diff --git a/src/main/ipc/teams.ts b/src/main/ipc/teams.ts
index 39760009..8f8c1fde 100644
--- a/src/main/ipc/teams.ts
+++ b/src/main/ipc/teams.ts
@@ -36,6 +36,7 @@ import {
   TEAM_GET_TASK_EXACT_LOG_DETAIL,
   TEAM_GET_TASK_EXACT_LOG_SUMMARIES,
   TEAM_GET_TASK_LOG_STREAM,
+  TEAM_GET_TASK_LOG_STREAM_SUMMARY,
   TEAM_KILL_PROCESS,
   TEAM_LAUNCH,
   TEAM_LEAD_ACTIVITY,
@@ -156,6 +157,7 @@ import type {
   BoardTaskExactLogDetailResult,
   BoardTaskExactLogSummariesResponse,
   BoardTaskLogStreamResponse,
+  BoardTaskLogStreamSummary,
   CreateTaskRequest,
   EffortLevel,
   GlobalTask,
@@ -562,6 +564,7 @@ export function registerTeamHandlers(ipcMain: IpcMain): void {
   ipcMain.handle(TEAM_GET_LOGS_FOR_TASK, handleGetLogsForTask);
   ipcMain.handle(TEAM_GET_TASK_ACTIVITY, handleGetTaskActivity);
   ipcMain.handle(TEAM_GET_TASK_ACTIVITY_DETAIL, handleGetTaskActivityDetail);
+  ipcMain.handle(TEAM_GET_TASK_LOG_STREAM_SUMMARY, handleGetTaskLogStreamSummary);
   ipcMain.handle(TEAM_GET_TASK_LOG_STREAM, handleGetTaskLogStream);
   ipcMain.handle(TEAM_GET_TASK_EXACT_LOG_SUMMARIES, handleGetTaskExactLogSummaries);
   ipcMain.handle(TEAM_GET_TASK_EXACT_LOG_DETAIL, handleGetTaskExactLogDetail);
@@ -638,6 +641,7 @@ export function removeTeamHandlers(ipcMain: IpcMain): void {
   ipcMain.removeHandler(TEAM_GET_LOGS_FOR_TASK);
   ipcMain.removeHandler(TEAM_GET_TASK_ACTIVITY);
   ipcMain.removeHandler(TEAM_GET_TASK_ACTIVITY_DETAIL);
+  ipcMain.removeHandler(TEAM_GET_TASK_LOG_STREAM_SUMMARY);
   ipcMain.removeHandler(TEAM_GET_TASK_LOG_STREAM);
   ipcMain.removeHandler(TEAM_GET_TASK_EXACT_LOG_SUMMARIES);
   ipcMain.removeHandler(TEAM_GET_TASK_EXACT_LOG_DETAIL);
@@ -2752,6 +2756,24 @@ async function handleGetTaskLogStream(
   );
 }
 
+async function handleGetTaskLogStreamSummary(
+  _event: IpcMainInvokeEvent,
+  teamName: unknown,
+  taskId: unknown
+): Promise<IpcResult<BoardTaskLogStreamSummary>> {
+  const vTeam = validateTeamName(teamName);
+  if (!vTeam.valid) {
+    return { success: false, error: vTeam.error ?? 'Invalid teamName' };
+  }
+  const vTask = validateTaskId(taskId);
+  if (!vTask.valid) {
+    return { success: false, error: vTask.error ?? 'Invalid taskId' };
+  }
+  return wrapTeamHandler('getTaskLogStreamSummary', () =>
+    getBoardTaskLogStreamService().getTaskLogStreamSummary(vTeam.value!, vTask.value!)
+  );
+}
+
 async function handleGetTaskExactLogSummaries(
   _event: IpcMainInvokeEvent,
   teamName: unknown,
diff --git a/src/main/services/team/TeamProvisioningService.ts b/src/main/services/team/TeamProvisioningService.ts
index c6b0d285..9e64bbae 100644
--- a/src/main/services/team/TeamProvisioningService.ts
+++ b/src/main/services/team/TeamProvisioningService.ts
@@ -98,6 +98,7 @@ import {
 } from './idleNotificationMainProcessSemantics';
 import { withInboxLock } from './inboxLock';
 import { getEffectiveInboxMessageId } from './inboxMessageIdentity';
+import { buildProgressAssistantOutput, buildProgressLogsTail } from './progressPayload';
 import { resolveDesktopTeammateModeDecision } from './runtimeTeammateMode';
 import {
   choosePreferredLaunchSnapshot,
@@ -206,7 +207,13 @@ const VERIFY_TIMEOUT_MS = 15_000;
 const VERIFY_POLL_MS = 500;
 const STDERR_RING_LIMIT = 64 * 1024;
 const STDOUT_RING_LIMIT = 64 * 1024;
-const LOG_PROGRESS_THROTTLE_MS = 300;
+// Progress emissions fan out the latest CLI tail + assistant output to the
+// renderer over IPC. Under load the previous 300ms cadence combined with an
+// unbounded payload (see `emitLogsProgress`) caused renderer OOM crashes
+// (≈3 full-history serializations per second, each holding thousands of
+// lines). The tail cap in `emitLogsProgress` bounds each payload; we also
+// slow the cadence to ~1s so Zustand can keep up on large teams.
+const LOG_PROGRESS_THROTTLE_MS = 1000;
 const UI_LOGS_TAIL_LIMIT = 128 * 1024;
 const PROBE_CACHE_TTL_MS = 36 * 60 * 60 * 1000;
 const PREFLIGHT_BINARY_TIMEOUT_MS = 8000;
@@ -2223,10 +2230,12 @@ function updateProgress(
     'pid' | 'error' | 'warnings' | 'cliLogsTail' | 'configReady' | 'messageSeverity'
   >
 ): TeamProvisioningProgress {
+  // Cap assistant output on every progress tick. `updateProgress` is invoked
+  // from ~20 event-driven sites (auth retries, stall warnings, spawn events),
+  // and an unbounded `provisioningOutputParts.join` was part of the same OOM
+  // class that `emitLogsProgress` already guards against.
   const assistantOutput =
-    run.provisioningOutputParts.length > 0
-      ? run.provisioningOutputParts.join('\n\n')
-      : run.progress.assistantOutput;
+    buildProgressAssistantOutput(run.provisioningOutputParts) ?? run.progress.assistantOutput;
   run.progress = {
     ...run.progress,
     state,
@@ -2357,10 +2366,22 @@ function extractCliLogsFromRun(run: ProvisioningRun): string | undefined {
   return extractLogsTail(run.stdoutBuffer, run.stderrBuffer);
 }
 
