feat(web): polish master chat with model selector, params config, and empty state (#519)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/chat/Chat.test.tsx

@@ -43,6 +43,15 @@ vi.mock("./ChatInput", () => ({
       Send
     </button>
   ),
+  DEFAULT_TEMPERATURE: 0.7,
+  DEFAULT_MAX_TOKENS: 4096,
+  DEFAULT_MODEL: "llama3.2",
+  AVAILABLE_MODELS: [
+    { id: "llama3.2", label: "Llama 3.2" },
+    { id: "claude-3.5-sonnet", label: "Claude 3.5 Sonnet" },
+    { id: "gpt-4o", label: "GPT-4o" },
+    { id: "deepseek-r1", label: "DeepSeek R1" },
+  ],
 }));
 
 const mockUseAuth = authModule.useAuth as MockedFunction<typeof authModule.useAuth>;

apps/web/src/components/chat/Chat.tsx

@@ -5,7 +5,8 @@ import { useAuth } from "@/lib/auth/auth-context";
 import { useChat } from "@/hooks/useChat";
 import { useWebSocket } from "@/hooks/useWebSocket";
 import { MessageList } from "./MessageList";
-import { ChatInput } from "./ChatInput";
+import { ChatInput, type ModelId, DEFAULT_TEMPERATURE, DEFAULT_MAX_TOKENS } from "./ChatInput";
+import { ChatEmptyState } from "./ChatEmptyState";
 import type { Message } from "@/hooks/useChat";
 
 export interface ChatRef {
@@ -59,6 +60,14 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
 
   const { user, isLoading: authLoading } = useAuth();
 
+  // Model and params state — initialized from ChatInput's persisted values
+  const [selectedModel, setSelectedModel] = useState<ModelId>("llama3.2");
+  const [temperature, setTemperature] = useState<number>(DEFAULT_TEMPERATURE);
+  const [maxTokens, setMaxTokens] = useState<number>(DEFAULT_MAX_TOKENS);
+
+  // Suggestion fill value: controls ChatInput's textarea content
+  const [suggestionValue, setSuggestionValue] = useState<string | undefined>(undefined);
+
   const {
     messages,
     isLoading: isChatLoading,
@@ -72,7 +81,9 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     startNewConversation,
     clearError,
   } = useChat({
-    model: "llama3.2",
+    model: selectedModel,
+    temperature,
+    maxTokens,
     ...(initialProjectId !== undefined && { projectId: initialProjectId }),
   });
 
@@ -88,6 +99,11 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
   const streamingMessageId =
     isStreaming && messages.length > 0 ? messages[messages.length - 1]?.id : undefined;
 
+  // Whether the conversation is empty (only welcome message or no messages)
+  const isEmptyConversation =
+    messages.length === 0 ||
+    (messages.length === 1 && messages[0]?.id === "welcome" && !isChatLoading && !isStreaming);
+
   useImperativeHandle(ref, () => ({
     loadConversation: async (cId: string): Promise<void> => {
       await loadConversation(cId);
@@ -122,16 +138,29 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
 
   useEffect(() => {
     const handleKeyDown = (e: KeyboardEvent): void => {
+      // Cmd/Ctrl + / : Focus input
       if ((e.ctrlKey || e.metaKey) && e.key === "/") {
         e.preventDefault();
         inputRef.current?.focus();
       }
+      // Cmd/Ctrl + N : Start new conversation
+      if ((e.ctrlKey || e.metaKey) && (e.key === "n" || e.key === "N")) {
+        e.preventDefault();
+        startNewConversation(null);
+        inputRef.current?.focus();
+      }
+      // Cmd/Ctrl + L : Clear / start new conversation
+      if ((e.ctrlKey || e.metaKey) && (e.key === "l" || e.key === "L")) {
+        e.preventDefault();
+        startNewConversation(null);
+        inputRef.current?.focus();
+      }
     };
     document.addEventListener("keydown", handleKeyDown);
     return (): void => {
       document.removeEventListener("keydown", handleKeyDown);
     };
-  }, []);
+  }, [startNewConversation]);
 
   // Show loading quips only during non-streaming load (initial fetch wait)
   useEffect(() => {
@@ -168,6 +197,14 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     [sendMessage]
   );
 
+  const handleSuggestionClick = useCallback((prompt: string): void => {
+    setSuggestionValue(prompt);
+    // Clear after a tick so input receives it, then focus
+    setTimeout(() => {
+      inputRef.current?.focus();
+    }, 0);
+  }, []);
+
   if (authLoading) {
     return (
       <div
@@ -214,6 +251,9 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
       {/* Messages Area */}
       <div className="flex-1 overflow-y-auto">
         <div className="mx-auto max-w-4xl px-4 py-6 lg:px-8">
+          {isEmptyConversation ? (
+            <ChatEmptyState onSuggestionClick={handleSuggestionClick} />
+          ) : (
             <MessageList
               messages={messages as (Message & { thinking?: string })[]}
               isLoading={isChatLoading}
@@ -221,6 +261,7 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
               {...(streamingMessageId != null ? { streamingMessageId } : {})}
               loadingQuip={loadingQuip}
             />
+          )}
           <div ref={messagesEndRef} />
         </div>
       </div>
@@ -288,6 +329,10 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
             inputRef={inputRef}
             isStreaming={isStreaming}
             onStopStreaming={abortStream}
+            onModelChange={setSelectedModel}
+            onTemperatureChange={setTemperature}
+            onMaxTokensChange={setMaxTokens}
+            {...(suggestionValue !== undefined ? { externalValue: suggestionValue } : {})}
           />
         </div>
       </div>

