Known gaps

• Widgets are anywidget-style (jupyter.widget). The classic ipywidgets controls (sliders, dropdowns) are Python classes, so they're not available.

• Inspection tooltips show what's found at runtime (type, signature, preview, properties), not TypeScript types or JSDoc. On Bun, workerd and celld, a getter on the path is reported but not called. History is kept for the current kernel session only.

• The debugger is for Node and Deno targets only. Breakpoints are per line, conditional breakpoints and logpoints aren't supported, variables can't be set from the debugger, and "copy to globals" isn't offered.

• npm: on Node, Bun, workerd and celld:

  • one npm alias per name@range (or exact version, when locked);
  • the cache is shared by every notebook, so peer dependencies resolve by real name from it;
  • a project's own package.json doesn't decide an npm: import's version (bare imports do use its node_modules).

• On Node, a .ts file a cell imports is loaded with Node's own type stripping, which rejects enum, namespace with values and parameter properties. Cells themselves accept them. See Architecture › Imported TypeScript files.

• No type checking. Deno doesn't type-check REPL cells either.

• Results are formatted by each runtime's own inspector: util.inspect on Node, Bun, workerd and celld, and Deno.inspect on Deno. On a fixture of 30 typical values, 23 format identically on Node and Deno. The rest differ in two ways:

  • strings are quoted '…' on Node and "…" on Deno, wherever they appear;
  • a displayed Error's stack also lists Node's own module-loader frames.

  That's deliberate: each runtime's users see the format they expect, and Node's inspector has no quote-style option, short of porting Deno's formatter. test/formatting.test.ts runs both runtimes on the fixture and fails if a new kind of difference appears (#17).

• WebGPU texture and buffer display is dropped.

• On Bun:

  • Interrupting a busy cell restarts Bun and loses state. An awaiting cell keeps it.
  • Top-level declarations are properties of globalThis. A const can be reassigned, and declaring a global's name (const fetch = ...) replaces that global rather than shadowing it.
  • Only a trailing expression statement shows a result: x does, but if (c) { x } doesn't.
  • Bun 1.4 can't import a module whose path contains ?.
  • No --deno-compat namespace.

• On workerd:

  • All cells share one request, so it never ends. Unlike production Workers, there is no per-request CPU or duration limit, and ctx.waitUntil isn't available in a cell.
  • No prompt() or confirm() answers: they return null, as without a stdin channel. jupyter.image(path) can't read files; pass the bytes.
  • Each imported module is bundled with its dependencies. Two imports that share a dependency each get their own copy.
  • Interrupting a busy cell restarts workerd and loses state.
  • Top-level declarations and results behave as on Bun: declarations are globalThis properties, and only a trailing expression shows a result.
  • In a Workers project, main is bundled with esbuild directly, not with wrangler's build. Custom build commands, alias and module rules aren't applied.

• On celld, as on workerd, except:

  • Only the binding and compatibility keys of a project's config are copied. assets, triggers and containers aren't, and neither is .dev.vars. Relative paths inside the copied keys resolve from .celld/cdp-kernel, not from the project.
  • Interrupting a busy cell restarts celld and loses state.