feat(ml): add context windowing, fix chat UI max-tokens
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- Add --max-context flag to serve (sliding window, default 4 messages)
  to prevent KV-cache explosion on multi-turn conversations
- Pass server max-tokens to chat UI HTML attribute instead of
  hardcoded 2048 in JavaScript
- Add chat.js and chat_embed.go for embedded LEM chat UI

Co-Authored-By: Virgil <virgil@lethean.io>
This commit is contained in:
Snider 2026-02-17 19:18:31 +00:00
parent c03c755104
commit e64fa7b4ff
3 changed files with 1178 additions and 7 deletions

832
cmd/ml/chat.js Normal file
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// src/styles.ts
var chatStyles = `
:host {
display: flex;
flex-direction: column;
background: var(--lem-bg, #1a1a1e);
color: var(--lem-text, #e0e0e0);
font-family: var(--lem-font, system-ui, -apple-system, sans-serif);
font-size: 14px;
line-height: 1.5;
border-radius: 12px;
overflow: hidden;
border: 1px solid rgba(255, 255, 255, 0.08);
}
.header {
display: flex;
align-items: center;
gap: 10px;
padding: 14px 18px;
background: rgba(255, 255, 255, 0.03);
border-bottom: 1px solid rgba(255, 255, 255, 0.06);
flex-shrink: 0;
}
.header-icon {
width: 28px;
height: 28px;
border-radius: 8px;
background: var(--lem-accent, #5865f2);
display: flex;
align-items: center;
justify-content: center;
font-size: 14px;
font-weight: 700;
color: #fff;
}
.header-title {
font-size: 15px;
font-weight: 600;
color: var(--lem-text, #e0e0e0);
}
.header-model {
font-size: 11px;
color: rgba(255, 255, 255, 0.35);
margin-left: auto;
font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
}
.header-status {
width: 8px;
height: 8px;
border-radius: 50%;
background: #43b581;
flex-shrink: 0;
}
.header-status.disconnected {
background: #f04747;
}
`;
var messagesStyles = `
:host {
display: block;
flex: 1;
overflow-y: auto;
overflow-x: hidden;
padding: 16px 0;
scroll-behavior: smooth;
}
:host::-webkit-scrollbar {
width: 6px;
}
:host::-webkit-scrollbar-track {
background: transparent;
}
:host::-webkit-scrollbar-thumb {
background: rgba(255, 255, 255, 0.12);
border-radius: 3px;
}
.empty {
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
height: 100%;
gap: 12px;
color: rgba(255, 255, 255, 0.25);
}
.empty-icon {
font-size: 36px;
opacity: 0.4;
}
.empty-text {
font-size: 14px;
}
`;
var messageStyles = `
:host {
display: block;
padding: 6px 18px;
}
:host([role="user"]) .bubble {
background: var(--lem-msg-user, #2a2a3e);
margin-left: 40px;
border-radius: 12px 12px 4px 12px;
}
:host([role="assistant"]) .bubble {
background: var(--lem-msg-assistant, #1e1e2a);
margin-right: 40px;
border-radius: 12px 12px 12px 4px;
}
.bubble {
padding: 10px 14px;
word-wrap: break-word;
overflow-wrap: break-word;
}
.role {
font-size: 11px;
font-weight: 600;
text-transform: uppercase;
letter-spacing: 0.5px;
margin-bottom: 4px;
color: rgba(255, 255, 255, 0.35);
}
:host([role="assistant"]) .role {
color: var(--lem-accent, #5865f2);
}
.content {
color: var(--lem-text, #e0e0e0);
line-height: 1.6;
}
.content p {
margin: 0 0 8px 0;
}
.content p:last-child {
margin-bottom: 0;
}
.content strong {
font-weight: 600;
color: #fff;
}
.content em {
font-style: italic;
color: rgba(255, 255, 255, 0.8);
}
.content code {
font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
font-size: 12px;
background: rgba(0, 0, 0, 0.3);
padding: 2px 5px;
border-radius: 4px;
color: #e8a0bf;
}
.content pre {
margin: 8px 0;
padding: 12px;
background: rgba(0, 0, 0, 0.35);
border-radius: 8px;
overflow-x: auto;
border: 1px solid rgba(255, 255, 255, 0.06);
}
.content pre code {
background: none;
padding: 0;
font-size: 12px;
color: #c9d1d9;
line-height: 1.5;
}
.think-panel {
margin: 6px 0 8px;
padding: 8px 12px;
background: rgba(88, 101, 242, 0.06);
border-left: 2px solid rgba(88, 101, 242, 0.3);