apps/web/src/components/chat/ChatEmptyState.test.tsx

@@ -0,0 +1,103 @@
+/**
+ * @file ChatEmptyState.test.tsx
+ * @description Tests for ChatEmptyState component: greeting, suggestions, click handling
+ */
+
+import { render, screen, fireEvent } from "@testing-library/react";
+import { describe, it, expect, vi } from "vitest";
+import { ChatEmptyState } from "./ChatEmptyState";
+
+describe("ChatEmptyState", () => {
+  it("should render the greeting heading", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    expect(screen.getByRole("heading", { name: /how can i help/i })).toBeDefined();
+  });
+
+  it("should render the empty state container", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    expect(screen.getByTestId("chat-empty-state")).toBeDefined();
+  });
+
+  it("should render four suggestion buttons", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    // Four suggestions
+    const buttons = screen.getAllByRole("button");
+    expect(buttons.length).toBe(4);
+  });
+
+  it("should render 'Explain this project' suggestion", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    expect(screen.getByText("Explain this project")).toBeDefined();
+  });
+
+  it("should render 'Help me debug' suggestion", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    expect(screen.getByText("Help me debug")).toBeDefined();
+  });
+
+  it("should render 'Write a test for' suggestion", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    expect(screen.getByText("Write a test for")).toBeDefined();
+  });
+
+  it("should render 'Refactor this code' suggestion", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    expect(screen.getByText("Refactor this code")).toBeDefined();
+  });
+
+  it("should call onSuggestionClick with the correct prompt when a suggestion is clicked", () => {
+    const onSuggestionClick = vi.fn();
+    render(<ChatEmptyState onSuggestionClick={onSuggestionClick} />);
+
+    const explainButton = screen.getByTestId("suggestion-explain-this-project");
+    fireEvent.click(explainButton);
+
+    expect(onSuggestionClick).toHaveBeenCalledOnce();
+    const [calledWith] = onSuggestionClick.mock.calls[0] as [string];
+    expect(calledWith).toContain("overview of this project");
+  });
+
+  it("should call onSuggestionClick for 'Help me debug' prompt", () => {
+    const onSuggestionClick = vi.fn();
+    render(<ChatEmptyState onSuggestionClick={onSuggestionClick} />);
+
+    const debugButton = screen.getByTestId("suggestion-help-me-debug");
+    fireEvent.click(debugButton);
+
+    expect(onSuggestionClick).toHaveBeenCalledOnce();
+    const [calledWith] = onSuggestionClick.mock.calls[0] as [string];
+    expect(calledWith).toContain("debugging");
+  });
+
+  it("should call onSuggestionClick for 'Write a test for' prompt", () => {
+    const onSuggestionClick = vi.fn();
+    render(<ChatEmptyState onSuggestionClick={onSuggestionClick} />);
+
+    const testButton = screen.getByTestId("suggestion-write-a-test-for");
+    fireEvent.click(testButton);
+
+    expect(onSuggestionClick).toHaveBeenCalledOnce();
+  });
+
+  it("should call onSuggestionClick for 'Refactor this code' prompt", () => {
+    const onSuggestionClick = vi.fn();
+    render(<ChatEmptyState onSuggestionClick={onSuggestionClick} />);
+
+    const refactorButton = screen.getByTestId("suggestion-refactor-this-code");
+    fireEvent.click(refactorButton);
+
+    expect(onSuggestionClick).toHaveBeenCalledOnce();
+    const [calledWith] = onSuggestionClick.mock.calls[0] as [string];
+    expect(calledWith).toContain("refactor");
+  });
+
+  it("should have accessible aria-label on each suggestion button", () => {
+    render(<ChatEmptyState onSuggestionClick={vi.fn()} />);
+    const buttons = screen.getAllByRole("button");
+    for (const button of buttons) {
+      const label = button.getAttribute("aria-label");
+      expect(label).toBeTruthy();
+      expect(label).toMatch(/suggestion:/i);
+    }
+  });
+});

