Create Evlog Framework Integration

Create evlog Framework Integration

Add a new framework integration to evlog. The recommended path is the manifest mode built on defineFrameworkIntegration from evlog/toolkit, for any framework with a request/response middleware shape. For frameworks with a fundamentally different lifecycle you'll fall back to the lower-level createMiddlewareLogger.

Two paths

• Manifest mode (preferred, ~30–80 lines of glue). Call defineFrameworkIntegration({ name, extractRequest, attachLogger, storage? }) once at module level, then write a tiny middleware that calls integration.start(ctx, options) and runs the framework's next() inside runWith. Reference implementations: all of packages/evlog/src/{hono,express,fastify,elysia,nestjs,orpc,react-router,sveltekit,workers}/index.ts use it.
• Custom mode: use createMiddlewareLogger directly when the framework's lifecycle doesn't fit a standard middleware. Current custom-mode integrations: Next.js (src/next/), Nitro v2/v3 (src/nitro/, src/nitro-v3/), Eve (src/eve/).

Manifest mode now covers all classic HTTP frameworks. Use custom mode only when you can't extract a request synchronously at the start of the lifecycle (server actions, module-level hooks, agent turns).

Required API surface (from AGENTS.md)

Every framework integration must expose:

1. evlog() middleware/plugin accepting the full BaseEvlogOptions (drain, enrich, keep, include, exclude, routes, plugins)
2. useLogger() (ALS-backed). Workers is the one sanctioned exception (ALS needs a compat flag there; defineWorkerFetch attaches the logger instead)
3. log.fork() support (automatic when storage is provided to the manifest)
4. The framework-native accessor (c.get('log'), req.log, event.locals.log, …)

PR Title

feat({framework}): add {Framework} middleware integration

Scope timing caveat: the semantic PR check reads its scope list from the base branch, so a brand-new scope can't validate the very PR that introduces it. Either register the scope in a small preceding PR, or use an unscoped title (feat: add {Framework} middleware integration) on the introducing PR.

Touchpoints Checklist

Important: Do NOT consider the task complete until all 15 touchpoints have been addressed.

Naming Conventions

Shared Utilities

All integrations share the same core utilities. Never reimplement logic that exists in shared/. These are also publicly available as evlog/toolkit for community-built integrations (see Custom Integration docs).

defineFrameworkIntegration automatically:

• normalizes both Web Headers and Node IncomingHttpHeaders (so you don't need to pick a header extractor)
• generates a requestId when none is present
• calls createMiddlewareLogger and surfaces its { logger, finish, skipped, middlewareOptions }
• attaches log.fork() automatically when storage is provided
• exposes runWith(fn) to run downstream handlers inside the integration's ALS
• forwards waitUntil when the runtime provides one (Workers, Hono on Workers)

Step 1: Integration Source

Create packages/evlog/src/{framework}/index.ts.

Template Structure (manifest mode)

import type { AuditableLogger } from '../audit'
import { defineFrameworkIntegration } from '../shared/integration'
import type { BaseEvlogOptions } from '../shared/middleware'
import { createLoggerStorage } from '../shared/storage'

const { storage, useLogger } = createLoggerStorage(
  'middleware context. Make sure the evlog middleware is registered before your routes.',
  'evlog:{framework}',
)

export type Evlog{Framework}Options = BaseEvlogOptions
export { useLogger }

// Type augmentation for typed logger access (framework-specific):
// - Express: declare module 'express-serve-static-core' { interface Request { log: AuditableLogger } }
// - Hono:    export type EvlogVariables = { Variables: { log: AuditableLogger } }

const integration = defineFrameworkIntegration<{Framework}Context>({
  name: '{framework}',
  extractRequest: (ctx) => ({
    method: /* ctx.method */,
    path: /* ctx.path */,
    headers: /* Web Headers OR Node headers OR plain object */,
    requestId: /* x-request-id header or undefined → auto-generated */,
  }),
  attachLogger: (ctx, logger) => {
    // Store in framework-idiomatic location:
    // - Hono:    c.set('log', logger)
    // - Express: req.log = logger
  },
  storage,
})

export function evlog(options: Evlog{Framework}Options = {}): FrameworkMiddleware {
  return async (ctx, next) => {
    const { skipped, finish, runWith } = integration.start(ctx, options)
    if (skipped) {
      await next()
      return
    }
    try {
      await runWith(() => next())
      await finish({ status: /* extract status from ctx */ })
    } catch (error) {
      await finish({ error: error as Error })
      throw error
    }
  }
}

Reference Implementations

• Hono: src/hono/index.ts. c.set('log', logger) + ALS useLogger(), streaming deferral via shouldDeferEmitForResponse, waitUntil detection
• Express: src/express/index.ts. req.log, ALS storage, res.on('finish') for terminal status
• Fastify: src/fastify/index.ts. Fastify hooks (onRequest / onResponse / onError), fastify-plugin wrapper
• Elysia: src/elysia/index.ts. Plugin with .derive({ as: 'global' }), storage.enterWith-style ALS, streaming deferral
• NestJS: src/nestjs/index.ts. EvlogModule.forRoot() / forRootAsync() on top of the manifest
• oRPC: src/orpc/index.ts. evlog() procedure middleware + withEvlog(handler) wrapper
• React Router: src/react-router/index.ts. loggerContext = createContext<AuditableLogger>()
• SvelteKit: src/sveltekit/index.ts. evlog() handle + evlogHandleError() + createEvlogHooks()
• Workers: src/workers/index.ts. defineWorkerFetch / withEvlog, no ALS useLogger() (compat-flag constraint)

