codex

Codex CLI Skill

Use this skill when FORGE needs to delegate coding work to Codex CLI.

Default operating pattern:

1. Explore in read-only sandbox mode.
2. Implement with bounded automatic execution.
3. Verify with deterministic checks.
4. Resume by session id when follow-up is needed.

Codex currently exposes its machine-readable interface as JSONL events. Treat the event stream as canonical and derive the final result from the last assistant message plus terminal usage events.

Capabilities

explore(prompt, repo_path)

Use for read-only planning and repo analysis.

Preferred command:

codex exec --json --sandbox read-only "$PROMPT"

Expected behavior:

• no file edits
• command execution restricted by sandbox mode
• progress available via item.started and item.completed

implement(prompt, repo_path, verify_cmd)

Use for bounded code changes.

Preferred command:

codex exec --json --full-auto "$PROMPT"

Prompt requirements:

• specify the target repo and allowed scope
• require minimal edits
• name the verification command
• require a final summary of what changed and what passed

Expected behavior:

• Codex may edit files and run shell commands
• progress is visible through JSONL events
• final answer is delivered as the last assistant message

review(prompt, repo_path)

Use for read-heavy verification.

Preferred command:

codex exec --json --sandbox read-only "$PROMPT"

Review prompts should ask for:

• findings first
• concrete file references
• missing verification
• residual risk

resume_session(session_id, prompt)

Use to continue a prior noninteractive session.

Preferred command:

codex exec resume "$SESSION_ID" "$PROMPT" --json

The CLI also supports:

codex exec resume --last "$PROMPT" --json

Session Adapter Mapping

FORGE session field	Codex CLI
prompt	positional prompt
agent = "codex"	codex exec
tools	no direct allowlist flag
workdir	process working directory or --cd
timeout	managed by FORGE wrapper
budget	no direct cost-cap flag observed
resume	codex exec resume <session-id> [prompt] --json
output_mode	--json
analysis mode	--sandbox read-only
bounded edit mode	--full-auto

AgentResult Mapping

Map the JSONL stream into AgentResult as follows:

Codex event or field	AgentResult field
thread.started.thread_id	session_id
final assistant item.completed	output
turn.completed.usage.input_tokens	tokens_in
turn.completed.usage.output_tokens	tokens_out
command execution items	progress_events
failed command items	progress metadata or error if terminal

Important limitation:

• Current codex exec --json does not emit a single terminal object equivalent to Claude's result schema.
• Cost is not directly exposed in the observed JSONL event stream.

Safety Rules

• Use --sandbox read-only for exploration and review.
• Use --full-auto only for bounded implementation tasks.
• Do not rely on prompt-only tool restrictions; Codex does not currently expose a Claude-style --allowedTools surface.
• Prefer one implementer session plus a separate reviewer session over parallel editing sessions.