apps/web/src/components/chat/ChatEmptyState.tsx

@@ -0,0 +1,99 @@
+"use client";
+
+interface Suggestion {
+  label: string;
+  prompt: string;
+}
+
+const SUGGESTIONS: Suggestion[] = [
+  {
+    label: "Explain this project",
+    prompt: "Can you give me an overview of this project and its key components?",
+  },
+  {
+    label: "Help me debug",
+    prompt: "I have a bug I need help debugging. Can you walk me through the process?",
+  },
+  {
+    label: "Write a test for",
+    prompt: "Can you help me write a test for the following function or component?",
+  },
+  {
+    label: "Refactor this code",
+    prompt: "I have some code I'd like to refactor for better readability and maintainability.",
+  },
+];
+
+interface ChatEmptyStateProps {
+  onSuggestionClick: (prompt: string) => void;
+}
+
+export function ChatEmptyState({ onSuggestionClick }: ChatEmptyStateProps): React.JSX.Element {
+  return (
+    <div
+      className="flex flex-col items-center justify-center gap-6 py-12 px-4 text-center"
+      data-testid="chat-empty-state"
+    >
+      {/* Icon */}
+      <div
+        className="flex h-16 w-16 items-center justify-center rounded-2xl"
+        style={{ backgroundColor: "rgb(var(--accent-primary) / 0.12)" }}
+      >
+        <svg
+          className="h-8 w-8"
+          style={{ color: "rgb(var(--accent-primary))" }}
+          fill="none"
+          viewBox="0 0 24 24"
+          stroke="currentColor"
+          strokeWidth={1.5}
+          aria-hidden="true"
+        >
+          <path d="M8 12h.01M12 12h.01M16 12h.01M21 12c0 4.418-4.03 8-9 8a9.863 9.863 0 01-4.255-.949L3 20l1.395-3.72C3.512 15.042 3 13.574 3 12c0-4.418 4.03-8 9-8s9 3.582 9 8z" />
+        </svg>
+      </div>
+
+      {/* Greeting */}
+      <div className="space-y-1">
+        <h3 className="text-lg font-semibold" style={{ color: "rgb(var(--text-primary))" }}>
+          How can I help you today?
+        </h3>
+        <p className="text-sm max-w-sm" style={{ color: "rgb(var(--text-secondary))" }}>
+          Ask me anything — I can help with code, explanations, debugging, and more.
+        </p>
+      </div>
+
+      {/* Suggestions */}
+      <div className="grid grid-cols-1 gap-2 w-full max-w-sm sm:grid-cols-2">
+        {SUGGESTIONS.map((suggestion) => (
+          <button
+            key={suggestion.label}
+            onClick={() => {
+              onSuggestionClick(suggestion.prompt);
+            }}
+            className="rounded-lg border px-3 py-2.5 text-left text-sm transition-all duration-150 hover:shadow-sm focus:outline-none focus:ring-2"
+            style={{
+              backgroundColor: "rgb(var(--surface-1))",
+              borderColor: "rgb(var(--border-default))",
+              color: "rgb(var(--text-secondary))",
+            }}
+            aria-label={`Suggestion: ${suggestion.label}`}
+            data-testid={`suggestion-${suggestion.label.toLowerCase().replace(/\s+/g, "-")}`}
+          >
+            <span
+              className="block text-xs font-medium mb-0.5"
+              style={{ color: "rgb(var(--text-primary))" }}
+            >
+              {suggestion.label}
+            </span>
+            <span
+              className="block text-xs leading-relaxed line-clamp-2"
+              style={{ color: "rgb(var(--text-muted))" }}
+            >
+              {suggestion.prompt}
+            </span>
+          </button>
+        ))}
+      </div>
+    </div>
+  );
+}

