log.audit({
  action: 'invoice.refund',
  actor: { type: 'user', id: user.id },
  target: { type: 'invoice', id: invoice.id },
  outcome: 'success',
})

npm install evlog

undefined

Useful flags: `--framework` (override detection: `nuxt`, `nitro`, `next`, `tanstack-start`, `hono`, `express`, `fastify`), `--prodDrain` (comma-separated: `axiom`, `otlp`, `posthog`, `sentry`, `better-stack`, `datadog`, `hyperdx`, `sazabi`, `loki`, `clickhouse`), `--extras` (`enrichers`, `pipeline`, `sampling`, `vite`, `error-catalog`, `audit-catalog`, `ai`, `better-auth`), `--enrichers`, `--sampling` (traffic tier: `all`, `low`, `medium`, `high`, `very-high`), `--apps` (monorepo: which workspace packages), `--no-install`. Review the `--dry-run` output with the user before applying. Docs: https://www.evlog.dev/cli/init

npx evlog map --no-write

What you get:

- A project score and which entry points are still dark
- **FIX FIRST**: the three most valuable places to fix
- **GOING FURTHER**: opportunities (catalogs, audit coverage, AI logging, auth identity) that never cost points
- Per-file inspect: `npx evlog map <file> --no-write` shows the shape the handler could take
- Re-run after fixes and watch the score move

Work FIX FIRST in order, keep changes minimal (`useLogger()`, `log.set()`, `log.audit()`, `createError({ why, fix })`), then re-run with `--no-write`. Omit `--no-write` only when the user wants `evlog.map.json` written.

undefined

`--baseline` compares the fresh scan against the committed `evlog.map.json`, **per entry point and per requirement**, so a refactor that instruments one route and breaks another fails even if the total score is unchanged. Disabling a passing check with a comment counts as a regression too. New uninstrumented routes are listed as `NEW AND DARK` without failing. Workflow: commit `evlog.map.json` once, add the `--baseline` run to CI, then re-run `map` without `--baseline` to accept an intentional change. Docs: https://www.evlog.dev/cli/ci

When the project has an `evlog.config.ts`, the gate can live there instead of in the CI step: `map: { minScore: 80, baseline: true }` makes a bare `evlog map` gate the same way, and a flag still wins. The same `map` block turns checks off for every entry point (`rules: { 'error-catalog': 'off' }`) and leaves entry points out by file glob (`ignore`). The CLI reads these values without running the file, so they must be literals. Docs: https://www.evlog.dev/cli/config

Early days: adapters and rules are still evolving; expect scores to move between releases. Docs: https://www.evlog.dev/cli/map · Rules: https://www.evlog.dev/cli/rules

---

// nuxt.config.ts
export default defineNuxtConfig({
  modules: ['evlog/nuxt'],
  evlog: {
    env: { service: 'my-app' },
    include: ['/api/**'],
  },
})

// server/api/checkout.post.ts — no imports needed
export default defineEventHandler(async (event) => {
  const log = useLogger(event)
  log.set({ user: { id: user.id, plan: user.plan } })
  return { success: true }
})

// evlog.config.ts
import { defineEvlog } from 'evlog'
import { createAxiomDrain } from 'evlog/axiom'

export default defineEvlog({
  service: 'my-app',
  drain: createAxiomDrain(),
})

// server/plugins/evlog-drain.ts
import { createAxiomDrain } from 'evlog/axiom'

export default defineNitroPlugin((nitroApp) => {
  nitroApp.hooks.hook('evlog:drain', createAxiomDrain())
})

// nuxt.config.ts
evlog: {
  transport: { enabled: true },  // logs sent to /api/_evlog/ingest
}