+/**
+ * Emit a throttled progress update for the renderer. Payloads are capped to a
+ * tail window so that the hot emission path (called every LOG_PROGRESS_THROTTLE_MS
+ * under streaming output) cannot accumulate into multi-megabyte IPC messages
+ * that would OOM the renderer's Zustand state. The full history stays in
+ * `run.claudeLogLines` / `run.provisioningOutputParts` for diagnostics and
+ * one-shot completion emissions that intentionally use `extractCliLogsFromRun`.
+ */
 function emitLogsProgress(run: ProvisioningRun): void {
-  const logsTail = extractCliLogsFromRun(run);
-  const assistantOutput =
-    run.provisioningOutputParts.length > 0 ? run.provisioningOutputParts.join('\n\n') : undefined;
+  // Prefer the line-buffered history (already chronological with [stdout]/[stderr]
+  // markers) and fall back to the legacy ring-buffer tail only when no lines
+  // have been captured yet (early in provisioning).
+  const logsTail =
+    buildProgressLogsTail(run.claudeLogLines) ??
+    extractLogsTail(run.stdoutBuffer, run.stderrBuffer);
+  const assistantOutput = buildProgressAssistantOutput(run.provisioningOutputParts);
 
   if (!logsTail && !assistantOutput) {
     return;
@@ -5113,7 +5134,9 @@ export class TeamProvisioningService {
             message: this.buildStallProgressMessage(silenceSec, elapsed),
             messageSeverity: 'warning' as const,
           }),
-          assistantOutput: run.provisioningOutputParts.join('\n\n'),
+          assistantOutput:
+            buildProgressAssistantOutput(run.provisioningOutputParts) ??
+            run.progress.assistantOutput,
         };
         run.onProgress(run.progress);
       } catch (err) {
@@ -9649,7 +9672,9 @@ export class TeamProvisioningService {
             updatedAt: nowIso(),
             message: retryText,
             messageSeverity: 'error' as const,
-            assistantOutput: run.provisioningOutputParts.join('\n\n'),
+            assistantOutput:
+              buildProgressAssistantOutput(run.provisioningOutputParts) ??
+              run.progress.assistantOutput,
           };
           run.onProgress(run.progress);
         }
diff --git a/src/main/services/team/progressPayload.ts b/src/main/services/team/progressPayload.ts
new file mode 100644
index 00000000..c2f4fce7
--- /dev/null
+++ b/src/main/services/team/progressPayload.ts
@@ -0,0 +1,52 @@
+/**
+ * Helpers that shape provisioning progress payloads before they are emitted
+ * to the renderer over IPC.
+ *
+ * Rationale: the renderer only renders a small "tail" preview of CLI logs
+ * and assistant output in ProvisioningProgressBlock / CliLogsRichView. Sending
+ * the full accumulated history on every throttled progress tick (≈ every
+ * second under load) serialized a multi-megabyte string over IPC and forced
+ * Zustand to produce a new immutable state object — which triggered renderer
+ * V8 OOM crashes for users with long-running teams. These helpers keep the
+ * hot emission path bounded while leaving the full history in-process for
+ * diagnostics and completion-time reports.
+ */
+
+export const PROGRESS_LOG_TAIL_LINES = 200;
+export const PROGRESS_OUTPUT_TAIL_PARTS = 20;
+
+/**
+ * Return the trailing `maxLines` of a line-buffered CLI log, joined with "\n"
+ * and trimmed. Returns `undefined` when the tail is empty so callers can
+ * skip emitting a noop update.
+ */
+export function buildProgressLogsTail(
+  lines: readonly string[],
+  maxLines: number = PROGRESS_LOG_TAIL_LINES
+): string | undefined {
+  if (lines.length === 0) {
+    return undefined;
+  }
+  const effectiveMax = Math.max(1, maxLines);
+  const tail = lines.length > effectiveMax ? lines.slice(-effectiveMax) : lines;
+  const joined = tail.join('\n').trim();
+  return joined.length === 0 ? undefined : joined;
+}
+
+/**
+ * Return the trailing `maxParts` of assistant output parts joined with a
+ * blank line, matching the renderer's rendering contract. Returns `undefined`
+ * when no parts are available.
+ */
+export function buildProgressAssistantOutput(
+  parts: readonly string[],
+  maxParts: number = PROGRESS_OUTPUT_TAIL_PARTS
+): string | undefined {
+  if (parts.length === 0) {
+    return undefined;
+  }
+  const effectiveMax = Math.max(1, maxParts);
+  const tail = parts.length > effectiveMax ? parts.slice(-effectiveMax) : parts;
+  const joined = tail.join('\n\n');
+  return joined.trim().length === 0 ? undefined : joined;
+}
diff --git a/src/main/services/team/taskLogs/stream/BoardTaskLogStreamService.ts b/src/main/services/team/taskLogs/stream/BoardTaskLogStreamService.ts
index 9549c819..3e0a3cec 100644
--- a/src/main/services/team/taskLogs/stream/BoardTaskLogStreamService.ts
+++ b/src/main/services/team/taskLogs/stream/BoardTaskLogStreamService.ts
@@ -19,6 +19,7 @@ import type {
   BoardTaskLogParticipant,
   BoardTaskLogSegment,
   BoardTaskLogStreamResponse,
+  BoardTaskLogStreamSummary,
   TeamTask,
 } from '@shared/types';
 