apps/web/src/components/chat/ChatInput.test.tsx

@@ -0,0 +1,293 @@
+/**
+ * @file ChatInput.test.tsx
+ * @description Tests for ChatInput: model selector, temperature/params, localStorage persistence
+ */
+
+import { render, screen, fireEvent, waitFor, within } from "@testing-library/react";
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import {
+  ChatInput,
+  AVAILABLE_MODELS,
+  DEFAULT_MODEL,
+  DEFAULT_TEMPERATURE,
+  DEFAULT_MAX_TOKENS,
+} from "./ChatInput";
+
+// Mock fetch for version.json
+beforeEach(() => {
+  global.fetch = vi.fn().mockRejectedValue(new Error("Not found"));
+});
+
+afterEach(() => {
+  vi.restoreAllMocks();
+  localStorage.clear();
+});
+
+/** Get the first non-default model from the list */
+function getNonDefaultModel(): (typeof AVAILABLE_MODELS)[number] {
+  const model = AVAILABLE_MODELS.find((m) => m.id !== DEFAULT_MODEL);
+  if (!model) throw new Error("No non-default model found");
+  return model;
+}
+
+describe("ChatInput — model selector", () => {
+  it("should render the model selector chip showing the default model", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    const defaultLabel =
+      AVAILABLE_MODELS.find((m) => m.id === DEFAULT_MODEL)?.label ?? DEFAULT_MODEL;
+    expect(screen.getByText(defaultLabel)).toBeDefined();
+  });
+
+  it("should open the model dropdown when the chip is clicked", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    const chip = screen.getByLabelText(/model:/i);
+    fireEvent.click(chip);
+
+    // The dropdown (listbox role) should be visible
+    const listbox = screen.getByRole("listbox", { name: /available models/i });
+    expect(listbox).toBeDefined();
+
+    // All model options should appear in the dropdown
+    const options = within(listbox).getAllByRole("option");
+    expect(options.length).toBe(AVAILABLE_MODELS.length);
+  });
+
+  it("should call onModelChange when a model is selected", async () => {
+    const onModelChange = vi.fn();
+    render(<ChatInput onSend={vi.fn()} onModelChange={onModelChange} />);
+
+    const chip = screen.getByLabelText(/model:/i);
+    fireEvent.click(chip);
+
+    const targetModel = getNonDefaultModel();
+    const listbox = screen.getByRole("listbox", { name: /available models/i });
+    const targetOption = within(listbox).getByText(targetModel.label);
+    fireEvent.click(targetOption);
+
+    await waitFor(() => {
+      const calls = onModelChange.mock.calls.map((c: unknown[]) => c[0]);
+      expect(calls).toContain(targetModel.id);
+    });
+  });
+
+  it("should persist the selected model in localStorage", async () => {
+    render(<ChatInput onSend={vi.fn()} />);
+
+    const chip = screen.getByLabelText(/model:/i);
+    fireEvent.click(chip);
+
+    const targetModel = getNonDefaultModel();
+    const listbox = screen.getByRole("listbox", { name: /available models/i });
+    const targetOption = within(listbox).getByText(targetModel.label);
+    fireEvent.click(targetOption);
+
+    await waitFor(() => {
+      expect(localStorage.getItem("chat:selectedModel")).toBe(targetModel.id);
+    });
+  });
+
+  it("should restore the model from localStorage on mount", async () => {
+    const targetModel = getNonDefaultModel();
+    localStorage.setItem("chat:selectedModel", targetModel.id);
+
+    render(<ChatInput onSend={vi.fn()} />);
+
+    await waitFor(() => {
+      expect(screen.getByText(targetModel.label)).toBeDefined();
+    });
+  });
+
+  it("should close the dropdown after selecting a model", async () => {
+    render(<ChatInput onSend={vi.fn()} />);
+
+    const chip = screen.getByLabelText(/model:/i);
+    fireEvent.click(chip);
+
+    const targetModel = getNonDefaultModel();
+    const listbox = screen.getByRole("listbox", { name: /available models/i });
+    const targetOption = within(listbox).getByText(targetModel.label);
+    fireEvent.click(targetOption);
+
+    // After selection, dropdown should close
+    await waitFor(() => {
+      expect(screen.queryByRole("listbox")).toBeNull();
+    });
+  });
+
+  it("should have aria-expanded on the model chip button", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    const chip = screen.getByLabelText(/model:/i);
+    expect(chip.getAttribute("aria-expanded")).toBe("false");
+
+    fireEvent.click(chip);
+    expect(chip.getAttribute("aria-expanded")).toBe("true");
+  });
+});
+
+describe("ChatInput — temperature and max tokens", () => {
+  it("should render the settings/params button", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    const settingsBtn = screen.getByLabelText(/chat parameters/i);
+    expect(settingsBtn).toBeDefined();
+  });
+
+  it("should open the params popover when settings button is clicked", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    const settingsBtn = screen.getByLabelText(/chat parameters/i);
+    fireEvent.click(settingsBtn);
+
+    expect(screen.getByLabelText(/temperature/i)).toBeDefined();
+    expect(screen.getByLabelText(/maximum tokens/i)).toBeDefined();
+  });
+
+  it("should show the default temperature value", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    fireEvent.click(screen.getByLabelText(/chat parameters/i));
+
+    const slider = screen.getByLabelText(/temperature/i);
+    expect(parseFloat((slider as HTMLInputElement).value)).toBeCloseTo(DEFAULT_TEMPERATURE);
+  });
+
+  it("should call onTemperatureChange when the slider is moved", async () => {
+    const onTemperatureChange = vi.fn();
+    render(<ChatInput onSend={vi.fn()} onTemperatureChange={onTemperatureChange} />);
+
+    fireEvent.click(screen.getByLabelText(/chat parameters/i));
+
+    const slider = screen.getByLabelText(/temperature/i);
+    fireEvent.change(slider, { target: { value: "1.2" } });
+
+    await waitFor(() => {
+      const calls = onTemperatureChange.mock.calls.map((c: unknown[]) => c[0]);
+      expect(calls).toContain(1.2);
+    });
+  });
+
+  it("should persist temperature in localStorage", async () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    fireEvent.click(screen.getByLabelText(/chat parameters/i));
+
+    const slider = screen.getByLabelText(/temperature/i);
+    fireEvent.change(slider, { target: { value: "0.5" } });
+
+    await waitFor(() => {
+      expect(localStorage.getItem("chat:temperature")).toBe("0.5");
+    });
+  });
+
+  it("should restore temperature from localStorage on mount", async () => {
+    localStorage.setItem("chat:temperature", "1.5");
+
+    const onTemperatureChange = vi.fn();
+    render(<ChatInput onSend={vi.fn()} onTemperatureChange={onTemperatureChange} />);
+
+    await waitFor(() => {
+      const calls = onTemperatureChange.mock.calls.map((c: unknown[]) => c[0]);
+      expect(calls).toContain(1.5);
+    });
+  });
+
+  it("should show the default max tokens value", () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    fireEvent.click(screen.getByLabelText(/chat parameters/i));
+
+    const input = screen.getByLabelText(/maximum tokens/i);
+    expect(parseInt((input as HTMLInputElement).value, 10)).toBe(DEFAULT_MAX_TOKENS);
+  });
+
+  it("should call onMaxTokensChange when the max tokens input changes", async () => {
+    const onMaxTokensChange = vi.fn();
+    render(<ChatInput onSend={vi.fn()} onMaxTokensChange={onMaxTokensChange} />);
+
+    fireEvent.click(screen.getByLabelText(/chat parameters/i));
+
+    const input = screen.getByLabelText(/maximum tokens/i);
+    fireEvent.change(input, { target: { value: "8192" } });
+
+    await waitFor(() => {
+      const calls = onMaxTokensChange.mock.calls.map((c: unknown[]) => c[0]);
+      expect(calls).toContain(8192);
+    });
+  });
+
+  it("should persist max tokens in localStorage", async () => {
+    render(<ChatInput onSend={vi.fn()} />);
+    fireEvent.click(screen.getByLabelText(/chat parameters/i));
+
+    const input = screen.getByLabelText(/maximum tokens/i);
+    fireEvent.change(input, { target: { value: "2000" } });
+
+    await waitFor(() => {
+      expect(localStorage.getItem("chat:maxTokens")).toBe("2000");
+    });
+  });
+
+  it("should restore max tokens from localStorage on mount", async () => {
+    localStorage.setItem("chat:maxTokens", "8000");
+
+    const onMaxTokensChange = vi.fn();
+    render(<ChatInput onSend={vi.fn()} onMaxTokensChange={onMaxTokensChange} />);
+
+    await waitFor(() => {
+      const calls = onMaxTokensChange.mock.calls.map((c: unknown[]) => c[0]);
+      expect(calls).toContain(8000);
+    });
+  });
+});
+
+describe("ChatInput — externalValue (suggestion fill)", () => {
+  it("should update the textarea when externalValue is provided", async () => {
+    const { rerender } = render(<ChatInput onSend={vi.fn()} />);
+
+    const textarea = screen.getByLabelText(/message input/i);
+    expect((textarea as HTMLTextAreaElement).value).toBe("");
+
+    rerender(<ChatInput onSend={vi.fn()} externalValue="Hello suggestion" />);
+
+    await waitFor(() => {
+      expect((textarea as HTMLTextAreaElement).value).toBe("Hello suggestion");
+    });
+  });
+});
+
+describe("ChatInput — send behavior", () => {
+  it("should call onSend with the message when the send button is clicked", async () => {
+    const onSend = vi.fn();
+    render(<ChatInput onSend={onSend} />);
+
+    const textarea = screen.getByLabelText(/message input/i);
+    fireEvent.change(textarea, { target: { value: "Hello world" } });
+
+    const sendButton = screen.getByLabelText(/send message/i);
+    fireEvent.click(sendButton);
+
+    await waitFor(() => {
+      expect(onSend).toHaveBeenCalledWith("Hello world");
+    });
+  });
+
+  it("should clear the textarea after sending", async () => {
+    const onSend = vi.fn();
+    render(<ChatInput onSend={onSend} />);
+
+    const textarea = screen.getByLabelText(/message input/i);
+    fireEvent.change(textarea, { target: { value: "Hello world" } });
+    fireEvent.click(screen.getByLabelText(/send message/i));
+
+    await waitFor(() => {
+      expect((textarea as HTMLTextAreaElement).value).toBe("");
+    });
+  });
+
+  it("should show the stop button when streaming", () => {
+    render(<ChatInput onSend={vi.fn()} isStreaming={true} />);
+    expect(screen.getByLabelText(/stop generating/i)).toBeDefined();
+  });
+
+  it("should call onStopStreaming when stop button is clicked", () => {
+    const onStop = vi.fn();
+    render(<ChatInput onSend={vi.fn()} isStreaming={true} onStopStreaming={onStop} />);
+    fireEvent.click(screen.getByLabelText(/stop generating/i));
+    expect(onStop).toHaveBeenCalledOnce();
+  });
+});

