A model that calls write_stdin with no live session probed sequential
session_ids (1, 2, 3, …), each failing, and the run ground on for a long
time before halting. The repeated-failure guard keys on a normalized,
80-char-truncated signature of the tool error, and the old message
"Unknown exec session_id %d" put the varying id inside that prefix, so
every probe produced a fresh signature and the 6x-same-error halt never
fired.
- Rewrite the unknown-session error so stable recovery guidance leads and
the id trails past the signature window: probing now collapses to one
signature and trips the halt, and the model is told how to recover
(start an exec_command, or use the file-edit tools).
- Pin session_id's schema Minimum to 1 so the advertised schema matches
the runtime floor (intArg min 1).
- system_prompt: state that session_id is only ever an id returned by a
still-running exec_command and must never be guessed or probed.
Tests pin the id-invariance of the signature and that distinct-id probing
now halts at the guard's stop threshold, plus the schema floor and the
recovery text. The TUI "Sent input" label on a failed write_stdin
(issue criterion 4) is a separate cosmetic concern in a shared hot path
and is left as a follow-up.