Add reactive machine acceptance projections

[SandroMaglione]

Summary

• Add projection-only AtomMachine.can overloads for fixed and atom-backed event inputs.
• Preserve startup, runtime, schema, terminal, equality, registry ownership, and weak-cache semantics across root machine bridges.
• Document React and family usage without a machine-specific hook or React memoization.

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change a publishable package

Validation

• pnpm check
• Automated type-performance measurement passed or was not required
• Automated runtime- and memory-performance measurement passed or was not required

Local pnpm perf:types and pnpm perf:runtime smoke tests also passed. CI base-versus-PR reports remain authoritative.

[github-actions]

Type performance

Measured with TypeScript 6.0.3 and skipLibCheck=true.

Scenario	Base	PR	Difference
Effect only	55	55	0 (0.0%)
Import effect-machine	55	55	0 (0.0%)
Machine.states (3 states)	3,039	3,039	0 (0.0%)
Machine.make (3 states, 2 events)	10,787	10,787	0 (0.0%)
machine.handle (3 states, 2 transitions)	28,551	28,551	0 (0.0%)
fluent transition (10 named branches)	122,775	122,775	0 (0.0%)
fluent invocation (state-dependent Effect)	108,429	108,429	0 (0.0%)
machine.handle (depth 24)	207,970	207,970	0 (0.0%)
machine.handle (wide depth 16)	236,332	236,332	0 (0.0%)
machine.handle (parallel/history/choice)	144,812	144,812	0 (0.0%)
machine definition (3 independent implementations)	143,617	143,617	0 (0.0%)
machine exact input/output/error/services	129,873	129,873	0 (0.0%)
execution adapter readiness	136,469	136,469	0 (0.0%)

Marginal instantiations are measured against the matching setup without that API call:

Scenario	Base	PR	Difference
Import effect-machine	0	0	0
Machine.states (3 states)	2,984	2,984	0 (0.0%)
Machine.make (3 states, 2 events)	7,740	7,740	0 (0.0%)
machine.handle (3 states, 2 transitions)	17,764	17,764	0 (0.0%)
fluent transition (10 named branches)	112,498	112,498	0 (0.0%)
fluent invocation (state-dependent Effect)	99,018	99,018	0 (0.0%)
machine.handle (depth 24)	187,474	187,474	0 (0.0%)
machine.handle (wide depth 16)	217,043	217,043	0 (0.0%)
machine.handle (parallel/history/choice)	124,167	124,167	0 (0.0%)
machine definition (3 independent implementations)	127,576	127,576	0 (0.0%)
machine exact input/output/error/services	115,217	115,217	0 (0.0%)
execution adapter readiness	106,299	106,299	0 (0.0%)

Check times (informational)

Scenario	Base	PR
Effect only	0.05s	0.03s
Import effect-machine	0.03s	0.03s
Machine.states (3 states)	0.10s	0.10s
Machine.make (3 states, 2 events)	0.16s	0.15s
machine.handle (3 states, 2 transitions)	0.26s	0.26s
fluent transition (10 named branches)	0.57s	0.57s
fluent invocation (state-dependent Effect)	0.55s	0.54s
machine.handle (depth 24)	0.79s	0.81s
machine.handle (wide depth 16)	0.82s	0.83s
machine.handle (parallel/history/choice)	0.66s	0.66s
machine definition (3 independent implementations)	0.66s	0.68s
machine exact input/output/error/services	0.64s	0.61s
execution adapter readiness	0.62s	0.62s

Type instantiations are the comparison metric. Check time varies with runner load and is informational only.

[github-actions]

Runtime performance

Median of 5 independent benchmark processes on AMD EPYC 7763 64-Core Processor with Node v24.19.0.

