dsh-pele-mermaid

dsh-pele-mermaid

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git clone https://github.com/lsy1998/dsh-pele-mermaid.git
cd dsh-pele-mermaid
npm install
npm run build

Render Mermaid fenced code blocks in the DeepSeek Harness (DSH) Web GUI as SVG diagrams with Pele — no mermaid.js runtime is bundled or loaded.

Topics: deepseek-harness · dsh-plugin · mermaid · plugin

Pele is the lightweight Mermaid-to-SVG renderer from the Obsidian team (pele@1.9.0, MIT). It supports the diagram types built into Mermaid 12.1.0 and is themed with CSS variables.

Every Mermaid code block gets a Code / Diagram toggle, a fullscreen zoom viewer, standalone SVG export, DSW theme adaptation, and a clean fallback to source when a diagram cannot be rendered.

• Package: dsh-pele-mermaid 0.1.4
• Intended profile: desktop, owned by the DSH Desktop application
• Renderer: pele@1.9.0, served from a same-origin plugin route

Features

• Renders mermaid, mermaidjs and mmd fenced code blocks, and also recovers DSH/Shiki's plain fallback (a code element with no language- class) when Pele recognizes a Mermaid keyword at the start of the block.
• Never enhances a code block labelled with another language-* class, and never touches inline code.
• Code / Diagram toggle buttons with aria-pressed; diagram view is the default, and the original pre element is preserved for code view.
• An icon-only toolbar: a badge naming the detected diagram type next to "Pele", the Diagram/Code toggle, then zoom out / zoom in / reset, fullscreen and Download SVG, split into two groups by a hairline. Every control is a 16px stroked icon whose localized name lives in aria-label and title, so the bar stays one row wide in a narrow chat column and nothing is lost to a hover or a screen reader.
• Zoom and pan in place: the Zoom in / Zoom out / Reset zoom buttons in the toolbar, hold Ctrl (or Cmd) and scroll the wheel to zoom at the pointer, drag to pan, and use +, -, 0 and the arrow keys. A plain wheel still scrolls the page. The state is per block and resets when the diagram re-renders.
• Fullscreen viewer: zoom in / out / reset / fit, drag to pan, Ctrl or Cmd + wheel to zoom at the pointer, Escape to close, focus trapped while open and returned to the trigger on close, role="dialog" and aria-modal="true". It opens at the inline zoom and restores the inline scroll position and zoom when you close it.
• Exports a standalone .svg file named pele-<type>-YYYYMMDD-HHmmss.svg whose root carries the resolved theme variables, so it looks the same outside DSH. The export is always the whole diagram at its natural size — zooming or panning first does not crop it.
• Adapts to the DSW light and dark themes by mapping DSW design tokens onto Pele CSS variables. Colour changes need no re-render; geometry-only changes re-render the affected diagrams.
• Falls back to the diagram source with a localized error message — including Pele's line and column when it provides them — instead of leaving a broken diagram.
• Rejects individual diagrams over 50,000 characters or 2,000 lines before rendering and keeps them as source with a localized notice.
• Localizes every plugin-owned string in English and Simplified Chinese, and switches live when the document language changes.
• Renders through a serial queue, yields between diagrams to keep the page responsive, and discards stale asynchronous results while a response is still streaming.
• Idempotent and disposable: repeated enable/disable cycles leave no duplicate toolbars, observers or listeners behind.
• Accessible: localized aria-labels, accessible names on rendered diagrams, polite aria-live status announcements, and preserved focus-visible outlines.

Requirements

• The DSH Web GUI with the desktop profile. This release was verified against the bundled desktop runtime 0.2.1-rc.2 (@deepseek-ai/dsh-desktop and @deepseek-ai/dsh 0.2.1-rc.2) and the standalone dsh CLI 0.1.7-rc.1.
• Node.js 22.18 or later for building from source (the version this release was built and tested with); the package declares engines.node >= 22.18.0.
• DSH is a developer preview. Its plugin loader and Markdown DOM may change between releases.

Install

The plugin ships as a DSH profile plugin bundle. Its package.json declares dsh.bundle.patch = ./cordis.patch.yml, which inserts the bundle entry ui-pele-mermaid.

Recommended: install from the DSH app (desktop profile)

The desktop profile is managed by the DSH Desktop / DSH Web application, so install from the app:

1. Clone the repository and build it:

   git clone https://github.com/lsy1998/dsh-pele-mermaid.git
   cd dsh-pele-mermaid
   npm install
   npm run build
   

2. Open the DSH Web GUI and select Plugins in the sidebar.

3. Install a plugin and point it at the absolute package directory you just cloned, for example C:\path\to\dsh-pele-mermaid (Resolve-Path prints it).

