Cross-Model Workflow
A workflow that combines Claude Code and Codex CLI across two terminals, leveraging each model's strengths for planning, review, implementation, and verification.
Workflow
┌─────────────────────────────────────────────────────────────────────────┐
│ CROSS-MODEL CLAUDE CODE + CODEX WORKFLOW │
├─────────────────────────────────────────────────────────────────────────┤
│ │
│ STEP 1: PLAN Claude Code │
│ ───────────── Opus 4.6 │
│ Open Claude Code in plan mode (Terminal 1). Plan Mode │
│ Claude interviews you via AskUserQuestion. │
│ Produces a phased plan with test gates. │
│ │
│ Output: plans/{feature-name}.md │
│ │
│ ▼ │
│ │
│ STEP 2: QA REVIEW Codex CLI │
│ ────────────────── GPT-5.4 │
│ Open Codex CLI in another terminal (Terminal 2). │
│ Codex reviews plan against the actual codebase. │
│ Inserts intermediate phases ("Phase 2.5") │
│ with "Codex Finding" headings. │
│ Adds to the plan — never rewrites original phases. │
│ │
│ Output: plans/{feature-name}.md (updated) │
│ │
│ ▼ │
│ │
│ STEP 3: IMPLEMENT Claude Code │
│ ────────────────── Opus 4.6 │
│ Start a new Claude Code session (Terminal 1). │
│ You implement phase-by-phase │
│ with test gates at each phase. │
│ │
│ ▼ │
│ │
│ STEP 4: VERIFY Codex CLI │
│ ──────────────── GPT-5.4 │
│ Start a new Codex CLI session (Terminal 2). │
│ Codex verifies the implementation │
│ against the plan. │
│ │
└─────────────────────────────────────────────────────────────────────────┘Step-by-Step Breakdown
Step 1: Plan (Claude Code -- Opus 4.6, Plan Mode)
Open Claude Code in plan mode in Terminal 1. Claude interviews you via AskUserQuestion to understand the feature requirements, then produces a phased plan with test gates.
TIP
Plan mode ensures Claude focuses on designing the approach rather than jumping straight into code. The interview-style interaction helps surface edge cases and requirements early.
Output: plans/{feature-name}.md
Step 2: QA Review (Codex CLI -- GPT-5.4)
Open Codex CLI in Terminal 2. Codex reviews the plan against the actual codebase, looking for gaps, conflicts, or missing steps. It inserts intermediate phases (e.g., "Phase 2.5") with "Codex Finding" headings.
Important
Codex adds to the plan -- it never rewrites the original phases. This preserves the original planning intent while augmenting it with codebase-aware insights.
Output: plans/{feature-name}.md (updated in-place)
Step 3: Implement (Claude Code -- Opus 4.6)
Start a new Claude Code session in Terminal 1. Implement the feature phase-by-phase, following the reviewed plan. Each phase has a test gate that must pass before moving to the next.
Step 4: Verify (Codex CLI -- GPT-5.4)
Start a new Codex CLI session in Terminal 2. Codex verifies the implementation against the plan, checking that all phases were completed and test gates were satisfied.
Why Cross-Model?
Benefits of Cross-Model Workflows
- Independent verification: A different model reviewing the plan catches blind spots that the planning model might miss
- Codebase grounding: Codex CLI reviews the plan against real code, not just abstract requirements
- Separation of concerns: Planning and review happen in separate contexts, reducing confirmation bias
- Test gate enforcement: Phase-by-phase implementation with verification ensures nothing is skipped