@@ -47,6 +48,11 @@ interface TimeWindow {
   endMs: number | null;
 }
 
+interface StreamLayout {
+  participants: BoardTaskLogParticipant[];
+  visibleSlices: StreamSlice[];
+}
+
 const BOARD_MCP_TOOL_PREFIXES = ['mcp__agent-teams__', 'mcp__agent_teams__'] as const;
 const INFERRED_WINDOW_GRACE_BEFORE_MS = 30_000;
 const INFERRED_WINDOW_GRACE_AFTER_MS = 15_000;
@@ -61,6 +67,12 @@ function emptyResponse(): BoardTaskLogStreamResponse {
   };
 }
 
+function emptySummary(): BoardTaskLogStreamSummary {
+  return {
+    segmentCount: 0,
+  };
+}
+
 function normalizeMemberName(value: string): string {
   return value.trim().toLowerCase();
 }
@@ -1018,6 +1030,46 @@ function compareSlices(left: StreamSlice, right: StreamSlice): number {
   return left.id.localeCompare(right.id);
 }
 
+function buildOrderedParticipants(visibleSlices: StreamSlice[]): BoardTaskLogParticipant[] {
+  const participantsByKey = new Map<string, BoardTaskLogParticipant>();
+  const participantOrder: string[] = [];
+
+  for (const slice of visibleSlices) {
+    if (participantsByKey.has(slice.participantKey)) {
+      continue;
+    }
+    participantsByKey.set(
+      slice.participantKey,
+      buildParticipant(slice.actor, slice.participantKey)
+    );
+    participantOrder.push(slice.participantKey);
+  }
+
+  return participantOrder
+    .map((key) => participantsByKey.get(key))
+    .filter((participant): participant is BoardTaskLogParticipant => Boolean(participant))
+    .sort((left, right) => {
+      if (left.isLead && !right.isLead) return 1;
+      if (!left.isLead && right.isLead) return -1;
+      return participantOrder.indexOf(left.key) - participantOrder.indexOf(right.key);
+    });
+}
+
+function countSegmentsFromSlices(visibleSlices: StreamSlice[]): number {
+  if (visibleSlices.length === 0) {
+    return 0;
+  }
+
+  let segmentCount = 1;
+  for (let index = 1; index < visibleSlices.length; index += 1) {
+    if (visibleSlices[index]?.participantKey !== visibleSlices[index - 1]?.participantKey) {
+      segmentCount += 1;
+    }
+  }
+
+  return segmentCount;
+}
+
 export class BoardTaskLogStreamService {
   constructor(
     private readonly recordSource: BoardTaskActivityRecordSource = new BoardTaskActivityRecordSource(),
@@ -1131,14 +1183,20 @@ export class BoardTaskLogStreamService {
     return inferredSlices.sort(compareSlices);
   }
 
-  async getTaskLogStream(teamName: string, taskId: string): Promise<BoardTaskLogStreamResponse> {
+  private async buildStreamLayout(teamName: string, taskId: string): Promise<StreamLayout> {
     if (!isBoardTaskExactLogsReadEnabled()) {
-      return emptyResponse();
+      return {
+        participants: [],
+        visibleSlices: [],
+      };
     }
 
     const records = await this.recordSource.getTaskRecords(teamName, taskId);
     if (records.length === 0) {
-      return emptyResponse();
+      return {
+        participants: [],
+        visibleSlices: [],
+      };
     }
 
     const fileVersionsByPath = await getBoardTaskExactLogFileVersions(
@@ -1154,7 +1212,10 @@ export class BoardTaskLogStreamService {
       .sort(compareCandidates);
 
     if (candidates.length === 0) {
-      return emptyResponse();
+      return {
+        participants: [],
+        visibleSlices: [],
+      };
     }
 
     const parsedMessagesByFile = await this.strictParser.parseFiles(
@@ -1202,7 +1263,10 @@ export class BoardTaskLogStreamService {
     }
 
     if (slices.length === 0) {
-      return emptyResponse();
+      return {
+        participants: [],
+        visibleSlices: [],
+      };
     }
 
     const inferredExecutionSlices = await this.buildInferredExecutionSlices(
@@ -1220,27 +1284,31 @@ export class BoardTaskLogStreamService {
     const visibleSlices =
       namedParticipantSlices.length > 0 ? namedParticipantSlices : deNoisedSlices;
 
