[Floating-Y]

Opening a standalone Block preview still imports every Block's raw source and transforms the entire registry, even before Code is opened.

Keep the literal metadata registry and lazy preview components lightweight. Import a separate source module only when Code opens, then load and transform that Block's files and required shared overview. Cache in-flight and successful results; remove failed requests from the cache. The Code panel shows loading/error/retry feedback and ignores results after unmount. File selection survives Preview → Code.

Preserves page-first order, displayed paths, copied contents, shared overview and its note, import rewriting, page metadata-export cleanup, preview behavior and install commands. No dependency or general loading framework added. Metadata parsing and registry generation remain unchanged.

Based on upstream dev daa7cf1 in a separate worktree; the original local route-loading branch was untouched. Checked upstream PRs: #59 separates the preview route; #32/#33 cover rewriting and metadata. None removes this eager source loading.

Validation

• Ubuntu CI web passed for commit 082d943: locked install, both regression suites, unmodified docs generation, registry consistency, typecheck and production build.

• node --test scripts/block-metadata.test.mjs: 8 passed.

• node --test scripts/block-sources.test.mjs: 4 passed. Executes real transpiled modules with mocked Vite glob boundaries; covers preview without source imports, selected Block/shared files, order/paths/transformations, own Block paths, concurrent/success reuse, failure and retry. Added to existing CI.

• npm run typecheck: passed.

• Docs/registry generation and production build passed with temporary Windows adaptations described below. Direct node node_modules/vite/bin/vite.js build --manifest passed too.

• registry.json, build scripts, dependencies and lockfile have no changes. Full diff and git diff --check reviewed. Commit is DCO signed off.

Production browser evidence

Served production files from fresh localhost origins with Cache-Control: no-store; recorded server requests and mapped built URLs through Vite's manifest.

• Cold /view/sidebar-07 and initial /blocks: 0 Block raw-source requests and 0 source-loader requests.
• Opening sidebar-07 Code: exactly its 6 files plus shared/overview.tsx; no other Block source.
• Recursive static-import closures for the HTML entry, standalone preview and Blocks page: 0 raw chunks, no source-loader module.
• Returned HTTP 503 once for a login raw chunk, separately for the source-loader module. Both show a local error; Retry sends a fresh request returning 200 and renders the source.
• Delayed an own Block source by 10 seconds, switched to Preview and another category: replacement panels show no stale source. Returning and reopening Code reuses the result, with one raw request total.
• Checked dark/light previews and sidebar interaction, file switching, overview, Copy and retained selection after reopening Code. Copied overview text exactly matches the original file with the existing CodeBlock trailing-newline handling; display comparison accounts for HTML newline normalization.

These are dependency/request observations, not measured compressed-transfer or load-time savings. No source-text byte total is presented as network savings.

Local Windows limitation

Unmodified npm run docs and npm run build were run and fail in the existing documentation generator on Windows/Node 22.15.0: CRLF heading parsing, then Windows paths producing an invalid slug. Registry generation also needs a Windows-compatible npx invocation.

For local generation/build verification only, normalized MDX line endings, temporarily normalized the slug path separator and invoked npx.cmd with a shell. Both script adaptations and content changes were restored before committing. This does not claim that the unmodified standard build passes locally; The Ubuntu CI run linked above passed the unmodified standard commands.

Firefox/Safari, physical devices, deployed compression and a before/after transfer benchmark were not tested. Do not auto-merge.