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feat(session-ui): render mermaid code blocks as diagrams in chat - #38175

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feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
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ben-fornefeld:mermaid-diagrams

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@ben-fornefeldben-fornefeld commented Jul 21, 2026•
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What

Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).

This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.

UX

  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.

How it works

  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.

Testing

  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.

Notes

  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).

Fullscreen viewer (added in iteration)

  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.

@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot added the needs:compliance This means the issue will auto-close after 2 hours. label Jul 21, 2026
@github-actions

github-actionsBot commented Jul 21, 2026

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This PR doesn't fully meet our contributing guidelines and PR template.

What needs to be fixed:

  • PR description is missing required template sections. Please use the PR template.

Please edit this PR description to address the above within 2 hours, or it will be automatically closed.

If you believe this was flagged incorrectly, please let a maintainer know.

@github-actions

github-actionsBot commented Jul 21, 2026

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The following comment was made by an LLM, it may be inaccurate:

Found a potential related PR:

PR #23688: feat(app): add markdown preview with mermaid diagram support

  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.

@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
@github-actionsgithub-actionsBot mentioned this pull request Jul 21, 2026
Open
@github-actions

github-actionsBot commented Jul 21, 2026

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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.

Feel free to open a new pull request that follows our guidelines.

@github-actionsgithub-actionsBot removed the needs:compliance This means the issue will auto-close after 2 hours. label Jul 21, 2026
@EugeneChan00EugeneChan00 mentioned this pull request Jul 31, 2026
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@ben-fornefeld
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

Copy link


Copy Markdown

What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
@github-actions
github-actionsBot
commented
Jul 21, 2026

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This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
@github-actions
github-actionsBot
commented
Jul 21, 2026

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Contributor
The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
@github-actionsgithub-actionsBot
mentioned this pull request
Jul 21, 2026

Open

@github-actions
github-actionsBot
commented
Jul 21, 2026

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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
Feel free to open a new pull request that follows our guidelines.
@github-actionsgithub-actionsBot
removed
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
@EugeneChan00EugeneChan00
mentioned this pull request
Jul 31, 2026
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@ben-fornefeld

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

Copy link


Copy Markdown

What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
@github-actions
github-actionsBot
commented
Jul 21, 2026

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This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
@github-actions
github-actionsBot
commented
Jul 21, 2026

Copy link


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Contributor
The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
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Jul 21, 2026

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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

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What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
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This means the issue will auto-close after 2 hours.
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This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
@github-actions
github-actionsBot
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The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
@github-actionsgithub-actionsBot
mentioned this pull request
Jul 21, 2026

Open

@github-actions
github-actionsBot
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Jul 21, 2026

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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
Feel free to open a new pull request that follows our guidelines.
@github-actionsgithub-actionsBot
removed
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
@EugeneChan00EugeneChan00
mentioned this pull request
Jul 31, 2026
 Draft

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@ben-fornefeld

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
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function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
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trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
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return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
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if (clean !== a.href) a.href = clean;
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mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

Copy link


Copy Markdown

What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
@github-actions
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Contributor
This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
@github-actions
github-actionsBot
commented
Jul 21, 2026

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Contributor
The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
@github-actionsgithub-actionsBot
mentioned this pull request
Jul 21, 2026

Open

@github-actions
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Contributor
This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
Feel free to open a new pull request that follows our guidelines.
@github-actionsgithub-actionsBot
removed
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
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@EugeneChan00EugeneChan00
mentioned this pull request
Jul 31, 2026
 Draft

6 tasks
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@ben-fornefeld

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

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Copy Markdown

What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
the 
needs:compliance
This means the issue will auto-close after 2 hours.
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This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
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The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
@github-actionsgithub-actionsBot
mentioned this pull request
Jul 21, 2026

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Jul 21, 2026

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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
Feel free to open a new pull request that follows our guidelines.
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This means the issue will auto-close after 2 hours.
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Jul 31, 2026
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, 'i');
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try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

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Copy Markdown

What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
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Jul 21, 2026

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This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
@github-actions
github-actionsBot
commented
Jul 21, 2026

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Contributor
The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
@github-actionsgithub-actionsBot
mentioned this pull request
Jul 21, 2026

Open

@github-actions
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Jul 21, 2026

