diff --git a/src/gateway/server-chat.ts b/src/gateway/server-chat.ts
index 330a0bcae..ea2220438 100644
--- a/src/gateway/server-chat.ts
+++ b/src/gateway/server-chat.ts
@@ -1,10 +1,18 @@
 import { normalizeVerboseLevel } from "../auto-reply/thinking.js";
 import { loadConfig } from "../config/config.js";
 import { type AgentEventPayload, getAgentRunContext } from "../infra/agent-events.js";
+import { isTruthyEnvValue } from "../infra/env.js";
 import { resolveHeartbeatVisibility } from "../infra/heartbeat-visibility.js";
 import { loadSessionEntry } from "./session-utils.js";
 import { formatForLog } from "./ws-log.js";
 
+const debugChatEnabled = isTruthyEnvValue(process.env.CLAWDBOT_DEBUG_CHAT);
+const debugChat = (message: string) => {
+  if (debugChatEnabled) {
+    console.log(`[DEBUG] ${message}`);
+  }
+};
+
 /**
  * Check if webchat broadcasts should be suppressed for heartbeat runs.
  * Returns true if the run is a heartbeat and showOk is false.
@@ -134,14 +142,14 @@ export function createAgentEventHandler({
   clearAgentRunContext,
 }: AgentEventHandlerOptions) {
   const emitChatDelta = (sessionKey: string, clientRunId: string, seq: number, text: string) => {
-    console.log(
-      `[DEBUG] emitChatDelta: sessionKey=${sessionKey} runId=${clientRunId} textLen=${text.length}`,
+    debugChat(
+      `emitChatDelta: sessionKey=${sessionKey} runId=${clientRunId} textLen=${text.length}`,
     );
     chatRunState.buffers.set(clientRunId, text);
     const now = Date.now();
     const last = chatRunState.deltaSentAt.get(clientRunId) ?? 0;
     if (now - last < 150) {
-      console.log(`[DEBUG] emitChatDelta: throttled (${now - last}ms < 150ms)`);
+      debugChat(`emitChatDelta: throttled (${now - last}ms < 150ms)`);
       return;
     }
     chatRunState.deltaSentAt.set(clientRunId, now);
@@ -158,12 +166,12 @@ export function createAgentEventHandler({
     };
     // Suppress webchat broadcast for heartbeat runs when showOk is false
     const suppressed = shouldSuppressHeartbeatBroadcast(clientRunId);
-    console.log(`[DEBUG] emitChatDelta: heartbeatSuppressed=${suppressed}`);
+    debugChat(`emitChatDelta: heartbeatSuppressed=${suppressed}`);
     if (!suppressed) {
-      console.log(`[DEBUG] emitChatDelta: calling broadcast("chat")`);
+      debugChat(`emitChatDelta: calling broadcast("chat")`);
       broadcast("chat", payload, { dropIfSlow: true });
     }
-    console.log(`[DEBUG] emitChatDelta: calling nodeSendToSession`);
+    debugChat(`emitChatDelta: calling nodeSendToSession`);
     nodeSendToSession(sessionKey, "chat", payload);
   };
 
@@ -226,11 +234,11 @@ export function createAgentEventHandler({
   };
 
   return (evt: AgentEventPayload) => {
-    console.log(`[DEBUG] agent event: runId=${evt.runId} stream=${evt.stream} seq=${evt.seq}`);
+    debugChat(`agent event: runId=${evt.runId} stream=${evt.stream} seq=${evt.seq}`);
     const chatLink = chatRunState.registry.peek(evt.runId);
-    console.log(`[DEBUG] chatLink: ${chatLink ? JSON.stringify(chatLink) : "null"}`);
+    debugChat(`chatLink: ${chatLink ? JSON.stringify(chatLink) : "null"}`);
     const sessionKey = chatLink?.sessionKey ?? resolveSessionKeyForRun(evt.runId);
-    console.log(`[DEBUG] sessionKey: ${sessionKey}`);
+    debugChat(`sessionKey: ${sessionKey}`);
     const clientRunId = chatLink?.clientRunId ?? evt.runId;
     const isAborted =
       chatRunState.abortedRuns.has(clientRunId) || chatRunState.abortedRuns.has(evt.runId);
@@ -262,11 +270,11 @@ export function createAgentEventHandler({
 
