Allow active states to omit schemas

[SandroMaglione]

Summary

• allow atomic, compound, parallel, and final active states to omit schema when they own no data
• preserve typed builders, handler contexts, snapshots, history, serialization, and selectors for structural states
• keep optimized execution fail-closed to the generic planner until indexed absent-value semantics are explicit
• migrate eight example machines and teach MachineTest.verify to validate structural configurations and history

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
• Automated type-performance measurement passed or was not required
• Automated runtime- and memory-performance measurement passed or was not required

Local validation included pnpm check, pnpm perf:types, pnpm perf:runtime, and pnpm check in the platformer, playground, and Pokémon example packages.

[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	3,039	+74 (+2.5%)
Machine.make (3 states, 2 events)	8,715	9,192	+477 (+5.5%)
machine.handle (3 states, 2 transitions)	23,492	25,009	+1,517 (+6.5%)
machine.handle (depth 24)	183,851	179,772	-4,079 (-2.2%)
machine.handle (wide depth 16)	214,189	209,566	-4,623 (-2.2%)
machine.handle (parallel/history/choice)	132,667	120,540	-12,127 (-9.1%)
machine.handle (4 successive calls)	128,674	118,189	-10,485 (-8.1%)
machine exact input/output/error/services	110,584	94,029	-16,555 (-15.0%)
execution adapter readiness	127,854	112,013	-15,841 (-12.4%)

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	2,984	+74 (+2.5%)
Machine.make (3 states, 2 events)	5,742	6,145	+403 (+7.0%)
machine.handle (3 states, 2 transitions)	14,777	15,817	+1,040 (+7.0%)
machine.handle (depth 24)	171,577	163,541	-8,036 (-4.7%)
machine.handle (wide depth 16)	202,224	194,396	-7,828 (-3.9%)
machine.handle (parallel/history/choice)	114,331	98,780	-15,551 (-13.6%)
machine.handle (4 successive calls)	113,703	101,001	-12,702 (-11.2%)
machine exact input/output/error/services	100,670	82,906	-17,764 (-17.6%)
execution adapter readiness	102,092	83,380	-18,712 (-18.3%)

Check times (informational)

Scenario	Base	PR
Effect only	0.03s	0.03s
Import effect-machine	0.03s	0.03s
Machine.defineStates (3 states)	0.09s	0.09s
Machine.make (3 states, 2 events)	0.15s	0.15s
machine.handle (3 states, 2 transitions)	0.23s	0.22s
machine.handle (depth 24)	0.63s	0.63s
machine.handle (wide depth 16)	0.70s	0.66s
machine.handle (parallel/history/choice)	0.57s	0.51s
machine.handle (4 successive calls)	0.55s	0.49s
machine exact input/output/error/services	0.47s	0.41s
execution adapter readiness	0.53s	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 INTEL(R) XEON(R) PLATINUM 8573C with Node v24.19.0.

Pull request baseline

Scenario	Effect Machine
Plan counter transitions	149,827 transitions/s
Drain burst with terminal fence	614,808 increments/s
Drain burst with a change observer	571,842 increments/s
Lookup and send to one child	506,050 increments/s
Start and stop a machine	202,388 machines/s
Start and stop a parent with one child	52,458 families/s
Plan transitions through a compound state	137,748 transitions/s
Plan transitions through parallel regions	105,362 transitions/s
Drain burst through a compound state	507,182 events/s
Drain burst through two parallel regions	487,666 events/s
Drain a compound-state burst with a change observer	488,340 events/s

Process runtime reference points

Scenario	Effect Machine
Start and stop a raw generic process	33,038 processes/s
Start and stop a raw compiled process	84,360 processes/s

Memory profile	Effect Machine
Idle machine	1.5 KiB
Raw generic managed process	12.7 KiB
Raw compiled process	2.8 KiB
Two independent idle machines	3.0 KiB
Idle parent with one child	4.8 KiB
Parent with observed child registry	9.0 KiB
Parent with observed invoked child snapshots	5.0 KiB

Effect Machine change from base

Metric	Base	Base variability	PR	PR variability	Difference
Plan counter transitions	148,717 transitions/s	1.2% MAD	149,827 transitions/s	1.6% MAD	+0.7%
Drain burst with terminal fence	584,286 increments/s	3.1% MAD	614,808 increments/s	2.5% MAD	+5.2%
Drain burst with a change observer	545,429 increments/s	3.1% MAD	571,842 increments/s	2.6% MAD	+4.8%
Lookup and send to one child	486,751 increments/s	3.8% MAD	506,050 increments/s	1.9% MAD	+4.0%
Start and stop a machine	202,511 machines/s	0.4% MAD	202,388 machines/s	0.9% MAD	-0.1%
Start and stop a parent with one child	54,532 families/s	0.8% MAD	52,458 families/s	0.5% MAD	-3.8%
Plan transitions through a compound state	135,423 transitions/s	1.4% MAD	137,748 transitions/s	0.3% MAD	+1.7%
Plan transitions through parallel regions	104,849 transitions/s	1.3% MAD	105,362 transitions/s	1.7% MAD	+0.5%
Drain burst through a compound state	509,092 events/s	0.9% MAD	507,182 events/s	2.1% MAD	-0.4%
Drain burst through two parallel regions	480,511 events/s	3.5% MAD	487,666 events/s	0.3% MAD	+1.5%
Drain a compound-state burst with a change observer	479,707 events/s	0.6% MAD	488,340 events/s	1.8% MAD	+1.8%
Idle machine heap per unit	1.5 KiB	0.1% MAD	1.5 KiB	0.1% MAD	-0.0%
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	0.2% MAD	2.8 KiB	0.0% MAD	-0.5%
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	0.1% MAD	+0.1%

Process runtime reference change from base

Metric	Base	Base variability	PR	PR variability	Difference
Start and stop a raw generic process	32,822 processes/s	1.3% MAD	33,038 processes/s	2.2% MAD	+0.7%
Start and stop a raw compiled process	83,850 processes/s	0.9% MAD	84,360 processes/s	0.8% MAD	+0.6%

Regression guard

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

Versions and interpretation

• Effect Machine: 0.7.0

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.