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fix(Logger): Support Cloudflare Workers by avoiding console.group when in workerd #5429

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fix(Logger): Support Cloudflare Workers by avoiding console.group when in workerd #5429

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52634f1
fix(Logger): Support Cloudflare Workers by avoiding console.group whe…
schickling Aug 24, 2025
8b95773
Improve workerd detection approach: treat as TTY instead of modifying…
schickling Aug 24, 2025
434e834
Remove duplicate isWorkerd definition
schickling Aug 24, 2025
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14 changes: 14 additions & 0 deletions .changeset/workerd-logger-fix.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
---
"effect": patch
---

fix(Logger): Support Cloudflare Workers by treating workerd as TTY environment

Fixes missing log messages in Cloudflare Workers where console.group methods are no-ops.

The pretty logger now:
- Detects workerd runtime using `navigator.userAgent === 'Cloudflare-Workers'`
- Routes workerd to TTY logger mode instead of browser mode
- Disables console.group calls in workerd (similar to existing Bun handling)

This ensures all log messages display correctly in Cloudflare Workers local development.
9 changes: 6 additions & 3 deletions packages/effect/src/internal/logger.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -332,7 +332,9 @@ const hasProcessStdout = typeof process === "object" &&
process.stdout !== null
const processStdoutIsTTY = hasProcessStdout &&
process.stdout.isTTY === true
const isWorkerd = typeof navigator !== "undefined" && navigator.userAgent === "Cloudflare-Workers"
const hasProcessStdoutOrDeno = hasProcessStdout || "Deno" in globalThis
const shouldUseTTYMode = hasProcessStdoutOrDeno || isWorkerd

/** @internal */
export const prettyLogger = (options?: {
Expand All @@ -342,7 +344,7 @@ export const prettyLogger = (options?: {
readonly mode?: "browser" | "tty" | "auto" | undefined
}) => {
const mode_ = options?.mode ?? "auto"
const mode = mode_ === "auto" ? (hasProcessStdoutOrDeno ? "tty" : "browser") : mode_
const mode = mode_ === "auto" ? (shouldUseTTYMode ? "tty" : "browser") : mode_
const isBrowser = mode === "browser"
const showColors = typeof options?.colors === "boolean" ? options.colors : processStdoutIsTTY || isBrowser
const formatDate = options?.formatDate ?? defaultDateFormat
Expand All @@ -357,6 +359,7 @@ const prettyLoggerTty = (options: {
readonly formatDate: (date: Date) => string
}) => {
const processIsBun = typeof process === "object" && "isBun" in process && process.isBun === true
const supportsConsoleGroup = !processIsBun && !isWorkerd
const color = options.colors ? withColor : withColorNoop
return makeLogger<unknown, void>(
({ annotations, cause, context, date, fiberId, logLevel, message: message_, spans }) => {
Expand Down Expand Up @@ -389,7 +392,7 @@ const prettyLoggerTty = (options: {
}

log(firstLine)
if (!processIsBun) console.group()
if (supportsConsoleGroup) console.group()

if (!Cause.isEmpty(cause)) {
log(Cause.pretty(cause, { renderErrorCause: true }))
Expand All @@ -407,7 +410,7 @@ const prettyLoggerTty = (options: {
}
}

if (!processIsBun) console.groupEnd()
if (supportsConsoleGroup) console.groupEnd()
}
)
}
Expand Down