Charon/docs/plans/current_spec.md

Major Dependency Upgrade Plan — ESLint v10, TypeScript 6.0, Vite 8

Date: 2026-03-12 Author: Planning Agent Status: Ready for Review Confidence Score: 82% (High for ESLint v10 + TS 6.0; Medium for Vite 8 — beta with Rolldown migration)

---

1. Executive Summary

This plan covers the upgrade of three major frontend toolchain dependencies in the Charon project:

Dependency	Current Version	Target Version	Status	Risk
ESLint	^9.39.3 <10.0.0	^10.0.0	Released	Medium — plugin compat gate
TypeScript	^5.9.3	^6.0.0	Beta (Feb 11) / RC (Mar 6)	Medium — 17+ deprecations
Vite	^7.3.1	8.0.0-beta.18	Beta (Dec 3, 2025)	High — beta, Rolldown replaces Rollup+esbuild

Key Findings

1. ESLint v10 is released with a comprehensive migration guide. The primary blocker is a note in lefthook.yml: "ESLint pinned at v9.x.x — do not upgrade until react-hooks plugin supports v10." The eslint-plugin-react-hooks@7.0.1 must be verified for ESLint v10 compatibility before proceeding.

2. TypeScript 6.0 is real (Beta: Feb 11, 2026; RC: Mar 6, 2026). It is explicitly designed as a bridge release between TS 5.9 and the native Go-based TS 7.0. It introduces 17+ deprecations/breaking changes (new defaults for strict, module, target, types, rootDir; removal of outFile, legacy module systems; deprecated baseUrl, moduleResolution: node). Charon's current tsconfig.json is well-positioned — it already uses moduleResolution: bundler, strict: true, and module: ESNext. The critical impact is the types default changing to [].

3. Vite 8 exists as 8.0.0-beta.18 (announced Dec 3, 2025). The headline change is Rolldown replaces both Rollup and esbuild. JS transforms and minification now use Oxc; CSS minification uses Lightning CSS. The build.rollupOptions config key is deprecated in favor of build.rolldownOptions, and output.manualChunks (object form) is removed. Charon's vite.config.ts uses rollupOptions with inlineDynamicImports: true — both need migration. Ecosystem packages (@vitejs/plugin-react, vitest) require beta versions for Vite 8 compatibility.

Recommended Execution Order

PR-1: TypeScript 6.0 upgrade (fewer external dependencies, most self-contained)
PR-2: ESLint v10 upgrade (blocked on plugin compat verification)
PR-3: Vite 8 upgrade (beta — stacked on PR-1 + PR-2 branch)

---

2. Current Dependency Inventory

Root package.json (/projects/Charon/package.json)

Package	Current Version	Category
typescript	^5.9.3	devDependency
vite	^7.3.1	devDependency
@playwright/test	^1.58.2	devDependency
prettier	^3.8.1	devDependency
markdownlint-cli2	^0.21.0	devDependency

Frontend package.json (/projects/Charon/frontend/package.json)

Package	Current Version	Category
typescript	^5.9.3	devDependency
vite	^7.3.1	devDependency
vitest	^4.0.18	devDependency
eslint	^9.39.3 <10.0.0	devDependency
@eslint/js	^9.39.3 <10.0.0	devDependency
@eslint/css	^1.0.0	devDependency
@eslint/json	^1.1.0	devDependency
@eslint/markdown	^7.5.1	devDependency
typescript-eslint	^8.57.0	devDependency
@typescript-eslint/eslint-plugin	^8.57.0	devDependency
@typescript-eslint/parser	^8.57.0	devDependency
@vitejs/plugin-react	^5.1.4	devDependency
@vitest/coverage-istanbul	^4.0.18	devDependency
@vitest/coverage-v8	^4.0.18	devDependency
@vitest/eslint-plugin	^1.6.10	devDependency
react	^19.2.4	dependency
react-dom	^19.2.4	dependency
react-router-dom	^7.13.1	dependency
@tanstack/react-query	^5.90.21	dependency

ESLint Plugin Inventory (18 plugins)

Plugin	Current Version	ESLint v10 Risk
eslint-plugin-react-hooks	^7.0.1	HIGH — explicit blocker in lefthook.yml
eslint-plugin-react-compiler	^19.1.0-rc.2	Medium — RC, check compat
eslint-plugin-react-refresh	^0.5.2	Low
eslint-plugin-import-x	^4.16.1	Low — modern fork
eslint-plugin-jsx-a11y	^6.10.2	Medium
eslint-plugin-security	^4.0.0	Low
eslint-plugin-sonarjs	^4.0.2	Low
eslint-plugin-unicorn	^63.0.0	Low — actively maintained
eslint-plugin-promise	^7.2.1	Low
eslint-plugin-unused-imports	^4.4.1	Low
eslint-plugin-no-unsanitized	^4.1.5	Medium
eslint-plugin-testing-library	^7.16.0	Low
typescript-eslint	^8.57.0	Low — tracks ESLint closely
@vitest/eslint-plugin	^1.6.10	Low
@eslint/css	^1.0.0	Low — official ESLint
@eslint/json	^1.1.0	Low — official ESLint
@eslint/markdown	^7.5.1	Low — official ESLint

Config Files Affected

File	Impact Area
frontend/tsconfig.json	TS 6.0 — types, lib, defaults
frontend/tsconfig.node.json	TS 6.0 — minor
frontend/tsconfig.build.json	TS 6.0 — extends base
frontend/eslint.config.js	ESLint v10 — plugin compat
eslint.config.js (root)	ESLint v10 — imports frontend config
frontend/package.json	All — version bumps
package.json (root)	TS + Vite version bumps
lefthook.yml	ESLint v10 — remove pin note
Dockerfile	Node.js version (already compatible)

Infrastructure

• Node.js: 24.14.0-alpine (Dockerfile) — meets all upgrade requirements
• No .npmrc file exists in the project
• Go: 1.26.1 (not affected by frontend upgrades)

