diff --git a/packages/app/src/plugins/client-state/connected-hosts.ts b/packages/app/src/plugins/client-state/connected-hosts.ts
new file mode 100644
index 0000000000..4dfffa6b8d
--- /dev/null
+++ b/packages/app/src/plugins/client-state/connected-hosts.ts
@@ -0,0 +1,72 @@
+import { getHostRuntimeStore } from "@/runtime/host-runtime";
+import type { PluginConnectedHostsSource } from "./source";
+
+interface PluginHostsRuntime {
+  getHosts(): readonly { serverId: string }[];
+  getSnapshot(serverId: string): { connectionStatus: string } | null | undefined;
+  subscribeAll(listener: () => void): () => void;
+  subscribeHostList(listener: () => void): () => void;
+  acquireDirectoryDemand(serverId: string): () => void;
+}
+
+export function createConnectedPluginHosts(
+  getRuntime: () => PluginHostsRuntime,
+): PluginConnectedHostsSource {
+  let snapshot: readonly string[] = [];
+  const listeners = new Set<() => void>();
+  let release: (() => void) | null = null;
+
+  const source: PluginConnectedHostsSource = {
+    getSnapshot() {
+      const runtime = getRuntime();
+      const next = runtime
+        .getHosts()
+        .filter((host) => runtime.getSnapshot(host.serverId)?.connectionStatus === "online")
+        .map((host) => host.serverId);
+      if (next.length !== snapshot.length || next.some((id, index) => id !== snapshot[index]))
+        snapshot = Object.freeze(next);
+      return snapshot;
+    },
+    subscribe(listener) {
+      listeners.add(listener);
+      if (!release) {
+        const runtime = getRuntime();
+        const demands = new Map<string, () => void>();
+        const reconcile = () => {
+          const ids = new Set(source.getSnapshot());
+          for (const [id, releaseDemand] of demands) {
+            if (!ids.has(id)) {
+              demands.delete(id);
+              releaseDemand();
+            }
+          }
+          for (const id of ids) {
+            if (!demands.has(id)) demands.set(id, runtime.acquireDirectoryDemand(id));
+          }
+        };
+        const notify = () => {
+          reconcile();
+          for (const subscriber of listeners) subscriber();
+        };
+        const releaseRuntime = runtime.subscribeAll(notify);
+        const releaseHosts = runtime.subscribeHostList(notify);
+        reconcile();
+        release = () => {
+          releaseRuntime();
+          releaseHosts();
+          for (const releaseDemand of demands.values()) releaseDemand();
+          demands.clear();
+        };
+      }
+      return () => {
+        listeners.delete(listener);
+        if (listeners.size === 0 && release) {
+          release();
+          release = null;
+        }
+      };
+    },
+  };
+  return source;
+}
+export const connectedPluginHosts = createConnectedPluginHosts(getHostRuntimeStore);
diff --git a/packages/app/src/plugins/client-state/fixtures.ts b/packages/app/src/plugins/client-state/fixtures.ts
new file mode 100644
index 0000000000..4439e385f4
--- /dev/null
+++ b/packages/app/src/plugins/client-state/fixtures.ts
@@ -0,0 +1,53 @@
+import type { Agent, WorkspaceDescriptor } from "@/stores/session-store";
+export const workspace: WorkspaceDescriptor = {
+  createdAt: null,
+  lastUserMessageAt: null,
+  id: "workspace-1",
+  projectId: "project-1",
+  projectDisplayName: "Paseo",
+  projectRootPath: "/repo/paseo",
+  workspaceDirectory: "/repo/paseo/review",
+  projectKind: "git",
+  workspaceKind: "worktree",
+  name: "Review",
+  title: "Plugin review",
+  pinnedAt: null,
+  status: "running",
+  statusEnteredAt: new Date("2026-08-16T10:00:00.000Z"),
+  archivingAt: null,
+  diffStat: { additions: 12, deletions: 3 },
+  scripts: [],
+};
+
+export const agent: Agent = {
+  serverId: "host-1",
+  id: "agent-1",
+  provider: "codex",
+  status: "running",
+  turn: { phase: "idle", cancellationRequestId: null },
+  createdAt: new Date("2026-08-16T10:01:00.000Z"),
+  updatedAt: new Date("2026-08-16T10:02:00.000Z"),
+  lastUserMessageAt: null,
+  lastActivityAt: new Date("2026-08-16T10:03:00.000Z"),
+  capabilities: {
+    supportsStreaming: true,
+    supportsSessionPersistence: true,
+    supportsDynamicModes: true,
+    supportsMcpServers: true,
+    supportsReasoningStream: true,
+    supportsToolInvocations: true,
+  },
+  currentModeId: "code",
+  availableModes: [],
+  pendingPermissions: [],
+  persistence: null,
+  title: "Implement plugin panels",
+  cwd: "/repo/paseo/review",
+  workspaceId: "workspace-1",
+  model: "gpt-5.6",
+  thinkingOptionId: "high",
+  requiresAttention: true,
+  attentionReason: "permission",
+  parentAgentId: null,
+  labels: { phase: "implementation" },
+};
diff --git a/packages/app/src/plugins/client-state/refs.ts b/packages/app/src/plugins/client-state/refs.ts
new file mode 100644
index 0000000000..edfdd9562c
--- /dev/null
+++ b/packages/app/src/plugins/client-state/refs.ts
@@ -0,0 +1,3 @@
+import { createEntityRefs } from "@getpaseo/plugin/client/host";
+
+export const entityRefs = createEntityRefs();
diff --git a/packages/app/src/plugins/client-state/snapshots.test.ts b/packages/app/src/plugins/client-state/snapshots.test.ts
index 0c90185e53..7d63b178ed 100644
--- a/packages/app/src/plugins/client-state/snapshots.test.ts
+++ b/packages/app/src/plugins/client-state/snapshots.test.ts
@@ -1,66 +1,20 @@
+import { i18n } from "@/i18n/i18next";
+import { fr } from "@/i18n/resources/fr";
 import { describe, expect, it } from "vitest";
-import type { Agent, WorkspaceDescriptor } from "@/stores/session-store";
-import { createPluginAgentSnapshot, createPluginWorkspaceSnapshot } from "./snapshots";
-
-const workspace: WorkspaceDescriptor = {
-  createdAt: null,
-  lastUserMessageAt: null,
-  id: "workspace-1",
-  projectId: "project-1",
-  projectDisplayName: "Paseo",
-  projectRootPath: "/repo/paseo",
-  workspaceDirectory: "/repo/paseo/review",
-  projectKind: "git",
-  workspaceKind: "worktree",
-  name: "Review",
-  title: "Plugin review",
-  pinnedAt: null,
-  status: "running",
-  statusEnteredAt: new Date("2026-08-16T10:00:00.000Z"),
-  archivingAt: null,
-  diffStat: { additions: 12, deletions: 3 },
-  scripts: [],
-};
-
-const agent: Agent = {
-  serverId: "host-1",
-  id: "agent-1",
-  provider: "codex",
-  status: "running",
-  turn: { phase: "idle", cancellationRequestId: null },
-  createdAt: new Date("2026-08-16T10:01:00.000Z"),
-  updatedAt: new Date("2026-08-16T10:02:00.000Z"),
-  lastUserMessageAt: null,
-  lastActivityAt: new Date("2026-08-16T10:03:00.000Z"),
-  capabilities: {
-    supportsStreaming: true,
-    supportsSessionPersistence: true,
-    supportsDynamicModes: true,
-    supportsMcpServers: true,
-    supportsReasoningStream: true,
-    supportsToolInvocations: true,
-  },
-  currentModeId: "code",
-  availableModes: [],
-  pendingPermissions: [],
-  persistence: null,
-  title: "Implement plugin panels",
-  cwd: "/repo/paseo/review",
-  workspaceId: "workspace-1",
-  model: "gpt-5.6",
-  thinkingOptionId: "high",
-  requiresAttention: true,
-  attentionReason: "permission",
-  parentAgentId: null,
-  labels: { phase: "implementation" },
-};
+import type { WorkspaceDescriptor } from "@/stores/session-store";
+import {
+  createPluginAgentSnapshot,
+  createPluginWorkspaceSnapshot,
+  createPluginProjectSnapshot,
+} from "./snapshots";
 
