feat: turn JSONL logging with live web viewer (v2) (#567)

Co-authored-by: Letta Code <noreply@letta.com>
2026-03-11 23:24:54 -07:00
parent 593b28892c
commit 6ecd78e294
10 changed files with 1098 additions and 5 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -60,3 +60,4 @@ bun.lock

 # Telegram MTProto session data (contains auth secrets)
 data/telegram-mtproto/
+logs/
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
    "setup": "tsx src/setup.ts",
    "dev": "tsx src/main.ts",
    "build": "tsc",
-    "postbuild": "cp -r src/looms/*.txt dist/looms/ && cp src/api/portal.html dist/api/portal.html && node scripts/fix-bin-permissions.mjs",
+    "postbuild": "cp -r src/looms/*.txt dist/looms/ && cp src/api/portal.html dist/api/portal.html && cp src/core/turn-viewer.html dist/core/ && node scripts/fix-bin-permissions.mjs",
    "prepare": "npx patch-package || true",
    "prepublishOnly": "npm run build && npm run test:run",
    "start": "node dist/main.js",
--- a/src/api/server.ts
+++ b/src/api/server.ts
@@ -5,6 +5,8 @@

 import * as http from 'http';
 import * as fs from 'fs';
+import { readFile } from 'node:fs/promises';
+import * as crypto from 'node:crypto';
 import { validateApiKey } from './auth.js';
 import type { SendMessageResponse, ChatRequest, ChatResponse, AsyncChatResponse, PairingListResponse, PairingApproveRequest, PairingApproveResponse } from './types.js';
 import { listPairingRequests, approvePairingCode } from '../pairing/store.js';
@@ -18,6 +20,7 @@ import {
  buildErrorResponse, buildModelList, validateChatRequest,
 } from './openai-compat.js';
 import type { OpenAIChatRequest } from './openai-compat.js';
+import { getTurnViewerHtml } from '../core/turn-viewer.js';

 import { createLogger } from '../logger.js';

@@ -40,6 +43,7 @@ interface ServerOptions {
  apiKey: string;
  host?: string;       // Bind address (default: 127.0.0.1 for security)
  corsOrigin?: string; // CORS origin (default: same-origin only)
+  turnLogFiles?: Record<string, string>; // agentName -> filePath; enables GET /turns viewer
  stores?: Map<string, Store>; // Agent stores for management endpoints
  agentChannels?: Map<string, string[]>; // Channel IDs per agent name
  sessionInvalidators?: Map<string, (key?: string) => void>; // Invalidate live sessions after store writes
@@ -49,6 +53,155 @@ interface ServerOptions {
 * Create and start the HTTP API server
 */
 export function createApiServer(deliverer: AgentRouter, options: ServerOptions): http.Server {
+  // ── Turn viewer SSE infrastructure ──────────────────────────────────────
+  interface SSEClient {
+    res: http.ServerResponse;
+    sentCount: number;
+    lastTurnId?: string;
+  }
+  const sseClientsByAgent = new Map<string, Set<SSEClient>>();
+  const broadcastQueues = new Map<string, Promise<void>>();
+
+  function getTurnId(turn: unknown): string | undefined {
+    if (!turn || typeof turn !== 'object') return undefined;
+    const id = (turn as { turnId?: unknown }).turnId;
+    return typeof id === 'string' && id.trim() ? id : undefined;
+  }
+
+  async function readTurns(filePath: string): Promise<unknown[]> {
+    try {
+      const content = await readFile(filePath, 'utf8');
+      return content.split('\n').filter(l => l.trim()).map(l => {
+        try { return JSON.parse(l); } catch { return null; }
+      }).filter(Boolean);
+    } catch { return []; }
+  }
+
+  async function broadcastNewTurns(agentName: string, filePath: string): Promise<void> {
+    const clients = sseClientsByAgent.get(agentName);
+    if (!clients || clients.size === 0) return;
+    const allTurns = await readTurns(filePath);
+    const currentLastTurnId = getTurnId(allTurns[allTurns.length - 1]);
+
+    for (const client of clients) {
+      // If the log was cleared, reset the client snapshot and UI.
+      if (allTurns.length === 0) {
+        const shouldReset = client.sentCount !== 0 || !!client.lastTurnId;
+        client.sentCount = 0;
+        client.lastTurnId = undefined;
+        if (shouldReset) {
+          const payload = `data: ${JSON.stringify({ type: 'init', turns: [] })}\n\n`;
+          try { client.res.write(payload); } catch { clients.delete(client); }
+        }
+        continue;
+      }
+
+      if (client.lastTurnId === currentLastTurnId && client.sentCount === allTurns.length) {
+        continue;
+      }
+
+      let turnsToAppend: unknown[] | null = null;
+      if (client.lastTurnId) {
+        let previousIndex = -1;
+        for (let i = allTurns.length - 1; i >= 0; i--) {
+          if (getTurnId(allTurns[i]) === client.lastTurnId) {
+            previousIndex = i;
+            break;
+          }
+        }
+        if (previousIndex >= 0) {
+          turnsToAppend = allTurns.slice(previousIndex + 1);
+        }
+      } else if (client.sentCount < allTurns.length) {
+        // Fallback for older records without turnId.
+        turnsToAppend = allTurns.slice(client.sentCount);
+      }
+
+      const appendTurns = turnsToAppend ?? [];
+      const shouldResync = turnsToAppend === null
+        || (appendTurns.length === 0 && (client.sentCount !== allTurns.length || client.lastTurnId !== currentLastTurnId));
+
+      const payload = shouldResync
+        ? `data: ${JSON.stringify({ type: 'init', turns: allTurns })}\n\n`
+        : appendTurns.length > 0
+          ? `data: ${JSON.stringify({ type: 'append', turns: appendTurns })}\n\n`
+          : null;
+
+      if (payload) {
+        try {
+          client.res.write(payload);
+        } catch {
+          clients.delete(client);
+          continue;
+        }
+      }
+
+      client.sentCount = allTurns.length;
+      client.lastTurnId = currentLastTurnId;
+    }
+  }
+
+  function enqueueBroadcast(agentName: string, filePath: string): void {
+    const prev = broadcastQueues.get(filePath) ?? Promise.resolve();
+    const next = prev.then(() => broadcastNewTurns(agentName, filePath)).catch(() => {});
+    broadcastQueues.set(filePath, next);
+  }
+
+  const watchers = new Map<string, fs.FSWatcher>();
+
+  function ensureWatching(agentName: string, filePath: string): void {
+    if (watchers.has(filePath)) return;
+    let watcher: fs.FSWatcher;
+    try {
+      watcher = fs.watch(filePath, { persistent: false }, (eventType) => {
+        if (eventType === 'rename') {
+          // Inode replaced (trim via atomic rename on Linux). Restart watcher.
+          watcher.close();
+          watchers.delete(filePath);
+          setTimeout(() => {
+            const clients = sseClientsByAgent.get(agentName);
+            if (clients && clients.size > 0) {
+              enqueueBroadcast(agentName, filePath);
+              ensureWatching(agentName, filePath);
+            }
+          }, 200);
+          return;
+        }
+        enqueueBroadcast(agentName, filePath);
+      });
+    } catch {
+      setTimeout(() => {
+        const clients = sseClientsByAgent.get(agentName);
+        if (clients && clients.size > 0) ensureWatching(agentName, filePath);
+      }, 2000);
+      return;
+    }
+    watcher.on('error', () => {
+      watcher.close();
+      watchers.delete(filePath);
+      // Auto-restart watcher after trim (inode replacement on Linux)
+      setTimeout(() => {
+        const clients = sseClientsByAgent.get(agentName);
+        if (clients && clients.size > 0) ensureWatching(agentName, filePath);
+      }, 500);
+    });
+    watchers.set(filePath, watcher);
+  }
+
+  function maybeUnwatch(filePath: string, clients: Set<SSEClient>): void {
+    if (clients.size === 0 && watchers.has(filePath)) {
+      watchers.get(filePath)!.close();
+      watchers.delete(filePath);
+      broadcastQueues.delete(filePath);
+    }
+  }
+
+  if (options.turnLogFiles) {
+    for (const agentName of Object.keys(options.turnLogFiles)) {
+      sseClientsByAgent.set(agentName, new Set());
+    }
+  }
+
  const server = http.createServer(async (req, res) => {
    // Set CORS headers (configurable origin, defaults to same-origin for security)
    const corsOrigin = options.corsOrigin || req.headers.origin || 'null';
@@ -70,6 +223,63 @@ export function createApiServer(deliverer: AgentRouter, options: ServerOptions):
      return;
    }

