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

Explicit triggers: user says "diagram", "visualize", "flowchart", "draw", "architecture diagram", "process flow", "ER diagram", "UML", "sequence diagram", "class diagram", "neural network", "model architecture"

Proactive triggers:

• Explaining a system with 3+ interacting components
• Describing a multi-step process or decision tree
• Comparing architectures or approaches side by side

Skip when: a simple list or table suffices, or user is in a quick Q&A flow

Prerequisites

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

# macOS (Homebrew — recommended)
brew install --cask drawio
draw.io --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
draw.io --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").

0. Auto-update (first use per conversation) — silently keep the skill current. Check the timestamp of \x3Cthis-skill-dir>/.last_update. If the file is missing or older than 24 hours, run:

   git -C \x3Cthis-skill-dir> pull --ff-only && date +%s > \x3Cthis-skill-dir>/.last_update
   

   If the pull fails (offline, conflict, not a git checkout, etc.), ignore the error and continue normally. Do not mention the update to the user unless they ask.

Step 0.5 — 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 \x3Cname> style", "with my \x3Cname> style", "in \x3Cname> mode", "in the style of \x3Cname>". A bare with \x3Cname> does not count — "draw a diagram with redis" names a component, not a style. If a clear match is found → active preset = \x3Cname>.
• 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/\x3Cname>.json, falling back to \x3Cthis-skill-dir>/styles/built-in/\x3Cname>.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 \x3Cname> (confidence: \x3Clevel>)." See the Applying a preset subsection below for how the preset changes color/shape/edge/font decisions.

1. Check deps — verify draw.io --version succeeds; note platform for correct CLI path
2. Plan — identify shapes, relationships, layout (LR or TB), group by tier/layer
3. Generate — write .drawio XML file to disk. 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. Save the clean preview as \x3Cname>.png (single extension). Embedding is 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 \x3Cname>.drawio.png to signal embedded XML. For PNG with -e, run the IEND repair snippet 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). See Export → Post-export PNG repair. Report file paths.

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.

• 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:

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 that captures a user's visual preferences — palette, shape vocabulary, fonts, edge style. When a preset is active, it fully replaces the built-in conventions described in the ### Applying a preset subsection below (under ## Draw.io XML Structure).

Locations, in lookup order:

1. ~/.drawio-skill/styles/\x3Cname>.json — user presets (survive git pull).
2. \x3Cthis-skill-dir>/styles/built-in/\x3Cname>.json — built-ins shipped with the skill (default, corporate, handdrawn).

A user preset shadows a built-in of the same name.

Only user presets can have "default": true. When the user says "make \x3Cbuilt-in-name> my default", copy the built-in JSON to ~/.drawio-skill/styles/\x3Cname>.json first, then set default: true on the copy — leave the shipped built-in untouched.

Name normalisation: always lowercase the user-provided name before writing or looking up files (the preset schema enforces lowercase; uppercase names will fail validation).

Learn flow

Triggers: "learn my style from \x3Cpath> as \x3Cname>", "save this as \x3Cname> style", "remember this style as \x3Cname>".

Dispatch by file extension:

• .drawio, .xml → XML path
• .png, .jpg, .jpeg, .svg (rasterized flat image) → image path

Steps:

1. Load the extraction reference. Read references/style-extraction.md into context.
2. Extract following the XML path or image path procedure in the reference.
3. Normalize and build candidate. Convert the user-provided preset name to lowercase. Use this normalized name for ALL file paths in this flow. Build the candidate preset JSON and write it to /tmp/drawio-preset-\x3Cname>.json (where \x3Cname> is the already-normalized name). Do not save to ~/.drawio-skill/styles/\x3Cname>.json yet.
4. Render a sample using the sample-diagram skeleton in references/style-extraction.md, parameterized by the candidate preset. Export PNG to ./preset-\x3Cname>-sample.png using the same draw.io -x -f png -e -s 2 -o ./preset-\x3Cname>-sample.png /tmp/drawio-preset-\x3Cname>.drawio command the main workflow uses.
5. Show the user:
   • Preset summary table (palette hex values, shapes per role, font, edge style, extras).
   • The sample PNG path (and embed the image if the environment supports it).
   • Provenance line: source.type, source.path, extracted_at, confidence.
6. Wait for approval:
   • "save" / "looks good" → write candidate to ~/.drawio-skill/styles/\x3Cname>.json. Create ~/.drawio-skill/styles/ if it doesn't exist. Delete tempfile and sample PNG.
   • "change \x3Cfield> to \x3Cvalue>" → edit the in-memory candidate, re-render, re-ask.
   • "cancel" / "abort" / "no" → delete tempfile and sample PNG; nothing saved.

Error behavior:

Management operations

All operations are natural language — no slash commands.

