diff --git a/src/cli/commands/memory.ts b/src/cli/commands/memory.ts
index eb11589..36d0597 100644
--- a/src/cli/commands/memory.ts
+++ b/src/cli/commands/memory.ts
@@ -2,7 +2,20 @@ import { input, select } from '@inquirer/prompts';
 import { addMemory, searchMemory, listMemory } from '../../core/services/memoryService.js';
 import type { Memory } from '../../core/schema.js';
 
-export async function memoryAdd(cwd: string, options: Partial<Memory> = {}): Promise<void> {
+export interface MemoryAddOptions {
+  title?: string;
+  category?: Memory['category'];
+  content?: string;
+  /** Raw --task option value: single ID, comma-sep IDs, or already an array. */
+  task?: string | string[];
+  /** Pre-resolved array of task IDs (takes precedence over task). */
+  relatedTasks?: string[];
+  tokens?: number;
+  duration?: number;
+  by?: string;
+}
+
+export async function memoryAdd(cwd: string, options: MemoryAddOptions = {}): Promise<void> {
   const title = options.title ?? await input({ message: 'Memory title:' });
   const category = options.category ?? await select({
     message: 'Category:',
@@ -16,7 +29,28 @@ export async function memoryAdd(cwd: string, options: Partial<Memory> = {}): Pro
   });
   const content = options.content ?? await input({ message: 'Content:' });
 
-  const memory = addMemory(cwd, { title, category, content });
+  // Resolve relatedTasks: explicit array wins; otherwise parse --task string.
+  const relatedTasks: string[] =
+    options.relatedTasks ??
+    (options.task
+      ? (Array.isArray(options.task)
+          ? options.task
+          : options.task
+              .split(',')
+              .map((s) => s.trim())
+              .filter(Boolean))
+      : []);
+
+  const memory = addMemory(cwd, {
+    title,
+    category,
+    content,
+    relatedTasks,
+    tokens: options.tokens,
+    duration: options.duration,
+    by: options.by,
+  } as Partial<Memory>);
+
   console.log(`Memory saved as ${memory.id}.`);
 }
 
diff --git a/src/cli/commands/task.ts b/src/cli/commands/task.ts
index fbebd44..c272e7f 100644
--- a/src/cli/commands/task.ts
+++ b/src/cli/commands/task.ts
@@ -42,7 +42,15 @@ export function taskClaim(cwd: string, id: string, agentName: string): void {
   console.log(`${id} claimed by ${agentName}.`);
 }
 
-export function taskDone(cwd: string, id: string): void {
-  doneTask(cwd, id);
+export function taskDone(
+  cwd: string,
+  id: string,
+  meta?: { tokens?: number; duration?: number; by?: string },
+): void {
+  doneTask(cwd, id, {
+    doneBy: meta?.by,
+    doneTokens: meta?.tokens,
+    doneDuration: meta?.duration,
+  });
   console.log(`${id} marked as done.`);
 }
diff --git a/src/cli/index.ts b/src/cli/index.ts
index 96f14d3..6a9c488 100644
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -108,15 +108,50 @@ export function createProgram(cwd: string): Command {
     .option('--title <title>', 'Title')
     .option('--category <category>', 'Category')
     .option('--content <content>', 'Content')
+    .option(
+      '--task <ids>',
+      'Link to task IDs (comma-separated, e.g. TSK-0001 or TSK-0001,TSK-0002)',
+    )
+    .option('--tokens <n>', 'Tokens consumed (optional, for activity timeline)')
+    .option('--duration <ms>', 'Duration in milliseconds (optional, for activity timeline)')
+    .option('--by <agent>', 'Agent that produced this result (optional)')
     .action(async (options) => {
       const { serverUrl, projectCwd } = await resolveContext(program, cwd);
+
+      // Parse CLI string values into the types the service expects.
+      const relatedTasks: string[] = options.task
+        ? (Array.isArray(options.task)
+            ? options.task
+            : options.task
+                .split(',')
+                .map((s: string) => s.trim())
+                .filter(Boolean))
+        : [];
+      const tokens = options.tokens != null ? Number(options.tokens) : undefined;
+      const duration = options.duration != null ? Number(options.duration) : undefined;
+
       if (serverUrl) {
         await runRemote(serverUrl, async () => {
-          const memory = await remoteClient.addMemory(serverUrl, options);
+          const memory = await remoteClient.addMemory(serverUrl, {
+            title: options.title as string | undefined,
+            category: options.category as string | undefined,
+            content: options.content as string | undefined,
+            relatedTasks,
+            tokens,
+            duration,
+            by: options.by as string | undefined,
+          } as Partial<import('../core/schema.js').Memory>);
           console.log(`Memory saved as ${memory.id}.`);
         });
       } else {
-        await memoryAdd(projectCwd, options);
+        await memoryAdd(projectCwd, {
+          title: options.title as string | undefined,
+          content: options.content as string | undefined,
+          relatedTasks,
+          tokens,
+          duration,
+          by: options.by as string | undefined,
+        });
       }
     });
   memoryCmd
@@ -220,15 +255,23 @@ export function createProgram(cwd: string): Command {
   taskCmd
     .command('done <id>')
     .description('Mark a task as done')
-    .action(async (id) => {
+    .option('--tokens <n>', 'Tokens consumed (optional, for activity timeline)')
+    .option('--duration <ms>', 'Duration in milliseconds (optional, for activity timeline)')
+    .option('--by <agent>', 'Agent that completed the task (optional)')
+    .action(async (id, options) => {
+      const meta = {
+        tokens: options.tokens != null ? Number(options.tokens) : undefined,
+        duration: options.duration != null ? Number(options.duration) : undefined,
+        by: options.by as string | undefined,
+      };
       const { serverUrl, projectCwd } = await resolveContext(program, cwd);
       if (serverUrl) {
         await runRemote(serverUrl, async () => {
-          await remoteClient.doneTask(serverUrl, id);
+          await remoteClient.doneTask(serverUrl, id, meta);
           console.log(`${id} marked as done.`);
         });
       } else {
-        taskDone(projectCwd, id);
+        taskDone(projectCwd, id, meta);
       }
     });
   program.addCommand(taskCmd);
diff --git a/src/cli/remoteClient.ts b/src/cli/remoteClient.ts
index c66c153..47aa0c2 100644
--- a/src/cli/remoteClient.ts
+++ b/src/cli/remoteClient.ts
@@ -1,4 +1,4 @@
-import type { Task, Handoff, Decision, Memory } from '../core/schema.js';
+import type { Task, Handoff, Decision, Memory, ActivityItem } from '../core/schema.js';
 import type { IndexEntry } from '../core/index.js';
 
 export class RemoteError extends Error {
@@ -58,8 +58,21 @@ export const remoteClient = {
     return request<Task>(baseUrl, 'PATCH', `/tasks/${id}`, { status: 'in_progress', assignedTo: agentName });
   },
 