+    // Turn viewer routes
+    if (options.turnLogFiles && req.method === 'GET') {
+      const agentNames = Object.keys(options.turnLogFiles);
+      const parsedUrl = new URL(req.url ?? '/', `http://localhost`);
+
+      const validateTurnAuth = (): boolean => {
+        if (validateApiKey(req.headers, options.apiKey)) return true;
+        const qKey = parsedUrl.searchParams.get('key') || '';
+        if (!qKey) return false;
+        const a = Buffer.from(qKey);
+        const b = Buffer.from(options.apiKey);
+        return a.length === b.length && crypto.timingSafeEqual(a, b);
+      };
+
+      if (parsedUrl.pathname === '/turns') {
+        res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
+        res.end(getTurnViewerHtml(agentNames));
+        return;
+      }
+      if (parsedUrl.pathname === '/turns/data') {
+        if (!validateTurnAuth()) { sendError(res, 401, 'Unauthorized'); return; }
+        const agentName = parsedUrl.searchParams.get('agent') || agentNames[0];
+        const filePath = options.turnLogFiles[agentName];
+        if (!filePath) { res.writeHead(404); res.end('Unknown agent'); return; }
+        res.writeHead(200, { 'Content-Type': 'application/json', 'Cache-Control': 'no-store' });
+        res.end(JSON.stringify(await readTurns(filePath)));
+        return;
+      }
+      if (parsedUrl.pathname === '/turns/stream') {
+        if (!validateTurnAuth()) { sendError(res, 401, 'Unauthorized'); return; }
+        const agentName = parsedUrl.searchParams.get('agent') || agentNames[0];
+        const filePath = options.turnLogFiles[agentName];
+        if (!filePath) { res.writeHead(404); res.end('Unknown agent'); return; }
+        res.writeHead(200, {
+          'Content-Type': 'text/event-stream',
+          'Cache-Control': 'no-store',
+          'Connection': 'keep-alive',
+          'X-Accel-Buffering': 'no',
+        });
+        const allTurns = await readTurns(filePath);
+        res.write(`data: ${JSON.stringify({ type: 'init', turns: allTurns })}\n\n`);
+        const clients = sseClientsByAgent.get(agentName)!;
+        const client: SSEClient = {
+          res,
+          sentCount: allTurns.length,
+          lastTurnId: getTurnId(allTurns[allTurns.length - 1]),
+        };
+        clients.add(client);
+        ensureWatching(agentName, filePath);
+        req.on('close', () => {
+          clients.delete(client);
+          maybeUnwatch(filePath, clients);
+        });
+        return;
+      }
+    }
+
    // Route: POST /api/v1/messages (unified: supports both text and files)
    if (req.url === '/api/v1/messages' && req.method === 'POST') {
      try {
--- a/src/config/types.ts
+++ b/src/config/types.ts
@@ -102,6 +102,10 @@ export interface AgentConfig {
    display?: DisplayConfig;
    allowedTools?: string[];       // Per-agent tool whitelist (overrides global/env ALLOWED_TOOLS)
    disallowedTools?: string[];    // Per-agent tool blocklist (overrides global/env DISALLOWED_TOOLS)
+    logging?: {
+      turnLogFile?: string;        // Path to JSONL file for turn logging (one record per agent turn)
+      maxTurns?: number;           // Max turns to retain in the log file (default: 1000, oldest trimmed)
+    };
  };
  /** Security settings */
  security?: {
@@ -195,6 +199,10 @@ export interface LettaBotConfig {
    display?: DisplayConfig;  // Show tool calls / reasoning in channel output
    allowedTools?: string[];       // Global tool whitelist (overridden by per-agent, falls back to ALLOWED_TOOLS env)
    disallowedTools?: string[];    // Global tool blocklist (overridden by per-agent, falls back to DISALLOWED_TOOLS env)
+    logging?: {
+      turnLogFile?: string;        // Global turn log file (overridden by per-agent)
+      maxTurns?: number;           // Global maxTurns default (overridden by per-agent)
+    };
  };

  // Polling - system-level background checks (Gmail, etc.)
--- a/src/core/bot.ts
+++ b/src/core/bot.ts
@@ -10,7 +10,7 @@ import { access, unlink, realpath, stat, constants } from 'node:fs/promises';
 import { execFile } from 'node:child_process';
 import { extname, resolve, join } from 'node:path';
 import type { ChannelAdapter } from '../channels/types.js';
-import type { BotConfig, InboundMessage, TriggerContext, StreamMsg } from './types.js';
+import type { BotConfig, InboundMessage, TriggerContext, TriggerType, StreamMsg } from './types.js';
 import { formatApiErrorForUser } from './errors.js';
 import { formatToolCallDisplay, formatReasoningDisplay, formatQuestionsForChannel } from './display.js';
 import type { AgentSession } from './interfaces.js';
@@ -24,6 +24,7 @@ import { parseDirectives, stripActionsBlock, type Directive } from './directives
 import { resolveEmoji } from './emoji.js';
 import { SessionManager } from './session-manager.js';
 import { createDisplayPipeline, type DisplayEvent, type CompleteEvent, type ErrorEvent } from './display-pipeline.js';
+import { TurnLogger, TurnAccumulator, generateTurnId, type TurnRecord } from './turn-logger.js';


 import { createLogger } from '../logger.js';
@@ -233,11 +234,15 @@ export class LettaBot implements AgentSession {

  private conversationOverrides: Set<string> = new Set();
  private readonly sessionManager: SessionManager;
+  private readonly turnLogger: TurnLogger | null;

  constructor(config: BotConfig) {
    this.config = config;
    mkdirSync(config.workingDir, { recursive: true });
    this.store = new Store('lettabot-agent.json', config.agentName);
+    this.turnLogger = config.logging?.turnLogFile
+      ? new TurnLogger(config.logging.turnLogFile, config.logging.maxTurns)
+      : null;
    if (config.reuseSession === false) {
      log.warn('Session reuse disabled (conversations.reuseSession=false): each foreground/background message uses a fresh SDK subprocess (~5s overhead per turn).');
    }
@@ -1172,7 +1177,7 @@ export class LettaBot implements AgentSession {
  private async processMessage(msg: InboundMessage, adapter: ChannelAdapter, retried = false): Promise<void> {
    // Track timing and last target
    const debugTiming = !!process.env.LETTABOT_DEBUG_TIMING;
-    const t0 = debugTiming ? performance.now() : 0;
+    const t0 = performance.now();
    const lap = (label: string) => {
      log.debug(`${label}: ${(performance.now() - t0).toFixed(0)}ms`);
    };
@@ -1278,6 +1283,10 @@ export class LettaBot implements AgentSession {
        adapter.sendTypingIndicator(msg.chatId).catch(() => {});
      }, 4000);