Apply name normalisation (lowercase) to all \x3Cname>, \x3Ca>, \x3Cb> arguments before any file operation.

Preset file validation

When loading any preset (for generation or management), do a lightweight structural check:

• Required top-level fields present (name, version, palette, roles, shapes, font, edges).
• version === 1.
• Every populated palette slot has both fillColor and strokeColor as #RRGGBB.
• confidence ∈ {"low", "medium", "high"} if present.

On validation failure:

• During generation: warn the user, fall back to built-in conventions for this one diagram, do not mutate the file.
• During learn: refuse to save the candidate; report which field failed.

Draw.io XML Structure

File skeleton

\x3C?xml version="1.0" encoding="UTF-8"?>
\x3Cmxfile host="drawio" version="26.0.0">
  \x3Cdiagram name="Page-1">
    \x3CmxGraphModel>
      \x3Croot>
        \x3CmxCell id="0" />
        \x3CmxCell id="1" parent="0" />
        \x3C!-- user shapes start at id="2" -->
      \x3C/root>
    \x3C/mxGraphModel>
  \x3C/diagram>
\x3C/mxfile>

Rules:

• id="0" and id="1" are required root cells — never omit them
• User shapes start at id="2" and increment sequentially
• All shapes have parent="1" (unless inside a container — then use container's id)
• All text uses html=1 in style for proper rendering
• Never use -- inside XML comments — it's illegal per XML spec and causes parse errors
• Escape special characters in attribute values: &, <, >, "
• Multi-line text in labels: use 
 for line breaks inside value attributes (not literal \ ). Example: value="Line 1
Line 2"

Shape types (vertex)

Required properties

\x3C!-- Rectangle / rounded box -->
\x3CmxCell id="2" value="Label" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" vertex="1" parent="1">
  \x3CmxGeometry x="100" y="100" width="160" height="60" as="geometry" />
\x3C/mxCell>

\x3C!-- Cylinder (database) -->
\x3CmxCell id="3" value="DB" style="shape=cylinder3;whiteSpace=wrap;html=1;fillColor=#f5f5f5;strokeColor=#666666;fontColor=#333333;" vertex="1" parent="1">
  \x3CmxGeometry x="350" y="100" width="120" height="80" as="geometry" />
\x3C/mxCell>

\x3C!-- Diamond (decision) -->
\x3CmxCell id="4" value="Check?" style="rhombus;whiteSpace=wrap;html=1;fillColor=#fff2cc;strokeColor=#d6b656;" vertex="1" parent="1">
  \x3CmxGeometry x="100" y="220" width="160" height="80" as="geometry" />
\x3C/mxCell>

Containers and groups

For architecture diagrams with nested elements, use draw.io's parent-child containment — do not just place shapes on top of larger shapes.

Key rules:

• Add pointerEvents=0; to container styles that should not capture connections between children
• Children set parent="containerId" and use coordinates relative to the container

\x3C!-- Swimlane container -->
\x3CmxCell id="svc1" value="User Service" style="swimlane;startSize=30;fillColor=#dae8fc;strokeColor=#6c8ebf;" vertex="1" parent="1">
  \x3CmxGeometry x="100" y="100" width="300" height="200" as="geometry"/>
\x3C/mxCell>
\x3C!-- Child inside container — coordinates relative to parent -->
\x3CmxCell id="api1" value="REST API" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="svc1">
  \x3CmxGeometry x="20" y="40" width="120" height="60" as="geometry"/>
\x3C/mxCell>
\x3CmxCell id="db1" value="Database" style="shape=cylinder3;whiteSpace=wrap;html=1;" vertex="1" parent="svc1">
  \x3CmxGeometry x="160" y="40" width="120" height="60" as="geometry"/>
\x3C/mxCell>

Connector (edge)

CRITICAL: Every edge mxCell must contain a \x3CmxGeometry relative="1" as="geometry" /> child element. Self-closing edge cells (\x3CmxCell ... edge="1" ... />) are invalid and will not render. Always use the expanded form.

\x3C!-- Directed arrow — always include rounded, orthogonalLoop, jettySize for clean routing -->
\x3CmxCell id="10" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="2" target="3">
  \x3CmxGeometry relative="1" as="geometry" />
\x3C/mxCell>

\x3C!-- Arrow with label + explicit entry/exit points to control direction -->
\x3CmxCell id="11" value="HTTP/REST" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;exitX=0.5;exitY=1;exitDx=0;exitDy=0;entryX=0.5;entryY=0;entryDx=0;entryDy=0;" edge="1" parent="1" source="2" target="4">
  \x3CmxGeometry relative="1" as="geometry" />
\x3C/mxCell>

