feat(KB-617): add Changes tab to task detail modal with file diffs

- Add modifiedFiles and baseCommitSha fields to task schema for tracking changes
- Capture list of modified files during task execution in the executor
- Add GET /tasks/:id/diff API endpoint to retrieve file list and patches
- Create TaskChangesTab component with expandable file diffs
- Integrate Changes tab into TaskDetailModal for in-progress, in-review, and done tasks
- Add CSS styles for diff viewer with syntax highlighting
- Update API client with fetchTaskDiff function and Project Management types

packages/cli/src/commands/task.ts

@@ -1416,7 +1416,7 @@ export async function runTaskPlan(initialPlanArg?: string, yesFlag = false): Pro
 
       try {
         showThinking();
-        result = await submitResponse(sessionId, response) as typeof result;
+        result = await submitResponse(sessionId, response as Record<string, unknown>) as typeof result;
         clearThinking();
       } catch (err) {
         clearThinking();

packages/core/src/db.test.ts

@@ -86,7 +86,7 @@ describe("Database", () => {
     });
 
     it("seeds schema version", () => {
-      expect(db.getSchemaVersion()).toBe(3);
+      expect(db.getSchemaVersion()).toBe(4);
     });
 
     it("seeds lastModified", () => {
@@ -109,7 +109,7 @@ describe("Database", () => {
 
     it("is idempotent - calling init() twice does not fail", () => {
       expect(() => db.init()).not.toThrow();
-      expect(db.getSchemaVersion()).toBe(3);
+      expect(db.getSchemaVersion()).toBe(4);
     });
 
     it("does not overwrite existing config on re-init", () => {
@@ -683,8 +683,8 @@ describe("schema migrations", () => {
     // Now run init() which should trigger migration
     db.init();
 
-    // Verify version bumped to 3 (includes both v1→v2 and v2→v3 migrations)
+    // Verify version bumped to 4 (includes v1→v2, v2→v3, and v3→v4 migrations)
-    expect(db.getSchemaVersion()).toBe(3);
+    expect(db.getSchemaVersion()).toBe(4);
 
     // Verify new columns exist and existing data is intact
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
@@ -709,11 +709,11 @@ describe("schema migrations", () => {
     const db = new Database(kbDir);
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(3);
+    expect(db.getSchemaVersion()).toBe(4);
 
     // Re-init should not fail
     db.init();
-    expect(db.getSchemaVersion()).toBe(3);
+    expect(db.getSchemaVersion()).toBe(4);
 
     db.close();
   });
@@ -804,11 +804,11 @@ describe("schema migrations", () => {
     // Insert a task on the v2 schema
     db.exec(`INSERT INTO tasks (id, description, "column", createdAt, updatedAt) VALUES ('KB-2', 'test v2', 'triage', '2025-01-01', '2025-01-01')`);
 
-    // Now run init() which should trigger v2→v3 migration
+    // Now run init() which should trigger migrations v2→v3→v4
     db.init();
 
-    // Verify version bumped to 3
+    // Verify version bumped to 4
-    expect(db.getSchemaVersion()).toBe(3);
+    expect(db.getSchemaVersion()).toBe(4);
 
     // Verify new columns exist and existing data is intact
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
@@ -864,7 +864,7 @@ describe("createDatabase factory", () => {
     const db = createDatabase(kbDir);
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(3);
+    expect(db.getSchemaVersion()).toBe(4);
     expect(db.getLastModified()).toBeGreaterThan(0);
 
     db.close();

packages/core/src/db.ts

@@ -58,7 +58,7 @@ export function fromJson<T>(json: string | null | undefined): T | undefined {
 
 // ── Schema Definition ────────────────────────────────────────────────
 
-const SCHEMA_VERSION = 3;
+const SCHEMA_VERSION = 4;
 
 const SCHEMA_SQL = `
 -- Tasks table with JSON columns for nested data
@@ -75,6 +75,7 @@ CREATE TABLE IF NOT EXISTS tasks (
   blockedBy TEXT,
   paused INTEGER DEFAULT 0,
   baseBranch TEXT,
+  baseCommitSha TEXT,
   modelPresetId TEXT,
   modelProvider TEXT,
   modelId TEXT,
@@ -99,7 +100,8 @@ CREATE TABLE IF NOT EXISTS tasks (
   issueInfo TEXT,
   mergeDetails TEXT,
   breakIntoSubtasks INTEGER DEFAULT 0,
-  enabledWorkflowSteps TEXT DEFAULT '[]'
+  enabledWorkflowSteps TEXT DEFAULT '[]',
+  modifiedFiles TEXT DEFAULT '[]'
 );
 
 -- Config table (single row with project settings)
@@ -322,6 +324,15 @@ export class Database {
       });
     }
 