+      const turnId = this.turnLogger ? generateTurnId() : '';
+      const turnAcc = this.turnLogger ? new TurnAccumulator() : null;
+      let turnWritten = false;
+
      try {
        let firstChunkLogged = false;
        const pipeline = createDisplayPipeline(run.stream(), {
@@ -1286,6 +1295,7 @@ export class LettaBot implements AgentSession {
        });

        for await (const event of pipeline) {
+          turnAcc?.feed(event);
          // Check for /cancel before processing each event
          if (this.cancelledKeys.has(convKey)) {
            log.info(`Stream cancelled by /cancel (key=${convKey})`);
@@ -1627,6 +1637,24 @@ export class LettaBot implements AgentSession {
      } finally {
        clearInterval(typingInterval);
        adapter.stopTypingIndicator?.(msg.chatId)?.catch(() => {});
+        // Write turn record (even partial turns on cancel/error)
+        if (this.turnLogger && turnAcc && !turnWritten) {
+          turnWritten = true;
+          const { events, output } = turnAcc.finalize();
+          this.turnLogger.write({
+            ts: new Date().toISOString(),
+            turnId,
+            trigger: 'user_message' as const,
+            channel: msg.channel,
+            chatId: msg.chatId,
+            userId: msg.userId,
+            input: typeof messageToSend === 'string' ? messageToSend : '[multimodal]',
+            events,
+            output: output || response,
+            durationMs: Math.round(performance.now() - t0),
+            error: lastErrorDetail?.message,
+          }).catch(() => {});
+        }
      }
      lap('stream complete');

@@ -1784,8 +1812,14 @@ export class LettaBot implements AgentSession {
    const convKey = this.resolveHeartbeatConversationKey();
    const acquired = await this.acquireLock(convKey);
    
+    const sendT0 = performance.now();
+    const sendTurnId = this.turnLogger ? generateTurnId() : '';
+    const sendTurnAcc = this.turnLogger ? new TurnAccumulator() : null;
+    let sendTurnWritten = false;
+
    try {
      let retried = false;
+
      while (true) {
        const { stream } = await this.sessionManager.runSession(text, { convKey, retried });

@@ -1796,6 +1830,7 @@ export class LettaBot implements AgentSession {
          let usedMessageCli = false;
          let lastErrorDetail: StreamErrorDetail | undefined;
          for await (const msg of stream()) {
+            sendTurnAcc?.feedRaw(msg);
            if (msg.type === 'tool_call') {
              this.sessionManager.syncTodoToolCall(msg);
              if (isSilent && msg.toolName === 'Bash') {
@@ -1930,6 +1965,21 @@ export class LettaBot implements AgentSession {
      if (this.config.reuseSession === false) {
        this.sessionManager.invalidateSession(convKey);
      }
+      // Write turn record
+      if (this.turnLogger && sendTurnAcc && !sendTurnWritten) {
+        sendTurnWritten = true;
+        const { events, output } = sendTurnAcc.finalize();
+        this.turnLogger.write({
+          ts: new Date().toISOString(),
+          turnId: sendTurnId,
+          trigger: context?.type ?? 'heartbeat',
+          channel: context?.sourceChannel,
+          input: text,
+          events,
+          output,
+          durationMs: Math.round(performance.now() - sendT0),
+        }).catch(() => {});
+      }
      this.releaseLock(convKey, acquired);
    }
  }
@@ -1944,20 +1994,42 @@ export class LettaBot implements AgentSession {
  ): AsyncGenerator<StreamMsg> {
    const convKey = this.resolveHeartbeatConversationKey();
    const acquired = await this.acquireLock(convKey);
+    const streamT0 = performance.now();
+    const streamTurnId = this.turnLogger ? generateTurnId() : '';
+    const streamTurnAcc = this.turnLogger ? new TurnAccumulator() : null;
+    let streamTurnError: string | undefined;

    try {
      const { stream } = await this.sessionManager.runSession(text, { convKey });

