feat(sessions): use 1-line generated session summary to describe sessions (#14467)

packages/core/src/services/sessionSummaryService.ts

@@ -0,0 +1,162 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { MessageRecord } from './chatRecordingService.js';
+import type { BaseLlmClient } from '../core/baseLlmClient.js';
+import { partListUnionToString } from '../core/geminiRequest.js';
+import { debugLogger } from '../utils/debugLogger.js';
+import type { Content } from '@google/genai';
+import { getResponseText } from '../utils/partUtils.js';
+
+const DEFAULT_MAX_MESSAGES = 20;
+const DEFAULT_TIMEOUT_MS = 5000;
+const MAX_MESSAGE_LENGTH = 500;
+
+const SUMMARY_PROMPT = `Summarize the user's primary intent or goal in this conversation in ONE sentence (max 80 characters).
+Focus on what the user was trying to accomplish.
+
+Examples:
+- "Add dark mode to the app"
+- "Fix authentication bug in login flow"
+- "Understand how the API routing works"
+- "Refactor database connection logic"
+- "Debug memory leak in production"
+
+Conversation:
+{conversation}
+
+Summary (max 80 chars):`;
+
+/**
+ * Options for generating a session summary.
+ */
+export interface GenerateSummaryOptions {
+  messages: MessageRecord[];
+  maxMessages?: number;
+  timeout?: number;
+}
+
+/**
+ * Service for generating AI summaries of chat sessions.
+ * Uses Gemini Flash Lite to create concise, user-intent-focused summaries.
+ */
+export class SessionSummaryService {
+  constructor(private readonly baseLlmClient: BaseLlmClient) {}
+
+  /**
+   * Generate a 1-line summary of a chat session focusing on user intent.
+   * Returns null if generation fails for any reason.
+   */
+  async generateSummary(
+    options: GenerateSummaryOptions,
+  ): Promise<string | null> {
+    const {
+      messages,
+      maxMessages = DEFAULT_MAX_MESSAGES,
+      timeout = DEFAULT_TIMEOUT_MS,
+    } = options;
+
+    try {
+      // Filter to user/gemini messages only (exclude system messages)
+      const filteredMessages = messages.filter((msg) => {
+        // Skip system messages (info, error, warning)
+        if (msg.type !== 'user' && msg.type !== 'gemini') {
+          return false;
+        }
+        const content = partListUnionToString(msg.content);
+        return content.trim().length > 0;
+      });
+
+      // Apply sliding window selection: first N + last N messages
+      let relevantMessages: MessageRecord[];
+      if (filteredMessages.length <= maxMessages) {
+        // If fewer messages than max, include all
+        relevantMessages = filteredMessages;
+      } else {
+        // Sliding window: take the first and last messages.
+        const firstWindowSize = Math.ceil(maxMessages / 2);
+        const lastWindowSize = Math.floor(maxMessages / 2);
+        const firstMessages = filteredMessages.slice(0, firstWindowSize);
+        const lastMessages = filteredMessages.slice(-lastWindowSize);
+        relevantMessages = firstMessages.concat(lastMessages);
+      }
+
+      if (relevantMessages.length === 0) {
+        debugLogger.debug('[SessionSummary] No messages to summarize');
+        return null;
+      }
+
+      // Format conversation for the prompt
+      const conversationText = relevantMessages
+        .map((msg) => {
+          const role = msg.type === 'user' ? 'User' : 'Assistant';
+          const content = partListUnionToString(msg.content);
+          // Truncate very long messages to avoid token limit
+          const truncated =
+            content.length > MAX_MESSAGE_LENGTH
+              ? content.slice(0, MAX_MESSAGE_LENGTH) + '...'
+              : content;
+          return `${role}: ${truncated}`;
+        })
+        .join('\n\n');
+
+      const prompt = SUMMARY_PROMPT.replace('{conversation}', conversationText);
+
+      // Create abort controller with timeout
+      const abortController = new AbortController();
+      const timeoutId = setTimeout(() => {
+        abortController.abort();
+      }, timeout);
+
+      try {
+        const contents: Content[] = [
+          {
+            role: 'user',
+            parts: [{ text: prompt }],
+          },
+        ];
+
+        const response = await this.baseLlmClient.generateContent({
+          modelConfigKey: { model: 'summarizer-default' },
+          contents,
+          abortSignal: abortController.signal,
+          promptId: 'session-summary-generation',
+        });
+
+        const summary = getResponseText(response);
+
+        if (!summary || summary.trim().length === 0) {
+          debugLogger.debug('[SessionSummary] Empty summary returned');
+          return null;
+        }
+
+        // Clean the summary
+        let cleanedSummary = summary
+          .replace(/\n+/g, ' ') // Collapse newlines to spaces
+          .replace(/\s+/g, ' ') // Normalize whitespace
+          .trim(); // Trim after all processing
+
+        // Remove quotes if the model added them
+        cleanedSummary = cleanedSummary.replace(/^["']|["']$/g, '');
+
+        debugLogger.debug(`[SessionSummary] Generated: "${cleanedSummary}"`);
+        return cleanedSummary;
+      } finally {
+        clearTimeout(timeoutId);
+      }
+    } catch (error) {
+      // Log the error but don't throw - we want graceful degradation
+      if (error instanceof Error && error.name === 'AbortError') {
+        debugLogger.debug('[SessionSummary] Timeout generating summary');
+      } else {
+        debugLogger.debug(
+          `[SessionSummary] Error generating summary: ${error instanceof Error ? error.message : String(error)}`,
+        );
+      }
+      return null;
+    }
+  }
+}