---

3. Breaking Changes Analysis

3.1 ESLint v10 Breaking Changes

Source: ESLint v10 Migration Guide

#	Breaking Change	Impact on Charon	Action Required
1	Node.js ≥ v20.19, v22.13, or v24 required	None — already on Node 24.14.0	None
2	eslint:recommended updated — 3 new rules: no-unassigned-vars, no-useless-assignment, preserve-caught-error	May flag new violations in codebase	Fix flagged code or disable rules
3	New config file lookup — searches from linted file, not cwd	Flat config already used; minor risk for monorepo patterns	Verify root config is found correctly
4	Old .eslintrc format completely removed	None — already using flat config	None
5	JSX references now tracked — fixes no-unused-vars for JSX components	Positive — fewer false positives	May surface new true positives
6	eslint-env comments reported as errors	Search codebase for /* eslint-env */	Remove if found
7	Jiti ≥ v2.2.0 required	Check transitive dep version	May need explicit install
8	Removed deprecated context members — context.getScope(), context.getAncestors(), etc.	Affects plugins, not our config directly	All 18 plugins must be compatible
9	Removed deprecated SourceCode methods	Same — plugin concern	Plugin compat verification
10	Program AST node range spans entire source	Unlikely to affect us	None

Critical Plugin Gate: The eslint-plugin-react-hooks compatibility with ESLint v10 must be verified. The lefthook.yml at line ~98 explicitly states: "NOTE: ESLint pinned at v9.x.x — do not upgrade until react-hooks plugin supports v10."

3.2 TypeScript 6.0 Breaking Changes

Source: TypeScript 6.0 Beta Announcement and 6.0 Deprecation List

Default Value Changes

Setting	Old Default	New Default	Charon Current	Action
strict	false	true	true (explicit)	None — already set
module	commonjs	esnext	ESNext (explicit)	None — already set
target	es5	es2025 (floating)	ES2022 (explicit)	None — already set
types	["*"] (all @types)	[] (none)	Not set	ACTION: Add "types": []
rootDir	inferred	. (tsconfig dir)	Not set	Verify — no emit, noEmit: true
noUncheckedSideEffectImports	false	true	Not set	Verify no side-effect import issues
libReplacement	true	false	Not set	None — improves perf

Deprecations (with ignoreDeprecations: "6.0" escape hatch)

Deprecation	Charon Uses?	Impact
target: es5	No (ES2022)	None
--outFile	No	None
--downlevelIteration	No	None
--moduleResolution node/node10	No (bundler)	None
--moduleResolution classic	No	None
--baseUrl	No	None
module: amd/umd/systemjs	No (ESNext)	None
esModuleInterop: false	Not explicitly set	None
allowSyntheticDefaultImports: false	Not set (true in tsconfig.node)	None
alwaysStrict: false	Not set (strict: true covers)	None
Legacy module keyword for namespaces	No	None
asserts keyword on imports	No	None
no-default-lib directives	No	None

New Features Available

Feature	Relevance
import defer syntax	Future use — deferred module evaluation
--module node20	Not needed — using bundler
es2025 target/lib	Can update target from ES2022 to ES2025
Temporal types	Available via esnext lib
dom.iterable included in dom	Can simplify lib array
--stableTypeOrdering	Useful for TS 7.0 migration prep
Expandable hovers	Editor UX improvement
Map.getOrInsert / getOrInsertComputed	Available via esnext lib
RegExp.escape	Available via es2025 lib
#/ subpath imports	Available for future module aliasing

lib.d.ts Changes — ArrayBuffer/Buffer Breaking Change

TypeScript 5.9 introduced a behavioral change where ArrayBuffer is no longer a supertype of several TypedArray types. This may cause errors like:

error TS2345: Argument of type 'ArrayBufferLike' is not assignable to parameter of type 'BufferSource'.
error TS2322: Type 'Buffer' is not assignable to type 'Uint8Array<ArrayBufferLike>'.

Mitigation: Ensure @types/node is at latest version. This is a 5.9 → 6.0 carryover that must be verified.

3.3 Vite 8 Breaking Changes

Source: Vite 8 Beta Announcement and Migration from v7 Guide

Version: 8.0.0-beta.18 (dist-tag: beta, announced Dec 3, 2025)

Core Architecture Change: Rolldown Replaces Rollup + esbuild

Vite 8's defining change is replacing two bundlers (esbuild for dev transforms, Rollup for production builds) with a single Rust-based toolchain:

Component	Vite 7	Vite 8	Impact on Charon
Bundler	Rollup	Rolldown (1.0.0-rc.8)	rollupOptions → rolldownOptions
JS Transforms	esbuild	Oxc (@oxc-project/runtime@0.115.0)	esbuild config key deprecated
JS Minification	esbuild	Oxc Minifier	Different minification assumptions
CSS Minification	esbuild	Lightning CSS (^1.31.1)	Slightly different output, bundle size may change
Dep Optimization	esbuild	Rolldown	optimizeDeps.esbuildOptions deprecated

Breaking Changes Impacting Charon

#	Breaking Change	Impact on Charon	Action Required
1	Node.js ^20.19.0 || >=22.12.0 required	None — already on Node 24.14.0	None
2	build.rollupOptions deprecated → build.rolldownOptions	HIGH — vite.config.ts uses rollupOptions	Rename config key
3	output.manualChunks object form removed, function form deprecated	HIGH — config sets manualChunks: undefined	Remove or migrate to codeSplitting
4	output.inlineDynamicImports — supported in Rolldown but deprecated in favor of codeSplitting: false (rolldown docs)	HIGH — config uses inlineDynamicImports: true as temporary workaround	Migrate to codeSplitting: false; inlineDynamicImports works as fallback
5	Default browser targets updated (Chrome 107→111, Firefox 104→114, Safari 16.0→16.4)	Low — Charon doesn't set explicit build.target	None — new defaults are fine
6	esbuild no longer a direct dependency	Low — Charon doesn't use esbuild config	None
7	Oxc Minifier replaces esbuild minifier	Low — different assumptions about source code	Test build output; verify no minification breakage
8	Lightning CSS for CSS minification	Low — may produce slightly different CSS output	Verify CSS output visually
9	Consistent CommonJS interop — default import behavior changes for CJS modules	Medium — could affect CJS dependencies (axios, etc.)	Test all runtime imports
10	Module resolution format sniffing removed — browser/module field heuristic gone	Low — modern packages use exports field	Verify no resolution regressions
11	@vitejs/plugin-react 5.x does NOT support Vite 8 — requires 6.0.0-beta.0	HIGH — must upgrade plugin-react	Upgrade to @vitejs/plugin-react@6.0.0-beta.0
12	Plugin-react 6.0 uses @rolldown/pluginutils instead of Rollup utils	Low — internal plugin change	None — handled by plugin upgrade

New Features Available

Feature	Relevance to Charon
Built-in tsconfig paths support (resolve.tsconfigPaths: true)	Could replace manual alias config if needed
emitDecoratorMetadata support	Not needed — Charon doesn't use decorators
Performance: 10–30× faster production builds	Direct benefit — faster Docker builds and CI
Full Bundle Mode (upcoming)	Future — 3× faster dev server startup
Module-level persistent cache (upcoming)	Future — faster rebuilds

Dockerfile Impact: Rollup Native Skip Flags

The current Dockerfile sets:

ENV npm_config_rollup_skip_nodejs_native=1 \
    ROLLUP_SKIP_NODEJS_NATIVE=1

These env vars are Rollup-specific for cross-platform builds. With Vite 8, Rollup is replaced by Rolldown, which uses its own native bindings (@rolldown/binding-linux-x64-musl for Alpine). These env vars become no-ops but do not cause harm. Rolldown's native bindings are installed per-platform by npm's optionalDependencies mechanism — the same mechanism that works for the $BUILDPLATFORM Docker flag.

