Strengthen machine strategy guardrails

[SandroMaglione]

Summary

• add test-only planner and process strategy selection so generic/indexed and generic/compiled implementations can be compared directly
• add focused and generated differential coverage for startup, targetless/reentry transitions, parallel transitions, invocation, terminal behavior, and retained snapshots
• extend runtime benchmarks with hierarchical/parallel planning, observed hierarchical execution, and generic process lifecycle reference points

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)
• Reviewed the automated type-performance report, when the public TypeScript API or inference changed (no public API change; local pnpm perf:types passes)
• Reviewed the automated runtime-performance report, when runtime behavior changed (local five-process base-versus-head comparison reviewed; hosted report pending)

[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)	0.12s	0.11s
Machine.make (3 states, 2 events)	0.17s	0.17s
machine.handle (3 states, 2 transitions)	0.24s	0.24s
machine.handle (depth 8)	0.55s	0.54s
machine.handle (depth 12)	0.60s	0.58s
machine.handle (depth 16)	0.65s	0.66s
machine.handle (depth 24)	0.71s	0.74s
machine.handle (wide depth 16)	0.83s	0.79s
machine.handle (parallel/history/choice)	0.66s	0.65s
machine.handle (4 successive calls)	0.62s	0.63s
machine exact input/output/error/services	0.54s	0.54s
execution adapter readiness	0.62s	0.61s

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 v24.18.0.

Pull request baseline

Scenario	Effect Machine	XState 5	XState 6 alpha
Plan counter transitions	123,092 transitions/s	132,420 transitions/s	13,100 transitions/s
Drain burst with terminal fence	497,342 increments/s	390,815 increments/s	191,987 increments/s
Drain burst with a change observer	462,729 increments/s	387,561 increments/s	190,492 increments/s
Lookup and send to one child	399,218 increments/s	385,972 increments/s	182,620 increments/s
Start and stop a machine	174,520 machines/s	185,185 machines/s	141,985 machines/s
Start and stop a parent with one child	39,766 families/s	69,219 families/s	39,798 families/s
Plan transitions through a compound state	117,598 transitions/s	—	—
Plan transitions through parallel regions	90,705 transitions/s	—	—
Drain burst through a compound state	529,554 events/s	343,348 events/s	188,523 events/s
Drain burst through two parallel regions	483,194 events/s	261,574 events/s	141,233 events/s
Drain a compound-state burst with a change observer	482,000 events/s	—	—

Effect runtime reference points

Scenario	Effect Machine	Effect runtime primitives
Start and stop a raw generic process	18,758 processes/s	—
Start and stop a raw compiled process	69,512 processes/s	—
Start and interrupt a suspended fiber	—	166,639 fibers/s
Start and stop a queue worker	—	116,877 workers/s
Start and stop an actor shell	—	106,758 actors/s
Start and stop two actor shells	—	64,520 families/s
Update an owner-only mutable snapshot	—	316,856,781 updates/s
Update a synchronized snapshot	—	1,533,173 updates/s
Create, resolve, and await a terminal latch	—	1,421,630 latches/s

Memory profile	Effect Machine	XState 5	XState 6 alpha	Effect runtime primitives
Idle machine	1.5 KiB	3.8 KiB	2.2 KiB	—
Raw generic managed process	12.1 KiB	—	—	—
Raw compiled process	2.6 KiB	—	—	—
Two independent idle machines	2.9 KiB	7.3 KiB	3.9 KiB	—
Idle parent with one child	4.8 KiB	5.5 KiB	4.0 KiB	—
Parent with observed child registry	9.0 KiB	—	—	—
Parent with observed invoked child snapshots	5.0 KiB	—	—	—
Suspended Effect fiber	—	—	—	0.6 KiB
Effect queue with waiting fiber	—	—	—	2.8 KiB
Effect mailbox actor shell	—	—	—	3.2 KiB
Two Effect actor shells	—	—	—	6.9 KiB

