feat(KB-617): add diff viewer tab to task detail modal

- Add modifiedFiles and baseCommitSha tracking during task execution - Create GET /tasks/:id/diff API endpoint for file list and patches - Build TaskChangesTab component with expandable file diffs - Integrate Changes tab into TaskDetailModal for in-progress, in-review, and done tasks - Add database columns and types for diff tracking - Update executor to capture modified files during agent sessions
2026-03-31 23:31:04 -07:00
parent 7eca797c0f
commit e5c598122f
12 changed files with 386 additions and 28 deletions
--- a/packages/cli/src/commands/task.ts
+++ b/packages/cli/src/commands/task.ts
@@ -1423,7 +1423,7 @@ export async function runTaskPlan(initialPlanArg?: string, yesFlag = false, proj

      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();
--- a/packages/core/src/db.test.ts
+++ b/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)
-    expect(db.getSchemaVersion()).toBe(3);
+    // Verify version bumped to 4 (includes v1→v2, v2→v3, and v3→v4 migrations)
+    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
-    expect(db.getSchemaVersion()).toBe(3);
+    // Verify version bumped to 4
+    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();
--- a/packages/core/src/db.ts
+++ b/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, () => { ... }); }
  }
--- a/packages/core/src/store.ts
+++ b/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
--- a/packages/core/src/types.ts
+++ b/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 */
--- a/packages/dashboard/app/api.ts
+++ b/packages/dashboard/app/api.ts
@@ -1868,3 +1868,14 @@ export function fetchProjectTasks(projectId: string, limit?: number, offset?: nu
 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`);
+}
--- a/packages/dashboard/app/components/SetupWizard.tsx
+++ b/packages/dashboard/app/components/SetupWizard.tsx
@@ -396,7 +396,7 @@ export function SetupWizard({ isOpen, onClose, onProjectCreated, onRegisterProje
              <button
                className="btn btn-primary"
                onClick={handleValidate}
-                disabled={state.isValidating || state.validationError}
+                disabled={state.isValidating || !!state.validationError}
              >
                {state.isValidating ? (
                  <>
--- a/packages/dashboard/app/components/TaskDetailModal.tsx
+++ b/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" ? (
--- a/packages/dashboard/app/styles.css
+++ b/packages/dashboard/app/styles.css
@@ -11812,3 +11812,134 @@ 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;
+}
--- a/packages/dashboard/src/mission-routes.ts
+++ b/packages/dashboard/src/mission-routes.ts
@@ -51,20 +51,29 @@ 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 {
-  return /^M-\d+$/.test(id);
+function validateMissionId(id: string | string[]): boolean {
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^M-\d+$/.test(str);
 }

-function validateMilestoneId(id: string): boolean {
-  return /^MS-\d+$/.test(id);
+function validateMilestoneId(id: string | string[]): boolean {
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^MS-\d+$/.test(str);
 }

-function validateSliceId(id: string): boolean {
-  return /^SL-\d+$/.test(id);
+function validateSliceId(id: string | string[]): boolean {
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^SL-\d+$/.test(str);
 }

-function validateFeatureId(id: string): boolean {
-  return /^F-\d+$/.test(id);
+function validateFeatureId(id: string | string[]): boolean {
+  const str = Array.isArray(id) ? id[0] : id;
+  return /^F-\d+$/.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 {
--- a/packages/dashboard/src/routes.ts
+++ b/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.
--- a/packages/engine/src/executor.ts
+++ b/packages/engine/src/executor.ts
@@ -457,6 +457,23 @@ 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);
@@ -571,6 +588,14 @@ 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) {
@@ -1067,6 +1092,61 @@ 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 ────────────────────────────────────────────

  /**