Action: Remove the Rollup skip flags from Dockerfile and verify cross-platform builds still work. Rolldown includes @rolldown/binding-linux-x64-musl which is exactly what Alpine requires.

---

4. Compatibility Matrix

ESLint v10 Plugin Compatibility Verification Matrix

Each plugin must be verified before the ESLint v10 upgrade. The agent performing PR-2 must run these checks:

# For each plugin, check peer dependency support
npm info eslint-plugin-react-hooks peerDependencies
npm info eslint-plugin-react-compiler peerDependencies
npm info eslint-plugin-jsx-a11y peerDependencies
npm info eslint-plugin-import-x peerDependencies
npm info eslint-plugin-security peerDependencies
npm info eslint-plugin-sonarjs peerDependencies
npm info eslint-plugin-unicorn peerDependencies
npm info eslint-plugin-promise peerDependencies
npm info eslint-plugin-unused-imports peerDependencies
npm info eslint-plugin-no-unsanitized peerDependencies
npm info eslint-plugin-testing-library peerDependencies
npm info eslint-plugin-react-refresh peerDependencies
npm info @vitest/eslint-plugin peerDependencies
npm info typescript-eslint peerDependencies
npm info @eslint/css peerDependencies
npm info @eslint/json peerDependencies
npm info @eslint/markdown peerDependencies

Decision Gate: If eslint-plugin-react-hooks does NOT support ESLint v10 in its peerDependencies, the ESLint v10 upgrade is BLOCKED. Do not use --legacy-peer-deps or --force as a workaround.

TypeScript 6.0 Ecosystem Compatibility

Tool	TS 6.0 Compat	Notes
typescript-eslint@8.57.0	Likely — tracks TS closely	Verify with npm install
vite@7.3.1	Yes — Vite uses esbuild/swc, not tsc directly	Type-check is separate
vitest@4.0.18	Yes — same reasoning	Type-check is separate
@vitejs/plugin-react@5.1.4	Yes	No TS compiler dependency
react@19.2.4 / @types/react	Yes	Ensure @types/react latest
@tanstack/react-query@5.90.21	Likely — popular library	TanStack already preparing for TS 6
knip@5.86.0	Verify	Uses TS programmatic API

Node.js Compatibility

Tool	Min Node.js	Charon Node.js	Status
ESLint v10	20.19 / 22.13 / 24+	24.14.0	Compatible
TypeScript 6.0	TBD (likely same as 5.9)	24.14.0	Compatible
Vite 7	20.19 / 22.12+	24.14.0	Compatible
Vite 8	20.19 / 22.12+	24.14.0	Compatible

Vite 8 Ecosystem Compatibility Matrix

All Vite-related packages must be updated together. Stable releases do not support Vite 8.

Package	Current Version	Vite 8 Compatible?	Required Version	Override Needed?
vite	^7.3.1	—	8.0.0-beta.18	No — direct install
@vitejs/plugin-react	^5.1.4	No (5.x peer: vite: ^4.2.0 || ^5.0.0 || ^6.0.0 || ^7.0.0)	6.0.0-beta.0 (peer: vite: ^8.0.0 — verified via npm info)	No — direct install
vitest	^4.0.18	No (deps: ^6.0.0 || ^7.0.0)	4.1.0-beta.6 (deps: ^6.0.0 || ^7.0.0 || ^8.0.0-0)	No — 4.1.0-beta.6 dep range includes Vite 8
@vitest/coverage-istanbul	^4.0.18	No (peer: vitest: 4.0.18)	4.1.0-beta.6	No — matches vitest beta
@vitest/coverage-v8	^4.0.18	No (peer: vitest: 4.0.18)	4.1.0-beta.6	No — matches vitest beta
@vitest/ui	^4.0.18	No (peer: vitest: 4.0.18)	4.1.0-beta.6	No — matches vitest beta
@vitest/eslint-plugin	^1.6.10	Yes (peer: vitest: *)	Keep current	No
@bgotink/playwright-coverage	^0.3.2	Yes (no Vite peer dep)	Keep current	No
@playwright/test	^1.58.2	Yes (no Vite peer dep)	Keep current	No

Key constraints:

• vitest@4.0.18 has vite in its dependencies (not peer deps) pinned to ^6.0.0 || ^7.0.0 — this will refuse Vite 8 unless overridden
• vitest@4.1.0-beta.6 extends this to ^6.0.0 || ^7.0.0 || ^8.0.0-0 — supports Vite 8 beta
• @vitejs/plugin-react@6.0.0-beta.0 peers on vite: ^8.0.0 (verified via npm info). New optional peer deps: @rolldown/plugin-babel and babel-plugin-react-compiler (both optional — not required)
• All @vitest/* packages at 4.1.0-beta.6 must be installed together (strict peer version matching: vitest: 4.1.0-beta.6)
• Since vitest@4.1.0-beta.6 already includes ^8.0.0-0 in its vite dependency range, and all @vitest/* packages peer to exact vitest: 4.1.0-beta.6, no npm overrides are needed when all packages are installed in lockstep at their beta versions

---

5. .npmrc Configuration

No .npmrc file currently exists in the project. No changes needed for these upgrades.

If plugin compatibility issues arise during ESLint v10 upgrade, do NOT create an .npmrc with legacy-peer-deps=true. Instead, wait for plugin updates or use granular overrides in package.json:

// package.json — ONLY if a specific plugin ships a fix before updating peerDeps
{
  "overrides": {
    "eslint-plugin-EXAMPLE": {
      "eslint": "^10.0.0"
    }
  }
}

---

6. Dockerfile Changes

No Dockerfile changes required for ESLint v10 or TypeScript 6.0.

