Migrate to Babel 8 (@babel/core / preset-react / preset-typescript 8.x)

[steilerDev]

Context

Dependabot repeatedly proposes bumping @babel/core, @babel/preset-react, @babel/preset-typescript from 7.x to 8.x (most recently in #1796). A naive 3-package bump breaks the client webpack build: @babel/preset-typescript@8 stops stripping TS types, so raw TypeScript reaches webpack's parser (37 × "Module parse failed: Unexpected token"). #1822 holds these three at 7.29.7 while taking the rest of the dev-dependency group.

Why it needs a dedicated migration

A coherent Babel 8 install requires migrating the entire Babel graph in one coordinated change, not just the 3 top-level packages:

• Transitive @babel/preset-env polyfill providers (babel-plugin-polyfill-corejs2/3, @babel/helper-define-polyfill-provider, @babel/preset-modules) currently declare peer @babel/core ^7.4.0 || ^8.0.0-0 <8.0.0 — i.e. they exclude stable Babel 8.
• Jest 30's Babel internals (babel-jest, babel-preset-current-node-syntax) must publish core-8-compatible peers first.
• Babel 8 raises the Node engine floor to ^22.18.0 || >=24.11.0 — pin .nvmrc/Dockerfile accordingly (currently bare 24).
• Preset config review: @babel/preset-typescript may need allowDeclareFields: true; @babel/preset-react runtime must be explicit (already set to automatic in client/webpack.config.cjs).

Acceptance

• Whole Babel graph on 8.x with no duplicate @babel/core@7 hoisted
• npm run build (client) and npm test (Jest) green
• Lockfile regenerated via full npm install
• Node engine floor pinned

References

• Superseded PR: chore(deps-dev): bump the dev-dependencies group across 1 directory with 13 updates #1796 · Partial bump: chore(deps-dev): bump dev-dependencies group, hold @babel/* (supersedes #1796) #1822
• Babel 8 migration guide: https://raw.githubusercontent.com/babel/website/main/docs/v8-migration.md

🤖 Filed by `/dependabot`

[steilerDev]

[orchestrator] Attempted during the 2026-07-06 batch run — BLOCKED, issue stays open. The ecosystem peers cited at filing time HAVE resolved (polyfill providers 1.0.0, babel-jest 30.4.1, preset-env 8.0.2 all accept core 8), but two deeper blockers were found:

1. Upstream Babel 8.0.0/8.0.1 regression: @babel/plugin-transform-typescript@8.0.0 fails to strip type arguments from call/new expressions (foo<T>(x), new Foo<T>(x)) while stripping ordinary annotations fine — isolated with a minimal transformSync repro, no webpack involved. This exactly matches the 37 client build errors (every one is a useState<T>()-style generic call). No 8.0.2+ exists yet.
2. Structural workspace peer-hoisting conflict: docs/ (Docusaurus → @docusaurus/babel, @svgr/webpack) keeps @babel/core@7 hoisted at the repo root; babel-loader (root-hoisted, core as a peerDependency) resolves core from its own physical location and therefore always binds to the root's 7.x — never the client's nested 8.x. npm overrides cannot force peer placement (three variants tried, incl. clean reinstall). A client-only coherent Babel 8 graph is impossible in this npm-workspaces layout while docs stays on Babel 7.

Re-check triggers: (a) a Babel patch >8.0.1 fixing call/new-expression type-argument stripping (watch changelogs), AND (b) either Docusaurus/svgr moving off Babel 7, babel-loader making core a real dependency, or migrating the docs toolchain in the same change (much larger blast radius).

Node engine floor pins (.nvmrc/Dockerfile → 24.11) were prepared but reverted with everything else — the tree is back to the verified-green Babel 7 baseline (npm run build + client jest confirmed). Keep holding @babel/* at 7.29.7 in Dependabot (#1822 policy stands).