\x3C!-- Arrow with waypoints — use when edge must route around other shapes -->
\x3CmxCell id="12" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="3" target="5">
  \x3CmxGeometry relative="1" as="geometry">
    \x3CArray as="points">
      \x3CmxPoint x="500" y="50" />
    \x3C/Array>
  \x3C/mxGeometry>
\x3C/mxCell>

Edge style rules:

• Animated connectors: add flowAnimation=1; to any edge style to show a moving dot animation along the arrow. Works in SVG export and draw.io desktop — ideal for data-flow and pipeline diagrams. Example: style="edgeStyle=orthogonalEdgeStyle;flowAnimation=1;rounded=1;..."
• Always include rounded=1;orthogonalLoop=1;jettySize=auto — these enable smart routing that avoids overlaps
• Pin exitX/exitY/entryX/entryY on every edge when a node has 2+ connections — distributes lines across the shape perimeter
• Add \x3CArray as="points"> waypoints when an edge must detour around an intermediate shape
• Leave room for arrowheads: the final straight segment between the last bend and the target shape must be ≥20px long. If too short, the arrowhead overlaps the bend and looks broken. Fix by increasing node spacing or adding explicit waypoints

Distributing connections on a shape

When multiple edges connect to the same shape, assign different entry/exit points to prevent stacking:

Rule: if a shape has N connections on one side, space them evenly (e.g., 3 connections on bottom → exitX = 0.25, 0.5, 0.75)

Applying a preset

When the Workflow's step Resolve active preset identified a preset, it fully replaces the built-in palette, shape keywords, edge defaults, and font for this diagram — do not mix values from the built-in color table below.

Color lookup. For each role a shape plays (service / database / queue / gateway / error / external / security), resolve preset.roles[role] to a slot name, then preset.palette[\x3Cslot>] to the (fillColor, strokeColor) pair. If roles[role] is unset or the resolved slot is null, follow this fallback ladder:

1. Try the role's canonical slot (service→primary, database→success, queue→warning, gateway→accent, error→danger, external→neutral, security→secondary).
2. If that slot is also empty, pick the most-populated non-null slot in the preset.
3. Never reach into the built-in color table below — the preset is authoritative.

Decision and container shapes are not in preset.roles — they have shape vocabulary (preset.shapes.decision, preset.shapes.container) but no role-to-slot mapping. Pick their colors as follows:

• Decision (rhombus) → use preset.palette.warning (the canonical yellow slot in the built-in conventions). If warning is empty, apply the slot-fallback ladder above starting from warning.
• Container (swimlane) → use the palette slot matching the tier/grouping the container represents (e.g., a "Services" tier container uses primary; a "Data" tier uses success). If no tier signal is available, default to primary.

Shape keywords. Use preset.shapes[role] as the prefix of the vertex style string (before whiteSpace=wrap;html=1;...). Example: for a database role, if preset.shapes.database = "shape=cylinder3", the vertex style starts shape=cylinder3;whiteSpace=wrap;html=1;fillColor=.... The six named shape keys are service, database, queue, decision, external, container. Roles gateway, error, and security reuse preset.shapes.service unless the preset explicitly populates a key with their name.

Edges. Use preset.edges.style as the base edge style string. Append preset.edges.arrow. Per-edge routing keys (exitX/exitY/entryX/entryY/...) are still added by the usual routing rules in the rest of this document. If the flow between two shapes matches a token from preset.edges.dashedFor (either because the user's prompt used that word, or because one end of the edge plays a role whose typical relation is "optional"), append ;dashed=1 to the edge style.

Fonts. Append fontFamily=\x3Cpreset.font.fontFamily>;fontSize=\x3Cpreset.font.fontSize> to every vertex style. Container headers and swimlane titles additionally get fontSize=\x3Cpreset.font.titleFontSize>;fontStyle=1 when preset.font.titleBold is true.

Extras.

• preset.extras.sketch === true → append sketch=1 to every vertex style and every edge style.
• preset.extras.globalStrokeWidth !== 1 (any value other than the drawio default of 1, including 0.5) → append strokeWidth=\x3Cn> to every vertex style and every edge style.

Interaction with diagram-type presets (ERD / UML / Sequence / ML / Flowchart). Diagram-type presets earlier in this document set structural style keywords that the user preset must preserve (e.g., ERD tables rely on shape=table;startSize=30;container=1;childLayout=tableLayout;...). The rule: keep the diagram-type preset's structural keywords, then layer the user preset's color / font / edge / extras on top. When a diagram-type preset hardcodes a color (fillColor=#dae8fc, etc.) that conflicts with the user preset, the user preset's color wins. Exception: fillColor=none is structural — do not replace it with a palette color.

Color palette (fillColor / strokeColor)

Used only when no preset is active (see "Applying a preset" above).

Layout tips

Spacing — scale with complexity:

Routing corridors: between shape rows/columns, leave an extra ~80px empty corridor where edges can route without crossing shapes. Never place a shape in a gap that edges need to traverse.