Vite 8 requires Dockerfile changes — the Rollup native skip flags become irrelevant:

  # Set environment to bypass native binary requirement for cross-arch builds
- ENV npm_config_rollup_skip_nodejs_native=1 \
-     ROLLUP_SKIP_NODEJS_NATIVE=1
+ # Vite 8 uses Rolldown (Rust native bindings, auto-resolved per platform)
+ # No skip flags needed — Rolldown's optionalDependencies handle cross-platform

Current Dockerfile state (frontend-builder stage):

FROM --platform=$BUILDPLATFORM node:24.14.0-alpine AS frontend-builder
# ...
ENV npm_config_rollup_skip_nodejs_native=1 \
    ROLLUP_SKIP_NODEJS_NATIVE=1
RUN npm ci
COPY frontend/ ./
RUN npm run build

• Node.js 24.14.0 meets Vite 8's requirement (^20.19.0 || >=22.12.0)
• npm ci will install Rolldown's @rolldown/binding-linux-x64-musl automatically on Alpine
• --platform=$BUILDPLATFORM ensures native bindings match the build machine architecture
• The VITE_APP_VERSION env var and build output (dist/) remain unchanged
• No new environment variables or build args needed

Future (Vite 8): If Vite 8 requires a higher Node.js, upgrade the base image at that time.

---

7. Config File Changes

7.1 TypeScript 6.0 — frontend/tsconfig.json

  {
    "compilerOptions": {
      "target": "ES2022",
+     // Consider upgrading to "ES2025" (TS 6.0 new target)
      "useDefineForClassFields": true,
-     "lib": ["ES2022", "DOM", "DOM.Iterable"],
+     "lib": ["ES2022", "DOM"],
+     // DOM.Iterable is now included in DOM as of TS 6.0
      "module": "ESNext",
      "skipLibCheck": true,

      /* Bundler mode */
      "moduleResolution": "bundler",
      "allowImportingTsExtensions": true,
      "isolatedModules": true,
      "moduleDetection": "force",
      "noEmit": true,
      "jsx": "react-jsx",

      /* Linting */
      "strict": true,
      "noUnusedLocals": true,
      "noUnusedParameters": true,
      "noFallthroughCasesInSwitch": true,
+
+     /* TS 6.0 — explicit types to override new default of [] */
+     "types": []
    },
    "include": ["src"],
    "references": [{ "path": "./tsconfig.node.json" }]
  }

Key changes:

1. "types": [] — Explicitly set to []. Charon uses noEmit: true and doesn't rely on global @types packages in the main tsconfig. All types come from explicit imports.
2. "lib" simplification — Remove "DOM.Iterable" since TS 6.0 includes it in "DOM" automatically.
3. "target" consideration — Can optionally upgrade from ES2022 to ES2025 to access RegExp.escape and other ES2025 types natively. Not required.

7.2 TypeScript 6.0 — frontend/tsconfig.node.json

  {
    "compilerOptions": {
      "composite": true,
      "skipLibCheck": true,
      "module": "ESNext",
      "moduleResolution": "bundler",
      "allowSyntheticDefaultImports": true,
-     "strict": true
+     "strict": true,
+     "types": []
    },
    "include": ["vite.config.ts"]
  }

Note: allowSyntheticDefaultImports is fine — TS 6.0 deprecates setting it to false, not true. Setting it to true remains valid.

7.3 ESLint v10 — frontend/package.json Version Caps

  "devDependencies": {
-   "eslint": "^9.39.3 <10.0.0",
+   "eslint": "^10.0.0",
-   "@eslint/js": "^9.39.3 <10.0.0",
+   "@eslint/js": "^10.0.0",
    // ... all other ESLint plugins may need version bumps
  }

7.4 ESLint v10 — frontend/eslint.config.js

Likely no structural changes needed since Charon already uses flat config. Potential changes:

• Remove any /* eslint-env */ comments found in source files
• Handle new eslint:recommended rules (no-unassigned-vars, no-useless-assignment, preserve-caught-error)
• Verify tseslint.config() wrapper compatibility

7.5 ESLint v10 — lefthook.yml

+ # NOTE: ESLint v10 is supported — plugin compatibility verified on [DATE]
- # NOTE: ESLint pinned at v9.x.x — do not upgrade until react-hooks plugin supports v10.

7.6 TypeScript 6.0 — package.json (Root + Frontend)

  "devDependencies": {
-   "typescript": "^5.9.3",
+   "typescript": "^6.0.0",
  }

---

8. Phase-by-Phase Implementation Plan

Phase 1: Pre-Upgrade Verification (Both PRs)

Owner: Frontend_Dev agent (or whoever picks up the PR)

1. Snapshot current state:

   cd /projects/Charon && npm run lint 2>&1 | tee /tmp/eslint-v9-baseline.log
   cd /projects/Charon/frontend && npx tsc --noEmit 2>&1 | tee /tmp/tsc-v5-baseline.log
   

2. Verify ESLint plugin compatibility (PR-2 gate):

   for plugin in eslint-plugin-react-hooks eslint-plugin-react-compiler \
     eslint-plugin-jsx-a11y eslint-plugin-import-x eslint-plugin-security \
     eslint-plugin-sonarjs eslint-plugin-unicorn eslint-plugin-promise \
     eslint-plugin-unused-imports eslint-plugin-no-unsanitized \
     eslint-plugin-testing-library eslint-plugin-react-refresh \
     @vitest/eslint-plugin typescript-eslint @eslint/css @eslint/json @eslint/markdown; do
     echo "=== $plugin ===" && npm info "$plugin" peerDependencies 2>/dev/null
   done
   

3. Search for eslint-env comments:

   grep -r "eslint-env" frontend/src/ --include="*.ts" --include="*.tsx" --include="*.js"
   

Phase 2: TypeScript 6.0 Upgrade (PR-1)

Scope: TypeScript version bump + tsconfig adjustments

1. Update typescript version in both package.json files:

   • Root: ^5.9.3 → ^6.0.0
   • Frontend: ^5.9.3 → ^6.0.0

2. Apply tsconfig changes (Section 7.1 and 7.2 above):

   • Add "types": [] to tsconfig.json and tsconfig.node.json
   • Remove "DOM.Iterable" from lib array (now included in "DOM")

3. Run npm install to update lock file

4. Run type-check and fix any new errors:

   cd frontend && npx tsc --noEmit
   

5. Common expected issues:

   • Missing types from @types/* packages (solved by "types": [] since we don't use globals)
   • ArrayBuffer/Buffer type narrowing (from TS 5.9 lib.d.ts changes)
   • Type argument inference changes (may need explicit type annotations)

6. Run full test suite:

   cd frontend && npx vitest run
   

7. Run Playwright E2E tests to verify build works:

   # The Dockerfile builds with npm ci && npm run build
   # Verify: cd frontend && npx vite build
   

Phase 3: ESLint v10 Upgrade (PR-2)

Prerequisite: Phase 1 plugin verification passes. eslint-plugin-react-hooks must declare ESLint v10 support.

