auto-tail

Waiting and working look identical from the outside. A log that stopped growing

at 17:36 with a live "waiting" agent on top of it cost an hour today. This skill

makes the log itself prove which one it is.

When to run it

• A background build/test/deploy is writing a log and you would otherwise idle.
• The user says "tail it", "how's the build", "is it still going".
• Before reporting "still running" to anyone. Never say that without a fresh status line.

How

~/.claude/skills/auto-tail/auto-tail.sh [LOG] [--pid N] [--every S] [--max S] [--once]

• LOG omitted = newest *.log under $CLAUDE_JOB_DIR/tmp, else the cwd.
• --pid is the writer's pid. With it, silence + alive = STALLED; silence + dead = DONE-?. Without it the tool can only say SILENT.
• --once prints one status line and the tail; use it to answer "tail it".
• No --once = loop every --every seconds until a terminal state or --max.
• Exit codes: 0 finished ok · 1 finished failed · 2 stalled/timed out · 3 no log.

Each round prints one line the user can read cold:

18:22:41  DONE-OK  dk-build5.log  lines=297  mtime=19s ago  success marker in last 40 lines, writer not running
  OK>   290:#29 naming to docker.io/library/crown-crown:latest done
  | #30 DONE 0.0s
  |  Image crown-crown Built

Rules

• Restate the state line in your own text. The user sees at most a few lines of tool output.
• STALLED means inspect the writer, not the log. ps, docker ps, the process's own stderr. Do not re-tail.
• DONE-FAIL means read the FAIL> lines and act. Do not rerun the same build hoping.
• Markers are regexes with sane defaults for docker, npm/next, cargo, pytest, gh. Override with --ok / --fail when a tool has its own vocabulary.
• In the sandboxed Bash of a background job, run the script from the worktree cwd with an absolute log path. Use mcp__axe-local__shell if the path is refused.
• Long loops: prefer run_in_background on the Bash call so the loop's notification wakes you, and keep --max under the tool timeout.

Related

feedback_cap_subagent_spend_and_require_incremental_writes, finding_gated_pipeline_marker_never_written (a marker nothing writes can only time out — check the WRITER).