+    if (version < 4) {
+      this.applyMigration(4, () => {
+        // Add modifiedFiles column to track files changed during agent execution
+        this.addColumnIfMissing("tasks", "modifiedFiles", "TEXT DEFAULT '[]'");
+        // Add baseCommitSha column to store the base commit for diff computation
+        this.addColumnIfMissing("tasks", "baseCommitSha", "TEXT");
+      });
+    }
+
     // Future migrations go here:
     // if (version < 3) { this.applyMigration(3, () => { ... }); }
   }

packages/core/src/store.ts

@@ -133,6 +133,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       blockedBy: row.blockedBy || undefined,
       paused: row.paused ? true : undefined,
       baseBranch: row.baseBranch || undefined,
+      baseCommitSha: row.baseCommitSha || undefined,
       modelPresetId: row.modelPresetId || undefined,
       modelProvider: row.modelProvider || undefined,
       modelId: row.modelId || undefined,
@@ -157,6 +158,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       mergeDetails: fromJson<import("./types.js").MergeDetails>(row.mergeDetails),
       breakIntoSubtasks: row.breakIntoSubtasks ? true : undefined,
       enabledWorkflowSteps: (() => { const e = fromJson<string[]>(row.enabledWorkflowSteps); return e && e.length > 0 ? e : undefined; })(),
+      modifiedFiles: (() => { const m = fromJson<string[]>(row.modifiedFiles); return m && m.length > 0 ? m : undefined; })(),
     };
   }
 
@@ -167,15 +169,15 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     this.db.prepare(`
       INSERT OR REPLACE INTO tasks (
         id, title, description, "column", status, size, reviewLevel, currentStep,
-        worktree, blockedBy, paused, baseBranch, modelPresetId, modelProvider,
+        worktree, blockedBy, paused, baseBranch, baseCommitSha, modelPresetId, modelProvider,
         modelId, validatorModelProvider, validatorModelId, mergeRetries, error,
         summary, thinkingLevel, createdAt, updatedAt, columnMovedAt,
         dependencies, steps, log, attachments, steeringComments,
         comments, workflowStepResults, prInfo, issueInfo, mergeDetails,
-        breakIntoSubtasks, enabledWorkflowSteps
+        breakIntoSubtasks, enabledWorkflowSteps, modifiedFiles
       ) VALUES (
         ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?,
-        ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?
+        ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?
       )
     `).run(
       task.id,
@@ -190,6 +192,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       task.blockedBy ?? null,
       task.paused ? 1 : 0,
       task.baseBranch ?? null,
+      task.baseCommitSha ?? null,
       task.modelPresetId ?? null,
       task.modelProvider ?? null,
       task.modelId ?? null,
@@ -214,6 +217,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       toJsonNullable(task.mergeDetails),
       task.breakIntoSubtasks ? 1 : 0,
       toJson(task.enabledWorkflowSteps || []),
+      toJson(task.modifiedFiles || []),
     );
     this.db.bumpLastModified();
   }
@@ -875,7 +879,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
 
   async updateTask(
     id: string,
-    updates: { title?: string; description?: string; prompt?: string; worktree?: string; status?: string | null; dependencies?: string[]; blockedBy?: string | null; paused?: boolean; baseBranch?: string; size?: "S" | "M" | "L"; reviewLevel?: number; mergeRetries?: number; modelProvider?: string | null; modelId?: string | null; validatorModelProvider?: string | null; validatorModelId?: string | null; error?: string | null; summary?: string | null; workflowStepResults?: import("./types.js").WorkflowStepResult[] | null },
+    updates: { title?: string; description?: string; prompt?: string; worktree?: string; status?: string | null; dependencies?: string[]; blockedBy?: string | null; paused?: boolean; baseBranch?: string; baseCommitSha?: string; size?: "S" | "M" | "L"; reviewLevel?: number; mergeRetries?: number; modelProvider?: string | null; modelId?: string | null; validatorModelProvider?: string | null; validatorModelId?: string | null; error?: string | null; summary?: string | null; workflowStepResults?: import("./types.js").WorkflowStepResult[] | null; modifiedFiles?: string[] | null },
   ): Promise<Task> {
     return this.withTaskLock(id, async () => {
       // Validate that task doesn't depend on itself
@@ -925,6 +929,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       }
       if (updates.paused !== undefined) task.paused = updates.paused || undefined;
       if (updates.baseBranch !== undefined) task.baseBranch = updates.baseBranch;
+      if (updates.baseCommitSha !== undefined) task.baseCommitSha = updates.baseCommitSha;
       if (updates.size !== undefined) task.size = updates.size;
       if (updates.reviewLevel !== undefined) task.reviewLevel = updates.reviewLevel;
       if (updates.mergeRetries !== undefined) task.mergeRetries = updates.mergeRetries;
@@ -963,6 +968,11 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       } else if (updates.workflowStepResults !== undefined) {
         task.workflowStepResults = updates.workflowStepResults;
       }
+      if (updates.modifiedFiles === null) {
+        task.modifiedFiles = undefined;
+      } else if (updates.modifiedFiles !== undefined) {
+        task.modifiedFiles = updates.modifiedFiles;
+      }
       task.updatedAt = new Date().toISOString();
 
       await this.atomicWriteTaskJson(dir, task);
@@ -1465,8 +1475,10 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
           breakIntoSubtasks: task.breakIntoSubtasks,
           paused: task.paused,
           baseBranch: task.baseBranch,
+          baseCommitSha: task.baseCommitSha,
           mergeRetries: task.mergeRetries,
           error: task.error,
+          modifiedFiles: task.modifiedFiles,
         };
 
