Sheet Splitter

---
name: sheet-splitter
description: >
  Split a bound drawing set PDF into individual sheet PDFs. Extracts sheet
  numbers from title blocks via vision, renames files. Triggers: 'split
  drawings', 'break up the drawing set', 'separate sheets'. Run after
  /project-setup.
argument-hint: "<drawing_set.pdf> [--output-dir <path>]"
disable-model-invocation: true
---

# Sheet Splitter

Splits a bound drawing set PDF into individual page PDFs. Mirrors what spec-splitter does for specifications.

## Pipeline Position
Run after `/project-setup` identifies bound drawing sets. Produces split PDFs and `sheet_index.yaml` consumed by `/schedule-extractor` and all drawing analysis skills.

This is valuable for:
- **Project teams**: Navigate drawings by sheet number instead of scrolling a multi-page PDF
- **Other skills**: schedule-extractor, tag-audit-and-takeoff, pe-review and every other drawing analysis skill work better with individual sheet files
- **AgentCM**: Split files become the basis for per-sheet structured data

## Workflow

```
Sheet Split Progress:
- [ ] Step 1: Check if drawings are already split
- [ ] Step 2: Locate the bound drawing set
- [ ] Step 3: Split into individual page PDFs
- [ ] Step 4: Extract sheet numbers from title blocks
- [ ] Step 5: Rename files with sheet number + title
- [ ] Step 6: Update project context
- [ ] Step 7: Write graph entry (AgentCM only)
```

### Step 1: Check if Drawings Are Already Split

Look for individual sheet PDFs. Drawings are already split if:
- **AgentCM**: `.construction/index/sheet_index.yaml` exists with individual sheet entries and file paths point to split PDFs
- Multiple PDFs exist with sheet number patterns in filenames (e.g., `A-1.1 - FLOOR PLAN.pdf`)
- A `sheet_index.yaml` exists in the drawings directory

If already split, report the count and skip. If AgentCM has the sheet index but files haven't been physically split on disk, offer to split using the existing metadata for naming.

### Step 2: Find ALL Drawing PDFs

Search the project directory for ALL PDFs that are drawings. Many projects have multiple drawing PDFs:
- **Multi-part sets**: Part1.pdf, Part2.pdf, Part3.pdf (split by file size)
- **Discipline sets**: Architectural.pdf, Civil.pdf, Electrical.pdf, Mechanical.pdf
- **Single combined**: one large PDF with all sheets

Search in:
- Folders named `drawings/`, `plans/`, `01 - Drawings/`, or similar (case-insensitive)
- The project root (some projects have no folder structure)
- Look for PDFs > 2MB with keywords: "plan", "drawing", "bid set", "dwg", discipline names

Process EACH PDF found. All split pages go to the same `sheets/` output directory.

If the user specifies a single file (`/sheet-splitter path/to/specific.pdf`), process only that file.

### Step 3: Split Pages

Run the split script on each drawing PDF found:

```bash
"${CLAUDE_PLUGIN_ROOT}/bin/construction-python" "${CLAUDE_SKILL_DIR}/scripts/split_drawing_set.py" \
  "{drawing_set.pdf}" \
  --output-dir "{drawings_directory}/sheets"
```

The script splits each page into its own PDF: `page_001.pdf`, `page_002.pdf`, etc. It does NOT attempt to read sheet numbers — that's unreliable across different title block formats.

### Step 4: Identify Sheets via Vision

After splitting, read each page to identify sheet numbers and titles:

Use PDF bookmarks and the title-block text layer only as candidates — they are often abbreviated or stale (e.g. a bookmark "Site Grading Plan" on a sheet printed "Proposed Site Plan"). The printed title block wins. Read the title block by vision whenever there is no candidate, the candidate disagrees with the title-block text, or the sheet number carries a suffix (e.g. `C9.04H`, `K-1.1`).

1. Rasterize the title block region of each page:
```bash
"${CLAUDE_PLUGIN_ROOT}/bin/construction-python" "${CLAUDE_PLUGIN_ROOT}/scripts/pdf/rasterize_page.py" "page_NNN.pdf" 1 --dpi 200 --output tb.png
```

2. Use vision on the rasterized title block: "Read the title block on this construction drawing. What is the sheet number and sheet title?"

3. Rename the file: `page_001.pdf` → `A-1.1 - FLOOR PLAN.pdf`

4. Update `sheet_index.yaml` with the identified sheet number, title, and discipline. When a bookmark title differs from the printed title, keep it as `bookmark_title`.

**Title blocks vary significantly across firms** — they can be on the east side, south side, or bottom-center. Some use VA standard forms, some use firm-specific formats. Vision handles all these variations.

### Step 5: Write Sheet Index

After identifying all sheets, write `{drawings_directory}/sheets/sheet_index.yaml` (shown below). Never write `.construction/index/` — that folder belongs to AgentCM; only read it.

### Output

```
sheets/
  A-1.1 - FLOOR PLAN.pdf         ← renamed by Claude via vision
  A-2.1 - ELEVATIONS.pdf
  S-1.1 - FOUNDATION PLAN.pdf
  page_006.pdf                    ← could not read title block
  ...
  sheet_index.yaml
```

### Step 6: Update Project Context

After splitting and identifying, update `.construction/skills/project_context.yaml` with:
- `documents.drawing_count`: number of sheets
- `documents.disciplines`: list of unique discipline prefixes found

### Step 7: Write Graph Entry (AgentCM only)

If AgentCM is present (`.construction/project.yaml` exists), write a graph entry:

```bash
"${CLAUDE_PLUGIN_ROOT}/bin/construction-python" "${CLAUDE_PLUGIN_ROOT}/scripts/graph/write_finding.py" \
  --type "drawings_split" \
  --title "Drawing set split: {N} sheets from {source_pdf}" \
  --data '{"sheet_count": N, "source_pdf": "...", "identified_count": M, "unidentified_count": K, "disciplines": ["A","S","M","E"]}'
```

Without AgentCM, skip — the `sheet_index.yaml` serves as the local record.

### Multi-Set Projects

When a project has multiple drawing set PDFs (e.g., Architectural, MEP, Civil as separate files), use the source PDF name as a subdirectory to avoid filename collisions:

```
sheets/
  Architectural_Bid_Set/
    page_001.pdf ... page_050.pdf
  MEP_Bid_Set/
    page_001.pdf ... page_030.pdf
  sheet_index.yaml  ← merged from all sets
```

Pass `--output-dir "{drawings_directory}/sheets/{source_pdf_stem}"` to the split script for each set. The `sheet_index.yaml` merge logic combines entries from all subdirectories into a single index.

Report to user: number of pages split, how many identified via vision, output location.

## File Safety
Never overwrite existing split sheet PDFs. If `sheets/` directory already contains files, check for conflicts before writing. The `sheet_index.yaml` merge uses additive logic — existing entries are preserved.

---

## Allowed Scripts

**Allowed scripts — exhaustive list.** Only execute these scripts during this skill:
- `scripts/split_drawing_set.py` — split bound PDF into per-page PDFs
- `${CLAUDE_PLUGIN_ROOT}/scripts/pdf/rasterize_page.py` — rasterize PDF pages for vision identification
- `${CLAUDE_PLUGIN_ROOT}/scripts/graph/write_finding.py` — graph entry (Step 7)