Compile source you did not write

A document may declare as many components and connections as it can place. Version 0.4 removed the 512-component and 2,048-connection ceilings entirely: the compiler is linear in both, and sixty-four thousand components compile in about a second.

That is the right default for source you control. It is the wrong default for source you do not — a Markdown fence from a comment, a pull request, a CMS field. For those, pass a budget.

01 / BudgetsReject an oversized document before routing it

compileSchematic(source, {
	...fence,
	limits: { components: 400, connections: 1_500, sourceCharacters: 64_000 }
});
// SchematicSyntaxError: Line 401: Schematic exceeds the 400 component limit.

The rejection happens at the declaration that crosses the ceiling, during parsing — before any geometry is validated, any wire is routed, or any markup is generated. That is the whole point: refusing cheaply is what a budget buys you.

port:IN "in" at (80, 150) #blue
resistor:R1 "1 k\Omega" at (300, 150) #amber
port:OUT "out" at (620, 150) #emerald
IN.out -> R1.in #blue [ortho]
R1.out -> OUT.in #emerald [ortho]

02 / FieldsEvery field is optional

Every field is optional and every omitted field keeps its default, so passing nothing compiles exactly as it did before the option existed. Infinity states no limit explicitly, which is what the two counts default to.

The defaults that remain bound allocation, not diagram size. They sit far past any readable drawing, so treat them as a backstop against a runaway input rather than as a policy you have chosen.

port:A "A" at (70, 100) #blue
resistor:R "R" at (330, 100) #amber [orientation=down]
component:BLOCK "obstacle" at (330, 250) #slate [width=150 height=70]
port:B "B" at (700, 100) #emerald
A.out -> R.in #blue [ortho]
R.out -> B.in #emerald [ortho]

03 / ContractWhat the compiler guarantees about a budget

A budget is resolved once per compilation and handed to both the parser and the renderer. An accessor cannot be generous to one pass and mean to the other, which would validate a document against neither.

A budget is not clamped to the defaults. A host that raises svgOutputBytes has decided it can afford the allocation; the compiler does not second-guess that.

A misspelled field is an error, not a no-op. limits: { component: 4 } throws Unknown compiler limit component. rather than silently doing nothing — a limit you believe you set and did not is worse than no limit at all.

SCHEMATIC_LIMITS reports the defaults. Its two unlimited counts are Infinity, which JSON.stringify renders as null; pass a replacer if you expose them over an API.

port:L "L" at (80, 110) #blue
port:R "R" at (660, 110) #blue
port:T "T" at (370, 230) #cyan [orientation=up]
port:B "B" at (370, 80) #cyan [orientation=down]
L.out -> R.in #blue [ortho net=DATA]
B.out -> T.in #cyan [ortho net=CLOCK]

04 / TimeA budget is not a timeout

Every field above bounds a size. None of them bounds time. A small document can still be expensive to route: orthogonal routing falls back to a sparse compressed-grid search, and congestion is what makes that search work, not declaration count.

Pair a budget with a time limit you enforce yourself — a worker with a deadline, an AbortSignal around the call site, a queue with a per-job ceiling. wireCrossings bounds the crossing pass specifically and is the closest thing to a work limit the compiler offers, but it is not a substitute.

port:A1 "A" at (80, 90) #blue
port:B1 "B" at (620, 230) #blue
port:A2 "A" at (80, 230) #amber
port:B2 "B" at (620, 90) #amber
A1.out -> B1.in #blue [ortho]
A2.out -> B2.in #amber [ortho]