-    const participantsByKey = new Map<string, BoardTaskLogParticipant>();
-    const participantOrder: string[] = [];
-    for (const slice of visibleSlices) {
-      if (participantsByKey.has(slice.participantKey)) {
-        continue;
-      }
-      participantsByKey.set(
-        slice.participantKey,
-        buildParticipant(slice.actor, slice.participantKey)
-      );
-      participantOrder.push(slice.participantKey);
+    return {
+      participants: buildOrderedParticipants(visibleSlices),
+      visibleSlices,
+    };
+  }
+
+  async getTaskLogStreamSummary(
+    teamName: string,
+    taskId: string
+  ): Promise<BoardTaskLogStreamSummary> {
+    const layout = await this.buildStreamLayout(teamName, taskId);
+    if (layout.visibleSlices.length === 0) {
+      return emptySummary();
     }
 
-    const orderedParticipants = participantOrder
-      .map((key) => participantsByKey.get(key))
-      .filter((participant): participant is BoardTaskLogParticipant => Boolean(participant))
-      .sort((left, right) => {
-        if (left.isLead && !right.isLead) return 1;
-        if (!left.isLead && right.isLead) return -1;
-        return participantOrder.indexOf(left.key) - participantOrder.indexOf(right.key);
-      });
+    return {
+      segmentCount: countSegmentsFromSlices(layout.visibleSlices),
+    };
+  }
+
+  async getTaskLogStream(teamName: string, taskId: string): Promise<BoardTaskLogStreamResponse> {
+    const layout = await this.buildStreamLayout(teamName, taskId);
+    if (layout.visibleSlices.length === 0) {
+      return emptyResponse();
+    }
 
     const segments: BoardTaskLogSegment[] = [];
     let currentSegmentSlices: StreamSlice[] = [];
@@ -1274,7 +1342,7 @@ export class BoardTaskLogStreamService {
       currentSegmentSlices = [];
     };
 
-    for (const slice of visibleSlices) {
+    for (const slice of layout.visibleSlices) {
       if (
         currentSegmentSlices.length > 0 &&
         currentSegmentSlices[0].participantKey !== slice.participantKey
@@ -1285,11 +1353,11 @@ export class BoardTaskLogStreamService {
     }
     flushSegment();
 
-    const namedParticipants = orderedParticipants.filter((participant) => !participant.isLead);
+    const namedParticipants = layout.participants.filter((participant) => !participant.isLead);
     const defaultFilter = namedParticipants.length === 1 ? namedParticipants[0].key : 'all';
 
     return {
-      participants: orderedParticipants,
+      participants: layout.participants,
       defaultFilter,
       segments,
     };
diff --git a/src/preload/constants/ipcChannels.ts b/src/preload/constants/ipcChannels.ts
index 27d3d0fb..95de628a 100644
--- a/src/preload/constants/ipcChannels.ts
+++ b/src/preload/constants/ipcChannels.ts
@@ -316,6 +316,9 @@ export const TEAM_GET_TASK_ACTIVITY_DETAIL = 'team:getTaskActivityDetail';
 /** Get one task-scoped log stream derived from explicit board-task activity */
 export const TEAM_GET_TASK_LOG_STREAM = 'team:getTaskLogStream';
 
+/** Get lightweight task log stream summary for header badges/live counters */
+export const TEAM_GET_TASK_LOG_STREAM_SUMMARY = 'team:getTaskLogStreamSummary';
+
 /** Get exact task-log summaries derived from explicit board-task activity records */
 export const TEAM_GET_TASK_EXACT_LOG_SUMMARIES = 'team:getTaskExactLogSummaries';
 
