diff --git a/README.md b/README.md
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+++ b/README.md
@@ -71,6 +71,7 @@ claude
 | **Skill** | Creates output independently (skill) | [`weather-svg-creator`](.claude/skills/weather-svg-creator/SKILL.md) |
 
 ## DEVELOPMENT WORKFLOWS
+- [Cross-Model Claude Code + Codex](development-workflows/cross-model-workflow/cross-model-workflow.md) [![Implemented](!/tags/implemented.svg)](development-workflows/cross-model-workflow/cross-model-workflow.md)
 - [RPI](development-workflows/rpi/rpi-workflow.md) [![Implemented](!/tags/implemented.svg)](development-workflows/rpi/rpi-workflow.md)
 - [Boris Feb26 workflow](https://x.com/bcherny/status/2017742741636321619)
 - [Ralph plugin with sandbox](https://www.youtube.com/watch?v=eAtvoGlpeRU) [![Implemented](!/tags/implemented.svg)](https://github.com/shanraisshan/novel-llm-26)
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+# Cross-Model Claude Code + Codex Development Workflow
+
+## 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-5.3          │
+│  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-5.3          │
+│  Start a new Codex CLI session (Terminal 2).                            │
+│  Codex verifies the implementation                                      │
+│  against the plan.                                                      │
+│                                                                         │
+└─────────────────────────────────────────────────────────────────────────┘
+```
+
+## How cross-model workflow actually looks in production
+
+![Cross-Model Workflow](assets/cross-model-workflow.png)
+
+*Last Updated: 2026-03-05*