dsh-mermaid-panel

A DeepSeek Harness client plugin that adds a Mermaid page to the right Sidebar. It renders the Mermaid diagrams in the conversation you are reading, without touching the conversation itself.

Published as dsh-mermaid-panel, not dsh-mermaid: that package name belongs to MrmoLabs/dsh-mermaid, which renders diagrams inline in the chat instead. The two do different things and can now be installed side by side.

What it does

• Registers one right-Sidebar page type (mermaid) and a guide capsule, so the empty Sidebar offers it as a door.
• Scans the rendered conversation for code blocks whose first line declares a Mermaid diagram, and renders them in the page's own React tree.
• Each card keeps the authored source one click away, plus copy.
• Each diagram zooms and pans in place; a full-screen view is one button away.
• Re-renders when the palette changes; the Sidebar's own docking, splitting, and per-Session tab persistence apply unchanged.

The chat's code block is never hidden or replaced. Copying the source from the transcript, quoting it, or letting the model read it back still works, and a change to the chat's DOM costs the page its input rather than the transcript.

What it deliberately does not do

• It does not modify DeepSeek Harness. Everything it uses is a declared public extension point: ctx.sidebarRightTabs, sidebar.right.pane.tab, and the ctx.locale / ctx.slots services.
• It does not render inline in the transcript. Replacing a chat code block in place would need a rendering seam that the product does not have, so the diagram lives in the Sidebar instead.

How it finds diagrams

The chat renders an unknown language as a plain code card with no language attribute, so the page reads the first declaration line and accepts:

• graph / flowchart followed by a direction (TB, TD, BT, RL, LR);
• a known diagram keyword such as sequenceDiagram, classDiagram, stateDiagram, erDiagram, gantt, pie, journey, gitGraph, mindmap, timeline, xychart-beta, quadrantChart, and the rest;
• leading blank lines, %% comments, and a YAML front-matter block.

Mermaid's own parser is the final word: a source that fails to render shows the failure notice and its source instead of a diagram.

Zooming

Every card is its own viewport, so a diagram can be examined without leaving the Sidebar.

• The wheel zooms around the pointer; −, +, and the percentage sit in the card's lower-right corner, on hover or while zoomed.
• Dragging pans, bounded to the diagram so it cannot be dragged out of its frame. Double-clicking, or Fit, returns it to the fitted size.
• The scale never goes below the fitted size: the card's ordinary rendering is the floor.

The card's Enlarge button opens the same diagram full screen, where the wheel, the buttons, + / -, Esc, and Fit all work over the whole window. A click on the diagram itself is a pan, not a way into that view.

Both views are portals or plain transforms inside the page: the full-screen one mounts on document.body so the Sidebar's scroll container cannot clip it, and neither keeps state once the card is gone.

Install

From the plugin market

The repository publishes a format 1 market index at

https://raw.githubusercontent.com/Natsubrei/dsh-mermaid-panel/main/index.json

Add it in Plugins → Discover → Add index, then install Mermaid diagrams from the list. Discover ships off by default: switch on Custom plugin markets under the Plugins page's experimental list first. The index entry pins a commit, so installation is reproducible and needs neither npm nor a token — DSH runs git against this repository.

The entry is generated, not hand-edited: npm run market reads package.json and the current commit and rewrites index.json. Run it after the commit that carries the built artifacts, then commit the index on its own.

From a checkout

node build.mjs

Then install the package directory as a bundle in the Harness profile, for example through the plugin manager's install_bundle action. The bundle patch inserts the entry into the profile's cordis.yml. client.js and client.mermaid.js are committed, so a Git install needs no build step.

Layout

File	Role
index.js	Host half. Rendering is browser-only, so it contributes nothing.
src/client.jsx	The page type, its body, and the scan. Built into client.js.
client.mermaid.js	The Mermaid engine as a lazy loader chunk, requested on the first diagram.
cordis.patch.yml	Inserts the plugin into the profile.
locale/en.json, locale/zh.json	Plugin-inventory title and description.
index.json	The market index this repository publishes; generated by scripts/market-index.mjs.
scripts/market-index.mjs	Rewrites index.json from package.json and the current commit.
AGENTS.md	The release steps, the distribution URLs, and the gotchas that otherwise cost an afternoon.

How to reach it

The page type contributes one guide capsule, the same door ui-sidebar-terminal uses. Open the right Sidebar and pick Mermaid on the guide page. If the Sidebar has exactly one door registered — ours, when no other type offers a guide capsule — the Sidebar seeds that page as its first tab instead of the guide; that seeding rule belongs to the Sidebar, not to this plugin.

Limits

• The page reads the DOM of the conversation that is on screen. If the chat's code-card markup changes, the page shows its empty state until the selectors are updated.
• Sources are read from what the chat has mounted, so history the chat has not rendered yet (virtualized or collapsed) is not included.
• An open page observes the document to notice a remounted conversation, so a streaming turn costs one debounced scan every ~240 ms.
• The engine is a 3.5 MB chunk, downloaded once per page load on first diagram.
• The full-screen view holds the SVG it opened with; a diagram that changes while the view is open updates in place, and its zoom stays where it was.