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qex for agents

This page is also in the binary. Run qex help agents to read it with no network.

The three commands

ID=$(qex submit --cpu 2 --mem 4GB -- uv run train.py)
qex wait $ID
qex logs $ID

qex submit writes the id to stdout and writes nothing else, so ID=$(qex submit ...) is correct. A warning goes to stderr.

For work that is short and heavy and that you wait for now — a test suite, a release build, a data conversion — put qex run in front instead:

qex run -- make test

The job goes in the queue, so the other people and agents on the machine keep the capacity they claimed. The output arrives as it happens, and the exit code is the exit code of the job.

What you give up. qex run ties the job to that command, but only for the stops that it can catch. Ctrl-C stops the job, and a SIGTERM on qex run stops the job. A SIGKILL, and the hangup that a terminal sends when it closes, do not reach the job: it continues, and qex list finds it. That is right for work you are waiting for and wrong for work that outlives your attention.

   
short, and you wait for it now qex run -- ...
long, or you come back to it qex submit, then qex status <id> --wait

Your session can stop, and the work continues

This is the property that makes qex safe for an agent that a person can stop.

The job is not a child of your shell, and it is not a child of your agent. qex starts a supervisor in its own session, and the supervisor starts the job.

Each row below is true for a job of qex run as well, with one exception: Ctrl-C or a SIGTERM on the waiting qex run stops the job. That is the only difference between the two commands; see above.

What happens to a job of qex submit The job
Somebody stops your agent continues
Your terminal closes continues
The coordinator stops, or a new version replaces it continues, and it still writes its result

Nothing is lost, because the record of the job is on the disk and not in the memory of a process. Your wait is the only thing that stops.

You can therefore attach the wait again, at any time, from any session:

qex submit --id-file build.id -- make    # session 1
# a person stops the agent here. `make` continues.
qex status "$(cat build.id)" --wait      # session 2, and the result is there

The id is the handle. That command gives the same answer whether the job operates now, stopped one second ago, or stopped last night.

Put the id file where it lasts longer than your session. Your project directory or your home directory is correct. A scratch directory that your harness owns is not correct, and neither is /tmp. The job continues when the session stops, but the file goes with the session, and you then have no handle for a job that still operates. qex gives a warning when the file goes to such a directory.

If you lose an id, qex list shows each job with its directory and its command, and qex list --cwd . shows the jobs of this directory only.

A monitor script cannot do this. A monitor holds the answer in its own memory: stop the monitor, and the answer is gone. Keep the id in a file, and the answer waits for you instead.

Before you start work again in a new session, ask first. qex list shows what already operates, and qex status <id> gives the result of what stopped. A person who stops you pays nothing, and a person who stops you and then gets the same build twice pays for it.

Do not write a monitor script

Every monitor that you write waits for a proxy: a pattern in the process list, a line in a log file, a file that appears. A proxy can become permanently false, and nothing tells the monitor. It then waits for ever.

Four monitors were measured on one machine in one day, and together they slept for 95 hours. Not one of the conditions could ever become true. Three of them:

while pgrep -f "solve.py"; do sleep 60; done      # matches its own command line
until grep -q "DONE" run.log; do sleep 60; done   # the writer was killed
until grep -q "READY" ~/other.log; do sleep 60; done  # that file never existed

A different user found another kind later, on a machine that two agents shared. It had slept for 63 hours:

while true; do M=$(ps -Ao args | grep -c solver)
               K=$(ssh other-host 'ps -Ao args | grep -c solver')
               [ $M -eq 0 ] && [ $K -eq 0 ] && break; sleep 300; done

It waits for a COUNT to reach zero. The work of its author finished two days before, and the work of the OTHER agent held the count above zero. It also opened about 750 connections to the other machine while it waited.

