Mermint Markdown Workflow

Use this workflow to render Markdown Mermaid blocks into GitHub-friendly <picture> markup and SVG assets. Prefer running mermint directly from this GitHub repo with npx; do not assume a local checkout or global install. For hand-drawn or architecture-beta work, do not stop at a successful SVG render. Rasterize previews, inspect them visually, and iterate until readability and aesthetics are acceptable in both themes.

Inputs To Confirm

Target markdown file (example: README.md)
SVG output directory (example: svgs)
In-place overwrite vs separate output path
Whether Mermaid source must be preserved (--keep-mermaid)
Whether hand-drawn tuning is allowed, or whether the user wants the existing style preserved

Preflight Checks

Before rendering, check:

node is installed and version >= 22
npx is available
network access is available, because the CLI is fetched from GitHub

Example:

node --version
npx --version

Standard Commands

Primary command:

npx --yes git+https://github.com/alessandrobologna/mermint.git \
  --input README.md \
  --svg-dir svgs \
  --keep-mermaid

Use explicit themes when you want stable readme-style output:

npx --yes git+https://github.com/alessandrobologna/mermint.git \
  --input README.md \
  --svg-dir svgs \
  --light-theme default \
  --theme dark \
  --keep-mermaid

For non-interactive in-place conversion (CI/automation), add --yes:

npx --yes git+https://github.com/alessandrobologna/mermint.git \
  --input README.md \
  --svg-dir svgs \
  --keep-mermaid \
  --yes

For a non-destructive preview, write to a separate markdown output:

npx --yes git+https://github.com/alessandrobologna/mermint.git \
  --input README.md \
  --output /tmp/README.rendered.md \
  --svg-dir /tmp/mermint-svgs \
  --keep-mermaid

Raster Preview Commands

After SVG rendering, rasterize both light and dark outputs to PNG previews before judging quality. Prefer representative backgrounds:

light preview background: #ffffff
dark preview background: #0d1117

Preferred command with rsvg-convert:

mkdir -p /tmp/mermint-previews

for svg in svgs/*-light.svg; do
  png="/tmp/mermint-previews/$(basename "${svg%.svg}.png")"
  rsvg-convert --background-color '#ffffff' "$svg" -o "$png"
done

for svg in svgs/*-dark.svg; do
  png="/tmp/mermint-previews/$(basename "${svg%.svg}.png")"
  rsvg-convert --background-color '#0d1117' "$svg" -o "$png"
done

Fallback with ImageMagick:

mkdir -p /tmp/mermint-previews

for svg in svgs/*-light.svg; do
  png="/tmp/mermint-previews/$(basename "${svg%.svg}.png")"
  magick -background '#ffffff' "$svg" -flatten "$png"
done

for svg in svgs/*-dark.svg; do
  png="/tmp/mermint-previews/$(basename "${svg%.svg}.png")"
  magick -background '#0d1117' "$svg" -flatten "$png"
done

If neither rasterizer is available, open the SVGs in a browser and capture screenshots of both the light and dark variants before approving the result.

Frontmatter / Init Conventions

This workflow supports source-level Mermaid config in frontmatter/init, including:

config.look
config.fontFamily
config.architecture.iconPacks
x-mermint.rough

mermint includes a built-in aws icon pack for Mermaid architecture diagrams. Use aws:<icon> directly without adding a URL or local icon-pack path.

When generating or revising AWS architecture diagrams, read references/aws-architecture-icons.md before inventing icon names. Prefer concrete AWS service icons over generic Mermaid shapes when the service is known. Examples:

use aws:simple-storage-service for S3-style storage instead of disk
use aws:dynamodb for DynamoDB-style state instead of database
use aws:simple-queue-service for SQS instead of a generic queue/storage symbol
use aws:amazon-simple-notification-service or aws:simple-notification-service for SNS
fall back to generic Mermaid shapes only when there is no suitable AWS service icon

Use config.architecture.iconPacks only when you need:

additional non-AWS icon packs
a local override for the built-in aws pack
a pinned custom AWS pack snapshot

Optional Hand-Drawn Tuning

Enable hand-drawn rendering with either:

config.look: handDrawn in frontmatter/init
--look handDrawn on the CLI

Tune the Rough.js pass with x-mermint.rough in source config, or with CLI flags when you want a one-off override.