         // Write to archivedTasks table in SQLite
@@ -2295,8 +2307,10 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         breakIntoSubtasks: task.breakIntoSubtasks,
         paused: task.paused,
         baseBranch: task.baseBranch,
+        baseCommitSha: task.baseCommitSha,
         mergeRetries: task.mergeRetries,
         error: task.error,
+        modifiedFiles: task.modifiedFiles,
       };
 
       // Write to archivedTasks table
@@ -2359,7 +2373,8 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       validatorModelProvider: entry.validatorModelProvider,
       validatorModelId: entry.validatorModelId,
       breakIntoSubtasks: entry.breakIntoSubtasks,
-      // Intentionally NOT restoring: worktree, status, blockedBy, paused, baseBranch, error, steeringComments
+      modifiedFiles: entry.modifiedFiles,
+      // Intentionally NOT restoring: worktree, status, blockedBy, paused, baseBranch, baseCommitSha, error, steeringComments
     };
 
     // Write task.json

packages/core/src/types.ts

@@ -387,6 +387,10 @@ export interface Task {
    *  unmerged branch. The executor reads this to branch from the
    *  dependency's branch instead of HEAD. Cleared after worktree creation. */
   baseBranch?: string;
+  /** Commit SHA of the base branch at worktree creation time.
+   *  Used for computing file diffs when reviewing task changes.
+   *  Set by the executor when creating the worktree. */
+  baseCommitSha?: string;
   attachments?: TaskAttachment[];
   steeringComments?: SteeringComment[];
   comments?: TaskComment[];
@@ -428,6 +432,8 @@ export interface Task {
   error?: string;
   /** Optional summary of what was changed/fixed when task is completed */
   summary?: string;
+  /** Files modified during agent execution, captured at task completion time */
+  modifiedFiles?: string[];
   /** ISO-8601 timestamp of when the task last entered its current column.
    *  Used to sort cards within a column so that recently-moved cards appear at the top. */
   columnMovedAt?: string;
@@ -523,6 +529,9 @@ export interface GlobalSettings {
   /** ntfy.sh topic name for push notifications. When set along with ntfyEnabled,
    *  notifications are sent to https://ntfy.sh/{topic} when tasks complete or fail. */
   ntfyTopic?: string;
+  /** Default project ID for the current user. Used to automatically select
+   *  the default project when opening the dashboard without a specific project. */
+  defaultProjectId?: string;
 }
 
 /**
@@ -682,6 +691,7 @@ export const DEFAULT_GLOBAL_SETTINGS: Required<Pick<GlobalSettings, "themeMode"
   defaultThinkingLevel: undefined,
   ntfyEnabled: false,
   ntfyTopic: undefined,
+  defaultProjectId: undefined,
 };
 
 /** Default values for project-level settings. */
@@ -740,6 +750,7 @@ export const GLOBAL_SETTINGS_KEYS: ReadonlyArray<keyof GlobalSettings> = [
   "defaultThinkingLevel",
   "ntfyEnabled",
   "ntfyTopic",
+  "defaultProjectId",
 ] as const;
 
 /** Keys that belong to the project settings scope. */
@@ -861,8 +872,11 @@ export interface ArchivedTaskEntry {
   breakIntoSubtasks?: boolean;
   paused?: boolean;
   baseBranch?: string;
+  baseCommitSha?: string;
   mergeRetries?: number;
   error?: string;
+  /** Files modified during agent execution, captured at task completion time */
+  modifiedFiles?: string[];
 }
 
