dsh-plugin-mermaid

When a DeepSeek Harness agent explains architecture, walks through a workflow, or writes technical documentation, it often needs flowcharts, sequence diagrams, or class diagrams. Previously the agent could only paste raw Mermaid source code into its reply, forcing the reader to copy it into an external tool to see the actual graphic. dsh-plugin-mermaid closes that gap: once installed, the agent calls the mermaid_render tool right after writing Mermaid code and receives an SVG image it can embed directly in the response, so the end user sees the rendered diagram with zero extra steps.

The entire rendering pipeline runs in-process: mermaid 11 handles parsing and layout, jsdom supplies the DOM layer, and the plugin patches the missing SVG text measurement APIs with a per-character width model that correctly sizes mixed CJK-Latin labels and multi-line text. No browser, no network access, fully offline. Tested and working for flowchart, sequenceDiagram, classDiagram, and pie. When rendering fails the tool returns the parser line number and expected token so the agent can self-correct and retry. In Web-chat mode images are served as absolute http URLs via a lightweight route; in headless mode a data-URI fallback is provided instead.

This plugin is ideal for anyone who wants their DeepSeek Harness agent to produce visual explanations inline-system design overviews, API call timelines, distribution breakdowns, and more. Pair it with dsh-image-zoom to click any rendered image and zoom in on details, bringing the experience close to a dedicated diagramming tool.