+import { workspace, agent } from "./fixtures";
 describe("plugin context snapshots", () => {
   it("commits a deeply immutable normalized workspace snapshot synchronously", () => {
-    const snapshot = createPluginWorkspaceSnapshot(workspace);
-    expect(createPluginWorkspaceSnapshot(workspace)).toBe(snapshot);
+    const snapshot = createPluginWorkspaceSnapshot(workspace, "host-1");
+    expect(createPluginWorkspaceSnapshot(workspace, "host-1")).toBe(snapshot);
 
-    expect(snapshot).toEqual({
+    expect(snapshot).toMatchObject({
       id: "workspace-1",
       projectId: "project-1",
       projectDisplayName: "Paseo",
@@ -90,7 +44,7 @@ describe("plugin context snapshots", () => {
     const snapshot = createPluginAgentSnapshot(agent, workspace.id);
     expect(createPluginAgentSnapshot(agent, workspace.id)).toBe(snapshot);
 
-    expect(snapshot).toEqual({
+    expect(snapshot).toMatchObject({
       id: "agent-1",
       workspaceId: "workspace-1",
       provider: "codex",
@@ -119,3 +73,82 @@ describe("plugin context snapshots", () => {
     expect(agent.labels).toEqual({ phase: "implementation" });
   });
 });
+
+describe("sidebar entity snapshots", () => {
+  it("interns cross-host references and preserves identity across unrelated reads", () => {
+    const first = createPluginWorkspaceSnapshot(workspace, "host-1");
+    const second = createPluginWorkspaceSnapshot(workspace, "host-2");
+    expect(first.ref).not.toBe(second.ref);
+    expect(first.ref.hostId).toBe("host-1");
+    expect(first.project.id).toBe(workspace.projectId);
+    expect(Object.isFrozen(first.labels)).toBe(true);
+    expect(createPluginWorkspaceSnapshot(workspace, "host-1")).toBe(first);
+    expect(createPluginAgentSnapshot(agent, workspace.id).workspace).toBe(first.ref);
+  });
+
+  it("invalidates a done workspace when its effective root-agent status changes", () => {
+    const idle: WorkspaceDescriptor = { ...workspace, status: "done" };
+    const before = createPluginWorkspaceSnapshot(idle, "host-1");
+    const activity = new Map([
+      [idle.id, { agentId: agent.id, status: "needs_input" as const, enteredAt: null }],
+    ]);
+    const after = createPluginWorkspaceSnapshot(idle, "host-1", {
+      workspaceAgentActivity: activity,
+    });
+    expect(before.indicator).toBe("done");
+    expect(after.status).toBe("done");
+    expect(after.indicator).toBe("needs_input");
+    expect(after.indicatorLabel).toBe("Needs input");
+    expect(after.ref).toBe(before.ref);
+    expect(
+      createPluginWorkspaceSnapshot(idle, "host-1", { workspaceAgentActivity: activity }),
+    ).toBe(after);
+  });
+
+  it("reads projects without requiring a workspace", () => {
+    const project = {
+      projectId: "empty",
+      projectDisplayName: "Empty",
+      projectCustomName: null,
+      projectRootPath: "/empty",
+      projectKind: "git" as const,
+    };
+    const snapshot = createPluginProjectSnapshot(project, "host-1");
+    expect(createPluginProjectSnapshot(project, "host-1")).toBe(snapshot);
+    expect(snapshot.displayName).toBe("Empty");
+    expect(snapshot.ref.id).toBe("empty");
+    expect(Object.isFrozen(snapshot)).toBe(true);
+  });
+});
+
+it("uses the app status labels and invalidates a snapshot on language change", async () => {
+  i18n.addResourceBundle("fr", "translation", fr);
+  const previousLanguage = i18n.language;
+  try {
+    await i18n.changeLanguage("en");
+    const english = createPluginWorkspaceSnapshot(workspace, "host-1");
+    expect(english.indicatorLabel).toBe("Working");
+    await i18n.changeLanguage("fr");
+    const french = createPluginWorkspaceSnapshot(workspace, "host-1");
+    expect(french).not.toBe(english);
+    expect(french.ref).toBe(english.ref);
+    expect(french.indicatorLabel).toBe("En cours");
+    expect(createPluginWorkspaceSnapshot(workspace, "host-1")).toBe(french);
+  } finally {
+    await i18n.changeLanguage(previousLanguage);
+  }
+});
+
+it("preserves the host-qualified parent of a remotely delegated agent", () => {
+  const child = {
+    ...agent,
+    serverId: "host-2",
+    parentAgentId: null,
+    labels: { "paseo.parent-server-id": "host-1", "paseo.parent-agent-id": "parent" },
+  };
+  expect(createPluginAgentSnapshot(child, workspace.id).parentAgent).toMatchObject({
+    hostId: "host-1",
+    id: "parent",
+    kind: "agent",
+  });
+});
diff --git a/packages/app/src/plugins/client-state/snapshots.ts b/packages/app/src/plugins/client-state/snapshots.ts
index 67a08830cd..ac810cf8f0 100644
--- a/packages/app/src/plugins/client-state/snapshots.ts
+++ b/packages/app/src/plugins/client-state/snapshots.ts
@@ -1,16 +1,57 @@
-import type { PluginAgentSnapshot, PluginWorkspaceSnapshot } from "@getpaseo/plugin";
-import type { Agent, WorkspaceDescriptor } from "@/stores/session-store";
+import { getParentAddressFromLabels } from "@getpaseo/protocol/agent-labels";
+import { i18n } from "@/i18n/i18next";
+import type {
+  PluginAgentSnapshot,
+  PluginWorkspaceSnapshot,
+  PluginProjectSnapshot,
+} from "@getpaseo/plugin";
+import type { Agent, WorkspaceDescriptor, ProjectDescriptor } from "@/stores/session-store";
 
-const workspaceSnapshots = new WeakMap<WorkspaceDescriptor, PluginWorkspaceSnapshot>();
+import { entityRefs } from "./refs";
+import { deriveEffectiveWorkspaceStatus } from "@/workspace-status";
+
+interface CachedWorkspace {
+  language: string;
+  snapshot: PluginWorkspaceSnapshot;
+}
+const workspaceSnapshots = new WeakMap<WorkspaceDescriptor, Map<string, CachedWorkspace>>();
 const agentSnapshots = new WeakMap<Agent, Map<string, PluginAgentSnapshot>>();
 
 export function createPluginWorkspaceSnapshot(
   workspace: WorkspaceDescriptor,
+  hostId: string,
+  context: Omit<Parameters<typeof deriveEffectiveWorkspaceStatus>[0], "workspace" | "serverId"> & {
+    parentAgent?: PluginWorkspaceSnapshot["parentAgent"];
+  } = {},
 ): PluginWorkspaceSnapshot {
-  const cached = workspaceSnapshots.get(workspace);
-  if (cached) return cached;
+  const indicator = deriveEffectiveWorkspaceStatus({
+    ...context,
+    workspace,
+    serverId: hostId,
+  }).status;
+  const parentAgent = context.parentAgent ?? null;
+  const cached = workspaceSnapshots.get(workspace)?.get(hostId);
+  if (
+    cached &&
+    cached.language === i18n.language &&
+    cached.snapshot.indicator === indicator &&
+    cached.snapshot.parentAgent === parentAgent
+  )
+    return cached.snapshot;
   const diffStat = workspace.diffStat ? Object.freeze({ ...workspace.diffStat }) : null;
   const snapshot = Object.freeze({
+    ref: entityRefs.workspace(hostId, workspace.id),
+    hostId,
+    project: entityRefs.project(hostId, workspace.projectId),
+    pinnedAt: workspace.pinnedAt ?? null,
+    labels: Object.freeze([...(workspace.labels ?? [])]),
+    background: workspace.background ?? false,
+    branch: workspace.gitRuntime?.currentBranch ?? null,
+    createdAt: serializeTimestamp(workspace.createdAt),
+    lastPromptAt: serializeTimestamp(workspace.lastUserMessageAt),
+    parentAgent,
+    indicator,
+    indicatorLabel: i18n.t(indicatorLabelKeys[indicator]),
     id: workspace.id,
     projectId: workspace.projectId,
     projectDisplayName: workspace.projectDisplayName,
@@ -21,18 +62,25 @@ export function createPluginWorkspaceSnapshot(
     name: workspace.name,
     title: workspace.title ?? null,
     status: workspace.status,
-    statusEnteredAt: workspace.statusEnteredAt?.toISOString() ?? null,
+    statusEnteredAt: serializeTimestamp(workspace.statusEnteredAt),
     archivingAt: workspace.archivingAt,
     diffStat,
   });
-  workspaceSnapshots.set(workspace, snapshot);
+  const byHost = workspaceSnapshots.get(workspace) ?? new Map<string, CachedWorkspace>();
+  byHost.set(hostId, { language: i18n.language, snapshot });
+  workspaceSnapshots.set(workspace, byHost);
   return snapshot;
 }
 
