[SandroMaglione]

Summary

• createMachineContext factories take no parameters or one options object. Each declared option, input or layer, is a required Provider prop of the same name and type.
• A machine that needs only a capability layer declares ({ layer }) instead of the (_: void, layer) placeholder.
• Options other than input and layer are a type error, so a capability cannot be passed under another name such as router.
• A factory without parameters, such as AtomMachine.factory(Machine) for a machine without input, is still passed directly and called without an options object.
• Breaking: a positional input factory, such as AtomMachine.factory(Machine) for a machine with input, is now a type error. Write ({ input }: { input: Input }) => AtomMachine.make(Machine, input).
• Docs, README, JSDoc, runtime tests and typetests are updated.

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change a publishable package

Minor changeset for @typeonce/effect-machine-react, with the migration.

Validation

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

Every pnpm check step passed locally, with two exceptions. The format check cannot download dprint plugins in this sandbox, so formatting was checked with the same plugin versions taken from npm. The devtools static-site test times out locally on unchanged main too. pnpm perf:types passed its budgets locally.

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Generated by Claude Code

[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.state (3 children)	2,664	2,664	0 (0.0%)
Machine.make (3 states, 2 events)	8,932	8,932	0 (0.0%)
machine.handle (3 states, 2 transitions)	39,449	39,449	0 (0.0%)
declared transition (10 named branches)	60,402	60,402	0 (0.0%)
atomic construction, guards, and reentry	85,710	85,710	0 (0.0%)
registered invocation (input-taking Effect)	39,819	39,819	0 (0.0%)
machine.handle (depth 24)	194,531	194,531	0 (0.0%)
machine.handle (wide depth 16)	218,238	218,238	0 (0.0%)
machine.handle (parallel/history/choice)	91,642	91,642	0 (0.0%)
machine definition (3 independent implementations)	99,173	99,173	0 (0.0%)
machine exact input/output/error/services	82,941	82,941	0 (0.0%)
execution adapter readiness	71,428	71,428	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.state (3 children)	2,609	2,609	0 (0.0%)
Machine.make (3 states, 2 events)	6,260	6,260	0 (0.0%)
machine.handle (3 states, 2 transitions)	30,517	30,517	0 (0.0%)
declared transition (10 named branches)	51,849	51,849	0 (0.0%)
atomic construction, guards, and reentry	70,370	70,370	0 (0.0%)
registered invocation (input-taking Effect)	32,682	32,682	0 (0.0%)
machine.handle (depth 24)	177,222	177,222	0 (0.0%)
machine.handle (wide depth 16)	201,707	201,707	0 (0.0%)
machine.handle (parallel/history/choice)	79,144	79,144	0 (0.0%)
machine definition (3 independent implementations)	88,492	88,492	0 (0.0%)
machine exact input/output/error/services	70,732	70,732	0 (0.0%)
execution adapter readiness	31,922	31,922	0 (0.0%)

Check times (informational)

Scenario	Base	PR
Effect only	0.02s	0.02s
Import effect-machine	0.02s	0.02s
Machine.state (3 children)	0.05s	0.05s
Machine.make (3 states, 2 events)	0.08s	0.08s
machine.handle (3 states, 2 transitions)	0.18s	0.18s
declared transition (10 named branches)	0.23s	0.24s
atomic construction, guards, and reentry	0.30s	0.30s
registered invocation (input-taking Effect)	0.19s	0.18s
machine.handle (depth 24)	0.36s	0.35s
machine.handle (wide depth 16)	0.42s	0.43s
machine.handle (parallel/history/choice)	0.32s	0.32s
machine definition (3 independent implementations)	0.32s	0.32s
machine exact input/output/error/services	0.31s	0.32s
execution adapter readiness	0.27s	0.26s

Type instantiations are the comparison metric. Check time varies with runner load and is informational only.