apps/web/src/components/chat/ChatInput.tsx

@@ -1,7 +1,66 @@
 "use client";
 
 import type { KeyboardEvent, RefObject } from "react";
-import { useCallback, useState, useEffect } from "react";
+import { useCallback, useState, useEffect, useRef } from "react";
+
+export const AVAILABLE_MODELS = [
+  { id: "llama3.2", label: "Llama 3.2" },
+  { id: "claude-3.5-sonnet", label: "Claude 3.5 Sonnet" },
+  { id: "gpt-4o", label: "GPT-4o" },
+  { id: "deepseek-r1", label: "DeepSeek R1" },
+] as const;
+
+export type ModelId = (typeof AVAILABLE_MODELS)[number]["id"];
+
+const STORAGE_KEY_MODEL = "chat:selectedModel";
+const STORAGE_KEY_TEMPERATURE = "chat:temperature";
+const STORAGE_KEY_MAX_TOKENS = "chat:maxTokens";
+
+export const DEFAULT_TEMPERATURE = 0.7;
+export const DEFAULT_MAX_TOKENS = 4096;
+export const DEFAULT_MODEL: ModelId = "llama3.2";
+
+function loadStoredModel(): ModelId {
+  try {
+    const stored = localStorage.getItem(STORAGE_KEY_MODEL);
+    if (stored && AVAILABLE_MODELS.some((m) => m.id === stored)) {
+      return stored as ModelId;
+    }
+  } catch {
+    // localStorage not available
+  }
+  return DEFAULT_MODEL;
+}
+
+function loadStoredTemperature(): number {
+  try {
+    const stored = localStorage.getItem(STORAGE_KEY_TEMPERATURE);
+    if (stored !== null) {
+      const parsed = parseFloat(stored);
+      if (!isNaN(parsed) && parsed >= 0 && parsed <= 2) {
+        return parsed;
+      }
+    }
+  } catch {
+    // localStorage not available
+  }
+  return DEFAULT_TEMPERATURE;
+}
+
+function loadStoredMaxTokens(): number {
+  try {
+    const stored = localStorage.getItem(STORAGE_KEY_MAX_TOKENS);
+    if (stored !== null) {
+      const parsed = parseInt(stored, 10);
+      if (!isNaN(parsed) && parsed >= 100 && parsed <= 32000) {
+        return parsed;
+      }
+    }
+  } catch {
+    // localStorage not available
+  }
+  return DEFAULT_MAX_TOKENS;
+}
 
 interface ChatInputProps {
   onSend: (message: string) => void;
@@ -9,6 +68,11 @@ interface ChatInputProps {
   inputRef?: RefObject<HTMLTextAreaElement | null>;
   isStreaming?: boolean;
   onStopStreaming?: () => void;
+  onModelChange?: (model: ModelId) => void;
+  onTemperatureChange?: (temperature: number) => void;
+  onMaxTokensChange?: (maxTokens: number) => void;
+  onSuggestionFill?: (text: string) => void;
+  externalValue?: string;
 }
 