     if (sessionKey) {
       nodeSendToSession(sessionKey, "agent", agentPayload);
-      console.log(
-        `[DEBUG] checking emitChatDelta: isAborted=${isAborted} stream=${evt.stream} hasText=${typeof evt.data?.text === "string"} text="${String(evt.data?.text ?? "").slice(0, 50)}..."`,
+      debugChat(
+        `checking emitChatDelta: isAborted=${isAborted} stream=${evt.stream} hasText=${typeof evt.data?.text === "string"} text="${String(evt.data?.text ?? "").slice(0, 50)}..."`,
       );
       if (!isAborted && evt.stream === "assistant" && typeof evt.data?.text === "string") {
-        console.log(`[DEBUG] calling emitChatDelta`);
+        debugChat(`calling emitChatDelta`);
         emitChatDelta(sessionKey, clientRunId, evt.seq, evt.data.text);
       } else if (!isAborted && (lifecyclePhase === "end" || lifecyclePhase === "error")) {
         if (chatLink) {
diff --git a/src/gateway/server-methods/chat.ts b/src/gateway/server-methods/chat.ts
index a43ff34b3..c5d711f60 100644
--- a/src/gateway/server-methods/chat.ts
+++ b/src/gateway/server-methods/chat.ts
@@ -1,6 +1,14 @@
 import { randomUUID } from "node:crypto";
 import fs from "node:fs";
 import path from "node:path";
+import { isTruthyEnvValue } from "../../infra/env.js";
+
+const debugChatEnabled = isTruthyEnvValue(process.env.CLAWDBOT_DEBUG_CHAT);
+const debugChat = (message: string) => {
+  if (debugChatEnabled) {
+    console.log(`[DEBUG] ${message}`);
+  }
+};
 
 import { CURRENT_SESSION_VERSION } from "@mariozechner/pi-coding-agent";
 import { resolveSessionAgentId } from "../../agents/agent-scope.js";
@@ -200,8 +208,12 @@ export const chatHandlers: GatewayRequestHandlers = {
     };
     const { cfg, storePath, entry } = loadSessionEntry(sessionKey);
     const sessionId = entry?.sessionId;
+    debugChat(
+      `chat.history: sessionKey="${sessionKey}" sessionId="${sessionId}" storePath="${storePath}" hasEntry=${!!entry}`,
+    );
     const rawMessages =
       sessionId && storePath ? readSessionMessages(sessionId, storePath, entry?.sessionFile) : [];
+    debugChat(`chat.history: rawMessages.length=${rawMessages.length}`);
     const hardMax = 1000;
     const defaultLimit = 200;
     const requested = typeof limit === "number" ? limit : defaultLimit;
diff --git a/ui/src/ui/app-gateway.ts b/ui/src/ui/app-gateway.ts
index 662fbb94e..6f607edff 100644
--- a/ui/src/ui/app-gateway.ts
+++ b/ui/src/ui/app-gateway.ts
@@ -10,6 +10,7 @@ import type { Tab } from "./navigation";
 import type { UiSettings } from "./storage";
 import { handleAgentEvent, resetToolStream, type AgentEventPayload } from "./app-tool-stream";
 import { flushChatQueueForEvent } from "./app-chat";
+import { debug } from "./debug";
 import {
   applySettings,
   loadCron,
@@ -81,10 +82,10 @@ function normalizeSessionKeyForDefaults(
 }
 
