[Greaker]

What

Moves nb-bond-api's test-transform toolchain to Babel 8: @babel/core 7.29.7 → 8.1.0 and @babel/preset-env 7.29.5 → 8.0.7, with babel-jest staying at 30.5.2. Supersedes #346, which only bumped the preset and cannot work alone (preset-env 8 peer-requires core 8).

Why the root package.json gains a dev dependency

babel-jest 30.5.2 accepts core 7 or 8 as a peer. With only the workspace bumped, npm hoists jest's own @babel/core 7 to the root, babel-jest resolves that copy, and the Babel 8 preset loads under core 7 (it happens to transform correctly here because the target is the current Node, but the pairing is unsupported). Pinning @babel/core 8.1.0 in the root devDependencies makes npm hoist core 8 instead, so babel-jest and the workspace share one Babel 8 copy.

An overrides entry on babel-jest was tried and rejected: it cascades into @jest/transform, which would then run on core 8 without being supported there (npm ls reports it invalid).

Resulting tree

• One @babel/core 8.1.0, shared by the workspace and babel-jest.
• Nested @babel/core 7.29.13 copies stay under @jest/transform, jest-config, jest-snapshot, istanbul-lib-instrument and eslint-plugin-react-hooks, which depend on core 7 directly. This is the unavoidable duplicate; npm ls reports the tree clean. @vitejs/plugin-react 6 no longer depends on Babel, so the old reason for deferring the upgrade no longer applies.
• Lockfile: re-resolved by removing only the Babel-related entries and letting npm rebuild them, so every non-Babel entry is unchanged. The new transitive packages are Babel 8's own (@jridgewell/gen-mapping beta, @types/gensync, @types/jsesc, empathic, flru, import-meta-resolve, js-tokens 10, verkit, and refreshed regexpu-core / regenerate / babel-plugin-polyfill-corejs3 1.0.0); resolve 1.22.12 and babel-plugin-polyfill-corejs2 / -regenerator drop out. The diff is large because npm moves the Babel entries; the package set is as above.

Babel 8 breaking changes against this repo

• Node floor ^22.18.0 || >=24.11.0: the repo pins Node 26.12.1.
• ESM-only packages: the only Babel config is services/nb-bond-api/babel.config.cjs (a plain preset-env entry with targets: { node: 'current' }), which Babel 8 still loads; no removed options are used.
• No other workspace uses Babel.

Verification

• nb-bond-api: lint, prettier --check, build, jest 39 suites / 293 tests (also with --no-cache).
• nb-ui: lint, prettier --check, build, vitest 27 files / 139 tests.
• npm ci from the committed lockfile; license inventory, node-version, image-hash-input, hygiene and link checks pass.
• npm audit: 5 low before, 5 low after (all the existing deepmerge / jest chain).

Rollout impact

Dev-only toolchain. The nb-bond-api and nb-ui image content hashes include the root manifest and lockfile, so both images rebuild once under new tags on the next local start; runtime code is unchanged.

docs/KNOWN_ISSUES.md: the "Babel 8 upgrade deferred" entry is replaced by a description of the resulting layout.