diff --git a/src/main/usageScan.test.ts b/src/main/usageScan.test.ts
index ad1b6c0..9e73fa3 100644
--- a/src/main/usageScan.test.ts
+++ b/src/main/usageScan.test.ts
@@ -47,4 +47,19 @@ describe('scanUsage', () => {
     expect(r.global.input).toBe(0);
     expect(r.byProject[0].sessions).toBe(0);
   });
+
+  it('sums active time from message gaps, capping idle stretches', () => {
+    const d = join(root, 'C--g-time');
+    mkdirSync(d, { recursive: true });
+    // 0m → 3m (active 3m) → 120m idle (skipped) → 121m (active 1m). Total active = 4m.
+    writeFileSync(join(d, 's.jsonl'), [
+      asst('claude-opus-4-8', { input_tokens: 1 }, '2026-06-01T10:00:00.000Z'),
+      asst('claude-opus-4-8', { input_tokens: 1 }, '2026-06-01T10:03:00.000Z'),
+      asst('claude-opus-4-8', { input_tokens: 1 }, '2026-06-01T12:00:00.000Z'),
+      asst('claude-opus-4-8', { input_tokens: 1 }, '2026-06-01T12:01:00.000Z'),
+    ].join('\n'));
+    const r = scanUsage([{ path: 'C:\\g\\time', name: 'time' }], root, Infinity);
+    expect(r.activeMs).toBe(4 * 60_000);
+    expect(r.byProject[0].activeMs).toBe(4 * 60_000);
+  });
 });
diff --git a/src/main/usageScan.ts b/src/main/usageScan.ts
index 63852ca..5922b2a 100644
--- a/src/main/usageScan.ts
+++ b/src/main/usageScan.ts
@@ -1,7 +1,7 @@
 import { readdirSync, readFileSync, existsSync, statSync } from 'node:fs';
 import { join } from 'node:path';
 import { encodeProjectPath } from '../shared/paths';
-import { emptyTotals, addUsage, estimateCost, MODEL_PRICING, type UsageTotals, type RawUsage } from '../shared/usage';
+import { emptyTotals, addUsage, estimateCost, activeMsFromTimestamps, MODEL_PRICING, type UsageTotals, type RawUsage } from '../shared/usage';
 import type { UsageReport, ProjectUsage, ModelUsage } from '../shared/types';
 
 // Cache: key = filepath + ':' + mtimeMs → parsed lines
@@ -31,13 +31,13 @@ export function scanUsage(repos: RepoRef[], claudeProjectsDir: string, sinceMs:
   const perModelGlobal = new Map<string, UsageTotals>();
   const perDay = new Map<string, UsageTotals>();
   const byProject: ProjectUsage[] = [];
-  let webSearch = 0, webFetch = 0, sessions = 0, hasUnknownModel = false;
+  let webSearch = 0, webFetch = 0, sessions = 0, hasUnknownModel = false, globalActiveMs = 0;
 
   for (const repo of repos) {
     const dir = join(claudeProjectsDir, encodeProjectPath(repo.path));
     const projTotals = emptyTotals();
     const projByModel = new Map<string, UsageTotals>();
-    let projSessions = 0, projUnknown = false;
+    let projSessions = 0, projUnknown = false, projActiveMs = 0;
 
     if (existsSync(dir)) {
       let files: string[] = [];
@@ -57,14 +57,17 @@ export function scanUsage(repos: RepoRef[], claudeProjectsDir: string, sinceMs:
           _fileCache.set(cacheKey, lines);
         }
         projSessions++;
+        const stamps: number[] = []; // in-range message timestamps, for active-time gaps
         for (const line of lines) {
           if (!line.trim()) continue;
           let o: { type?: string; timestamp?: string; message?: { model?: string; usage?: RawUsage & { server_tool_use?: { web_search_requests?: number; web_fetch_requests?: number } } } };
           try { o = JSON.parse(line); } catch { continue; }
-          const u = o.message?.usage;
-          if (o.type !== 'assistant' || !u) continue;
           const day = dayKey(o.timestamp, fileMs);
           if (sinceMs !== Infinity && new Date(day + 'T00:00:00.000Z').getTime() < sinceMs) continue;
+          // Collect every line's timestamp (user + assistant + tool) so gaps reflect real wall-clock activity.
+          if (o.timestamp) { const ms = new Date(o.timestamp).getTime(); if (!Number.isNaN(ms)) stamps.push(ms); }
+          const u = o.message?.usage;
+          if (o.type !== 'assistant' || !u) continue;
           const model = o.message?.model ?? 'unknown';
           if (!MODEL_PRICING[model]) { hasUnknownModel = true; projUnknown = true; }
           Object.assign(global, addUsage(global, u));
@@ -75,13 +78,16 @@ export function scanUsage(repos: RepoRef[], claudeProjectsDir: string, sinceMs:
           webSearch += u.server_tool_use?.web_search_requests ?? 0;
           webFetch += u.server_tool_use?.web_fetch_requests ?? 0;
         }
+        projActiveMs += activeMsFromTimestamps(stamps);
       }
     }
 