 export function createPluginAgentSnapshot(agent: Agent, workspaceId: string): PluginAgentSnapshot {
   const cached = agentSnapshots.get(agent)?.get(workspaceId);
   if (cached) return cached;
+  const parent = getParentAddressFromLabels(agent.labels, agent.serverId);
   const snapshot = Object.freeze({
+    ref: entityRefs.agent(agent.serverId, agent.id),
+    hostId: agent.serverId,
+    workspace: entityRefs.workspace(agent.serverId, workspaceId),
+    parentAgent: parent ? entityRefs.agent(parent.serverId, parent.agentId) : null,
     id: agent.id,
     workspaceId,
     provider: agent.provider,
@@ -55,3 +103,36 @@ export function createPluginAgentSnapshot(agent: Agent, workspaceId: string): Pl
   agentSnapshots.set(agent, byWorkspace);
   return snapshot;
 }
+
+const indicatorLabelKeys = {
+  needs_input: "sidebar.statusBucket.needsInput",
+  failed: "sidebar.statusBucket.failed",
+  running: "sidebar.statusBucket.working",
+  attention: "sidebar.statusBucket.readyToReview",
+  done: "sidebar.statusBucket.done",
+} as const;
+const projectSnapshots = new WeakMap<ProjectDescriptor, Map<string, PluginProjectSnapshot>>();
+
+export function createPluginProjectSnapshot(
+  project: ProjectDescriptor,
+  hostId: string,
+): PluginProjectSnapshot {
+  const cached = projectSnapshots.get(project)?.get(hostId);
+  if (cached) return cached;
+  const snapshot = Object.freeze({
+    ref: entityRefs.project(hostId, project.projectId),
+    hostId,
+    displayName: project.projectCustomName ?? project.projectDisplayName,
+    rootPath: project.projectRootPath,
+    kind: project.projectKind,
+    iconRevision: project.projectCustomIconRevision ?? project.projectIconRevision ?? null,
+  });
+  const byHost = projectSnapshots.get(project) ?? new Map<string, PluginProjectSnapshot>();
+  byHost.set(hostId, snapshot);
+  projectSnapshots.set(project, byHost);
+  return snapshot;
+}
+
+function serializeTimestamp(value: Date | null): string | null {
+  return value ? value.toISOString() : null;
+}
diff --git a/packages/app/src/plugins/client-state/source-retention.test.ts b/packages/app/src/plugins/client-state/source-retention.test.ts
new file mode 100644
index 0000000000..b11fc5d731
--- /dev/null
+++ b/packages/app/src/plugins/client-state/source-retention.test.ts
@@ -0,0 +1,55 @@
+import { setFlagsFromString } from "node:v8";
+import { runInNewContext } from "node:vm";
+import { setImmediate } from "node:timers/promises";
+import { expect, it } from "vitest";
+import { useSessionStore } from "@/stores/session-store";
+import { createPluginClientStateSource } from "./source";
+import { workspace } from "./fixtures";
+
+setFlagsFromString("--expose_gc");
+const collectGarbage: () => void = runInNewContext("gc");
+setFlagsFromString("--no-expose_gc");
+
+function observeHost() {
+  const hostId = "removed-plugin-host";
+  let hosts = [hostId];
+  const store = useSessionStore.getState();
+  store.initializeSession(hostId, null);
+  store.setWorkspaces(hostId, new Map([[workspace.id, { ...workspace }]]));
+  const source = createPluginClientStateSource(undefined, {
+    hosts: { getSnapshot: () => hosts, subscribe: () => () => {} },
+  });
+  const release = source.subscribe(() => source.getSnapshot());
+  source.getSnapshot();
+  const reference = new WeakRef(useSessionStore.getState().sessions[hostId]!.workspaces);
+  const remove = () => {
+    hosts = [];
+    store.clearSession(hostId);
+  };
+  return { reference, release, remove };
+}
+
+it("releases removed hosts' projected data while other plugin readers remain", async () => {
+  const { reference, release, remove } = observeHost();
+  remove();
+  try {
+    for (let attempt = 0; attempt < 3; attempt++) {
+      await setImmediate();
+      collectGarbage();
+    }
+    expect(reference.deref()).toBeUndefined();
+  } finally {
+    release();
+  }
+});
+
+it("releases previous projections when the last plugin reader leaves", async () => {
+  const { reference, release, remove } = observeHost();
+  release();
+  remove();
+  for (let attempt = 0; attempt < 3; attempt++) {
+    await setImmediate();
+    collectGarbage();
+  }
+  expect(reference.deref()).toBeUndefined();
+});
diff --git a/packages/app/src/plugins/client-state/source.browser.test.tsx b/packages/app/src/plugins/client-state/source.browser.test.tsx
new file mode 100644
index 0000000000..5a0b3f3811
--- /dev/null
+++ b/packages/app/src/plugins/client-state/source.browser.test.tsx
@@ -0,0 +1,320 @@
+import { createConnectedPluginHosts } from "./connected-hosts";
+import { i18n } from "@/i18n/i18next";
+import { fr } from "@/i18n/resources/fr";
+import React, { act } from "react";
+import { createRoot, type Root } from "react-dom/client";
+import { afterEach, describe, expect, it } from "vitest";
+import { PluginClientStateProvider } from "@getpaseo/plugin/client/host";
+import {
+  useAgents,
+  useWorkspaces,
+  useWorkspace,
+  useAgent,
+  type WorkspaceRef,
+  type AgentRef,
+} from "@getpaseo/plugin/client";
+import { useSessionStore, type Agent } from "@/stores/session-store";
+import { createPluginClientStateSource, type PluginConnectedHostsSource } from "./source";
+import { agent, workspace } from "./fixtures";
+
+let root: Root | null = null;
+let container: HTMLDivElement | null = null;
+const renders = new Map<string, number>();
+function count(key: string) {
+  renders.set(key, (renders.get(key) ?? 0) + 1);
+}
+function WorkspaceRow({ reference }: { reference: WorkspaceRef }) {
+  const item = useWorkspace(reference);
+  count(reference.key);
+  return (
+    <div>
+      {item?.name}:{item?.indicator}
+    </div>
+  );
+}
+function Workspaces() {
+  count("workspaces");
+  const items = useWorkspaces({ orderBy: "name" });
+  return (
+    <div>
+      {items.map((reference) => (
+        <WorkspaceRow key={reference.key} reference={reference} />
+      ))}
+    </div>
+  );
+}
+function SelectedWorkspace({ reference }: { reference: WorkspaceRef }) {
+  const name = useWorkspace(reference, (item) => ({ name: item.name }));
+  const custom = useWorkspace(reference, undefined, (a, b) => a?.name === b?.name);
+  count("selected");
+  return (
+    <div>
+      {name?.name}:{custom?.name}
+    </div>
+  );
+}
+function AgentRow({ reference }: { reference: AgentRef }) {
+  const item = useAgent(reference);
+  return <div>{item?.title}</div>;
+}
+function AgentSection({ section }: { section: string }) {
+  const agents = useAgents({
+    where: (item) => (item.requiresAttention ? "waiting" : item.status) === section,
+  });
+  count(section);
+  return (
+    <div>
+      {agents.map((reference) => (
+        <AgentRow key={reference.key} reference={reference} />
+      ))}
+    </div>
+  );
+}
+function Agents() {
+  return (
+    <div>
+      <AgentSection section="running" />
+      <AgentSection section="waiting" />
+      <AgentSection section="idle" />
+    </div>
+  );
+}
+function seedHost(hostId: string) {
+  const store = useSessionStore.getState();
+  store.initializeSession(hostId, null);
+  store.setWorkspaces(
+    hostId,
+    new Map([
+      ["workspace-1", { ...workspace, id: "workspace-1", status: "done", name: "First" }],
+      ["workspace-2", { ...workspace, id: "workspace-2", status: "done", name: "Second" }],
+    ]),
+  );
+  store.setProjects(hostId, [
+    {
+      projectId: "empty",
+      projectDisplayName: "Empty project",
+      projectCustomName: null,
+      projectRootPath: "/empty",
+      projectKind: "git",
+    },
+  ]);
+  store.setAgents(
+    hostId,
+    new Map<string, Agent>([
+      [
+        "agent-1",
+        {
+          ...agent,
+          serverId: hostId,
+          id: "agent-1",
+          workspaceId: "workspace-1",
+          status: "running",
+          requiresAttention: false,
+          attentionReason: null,
+          turn: { phase: "open", turnId: null, startedAt: null, cancellationRequestId: null },
+        },
+      ],
+      [
+        "agent-2",
+        {
+          ...agent,
+          serverId: hostId,
+          id: "agent-2",
+          workspaceId: "workspace-2",
+          status: "running",
+          requiresAttention: false,
+          attentionReason: null,
