The executor seam collapses run()/start() (and the planned begin()) into one
resolve() + execute(): the handle IS the live process, and the foreground
result, the background cursor, and the deadline's promotion offer are
projections over the same spawn. ShellExecSpec.onExpiry ('kill' default /
'offer' / 'none') replaces the implicit method split; one stdout budget applies
everywhere, the 'start ignores timeoutMs' wart dies, and sync spawn throws are
contained into the same settled-killed handle as async rejections (result()
rejects with the original error, identity preserved for the sandbox
classification).
The promotion offer settles exactly once and never rejects — offer at an
'offer' deadline while running, undefined when the process settles first — so
'await execution.promotion' alone distinguishes the outcomes. An offer must be
answered synchronously; an unanswered one auto-declines back to the
kill-on-timeout behavior. accept() ends the deadline and detaches the caller's
abort signal; decline() kills and classifies timedOut.
tool-bash and tool-pwsh promote on timeout by default (promoteOnTimeout: true,
inert without run_in_background or a job registry): at the offer the running
handle registers as a job with the same hooks as run_in_background, mirrors
into ctx.activities (the web task list streams it, stop control included), and
the call returns { kind: 'promoted', jobId, timeoutMs, output } carrying the
output so far — the job cursor continues exactly after it. Any promotion
failure declines and falls back to the plain timeout kill. Descriptions and
the timeoutMs schema text advertise the semantics only when they hold;
recorded-session and web snapshot fixtures re-recorded with them.
Also repairs the four CI failures from the human-kill push: ui-activity's
missing dsh-session peer declaration (static + windows observational), the
observe owner-arm/outer-catch and killJob-stub coverage gaps, tool-workflow's
owned-run arm, and the timing-dependent projection-cache interval flush test
(now poll-based for coarse Windows timers).
Peer evidence and rejected alternatives (Codex's session model, a third seam
method, a second threshold knob) in the Agent Note
2026-08-26-shell-execute-timeout-promotion.
Yichen Jiang
d6bebc5783