     sessions += projSessions;
+    globalActiveMs += projActiveMs;
     byProject.push({
       path: repo.path, name: repo.name, sessions: projSessions,
       totals: projTotals, costEstimate: sumModelCost(projByModel), hasUnknownModel: projUnknown,
+      activeMs: projActiveMs,
     });
   }
 
@@ -92,5 +98,5 @@ export function scanUsage(repos: RepoRef[], claudeProjectsDir: string, sinceMs:
     day, tokens: tokensOf(t), cost: null as number | null,
   }));
 
-  return { global, globalCost: sumModelCost(perModelGlobal), hasUnknownModel, webSearch, webFetch, sessions, byModel, byProject, daily };
+  return { global, globalCost: sumModelCost(perModelGlobal), hasUnknownModel, webSearch, webFetch, sessions, activeMs: globalActiveMs, byModel, byProject, daily };
 }
diff --git a/src/renderer/locales/en.json b/src/renderer/locales/en.json
index ed1f152..3cdbf47 100644
--- a/src/renderer/locales/en.json
+++ b/src/renderer/locales/en.json
@@ -44,6 +44,8 @@
   "usage.cache_r": "Cache R",
   "usage.web": "web",
   "usage.sessions": "sessions",
+  "usage.active_time": "Active time",
+  "usage.col_time": "Time",
   "usage.daily_tokens": "Daily tokens",
   "usage.col_project": "Project",
   "usage.col_cost": "Est. cost",
diff --git a/src/renderer/locales/ja.json b/src/renderer/locales/ja.json
index cc80f0d..afdcefe 100644
--- a/src/renderer/locales/ja.json
+++ b/src/renderer/locales/ja.json
@@ -44,6 +44,8 @@
   "usage.cache_r": "キャッシュ R",
   "usage.web": "web",
   "usage.sessions": "セッション",
+  "usage.active_time": "作業時間",
+  "usage.col_time": "時間",
   "usage.daily_tokens": "日別トークン",
   "usage.col_project": "プロジェクト",
   "usage.col_cost": "推定コスト",
diff --git a/src/renderer/locales/ko.json b/src/renderer/locales/ko.json
index 6745684..b69e574 100644
--- a/src/renderer/locales/ko.json
+++ b/src/renderer/locales/ko.json
@@ -44,6 +44,8 @@
   "usage.cache_r": "캐시 R",
   "usage.web": "web",
   "usage.sessions": "세션",
+  "usage.active_time": "작업 시간",
+  "usage.col_time": "시간",
   "usage.daily_tokens": "일별 토큰",
   "usage.col_project": "프로젝트",
   "usage.col_cost": "추정비용",
diff --git a/src/renderer/locales/zh.json b/src/renderer/locales/zh.json
index 58e83dc..ee8577d 100644
--- a/src/renderer/locales/zh.json
+++ b/src/renderer/locales/zh.json
@@ -44,6 +44,8 @@
   "usage.cache_r": "缓存 R",
   "usage.web": "web",
   "usage.sessions": "会话",
+  "usage.active_time": "工作时间",
+  "usage.col_time": "时间",
   "usage.daily_tokens": "每日令牌",
   "usage.col_project": "项目",
   "usage.col_cost": "预估费用",
diff --git a/src/renderer/usageView.ts b/src/renderer/usageView.ts
index 5f28758..96be1b8 100644
--- a/src/renderer/usageView.ts
+++ b/src/renderer/usageView.ts
@@ -1,4 +1,5 @@
 import { barChart, shareBar } from './charts';
+import { formatDuration } from '../shared/usage';
 import { tr, localeTag } from './i18n-runtime';
 
 type UsageReport = Awaited<ReturnType<Window['devdeck']['usageReport']>>;
@@ -13,7 +14,7 @@ const COLORS = ['#6366f1', '#3b82f6', '#d98a1f', '#e0623f', '#9aa1ad'];
 