-  async doneTask(baseUrl: string, id: string): Promise<Task> {
-    return request<Task>(baseUrl, 'PATCH', `/tasks/${id}`, { status: 'done' });
+  async doneTask(
+    baseUrl: string,
+    id: string,
+    meta?: { tokens?: number; duration?: number; by?: string },
+  ): Promise<Task> {
+    return request<Task>(baseUrl, 'PATCH', `/tasks/${id}`, {
+      status: 'done',
+      doneTokens: meta?.tokens,
+      doneDuration: meta?.duration,
+      doneBy: meta?.by,
+    });
+  },
+
+  async getTaskActivity(baseUrl: string, id: string): Promise<ActivityItem[]> {
+    return request<ActivityItem[]>(baseUrl, 'GET', `/tasks/${id}/activity`);
   },
 
   async createHandoff(baseUrl: string, options: Partial<Handoff>): Promise<Handoff> {
diff --git a/src/core/index.ts b/src/core/index.ts
index d60669a..2b10c4b 100644
--- a/src/core/index.ts
+++ b/src/core/index.ts
@@ -20,6 +20,10 @@ export interface IndexEntry {
   toRole?: string;
   fromAgent?: string;
   toAgent?: string;
+  // Handoff → task link
+  taskId?: string;
+  // Memory → task links (JSON array string, e.g. '["TSK-0001"]')
+  relatedTasks?: string;
 }
 
 export class Index {
@@ -45,16 +49,18 @@ export class Index {
         fromRole TEXT,
         toRole TEXT,
         fromAgent TEXT,
-        toAgent TEXT
+        toAgent TEXT,
+        taskId TEXT,
+        relatedTasks TEXT
       );
       CREATE VIRTUAL TABLE IF NOT EXISTS search USING fts5(id, title, content);
     `);
 
-    // Migration: add handoff-routing columns to existing DBs that pre-date this schema.
+    // Migration: add columns to existing DBs that pre-date this schema.
     const existingCols = new Set(
       (this.db.pragma('table_info(entities)') as Array<{ name: string }>).map((r) => r.name),
     );
-    for (const col of ['fromRole', 'toRole', 'fromAgent', 'toAgent']) {
+    for (const col of ['fromRole', 'toRole', 'fromAgent', 'toAgent', 'taskId', 'relatedTasks']) {
       if (!existingCols.has(col)) {
         this.db.exec(`ALTER TABLE entities ADD COLUMN ${col} TEXT`);
       }
@@ -71,17 +77,20 @@ export class Index {
       toRole: null,
       fromAgent: null,
       toAgent: null,
+      taskId: null,
+      relatedTasks: null,
       ...entry,
     };
 
     const insert = this.db.prepare(`
-      INSERT INTO entities (id, type, title, content, filePath, createdAt, updatedAt, status, role, assignedTo, tags, fromRole, toRole, fromAgent, toAgent)
-      VALUES (@id, @type, @title, @content, @filePath, @createdAt, @updatedAt, @status, @role, @assignedTo, @tags, @fromRole, @toRole, @fromAgent, @toAgent)
+      INSERT INTO entities (id, type, title, content, filePath, createdAt, updatedAt, status, role, assignedTo, tags, fromRole, toRole, fromAgent, toAgent, taskId, relatedTasks)
+      VALUES (@id, @type, @title, @content, @filePath, @createdAt, @updatedAt, @status, @role, @assignedTo, @tags, @fromRole, @toRole, @fromAgent, @toAgent, @taskId, @relatedTasks)
       ON CONFLICT(id) DO UPDATE SET
         type=@type, title=@title, content=@content, filePath=@filePath,
         createdAt=@createdAt, updatedAt=@updatedAt, status=@status, role=@role,
         assignedTo=@assignedTo, tags=@tags,
-        fromRole=@fromRole, toRole=@toRole, fromAgent=@fromAgent, toAgent=@toAgent
+        fromRole=@fromRole, toRole=@toRole, fromAgent=@fromAgent, toAgent=@toAgent,
+        taskId=@taskId, relatedTasks=@relatedTasks
     `);
     insert.run(params);
 
@@ -129,6 +138,26 @@ export class Index {
     return stmt.all(params) as IndexEntry[];
   }
 
+  /** Returns all handoff entries whose taskId matches the given task ID. */
+  listHandoffsByTask(taskId: string): IndexEntry[] {
+    const stmt = this.db.prepare(
+      "SELECT * FROM entities WHERE type = 'handoff' AND taskId = @taskId ORDER BY createdAt ASC",
+    );
+    return stmt.all({ taskId }) as IndexEntry[];
+  }
+
+  /**
+   * Returns all memory entries whose relatedTasks JSON array contains the given
+   * task ID. Uses a LIKE search on the serialised JSON string — safe because
+   * task IDs follow the form TSK-NNNN and cannot be substrings of each other.
+   */
+  listMemoryByTask(taskId: string): IndexEntry[] {
+    const stmt = this.db.prepare(
+      "SELECT * FROM entities WHERE type = 'memory' AND relatedTasks LIKE @pattern ORDER BY createdAt ASC",
+    );
+    return stmt.all({ pattern: `%${taskId}%` }) as IndexEntry[];
+  }
+
   close(): void {
     this.db.close();
   }
diff --git a/src/core/schema.ts b/src/core/schema.ts
index fdc6262..38a87ee 100644
--- a/src/core/schema.ts
+++ b/src/core/schema.ts
@@ -21,6 +21,10 @@ export const TaskSchema = z.object({
   tags: z.array(z.string()).default([]),
   acceptanceCriteria: z.array(z.string()).default([]),
   sourceHandoff: z.string().optional(),
+  // Optional completion metadata (set via `task done --tokens --duration --by`)
+  doneBy: z.string().optional(),
+  doneTokens: z.number().int().nonnegative().optional(),
+  doneDuration: z.number().int().nonnegative().optional(),
 });
 