+          turn: { phase: "open", turnId: null, startedAt: null, cancellationRequestId: null },
+        },
+      ],
+    ]),
+  );
+}
+it("keeps archived agents readable individually while excluding them from collections", () => {
+  seedHost("host-1");
+  const source = createPluginClientStateSource("host-1", { hosts: new ConnectedHosts() });
+  const reference = source.getSnapshot().agents[0]!.ref;
+  useSessionStore.getState().setAgents(
+    "host-1",
+    new Map([
+      [
+        agent.id,
+        {
+          ...agent,
+          archivedAt: new Date("2026-11-01T00:00:00.000Z"),
+        },
+      ],
+    ]),
+  );
+  expect(source.getSnapshot().agents).toEqual([]);
+  expect(source.getAgent(reference)?.title).toBe(agent.title);
+  expect(source.getAgent(agent.id)).toBe(source.getAgent(reference));
+});
+
+it("demands directories for connected hosts and releases them with its last reader", () => {
+  const hostId = "plugin-demand-host";
+  let online = true;
+  let demands = 0;
+  const listeners = new Set<() => void>();
+  const hosts = createConnectedPluginHosts(() => ({
+    getHosts: () => [{ serverId: hostId }],
+    getSnapshot: () => ({ connectionStatus: online ? "online" : "offline" }),
+    subscribeAll: (listener) => {
+      listeners.add(listener);
+      return () => {
+        listeners.delete(listener);
+      };
+    },
+    subscribeHostList: () => () => {},
+    acquireDirectoryDemand: () => {
+      demands++;
+      seedHost(hostId);
+      return () => {
+        demands--;
+      };
+    },
+  }));
+  const source = createPluginClientStateSource(undefined, { hosts });
+  const first = source.subscribe(() => {});
+  const second = source.subscribe(() => {});
+  expect(demands).toBe(1);
+  expect(source.getSnapshot().workspaces.map((item) => item.hostId)).toEqual([hostId, hostId]);
+  useSessionStore
+    .getState()
+    .setWorkspaces(
+      hostId,
+      (previous) =>
+        new Map([...previous].map(([id, item]) => [id, { ...item, name: "Live update" }])),
+    );
+  expect(source.getSnapshot().workspaces.map((item) => item.name)).toEqual([
+    "Live update",
+    "Live update",
+  ]);
+  online = false;
+  for (const listener of listeners) listener();
+  expect(demands).toBe(0);
+  expect(source.getSnapshot().workspaces).toEqual([]);
+  online = true;
+  for (const listener of listeners) listener();
+  expect(demands).toBe(1);
+  first();
+  expect(demands).toBe(1);
+  second();
+  expect(demands).toBe(0);
+  expect(listeners.size).toBe(0);
+});
+
+function waitForInput() {
+  useSessionStore.getState().setAgents("host-1", (previous) => {
+    const current = previous.get("agent-1");
+    if (!current) throw new Error("Missing test agent");
+    const next = new Map(previous);
+    next.set(current.id, {
+      ...current,
+      status: "idle",
+      turn: { phase: "idle", cancellationRequestId: null },
+      requiresAttention: true,
+      attentionReason: "permission",
+    });
+    return next;
+  });
+}
+class ConnectedHosts implements PluginConnectedHostsSource {
+  private ids: readonly string[] = ["host-1"];
+  private listeners = new Set<() => void>();
+  getSnapshot = () => this.ids;
+  subscribe = (listener: () => void) => {
+    this.listeners.add(listener);
+    return () => {
+      this.listeners.delete(listener);
+    };
+  };
+  connect(id: string) {
+    this.ids = [...this.ids, id];
+    for (const listener of this.listeners) listener();
+  }
+}
+function mount(children: React.ReactNode, hosts = new ConnectedHosts()) {
+  const source = createPluginClientStateSource("host-1", { hosts });
+  container = document.createElement("div");
+  document.body.appendChild(container);
+  root = createRoot(container);
+  act(() =>
+    root?.render(<PluginClientStateProvider source={source}>{children}</PluginClientStateProvider>),
+  );
+  return source;
+}
+afterEach(() => {
+  act(() => root?.unmount());
+  container?.remove();
+  root = null;
+  container = null;
+  useSessionStore.getState().clearSession("host-1");
+  useSessionStore.getState().clearSession("host-2");
+  renders.clear();
+});
+
+describe("sidebar data hooks through the app store and plugin provider", () => {
+  it("renders only one workspace row when its root agent starts waiting", () => {
+    seedHost("host-1");
+    const source = mount(<Workspaces />);
+    const first = source.getSnapshot().workspaces[0]!;
+    const second = source.getSnapshot().workspaces[1]!;
+    const before = source.getSnapshot();
+    act(waitForInput);
+    expect(renders.get("workspaces")).toBe(1);
+    expect(renders.get(first.ref.key)).toBe(2);
+    expect(renders.get(second.ref.key)).toBe(1);
+    expect(source.getSnapshot().workspaces[0]?.indicator).toBe("needs_input");
+    expect(source.getSnapshot().workspaces[1]).toBe(before.workspaces[1]);
+  });
+  it("moves the agent and renders only its two affected sections without memo", () => {
+    seedHost("host-1");
+    mount(<Agents />);
+    act(waitForInput);
+    expect(renders.get("running")).toBe(2);
+    expect(renders.get("waiting")).toBe(2);
+    expect(renders.get("idle")).toBe(1);
+  });
+  it("uses shallow selected equality and custom equality without a selector", () => {
+    seedHost("host-1");
+    const source = createPluginClientStateSource("host-1", { hosts: new ConnectedHosts() });
+    mount(<SelectedWorkspace reference={source.getSnapshot().workspaces[0]!.ref} />);
+    act(waitForInput);
+    expect(renders.get("selected")).toBe(1);
+  });
+  it("refreshes translated labels through the subscribed source when language changes", async () => {
+    seedHost("host-1");
+    i18n.addResourceBundle("fr", "translation", fr);
+    const source = mount(<Workspaces />);
+    const before = source.getSnapshot().workspaces[0]!;
+    const previousLanguage = i18n.language;
+    try {
+      await act(async () => {
+        await i18n.changeLanguage("fr");
+      });
+      const after = source.getSnapshot().workspaces[0]!;
+      expect(after).not.toBe(before);
+      expect(after.indicatorLabel).toBe("En cours");
+      expect(after.ref).toBe(before.ref);
+      expect(renders.get(before.ref.key)).toBe(2);
+      expect(renders.get("workspaces")).toBe(1);
+    } finally {
+      await act(async () => {
+        await i18n.changeLanguage(previousLanguage);
+      });
+    }
+  });
+  it("adds a newly connected host and exposes projects with no workspaces", () => {
+    seedHost("host-1");
+    seedHost("host-2");
+    const hosts = new ConnectedHosts();
+    const source = mount(<Workspaces />, hosts);
+    expect(source.getSnapshot().workspaces).toHaveLength(2);
+    expect(source.getSnapshot().projects[0]?.displayName).toBe("Empty project");
+    act(() => hosts.connect("host-2"));
+    expect(source.getSnapshot().workspaces).toHaveLength(4);
+    expect(source.getSnapshot().projects).toHaveLength(2);
+    expect(new Set(source.getSnapshot().workspaces.map((item) => item.ref.key)).size).toBe(4);
+  });
+});
diff --git a/packages/app/src/plugins/client-state/source.ts b/packages/app/src/plugins/client-state/source.ts
index 142c1f3575..03a2a47296 100644
--- a/packages/app/src/plugins/client-state/source.ts
+++ b/packages/app/src/plugins/client-state/source.ts
@@ -1,21 +1,226 @@
-import type { PluginClientStateSource } from "@getpaseo/plugin/client/host";
-import { useSessionStore } from "@/stores/session-store";
-import { selectWorkspace } from "@/stores/session-store-hooks/selectors";
+import { i18n } from "@/i18n/i18next";
+import type { PluginClientSnapshot, PluginClientStateSource } from "@getpaseo/plugin/client/host";
+import type { PluginTerminalSnapshot } from "@getpaseo/plugin";
+import { useCreateFlowStore } from "@/stores/create-flow-store";
+import { useSessionStore, type SessionState } from "@/stores/session-store";
 import { normalizeWorkspaceOpaqueId } from "@/utils/workspace-identity";
-import { createPluginAgentSnapshot, createPluginWorkspaceSnapshot } from "./snapshots";
+import { connectedPluginHosts } from "./connected-hosts";
+import { entityRefs } from "./refs";
+import {
+  createPluginAgentSnapshot,
+  createPluginProjectSnapshot,
+  createPluginWorkspaceSnapshot,
+} from "./snapshots";
 
