Large Mermaid flowcharts were still hard to inspect in the desktop chat surface because ultra-wide SVGs could be squeezed or opened at an unhelpful crop. Normalize the rendered SVG, keep edge strokes visible while preserving author styles, and add fit-first overview rendering for both inline chat cards and the preview modal.
Constraint: Mermaid emits SVG sized for generic web pages, while desktop chat needs readable SVG behavior inside constrained WebView panels.
Rejected: Replace Mermaid with a node-canvas library | it would not be a drop-in renderer for Mermaid syntax and would add unnecessary dependency and migration risk.
Confidence: high
Scope-risk: moderate
Directive: Keep SVG normalization additive; do not override explicit linkStyle or marker paint without adding a regression test.
Tested: bun run check:desktop
Tested: Real desktop frontend visual QA with complex Mermaid screenshots at Fit, 25%, 50%, 75%, 100%, and 125%.
Not-tested: Packaged Tauri WebView smoke.
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