Add causal runtime verification laws

[SandroMaglione]

Summary

• add reusable snapshot, command, and transcript runtime invariants with filtering, observation requirements, aggregate reports, and exact violation locations
• add verifyCausalCommands for law-oriented causal tests without a dummy reference model, plus explicit planner/runtime agreement assertions
• retain stable public microstep snapshots for acknowledged probe sends while keeping cloning out of ordinary production sends
• document the new testing workflow and add runtime, property-based, regression, and type-inference 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 (no examples changed)
• Reviewed the automated type-performance report, when the public TypeScript API or inference changed
• Reviewed the automated runtime-performance report, when runtime behavior changed

Local validation also included pnpm perf:types and two successful pnpm perf:runtime runs. The automated base-versus-PR performance reports will be reviewed before merge.

[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	0.02s	0.02s
Import effect-machine	0.02s	0.02s
Machine.defineStates (3 states)	0.07s	0.07s
Machine.make (3 states, 2 events)	0.10s	0.11s
machine.handle (3 states, 2 transitions)	0.18s	0.15s
machine.handle (depth 8)	0.38s	0.33s
machine.handle (depth 12)	0.37s	0.37s
machine.handle (depth 16)	0.39s	0.38s
machine.handle (depth 24)	0.43s	0.43s
machine.handle (wide depth 16)	0.49s	0.49s
machine.handle (parallel/history/choice)	0.40s	0.41s
machine.handle (4 successive calls)	0.38s	0.38s
machine exact input/output/error/services	0.34s	0.36s
execution adapter readiness	0.38s	0.40s

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	123,093 transitions/s	135,046 transitions/s	13,210 transitions/s
Drain burst with terminal fence	484,429 increments/s	388,908 increments/s	192,950 increments/s
Drain burst with a change observer	455,881 increments/s	385,859 increments/s	193,269 increments/s
Lookup and send to one child	390,296 increments/s	383,089 increments/s	185,462 increments/s
Start and stop a machine	168,606 machines/s	187,266 machines/s	144,446 machines/s
Start and stop a parent with one child	35,635 families/s	69,027 families/s	40,558 families/s
Plan transitions through a compound state	118,276 transitions/s	—	—
Plan transitions through parallel regions	91,237 transitions/s	—	—
Drain burst through a compound state	494,808 events/s	343,542 events/s	188,141 events/s
Drain burst through two parallel regions	461,266 events/s	260,927 events/s	143,118 events/s
Drain a compound-state burst with a change observer	452,524 events/s	—	—

Effect runtime reference points

Scenario	Effect Machine	Effect runtime primitives
Start and stop a raw generic process	16,512 processes/s	—
Start and stop a raw compiled process	66,234 processes/s	—
Start and interrupt a suspended fiber	—	163,908 fibers/s
Start and stop a queue worker	—	116,198 workers/s
Start and stop an actor shell	—	106,417 actors/s
Start and stop two actor shells	—	62,937 families/s
Update an owner-only mutable snapshot	—	316,856,781 updates/s
Update a synchronized snapshot	—	1,523,415 updates/s
Create, resolve, and await a terminal latch	—	1,412,635 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	12.7 KiB	—	—	—
Raw compiled process	2.8 KiB	—	—	—
Two independent idle machines	3.0 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	—	—	—	6.8 KiB

Effect Machine change from base

Metric	Base	Base variability	PR	PR variability	Difference
Plan counter transitions	124,150 transitions/s	2.1% MAD	123,093 transitions/s	0.6% MAD	-0.9%
Drain burst with terminal fence	495,957 increments/s	2.4% MAD	484,429 increments/s	2.9% MAD	-2.3%
Drain burst with a change observer	455,748 increments/s	2.2% MAD	455,881 increments/s	3.5% MAD	+0.0%
Lookup and send to one child	388,579 increments/s	1.6% MAD	390,296 increments/s	3.4% MAD	+0.4%
Start and stop a machine	168,322 machines/s	2.0% MAD	168,606 machines/s	1.3% MAD	+0.2%
Start and stop a parent with one child	33,563 families/s	2.0% MAD	35,635 families/s	6.6% MAD	+6.2%
Plan transitions through a compound state	118,772 transitions/s	2.3% MAD	118,276 transitions/s	0.7% MAD	-0.4%
Plan transitions through parallel regions	90,027 transitions/s	2.4% MAD	91,237 transitions/s	0.8% MAD	+1.3%
Drain burst through a compound state	503,480 events/s	1.9% MAD	494,808 events/s	1.3% MAD	-1.7%
Drain burst through two parallel regions	462,934 events/s	0.3% MAD	461,266 events/s	1.0% MAD	-0.4%
Drain a compound-state burst with a change observer	462,848 events/s	1.6% MAD	452,524 events/s	1.8% MAD	-2.2%
Idle machine heap per unit	1.5 KiB	0.2% MAD	1.5 KiB	0.1% MAD	+0.3%
Raw generic managed process heap per unit	12.7 KiB	0.0% MAD	12.7 KiB	0.0% MAD	-0.0%
Raw compiled process heap per unit	2.8 KiB	0.5% MAD	2.8 KiB	0.1% MAD	-0.1%
Two independent idle machines heap per unit	3.0 KiB	0.0% MAD	3.0 KiB	0.0% MAD	+0.1%
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	-0.2%
Parent with observed invoked child snapshots heap per unit	5.0 KiB	0.1% MAD	5.0 KiB	0.1% MAD	+0.0%

Effect runtime reference change from base

Metric	Base	Base variability	PR	PR variability	Difference
Start and stop a raw generic process	16,275 processes/s	2.7% MAD	16,512 processes/s	0.6% MAD	+1.5%
Start and stop a raw compiled process	66,765 processes/s	1.2% MAD	66,234 processes/s	0.5% MAD	-0.8%
Start and interrupt a suspended fiber	165,810 fibers/s	1.2% MAD	163,908 fibers/s	1.2% MAD	-1.1%
Start and stop a queue worker	115,929 workers/s	1.9% MAD	116,198 workers/s	0.2% MAD	+0.2%
Start and stop an actor shell	107,910 actors/s	1.2% MAD	106,417 actors/s	0.3% MAD	-1.4%
Start and stop two actor shells	66,278 families/s	2.3% MAD	62,937 families/s	3.9% MAD	-5.0%
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	1,542,222 updates/s	1.4% MAD	1,523,415 updates/s	1.3% MAD	-1.2%
Create, resolve, and await a terminal latch	1,426,218 latches/s	4.8% MAD	1,412,635 latches/s	3.3% MAD	-1.0%

Versions and interpretation

• Effect Machine: 0.4.0
• 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.