      try {
-        yield* stream();
+        for await (const msg of stream()) {
+          streamTurnAcc?.feedRaw(msg);
+          yield msg;
+        }
      } catch (error) {
        this.sessionManager.invalidateSession(convKey);
+        streamTurnError = error instanceof Error ? error.message : String(error);
        throw error;
      }
    } finally {
      if (this.config.reuseSession === false) {
        this.sessionManager.invalidateSession(convKey);
      }
+      if (this.turnLogger && streamTurnAcc) {
+        const { events, output } = streamTurnAcc.finalize();
+        this.turnLogger.write({
+          ts: new Date().toISOString(),
+          turnId: streamTurnId,
+          trigger: context?.type ?? 'heartbeat',
+          channel: context?.sourceChannel,
+          input: text,
+          events,
+          output,
+          durationMs: Math.round(performance.now() - streamT0),
+          error: streamTurnError,
+        }).catch(() => {});
+      }
      this.releaseLock(convKey, acquired);
    }
  }
--- a/src/core/turn-logger.ts
+++ b/src/core/turn-logger.ts
@@ -0,0 +1,222 @@
+/**
+ * Turn logger -- writes one JSONL record per agent turn.
+ *
+ * TurnLogger handles file I/O with write serialization and bounded retention.
+ * TurnAccumulator collects DisplayEvents during a turn and produces a TurnRecord.
+ */
+
+import { appendFile, readFile, writeFile, rename } from 'node:fs/promises';
+import { mkdirSync, readFileSync } from 'node:fs';
+import { dirname } from 'node:path';
+import { randomUUID } from 'node:crypto';
+import { createLogger } from '../logger.js';
+import type { DisplayEvent } from './display-pipeline.js';
+import type { TriggerType, StreamMsg } from './types.js';
+
+const log = createLogger('TurnLogger');
+
+// ---------------------------------------------------------------------------
+// Types
+// ---------------------------------------------------------------------------
+
+export type TurnEvent =
+  | { type: 'reasoning'; content: string }
+  | { type: 'tool_call'; id: string; name: string; args: unknown }
+  | { type: 'tool_result'; id: string; content: string; isError: boolean };
+
+export interface TurnRecord {
+  ts: string;
+  turnId: string;
+  trigger: TriggerType;
+  channel?: string;
+  chatId?: string;
+  userId?: string;
+  input: string;
+  events: TurnEvent[];
+  output: string;
+  durationMs?: number;
+  error?: string;
+}
+
+// ---------------------------------------------------------------------------
+// Constants
+// ---------------------------------------------------------------------------
+
+const DEFAULT_MAX_TURNS = 1000;
+const MAX_TOOL_RESULT_BYTES = 4 * 1024;
+
+// ---------------------------------------------------------------------------
+// TurnAccumulator
+// ---------------------------------------------------------------------------
+
+/**
+ * Collects DisplayEvents during a single agent turn and produces a TurnRecord.
+ * Works with the DisplayPipeline's event types -- no raw StreamMsg handling.
+ */
+export class TurnAccumulator {
+  private _events: TurnEvent[] = [];
+  private _output = '';
+  // For feedRaw() only (sendToAgent/streamToAgent paths)
+  private _reasoningAcc = '';
+  private _lastRawType: string | null = null;
+
+  /** Feed a DisplayEvent from the pipeline. */
+  feed(event: DisplayEvent): void {
+    switch (event.type) {
+      case 'reasoning':
+        // Pipeline already accumulates and flushes reasoning chunks,
+        // so each reasoning event is a complete block.
+        this._events.push({ type: 'reasoning', content: event.content });
+        break;
+      case 'tool_call':
+        this._events.push({
+          type: 'tool_call',
+          id: event.id,
+          name: event.name,
+          args: event.args,
+        });
+        break;
+      case 'tool_result': {
+        const content = event.content.length > MAX_TOOL_RESULT_BYTES
+          ? event.content.slice(0, MAX_TOOL_RESULT_BYTES) + '…[truncated]'
+          : event.content;
+        this._events.push({
+          type: 'tool_result',
+          id: event.toolCallId,
+          content,
+          isError: event.isError,
+        });
+        break;
+      }
+      case 'text':
+        this._output += event.delta;
+        break;
+    }
+  }
+
+  /**
+   * Feed a raw StreamMsg (for sendToAgent/streamToAgent which don't use DisplayPipeline).
+   * Handles reasoning accumulation inline since there's no pipeline to do it.
+   */
+  feedRaw(msg: StreamMsg): void {
+    // Flush reasoning on transition away from reasoning
+    if (this._lastRawType === 'reasoning' && msg.type !== 'reasoning' && this._reasoningAcc.trim()) {
+      this._events.push({ type: 'reasoning', content: this._reasoningAcc.trim() });
+      this._reasoningAcc = '';
+    }
+    switch (msg.type) {
+      case 'reasoning':
+        this._reasoningAcc += msg.content || '';
+        break;
+      case 'tool_call':
+        this._events.push({
+          type: 'tool_call',
+          id: msg.toolCallId || '',
+          name: msg.toolName || 'unknown',
+          args: (msg as any).toolInput ?? (msg as any).rawArguments ?? null,
+        });
+        break;
+      case 'tool_result': {
+        const raw = (msg as any).content ?? '';
+        const str = typeof raw === 'string' ? raw : JSON.stringify(raw);
+        this._events.push({
+          type: 'tool_result',
+          id: msg.toolCallId || '',
+          content: str.length > MAX_TOOL_RESULT_BYTES
+            ? str.slice(0, MAX_TOOL_RESULT_BYTES) + '…[truncated]'
+            : str,
+          isError: !!msg.isError,
+        });
+        break;
+      }
+      case 'assistant':
+        this._output += msg.content || '';
+        break;
+    }
+    if (msg.type !== 'stream_event') this._lastRawType = msg.type;
+  }
+
+  /** Return the accumulated events and output text. */
+  finalize(): { events: TurnEvent[]; output: string } {
+    // Flush trailing reasoning
+    if (this._reasoningAcc.trim()) {
+      this._events.push({ type: 'reasoning', content: this._reasoningAcc.trim() });
+      this._reasoningAcc = '';
+    }
+    return { events: this._events, output: this._output };
+  }
+}
+
+// ---------------------------------------------------------------------------
+// TurnLogger
+// ---------------------------------------------------------------------------
+
+export class TurnLogger {
+  private filePath: string;
+  private maxTurns: number;
+  private ready = false;
+  private lineCount = 0;
+  private writeQueue = Promise.resolve();
+
+  constructor(filePath: string, maxTurns = DEFAULT_MAX_TURNS) {
+    this.filePath = filePath;
+    if (!Number.isInteger(maxTurns) || maxTurns <= 0) {
+      throw new Error(`TurnLogger: maxTurns must be a positive integer (got ${maxTurns})`);
+    }
+    this.maxTurns = maxTurns;
+    try {
+      mkdirSync(dirname(filePath), { recursive: true });
+      this.ready = true;
+      try {
+        const existing = readFileSync(filePath, 'utf8');
+        this.lineCount = existing.split('\n').filter(l => l.trim()).length;
+      } catch {
+        this.lineCount = 0;
+      }
+    } catch (err) {
+      log.warn(`Failed to create log directory for ${filePath}:`, err instanceof Error ? err.message : err);
+    }
+  }
+
+  /** Serialized write -- prevents concurrent trim races. */
+  async write(record: TurnRecord): Promise<void> {
+    if (!this.ready) return;
+    this.writeQueue = this.writeQueue.then(() => this._write(record)).catch(() => {});
+    return this.writeQueue;
+  }
+
+  private async _write(record: TurnRecord): Promise<void> {
+    try {
+      await appendFile(this.filePath, JSON.stringify(record) + '\n');
+      this.lineCount++;
+      if (this.lineCount > this.maxTurns) {
+        await this.trim();
+      }
+    } catch (err) {
+      log.warn(`Failed to write turn record:`, err instanceof Error ? err.message : err);
+    }
+  }
+
+  private async trim(): Promise<void> {
+    try {
+      const content = await readFile(this.filePath, 'utf8');
+      const lines = content.split('\n').filter(l => l.trim());
+      const trimmed = lines.slice(lines.length - this.maxTurns).join('\n') + '\n';
+      const tmp = this.filePath + '.tmp';
+      await writeFile(tmp, trimmed);
+      await rename(tmp, this.filePath);
+      this.lineCount = this.maxTurns;
+    } catch (err) {