 /** Type of planning question presented to the user */

packages/dashboard/app/api.ts

@@ -1722,3 +1722,160 @@ export async function summarizeTitle(
 
   return data.title;
 }
+
+// ── Project Management API (Multi-Project Support) ───────────────────────
+
+/** Project information returned by project endpoints */
+export interface ProjectInfo {
+  id: string;
+  name: string;
+  path: string;
+  status: "active" | "paused" | "errored" | "initializing";
+  isolationMode: "in-process" | "child-process";
+  createdAt: string;
+  updatedAt: string;
+  lastActivityAt?: string;
+}
+
+/** Project health metrics */
+export interface ProjectHealth {
+  projectId: string;
+  status: "active" | "paused" | "errored" | "initializing";
+  activeTaskCount: number;
+  inFlightAgentCount: number;
+  lastActivityAt?: string;
+  lastErrorAt?: string;
+  lastErrorMessage?: string;
+  totalTasksCompleted: number;
+  totalTasksFailed: number;
+  averageTaskDurationMs?: number;
+  updatedAt: string;
+}
+
+/** Unified activity feed entry */
+export interface ActivityFeedEntry {
+  id: string;
+  timestamp: string;
+  type: "task:created" | "task:moved" | "task:updated" | "task:deleted" | "task:merged" | "task:failed" | "settings:updated";
+  projectId: string;
+  projectName: string;
+  taskId?: string;
+  taskTitle?: string;
+  details: string;
+  metadata?: Record<string, unknown>;
+}
+
+/** Input for creating a new project */
+export interface ProjectCreateInput {
+  name: string;
+  path: string;
+  isolationMode?: "in-process" | "child-process";
+}
+
+/** Options for fetching activity feed */
+export interface FeedOptions {
+  limit?: number;
+  since?: string;
+  projectId?: string;
+  type?: ActivityFeedEntry["type"];
+}
+
+/** Global concurrency state across all projects */
+export interface GlobalConcurrencyState {
+  globalMaxConcurrent: number;
+  currentlyActive: number;
+  queuedCount: number;
+  projectsActive: Record<string, number>;
+}
+
+/** First run status response */
+export interface FirstRunStatus {
+  hasProjects: boolean;
+  singleProjectPath: string | null;
+}
+
+/** Fetch all registered projects */
+export function fetchProjects(): Promise<ProjectInfo[]> {
+  return api<ProjectInfo[]>("/projects");
+}
+
+/** Register a new project */
+export function registerProject(input: ProjectCreateInput): Promise<ProjectInfo> {
+  return api<ProjectInfo>("/projects", {
+    method: "POST",
+    body: JSON.stringify(input),
+  });
+}
+
+/** Unregister a project */
+export function unregisterProject(id: string): Promise<void> {
+  return api<void>(`/projects/${encodeURIComponent(id)}`, {
+    method: "DELETE",
+  });
+}
+
+/** Fetch health metrics for a specific project */
+export function fetchProjectHealth(id: string): Promise<ProjectHealth> {
+  return api<ProjectHealth>(`/projects/${encodeURIComponent(id)}/health`);
+}
+
+/** Fetch unified activity feed */
+export function fetchActivityFeed(options?: FeedOptions): Promise<ActivityFeedEntry[]> {
+  const params = new URLSearchParams();
+  if (options?.limit !== undefined) params.set("limit", String(options.limit));
+  if (options?.since) params.set("since", options.since);
+  if (options?.projectId) params.set("projectId", options.projectId);
+  if (options?.type) params.set("type", options.type);
+  
+  const query = params.size > 0 ? `?${params.toString()}` : "";
+  return api<ActivityFeedEntry[]>(`/activity-feed${query}`);
+}
+
+/** Pause a project */
+export function pauseProject(id: string): Promise<ProjectInfo> {
+  return api<ProjectInfo>(`/projects/${encodeURIComponent(id)}/pause`, {
+    method: "POST",
+  });
+}
+
+/** Resume a paused project */
+export function resumeProject(id: string): Promise<ProjectInfo> {
+  return api<ProjectInfo>(`/projects/${encodeURIComponent(id)}/resume`, {
+    method: "POST",
+  });
+}
+
+/** Fetch first run status to detect if user needs setup wizard */
+export function fetchFirstRunStatus(): Promise<FirstRunStatus> {
+  return api<FirstRunStatus>("/first-run-status");
+}
+
+/** Fetch global concurrency state */
+export function fetchGlobalConcurrency(): Promise<GlobalConcurrencyState> {
+  return api<GlobalConcurrencyState>("/global-concurrency");
+}
+
+/** Fetch tasks for a specific project */
+export function fetchProjectTasks(projectId: string, limit?: number, offset?: number): Promise<Task[]> {
+  const params = new URLSearchParams();
+  params.set("projectId", projectId);
+  if (limit !== undefined) params.set("limit", String(limit));
+  if (offset !== undefined) params.set("offset", String(offset));
+  return api<Task[]>(`/tasks?${params.toString()}`);
+}
+
+/** Fetch project-specific config */
+export function fetchProjectConfig(projectId: string): Promise<{ maxConcurrent: number; rootDir: string }> {
+  return api<{ maxConcurrent: number; rootDir: string }>(`/projects/${encodeURIComponent(projectId)}/config`);
+}
+
+/** Diff information for a task */
+export interface TaskDiff {
+  files: string[];
+  diffs: Record<string, { stat: string; patch: string }>;
+}
+
+/** Fetch diff information for a task */
+export function fetchTaskDiff(taskId: string): Promise<TaskDiff> {
+  return api<TaskDiff>(`/tasks/${encodeURIComponent(taskId)}/diff`);
+}

