diff --git a/packages/core/src/__tests__/metadata.test.ts b/packages/core/src/__tests__/metadata.test.ts
index 03962c370..ca62f8115 100644
--- a/packages/core/src/__tests__/metadata.test.ts
+++ b/packages/core/src/__tests__/metadata.test.ts
@@ -323,6 +323,116 @@ describe("readArchivedMetadataRaw", () => {
   });
 });
 
+describe("atomic writes", () => {
+  it("writeMetadata leaves no .tmp files behind", () => {
+    writeMetadata(dataDir, "atomic-1", {
+      worktree: "/tmp/w",
+      branch: "main",
+      status: "working",
+    });
+
+    const files = readdirSync(dataDir);
+    const tmpFiles = files.filter((f) => f.includes(".tmp."));
+    expect(tmpFiles).toHaveLength(0);
+    // Verify the actual file was written correctly
+    const meta = readMetadata(dataDir, "atomic-1");
+    expect(meta!.status).toBe("working");
+  });
+
+  it("updateMetadata leaves no .tmp files behind", () => {
+    writeMetadata(dataDir, "atomic-2", {
+      worktree: "/tmp/w",
+      branch: "main",
+      status: "spawning",
+    });
+
+    updateMetadata(dataDir, "atomic-2", { status: "working" });
+
+    const files = readdirSync(dataDir);
+    const tmpFiles = files.filter((f) => f.includes(".tmp."));
+    expect(tmpFiles).toHaveLength(0);
+    const meta = readMetadata(dataDir, "atomic-2");
+    expect(meta!.status).toBe("working");
+  });
+
+  it("concurrent writeMetadata calls do not produce corrupt files", () => {
+    // Simulate rapid sequential writes (synchronous, so they serialize naturally,
+    // but each individual write must be atomic — no partial content)
+    for (let i = 0; i < 20; i++) {
+      writeMetadata(dataDir, "atomic-3", {
+        worktree: "/tmp/w",
+        branch: `branch-${i}`,
+        status: "working",
+        summary: `iteration ${i}`,
+      });
+    }
+
+    const meta = readMetadata(dataDir, "atomic-3");
+    expect(meta).not.toBeNull();
+    expect(meta!.branch).toBe("branch-19");
+    expect(meta!.summary).toBe("iteration 19");
+
+    // No leftover temp files
+    const files = readdirSync(dataDir);
+    const tmpFiles = files.filter((f) => f.includes(".tmp."));
+    expect(tmpFiles).toHaveLength(0);
+  });
+});
+
+describe("restoredAt persistence", () => {
+  it("roundtrips restoredAt through writeMetadata and readMetadata", () => {
+    const now = new Date().toISOString();
+    writeMetadata(dataDir, "restore-1", {
+      worktree: "/tmp/w",
+      branch: "main",
+      status: "working",
+      restoredAt: now,
+    });
+
+    const meta = readMetadata(dataDir, "restore-1");
+    expect(meta).not.toBeNull();
+    expect(meta!.restoredAt).toBe(now);
+  });
+
+  it("restoredAt is persisted in the key=value file", () => {
+    const now = "2026-03-01T12:00:00.000Z";
+    writeMetadata(dataDir, "restore-2", {
+      worktree: "/tmp/w",
+      branch: "main",
+      status: "working",
+      restoredAt: now,
+    });
+
+    const content = readFileSync(join(dataDir, "restore-2"), "utf-8");
+    expect(content).toContain(`restoredAt=${now}`);
+  });
+
+  it("restoredAt is undefined when not set", () => {
+    writeMetadata(dataDir, "restore-3", {
+      worktree: "/tmp/w",
+      branch: "main",
+      status: "working",
+    });
+
+    const meta = readMetadata(dataDir, "restore-3");
+    expect(meta!.restoredAt).toBeUndefined();
+  });
+
+  it("updateMetadata can set restoredAt on an existing session", () => {
+    writeMetadata(dataDir, "restore-4", {
+      worktree: "/tmp/w",
+      branch: "main",
+      status: "working",
+    });
+
+    const now = new Date().toISOString();
+    updateMetadata(dataDir, "restore-4", { restoredAt: now });
+
+    const meta = readMetadata(dataDir, "restore-4");
+    expect(meta!.restoredAt).toBe(now);
+  });
+});
+
 describe("listMetadata", () => {
   it("lists all session IDs", () => {
     writeMetadata(dataDir, "app-1", { worktree: "/tmp", branch: "a", status: "s" });
diff --git a/packages/core/src/metadata.ts b/packages/core/src/metadata.ts
index 3a9685b07..3d70e52d9 100644
--- a/packages/core/src/metadata.ts
+++ b/packages/core/src/metadata.ts
@@ -22,6 +22,7 @@
 import {
   readFileSync,
   writeFileSync,
+  renameSync,
   existsSync,
   mkdirSync,
   unlinkSync,
@@ -63,6 +64,16 @@ function serializeMetadata(data: Record<string, string>): string {
   );
 }
 