// lib/evlog.ts
import type { DrainContext } from 'evlog'
import { createEvlog } from 'evlog/next'
import { createUserAgentEnricher, createRequestSizeEnricher } from 'evlog/enrichers'
import { createDrainPipeline } from 'evlog/pipeline'

const enrichers = [createUserAgentEnricher(), createRequestSizeEnricher()]
const pipeline = createDrainPipeline<DrainContext>({ batch: { size: 50, intervalMs: 5000 } })
const drain = pipeline(createAxiomDrain({ dataset: 'logs', apiKey: process.env.AXIOM_API_KEY! }))

export const { withEvlog, useLogger, log, createError } = createEvlog({
  service: 'my-app',
  sampling: {
    rates: { info: 10 },
    keep: [{ status: 400 }, { duration: 1000 }],
  },
  routes: {
    '/api/auth/**': { service: 'auth-service' },
    '/api/checkout/**': { service: 'checkout-service' },
  },
  keep: (ctx) => {
    const user = ctx.context.user as { premium?: boolean } | undefined
    if (user?.premium) ctx.shouldKeep = true
  },
  enrich: (ctx) => {
    for (const enricher of enrichers) enricher(ctx)
  },
  drain,
})

// app/api/checkout/route.ts
import { withEvlog, useLogger } from '@/lib/evlog'

export const POST = withEvlog(async (request: Request) => {
  const log = useLogger()  // Zero arguments — uses AsyncLocalStorage
  log.set({ user: { id: 'user_123', plan: 'enterprise' } })
  log.set({ cart: { items: 3, total: 14999 } })
  return Response.json({ success: true })
})

// app/actions.ts
'use server'
import { withEvlog, useLogger } from '@/lib/evlog'

export const checkout = withEvlog(async (formData: FormData) => {
  const log = useLogger()
  log.set({ action: 'checkout', source: 'server-action' })
  return { success: true }
})

// proxy.ts
import { evlogMiddleware } from 'evlog/next'
export const proxy = evlogMiddleware()
export const config = { matcher: ['/api/:path*'] }

// app/layout.tsx
import { EvlogProvider } from 'evlog/next/client'

export default function Layout({ children }: { children: React.ReactNode }) {
  return (
    <html lang="en">
      <body>
        <EvlogProvider service="my-app" transport={{ enabled: true, endpoint: '/api/evlog/ingest' }}>
          {children}
        </EvlogProvider>
      </body>
    </html>
  )
}

'use client'
import { log, setIdentity, clearIdentity } from 'evlog/next/client'

setIdentity({ userId: 'usr_123' })
log.info({ action: 'checkout_click' })
clearIdentity()

// app/api/evlog/ingest/route.ts
import { NextRequest } from 'next/server'

const VALID_LEVELS = ['info', 'error', 'warn', 'debug'] as const

export async function POST(request: NextRequest) {
  const origin = request.headers.get('origin')
  const host = request.headers.get('host')
  if (origin && new URL(origin).host !== host) {
    return Response.json({ error: 'Invalid origin' }, { status: 403 })
  }
  const body = await request.json()
  if (!body?.timestamp || !body?.level || !VALID_LEVELS.includes(body.level)) {
    return Response.json({ error: 'Invalid payload' }, { status: 400 })
  }
  const { service: _, ...sanitized } = body
  console.log('[CLIENT LOG]', JSON.stringify({ ...sanitized, service: 'my-app', source: 'client' }))
  return new Response(null, { status: 204 })
}

// src/hooks.server.ts
import { initLogger } from 'evlog'
import { createEvlogHooks } from 'evlog/sveltekit'

initLogger({ env: { service: 'my-app' } })

export const { handle, handleError } = createEvlogHooks()

// src/routes/api/users/[id]/+server.ts
import { json } from '@sveltejs/kit'

export const GET = ({ locals, params }) => {
  locals.log.set({ user: { id: params.id } })
  return json({ id: params.id })
}

import { useLogger } from 'evlog/sveltekit'

async function findUsers() {
  const log = useLogger()
  log.set({ db: { query: 'SELECT * FROM users' } })
}

import { createAxiomDrain } from 'evlog/axiom'

export const { handle, handleError } = createEvlogHooks({
  include: ['/api/**'],
  drain: createAxiomDrain(),
  enrich: (ctx) => { ctx.event.region = process.env.FLY_REGION },
  keep: (ctx) => {
    if (ctx.duration && ctx.duration > 2000) ctx.shouldKeep = true
  },
})

// nitro.config.ts
import { defineConfig } from 'nitro'
import evlog from 'evlog/nitro/v3'

export default defineConfig({
  modules: [evlog({ env: { service: 'my-api' } })],
})

