{"record":{"id":"8602b786ba22869c","repo":"slopus/happy","slug":"failed-to-create-tmux-window-createresult-stde","errorCode":null,"errorMessage":"Failed to create tmux window: ${createResult?.stderr}","messagePattern":"Failed to create tmux window: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"packages/happy-cli/src/utils/tmux.ts","lineNumber":839,"sourceCode":"                        .replace(/`/g, '\\\\`');    // Backticks\n\n                    createWindowArgs.push('-e', `${key}=\"${escapedValue}\"`);\n                }\n                logger.debug(`[TMUX] Setting ${Object.keys(env).length} environment variables in tmux window`);\n            }\n\n            // Add the command to run in the window (runs immediately when window is created)\n            createWindowArgs.push(fullCommand);\n\n            // Add -P flag to print the pane PID immediately\n            createWindowArgs.push('-P');\n            createWindowArgs.push('-F', '#{pane_pid}');\n\n            // Create window with command and get PID immediately\n            const createResult = await this.executeTmuxCommand(createWindowArgs, sessionName);\n\n            if (!createResult || createResult.returncode !== 0) {\n                throw new Error(`Failed to create tmux window: ${createResult?.stderr}`);\n            }\n\n            // Extract the PID from the output\n            const panePid = parseInt(createResult.stdout.trim());\n            if (isNaN(panePid)) {\n                throw new Error(`Failed to extract PID from tmux output: ${createResult.stdout}`);\n            }\n\n            logger.debug(`[TMUX] Spawned command in tmux session ${sessionName}, window ${windowName}, PID ${panePid}`);\n\n            // Return tmux session info and PID\n            const sessionIdentifier: TmuxSessionIdentifier = {\n                session: sessionName,\n                window: windowName\n            };\n\n            return {\n                success: true,","sourceCodeStart":821,"sourceCodeEnd":857,"githubUrl":"https://github.com/slopus/happy/blob/b824cd0a4681d41af631a8e422a813873e4455b0/packages/happy-cli/src/utils/tmux.ts#L821-L857","documentation":"spawnInTmux creates the target window with `tmux new-window ... -F '#{pane_pid}'` to immediately capture the spawned process's PID. If executeTmuxCommand returns null or a non-zero returncode, it throws this Error embedding tmux's stderr, meaning the window (and thus the command) could not be created.","triggerScenarios":"Calling spawnInTmux when the tmux new-window invocation fails: session doesn't exist and wasn't created, invalid window/command arguments, tmux server errors ('no server running', 'create window failed'), or duplicate window name without -a.","commonSituations":"Target tmux session killed between availability check and window creation; shell command string with quoting issues; tmux version differences in flag support; server socket permission problems; hitting tmux limits on windows per session.","solutions":["Read the stderr embedded in the message — it contains tmux's own failure reason.","Ensure the session exists first (tmux new-session -d) or pass a session name spawnInTmux can create.","Check the command string is a valid shell command and properly quoted.","Retry: this is often transient (server restart, race with session termination).","Verify tmux works manually: tmux new-window -t happy -F '#{pane_pid}' 'echo hi'."],"exampleFix":"// before\nawait tmux.spawnInTmux(cmd, 'gone-session'); // may throw create-window failure\n// after\nif (!tmux.hasSession('gone-session')) await tmux.createTmuxSession('gone-session');\nawait tmux.spawnInTmux(cmd, 'gone-session');","handlingStrategy":"retry","validationCode":"// ensure the target session exists before spawning a window in it\nconst sessions = await execFileP('tmux', ['list-sessions', '-F', '#{session_name}']).catch(() => '');\nif (!sessions.split('\\n').includes(sessionName)) {\n  await execFileP('tmux', ['new-session', '-d', '-s', sessionName]);\n}","typeGuard":null,"tryCatchPattern":"try {\n  await tmux.spawnInTmux(cmd, sessionName);\n} catch (err) {\n  if ((err as Error).message.startsWith('Failed to create tmux window')) {\n    logger.error('tmux stderr:', (err as Error).message);\n    await recreateSession(sessionName); // then retry once\n    await tmux.spawnInTmux(cmd, sessionName);\n  } else throw err;\n}","preventionTips":["Surface the embedded tmux stderr — it names the real cause.","Create the session explicitly before adding windows.","Quote shell commands passed to spawnInTmux.","Avoid deleting sessions while spawns are in flight."],"tags":["tmux","process","command-failed"],"backgroundTag":"tmux-command-failed","analyzedSha":"b824cd0a4681d41af631a8e422a813873e4455b0","analyzedAt":"2026-08-31T23:12:36.205Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-08T05:18:18.240Z"}