 export function ChatInput({
@@ -17,9 +81,52 @@ export function ChatInput({
   inputRef,
   isStreaming = false,
   onStopStreaming,
+  onModelChange,
+  onTemperatureChange,
+  onMaxTokensChange,
+  externalValue,
 }: ChatInputProps): React.JSX.Element {
   const [message, setMessage] = useState("");
   const [version, setVersion] = useState<string | null>(null);
+  const [selectedModel, setSelectedModel] = useState<ModelId>(DEFAULT_MODEL);
+  const [temperature, setTemperature] = useState<number>(DEFAULT_TEMPERATURE);
+  const [maxTokens, setMaxTokens] = useState<number>(DEFAULT_MAX_TOKENS);
+  const [isModelDropdownOpen, setIsModelDropdownOpen] = useState(false);
+  const [isParamsOpen, setIsParamsOpen] = useState(false);
+
+  const modelDropdownRef = useRef<HTMLDivElement>(null);
+  const paramsDropdownRef = useRef<HTMLDivElement>(null);
+
+  // Stable refs for callbacks so the mount effect stays dependency-free
+  const onModelChangeRef = useRef(onModelChange);
+  onModelChangeRef.current = onModelChange;
+  const onTemperatureChangeRef = useRef(onTemperatureChange);
+  onTemperatureChangeRef.current = onTemperatureChange;
+  const onMaxTokensChangeRef = useRef(onMaxTokensChange);
+  onMaxTokensChangeRef.current = onMaxTokensChange;
+
+  // Load persisted values from localStorage on mount only
+  useEffect(() => {
+    const storedModel = loadStoredModel();
+    const storedTemperature = loadStoredTemperature();
+    const storedMaxTokens = loadStoredMaxTokens();
+
+    setSelectedModel(storedModel);
+    setTemperature(storedTemperature);
+    setMaxTokens(storedMaxTokens);
+
+    // Notify parent of initial values via refs to avoid stale closure
+    onModelChangeRef.current?.(storedModel);
+    onTemperatureChangeRef.current?.(storedTemperature);
+    onMaxTokensChangeRef.current?.(storedMaxTokens);
+  }, []);
+
+  // Sync external value (e.g. from suggestion clicks)
+  useEffect(() => {
+    if (externalValue !== undefined) {
+      setMessage(externalValue);
+    }
+  }, [externalValue]);
 
   useEffect(() => {
     interface VersionData {
@@ -40,6 +147,22 @@ export function ChatInput({
       });
   }, []);
 
+  // Close dropdowns on outside click
+  useEffect(() => {
+    const handleClickOutside = (e: MouseEvent): void => {
+      if (modelDropdownRef.current && !modelDropdownRef.current.contains(e.target as Node)) {
+        setIsModelDropdownOpen(false);
+      }
+      if (paramsDropdownRef.current && !paramsDropdownRef.current.contains(e.target as Node)) {
+        setIsParamsOpen(false);
+      }
+    };
+    document.addEventListener("mousedown", handleClickOutside);
+    return (): void => {
+      document.removeEventListener("mousedown", handleClickOutside);
+    };
+  }, []);
+
   const handleSubmit = useCallback(() => {
     if (message.trim() && !disabled && !isStreaming) {
       onSend(message);
@@ -65,6 +188,49 @@ export function ChatInput({
     [handleSubmit]
   );
 
+  const handleModelSelect = useCallback(
+    (model: ModelId): void => {
+      setSelectedModel(model);
+      try {
+        localStorage.setItem(STORAGE_KEY_MODEL, model);
+      } catch {
+        // ignore
+      }
+      onModelChange?.(model);
+      setIsModelDropdownOpen(false);
+    },
+    [onModelChange]
+  );
+
+  const handleTemperatureChange = useCallback(
+    (value: number): void => {
+      setTemperature(value);
+      try {
+        localStorage.setItem(STORAGE_KEY_TEMPERATURE, value.toString());
+      } catch {
+        // ignore
+      }
+      onTemperatureChange?.(value);
+    },
+    [onTemperatureChange]
+  );
+
+  const handleMaxTokensChange = useCallback(
+    (value: number): void => {
+      setMaxTokens(value);
+      try {
+        localStorage.setItem(STORAGE_KEY_MAX_TOKENS, value.toString());
+      } catch {
+        // ignore
+      }
+      onMaxTokensChange?.(value);
+    },
+    [onMaxTokensChange]
+  );
+
+  const selectedModelLabel =
+    AVAILABLE_MODELS.find((m) => m.id === selectedModel)?.label ?? selectedModel;
+
   const characterCount = message.length;
   const maxCharacters = 4000;
   const isNearLimit = characterCount > maxCharacters * 0.9;
@@ -72,7 +238,230 @@ export function ChatInput({
   const isInputDisabled = disabled ?? false;
 