4. Let the run finish and enable the bundle it added.

5. Restart DSH Web, or refresh the page, and open a session that contains a Mermaid block.

The app performs the package-manager call itself and registers the new bundle. The equivalent invocation is:

dsh plugin --profile desktop add -w --save-exact <absolute-path-to-dsh-pele-mermaid>

Verified caveat. A standalone dsh CLI refuses the desktop profile: dsh plugin --profile desktop --help exits with status 1 and prints error: profile "desktop" is managed exclusively by the Electron application; the guard is present in both the globally installed @deepseek-ai/dsh 0.1.7-rc.1 and the bundled 0.2.1-rc.2. Run that form from the app-managed context (the Plugins page), not from a plain terminal. --profile web is the CLI-installable alternative.

Command line (web profile)

dsh plugin --profile web add -w --save-exact <absolute-path-to-dsh-pele-mermaid>

Without a global dsh command, invoke the published CLI through npx (needs network access):

npx.cmd --yes @deepseek-ai/dsh plugin --profile web add -w --save-exact <absolute-path-to-dsh-pele-mermaid>

Restart DSH Web or refresh the page after installing.

Installer script

bin/dsh-pele-mermaid.mjs (also exposed as the dsh-pele-mermaid bin) wraps the same command:

# run from the package directory
node bin/dsh-pele-mermaid.mjs install
node bin/dsh-pele-mermaid.mjs install --profile web --source .
node bin/dsh-pele-mermaid.mjs uninstall --profile web
node bin/dsh-pele-mermaid.mjs --help

• install [--profile <name>] [--source <spec>] and uninstall [--profile <name>].
• --profile defaults to web, because the CLI cannot manage desktop; --profile desktop is refused with an explanatory message.
• --source accepts a package spec, an absolute path, or a ./-relative path resolved against the current directory; without it the script installs the package directory it lives in.
• --help prints bilingual English / Simplified Chinese usage.
• The script forwards to dsh plugin --profile <name> add -w --save-exact <spec> (uninstall: remove -w <name>) and exits non-zero with a clear message when dsh is missing.

For the desktop profile, use the app Plugins page instead: the CLI cannot manage it.

Update and uninstall

Web profile:

dsh plugin --profile web update -w dsh-pele-mermaid
dsh plugin --profile web remove -w dsh-pele-mermaid

For the desktop profile, update or remove the bundle from the app's Plugins page.

Restart DSH Web, or refresh the page, after updating or uninstalling.

Usage

Ask a model to output a Mermaid fenced code block:

```mermaid
flowchart LR
  A[Code] --> B[Diagram]
```

The block becomes a card that wraps the original pre. Diagram view is shown first; the Code control reveals the untouched source, and Diagram switches back. The fullscreen and download icons are available whenever a diagram rendered successfully.

Behaviour and limits

Note that Pele itself also defaults its source limit to 50,000 characters and rejects an over-limit source with a limit error, so both checks agree.

Theming

The plugin maps DSW design tokens onto Pele's CSS variables and emits them on its .dsh-pm container, where Pele inherits them. The first defined token wins; when a token is empty, Pele's own default is left in place.

Pele variables that are not mapped — for example --pele-critical and --pele-series-1 through --pele-series-8 — keep Pele's built-in defaults. Diagram-level style, classDef and linkStyle colours are fixed by the diagram and do not follow the theme.

Our own chrome (toolbar, badge, buttons, viewer) uses DSW design tokens — --dsw-alias-*, --ds-font-family-code and --dsw-font-markdown-code-block — with a literal fallback for every value, and respects prefers-reduced-motion.

Architecture

The package is a dual-face DSH plugin bundle:

• Host face — lib/index.js is a Cordis (Node) plugin that injects webServer and registers one exact route, /dsh-pele-mermaid/pele-runtime.js. A GET or HEAD request gets the vendored Pele script as text/javascript with an immutable cache header; anything else gets 404 or 405. The route is registered inside ctx.effect(...) so it is removed on disposal.
• Client face — lib/client.js registers itself with the DSH client module loader as @lsy1998/dsh-pele-mermaid (the package name; the loader matches it against each boot-graph row's id). It does not bundle Pele. The first detected Mermaid block injects <script data-dsh-pele-runtime src="/dsh-pele-mermaid/pele-runtime.js">; the loader is idempotent, dedupes concurrent calls, and window.pele becomes the Pele instance.
• Runtime copy — lib/pele-runtime.js is an unmodified copy of node_modules/pele/dist/pele.global.js from pele@1.9.0 (706,153 bytes, sha256 323c16de7844d4b609743f70449ebce041a531e4f48f23b1e9e7ec9d3b917287). The build copies it byte-for-byte; it is generated, never hand-edited.

