/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, and records where the
  cover sheet's drawing index disagrees with the set, logging the ones that need
  an RFI for rfi-drafter. 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

In an AgentCM project the app splits drawing sets (Split & Rename), and this skill only says so (Step 1).

Workflow

Sheet Split Progress:
- [ ] Step 1: Check the mode, and whether 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, rename files with sheet number + title
- [ ] Step 5: Check the sheets against the drawing index
- [ ] Step 6: Write the sheet index
- [ ] Step 7: Update project context

Step 1: Check the Mode, and Whether Drawings Are Already Split

First read `.construction/project.yaml`. If it exists, AgentCM manages this folder: do not split, rename or index anything.

• Read `.construction/index/sheet_index.yaml`. When its entries carry AgentCM's sheet ids (a `sheets:` list whose entries each have an `id:`), report how many sheets AgentCM holds and tell the PE that a new or reissued bound set is split with **Split & Rename** in AgentCM, which keeps every sheet's id. A split made here writes PDFs AgentCM never registers, and its Rescan would index them as a second drawing set. Then stop.
• When that file is missing, or its entries have no `id` (an older sheet-splitter wrote a `pages:` list with `filename` and `page_index`), say which, say that this skill does not guess sheet ids, and stop. Do not edit the file.

Without `.construction/project.yaml`, drawings are already split if:

• 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.

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:

"${CLAUDE_PLUGIN_ROOT}/bin/construction-python" "${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, from the project folder:

mkdir -p ".construction/skills/sheet-splitter/pages"
"${CLAUDE_PLUGIN_ROOT}/bin/construction-python" "${CLAUDE_PLUGIN_ROOT}/scripts/pdf/rasterize_page.py" "{sheets_dir}/page_NNN.pdf" 1 --dpi 200 --output ".construction/skills/sheet-splitter/pages/tb_NNN.png"

Title-block images are working data: keep them under `.construction/skills/sheet-splitter/pages/`. Never put them in the sheets folder, where the PE's split sheets are, and never in `/tmp` or any other folder outside the project.

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: Check the Sheets Against the Drawing Index

The cover or title sheet usually lists every sheet in a drawing index (also called a sheet index or list of drawings). When the set has one, compare it with the title blocks read in Step 4. The title blocks still name the files; the index only shows where the set disagrees with itself.

1. Read the index sheet's tex