// routes/api/checkout.post.ts
import { defineHandler } from 'nitro/h3'
import { useLogger } from 'evlog/nitro/v3'

export default defineHandler(async (event) => {
  const log = useLogger(event)
  log.set({ action: 'checkout' })
  return { ok: true }
})

// nitro.config.ts
import { defineConfig } from 'nitro'
import evlog from 'evlog/nitro/v3'

export default defineConfig({
  experimental: { asyncContext: true },
  modules: [evlog({ env: { service: 'my-app' } })],
})

// src/routes/__root.tsx
import { createMiddleware } from '@tanstack/react-start'
import { evlogErrorHandler } from 'evlog/nitro/v3'

export const Route = createRootRoute({
  server: {
    middleware: [createMiddleware().server(evlogErrorHandler)],
  },
})

import { useRequest } from 'nitro/context'
import type { RequestLogger } from 'evlog'

const req = useRequest()
const log = req.context.log as RequestLogger
log.set({ user: { id: 'user_123' } })

// nitro.config.ts
import { defineNitroConfig } from 'nitropack/config'
import evlog from 'evlog/nitro'

export default defineNitroConfig({
  modules: [evlog({ env: { service: 'my-api' } })],
})

// src/app.module.ts
import { Module } from '@nestjs/common'
import { EvlogModule } from 'evlog/nestjs'

@Module({
  imports: [EvlogModule.forRoot()],
})
export class AppModule {}

import { useLogger } from 'evlog/nestjs'

async function findUsers() {
  const log = useLogger()
  log.set({ db: { query: 'SELECT * FROM users' } })
}

import { createAxiomDrain } from 'evlog/axiom'

EvlogModule.forRoot({
  include: ['/api/**'],
  drain: createAxiomDrain(),
  enrich: (ctx) => { ctx.event.region = process.env.FLY_REGION },
  keep: (ctx) => {
    if (ctx.duration && ctx.duration > 2000) ctx.shouldKeep = true
  },
})

EvlogModule.forRootAsync({
  imports: [ConfigModule],
  inject: [ConfigService],
  useFactory: (config) => ({
    drain: createAxiomDrain({ apiKey: config.get('AXIOM_API_KEY') }),
  }),
})

import express from 'express'
import { initLogger } from 'evlog'
import { evlog, useLogger } from 'evlog/express'

initLogger({ env: { service: 'my-api' } })

const app = express()
app.use(evlog())

app.get('/api/users', (req, res) => {
  req.log.set({ users: { count: 42 } })
  res.json({ users: [] })
})

import { useLogger } from 'evlog/express'

async function findUsers() {
  const log = useLogger()
  log.set({ db: { query: 'SELECT * FROM users' } })
}

import { createAxiomDrain } from 'evlog/axiom'

app.use(evlog({
  include: ['/api/**'],
  drain: createAxiomDrain(),
  enrich: (ctx) => { ctx.event.region = process.env.FLY_REGION },
  keep: (ctx) => {
    if (ctx.duration && ctx.duration > 2000) ctx.shouldKeep = true
  },
}))

import { Hono } from 'hono'
import { initLogger } from 'evlog'
import { evlog, type EvlogVariables } from 'evlog/hono'

initLogger({ env: { service: 'my-api' } })

const app = new Hono<EvlogVariables>()
app.use(evlog())

app.get('/api/users', (c) => {
  const log = c.get('log')
  log.set({ users: { count: 42 } })
  return c.json({ users: [] })
})

import { useLogger } from 'evlog/hono'

async function findUsers() {
  const log = useLogger()
  log.set({ db: { query: 'SELECT * FROM users' } })
}

import { createError, parseError } from 'evlog'
import type { ContentfulStatusCode } from 'hono/utils/http-status'

app.onError((error, c) => {
  c.get('log').error(error)
  const parsed = parseError(error)
  return c.json(
    { message: parsed.message, why: parsed.why, fix: parsed.fix, link: parsed.link },
    parsed.status as ContentfulStatusCode,
  )
})

import { createAxiomDrain } from 'evlog/axiom'

app.use(evlog({
  include: ['/api/**'],
  drain: createAxiomDrain(),
  enrich: (ctx) => { ctx.event.region = process.env.FLY_REGION },
  keep: (ctx) => {
    if (ctx.duration && ctx.duration > 2000) ctx.shouldKeep = true
  },
}))