drawio-skill

Draw.io Diagrams

Overview

Generate .drawio XML files and export to PNG/SVG/PDF/JPG locally using the native draw.io desktop app CLI.

Supported formats: PNG, SVG, PDF, JPG — no browser automation needed.

PNG, SVG, and PDF exports support --embed-diagram (-e) — the exported file contains the full diagram XML, so opening it in draw.io recovers the editable diagram. Use double extensions (name.drawio.png) to signal embedded XML.

When to use / when NOT to use

Use this skill for: polished, precise diagrams (architecture, network, strict UML, ERD), anything needing solid opaque fills, 10,000+ stock/branded shapes, swimlanes, or custom geometry, exported as editable PNG/SVG/PDF.

Do NOT use it — route elsewhere — for:

• A casual hand-drawn / whiteboard look → excalidraw or tldraw.
• Diagrams-as-code that live in git / render in Markdown → mermaid (general) or plantuml (UML).
• Freeform infinite-canvas sketching or freehand strokes → tldraw.

Bundled resources

When the workflow references one of these, read it on demand — none of them need to be in context up front.

File	Read it when
references/toolbox.md	You're not sure which bundled script fits a request, or want to chain several — a map of all 25 scripts grouped by use-case (author / import code / import IaC / live infra / compare / reverse-export / utilities) with an "I have X, I want Y → use Z" guide
references/xml-authoring.md	You're about to hand-write .drawio XML (workflow step 3) — file skeleton, shape/edge cells, containers, connection distribution, palette, spacing/grid rules. Not needed when a bundled generator writes the XML
references/mermaid-authoring.md	The diagram is a standard type with no custom styling/icon needs (flowchart, state, gantt, mindmap, timeline, journey, pie, …) and the CLI is ≥ v30 — author it as Mermaid text and let the CLI convert to native .drawio (structure only, layout free). Also documents the CLI's ELK --layout pass for XML
references/diagram-types.md	The user names a specific diagram type (ERD, UML class, sequence, C4, architecture, ML/DL, flowchart)
references/shapes.md + scripts/shapesearch.py	The diagram needs a specific shape — a cloud icon (AWS/Azure/GCP), Cisco/Kubernetes/network symbol, UML/BPMN/ER/electrical/P&ID element — or any time you'd otherwise guess a style= string. shapesearch.py "<keywords>" returns the exact official style for 10k+ shapes
scripts/aiicons.py	The diagram involves an AI/LLM brand (OpenAI, Claude, Gemini, Mistral, Llama, HuggingFace, Ollama, LangChain, …) — aiicons.py "<brand>" returns a draw.io image style for the brand logo (lobe-icons via CDN; --embed to inline). draw.io has no built-in AI logos. See references/shapes.md → "AI / LLM brand logos"
references/style-presets.md	The user asks to learn / save / list / set-default / delete a style preset, or you've resolved an active preset and need the application rules
references/style-extraction.md	You're inside the Learn flow and need the extraction procedure (called from style-presets.md)
references/troubleshooting.md	An export fails, vision rejects a PNG, or a rendering looks wrong
scripts/repair_png.py	After every -e PNG export — fixes draw.io's truncated IEND chunk (issue #8)
scripts/encode_drawio_url.py	The CLI is unavailable and you need a browser-fallback diagrams.net URL (--edit for an editable editor URL)
references/autolayout.md	The diagram is large or layout-heavy (dependency/call graph, code structure, >~15 nodes) and you want Graphviz to place nodes + route edges instead of hand-placing coordinates
scripts/pyimports.py · jsimports.py · goimports.py · rustimports.py	The user wants to visualize a Python, JS/TS, Go, or Rust project structure — extracts the import graph (transitive-reduced, optional --group containers, nested by sub-package) for autolayout
scripts/pyclasses.py	The user wants a Python class hierarchy / class diagram — extracts classes + inheritance edges (boxed by module with --group) for autolayout
scripts/tfimports.py · k8simports.py · composeimports.py	The user wants to visualize declared infrastructure (Terraform .tf, Kubernetes manifests, or docker-compose) — extracts the resource/service reference graph (official AWS/Azure/GCP/K8s icons for tf/k8s; service boxes + volume cylinders for compose) for autolayout
scripts/tfstate.py · dockerimports.py (+ k8simports.py)	The user wants to draw what is ACTUALLY running / deployed — pipe terraform show -json (deployed state), docker inspect $(docker ps -q) (live containers), or kubectl get all,ing,cm,secret,pvc -o json (live cluster, via k8simports) and get the real topology with the same official icons. See references/live-infra.md
scripts/drawiodiff.py	The user wants to compare / diff two diagrams or two snapshots ("what changed", infra drift) — drawiodiff.py old.drawio new.drawio -o diff.json emits a colour-coded graph (added=green, removed=red, changed=orange, same=grey) for autolayout. Matches by cell id (importer/live-snapshot output) or --by-label (hand-drawn)
scripts/timelapse.py	The user wants an architecture time-lapse / to see how a codebase's structure evolved over git history — timelapse.py <dir> --importer pyimports re-runs an importer at each sampled commit and assembles a self-contained HTML player (embedded frames, play/step controls). Best on a package with real import edges (point <dir> at the module root)
scripts/explain.py	The user wants to describe / document / summarize an existing .drawio in words (reverse of generating one) — explain.py diagram.drawio emits structured Markdown: components grouped by container/tier, relations (A —label→ B), per-page sections for multi-page/C4. Good for a README/PR summary or a text-only read-out
scripts/drawio2pptx.py	The user wants a PowerPoint deck / slides from a diagram — drawio2pptx.py diagram.drawio -o deck.pptx puts each page on its own 16:9 slide (page name as title), so a multi-page C4 model becomes a ready-to-present deck. Needs python-pptx (pip install python-pptx) + the draw.io CLI
scripts/svgflow.py	The user wants an animated / "flowing" diagram (data-flow, moving edges) — svgflow.py diagram.drawio -o flow.svg exports to SVG and makes every edge a marching-ants animation (dashes travel along the arrows). Self-contained looping .svg that renders on GitHub / any browser; --speed / --dash / --reverse
scripts/drawio2mermaid.py	The user wants to convert a .drawio into Mermaid text (diagrams-as-code for a Markdown file that GitHub renders) — drawio2mermaid.py diagram.drawio emits a flowchart (containers → subgraphs, edge labels kept, cylinder/rhombus shapes mapped); --fenced wraps in ```mermaid, multi-page → one graph per page. Structural only (styling/icons don't survive)
scripts/sqlerd.py	The user wants an ER diagram from SQL DDL — parses CREATE TABLE statements into per-table nodes (columns with PK/FK markers) and crow's-foot FK edges for autolayout
scripts/seqlayout.py	The user wants a sequence diagram — describe participants + messages as JSON and the script computes all lifeline/activation/arrow geometry deterministically (no hand-placed coordinates, no Graphviz needed)
scripts/c4.py	The user wants a C4 model (System Context / Container / Component) — levels JSON in, one multi-page .drawio out with official C4 shapes/colors and click-to-drill-down links between levels
scripts/validate.py	You generated a .drawio (especially via autolayout or for a large hand-placed diagram) and want a fast deterministic structural lint (dangling edges, dup/reserved ids, broken parents, overlaps) before the vision self-check. --score prints a readability score for comparing layout variants

