MolyKit Skill
Best practices for building AI chat interfaces with Makepad using MolyKit - a toolkit for cross-platform AI chat applications.
Source codebase: /Users/zhangalex/Work/Projects/FW/robius/moly/moly-kit
When to Use
Use this skill when:
- Building AI chat interfaces with Makepad
- Integrating OpenAI or other LLM APIs
- Implementing cross-platform async for native and WASM
- Creating chat widgets (messages, prompts, avatars)
- Handling SSE streaming responses
- Keywords: molykit, moly-kit, ai chat, bot client, openai makepad, chat widget, sse streaming
Overview
MolyKit provides:
- Cross-platform async utilities (PlatformSend, spawn(), ThreadToken)
- Ready-to-use chat widgets (Chat, Messages, PromptInput, Avatar)
- BotClient trait for AI provider integration
- OpenAI-compatible client with SSE streaming
- Protocol types for messages, bots, and tool calls
- MCP (Model Context Protocol) support
Version and trust boundaries
The author-local source path and llms.txt below are not bundled. Locate the installed MolyKit revision and verify its signatures before adapting these partial Rust sketches; ellipses and trait declarations are not standalone compilable programs. ThreadToken does not make arbitrary thread-local values safely accessible from any native thread: obey the implementation's originating-thread constraints. Keep provider keys in a native/server secret store, never a browser/WASM bundle. Treat model tool calls and attachments as untrusted input requiring application authorization. SSE parsing must buffer across chunk boundaries, handle CRLF/multiline data, cancellation and size limits; splitting individual network chunks on two newlines is insufficient.
Cross-Platform Async Patterns
PlatformSend - Send Only on Native
rust
/// Implies Send only on native platforms, not on WASM
/// - On native: implemented by types that implement Send
/// - On WASM: implemented by ALL types
pub trait PlatformSend: PlatformSendInner {}
/// Boxed future type for cross-platform use
pub type BoxPlatformSendFuture<'a, T> = Pin<Box<dyn PlatformSendFuture<Output = T> + 'a>>;
/// Boxed stream type for cross-platform use
pub type BoxPlatformSendStream<'a, T> = Pin<Box<dyn PlatformSendStream<Item = T> + 'a>>;
Platform-Agnostic Spawning
rust
/// Runs a future independently
/// - Uses tokio on native (requires Send)
/// - Uses wasm-bindgen-futures on WASM (no Send required)
pub fn spawn(fut: impl PlatformSendFuture<Output = ()> + 'static);
// Usage
spawn(async move {
let result = fetch_data().await;
Cx::post_action(DataReady(result));
SignalToUI::set_ui_signal();
});
Task Cancellation with AbortOnDropHandle
rust
/// Handle that aborts its future when dropped
pub struct AbortOnDropHandle(AbortHandle);
// Usage - task cancelled when widget dropped
#[rust]
task_handle: Option<AbortOnDropHandle>,
fn start_task(&mut self) {
let (future, handle) = abort_on_drop(async move {
// async work...
});
self.task_handle = Some(handle);
spawn(async move { let _ = future.await; });
}
ThreadToken for Non-Send Types on WASM
rust
/// Store non-Send value in thread-local, access via token
pub struct ThreadToken<T: 'static>;
impl<T> ThreadToken<T> {
pub fn new(value: T) -> Self;
pub fn peek<R>(&self, f: impl FnOnce(&T) -> R) -> R;
pub fn peek_mut<R>(&self, f: impl FnOnce(&mut T) -> R) -> R;
}
// Usage - wrap non-Send type for use across Send boundaries
let token = ThreadToken::new(non_send_value);
spawn(async move {
token.peek(|value| {
// use value...
});
});
BotClient Trait
Implementing AI Provider Integration
rust
pub trait BotClient: Send {
/// Send message with streamed response
fn send(
&mut self,
bot_id: &BotId,
messages: &[Message],
tools: &[Tool],
) -> BoxPlatformSendStream<'static, ClientResult<MessageContent>>;
/// Get available bots/models
fn bots(&self) -> BoxPlatformSendFuture<'static, ClientResult<Vec<Bot>>>;
/// Clone for passing around
fn clone_box(&self) -> Box<dyn BotClient>;
}
// Usage
let mut client = OpenAIClient::new("https://api.openai.com/v1".into());
client.set_key("sk-...")?;
let context = BotContext::from(client);
BotContext - Sharable Wrapper
rust
/// Sharable wrapper with loaded bots for sync UI access
pub struct BotContext(Arc<Mutex<InnerBotContext>>);
impl BotContext {
pub fn load(&mut self) -> BoxPlatformSendFuture<ClientResult<()>>;
pub fn bots(&self) -> Vec<Bot>;
pub fn get_bot(&self, id: &BotId) -> Option<Bot>;
pub fn client(&self) -> Box<dyn BotClient>;
}
// Usage
let mut context = BotContext::from(client);
spawn(async move {
if let Err(errors) = context.load().await.into_result() {
// handle errors
}
Cx::post_action(BotsLoaded);
});
Protocol Types
Message Structure
rust
pub struct Message {
pub from: EntityId, // User, System, Bot(BotId), App