 export const HandoffSchema = z.object({
@@ -61,8 +65,23 @@ export const MemorySchema = z.object({
   relatedDecisions: z.array(z.string()).default([]),
   createdAt: z.string().datetime(),
   updatedAt: z.string().datetime(),
+  // Optional agent-supplied metadata (set via `memory add --tokens --duration --by`)
+  tokens: z.number().int().nonnegative().optional(),
+  duration: z.number().int().nonnegative().optional(),
+  by: z.string().optional(),
 });
 
+// Activity timeline item returned by GET /tasks/:id/activity
+export const ActivityItemSchema = z.object({
+  at: z.string().datetime(),
+  kind: z.enum(['created', 'handoff', 'result', 'status']),
+  actor: z.string(),
+  summary: z.string(),
+  meta: z.record(z.unknown()).optional(),
+});
+
+export type ActivityItem = z.infer<typeof ActivityItemSchema>;
+
 export const StatusSchema = z.object({
   generatedAt: z.string().datetime(),
   activeTasks: z.array(z.string()).default([]),
diff --git a/src/core/services/activityService.ts b/src/core/services/activityService.ts
new file mode 100644
index 0000000..b4f4773
--- /dev/null
+++ b/src/core/services/activityService.ts
@@ -0,0 +1,137 @@
+import { getTask } from './taskService.js';
+import { Index } from '../index.js';
+import { readEntity } from '../files.js';
+import { MemorySchema } from '../schema.js';
+import type { ActivityItem } from '../schema.js';
+
+/**
+ * Build a time-sorted activity timeline for a single task.
+ *
+ * Sources (all assembled without rebuilding existing data):
+ *   - Task file   → "created" event + final status/assignee event
+ *   - Handoffs    → "handoff" events (filtered from SQLite by taskId)
+ *   - Memory      → "result" events (filtered from SQLite by relatedTasks)
+ *
+ * Each item: { at, kind, actor, summary, meta? }
+ * The meta object carries tokens/duration badges when the agent supplied them,
+ * and routing details (fromRole/toRole) for handoff items.
+ */
+export function getTaskActivity(cwd: string, taskId: string): ActivityItem[] {
+  const { task } = getTask(cwd, taskId);
+
+  const items: ActivityItem[] = [];
+
+  // ── 1. Created event ─────────────────────────────────────────────────────
+  items.push({
+    at: task.createdAt,
+    kind: 'created',
+    actor: task.role ?? 'user',
+    summary: 'Task created',
+  });
+
+  // ── 2. Handoff events ────────────────────────────────────────────────────
+  const index = new Index(cwd);
+  const handoffEntries = index.listHandoffsByTask(taskId);
+  index.close();
+
+  for (const h of handoffEntries) {
+    const from = h.fromRole ?? '?';
+    const to = h.toRole ?? '?';
+    const meta: Record<string, unknown> = {
+      handoffId: h.id,
+      fromRole: h.fromRole,
+      toRole: h.toRole,
+    };
+    if (h.fromAgent) meta.fromAgent = h.fromAgent;
+    if (h.toAgent) meta.toAgent = h.toAgent;
+
+    items.push({
+      at: h.createdAt,
+      kind: 'handoff',
+      actor: `${from} → ${to}`,
+      summary: h.title,
+      meta,
+    });
+  }
+
+  // ── 3. Memory / result events ────────────────────────────────────────────
+  const memIndex = new Index(cwd);
+  const memEntries = memIndex.listMemoryByTask(taskId);
+  memIndex.close();
+
+  for (const entry of memEntries) {
+    // Read the file to get category, tokens, duration, by (not stored in index)
+    let category: string = 'technical';
+    let tokens: number | undefined;
+    let duration: number | undefined;
+    let by: string | undefined;
+
+    try {
+      const { frontmatter } = readEntity(entry.filePath);
+      const parsed = MemorySchema.safeParse(frontmatter);
+      if (parsed.success) {
+        category = parsed.data.category;
+        tokens = parsed.data.tokens;
+        duration = parsed.data.duration;
+        by = parsed.data.by;
+      }
+    } catch {
+      // File unreadable — use index-level data and defaults
+    }
+
+    const meta: Record<string, unknown> = { memoryId: entry.id, category };
+    if (tokens != null) meta.tokens = tokens;
+    if (duration != null) meta.duration = duration;
+    if (by != null) meta.by = by;
+
+    items.push({
+      at: entry.createdAt,
+      kind: 'result',
+      actor: category,
+      summary: entry.title,
+      meta,
+    });
+  }
+
+  // ── 4. Current status event (only when task has progressed past "open") ──
+  // We use updatedAt as the timestamp; this is a best-effort reconstruction
+  // since we don't yet have a persistent per-transition audit log.
+  if (task.status !== 'open') {
+    let summary: string;
+    switch (task.status) {
+      case 'in_progress':
+        summary = task.assignedTo ? `Claimed by ${task.assignedTo}` : 'Claimed';
+        break;
+      case 'review':
+        summary = 'Submitted for review';
+        break;
+      case 'done':
+        summary = 'Task completed';
+        break;
+      case 'cancelled':
+        summary = 'Task cancelled';
+        break;
+      default:
+        summary = `Status: ${task.status}`;
+    }
+
+    const meta: Record<string, unknown> = { status: task.status };
+    if (task.assignedTo) meta.assignedTo = task.assignedTo;
+    if (task.doneBy) meta.by = task.doneBy;
+    if (task.doneTokens != null) meta.tokens = task.doneTokens;
+    if (task.doneDuration != null) meta.duration = task.doneDuration;
+
+    items.push({
+      at: task.updatedAt,
+      kind: 'status',
+      actor: task.doneBy ?? task.assignedTo ?? task.role ?? 'unknown',
+      summary,
+      meta,
+    });
+  }
+
+  // ── Sort by timestamp, ascending ──────────────────────────────────────────
+  items.sort((a, b) => a.at.localeCompare(b.at));
+
+  return items;
+}
diff --git a/src/core/services/handoffService.ts b/src/core/services/handoffService.ts
index 8eb8c86..d4c6de4 100644
--- a/src/core/services/handoffService.ts
+++ b/src/core/services/handoffService.ts
@@ -38,6 +38,7 @@ export function createHandoff(cwd: string, options: Partial<Handoff> = {}): Hand
     toRole: handoff.toRole,
     fromAgent: handoff.fromAgent,
     toAgent: handoff.toAgent,
+    taskId: handoff.taskId,
   });
   index.close();
 