1. Remove version cap and update ESLint packages:

   cd frontend
   npm install -D eslint@^10.0.0 @eslint/js@^10.0.0
   

2. Update any plugins that need version bumps for ESLint v10 compat

3. Run ESLint and compare against baseline:

   cd /projects/Charon && npm run lint 2>&1 | tee /tmp/eslint-v10-output.log
   diff /tmp/eslint-v9-baseline.log /tmp/eslint-v10-output.log
   

4. Address new violations from updated eslint:recommended:

   • no-unassigned-vars — variables declared but never assigned
   • no-useless-assignment — assignments that are immediately overwritten
   • preserve-caught-error — catch clause variables that are declared but unused

5. Remove any /* eslint-env */ comments found in Phase 1

6. Update lefthook.yml — remove the ESLint v9 pin note

7. Run full test suite to confirm no regressions

Phase 4: Integration Testing

1. Full lint + type-check:

   cd /projects/Charon && npm run lint && cd frontend && npx tsc --noEmit
   

2. Frontend build:

   cd frontend && npx vite build
   

3. Unit tests:

   cd frontend && npx vitest run
   

4. Playwright E2E tests (all browsers):

   npx playwright test --project=chromium
   npx playwright test --project=firefox
   npx playwright test --project=webkit
   

5. Docker build verification:

   docker build -t charon:upgrade-test .
   

Phase 5: Vite 8 Upgrade (PR-3 — stacked commit on same branch)

Prerequisites: PR-1 (TypeScript 6.0) and PR-2 (ESLint v10) already committed on branch.

Scope: Vite ^7.3.1 → 8.0.0-beta.18, plugin-react ^5.1.4 → 6.0.0-beta.0, vitest ^4.0.18 → 4.1.0-beta.6, vite.config.ts migration, Dockerfile cleanup.

Step 1: Install Vite 8 and ecosystem packages

cd /projects/Charon/frontend

# Core Vite upgrade
npm install -D vite@8.0.0-beta.18

# Plugin-react upgrade (6.x required for Vite 8)
npm install -D @vitejs/plugin-react@6.0.0-beta.0

# Vitest + coverage upgrades (4.1.0-beta.6 supports Vite 8)
npm install -D vitest@4.1.0-beta.6 \
  @vitest/coverage-istanbul@4.1.0-beta.6 \
  @vitest/coverage-v8@4.1.0-beta.6 \
  @vitest/ui@4.1.0-beta.6

Step 2: Update root package.json (direct version bump only — no overrides)

The root package.json only has vite as a direct devDependency (used by Playwright). It does not need overrides — just a version bump:

cd /projects/Charon
npm install -D vite@8.0.0-beta.18

Step 3: Verify peer dep resolution (overrides likely NOT needed)

With all packages at their Vite 8-compatible versions, overrides should not be necessary:

• vitest@4.1.0-beta.6 depends on vite: ^6.0.0 || ^7.0.0 || ^8.0.0-0 — already includes Vite 8
• @vitejs/plugin-react@6.0.0-beta.0 peers on vite: ^8.0.0 — matches
• All @vitest/*@4.1.0-beta.6 peer on vitest: 4.1.0-beta.6 — matches when installed in lockstep

Run npm install and check for peer dep warnings. Only add overrides in frontend/package.json (following the established pattern from TS 6.0 and ESLint v10 phases) if specific transitive packages fail to resolve:

// frontend/package.json — ONLY if npm install reports unresolved peer deps
{
  "overrides": {
    // ... existing TS and ESLint overrides ...
    // Add scoped overrides ONLY for the specific package that fails, e.g.:
    // "some-transitive-package": { "vite": "8.0.0-beta.18" }
  }
}

Do NOT add a top-level "vite": "8.0.0-beta.18" override — this forces every transitive Vite consumer to resolve to the beta, which is overly broad. If a broad override is truly needed after testing, add it with a comment explaining which transitive package requires it.

Step 4: Migrate vite.config.ts

  import react from '@vitejs/plugin-react'
  import { defineConfig } from 'vite'

  export default defineConfig({
    plugins: [react()],
    server: {
      port: 5173,
      proxy: {
        '/api': {
          target: 'http://localhost:8080',
          changeOrigin: true
        }
      }
    },
    build: {
      outDir: 'dist',
      sourcemap: true,
-     // TEMPORARY: Disable code splitting to diagnose React initialization issue
-     // If this works, the problem is module loading order in async chunks
      chunkSizeWarningLimit: 2000,
-     rollupOptions: {
-       output: {
-         // Disable code splitting - bundle everything into one file
-         manualChunks: undefined,
-         inlineDynamicImports: true
-       }
-     }
+     rolldownOptions: {
+       output: {
+         // Disable code splitting — single bundle for React init stability
+         // codeSplitting: false is the Rolldown-native approach
+         // (inlineDynamicImports is deprecated in Rolldown)
+         codeSplitting: false
+       }
+     }
    }
  })

Key changes:

1. rollupOptions → rolldownOptions (Rollup config key deprecated)
2. manualChunks: undefined removed (object form no longer supported; was already a no-op since undefined)
3. inlineDynamicImports: true replaced with codeSplitting: false — the Rolldown-native equivalent. Rolldown supports inlineDynamicImports but marks it as deprecated in favor of codeSplitting: false.
4. The TEMPORARY comment is preserved in intent — this workaround may still be needed

Fallback if codeSplitting: false behaves differently than expected:

build: {
  rolldownOptions: {
    output: {
      // Deprecated but still functional in Rolldown 1.0.0-rc.8
      inlineDynamicImports: true
    }
  }
}

Step 5: Update Dockerfile

Remove the now-irrelevant Rollup native skip flags:

