{"record":{"id":"fbaa2a23777cec0d","repo":"Hmbown/CodeWhale","slug":"failed-to-capture-stderr","errorCode":null,"errorMessage":"Failed to capture stderr","messagePattern":"Failed to capture stderr","errorType":"exception","errorClass":"anyhow::Error","httpStatus":null,"severity":"error","filePath":"crates/tui/src/tools/shell.rs","lineNumber":2545,"sourceCode":"                if let (Some(reader), Some(output)) = (combined_reader, bounded_output.as_ref()) {\n                    (\n                        Some(spawn_bounded_reader_thread(reader, Arc::clone(output))),\n                        None,\n                    )\n                } else {\n                    let stdout_handle = child.stdout.take().ok_or_else(|| {\n                        #[cfg(windows)]\n                        terminate_unregistered_process(&mut child, windows_job.as_ref());\n                        #[cfg(not(windows))]\n                        terminate_unregistered_process(&mut child);\n                        anyhow!(\"Failed to capture stdout\")\n                    })?;\n                    let stderr_handle = child.stderr.take().ok_or_else(|| {\n                        #[cfg(windows)]\n                        terminate_unregistered_process(&mut child, windows_job.as_ref());\n                        #[cfg(not(windows))]\n                        terminate_unregistered_process(&mut child);\n                        anyhow!(\"Failed to capture stderr\")\n                    })?;\n                    (\n                        Some(spawn_reader_thread(\n                            stdout_handle,\n                            Arc::clone(&stdout_buffer),\n                        )),\n                        stderr_buffer\n                            .as_ref()\n                            .map(|buffer| spawn_reader_thread(stderr_handle, Arc::clone(buffer))),\n                    )\n                };\n\n            (\n                ShellChild::Process(child),\n                stdin_handle,\n                stdout_thread,\n                stderr_thread,\n            )","sourceCodeStart":2527,"sourceCodeEnd":2563,"githubUrl":"https://github.com/Hmbown/CodeWhale/blob/0c42157ee52f9d55af2b506d71b46249910f77d3/crates/tui/src/tools/shell.rs#L2527-L2563","documentation":"Mirror of the stdout case: in the separated-stream path the child must have a piped stderr handle (child.stderr.take()); if None, the child is terminated and 'Failed to capture stderr' returns. Note that some modes (tty, persist_pending, small_contract) intentionally leave the stderr buffer unset, but the handle itself must still exist when this branch runs — None here means the spawn did not pipe stderr at all, an internal invariant break.","triggerScenarios":"Child spawned without Stdio::piped() stderr while the separated-reader path assumes it; internal regression or platform spawn quirk, not a caller-selectable condition.","commonSituations":"Rare; not triggerable through documented tool options. Would appear after modifying spawn stdio configuration.","solutions":["Retry the command once to rule out a transient spawn issue.","If reproducible, report upstream with command, flags (background, tty, persist), and platform.","Workaround: background execution with bounded/combined output avoids the separated stderr thread."],"exampleFix":null,"handlingStrategy":"retry","validationCode":null,"typeGuard":null,"tryCatchPattern":"let out = match exec_shell(cmd, dir, opts).await {\n    Ok(o) => o,\n    Err(e) if e.to_string().contains(\"Failed to capture stderr\") => {\n        exec_shell(cmd, dir, opts).await\n            .or_else(|_| exec_shell_background_bounded(cmd, dir))?\n    }\n    Err(e) => return Err(e),\n};","preventionTips":["Use background/bounded output capture when you depend on stderr content.","Capture the exact command and spawn options if seen — it indicates a spawn/capture mismatch, not a caller error."],"tags":["shell","process-io","stderr","spawn","invariant"],"backgroundTag":"process-io-capture-failed","analyzedSha":"0c42157ee52f9d55af2b506d71b46249910f77d3","analyzedAt":"2026-08-20T21:50:45.477Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}