diff --git a/src/core/services/memoryService.ts b/src/core/services/memoryService.ts
index b5952b1..7156112 100644
--- a/src/core/services/memoryService.ts
+++ b/src/core/services/memoryService.ts
@@ -18,6 +18,9 @@ export function addMemory(cwd: string, options: Partial<Memory> = {}): Memory {
     relatedDecisions: options.relatedDecisions ?? [],
     createdAt: now,
     updatedAt: now,
+    tokens: options.tokens,
+    duration: options.duration,
+    by: options.by,
   });
 
   const filePath = join(getEntityDir(cwd, 'memory'), `${memory.id}.md`);
@@ -33,6 +36,7 @@ export function addMemory(cwd: string, options: Partial<Memory> = {}): Memory {
     createdAt: memory.createdAt,
     updatedAt: memory.updatedAt,
     tags: JSON.stringify(memory.tags),
+    relatedTasks: JSON.stringify(memory.relatedTasks),
   });
   index.close();
 
diff --git a/src/core/services/taskService.ts b/src/core/services/taskService.ts
index 38ad63a..9fde0fd 100644
--- a/src/core/services/taskService.ts
+++ b/src/core/services/taskService.ts
@@ -59,8 +59,17 @@ export function claimTask(cwd: string, id: string, agentName: string): Task {
   return updateTask(cwd, id, { status: 'in_progress', assignedTo: agentName });
 }
 
-export function doneTask(cwd: string, id: string): Task {
-  return updateTask(cwd, id, { status: 'done' });
+export function doneTask(
+  cwd: string,
+  id: string,
+  meta?: { doneBy?: string; doneTokens?: number; doneDuration?: number },
+): Task {
+  return updateTask(cwd, id, {
+    status: 'done',
+    doneBy: meta?.doneBy,
+    doneTokens: meta?.doneTokens,
+    doneDuration: meta?.doneDuration,
+  });
 }
 
 export function reviewTask(cwd: string, id: string): Task {
diff --git a/src/server/board.ts b/src/server/board.ts
index dc2a9a0..90edd99 100644
--- a/src/server/board.ts
+++ b/src/server/board.ts
@@ -4,12 +4,10 @@
  * Design constraints (MVP — maximum simplicity):
  *  - One static HTML page: inline CSS + JS, no build step, no framework, no npm deps.
  *  - Reads only the existing same-origin endpoints (`/tasks`, `/handoffs`,
- *    `/decisions`). It never mutates state — purely an observability surface.
+ *    `/decisions`, `/tasks/:id/activity`). It never mutates state.
  *  - Auto-refreshes on a small interval via `setInterval` + `fetch`.
- *
- * The column skeleton is rendered server-side so the markup (and its
- * `data-column` markers) exist even before the client JS runs; JS only fills
- * the cards.
+ *  - Each task card is clickable: expanding it fetches and renders the
+ *    per-task activity timeline (created → handoff → result → status).
  */
 
 export interface BoardColumn {
@@ -118,7 +116,10 @@ export function renderBoardHtml(): string {
       border-left: 3px solid var(--accent);
       border-radius: 8px;
       padding: 8px 10px;
+      cursor: pointer;
+      user-select: none;
     }
+    .card:hover { border-color: rgba(139,148,158,.5); }
     .column[data-column="open"] .card { border-left-color: var(--open); }
     .column[data-column="in_progress"] .card { border-left-color: var(--in_progress); }
     .column[data-column="review"] .card { border-left-color: var(--review); }
@@ -136,6 +137,35 @@ export function renderBoardHtml(): string {
     .badge.agent { background: rgba(63,185,80,.12); color: var(--done); border-color: rgba(63,185,80,.25); }
     .empty { color: var(--muted); font-size: 12px; padding: 4px 2px; }
 