border-radius: 0 6px 6px 0;
font-size: 12px;
color: rgba(255, 255, 255, 0.45);
line-height: 1.5;
max-height: 200px;
overflow-y: auto;
}
.think-panel::-webkit-scrollbar {
width: 4px;
}
.think-panel::-webkit-scrollbar-thumb {
background: rgba(255, 255, 255, 0.1);
border-radius: 2px;
}
.think-label {
font-size: 10px;
font-weight: 600;
text-transform: uppercase;
letter-spacing: 0.5px;
color: rgba(88, 101, 242, 0.5);
margin-bottom: 4px;
cursor: pointer;
user-select: none;
}
.think-label:hover {
color: rgba(88, 101, 242, 0.7);
}
.think-panel.collapsed .think-content {
display: none;
}
.cursor {
display: inline-block;
width: 7px;
height: 16px;
background: var(--lem-accent, #5865f2);
border-radius: 1px;
animation: blink 0.8s step-end infinite;
vertical-align: text-bottom;
margin-left: 2px;
}
@keyframes blink {
50% { opacity: 0; }
}
`;
var inputStyles = `
:host {
display: block;
padding: 12px 16px 16px;
border-top: 1px solid rgba(255, 255, 255, 0.06);
flex-shrink: 0;
}
.input-wrapper {
display: flex;
align-items: flex-end;
gap: 10px;
background: rgba(255, 255, 255, 0.05);
border: 1px solid rgba(255, 255, 255, 0.08);
border-radius: 12px;
padding: 8px 12px;
transition: border-color 0.15s;
}
.input-wrapper:focus-within {
border-color: var(--lem-accent, #5865f2);
}
textarea {
flex: 1;
background: none;
border: none;
outline: none;
color: var(--lem-text, #e0e0e0);
font-family: inherit;
font-size: 14px;
line-height: 1.5;
resize: none;
max-height: 120px;
min-height: 22px;
padding: 0;
}
textarea::placeholder {
color: rgba(255, 255, 255, 0.25);
}
.send-btn {
background: var(--lem-accent, #5865f2);
border: none;
border-radius: 8px;
color: #fff;
width: 32px;
height: 32px;
cursor: pointer;
display: flex;
align-items: center;
justify-content: center;
flex-shrink: 0;
transition: opacity 0.15s, transform 0.1s;
}
.send-btn:hover {
opacity: 0.85;
}
.send-btn:active {
transform: scale(0.95);
}
.send-btn:disabled {
opacity: 0.3;
cursor: default;
transform: none;
}
.send-btn svg {
width: 16px;
height: 16px;
}
`;
// src/lem-messages.ts
var LemMessages = class extends HTMLElement {
shadow;
container;
emptyEl;
shouldAutoScroll = true;
constructor() {
super();
this.shadow = this.attachShadow({ mode: "open" });
}
connectedCallback() {
const style = document.createElement("style");
style.textContent = messagesStyles;
this.container = document.createElement("div");
this.emptyEl = document.createElement("div");
this.emptyEl.className = "empty";
const emptyIcon = document.createElement("div");
emptyIcon.className = "empty-icon";
emptyIcon.textContent = "\u2728";
const emptyText = document.createElement("div");
emptyText.className = "empty-text";
emptyText.textContent = "Start a conversation";
this.emptyEl.appendChild(emptyIcon);
this.emptyEl.appendChild(emptyText);
this.shadow.appendChild(style);
this.shadow.appendChild(this.emptyEl);
this.shadow.appendChild(this.container);
this.addEventListener("scroll", () => {
const threshold = 60;
this.shouldAutoScroll = this.scrollHeight - this.scrollTop - this.clientHeight < threshold;
});
}
addMessage(role, text) {
this.emptyEl.style.display = "none";
const msg = document.createElement("lem-message");
msg.setAttribute("role", role);
this.container.appendChild(msg);
if (text) {
msg.text = text;
}
this.scrollToBottom();
return msg;
}
scrollToBottom() {
if (this.shouldAutoScroll) {
requestAnimationFrame(() => {
this.scrollTop = this.scrollHeight;
});
}
}
clear() {
this.container.replaceChildren();
this.emptyEl.style.display = "";
this.shouldAutoScroll = true;
}
};
customElements.define("lem-messages", LemMessages);
// src/markdown.ts
function escapeHtml(text) {
return text.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;").replace(/"/g, "&quot;");
}
function parseInline(text) {
let result = escapeHtml(text);
result = result.replace(/`([^`]+)`/g, "<code>$1</code>");
