# Behavior traces — honojs/hono

> Canonical page: https://codevetter.com/unpack/hono/behavior-traces

# Behavior traces — honojs/hono

Scanned commit f23b146afcec63606144cde50b5fbd360dd60238 (2026-10-01). Generated by codevetter codevetter 1.15.0 on 2026-10-02.

Source inspection; upstream code and tests were not executed.

Source reads followed registration and first-request routing, validated requests, cache persistence, Lambda translation and static generation. These traces describe function order and branches rather than executed observations. The default router becomes fixed after its first match. SSG executes application handlers as part of both route discovery and output production.
- Startup registration: new Hono() calls HonoBase's constructor, initializes registration functions, selects SmartRouter, and app.get()/use() call #addRoute() to append metadata and router entries. — [src/hono.ts#L26-32](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono.ts#L26-L32) [src/hono-base.ts#L127-175](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L127-L175) [src/hono-base.ts#L388-399](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L388-L399)
- First request: fetch() → #dispatch() → getPath() → SmartRouter.match(); SmartRouter replays stored routes into candidates, skips UnsupportedPathError, and replaces match with the selected router's bound implementation. — [src/hono-base.ts#L420-429](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L420-L429) [src/hono-base.ts#L481-487](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L481-L487) [src/router/smart-router/router.ts#L21-60](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/router/smart-router/router.ts#L21-L60)
- Single-handler GET: #dispatch() invokes the handler directly; a returned Response is delivered and Promise rejection reaches #handleError(). For a Promise resolving without a response, a finalized Context returns c.res; otherwise notFound is used. A synchronous nullish return falls back to notFound. — [src/hono-base.ts#L431-449](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L431-L449) [src/hono-base.ts#L401-406](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L401-L406)
- Validated POST: compose.dispatch() invokes validator('json') → req.json() → cached text → JSON.parse() → validationFunc(); transformed output enters addValidatedData(), next() reaches the handler, and c.json() serializes its response. — [src/compose.ts#L42-49](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/compose.ts#L42-L49) [src/validator/validator.ts#L93-103](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/validator/validator.ts#L93-L103) [src/validator/validator.ts#L162-170](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/validator/validator.ts#L162-L170) [src/request.ts#L258-260](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/request.ts#L258-L260)
- Malformed JSON: validator catches body parsing failure and throws HTTPException(400); compose catches Error instances and passes them to onError, while the default handler uses getResponse(). — [src/validator/validator.ts#L98-103](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/validator/validator.ts#L98-L103) [src/compose.ts#L47-58](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/compose.ts#L47-L58) [src/hono-base.ts#L35-41](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/hono-base.ts#L35-L41)
- Cache hit: cache middleware checks method and Authorization, computes a QUERY digest when needed, generates the key, opens caches, matches it and returns a new Response without calling downstream handlers. — [src/middleware/cache/index.ts#L266-304](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/middleware/cache/index.ts#L266-L304)
- Cache miss and persistence: cache.match() misses → await next() → status/Vary/Cache-Control/Set-Cookie checks → response.clone() → awaited cache.put() or executionCtx.waitUntil(cache.put()). — [src/middleware/cache/index.ts#L72-80](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/middleware/cache/index.ts#L72-L80) [src/middleware/cache/index.ts#L300-322](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/middleware/cache/index.ts#L300-L322)
- Lambda request: handle(app) chooses getProcessor(), calls createRequest(), passes event/requestContext/lambdaContext to app.fetch(), then calls createResult(); request-construction TypeErrors become 400 results. — [adapters/aws-lambda/src/handler.ts#L256-278](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/adapters/aws-lambda/src/handler.ts#L256-L278) [adapters/aws-lambda/src/handler.ts#L322-345](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/adapters/aws-lambda/src/handler.ts#L322-L345) [adapters/aws-lambda/src/handler.ts#L348-389](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/adapters/aws-lambda/src/handler.ts#L348-L389)
- Static generation: toSSG() combines hooks → fetchRoutesContent() filters routes and calls app.fetch() for metadata → parameter expansion calls app.request() → response hooks transform/filter content → saveContentToFile() creates directories and writes files. — [src/helper/ssg/ssg.ts#L225-250](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/ssg/ssg.ts#L225-L250) [src/helper/ssg/ssg.ts#L260-289](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/ssg/ssg.ts#L260-L289) [src/helper/ssg/ssg.ts#L310-334](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/ssg/ssg.ts#L310-L334) [src/helper/ssg/ssg.ts#L421-451](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/ssg/ssg.ts#L421-L451)
- SSE output: streamSSE() constructs TransformStream/SSEStreamingApi, sets protocol headers and starts run(); callback writeSSE() escapes line structure and writes framed events, and run() closes the stream in finally. — [src/helper/streaming/sse.ts#L18-45](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/streaming/sse.ts#L18-L45) [src/helper/streaming/sse.ts#L48-68](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/streaming/sse.ts#L48-L68) [src/helper/streaming/sse.ts#L73-100](https://github.com/honojs/hono/blob/f23b146afcec63606144cde50b5fbd360dd60238/src/helper/streaming/sse.ts#L73-L100)

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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