The last three hold no pattern fault. They are careful commands. The fault is the proxy: a log line is evidence of the work, and evidence stops when the work stops, in a way that the monitor cannot see. On a machine that two agents share, “wait until nothing matches” can never become true, because the condition depends on somebody else.

qex waits for the process, and not for a proxy of the process.

qex watchers

That command finds the monitors of this kind on your machine. It removes its own process and the processes that started it before it reports anything, so it never finds itself.

If you operate inside a harness

qex wait blocks, and your harness — not qex — reports when a background command ends. Put the two together:

ID=$(qex submit -- make test)   # gives the id at once
qex status $ID --wait           # run THIS in the background of your harness

Use qex status --wait and not qex wait here. It blocks in the same way and gives the same exit code, and its output also holds the state, the exit code and the last lines of the error output. One command gives everything.

The exit codes

Code Meaning
0 The job succeeded.
1 The job failed.
124 Your wait reached its time limit. The job continues.
125 Something stopped the job: kill, timeout or out-of-memory.
126 The job did not run, because a job that it needed failed.
127 There is no job with that id.

The code 124 has the same meaning as the code of the timeout command. A timeout on qex wait stops your wait only. It does not stop the job.

Two fields that need care

pid is null after the job stops. While the job operates, pid gives the process. After the job stops, the machine can give that number to a different process, so qex removes it. The historical value is in last_pid, and it is for a reader only: never send a signal to it. To stop a job, use qex kill <id>, which is correct at each moment.

A claim is a promise, and not a measurement. Give guess when you do not know the size, and read usage in qex status --json after the job to learn the true size. qex also learns it for you and uses it for the next job of the same command in the same directory.

Tell the people who make qex

qex exists because somebody measured their own monitor scripts and gave the numbers: four of them on one machine, 95 hours between them. Every part of this page came from a report of that kind.

Something helped you — leave a comment on the testimonials issue. Give the number if you have one: the hours, the jobs, the size of the machine. Say which model you are and which harness runs you, because the faults are not the same in each harness: one owns a scratch directory and loses an id file, another reports a background command and needs qex status --wait instead of qex wait.

A recipe that is not in the documentation — the tips and tricks issue. qex has no timer of its own, because cron with qex submit --lock does it better; that recipe is there, with the guard that stops the queue from growing at each tick.

Something did not work — look for it first, and add to what is there.

gh issue list --repo stephenc/qex --state all --search "the words of your fault"
gh issue comment <number> --repo stephenc/qex      # add your machine and harness

A second report of one fault is useful: it says that the fault is common, and it frequently holds the detail that the first one did not. A second issue for one fault is not: it divides the answer between two pages, and the person who corrects it must read both and close one. Search the closed issues as well — your fault may be corrected already, in a version later than yours.

Open a new issue when nothing matches. A small fault is worth one: an option that you looked for and did not find, a message that made you look in the wrong place, an exit code that surprised you. Those reports are the ones that make a tool good, and each is cheaper to correct than the hour it costs the next reader.

Give four things, and no more:

  1. The command that you gave, in full.
  2. What qex wrote, in full. Use --json where the command has it.
  3. What you expected instead.
  4. qex version, and qex info --no-start if a coordinator operated.

Never put the output of --show-env in a public page, and never anything that a token can hide in. qex submit copies the environment of your shell to spec.json, so that output is a secret. See security.

If you cannot reach GitHub, give the words to the person that you work with and let them decide whether to send them.

Install this page as a skill

Your operator can put this material where you load it without asking:

mkdir -p ~/.claude/skills/qex
curl -fsSL https://raw.githubusercontent.com/stephenc/qex/main/skills/qex/SKILL.md \
  -o ~/.claude/skills/qex/SKILL.md

The page is ordinary Markdown, so it goes into AGENTS.md, a rule file or a prompt with no change. qex help agents holds the same material inside the binary, for a machine with no network.

Everything else

qex help <topic> covers job-file, resources, states, exit-codes and config. qex schema job and qex schema status give the JSON Schema of each format. See the reference for the full command list.