result = result.replace(/\*\*(.+?)\*\*/g, "<strong>$1</strong>");
result = result.replace(/__(.+?)__/g, "<strong>$1</strong>");
result = result.replace(/(?<!\w)\*([^*]+)\*(?!\w)/g, "<em>$1</em>");
result = result.replace(/(?<!\w)_([^_]+)_(?!\w)/g, "<em>$1</em>");
return result;
}
function renderMarkdown(text) {
const lines = text.split("\n");
const output = [];
let inCodeBlock = false;
let codeLines = [];
let codeLang = "";
for (const line of lines) {
if (line.trimStart().startsWith("```")) {
if (!inCodeBlock) {
inCodeBlock = true;
codeLang = line.trimStart().slice(3).trim();
codeLines = [];
} else {
const langAttr = codeLang ? ` data-lang="${escapeHtml(codeLang)}"` : "";
output.push(
`<pre${langAttr}><code>${escapeHtml(codeLines.join("\n"))}</code></pre>`
);
inCodeBlock = false;
codeLines = [];
codeLang = "";
}
continue;
}
if (inCodeBlock) {
codeLines.push(line);
continue;
}
if (line.trim() === "") {
output.push("");
continue;
}
output.push(parseInline(line));
}
if (inCodeBlock) {
const langAttr = codeLang ? ` data-lang="${escapeHtml(codeLang)}"` : "";
output.push(
`<pre${langAttr}><code>${escapeHtml(codeLines.join("\n"))}</code></pre>`
);
}
const paragraphs = [];
let current = [];
for (const line of output) {
if (line === "") {
if (current.length > 0) {
paragraphs.push(wrapParagraph(current));
current = [];
}
} else {
current.push(line);
}
}
if (current.length > 0) {
paragraphs.push(wrapParagraph(current));
}
return paragraphs.join("");
}
function wrapParagraph(lines) {
const joined = lines.join("<br>");
if (joined.startsWith("<pre")) return joined;
return `<p>${joined}</p>`;
}
// src/lem-message.ts
var LemMessage = class extends HTMLElement {
shadow;
thinkPanel;
thinkContent;
thinkLabel;
contentEl;
cursorEl;
_text = "";
_streaming = false;
_thinkCollapsed = false;
constructor() {
super();
this.shadow = this.attachShadow({ mode: "open" });
}
connectedCallback() {
const role = this.getAttribute("role") || "user";
const style = document.createElement("style");
style.textContent = messageStyles;
const bubble = document.createElement("div");
bubble.className = "bubble";
const roleEl = document.createElement("div");
roleEl.className = "role";
roleEl.textContent = role === "assistant" ? "LEM" : "You";
this.thinkPanel = document.createElement("div");
this.thinkPanel.className = "think-panel";
this.thinkPanel.style.display = "none";
this.thinkLabel = document.createElement("div");
this.thinkLabel.className = "think-label";
this.thinkLabel.textContent = "\u25BC reasoning";
this.thinkLabel.addEventListener("click", () => {
this._thinkCollapsed = !this._thinkCollapsed;
this.thinkPanel.classList.toggle("collapsed", this._thinkCollapsed);
this.thinkLabel.textContent = this._thinkCollapsed ? "\u25B6 reasoning" : "\u25BC reasoning";
});
this.thinkContent = document.createElement("div");
this.thinkContent.className = "think-content";
this.thinkPanel.appendChild(this.thinkLabel);
this.thinkPanel.appendChild(this.thinkContent);
this.contentEl = document.createElement("div");
this.contentEl.className = "content";
bubble.appendChild(roleEl);
if (role === "assistant") {
bubble.appendChild(this.thinkPanel);
}
bubble.appendChild(this.contentEl);
this.shadow.appendChild(style);
this.shadow.appendChild(bubble);
if (this._text) {
this.render();
}
}
get text() {
return this._text;
}
set text(value) {
this._text = value;
this.render();
}
get streaming() {
return this._streaming;
}
set streaming(value) {
this._streaming = value;
this.render();
}
appendToken(token) {
this._text += token;
this.render();
}
/**
* Splits text into think/response portions and renders each.
*
* Safety: renderMarkdown() escapes all HTML entities (& < > ") before any
* inline formatting is applied. The source is the local MLX model output,
* not arbitrary user HTML. Shadow DOM provides additional isolation.