diff --git a/src/preload/index.ts b/src/preload/index.ts
index b6b9603e..ac737d09 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -140,6 +140,7 @@ import {
   TEAM_GET_TASK_EXACT_LOG_DETAIL,
   TEAM_GET_TASK_EXACT_LOG_SUMMARIES,
   TEAM_GET_TASK_LOG_STREAM,
+  TEAM_GET_TASK_LOG_STREAM_SUMMARY,
   TEAM_KILL_PROCESS,
   TEAM_LAUNCH,
   TEAM_LEAD_ACTIVITY,
@@ -244,6 +245,7 @@ import type {
   BoardTaskExactLogDetailResult,
   BoardTaskExactLogSummariesResponse,
   BoardTaskLogStreamResponse,
+  BoardTaskLogStreamSummary,
   ChangeStats,
   ClaudeRootFolderSelection,
   ClaudeRootInfo,
@@ -998,6 +1000,13 @@ const electronAPI: ElectronAPI = {
         activityId
       );
     },
+    getTaskLogStreamSummary: async (teamName: string, taskId: string) => {
+      return invokeIpcWithResult<BoardTaskLogStreamSummary>(
+        TEAM_GET_TASK_LOG_STREAM_SUMMARY,
+        teamName,
+        taskId
+      );
+    },
     getTaskLogStream: async (teamName: string, taskId: string) => {
       return invokeIpcWithResult<BoardTaskLogStreamResponse>(
         TEAM_GET_TASK_LOG_STREAM,
diff --git a/src/renderer/api/httpClient.ts b/src/renderer/api/httpClient.ts
index 80c3ee93..7037e29e 100644
--- a/src/renderer/api/httpClient.ts
+++ b/src/renderer/api/httpClient.ts
@@ -14,6 +14,7 @@ import type {
   BoardTaskExactLogDetailResult,
   BoardTaskExactLogSummariesResponse,
   BoardTaskLogStreamResponse,
+  BoardTaskLogStreamSummary,
   ClaudeMdFileInfo,
   ClaudeRootFolderSelection,
   ClaudeRootInfo,
@@ -836,6 +837,10 @@ export class HttpAPIClient implements ElectronAPI {
       console.warn('[HttpAPIClient] getTaskActivityDetail is not available in browser mode');
       return { status: 'missing' };
     },
+    getTaskLogStreamSummary: async (): Promise<BoardTaskLogStreamSummary> => {
+      console.warn('[HttpAPIClient] getTaskLogStreamSummary is not available in browser mode');
+      return { segmentCount: 0 };
+    },
     getTaskLogStream: async (): Promise<BoardTaskLogStreamResponse> => {
       console.warn('[HttpAPIClient] getTaskLogStream is not available in browser mode');
       return {
diff --git a/src/renderer/components/team/dialogs/TaskDetailDialog.tsx b/src/renderer/components/team/dialogs/TaskDetailDialog.tsx
index 3851faef..f89efcc5 100644
--- a/src/renderer/components/team/dialogs/TaskDetailDialog.tsx
+++ b/src/renderer/components/team/dialogs/TaskDetailDialog.tsx
@@ -159,6 +159,7 @@ export const TaskDetailDialog = ({
   const [executionPreviewOnline, setExecutionPreviewOnline] = useState(false);
   const [logsSectionOpen, setLogsSectionOpen] = useState(false);
   const [taskLogActivityActive, setTaskLogActivityActive] = useState(false);
+  const [taskLogStreamCount, setTaskLogStreamCount] = useState<number | undefined>(undefined);
   const [changesSectionOpen, setChangesSectionOpen] = useState(false);
   const [taskChangesFiles, setTaskChangesFiles] = useState<FileChangeSummary[] | null>(null);
   const [taskChangesLoading, setTaskChangesLoading] = useState(false);
@@ -236,6 +237,7 @@ export const TaskDetailDialog = ({
     setExecutionPreviewOnline(false);
     setLogsSectionOpen(false);
     setTaskLogActivityActive(false);
+    setTaskLogStreamCount(undefined);
   }, [open, currentTask?.id]);
 
   const [replyTo, setReplyTo] = useState<{
@@ -1263,6 +1265,7 @@ export const TaskDetailDialog = ({
                 key={`task-logs:${currentTask.id}`}
                 title="Task Logs"
                 icon={<ScrollText size={14} />}
+                badge={taskLogStreamCount}
                 headerExtra={
                   taskLogActivityActive ? (
                     <OngoingIndicator size="sm" title="New task logs arriving" />
@@ -1288,6 +1291,7 @@ export const TaskDetailDialog = ({
                     showLeadPreview={allowLeadExecutionPreview && isLeadOwnedTask}
                     onPreviewOnlineChange={setExecutionPreviewOnline}
                     onTaskLogActivityChange={setTaskLogActivityActive}
+                    onTaskLogCountChange={setTaskLogStreamCount}
                   />
                 </div>
               </CollapsibleTeamSection>
diff --git a/src/renderer/components/team/taskLogs/TaskLogsPanel.tsx b/src/renderer/components/team/taskLogs/TaskLogsPanel.tsx
index 71570643..4c0582ff 100644
--- a/src/renderer/components/team/taskLogs/TaskLogsPanel.tsx
+++ b/src/renderer/components/team/taskLogs/TaskLogsPanel.tsx
@@ -24,9 +24,11 @@ interface TaskLogsPanelProps {
   showLeadPreview?: boolean;
   onPreviewOnlineChange?: (isOnline: boolean) => void;
   onTaskLogActivityChange?: (isActive: boolean) => void;
+  onTaskLogCountChange?: (count: number | undefined) => void;
 }
 
 const TASK_LOG_ACTIVITY_PULSE_MS = 1800;
+const TASK_LOG_COUNT_RELOAD_DEBOUNCE_MS = 350;
 
 export const TaskLogsPanel = ({
   teamName,
@@ -40,6 +42,7 @@ export const TaskLogsPanel = ({
   showLeadPreview = false,
   onPreviewOnlineChange,
   onTaskLogActivityChange,
+  onTaskLogCountChange,
 }: TaskLogsPanelProps): React.JSX.Element => {
   const availableTabs = useMemo<TaskLogsTab[]>(() => {
     const tabs: TaskLogsTab[] = [];
@@ -56,9 +59,13 @@ export const TaskLogsPanel = ({
   const defaultTab = availableTabs[0] ?? 'sessions';
   const [activeTab, setActiveTab] = useState<TaskLogsTab>(defaultTab);
   const [isTaskLogActivityActive, setIsTaskLogActivityActive] = useState(false);
+  const [taskLogSegmentCount, setTaskLogSegmentCount] = useState<number | null>(null);
   const [hasOpenedContent, setHasOpenedContent] = useState(isOpen);
   const pulseTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const countReloadTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const countRequestSeqRef = useRef(0);
   const taskLogTrackingEnabled = task.status === 'in_progress' && availableTabs.includes('stream');
+  const taskLogSummaryEnabled = availableTabs.includes('stream');
 
   useEffect(() => {
     setActiveTab(defaultTab);
@@ -80,14 +87,50 @@ export const TaskLogsPanel = ({
     onTaskLogActivityChange?.(isTaskLogActivityActive);
   }, [isTaskLogActivityActive, onTaskLogActivityChange]);
 
