[bbrt] Model can set title, improved instructions, misc fixes (#4135)

- The model can call "set_title" to set the title.
- New better shorter default system instructions.
- Auto focus prompt when changing session
- Fix bug where active tools were not updated for each iteration of a
chain of tool calls

packages/bbrt/src/components/main.ts

@@ -40,9 +40,9 @@ import { readBoardServersFromIndexedDB } from "../breadboard/indexed-db-servers.
 import type { BBRTDriver } from "../drivers/driver-interface.js";
 import { GeminiDriver } from "../drivers/gemini.js";
 import { OpenAiDriver } from "../drivers/openai.js";
+import { SYSTEM_INSTRUCTION } from "../instructions/system-instruction.js";
 import { Conversation } from "../llm/conversation.js";
 import type { CutEvent, ForkEvent, RetryEvent } from "../llm/events.js";
-import { BREADBOARD_ASSISTANT_SYSTEM_INSTRUCTION } from "../llm/system-instruction.js";
 import { IndexedDBSettingsSecrets } from "../secrets/indexed-db-secrets.js";
 import type { SecretsProvider } from "../secrets/secrets-provider.js";
 import { ReactiveAppState } from "../state/app.js";
@@ -58,6 +58,7 @@ import { DisplayFile } from "../tools/files/display-file.js";
 import { ReadFile } from "../tools/files/read-file.js";
 import { WriteFile } from "../tools/files/write-file.js";
 import { BoardLister } from "../tools/list-tools.js";
+import { SetTitleTool } from "../tools/set-title.js";
 import { type BBRTTool } from "../tools/tool-types.js";
 import { connectedEffect } from "../util/connected-effect.js";
 import type { Result } from "../util/result.js";
@@ -203,6 +204,15 @@ export class BBRTMain extends SignalWatcher(LitElement) {
         () => this.#sessionState
       ),
 
+      // Meta
+      new SetTitleTool((title) => {
+        if (!this.#sessionState) {
+          return { ok: false, error: "No active session" };
+        }
+        this.#sessionState.title = title;
+        return { ok: true, value: undefined };
+      }),
+
       // Files
       new ReadFile(this.#artifacts),
       new WriteFile(this.#artifacts, this.#displayFile),
@@ -224,7 +234,7 @@ export class BBRTMain extends SignalWatcher(LitElement) {
 
     const sessionStore = new SessionStore({
       defaults: {
-        systemPrompt: BREADBOARD_ASSISTANT_SYSTEM_INSTRUCTION,
+        systemPrompt: SYSTEM_INSTRUCTION,
         driverId: this.#drivers.keys().next().value!,
         activeToolIds: standardTools.map((tool) => tool.metadata.id),
       },
@@ -345,6 +355,7 @@ export class BBRTMain extends SignalWatcher(LitElement) {
         <bbrt-session-picker
           .appState=${this.#appState}
           .sessionStore=${this.#sessions}
+          @bbrt-focus-prompt=${this.#onFocusPrompt}
         ></bbrt-session-picker>
         <bbrt-tool-palette
           .conversation=${this.#conversation}
@@ -468,6 +479,10 @@ export class BBRTMain extends SignalWatcher(LitElement) {
     });
   }
 
+  #onFocusPrompt() {
+    this.#prompt.value?.focus();
+  }
+
   #findEventIndexForTurn(turn: ReactiveTurnState) {
     if (!this.#sessionState) {
       return -1;

packages/bbrt/src/components/session-picker.ts

@@ -131,6 +131,9 @@ export class BBRTSesssionPicker extends SignalWatcher(LitElement) {
       this.sessionStore.createSession(brief).then((result) => {
         if (result.ok) {
           appState.activeSessionId = brief.id;
+          this.dispatchEvent(
+            new Event("bbrt-focus-prompt", { bubbles: true, composed: true })
+          );
         } else {
           // TODO(aomarks) Show an error.
           console.error(`Failed to create session: ${result.error}`);
@@ -145,6 +148,9 @@ export class BBRTSesssionPicker extends SignalWatcher(LitElement) {
     // TODO(aomarks) Make this a real hyperlink, syncronize session via hash.
     if (this.appState) {
       this.appState.activeSessionId = sessionId;
+      this.dispatchEvent(
+        new Event("bbrt-focus-prompt", { bubbles: true, composed: true })
+      );
     }
   }
 

packages/bbrt/src/instructions/system-instruction.ts

@@ -0,0 +1,22 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export const SYSTEM_INSTRUCTION = `
+- You must use the "set_title" function within the first 2-3 turns of the
+  conversation, with a best effort concise title.
+
+- If the user asks to make something such as a document, report, post, or any
+  other kind of text artifact, you must use the "write_file" function to create
+  a new markdown file.
+
+- Never call "display_file" unless you need to show an old file. Never try to
+  provide a link to a file you have written. Never duplicate the contents of
+  a file you have just written in your resposne.
+
+- You have access to hundreds of additional tools, particularly for image and
+  audio generation, and for connecting to external services. To discover them,
+  first call "list_tools", and then call "activate_tool" with specific tool ids.
+`;

packages/bbrt/src/llm/conversation.ts

@@ -100,10 +100,12 @@ export class Conversation {
     );
 
     const done = (async (): Promise<void> => {
-      const activeTools = await this.#getActiveTools();
       let remainingModelCalls = 1 + Math.max(0, MAX_TOOL_ITERATIONS);
       let functionCalls: ReactiveFunctionCallState[];
       do {
+        // Note that tools can change between iterations, since "activate_tool"
+        // could be called.
+        const activeTools = await this.#getActiveTools();
         const allowFunctionCalls = remainingModelCalls > 1;
         functionCalls = (
           await this.#callModel(

packages/bbrt/src/tools/set-title.ts

@@ -0,0 +1,64 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import "../components/activate-modal.js";
+import type { EmptyObject } from "../util/empty-object.js";
+import type { Result } from "../util/result.js";
+import type { BBRTTool, BBRTToolAPI, BBRTToolMetadata } from "./tool-types.js";
+
+interface Inputs {
+  title: string;
+}
+
+type Callback = (title: string) => Result<void>;
+
+export class SetTitleTool implements BBRTTool<Inputs, EmptyObject> {
+  #callback: Callback;
+
+  constructor(callback: Callback) {
+    this.#callback = callback;
+  }
+
+  readonly metadata: BBRTToolMetadata = {
+    id: "set_title",
+    title: "Set Title",
+    description: "Set the title of the conversation.",
+    icon: "/bbrt/images/tool.svg",
+  };
+
+  async api(): Promise<Result<BBRTToolAPI>> {
+    return {
+      ok: true as const,
+      value: {
+        inputSchema: {
+          type: "object",
+          properties: {
+            title: {
+              type: "string",
+              description: "The new title.",
+            },
+          },
+        },
+        outputSchema: {
+          type: "object",
+          properties: {},
+        },
+      } satisfies BBRTToolAPI,
+    };
+  }
+
+  execute(args: Inputs) {
+    return { result: this.#execute(args) };
+  }
+
+  async #execute({ title }: Inputs): Promise<Result<{ data: EmptyObject }>> {
+    const result = this.#callback(title);
+    if (!result.ok) {
+      return result;
+    }
+    return { ok: true, value: { data: {} } };
+  }
+}