 function applySessionDefaults(host: GatewayHost, defaults?: SessionDefaultsSnapshot) {
-  console.log(`[DEBUG UI] applySessionDefaults: defaults=${JSON.stringify(defaults)}`);
-  console.log(`[DEBUG UI] applySessionDefaults: host.sessionKey="${host.sessionKey}" host.settings.sessionKey="${host.settings.sessionKey}"`);
+  debug(`applySessionDefaults: defaults=${JSON.stringify(defaults)}`);
+  debug(`applySessionDefaults: host.sessionKey="${host.sessionKey}" host.settings.sessionKey="${host.settings.sessionKey}"`);
   if (!defaults?.mainSessionKey) {
-    console.log(`[DEBUG UI] applySessionDefaults: no mainSessionKey, returning early`);
+    debug(`applySessionDefaults: no mainSessionKey, returning early`);
     return;
   }
   const resolvedSessionKey = normalizeSessionKeyForDefaults(host.sessionKey, defaults);
@@ -96,7 +97,7 @@ function applySessionDefaults(host: GatewayHost, defaults?: SessionDefaultsSnaps
     host.settings.lastActiveSessionKey,
     defaults,
   );
-  console.log(`[DEBUG UI] applySessionDefaults: resolved="${resolvedSessionKey}" settingsResolved="${resolvedSettingsSessionKey}"`);
+  debug(`applySessionDefaults: resolved="${resolvedSessionKey}" settingsResolved="${resolvedSettingsSessionKey}"`);
   const nextSessionKey = resolvedSessionKey || resolvedSettingsSessionKey || host.sessionKey;
   const nextSettings = {
     ...host.settings,
@@ -106,9 +107,9 @@ function applySessionDefaults(host: GatewayHost, defaults?: SessionDefaultsSnaps
   const shouldUpdateSettings =
     nextSettings.sessionKey !== host.settings.sessionKey ||
     nextSettings.lastActiveSessionKey !== host.settings.lastActiveSessionKey;
-  console.log(`[DEBUG UI] applySessionDefaults: nextSessionKey="${nextSessionKey}" shouldUpdate=${shouldUpdateSettings}`);
+  debug(`applySessionDefaults: nextSessionKey="${nextSessionKey}" shouldUpdate=${shouldUpdateSettings}`);
   if (nextSessionKey !== host.sessionKey) {
-    console.log(`[DEBUG UI] applySessionDefaults: updating host.sessionKey from "${host.sessionKey}" to "${nextSessionKey}"`);
+    debug(`applySessionDefaults: updating host.sessionKey from "${host.sessionKey}" to "${nextSessionKey}"`);
     host.sessionKey = nextSessionKey;
   }
   if (shouldUpdateSettings) {
@@ -197,13 +198,18 @@ function handleGatewayEventUnsafe(host: GatewayHost, evt: GatewayEventFrame) {
       );
     }
     const state = handleChatEvent(host as unknown as MoltbotApp, payload);
+    // Force Lit to re-render after chatStream mutation
+    if (state === "delta") {
+      (host as unknown as MoltbotApp).requestUpdate();
+    }
     if (state === "final" || state === "error" || state === "aborted") {
       resetToolStream(host as unknown as Parameters<typeof resetToolStream>[0]);
       void flushChatQueueForEvent(
         host as unknown as Parameters<typeof flushChatQueueForEvent>[0],
       );
     }
-    if (state === "final") void loadChatHistory(host as unknown as MoltbotApp);
+    // Don't call loadChatHistory - we already added the message from the final payload
+    // loadChatHistory returns 0 messages because the session transcript file doesn't exist
     return;
   }
 
diff --git a/ui/src/ui/app-render.ts b/ui/src/ui/app-render.ts
index 422af6863..daa948a72 100644
--- a/ui/src/ui/app-render.ts
+++ b/ui/src/ui/app-render.ts
@@ -3,6 +3,7 @@ import { html, nothing } from "lit";
 import type { GatewayBrowserClient, GatewayHelloOk } from "./gateway";
 import type { AppViewState } from "./app-view-state";
 import { parseAgentSessionKey } from "../../../src/routing/session-key.js";
+import { debug } from "./debug";
 import {
   TAB_GROUPS,
   iconForTab,
@@ -427,7 +428,7 @@ export function renderApp(state: AppViewState) {
           : nothing}
 
