Several algorithmic inefficiencies were causing unnecessary overhead during builds, particularly in large projects with many dependencies and CSS files.

Changes

Path resolution (src/utils/fs.ts)

• Remove duplicate slice() call in lowestCommonAncestor loop
• Add early exit when no common ancestor exists

External dependency resolution (src/features/external.ts)

• Replace Array.some() with Set-based O(1) lookups for exact package matches
• Optimize subpath imports (e.g., react/jsx-runtime) to extract package name once

// Before: O(n) linear search per module
deps.some((dep) => id === dep || id.startsWith(`${dep}/`))

// After: O(1) hash lookup
if (depsSet.has(id)) return true
const slashIndex = id.indexOf('/')
if (slashIndex > 0 && depsSet.has(id.slice(0, slashIndex))) return true

CSS code splitting (src/features/css.ts)

• Replace O(n²) nested chunk-CSS matching loop with indexed O(n) lookup
• Build chunk name index for O(1) access instead of scanning all chunks per CSS file

Pattern matching (src/utils/general.ts)

• Cache compiled picomatch matchers to avoid recompilation
• Add fast path for exact string matches
• Implement 500-entry cache limit to prevent unbounded growth

Plugin initialization (src/features/node-protocol.ts)

• Hoist regex compilation to module level (once) instead of per-plugin instantiation

Environment filtering (src/config/options.ts)

• Check undefined values before expensive prefix matching to short-circuit early

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