Supported rough keys:

roughness
fillWeight
fillStyle
hachureGap
hachureAngle
bowing
strokeWidth
seed
disableMultiStroke
disableMultiStrokeFill
preserveVertices

Important behavior:

rough precedence is CLI > source config > defaults
--look classic is incompatible with rough overrides
built-in aws icons work normally in hand-drawn mode
hand-drawn architecture-beta diagrams with icon references default to fillStyle: solid for icon legibility unless you explicitly set a fill style

Example with AWS icons and source-level Rough.js tuning:

---
config:
  look: handDrawn
x-mermint:
  rough:
    roughness: 0.55
    fillStyle: cross-hatch
    hachureGap: 1
    bowing: 0.8
    seed: 42
---
architecture-beta
  group api(aws:aws-api-gateway)[API Layer]
  service gateway(aws:aws-api-gateway)[API Gateway] in api
  group compute(aws:aws-lambda)[Compute]
  service fn(aws:aws-lambda)[Lambda] in compute
  gateway:R --> L:fn

Equivalent CLI shape for a one-off render:

npx --yes git+https://github.com/alessandrobologna/mermint.git \
  --input README.md \
  --svg-dir svgs \
  --keep-mermaid \
  --look handDrawn \
  --roughness 0.55 \
  --fill-style cross-hatch \
  --hachure-gap 1 \
  --bowing 0.8 \
  --seed 42

AWS Architecture Example

Built-in AWS icons with no extra pack config:

Legibility note:

if you use hand-drawn mode with architecture icons and do not specify fillStyle, mermint now defaults those diagrams to fillStyle: solid
set x-mermint.rough.fillStyle or --fill-style explicitly if you want hachure, cross-hatch, or another Rough.js fill style instead

---
config:
  look: handDrawn
---
architecture-beta
  group api(aws:aws-api-gateway)[API Layer]
  service gateway(aws:aws-api-gateway)[API Gateway] in api

  group compute(aws:aws-lambda)[Compute]
  service lambda(aws:aws-lambda)[Lambda] in compute

  group messaging(aws:simple-queue-service)[Messaging]
  service queue(aws:simple-queue-service)[SQS] in messaging

  gateway:R --> L:lambda
  lambda:B --> T:queue

Override the built-in aws pack only when needed:

---
config:
  architecture:
    iconPacks:
      aws: ./aws-architecture-service-icons.json
---
architecture-beta
  service queue(aws:simple-queue-service)[SQS]

If icon packs use relative paths, they resolve from:

diagram mode: directory of the input .mmd file
markdown mode: directory of the markdown file

`architecture-beta` Guardrails

architecture-beta is less predictable than simpler Mermaid diagram types. A render can succeed and still produce an unusable layout.

Prefer these constraints when creating or revising architecture diagrams:

keep labels short and conservative
avoid slash-heavy or punctuation-heavy labels unless you render-test them
avoid decorative edge labels unless they carry essential meaning
use junction for optional branches or fan-out instead of forcing extra direct edges between services

Recommended optional-branch pattern:

architecture-beta
  service relay(aws:kinesis-data-streams)[Relay]
  junction fanout
  service collector(aws:amazon-opensearch-service)[Collector]
  service archive(aws:simple-storage-service)[Archive]

  relay:R --> L:fanout
  fanout:T --> B:collector
  fanout:B --> T:archive

Fallback rule:

if architecture-beta still overlaps after one conservative rewrite, stop and either simplify further with a junction-based branch or ask whether to switch to flowchart while preserving the architecture meaning

Visual Inspection Workflow

For architecture-beta and hand-drawn output, use an image-capable model or visual inspection pass on rasterized PNG previews. Do not rely only on Mermaid parse success or SVG existence.

Inspect both:

the light-theme PNG on a light background
the dark-theme PNG on a dark background

When an image-capable model is available, provide both PNGs and ask it to evaluate:

readability at normal README viewing size
overlap, clipping, and cramped layout
contrast and legibility in both themes
icon clarity and whether hatching interferes with service recognition
whether the hand-drawn treatment feels intentional rather than noisy

If no visual model is available, do the same checklist manually in an image viewer or browser.