*/
render() {
if (!this.contentEl) return;
const { think, response } = this.splitThink(this._text);
if (think !== null && this.thinkPanel) {
this.thinkPanel.style.display = "";
this.thinkContent.textContent = think;
}
const responseHtml = renderMarkdown(response);
this.contentEl.innerHTML = responseHtml;
if (this._streaming) {
if (!this.cursorEl) {
this.cursorEl = document.createElement("span");
this.cursorEl.className = "cursor";
}
if (think !== null && !this._text.includes("</think>")) {
this.thinkContent.appendChild(this.cursorEl);
} else {
const lastChild = this.contentEl.lastElementChild || this.contentEl;
lastChild.appendChild(this.cursorEl);
}
}
}
/**
* Split raw text into think content and response content.
* Returns { think: string | null, response: string }
*/
splitThink(text) {
const thinkStart = text.indexOf("<think>");
if (thinkStart === -1) {
return { think: null, response: text };
}
const afterOpen = thinkStart + "<think>".length;
const thinkEnd = text.indexOf("</think>", afterOpen);
if (thinkEnd === -1) {
return {
think: text.slice(afterOpen).trim(),
response: text.slice(0, thinkStart).trim()
};
}
const thinkText = text.slice(afterOpen, thinkEnd).trim();
const beforeThink = text.slice(0, thinkStart).trim();
const afterThink = text.slice(thinkEnd + "</think>".length).trim();
const response = [beforeThink, afterThink].filter(Boolean).join("\n");
return { think: thinkText, response };
}
};
customElements.define("lem-message", LemMessage);
// src/lem-input.ts
var LemInput = class extends HTMLElement {
shadow;
textarea;
sendBtn;
_disabled = false;
constructor() {
super();
this.shadow = this.attachShadow({ mode: "open" });
}
connectedCallback() {
const style = document.createElement("style");
style.textContent = inputStyles;
const wrapper = document.createElement("div");
wrapper.className = "input-wrapper";
this.textarea = document.createElement("textarea");
this.textarea.rows = 1;
this.textarea.placeholder = "Message LEM...";
this.sendBtn = document.createElement("button");
this.sendBtn.className = "send-btn";
this.sendBtn.type = "button";
this.sendBtn.disabled = true;
this.sendBtn.appendChild(this.createSendIcon());
wrapper.appendChild(this.textarea);
wrapper.appendChild(this.sendBtn);
this.shadow.appendChild(style);
this.shadow.appendChild(wrapper);
this.textarea.addEventListener("input", () => {
this.textarea.style.height = "auto";
this.textarea.style.height = Math.min(this.textarea.scrollHeight, 120) + "px";
this.sendBtn.disabled = this._disabled || this.textarea.value.trim() === "";
});
this.textarea.addEventListener("keydown", (e) => {
if (e.key === "Enter" && !e.shiftKey) {
e.preventDefault();
this.submit();
}
});
this.sendBtn.addEventListener("click", () => this.submit());
}
/** Build the send arrow SVG using DOM API (no innerHTML) */
createSendIcon() {
const ns = "http://www.w3.org/2000/svg";
const svg = document.createElementNS(ns, "svg");
svg.setAttribute("viewBox", "0 0 24 24");
svg.setAttribute("fill", "none");
svg.setAttribute("stroke", "currentColor");
svg.setAttribute("stroke-width", "2");
svg.setAttribute("stroke-linecap", "round");
svg.setAttribute("stroke-linejoin", "round");
svg.setAttribute("width", "16");
svg.setAttribute("height", "16");
const line = document.createElementNS(ns, "line");
line.setAttribute("x1", "22");
line.setAttribute("y1", "2");
line.setAttribute("x2", "11");
line.setAttribute("y2", "13");
const polygon = document.createElementNS(ns, "polygon");
polygon.setAttribute("points", "22 2 15 22 11 13 2 9 22 2");
svg.appendChild(line);
svg.appendChild(polygon);
return svg;
}
submit() {
const text = this.textarea.value.trim();
if (!text || this._disabled) return;
this.dispatchEvent(
new CustomEvent("lem-send", {
bubbles: true,
composed: true,
detail: { text }
})
);
this.textarea.value = "";
this.textarea.style.height = "auto";
this.sendBtn.disabled = true;
this.textarea.focus();
}
get disabled() {
return this._disabled;
}
set disabled(value) {
this._disabled = value;
this.textarea.disabled = value;
this.sendBtn.disabled = value || this.textarea.value.trim() === "";