Grid alignment: snap all x, y, width, height values to multiples of 10 — this ensures shapes align cleanly on draw.io's default grid and makes manual editing easier.

General rules:

• Plan a grid before assigning x/y coordinates — sketch node positions on paper/mentally first
• Group related nodes in the same horizontal or vertical band
• Use swimlane cells for logical grouping with visible borders
• Place heavily-connected "hub" nodes centrally so edges radiate outward instead of crossing
• To force straight vertical connections, pin entry/exit points explicitly on edges: exitX=0.5;exitY=1;exitDx=0;exitDy=0;entryX=0.5;entryY=0;entryDx=0;entryDy=0
• Always center-align a child node under its parent (same center x) to avoid diagonal routing
• Event bus pattern: place Kafka/bus nodes in the center of the service row, not below — services on either side can reach it with short horizontal arrows (exitX=1 left side, exitX=0 right side), eliminating all line crossings
• Horizontal connections (exitX=1 or exitX=0) never cross vertical nodes in the same row; use them for peer-to-peer and publish connections

Avoiding edge-shape overlap:

• Before finalizing coordinates, trace each edge path mentally — if it must cross an unrelated shape, either move the shape or add waypoints
• For tree/hierarchical layouts: assign nodes to layers (rows), connect only between adjacent layers to minimize crossings
• For star/hub layouts: place the hub center, satellites around it — edges stay short and radial
• When an edge must span multiple rows/columns, route it along the outer corridor, not through the middle of the diagram

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.

# Preview PNG (use this in step 4, before self-check) — NO -e
draw.io -x -f png -s 2 -o diagram.png input.drawio

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

# PDF export (final)
draw.io -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 && draw.io -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 (no IEND chunk).

Run this immediately after every -e PNG export:

python3 - "diagram.drawio.png" \x3C\x3C'PY'
import sys
p = sys.argv[1]
data = open(p, 'rb').read()
IEND = b'\x00\x00\x00\x00IEND\xaeB`\x82'
if not data.endswith(IEND):
    if data.endswith(b'\x00\x00\x00\x00'):  # truncated length field
        data = data[:-4]
    open(p, 'wb').write(data + IEND)
    print(f"repaired {p}")
PY

The endswith(IEND) guard makes this a no-op if 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 the IEND repair snippet (see Post-export PNG repair). SVG/PDF unaffected.
• -s — scale: 1, 2, 3 (2 recommended for PNG)
• -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.
• -b — border width around diagram (default: 0, recommend 10)
• -t — transparent background (PNG only)
• --page-index 0 — export specific page (default: all)

Browser fallback (no CLI needed)

When the draw.io desktop CLI is unavailable, generate a browser-editable URL by deflate-compressing and base64-encoding the XML:

# Encode .drawio XML into a diagrams.net URL
python3 -c "
import zlib, base64, urllib.parse, sys
xml = open(sys.argv[1]).read()
# Raw deflate (no zlib header) — diagrams.net uses mxGraph's raw inflate
c = zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS)
compressed = c.compress(xml.encode('utf-8')) + c.flush()
# Standard base64 (atob rejects url-safe -/_); strip any newlines
encoded = base64.b64encode(compressed).decode('utf-8').replace('\
', '')
print('https://viewer.diagrams.net/?tags=%7B%7D&lightbox=1&edit=_blank#R' + urllib.parse.quote(encoded, safe=''))
" input.drawio

This produces a client-side URL that opens the diagram in the browser for viewing and editing. No data is uploaded to any server — the entire diagram XML is encoded in the URL fragment (after #), which is never sent to the server. Useful when the user cannot install the desktop app.

Fallback chain

When tools are unavailable, degrade gracefully:

Checking if draw.io is in PATH

# Try short command first
if command -v draw.io &>/dev/null; then
  DRAWIO="draw.io"
elif [ -f "/Applications/draw.io.app/Contents/MacOS/draw.io" ]; then
  DRAWIO="/Applications/draw.io.app/Contents/MacOS/draw.io"
else
  echo "draw.io not found — install from https://github.com/jgraph/drawio-desktop/releases"
fi

Common Mistakes

Diagram Type Presets

When the user requests a specific diagram type, apply the matching preset below for shapes, styles, and layout conventions.

ERD (Entity-Relationship Diagram)

UML Class Diagram

Sequence Diagram

Architecture Diagram

ML / Deep Learning Model Diagram

For neural network architecture diagrams — ideal for papers targeting NeurIPS, ICML, ICLR.

Tensor shape convention: annotate each layer with input/output tensor dimensions in (B, C, H, W) or (B, T, D) format. Place dimensions as the second line of the label using 
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Flowchart (enhanced)