-export function createPluginClientStateSource(serverId: string): PluginClientStateSource {
+export interface PluginConnectedHostsSource {
+  subscribe(listener: () => void): () => void;
+  getSnapshot(): readonly string[];
+}
+
+export interface PluginTerminalsSource {
+  subscribe(listener: () => void): () => void;
+  getSnapshot(): readonly PluginTerminalSnapshot[];
+}
+
+const emptyTerminals: readonly PluginTerminalSnapshot[] = Object.freeze([]);
+const noTerminals: PluginTerminalsSource = {
+  subscribe: () => () => {},
+  getSnapshot: () => emptyTerminals,
+};
+const listeners = new Set<() => void>();
+let releaseStores: (() => void) | null = null;
+
+// Every plugin host shares one subscription to each app store.
+function subscribeStores(listener: () => void): () => void {
+  if (!releaseStores) {
+    const notify = () => {
+      for (const subscriber of listeners) subscriber();
+    };
+    i18n.on("languageChanged", notify);
+    const releaseSession = useSessionStore.subscribe((state) => {
+      for (const hostId of hostProjections.keys()) {
+        if (!state.sessions[hostId]) hostProjections.delete(hostId);
+      }
+      notify();
+    });
+    const releaseCreate = useCreateFlowStore.subscribe(notify);
+    releaseStores = () => {
+      i18n.off("languageChanged", notify);
+      releaseSession();
+      releaseCreate();
+    };
+  }
+  listeners.add(listener);
+  return () => {
+    listeners.delete(listener);
+    if (listeners.size === 0 && releaseStores) {
+      releaseStores();
+      releaseStores = null;
+      hostProjections.clear();
+    }
+  };
+}
+
+interface HostProjection {
+  language: string;
+  workspaces: SessionState["workspaces"];
+  agents: SessionState["agents"];
+  projects: SessionState["projects"];
+  activity: SessionState["workspaceAgentActivity"];
+  pending: ReturnType<typeof useCreateFlowStore.getState>["pendingByDraftId"];
+  snapshot: Omit<PluginClientSnapshot, "terminals">;
+  workspaceById: Map<string, PluginClientSnapshot["workspaces"][number]>;
+  agentById: Map<string, PluginClientSnapshot["agents"][number]>;
+  projectById: Map<string, PluginClientSnapshot["projects"][number]>;
+}
+const hostProjections = new Map<string, HostProjection>();
+
+function projectHost(hostId: string): HostProjection | null {
+  const session = useSessionStore.getState().sessions[hostId];
+  if (!session) {
+    hostProjections.delete(hostId);
+    return null;
+  }
+  const pending = useCreateFlowStore.getState().pendingByDraftId;
+  const previous = hostProjections.get(hostId);
+  const unchanged =
+    previous &&
+    previous.language === i18n.language &&
+    previous.workspaces === session.workspaces &&
+    previous.agents === session.agents &&
+    previous.projects === session.projects &&
+    previous.activity === session.workspaceAgentActivity &&
+    previous.pending === pending;
+  if (unchanged) return previous;
+  const workspaces = Array.from(session.workspaces.values(), (workspace) => {
+    const activity = session.workspaceAgentActivity.get(workspace.id);
+    const root = activity ? session.agents.get(activity.agentId) : undefined;
+    return createPluginWorkspaceSnapshot(workspace, hostId, {
+      pendingCreateAttempts: pending,
+      workspaceAgentActivity: session.workspaceAgentActivity,
+      parentAgent: root ? createPluginAgentSnapshot(root, workspace.id).parentAgent : null,
+    });
+  });
+  const agents: PluginClientSnapshot["agents"][number][] = [];
+  for (const agent of session.agents.values()) {
+    const workspaceId = normalizeWorkspaceOpaqueId(agent.workspaceId);
+    if (!workspaceId || agent.archivedAt) continue;
+    agents.push(createPluginAgentSnapshot(agent, workspaceId));
+  }
+  const projects = Array.from(session.projects.values(), (project) =>
+    createPluginProjectSnapshot(project, hostId),
+  );
+  const projection: HostProjection = {
+    language: i18n.language,
+    workspaces: session.workspaces,
+    agents: session.agents,
+    projects: session.projects,
+    activity: session.workspaceAgentActivity,
+    pending,
+    snapshot: {
+      workspaces: Object.freeze(workspaces),
+      agents: Object.freeze(agents),
+      projects: Object.freeze(projects),
+    },
+    workspaceById: new Map(workspaces.map((workspace) => [workspace.id, workspace])),
+    agentById: new Map(agents.map((agent) => [agent.id, agent])),
+    projectById: new Map(projects.map((project) => [project.ref.id, project])),
+  };
+  hostProjections.set(hostId, projection);
+  return projection;
+}
+
+function sameSequence<T>(left: readonly T[], right: readonly T[]): boolean {
+  return left.length === right.length && left.every((value, index) => value === right[index]);
+}
+
+/** A host scope only resolves legacy string ids. Ref lookups and collections span hosts. */
+export function createPluginClientStateSource(
+  serverId?: string,
+  options: { hosts?: PluginConnectedHostsSource; terminals?: PluginTerminalsSource } = {},
+): PluginClientStateSource {
+  const terminals = options.terminals ?? noTerminals;
+  const hosts = options.hosts ?? connectedPluginHosts;
+  const subscribers = new Set<() => void>();
+  let release: (() => void) | null = null;
+  let previousProjections: readonly HostProjection[] = [];
+  let previousTerminals = emptyTerminals;
+  let snapshot: PluginClientSnapshot = {
+    workspaces: [],
+    agents: [],
+    projects: [],
+    terminals: emptyTerminals,
+  };
+  function getSnapshot(): PluginClientSnapshot {
+    const ids = hosts.getSnapshot();
+    const projections: HostProjection[] = [];
+    for (const id of ids) {
+      const projection = projectHost(id);
+      if (projection) projections.push(projection);
+    }
+    const terminalSnapshots = terminals.getSnapshot();
+    if (sameSequence(previousProjections, projections) && previousTerminals === terminalSnapshots)
+      return snapshot;
+    previousProjections = projections;
+    previousTerminals = terminalSnapshots;
+    snapshot = Object.freeze({
+      workspaces: Object.freeze(projections.flatMap((host) => host.snapshot.workspaces)),
+      agents: Object.freeze(projections.flatMap((host) => host.snapshot.agents)),
+      projects: Object.freeze(projections.flatMap((host) => host.snapshot.projects)),
+      terminals: terminalSnapshots,
+    });
+    return snapshot;
+  }
   return {
-    subscribe: useSessionStore.subscribe,
-    getWorkspace(workspaceId) {
-      const workspace = selectWorkspace(useSessionStore.getState(), serverId, workspaceId);
-      return workspace ? createPluginWorkspaceSnapshot(workspace) : null;
+    subscribe(listener) {
+      subscribers.add(listener);
+      if (!release) {
+        const notify = () => {
+          for (const subscriber of subscribers) subscriber();
+        };
+        const releaseStore = subscribeStores(notify);
+        const releaseHosts = hosts.subscribe(notify);
+        const releaseTerminals = terminals.subscribe(notify);
+        release = () => {
+          releaseStore();
+          releaseHosts();
+          releaseTerminals();
+        };
+      }
+      return () => {
+        subscribers.delete(listener);
+        if (subscribers.size === 0 && release) {
+          release();
+          release = null;
+          previousProjections = [];
+          previousTerminals = emptyTerminals;
+          snapshot = { workspaces: [], agents: [], projects: [], terminals: emptyTerminals };
+        }
+      };
+    },
+    getSnapshot,
+    getWorkspace(reference) {
+      const ref =
+        typeof reference === "string" && serverId
+          ? entityRefs.workspace(serverId, reference)
+          : reference;
+      if (typeof ref === "string") return null;
+      return projectHost(ref.hostId)?.workspaceById.get(ref.id) ?? null;
     },
-    getAgent(agentId) {
-      const session = useSessionStore.getState().sessions[serverId];
-      const agent = session?.agents.get(agentId) ?? session?.agentDetails.get(agentId) ?? null;
-      const workspaceId = normalizeWorkspaceOpaqueId(agent?.workspaceId);
-      return agent && workspaceId ? createPluginAgentSnapshot(agent, workspaceId) : null;
+    getAgent(reference) {
+      const ref =
+        typeof reference === "string" && serverId
+          ? entityRefs.agent(serverId, reference)
+          : reference;
+      if (typeof ref === "string") return null;
+      const projected = projectHost(ref.hostId)?.agentById.get(ref.id);
+      if (projected) return projected;
+      const session = useSessionStore.getState().sessions[ref.hostId];
+      const detail = session?.agents.get(ref.id) ?? session?.agentDetails.get(ref.id);
+      const workspaceId = normalizeWorkspaceOpaqueId(detail?.workspaceId);
+      return detail && workspaceId ? createPluginAgentSnapshot(detail, workspaceId) : null;
     },
+    getProject: (ref) => projectHost(ref.hostId)?.projectById.get(ref.id) ?? null,
+    getTerminal: (ref) => terminals.getSnapshot().find((terminal) => terminal.ref === ref) ?? null,
   };
 }
diff --git a/packages/app/src/plugins/command-center/contributions.test.ts b/packages/app/src/plugins/command-center/contributions.test.ts
index e8aea62ede..b2fd0891c9 100644
--- a/packages/app/src/plugins/command-center/contributions.test.ts
+++ b/packages/app/src/plugins/command-center/contributions.test.ts
@@ -13,7 +13,20 @@ import { z } from "zod";
 import type { InstalledPlugin } from "../types";
 import { buildPluginCommandCenterContributions } from "./contributions";
 