- ENV npm_config_rollup_skip_nodejs_native=1 \
-     ROLLUP_SKIP_NODEJS_NATIVE=1
+ # Vite 8: Rolldown native bindings auto-resolved per platform via optionalDependencies

Step 6: Run npm install to regenerate lock file

cd /projects/Charon && npm install
cd /projects/Charon/frontend && npm install

Step 7: Verify builds and tests

# 1. Frontend build (most critical — tests Rolldown bundling)
cd /projects/Charon/frontend && npx vite build

# 2. Type-check (should be unaffected)
cd /projects/Charon/frontend && npx tsc --noEmit

# 3. Lint (should be unaffected)
cd /projects/Charon && npm run lint

# 4. Unit tests
cd /projects/Charon/frontend && npx vitest run

# 5. Docker build (tests Rolldown on Alpine/musl)
docker build -t charon:vite8-test .

# 6. Playwright E2E (tests the built app end-to-end)
cd /projects/Charon && npx playwright test --project=firefox

# 7. CJS interop smoke test (verify axios, react-hot-toast, react-hook-form)
# Run the app and manually verify pages that use CJS dependencies render correctly
# See Step 9 for detailed CJS interop verification checklist

Step 8: Verify build output

# Compare build output size and structure
ls -la frontend/dist/assets/
# Should still produce index-*.js, index-*.css
# With codeSplitting: false, should be a single JS bundle

Step 9: Verify CJS interop (Vite 8 behavior change)

Vite 8's consistent CJS interop may affect imports from CJS packages like axios and react-hot-toast. Explicitly verify these packages work at runtime:

# After Docker build or vite build + preview:
# 1. Verify axios API calls work (CJS package with __esModule flag)
#    - Navigate to any page that makes API calls (e.g., Dashboard)
#    - Check browser console for "default is not a function" errors
# 2. Verify react-hot-toast renders (CJS package)
#    - Trigger a toast notification (e.g., save settings)
#    - Check browser console for import errors
# 3. Verify react-hook-form works (CJS interop)
#    - Open any form page, submit a form

If any runtime errors appear (e.g., default is not a function), use the temporary escape hatch:

// vite.config.ts — ONLY if CJS interop breaks
export default defineConfig({
  legacy: {
    inconsistentCjsInterop: true
  }
})

Step 10: Update ARCHITECTURE.md

Update the Frontend technology stack table and directory structure to reflect current versions:

  ### Frontend
  | Component | Technology | Version | Purpose |
- | **Build Tool** | Vite | 6.1.9 | Fast bundler and dev server |
+ | **Build Tool** | Vite | 8.0.0-beta.18 | Fast bundler and dev server |
- | **CSS Framework** | Tailwind CSS | 3.x | Utility-first CSS |
+ | **CSS Framework** | Tailwind CSS | 4.2.1 | Utility-first CSS |
- | **Unit Testing** | Vitest | 2.x | Fast unit test runner |
+ | **Unit Testing** | Vitest | 4.1.0-beta.6 | Fast unit test runner |
- | **E2E Testing** | Playwright | 1.50.x | Browser automation |
+ | **E2E Testing** | Playwright | 1.58.2 | Browser automation |

Also fix the directory structure reference:

- │   └── vite.config.js          # Vite configuration
+ │   └── vite.config.ts          # Vite configuration

---

9. Rollback Strategy

TypeScript 6.0 Rollback (PR-1)

1. Revert package.json changes (both root and frontend):

   - "typescript": "^6.0.0"
   + "typescript": "^5.9.3"
   

2. Revert tsconfig.json changes (remove "types": [], restore "DOM.Iterable")

3. Run npm install to restore lock file

4. Verify: cd frontend && npx tsc --noEmit && npx vitest run

Risk: Low — TypeScript version is a devDependency only. No runtime impact. git revert of the PR commit is sufficient.

ESLint v10 Rollback (PR-2)

1. Revert package.json changes:

   - "eslint": "^10.0.0"
   + "eslint": "^9.39.3 <10.0.0"
   - "@eslint/js": "^10.0.0"
   + "@eslint/js": "^9.39.3 <10.0.0"
   

2. Revert any plugin version bumps

3. Revert lefthook.yml comment change

4. Run npm install to restore lock file

5. Verify: cd /projects/Charon && npm run lint

Risk: Low — ESLint is a devDependency only. Code changes (fixing new rule violations) are harmless to keep even if ESLint is rolled back.

Vite 8 Rollback (PR-3 commit)

1. Revert vite version in both package.json files:

   - "vite": "8.0.0-beta.18"
   + "vite": "^7.3.1"
   

2. Revert ecosystem packages in frontend/package.json:

   - "@vitejs/plugin-react": "6.0.0-beta.0"
   + "@vitejs/plugin-react": "^5.1.4"
   - "vitest": "4.1.0-beta.6"
   + "vitest": "^4.0.18"
   - "@vitest/coverage-istanbul": "4.1.0-beta.6"
   + "@vitest/coverage-istanbul": "^4.0.18"
   - "@vitest/coverage-v8": "4.1.0-beta.6"
   + "@vitest/coverage-v8": "^4.0.18"
   - "@vitest/ui": "4.1.0-beta.6"
   + "@vitest/ui": "^4.0.18"
   

3. Revert vite.config.ts: rolldownOptions → rollupOptions, restore manualChunks: undefined

4. Revert Dockerfile: restore ROLLUP_SKIP_NODEJS_NATIVE=1 env vars

5. Remove Vite 8 overrides from frontend/package.json

6. Run npm install to restore lock file

7. Verify: cd frontend && npx vite build && npx vitest run

Risk: Medium — Vite 8 is a pre-release beta. More likely to need rollback than stable upgrades. Since this is a stacked commit on the same branch, git revert HEAD cleanly removes only the Vite 8 changes while preserving TS 6.0 and ESLint v10.

