Measure scaling and bound every host

01 / CompilerRead scaling and size as separate budgets

Version 0.4 has no default component or connection count. Note that this is a compiler capability, not permission for a public endpoint to accept arbitrary work — the two are easy to confuse and expensive to confuse. Whenever the source is not ours, set components, connections, sourceCharacters, wireCrossings, and svgOutputBytes through the per-compilation limits option.

A wall-clock deadline is still required on top of that, because every one of those fields bounds a size and none of them bounds time. A small document with pathological geometry can be expensive to route, and no count of output bytes will catch it.

port:M "M" at (70, 100) #cyan
inductor:LR "L" at (330, 100) #purple [orientation=down]
component:CAN "screen" at (330, 250) #slate [width=150 height=70]
port:N "N" at (700, 100) #emerald

M.out -> LR.in #cyan [ortho]
LR.out -> N.in #emerald [ortho]

The release gate measures two different client costs. A tree-shaken host that imports only compileSchematic must remain below 32 KiB gzip; the complete public entry, which includes exports a given host may never call, must remain below 35 KiB gzip. Both are budgets, not claims that TypeScript declarations, the npm tarball, installed files, or a website route have the same size. Run bun run size on the exact release commit instead of repeating a registry screenshot as a bundle measurement.

Scaling is gated independently. The 0.4 release measured 64,000 components with 32,000 connections at roughly one second and a flat cost near 16 µs per component from 8,000 upward; 11,200 components with 800 obstacle-dodging orthogonal traces measured about 130 ms. Those are warm figures from one Apple Silicon/Node configuration. The durable claim is the guarded slope, not the absolute millisecond value.

02 / HostIsolate deadlines and cap amplification

The official compile endpoint applies limits stricter than the library defaults, rejects oversized request bodies before JSON allocation, rate-limits by client, and runs a compilation outside the request thread. A deadline can terminate that worker; Promise.race around synchronous compilation cannot. Concurrency and queue depth are finite, and a full queue returns a retryable capacity error instead of multiplying memory by the rate-limit burst.

clock:CK "CLK" at (90, 120) #purple
register:RG "latch" at (340, 120) #cyan [width=1]
port:D "D" at (620, 120) #emerald

CK.out -> RG.clock #purple [digital ortho]
RG.out1 -> D.in #emerald [digital line]

Successful and line-numbered failed compilations share a SHA-256-keyed LRU capped at 64 entries and 16 MiB. The cache key includes mode, bounds, title, and source; hits refresh recency. Registry data uses one immutable stale-while-revalidate snapshot and one in-flight refresh promise. Documentation and simulation caches are keyed by finite registries rather than user input.

The browser IDE compiles locally in a lazily started native worker containing @schemd/core and uses the endpoint only as a fallback. That removes a network round trip and server work from normal typing, and the worker boundary lets a deadline terminate a pathological local compile, without putting the compiler on documentation, catalogue, or simulation critical paths. The website build budget verifies both facts from Vite’s manifest.

Performance work is not finished when one benchmark turns green. Re-run bun run benchmark on the target hardware, read p95 and p99 under concurrent load rather than a warm median, and measure the serialized response — not only parser time — before raising any public-host budget.