+    /* ── Activity timeline ─────────────────────────────────────────────────── */
+    .timeline {
+      display: none;
+      margin-top: 8px;
+      padding-top: 8px;
+      border-top: 1px solid var(--border);
+    }
+    .card.expanded .timeline { display: block; }
+    .tl-row {
+      display: flex; align-items: baseline; gap: 6px; flex-wrap: wrap;
+      padding: 4px 0; border-top: 1px solid rgba(48,54,61,.5); font-size: 12px;
+    }
+    .tl-row:first-child { border-top: 0; }
+    .tl-when { color: var(--muted); font-size: 11px; white-space: nowrap; min-width: 52px; }
+    .tl-kind {
+      font-size: 10px; border-radius: 999px; padding: 1px 6px;
+      border: 1px solid transparent; white-space: nowrap;
+    }
+    .tl-kind-created  { background: rgba(48,54,61,.6);     color: var(--muted);   border-color: var(--border); }
+    .tl-kind-handoff  { background: rgba(88,166,255,.12);  color: var(--accent);  border-color: rgba(88,166,255,.25); }
+    .tl-kind-result   { background: rgba(63,185,80,.12);   color: var(--done);    border-color: rgba(63,185,80,.25); }
+    .tl-kind-status   { background: rgba(210,153,34,.12);  color: var(--review);  border-color: rgba(210,153,34,.25); }
+    .tl-actor { color: var(--muted); font-size: 11px; white-space: nowrap; }
+    .tl-summary { flex: 1; min-width: 0; word-break: break-word; }
+    .tl-meta { display: flex; gap: 4px; flex-wrap: wrap; }
+    .badge.tl-tokens { background: rgba(163,113,247,.12); color: #a371f7; border-color: rgba(163,113,247,.25); }
+    .badge.tl-dur    { background: rgba(255,166,87,.12);  color: #ffa657; border-color: rgba(255,166,87,.25); }
+    .tl-loading, .tl-empty { color: var(--muted); font-size: 12px; padding: 2px 0; }
+
     .panels {
       display: grid; grid-template-columns: 1fr 1fr; gap: 12px;
       margin-top: 20px;
@@ -199,19 +229,73 @@ ${columnSkeleton()}
       if (s < 86400) return Math.floor(s / 3600) + 'h ago';
       return Math.floor(s / 86400) + 'd ago';
     }
+    function msToHuman(ms) {
+      if (ms < 1000) return ms + 'ms';
+      if (ms < 60000) return Math.round(ms / 1000) + 's';
+      if (ms < 3600000) return Math.round(ms / 60000) + 'm';
+      return Math.round(ms / 3600000) + 'h';
+    }
     async function getJSON(path) {
       var res = await fetch(path, { headers: { accept: 'application/json' } });
       if (!res.ok) throw new Error(path + ' -> ' + res.status);
       return res.json();
     }
+
+    // ── Activity timeline ──────────────────────────────────────────────────
+    function renderTimelineItems(items) {
+      if (!items || !items.length) return '<div class="tl-empty">no activity yet</div>';
+      return items.map(function(item) {
+        var meta = '';
+        if (item.meta) {
+          if (item.meta.tokens != null) {
+            meta += '<span class="badge tl-tokens">' + esc(item.meta.tokens) + '&thinsp;tok</span>';
+          }
+          if (item.meta.duration != null) {
+            meta += '<span class="badge tl-dur">' + esc(msToHuman(item.meta.duration)) + '</span>';
+          }
+        }
+        return '<div class="tl-row">' +
+          '<span class="tl-when">' + esc(ago(item.at)) + '</span>' +
+          '<span class="tl-kind tl-kind-' + esc(item.kind) + '">' + esc(item.kind) + '</span>' +
+          '<span class="tl-actor">' + esc(item.actor) + '</span>' +
+          '<span class="tl-summary">' + esc(item.summary) + '</span>' +
+          (meta ? '<span class="tl-meta">' + meta + '</span>' : '') +
+          '</div>';
+      }).join('');
+    }
+
+    function loadTimeline(card, id) {
+      var tl = card.querySelector('.timeline');
+      if (!tl) return;
+      tl.innerHTML = '<div class="tl-loading">loading…</div>';
+      getJSON('/tasks/' + encodeURIComponent(id) + '/activity')
+        .then(function(items) { tl.innerHTML = renderTimelineItems(items); })
+        .catch(function() { tl.innerHTML = '<div class="tl-empty">could not load activity</div>'; });
+    }
+
+    // Delegate click handling to the board container so it survives re-renders.
+    document.getElementById('board').addEventListener('click', function(e) {
+      var card = e.target.closest('.card[data-id]');
+      if (!card) return;
+      var id = card.dataset.id;
+      var wasExpanded = card.classList.contains('expanded');
+      card.classList.toggle('expanded');
+      // Only fetch when opening (not on every toggle so cached content stays).
+      if (!wasExpanded) loadTimeline(card, id);
+    });
+
+    // ── Task card rendering ────────────────────────────────────────────────
     function taskCard(t) {
       var tags = '';
       if (t.role) tags += '<span class="badge role">' + esc(t.role) + '</span>';
       if (t.assignedTo) tags += '<span class="badge agent">@' + esc(t.assignedTo) + '</span>';
-      return '<div class="card">' +
-        '<div class="id">' + esc(t.id) + '</div>' +
-        '<div class="title">' + esc(t.title) + '</div>' +
-        (tags ? '<div class="tags">' + tags + '</div>' : '') +
+      return '<div class="card" data-id="' + esc(t.id) + '">' +
+        '<div class="card-head">' +
+          '<div class="id">' + esc(t.id) + '</div>' +
+          '<div class="title">' + esc(t.title) + '</div>' +
+          (tags ? '<div class="tags">' + tags + '</div>' : '') +
+        '</div>' +
+        '<div class="timeline"></div>' +
         '</div>';
     }
     function renderBoard(tasks) {
@@ -223,17 +307,29 @@ ${columnSkeleton()}
       });
       COLUMNS.forEach(function (k) {
         var list = byCol[k];
-        var cards = document.querySelector('[data-cards="' + k + '"]');
+        var cardsEl = document.querySelector('[data-cards="' + k + '"]');
         var count = document.querySelector('[data-count="' + k + '"]');
         if (count) count.textContent = String(list.length);
-        if (!cards) return;
-        cards.innerHTML = list.length
+        if (!cardsEl) return;
+
+        // Preserve expanded state: collect which IDs are expanded before re-render.
+        var expanded = {};
+        cardsEl.querySelectorAll('.card.expanded[data-id]').forEach(function(c) {
+          expanded[c.dataset.id] = true;
+        });
+
+        cardsEl.innerHTML = list.length
           ? list.map(taskCard).join('')
           : '<div class="empty">—</div>';
+
+        // Re-expand any cards that were open, but do NOT re-fetch; keep old content.
+        Object.keys(expanded).forEach(function(id) {
+          var card = cardsEl.querySelector('.card[data-id="' + id + '"]');
+          if (card) card.classList.add('expanded');
+        });
       });
     }
     function handoffRoute(h) {
-      // Build "fromRole[@fromAgent] → toRole[@toAgent]" label
       var from = esc(h.fromRole || '?');
       var to   = esc(h.toRole   || '?');
       if (h.fromAgent) from += '<span class="badge agent">@' + esc(h.fromAgent) + '</span>';
diff --git a/src/server/routes.ts b/src/server/routes.ts
index f83c1da..cda6d2a 100644
--- a/src/server/routes.ts
+++ b/src/server/routes.ts
@@ -1,5 +1,6 @@
 import { FastifyInstance, FastifyReply } from 'fastify';
 import { createTask, listTasks, getTask, claimTask, doneTask, reviewTask, cancelTask, reopenTask } from '../core/services/taskService.js';
+import { getTaskActivity } from '../core/services/activityService.js';
 import { createHandoff, listHandoffs, getHandoff } from '../core/services/handoffService.js';
 import { createDecision, listDecisions } from '../core/services/decisionService.js';
 import { addMemory, searchMemory, listMemory } from '../core/services/memoryService.js';
@@ -115,6 +116,15 @@ export async function registerRoutes(app: FastifyInstance, cwd: string): Promise
     }
   });
 
