Codex

Codex CLI

Delegate coding tasks to Codex via the Hermes terminal. Codex is OpenAI's autonomous coding agent CLI.

Prerequisites

• Codex installed: npm install -g @openai/codex
• OpenAI API key configured
• Must run inside a git repository — Codex refuses to run outside one
• Use pty=true in terminal calls — Codex is an interactive terminal app

One-Shot Tasks

terminal(command="codex exec 'Add dark mode toggle to settings'", workdir="~/project", pty=true)

For scratch work (Codex needs a git repo):

terminal(command="cd $(mktemp -d) && git init && codex exec 'Build a snake game in Python'", pty=true)

Background Mode (Long Tasks)

# Robust background pattern: redirect stdin so Codex doesn't hang waiting for extra input
# Prefer --sandbox workspace-write; older notes/examples may use deprecated --full-auto.
terminal(command="codex exec --sandbox workspace-write 'Refactor the auth module' < /dev/null 2>&1 | tee /tmp/codex-auth.log", workdir="~/project", background=true, notify_on_complete=true)
# Returns session_id

# Monitor progress
process(action="poll", session_id="<id>")
process(action="log", session_id="<id>")

# Kill if needed
process(action="kill", session_id="<id>")

Critical learned behavior:

• In Hermes background mode, codex exec ... may print Reading additional input from stdin... and then hang indefinitely if stdin is left open.
• For non-interactive/background runs, always add < /dev/null.
• When the prompt is long, write it to a file and prefer stdin-as-prompt syntax: codex exec --sandbox workspace-write -C /abs/repo - < /abs/prompt.md > /tmp/codex-task.log 2>&1. Do not combine a prompt argument with piped stdin unless you intentionally want stdin appended as a <stdin> block.
• For read-only adversarial reviews, use the compact non-interactive pattern codex exec -C /abs/repo -s read-only - < /abs/review-prompt.md > /tmp/codex-review.out 2>&1; see references/codex-exec-review-patterns.md.
• Before adding approval/sandbox flags to codex exec, check codex exec --help; unsupported top-level/legacy flags can fail the run before review starts.
• If a background Codex run shows no progress and the output file only contains the stdin message, kill it and relaunch with stdin-as-prompt syntax (- < prompt.md) or with stdin redirected.
• In some sandboxed environments, Codex review/read-only analysis runs may emit bwrap: loopback: Failed RTM_NEWADDR: Operation not permitted when trying to shell-read local files. The run may still finish using only prompt-provided context, but its retrieval adequacy is degraded. For adversarial reviews, prefer embedding the full plan text in the prompt instead of assuming Codex can read repo files itself. For trusted local read-only analysis lanes where the sandbox blocks all file inspection, relaunch with --dangerously-bypass-approvals-and-sandbox only after the prompt states a no-write contract, uses absolute paths for prompt files, redirects stdin from /dev/null, and writes findings to a temp output file for orchestrator review.
• If Codex returns MAJOR, convert blockers into tests or explicit checks, fix under TDD, regenerate the prompt from the latest diff/artifacts, and rerun from a fresh log path before closeout.
• Do not point --output-last-message at the same artifact the prompt asks Codex to write. The CLI writes its final assistant message to that path at process exit and can overwrite a longer report that Codex created during the run. Use a separate --output-last-message /tmp/codex-last.md path, or rely on shell stdout redirection/logs and have the orchestrator copy the desired artifact after verification.

Key Flags

PR Reviews

Clone to a temp directory for safe review:

terminal(command="REVIEW=$(mktemp -d) && git clone https://github.com/user/repo.git $REVIEW && cd $REVIEW && gh pr checkout 42 && codex review --base origin/main", pty=true)

Parallel Issue Fixing with Worktrees

# Create worktrees
terminal(command="git worktree add -b fix/issue-78 /tmp/issue-78 main", workdir="~/project")
terminal(command="git worktree add -b fix/issue-99 /tmp/issue-99 main", workdir="~/project")

# Launch Codex in each
terminal(command="codex --yolo exec 'Fix issue #78: <description>. Commit when done.'", workdir="/tmp/issue-78", background=true, pty=true)
terminal(command="codex --yolo exec 'Fix issue #99: <description>. Commit when done.'", workdir="/tmp/issue-99", background=true, pty=true)

# Monitor
process(action="list")

# After completion, push and create PRs
terminal(command="cd /tmp/issue-78 && git push -u origin fix/issue-78")
terminal(command="gh pr create --repo user/repo --head fix/issue-78 --title 'fix: ...' --body '...'")

# Cleanup
terminal(command="git worktree remove /tmp/issue-78", workdir="~/project")

Batch PR Reviews

# Fetch all PR refs
terminal(command="git fetch origin '+refs/pull/*/head:refs/remotes/origin/pr/*'", workdir="~/project")

# Review multiple PRs in parallel
terminal(command="codex exec 'Review PR #86. git diff origin/main...origin/pr/86'", workdir="~/project", background=true, pty=true)
terminal(command="codex exec 'Review PR #87. git diff origin/main...origin/pr/87'", workdir="~/project", background=true, pty=true)

# Post results
terminal(command="gh pr comment 86 --body '<review>'", workdir="~/project")

Rules

1. Use PTY for interactive sessions — codex TUI/review sessions need pty=true; pure codex exec - < prompt.md > log 2>&1 background jobs can run without PTY and are often safer for non-interactive Hermes orchestration.
2. Git repo required — Codex won't run outside a git directory. Use mktemp -d && git init for scratch
3. Use exec for one-shots — codex exec "prompt" runs and exits cleanly
4. --sandbox workspace-write for building — auto-approves changes within the workspace sandbox; --full-auto is deprecated and should only appear in legacy command transcripts
5. Background for long tasks — use background=true and monitor with process tool plus PID/ps checks when launching through shell wrappers
6. Don't interfere — monitor with poll/log, be patient with long-running tasks
7. Parallel is fine — run multiple Codex processes at once for batch work