---

10. Testing Strategy

Automated Test Coverage

Test Layer	Tool	What It Validates
Type checking	tsc --noEmit	TS 6.0 compatibility, tsconfig changes
Linting	eslint	ESLint v10 config + plugin compat
Unit tests	vitest run	No runtime regressions from TS changes
E2E tests	Playwright (Chromium, Firefox, WebKit)	Full app build + functionality
Docker build	docker build	Dockerfile still works with new deps
Pre-commit hooks	lefthook	All hooks pass with new versions

Specific Test Scenarios for TS 6.0

1. Build output verification:

   cd frontend && npx vite build
   # Verify dist/ output is correct, no new warnings
   

2. Type-check with --stableTypeOrdering (prep for TS 7.0):

   cd frontend && npx tsc --noEmit --stableTypeOrdering
   # Note any differences — these will be real in TS 7.0
   

3. Verify no @types resolution issues:

   # With types: [], ensure no global type errors appear
   cd frontend && npx tsc --noEmit 2>&1 | grep "Cannot find"
   

Specific Test Scenarios for ESLint v10

1. Verify all 18 plugins load without errors:

   cd /projects/Charon && npx eslint --print-config frontend/src/App.tsx | head -20
   

2. Count new violations vs baseline:

   npx eslint frontend/src/ --format json 2>/dev/null | jq '.[] | .errorCount' | paste -sd+ | bc
   

3. Verify config lookup works correctly in monorepo:

   # Lint a file from the root — should find root eslint.config.js
   npx eslint frontend/src/App.tsx
   

---

11. Commit Slicing Strategy

Decision: 3 Stacked Commits on Single Branch

Trigger reasons:

• Cross-domain changes (TS and ESLint are independent tools)
• Risk isolation (if one breaks, the other can still merge)
• Review size (each PR is focused and reviewable)
• Plugin compatibility gate (ESLint v10 may be blocked)

PR-1: TypeScript 6.0 Upgrade

Attribute	Detail
Scope	TypeScript ^5.9.3 → ^6.0.0, tsconfig changes, fix type errors
Files	package.json (root), frontend/package.json, package-lock.json, frontend/tsconfig.json, frontend/tsconfig.node.json, possibly source files with type fixes
Dependencies	None — can start immediately
Validation Gate	tsc --noEmit passes, vitest run passes, vite build succeeds, Docker build succeeds
Estimated Complexity	Medium — mostly defaults are already correct, types: [] is the main change
Rollback	git revert + npm install

PR-2: ESLint v10 Upgrade

Attribute	Detail
Scope	ESLint ^9.x → ^10.0.0, plugin updates, fix new violations, update lefthook
Files	frontend/package.json, package-lock.json, frontend/eslint.config.js (if needed), lefthook.yml, source files with new violations
Dependencies	BLOCKED until eslint-plugin-react-hooks declares ESLint v10 support
Validation Gate	npm run lint passes, all plugins load, no new unhandled violations
Estimated Complexity	Medium — depends on plugin ecosystem readiness
Rollback	git revert + npm install

PR-3: Vite 8 Upgrade (stacked commit on same branch)

Attribute	Detail
Scope	Vite 7→8, plugin-react 5→6, vitest 4.0→4.1-beta, vite.config.ts migration, Dockerfile cleanup
Files	package.json (root), frontend/package.json, package-lock.json, frontend/vite.config.ts, Dockerfile, ARCHITECTURE.md
Dependencies	PR-1 (TS 6.0) and PR-2 (ESLint v10) already committed on branch
Validation Gate	vite build succeeds with Rolldown, vitest run passes, Docker build succeeds, Playwright E2E passes
Estimated Complexity	High — beta software, bundler engine swap (Rollup→Rolldown), multiple ecosystem packages at beta versions
Rollback	git revert HEAD — cleanly removes only the Vite 8 commit

npm Overrides for PR-3

No overrides expected when all packages are installed at their beta versions in lockstep:

• vitest@4.1.0-beta.6 deps include vite: ^8.0.0-0 — resolves Vite 8 without override
• @vitest/*@4.1.0-beta.6 peer on vitest: 4.1.0-beta.6 — satisfied by direct install

If npm install fails, add scoped overrides in frontend/package.json only for the failing package. Do not add a broad "vite": "8.0.0-beta.18" override.

Contingency

• If TS 6.0 stable is delayed past RC, pin to typescript@6.0.0-rc temporarily
• If ESLint v10 plugin compat is blocked for >30 days, consider temporarily dropping the blocker plugin or using --rulesdir workaround
• If a plugin is permanently abandoned, research replacement plugins
• If Vite 8 beta has blocking regressions, git revert the Vite 8 commit and wait for the next beta or stable release — TS 6.0 + ESLint v10 upgrades remain unaffected
• If vitest@4.1.0-beta.6 fails tests, try pinning vitest@4.0.18 with an overrides entry for its vite dependency (force it to accept ^8.0.0-0)
• If Rolldown's codeSplitting: false behaves differently than expected, try the deprecated inlineDynamicImports: true as a fallback, or re-investigate the React initialization issue that motivated the workaround

---

12. Known Issues & Gotchas

ESLint v10

1. react-hooks plugin blocker — lefthook.yml explicitly states the upgrade is blocked until eslint-plugin-react-hooks supports v10. This is the #1 risk.

2. Config file lookup change — ESLint v10 finds config files starting from the linted file and walking up. In Charon's monorepo setup (root eslint.config.js imports frontend/eslint.config.js), verify the root config is still discovered when linting frontend/src/**.

3. Jiti dependency — ESLint v10 requires jiti >= v2.2.0 for loading config files. This is typically a transitive dependency but may need explicit installation if conflicts arise.

4. Plugin API breakage — Plugins that use deprecated context.getScope(), context.getAncestors(), context.parserOptions, or context.parserPath will break. All 18 plugins must be verified.

TypeScript 6.0

1. types: [] default — This is the highest-impact change for Charon. Without explicitly setting "types", TS 6.0 will not auto-load any @types/* packages. Since Charon uses noEmit: true and explicit imports, this should be fine, but test thoroughly.

2. TS 6.0 is a transition release — It is explicitly designed as a bridge to TS 7.0 (native Go port). Adopting TS 6.0 now prepares us for TS 7.0 later. The ignoreDeprecations: "6.0" escape hatch exists if needed.

3. typescript-eslint compatibility — If typescript-eslint@8.57.0 doesn't support TS 6.0, we may need to update it. Check for a release that adds TS 6.0 support.

4. knip compatibility — knip (^5.86.0) uses TS programmatic API internally. Verify it works with TS 6.0.

5. ArrayBuffer/Buffer types — TS 5.9 changes to lib.d.ts around ArrayBuffer not being a supertype of TypedArray may surface with TS 6.0. Ensure @types/node is at latest.

6. ts5to6 migration tool — The experimental ts5to6 tool can automatically adjust baseUrl and rootDir. Charon doesn't use baseUrl, so this is of limited value, but worth knowing about.

Vite 8

1. Beta software — 8.0.0-beta.18 is pre-release. Expect edge cases and undocumented behavior. File issues at https://github.com/vitejs/rolldown-vite/issues.