 let viewEl: HTMLElement;
 let activeRange = '30d';
-let sortKey: 'cost' | 'input' | 'output' | 'sessions' = 'cost';
+let sortKey: 'cost' | 'input' | 'output' | 'sessions' | 'active' = 'cost';
 let sortDir: 'desc' | 'asc' = 'desc';
 
 function fmt(n: number): string { return new Intl.NumberFormat(localeTag()).format(n); }
@@ -52,6 +53,7 @@ function render(r: UsageReport): void {
     [tr('usage.input'), fmt(r.global.input)], [tr('usage.output'), fmt(r.global.output)],
     [tr('usage.cache_w'), fmt(r.global.cacheWrite)], [tr('usage.cache_r'), fmt(r.global.cacheRead)],
     [tr('usage.web'), `${r.webSearch + r.webFetch}`], [tr('usage.sessions'), `${r.sessions}`],
+    [tr('usage.active_time'), formatDuration(r.activeMs)],
   ] as [string, string][]).map(([k, v]) => { const d = document.createElement('div'); d.className = 'stat'; d.innerHTML = `<b></b><span></span>`; d.querySelector('b')!.textContent = v; d.querySelector('span')!.textContent = k; return d; }));
   sum.appendChild(stats);
   sum.appendChild(shareBar(r.byModel.map((m, i) => ({ label: m.model, value: m.totals.input + m.totals.output, color: COLORS[i % COLORS.length] }))));
@@ -75,13 +77,14 @@ function render(r: UsageReport): void {
   }
 
   const rows = [...r.byProject].filter((p) => p.sessions > 0).sort((a, b) => {
-    const av = sortKey === 'cost' ? (a.costEstimate ?? -1) : sortKey === 'sessions' ? a.sessions : a.totals[sortKey];
-    const bv = sortKey === 'cost' ? (b.costEstimate ?? -1) : sortKey === 'sessions' ? b.sessions : b.totals[sortKey];
+    const val = (p: typeof a): number =>
+      sortKey === 'cost' ? (p.costEstimate ?? -1) : sortKey === 'sessions' ? p.sessions : sortKey === 'active' ? p.activeMs : p.totals[sortKey];
+    const av = val(a), bv = val(b);
     return sortDir === 'desc' ? bv - av : av - bv;
   });
   const table = document.createElement('table'); table.className = 'usage-table';
   const head = document.createElement('tr');
-  for (const [key, label] of [['name', tr('usage.col_project')], ['sessions', tr('proj.sessions')], ['input', tr('usage.input')], ['output', tr('usage.output')], ['cost', tr('usage.col_cost')]] as const) {
+  for (const [key, label] of [['name', tr('usage.col_project')], ['sessions', tr('proj.sessions')], ['active', tr('usage.col_time')], ['input', tr('usage.input')], ['output', tr('usage.output')], ['cost', tr('usage.col_cost')]] as const) {
     const th = document.createElement('th');
     const isSortable = key !== 'name';
     const isActive = isSortable && key === sortKey;
@@ -110,7 +113,7 @@ function render(r: UsageReport): void {
   table.appendChild(head);
   for (const p of rows) {
     const tr2 = document.createElement('tr');
-    const cells = [p.name, String(p.sessions), fmt(p.totals.input), fmt(p.totals.output), usd(p.costEstimate)];
+    const cells = [p.name, String(p.sessions), formatDuration(p.activeMs), fmt(p.totals.input), fmt(p.totals.output), usd(p.costEstimate)];
     for (const c of cells) { const td = document.createElement('td'); td.textContent = c; tr2.appendChild(td); }
     table.appendChild(tr2);
   }
diff --git a/src/shared/types.ts b/src/shared/types.ts
index b085d41..f7942aa 100644
--- a/src/shared/types.ts
+++ b/src/shared/types.ts
@@ -13,10 +13,14 @@ export interface ModelUsage { model: string; totals: UsageTotals; costEstimate:
 export interface ProjectUsage {
   path: string; name: string; sessions: number;
   totals: UsageTotals; costEstimate: number | null; hasUnknownModel: boolean;
+  /** Active working time (sum of message gaps within the idle cap), in ms. */
+  activeMs: number;
 }
 export interface UsageReport {
   global: UsageTotals; globalCost: number | null; hasUnknownModel: boolean;
   webSearch: number; webFetch: number; sessions: number;
+  /** Total active working time across all scanned sessions, in ms. */
+  activeMs: number;
   byModel: ModelUsage[];
   byProject: ProjectUsage[];
   daily: { day: string; cost: number | null; tokens: number }[];
diff --git a/src/shared/usage.test.ts b/src/shared/usage.test.ts
index 2853e2d..1d68a5a 100644
--- a/src/shared/usage.test.ts
+++ b/src/shared/usage.test.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { emptyTotals, addUsage, estimateCost, MODEL_PRICING } from './usage';
+import { emptyTotals, addUsage, estimateCost, MODEL_PRICING, activeMsFromTimestamps, formatDuration, ACTIVE_GAP_CAP_MS } from './usage';
 