+  app.get('/tasks/:id/activity', async (request, reply) => {
+    const { id } = request.params as { id: string };
+    try {
+      return getTaskActivity(cwd, id);
+    } catch {
+      return notFound(reply, 'Task');
+    }
+  });
+
   app.patch('/tasks/:id', async (request, reply) => {
     const { id } = request.params as { id: string };
     const patch = request.body as Partial<Task>;
@@ -126,7 +136,11 @@ export async function registerRoutes(app: FastifyInstance, cwd: string): Promise
         task = claimTask(cwd, id, patch.assignedTo);
         break;
       case 'done':
-        task = doneTask(cwd, id);
+        task = doneTask(cwd, id, {
+          doneBy: patch.doneBy as string | undefined,
+          doneTokens: patch.doneTokens as number | undefined,
+          doneDuration: patch.doneDuration as number | undefined,
+        });
         break;
       case 'review':
         task = reviewTask(cwd, id);
diff --git a/tests/activityService.test.ts b/tests/activityService.test.ts
new file mode 100644
index 0000000..7901075
--- /dev/null
+++ b/tests/activityService.test.ts
@@ -0,0 +1,148 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { mkdtempSync, rmSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { createTask, claimTask, doneTask } from '../src/core/services/taskService.js';
+import { createHandoff } from '../src/core/services/handoffService.js';
+import { addMemory } from '../src/core/services/memoryService.js';
+import { getTaskActivity } from '../src/core/services/activityService.js';
+
+describe('activityService', () => {
+  let cwd: string;
+
+  beforeEach(() => { cwd = mkdtempSync(join(tmpdir(), 'ah-act-')); });
+  afterEach(() => { rmSync(cwd, { recursive: true, force: true }); });
+
+  it('returns a "created" event for every task', () => {
+    const task = createTask(cwd, { title: 'Auth refactor', role: 'implementer' });
+    const items = getTaskActivity(cwd, task.id);
+    expect(items.length).toBeGreaterThanOrEqual(1);
+    const created = items.find((i) => i.kind === 'created');
+    expect(created).toBeDefined();
+    expect(created!.at).toBe(task.createdAt);
+    expect(created!.summary).toBe('Task created');
+  });
+
+  it('does not include a status event for an open task', () => {
+    const task = createTask(cwd, { title: 'Open task', role: 'architect' });
+    const items = getTaskActivity(cwd, task.id);
+    expect(items.every((i) => i.kind !== 'status')).toBe(true);
+  });
+
+  it('includes a status event once a task is claimed', () => {
+    const task = createTask(cwd, { title: 'Claim me', role: 'implementer' });
+    claimTask(cwd, task.id, 'codex');
+    const items = getTaskActivity(cwd, task.id);
+    const status = items.find((i) => i.kind === 'status');
+    expect(status).toBeDefined();
+    expect(status!.summary).toBe('Claimed by codex');
+    expect(status!.meta?.assignedTo).toBe('codex');
+  });
+
+  it('includes a status event with tokens/duration when task is done with metadata', () => {
+    const task = createTask(cwd, { title: 'Finish me', role: 'implementer' });
+    doneTask(cwd, task.id, { doneBy: 'claude', doneTokens: 8500, doneDuration: 120_000 });
+    const items = getTaskActivity(cwd, task.id);
+    const status = items.find((i) => i.kind === 'status');
+    expect(status).toBeDefined();
+    expect(status!.summary).toBe('Task completed');
+    expect(status!.meta?.tokens).toBe(8500);
+    expect(status!.meta?.duration).toBe(120_000);
+    expect(status!.meta?.by).toBe('claude');
+  });
+
+  it('includes handoff events linked by taskId', () => {
+    const task = createTask(cwd, { title: 'Delegated task', role: 'architect' });
+    createHandoff(cwd, {
+      fromRole: 'architect',
+      toRole: 'implementer',
+      fromAgent: 'claude',
+      toAgent: 'codex',
+      taskId: task.id,
+      summary: 'Design is ready',
+    });
+    const items = getTaskActivity(cwd, task.id);
+    const handoff = items.find((i) => i.kind === 'handoff');
+    expect(handoff).toBeDefined();
+    expect(handoff!.summary).toBe('Design is ready');
+    expect(handoff!.actor).toBe('architect → implementer');
+    expect(handoff!.meta?.fromAgent).toBe('claude');
+    expect(handoff!.meta?.toAgent).toBe('codex');
+  });
+
+  it('does NOT include handoffs for other tasks', () => {
+    const taskA = createTask(cwd, { title: 'A', role: 'implementer' });
+    const taskB = createTask(cwd, { title: 'B', role: 'architect' });
+    createHandoff(cwd, {
+      fromRole: 'architect',
+      toRole: 'implementer',
+      taskId: taskB.id,
+      summary: 'For B only',
+    });
+    const items = getTaskActivity(cwd, taskA.id);
+    expect(items.every((i) => i.kind !== 'handoff')).toBe(true);
+  });
+
+  it('includes memory/result events linked via relatedTasks', () => {
+    const task = createTask(cwd, { title: 'Build DNS cache', role: 'implementer' });
+    addMemory(cwd, {
+      title: 'DNS TTL observation',
+      category: 'technical',
+      content: 'Default TTL is 300s',
+      relatedTasks: [task.id],
+    });
+    const items = getTaskActivity(cwd, task.id);
+    const result = items.find((i) => i.kind === 'result');
+    expect(result).toBeDefined();
+    expect(result!.summary).toBe('DNS TTL observation');
+    expect(result!.actor).toBe('technical');
+    expect(result!.meta?.category).toBe('technical');
+  });
+
+  it('surfaces tokens and duration from memory in the result meta', () => {
+    const task = createTask(cwd, { title: 'Perf tuning', role: 'implementer' });
+    addMemory(cwd, {
+      title: 'Profiling results',
+      category: 'implementation',
+      content: '50ms p99',
+      relatedTasks: [task.id],
+      tokens: 2000,
+      duration: 45_000,
+      by: 'kimi',
+    });
+    const items = getTaskActivity(cwd, task.id);
+    const result = items.find((i) => i.kind === 'result');
+    expect(result!.meta?.tokens).toBe(2000);
+    expect(result!.meta?.duration).toBe(45_000);
+    expect(result!.meta?.by).toBe('kimi');
+  });
+
+  it('does NOT include memory linked to other tasks', () => {
+    const taskA = createTask(cwd, { title: 'A', role: 'implementer' });
+    const taskB = createTask(cwd, { title: 'B', role: 'implementer' });
+    addMemory(cwd, {
+      title: 'About B',
+      category: 'lesson',
+      content: 'lesson',
+      relatedTasks: [taskB.id],
+    });
+    const items = getTaskActivity(cwd, taskA.id);
+    expect(items.every((i) => i.kind !== 'result')).toBe(true);
+  });
+
+  it('returns items sorted by timestamp ascending', () => {
+    const task = createTask(cwd, { title: 'Sorted timeline', role: 'implementer' });
+    createHandoff(cwd, { fromRole: 'architect', toRole: 'implementer', taskId: task.id, summary: 'H1' });
+    addMemory(cwd, { title: 'M1', category: 'lesson', content: 'x', relatedTasks: [task.id] });
+    claimTask(cwd, task.id, 'codex');
+
+    const items = getTaskActivity(cwd, task.id);
+    for (let i = 1; i < items.length; i++) {
+      expect(items[i].at >= items[i - 1].at).toBe(true);
+    }
+  });
+
+  it('throws when the task does not exist', () => {
+    expect(() => getTaskActivity(cwd, 'TSK-9999')).toThrow();
+  });
+});
diff --git a/tests/handoffService.test.ts b/tests/handoffService.test.ts
index 4eb1b5a..875c1ac 100644
--- a/tests/handoffService.test.ts
+++ b/tests/handoffService.test.ts
@@ -3,6 +3,7 @@ import { mkdtempSync, rmSync } from 'fs';
 import { tmpdir } from 'os';
 import { join } from 'path';
 import { createHandoff, listHandoffs, getHandoff } from '../src/core/services/handoffService.js';
+import { Index } from '../src/core/index.js';
 
