<purpose>
Insert a decimal phase for urgent work discovered mid-milestone between existing integer phases. Uses decimal numbering (72.1, 72.2, etc.) to preserve the logical sequence of planned phases while accommodating urgent insertions without renumbering the entire roadmap.
</purpose>

<required_reading>
Read all files referenced by the invoking prompt's execution_context before starting.
</required_reading>

<process>

<step name="parse_arguments">
Parse the command arguments:
- First argument: integer phase number to insert after
- Remaining arguments: phase description

Example: `/gsd:insert-phase 72 Fix critical auth bug`
-> after = 72
-> description = "Fix critical auth bug"

Validation:

```bash
if [ $# -lt 2 ]; then
  echo "ERROR: Both phase number and description required"
  echo "Usage: /gsd:insert-phase <after> <description>"
  echo "Example: /gsd:insert-phase 72 Fix critical auth bug"
  exit 1
fi
```

Parse first argument as integer:

```bash
after_phase=$1
shift
description="$*"

# Validate after_phase is an integer
if ! [[ "$after_phase" =~ ^[0-9]+$ ]]; then
  echo "ERROR: Phase number must be an integer"
  exit 1
fi
```

</step>

<step name="init_context">
Load phase operation context:

```bash
INIT=$(node ~/.claude/get-shit-done/bin/gsd-tools.js init phase-op "${after_phase}")
```

Check `roadmap_exists` from init JSON. If false:
```
ERROR: No roadmap found (.planning/ROADMAP.md)
```
Exit.

Read roadmap content for parsing.
</step>

<step name="verify_target_phase">
Verify that the target phase exists in the roadmap:

1. Search for "### Phase {after_phase}:" heading
2. If not found:

   ```
   ERROR: Phase {after_phase} not found in roadmap
   Available phases: [list phase numbers]
   ```

   Exit.

3. Verify phase is in current milestone (not completed/archived)
</step>

<step name="find_existing_decimals">
Calculate next decimal phase number:

```bash
DECIMAL_INFO=$(node ~/.claude/get-shit-done/bin/gsd-tools.js phase next-decimal "${after_phase}")
```

Extract from JSON:
- `next`: The next available decimal (e.g., "06.1", "06.3")
- `existing`: Array of existing decimals (e.g., ["06.1", "06.2"])
- `base_phase`: Normalized base phase (e.g., "06")

Store the result:
```bash
decimal_phase=$(echo "$DECIMAL_INFO" | jq -r '.next')
```

Examples:
- Phase 72 with no decimals -> next is 72.1
- Phase 72 with 72.1 -> next is 72.2
- Phase 72 with 72.1, 72.2 -> next is 72.3
</step>

<step name="generate_slug">
Convert the phase description to a kebab-case slug.

Use `generate-slug` command (init phase-op provides `phase_slug` for existing phase, but this is a new phase):
```bash
slug=$(node ~/.claude/get-shit-done/bin/gsd-tools.js generate-slug "$description" --raw)
```

Phase directory name: `{decimal-phase}-{slug}`
Example: `06.1-fix-critical-auth-bug` (phase 6 insertion)
</step>

<step name="create_phase_directory">
Create the phase directory structure:

```bash
phase_dir=".planning/phases/${decimal_phase}-${slug}"
mkdir -p "$phase_dir"
```

Confirm: "Created directory: $phase_dir"
</step>

<step name="update_roadmap">
Insert the new phase entry into the roadmap:

1. Find insertion point: immediately after Phase {after_phase}'s content (before next phase heading or "---")
2. Insert new phase heading with (INSERTED) marker:

   ```
   ### Phase {decimal_phase}: {Description} (INSERTED)

   **Goal:** [Urgent work - to be planned]
   **Depends on:** Phase {after_phase}
   **Plans:** 0 plans

   Plans:
   - [ ] TBD (run /gsd:plan-phase {decimal_phase} to break down)

   **Details:**
   [To be added during planning]
   ```

3. Write updated roadmap back to file

The "(INSERTED)" marker helps identify decimal phases as urgent insertions.

Preserve all other content exactly (formatting, spacing, other phases).
</step>

<step name="update_project_state">
Update STATE.md to reflect the inserted phase:

1. Read `.planning/STATE.md`
2. Under "## Accumulated Context" -> "### Roadmap Evolution" add entry:
   ```
   - Phase {decimal_phase} inserted after Phase {after_phase}: {description} (URGENT)
   ```

If "Roadmap Evolution" section doesn't exist, create it.

Add note about insertion reason if appropriate.
</step>

<step name="completion">
Present completion summary:

```
Phase {decimal_phase} inserted after Phase {after_phase}:
- Description: {description}
- Directory: .planning/phases/{decimal-phase}-{slug}/
- Status: Not planned yet
- Marker: (INSERTED) - indicates urgent work

Roadmap updated: {roadmap-path}
Project state updated: .planning/STATE.md

---

## Next Up

**Phase {decimal_phase}: {description}** -- urgent insertion

`/gsd:plan-phase {decimal_phase}`

<sub>`/clear` first -> fresh context window</sub>

---

**Also available:**
- Review insertion impact: Check if Phase {next_integer} dependencies still make sense
- Review roadmap

---
```
</step>

</process>

<anti_patterns>

- Don't use this for planned work at end of milestone (use /gsd:add-phase)
- Don't insert before Phase 1 (decimal 0.1 makes no sense)
- Don't renumber existing phases
- Don't modify the target phase content
- Don't create plans yet (that's /gsd:plan-phase)
- Don't commit changes (user decides when to commit)
</anti_patterns>

<success_criteria>
Phase insertion is complete when:

- [ ] Phase directory created: `.planning/phases/{N.M}-{slug}/`
- [ ] Roadmap updated with new phase entry (includes "(INSERTED)" marker)
- [ ] Phase inserted in correct position (after target phase, before next integer phase)
- [ ] STATE.md updated with roadmap evolution note
- [ ] Decimal number calculated correctly (based on existing decimals)
- [ ] User informed of next steps and dependency implications
</success_criteria>