| name | ui |
| description | How to choose between markdown, HTML messages, and UI plugins in the local web chat — and how to render each well. Use whenever you are about to call `send_message` to a web-chat channel, especially when the content has structure (rows, columns, statuses, a state machine, multiple linked things) or when the right answer is "let me show you", not "let me tell you". Do not use for Discord channels — HTML is rejected there. |
Choosing the right surface
There are three surfaces in the local web UI. Pick by asking what shape the content has, not how long it is.
| Surface | When | What it gives you | What it costs |
|---|
| Markdown message | Quick reply, single point, conversational. | Cheap, scrollable with the chat. | Linear — every reply pushes older ones up. |
| HTML message | One-off rich artifact: a table, a status card, a small dashboard, a diagram, a labelled diff. The shape is non-linear but the lifetime is "until the next message scrolls it away." | Tables, grids, layered SVG, color/typography, and small scripts under your control. Renders inline in chat. Can use parent-owned data-strix-action hooks or window.strix. | Ephemeral; sandboxed with no same-origin access. Cream background — see below. |
| UI plugin | A frame of mind that is not linear like chat. Persistent. Tim wants to see what we're talking about, not just discuss it. Example: chainlink issues — the chat thread talks about them, the plugin shows them, with detail views, filters, status. | A live, interactive, scrollable side panel that survives across turns. Full JS, can poll, can show fresh state. | Costs a server. Has a contract: see ui-plugins.md. |
Mental model (from Tim, 2026-05-12):
"I want UI plugins to share a frame of mind that's not linear like chat. With chainlink, I couldn't see any of the chainlink issues — now I can."
If you find yourself describing state in prose ("here are the 7 open RLS findings, here are their statuses, here's which ones map to PR #X..."), you're papering over a missing UI plugin. Either fire off an HTML message now and propose the plugin, or just build the plugin.
Rule of thumb (when in doubt)
- Quick reply, no shape? → markdown.
- One artifact you wouldn't want to scroll back to find? → HTML message. Make it dense and self-contained.
- The user is going to want to see this same thing again tomorrow, with fresh data? → UI plugin. Read
ui-plugins.md.
Bias toward richer surfaces, not less. A markdown wall-of-bullets where an HTML table would do is a missed affordance.
Rendering HTML messages
HTML messages render inside a sandboxed iframe in the local web UI. They will be rejected by Discord — for Discord, fall back to markdown.
The chat surface
The chat surface can be light or dark. HTML message iframes are transparent over the current agent-message surface: approximately rgba(255, 250, 241, 0.84) in light mode and rgba(23, 33, 43, 0.9) in dark mode.
Safe strategies:
- Be theme-independent. Use explicit foreground/background contrast that works in both light and dark themes.
- Paint your own opaque background. Set
html, body { background: <your color>; } full-bleed (not just on a card) so contrast is fully under your control. Use this for dashboards, dark-mode mock-ups, or anything image-y.
- Adapt scripted HTML. If scripts are enabled, listen for
window.message events of type strix:theme with { theme, background, text, muted, accent } and adjust your CSS variables when the user switches theme. The harness pushes the theme once on frame load and again on every toggle. If your listener registers asynchronously (after load), call window.strix.requestTheme() right after you attach it — the harness re-sends the current theme so you don't miss the initial state.
Do not: assume a fixed light or dark canvas unless you provide it yourself. Light text can disappear on light surfaces; dark text can disappear on dark surfaces.
Script sandbox
HTML messages use sandbox="allow-scripts allow-forms" — scripts and forms work, but the frame has an opaque origin. Do not assume same-origin access. The reply cannot read the parent DOM, and the parent cannot inspect the reply DOM after load.
For parent-owned interactions, use the HTML action API in html-actions.md. The harness injects a tiny bridge that lets links, buttons, forms, and scripts ask the parent app to do controlled things like navigate a widget, send a chat message, or continue from the current HTML reply's agent context.
If the interaction should persist across turns or act as a reusable app surface, build a UI plugin.
Sizing
The harness injects a ResizeObserver bridge that posts height updates to the parent. Do not try to fix a height. Width is capped at min(42rem, 92%). If your script changes layout in an unusual way, call window.strix.resize().
Linking to UI plugins from chat messages
When a UI plugin is running, you can link to its internal routes from chat. Clicking the link navigates the plugin's widget, instead of opening a new tab. This is the bridge between chat (the conversation) and the plugin (the frame of mind).
For explicit buttons/forms and the JavaScript postMessage bridge, read html-actions.md. Plain links remain the simplest option when all you need is widget navigation.
URL shapes
| From | href format | Mechanism |
|---|
| Markdown message | /ui/<plugin>/<path> | Delegated click handler on the chat container. Parent intercepts and sets the plugin iframe's src. |
| HTML message (sandboxed, opaque origin) | Prefer /ui/<plugin>/<path>; the injected bridge routes it through the parent. Explicit buttons can use data-strix-action="widget.navigate". #/ui/<plugin>/<path> with target="_top" is a legacy compatibility escape hatch only. | Injected bridge + parent-owned postMessage handling; optional hash routing. |
<plugin> must match the name field in the plugin's ui.json. <path> is whatever route the plugin's own server serves.
Examples
See [chainlink #567](/ui/chainlink/issue/567) for the detail.
<a href="/ui/chainlink/issue/567">chainlink #567</a>
<a href="#/ui/chainlink/issue/567" target="_top">chainlink #567 (hash)</a>
<button type="button" data-strix-action="widget.navigate" data-strix-widget="chainlink" data-strix-path="/issue/567">chainlink #567</button>
When the link is clicked:
- If the plugin is running, the widget un-minimizes, scrolls into view, and navigates to
/<path>.
- If the plugin is known but not yet running (still booting), the click is claimed (no new tab opens) but nothing else happens. The user can re-click after it boots.
- If the plugin is unknown, the click falls through to normal browser behavior (which, for
/ui/<plugin>/..., means a 404 on a new tab — usually a sign you should remove the link).
When to add a plugin link
Anywhere a piece of state has a "canonical view" in a UI plugin, link to it instead of pasting its contents. A chainlink issue ID → a /ui/chainlink/issue/<id> link. A trace ID → /ui/traces/<id>. The link is cheap; the plugin already knows how to render the detail well.
This is the highest-leverage move enabled by the plugin system. Use it often.
Cross-references
ui-plugins.md — how to design, ship, and reason about UI plugins themselves (the plugin contract, lifecycle, port assignment, ui.json schema, security model).html-actions.md — the parent-owned HTML action API and the equivalent postMessage bridge for trusted scripted frames.memory skill — for deciding what state belongs in a plugin's data store vs. a memory block vs. a state file.