+      log.warn(`Failed to trim turn log:`, err instanceof Error ? err.message : err);
+    }
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+/** Generate a unique turn ID. */
+export function generateTurnId(): string {
+  return randomUUID();
+}
--- a/src/core/turn-viewer.html
+++ b/src/core/turn-viewer.html
@@ -0,0 +1,510 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<meta charset="UTF-8">
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<title>Turn Viewer</title>
+<style>
+*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
+:root{
+  --bg:#0f1117;--surface:#1a1d27;--surface2:#22263a;--border:#2e3348;
+  --accent:#6c8ef7;--accent2:#a78bfa;
+  --text:#e2e6f0;--text2:#8b92a8;--text3:#5a6080;
+  --green:#4ade80;--red:#f87171;--yellow:#fbbf24;
+  --rb:#1e1a2e;--rbd:#5b4daa;
+  --tb:#172434;--tbd:#2563eb;
+  --trb:#1a2d1a;--trbd:#16a34a;
+  --treb:#2d1a1a;--trebd:#dc2626;
+}
+body{background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;font-size:14px;height:100vh;display:flex;flex-direction:column;overflow:hidden}
+.header{padding:12px 20px;background:var(--surface);border-bottom:1px solid var(--border);display:flex;align-items:center;gap:12px;flex-shrink:0}
+.header h1{font-size:16px;font-weight:600}
+.file-path{font-size:11px;color:var(--text3);font-family:monospace}
+.turn-count{font-size:12px;color:var(--text2);margin-left:auto}
+.status-dot{width:8px;height:8px;border-radius:50%;background:var(--green);flex-shrink:0}
+.status-dot.stale{background:var(--text3)}
+.status-dot.live{animation:pulse 2s infinite}
+@keyframes pulse{0%,100%{opacity:1}50%{opacity:.4}}
+.filters{padding:10px 20px;background:var(--surface);border-bottom:1px solid var(--border);display:flex;align-items:center;gap:10px;flex-wrap:wrap;flex-shrink:0}
+.filter-label{font-size:11px;color:var(--text3);text-transform:uppercase;letter-spacing:.05em}
+.filter-group{display:flex;gap:4px;align-items:center}
+.tab{padding:4px 12px;border-radius:20px;border:1px solid var(--border);background:transparent;color:var(--text2);font-size:13px;cursor:pointer;transition:all .15s}
+.tab:hover{border-color:var(--accent);color:var(--text)}
+.tab.active{background:var(--accent);border-color:var(--accent);color:#fff;font-weight:600}
+.search-input{padding:4px 12px;border-radius:20px;border:1px solid var(--border);background:var(--surface2);color:var(--text);font-size:13px;outline:none;width:180px}
+.search-input:focus{border-color:var(--accent)}
+.search-input::placeholder{color:var(--text3)}
+.table-wrapper{flex:1;overflow-y:auto}
+table{width:100%;border-collapse:collapse}
+thead{position:sticky;top:0;z-index:10;background:var(--surface2)}
+th{padding:9px 14px;text-align:left;font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:.06em;color:var(--text3);border-bottom:1px solid var(--border);white-space:nowrap}
+td{padding:9px 14px;border-bottom:1px solid var(--border);vertical-align:top}
+tr:hover td{background:var(--surface2);cursor:pointer}
+.col-time{width:155px;color:var(--text2);font-size:12px;font-family:monospace;white-space:nowrap}
+.col-trigger{width:130px}
+.col-channel{width:100px}
+.col-events{width:65px;text-align:center;color:var(--text2);font-size:12px}
+.col-duration{width:80px;text-align:right;color:var(--text2);font-size:12px;font-family:monospace;white-space:nowrap}
+.truncated{white-space:nowrap;overflow:hidden;text-overflow:ellipsis;max-width:260px;color:var(--text2);font-size:13px}
+.empty-state{padding:60px;text-align:center;color:var(--text3)}
+.empty-state p{margin-top:8px;font-size:13px}
+.badge{display:inline-block;padding:2px 8px;border-radius:10px;font-size:11px;font-weight:600;letter-spacing:.03em}
+.badge-user_message{background:#1e3a5f;color:#60a5fa}
+.badge-heartbeat{background:#3b2d14;color:#fbbf24}
+
+.badge-cron{background:#2d1e3a;color:#c084fc}
+.badge-webhook{background:#2d1e1e;color:#f87171}
+.badge-feed{background:#1e2d3a;color:#38bdf8}
+.badge-channel{background:var(--surface2);color:var(--text2);border:1px solid var(--border)}
+.detail-overlay{position:fixed;inset:0;background:rgba(0,0,0,.5);z-index:100;display:none}
+.detail-overlay.open{display:block}
+.detail-panel{position:fixed;top:0;right:0;bottom:0;width:660px;max-width:90vw;background:var(--surface);border-left:1px solid var(--border);overflow-y:auto;z-index:101;transform:translateX(100%);transition:transform .2s ease;display:flex;flex-direction:column}
+.detail-panel.open{transform:translateX(0)}
+.detail-header{padding:14px 18px;border-bottom:1px solid var(--border);display:flex;align-items:flex-start;gap:10px;flex-shrink:0;background:var(--surface);position:sticky;top:0;z-index:5}
+.detail-meta{flex:1;min-width:0}
+.detail-ts{font-size:12px;color:var(--text3);font-family:monospace}
+.detail-trigger-row{display:flex;gap:8px;align-items:center;margin-top:4px;flex-wrap:wrap}
+.close-btn{background:none;border:none;color:var(--text3);font-size:20px;cursor:pointer;padding:0 4px;line-height:1;flex-shrink:0}
+.close-btn:hover{color:var(--text)}
+.detail-body{padding:18px;display:flex;flex-direction:column;gap:18px}
+.section{display:flex;flex-direction:column;gap:8px}
+.section-label{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:.08em;color:var(--text3)}
+.msg-box{background:var(--surface2);border:1px solid var(--border);border-radius:8px;padding:12px 14px;font-size:13px;color:var(--text);line-height:1.6;white-space:pre-wrap;word-break:break-word;max-height:280px;overflow-y:auto}
+.msg-box.output{border-color:var(--accent2);background:#1a1a2e}
+.events-list{display:flex;flex-direction:column;gap:6px}
+.event{border-radius:8px;overflow:hidden}
+.event-hdr{padding:7px 12px;display:flex;align-items:center;gap:8px;font-size:12px;font-weight:600;cursor:pointer;user-select:none}
+.event-hdr:hover{filter:brightness(1.1)}
+.event-toggle{font-size:10px;margin-left:auto;opacity:.7}
+.event-bdy{padding:10px 12px;font-size:12px;font-family:'SF Mono','Fira Code',monospace;white-space:pre-wrap;word-break:break-word;line-height:1.5;max-height:360px;overflow-y:auto}
+.ev-reasoning{background:var(--rb);border:1px solid var(--rbd)}
+.ev-reasoning .event-hdr{background:var(--rbd);color:#c4b5fd}
+.ev-reasoning .event-bdy{color:#ddd6fe;font-family:inherit;font-style:italic;font-size:13px}
+.ev-tool_call{background:var(--tb);border:1px solid var(--tbd)}
+.ev-tool_call .event-hdr{background:var(--tbd);color:#93c5fd}
+.ev-tool_call .event-bdy{color:#bfdbfe}
+.ev-tool_result{background:var(--trb);border:1px solid var(--trbd)}
+.ev-tool_result .event-hdr{background:var(--trbd);color:#bbf7d0}
+.ev-tool_result .event-bdy{color:#d1fae5}
+.ev-tool_result.is-error{background:var(--treb);border-color:var(--trebd)}
+.ev-tool_result.is-error .event-hdr{background:var(--trebd);color:#fecaca}
+.ev-tool_result.is-error .event-bdy{color:#fee2e2}
+.no-events{color:var(--text3);font-size:13px;font-style:italic}
+::-webkit-scrollbar{width:6px;height:6px}
+::-webkit-scrollbar-track{background:transparent}
+::-webkit-scrollbar-thumb{background:var(--border);border-radius:3px}
+::-webkit-scrollbar-thumb:hover{background:var(--text3)}
+.auth-overlay{position:fixed;inset:0;background:var(--bg);z-index:200;display:flex;align-items:center;justify-content:center}
+.auth-box{background:var(--surface);border:1px solid var(--border);border-radius:12px;padding:28px 24px;width:340px}
+.auth-box h2{font-size:16px;font-weight:600;margin-bottom:18px;color:var(--text)}
+.auth-box label{display:block;font-size:12px;color:var(--text3);margin-bottom:6px}
+.auth-box input{width:100%;padding:8px 10px;background:var(--bg);border:1px solid var(--border);border-radius:6px;color:var(--text);font-size:13px;font-family:monospace;outline:none}
+.auth-box input:focus{border-color:var(--accent)}
+.auth-box button{margin-top:12px;width:100%;padding:9px;background:var(--accent);color:#fff;border:none;border-radius:6px;font-size:13px;font-weight:600;cursor:pointer}
+.auth-box button:hover{opacity:.9}
+.auth-err{color:#f87171;font-size:12px;margin-top:8px;display:none}
+</style>
+</head>
+<body>
+<div class="auth-overlay" id="authOverlay">
+  <div class="auth-box">
+    <h2>Turn Viewer</h2>
+    <label for="apiKeyInput">API Key</label>
+    <input type="password" id="apiKeyInput" placeholder="Paste your API key" autocomplete="off"
+      onkeydown="if(event.key==='Enter')document.getElementById('authSubmit').click()">
+    <button id="authSubmit">Connect</button>