+  useEffect(() => {
+    onTaskLogCountChange?.(
+      taskLogSegmentCount != null && taskLogSegmentCount > 0 ? taskLogSegmentCount : undefined
+    );
+  }, [onTaskLogCountChange, taskLogSegmentCount]);
+
   useEffect(() => {
     if (pulseTimerRef.current) {
       clearTimeout(pulseTimerRef.current);
       pulseTimerRef.current = null;
     }
+    if (countReloadTimerRef.current) {
+      clearTimeout(countReloadTimerRef.current);
+      countReloadTimerRef.current = null;
+    }
+    countRequestSeqRef.current += 1;
     setIsTaskLogActivityActive(false);
+    setTaskLogSegmentCount(null);
   }, [task.id]);
 
+  useEffect(() => {
+    if (!taskLogSummaryEnabled || !api.teams.getTaskLogStreamSummary) {
+      setTaskLogSegmentCount(null);
+      return;
+    }
+
+    const requestSeq = countRequestSeqRef.current + 1;
+    countRequestSeqRef.current = requestSeq;
+
+    void Promise.resolve(api.teams.getTaskLogStreamSummary(teamName, task.id))
+      .then((summary) => {
+        if (countRequestSeqRef.current !== requestSeq) {
+          return;
+        }
+        setTaskLogSegmentCount(summary.segmentCount);
+      })
+      .catch(() => {
+        if (countRequestSeqRef.current !== requestSeq) {
+          return;
+        }
+        setTaskLogSegmentCount((prev) => prev);
+      });
+  }, [task.id, taskLogSummaryEnabled, teamName]);
+
   useEffect(() => {
     if (!taskLogTrackingEnabled || !api.teams.setTaskLogStreamTracking) {
       return;
@@ -107,10 +150,39 @@ export const TaskLogsPanel = ({
         clearTimeout(pulseTimerRef.current);
         pulseTimerRef.current = null;
       }
+      if (countReloadTimerRef.current) {
+        clearTimeout(countReloadTimerRef.current);
+        countReloadTimerRef.current = null;
+      }
       setIsTaskLogActivityActive(false);
       return;
     }
 
+    const scheduleCountReload = (): void => {
+      if (!api.teams.getTaskLogStreamSummary) {
+        return;
+      }
+      if (typeof document !== 'undefined' && document.visibilityState === 'hidden') {
+        return;
+      }
+      if (countReloadTimerRef.current) {
+        clearTimeout(countReloadTimerRef.current);
+      }
+      countReloadTimerRef.current = setTimeout(() => {
+        countReloadTimerRef.current = null;
+        const requestSeq = countRequestSeqRef.current + 1;
+        countRequestSeqRef.current = requestSeq;
+        void Promise.resolve(api.teams.getTaskLogStreamSummary(teamName, task.id))
+          .then((summary) => {
+            if (countRequestSeqRef.current !== requestSeq) {
+              return;
+            }
+            setTaskLogSegmentCount(summary.segmentCount);
+          })
+          .catch(() => undefined);
+      }, TASK_LOG_COUNT_RELOAD_DEBOUNCE_MS);
+    };
+
     const unsubscribe = api.teams.onTeamChange?.((_event, event) => {
       if (
         event.teamName !== teamName ||
@@ -128,13 +200,31 @@ export const TaskLogsPanel = ({
         pulseTimerRef.current = null;
         setIsTaskLogActivityActive(false);
       }, TASK_LOG_ACTIVITY_PULSE_MS);
+      scheduleCountReload();
     });
 
+    const handleVisibilityChange = (): void => {
+      if (document.visibilityState === 'visible') {
+        scheduleCountReload();
+      }
+    };
+
+    if (typeof document !== 'undefined') {
+      document.addEventListener('visibilitychange', handleVisibilityChange);
+    }
+
     return () => {
       if (pulseTimerRef.current) {
         clearTimeout(pulseTimerRef.current);
         pulseTimerRef.current = null;
       }
+      if (countReloadTimerRef.current) {
+        clearTimeout(countReloadTimerRef.current);
+        countReloadTimerRef.current = null;
+      }
+      if (typeof document !== 'undefined') {
+        document.removeEventListener('visibilitychange', handleVisibilityChange);
+      }
       if (typeof unsubscribe === 'function') {
         unsubscribe();
       }
diff --git a/src/shared/types/api.ts b/src/shared/types/api.ts
index d864189b..dc101003 100644
--- a/src/shared/types/api.ts
+++ b/src/shared/types/api.ts
@@ -45,6 +45,7 @@ import type {
   BoardTaskExactLogDetailResult,
   BoardTaskExactLogSummariesResponse,
   BoardTaskLogStreamResponse,
+  BoardTaskLogStreamSummary,
   CreateTaskRequest,
   CrossTeamMessage,
   CrossTeamSendRequest,
@@ -495,6 +496,7 @@ export interface TeamsAPI {
     taskId: string,
     activityId: string
   ) => Promise<BoardTaskActivityDetailResult>;
+  getTaskLogStreamSummary: (teamName: string, taskId: string) => Promise<BoardTaskLogStreamSummary>;
   getTaskLogStream: (teamName: string, taskId: string) => Promise<BoardTaskLogStreamResponse>;
   getTaskExactLogSummaries: (
     teamName: string,
diff --git a/src/shared/types/team.ts b/src/shared/types/team.ts
index a73e24c8..195fc79d 100644
--- a/src/shared/types/team.ts
+++ b/src/shared/types/team.ts
@@ -342,6 +342,10 @@ export interface BoardTaskLogStreamResponse {
   segments: BoardTaskLogSegment[];
 }
 