this.textarea.placeholder = value ? "LEM is thinking..." : "Message LEM...";
}
focus() {
this.textarea?.focus();
}
};
customElements.define("lem-input", LemInput);
// src/lem-chat.ts
var LemChat = class extends HTMLElement {
shadow;
messages;
input;
statusEl;
history = [];
abortController = null;
static get observedAttributes() {
return ["endpoint", "model", "system-prompt", "max-tokens", "temperature"];
}
constructor() {
super();
this.shadow = this.attachShadow({ mode: "open" });
}
connectedCallback() {
const style = document.createElement("style");
style.textContent = chatStyles;
const header = document.createElement("div");
header.className = "header";
this.statusEl = document.createElement("div");
this.statusEl.className = "header-status";
const icon = document.createElement("div");
icon.className = "header-icon";
icon.textContent = "L";
const title = document.createElement("div");
title.className = "header-title";
title.textContent = "LEM";
const modelLabel = document.createElement("div");
modelLabel.className = "header-model";
modelLabel.textContent = this.getAttribute("model") || "local";
header.appendChild(this.statusEl);
header.appendChild(icon);
header.appendChild(title);
header.appendChild(modelLabel);
this.messages = document.createElement("lem-messages");
this.input = document.createElement("lem-input");
this.shadow.appendChild(style);
this.shadow.appendChild(header);
this.shadow.appendChild(this.messages);
this.shadow.appendChild(this.input);
this.addEventListener("lem-send", ((e) => {
this.handleSend(e.detail.text);
}));
const systemPrompt = this.getAttribute("system-prompt");
if (systemPrompt) {
this.history.push({ role: "system", content: systemPrompt });
}
this.checkConnection();
requestAnimationFrame(() => this.input.focus());
}
disconnectedCallback() {
this.abortController?.abort();
}
get endpoint() {
const attr = this.getAttribute("endpoint");
if (!attr) return window.location.origin;
return attr;
}
get model() {
return this.getAttribute("model") || "";
}
get maxTokens() {
const val = this.getAttribute("max-tokens");
return val ? parseInt(val, 10) : 2048;
}
get temperature() {
const val = this.getAttribute("temperature");
return val ? parseFloat(val) : 0.7;
}
async checkConnection() {
try {
const resp = await fetch(`${this.endpoint}/v1/models`, {
signal: AbortSignal.timeout(3e3)
});
this.statusEl.classList.toggle("disconnected", !resp.ok);
} catch {
this.statusEl.classList.add("disconnected");
}
}
async handleSend(text) {
this.messages.addMessage("user", text);
this.history.push({ role: "user", content: text });
const assistantMsg = this.messages.addMessage("assistant");
assistantMsg.streaming = true;
this.input.disabled = true;
this.abortController?.abort();
this.abortController = new AbortController();
let fullResponse = "";
try {
const response = await fetch(`${this.endpoint}/v1/chat/completions`, {
method: "POST",
headers: { "Content-Type": "application/json" },
signal: this.abortController.signal,
body: JSON.stringify({
model: this.model,
messages: this.history,
max_tokens: this.maxTokens,
temperature: this.temperature,
stream: true
})
});
if (!response.ok) {
throw new Error(`Server error: ${response.status}`);
}
if (!response.body) {
throw new Error("No response body");
}
const reader = response.body.getReader();
const decoder = new TextDecoder();
let buffer = "";
while (true) {
const { done, value } = await reader.read();
if (done) break;
buffer += decoder.decode(value, { stream: true });
const lines = buffer.split("\n");
buffer = lines.pop() || "";
for (const line of lines) {
if (!line.startsWith("data: ")) continue;
const data = line.slice(6).trim();
if (data === "[DONE]") continue;
try {
const chunk = JSON.parse(data);
const delta = chunk.choices?.[0]?.delta;
if (delta?.content) {
fullResponse += delta.content;
assistantMsg.appendToken(delta.content);
this.messages.scrollToBottom();
}
} catch {
}
}
}
} catch (err) {
if (err instanceof Error && err.name === "AbortError") {
} else {
const errorText = err instanceof Error ? err.message : "Connection failed";
if (!fullResponse) {
