What
When set, OpenTelemetry diagnostic errors are written directly to stderr in addition to the internal debug log. Useful when debugging custom telemetry or OTEL integrations.
Usage
CLAUDE_CODE_OTEL_DIAG_STDERR=1 claude
# OTEL errors now appear on stderr prefixed with "[3P telemetry] OTEL diag error:"Details
- Without this flag, OTEL errors only appear in the internal log (visible via
/debug) - With the flag, errors are also streamed to
process.stderrimmediately - The flag is stripped before spawning subprocesses so it doesn't leak
Evidence
New stderr path (search for "CLAUDE_CODE_OTEL_DIAG_STDERR")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.