Speckl

What Speckl Does

Speckl is a compiler for state machine specifications. You write what your system should do in SpeckDL — a typed specification language with states, actions, invariants, and guard conditions. The compiler produces five auditable artifacts from a single spec:

Fulfills NIST SA-11 (human-in-the-loop for automated outputs) — every AI-generated or hand-written spec is compiled through a deterministic pipeline. No LLMs in the compiler. Same input, same output, every time.

• Provenance is embedded by construction — not bolted on after the fact
• 41 tests passing, < 2 seconds to run the full suite
• 11 example specks: ToggleSwitch → TwoPhaseCommit → Paxos → Raft
• Dual-target: TypeScript state machine classes + verified WASM from the same spec
• Zero external services — everything runs locally

SpeckDL by Example

SpeckDL is a typed specification language for state machines. Define your states, actions, preconditions, and mutations — the compiler handles the rest.

// A simple toggle switch — compiles to TypeScript + WASM + 3 provenance artifacts
spec ToggleSwitch {
  type Status = enum { On, Off }

  state {
    status: Status = Status.Off
  }

  init Start() {
    set status = Status.On
  }

  action Flip() {
    require status == Status.On
    set status = Status.Off
    emit "TurnedOff"
  }

  action FlipBack() {
    require status == Status.Off
    set status = Status.On
    emit "TurnedOn"
  }

  invariant "At most one pending action" {
    !(status == Status.Flip && !(status == Status.FlipBack))
  }
}

Type system: Int · Float · Bool · String · Enum · Struct · List<T> · Set<T> · Map<K,V>  |  Keywords: spec · type · state · init · action · require · set · emit · invariant

Real Examples

Strategy Ladder

Speckl follows a four-step strategy — each step validates the market before building the next:

Try It

# Clone the repo
git clone https://os.scoble.me/forgejo/sscoble/speckl.git
cd speckl/compiler

# Build and run tests (41 tests, ~2s)
npm install
npm test

# Compile a spec to all 5 artifacts
node dist/index.js ../examples/TwoPhaseCommit.speck -o out/twophase

# Check TypeScript validity
npx tsc --noEmit -p out/twophase

# Validate WASM (requires wabt)
wat2wasm out/twophase/TwoPhaseCommit.wat