assistantMsg.text = `\u26A0\uFE0F ${errorText}`;
}
this.statusEl.classList.add("disconnected");
}
} finally {
assistantMsg.streaming = false;
this.input.disabled = false;
this.input.focus();
this.abortController = null;
if (fullResponse) {
this.history.push({ role: "assistant", content: fullResponse });
}
}
}
};
customElements.define("lem-chat", LemChat);
export {
LemChat
};

44
cmd/ml/chat_embed.go Normal file
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@ -0,0 +1,44 @@
package ml
import (
_ "embed"
)
//go:embed chat.js
var lemChatJS []byte
const chatHTML = `<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>LEM Chat</title>
<style>
* { margin: 0; padding: 0; box-sizing: border-box; }
html, body { height: 100%%; background: #111; }
body {
display: flex;
align-items: center;
justify-content: center;
font-family: system-ui, -apple-system, sans-serif;
}
lem-chat {
width: 720px;
height: 85vh;
max-height: 800px;
}
@media (max-width: 768px) {
lem-chat { width: 100%%; height: 100%%; max-height: none; border-radius: 0; }
}
</style>
</head>
<body>
<lem-chat
endpoint=""
model="%s"
system-prompt=""
max-tokens="%d"
></lem-chat>
<script type="module" src="/chat.js"></script>
</body>
</html>`

View file

@ -1,15 +1,21 @@
package ml
import (
"context"
"encoding/json"
"fmt"
"io"
"log/slog"
"net/http"
"os"
"os/signal"
"runtime"
"sync/atomic"
"syscall"
"time"
"forge.lthn.ai/core/go/pkg/cli"
"forge.lthn.ai/core/go/pkg/ml"
"forge.lthn.ai/core/go-ai/ml"
)
var serveCmd = &cli.Command{
@ -22,11 +28,21 @@ var serveCmd = &cli.Command{
var (
serveBind string
serveModelPath string
serveThreads int
serveMaxTokens int
serveTimeout int
serveMaxRequests int
serveMaxContext int
)
func init() {
serveCmd.Flags().StringVar(&serveBind, "bind", "0.0.0.0:8090", "Address to bind")
serveCmd.Flags().StringVar(&serveModelPath, "model-path", "", "Path to model directory (for mlx backend)")
serveCmd.Flags().IntVar(&serveThreads, "threads", 0, "Max CPU threads (0 = all available)")
serveCmd.Flags().IntVar(&serveMaxTokens, "max-tokens", 4096, "Default max tokens per request")
serveCmd.Flags().IntVar(&serveTimeout, "timeout", 300, "Request timeout in seconds")
serveCmd.Flags().IntVar(&serveMaxRequests, "max-requests", 1, "Max concurrent requests (Metal is single-stream)")
serveCmd.Flags().IntVar(&serveMaxContext, "max-context", 4, "Max chat messages to keep (sliding window, 0=unlimited)")
}
type completionRequest struct {
@ -34,6 +50,7 @@ type completionRequest struct {
Prompt string `json:"prompt"`
MaxTokens int `json:"max_tokens"`
Temperature float64 `json:"temperature"`
Stream bool `json:"stream"`
}
type completionResponse struct {
@ -56,6 +73,7 @@ type chatRequest struct {
Messages []ml.Message `json:"messages"`
MaxTokens int `json:"max_tokens"`
Temperature float64 `json:"temperature"`
Stream bool `json:"stream"`
}
type chatResponse struct {
@ -72,6 +90,40 @@ type chatChoice struct {
FinishReason string `json:"finish_reason"`
}
// SSE streaming types (OpenAI chunk format)
type chatChunkResponse struct {
ID string `json:"id"`
Object string `json:"object"`
Created int64 `json:"created"`
Model string `json:"model"`
Choices []chatChunkChoice `json:"choices"`
}
type chatChunkChoice struct {
Delta chatChunkDelta `json:"delta"`
Index int `json:"index"`
FinishReason *string `json:"finish_reason"`
}
type chatChunkDelta struct {
Role string `json:"role,omitempty"`
Content string `json:"content,omitempty"`
}
type completionChunkResponse struct {
ID string `json:"id"`
Object string `json:"object"`
Created int64 `json:"created"`
Model string `json:"model"`
Choices []completionChunkChoice `json:"choices"`
}
type completionChunkChoice struct {
Text string `json:"text"`
Index int `json:"index"`
FinishReason *string `json:"finish_reason"`
}
type usageInfo struct {
PromptTokens int `json:"prompt_tokens"`
CompletionTokens int `json:"completion_tokens"`
@ -79,16 +131,54 @@ type usageInfo struct {
}
func runServe(cmd *cli.Command, args []string) error {
// Try native MLX backend first (macOS arm64 with mlx tag + model-path set),
// fall back to HTTP proxy backend.