+export interface BoardTaskLogStreamSummary {
+  segmentCount: number;
+}
+
 export interface TaskComment {
   id: string;
   author: string;
diff --git a/test/main/services/team/BoardTaskLogStreamService.test.ts b/test/main/services/team/BoardTaskLogStreamService.test.ts
index 7c1220ef..18295fa2 100644
--- a/test/main/services/team/BoardTaskLogStreamService.test.ts
+++ b/test/main/services/team/BoardTaskLogStreamService.test.ts
@@ -181,6 +181,63 @@ describe('BoardTaskLogStreamService', () => {
     expect(buildBundleChunks.mock.calls[0]?.[0]).toHaveLength(2);
   });
 
+  it('returns lightweight segment count without building stream chunks', async () => {
+    const tom = {
+      memberName: 'tom',
+      role: 'member' as const,
+      sessionId: 'session-tom',
+      agentId: 'agent-tom',
+      isSidechain: true,
+    };
+    const alice = {
+      memberName: 'alice',
+      role: 'member' as const,
+      sessionId: 'session-alice',
+      agentId: 'agent-alice',
+      isSidechain: true,
+    };
+    const candidates = [
+      makeCandidate('c1', '2026-04-12T16:00:00.000Z', tom, 'tool-1'),
+      makeCandidate('c2', '2026-04-12T16:01:00.000Z', tom, 'tool-2'),
+      makeCandidate('c3', '2026-04-12T16:02:00.000Z', alice, 'tool-3'),
+      makeCandidate('c4', '2026-04-12T16:03:00.000Z', tom, 'tool-4'),
+    ];
+
+    const recordSource = {
+      getTaskRecords: vi.fn(async () => candidates.flatMap((candidate) => candidate.records)),
+    };
+    const summarySelector = {
+      selectSummaries: vi.fn(() => candidates),
+    };
+    const strictParser = {
+      parseFiles: vi.fn(async () => new Map([['/tmp/task.jsonl', []]])),
+    };
+    const detailSelector = {
+      selectDetail: vi.fn(({ candidate }: { candidate: BoardTaskExactLogBundleCandidate }) => ({
+        id: candidate.id,
+        timestamp: candidate.timestamp,
+        actor: candidate.actor,
+        source: candidate.source,
+        records: candidate.records,
+        filteredMessages: [makeMessage(candidate.id, candidate.timestamp, candidate.id)],
+      })),
+    };
+    const buildBundleChunks = vi.fn((messages: ParsedMessage[]) => [{ id: messages[0]?.uuid }]);
+
+    const service = new BoardTaskLogStreamService(
+      recordSource as never,
+      summarySelector as never,
+      strictParser as never,
+      detailSelector as never,
+      { buildBundleChunks } as never,
+    );
+
+    await expect(service.getTaskLogStreamSummary('demo', 'task-a')).resolves.toEqual({
+      segmentCount: 3,
+    });
+    expect(buildBundleChunks).not.toHaveBeenCalled();
+  });
+
   it('merges duplicate message uuids inside one participant segment before chunk building', async () => {
     const tom = {
       memberName: 'tom',
diff --git a/test/main/services/team/progressPayload.test.ts b/test/main/services/team/progressPayload.test.ts
new file mode 100644
index 00000000..8265d24e
--- /dev/null
+++ b/test/main/services/team/progressPayload.test.ts
@@ -0,0 +1,77 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  PROGRESS_LOG_TAIL_LINES,
+  PROGRESS_OUTPUT_TAIL_PARTS,
+  buildProgressAssistantOutput,
+  buildProgressLogsTail,
+} from '../../../../src/main/services/team/progressPayload';
+
+describe('buildProgressLogsTail', () => {
+  it('returns undefined for an empty buffer', () => {
+    expect(buildProgressLogsTail([])).toBeUndefined();
+  });
+
+  it('returns undefined when all lines are whitespace', () => {
+    expect(buildProgressLogsTail(['', '   ', '\t'])).toBeUndefined();
+  });
+
+  it('returns the full buffer joined when below the limit', () => {
+    const lines = ['alpha', 'beta', 'gamma'];
+    expect(buildProgressLogsTail(lines, 10)).toBe('alpha\nbeta\ngamma');
+  });
+
+  it('caps the payload to the last N lines once the limit is exceeded', () => {
+    const lines = Array.from({ length: 1_000 }, (_, i) => `line-${i}`);
+    const result = buildProgressLogsTail(lines, 50);
+    expect(result).toBeDefined();
+    const parts = result!.split('\n');
+    expect(parts).toHaveLength(50);
+    expect(parts[0]).toBe('line-950');
+    expect(parts[parts.length - 1]).toBe('line-999');
+  });
+
+  it('uses the default tail size when the caller does not override it', () => {
+    const lines = Array.from({ length: PROGRESS_LOG_TAIL_LINES + 250 }, (_, i) => `l${i}`);
+    const result = buildProgressLogsTail(lines);
+    expect(result).toBeDefined();
+    expect(result!.split('\n')).toHaveLength(PROGRESS_LOG_TAIL_LINES);
+  });
+
+  it('keeps payload size bounded for pathological inputs (50k lines)', () => {
+    const lines = Array.from({ length: 50_000 }, (_, i) => `line-${i}`);
+    const result = buildProgressLogsTail(lines);
+    expect(result).toBeDefined();
+    // Regression guard: a full-buffer join of 50k synthetic lines would exceed
+    // 400k chars. The tail must stay well below that.
+    expect(result!.length).toBeLessThan(50_000);
+  });
+
+  it('coerces non-positive limits to at least one line', () => {
+    expect(buildProgressLogsTail(['a', 'b', 'c'], 0)).toBe('c');
+    expect(buildProgressLogsTail(['a', 'b', 'c'], -5)).toBe('c');
+  });
+});
+
+describe('buildProgressAssistantOutput', () => {
+  it('returns undefined when there are no parts', () => {
+    expect(buildProgressAssistantOutput([])).toBeUndefined();
+  });
+
+  it('joins parts with a blank-line separator when below the limit', () => {
+    expect(buildProgressAssistantOutput(['first', 'second'], 10)).toBe('first\n\nsecond');
+  });
+
+  it('caps to the last N parts once the limit is exceeded', () => {
+    const parts = Array.from({ length: 200 }, (_, i) => `p${i}`);
+    const result = buildProgressAssistantOutput(parts, 5);
+    expect(result).toBe('p195\n\np196\n\np197\n\np198\n\np199');
+  });
+
+  it('uses the default tail size when the caller does not override it', () => {
+    const parts = Array.from({ length: PROGRESS_OUTPUT_TAIL_PARTS + 10 }, (_, i) => `p${i}`);
+    const result = buildProgressAssistantOutput(parts);
+    expect(result).toBeDefined();
+    expect(result!.split('\n\n')).toHaveLength(PROGRESS_OUTPUT_TAIL_PARTS);
+  });
+});
diff --git a/test/renderer/components/team/taskLogs/TaskLogsPanel.test.ts b/test/renderer/components/team/taskLogs/TaskLogsPanel.test.ts
index cedb1bb9..ea3734c7 100644
--- a/test/renderer/components/team/taskLogs/TaskLogsPanel.test.ts
+++ b/test/renderer/components/team/taskLogs/TaskLogsPanel.test.ts
@@ -9,6 +9,9 @@ import type { TeamTaskWithKanban } from '../../../../../src/shared/types';
 