         ${state.tab === "chat"
-          ? renderChat({
+          ? (() => { debug(`RENDER chatStream="${state.chatStream?.slice(0, 50) ?? "null"}..." chatRunId="${state.chatRunId}" messages=${state.chatMessages?.length ?? 0}`); return renderChat({
               sessionKey: state.sessionKey,
               onSessionKeyChange: (next) => {
                 state.sessionKey = next;
@@ -497,7 +498,7 @@ export function renderApp(state: AppViewState) {
               onSplitRatioChange: (ratio: number) => state.handleSplitRatioChange(ratio),
               assistantName: state.assistantName,
               assistantAvatar: state.assistantAvatar,
-            })
+            }); })()
           : nothing}
 
         ${state.tab === "config"
diff --git a/ui/src/ui/app-settings.ts b/ui/src/ui/app-settings.ts
index 7e3ab29cf..fffc0bd3f 100644
--- a/ui/src/ui/app-settings.ts
+++ b/ui/src/ui/app-settings.ts
@@ -16,6 +16,7 @@ import { startThemeTransition, type ThemeTransitionContext } from "./theme-trans
 import { scheduleChatScroll, scheduleLogsScroll } from "./app-scroll";
 import { startLogsPolling, stopLogsPolling, startDebugPolling, stopDebugPolling } from "./app-polling";
 import { refreshChat } from "./app-chat";
+import { setDebugEnabled } from "./debug";
 import type { MoltbotApp } from "./app";
 
 type SettingsHost = {
@@ -43,6 +44,7 @@ export function applySettings(host: SettingsHost, next: UiSettings) {
   };
   host.settings = normalized;
   saveSettings(normalized);
+  setDebugEnabled(normalized.debugLogs);
   if (next.theme !== host.theme) {
     host.theme = next.theme;
     applyResolvedTheme(host, resolveTheme(next.theme));
diff --git a/ui/src/ui/controllers/chat.ts b/ui/src/ui/controllers/chat.ts
index 9432feac7..0420493dc 100644
--- a/ui/src/ui/controllers/chat.ts
+++ b/ui/src/ui/controllers/chat.ts
@@ -2,6 +2,7 @@ import { extractText } from "../chat/message-extract";
 import type { GatewayBrowserClient } from "../gateway";
 import { generateUUID } from "../uuid";
 import type { ChatAttachment } from "../ui-types";
+import { debug } from "../debug";
 
 export type ChatState = {
   client: GatewayBrowserClient | null;
@@ -28,7 +29,11 @@ export type ChatEventPayload = {
 };
 
 export async function loadChatHistory(state: ChatState) {
-  if (!state.client || !state.connected) return;
+  debug(`loadChatHistory: starting, sessionKey="${state.sessionKey}"`);
+  if (!state.client || !state.connected) {
+    debug(`loadChatHistory: aborted - not connected`);
+    return;
+  }
   state.chatLoading = true;
   state.lastError = null;
   try {
@@ -36,9 +41,11 @@ export async function loadChatHistory(state: ChatState) {
       sessionKey: state.sessionKey,
       limit: 200,
     })) as { messages?: unknown[]; thinkingLevel?: string | null };
+    debug(`loadChatHistory: got ${res.messages?.length ?? 0} messages`);
     state.chatMessages = Array.isArray(res.messages) ? res.messages : [];
     state.chatThinkingLevel = res.thinkingLevel ?? null;
   } catch (err) {
+    debug(`loadChatHistory: error - ${err}`);
     state.lastError = String(err);
   } finally {
     state.chatLoading = false;
@@ -159,10 +166,11 @@ export function handleChatEvent(
   state: ChatState,
   payload?: ChatEventPayload,
 ) {
-  console.log(`[DEBUG UI] handleChatEvent: payload.sessionKey="${payload?.sessionKey}" state.sessionKey="${state.sessionKey}"`);
+  debug(`handleChatEvent: payload.sessionKey="${payload?.sessionKey}" state.sessionKey="${state.sessionKey}"`);
+  debug(`handleChatEvent: payload.runId="${payload?.runId}" state.chatRunId="${state.chatRunId}" payload.state="${payload?.state}"`);
   if (!payload) return null;
   if (payload.sessionKey !== state.sessionKey) {
-    console.log(`[DEBUG UI] handleChatEvent: sessionKey mismatch, ignoring event`);
+    debug(`handleChatEvent: sessionKey mismatch, ignoring event`);
     return null;
   }
 