+import { entityRefs } from "../client-state/refs";
 const workspace: PluginWorkspaceSnapshot = {
+  ref: entityRefs.workspace("host-1", "workspace-1"),
+  hostId: "host-1",
+  project: entityRefs.project("host-1", "project-1"),
+  pinnedAt: null,
+  labels: [],
+  background: false,
+  branch: null,
+  createdAt: null,
+  lastPromptAt: null,
+  parentAgent: null,
+  indicator: "running",
+  indicatorLabel: "Running",
   id: "workspace-1",
   projectId: "project-1",
   projectDisplayName: "Paseo",
@@ -30,6 +43,10 @@ const workspace: PluginWorkspaceSnapshot = {
 };
 
 const agent: PluginAgentSnapshot = {
+  ref: entityRefs.agent("host-1", "agent-1"),
+  hostId: "host-1",
+  workspace: workspace.ref,
+  parentAgent: null,
   id: "agent-1",
   workspaceId: workspace.id,
   provider: "codex",
@@ -131,6 +148,15 @@ function stateSource() {
     subscribe() {
       return () => {};
     },
+    getSnapshot() {
+      return { workspaces: [workspace], agents: [agent], projects: [], terminals: [] };
+    },
+    getProject() {
+      return null;
+    },
+    getTerminal() {
+      return null;
+    },
     getWorkspace(id: string) {
       return id === workspace.id ? workspace : null;
     },
diff --git a/packages/app/src/plugins/timeline/view.test.tsx b/packages/app/src/plugins/timeline/view.test.tsx
index ff3ba9fd6b..7d96747279 100644
--- a/packages/app/src/plugins/timeline/view.test.tsx
+++ b/packages/app/src/plugins/timeline/view.test.tsx
@@ -9,7 +9,8 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 const hostClient = vi.hoisted(() => ({ invokePluginRpc: async () => null }));
 const selectedHost = vi.hoisted(() => ({ client: null as DaemonClient | null }));
-vi.mock("@/runtime/host-runtime", () => ({
+vi.mock("@/runtime/host-runtime", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("@/runtime/host-runtime")>()),
   useHostRuntimeClient: () => selectedHost.client ?? (hostClient as unknown as DaemonClient),
   useHosts: () => [{ serverId: "host-1", label: "Local" }],
 }));
diff --git a/packages/app/src/screens/settings/plugins-page.test.tsx b/packages/app/src/screens/settings/plugins-page.test.tsx
index 8a502749db..dfb16ccfa7 100644
--- a/packages/app/src/screens/settings/plugins-page.test.tsx
+++ b/packages/app/src/screens/settings/plugins-page.test.tsx
@@ -20,7 +20,8 @@ const runtime = vi.hoisted(() => ({
   client: null as DaemonClient | null,
 }));
 
-vi.mock("@/runtime/host-runtime", () => ({
+vi.mock("@/runtime/host-runtime", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("@/runtime/host-runtime")>()),
   useHostRuntimeClient: () => runtime.client,
   useHostRuntimeIsConnected: () => runtime.connected,
 }));
diff --git a/packages/plugin/src/boundaries.test.ts b/packages/plugin/src/boundaries.test.ts
index c28bbc8d68..263a791dd6 100644
--- a/packages/plugin/src/boundaries.test.ts
+++ b/packages/plugin/src/boundaries.test.ts
@@ -388,3 +388,29 @@ describe("plugin subscription SDK boundary", () => {
     ).toEqual([]);
   });
 });
+
+describe("sidebar data SDK boundary", () => {
+  it("accepts references and preserves string-id panel consumers", () => {
+    expect(
+      typeErrors(`
+      import { useWorkspace, useAgent, type WorkspaceRef, type AgentRef, useProject, useTerminal, useWorkspaces, useAgents, useProjects, useTerminals, type ProjectRef, type TerminalRef, type Query, type Group } from "@getpaseo/plugin/client";
+      import type { PluginWorkspaceSnapshot } from "@getpaseo/plugin";
+      function Panel({ workspace, agent }: { workspace: WorkspaceRef; agent: AgentRef }) {
+        const snapshot: PluginWorkspaceSnapshot | null = useWorkspace(workspace);
+        const title: string | null = useWorkspace("workspace", item => item.name);
+        const status = useAgent(agent, item => ({ status: item.status }), (a, b) => a?.status === b?.status);
+        const agentSnapshot = useAgent(agent);
+        const custom = useWorkspace(workspace, undefined, (a, b) => a?.name === b?.name);
+        const workspaces: readonly WorkspaceRef[] = useWorkspaces({ orderBy: "name" });
+        const groups: readonly Group<AgentRef>[] = useAgents({ groupBy: item => item.status });
+        const projects: readonly ProjectRef[] = useProjects({ hosts: [workspace.hostId] });
+        const terminals: readonly TerminalRef[] = useTerminals();
+        if (projects[0]) useProject(projects[0], item => item.displayName);
+        if (terminals[0]) useTerminal(terminals[0]);
+        const query: Query<PluginWorkspaceSnapshot> = { hosts: [workspace.hostId], orderBy: ["name", "desc"] };
+        return null;
+      }
+    `),
+    ).toEqual([]);
+  });
+});
diff --git a/packages/plugin/src/client/client-state.tsx b/packages/plugin/src/client/client-state.tsx
index b1c853ecec..ee8a36e10e 100644
--- a/packages/plugin/src/client/client-state.tsx
+++ b/packages/plugin/src/client/client-state.tsx
@@ -1,12 +1,29 @@
-import { createContext, useContext, type ReactNode } from "react";
+import { createContext, useContext, useMemo, type ReactNode } from "react";
 import { useSyncExternalStoreWithSelector } from "use-sync-external-store/shim/with-selector";
-import type { PluginAgentSnapshot, PluginWorkspaceSnapshot } from "../contracts.js";
+import type { AgentRef, WorkspaceRef, ProjectRef, TerminalRef } from "../refs.js";
+import type {
+  PluginAgentSnapshot,
+  PluginWorkspaceSnapshot,
+  PluginProjectSnapshot,
+  PluginTerminalSnapshot,
+} from "../contracts.js";
+import { createCollectionQuery, type Query, type Group } from "./query.js";
 import { shallowEqual } from "./shallow.js";
 
 export interface PluginClientStateSource {
   subscribe(listener: () => void): () => void;
-  getWorkspace(id: string): PluginWorkspaceSnapshot | null;
-  getAgent(id: string): PluginAgentSnapshot | null;
+  getWorkspace(id: string | WorkspaceRef): PluginWorkspaceSnapshot | null;
+  getAgent(id: string | AgentRef): PluginAgentSnapshot | null;
+  getProject(ref: ProjectRef): PluginProjectSnapshot | null;
+  getTerminal(ref: TerminalRef): PluginTerminalSnapshot | null;
+  getSnapshot(): PluginClientSnapshot;
+}
+
+export interface PluginClientSnapshot {
+  readonly workspaces: readonly PluginWorkspaceSnapshot[];
+  readonly agents: readonly PluginAgentSnapshot[];
+  readonly projects: readonly PluginProjectSnapshot[];
+  readonly terminals: readonly PluginTerminalSnapshot[];
 }
 
 const PluginClientStateContext = createContext<PluginClientStateSource | null>(null);
@@ -15,44 +32,89 @@ export function usePluginClientStateSource(): PluginClientStateSource | null {
   return useContext(PluginClientStateContext);
 }
 