Pull request baseline

Scenario	Effect Machine
Plan counter transitions	122,233 transitions/s
Drain burst with terminal fence	388,588 increments/s
Drain burst with a change observer	361,961 increments/s
Lookup and send to one child	316,825 increments/s
Start and stop a machine	140,786 machines/s
Start and stop a parent with one child	28,981 families/s
Plan transitions through a compound state	106,216 transitions/s
Plan transitions through parallel regions	87,456 transitions/s
Drain burst through a compound state	304,649 events/s
Drain burst through two parallel regions	302,918 events/s
Drain a compound-state burst with a change observer	288,339 events/s

Process runtime reference points

Scenario	Effect Machine
Start and stop a raw generic process	15,379 processes/s
Start and stop a raw compiled process	61,271 processes/s

Memory profile	Effect Machine
Idle machine	1.7 KiB
Raw generic managed process	13.9 KiB
Raw compiled process	3.2 KiB
Two independent idle machines	3.3 KiB
Idle parent with one child	5.7 KiB
Parent with observed child registry	9.8 KiB
Parent with observed invoked child snapshots	6.3 KiB

Effect Machine change from base

Metric	Base	Base variability	PR	PR variability	Difference
Plan counter transitions	123,188 transitions/s	0.5% MAD	122,233 transitions/s	0.2% MAD	-0.8%
Drain burst with terminal fence	388,014 increments/s	0.5% MAD	388,588 increments/s	0.6% MAD	+0.1%
Drain burst with a change observer	363,373 increments/s	0.7% MAD	361,961 increments/s	0.2% MAD	-0.4%
Lookup and send to one child	317,713 increments/s	0.6% MAD	316,825 increments/s	0.3% MAD	-0.3%
Start and stop a machine	144,655 machines/s	0.6% MAD	140,786 machines/s	0.9% MAD	-2.7%
Start and stop a parent with one child	28,889 families/s	1.5% MAD	28,981 families/s	0.6% MAD	+0.3%
Plan transitions through a compound state	106,734 transitions/s	0.5% MAD	106,216 transitions/s	1.1% MAD	-0.5%
Plan transitions through parallel regions	87,205 transitions/s	2.2% MAD	87,456 transitions/s	1.0% MAD	+0.3%
Drain burst through a compound state	305,443 events/s	0.6% MAD	304,649 events/s	0.6% MAD	-0.3%
Drain burst through two parallel regions	300,677 events/s	0.6% MAD	302,918 events/s	0.5% MAD	+0.7%
Drain a compound-state burst with a change observer	292,000 events/s	1.0% MAD	288,339 events/s	0.5% MAD	-1.3%
Idle machine heap per unit	1.7 KiB	0.2% MAD	1.7 KiB	0.0% MAD	-0.2%
Raw generic managed process heap per unit	13.9 KiB	0.0% MAD	13.9 KiB	0.0% MAD	0.0%
Raw compiled process heap per unit	3.1 KiB	0.2% MAD	3.2 KiB	0.2% MAD	+0.4%
Two independent idle machines heap per unit	3.3 KiB	0.0% MAD	3.3 KiB	0.0% MAD	-0.0%
Idle parent with one child heap per unit	5.7 KiB	0.0% MAD	5.7 KiB	0.0% MAD	-0.0%
Parent with observed child registry heap per unit	9.8 KiB	0.0% MAD	9.8 KiB	0.0% MAD	+0.0%
Parent with observed invoked child snapshots heap per unit	6.3 KiB	0.0% MAD	6.3 KiB	0.1% MAD	0.0%

Process runtime reference change from base

Metric	Base	Base variability	PR	PR variability	Difference
Start and stop a raw generic process	15,377 processes/s	2.3% MAD	15,379 processes/s	0.9% MAD	+0.0%
Start and stop a raw compiled process	61,801 processes/s	0.5% MAD	61,271 processes/s	0.9% MAD	-0.9%

Regression guard

No large, noise-adjusted throughput or heap regressions detected.

Versions and interpretation

• Effect Machine: 0.30.0

Higher throughput is better; lower heap is better. Variability is the median absolute deviation across independent processes, relative to their median. Small differences on shared GitHub-hosted hardware remain informational; the required guard rejects only large changes beyond the measured noise allowance.