 describe('addUsage', () => {
   it('accumulates the four token categories', () => {
@@ -26,3 +26,42 @@ describe('estimateCost', () => {
     expect(MODEL_PRICING['claude-opus-4-8']).toBeDefined();
   });
 });
+
+describe('activeMsFromTimestamps', () => {
+  const T = (min: number) => Date.UTC(2026, 5, 1, 10, 0, 0) + min * 60_000;
+
+  it('sums consecutive gaps within the idle cap', () => {
+    // gaps: 2m, 3m — both <= 5m → 5m total
+    expect(activeMsFromTimestamps([T(0), T(2), T(5)])).toBe(5 * 60_000);
+  });
+
+  it('excludes gaps larger than the idle cap (overnight / away)', () => {
+    // 2m active, then a 600m idle gap (skipped), then 1m active → 3m total
+    expect(activeMsFromTimestamps([T(0), T(2), T(602), T(603)])).toBe(3 * 60_000);
+  });
+
+  it('drops a gap exactly over the cap but keeps one exactly at the cap', () => {
+    const capMin = ACTIVE_GAP_CAP_MS / 60_000;
+    expect(activeMsFromTimestamps([T(0), T(capMin)])).toBe(ACTIVE_GAP_CAP_MS);
+    expect(activeMsFromTimestamps([T(0), T(capMin + 1)])).toBe(0);
+  });
+
+  it('sorts unordered input and returns 0 for <2 stamps', () => {
+    expect(activeMsFromTimestamps([T(2), T(0), T(5)])).toBe(5 * 60_000);
+    expect(activeMsFromTimestamps([T(0)])).toBe(0);
+    expect(activeMsFromTimestamps([])).toBe(0);
+  });
+});
+
+describe('formatDuration', () => {
+  it('formats hours and minutes', () => {
+    expect(formatDuration((14 * 60 + 9) * 60_000)).toBe('14h 9m');
+  });
+  it('drops the hours part below one hour', () => {
+    expect(formatDuration(45 * 60_000)).toBe('45m');
+  });
+  it('floors to whole minutes and clamps negatives to 0m', () => {
+    expect(formatDuration(59_000)).toBe('0m');
+    expect(formatDuration(-1000)).toBe('0m');
+  });
+});
diff --git a/src/shared/usage.ts b/src/shared/usage.ts
index 976c2ea..2431299 100644
--- a/src/shared/usage.ts
+++ b/src/shared/usage.ts
@@ -19,6 +19,33 @@ export const MODEL_PRICING: Record<string, PriceCard> = {
   'claude-haiku-4-5': { input: 1, output: 5, cacheWrite: 1.25, cacheRead: 0.1 },
 };
 
+/**
+ * Gap between two consecutive session messages longer than this counts as idle
+ * (overnight, stepped away) and is excluded from "active" time. Keeps the summed
+ * working time meaningful instead of the full first→last span the terminal ⏱️ shows.
+ */
+export const ACTIVE_GAP_CAP_MS = 5 * 60 * 1000;
+
+/** Sum of consecutive-timestamp gaps that are within the idle cap. Input may be unsorted. */
+export function activeMsFromTimestamps(timestampsMs: number[]): number {
+  if (timestampsMs.length < 2) return 0;
+  const sorted = [...timestampsMs].sort((a, b) => a - b);
+  let active = 0;
+  for (let i = 1; i < sorted.length; i++) {
+    const gap = sorted[i] - sorted[i - 1];
+    if (gap > 0 && gap <= ACTIVE_GAP_CAP_MS) active += gap;
+  }
+  return active;
+}
+
+/** Human-friendly duration: "14h 9m", "45m", "0m". Floors to whole minutes. */
+export function formatDuration(ms: number): string {
+  const totalMin = Math.floor(Math.max(0, ms) / 60000);
+  const h = Math.floor(totalMin / 60);
+  const m = totalMin % 60;
+  return h > 0 ? `${h}h ${m}m` : `${m}m`;
+}
+
 export function emptyTotals(): UsageTotals { return { input: 0, output: 0, cacheWrite: 0, cacheRead: 0 }; }
 
 export function addUsage(t: UsageTotals, u: RawUsage): UsageTotals {