Key Architecture Rules

1. Prefer defineFrameworkIntegration: it handles header normalization, request-id generation, ALS, fork attachment, and waitUntil.
2. Status / error reporting stays framework-side: call finish({ status }) on success and finish({ error }) on failure. finish runs emit + enrich + drain + plugin hooks.
3. Re-throw errors after finish({ error }) so the framework's own error handler still runs.
4. Streaming responses: if the framework can return streaming bodies, defer the emit until the stream closes (shouldDeferEmitForResponse; see Hono and Elysia).
5. Framework SDK is an optional peer dependency: never bundle it.
6. Never duplicate pipeline logic: runEnrichAndDrain is internal to createMiddlewareLogger/finish.
7. Export type helpers for typed context access (e.g., EvlogVariables for Hono).

When to fall back to custom mode

Use createMiddlewareLogger directly (skipping defineFrameworkIntegration) when:

• The middleware doesn't have a clear "request entry / response exit" pair (Next.js App Router server actions, Eve agent turns).
• Logger creation spans multiple lifecycle phases owned by a module system (Nitro plugins + hooks).
• The status is not knowable until after the response stream completes and the framework gives you no hook for it.

Step 2: Build Config

Add a build entry in packages/evlog/tsdown.config.ts:

'{framework}/index': 'src/{framework}/index.ts',

Also add the framework SDK to the external array (e.g., 'elysia', 'fastify').

Step 3: Package Exports

In packages/evlog/package.json:

In exports (after the last framework entry):

"./{framework}": {
  "types": "./dist/{framework}/index.d.mts",
  "import": "./dist/{framework}/index.mjs"
}

In typesVersions["*"]: "{framework}": ["./dist/{framework}/index.d.mts"]

In peerDependencies (version range) + peerDependenciesMeta ("optional": true), and add the framework name to keywords.

Exports without matching tsdown.config.ts entries fail test/toolkit/api-surface.test.ts.

Step 4: Tests

Create packages/evlog/test/frameworks/{framework}.test.ts. Read packages/evlog/test/README.md first, especially the Framework runtime fidelity table.

Two non-negotiables:

1. Real request driver. Use the framework's own driver: supertest (Express/NestJS), app.request() (Hono), app.inject() (Fastify), app.handle(new Request(...)) (Elysia). If no Node-friendly driver exists, call the user-facing contract directly with realistic input shapes (see the SvelteKit and React Router tests). Never extract internals to test a substitute.
2. Wire the shared matrix. Call describeStandardHttpMatrix({ name, mount }) from test/helpers/frameworkMatrix.ts. It covers the standard sweep (event emission, x-request-id, route service) for every HTTP framework.

On top of the matrix, cover the framework-specific surface:

1. Framework-native accessor returns the logger (c.get('log'), req.log, …)
2. Error handling. Errors captured, event has error level + details, error re-thrown
3. Route filtering. Skipped routes don't create a logger, skip drain/enrich
4. Context accumulation. logger.set() data appears in the emitted event
5. Drain / enrich / keep callbacks (use createPipelineSpies(), assertHttpEventEmitted, waitForDrainCalls, findEventViaDrain from test/helpers/framework.ts)
6. Drain/enrich error resilience. Errors there never break the request
7. useLogger(): same logger as the native accessor, works across async boundaries, throws outside context. Skip it for an integration without ALS, and test the accessor it ships instead: on Workers that is the handler's fourth argument, from defineWorkerFetch / withEvlog
8. Streaming (if applicable). Event deferred until the body closes

Use fake timers for anything time-based; defined() instead of !.

Step 5: Framework Docs Page

Create apps/docs/content/4.integrate/frameworks/{NN}.{framework}.md with a comprehensive, self-contained guide. Check existing files for the next zero-padded number.

Frontmatter:

---
title: {Framework}
description: Using evlog with {Framework} — automatic wide events, structured errors, drain adapters, enrichers, and tail sampling in {Framework} applications.
navigation:
  title: {Framework}
  icon: i-simple-icons-{framework}
links:
  - label: Source Code
    icon: i-simple-icons-github
    to: https://github.com/evloghq/evlog/tree/main/examples/{framework}
    color: neutral
    variant: subtle
---

Sections (follow the Express/Hono/Elysia pages as reference):

1. Quick Start: install + register middleware (copy-paste minimum setup)
2. Wide Events: progressive log.set() usage
3. useLogger(): accessing the logger from services without passing the request, or, for an integration without ALS, the accessor it ships in its place
4. Error Handling: createError() + parseError() + framework error handler
5. Drain & Enrichers: middleware options with inline example
6. Pipeline (Batching & Retry): createDrainPipeline example
7. Tail Sampling: keep callback
8. Route Filtering: include / exclude / routes
9. Client-Side Logging: HTTP drain (evlog/http) (only if the framework has a client-side story)
10. Run Locally: clone + pnpm example {framework}
11. Card group linking to GitHub source

Step 6: Overview & Installation Cards

In apps/docs/content/4.integrate/frameworks/00.overview.md:

1. Add a row to the Overview table: framework name, import, type, logger access, status
2. Add a card in the appropriate section, and a row in the API cheat sheet if the bootstrap/access pattern is new

In apps/docs/content/1.start/3.installation.md: add a card in the "Choose Your Framework" ::card-group, in the same order as the frameworks overview.

