[Sequela02]

Records stage 10's machine syntax before its conformance cases, with the probe that chose how an event states the next state.

What changes

• docs/design/syntax.md: a Machines section and decision 7.
  • A machine has state, init, event, observers (fn), invariant and helper invariant.
  • An event states its next state as next { field: value }. A field it doesn't list keeps its value, and every expression reads the state before the event.
  • Invariants are written over fields, since a specification can't call a function.
  • Events take intent and requires only, and next is a reserved word.
  • A sequence example takes the form example Machine … gives.
• docs/design/probes/2026-11-12-machine-updates/: the probe.
  • Three forms: field = value, next { field: value } and field' = value.
  • Twenty-four replies: four Claude models, plus ChatGPT, Grok, DeepSeek and Gemini through their public interfaces. Qwen wasn't run.
  • Every reply was right on tracing, frame and immutability. On reading a field after setting it, 7 of 8 read = as updating in order, all 8 read next { } as the state before the event, and 7 of 8 read the prime the same way.
  • The rule written before the runs would have kept =. The maintainers chose next { }, and the README states why.
• ROADMAP.md and constraint row 10: the boundary checks helper invariants too. Event overflow obligations assume them; without them, a state from TypeScript makes time + 60 overflow, per the stage 10 measurement.

Verification

• cargo fmt --all --check, cargo clippy --workspace --all-targets --locked -- -D warnings and cargo test --workspace --locked (85 passed, 1 ignored, with the pinned solvers) pass. This change touches no code.
• The probe's answer key and decision rule were written before any run. The replies are condensed in replies.md.

Not established:

• No person read the variants.
• One run per reader.
• The public interfaces' model versions weren't recorded.
• Grok searched the web on one reply despite the instruction.

Risk note

Two-way door, no behavior change: documentation only, and nothing parses machine yet. Blast radius: the syntax stage 10's conformance cases and compiler will follow. Evidence: the probe above.

Refs #82