Codex App Compatibility Implementation Plan

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (- [ ]) syntax for tracking.

Goal: Make using-git-worktrees, finishing-a-development-branch, and related skills work in the Codex App's sandboxed worktree environment without breaking existing behavior.

Architecture: Read-only environment detection (git-dir vs git-common-dir) at the start of two skills. If already in a linked worktree, skip creation. If on detached HEAD, emit a handoff payload instead of the 4-option menu. Sandbox fallback catches permission errors during worktree creation.

Tech Stack: Git, Markdown (skill files are instruction documents, not executable code)

Spec: docs/superpowers/specs/2026-03-23-codex-app-compatibility-design.md

---

File Structure

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Task 1: Add Step 0 to using-git-worktrees

Files:

• Modify: skills/using-git-worktrees/SKILL.md:14-15 (insert after Overview, before Directory Selection Process)

• Step 1: Read the current skill file

Read skills/using-git-worktrees/SKILL.md in full. Identify the exact insertion point: after the "Announce at start" line (line 14) and before "## Directory Selection Process" (line 16).

• Step 2: Insert Step 0 section

Insert the following between the Overview section and "## Directory Selection Process":

## Step 0: Check if Already in an Isolated Workspace

Before creating a worktree, check if one already exists:

```bash
GIT_DIR=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
GIT_COMMON=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)
BRANCH=$(git branch --show-current)

If GIT_DIR differs from GIT_COMMON: You are already inside a linked worktree (created by the Codex App, Claude Code's Agent tool, a previous skill run, or the user). Do NOT create another worktree. Instead:

1. Run project setup (auto-detect package manager as in "Run Project Setup" below)
2. Verify clean baseline (run tests as in "Verify Clean Baseline" below)
3. Report with branch state:
   • On a branch: "Already in an isolated workspace at <path> on branch <name>. Tests passing. Ready to implement."
   • Detached HEAD: "Already in an isolated workspace at <path> (detached HEAD, externally managed). Tests passing. Note: branch creation needed at finish time. Ready to implement."

After reporting, STOP. Do not continue to Directory Selection or Creation Steps.

If GIT_DIR equals GIT_COMMON: Proceed with the full worktree creation flow below.

Sandbox fallback: If you proceed to Creation Steps but git worktree add -b fails with a permission error (e.g., "Operation not permitted"), treat this as a late-detected restricted environment. Fall back to the behavior above — run setup and baseline tests in the current directory, report accordingly, and STOP.

- [ ] **Step 3: Verify the insertion**

Read the file again. Confirm:
- Step 0 appears between Overview and Directory Selection Process
- The rest of the file (Directory Selection, Safety Verification, Creation Steps, etc.) is unchanged
- No duplicate sections or broken markdown

- [ ] **Step 4: Commit**

```bash
git add skills/using-git-worktrees/SKILL.md
git commit -m "feat(using-git-worktrees): add Step 0 environment detection (PRI-823)

Skip worktree creation when already in a linked worktree. Includes
sandbox fallback for permission errors on git worktree add."

---

Task 2: Update using-git-worktrees Integration section

Files:

• Modify: skills/using-git-worktrees/SKILL.md:211-215 (Integration > Called by)

• Step 1: Update the three "Called by" entries

Change lines 212-214 from:

- **brainstorming** (Phase 4) - REQUIRED when design is approved and implementation follows
- **subagent-driven-development** - REQUIRED before executing any tasks
- **executing-plans** - REQUIRED before executing any tasks

To:

- **brainstorming** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)
- **subagent-driven-development** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)
- **executing-plans** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)

• Step 2: Verify the Integration section

Read the Integration section. Confirm all three entries are updated, "Pairs with" is unchanged.

• Step 3: Commit

git add skills/using-git-worktrees/SKILL.md
git commit -m "docs(using-git-worktrees): update Integration descriptions (PRI-823)

Clarify that skill ensures a workspace exists, not that it always creates one."

---

Task 3: Add Step 1.5 to finishing-a-development-branch

Files:

• Modify: skills/finishing-a-development-branch/SKILL.md:38 (insert after Step 1, before Step 2)

• Step 1: Read the current skill file

Read skills/finishing-a-development-branch/SKILL.md in full. Identify the insertion point: after "If tests pass: Continue to Step 2." (line 38) and before "### Step 2: Determine Base Branch" (line 40).

