Add explicit runtime command semantics

[SandroMaglione]

Summary

• replace the ambiguous runtime command entry point with explicit runEnqueuedCommands and runCausalCommands APIs
• retain exact probe evidence for causally processed sends, including ignored, targetless, raised-event, stopped, and failed commands
• add probe-bound asynchronous waits, typed causal transcripts and failures, explicit transcript formatters, and deprecated compatibility aliases
• document when to choose enqueue versus causal command semantics

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
• Reviewed the automated type-performance report, when the public TypeScript API or inference changed
• Reviewed the automated runtime-performance report, when runtime behavior changed

Additional local validation:

• pnpm vitest run test/testing/Runtime.test.ts test/testing/Probe.test.ts
• pnpm exec tstyche typetest/testing/Probe.tst.ts typetest/testing/MachineTest.tst.ts
• pnpm perf:types
• pnpm perf:runtime

No examples changed. The production machine runtime and hot path are unchanged; the new causal runner composes the testing-only probe capability.

[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)	0.11s	0.11s
Machine.make (3 states, 2 events)	0.17s	0.16s
machine.handle (3 states, 2 transitions)	0.23s	0.23s
machine.handle (depth 8)	0.58s	0.51s
machine.handle (depth 12)	0.59s	0.58s
machine.handle (depth 16)	0.62s	0.62s
machine.handle (depth 24)	0.71s	0.70s
machine.handle (wide depth 16)	0.79s	0.77s
machine.handle (parallel/history/choice)	0.65s	0.63s
machine.handle (4 successive calls)	0.60s	0.61s
machine exact input/output/error/services	0.56s	0.53s
execution adapter readiness	0.59s	0.60s

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	132,885 transitions/s	133,989 transitions/s	13,095 transitions/s
Drain burst with terminal fence	526,504 increments/s	390,277 increments/s	197,283 increments/s
Drain burst with a change observer	484,096 increments/s	388,394 increments/s	196,077 increments/s
Lookup and send to one child	418,906 increments/s	384,531 increments/s	187,830 increments/s
Start and stop a machine	176,678 machines/s	186,567 machines/s	146,370 machines/s
Start and stop a parent with one child	36,790 families/s	69,411 families/s	40,925 families/s
Plan transitions through a compound state	120,090 transitions/s	—	—
Plan transitions through parallel regions	93,432 transitions/s	—	—
Drain burst through a compound state	524,260 events/s	345,439 events/s	191,865 events/s
Drain burst through two parallel regions	472,517 events/s	262,759 events/s	145,223 events/s
Drain a compound-state burst with a change observer	475,516 events/s	—	—

Effect runtime reference points

Scenario	Effect Machine	Effect runtime primitives
Start and stop a raw generic process	16,840 processes/s	—
Start and stop a raw compiled process	68,790 processes/s	—
Start and interrupt a suspended fiber	—	166,639 fibers/s
Start and stop a queue worker	—	116,333 workers/s
Start and stop an actor shell	—	107,793 actors/s
Start and stop two actor shells	—	66,854 families/s
Update an owner-only mutable snapshot	—	316,856,781 updates/s
Update a synchronized snapshot	—	1,593,052 updates/s
Create, resolve, and await a terminal latch	—	1,449,773 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	5.3 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	125,920 transitions/s	1.8% MAD	132,885 transitions/s	2.4% MAD	+5.5%
Drain burst with terminal fence	493,771 increments/s	2.7% MAD	526,504 increments/s	2.0% MAD	+6.6%
Drain burst with a change observer	469,398 increments/s	3.1% MAD	484,096 increments/s	0.7% MAD	+3.1%
Lookup and send to one child	408,968 increments/s	3.1% MAD	418,906 increments/s	1.0% MAD	+2.4%
Start and stop a machine	170,039 machines/s	1.0% MAD	176,678 machines/s	0.2% MAD	+3.9%
Start and stop a parent with one child	37,022 families/s	8.8% MAD	36,790 families/s	9.5% MAD	-0.6%
Plan transitions through a compound state	118,918 transitions/s	1.1% MAD	120,090 transitions/s	0.4% MAD	+1.0%
Plan transitions through parallel regions	91,254 transitions/s	1.0% MAD	93,432 transitions/s	0.3% MAD	+2.4%
Drain burst through a compound state	506,314 events/s	1.0% MAD	524,260 events/s	0.1% MAD	+3.5%
Drain burst through two parallel regions	465,120 events/s	0.3% MAD	472,517 events/s	0.3% MAD	+1.6%
Drain a compound-state burst with a change observer	461,907 events/s	0.7% MAD	475,516 events/s	0.4% MAD	+2.9%
Idle machine heap per unit	1.5 KiB	0.2% MAD	1.5 KiB	0.1% MAD	+0.2%
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	0.3% MAD	-0.2%
Two independent idle machines heap per unit	3.0 KiB	0.0% MAD	3.0 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	0.1% MAD	5.0 KiB	0.0% MAD	+0.2%

Effect runtime reference change from base

Metric	Base	Base variability	PR	PR variability	Difference
Start and stop a raw generic process	16,795 processes/s	1.2% MAD	16,840 processes/s	0.5% MAD	+0.3%
Start and stop a raw compiled process	68,932 processes/s	0.8% MAD	68,790 processes/s	0.6% MAD	-0.2%
Start and interrupt a suspended fiber	164,177 fibers/s	1.5% MAD	166,639 fibers/s	1.2% MAD	+1.5%
Start and stop a queue worker	115,660 workers/s	1.3% MAD	116,333 workers/s	1.0% MAD	+0.6%
Start and stop an actor shell	106,530 actors/s	0.9% MAD	107,793 actors/s	1.1% MAD	+1.2%
Start and stop two actor shells	64,313 families/s	2.6% MAD	66,854 families/s	0.9% MAD	+4.0%
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	1,556,386 updates/s	0.2% MAD	1,593,052 updates/s	1.3% MAD	+2.4%
Create, resolve, and await a terminal latch	1,460,146 latches/s	0.7% MAD	1,449,773 latches/s	0.4% MAD	-0.7%

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.