Effect Machine change from base

Metric	Base	Base variability	PR	PR variability	Difference
Plan counter transitions	122,729 transitions/s	0.3% MAD	123,092 transitions/s	0.1% MAD	+0.3%
Drain burst with terminal fence	491,513 increments/s	1.8% MAD	497,342 increments/s	1.1% MAD	+1.2%
Drain burst with a change observer	453,933 increments/s	0.6% MAD	462,729 increments/s	0.1% MAD	+1.9%
Lookup and send to one child	388,179 increments/s	0.8% MAD	399,218 increments/s	2.5% MAD	+2.8%
Start and stop a machine	174,795 machines/s	1.8% MAD	174,520 machines/s	0.7% MAD	-0.2%
Start and stop a parent with one child	40,344 families/s	1.4% MAD	39,766 families/s	0.7% MAD	-1.4%
Plan transitions through a compound state	118,935 transitions/s	1.9% MAD	117,598 transitions/s	0.4% MAD	-1.1%
Plan transitions through parallel regions	90,491 transitions/s	0.3% MAD	90,705 transitions/s	0.2% MAD	+0.2%
Drain burst through a compound state	529,061 events/s	1.2% MAD	529,554 events/s	0.2% MAD	+0.1%
Drain burst through two parallel regions	483,204 events/s	0.4% MAD	483,194 events/s	1.2% MAD	-0.0%
Drain a compound-state burst with a change observer	479,766 events/s	0.3% MAD	482,000 events/s	1.7% MAD	+0.5%
Idle machine heap per unit	1.5 KiB	0.1% MAD	1.5 KiB	0.2% MAD	-0.0%
Raw generic managed process heap per unit	12.1 KiB	0.0% MAD	12.1 KiB	0.0% MAD	0.0%
Raw compiled process heap per unit	2.6 KiB	0.0% MAD	2.6 KiB	0.0% MAD	-0.0%
Two independent idle machines heap per unit	2.9 KiB	0.0% MAD	2.9 KiB	0.0% MAD	+0.0%
Idle parent with one child heap per unit	4.8 KiB	0.0% MAD	4.8 KiB	0.0% MAD	-0.0%
Parent with observed child registry heap per unit	9.0 KiB	0.0% MAD	9.0 KiB	0.0% MAD	+0.0%
Parent with observed invoked child snapshots heap per unit	5.0 KiB	0.0% MAD	5.0 KiB	0.2% MAD	-0.0%

Effect runtime reference change from base

Metric	Base	Base variability	PR	PR variability	Difference
Start and stop a raw generic process	18,958 processes/s	1.2% MAD	18,758 processes/s	3.2% MAD	-1.1%
Start and stop a raw compiled process	68,273 processes/s	0.9% MAD	69,512 processes/s	0.7% MAD	+1.8%
Start and interrupt a suspended fiber	166,917 fibers/s	1.2% MAD	166,639 fibers/s	0.8% MAD	-0.2%
Start and stop a queue worker	117,275 workers/s	0.6% MAD	116,877 workers/s	1.5% MAD	-0.3%
Start and stop an actor shell	106,304 actors/s	1.1% MAD	106,758 actors/s	1.1% MAD	+0.4%
Start and stop two actor shells	66,322 families/s	0.9% MAD	64,520 families/s	2.5% MAD	-2.7%
Update an owner-only mutable snapshot	316,856,781 updates/s	0.0% MAD	316,856,781 updates/s	0.0% MAD	0.0%
Update a synchronized snapshot	1,536,856 updates/s	0.6% MAD	1,533,173 updates/s	1.1% MAD	-0.2%
Create, resolve, and await a terminal latch	1,388,465 latches/s	4.0% MAD	1,421,630 latches/s	1.5% MAD	+2.4%

Versions and interpretation

• Effect Machine: 0.3.0
• XState 5: 5.32.5
• XState 6 alpha: 6.0.0-alpha.31
• Effect runtime primitives: 4.0.0-beta.107

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.