# System map — koajs/koa

> Canonical page: https://codevetter.com/unpack/koa/system-map

# System map — koajs/koa

Scanned commit 824c1cf8de9a91a2941973b25dc8a3d3029b9e4f (2026-09-18). Generated by codevetter codevetter 1.15.0 on 2026-10-02.

Source inspection; upstream code and tests were not executed.

The runtime centers on an EventEmitter-based Application and three linked HTTP wrapper prototypes. Consumers instantiate the library and choose their server and middleware stack. Packaging, CI, and publishing are separate from request execution.
- package.json identifies koa 3.2.1, requires Node >=18, resolves CommonJS to lib/application.js, and resolves ESM to generated dist/koa.mjs. — [package.json#L2-15](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/package.json#L2-L15) [package.json#L65-70](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/package.json#L65-L70)
- Application extends EventEmitter; its constructor owns middleware, settings, and application-specific context/request/response prototypes. — [lib/application.js#L66-100](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L66-L100)
- listen() wraps callback() in http.createServer(); callback() can also be supplied to consumer-created HTTP or HTTPS servers. — [lib/application.js#L128-132](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L128-L132) [docs/api/index.md#L126-145](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/docs/api/index.md#L126-L145)
- createContext() connects the Node req/res pair to context, request, and response wrappers, records originalUrl, and creates a fresh state object. — [lib/application.js#L228-243](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L228-L243) [lib/context.js#L195-213](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/context.js#L195-L213)
- Request handling delegates middleware composition to koa-compose, completion detection to on-finished, and response streaming to Node Stream.pipeline. — [lib/application.js#L14-16](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L14-L16) [lib/application.js#L182-219](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L182-L219) [lib/application.js#L334-343](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L334-L343)
- The core state boundary is request-local ctx.state and optional AsyncLocalStorage; the documented database integration is a consumer-supplied app.context.db reference. — [lib/application.js#L192-204](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L192-L204) [lib/application.js#L241-242](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/lib/application.js#L241-L242) [docs/api/index.md#L195-210](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/docs/api/index.md#L195-L210)
- npm scripts provide node --test, c8 coverage, Standard linting, and gen-esm-wrapper building; prepare invokes the build, and published files include dist and lib. — [package.json#L17-25](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/package.json#L17-L25) [package.json#L68-70](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/package.json#L68-L70)
- CI installs, lints, measures coverage, and uploads to Codecov; a separate tag/manual workflow installs and publishes to npm with id-token permission. — [.github/workflows/node.js.yml#L14-30](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/.github/workflows/node.js.yml#L14-L30) [.github/workflows/npm-publish.yml#L15-31](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/.github/workflows/npm-publish.yml#L15-L31) [.github/workflows/npm-publish.yml#L37-50](https://github.com/koajs/koa/blob/824c1cf8de9a91a2941973b25dc8a3d3029b9e4f/.github/workflows/npm-publish.yml#L37-L50)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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