dsh-plugin-canvas-pro

When an agent in DeepSeek Harness produces an HTML page or a Mermaid diagram and you want to tweak one line, swap a color, or roll back a step, you are usually forced to regenerate the whole document. dsh-plugin-canvas-pro turns canvas artifacts into a first-class workspace for the agent: a Canvas button appears in the Web session header, a resizable drawer previews HTML, Markdown, Mermaid, SVG, and React source in a sandboxed iframe, and eight model tools let the agent create, patch by selection or line range, read the current content, inspect the latest text selection, list snapshots, diff versions, revert a past state, and export in multiple formats.

Three capabilities stand out. First, text selection is a first-class agent input: highlight a span in the preview to fire Explain, Refactor, Fix, or a custom prompt straight into the current chat, and the agent can also read that span via get_canvas_selection. Second, every patch becomes a snapshot; the agent can list, take a unified or split diff, and revert to a previous state without rewriting the file from scratch. Third, export is a model tool, not just a UI button: export_canvas_artifact returns Markdown, standalone HTML, SVG, PNG (with SVG fallback), or a JSON archive, all callable mid-conversation.

This plugin suits teams that build and iterate on rich-text artifacts inside DSH: sketching Mermaid architecture diagrams with targeted node edits, refining HTML prototypes through successive partial patches and version comparisons, or exporting the final result as a PNG for a deck. Artifacts persist locally under $DSH_HOME and survive Web restarts, with no external service dependency.