Prevent ESLint v10 updates until plugin ecosystem compatibility

.github/dependabot.yml

@@ -15,6 +15,12 @@ updates:
     labels:
       - "dependencies"
       - "security"
+    ignore:
+      # Ignore ESLint major version updates until plugin ecosystem catches up
+      - dependency-name: "eslint"
+        update-types: ["version-update:semver-major"]
+      - dependency-name: "@eslint/js"
+        update-types: ["version-update:semver-major"]
     groups:
       production-dependencies:
         patterns:

docs/ci-failure-investigation.md

@@ -0,0 +1,165 @@
+# CI Failure Investigation Report
+
+**Date**: 2026-02-10  
+**Investigated by**: GitHub Copilot Coding Agent  
+**Status**: RESOLVED - No action required
+
+## Executive Summary
+
+All 6 CI checks are failing on PR #5 (Dependabot dependency update) due to ESLint v10 incompatibility with current ESLint plugins. The **main repository is healthy and requires no changes**. PR #5 should be rejected or held until the plugin ecosystem updates.
+
+## Failing Checks (PR #5)
+
+1. ❌ CI / Build (pull_request) - Failed after 6s
+2. ❌ CI / E2E Tests (pull_request) - Failed after 6s  
+3. ❌ CI / Lint (pull_request) - Failed after 5s
+4. ❌ CI / Security Audit (pull_request) - Failed after 5s
+5. ❌ CI / Type Check (pull_request) - Failed after 9s
+6. ❌ CI / Unit Tests (pull_request) - Failed after 7s
+
+## Root Cause Analysis
+
+### The Problem
+
+PR #5 (Dependabot) attempted to update the following packages:
+
+| Package | From | To | Status |
+|---------|------|----|----|
+| `@eslint/js` | 9.39.2 | 10.0.1 | ⚠️ Breaking |
+| `eslint` | 9.39.2 | 10.0.0 | ⚠️ Breaking |
+| `@types/node` | 24.10.12 | 25.2.2 | ✓ OK |
+| `@vitejs/plugin-react` | 5.1.3 | 5.1.4 | ✓ OK |
+| `eslint-plugin-react-refresh` | 0.4.26 | 0.5.0 | ⚠️ Needs ESLint >=9 |
+| `globals` | 16.5.0 | 17.3.0 | ✓ OK |
+
+### Dependency Conflict
+
+All jobs failed at the `npm ci` step with the following error:
+
+```
+npm error ERESOLVE could not resolve
+npm error While resolving: eslint-plugin-jsx-a11y@6.10.2
+npm error Found: eslint@10.0.0
+npm error Could not resolve dependency:
+npm error peer eslint@"^3 || ^4 || ^5 || ^6 || ^7 || ^8 || ^9" from eslint-plugin-jsx-a11y@6.10.2
+```
+
+### Plugin Compatibility Status
+
+| Plugin | Current Version | ESLint v10 Support |
+|--------|----------------|-------------------|
+| `eslint-plugin-jsx-a11y` | 6.10.2 | ❌ Max: `^9` |
+| `eslint-plugin-react-hooks` | 7.0.1 | ❌ Max: `^9.0.0` |
+| `eslint-plugin-react-refresh` | 0.5.0 | ✓ `>=9` (likely works) |
+| `eslint-plugin-security` | 3.0.1 | ⚠️ Unknown |
+
+**Conclusion**: ESLint v10 was released very recently (2026-02) and the plugin ecosystem has not yet updated to support it.
+
+## Current Repository Status (Main Branch)
+
+### Dependencies (Correct State)
+
+```json
+{
+  "eslint": "^9.39.1",
+  "@eslint/js": "^9.39.1",
+  "eslint-plugin-jsx-a11y": "^6.10.2",
+  "eslint-plugin-react-hooks": "^7.0.1",
+  "eslint-plugin-react-refresh": "^0.4.24",
+  "eslint-plugin-security": "^3.0.1"
+}
+```
+
+### CI Verification (All Passing ✅)
+
+Verified locally on `copilot/fix-failing-checks` branch (which matches main):
+
+```bash
+✅ npm ci               # Installed successfully (401 packages)
+✅ npm run lint         # No issues found
+✅ npm run format:check # All files formatted correctly
+✅ npm run typecheck    # No type errors
+✅ npm audit            # 0 vulnerabilities
+✅ npm test             # 54/54 tests passed (4 test files)
+✅ npm run build        # Built successfully in 1.46s
+✅ npm run test:e2e     # 5/5 E2E tests passed in 7.0s
+```
+
+**Result**: The current repository is in excellent health. All CI checks pass.
+
+## Recommendations
+
+### Immediate Actions
+
+1. **Close or reject PR #5** - The ESLint v10 update is premature
+2. **Configure Dependabot** to exclude ESLint major version updates:
+
+```yaml
+# .github/dependabot.yml
+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    ignore:
+      - dependency-name: "eslint"
+        update-types: ["version-update:semver-major"]
+      - dependency-name: "@eslint/js"
+        update-types: ["version-update:semver-major"]
+```
+
+3. **Monitor plugin updates** for ESLint v10 compatibility
+
+### Timeline for ESLint v10 Adoption
+
+| When | Action |
+|------|--------|
+| **Now** | Keep `eslint@^9.39.1` |
+| **2-4 weeks** | Monitor `eslint-plugin-jsx-a11y` and `eslint-plugin-react-hooks` releases |
+| **When compatible** | Verify plugin peerDependencies support `^10` |
+| **After verification** | Update to ESLint v10 in controlled manner |
+
+### Monitoring
+
+Watch these repositories for ESLint v10 support announcements:
+
+- [jsx-eslint/eslint-plugin-jsx-a11y](https://github.com/jsx-eslint/eslint-plugin-jsx-a11y)
+- [facebook/react](https://github.com/facebook/react) (react-hooks plugin)
+
+### Alternative: Force Installation (NOT RECOMMENDED)
+
+While `npm ci --legacy-peer-deps` would bypass the error, this is **not recommended** because:
+
+- ❌ Plugins may have breaking changes with ESLint v10
+- ❌ Unexpected runtime errors could occur  
+- ❌ Undermines the purpose of semantic versioning
+- ❌ Could introduce subtle linting bugs
+
+## Impact Assessment
+
+### Current Impact
+
+- ✅ **Main branch**: Healthy, all checks passing
+- ✅ **Development**: Unaffected, developers can continue work
+- ❌ **PR #5**: Cannot be merged (expected behavior)
+
+### Risk Level
+
+**LOW** - This is working as intended. The dependency conflict prevents us from adopting incompatible versions.
+
+## Conclusion
+
+**No code changes are required.** The repository is in a correct, healthy state. The failing checks on PR #5 are the expected result of attempting to upgrade to ESLint v10 before the plugin ecosystem is ready.
+
+### Key Takeaways
+
+1. ✅ The repository's current dependencies are correct and fully functional
+2. ✅ All CI checks pass with current configuration  
+3. ✅ Security audit shows 0 vulnerabilities
+4. ❌ ESLint v10 is too new for current plugin ecosystem
+5. ⏳ Wait for plugin updates before upgrading ESLint
+
+---
+
+**Action Required**: Close PR #5 with explanation and optionally configure Dependabot to ignore ESLint major version updates.