+    <div class="auth-err" id="authErr">Invalid API key</div>
+  </div>
+</div>
+
+<div class="header">
+  <h1>Turn Viewer</h1>
+  <span class="file-path" id="agentLabel" style="display:__LABEL_DISPLAY__">__DEFAULT_AGENT__</span>
+  <select id="agentSelect" style="display:__SELECT_DISPLAY__;background:var(--surface2);color:var(--text);border:1px solid var(--border);border-radius:6px;padding:3px 8px;font-size:13px;cursor:pointer;outline:none">
+    __AGENT_OPTIONS__
+  </select>
+  <span class="turn-count" id="turnCount"></span>
+  <div class="status-dot stale" id="statusDot" title="Connecting&hellip;"></div>
+</div>
+
+<div class="filters">
+  <span class="filter-label">Trigger</span>
+  <div class="filter-group" id="triggerTabs">
+    <button class="tab active" data-trigger="all">All</button>
+    <button class="tab" data-trigger="user_message">User Message</button>
+    <button class="tab" data-trigger="heartbeat">Heartbeat</button>
+    <button class="tab" data-trigger="cron">Cron</button>
+    <button class="tab" data-trigger="webhook">Webhook</button>
+    <button class="tab" data-trigger="feed">Feed</button>
+  </div>
+  <div class="filter-group" id="channelFilterGroup" style="display:none">
+    <span class="filter-label">Channel</span>
+    <div id="channelTabs"></div>
+  </div>
+  <div class="filter-group" style="margin-left:auto">
+    <input class="search-input" id="searchInput" type="text" placeholder="Search input / output&hellip;">
+  </div>
+</div>
+
+<div class="table-wrapper" id="tableWrapper">
+  <table>
+    <thead>
+      <tr>
+        <th class="col-time">Time</th>
+        <th class="col-trigger">Trigger</th>
+        <th class="col-channel">Channel</th>
+        <th class="col-events">Events</th>
+        <th class="col-duration">Duration</th>
+        <th>Input</th>
+        <th>Output</th>
+      </tr>
+    </thead>
+    <tbody id="tableBody"></tbody>
+  </table>
+  <div class="empty-state" id="emptyState" style="display:none">
+    <div style="font-size:32px">&#x1F4CB;</div>
+    <p id="emptyMsg">Waiting for turns&hellip;</p>
+  </div>
+</div>
+
+<div class="detail-overlay" id="detailOverlay"></div>
+<div class="detail-panel" id="detailPanel">
+  <div class="detail-header">
+    <div class="detail-meta">
+      <div class="detail-ts" id="detailTs"></div>
+      <div class="detail-trigger-row">
+        <span id="detailTrigger"></span>
+        <span id="detailChannel"></span>
+        <span style="font-size:11px;color:var(--text3)" id="detailUserId"></span>
+        <span style="font-size:11px;color:var(--text3);margin-left:auto;font-family:monospace" id="detailDuration"></span>
+      </div>
+      <div style="font-size:10px;color:var(--text3);font-family:monospace;margin-top:2px" id="detailTurnId"></div>
+    </div>
+    <button class="close-btn" id="closeBtn">&#x2715;</button>
+  </div>
+  <div class="detail-body">
+    <div class="section">
+      <div class="section-label">Input</div>
+      <div class="msg-box" id="detailInput"></div>
+    </div>
+    <div class="section">
+      <div class="section-label">Events (<span id="detailEventsCount">0</span>)</div>
+      <div class="events-list" id="detailEvents"></div>
+    </div>
+    <div class="section">
+      <div class="section-label">Output</div>
+      <div class="msg-box output" id="detailOutput"></div>
+    </div>
+  </div>
+</div>
+
+<script>
+(function() {
+var AGENT_NAMES = __AGENT_NAMES_JSON__;
+var activeAgent = AGENT_NAMES[0] || '';
+var allTurns = [];
+var activeTrigger = 'all';
+var activeChannel = 'all';
+var searchQuery = '';
+var openTurnId = null;
+var apiKey = sessionStorage.getItem('tv_key') || '';
+
+function esc(s) {
+  return String(s).replace(/&/g,'&amp;').replace(/</g,'&lt;').replace(/>/g,'&gt;').replace(/"/g,'&quot;');
+}
+
+function fmtTime(ts) {
+  if (!ts) return '\u2014';
+  var d = new Date(ts);
+  if (isNaN(d.getTime())) return ts;
+  var p = function(n){return n<10?'0'+n:''+n;};
+  var mo = ['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec'];
+  return mo[d.getMonth()]+' '+p(d.getDate())+' '+p(d.getHours())+':'+p(d.getMinutes())+':'+p(d.getSeconds());
+}
+
+function triggerBadge(t) {
+  return '<span class="badge badge-'+esc(t||'unknown')+'">'+esc(t||'unknown')+'</span>';
+}
+function channelBadge(c) {
+  return c ? '<span class="badge badge-channel">'+esc(c)+'</span>' : '';
+}
+function fmtDuration(ms) {
+  if (ms == null) return '<span style="color:var(--text3)">\u2014</span>';
+  if (ms < 1000) return ms + 'ms';
+  if (ms < 60000) return (ms / 1000).toFixed(1) + 's';
+  return Math.floor(ms / 60000) + 'm ' + ((ms % 60000) / 1000).toFixed(0) + 's';
+}
+
+function trunc(str, n) {
+  n = n||120;
+  if (!str) return '<span style="color:var(--text3);font-style:italic">\u2014</span>';
+  str = str.trim();
+  return str.length > n ? esc(str.slice(0,n))+'<span style="color:var(--text3)">\u2026</span>' : esc(str);
+}
+
+function getChannels() {
+  var seen = {};
+  allTurns.forEach(function(t){ if (t.trigger==='user_message'&&t.channel) seen[t.channel]=true; });
+  return Object.keys(seen).sort();
+}
+
+function filterTurns() {
+  return allTurns.filter(function(t) {
+    if (activeTrigger !== 'all' && t.trigger !== activeTrigger) return false;
+    if (activeTrigger === 'user_message' && activeChannel !== 'all' && t.channel !== activeChannel) return false;
+    if (searchQuery) {
+      var q = searchQuery.toLowerCase();
+      if (((t.input||'').toLowerCase().indexOf(q)===-1) && ((t.output||'').toLowerCase().indexOf(q)===-1)) return false;
+    }
+    return true;
+  });
+}
+
+function setTurns(turns) {
+  allTurns = turns.slice().reverse(); // newest first
+  render();
+}
+
+function render() {
+  renderTriggerTabs();
+  renderChannelTabs();
+  renderTable();
+}
+
+function renderTriggerTabs() {
+  document.querySelectorAll('#triggerTabs .tab').forEach(function(btn) {
+    btn.classList.toggle('active', btn.getAttribute('data-trigger') === activeTrigger);
+  });
+}
+
+function renderChannelTabs() {
+  var group = document.getElementById('channelFilterGroup');
+  var container = document.getElementById('channelTabs');
+  if (activeTrigger !== 'user_message') { group.style.display = 'none'; return; }
+  var channels = getChannels();
+  if (!channels.length) { group.style.display = 'none'; return; }
+  group.style.display = 'flex';
+  container.innerHTML = ['all'].concat(channels).map(function(ch) {
+    return '<button class="tab'+(activeChannel===ch?' active':'')+'" data-channel="'+esc(ch)+'">'+(ch==='all'?'All':esc(ch))+'</button>';
+  }).join('');
+  container.querySelectorAll('[data-channel]').forEach(function(btn) {
+    btn.addEventListener('click', function() {
+      activeChannel = btn.getAttribute('data-channel');
+      renderChannelTabs();
+      renderTable();
+    });
+  });
+}
+
+function renderTable() {
+  var turns = filterTurns();
+  var tbody = document.getElementById('tableBody');
+  var empty = document.getElementById('emptyState');
+  document.getElementById('turnCount').textContent =
+    allTurns.length === turns.length ? allTurns.length+' turns' : turns.length+' / '+allTurns.length+' turns';
+
+  if (!turns.length) {
+    tbody.innerHTML = '';
+    empty.style.display = 'block';
+    document.getElementById('emptyMsg').textContent =
+      allTurns.length === 0 ? 'Waiting for turns\u2026' : 'No turns match the current filter.';
+    return;
+  }
+  empty.style.display = 'none';
+
+  tbody.innerHTML = turns.map(function(t, i) {
+    return '<tr data-idx="'+i+'">'+
+      '<td class="col-time">'+fmtTime(t.ts)+'</td>'+
+      '<td class="col-trigger">'+triggerBadge(t.trigger)+'</td>'+
+      '<td class="col-channel">'+channelBadge(t.channel)+'</td>'+
+      '<td class="col-events">'+((t.events||[]).length)+'</td>'+
+      '<td class="col-duration">'+fmtDuration(t.durationMs)+'</td>'+
+      '<td><div class="truncated">'+trunc(t.input)+'</div></td>'+
+      '<td><div class="truncated">'+trunc(t.output)+'</div></td>'+
+      '</tr>';
+  }).join('');
+
+  tbody.querySelectorAll('tr').forEach(function(row) {
+    row.addEventListener('click', function() {
+      openDetail(turns[parseInt(row.getAttribute('data-idx'),10)]);
+    });
+  });
+
+  // Re-open detail panel if it was open and the turn still exists
+  if (openTurnId) {
+    var match = turns.find(function(t){ return t.turnId === openTurnId; });
