Core Changes

• Move config.turbopack.moduleIds to config.experimental.turbopackModuleIds: #84230
• Show invalid default export errors during prerendering: #84242
• fix: make sure caller exists in babel preset: #84154
• [mcp] allow to enable mcp server through env var: #84278
• fix(metadata): make formatDetection respect true/false properly: #83924
• Upgrade React from b0c1dc01-20250925 to df38ac9a-20250926: #84276
• Add a --webpack flag and default --turbopack to true: #84216
• fix: Update URL resolution logic to handle search parameters on root path /?foo=bar: #78262
• [Breaking] Remove deprecated sync access to Dynamic APIs: #84179

Misc Changes

• Turbopack: Scope with work queue: #84225
• [test] Make Undefined default export an e2e test suite: #84240
• [turbopack] Conditionally create pages router data endpoints.: #84194
• Turbopack: parallel connect children: #84173
• Turbopack: count turbo_tasks::run as foreground tasks to avoid being idle: #84245
• Turbopack: make persistent caching log line more clear: #84262
• Turbopack: make tracing nicer: #84263
• docs:Small improvement on the contribution guide for clarity: #84200
• Turbopack: Remove not-very-useful "Finished writing to disk in" log line: #84244
• Turbopack: follow up changes from parallel children: #84219
• [turbopack] Simplify take_issues and peek issues: #84199
• Update Rspack development test manifest: #84260
• Update Rspack production test manifest: #84259

Credits

Huge thanks to @devjiwonchoi, @sokra, @unstubbable, @lukesandberg, @FelipeChicaiza, @bgw, @kevva, @huozhi, @m1abdullahh, @vercel-release-bot, and @F7b5 for helping!