Silgi — Type-safe RPC for TypeScript

Trace Better Auth operations in silgi analytics — login flows, OAuth, session management with structured attributes.

The Better Auth integration traces every auth operation — sign-in, sign-up, OAuth flows, session management — into silgi analytics. Each operation appears as a span with user.id, session.id, auth.operation, and success/failure status. Two integration points cover both HTTP requests and programmatic API calls.

Setup

bash pnpm add silgi better-auth

bash npm install silgi better-auth

bash bun add silgi better-auth

There are two ways to trace auth operations:

tracing() plugin — traces HTTP-level auth requests (sign-in forms, OAuth callbacks)
instrumentBetterAuth() — traces programmatic auth.api.* calls (server-side session fetches, background jobs)

Use one or both depending on your setup.

Plugin setup

Add tracing() to your Better Auth plugins. Pass createAuthMiddleware from better-auth/api so the plugin can wrap the after-hook handler:

auth.ts

import {  } from 'better-auth'
import {  } from 'better-auth/api'
import {  } from 'silgi/better-auth'

export const  = ({
  : { : process.env.DATABASE_URL! },
  : [({  })],
})

Handler setup

In your silgi handler, call setRequestContext(request, ctx) before passing the request to Better Auth. This bridges the silgi request context to the auth plugin via a GC-friendly WeakMap — no mutation of the Request object.

server.ts

import {  } from 'silgi'
import {  } from 'silgi/better-auth'
import {  } from './auth'

const  = ()

const  = .(async ({ ,  }) => {
  (, )
  return .handler()
})

const  = .({
  : { :  },
})

export default { : .() }

setRequestContext(request, ctx) must run before auth.handler(request). Without it the plugin has no access to the request trace and spans are silently skipped.

The legacy (request as any).__silgiCtx = ctx assignment still works as a fallback for existing code, but new code should prefer setRequestContext — it avoids mutating the Request and releases the entry automatically when the Request is GC'd.

What gets captured

Each auth operation produces a span with these attributes:

Attribute	Type	Description
`auth.operation`	`string`	Operation name (`signin`, `signup`, `signout`, `get_session`, etc.)
`auth.method`	`string`	Auth method (`email`, `oauth`)
`auth.provider`	`string`	OAuth provider name (`google`, `github`, etc.)
`auth.success`	`boolean`	Whether the operation succeeded
`user.id`	`string`	Authenticated user's ID
`user.email`	`string`	Authenticated user's email
`session.id`	`string`	Session ID

Operation mapping

The plugin maps Better Auth URL paths to structured span names:

Path	Span name	Operation
`/sign-up/email`	`auth.signup.email`	`signup`
`/sign-in/email`	`auth.signin.email`	`signin`
`/sign-out`	`auth.signout`	`signout`
`/get-session`	`auth.get_session`	`get_session`
`/update-user`	`auth.update_user`	`update_user`
`/delete-user`	`auth.delete_user`	`delete_user`
`/change-password`	`auth.change_password`	`change_password`
`/change-email`	`auth.change_email`	`change_email`
`/verify-email`	`auth.verify_email`	`verify_email`
`/forget-password`	`auth.forgot_password`	`forgot_password`
`/reset-password`	`auth.reset_password`	`reset_password`
`/list-sessions`	`auth.list_sessions`	`list_sessions`
`/revoke-session`	`auth.revoke_session`	`revoke_session`
`/sign-in/{provider}`	`auth.oauth.initiate.{provider}`	`oauth_initiate`
`/callback/{provider}`	`auth.oauth.callback.{provider}`	`oauth_callback`

Unrecognized paths fall back to auth.{last_segment} with operation unknown.

Programmatic API tracing

For server-side calls to auth.api.* (session validation, background user management), use instrumentBetterAuth with withCtx:

auth.ts

import {  } from 'better-auth'
import {  } from 'silgi/better-auth'

export const  = (
  ({
    : { : process.env.DATABASE_URL! },
  }),
)

Then wrap API calls in withCtx:

server.ts

import {  } from 'silgi'
import {  } from 'silgi/better-auth'
import {  } from './auth'

const  = ()

const  = .(async ({ ,  }) => {
  return (, () => .api.getSession({ : .headers }))
})

Programmatic spans are named auth.api.{operation} (e.g. auth.api.get_session, auth.api.signin). All known API methods are mapped to their operation names automatically. Unknown methods are also traced using a camelCase-to-snake_case conversion of the method name.

Configuration

Options for the tracing() plugin:

Name	Type	Default	Description
`captureInput`	`boolean`	`true`	Capture request body as span input
`captureOutput`	`boolean`	`true`	Capture response data as span output
`createAuthMiddleware`	`function`	`undefined`	Pass `createAuthMiddleware` from `better-auth/api` to wrap the after-hook handler

Better Auth