   return (
-    <div className="space-y-3">
+    <div className="space-y-2">
+      {/* Model Selector + Params Row */}
+      <div className="flex items-center gap-2">
+        {/* Model Selector */}
+        <div className="relative" ref={modelDropdownRef}>
+          <button
+            type="button"
+            onClick={() => {
+              setIsModelDropdownOpen((prev) => !prev);
+              setIsParamsOpen(false);
+            }}
+            className="flex items-center gap-1.5 rounded-full border px-2.5 py-1 text-xs font-medium transition-colors hover:bg-black/5 focus:outline-none focus:ring-2"
+            style={{
+              borderColor: "rgb(var(--border-default))",
+              backgroundColor: "rgb(var(--surface-1))",
+              color: "rgb(var(--text-secondary))",
+            }}
+            aria-label={`Model: ${selectedModelLabel}. Click to change`}
+            aria-expanded={isModelDropdownOpen}
+            aria-haspopup="listbox"
+            title="Select AI model"
+          >
+            <svg
+              className="h-3 w-3 flex-shrink-0"
+              fill="none"
+              viewBox="0 0 24 24"
+              stroke="currentColor"
+              strokeWidth={2}
+              aria-hidden="true"
+            >
+              <circle cx="12" cy="12" r="3" />
+              <path d="M12 1v4M12 19v4M4.22 4.22l2.83 2.83M16.95 16.95l2.83 2.83M1 12h4M19 12h4M4.22 19.78l2.83-2.83M16.95 7.05l2.83-2.83" />
+            </svg>
+            <span>{selectedModelLabel}</span>
+            <svg
+              className={`h-3 w-3 transition-transform ${isModelDropdownOpen ? "rotate-180" : ""}`}
+              fill="none"
+              viewBox="0 0 24 24"
+              stroke="currentColor"
+              strokeWidth={2}
+              aria-hidden="true"
+            >
+              <path d="M6 9l6 6 6-6" />
+            </svg>
+          </button>
+
+          {/* Model Dropdown */}
+          {isModelDropdownOpen && (
+            <div
+              className="absolute bottom-full left-0 mb-1 z-50 min-w-[160px] rounded-lg border shadow-lg"
+              style={{
+                backgroundColor: "rgb(var(--surface-0))",
+                borderColor: "rgb(var(--border-default))",
+              }}
+              role="listbox"
+              aria-label="Available models"
+            >
+              {AVAILABLE_MODELS.map((model) => (
+                <button
+                  key={model.id}
+                  role="option"
+                  aria-selected={model.id === selectedModel}
+                  onClick={() => {
+                    handleModelSelect(model.id);
+                  }}
+                  className="w-full px-3 py-2 text-left text-xs transition-colors first:rounded-t-lg last:rounded-b-lg hover:bg-black/5"
+                  style={{
+                    color:
+                      model.id === selectedModel
+                        ? "rgb(var(--accent-primary))"
+                        : "rgb(var(--text-primary))",
+                    fontWeight: model.id === selectedModel ? 600 : 400,
+                  }}
+                >
+                  {model.label}
+                  {model.id === selectedModel && (
+                    <svg
+                      className="inline-block ml-1.5 h-3 w-3"
+                      fill="none"
+                      viewBox="0 0 24 24"
+                      stroke="currentColor"
+                      strokeWidth={3}
+                      aria-hidden="true"
+                    >
+                      <path d="M5 13l4 4L19 7" />
+                    </svg>
+                  )}
+                </button>
+              ))}
+            </div>
+          )}
+        </div>
+
+        {/* Settings / Params Icon */}
+        <div className="relative" ref={paramsDropdownRef}>
+          <button
+            type="button"
+            onClick={() => {
+              setIsParamsOpen((prev) => !prev);
+              setIsModelDropdownOpen(false);
+            }}
+            className="flex items-center justify-center rounded-full border p-1 transition-colors hover:bg-black/5 focus:outline-none focus:ring-2"
+            style={{
+              borderColor: "rgb(var(--border-default))",
+              backgroundColor: isParamsOpen ? "rgb(var(--surface-2))" : "rgb(var(--surface-1))",
+              color: "rgb(var(--text-muted))",
+            }}
+            aria-label="Chat parameters"
+            aria-expanded={isParamsOpen}
+            aria-haspopup="dialog"
+            title="Configure temperature and max tokens"
+          >
+            <svg
+              className="h-3.5 w-3.5"
+              fill="none"
+              viewBox="0 0 24 24"
+              stroke="currentColor"
+              strokeWidth={2}
+              aria-hidden="true"
+            >
+              <path d="M12 6V4m0 2a2 2 0 100 4m0-4a2 2 0 110 4m-6 8a2 2 0 100-4m0 4a2 2 0 110-4m0 4v2m0-6V4m6 6v10m6-2a2 2 0 100-4m0 4a2 2 0 110-4m0 4v2m0-6V4" />
+            </svg>
+          </button>
+
+          {/* Params Popover */}
+          {isParamsOpen && (
+            <div
+              className="absolute bottom-full left-0 mb-1 z-50 w-64 rounded-lg border p-4 shadow-lg"
+              style={{
+                backgroundColor: "rgb(var(--surface-0))",
+                borderColor: "rgb(var(--border-default))",
+              }}
+              role="dialog"
+              aria-label="Chat parameters"
+            >
+              <h3
+                className="mb-3 text-xs font-semibold uppercase tracking-wide"
+                style={{ color: "rgb(var(--text-muted))" }}
+              >
+                Parameters
+              </h3>
+
+              {/* Temperature */}
+              <div className="mb-4">
+                <div className="mb-1.5 flex items-center justify-between">
+                  <label
+                    className="text-xs font-medium"
+                    style={{ color: "rgb(var(--text-secondary))" }}
+                    htmlFor="temperature-slider"
+                  >
+                    Temperature
+                  </label>
+                  <span
+                    className="text-xs font-mono tabular-nums"
+                    style={{ color: "rgb(var(--accent-primary))" }}
+                  >
+                    {temperature.toFixed(1)}
+                  </span>
+                </div>
+                <input
+                  id="temperature-slider"
+                  type="range"
+                  min={0}
+                  max={2}
+                  step={0.1}
+                  value={temperature}
+                  onChange={(e) => {
+                    handleTemperatureChange(parseFloat(e.target.value));
+                  }}
+                  className="w-full h-1.5 rounded-full appearance-none cursor-pointer"
+                  style={{
+                    accentColor: "rgb(var(--accent-primary))",
+                    backgroundColor: "rgb(var(--surface-2))",
+                  }}
+                  aria-label={`Temperature: ${temperature.toFixed(1)}`}
+                />
+                <div
+                  className="mt-1 flex justify-between text-[10px]"
+                  style={{ color: "rgb(var(--text-muted))" }}
+                >
+                  <span>Precise</span>
+                  <span>Creative</span>
+                </div>
+              </div>
+
+              {/* Max Tokens */}
+              <div>
+                <label
+                  className="mb-1.5 block text-xs font-medium"
+                  style={{ color: "rgb(var(--text-secondary))" }}
+                  htmlFor="max-tokens-input"
+                >
+                  Max Tokens
+                </label>
+                <input
+                  id="max-tokens-input"
+                  type="number"
+                  min={100}
+                  max={32000}
+                  step={100}
+                  value={maxTokens}
+                  onChange={(e) => {
+                    const val = parseInt(e.target.value, 10);
+                    if (!isNaN(val) && val >= 100 && val <= 32000) {
+                      handleMaxTokensChange(val);
+                    }
+                  }}
+                  className="w-full rounded-md border px-2.5 py-1.5 text-xs outline-none focus:ring-2"
+                  style={{
+                    backgroundColor: "rgb(var(--surface-1))",
+                    borderColor: "rgb(var(--border-default))",
+                    color: "rgb(var(--text-primary))",
+                  }}
+                  aria-label="Maximum tokens"
+                />
+                <p className="mt-1 text-[10px]" style={{ color: "rgb(var(--text-muted))" }}>
+                  100 – 32,000
+                </p>
+              </div>
+            </div>
+          )}
+        </div>
+      </div>
+
       {/* Input Container */}
       <div
         className="relative rounded-lg border transition-all duration-150"

