BPMN to Draw.io Converter

Overview

This skill converts BPMN 2.0 XML files into Draw.io native format (.drawio) using the bpmn2drawio Python tool. The tool provides:

• Automatic Graphviz-based layout for files without DI coordinates
• Four built-in themes with custom YAML branding support
• Visual markers for gateways (X, +, O) and task/event icons
• Complete swimlane support with proper hierarchy
• Model validation with error recovery

Conversion Workflow

Follow these steps in order. The workflow automatically handles dependency installation.

Step 1: Set Up Tool Path

The tool is bundled in the plugin's tools/bpmn2drawio/ directory. Use ${CLAUDE_PLUGIN_ROOT} for the plugin path (auto-set for marketplace-installed plugins):

# Use CLAUDE_PLUGIN_ROOT (auto-set for marketplace-installed plugins)
PLUGIN_DIR="${CLAUDE_PLUGIN_ROOT:-/path/to/plugins/bpmn-plugin}"
TOOL_SRC="$PLUGIN_DIR/tools/bpmn2drawio/src"

Step 2: Check and Install Python Dependencies

Check for required Python packages and install any that are missing:

# Check which packages are missing
python -c "import lxml" 2>/dev/null || echo "lxml: MISSING"
python -c "import networkx" 2>/dev/null || echo "networkx: MISSING"
python -c "import yaml" 2>/dev/null || echo "pyyaml: MISSING"
python -c "import pygraphviz" 2>/dev/null || echo "pygraphviz: MISSING (requires Graphviz)"

If any packages are missing (except pygraphviz), ask the user:

"The following Python packages are missing: [list]. Install them now with pip install [packages]?"

If user approves:

pip install lxml networkx pyyaml

Note: pygraphviz is handled separately in Step 3 because it requires Graphviz.

Step 3: Check Graphviz and pygraphviz

The tool's default --layout auto resolves to preserve — using the file's own BPMN DI coordinates — only when every element in the file already has a position, and falls back to Graphviz-based layout otherwise. Graphviz is therefore not required for files with complete DI coordinates, but you can't know in advance which files those are, so check availability up front:

# Check for Graphviz
dot -V 2>/dev/null && echo "Graphviz: OK" || echo "Graphviz: MISSING"

If Graphviz is missing, display this standardized error:

Error: Required dependency 'graphviz' not found

/bpmn-to-drawio requires Graphviz when a BPMN file's DI coordinates are
missing or incomplete (the default --layout auto falls back to Graphviz
in that case).

Installation instructions:
  Windows: choco install graphviz
  macOS:   brew install graphviz
  Linux:   sudo apt install graphviz libgraphviz-dev

After installing Graphviz, also install the Python bindings:
  pip install pygraphviz

After installing, run the command again.

Note: If your BPMN file already has COMPLETE layout coordinates (every
element positioned), --layout auto will use them and Graphviz is not
needed. Do not force --layout=preserve as a workaround unless you have
verified the file's DI is complete — on a partially-positioned file it
strands the unpositioned elements at (0,0) instead of laying them out.

If user wants to install Graphviz, guide them through:

# Detect OS and install
if [[ "$OSTYPE" == "linux-gnu"* ]]; then
    sudo apt-get update && sudo apt-get install -y graphviz libgraphviz-dev
elif [[ "$OSTYPE" == "darwin"* ]]; then
    brew install graphviz
elif [[ "$OSTYPE" == "msys" ]] || [[ "$OSTYPE" == "cygwin" ]] || [[ -n "$WINDIR" ]]; then
    choco install graphviz -y
fi

After Graphviz is installed, install pygraphviz:

pip install pygraphviz

Step 4: Analyze Source BPMN

Check for structural complexity — used later to populate the conversion summary:

• <bpmn:participant> - Multiple pools
• <bpmn:lane> - Swimlanes present

The tool's --layout auto (the default; see Step 5) inspects the parsed model and resolves the layout mode itself. Do not grep the file for DI coordinates here to pre-select a --layout flag — that duplicates a decision the tool already makes correctly.

Step 5: Run Conversion

Default (--layout auto) — let the tool decide:

PYTHONPATH="$TOOL_SRC" python -m bpmn2drawio input.bpmn output.drawio

This is the recommended invocation for nearly all conversions. auto is the default when --layout is omitted; the tool inspects the parsed model and resolves preserve or graphviz itself — no pre-check of the file's DI content required.

Explicit override — only after verifying the file's DI is complete:

PYTHONPATH="$TOOL_SRC" python -m bpmn2drawio input.bpmn output.drawio --layout=preserve

Forcing preserve on a file whose DI is missing or incomplete strands the unpositioned elements at (0,0). Prefer the default auto unless you have specifically verified every element already has a position.

Explicit override — force Graphviz even if DI coordinates exist:

PYTHONPATH="$TOOL_SRC" python -m bpmn2drawio input.bpmn output.drawio --layout=graphviz

With theme:

PYTHONPATH="$TOOL_SRC" python -m bpmn2drawio input.bpmn output.drawio --theme=blueprint

Verbose output for debugging:

PYTHONPATH="$TOOL_SRC" python -m bpmn2drawio input.bpmn output.drawio --verbose

Step 6: Validate Output

Verify the conversion succeeded:

# Check file was created and has content
ls -la output.drawio
head -30 output.drawio

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CLI Reference

Full command syntax, arguments, --theme/--layout/--direction/etc. options, and direction values — see ../references/bpmn2drawio-reference.md#cli-reference.