 describe('handoffService', () => {
   let cwd: string;
@@ -46,4 +47,25 @@ describe('handoffService', () => {
     expect(items[0].fromAgent).toBe('claude');
     expect(items[0].toAgent).toBe('codex');
   });
+
+  it('listHandoffsByTask returns only handoffs linked to that taskId', () => {
+    createHandoff(cwd, { fromRole: 'architect', toRole: 'implementer', taskId: 'TSK-0001', summary: 'For 0001' });
+    createHandoff(cwd, { fromRole: 'reviewer', toRole: 'implementer', taskId: 'TSK-0002', summary: 'For 0002' });
+    createHandoff(cwd, { fromRole: 'tester', toRole: 'implementer', summary: 'No task' });
+
+    const index = new Index(cwd);
+    const results = index.listHandoffsByTask('TSK-0001');
+    index.close();
+
+    expect(results).toHaveLength(1);
+    expect(results[0].title).toBe('For 0001');
+  });
+
+  it('listHandoffsByTask returns empty when no handoff links to the task', () => {
+    createHandoff(cwd, { fromRole: 'architect', toRole: 'implementer', taskId: 'TSK-0002', summary: 'Other' });
+    const index = new Index(cwd);
+    const results = index.listHandoffsByTask('TSK-0001');
+    index.close();
+    expect(results).toHaveLength(0);
+  });
 });
diff --git a/tests/memoryService.test.ts b/tests/memoryService.test.ts
index 4bc08c7..37f9a83 100644
--- a/tests/memoryService.test.ts
+++ b/tests/memoryService.test.ts
@@ -3,6 +3,7 @@ import { mkdtempSync, rmSync } from 'fs';
 import { tmpdir } from 'os';
 import { join } from 'path';
 import { addMemory, searchMemory, listMemory } from '../src/core/services/memoryService.js';
+import { Index } from '../src/core/index.js';
 
