than no map. Everything follows from that.
verified status is earned empirically, not editorially: real projects, both bundlers, dev and production, on pinned versions. The process regularly finds things the docs get wrong — those findings ship in the maps.verification_level, source_count, pre-release warnings), so agents can weigh answers instead of trusting blindly.Narrow and deep, on purpose: fast-moving AI and JavaScript frameworks first, correctness over coverage always.
Zero-config serves the bundled maps over stdio. Set PORT for HTTP mode (/mcp, legacy /sse, health at /). Set SUPABASE_URL + SUPABASE_ANON_KEY to serve from Postgres (schema/schema.sql, then npm run seed). Missing config never crashes — it falls back and says so on stderr.
src/types/migration-map.ts — validation rejects anything malformed before it can ever be served.draft. verified is earned by testing snippets on real builds of the pinned versions. Retired maps become stale — excluded from serving, kept as record.npm run smoke must pass. Don't guess versions or API names: if it's not in an official source, flag it in the PR instead.Free public beta — hosted endpoint and npm package open to everyone. Next: more maps (Tailwind 3→4, React 18→19, Zod 3→4, AI SDK 5→6), more high-verification promotions, project-aware compatibility analysis. Details will be announced.
Read-only by construction: every tool is a lookup over curated data. No code execution, no request-time fetching, no access to your project or filesystem. The hosted endpoint sees only tool arguments (package names, version strings); sessions are ephemeral, in-memory, and isolated. Report issues via GitHub security advisories.
Source-available under BSL 1.1: self-hosting for your own use — personal, team, company-internal — is always permitted; reselling it as a competing hosted service isn't. Converts automatically to Apache 2.0 on July 4, 2030.
Built with TypeScript, the official MCP SDK, Zod, and Supabase. Serving live at asynthetic.up.railway.app/mcp.