// Cap CPU threads
if serveThreads > 0 {
prev := runtime.GOMAXPROCS(serveThreads)
slog.Info("ml serve: capped threads", "threads", serveThreads, "previous", prev)
}
backend, err := createServeBackend()
if err != nil {
return err
}
// Check if backend supports streaming
streamer, canStream := backend.(ml.StreamingBackend)
// Request tracking
var activeRequests atomic.Int32
startTime := time.Now()
mux := http.NewServeMux()
// Health endpoint
mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
json.NewEncoder(w).Encode(map[string]any{
"status": "ok",
"model": backend.Name(),
"uptime_seconds": int(time.Since(startTime).Seconds()),
"active_requests": activeRequests.Load(),
"max_threads": runtime.GOMAXPROCS(0),
"max_tokens": serveMaxTokens,
"max_context": serveMaxContext,
})
})
mux.HandleFunc("POST /v1/completions", func(w http.ResponseWriter, r *http.Request) {
// Concurrency gate
if int(activeRequests.Load()) >= serveMaxRequests {
http.Error(w, `{"error":"server busy, max concurrent requests reached"}`, http.StatusTooManyRequests)
return
}
activeRequests.Add(1)
defer activeRequests.Add(-1)
// Request timeout
ctx, cancel := context.WithTimeout(r.Context(), time.Duration(serveTimeout)*time.Second)
defer cancel()
r = r.WithContext(ctx)
body, _ := io.ReadAll(r.Body)
var req completionRequest
if err := json.Unmarshal(body, &req); err != nil {
@ -96,12 +186,67 @@ func runServe(cmd *cli.Command, args []string) error {
return
}
// Enforce server-level max-tokens cap
if req.MaxTokens == 0 || req.MaxTokens > serveMaxTokens {
req.MaxTokens = serveMaxTokens
}
opts := ml.GenOpts{
Temperature: req.Temperature,
MaxTokens: req.MaxTokens,
Model: req.Model,
}
// Streaming path
if req.Stream && canStream {
id := fmt.Sprintf("cmpl-%d", time.Now().UnixNano())
created := time.Now().Unix()
w.Header().Set("Content-Type", "text/event-stream")
w.Header().Set("Cache-Control", "no-cache")
w.Header().Set("Connection", "keep-alive")
w.Header().Set("X-Accel-Buffering", "no")
flusher, ok := w.(http.Flusher)
if !ok {
http.Error(w, "streaming not supported", 500)
return
}
err := streamer.GenerateStream(r.Context(), req.Prompt, opts, func(token string) error {
chunk := completionChunkResponse{
ID: id,
Object: "text_completion",
Created: created,
Model: backend.Name(),
Choices: []completionChunkChoice{{Text: token}},
}
data, _ := json.Marshal(chunk)
fmt.Fprintf(w, "data: %s\n\n", data)
flusher.Flush()
return nil
})
if err != nil {
slog.Error("stream error", "err", err)
}
// Send final chunk with finish_reason
stop := "stop"
final := completionChunkResponse{
ID: id,
Object: "text_completion",
Created: created,
Model: backend.Name(),
Choices: []completionChunkChoice{{FinishReason: &stop}},
}
data, _ := json.Marshal(final)
fmt.Fprintf(w, "data: %s\n\n", data)
fmt.Fprintf(w, "data: [DONE]\n\n")
flusher.Flush()
return
}
// Non-streaming path
text, err := backend.Generate(r.Context(), req.Prompt, opts)
if err != nil {
http.Error(w, err.Error(), 500)
@ -121,6 +266,19 @@ func runServe(cmd *cli.Command, args []string) error {
})
mux.HandleFunc("POST /v1/chat/completions", func(w http.ResponseWriter, r *http.Request) {
// Concurrency gate
if int(activeRequests.Load()) >= serveMaxRequests {
http.Error(w, `{"error":"server busy, max concurrent requests reached"}`, http.StatusTooManyRequests)
return
}
activeRequests.Add(1)
defer activeRequests.Add(-1)
// Request timeout
ctx, cancel := context.WithTimeout(r.Context(), time.Duration(serveTimeout)*time.Second)
defer cancel()
r = r.WithContext(ctx)
body, _ := io.ReadAll(r.Body)
var req chatRequest
if err := json.Unmarshal(body, &req); err != nil {
@ -128,12 +286,97 @@ func runServe(cmd *cli.Command, args []string) error {
return
}
// Enforce server-level max-tokens cap
if req.MaxTokens == 0 || req.MaxTokens > serveMaxTokens {
req.MaxTokens = serveMaxTokens
}
// Sliding window: keep system prompt (if any) + last N messages
// Prevents KV-cache explosion on multi-turn conversations
if serveMaxContext > 0 && len(req.Messages) > serveMaxContext {
var kept []ml.Message
rest := req.Messages
// Preserve system message if present
if len(rest) > 0 && rest[0].Role == "system" {
kept = append(kept, rest[0])
rest = rest[1:]
}
// Keep only the last N user/assistant messages
if len(rest) > serveMaxContext {
rest = rest[len(rest)-serveMaxContext:]
}
req.Messages = append(kept, rest...)