Prerequisites

The draw.io desktop app must be installed and the CLI accessible:

macOS sandbox / sandbox isolation note (e.g., codex.app): In some sandboxed macOS environments, invoking the draw.io desktop CLI (even drawio --version) can crash the draw.io process or produce no output. If that happens, treat the CLI as unavailable in this sandbox isolation — do not keep retrying inside the sandbox. Prefer a non-sandboxed host environment (outside sandbox isolation) for any CLI export work, or use the browser fallback / XML-only outputs.

# macOS (Homebrew — recommended; CLI binary is `drawio`, not `draw.io`)
brew install --cask drawio
drawio --version

# macOS (full path if not in PATH)
/Applications/draw.io.app/Contents/MacOS/draw.io --version

# Windows
"C:\Program Files\draw.io\draw.io.exe" --version

# Linux
drawio --version

Install draw.io desktop if missing:

• macOS: brew install --cask drawio or download from https://github.com/jgraph/drawio-desktop/releases
• Windows: download installer from https://github.com/jgraph/drawio-desktop/releases
• Linux: download .deb/.rpm from https://github.com/jgraph/drawio-desktop/releases — do not use snap (AppArmor sandbox denies secrets/keyring on servers, causes crash)

Workflow

Before starting the workflow, assess whether the user's request is specific enough. If key details are missing, ask 1-3 focused questions:

• Diagram type — which preset? (ERD, UML, Sequence, Architecture, ML/DL, Flowchart, or general)
• Output format — PNG (default), SVG, PDF, or JPG?
• Output location — default is the user's working dir; honor any explicit path the user gives (e.g. "put it in ./artifacts/"). Don't ask if they didn't mention one.
• Scope/fidelity — how many components? Any specific technologies or labels?

