React Reconciler PerformanceMeasure Leak

Symptom

After the ink 6→7 upgrade (v0.15.11), moderate CLI usage caused heap to grow to 300+ MB. RSS climbed steadily and never stabilized.

Diagnosis

Snapshot comparison

Took 5 snapshots over ~25 minutes of normal usage.

Snapshot #1 (baseline):

PerformanceMeasure: count=184, retainedSize=184 kB

Snapshot #5 (after activity):

PerformanceMeasure: count=150,716, retainedSize=146,798 kB (~143 MB)

Growth: ~800x over the session. Linear with number of React renders.

Retainer chain

chrome-devtools get_node_retainers <snapshot> 1003471

Showed PerformanceMeasure instances retained by (object elements) → Array — the global measureEntryBuffer that Node.js maintains for performance.measure() calls.

Source identification

react-reconciler ≥0.33 (pulled in by ink 7) calls performance.measure() on every component render in its development build. The dev/prod build is selected at runtime via process.env.NODE_ENV. Since the esbuild config never set NODE_ENV to "production", the bundle shipped both builds and selected dev at runtime.

Fix

Set process.env.NODE_ENV to "production" in esbuild's define map so the conditional require resolves statically and the entire 15K-line dev build is tree-shaken:

// esbuild.config.js
define: {
  'process.env.NODE_ENV': JSON.stringify('production'),
}

Bundle shrank by ~700 KB / 15,800 lines. PerformanceMeasure objects no longer accumulate.

Commit

dbdc94be9 — fix(build): tree-shake React reconciler dev build to prevent PerformanceMeasure leak