slog.Debug("ml serve: context window applied", "kept", len(req.Messages))
}
opts := ml.GenOpts{
Temperature: req.Temperature,
MaxTokens: req.MaxTokens,
Model: req.Model,
}
// Streaming path
if req.Stream && canStream {
id := fmt.Sprintf("chatcmpl-%d", time.Now().UnixNano())
created := time.Now().Unix()
w.Header().Set("Content-Type", "text/event-stream")
w.Header().Set("Cache-Control", "no-cache")
w.Header().Set("Connection", "keep-alive")
w.Header().Set("X-Accel-Buffering", "no")
flusher, ok := w.(http.Flusher)
if !ok {
http.Error(w, "streaming not supported", 500)
return
}
// Send initial role chunk
roleChunk := chatChunkResponse{
ID: id,
Object: "chat.completion.chunk",
Created: created,
Model: backend.Name(),
Choices: []chatChunkChoice{{Delta: chatChunkDelta{Role: "assistant"}}},
}
data, _ := json.Marshal(roleChunk)
fmt.Fprintf(w, "data: %s\n\n", data)
flusher.Flush()
err := streamer.ChatStream(r.Context(), req.Messages, opts, func(token string) error {
chunk := chatChunkResponse{
ID: id,
Object: "chat.completion.chunk",
Created: created,
Model: backend.Name(),
Choices: []chatChunkChoice{{Delta: chatChunkDelta{Content: token}}},
}
data, _ := json.Marshal(chunk)
fmt.Fprintf(w, "data: %s\n\n", data)
flusher.Flush()
return nil
})
if err != nil {
slog.Error("stream error", "err", err)
}
// Send final chunk with finish_reason
stop := "stop"
final := chatChunkResponse{
ID: id,
Object: "chat.completion.chunk",
Created: created,
Model: backend.Name(),
Choices: []chatChunkChoice{{Delta: chatChunkDelta{}, FinishReason: &stop}},
}
data, _ = json.Marshal(final)
fmt.Fprintf(w, "data: %s\n\n", data)
fmt.Fprintf(w, "data: [DONE]\n\n")
flusher.Flush()
return
}
// Non-streaming path
text, err := backend.Chat(r.Context(), req.Messages, opts)
if err != nil {
http.Error(w, err.Error(), 500)
@ -171,7 +414,59 @@ func runServe(cmd *cli.Command, args []string) error {
json.NewEncoder(w).Encode(resp)
})
slog.Info("ml serve: starting", "bind", serveBind, "backend", backend.Name())
// Serve the lem-chat UI at root — same origin, no CORS needed
mux.HandleFunc("GET /chat.js", func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/javascript")
w.Write(lemChatJS)
})
mux.HandleFunc("GET /", func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/" {
http.NotFound(w, r)
return
}
w.Header().Set("Content-Type", "text/html; charset=utf-8")
fmt.Fprintf(w, chatHTML, backend.Name(), serveMaxTokens)
})
slog.Info("ml serve: starting",
"bind", serveBind,
"backend", backend.Name(),
"streaming", canStream,
"threads", runtime.GOMAXPROCS(0),
"max_tokens", serveMaxTokens,
"max_context_msgs", serveMaxContext,
"timeout_s", serveTimeout,
"max_requests", serveMaxRequests,
)
fmt.Printf("Serving on http://%s\n", serveBind)
return http.ListenAndServe(serveBind, mux)
// Graceful shutdown on SIGINT/SIGTERM
srv := &http.Server{
Addr: serveBind,
Handler: mux,
}
errCh := make(chan error, 1)
go func() {
errCh <- srv.ListenAndServe()
}()
sigCh := make(chan os.Signal, 1)
signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
select {
case sig := <-sigCh:
slog.Info("ml serve: shutting down", "signal", sig)
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
if err := srv.Shutdown(ctx); err != nil {
slog.Error("ml serve: shutdown error", "err", err)
return err
}
slog.Info("ml serve: stopped cleanly")
return nil
case err := <-errCh:
return err
}
}