Skip clarification if the request already specifies these details or is clearly simple (e.g., "draw a flowchart of X").

Step 0 — Resolve active preset. Determine which (if any) user-defined style preset applies to this generation.

• Scan the user's message for a phrase that clearly names a style preset: "use my <name> style", "with my <name> style", "in <name> mode", "in the style of <name>". A bare with <name> does not count — "draw a diagram with redis" names a component, not a style. If a clear match is found → active preset = <name>.
• Else, check ~/.drawio-skill/styles/ for any file with "default": true. If found → active preset = that one.
• Else → no preset active; fall through to the built-in color/shape/edge conventions for the rest of the workflow.

Load the preset JSON from ~/.drawio-skill/styles/<name>.json, falling back to <this-skill-dir>/styles/built-in/<name>.json. If the named preset exists in neither location, tell the user the name is unknown, list the available presets (user dir + built-in), and stop — do not silently fall back to defaults.

When a preset loads successfully, mention it in the first line of the reply: "Using preset <name> (confidence: <level>)." See references/style-presets.md → "Applying a preset" for how the preset changes color/shape/edge/font decisions.

1. Check deps — resolve which name the binary has on this system and use that name verbatim in every subsequent command in this workflow. Try in order: (a) drawio --version (the canonical name for Homebrew cask, jgraph .deb/.rpm, Arch AUR), (b) draw.io --version (older builds, some custom symlinks, some distro packages), (c) macOS .app direct: /Applications/draw.io.app/Contents/MacOS/draw.io --version, (d) Windows: "C:\Program Files\draw.io\draw.io.exe" --version. The first one that prints a version is your binary; remember the exact path/name and substitute it for drawio in every export command below. Do not copy the example commands verbatim if your binary is named differently — the examples use drawio only because it's the most common. On macOS-Homebrew, drawio is just a thin wrapper script that execs /Applications/draw.io.app/Contents/MacOS/draw.io — they run the same engine, so candidate (c) is only needed when the drawio wrapper is absent (e.g. the app was installed by drag-and-drop without the cask). Also note the major version the command printed: ≥ 30 unlocks Mermaid→.drawio conversion and the ELK --layout pass (see references/mermaid-authoring.md); on ≤ 29 both are unavailable — .mmd input fails and --layout corrupts argument parsing — so never emit those flags there.
2. Plan — identify shapes, relationships, layout (LR or TB), group by tier/layer
3. Generate — produce the .drawio file, choosing the authoring mode: (a) Mermaid → CLI convert when the diagram is a standard type with no custom styling/icon needs and the CLI is ≥ v30 — write a .mmd and run drawio -x -f xml -o <name>.drawio <name>.mmd, see references/mermaid-authoring.md (structure only; layout comes free; never --layout afterwards). (b) Hand-written XML for custom styling, vendor icons, swimlanes, precise geometry — read references/xml-authoring.md first (skeleton, cell forms, palette, spacing rules). (c) A bundled generator for the data-driven cases below. For large or layout-heavy diagrams (dependency/call graphs, code structure, >~15 nodes), don't hand-place — describe the graph as JSON and run python3 <this-skill-dir>/scripts/autolayout.py graph.json -o <name>.drawio to compute node positions + orthogonal edge routing via Graphviz (see references/autolayout.md; add --tune to auto-pick the more readable direction). For a Python / JS-TS / Go / Rust project, the matching importer (scripts/pyimports.py, jsimports.py, goimports.py, or rustimports.py) extracts the import graph (transitive-reduced; add --group to box modules by sub-package, nested for deep trees) ready for autolayout; for a Python class hierarchy, scripts/pyclasses.py extracts classes + inheritance instead; for Terraform / Kubernetes / docker-compose (scripts/tfimports.py, k8simports.py, composeimports.py), the importer extracts the resource/service reference graph — tf/k8s nodes resolve to their official cloud icons automatically; to draw what is actually running rather than the declared config, pipe terraform show -json into scripts/tfstate.py or docker inspect $(docker ps -q) into scripts/dockerimports.py (k8simports.py already accepts live kubectl get ... -o json) — see references/live-infra.md; for an ER diagram