+/**
+ * Atomically write a file by writing to a temp file then renaming.
+ * rename() is atomic on POSIX, so concurrent writers never produce torn data.
+ */
+function atomicWriteFileSync(filePath: string, content: string): void {
+  const tmpPath = `${filePath}.tmp.${process.pid}.${Date.now()}`;
+  writeFileSync(tmpPath, content, "utf-8");
+  renameSync(tmpPath, filePath);
+}
+
 /** Validate sessionId to prevent path traversal. */
 const VALID_SESSION_ID = /^[a-zA-Z0-9_-]+$/;
 
@@ -100,6 +111,7 @@ export function readMetadata(dataDir: string, sessionId: SessionId): SessionMeta
     agent: raw["agent"],
     createdAt: raw["createdAt"],
     runtimeHandle: raw["runtimeHandle"],
+    restoredAt: raw["restoredAt"],
     role: raw["role"],
     dashboardPort: raw["dashboardPort"] ? Number(raw["dashboardPort"]) : undefined,
     terminalWsPort: raw["terminalWsPort"] ? Number(raw["terminalWsPort"]) : undefined,
@@ -144,6 +156,7 @@ export function writeMetadata(
   if (metadata.agent) data["agent"] = metadata.agent;
   if (metadata.createdAt) data["createdAt"] = metadata.createdAt;
   if (metadata.runtimeHandle) data["runtimeHandle"] = metadata.runtimeHandle;
+  if (metadata.restoredAt) data["restoredAt"] = metadata.restoredAt;
   if (metadata.role) data["role"] = metadata.role;
   if (metadata.dashboardPort !== undefined)
     data["dashboardPort"] = String(metadata.dashboardPort);
@@ -152,7 +165,7 @@ export function writeMetadata(
   if (metadata.directTerminalWsPort !== undefined)
     data["directTerminalWsPort"] = String(metadata.directTerminalWsPort);
 
-  writeFileSync(path, serializeMetadata(data), "utf-8");
+  atomicWriteFileSync(path, serializeMetadata(data));
 }
 
 /**
@@ -183,7 +196,7 @@ export function updateMetadata(
   }
 
   mkdirSync(dirname(path), { recursive: true });
-  writeFileSync(path, serializeMetadata(existing), "utf-8");
+  atomicWriteFileSync(path, serializeMetadata(existing));
 }
 
 /**
diff --git a/packages/core/src/session-manager.ts b/packages/core/src/session-manager.ts
index a6b5ca038..126d4934e 100644
--- a/packages/core/src/session-manager.ts
+++ b/packages/core/src/session-manager.ts
@@ -152,6 +152,7 @@ function metadataToSession(
     agentInfo: meta["summary"] ? { summary: meta["summary"], agentSessionId: null } : null,
     createdAt: meta["createdAt"] ? new Date(meta["createdAt"]) : (createdAt ?? new Date()),
     lastActivityAt: modifiedAt ?? new Date(),
+    restoredAt: meta["restoredAt"] ? new Date(meta["restoredAt"]) : undefined,
     metadata: meta,
   };
 }
diff --git a/packages/web/src/__tests__/get-attention-level.test.ts b/packages/web/src/__tests__/get-attention-level.test.ts
index 0874cb739..4856c745f 100644
--- a/packages/web/src/__tests__/get-attention-level.test.ts
+++ b/packages/web/src/__tests__/get-attention-level.test.ts
@@ -68,6 +68,21 @@ describe("getAttentionLevel", () => {
       expect(getAttentionLevel(session)).toBe("respond");
     });
 
+    it("returns respond when status is errored even if activity is active", () => {
+      const session = makeSession({ status: "errored", activity: "active" });
+      expect(getAttentionLevel(session)).toBe("respond");
+    });
+
+    it("returns respond when status is needs_input even if activity is active", () => {
+      const session = makeSession({ status: "needs_input", activity: "active" });
+      expect(getAttentionLevel(session)).toBe("respond");
+    });
+
+    it("returns respond when status is stuck even if activity is active", () => {
+      const session = makeSession({ status: "stuck", activity: "active" });
+      expect(getAttentionLevel(session)).toBe("respond");
+    });
+
     it("merge takes priority over respond (mergeable PR + blocked agent)", () => {
       const pr = makePR({
         mergeability: {
diff --git a/packages/web/src/components/Dashboard.tsx b/packages/web/src/components/Dashboard.tsx
index 9eea166ea..054346823 100644
--- a/packages/web/src/components/Dashboard.tsx
+++ b/packages/web/src/components/Dashboard.tsx
@@ -229,7 +229,7 @@ function StatusLine({ stats }: { stats: DashboardStats }) {
   const parts: Array<{ value: number; label: string; color?: string }> = [
     { value: stats.totalSessions, label: "sessions" },
     ...(stats.workingSessions > 0
-      ? [{ value: stats.workingSessions, label: "active", color: "var(--color-status-working)" }]
+      ? [{ value: stats.workingSessions, label: "working", color: "var(--color-status-working)" }]
       : []),
     ...(stats.openPRs > 0 ? [{ value: stats.openPRs, label: "PRs" }] : []),
     ...(stats.needsReview > 0
diff --git a/packages/web/src/lib/__tests__/serialize.test.ts b/packages/web/src/lib/__tests__/serialize.test.ts
index 49e56c3ba..7742aaf1e 100644
--- a/packages/web/src/lib/__tests__/serialize.test.ts
+++ b/packages/web/src/lib/__tests__/serialize.test.ts
@@ -20,6 +20,7 @@ import {
   enrichSessionAgentSummary,
   enrichSessionIssueTitle,
   enrichSessionsMetadata,
+  computeStats,
 } from "../serialize";
 import { prCache, prCacheKey } from "../cache";
 import type { DashboardSession } from "../types";
@@ -947,6 +948,67 @@ describe("enrichSessionsMetadata", () => {
   });
 });
 
