JavaScript / TypeScript Project Detection

Read this before editing a JS/TS project. Instrument every runtime in the app, not just the first package.json you find.

Locate The Package Boundary

Find all package.json files, ignoring node_modules, build output, generated clients, and vendored examples unless the user explicitly targets them.
If the repo has workspaces, identify which workspace owns the app entrypoint. Install dependencies in that workspace.
Choose the package manager from lockfiles:
- pnpm-lock.yaml: pnpm add
- yarn.lock: yarn add
- bun.lock or bun.lockb: bun add
- package-lock.json: npm install
- no lockfile: preserve the scripts' existing manager when obvious, otherwise use npm install
If a package already has a Logfire or OpenTelemetry setup, extend it instead of adding a duplicate provider.

Inspect dependencies, devDependencies, scripts, config files, and entrypoints.

Signal	Treat as	Read
`next`, `next.config.*`, `app/`, `pages/`	Next.js	nextjs.md
`express`, `fastify`, `koa`, Node server scripts, `src/server.`, `src/app.`	Node server	node-runtime.md
`vite`, `react`, `@vitejs/*`, `src/main.tsx`, browser-only SPA	Browser app	react-browser.md
`wrangler.*`, `@cloudflare/workers-types`, scripts invoking `wrangler`	Cloudflare Workers	cloudflare-and-deno.md
`deno.json`, `deno.lock`, Deno task scripts	Deno	cloudflare-and-deno.md
`ai`, `@ai-sdk/*`	Vercel AI SDK calls	ai-sdk.md
Existing `@opentelemetry/`, `@vercel/otel`, `instrumentation.ts`, `OTEL_` env docs	Existing OTel	Extend current setup

Do not create a second global tracer provider in the same runtime.
If @vercel/otel is present in Next.js, add Logfire OTLP env vars and use the logfire package for manual spans.
If a Node app already has a custom NodeSDK, add Logfire exporters/processors only if the current SDK structure is clear. Otherwise ask before replacing custom OTel wiring.
If OpenTelemetry env vars already point to another backend, preserve them unless the user explicitly wants Logfire to replace that backend. Prefer documenting the conflict over silently changing production export destinations.

Node auto-instrumentation must be loaded before instrumented libraries are imported.
Framework files that run in both server and browser contexts must not import @pydantic/logfire-node or read server secrets from client code.
Browser instrumentation must run in browser-only modules ('use client', client entrypoint, or dynamic import with SSR disabled).
For monorepos, add one service name per deployable service, not one name for the whole repo.