new·The score now tells you which way it movedA brain's exam only ever grows: its own material writes questions, and so does every question a real caller asked and did not get answered. The score is a percentage over that growing set, so a brain that learned more could post a smaller number — and this week three did. One of them answered two MORE questions than the week before and showed eighteen points less. Printed as a single percentage, that reads as decline to a reader and as punishment to anyone who contributes material.all news →
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explore / Backend & APIs / mozg

Bun

Answer questions about Bun as documented today: the runtime APIs with their exact signatures, the bundler and its options, the package manager commands, the test runner, Node.js compatibility and its limits, and the guides — current behaviour, not Node behaviour guessed by analogy.

3,530 notes across 5 brains · updated 2026-08-14 · trained 92%

since last sitting: +92 newly passed — this brain is learning · the verified changelog →

use this brain
# sign in to get a token
$ claude mcp add --transport http mozg \
https://mozg.sh/mcp --header "Authorization: Bearer …"
> use mozg/bun — …
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Ask it things like

answers 92/100 on its latest exam
What are the Bun.listen() and Bun.connect() APIs used for?Runtime APIs — Networking & Sockets✓
What are Bun.spawn() and Bun.spawnSync() used for?Runtime APIs — Shell & Child Processes✓
What is the signature and return type of Bun.sleep()?Runtime APIs — Timing & Delays✓
How does Bun.sleepSync() differ from Bun.sleep()?Runtime APIs — Timing & Delays✓
What minification modes are available in Bun.build?Bundler & Build✓
What does Bun.build() root option do?Bundler & Build✓
What does Bun.build() naming.chunk do?Bundler & Build✓
How does dead code elimination work after macro inlining?Bundler & Build✓

What is inside

asking this brain searches all 4
Bun · BundlerAnswer questions about the Bun bundler: Bun.build and its exact options, loaders, plugins, macros, and the executables and CSS features.408 notes92%Bun · Package managerAnswer questions about bun's package manager exactly as specified: install, add, remove, update, link, publish, x and the rest — each command's flags, workspaces, lockfile and registry configuration.277 notes74%Bun · RuntimeAnswer questions about the Bun runtime exactly as specified: Bun.serve, Bun.file and file I/O, Bun.$ shell, SQLite, WebSockets, TCP, transpiler and every other Bun.* API with its arguments and options, plus Node compatibility details.1522 notes76%Bun · Test runnerAnswer questions about the Bun test runner: writing tests, the expect matchers, mocking, snapshots, coverage, and how it differs from Jest where the docs say so.258 notes88%

What it can answer

100 coverage checks
92%
Answers 92 of the exam's 100 questionsIt answers 92 questions, 92 more than last time, out of an exam that grew by 100.Nothing it used to answer has stopped working.
▲Package Manager18 / 19
▲Bundler & Build10 / 11
▲CSS Bundler10 / 12
▲Runtime APIs — Shell & Child Processes8 / 9
▲Test Runner8 / 10
✓Bundler Loaders5 / 5
✓Runtime APIs — HTTP Server5 / 5
✓Runtime APIs — Networking & Sockets5 / 5
✓Runtime APIs — WebSockets5 / 5
✓Runtime APIs — File I/O & Streams4 / 4
✓Runtime APIs — Memory & Binary4 / 4
✓Runtime APIs — Timing & Delays4 / 4
✓Runtime APIs — Compression3 / 3
▲Runtime APIs — Hashing & Random3 / 4
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Attacks survived

re-run weekly · 2026-08-10
✓gate-battery12/12 known hostile payloads caught by the ingest gate
✓injection-corpusevery active note scanned — no steering language
✓secret-corpusevery active note scanned — no keys or credentials

heuristic scans against known attack classes — measured and dated, not a promise of unpoisonability

Inside

  • bun build --format supported values · bundler & build
  • bun build --chunk-naming replaces esbuild --chunk-names · bundler & build
  • Bun bundler performance vs esbuild · bundler & build
  • bun build --external syntax differs from esbuild · bundler & build
  • bun build does not support syntactic down-leveling · bundler & build
  • bun build --asset-naming replaces esbuild --asset-names · bundler & build
  • Bun bundler bundles by default · bundler & build
  • Bun bundler has no built-in development server · bundler & build
  • CLI flag syntax differences between esbuild and bun build · bundler & build
  • bun build --define syntax differs from esbuild · bundler & build
  • bun build --loader syntax and supported loaders differ from esbuild · bundler & build
  • bun build --target replaces esbuild --platform · bundler & build
  • bun build --no-bundle disables bundling · bundler & build
  • bun build --entry-naming replaces esbuild --entry-names · bundler & build

Licence

CC BY-NC-SA 4.0

Use it, copy it, build on it, with credit. Selling it is not allowed.