+    if (match) openDetail(match);
+    else openTurnId = null;
+  }
+}
+
+function renderEvent(e, i) {
+  if (e.type === 'reasoning') {
+    return '<div class="event ev-reasoning">'+
+      '<div class="event-hdr"><span>&#x1F4AD; Reasoning #'+(i+1)+'</span><span class="event-toggle">&#x25B2;</span></div>'+
+      '<div class="event-bdy">'+esc(e.content||'')+'</div></div>';
+  }
+  if (e.type === 'tool_call') {
+    var args=''; try{args=JSON.stringify(e.args,null,2);}catch(ex){args=String(e.args);}
+    return '<div class="event ev-tool_call">'+
+      '<div class="event-hdr"><span>&#x2699;&#xFE0F; '+esc(e.name||'unknown')+'</span>'+
+      '<span style="font-family:monospace;opacity:.5;font-size:11px">'+esc((e.id||'').slice(0,12))+'</span>'+
+      '<span class="event-toggle">&#x25B2;</span></div>'+
+      '<div class="event-bdy">'+esc(args)+'</div></div>';
+  }
+  if (e.type === 'tool_result') {
+    var errCls=e.isError?' is-error':'', icon=e.isError?'&#x274C;':'&#x2705;';
+    return '<div class="event ev-tool_result'+errCls+'">'+
+      '<div class="event-hdr"><span>'+icon+' Result'+(e.isError?' (error)':'')+'</span>'+
+      '<span style="font-family:monospace;opacity:.5;font-size:11px">'+esc((e.id||'').slice(0,12))+'</span>'+
+      '<span class="event-toggle">&#x25B2;</span></div>'+
+      '<div class="event-bdy">'+esc(e.content||'')+'</div></div>';
+  }
+  return '<div style="border:1px solid var(--border);border-radius:8px;padding:8px 12px;color:var(--text3);font-size:12px">Unknown event: '+esc(e.type)+'</div>';
+}
+
+function openDetail(turn) {
+  if (!turn) return;
+  openTurnId = turn.turnId;
+  document.getElementById('detailTs').textContent = fmtTime(turn.ts);
+  document.getElementById('detailTrigger').innerHTML = triggerBadge(turn.trigger);
+  document.getElementById('detailChannel').innerHTML = channelBadge(turn.channel);
+  document.getElementById('detailUserId').textContent = turn.userId ? 'user: '+turn.userId : '';
+  document.getElementById('detailDuration').innerHTML = turn.durationMs != null ? fmtDuration(turn.durationMs) : '';
+  document.getElementById('detailTurnId').textContent = turn.turnId ? 'turn: '+turn.turnId : '';
+  document.getElementById('detailInput').textContent = turn.input||'(empty)';
+  document.getElementById('detailOutput').textContent = turn.output||'(empty)';
+  var events = turn.events||[];
+  document.getElementById('detailEventsCount').textContent = events.length;
+  var evList = document.getElementById('detailEvents');
+  evList.innerHTML = events.length===0
+    ? '<div class="no-events">No events recorded for this turn.</div>'
+    : events.map(renderEvent).join('');
+  evList.querySelectorAll('.event-hdr').forEach(function(h) {
+    h.addEventListener('click', function() {
+      var body=h.nextElementSibling, toggle=h.querySelector('.event-toggle');
+      var hidden=body.style.display==='none';
+      body.style.display=hidden?'':'none';
+      toggle.innerHTML=hidden?'&#x25B2;':'&#x25BC;';
+    });
+  });
+  document.getElementById('detailPanel').classList.add('open');
+  document.getElementById('detailOverlay').classList.add('open');
+}
+
+function closeDetail() {
+  openTurnId = null;
+  document.getElementById('detailPanel').classList.remove('open');
+  document.getElementById('detailOverlay').classList.remove('open');
+}
+
+document.getElementById('closeBtn').addEventListener('click', closeDetail);
+document.getElementById('detailOverlay').addEventListener('click', closeDetail);
+document.addEventListener('keydown', function(e){ if(e.key==='Escape') closeDetail(); });
+
+document.querySelectorAll('#triggerTabs .tab').forEach(function(btn) {
+  btn.addEventListener('click', function() {
+    activeTrigger = btn.getAttribute('data-trigger');
+    activeChannel = 'all';
+    render();
+  });
+});
+
+document.getElementById('searchInput').addEventListener('input', function(e) {
+  searchQuery = e.target.value;
+  renderTable();
+});
+
+// ── Agent selector ─────────────────────────────────────────────────────────
+var agentSelect = document.getElementById('agentSelect');
+if (agentSelect) {
+  agentSelect.addEventListener('change', function() {
+    activeAgent = agentSelect.value;
+    allTurns = [];
+    activeTrigger = 'all';
+    activeChannel = 'all';
+    openTurnId = null;
+    render();
+    switchAgent();
+  });
+}
+
+// ── Live data via SSE ──────────────────────────────────────────────────────
+var dot = document.getElementById('statusDot');
+var currentEs = null;
+
+function connect() {
+  if (currentEs) { currentEs.close(); currentEs = null; }
+  var params = new URLSearchParams();
+  if (activeAgent) params.set('agent', activeAgent);
+  params.set('key', apiKey);
+  var url = '/turns/stream?' + params.toString();
+  var es = new EventSource(url);
+  currentEs = es;
+  es.onopen = function() {
+    dot.className = 'status-dot live';
+    dot.title = 'Live \u2014 auto-updating';
+  };
+  es.onmessage = function(e) {
+    try {
+      var msg = JSON.parse(e.data);
+      if (msg.type === 'init') { setTurns(msg.turns); }
+      else if (msg.type === 'append' && msg.turns && msg.turns.length > 0) {
+        allTurns = msg.turns.concat(allTurns);
+        render();
+      }
+    } catch(ex) {}
+  };
+  es.onerror = function() {
+    if (es !== currentEs) return; // stale, ignore
+    dot.className = 'status-dot stale';
+    dot.title = 'Disconnected \u2014 reconnecting\u2026';
+    es.close();
+    currentEs = null;
+    setTimeout(connect, 3000);
+  };
+}
+
+function switchAgent() {
+  var params = new URLSearchParams();
+  if (activeAgent) params.set('agent', activeAgent);
+  var url = '/turns/data?' + params.toString();
+  fetch(url, { headers: { 'X-Api-Key': apiKey } })
+    .then(function(r) {
+      if (r.status === 401) { showAuth(); throw new Error('Unauthorized'); }
+      return r.json();
+    })
+    .then(setTurns)
+    .catch(function(){});
+  connect();
+}
+
+function showAuth() {
+  document.getElementById('authOverlay').style.display = 'flex';
+}
+
+function hideAuth() {
+  document.getElementById('authOverlay').style.display = 'none';
+}
+
+document.getElementById('authSubmit').addEventListener('click', function() {
+  var k = document.getElementById('apiKeyInput').value.trim();
+  if (!k) return;
+  apiKey = k;
+  sessionStorage.setItem('tv_key', k);
+  document.getElementById('authErr').style.display = 'none';
+  hideAuth();
+  switchAgent();
+});
+
+// Initial load — show login if no key stored, otherwise load directly
+if (apiKey) {
+  hideAuth();
+  switchAgent();
+} else {
+  showAuth();
+}
+})();
+</script>
+</body>
+</html>
--- a/src/core/turn-viewer.ts
+++ b/src/core/turn-viewer.ts
@@ -0,0 +1,38 @@
+/**
+ * Turn viewer SPA — served by the API server at GET /turns.
+ *
+ * The HTML lives in turn-viewer.html (same directory).
+ * getTurnViewerHtml() injects agent metadata via simple token substitution
+ * so the template file can be edited and linted independently.
+ */
+
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+let TEMPLATE: string;
+try {
+  TEMPLATE = readFileSync(join(__dirname, 'turn-viewer.html'), 'utf8');
+} catch {
+  throw new Error('turn-viewer.html not found -- did you run npm run build?');
+}
+
+function escHtml(s: string): string {
+  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
+}
+
+export function getTurnViewerHtml(agentNames: string[]): string {
+  const multiAgent = agentNames.length > 1;
+  const defaultAgent = agentNames[0] ?? '';
+  // Escape </script> to prevent XSS if an agent name contains it
+  const agentNamesJson = JSON.stringify(agentNames).replace(/<\/script>/gi, '<\\/script>');
+  const agentOptions = agentNames.map(n => `<option value="${escHtml(n)}">${escHtml(n)}</option>`).join('');
+
+  return TEMPLATE
+    .replaceAll('__AGENT_NAMES_JSON__', agentNamesJson)
+    .replaceAll('__DEFAULT_AGENT__', escHtml(defaultAgent))
+    .replaceAll('__LABEL_DISPLAY__', multiAgent ? 'none' : 'inline')
+    .replaceAll('__SELECT_DISPLAY__', multiAgent ? 'inline-block' : 'none')
+    .replaceAll('__AGENT_OPTIONS__', agentOptions);
+}
--- a/src/core/types.ts
+++ b/src/core/types.ts
@@ -192,6 +192,12 @@ export interface BotConfig {
  sendFileMaxSize?: number; // Max file size in bytes for <send-file> (default: 50MB)
  sendFileCleanup?: boolean; // Allow <send-file cleanup="true"> to delete files after send (default: false)