from SQL DDL, scripts/sqlerd.py parses CREATE TABLE into table nodes + crow's-foot FK edges. For a sequence diagram, skip autolayout entirely — describe participants + messages as JSON and run python3 <this-skill-dir>/scripts/seqlayout.py seq.json -o <name>.drawio (deterministic lifeline/activation/arrow geometry; see the script docstring for the JSON schema). For a C4 model, python3 <this-skill-dir>/scripts/c4.py c4.json -o <name>.drawio emits the full multi-page Context→Container→Component set with drill-down links (schema in the script docstring). For complex architecture diagrams with many visible edge labels, give labels labelBackgroundColor=#ffffff;fontSize=11 and use edge geometry x/y offsets plus <mxPoint as="offset" /> to move long labels into nearby whitespace instead of relying on draw.io's default midpoint placement. After generating any .drawio, run python3 <this-skill-dir>/scripts/validate.py <name>.drawio for a fast structural lint (dangling edges, dup ids, overlaps) before exporting. Default output dir is the user's working dir; if the user specified an output path or directory (e.g. ./artifacts/, docs/images/), use that instead — mkdir -p the target dir first. Apply the same dir choice to PNG/SVG/PDF exports in steps 4 and 7.
4. Export draft — run CLI to produce a preview PNG. Do NOT pass -e at this step — the embedded zTXt mxGraphModel chunk it adds causes vision APIs (Claude included) to return 400 "Could not process image" in step 5. Cap the preview width with --width 2000 (not -s 2) — Claude's vision API rejects images larger than 2576×2576px with "Unable to resize image — dimensions exceed the 2576x2576px limit", and -s 2 on a medium-or-larger diagram easily overshoots that ceiling. Save the clean preview as <name>.png (single extension). Embedding and full-resolution scale are for the final export only (step 7).
5. Self-check — use the agent's built-in vision capability to read the exported PNG, catch obvious issues, auto-fix before showing user (requires a vision-enabled model such as Claude Sonnet/Opus). If reading the PNG returns a 400 / "Could not process image" error, you almost certainly exported with -e by mistake — re-export without -e and retry once. If it still fails, skip self-check and continue to step 6.
6. Review loop — show image to user, collect feedback, apply targeted XML edits, re-export, repeat until approved
7. Final export — re-export the approved version to all requested formats. Use -e here (PNG/SVG/PDF) so the deliverable stays editable in draw.io; save as <name>.drawio.png to signal embedded XML. For PNG with -e, run python3 <this-skill-dir>/scripts/repair_png.py <name>.drawio.png immediately after — draw.io's CLI truncates the IEND chunk in -e PNG output (8 bytes missing), producing a corrupt file that vision APIs and strict PNG decoders reject (issue #8). Report file paths.

If drawio --version crashes or prints nothing (common in restricted macOS sandbox isolation like codex.app):

• Do not keep retrying CLI invocations inside the sandbox.
• Skip steps 4, 5, 6, and 7 (CLI export + PNG-based review) and use Browser fallback (scripts/encode_drawio_url.py) or deliver the .drawio XML only.
• If the user needs PNG/SVG/PDF outputs, ask them to run the export commands in a non-sandboxed host environment (outside sandbox isolation) and share the resulting files.

Escalation rule:

• If the binary exists on PATH (or known app path exists) but execution fails with abnormal exit, empty output, Electron startup failure, display/session error, or likely sandbox restriction, prefer one escalated retry before falling back.
• If the binary is missing entirely, do not escalate just to search more aggressively; go to install guidance or fallback.

Step 5: Self-Check

After exporting the draft PNG, use the agent's vision capability (e.g., Claude's image input) to read the image and check for these issues before showing the user. If the agent does not support vision, skip self-check and show the PNG directly.

Important: the draft PNG read here must have been exported without -e. Draw.io's -e flag emits a PNG with a truncated IEND chunk (8 bytes of type+CRC missing) that the Anthropic vision API rejects with 400 "Could not process image" (issue #8). The simplest fix for the preview step is to skip -e entirely; the final export in step 7 keeps -e and runs the repair snippet. If you see the 400 error here, re-export without -e and retry once; if it still fails (any other reason), skip self-check and proceed to step 6.