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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
Feel free to open a new pull request that follows our guidelines.
@github-actionsgithub-actionsBot
removed
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
@EugeneChan00EugeneChan00
mentioned this pull request
Jul 31, 2026
 Draft

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@ben-fornefeld

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
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filter: invert(1) hue-rotate(180deg) !important;
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::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
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::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
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console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
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} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
feat(session-ui): render mermaid code blocks as diagrams in chat by ben-fornefeld · Pull Request #38175 · anomalyco/opencode · GitHub
Skip to content
feat(session-ui): render mermaid code blocks as diagrams in chat - #38175
Closed
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Closed
feat(session-ui): render mermaid code blocks as diagrams in chat#38175
ben-fornefeld wants to merge 8 commits into
anomalyco:devfrom 
ben-fornefeld:mermaid-diagrams
Conversation
@ben-fornefeld
@ben-fornefeldben-fornefeld
commented
Jul 21, 2026•

edited

Loading

Copy link


Copy Markdown

What
Mermaid fenced code blocks now render as diagrams by default in the chat markdown view. The code block keeps its copy button, which continues to copy the original mermaid source (not the rendered SVG).
This targets the desktop app, but the change lives in the shared session-uiMarkdown component that powers desktop chat (and web), so both benefit at no cost to bundles that never show a diagram.
UX
  • Every ```mermaid block in a chat message renders as a chart.
  • Hovering the block shows the existing copy button (top-right); clicking it copies the raw mermaid code.
  • While a message is still streaming (or if the diagram fails to parse), the raw source is shown instead, so the block is never empty or broken.
How it works
  • markdown-stream.ts: settled (non-streaming) messages are one "full" block, so mermaid fences are now split into standalone code blocks. Both the streaming and settled paths therefore flow through a single diagram handler. Non-mermaid content stays coalesced, and messages with link reference definitions fall back to the existing single-block behavior.
  • markdown-mermaid.ts (new): lazily import("mermaid") (code-split; only loaded when a diagram appears), serialized renders (mermaid keeps global state + scratch DOM), securityLevel: "strict", and a reactive data-color-scheme signal so diagrams re-render when the app theme flips.
  • markdown.tsx: mermaid code blocks are routed to an imperative renderer that keeps a hidden <pre><code> source (for copy + fallback) alongside the rendered SVG, guarded against stale async renders. No morphdom is involved for mermaid.
  • markdown.css: source/diagram visibility driven by data-mermaid-state.
Testing
  • bun test src in packages/session-ui (83 pass), including new unit tests for the mermaid language/theme helpers and the settled-mode fence splitting.
  • bun typecheck across the workspace (all 30 packages).
  • Storybook: the UI/Markdown fixture now includes a mermaid flowchart for visual verification.
Notes
  • Diagrams use a curated slate theme (light + dark) on mermaid's base theme engine: neutral node surfaces, contrasty edges, and eight desaturated categorical hues for state/timeline/git scales. It does not yet adapt to custom OpenCode theme palettes (would need CSS-var probing; noted as a possible follow-up).
  • Mermaid fences nested inside list items still render as code (same limitation as the streaming code splitter).
Fullscreen viewer (added in iteration)
  • Clicking a rendered diagram — or the hover-revealed expand button next to the copy button — opens a fullscreen viewer (Kobalte Dialog: Escape, focus trap, backdrop click all close it).
  • Zoom in/out via toolbar buttons or Ctrl/⌘+wheel; the percentage readout resets to fit-to-viewport. Initial zoom fits the screen without upscaling small diagrams.
  • The viewer re-renders the SVG with a fresh element ID (no ID collisions with the inline chart) and tracks theme changes while open.
@ben-fornefeld
feat(session-ui): render mermaid code blocks as diagrams in chat
bfe69bb
Mermaid fenced code blocks now render as charts by default in the chat
markdown view (desktop and web), while the code block's copy button keeps
copying the original mermaid source.
- Split settled mermaid fences into standalone code blocks so both the
streaming and settled render paths route through one diagram handler.
- Render diagrams from a lazily imported, serialized mermaid instance and
fall back to the source while streaming, incomplete, or on parse errors.