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -13,6 +13,7 @@ import { ModelSelectorTab } from "./ModelSelectorTab";
 import { PrSection } from "./PrSection";
 import { TaskComments } from "./TaskComments";
 import { MergeDetails } from "./MergeDetails";
+import { TaskChangesTab } from "./TaskChangesTab";
 
 interface ModelSelection {
   provider?: string;
@@ -105,7 +106,7 @@ export function TaskDetailModal({
   addToast,
   githubTokenConfigured,
 }: TaskDetailModalProps) {
-  const [activeTab, setActiveTab] = useState<"definition" | "activity" | "agent-log" | "steering" | "comments" | "model">("definition");
+  const [activeTab, setActiveTab] = useState<"definition" | "activity" | "agent-log" | "changes" | "steering" | "comments" | "model">("definition");
   const [attachments, setAttachments] = useState<TaskAttachment[]>(task.attachments || []);
   const [uploading, setUploading] = useState(false);
   const [dependencies, setDependencies] = useState<string[]>(task.dependencies || []);
@@ -671,6 +672,14 @@ export function TaskDetailModal({
             >
               Agent Log
             </button>
+            {(task.column === "in-progress" || task.column === "in-review" || task.column === "done") && (
+              <button
+                className={`detail-tab${activeTab === "changes" ? " detail-tab-active" : ""}`}
+                onClick={() => setActiveTab("changes")}
+              >
+                Changes
+              </button>
+            )}
             <button
               className={`detail-tab${activeTab === "steering" ? " detail-tab-active" : ""}`}
               onClick={() => setActiveTab("steering")}
@@ -703,6 +712,8 @@ export function TaskDetailModal({
                 validatorModel={getValidatorSelection(task)}
               />
             </div>
+          ) : activeTab === "changes" ? (
+            <TaskChangesTab taskId={task.id} worktree={task.worktree} />
           ) : activeTab === "steering" ? (
             <SteeringTab task={task} addToast={addToast} />
           ) : activeTab === "comments" ? (

packages/dashboard/app/styles.css

@@ -11054,3 +11054,134 @@ html .column.drag-over * {
 [data-theme="light"] .gm-load-more:hover {
   background: rgba(0, 0, 0, 0.03);
 }
+
+/* ── Task Changes Tab Styles ─────────────────────────────────────────────── */
+
+.task-changes-tab {
+  padding: 16px;
+}
+
+.changes-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 16px;
+}
+
+.changes-header h4 {
+  margin: 0;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 14px;
+  font-weight: 500;
+}
+
+.changes-file-list {
+  border: 1px solid var(--border, #30363d);
+  border-radius: 8px;
+  overflow: hidden;
+}
+
+.changes-file-item {
+  border-bottom: 1px solid var(--border, #30363d);
+}
+
+.changes-file-item:last-child {
+  border-bottom: none;
+}
+
+.changes-file-item.expanded {
+  background: var(--bg-secondary, #161b22);
+}
+
+.changes-file-header {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 10px 12px;
+  background: none;
+  border: none;
+  width: 100%;
+  text-align: left;
+  cursor: pointer;
+  color: var(--text-primary, #c9d1d9);
+  font-size: 13px;
+  transition: background 0.15s;
+}
+
+.changes-file-header:hover {
+  background: var(--bg-hover, #1f242c);
+}
+
+.changes-file-toggle {
+  display: flex;
+  align-items: center;
+  color: var(--text-secondary, #8b949e);
+  flex-shrink: 0;
+}
+
+.changes-file-status {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 20px;
+  height: 20px;
+  border-radius: 4px;
+  font-size: 11px;
+  font-weight: 600;
+  flex-shrink: 0;
+}
+
+.changes-file-path {
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+}
+
+.changes-file-stat {
+  color: var(--text-secondary, #8b949e);
+  font-size: 11px;
+  flex-shrink: 0;
+  margin-left: 8px;
+}
+
+.changes-file-content {
+  border-top: 1px solid var(--border, #30363d);
+  background: var(--bg-primary, #0d1117);
+}
+
+.changes-diff-patch {
+  margin: 0;
+  padding: 12px;
+  font-size: 12px;
+  line-height: 1.5;
+  overflow-x: auto;
+  white-space: pre;
+  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  color: var(--text-primary, #c9d1d9);
+}
+
+.changes-diff-patch code {
+  background: none;
+  padding: 0;
+}
+
+/* Syntax highlighting for diff */
+.changes-diff-patch .diff-add,
+.changes-diff-patch [data-prefix="+"] {
+  color: #3fb950;
+}
+
+.changes-diff-patch .diff-del,
+.changes-diff-patch [data-prefix="-"] {
+  color: #f85149;
+}
+
+.changes-diff-patch .diff-hunk,
+.changes-diff-patch [data-prefix="@@"] {
+  color: #58a6ff;
+}

packages/dashboard/src/mission-routes.ts

@@ -25,6 +25,8 @@ import type {
   FeatureCreateInput,
   MissionStatus,
   MilestoneStatus,
+  SliceStatus,
+  FeatureStatus,
   InterviewState,
 } from "@fusion/core";
 import {
@@ -41,20 +43,29 @@ function validateUuid(id: string): boolean {
   return /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i.test(id);
 }
 