apps/web/src/components/chat/ChatOverlay.test.tsx

@@ -250,6 +250,46 @@ describe("ChatOverlay", () => {
     });
   });
 
+  describe("new conversation button", () => {
+    it("should render the new conversation button when chat is open", async () => {
+      const { useChatOverlay } = await import("../../hooks/useChatOverlay");
+      vi.mocked(useChatOverlay).mockReturnValue({
+        isOpen: true,
+        isMinimized: false,
+        open: mockOpen,
+        close: mockClose,
+        minimize: mockMinimize,
+        expand: mockExpand,
+        toggle: mockToggle,
+        toggleMinimize: mockToggleMinimize,
+      });
+
+      render(<ChatOverlay />);
+
+      const newConvBtn = screen.getByRole("button", { name: /new conversation/i });
+      expect(newConvBtn).toBeDefined();
+    });
+
+    it("should have a tooltip on the new conversation button", async () => {
+      const { useChatOverlay } = await import("../../hooks/useChatOverlay");
+      vi.mocked(useChatOverlay).mockReturnValue({
+        isOpen: true,
+        isMinimized: false,
+        open: mockOpen,
+        close: mockClose,
+        minimize: mockMinimize,
+        expand: mockExpand,
+        toggle: mockToggle,
+        toggleMinimize: mockToggleMinimize,
+      });
+
+      render(<ChatOverlay />);
+
+      const newConvBtn = screen.getByRole("button", { name: /new conversation/i });
+      expect(newConvBtn.getAttribute("title")).toContain("Cmd+N");
+    });
+  });
+
   describe("responsive design", () => {
     it("should render as a sidebar on desktop", () => {
       render(<ChatOverlay />);

apps/web/src/components/chat/ChatOverlay.tsx

@@ -164,6 +164,27 @@ export function ChatOverlay(): React.JSX.Element {
 
           {/* Header Controls */}
           <div className="flex items-center gap-1">
+            {/* New Conversation Button */}
+            <button
+              onClick={() => {
+                chatRef.current?.startNewConversation(null);
+              }}
+              className="rounded p-1.5 transition-colors hover:bg-black/5 focus:outline-none focus:ring-2"
+              aria-label="New conversation"
+              title="New conversation (Cmd+N)"
+            >
+              <svg
+                className="h-4 w-4"
+                style={{ color: "rgb(var(--text-secondary))" }}
+                fill="none"
+                viewBox="0 0 24 24"
+                stroke="currentColor"
+                strokeWidth={2}
+              >
+                <path d="M12 4v16m8-8H4" />
+              </svg>
+            </button>
+
             {/* Minimize Button */}
             <button
               onClick={minimize}

apps/web/src/components/chat/index.ts

@@ -11,9 +11,17 @@
  */
 
 export { Chat, type ChatRef, type NewConversationData } from "./Chat";
-export { ChatInput } from "./ChatInput";
+export {
+  ChatInput,
+  AVAILABLE_MODELS,
+  DEFAULT_MODEL,
+  DEFAULT_TEMPERATURE,
+  DEFAULT_MAX_TOKENS,
+} from "./ChatInput";
+export type { ModelId } from "./ChatInput";
 export { MessageList } from "./MessageList";
 export { ConversationSidebar, type ConversationSidebarRef } from "./ConversationSidebar";
 export { BackendStatusBanner } from "./BackendStatusBanner";
 export { ChatOverlay } from "./ChatOverlay";
+export { ChatEmptyState } from "./ChatEmptyState";
 export type { Message } from "@/hooks/useChat";