+describe("computeStats", () => {
+  function makeDashboard(overrides: Partial<DashboardSession> = {}): DashboardSession {
+    return {
+      id: "test-1",
+      projectId: "test",
+      status: "working",
+      activity: "active",
+      branch: "feat/test",
+      issueId: null,
+      issueUrl: null,
+      issueLabel: null,
+      issueTitle: null,
+      summary: null,
+      summaryIsFallback: false,
+      createdAt: new Date().toISOString(),
+      lastActivityAt: new Date().toISOString(),
+      pr: null,
+      metadata: {},
+      ...overrides,
+    };
+  }
+
+  it("counts active sessions as working", () => {
+    const sessions = [makeDashboard({ activity: "active" })];
+    expect(computeStats(sessions).workingSessions).toBe(1);
+  });
+
+  it("counts idle sessions as working", () => {
+    const sessions = [makeDashboard({ activity: "idle" })];
+    expect(computeStats(sessions).workingSessions).toBe(1);
+  });
+
+  it("counts ready sessions as working", () => {
+    const sessions = [makeDashboard({ activity: "ready" })];
+    expect(computeStats(sessions).workingSessions).toBe(1);
+  });
+
+  it("excludes exited sessions from working count", () => {
+    const sessions = [makeDashboard({ activity: "exited" })];
+    expect(computeStats(sessions).workingSessions).toBe(0);
+  });
+
+  it("excludes sessions with null activity from working count", () => {
+    const sessions = [makeDashboard({ activity: null })];
+    expect(computeStats(sessions).workingSessions).toBe(0);
+  });
+
+  it("counts mixed activity states correctly", () => {
+    const sessions = [
+      makeDashboard({ id: "s1", activity: "active" }),
+      makeDashboard({ id: "s2", activity: "idle" }),
+      makeDashboard({ id: "s3", activity: "ready" }),
+      makeDashboard({ id: "s4", activity: "exited" }),
+      makeDashboard({ id: "s5", activity: null }),
+    ];
+    const stats = computeStats(sessions);
+    expect(stats.totalSessions).toBe(5);
+    expect(stats.workingSessions).toBe(3); // active + idle + ready
+  });
+});
+
 describe("basicPRToDashboard defaults", () => {
   it("should not look like failing CI", () => {
     const pr = createPRInfo();
diff --git a/packages/web/src/lib/serialize.ts b/packages/web/src/lib/serialize.ts
index b4a31e032..d38ae5ff9 100644
--- a/packages/web/src/lib/serialize.ts
+++ b/packages/web/src/lib/serialize.ts
@@ -380,7 +380,7 @@ export async function enrichSessionsMetadata(
 export function computeStats(sessions: DashboardSession[]): DashboardStats {
   return {
     totalSessions: sessions.length,
-    workingSessions: sessions.filter((s) => s.activity === "active").length,
+    workingSessions: sessions.filter((s) => s.activity !== null && s.activity !== "exited").length,
     openPRs: sessions.filter((s) => s.pr?.state === "open").length,
     needsReview: sessions.filter((s) => s.pr && !s.pr.isDraft && s.pr.reviewDecision === "pending")
       .length,
diff --git a/packages/web/src/lib/types.ts b/packages/web/src/lib/types.ts
index b90e48bf5..1d6165381 100644
--- a/packages/web/src/lib/types.ts
+++ b/packages/web/src/lib/types.ts
@@ -187,16 +187,18 @@ export function getAttentionLevel(session: DashboardSession): AttentionLevel {
   }
 
   // ── Respond: agent is waiting for human input ─────────────────────
+  // Check status-based error conditions first — these are authoritative
+  // and should not be masked by a stale activity value.
   if (
-    session.activity === ACTIVITY_STATE.WAITING_INPUT ||
-    session.activity === ACTIVITY_STATE.BLOCKED
+    session.status === SESSION_STATUS.ERRORED ||
+    session.status === SESSION_STATUS.NEEDS_INPUT ||
+    session.status === SESSION_STATUS.STUCK
   ) {
     return "respond";
   }
   if (
-    session.status === SESSION_STATUS.NEEDS_INPUT ||
-    session.status === SESSION_STATUS.STUCK ||
-    session.status === SESSION_STATUS.ERRORED
+    session.activity === ACTIVITY_STATE.WAITING_INPUT ||
+    session.activity === ACTIVITY_STATE.BLOCKED
   ) {
     return "respond";
   }