 const apiState = {
   onTeamChange: vi.fn<(callback: (event: unknown, data: TeamChangeEvent) => void) => () => void>(),
+  getTaskLogStreamSummary: vi.fn<
+    (teamName: string, taskId: string) => Promise<{ segmentCount: number }>
+  >(),
   setTaskLogStreamTracking: vi.fn<(teamName: string, enabled: boolean) => Promise<void>>(),
 };
 
@@ -17,6 +20,8 @@ vi.mock('@renderer/api', () => ({
     teams: {
       onTeamChange: (...args: Parameters<typeof apiState.onTeamChange>) =>
         apiState.onTeamChange(...args),
+      getTaskLogStreamSummary: (...args: Parameters<typeof apiState.getTaskLogStreamSummary>) =>
+        apiState.getTaskLogStreamSummary(...args),
       setTaskLogStreamTracking: (...args: Parameters<typeof apiState.setTaskLogStreamTracking>) =>
         apiState.setTaskLogStreamTracking(...args),
     },
@@ -168,7 +173,9 @@ describe('TaskLogsPanel', () => {
     taskLogStreamProps.calls = [];
     executionSessionsProps.calls = [];
     apiState.onTeamChange.mockReset();
+    apiState.getTaskLogStreamSummary.mockReset();
     apiState.setTaskLogStreamTracking.mockReset();
+    apiState.getTaskLogStreamSummary.mockResolvedValue({ segmentCount: 0 });
     vi.useRealTimers();
     vi.unstubAllGlobals();
   });
@@ -484,4 +491,53 @@ describe('TaskLogsPanel', () => {
       await flushMicrotasks();
     });
   });
+
+  it('loads task log count for the header badge and refreshes it on matching live updates', async () => {
+    vi.stubGlobal('IS_REACT_ACT_ENVIRONMENT', true);
+    vi.useFakeTimers();
+
+    const counts: Array<number | undefined> = [];
+    let handler: ((event: unknown, data: TeamChangeEvent) => void) | null = null;
+    apiState.onTeamChange.mockImplementation((callback) => {
+      handler = callback;
+      return () => {
+        handler = null;
+      };
+    });
+    apiState.getTaskLogStreamSummary
+      .mockResolvedValueOnce({ segmentCount: 4 })
+      .mockResolvedValueOnce({ segmentCount: 5 });
+
+    const host = document.createElement('div');
+    document.body.appendChild(host);
+    const root = createRoot(host);
+
+    await act(async () => {
+      root.render(
+        React.createElement(TaskLogsPanel, {
+          teamName: 'demo',
+          task: makeTask(),
+          onTaskLogCountChange: (count) => counts.push(count),
+        })
+      );
+      await flushMicrotasks();
+    });
+
+    expect(apiState.getTaskLogStreamSummary).toHaveBeenCalledWith('demo', 'task-1');
+    expect(counts).toEqual([undefined, 4]);
+
+    await act(async () => {
+      handler?.(null, { teamName: 'demo', type: 'task-log-change', taskId: 'task-1' });
+      vi.advanceTimersByTime(350);
+      await flushMicrotasks();
+    });
+
+    expect(apiState.getTaskLogStreamSummary).toHaveBeenCalledTimes(2);
+    expect(counts).toEqual([undefined, 4, 5]);
+
+    await act(async () => {
+      root.unmount();
+      await flushMicrotasks();
+    });
+  });
 });