@@ -173,19 +181,27 @@ export function handleChatEvent(
     state.chatRunId &&
     payload.runId !== state.chatRunId
   ) {
+    debug(`handleChatEvent: runId mismatch (payload=${payload.runId} state=${state.chatRunId}), dropping non-final`);
     if (payload.state === "final") return "final";
     return null;
   }
 
   if (payload.state === "delta") {
     const next = extractText(payload.message);
+    debug(`handleChatEvent: delta event, extracted text="${next?.slice(0, 50)}..."`);
     if (typeof next === "string") {
       const current = state.chatStream ?? "";
       if (!current || next.length >= current.length) {
+        debug(`handleChatEvent: updating chatStream (len ${current.length} -> ${next.length})`);
         state.chatStream = next;
       }
     }
   } else if (payload.state === "final") {
+    // Add the final message to chatMessages if present
+    if (payload.message) {
+      debug(`handleChatEvent: final with message, adding to chatMessages`);
+      state.chatMessages = [...state.chatMessages, payload.message];
+    }
     state.chatStream = null;
     state.chatRunId = null;
     state.chatStreamStartedAt = null;
diff --git a/ui/src/ui/debug.ts b/ui/src/ui/debug.ts
new file mode 100644
index 000000000..ad85b64b4
--- /dev/null
+++ b/ui/src/ui/debug.ts
@@ -0,0 +1,38 @@
+/**
+ * Debug logging utility for the UI.
+ * Controlled by the debugLogs setting in UI settings.
+ * Can also be enabled via:
+ *   - localStorage.setItem('moltbot-ui-debug', 'true')
+ *   - window.MOLTBOT_UI_DEBUG = true
+ */
+
+declare global {
+  interface Window {
+    MOLTBOT_UI_DEBUG?: boolean;
+  }
+}
+
+let debugEnabled = false;
+
+export function setDebugEnabled(enabled: boolean): void {
+  debugEnabled = enabled;
+}
+
+export function isDebugEnabled(): boolean {
+  if (debugEnabled) return true;
+  if (typeof window !== "undefined") {
+    if (window.MOLTBOT_UI_DEBUG) return true;
+    try {
+      return localStorage.getItem("moltbot-ui-debug") === "true";
+    } catch {
+      return false;
+    }
+  }
+  return false;
+}
+
+export function debug(message: string, ...args: unknown[]): void {
+  if (isDebugEnabled()) {
+    console.log(`[DEBUG UI] ${message}`, ...args);
+  }
+}
diff --git a/ui/src/ui/storage.ts b/ui/src/ui/storage.ts
index 4b1836bfb..c0759287b 100644
--- a/ui/src/ui/storage.ts
+++ b/ui/src/ui/storage.ts
@@ -13,6 +13,7 @@ export type UiSettings = {
   splitRatio: number; // Sidebar split ratio (0.4 to 0.7, default 0.6)
   navCollapsed: boolean; // Collapsible sidebar state
   navGroupsCollapsed: Record<string, boolean>; // Which nav groups are collapsed
+  debugLogs: boolean; // Enable verbose debug logging in browser console
 };
 
 export function loadSettings(): UiSettings {
@@ -32,6 +33,7 @@ export function loadSettings(): UiSettings {
     splitRatio: 0.6,
     navCollapsed: false,
     navGroupsCollapsed: {},
+    debugLogs: false,
   };
 
   try {
@@ -84,6 +86,10 @@ export function loadSettings(): UiSettings {
         parsed.navGroupsCollapsed !== null
           ? parsed.navGroupsCollapsed
           : defaults.navGroupsCollapsed,
+      debugLogs:
+        typeof parsed.debugLogs === "boolean"
+          ? parsed.debugLogs
+          : defaults.debugLogs,
     };
   } catch {
     return defaults;