Add React-owned machine atoms

[SandroMaglione]

Summary

• add @typeonce/effect-machine-react with useMachineAtom for stable React ownership without whole-machine subscriptions
• make state-path selector atoms stable for repeated machine/path lookups, including child selectors, while preserving weak lifetime semantics
• document React-owned state-slot rendering and retain AtomMachine.family for shared keyed lookup
• add React lifecycle, render-isolation, registry, SSR, selector-identity, GC-retention, type, and packed-consumer coverage

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

[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	0.02s	0.02s
Import effect-machine	0.02s	0.02s
Machine.states (3 states)	0.08s	0.07s
Machine.make (3 states, 2 events)	0.13s	0.12s
machine.handle (3 states, 2 transitions)	0.19s	0.20s
fluent transition (10 named branches)	0.42s	0.43s
fluent invocation (state-dependent Effect)	0.43s	0.42s
machine.handle (depth 24)	0.63s	0.65s
machine.handle (wide depth 16)	0.62s	0.63s
machine.handle (parallel/history/choice)	0.51s	0.50s
machine definition (3 independent implementations)	0.51s	0.52s
machine exact input/output/error/services	0.48s	0.47s
execution adapter readiness	0.48s	0.48s

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	127,467 transitions/s
Drain burst with terminal fence	399,408 increments/s
Drain burst with a change observer	374,006 increments/s
Lookup and send to one child	328,113 increments/s
Start and stop a machine	144,030 machines/s
Start and stop a parent with one child	30,486 families/s
Plan transitions through a compound state	108,547 transitions/s
Plan transitions through parallel regions	90,068 transitions/s
Drain burst through a compound state	309,571 events/s
Drain burst through two parallel regions	308,138 events/s
Drain a compound-state burst with a change observer	292,920 events/s

Process runtime reference points

Scenario	Effect Machine
Start and stop a raw generic process	15,957 processes/s
Start and stop a raw compiled process	62,305 processes/s

Memory profile	Effect Machine
Idle machine	1.7 KiB
Raw generic managed process	13.9 KiB
Raw compiled process	3.1 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	125,208 transitions/s	0.4% MAD	127,467 transitions/s	2.1% MAD	+1.8%
Drain burst with terminal fence	396,810 increments/s	0.5% MAD	399,408 increments/s	0.1% MAD	+0.7%
Drain burst with a change observer	367,707 increments/s	0.1% MAD	374,006 increments/s	0.9% MAD	+1.7%
Lookup and send to one child	323,309 increments/s	0.1% MAD	328,113 increments/s	0.4% MAD	+1.5%
Start and stop a machine	146,778 machines/s	0.3% MAD	144,030 machines/s	1.2% MAD	-1.9%
Start and stop a parent with one child	30,001 families/s	1.1% MAD	30,486 families/s	1.2% MAD	+1.6%
Plan transitions through a compound state	105,670 transitions/s	0.5% MAD	108,547 transitions/s	2.1% MAD	+2.7%
Plan transitions through parallel regions	88,233 transitions/s	1.3% MAD	90,068 transitions/s	0.2% MAD	+2.1%
Drain burst through a compound state	308,355 events/s	0.5% MAD	309,571 events/s	0.6% MAD	+0.4%
Drain burst through two parallel regions	308,000 events/s	0.1% MAD	308,138 events/s	0.5% MAD	+0.0%
Drain a compound-state burst with a change observer	291,772 events/s	0.1% MAD	292,920 events/s	1.1% MAD	+0.4%
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	0.1% MAD	3.1 KiB	0.0% MAD	-0.1%
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	0.1% 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	15,579 processes/s	0.5% MAD	15,957 processes/s	0.5% MAD	+2.4%
Start and stop a raw compiled process	62,854 processes/s	2.4% MAD	62,305 processes/s	0.9% MAD	-0.9%

Regression guard

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

Versions and interpretation

• Effect Machine: 0.28.0

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.