Compact compiled statechart runtimes

[SandroMaglione]

Summary

• run compiled statecharts with a single fiber that owns event processing and terminal publication
• use the same compiled kernel for roots and invoked machine children while preserving the existing generic Machine.logic worker/supervisor contract
• preserve terminal snapshot freezing and concurrent-stop arbitration, with focused regression coverage

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change src/ or package.json

Validation

• pnpm check
• Relevant example checks, when examples changed (not applicable; no examples changed)
• Reviewed the automated type-performance report, when the public TypeScript API or inference changed (local pnpm perf:types passes; no public API change)
• Reviewed the automated runtime-performance report, when runtime behavior changed

[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.defineStates (3 states)	2,965	2,965	0 (0.0%)
Machine.make (3 states, 2 events)	8,715	8,715	0 (0.0%)
machine.handle (3 states, 2 transitions)	23,492	23,492	0 (0.0%)
machine.handle (depth 8)	117,075	117,075	0 (0.0%)
machine.handle (depth 12)	129,713	129,713	0 (0.0%)
machine.handle (depth 16)	145,055	145,055	0 (0.0%)
machine.handle (depth 24)	183,851	183,851	0 (0.0%)
machine.handle (wide depth 16)	214,189	214,189	0 (0.0%)
machine.handle (parallel/history/choice)	132,667	132,667	0 (0.0%)
machine.handle (4 successive calls)	128,674	128,674	0 (0.0%)
machine exact input/output/error/services	110,584	110,584	0 (0.0%)
execution adapter readiness	127,854	127,854	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.defineStates (3 states)	2,910	2,910	0 (0.0%)
Machine.make (3 states, 2 events)	5,742	5,742	0 (0.0%)
machine.handle (3 states, 2 transitions)	14,777	14,777	0 (0.0%)
machine.handle (depth 8)	109,601	109,601	0 (0.0%)
machine.handle (depth 12)	121,039	121,039	0 (0.0%)
machine.handle (depth 16)	135,181	135,181	0 (0.0%)
machine.handle (depth 24)	171,577	171,577	0 (0.0%)
machine.handle (wide depth 16)	202,224	202,224	0 (0.0%)
machine.handle (parallel/history/choice)	114,331	114,331	0 (0.0%)
machine.handle (4 successive calls)	113,703	113,703	0 (0.0%)
machine exact input/output/error/services	100,670	100,670	0 (0.0%)
execution adapter readiness	102,092	102,092	0 (0.0%)

Check times (informational)

Scenario	Base	PR
Effect only	0.03s	0.03s
Import effect-machine	0.03s	0.03s
Machine.defineStates (3 states)	0.10s	0.09s
Machine.make (3 states, 2 events)	0.14s	0.15s
machine.handle (3 states, 2 transitions)	0.20s	0.23s
machine.handle (depth 8)	0.47s	0.47s
machine.handle (depth 12)	0.50s	0.52s
machine.handle (depth 16)	0.55s	0.54s
machine.handle (depth 24)	0.62s	0.65s
machine.handle (wide depth 16)	0.69s	0.71s
machine.handle (parallel/history/choice)	0.56s	0.57s
machine.handle (4 successive calls)	0.54s	0.56s
machine exact input/output/error/services	0.48s	0.48s
execution adapter readiness	0.59s	0.54s

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 INTEL(R) XEON(R) PLATINUM 8573C with Node v24.18.0.

Pull request baseline

Scenario	Effect Machine	XState 5	XState 6 alpha
Plan counter transitions	119,017 transitions/s	144,972 transitions/s	110,502 transitions/s
Drain burst with terminal fence	90,477 increments/s	401,466 increments/s	104,671 increments/s
Drain burst with a change observer	74,619 increments/s	403,227 increments/s	104,855 increments/s
Lookup and send to one child	80,430 increments/s	404,654 increments/s	101,128 increments/s
Start and stop a machine	26,680 machines/s	199,402 machines/s	77,567 machines/s
Start and stop a parent with one child	8,325 families/s	76,864 families/s	32,458 families/s

Memory profile	Effect Machine	XState 5	XState 6 alpha	Effect runtime primitives
Idle machine	14.0 KiB	3.8 KiB	6.1 KiB	—
Raw managed process	13.2 KiB	—	—	—
Two independent idle machines	27.4 KiB	7.3 KiB	11.8 KiB	—
Idle parent with one child	35.2 KiB	5.5 KiB	8.8 KiB	—
Parent with observed child registry	46.7 KiB	—	—	—
Parent with observed invoked child snapshots	35.4 KiB	—	—	—
Suspended Effect fiber	—	—	—	0.7 KiB
Effect queue with waiting fiber	—	—	—	2.8 KiB
Effect mailbox actor shell	—	—	—	3.2 KiB

Effect Machine change from base

Metric	Base	Base variability	PR	PR variability	Difference
Plan counter transitions	120,620 transitions/s	1.5% MAD	119,017 transitions/s	1.1% MAD	-1.3%
Drain burst with terminal fence	89,850 increments/s	1.5% MAD	90,477 increments/s	1.2% MAD	+0.7%
Drain burst with a change observer	74,174 increments/s	1.6% MAD	74,619 increments/s	0.9% MAD	+0.6%
Lookup and send to one child	80,429 increments/s	1.2% MAD	80,430 increments/s	1.5% MAD	+0.0%
Start and stop a machine	24,726 machines/s	2.3% MAD	26,680 machines/s	0.3% MAD	+7.9%
Start and stop a parent with one child	7,554 families/s	1.0% MAD	8,325 families/s	0.1% MAD	+10.2%
Idle machine heap per unit	14.8 KiB	0.0% MAD	14.0 KiB	0.0% MAD	-5.4%
Raw managed process heap per unit	13.2 KiB	0.0% MAD	13.2 KiB	0.0% MAD	+0.0%
Two independent idle machines heap per unit	28.9 KiB	0.0% MAD	27.4 KiB	0.0% MAD	-5.4%
Idle parent with one child heap per unit	36.8 KiB	0.0% MAD	35.2 KiB	0.0% MAD	-4.2%
Parent with observed child registry heap per unit	48.2 KiB	0.0% MAD	46.7 KiB	0.0% MAD	-3.2%
Parent with observed invoked child snapshots heap per unit	37.0 KiB	0.0% MAD	35.4 KiB	0.0% MAD	-4.2%

Versions and interpretation

• Effect Machine: 0.3.0
• XState 5: 5.32.5
• XState 6 alpha: 6.0.0-alpha.27
• Effect runtime primitives: 4.0.0-beta.105

Higher throughput is better; lower heap is better. Variability is the median absolute deviation across independent processes, relative to their median. Runtime measurements on shared GitHub-hosted hardware remain informational, so small differences should be confirmed across multiple workflow runs.