claude-print-subprocess-error-streams

When a Claude CLI subprocess fails non-zero, the actual session error is often hidden in stdout instead of stderr. You need to capture both streams and validate JSON output for is_error payloads to surface the real failure message.

To capture stderr and stdout from a Claude CLI subprocess in Python, update your wrapper to raise an error including both streams on any non-zero return code. This dual-stream error reporting ensures hidden session failures become visible during batch automation.

To handle JSON error envelopes from Claude CLI in Python scripts, parse the stdout payload when using the --output-format json flag. You must explicitly check the output for an is_error flag to identify and extract the actual session failure details.

The best way to debug empty stderr from a Claude CLI batch automation script is to inspect stdout. Claude session failures often appear only in standard output, so surfacing and parsing both streams reveals the hidden transient failures or broken wrapper errors.

Yes, you can use Python subprocess to diagnose transient failures in Claude CLI workflows by capturing both stdout and stderr. This approach exposes hidden session errors and validates JSON output to pinpoint the exact failure cause in scripted invocations.