codex-delegate

Codex Delegate Skill

Claude is the supervisor. Codex CLI runs the mechanical work. Claude plans, constrains scope, reviews the diff, and verifies outcomes.

Why use this instead of raw codex exec

This wrapper is not cosmetic. It exists because every shipping task that bypasses it loses one of three things that have caused real incidents:

What the wrapper handles	What raw codex exec costs you
stdin closure (</dev/null)	Codex hangs indefinitely (issue #20919). One session hit a 25-minute zero-byte hang on 2026-05-14 because the supervising agent forgot the redirect.
.result.json structured contract (status / risks / files_changed / tests_run)	You parse raw stdout. On a 10 MB log this is multi-thousand tokens of grep + interpretation per run.
Brief template (references/task-template.md)	Codex drifts. F11 (over-applied a sweep rule to the meta-doc documenting the rule) and F12 (injected unrequested "Attributions: Karpathy, Simon Willison, ..." lines) both shipped from no-brief raw invocations.

Measured token savings (real dogfood, not estimates)

From a 6-round mixed-workload session (awesome-agentic-ai-zh 2026-05-14, see agent-collab-skills/docs/measured-benefits.md):

Workload	Saving vs Claude-inline	When it applies to you
Mechanical sweep × 2 parallel (e.g., term replacement, § strip, doc renumber)	~7× token reduction + caught 4 drift files	Repo with > 20 files needing the same edit
Mirror sync (zh-TW → zh-Hans + en, 8 files)	17-22× token reduction	Multi-locale docs / curricula
Multi-file rename / typed-API migration	~3× (extrapolated from Phase D title-sweep)	> 10 files following one pattern
Single-file < 50 line fix	~1× (don't bother)	Use Claude direct Edit
Architecture / debugging / security review	1× (skill cannot help)	Claude direct

The wrapper helps for token-heavy mechanical work. It does not help for judgment-heavy work — be honest about which one your task is.

Anti-patterns this skill prevents

• F11: Codex over-applies a sweep rule to documentation describing that rule. Prevented by agent-task-splitter brief that explicitly lists in-scope files.
• F14: Operator (Claude) defaults to Bash("codex exec ...") despite the rule saying use Skill("codex-delegate"). Prevented by a PreToolUse hook on the operator side (template below).
• Codex hang: 25-minute zero-byte run on 2026-05-14 because raw codex exec was invoked without </dev/null. Prevented by wrapper's mandatory stdin closure.

CLAUDE.md snippet to enforce routing

Drop this into your ~/.claude/CLAUDE.md (or repo-level CLAUDE.md) to make the rule operational rather than aspirational:

## Codex routing rule (enforced)

For any task that is mechanical, multi-file, has a clear pattern, or
batch-edits ≥ 5 files: invoke `Skill("codex-delegate", args="brief=...")`.
Do NOT use `Bash("codex exec ...")` for shipping tasks — it loses stdin
closure (codex hangs), the `.result.json` contract (no structured status),
and the brief template (Codex drifts F11/F12).

Optional mechanical enforcement: a PreToolUse hook on Bash that nudges raw
`codex exec` toward `Skill("codex-delegate")`. Reference implementation:
https://github.com/WenyuChiou/dotfiles-claude/blob/main/hooks/check_codex_skill_routing.py

→ The hook is non-blocking (warns only) so you can still run codex --version / codex exec resume / codex exec review without friction. Replace return 0 with return 2 in the hook to make it block instead of warn.

Hard rules

• Before invoking the wrapper, run codex --version via Bash. If it fails, stop and tell the user to npm install -g @openai/codex.
• When calling codex exec directly (not through the wrapper), close stdin explicitly (</dev/null); the wrapper handles this internally.
• Wrapper run leaves machine-readable status at <log-file>.result.json. Acceptance is Claude's job, not the wrapper's.
• Do not wrap the wrapper in Start-Process. Call it inline so file writes persist.

When to delegate

Mechanical → codex · Reasoning → claude · Long-context synthesis → gemini.

Full routing table and good/bad examples: references/delegation-targets.md.

Workflow

1. Brief: write .ai/codex_task_<name>.md with Context / Goal / Constraints / Acceptance. Template: references/task-template.md. For a judgment-sensitive task (debugging, write-capable change, review, research) — where an unsupported guess or a half-finished fix would hurt — also add the XML prompt blocks from references/codex-prompt-blocks.md to the Goal/Constraints. A pure mechanical sweep does not need them. If the brief was already written by agent-task-splitter at .ai/codex_task_<NNN>_<slug>.md, read .coord/plan.yml for round context first.

2. Run: from Claude Code Bash, invoke the wrapper from its install location:

   bash ~/.claude/skills/codex-delegate/scripts/run_codex.sh \
     --prompt "Read .ai/codex_task_<name>.md and execute all instructions inside." \
     --repo "$PWD" \
     --log-file .ai/codex_log_<name>.txt
   

   --repo defaults to the caller's $PWD; pass --repo "$PWD" explicitly only if you want to be defensive about the working directory at invocation. On non-Claude-Code agentskills.io hosts, substitute the host's skills directory (e.g. ~/.hermes/skills/<category>/codex-delegate/scripts/run_codex.sh). PowerShell variant + env vars: references/wrapper.md.

3. Read status: cat .ai/codex_log_<name>.txt.result.json.

   • success → diff still needs review.
   • fallback → Codex quota hit; Claude must take over.
   • error → wrapper failed; check <log>.error.

4. Accept: read the diff, confirm scope, run the verification commands listed in the task file. Reject if Codex drifted. Extended checklist: references/review-checklist.md.

Output contract

.result.json includes at minimum: status (success|fallback|error), delegate ("codex"), model, log_file, output_file, summary, risks, files_changed, tests_run, timestamp_utc. Full schema and status semantics: references/output-contract.md.

Compatibility

• Tested with @openai/codex 0.128.0 (May 2026). Should work with any version that accepts codex exec --sandbox workspace-write.
• Default model: gpt-5.5 (bumped from gpt-5.4 on 2026-05-14 per operator preference; override via --model or -Model). gpt-5.4 remains available and is ~3× cheaper per token if cost-sensitive — trade-offs and an A/B-test recipe live in references/model-selection.md. Other models on your CLI: see codex models.
• Wrapper calls codex exec --sandbox workspace-write -C <repo> -m <model>. The older --full-auto flag is deprecated in 0.128+ and was replaced.
• codex exec runs in non-interactive mode and auto-approves (no --ask-for-approval flag exists on exec; that flag is top-level only).
• Direct codex exec calls must close stdin (</dev/null) to avoid the historical hang (issue #20919).
• PowerShell wrapper requires $ErrorActionPreference to NOT be Stop so stderr writes (warnings, banners) don't trip the catch block.

See also

• references/delegation-targets.md — when to use vs avoid
• references/wrapper.md — full wrapper invocation, env vars, Windows runner notes
• references/task-template.md — task brief template
• references/codex-prompt-blocks.md — XML prompt blocks + recipes + anti-patterns for judgment-sensitive briefs
• references/output-contract.md — full .result.json schema, status semantics, .fallback_claude quota sentinel
• references/review-checklist.md — extended acceptance gate
• references/patterns.md — five single-task delegation shapes (context file, parallel, resume, structured output, review mode)
• references/multi-agent.md — leaf role in router/leaves architecture; when to route through research-hub-multi-ai or agent-task-splitter
• references/examples.md — concrete invocation examples on codex-cli 0.128.0+ syntax
• references/model-selection.md — gpt-5.4 vs gpt-5.5 trade-offs (A/B-tested) + when to override the default