# Summary
Claude Code supports a useful prompt-plus-stdin workflow:
```bash
echo "complex input..." | claude -p "summarize concisely"
```
Codex previously did not support the equivalent `codex exec` form. While
`codex exec` could read the prompt from stdin, it could not combine
piped input with an explicit prompt argument.
This change adds that missing workflow:
```bash
echo "complex input..." | codex exec "summarize concisely"
```
With this change, when `codex exec` receives both a positional prompt
and piped stdin, the prompt remains the instruction and stdin is passed
along as structured `<stdin>...</stdin>` context.
Example:
```bash
curl https://jsonplaceholder.typicode.com/comments \
| ./target/debug/codex exec --skip-git-repo-check "format the top 20 items into a markdown table" \
> table.md
```
This PR also adds regression coverage for:
- prompt argument + piped stdin
- legacy stdin-as-prompt behavior
- `codex exec -` forced-stdin behavior
- empty-stdin error cases
---------
Co-authored-by: Codex <noreply@openai.com>
