> ## Documentation Index > Fetch the complete documentation index at: https://docs.withboundary.com/llms.txt > Use this file to discover all available pages before exploring further. # createBoundaryLogger > Full options reference for the SDK logger factory ```typescript theme={null} import { createBoundaryLogger } from "@withboundary/sdk"; ``` ## Signature ```typescript theme={null} function createBoundaryLogger( options?: BoundaryLoggerOptions, ): BoundaryLogger | null; ``` ### Returns * A `BoundaryLogger` when either `apiKey` (or `BOUNDARY_API_KEY` env var) or `write` is configured. * `null` otherwise — the dev-safe fallback. Passing `null` to `defineContract({ logger })` is a no-op. ## `BoundaryLoggerOptions` | Option | Type | Default | Description | | -------------------- | -------------------------------------------- | -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `apiKey` | `string` | `process.env.BOUNDARY_API_KEY` | Boundary ingest credential | | `environment` | `"production" \| "staging" \| "development"` | — | Bucket events on the dashboard | | `endpoint` | `string` | `"https://api.withboundary.com"` | Override the ingest endpoint (self-host, proxy) | | `model` | `string` | — | Default LLM label stamped onto every event; overridable per-call | | `capture` | `Partial` | see below | Which buckets of data to ship | | `redact` | `RedactionOptions` | — | `fields` / `patterns` / `custom` scrubbing | | `batch.size` | `number` | `20` | Flush when queue hits this length. Small enough that low-traffic apps don't wait long for the first flush; large enough that bursts coalesce into one POST. | | `batch.intervalMs` | `number` | `5000` | Periodic flush cadence. Caps the worst-case time between an event firing and showing up on the dashboard. Set to `0` to disable the timer (recommended on Cloudflare Workers / Vercel Edge — the isolate freezes between requests, so timers are unreliable). | | `batch.maxQueueSize` | `number` | `1000` | Drop-oldest overflow threshold. Bounds memory during a backend outage. Tighten to \~100 on serverless/edge runtimes that recycle frequently. | | `beforeSend` | `(event) => BoundaryLogEvent \| null` | — | Last-chance transform or drop | | `write` | `(events) => void \| Promise` | — | Custom sink; fires alongside `apiKey` | | `flushOnExit` | `boolean` | `true` | Attach runtime lifecycle drain hooks | | `onError` | `(err) => void` | one-time `console.warn` | Permanent drop callback | | `fetch` | `typeof fetch` | `globalThis.fetch` | Injected fetch (tests, polyfills) | ### Default capture policy ```typescript theme={null} { inputs: false, outputs: false, repairs: true, } ``` Three optional buckets. Raw LLM inputs and outputs are off by default; repair messages are on so the dashboard can show how the model recovered. Failure attribution (`category`, `issues`, `ruleFailures`) and run metadata are always sent — they aren't gated. See [Capture policy](/sdk/capture-policy). ### Tuning by platform | Runtime | Recommended overrides | Why | | -------------------------------- | ---------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- | | Long-running Node | Defaults | The 5s timer drains continuously; 1000-event queue absorbs short outages. | | AWS Lambda / Vercel Functions | `batch.maxQueueSize: 100`, optionally tighter `batch.size` | Containers freeze between invocations; flushes happen via `flush()` in your handler's `finally` block, not the timer. | | Cloudflare Workers / Vercel Edge | `batch.intervalMs: 0`, `batch.maxQueueSize: 100`, drain via `ctx.waitUntil(logger.flush())` | Timers are unreliable when the isolate freezes; explicit drain on the request lifecycle is the only reliable path. | | Browser | `batch.size: 10`, `batch.intervalMs: 2000`, `batch.maxQueueSize: 100`, `write` to your authenticated proxy | Browsers die more often than servers; smaller, faster batches, never an `apiKey` in the bundle. | See [Node](/sdk/platforms/node), [Vercel & Lambda](/sdk/platforms/vercel-aws-lambda), [Cloudflare Workers & Edge](/sdk/platforms/cloudflare-workers-edge), and [Browser](/sdk/platforms/browser) for full per-runtime patterns. ## `BoundaryLogger` The returned object: ```typescript theme={null} type BoundaryLogger = ContractLogger & { flush: (timeoutMs?: number) => Promise; shutdown: (timeoutMs?: number) => Promise; }; ``` * Implements every `ContractLogger` hook (assign it directly to `defineContract({ logger })`). * `flush(timeoutMs?)` — drain the queue; logger stays active. * `shutdown(timeoutMs?)` — drain, stop the timer, disable further sends. Idempotent. See [Shutdown](/sdk/shutdown) for timeout semantics and per-platform recipes. ## Minimal example ```typescript theme={null} import { createBoundaryLogger } from "@withboundary/sdk"; import { defineContract } from "@withboundary/contract"; const logger = createBoundaryLogger({ environment: "production", }); const contract = defineContract({ name: "lead-scoring", schema, rules, logger, }); ``` ## Full example ```typescript theme={null} const logger = createBoundaryLogger({ apiKey: process.env.BOUNDARY_API_KEY, environment: "production", model: "gpt-4.1", capture: { inputs: false, outputs: false, repairs: true, }, redact: { fields: ["ssn", "email"], patterns: [/\b\d{3}-\d{2}-\d{4}\b/], custom: (value, path) => path.at(-1) === "customerId" && typeof value === "string" ? `cust_${hash(value).slice(0, 10)}` : value, }, batch: { size: 50, intervalMs: 2000, maxQueueSize: 2000, }, beforeSend(event) { return event.contractName === "health-check" ? null : event; }, write(events) { for (const e of events) console.log(JSON.stringify(e)); }, onError(err) { metrics.increment("boundary.drop"); }, }); ``` ## Related types * [`BoundaryLogEvent`](/sdk/boundary-log-event) — the wire format * [`CapturePolicy`](/sdk/capture-policy) — the three buckets, plus the always-on fields * [`RedactionOptions`](/sdk/redaction) — `fields` / `patterns` / `custom` * Full SDK types: [Types reference](/api-reference/types) ## See also Install and wire the logger flush + shutdown + signal handling