logger

captureAnyUnhandledRejection() installs process.on('unhandledRejection') → log.error and process.on('uncaughtException') → log.fatal + process.exit(1) so process-level failures land in your channels and a fatal crash is never silently swallowed into exit 0. Triggers: `captureAnyUnhandledRejection`, `exitOnUncaughtException`, `unhandledRejection`, `uncaughtException`, `log.error`, `log.fatal`; "log unhandled promise rejections", "catch uncaught exceptions to a file", "record crashes before exit", "server exits 0 with no error", "silent exit / production server stopped", "global error handler with logger"; typical import `import { captureAnyUnhandledRejection, log } from "@warlock.js/logger"`. Skip: flushing — `@warlock.js/logger/flush-logs-on-shutdown/SKILL.md`; filtering — `@warlock.js/logger/filter-log-entries/SKILL.md`; competing `Sentry.init`, `@sentry/node`; native `process.on('unhandledRejection')`.

Drain buffered channels before exit — log.flushSync() or log.configure({autoFlushOn: ['SIGINT', 'SIGTERM', 'beforeExit']}) installs handlers that re-raise the signal. Triggers: `log.flush`, `log.flushSync`, `autoFlushOn`, `enableAutoFlush`, `disableAutoFlush`, `SIGINT`, `SIGTERM`, `beforeExit`; "drain logs before exit", "await log.flush() before process.exit", "drain async or network channels on shutdown", "wire SIGTERM for container shutdown", "my logs never showed after a crash", "graceful shutdown logging"; typical import `import { log, FileLog } from "@warlock.js/logger"`. Skip: error capture — `@warlock.js/logger/capture-unhandled-errors/SKILL.md`; custom sinks — `@warlock.js/logger/write-custom-log-channel/SKILL.md`; competing `pino.final`, `winston.end`; native `process.on('exit')`.

Front-door orientation for `@warlock.js/logger` — structured channel-based logging with six severity levels (debug / info / warn / error / success / fatal), PII redaction floor, buffered file/JSON channels, optional SentryLog forwarding, async log.flush() + signal-flush on shutdown, ergonomic helpers (timer, assert). Standalone — no `@warlock.js/core` required. TRIGGER when: code imports anything from `@warlock.js/logger`; user asks "what does @warlock.js/logger do", "compare with pino / winston / bunyan", "structured logging for Node", "which logger should I use", "how do channels work"; package.json adds `@warlock.js/logger`. Skip: specific task already known — load the matching task skill directly (`logger-basics`, `configure-logger`, `pick-log-channel`, `write-custom-log-channel`, `ship-logs-to-sentry`, `redact-sensitive-log-fields`, `filter-log-entries`, `flush-logs-on-shutdown`, `capture-unhandled-errors`, `use-log-helpers`, `test-logging-code`); plain `console.log` in throwaway scripts.

Test code that touches the logger — silence globally via log.setChannels([]) in setupFiles, assert specific log lines via a capturing LogChannel subclass (prefer it over vi.spyOn — it asserts on delivered entries, not just method calls, and isolates the shared singleton cleanly). Triggers: `log.setChannels`, `LogChannel`, `LoggingData`, `Logger`, `log.channels`; "silence logger in vitest", "assert a log line was emitted", "capture log output in tests", "test code that logs"; typical import `import { log, Logger, LogChannel, type LoggingData } from "@warlock.js/logger"`. Skip: custom sinks — `@warlock.js/logger/write-custom-log-channel/SKILL.md`; filtering — `@warlock.js/logger/filter-log-entries/SKILL.md`; competing `vi.spyOn(console)`, `jest.spyOn`.

Pick one of the four built-in channels — ConsoleLog (terminal), FileLog (plain text on disk), JSONFileLog (structured JSON for aggregators like Loki / Datadog / Elastic), SentryLog (forwards errors + breadcrumbs to Sentry). Triggers: `ConsoleLog`, `FileLog`, `JSONFileLog`, `SentryLog`, `chunk`, `rotate`, `groupBy`, `maxFileSize`, `showContext`, `log.channel`; "log to a file", "rotate log files", "daily log chunks", "json logs for datadog / loki / elastic", "send logs to Sentry"; typical import `import { ConsoleLog, FileLog, JSONFileLog, SentryLog } from "@warlock.js/logger"`. Skip: Sentry-specific setup — `@warlock.js/logger/ship-logs-to-sentry/SKILL.md`; custom sinks — `@warlock.js/logger/write-custom-log-channel/SKILL.md`; registration — `@warlock.js/logger/configure-logger/SKILL.md`; competing libs `winston-daily-rotate-file`, `pino-pretty`.

