feat(coding-agent): added auto session titles for better identification

- Added automatic session title generation using small models (Haiku/GPT-4o-mini/Flash) to improve session identification.
- Implemented terminal window title updates to display current session context.
- Updated session selector to show title with dimmed first message preview for better session browsing.
- Extended SessionInfo and SessionHeader interfaces to persist and display generated titles.
- Added title model preference hierarchy with fallback to any available model for reliability.

packages/coding-agent/CHANGELOG.md

@@ -20,6 +20,7 @@
 ### Fixed
 
 - Recent sessions now show in welcome banner (was never wired up).
+- Auto-generated session titles: Sessions are now automatically titled based on the first message using a small model (Haiku/GPT-4o-mini/Flash). Titles are shown in the terminal window title, recent sessions list, and --resume picker. The resume picker shows title with dimmed first message preview below.
 
 ## [1.340.0] - 2026-01-03
 

packages/coding-agent/src/core/session-manager.ts

@@ -156,6 +156,7 @@ export interface SessionContext {
 export interface SessionInfo {
 	path: string;
 	id: string;
+	title?: string;
 	created: Date;
 	modified: Date;
 	messageCount: number;
@@ -486,15 +487,16 @@ export function getRecentSessions(sessionDir: string, limit = 3): RecentSessionI
 			.filter(isValidSessionFile)
 			.map((path) => {
 				const stat = statSync(path);
-				// Try to get session name from first line
+				// Try to get session title or id from first line
 				let name = path.split("/").pop()?.replace(".jsonl", "") ?? "Unknown";
 				try {
 					const content = readFileSync(path, "utf-8");
 					const firstLine = content.split("\n")[0];
 					if (firstLine) {
 						const header = JSON.parse(firstLine) as SessionHeader;
-						if (header.type === "session" && header.id) {
-							name = header.id;
+						if (header.type === "session") {
+							// Prefer title over id
+							name = header.title ?? header.id ?? name;
 						}
 					}
 				} catch {
@@ -506,7 +508,7 @@ export function getRecentSessions(sessionDir: string, limit = 3): RecentSessionI
 			.slice(0, limit);
 
 		return files.map((f) => ({
-			name: f.name.length > 30 ? `${f.name.slice(0, 27)}...` : f.name,
+			name: f.name.length > 40 ? `${f.name.slice(0, 37)}...` : f.name,
 			path: f.path,
 			timeAgo: formatTimeAgo(f.mtime),
 		}));
@@ -528,6 +530,7 @@ export function getRecentSessions(sessionDir: string, limit = 3): RecentSessionI
  */
 export class SessionManager {
 	private sessionId: string = "";
+	private sessionTitle: string | undefined;
 	private sessionFile: string | undefined;
 	private sessionDir: string;
 	private cwd: string;
@@ -560,6 +563,7 @@ export class SessionManager {
 			this.fileEntries = loadEntriesFromFile(this.sessionFile);
 			const header = this.fileEntries.find((e) => e.type === "session") as SessionHeader | undefined;
 			this.sessionId = header?.id ?? crypto.randomUUID();
+			this.sessionTitle = header?.title;
 
 			if (migrateToCurrentVersion(this.fileEntries)) {
 				this._rewriteFile();
@@ -640,6 +644,31 @@ export class SessionManager {
 		return this.sessionFile;
 	}
 
+	getSessionTitle(): string | undefined {
+		return this.sessionTitle;
+	}
+
+	setSessionTitle(title: string): void {
+		this.sessionTitle = title;
+		// Update the session file header with the title
+		if (this.persist && this.sessionFile && existsSync(this.sessionFile)) {
+			try {
+				const content = readFileSync(this.sessionFile, "utf-8");
+				const lines = content.split("\n");
+				if (lines.length > 0) {
+					const header = JSON.parse(lines[0]) as SessionHeader;
+					if (header.type === "session") {
+						header.title = title;
+						lines[0] = JSON.stringify(header);
+						writeFileSync(this.sessionFile, lines.join("\n"));
+					}
+				}
+			} catch {
+				// Ignore errors updating title
+			}
+		}
+	}
+
 	_persist(entry: SessionEntry): void {
 		if (!this.persist || !this.sessionFile) return;
 
@@ -1122,7 +1151,7 @@ export class SessionManager {
 					if (lines.length === 0) continue;
 