Quality Rubric

Treat the result as acceptable only when all of the following pass:

Layout: nodes, labels, icons, and edge labels do not overlap or clip.
Readability: labels are readable without zooming excessively and line crossings do not obscure meaning.
Theme contrast: the light variant reads cleanly on #ffffff, and the dark variant reads cleanly on #0d1117.
Icon clarity: AWS or other service icons remain recognizable and are not muddied by hatching or stroke noise.
Hand-drawn balance: the diagram feels organic, but not shaky, fuzzy, or visually exhausting.
Fill control: fills and hatching add texture without overpowering text, icons, or edge direction.
Visual consistency: light and dark variants feel like the same diagram, not two different layouts or densities.

Use a simple decision per preview:

pass: no change needed
adjust: structurally correct, but visual tuning is still needed
fail: layout or readability is not acceptable

Iterative Tuning Loop

When visual inspection finds problems:

Change only one or two rough parameters at a time.
Re-render the SVGs.
Re-rasterize both light and dark previews.
Re-run the visual inspection on both themes.
Stop once the rubric passes, or simplify the diagram structure if tuning alone is no longer helping.

Prefer two or three small iterations over one large uncontrolled change.

Symptom-driven parameter guide:

Too noisy or shaky:
- lower roughness
- lower bowing
- consider disableMultiStroke: true
- consider preserveVertices: true
Hatching is too dense or text/icons feel muddy:
- increase hachureGap
- lower fillWeight
- consider fillStyle: solid for icon-heavy architecture diagrams
Diagram feels too sterile or over-clean:
- increase roughness slightly
- increase bowing slightly
- decrease hachureGap slightly if fill texture is too sparse
Same structure, but a particular seed looks awkward:
- keep the geometry the same and change seed
Strokes or fill lines are too faint:
- increase strokeWidth
- increase fillWeight
Fine geometry is being distorted too much:
- lower roughness
- lower bowing
- enable preserveVertices

Practical defaults for iterative experiments:

adjust roughness in small steps such as 0.05
adjust fillWeight in small steps such as 0.1
adjust hachureGap in small steps such as 0.5
adjust bowing in small steps such as 0.1
keep seed fixed while tuning other parameters, then vary seed only after the style is close

Verification Checklist

After rendering:

Confirm markdown contains <picture> blocks:

rg -n "<picture>" README.md

If --keep-mermaid is expected, confirm preserved source blocks:

rg -n "data-mermint-source=\"true\"" README.md

Confirm SVG assets exist and are non-empty:

ls -la svgs

Rasterize both *-light.svg and *-dark.svg outputs to PNG previews on representative backgrounds.
Inspect both PNGs with an image-capable model or a manual visual pass.
Apply the quality rubric.
If the result is only adjust, iterate with small rough-parameter changes and re-check both themes.
For architecture-beta, do not accept the output just because it rendered successfully. Labels still need to be readable, icons need to stay legible, and the final layout must be usable in both themes.

Failure Recovery

If node --version is lower than 22, upgrade Node before running mermint.
If npx is unavailable, install a recent Node.js distribution that includes npm/npx.
If Playwright browsers are missing:

npx playwright install

If the error says Executable doesn't exist at .../chromium_headless_shell-<rev>/..., a generic npx playwright install may have installed the wrong browser revision for the Playwright version that mermint resolved.
In a local checkout, install the headless shell with the exact Playwright version from node_modules instead of relying on an unpinned CLI:

PLAYWRIGHT_VERSION=$(node -p "require('./node_modules/playwright/package.json').version")
npx --yes playwright@$PLAYWRIGHT_VERSION install chromium-headless-shell

If you are running mermint via npx --yes git+https://github.com/alessandrobologna/mermint.git ... and still hit the same chromium_headless_shell-<rev> error, do not keep retrying an unpinned npx playwright install. Re-run with a version-pinned Playwright CLI or switch to a local checkout long enough to discover the resolved version first.
If verification uses rg and it is unavailable, use grep instead.
If PNG preview generation is needed and rsvg-convert is unavailable, try magick.
If both rasterizers are unavailable, open the SVG in a browser and capture screenshots instead of skipping visual review.
If rendering fails due to invalid source rough config, fix x-mermint.rough values in source or remove conflicting --look classic.
If repeated rough tuning still produces a crowded or unreadable architecture-beta layout, simplify labels and edges or switch to a less layout-fragile Mermaid diagram type.

mermint-markdown-workflow