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Themes

Built-in theme options (default, blueprint, monochrome, high_contrast) and custom YAML brand configuration (event/task/gateway/swimlane colors, lane-color pattern matching) — see ../references/bpmn2drawio-reference.md#themes.

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Dependencies

Dependencies are checked and installed automatically during the conversion workflow (Steps 2-3).

Python Packages

• lxml - XML parsing
• networkx - Graph algorithms
• pyyaml - YAML configuration parsing
• pygraphviz - Graphviz Python bindings (requires Graphviz)

System Dependencies

• Graphviz - Required for automatic layout generation
  • Not required when the file has complete DI coordinates — the default --layout auto resolves to preserve automatically in that case

Manual Installation (if needed)

Python packages:

pip install lxml networkx pyyaml pygraphviz

Graphviz:

• Ubuntu/Debian: sudo apt-get install graphviz libgraphviz-dev
• macOS: brew install graphviz
• Windows: choco install graphviz

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Python API

For programmatic use within scripts (Converter, parse_bpmn, validate_model) — see ../references/bpmn2drawio-reference.md#python-api.

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Supported BPMN Elements

Full tables of supported Events, Activities, Gateways, Flows, and Containers (pools/lanes) — see ../references/bpmn2drawio-reference.md#supported-bpmn-elements.

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Troubleshooting

Common Issues

Issue	Cause	Solution
ModuleNotFoundError: bpmn2drawio	PYTHONPATH not set	Set PYTHONPATH="$TOOL_SRC" before running
ModuleNotFoundError: lxml	Missing dependency	Run pip install lxml
ModuleNotFoundError: pygraphviz	Graphviz not installed	Install Graphviz first, then pip install pygraphviz
Empty output file	Invalid BPMN input	Check BPMN file validity
Elements overlapping / stranded at (0,0)	--layout=preserve forced on a file with incomplete DI	Don't force --layout=preserve — use the default --layout auto, which already falls back to Graphviz for incomplete DI
Wrong flow direction	Default is LR	Use --direction=TB for vertical

Validation Errors

If the tool reports validation warnings:

# Run with verbose to see details
bpmn2drawio input.bpmn output.drawio --verbose

Common validation issues:

• Orphan elements: Tasks not connected to flows
• Missing end events: Process has no termination
• Dangling sequence flows: Flow references non-existent element

The tool attempts recovery for most issues but warnings indicate potential problems.

Manual Inspection

If output doesn't render correctly in Draw.io:

1. Open the .drawio file in a text editor
2. Check for <mxCell> elements with valid geometry
3. Verify cross-lane edges have parent="1"
4. Check that all referenced IDs exist

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Output Format

Conversion Summary

After successful conversion, report:

## Draw.io Conversion Summary

**Source File:** input.bpmn
**Output File:** output.drawio
**Theme:** default
**Layout:** graphviz
**Direction:** LR

### Elements Converted:
- Pools: X
- Lanes: X
- Tasks: X
- Gateways: X
- Events: X
- Sequence Flows: X
- Message Flows: X

### Validation:
✓ All elements converted successfully
✓ No orphan elements detected
✓ All flows connected

### Next Steps:
- Open output.drawio in Draw.io Desktop or diagrams.net
- Verify visual layout matches expectations
- Adjust element positions if needed

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Fallback: Manual Conversion

If the bpmn2drawio tool is unavailable and cannot be installed, fall back to manual conversion using the reference documents:

1. Conversion Standard: ../references/BPMN-to-DrawIO-Conversion-Standard.md
2. Element Styles: ../templates/element-styles.yaml
3. Draw.io Skeleton: ../templates/drawio-skeleton.xml

Manual Conversion Steps

1. Parse BPMN XML to extract elements, flows, and DI coordinates
2. Build coordinate registry for all elements
3. Generate Draw.io XML structure
4. Create pool and lane hierarchy
5. Place elements within lanes
6. Generate edges (intra-lane with relative coords, cross-lane with absolute)
7. Write output file

Critical Rules for Manual Conversion:

• Cross-lane edges MUST have parent="1" with absolute mxPoint coordinates
• Lane positions are relative to their parent pool
• Element positions are relative to their parent lane
• Always calculate absolute coordinates for cross-lane edge routing

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Performance

BPMN Size	Elements	Expected Duration	Notes
Small	5-15	Under 10 seconds	Simple processes, single pool
Medium	15-50	10-30 seconds	Multiple lanes, moderate gateways
Large	50-100	30-90 seconds	Multiple pools, complex routing
Very large	100+	1-3 minutes	Graphviz layout dominates at scale

Duration is dominated by Graphviz layout computation for files whose DI coordinates are missing or incomplete. When a file's DI coordinates are complete, the default --layout auto resolves to preserve automatically and conversion finishes in under 5 seconds regardless of size — no flag needed. Do not force --layout=preserve on a file with incomplete DI as a speed optimization: unpositioned elements are stranded at (0,0) instead of being laid out. Dependency installation (first run only) may add 30-60 seconds.

References

• Bundled Tool: ../tools/bpmn2drawio/ (source code included in this plugin)
• Original Repository: https://github.com/davistroy/bpmn/tree/main/bpmn2drawio
• Conversion Standard: ../references/BPMN-to-DrawIO-Conversion-Standard.md
• Element Styles: ../templates/element-styles.yaml
• Draw.io Skeleton: ../templates/drawio-skeleton.xml
• Example Files: ../examples/