-function validateMissionId(id: string): boolean {
+function validateMissionId(id: string | string[]): boolean {
-  return /^M-\d+$/.test(id);
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^M-\d+$/.test(str);
 }
 
-function validateMilestoneId(id: string): boolean {
+function validateMilestoneId(id: string | string[]): boolean {
-  return /^MS-\d+$/.test(id);
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^MS-\d+$/.test(str);
 }
 
-function validateSliceId(id: string): boolean {
+function validateSliceId(id: string | string[]): boolean {
-  return /^SL-\d+$/.test(id);
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^SL-\d+$/.test(str);
 }
 
-function validateFeatureId(id: string): boolean {
+function validateFeatureId(id: string | string[]): boolean {
-  return /^F-\d+$/.test(id);
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^F-\d+$/.test(str);
+}
+
+/** Helper to extract string from Express param (handles string | string[]) */
+function paramString(value: string | string[]): string {
+  return Array.isArray(value) ? value[0] : value;
 }
 
 function validateTitle(title: unknown): string {
@@ -174,7 +185,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/:missionId",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
 
       if (!validateMissionId(missionId)) {
         res.status(400).json({ error: "Invalid mission ID format" });
@@ -198,7 +209,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.patch(
     "/:missionId",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
       const { title, description, status } = req.body;
 
       if (!validateMissionId(missionId)) {
@@ -243,7 +254,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.delete(
     "/:missionId",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
 
       if (!validateMissionId(missionId)) {
         res.status(400).json({ error: "Invalid mission ID format" });
@@ -268,7 +279,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/:missionId/status",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
 
       if (!validateMissionId(missionId)) {
         res.status(400).json({ error: "Invalid mission ID format" });
@@ -295,7 +306,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/:missionId/interview-state",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
 
       if (!validateMissionId(missionId)) {
         res.status(400).json({ error: "Invalid mission ID format" });
@@ -319,7 +330,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/:missionId/interview-state",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
       const { state } = req.body;
 
       if (!validateMissionId(missionId)) {
@@ -351,7 +362,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/:missionId/milestones",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
 
       if (!validateMissionId(missionId)) {
         res.status(400).json({ error: "Invalid mission ID format" });
@@ -378,7 +389,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/:missionId/milestones",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
       const { title, description, dependencies } = req.body;
 
       if (!validateMissionId(missionId)) {
@@ -414,7 +425,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/:missionId/milestones/reorder",
     asyncHandler(async (req, res) => {
-      const { missionId } = req.params;
+      const missionId = paramString(req.params.missionId);
 
       if (!validateMissionId(missionId)) {
         res.status(400).json({ error: "Invalid mission ID format" });
@@ -456,7 +467,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/milestones/:milestoneId",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
 
       if (!validateMilestoneId(milestoneId)) {
         res.status(400).json({ error: "Invalid milestone ID format" });
@@ -480,7 +491,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.patch(
     "/milestones/:milestoneId",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
       const { title, description, status, dependencies } = req.body;
 
       if (!validateMilestoneId(milestoneId)) {
@@ -528,7 +539,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.delete(
     "/milestones/:milestoneId",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
 
       if (!validateMilestoneId(milestoneId)) {
         res.status(400).json({ error: "Invalid milestone ID format" });
@@ -555,7 +566,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/milestones/:milestoneId/interview-state",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
 
       if (!validateMilestoneId(milestoneId)) {
         res.status(400).json({ error: "Invalid milestone ID format" });
@@ -579,7 +590,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/milestones/:milestoneId/interview-state",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
       const { state } = req.body;
 
       if (!validateMilestoneId(milestoneId)) {
@@ -611,7 +622,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/milestones/:milestoneId/slices",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
 
       if (!validateMilestoneId(milestoneId)) {
         res.status(400).json({ error: "Invalid milestone ID format" });
@@ -638,7 +649,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/milestones/:milestoneId/slices",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
       const { title, description } = req.body;
 
       if (!validateMilestoneId(milestoneId)) {
@@ -672,7 +683,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/milestones/:milestoneId/slices/reorder",
     asyncHandler(async (req, res) => {
-      const { milestoneId } = req.params;
+      const milestoneId = paramString(req.params.milestoneId);
 
       if (!validateMilestoneId(milestoneId)) {
         res.status(400).json({ error: "Invalid milestone ID format" });
@@ -714,7 +725,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/slices/:sliceId",
     asyncHandler(async (req, res) => {
-      const { sliceId } = req.params;
+      const sliceId = paramString(req.params.sliceId);
 