Two DX shortcuts on every Logger — log.assert(condition, module, action, message, context?) logs an error when condition is falsy (free on the happy path), log.timer(module, action) returns an end-function emitting an info entry with measured duration. Triggers: `log.assert`, `log.timer`, `durationMs`; "assert an invariant via logger", "measure how long an operation took", "time a request", "log operation duration"; typical import `import { log } from "@warlock.js/logger"`. Skip: basics — `@warlock.js/logger/logger-basics/SKILL.md`; filtering — `@warlock.js/logger/filter-log-entries/SKILL.md`; competing `console.assert`, `console.time`, `console.timeEnd`, `perf_hooks.performance.now`.

Drop log entries — per-channel levels whitelist, per-channel filter predicate, logger-wide setMinLevel(level) fast path. Triggers: `levels`, `filter`, `minLevel`, `log.setMinLevel`, `shouldBeLogged`, `LoggingData`, `LogLevel`; "silence a noisy module", "route errors to a dedicated file", "raise global severity floor", "drop debug logs in prod"; typical import `import { log } from "@warlock.js/logger"`. Skip: custom sinks — `@warlock.js/logger/write-custom-log-channel/SKILL.md`; channel picks — `@warlock.js/logger/pick-log-channel/SKILL.md`; competing libs `pino.levels`, `winston.format.filter`, `debug` env var.

Start with @warlock.js/logger — the log singleton, six levels (debug / info / warn / error / success / fatal), channel fan-out, foundations. Triggers: `log`, `Logger`, `log.info`, `log.error`, `log.fatal`, `log.debug`, `log.warn`, `log.success`, `ConsoleLog`, `FileLog`, `JSONFileLog`; "how do I log in node", "warlock logger basics", "which logger skill do I need"; typical import `import { log, ConsoleLog, FileLog } from "@warlock.js/logger"`. Skip: channel picks — `@warlock.js/logger/pick-log-channel/SKILL.md`; setup — `@warlock.js/logger/configure-logger/SKILL.md`; competing libs `winston`, `pino`, `bunyan`, `log4js`, `signale`; native `console.log`.

Forward log entries to Sentry with the SentryLog channel — error/warn become events (captureException/captureMessage), every other level a breadcrumb (no quota). @sentry/node is an OPTIONAL peer, lazily imported. Triggers: `SentryLog`, `@sentry/node`, `eventLevels`, `flushTimeout`, `Sentry.flush`, `captureException`, `addBreadcrumb`, `withScope`; "send logs to Sentry", "report errors to Sentry", "Sentry log channel", "Sentry breadcrumbs from logs", "log channel for Sentry"; typical import `import { SentryLog } from "@warlock.js/logger"`. Skip: file/console channels — `@warlock.js/logger/pick-log-channel/SKILL.md`; custom sinks — `@warlock.js/logger/write-custom-log-channel/SKILL.md`; graceful-shutdown flushing — `@warlock.js/logger/flush-logs-on-shutdown/SKILL.md`; Slack alerting recipe.

Extend the abstract LogChannel class for custom sinks — Slack, database, HTTP endpoint, in-memory buffer. Triggers: `LogChannel`, `LogContract`, `LoggingData`, `shouldBeLogged`, `init`, `flush`, `flushSync`, `terminal`; "log to slack", "log to a database", "send logs to datadog / loki HTTP api", "in-memory test capture channel", "build a custom log sink"; typical import `import { LogChannel, type LoggingData, type LogContract } from "@warlock.js/logger"`. Skip: built-in channels — `@warlock.js/logger/pick-log-channel/SKILL.md`; filtering — `@warlock.js/logger/filter-log-entries/SKILL.md`; competing libs `winston-transport`, `pino-transport`.

Register channels via log.addChannel / log.setChannels / log.configure({channels, autoFlushOn, redact, minLevel}) at boot. Triggers: `log.configure`, `log.addChannel`, `log.setChannels`, `Logger`, `autoFlushOn`, `disableAutoFlush`; "wire channels at startup", "branch logger by NODE_ENV", "isolate a library's logger", "replace channel list"; typical import `import { log, Logger, ConsoleLog, FileLog } from "@warlock.js/logger"`. Skip: channel picks — `@warlock.js/logger/pick-log-channel/SKILL.md`; flushing — `@warlock.js/logger/flush-logs-on-shutdown/SKILL.md`; redaction — `@warlock.js/logger/redact-sensitive-log-fields/SKILL.md`; competing libs `winston.createLogger`, `pino`.

Strip secrets from log output — two-layer additive redaction via log.configure({redact: {paths}}) (logger floor) + per-channel redact (more paths on top). Dotted glob paths (*, **). Triggers: `redact`, `paths`, `censor`, `log.setRedact`, `applyRedact`; "redact passwords in logs", "strip tokens from log output", "hide authorization headers", "scrub PII before logging"; typical import `import { log } from "@warlock.js/logger"`. Skip: filtering — `@warlock.js/logger/filter-log-entries/SKILL.md`; custom sinks — `@warlock.js/logger/write-custom-log-channel/SKILL.md`; competing libs `pino.redact`, `fast-redact`.