Check	What to look for	Auto-fix action
Overlapping shapes	Two or more shapes stacked on top of each other	Shift shapes apart by ≥200px
Clipped labels	Text cut off at shape boundaries	Increase shape width/height to fit label
Missing connections	Arrows that don't visually connect to shapes	Verify source/target ids match existing cells
Off-canvas shapes	Shapes at negative coordinates or far from the main group	Move to positive coordinates near the cluster
Edge-shape overlap	An edge/arrow visually crosses through an unrelated shape	Add waypoints (<Array as="points">) to route around the shape, or increase spacing between shapes
Stacked edges	Multiple edges overlap each other on the same path	Distribute entry/exit points across the shape perimeter (use different exitX/entryX values)
Edge-label overlap	Edge text overlaps another label, line, or node in the exported PNG	Keep the label on the edge, add a white label background, and move it locally with edge geometry x/y offsets into adjacent whitespace

• Max 2 self-check rounds — if issues remain after 2 fixes, show the user anyway
• Re-export after each fix and re-read the new PNG

Step 6: Review Loop

After self-check, show the exported image and ask the user for feedback.

Targeted edit rules — for each type of feedback, apply the minimal XML change:

User request	XML edit action
Change color of X	Find mxCell by value matching X, update fillColor/strokeColor in style
Add a new node	Append a new mxCell vertex with next available id, position near related nodes
Remove a node	Delete the mxCell vertex and any edges with matching source/target
Move shape X	Update x/y in the mxGeometry of the matching mxCell
Resize shape X	Update width/height in the mxGeometry of the matching mxCell
Add arrow from A to B	Append a new mxCell edge with source/target matching A and B ids
Change label text	Update the value attribute of the matching mxCell
Change layout direction	Full regeneration — rebuild XML with new orientation

Rules:

• For single-element changes: edit existing XML in place — preserves layout tuning from prior iterations
• For layout-wide changes (e.g., swap LR↔TB, "start over"): regenerate full XML
• Overwrite the same {name}.png (no -e) each iteration — do not create v1, v2, v3 files. -e is reserved for the final export in step 7.
• After applying edits, re-export and show the updated image
• Loop continues until user says approved / done / LGTM
• Safety valve: after 5 iteration rounds, suggest the user open the .drawio file in draw.io desktop for fine-grained adjustments

Step 7: Final Export

Once the user approves:

• Export to all requested formats (PNG, SVG, PDF, JPG) — default to PNG if not specified
• Report file paths for both the .drawio source file and exported image(s)
• Auto-launch: offer to open the .drawio file in draw.io desktop for fine-tuning — open diagram.drawio (macOS), xdg-open (Linux), start (Windows)
• Confirm files are saved and ready to use

Style Presets

A style preset is a named JSON file capturing a user's visual preferences (palette, shapes, font, edges). When active, it fully replaces the built-in color/shape conventions in this skill.

Lookup order when SKILL.md's Step 0 resolves a preset name:

1. ~/.drawio-skill/styles/<name>.json — user presets (survive git pull)
2. <this-skill-dir>/styles/built-in/<name>.json — shipped built-ins (default, corporate, handdrawn, colorblind-safe, dark)

Always lowercase the user-provided name before any file operation — the schema enforces lowercase.

For everything else — Learn flow (extracting a preset from a file), management ops (list/default/delete/rename), application rules (color lookup, shape keywords, edges, fonts, extras, interaction with diagram-type presets), and validation — read references/style-presets.md. It's only needed when the user invokes those flows or when an active preset must be applied to the current generation.

Authoring .drawio XML

Before hand-writing any .drawio XML (step 3), read references/xml-authoring.md — file skeleton, shape/edge cell forms, containers, connection-point distribution, color palette, and spacing/grid rules all live there. Skip it only when a bundled generator writes the XML for you (autolayout.py + importers, seqlayout.py).

Two rules worth stating even here: never reuse ids 0/1 (reserved root cells), and every edge mxCell needs a <mxGeometry relative="1" as="geometry" /> child — self-closing edge cells do not render.

Export

Commands

There are two export modes:

• Preview / self-check (step 4 of the workflow) — no -e. Output diagram.png. Required for vision self-check; using -e here triggers a 400 "Could not process image" error from the vision API (issue #8).
• Final / deliverable (step 7) — pass -e. Output diagram.drawio.png. The embedded XML keeps the file editable in draw.io.