-function usePluginEntity<Entity, Selection>(input: {
-  id: string;
-  read(source: PluginClientStateSource, id: string): Entity | null;
-  selector(entity: Entity): Selection;
-}): Selection | null {
-  const source = usePluginClientStateSource();
-  if (!source) throw new Error("Plugin state hooks must run inside a workspace panel");
-  return useSyncExternalStoreWithSelector(
-    source.subscribe,
-    () => input.read(source, input.id),
-    () => input.read(source, input.id),
-    (entity) => (entity ? input.selector(entity) : null),
-    shallowEqual,
-  );
+/** Shared selection semantics for host surfaces and plugin entities. */
+export function usePaseoSelector<Entity, Selection>(
+  source: { subscribe(listener: () => void): () => void },
+  read: () => Entity,
+  selector: (entity: Entity) => Selection,
+  equals: (left: Selection, right: Selection) => boolean = shallowEqual,
+): Selection {
+  return useSyncExternalStoreWithSelector(source.subscribe, read, read, selector, equals);
 }
 
-export function useWorkspace<Selection>(
-  workspaceId: string,
-  selector: (workspace: PluginWorkspaceSnapshot) => Selection,
-): Selection | null {
-  return usePluginEntity({
-    id: workspaceId,
-    read: (source, id) => source.getWorkspace(id),
-    selector,
-  });
+type Equality<T> = { equals(left: T, right: T): boolean }["equals"];
+
+function createEntityHook<Ref, Entity>(
+  read: (source: PluginClientStateSource, ref: Ref) => Entity | null,
+) {
+  function useEntity(
+    ref: Ref,
+    selector?: undefined,
+    equals?: Equality<Entity | null>,
+  ): Entity | null;
+  function useEntity<Selection>(
+    ref: Ref,
+    selector: (entity: Entity) => Selection,
+    equals?: Equality<Selection | null>,
+  ): Selection | null;
+  function useEntity<Selection>(
+    ref: Ref,
+    selector?: (entity: Entity) => Selection,
+    equals?: Equality<Entity | Selection | null>,
+  ): Entity | Selection | null {
+    const source = usePluginClientStateSource();
+    if (!source) throw new Error("Plugin state hooks must run inside a plugin host");
+    function select(entity: Entity | null): Entity | Selection | null {
+      return entity !== null && selector ? selector(entity) : entity;
+    }
+    const equality = equals ?? (selector ? shallowEqual : Object.is);
+    return usePaseoSelector(source, () => read(source, ref), select, equality);
+  }
+  return useEntity;
 }
 
-export function useAgent<Selection>(
-  agentId: string,
-  selector: (agent: PluginAgentSnapshot) => Selection,
-): Selection | null {
-  return usePluginEntity({
-    id: agentId,
-    read: (source, id) => source.getAgent(id),
-    selector,
-  });
+// COMPAT(plugin-entity-id): string ids accepted since 0.16; remove after 2027-03.
+export const useWorkspace = createEntityHook((source, ref: WorkspaceRef | string) =>
+  source.getWorkspace(ref),
+);
+// COMPAT(plugin-entity-id): string ids accepted since 0.16; remove after 2027-03.
+export const useAgent = createEntityHook((source, ref: AgentRef | string) => source.getAgent(ref));
+export const useProject = createEntityHook((source, ref: ProjectRef) => source.getProject(ref));
+export const useTerminal = createEntityHook((source, ref: TerminalRef) => source.getTerminal(ref));
+
+function createCollectionHook<Snapshot extends { readonly ref: unknown; readonly hostId: string }>(
+  read: (source: PluginClientStateSource) => readonly Snapshot[],
+) {
+  function useCollection(
+    query: Query<Snapshot> & { groupBy: NonNullable<Query<Snapshot>["groupBy"]> },
+  ): readonly Group<Snapshot["ref"]>[];
+  function useCollection(
+    query?: Query<Snapshot> & { groupBy?: undefined },
+  ): readonly Snapshot["ref"][];
+  function useCollection(
+    query: Query<Snapshot>,
+  ): readonly Snapshot["ref"][] | readonly Group<Snapshot["ref"]>[];
+  function useCollection(
+    query: Query<Snapshot> = {},
+  ): readonly Snapshot["ref"][] | readonly Group<Snapshot["ref"]>[] {
+    const source = usePluginClientStateSource();
+    if (!source) throw new Error("Plugin state hooks must run inside a plugin host");
+    const project = useMemo(() => createCollectionQuery<Snapshot>(), []);
+    return usePaseoSelector(
+      source,
+      () => read(source),
+      (snapshots) => project(snapshots, query),
+      Object.is,
+    );
+  }
+  return useCollection;
 }
 
+export const useWorkspaces = createCollectionHook((source) => source.getSnapshot().workspaces);
+export const useAgents = createCollectionHook((source) => source.getSnapshot().agents);
+export const useProjects = createCollectionHook((source) => source.getSnapshot().projects);
+export const useTerminals = createCollectionHook((source) => source.getSnapshot().terminals);
+
 export function PluginClientStateProvider({
   children,
   source,
diff --git a/packages/plugin/src/client/host.ts b/packages/plugin/src/client/host.ts
index 2ec1f57b2e..724cfab437 100644
--- a/packages/plugin/src/client/host.ts
+++ b/packages/plugin/src/client/host.ts
@@ -1,6 +1,11 @@
 import type { PluginText } from "../text.js";
 import { PluginAttachmentSearchPayloadSchema } from "../attachments.js";
-export { PluginClientStateProvider, type PluginClientStateSource } from "./client-state.js";
+export {
+  PluginClientStateProvider,
+  usePaseoSelector,
+  type PluginClientStateSource,
+  type PluginClientSnapshot,
+} from "./client-state.js";
 export {
   usePluginRuntimeContextBridge,
   type PluginRuntimeContextBridge,
@@ -31,3 +36,5 @@ export {
   isPluginMessage,
 } from "./translations.js";
 export type { PluginLocaleSource } from "./translations.js";
+
+export { createEntityRefs } from "./refs.js";
diff --git a/packages/plugin/src/client/index.ts b/packages/plugin/src/client/index.ts
index ffaf0782d5..9d7c52ddcc 100644
--- a/packages/plugin/src/client/index.ts
+++ b/packages/plugin/src/client/index.ts
@@ -70,7 +70,16 @@ export {
   useFileUrl,
 } from "./file.js";
 export { usePaseo } from "./paseo-context.js";
-export { useAgent, useWorkspace } from "./client-state.js";
+export {
+  useAgent,
+  useWorkspace,
+  useProject,
+  useTerminal,
+  useWorkspaces,
+  useAgents,
+  useProjects,
+  useTerminals,
+} from "./client-state.js";
 export { useRpc, useSubscription, type PluginSubscriptionState } from "./rpc-context.js";
 export type {
   PluginSubscribeOptions,
@@ -102,3 +111,6 @@ export type { PluginI18n } from "./translations.js";
 export type { PluginText, PluginMessage, PluginTranslations } from "../text.js";
 
