When continuing a previous session, use codex exec resume --last via stdin. IMPORTANT: When resuming, you CANNOT specify model, reasoning effort, or other flags—the session retains all settings from the original run. Resume syntax: echo "your prompt here" | codex exec resume --last
Run the command, capture stdout/stderr, and summarize the outcome for the user.
Quick Reference
Use case
Sandbox mode
Key flags
Read-only review or analysis
read-only
--sandbox read-only
Apply local edits
workspace-write
--sandbox workspace-write --full-auto
Permit network or broad access
danger-full-access
--sandbox danger-full-access --full-auto
Resume recent session
Inherited from original
echo "prompt" | codex exec resume --last (no flags allowed)
Run from another directory
Match task needs
-C <DIR> plus other flags
Following Up
After every codex command, immediately use AskUserQuestion to confirm next steps, collect clarifications, or decide whether to resume with codex exec resume --last.
When resuming, pipe the new prompt via stdin: echo "new prompt" | codex exec resume --last. The resumed session automatically uses the same model, reasoning effort, and sandbox mode from the original session.
Restate the chosen model, reasoning effort, and sandbox mode when proposing follow-up actions.
Error Handling
Stop and report failures whenever codex --version or a codex exec command exits non-zero; request direction before retrying.
Before you use high-impact flags (--full-auto, --sandbox danger-full-access, --skip-git-repo-check) ask the user for permission using AskUserQuestion unless it was already given.
When output includes warnings or partial results, summarize them and ask how to adjust using AskUserQuestion.
