Codex Exec — one-shot runtime adapter

Run exactly one caller-supplied Codex prompt as one process and capture its result. This skill does not choose work, retry, validate or continue.

Rules that change the command

• Sandbox from declared effects. -s read-only for review or analysis, workspace-write only for authorized edits, and network or wider access only when the caller explicitly requires those effects. "In case it needs it" is not a declared effect. -s limits only Codex's shell commands; the user's config.toml still starts its MCP servers. For review and CI add --ignore-user-config (auth still loads) and --ephemeral, or report the inherited MCP servers as undeclared effects. A permission denial inside the run (EPERM, "Operation not permitted") shows only what the mode blocks, not whether the host or the code would fail. Quote it and report the check as sandbox-limited under not run / not_checked: neither a pass nor a failed check. A host-side observation still stands; a host run is the caller's decision.
• Close stdin. codex exec reads the prompt from stdin when no prompt argument is given, and appends piped stdin to a prompt argument. A non-TTY run (CI, a script) with an open stdin can wait forever: the stdin hang. Feed the prompt on stdin and let it end, or redirect </dev/null.
• One deadline, never renewed. Fix one absolute deadline before the first attempt. Each invocation, including any retry the caller decides to make, gets only the time left before that deadline. A retry never gets a fresh budget: a loop that gives each attempt its own new timeout has silently multiplied the caller's bound. A missing, zero, negative or malformed bound prevents launch; an expired deadline stops before dispatch.
• No retry here. Report a timeout, error or empty output as it is. Another invocation is the caller's decision, under the same deadline.
• Capped capture, typed exit. Capture output to a file under a byte cap and report the exit status. A timeout is not a result.

Run it

In an AgentOps source checkout, use the guarded library. It enforces the deadline, the combined output cap (10 MiB default), process-group cleanup and echo detection:

# AGENTOPS_ROOT: the agentops source checkout. DEADLINE_EPOCH: absolute Unix
# time fixed once by the caller and reused by every invocation in its scope.
. "$AGENTOPS_ROOT/scripts/lib/codex-exec.sh"
CODEX_EXEC_EXTRA_ARGS=(--ignore-user-config --ephemeral)
CODEX_EXEC_DIR="$WORKSPACE" CODEX_EXEC_SANDBOX=read-only \
CODEX_EXEC_PROMPT_FILE="$PROMPT_FILE" CODEX_EXEC_DEADLINE_EPOCH="$DEADLINE_EPOCH" \
CODEX_EXEC_MAX_OUTPUT_BYTES=10485760 CODEX_EXEC_OUT_FILE="$OUTPUT" \
  codex_exec_guarded </dev/null

Outside a Git repository add CODEX_EXEC_SKIP_GIT_CHECK=1; to keep the final message outside the cap, add -o "$LAST" to that array (assigned on its own line).

An installed skill ships no scripts, so scripts/lib/codex-exec.sh is absent outside a source checkout. Run codex exec directly instead, with bash or zsh (flags as of codex-cli 0.163.0; confirm with codex exec --help; add --skip-git-repo-check and -o <file> as above):

case "${DEADLINE_EPOCH:-}" in ''|0*|*[!0-9]*) echo "no valid deadline; not launched" >&2; exit 2;; esac
TO=$(command -v timeout || command -v gtimeout) || { echo "no timeout; not launched" >&2; exit 2; }
remaining=$(( DEADLINE_EPOCH - $(date +%s) - 10 ))  # keep the 10 s KILL grace inside
[ "$remaining" -gt 0 ] || { echo "deadline passed or within 10 s; not launched" >&2; exit 124; }
set -o pipefail  # bash and zsh: $? is the failing stage, not head's
"$TO" -k 10 "$remaining" \
  codex exec --ignore-user-config --ephemeral -C "$WORKSPACE" -s read-only - <"$PROMPT_FILE" 2>&1 \
  | head -c 10485760 >"$OUTPUT"
rc=$?  # 124 timed out, 137 killed after grace, 127 no codex, else codex's status

An output file exactly at the cap was truncated, and its status reflects the closed pipe, not a review. The fallback has no survivor check or echo detection; report both as not enforced.

Exit codes (guarded library)

Reserved codes are runtime evidence, never a semantic verdict. A Codex 124 or 137 returns 124 with the STALL line; a Codex 2, 122, 123, 129, 130 or 143 returns with no codex-exec: stderr line, so check stderr, the capture and elapsed time before reading one as the runner's. Guarded runner internals covers inputs, host requirements, process supervision and the external sandbox wrapper.

Report, then stop

command:  exact argv or library call (prompt by reference)
sandbox:  -s value and the declared effect that needs it
bound:    absolute deadline and seconds remaining at launch
capture:  output path, byte cap, truncated yes/no
exit:     status and its meaning from the table
cleanup:  library result, or "not enforced" for the direct fallback

A Codex validator follows the judgment receipt convention and the model-dispatch recipe: a requested model flag or the model's own description does not prove which model ran. Siblings: claude-exec (one headless Claude prompt), agy-native (AGY) and agent-native (worker batches).