 describe('memoryService', () => {
   let cwd: string;
@@ -16,4 +17,46 @@ describe('memoryService', () => {
     expect(searchMemory(cwd, 'TTL')).toHaveLength(1);
     expect(listMemory(cwd)).toHaveLength(1);
   });
+
+  it('stores relatedTasks in the memory object', () => {
+    const m = addMemory(cwd, {
+      title: 'TTL lesson',
+      category: 'lesson',
+      content: 'Use short TTL',
+      relatedTasks: ['TSK-0001', 'TSK-0002'],
+    });
+    expect(m.relatedTasks).toEqual(['TSK-0001', 'TSK-0002']);
+  });
+
+  it('stores optional tokens, duration, by fields', () => {
+    const m = addMemory(cwd, {
+      title: 'Perf stats',
+      category: 'implementation',
+      content: 'p99=50ms',
+      tokens: 1500,
+      duration: 30_000,
+      by: 'kimi',
+    });
+    expect(m.tokens).toBe(1500);
+    expect(m.duration).toBe(30_000);
+    expect(m.by).toBe('kimi');
+  });
+
+  it('listMemoryByTask returns entries linked to a given task', () => {
+    addMemory(cwd, { title: 'Related', category: 'technical', content: 'x', relatedTasks: ['TSK-0042'] });
+    addMemory(cwd, { title: 'Unrelated', category: 'technical', content: 'y', relatedTasks: ['TSK-0099'] });
+    const index = new Index(cwd);
+    const results = index.listMemoryByTask('TSK-0042');
+    index.close();
+    expect(results).toHaveLength(1);
+    expect(results[0].title).toBe('Related');
+  });
+
+  it('listMemoryByTask returns empty when no memory is linked', () => {
+    addMemory(cwd, { title: 'Other', category: 'technical', content: 'y', relatedTasks: ['TSK-0099'] });
+    const index = new Index(cwd);
+    const results = index.listMemoryByTask('TSK-0001');
+    index.close();
+    expect(results).toHaveLength(0);
+  });
 });
diff --git a/tests/server.test.ts b/tests/server.test.ts
index a567190..92e3dac 100644
--- a/tests/server.test.ts
+++ b/tests/server.test.ts
@@ -121,6 +121,64 @@ describe('server routes', () => {
     expect(html).toContain('setInterval(refresh');
   });
 
+  // ── Activity timeline endpoint ─────────────────────────────────────────
+  it('GET /tasks/:id/activity returns 404 for unknown task', async () => {
+    const res = await app.inject({ method: 'GET', url: '/tasks/TSK-9999/activity' });
+    expect(res.statusCode).toBe(404);
+  });
+
+  it('GET /tasks/:id/activity returns a created event', async () => {
+    await app.inject({ method: 'POST', url: '/tasks', payload: { title: 'Auth', role: 'implementer' } });
+    const res = await app.inject({ method: 'GET', url: '/tasks/TSK-0001/activity' });
+    expect(res.statusCode).toBe(200);
+    const items = JSON.parse(res.payload) as Array<{ kind: string; summary: string }>;
+    expect(items.some((i) => i.kind === 'created')).toBe(true);
+  });
+
+  it('GET /tasks/:id/activity includes handoff events linked by taskId', async () => {
+    await app.inject({ method: 'POST', url: '/tasks', payload: { title: 'Auth', role: 'implementer' } });
+    await app.inject({
+      method: 'POST',
+      url: '/handoffs',
+      payload: { fromRole: 'architect', toRole: 'implementer', taskId: 'TSK-0001', summary: 'Design done' },
+    });
+    const res = await app.inject({ method: 'GET', url: '/tasks/TSK-0001/activity' });
+    const items = JSON.parse(res.payload) as Array<{ kind: string; summary: string }>;
+    const handoff = items.find((i) => i.kind === 'handoff');
+    expect(handoff).toBeDefined();
+    expect(handoff!.summary).toBe('Design done');
+  });
+
+  it('GET /tasks/:id/activity includes memory result events linked by relatedTasks', async () => {
+    await app.inject({ method: 'POST', url: '/tasks', payload: { title: 'DNS task', role: 'implementer' } });
+    await app.inject({
+      method: 'POST',
+      url: '/memory',
+      payload: { title: 'TTL insight', category: 'technical', content: 'Use 300s', relatedTasks: ['TSK-0001'] },
+    });
+    const res = await app.inject({ method: 'GET', url: '/tasks/TSK-0001/activity' });
+    const items = JSON.parse(res.payload) as Array<{ kind: string; summary: string }>;
+    const result = items.find((i) => i.kind === 'result');
+    expect(result).toBeDefined();
+    expect(result!.summary).toBe('TTL insight');
+  });
+
+  it('GET /tasks/:id/activity includes tokens/duration from done metadata', async () => {
+    await app.inject({ method: 'POST', url: '/tasks', payload: { title: 'Work', role: 'implementer' } });
+    await app.inject({
+      method: 'PATCH',
+      url: '/tasks/TSK-0001',
+      payload: { status: 'done', doneTokens: 5000, doneDuration: 60000, doneBy: 'claude' },
+    });
+    const res = await app.inject({ method: 'GET', url: '/tasks/TSK-0001/activity' });
+    const items = JSON.parse(res.payload) as Array<{ kind: string; meta?: Record<string, unknown> }>;
+    const status = items.find((i) => i.kind === 'status');
+    expect(status).toBeDefined();
+    expect(status!.meta?.tokens).toBe(5000);
+    expect(status!.meta?.duration).toBe(60000);
+    expect(status!.meta?.by).toBe('claude');
+  });
+
   it('board HTML contains the who-arrow rendering logic', async () => {
     const res = await app.inject({ method: 'GET', url: '/board' });
     const html = res.payload;
@@ -131,6 +189,23 @@ describe('server routes', () => {
     expect(html).toContain('who-cell');
   });
 
+  it('board HTML contains activity timeline expansion logic', async () => {
+    const res = await app.inject({ method: 'GET', url: '/board' });
+    const html = res.payload;
+    // Cards must be clickable and carry a data-id attribute
+    expect(html).toContain('data-id');
+    // The timeline div must be present inside cards
+    expect(html).toContain('class="timeline"');
+    // The activity fetch must call the /activity endpoint
+    expect(html).toContain('/activity');
+    // The expansion toggle CSS class must exist
+    expect(html).toContain('expanded');
+    // Token and duration badges must be defined
+    expect(html).toContain('tl-tokens');
+    expect(html).toContain('tl-dur');
+    expect(html).toContain('msToHuman');
+  });
+
   it('GET /handoffs returns fromRole and toRole fields', async () => {
     await app.inject({
       method: 'POST',