Published package contents (11 files): package.json, cordis.patch.yml, lib/index.js, lib/client.js, lib/pele-runtime.js, bin/dsh-pele-mermaid.mjs, icon.svg, README.md, README.zh-CN.md, CHANGELOG.md and LICENSE.

Security

Pele escapes diagram text and renders it as SVG shapes, text, links and images; it does not turn diagram source into scripts, event handlers or HTML labels, and JavaScript callbacks in click statements are ignored. Links are limited to http, https, mailto and tel and images to http and https; javascript:, data: and vbscript: are always blocked, and links get rel="noopener".

This plugin's responsibilities:

• Error messages and diagram source are always written with textContent, never innerHTML, because Pele error messages embed the offending source line.
• The icons option returns null, so the plugin never injects third-party icon markup.
• Pele's own size limits stay in force (50,000-character source by default).
• The Pele runtime is served from the plugin's own same-origin route; no CDN is used.

Compatibility

• Pele 1.9.0 (MIT, obsidianmd/pele).
• Mermaid 12.1.0 syntax coverage, which is what Pele implements. Diagram types Pele does not recognize fall back to source with an unsupported-diagram message.
• DSH developer preview. Verified against the bundled desktop runtime 0.2.1-rc.2 and the dsh CLI 0.1.7-rc.1 on Windows, Node.js v22.18.0, npm 10.9.3 and pnpm 11.21.0.

Finding plugins

This repository carries the deepseek-harness and dsh-plugin topics, so it is listed with the other DeepSeek Harness plugins — browse them with GitHub topic: deepseek-harness and GitHub topic: dsh-plugin.

More DSH plugins and a one-click installer live at dshmarket.com.

Develop from source

npm install
npm run build
npm run check
npm test
npm run test:offline

• npm run build runs scripts/build.mjs: esbuild bundles src/client.js to lib/client.js (ES2022, minified, wrapped in the window.__ModuleLoader__.load(...) contract) and copies the Pele global script to lib/pele-runtime.js, recording its sha256.
• lib/client.js and lib/pele-runtime.js are generated by npm run build, but they are committed on purpose: a DSH profile can install this plugin straight from the GitHub source (github:lsy1998/dsh-pele-mermaid), and that install path runs no build step, so the browser bundle and the Pele runtime have to be in the repository. Re-run npm run build and commit the result whenever you change anything under src/. lib/index.js is hand-written source and the build fails fast if it is missing.
• The build runs from the prepack script, not prepare. pnpm 11 refuses to install a git-hosted dependency that declares an install-time lifecycle script (prepare, preinstall, install, postinstall) unless the consumer allowlists it in pnpm-workspace.yaml; the DSH CLI owns that file, so an installer cannot approve the script there and the install fails with ERR_PNPM_GIT_DEP_PREPARE_NOT_ALLOWED. Because the build outputs are committed, the install path needs no script at all — prepack still rebuilds fresh artifacts when the package is packed or published.
• npm run check runs node --check on the JavaScript it ships and builds (including the built lib/client.js and the installer), then npm run test:offline.
• npm test runs node --test test/. It uses happy-dom and needs no network or browser, but node starts one child process per test file.
• npm run test:offline runs the same suite in one process with node --test --experimental-test-isolation=none "test/**/*.test.mjs". Use this in sandboxes that block node's per-file test child processes, where npm test fails with a spawn EPERM error; npm run check already uses it.

On PowerShell hosts that block npm.ps1, use npm.cmd instead. Sandboxed environments that block npm lifecycle scripts may need --ignore-scripts (the esbuild binary ships prebuilt).

Troubleshooting

• A block stays as source. Check that it is over the 50,000-character or 2,000-line limit, or that it is valid Mermaid 12.1.0 syntax; both cases deliberately keep the source and show a localized message instead of a diagram.
• Nothing renders at all. Confirm the ui-pele-mermaid bundle is enabled in the profile and that the app was restarted or the page refreshed after installation.
• Colours or text geometry look stale after a theme change. Colours are inherited and update without a re-render; font or geometry changes re-render the diagrams through Pele.
• The installer rejects a path. On Windows it refuses --profile or --source values that contain & | < > ^ % ! ( ) or quotes; use a path without those characters.

License

MIT for this plugin, Copyright (c) 2026 dsh-pele-mermaid contributors.

lib/pele-runtime.js is an unmodified copy of pele@1.9.0 dist/pele.global.js, MIT, Copyright (c) 2026 kepano — obsidianmd/pele, by the Obsidian team. See LICENSE for the full third-party notice.