+  // Logging
+  logging?: {
+    turnLogFile?: string; // Path to JSONL file for turn logging (one record per agent turn)
+    maxTurns?: number;    // Max turns to retain in the log file (default: 1000, oldest trimmed)
+  };
+
  // Cron
  cronStorePath?: string; // Resolved cron store path (per-agent in multi-agent mode)

--- a/src/main.ts
+++ b/src/main.ts
@@ -259,6 +259,25 @@ async function main() {
  const isMultiAgent = agents.length > 1;
  log.info(`${agents.length} agent(s) configured: ${agents.map(a => a.name).join(', ')}`);
  
+  // Validate agent names are unique
+  const agentNames = agents.map(a => a.name);
+  const duplicateAgentName = agentNames.find((n, i) => agentNames.indexOf(n) !== i);
+  if (duplicateAgentName) {
+    log.error(`Multiple agents share the same name: "${duplicateAgentName}". Each agent must have a unique name.`);
+    process.exit(1);
+  }
+
+  // Validate no two agents share the same turnLogFile
+  const turnLogFilePaths = agents
+    .map(a => (a.features?.logging ?? yamlConfig.features?.logging)?.turnLogFile)
+    .filter((p): p is string => !!p)
+    .map(p => resolve(p));
+  const duplicateTurnLog = turnLogFilePaths.find((p, i) => turnLogFilePaths.indexOf(p) !== i);
+  if (duplicateTurnLog) {
+    log.error(`Multiple agents share the same turnLogFile: "${duplicateTurnLog}". Each agent must use a unique log file path.`);
+    process.exit(1);
+  }
+
  // Validate at least one agent has channels
  const totalChannels = agents.reduce((sum, a) => sum + Object.keys(a.channels).length, 0);
  if (totalChannels === 0) {
@@ -351,6 +370,7 @@ async function main() {
      maxSessions: agentConfig.conversations?.maxSessions,
      reuseSession: agentConfig.conversations?.reuseSession,
      redaction: agentConfig.security?.redaction,
+      logging: agentConfig.features?.logging ?? yamlConfig.features?.logging,
      cronStorePath,
      skills: {
        cronEnabled: agentConfig.features?.cron ?? globalConfig.cronEnabled,
@@ -530,11 +550,17 @@ async function main() {
  const apiPort = parseInt(process.env.PORT || '8080', 10);
  const apiHost = process.env.API_HOST || (isContainerDeploy ? '0.0.0.0' : undefined); // Container platforms need 0.0.0.0 for health checks
  const apiCorsOrigin = process.env.API_CORS_ORIGIN; // undefined = same-origin only
+  const turnLogFiles: Record<string, string> = {};
+  for (const a of agents) {
+    const logging = a.features?.logging ?? yamlConfig.features?.logging;
+    if (logging?.turnLogFile) turnLogFiles[a.name] = logging.turnLogFile;
+  }
  const apiServer = createApiServer(gateway, {
    port: apiPort,
    apiKey: apiKey,
    host: apiHost,
    corsOrigin: apiCorsOrigin,
+    turnLogFiles: Object.keys(turnLogFiles).length > 0 ? turnLogFiles : undefined,
    stores: agentStores,
    agentChannels: agentChannelMap,
    sessionInvalidators,