2. Rolldown bundler is RC, not stable — Vite 8 depends on rolldown@1.0.0-rc.8. Rolldown is feature-complete but may have edge cases with complex chunk splitting configurations.

3. codeSplitting: false replaces inlineDynamicImports: true — frontend/vite.config.ts has a TEMPORARY workaround for a "React init issue". Rolldown supports inlineDynamicImports but marks it as deprecated in favor of codeSplitting: false. The migration uses codeSplitting: false as the primary approach; inlineDynamicImports: true can be used as a deprecated fallback.

4. Oxc Minifier assumptions differ from esbuild — The Oxc Minifier makes different assumptions about source code than esbuild. If runtime errors appear after build but not in dev, the minifier is the likely culprit. Use build.minify: false temporarily to diagnose.

5. CJS interop behavior change — Vite 8 changes how default imports from CommonJS modules work. Packages like axios (CJS) may be affected. The legacy.inconsistentCjsInterop: true escape hatch exists if needed.

6. All ecosystem packages are beta — @vitejs/plugin-react@6.0.0-beta.0, vitest@4.1.0-beta.6, and all @vitest/* packages are pre-release. They are tightly version-locked (e.g., @vitest/coverage-v8 peers to exact vitest: 4.1.0-beta.6).

7. Plugin-react 6.0 API change — The new @vitejs/plugin-react@6.0.0-beta.0 uses @rolldown/pluginutils internally instead of @rollup/pluginutils. The public API (react() call in config) appears unchanged. New optional peer deps (@rolldown/plugin-babel, babel-plugin-react-compiler) are not required for Charon's usage.

8. Lightning CSS may increase CSS bundle size — Lightning CSS produces slightly different output than esbuild's CSS minifier. Verify CSS output and check for visual regressions.

9. Cross-platform Docker builds — Rolldown uses native Rust bindings per platform (@rolldown/binding-linux-x64-musl for Alpine). The --platform=$BUILDPLATFORM Docker flag ensures the correct binding is installed. If cross-arch builds fail, verify the correct @rolldown/binding-* package is being resolved.

---

13. Risk Assessment

Risk	Probability	Impact	Mitigation
eslint-plugin-react-hooks doesn't support ESLint v10	Medium	High — blocks PR-2 entirely	Monitor npm for updates; check GitHub issues
Other ESLint plugins break on v10	Low	Medium — individual plugins can be disabled	Verify all 18 plugins; have disable config ready
TS 6.0 types: [] causes unexpected errors	Medium	Low — easy to fix by adding types	Test with tsc --noEmit; add specific types
typescript-eslint incompatible with TS 6.0	Low	Medium — blocks type-aware linting	Check releases; may need to update
knip breaks with TS 6.0	Low	Low — knip is optional tooling	Test separately; pin if needed
TS 6.0 stable delayed	Low	Low — RC already available	Use RC or pin beta
Vite 8 beta breaks production build	Medium	High — blocks Docker/deployment	Test vite build thoroughly; rollback with git revert
Rolldown CJS interop breaks runtime imports	Medium	Medium — runtime errors on CJS packages	Test all CJS deps (axios, etc.); use legacy.inconsistentCjsInterop escape
Oxc Minifier causes runtime errors	Low	High — minification bugs are subtle	Compare dev vs prod behavior; use build.minify: false to diagnose
vitest@4.1.0-beta.6 incompatible with test suite	Low	Medium — blocks unit test validation	Pin to 4.0.18 + override vite peer if needed
@vitejs/plugin-react@6.0.0-beta.0 breaks React HMR	Low	Medium — dev experience degraded	Rollback to 5.1.4 + Vite 7 if critical
Rolldown native binding fails on Alpine cross-build	Low	High — blocks Docker build entirely	Verify @rolldown/binding-linux-x64-musl resolves; fall back to non-cross-platform build
Lightning CSS produces visual CSS regressions	Low	Low — cosmetic issues only	Visual diff E2E screenshots
Docker build fails after upgrades	Low	Medium — blocks CI/deployment	Test Docker build in PR CI
Playwright E2E failures from TS changes	Very Low	High — blocks merge	Run full E2E suite before merge

Overall Risk: MEDIUM-HIGH

• TypeScript 6.0 is well-characterized and Charon's tsconfig is well-aligned with the new defaults
• ESLint v10 is dependent on ecosystem readiness (plugin compatibility)
• Vite 8 is the highest-risk change — beta software with a complete bundler engine swap (Rollup→Rolldown). The saving grace is that all three upgrades are separate commits on the same branch, enabling surgical rollback of just the Vite 8 commit if needed

---

Acceptance Criteria

PR-1 (TypeScript 6.0)

• typescript upgraded to ^6.0.0 in root and frontend package.json
• tsconfig.json updated with types: [] and simplified lib
• tsc --noEmit passes with zero errors
• vitest run passes all tests
• vite build produces correct output
• Docker build succeeds
• No new ignoreDeprecations usage (clean upgrade)

PR-2 (ESLint v10)

• Plugin compatibility verified for all 18 plugins
• eslint and @eslint/js upgraded to ^10.0.0
• Version cap (<10.0.0) removed from both packages
• npm run lint passes (new violations fixed)
• lefthook.yml pin note removed/updated
• All pre-commit hooks pass

PR-3 (Vite 8)

• vite upgraded to 8.0.0-beta.18 in root and frontend package.json
• @vitejs/plugin-react upgraded to 6.0.0-beta.0
• vitest upgraded to 4.1.0-beta.6 with matching @vitest/* packages
• vite.config.ts migrated: rollupOptions → rolldownOptions, manualChunks removed
• npm overrides verified: no broad overrides needed (or scoped overrides added with justification)
• Dockerfile: Rollup native skip flags removed
• vite build produces correct output with Rolldown bundler
• vitest run passes all unit tests
• tsc --noEmit still passes (unchanged from PR-1)
• Docker build succeeds with Rolldown on Alpine/musl
• Playwright E2E tests pass (all browsers)
• No CJS interop runtime errors (axios, react-hot-toast, etc.)
• CJS interop verified: axios API calls, react-hot-toast renders, react-hook-form submits work
• CSS output visually correct (Lightning CSS minification)
• ARCHITECTURE.md updated: Vite 8.0.0-beta.18, Vitest 4.1.0-beta.6, Playwright 1.58.2, Tailwind CSS 4.2.1, vite.config.ts filename
• Pre-commit hooks pass (lefthook)