We left a counter running.
Then came back.

We downloaded the official Apple silicon binary for Herdr 0.9.5 and matched its published SHA-256. A temporary configuration and a named proof session kept the experiment separate from personal sessions. The panes used a non-login shell. No account, plugin, model or remote host was connected.

The program below writes its process ID and a sequence number to heartbeat.jsonl. That file lets us observe progress while no client is attached. It also prints the same values in the terminal.

import os, time, pathlib
p = pathlib.Path("heartbeat.jsonl")
i = 0
while True:
    i += 1
    with p.open("a") as f:
        f.write(f"{os.getpid()} {i}\n")
    print("heartbeat", os.getpid(), i, flush=True)
    time.sleep(0.25)

Download the original heartbeat program · Observed results as JSON

1. Create an empty test directory, save the heartbeat program there, and start a new named session: herdr --session exit-practice. Use a name that is not already in use.
2. Inside the pane, change to that directory and run python3 -u heartbeat.py. Leave it a moment to write a few lines.
3. Press Ctrl+B, release, then q. From your ordinary shell, read the last line of heartbeat.jsonl twice with a short gap. A larger counter under the same PID is evidence of ongoing progress.
4. Run herdr --session exit-practice again. Observe the continuing output. Press Ctrl+C to stop this test program.
5. For the restart comparison, run the test program again, add a second empty pane, and detach. Save anything else before stopping the test session with herdr session stop exit-practice.
6. Open herdr --session exit-practice again. Compare the layout and directory with the heartbeat file. Our file did not keep growing. Finish by stopping this disposable session.

Use only the test session and directory you created. The sample appends to its local file until interrupted; remove your test files when you no longer need them. Your PIDs and line counts will differ.

We did not reboot, sleep the computer, test a broken network, connect through SSH, upgrade with live handoff, enable pane-history replay, or resume an AI conversation. We did not test Windows or Linux. A program may catch Ctrl+C differently, require its own cleanup, or finish unsuccessfully while you are detached.

The general distinctions match Herdr’s documentation; the exact numbers and drawings come from our own controlled run. Herdr can change these behaviors in later releases. Check your installed version with herdr --version.

A single old line on screen proves only that text exists. To check ongoing progress in your disposable heartbeat exercise, preserve two observations of the file with a known gap between them. Keep the session name, command and actual observation times beside the results.

The example file is named heartbeat.jsonl, but the program above writes two whitespace-separated integers per line: process ID and counter. It does not write JSON records. The small reader below accepts that exact format and outputs a JSON summary; it never attaches to Herdr, signals a process or changes the input file.

python3 inspect-heartbeat.py heartbeat.jsonl

Download the read-only counter inspector · Python · Keep a deliberately synthetic three-line input

Three summaries mean different things.

Same PID, higher counter in the later observation

The recorded program made progress between observations. That supports this program's continuation during the interval; it does not establish that every pane or application succeeded.

Same last line in both observations

No additional line was observed. The program may be stopped, blocked, writing elsewhere or simply not due to write yet. Check the exact file and the job's own state; do not label every unchanged file a dead session.

Different PID or a counter that restarts

The evidence no longer describes one uninterrupted counter sequence. A restarted program, a reused file or several writers can produce this pattern. Keep the boundary rather than merging everything into one long run.

Use the summary as a pointer to evidence.

The inspector reports the number of valid records, first and last record, all observed PIDs, counter resets and malformed line numbers. A malformed line is retained as a reported problem; it is not silently counted as a heartbeat. The script does not identify which current operating-system process owns a historical PID.

For a second observation, run the same read-only command again after a meaningful interval for your program. Save both outputs if you need a record. Compare their last PID and counter, then check the actual job's result. Do not repeatedly restart a job merely because you have not yet found its output; a second invocation may create duplicate work.

The official session-state reference describes persistence features. Our original 0.9.5 run above remains the only native Herdr test claimed here. This new inspector was checked with synthetic text; it does not add evidence about sleep, SSH, upgrades or later versions.

StillShell publishes an independent visual explanation of Herdr. It is not an official Herdr site and does not represent any former organisation associated with this domain. Original diagrams, prose and heartbeat example are offered under CC0; upstream software retains its own licence.

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