• Step 2: Insert Step 1.5 section

Insert the following between Step 1 and Step 2:

### Step 1.5: Detect Environment

```bash
GIT_DIR=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
GIT_COMMON=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)
BRANCH=$(git branch --show-current)

Path A — GIT_DIR differs from GIT_COMMON AND BRANCH is empty (externally managed worktree, detached HEAD):

First, ensure all work is staged and committed (git add + git commit).

Then present this to the user (do NOT present the 4-option menu):

Implementation complete. All tests passing.
Current HEAD: <full-commit-sha>

This workspace is externally managed (detached HEAD).
I cannot create branches, push, or open PRs from here.

⚠ These commits are on a detached HEAD. If you do not create a branch,
they may be lost when this workspace is cleaned up.

If your host application provides these controls:
- "Create branch" — to name a branch, then commit/push/PR
- "Hand off to local" — to move changes to your local checkout

Suggested branch name: <ticket-id/short-description>
Suggested commit message: <summary-of-work>

Branch name: use ticket ID if available (e.g., pri-823/codex-compat), otherwise slugify the first 5 words of the plan title, otherwise omit. Avoid sensitive content in branch names.

Skip to Step 5 (cleanup is a no-op — see guard below).

Path B — GIT_DIR differs from GIT_COMMON AND BRANCH exists (externally managed worktree, named branch):

Proceed to Step 2 and present the 4-option menu as normal.

Path C — GIT_DIR equals GIT_COMMON (normal environment):

Proceed to Step 2 and present the 4-option menu as normal.

- [ ] **Step 3: Verify the insertion**

Read the file again. Confirm:
- Step 1.5 appears between Step 1 and Step 2
- Steps 2-5 are unchanged
- Path A handoff includes commit SHA and data loss warning
- Paths B and C proceed to Step 2 normally

- [ ] **Step 4: Commit**

```bash
git add skills/finishing-a-development-branch/SKILL.md
git commit -m "feat(finishing-a-development-branch): add Step 1.5 environment detection (PRI-823)

Detect externally managed worktrees with detached HEAD and emit handoff
payload instead of 4-option menu. Includes commit SHA and data loss warning."

---

Task 4: Add Step 5 cleanup guard to finishing-a-development-branch

Files:

• Modify: skills/finishing-a-development-branch/SKILL.md (Step 5: Cleanup Worktree — find by section heading, line numbers will have shifted after Task 3)

• Step 1: Read the current Step 5 section

Find the "### Step 5: Cleanup Worktree" section in skills/finishing-a-development-branch/SKILL.md (line numbers will have shifted after Task 3's insertion). The current Step 5 is:

### Step 5: Cleanup Worktree

**For Options 1, 2, 4:**

Check if in worktree:
```bash
git worktree list | grep $(git branch --show-current)

If yes:

git worktree remove <worktree-path>

For Option 3: Keep worktree.

- [ ] **Step 2: Add the cleanup guard before existing logic**

Replace the Step 5 section with:

```markdown
### Step 5: Cleanup Worktree

**First, check if worktree is externally managed:**

```bash
GIT_DIR=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
GIT_COMMON=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)

If GIT_DIR differs from GIT_COMMON: skip worktree removal — the host environment owns this workspace.

Otherwise, for Options 1 and 4:

Check if in worktree:

git worktree list | grep $(git branch --show-current)

If yes:

git worktree remove <worktree-path>

For Option 3: Keep worktree.

Note: the original text said "For Options 1, 2, 4" but the Quick Reference table and Common Mistakes section say "Options 1 & 4 only." This edit aligns Step 5 with those sections.

- [ ] **Step 3: Verify the replacement**

Read Step 5. Confirm:
- Cleanup guard (re-detection) appears first
- Existing removal logic preserved for non-externally-managed worktrees
- "Options 1 and 4" (not "1, 2, 4") matches Quick Reference and Common Mistakes

- [ ] **Step 4: Commit**

```bash
git add skills/finishing-a-development-branch/SKILL.md
git commit -m "feat(finishing-a-development-branch): add Step 5 cleanup guard (PRI-823)

Re-detect externally managed worktree at cleanup time and skip removal.
Also fixes pre-existing inconsistency: cleanup now correctly says
Options 1 and 4 only, matching Quick Reference and Common Mistakes."

