feat(ci): bundle-size budget gate (warn-only until baseline enforced)

[BigSimmo]

What

First Tier D item. Protects the repo's perf/bundle-hygiene work from silent regression — a heavy new dependency, or an accidental client-side import of a big module (the "snapshot imported client-side" mistake flagged as a never-do).

• scripts/check-bundle-budget.mjs — measures .next client chunk sizes (raw + gzip), compares total gzip to a committed baseline with a tolerance; --update records the baseline; skips cleanly when there's no build output. Pure measureChunks/compareToBudget are exported and unit-tested.
• bundle-budget.json — ships enforce:false, totalGzipBytes:null → WARN-ONLY. It never blocks a PR until you capture a baseline and opt in.
• ci.yml — a warn-only "Bundle budget" step after Build (cannot fail a run yet).

Rollout (operator, when ready)

1. After a known-good npm run build: npm run check:bundle-budget -- --update to record the baseline gzip size.
2. Set "enforce": true in bundle-budget.json (and tune tolerancePct, default 10%).
3. CI now fails on >tolerance growth; refresh intentionally with --update.

Verification

6/6 vitest (measure + compare logic), no-build smoke (skips), check:github-actions, eslint, tsc (own files clean), prettier — all green.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added automated monitoring of client JavaScript bundle sizes.
  • Bundle-size checks report gzip totals, largest chunks, and changes against a configurable baseline.
  • Added options to update the baseline or output structured results.

• Bug Fixes

  • CI now detects bundle-size growth and warns when configured limits are exceeded.

• Tests

  • Added coverage for bundle measurement, tolerance handling, enforcement, and warning behavior.

[supabase]

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[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 44bddbcf-b0a9-49af-b68d-1805091a895e

📥 Commits

Reviewing files that changed from the base of the PR and between 5098fe3 and a9d09ad.

📒 Files selected for processing (6)

• .github/workflows/ci.yml
• bundle-budget.json
• package.json
• scripts/check-bundle-budget.mjs
• scripts/ci-change-scope.mjs
• tests/bundle-budget.test.ts

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📝 Walkthrough

Walkthrough

Adds a warn-only client JavaScript bundle budget checker that measures Next.js chunk sizes, compares them with a configurable baseline, exposes an npm command, runs in CI, and includes unit and scope-classifier tests.

Changes

Bundle budget enforcement

Layer / File(s)	Summary
Bundle measurement and budget comparison bundle-budget.json, scripts/check-bundle-budget.mjs	Measures raw and gzip sizes for built JavaScript chunks, compares totals against tolerance and enforcement settings, supports baseline updates and JSON output, and reports exit statuses.
Budget behavior validation tests/bundle-budget.test.ts	Tests chunk aggregation, gzip ranking, missing baselines, tolerance boundaries, and warn-versus-fail enforcement.
CI command and change-scope integration package.json, .github/workflows/ci.yml, scripts/ci-change-scope.mjs	Registers and runs the checker in the build job and classifies its configuration and implementation files as build-scope changes with self-test coverage.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant CI
  participant NpmScript
  participant BundleBudgetChecker
  participant BuildOutput
  participant BudgetConfig
  CI->>NpmScript: run check:bundle-budget
  NpmScript->>BundleBudgetChecker: invoke CLI
  BundleBudgetChecker->>BuildOutput: measure JavaScript chunk sizes
  BundleBudgetChecker->>BudgetConfig: load baseline and tolerance
  BundleBudgetChecker-->>CI: emit verdict and exit code

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Possibly related PRs

• BigSimmo/Database#454: Introduces the CI change-scope classifier that this change extends for bundle-budget files.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/bundle-budget

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