 					// Check first line for valid session header
-					let header: { type: string; id: string; timestamp: string } | null = null;
+					let header: { type: string; id: string; title?: string; timestamp: string } | null = null;
 					try {
 						const first = JSON.parse(lines[0]);
 						if (first.type === "session" && first.id) {
@@ -1168,6 +1197,7 @@ export class SessionManager {
 					sessions.push({
 						path: file,
 						id: header.id,
+						title: header.title,
 						created: new Date(header.timestamp),
 						modified: stats.mtime,
 						messageCount,

packages/coding-agent/src/core/title-generator.ts

@@ -0,0 +1,108 @@
+/**
+ * Generate session titles using a small, fast model.
+ */
+
+import type { Model } from "@oh-my-pi/pi-ai";
+import { completeSimple } from "@oh-my-pi/pi-ai";
+import type { ModelRegistry } from "./model-registry.js";
+
+const TITLE_SYSTEM_PROMPT = `Generate a very short title (3-6 words) for a coding session based on the user's first message. The title should capture the main task or topic. Output ONLY the title, nothing else. No quotes, no punctuation at the end.
+
+Examples:
+- "Fix TypeScript compilation errors"
+- "Add user authentication"
+- "Refactor database queries"
+- "Debug payment webhook"
+- "Update React components"`;
+
+const MAX_INPUT_CHARS = 2000;
+
+/**
+ * Find the best available model for title generation.
+ * Prefers small, fast models in this order:
+ * 1. Claude Haiku (anthropic)
+ * 2. GPT-4o-mini (openai)
+ * 3. Gemini Flash (google)
+ * 4. Any available model
+ */
+export async function findTitleModel(registry: ModelRegistry): Promise<Model<any> | null> {
+	const preferences = [
+		{ provider: "anthropic", pattern: /haiku/i },
+		{ provider: "openai", pattern: /gpt-4o-mini|gpt-4\.1-mini/i },
+		{ provider: "google", pattern: /flash/i },
+		{ provider: "anthropic", pattern: /sonnet/i },
+	];
+
+	for (const pref of preferences) {
+		const models = registry.getAll().filter((m) => m.provider === pref.provider && pref.pattern.test(m.id));
+		for (const model of models) {
+			if (await registry.getApiKey(model)) {
+				return model;
+			}
+		}
+	}
+
+	// Fallback to any available model
+	for (const model of registry.getAll()) {
+		if (await registry.getApiKey(model)) {
+			return model;
+		}
+	}
+
+	return null;
+}
+
+/**
+ * Generate a title for a session based on the first user message.
+ */
+export async function generateSessionTitle(firstMessage: string, registry: ModelRegistry): Promise<string | null> {
+	const model = await findTitleModel(registry);
+	if (!model) return null;
+
+	const apiKey = await registry.getApiKey(model);
+	if (!apiKey) return null;
+
+	// Truncate message if too long
+	const truncatedMessage =
+		firstMessage.length > MAX_INPUT_CHARS ? `${firstMessage.slice(0, MAX_INPUT_CHARS)}...` : firstMessage;
+
+	try {
+		const response = await completeSimple(
+			model,
+			{
+				systemPrompt: TITLE_SYSTEM_PROMPT,
+				messages: [{ role: "user", content: truncatedMessage, timestamp: Date.now() }],
+			},
+			{
+				apiKey,
+				maxTokens: 30,
+			},
+		);
+
+		// Extract title from response text content
+		let title = "";
+		for (const content of response.content) {
+			if (content.type === "text") {
+				title += content.text;
+			}
+		}
+		title = title.trim();
+
+		if (!title || title.length > 60) {
+			return null;
+		}
+
+		// Clean up: remove quotes, trailing punctuation
+		return title.replace(/^["']|["']$/g, "").replace(/[.!?]$/, "");
+	} catch {
+		return null;
+	}
+}
+
+/**
+ * Set the terminal title using ANSI escape sequences.
+ */
+export function setTerminalTitle(title: string): void {
+	// OSC 2 sets the window title
+	process.stdout.write(`\x1b]2;${title}\x07`);
+}

packages/coding-agent/src/modes/interactive/components/session-selector.ts

@@ -90,7 +90,7 @@ class SessionList implements Component {
 		);
 		const endIndex = Math.min(startIndex + this.maxVisible, this.filteredSessions.length);
 
-		// Render visible sessions (2 lines per session + blank line)
+		// Render visible sessions (2-3 lines per session + blank line)
 		for (let i = startIndex; i < endIndex; i++) {
 			const session = this.filteredSessions[i];
 			const isSelected = i === this.selectedIndex;
@@ -98,19 +98,32 @@ class SessionList implements Component {
 			// Normalize first message to single line
 			const normalizedMessage = session.firstMessage.replace(/\n/g, " ").trim();
 
-			// First line: cursor + message (truncate to visible width)
+			// First line: cursor + title (or first message if no title)
 			const cursor = isSelected ? theme.fg("accent", "› ") : "  ";
-			const maxMsgWidth = width - 2; // Account for cursor (2 visible chars)
-			const truncatedMsg = truncateToWidth(normalizedMessage, maxMsgWidth, "...");
-			const messageLine = cursor + (isSelected ? theme.bold(truncatedMsg) : truncatedMsg);
+			const maxWidth = width - 2; // Account for cursor (2 visible chars)
 