---

Task 5: Update Integration lines in subagent-driven-development and executing-plans

Files:

• Modify: skills/subagent-driven-development/SKILL.md:268

• Modify: skills/executing-plans/SKILL.md:68

• Step 1: Update subagent-driven-development

Change line 268 from:

- **superpowers:using-git-worktrees** - REQUIRED: Set up isolated workspace before starting

To:

- **superpowers:using-git-worktrees** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)

• Step 2: Update executing-plans

Change line 68 from:

- **superpowers:using-git-worktrees** - REQUIRED: Set up isolated workspace before starting

To:

- **superpowers:using-git-worktrees** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)

• Step 3: Verify both files

Read line 268 of skills/subagent-driven-development/SKILL.md and line 68 of skills/executing-plans/SKILL.md. Confirm both say "Ensures isolated workspace (creates one or verifies existing)".

• Step 4: Commit

git add skills/subagent-driven-development/SKILL.md skills/executing-plans/SKILL.md
git commit -m "docs(sdd, executing-plans): update worktree Integration descriptions (PRI-823)

Clarify that using-git-worktrees ensures a workspace exists rather than
always creating one."

---

Task 6: Add environment detection docs to codex-tools.md

Files:

• Modify: skills/using-superpowers/references/codex-tools.md:25 (append at end)

• Step 1: Read the current file

Read skills/using-superpowers/references/codex-tools.md in full. Confirm it ends at line 25-26 after the multi_agent section.

• Step 2: Append two new sections

Add at the end of the file:

## Environment Detection

Skills that create worktrees or finish branches should detect their
environment with read-only git commands before proceeding:

```bash
GIT_DIR=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
GIT_COMMON=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)
BRANCH=$(git branch --show-current)

• GIT_DIR != GIT_COMMON → already in a linked worktree (skip creation)
• BRANCH empty → detached HEAD (cannot branch/push/PR from sandbox)

See using-git-worktrees Step 0 and finishing-a-development-branch Step 1.5 for how each skill uses these signals.

Codex App Finishing

When the sandbox blocks branch/push operations (detached HEAD in an externally managed worktree), the agent commits all work and informs the user to use the App's native controls:

• "Create branch" — names the branch, then commit/push/PR via App UI
• "Hand off to local" — transfers work to the user's local checkout

The agent can still run tests, stage files, and output suggested branch names, commit messages, and PR descriptions for the user to copy.

- [ ] **Step 3: Verify the additions**

Read the full file. Confirm:
- Two new sections appear after the existing content
- Bash code block renders correctly (not escaped)
- Cross-references to Step 0 and Step 1.5 are present

- [ ] **Step 4: Commit**

```bash
git add skills/using-superpowers/references/codex-tools.md
git commit -m "docs(codex-tools): add environment detection and App finishing docs (PRI-823)

Document the git-dir vs git-common-dir detection pattern and the Codex
App's native finishing flow for skills that need to adapt."

---

Task 7: Automated test — environment detection

Files:

• Create: tests/codex-app-compat/test-environment-detection.sh

• Step 1: Create test directory

mkdir -p tests/codex-app-compat

• Step 2: Write the detection test script

Create tests/codex-app-compat/test-environment-detection.sh:

#!/usr/bin/env bash
set -euo pipefail

# Test environment detection logic from PRI-823
# Tests the git-dir vs git-common-dir comparison used by
# using-git-worktrees Step 0 and finishing-a-development-branch Step 1.5

PASS=0
FAIL=0
TEMP_DIR=$(mktemp -d)
trap "rm -rf $TEMP_DIR" EXIT

log_pass() { echo "  PASS: $1"; PASS=$((PASS + 1)); }
log_fail() { echo "  FAIL: $1"; FAIL=$((FAIL + 1)); }

# Helper: run detection and return "linked" or "normal"
detect_worktree() {
  local git_dir git_common
  git_dir=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
  git_common=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)
  if [ "$git_dir" != "$git_common" ]; then
    echo "linked"
  else
    echo "normal"
  fi
}

echo "=== Test 1: Normal repo detection ==="
cd "$TEMP_DIR"
git init test-repo > /dev/null 2>&1
cd test-rep