core: drop the dead version counter + hardening/perf pass over notify, teardown, and computed

[ivanbanov]

What

Started as removing MachineClass.version (write-only, bumped every notify, read by nothing). The code-review pass that confirmed it was dead surfaced a set of real defects and hot-path waste next to it — this PR lands the whole sweep over machine.ts, compose.ts, connector.ts, store.ts, and computed.ts.

Fixes

• Unsubscribing is final, even mid-notify. A nested notify (a send from inside a subscriber) rebuilt the iteration snapshot and resurrected listeners removed earlier in the pass. The machine, connector, and store all had a variant of this; the hardened loop now lives in one primitive (broadcast.ts) they all share:

  for (const l of snap) {
    if ((!dirty && snap === snapshot) || listeners.has(l)) l()
  }

• A throwing effect cleanup no longer leaks the rest. Every cleanup runs, the list clears, the first error rethrows after the pass — the next stop can't double-run them.

• Manual sync()/combine().subscribe() disposers detach from the group registry. Long-lived compositions with subscribe/unsubscribe churn no longer grow it without bound; stop() no longer re-runs hand-run disposers.

Perf

• Computed recompute allocates nothing (was 7 objects/hit): dep keys/values sit in reused parallel buffers, captured at read time inside the tracking proxies — the post-pass that re-read every dep is gone.
• machine.select is built once (stable identity, safe for dependency arrays); watcher field sources bind once at start; store.set/setContext share one shouldPatch probe.

Benchmark on the same machine — main measured once in a worktree, branch is the average of 4 clean runs:

Scenario	main	branch (4-run avg)
Single-event throughput	8.98 M	11.6 M
Irrelevant write, 5000 cells	1.44 M	4.4 M
Computed recompute	3.26 M	4.9 M
4-deep computed chain	869 K	1.5 M
Memory, 64-field (KB/machine)	4.10	4.35

The memory row is the one debit (+0.25 KB/machine from the per-instance broadcast closures). The documented tables (benchmark README, core README, website, root README) were re-baselined in this PR on the same 4-run average.

Naming

bump() → notify() (nothing left to bump), installComputed → defineComputed (it defines getters).

Checks

• Core: 175/175 tests (13 new — re-entrancy, cleanup-throw, broadcast contract, compose/store dispose, select identity). Monorepo: 2307/2307.
• Typecheck, lint, format — clean.
• Changeset: one patch for @dunky.dev/state-machine covering the consumer-visible fixes.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
dunky-state-machine	Ready	Preview	Aug 20, 2026 3:32pm