-			// Second line: metadata (dimmed) - also truncate for safety
+			if (session.title) {
+				// Has title: show title on first line, dimmed first message on second line
+				const truncatedTitle = truncateToWidth(session.title, maxWidth, "...");
+				const titleLine = cursor + (isSelected ? theme.bold(truncatedTitle) : truncatedTitle);
+				lines.push(titleLine);
+
+				// Second line: dimmed first message preview
+				const truncatedPreview = truncateToWidth(normalizedMessage, maxWidth, "...");
+				lines.push(`  ${theme.fg("dim", truncatedPreview)}`);
+			} else {
+				// No title: show first message as main line
+				const truncatedMsg = truncateToWidth(normalizedMessage, maxWidth, "...");
+				const messageLine = cursor + (isSelected ? theme.bold(truncatedMsg) : truncatedMsg);
+				lines.push(messageLine);
+			}
+
+			// Metadata line: date + message count
 			const modified = formatDate(session.modified);
 			const msgCount = `${session.messageCount} message${session.messageCount !== 1 ? "s" : ""}`;
 			const metadata = `  ${modified} · ${msgCount}`;
 			const metadataLine = theme.fg("dim", truncateToWidth(metadata, width, ""));
 
-			lines.push(messageLine);
 			lines.push(metadataLine);
 			lines.push(""); // Blank line between sessions
 		}

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -31,6 +31,7 @@ import { createCompactionSummaryMessage } from "../../core/messages.js";
 import { getRecentSessions, type SessionContext, SessionManager } from "../../core/session-manager.js";
 import { loadSkills } from "../../core/skills.js";
 import { loadProjectContextFiles } from "../../core/system-prompt.js";
+import { generateSessionTitle, setTerminalTitle } from "../../core/title-generator.js";
 import type { TruncationResult } from "../../core/tools/truncate.js";
 import { getChangelogPath, parseChangelog } from "../../utils/changelog.js";
 import { copyToClipboard, readImageFromClipboard } from "../../utils/clipboard.js";
@@ -141,6 +142,9 @@ export class InteractiveMode {
 	// Custom tools for custom rendering
 	private customTools: Map<string, LoadedCustomTool>;
 
+	// Title generation state
+	private titleGenerationAttempted = false;
+
 	// Convenience accessors
 	private get agent() {
 		return this.session.agent;
@@ -245,6 +249,13 @@ export class InteractiveMode {
 		// Add welcome header
 		const welcome = new WelcomeComponent(this.version, modelName, providerName, recentSessions, lspServerInfo);
 
+		// Set terminal title if session already has one (resumed session)
+		const existingTitle = this.sessionManager.getSessionTitle();
+		if (existingTitle) {
+			setTerminalTitle(`pi: ${existingTitle}`);
+			this.titleGenerationAttempted = true; // Don't try to generate again
+		}
+
 		// Setup UI layout
 		this.ui.addChild(new Spacer(1));
 		this.ui.addChild(welcome);
@@ -1042,6 +1053,12 @@ export class InteractiveMode {
 				}
 				this.pendingTools.clear();
 				this.ui.requestRender();
+
+				// Generate session title after first turn (if not already titled)
+				if (!this.titleGenerationAttempted && !this.sessionManager.getSessionTitle()) {
+					this.titleGenerationAttempted = true;
+					this.maybeGenerateTitle();
+				}
 				break;
 
 			case "auto_compaction_start": {
@@ -1569,6 +1586,41 @@ export class InteractiveMode {
 		this.ui.requestRender();
 	}
 
+	/**
+	 * Generate a title for the session based on the first user message.
+	 * Runs in background, doesn't block UI.
+	 */
+	private maybeGenerateTitle(): void {
+		// Find the first user message
+		const messages = this.agent.state.messages;
+		const firstUserMessage = messages.find((m) => m.role === "user");
+		if (!firstUserMessage) return;
+
+		// Extract text content
+		let messageText = "";
+		for (const content of firstUserMessage.content) {
+			if (typeof content === "string") {
+				messageText += content;
+			} else if (content.type === "text") {
+				messageText += content.text;
+			}
+		}
+		if (!messageText.trim()) return;
+
+		// Generate title in background
+		const registry = this.session.modelRegistry;
+		generateSessionTitle(messageText, registry)
+			.then((title) => {
+				if (title) {
+					this.sessionManager.setSessionTitle(title);
+					setTerminalTitle(`pi: ${title}`);
+				}
+			})
+			.catch(() => {
+				// Ignore title generation errors
+			});
+	}
+
 	private updatePendingMessagesDisplay(): void {
 		this.pendingMessagesContainer.clear();
 		const queuedMessages = this.session.getQueuedMessages();