       if (!validateSliceId(sliceId)) {
         res.status(400).json({ error: "Invalid slice ID format" });
@@ -738,7 +749,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.patch(
     "/slices/:sliceId",
     asyncHandler(async (req, res) => {
-      const { sliceId } = req.params;
+      const sliceId = paramString(req.params.sliceId);
       const { title, description, status } = req.body;
 
       if (!validateSliceId(sliceId)) {
@@ -783,7 +794,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.delete(
     "/slices/:sliceId",
     asyncHandler(async (req, res) => {
-      const { sliceId } = req.params;
+      const sliceId = paramString(req.params.sliceId);
 
       if (!validateSliceId(sliceId)) {
         res.status(400).json({ error: "Invalid slice ID format" });
@@ -808,7 +819,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/slices/:sliceId/activate",
     asyncHandler(async (req, res) => {
-      const { sliceId } = req.params;
+      const sliceId = paramString(req.params.sliceId);
 
       if (!validateSliceId(sliceId)) {
         res.status(400).json({ error: "Invalid slice ID format" });
@@ -837,7 +848,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/slices/:sliceId/features",
     asyncHandler(async (req, res) => {
-      const { sliceId } = req.params;
+      const sliceId = paramString(req.params.sliceId);
 
       if (!validateSliceId(sliceId)) {
         res.status(400).json({ error: "Invalid slice ID format" });
@@ -862,7 +873,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/slices/:sliceId/features",
     asyncHandler(async (req, res) => {
-      const { sliceId } = req.params;
+      const sliceId = paramString(req.params.sliceId);
       const { title, description, acceptanceCriteria } = req.body;
 
       if (!validateSliceId(sliceId)) {
@@ -898,7 +909,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.get(
     "/features/:featureId",
     asyncHandler(async (req, res) => {
-      const { featureId } = req.params;
+      const featureId = paramString(req.params.featureId);
 
       if (!validateFeatureId(featureId)) {
         res.status(400).json({ error: "Invalid feature ID format" });
@@ -922,7 +933,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.patch(
     "/features/:featureId",
     asyncHandler(async (req, res) => {
-      const { featureId } = req.params;
+      const featureId = paramString(req.params.featureId);
       const { title, description, acceptanceCriteria, status } = req.body;
 
       if (!validateFeatureId(featureId)) {
@@ -970,7 +981,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.delete(
     "/features/:featureId",
     asyncHandler(async (req, res) => {
-      const { featureId } = req.params;
+      const featureId = paramString(req.params.featureId);
 
       if (!validateFeatureId(featureId)) {
         res.status(400).json({ error: "Invalid feature ID format" });
@@ -995,7 +1006,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/features/:featureId/link-task",
     asyncHandler(async (req, res) => {
-      const { featureId } = req.params;
+      const featureId = paramString(req.params.featureId);
       const { taskId } = req.body;
 
       if (!validateFeatureId(featureId)) {
@@ -1034,7 +1045,7 @@ export function createMissionRouter(store: TaskStore): Router {
   router.post(
     "/features/:featureId/unlink-task",
     asyncHandler(async (req, res) => {
-      const { featureId } = req.params;
+      const featureId = paramString(req.params.featureId);
 
       if (!validateFeatureId(featureId)) {
         res.status(400).json({ error: "Invalid feature ID format" });

packages/dashboard/src/routes.ts

@@ -1841,6 +1841,82 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
     }
   });
 
+  /**
+   * GET /api/tasks/:id/diff
+   * Get detailed diff information for files modified during task execution.
+   * Returns: { files: string[]; diffs: Record<string, { stat: string; patch: string }> }
+   */
+  router.get("/tasks/:id/diff", async (req, res) => {
+    try {
+      const task = await store.getTask(req.params.id);
+      
+      // Only tasks with worktrees can have diffs
+      if (!task.worktree || !existsSync(task.worktree)) {
+        res.json({ files: [], diffs: {} });
+        return;
+      }
+
+      // Use stored modifiedFiles if available, otherwise compute on-the-fly
+      let files = task.modifiedFiles;
+      
+      if (!files || files.length === 0) {
+        // Fallback: compute files using git diff
+        try {
+          const baseRef = task.baseCommitSha ?? "HEAD~1";
+          const output = execSync(`git diff --name-only ${baseRef}..HEAD`, {
+            cwd: task.worktree,
+            encoding: "utf-8",
+            timeout: 5000,
+          }).trim();
+          files = output ? output.split("\n").filter(Boolean) : [];
+        } catch {
+          files = [];
+        }
+      }
+
+      if (files.length === 0) {
+        res.json({ files: [], diffs: {} });
+        return;
+      }
+
+      // Compute diffs for each file
+      const diffs: Record<string, { stat: string; patch: string }> = {};
+      const baseRef = task.baseCommitSha ?? "HEAD~1";
+
+      for (const file of files) {
+        try {
+          // Get stat for this file
+          const stat = execSync(`git diff --stat ${baseRef}..HEAD -- "${file}"`, {
+            cwd: task.worktree,
+            encoding: "utf-8",
+            timeout: 5000,
+          }).trim();
+
+          // Get patch for this file
+          const patch = execSync(`git diff ${baseRef}..HEAD -- "${file}"`, {
+            cwd: task.worktree,
+            encoding: "utf-8",
+            timeout: 10000,
+          });
+
+          diffs[file] = { stat, patch };
+        } catch (err: any) {
+          // Log error but continue with other files
+          console.warn(`Failed to get diff for ${file}:`, err.message);
+          diffs[file] = { stat: "", patch: "" };
+        }
+      }
+
+      res.json({ files, diffs });
+    } catch (err: any) {
+      if (err.code === "ENOENT") {
+        res.status(404).json({ error: `Task ${req.params.id} not found` });
+      } else {
+        res.status(500).json({ error: err.message || "Internal server error" });
+      }
+    }
+  });
+
   /**
    * GET /api/tasks/:id/workflow-results
    * Get workflow step execution results for a task.