- Track the app color scheme via a reactive signal on data-color-scheme so
diagrams re-render when the theme flips.
@github-actionsgithub-actionsBot
added
the 
needs:compliance
This means the issue will auto-close after 2 hours.
label
Jul 21, 2026
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This PR doesn't fully meet our contributing guidelines and PR template.
What needs to be fixed:
  • PR description is missing required template sections. Please use the PR template.
Please edit this PR description to address the above within 2 hours, or it will be automatically closed.
If you believe this was flagged incorrectly, please let a maintainer know.
@github-actions
github-actionsBot
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Contributor
The following comment was made by an LLM, it may be inaccurate:
Found a potential related PR:
PR #23688: feat(app): add markdown preview with mermaid diagram support
  • feat(app): add markdown preview with mermaid diagram support #23688
  • This PR also deals with mermaid diagram support, though it appears to be targeted at the app markdown preview feature rather than the session-ui chat markdown component. It may be worth checking if this addresses the same or overlapping functionality, or if it's a separate earlier effort that should be referenced or reconciled.
@ben-fornefeld
refactor(session-ui): tighten mermaid block rendering
afa96d6
- Gate the settled-path mermaid split behind a fence regex so messages
without diagrams stay lexer-free.
- Collapse the mermaid/shiki resource branches into one block construction.
- Track only the last started render (source, scheme, request) per block;
failed parses no longer re-render on identical effect re-runs.
- Drop dead rejection handling from the serialized render queue.
@ben-fornefeld
feat(session-ui): fullscreen mermaid viewer with zoom
09c72e8
Clicking a rendered mermaid diagram (or the new hover-revealed expand
button beside the copy button) opens a fullscreen viewer.
- Viewer uses Kobalte Dialog primitives for Escape, focus trap, and
portal; re-renders the SVG fresh so IDs never collide with the inline
chart, and follows theme flips while open.
- Zoom via toolbar buttons, Ctrl/Cmd+wheel, and a percentage readout
that resets to fit; initial zoom fits the viewport without upscaling.
- Expand button reuses the mounted-host pattern of the copy button and
only appears once the diagram has rendered.
- Adds a minus icon and ui.mermaid.* strings (locales fall back to en).
@ben-fornefeld
feat(session-ui): canvas-style mermaid viewer interactions
96c81b3
- Replace the scroll container with a transform-driven canvas: drag to
pan, plain wheel pans, ctrl/cmd + wheel (trackpad pinch) zooms at the
cursor, double-click zooms in, toolbar buttons zoom at center, and the
percentage readout resets to a centered fit.
- Viewer panel now spans the viewport with padding to its edges.
- Fit fills the padded canvas (vector output upscales crisply) and the
camera math lives in pure, tested helpers.
- Swap the expand icon for a new four-corner fullscreen icon.
@ben-fornefeld
fix(session-ui): coalesce mermaid viewer camera updates per frame
b10d706
Wheel and pointer events fire faster than the display refreshes, so the
viewer now keeps the camera in a plain value and writes the stage
transform directly in one requestAnimationFrame per burst instead of
per-event reactive style updates. Only the toolbar percentage readout
stays on a signal.
@ben-fornefeld
fix(session-ui): focus mermaid viewer canvas instead of first toolbar…
791caad
… button
@ben-fornefeld
feat(session-ui): slate mermaid theme for light and dark
973dfa5
Replace mermaid's stock default/dark themes with a curated slate palette
on the "base" theme engine: neutral node surfaces, higher-contrast edges
and borders, amber-tinted notes, and eight desaturated categorical hues
(cScale/git scales) so large state, timeline, and git charts stay
parseable. Diagram text uses the app sans font resolved to a concrete
value, since mermaid measures text with it.
@ben-fornefeld
feat(session-ui): semantic node coloring for mermaid flowcharts
aab567f
Flowchart nodes all render as class="node default", so per-type color
comes from two layers injected via themeCSS (stylis scopes it under the
diagram id):
- Shape buckets: polygons (decisions and branch-like shapes) tint amber,
circles and stadium groups (terminals) tint blue, cylinder paths
(storage) tint violet, and plain rects stay slate.
- Semantic author classes: `A:::info|success|warning|danger|muted` pass
through without a classDef and style any shape with theme-consistent
accents in both schemes; explicit classDef inline styles still win.
Adds a MermaidShapes story covering every node shape, edge style,
subgraph, and a `:::warning` node for tuning.
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This pull request has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
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Jul 21, 2026
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mentioned this pull request
Jul 31, 2026
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@ben-fornefeld