Step 7: Landing Page

In apps/docs/content/0.landing.md, find the FeatureFrameworks MDC section (slots #nuxt, #nextjs, #hono, …) and add a new slot:

  #{framework}
  ```ts [src/index.ts]
  // Framework-specific code example showing evlog usage

## Step 8: FeatureFrameworks Component

Update `apps/docs/app/components/features/FeatureFrameworks.vue`:

1. Add the framework to the `frameworks` array with its icon and the next available `tab` index
2. Add a `<div v-if="activeTab === {N}">` with `<slot name="{framework}" />` in the template

Icons use Simple Icons format: `i-simple-icons-{name}`.

## Step 9: Update the Public Skill

In `skills/review-logging-patterns/SKILL.md` (published on evlog.dev):

1. Add `### {Framework}` in the **"Framework Setup"** section, in the same order as the docs
2. Include: import + `initLogger` + middleware setup; native logger access; a `useLogger()` snippet, or the accessor that replaces it when the integration has no ALS; full pipeline example (`drain`, `enrich`, `keep`)
3. Update the `description:` line in the YAML frontmatter to mention the new framework name

## Step 10: Update README

In `packages/evlog/README.md` (root `README.md` is a symlink):

1. Add a `## {Framework}` section near the other framework sections with a minimal setup snippet and a link to the example app
2. Add a row to the **Framework Support** table

Keep the snippet short: init, register middleware, one route handler showing logger access.

## Step 11: Example App

Create `examples/{framework}/` with a runnable app demonstrating all evlog features. It is auto-discovered by the root runner: `pnpm example {framework}` (which loads the root `.env` via dotenv, so no root `package.json` change is needed).

The app must include:

1. **`evlog()` middleware** with `drain` (PostHog) and `enrich` callbacks
2. **Health route**: basic `log.set()` usage
3. **Data route**: context accumulation with user/business data, using `useLogger()` in a service function, or the integration's own accessor when it has no ALS
4. **Error route**: `createError()` with status/why/fix/link
5. **Error handler**: framework's error handler with `parseError()` + manual `log.error()`
6. **Test UI**: served at `/`, a self-contained HTML page with buttons to hit each route and display JSON responses

**Drain must use PostHog** (`createPostHogDrain()` from `evlog/posthog`). `POSTHOG_API_KEY` is set in the root `.env` (maintainer's key, not committed), so every example exercises a real external drain. Without the env var the drain resolves to `null` and skips, so someone cloning the repo sends nothing anywhere unless they opt in with their own key. Enable pretty printing for readable local output.

**Type the `enrich` callback parameter explicitly**, as `(ctx: EnrichContext) => ...` with `type EnrichContext` imported from `evlog`.

### Test UI

Reference: `examples/hono/src/ui.ts`, a single `src/ui.ts` exporting `testUI()` returning a self-contained dark-theme HTML string (route list with method badges, click-to-fetch, JSON display, status colors, response time). Register the `/` route **before** the evlog middleware so it isn't logged.

### Required files

| File | Purpose |
|------|---------|
| `src/index.ts` | App with all features demonstrated |
| `src/ui.ts` | Test UI |
| `package.json` | `dev` and `start` scripts (`bun --watch src/index.ts` / `bun src/index.ts`) |
| `tsconfig.json` | TypeScript config (if needed) |
| `README.md` | How to run + link to the UI |

There is also `examples/community-framework-skeleton/` showing the community-facing (toolkit-only) variant, so keep it in mind if the new integration changes the toolkit contract.

## Step 12: Changeset

Create `.changeset/{framework}-integration.md`:

```markdown
---
"evlog": minor
---

feat({framework}): add {Framework} middleware integration (`evlog/{framework}`) with automatic wide-event logging, drain, enrich, and tail sampling support

Step 13: PR Scopes

Add {framework} to the scopes list in .github/workflows/semantic-pull-request.yml and to the Scopes section of .github/pull_request_template.md, in alphabetical order. Remember the timing caveat from the PR Title section: this registration only takes effect for PRs whose base branch already contains it.

Verification

After a clean install, run pnpm run dev:prepare from the repo root first, then:

pnpm run dev:prepare
cd packages/evlog
pnpm run build    # required before test — api-surface snapshot is gated on dist/
pnpm run test
pnpm run lint

Then type-check the example:

cd examples/{framework}
pnpm exec tsc --noEmit