packages/engine/src/executor.ts

@@ -455,6 +455,23 @@ export class TaskExecutor {
         worktreePath = await this.createWorktree(branchName, worktreePath, task.id);
       }
 
+      // Capture the base commit SHA for diff computation
+      // This is done after worktree creation when we're on the new branch
+      if (!task.baseCommitSha) {
+        try {
+          const baseCommitSha = execSync("git rev-parse HEAD", {
+            cwd: worktreePath,
+            stdio: "pipe",
+            encoding: "utf-8",
+          }).trim();
+          await this.store.updateTask(task.id, { baseCommitSha });
+          executorLog.log(`${task.id}: captured baseCommitSha ${baseCommitSha.slice(0, 7)}`);
+        } catch (err: any) {
+          executorLog.log(`Failed to capture baseCommitSha for ${task.id}: ${err.message}`);
+          // Non-fatal: task can continue without baseCommitSha
+        }
+      }
+
       this.activeWorktrees.set(task.id, worktreePath);
 
       this.options.onStart?.(task, worktreePath);
@@ -569,6 +586,14 @@ export class TaskExecutor {
           }
 
           if (taskDone) {
+            // Capture modified files before running workflow steps
+            const updatedTask = await this.store.getTask(task.id);
+            const modifiedFiles = this.captureModifiedFiles(worktreePath, updatedTask.baseCommitSha);
+            if (modifiedFiles.length > 0) {
+              await this.store.updateTask(task.id, { modifiedFiles });
+              executorLog.log(`${task.id}: captured ${modifiedFiles.length} modified files`);
+            }
+
             // Run workflow steps before moving to in-review
             const workflowSuccess = await this.runWorkflowSteps(task, worktreePath, settings);
             if (!workflowSuccess) {
@@ -1065,6 +1090,61 @@ export class TaskExecutor {
     await this.store.logEntry(taskId, "Execution stopped — work discarded, moved to triage for re-specification");
   }
 
+  /**
+   * Capture the list of files modified during agent execution.
+   * Uses git diff against the stored baseCommitSha to determine what changed.
+   * Returns an empty array if no changes or if git commands fail.
+   */
+  private captureModifiedFiles(worktreePath: string, baseCommitSha?: string): string[] {
+    try {
+      // Determine the base reference for diff
+      // If baseCommitSha is stored, use it; otherwise fall back to merge-base with HEAD
+      let baseRef = baseCommitSha;
+      if (!baseRef) {
+        // Try to find merge-base with main/master as fallback
+        try {
+          baseRef = execSync("git merge-base HEAD origin/main 2>/dev/null || git merge-base HEAD main", {
+            cwd: worktreePath,
+            stdio: "pipe",
+            encoding: "utf-8",
+          }).trim();
+        } catch {
+          // If merge-base fails, use HEAD~1 as last resort
+          try {
+            baseRef = execSync("git rev-parse HEAD~1", {
+              cwd: worktreePath,
+              stdio: "pipe",
+              encoding: "utf-8",
+            }).trim();
+          } catch {
+            executorLog.log(`Could not determine base commit for diff in ${worktreePath}`);
+            return [];
+          }
+        }
+      }
+
+      if (!baseRef) {
+        return [];
+      }
+
+      // Get list of modified files using git diff --name-only
+      const output = execSync(`git diff --name-only ${baseRef}..HEAD`, {
+        cwd: worktreePath,
+        stdio: "pipe",
+        encoding: "utf-8",
+      }).trim();
+
+      if (!output) {
+        return [];
+      }
+
+      return output.split("\n").filter(Boolean);
+    } catch (err: any) {
+      executorLog.log(`Failed to capture modified files: ${err.message}`);
+      return [];
+    }
+  }
+
   // ── Worktree management ────────────────────────────────────────────
 
   /**