# feat: soft run control via code_saturne `control_file`

[florian-simvia]

Problem

To adjust a running case today, the only option is a hard kill + restart from
checkpoint — brutal, and it discards in-flight work. code_saturne already exposes a
lightweight steering mechanism (control_file, dropped in the run dir and polled by the
solver each time step) that csauto doesn't surface.

Proposal

Surface control_file in the CLI and the dashboard instead of killing:

• Graceful stop — set the last time step to the current one (clean stop + checkpoint).
• Extend — raise max_time_step by N without restarting.
• Checkpoint now — request a checkpoint at the next step.
• Flush logs.

csauto control RUNS case0007 --stop          # graceful stop
csauto control RUNS case0007 --extend 500     # +500 time steps
csauto control RUNS case0007 --checkpoint

Notes

• "Extend" is the high-value one: it avoids the kill + restart-from-checkpoint round-trip.
• Exact directive syntax follows the installed code_saturne version — read from docs, don't
  hardcode; write the control_file into the active RESU/<run> dir.
• Dashboard: add "Stop gracefully" + "Extend" actions alongside the existing hard "Kill"
  (which stays as a fallback). Log each action to .csauto.history.jsonl.

Acceptance criteria

• control --stop produces a clean stop + checkpoint (no orphaned process).
• control --extend N continues a running case without restart.
• control --checkpoint triggers a checkpoint at the next step.
• Actions surfaced in the dashboard and logged to history.
• Docs + tests (control_file written correctly and picked up by the solver).