pub metadata: MessageMetadata,
pub content: MessageContent,
}
pub struct MessageContent {
pub text: String, // Main content (markdown)
pub reasoning: String, // AI reasoning/thinking
pub citations: Vec<String>, // Source URLs
pub attachments: Vec<Attachment>,
pub tool_calls: Vec<ToolCall>,
pub tool_results: Vec<ToolResult>,
}
pub struct MessageMetadata {
pub is_writing: bool, // Still being streamed
pub created_at: DateTime<Utc>,
}
Bot Identification
rust
/// Globally unique bot ID: <len>;<id>@<provider>
pub struct BotId(Arc<str>);
impl BotId {
pub fn new(id: &str, provider: &str) -> Self;
pub fn id(&self) -> &str; // provider-local id
pub fn provider(&self) -> &str; // provider domain
}
// Example: BotId::new("gpt-4", "api.openai.com")
// -> "5;gpt-4@api.openai.com"
Widget Patterns
Slot Widget - Runtime Content Replacement
rust
live_design! {
pub Slot = {{Slot}} {
width: Fill, height: Fit,
slot = <View> {} // default content
}
}
// Usage - replace content at runtime
let mut slot = widget.slot(id!(content));
if let Some(custom) = client.content_widget(cx, ...) {
slot.replace(custom);
} else {
slot.restore(); // back to default
slot.default().as_standard_message_content().set_content(cx, &content);
}
Avatar Widget - Text/Image Toggle
rust
live_design! {
pub Avatar = {{Avatar}} <View> {
grapheme = <RoundedView> {
visible: false,
label = <Label> { text: "P" }
}
dependency = <RoundedView> {
visible: false,
image = <Image> {}
}
}
}
impl Widget for Avatar {
fn draw_walk(&mut self, cx: &mut Cx2d, ...) -> DrawStep {
if let Some(avatar) = &self.avatar {
match avatar {
Picture::Grapheme(g) => {
self.view(id!(grapheme)).set_visible(cx, true);
self.view(id!(dependency)).set_visible(cx, false);
self.label(id!(label)).set_text(cx, &g);
}
Picture::Dependency(d) => {
self.view(id!(dependency)).set_visible(cx, true);
self.view(id!(grapheme)).set_visible(cx, false);
self.image(id!(image)).load_image_dep_by_path(cx, d.as_str());
}
}
}
self.deref.draw_walk(cx, scope, walk)
}
}
PromptInput Widget
rust
#[derive(Live, Widget)]
pub struct PromptInput {
#[deref] deref: CommandTextInput,
#[live] pub send_icon: LiveValue,
#[live] pub stop_icon: LiveValue,
#[rust] pub task: Task, // Send or Stop
#[rust] pub interactivity: Interactivity,
}
impl PromptInput {
pub fn submitted(&self, actions: &Actions) -> bool;
pub fn reset(&mut self, cx: &mut Cx);
pub fn set_send(&mut self);
pub fn set_stop(&mut self);
pub fn enable(&mut self);
pub fn disable(&mut self);
}
Messages Widget - Conversation View
rust
#[derive(Live, Widget)]
pub struct Messages {
#[deref] deref: View,
#[rust] pub messages: Vec<Message>,
#[rust] pub bot_context: Option<BotContext>,
}
impl Messages {
pub fn set_messages(&mut self, messages: Vec<Message>, scroll_to_bottom: bool);
pub fn scroll_to_bottom(&mut self, cx: &mut Cx, triggered_by_stream: bool);
pub fn is_at_bottom(&self) -> bool;
}
UiRunner Pattern for Async-to-UI
rust
impl Widget for PromptInput {
fn handle_event(&mut self, cx: &mut Cx, event: &Event, scope: &mut Scope) {
self.deref.handle_event(cx, event, scope);
self.ui_runner().handle(cx, event, scope, self);
if self.button(id!(attach)).clicked(event.actions()) {
let ui = self.ui_runner();
Attachment::pick_multiple(move |result| match result {
Ok(attachments) => {
ui.defer_with_redraw(move |me, cx, _| {
me.attachment_list_ref().write().attachments.extend(attachments);
});
}
Err(_) => {}
});
}
}
}
SSE Streaming
rust
/// Parse SSE byte stream into message stream
pub fn parse_sse<S, B, E>(s: S) -> impl Stream<Item = Result<String, E>>
where
S: Stream<Item = Result<B, E>>,
B: AsRef<[u8]>,
{
// Split on "\n\n", extract "data:" content
// Filter comments and [DONE] messages
}
// Usage in BotClient::send
fn send(&mut self, ...) -> BoxPlatformSendStream<...> {
let stream = stream! {
let response = client.post(url).send().await?;
let events = parse_sse(response.bytes_stream());
for await event in events {
let completion: Completion = serde_json::from_str(&event)?;
content.text.push_str(&completion.delta.content);
yield ClientResult::new_ok(content.clone());
}
};
Box::pin(stream)
}
Best Practices
- Use PlatformSend for cross-platform: Same code works on native and WASM
- Use spawn() not tokio::spawn: Platform-agnostic task spawning
- Use AbortOnDropHandle: Cancel tasks when widget drops
- Use ThreadToken for non-Send on WASM: Thread-local storage with token access
- Use Slot for custom content: Allow BotClient to provide custom widgets
- Use read()/write() pattern: Safe borrow access via WidgetRef
- Use UiRunner::defer_with_redraw: Update widget from async context
- Handle ClientResult partial success: May have value AND errors
Reference Files
llms.txt - Complete MolyKit API reference
Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.