feat(session): add optional end-of-session summarization

src/session/endSummary.ts

@@ -0,0 +1,88 @@
+import type { AgentOrchestrator } from '../backends/native/orchestrator.js';
+import type { Message } from '../models/types.js';
+import { getMessageText } from '../models/media.js';
+import type { MemoryStore } from '../memory/store.js';
+import type { ModelTier } from '../models/router.js';
+
+export interface SessionEndSummaryConfig {
+  enabled: boolean;
+  tier: ModelTier;
+  maxMessages: number;
+  maxInputChars: number;
+  maxTokens: number;
+  writeToMemory: boolean;
+  memoryNamespace: string;
+}
+
+export interface SessionEndSummaryResult {
+  summary: string;
+  namespace?: string;
+}
+
+const SESSION_END_SUMMARY_PROMPT = [
+  'Summarize this completed conversation for future continuity.',
+  'Focus on durable facts, decisions, preferences, unresolved tasks, and next steps.',
+  'Be concise and structured with short bullets.',
+  'Do not include private secrets.',
+].join(' ');
+
+function sanitizeSessionId(sessionId: string): string {
+  return sessionId
+    .replace(/:/g, '/')
+    .replace(/[^a-zA-Z0-9/_-]+/g, '_')
+    .replace(/_+/g, '_');
+}
+
+function formatHistory(messages: Message[], maxInputChars: number): string {
+  const text = messages
+    .map((msg) => `${msg.role}: ${getMessageText(msg)}`)
+    .join('\n\n');
+  if (text.length <= maxInputChars) {
+    return text;
+  }
+  return text.slice(text.length - maxInputChars);
+}
+
+export async function summarizeSessionOnEnd(opts: {
+  agent: AgentOrchestrator;
+  sessionId: string;
+  history: Message[];
+  config: SessionEndSummaryConfig;
+  memoryStore?: MemoryStore;
+}): Promise<SessionEndSummaryResult | null> {
+  if (!opts.config.enabled || opts.history.length === 0) {
+    return null;
+  }
+
+  const selected = opts.history.slice(-opts.config.maxMessages);
+  const conversation = formatHistory(selected, opts.config.maxInputChars);
+  if (!conversation.trim()) {
+    return null;
+  }
+
+  const result = await opts.agent.delegate({
+    tier: opts.config.tier,
+    systemPrompt: SESSION_END_SUMMARY_PROMPT,
+    message: conversation,
+    maxTokens: opts.config.maxTokens,
+  });
+
+  const summary = result.content.trim();
+  if (!summary) {
+    return null;
+  }
+
+  let namespace: string | undefined;
+  if (opts.memoryStore && opts.config.writeToMemory) {
+    namespace = `${opts.config.memoryNamespace}/${sanitizeSessionId(opts.sessionId)}`;
+    const block = `## ${new Date().toISOString()}\n\n${summary}\n\n`;
+    opts.memoryStore.write(namespace, block, 'append');
+  }
+
+  return { summary, namespace };
+}
+
+export const sessionEndSummaryInternals = {
+  sanitizeSessionId,
+  formatHistory,
+};