All commands below write drawio as a placeholder for the binary you resolved in Step 1. If your binary is on PATH as draw.io (with dot — some older or distro-packaged installs), substitute draw.io throughout. If only the macOS .app or Windows .exe is available, use the full path variant shown a few lines down.

# Preview PNG (use this in step 4, before self-check) — NO -e, width-capped to stay under vision's 2576px ceiling
drawio -x -f png --width 2000 -o diagram.png input.drawio

# Final PNG (step 7, after user approval) — WITH -e, double extension
drawio -x -f png -e -s 2 -o diagram.drawio.png input.drawio

# macOS — full path (if not in PATH); preview / final variants
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f png --width 2000 -o diagram.png input.drawio
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f png -e -s 2 -o diagram.drawio.png input.drawio

# Windows
"C:\Program Files\draw.io\draw.io.exe" -x -f png -e -s 2 -o diagram.drawio.png input.drawio

# Linux (headless — requires xvfb-run; on servers add HOME and --disable-gpu)
export HOME=${HOME:-/tmp}
xvfb-run -a --server-args="-screen 0 1280x1024x24" \
  drawio -x -f png -e -s 2 -o diagram.drawio.png input.drawio --disable-gpu
# Running as root (CI / Docker)? Append --no-sandbox AT THE END (placing it earlier makes drawio treat it as the input filename)

# SVG export (final — -e is safe; SVG is text)
drawio -x -f svg -e -o diagram.svg input.drawio

# PDF export (final)
drawio -x -f pdf -e -o diagram.pdf input.drawio

# Custom output directory (e.g. CI artifacts dir) — create if missing, then export there
mkdir -p ./artifacts && drawio -x -f png -e -s 2 -o ./artifacts/diagram.drawio.png input.drawio

Post-export PNG repair (required after -e PNG export)

draw.io CLI truncates the IEND chunk when emitting -e PNGs — the file ends with the 4-byte IEND length field but the IEND type + CRC (8 bytes) are missing. Result: vision APIs return 400 "Could not process image" and strict PNG decoders error out. SVG/PDF are unaffected.

Run this immediately after every -e PNG export:

python3 <this-skill-dir>/scripts/repair_png.py diagram.drawio.png

The script's endswith(IEND) guard makes it a no-op once draw.io fixes the bug upstream — safe to run unconditionally.

Key flags:

• -x — export mode (required)
• -f — format: png, svg, pdf, jpg
• -e — embed diagram XML in output (PNG, SVG, PDF) — exported file remains editable in draw.io. Skip for the preview PNG used in step 5 self-check — -e PNGs have a truncated IEND chunk that vision APIs reject (issue #8). For final PNG export, keep -e and run scripts/repair_png.py (see Post-export PNG repair). SVG/PDF unaffected.
• -s — scale: 1, 2, 3 (2 recommended for final PNG; do NOT use for the step-4 preview — see --width)
• --width <px> — target width in pixels (no short form; -w does not exist and silently breaks the input-file parser). Use --width 2000 for the step-4 preview to keep the PNG under Claude's 2576×2576 vision ceiling. There's also a --height <px> flag for tall-narrow diagrams. Don't combine --width with -s.
• -o — output file path; accepts any directory (e.g. ./artifacts/diagram.drawio.png) — mkdir -p the target dir first. Use .drawio.png double extension when embedding.
• --layout <preset|json> — CLI ≥ v30 only — ELK auto-layout pass on XML input (verticalFlow, horizontalFlow, verticalTree, horizontalTree, radialTree, organic, or a custom ELK JSON array). Alternative to autolayout.py when Graphviz is missing; never combine with Mermaid-converted files (already laid out). On ≤ 29 this flag breaks argument parsing — don't emit it. See references/mermaid-authoring.md
• -b — border width around diagram (default: 0, recommend 10)
• -t — transparent background (PNG only)
• --page-index <n> — export one page of a multi-page file. 1-based in current drawio-desktop (verified on 29.7.8: --page-index 2 exports the second page; older docs claimed 0-based). Default: first page. --page-range 2..3 also works

Browser fallback (no CLI needed)

When the draw.io desktop CLI is unavailable, generate a client-side URL:

python3 <this-skill-dir>/scripts/encode_drawio_url.py input.drawio          # read-only viewer
python3 <this-skill-dir>/scripts/encode_drawio_url.py --edit input.drawio    # opens in the editor

Default prints a https://viewer.diagrams.net/...#R… viewer URL; --edit prints a https://app.diagrams.net/...#create=… URL that opens straight into the editable editor. Either way the diagram XML is encodeURIComponent-encoded, deflate-compressed, and base64'd into the URL fragment — the fragment (after #) is never sent to the server, so nothing is uploaded. The encodeURIComponent step is mandatory: without it, any diagram containing a literal % or non-ASCII (e.g. CJK) label makes the browser throw "URI malformed" and the diagram never opens.

Open the URL with open "$URL" (macOS) / xdg-open "$URL" (Linux). On WSL2 / Windows, cmd.exe drops the #fragment — write a .url shortcut file and open that instead (see references/troubleshooting.md → "WSL2 / Windows specifics").

Fallback chain

When tools are unavailable, degrade gracefully:

Scenario	Behavior
draw.io CLI missing, Python available	Use browser fallback (diagrams.net URL)
draw.io CLI missing, Python missing	Generate .drawio XML only; instruct user to open in draw.io desktop or diagrams.net manually
draw.io CLI crashes / no output in macOS sandbox isolation	Treat CLI as unavailable in-sandbox; use browser fallback / XML-only; ask user to run CLI exports in a non-sandboxed host environment
Vision unavailable for self-check	Skip self-check (step 5); proceed directly to showing user the exported PNG
Export fails (Chromium/display issues)	On Linux, retry with xvfb-run -a; if still failing, deliver .drawio XML and suggest manual export
Export fails on Linux server (headless)	Try in order: (1) xvfb-run -a, (2) append --no-sandbox at the very end if root, (3) add --disable-gpu, (4) export HOME=/tmp, (5) install apt deps (libgtk-3-0 libnotify4 libnss3 libgbm1 libasound2t64 etc.), (6) fall back to tomkludy/drawio-renderer Docker (REST API for headless export)

Checking if drawio is in PATH

# Prefer the Homebrew / Linux-package binary name (no dot)
if command -v drawio &>/dev/null; then
  DRAWIO="drawio"
# Fall back to the dot-named binary (older installs, manual symlinks)
elif command -v draw.io &>/dev/null; then
  DRAWIO="draw.io"
# macOS .app bundle (binary inside the bundle keeps the dot)
elif [ -f "/Applications/draw.io.app/Contents/MacOS/draw.io" ]; then
  DRAWIO="/Applications/draw.io.app/Contents/MacOS/draw.io"
# WSL2: the CLI is the Windows desktop exe, reached via /mnt/c (note the space)
elif grep -qi microsoft /proc/version 2>/dev/null && [ -f "/mnt/c/Program Files/draw.io/draw.io.exe" ]; then
  DRAWIO="/mnt/c/Program Files/draw.io/draw.io.exe"
else
  echo "drawio not found — install from https://github.com/jgraph/drawio-desktop/releases (Homebrew: brew install --cask drawio)"
fi

On WSL2 / native Windows, opening exported files and browser-fallback URLs needs path conversion + a .url-file workaround (cmd.exe drops URL #fragments) — see the "WSL2 / Windows specifics" section in references/troubleshooting.md.

Common Mistakes

When something looks wrong (export fails, vision rejects a PNG, layout broken, edges misroute), see references/troubleshooting.md for a row-by-row mistake → fix table.

Diagram Type Presets

When the user requests a specific diagram type, read references/diagram-types.md for the matching preset (shapes, edges, layout direction). Pick by user phrasing:

User says	Section in references/diagram-types.md
"ER diagram", "schema diagram", "data model"	ERD
"UML class diagram", "class diagram"	UML Class
"sequence diagram", "interaction diagram", "lifeline"	Sequence
"architecture", "system diagram", "service diagram"	Architecture
"neural network", "model architecture", "ML diagram", "deep learning"	ML / Deep Learning Model
"flowchart", "decision tree", "process flow"	Flowchart
"C4", "system context diagram", "container diagram", "component diagram"	C4 Model

The diagram-type preset sets structural style keywords. If a user style preset is also active (see ## Style Presets), keep the structural keywords and layer color/font/edge/extras on top — read references/style-presets.md → "Interaction with diagram-type presets" for the merge rules.