 export { useTabState } from "./tab.js";
+
+export type { WorkspaceRef, AgentRef, ProjectRef, TerminalRef } from "../refs.js";
+export type { Query, Group, GroupKey } from "./query.js";
diff --git a/packages/plugin/src/client/query.test.ts b/packages/plugin/src/client/query.test.ts
new file mode 100644
index 0000000000..ce0dd9bd3c
--- /dev/null
+++ b/packages/plugin/src/client/query.test.ts
@@ -0,0 +1,58 @@
+import { describe, expect, it } from "vitest";
+import { createCollectionQuery, type GroupKey } from "./query.js";
+
+const first = Object.freeze({ key: "a" });
+const second = Object.freeze({ key: "b" });
+const work: GroupKey = "work";
+const snapshots = [
+  { ref: first, hostId: "one", title: "A", status: "running", labels: [work, work] },
+  { ref: second, hostId: "two", title: "B", status: "idle", labels: ["home"] },
+];
+
+describe("collection query structural sharing", () => {
+  it("preserves collection identity when a row changes without changing membership", () => {
+    const project = createCollectionQuery<(typeof snapshots)[number]>();
+    const before = project(snapshots);
+    const after = project([{ ...snapshots[0]!, status: "waiting" }, snapshots[1]!]);
+    expect(after).toBe(before);
+    expect(after).toEqual([first, second]);
+  });
+
+  it("shares unaffected groups and deduplicates membership", () => {
+    const project = createCollectionQuery<(typeof snapshots)[number]>();
+    const query = { groupBy: (item: (typeof snapshots)[number]) => item.labels };
+    const before = project(snapshots, query);
+    const after = project([{ ...snapshots[0]!, labels: ["new"] }, snapshots[1]!], query);
+    expect(after[1]).toBe(before[1]);
+    expect(before[0]).toEqual({ key: "work", title: null, color: null, items: [first] });
+    expect(after[0]).toEqual({ key: "new", title: null, color: null, items: [first] });
+    expect(project([{ ...snapshots[0]!, labels: ["new"] }, snapshots[1]!], query)).toBe(after);
+  });
+
+  it("filters hosts and predicates before sorting", () => {
+    const project = createCollectionQuery<(typeof snapshots)[number]>();
+    expect(project(snapshots, { hosts: ["two"] })).toEqual([second]);
+    expect(project(snapshots, { where: (item) => item.status === "running" })).toEqual([first]);
+    expect(project(snapshots, { orderBy: ["title", "desc"] })).toEqual([second, first]);
+    expect(project(snapshots, { orderBy: (a, b) => a.title.localeCompare(b.title) })).toEqual([
+      first,
+      second,
+    ]);
+  });
+
+  it("keeps nulls last in either direction and metadata from the first group", () => {
+    const project = createCollectionQuery<{
+      ref: typeof first;
+      hostId: string;
+      title: string | null;
+    }>();
+    const items = [
+      { ref: first, hostId: "one", title: null },
+      { ref: second, hostId: "one", title: "Z" },
+    ];
+    expect(project(items, { orderBy: ["title", "desc"] })).toEqual([second, first]);
+    expect(
+      project(items, { groupBy: (item) => ({ key: "all", title: item.title ?? "First" }) }),
+    ).toEqual([{ key: "all", title: "First", color: null, items: [first, second] }]);
+  });
+});
diff --git a/packages/plugin/src/client/query.ts b/packages/plugin/src/client/query.ts
new file mode 100644
index 0000000000..8e291602ca
--- /dev/null
+++ b/packages/plugin/src/client/query.ts
@@ -0,0 +1,115 @@
+interface GroupDescriptor {
+  readonly key: string;
+  readonly title?: string;
+  readonly color?: string;
+}
+
+export type GroupKey = string | GroupDescriptor;
+
+export interface Query<Snapshot> {
+  readonly hosts?: readonly string[];
+  readonly where?: (item: Snapshot) => boolean;
+  readonly orderBy?:
+    | keyof Snapshot
+    | readonly [keyof Snapshot, "asc" | "desc"]
+    | ((a: Snapshot, b: Snapshot) => number);
+  readonly groupBy?: (item: Snapshot) => GroupKey | readonly GroupKey[];
+}
+
+export interface Group<Ref> {
+  readonly key: string;
+  readonly title: string | null;
+  readonly color: string | null;
+  readonly items: readonly Ref[];
+}
+
+function groupKeys(value: GroupKey | readonly GroupKey[]): readonly GroupKey[] {
+  if (typeof value === "string") return [value];
+  if ("key" in value) return [value];
+  return value;
+}
+
+interface Referenced {
+  readonly hostId: string;
+  readonly ref: unknown;
+}
+
+function sameSequence<T>(left: readonly T[], right: readonly T[]): boolean {
+  return left.length === right.length && left.every((item, index) => item === right[index]);
+}
+
+function compareValues(left: unknown, right: unknown, direction: number): number {
+  if (Object.is(left, right)) return 0;
+  if (left === null || left === undefined) return 1;
+  if (right === null || right === undefined) return -1;
+  if (typeof left === "number" && typeof right === "number") return (left - right) * direction;
+  return String(left).localeCompare(String(right)) * direction;
+}
+
+/** A hook owns one projection; sharing survives both source and query changes. */
+export function createCollectionQuery<Snapshot extends Referenced>() {
+  type Ref = Snapshot["ref"];
+  let previousItems: readonly Ref[] = Object.freeze([]);
+  let previousGroups: readonly Group<Ref>[] = Object.freeze([]);
+
+  return function project(
+    snapshots: readonly Snapshot[],
+    query: Query<Snapshot> = {},
+  ): readonly Ref[] | readonly Group<Ref>[] {
+    const items = snapshots.filter((item) => {
+      if (query.hosts && !query.hosts.includes(item.hostId)) return false;
+      return !query.where || query.where(item);
+    });
+    const order = query.orderBy;
+    if (typeof order === "function") items.sort(order);
+    else if (order !== undefined) {
+      const field = typeof order === "object" ? order[0] : order;
+      const direction = typeof order === "object" && order[1] === "desc" ? -1 : 1;
+      items.sort((a, b) => compareValues(a[field], b[field], direction));
+    }
+    if (!query.groupBy) {
+      const refs = items.map((item) => item.ref);
+      if (!sameSequence(previousItems, refs)) previousItems = Object.freeze(refs);
+      return previousItems;
+    }
+    const groups = new Map<
+      string,
+      { key: string; title: string | null; color: string | null; items: Ref[] }
+    >();
+    for (const item of items) {
+      const grouping = query.groupBy(item);
+      const keys = groupKeys(grouping);
+      const seen = new Set<string>();
+      for (const value of keys) {
+        const descriptor = typeof value === "string" ? { key: value } : value;
+        if (seen.has(descriptor.key)) continue;
+        seen.add(descriptor.key);
+        let group = groups.get(descriptor.key);
+        if (!group) {
+          group = {
+            key: descriptor.key,
+            title: descriptor.title ?? null,
+            color: descriptor.color ?? null,
+            items: [],
+          };
+          groups.set(descriptor.key, group);
+        }
+        group.items.push(item.ref);
+      }
+    }
+    const oldGroups = new Map(previousGroups.map((group) => [group.key, group]));
+    const nextGroups = Array.from(groups.values(), (group) => {
+      const previous = oldGroups.get(group.key);
+      if (
+        previous &&
+        previous.title === group.title &&
+        previous.color === group.color &&
+        sameSequence(previous.items, group.items)
+      )
+        return previous;
+      return Object.freeze({ ...group, items: Object.freeze(group.items) });
+    });
+    if (!sameSequence(previousGroups, nextGroups)) previousGroups = Object.freeze(nextGroups);
+    return previousGroups;
+  };
+}
diff --git a/packages/plugin/src/client/refs.test.ts b/packages/plugin/src/client/refs.test.ts
new file mode 100644
index 0000000000..93407414fc
--- /dev/null
+++ b/packages/plugin/src/client/refs.test.ts
@@ -0,0 +1,24 @@
+import { describe, expect, it } from "vitest";
+import { createEntityRefs } from "./refs.js";
+
+describe("session entity references", () => {
+  it("interns frozen references separately by kind, host and entity", () => {
+    const refs = createEntityRefs();
+    for (const reference of [refs.workspace, refs.agent, refs.project, refs.terminal]) {
+      const first = reference("host", "entity");
+      expect(reference("host", "entity")).toBe(first);
+      expect(Object.isFrozen(first)).toBe(true);
+      expect(reference("other", "entity")).not.toBe(first);
+      expect(reference("host", "other")).not.toBe(first);
+    }
+    expect(refs.workspace("host", "entity")).not.toBe(refs.agent("host", "entity"));
+  });
+
+  it("keeps opaque ids unambiguous and interning scoped to one app session", () => {
+    const refs = createEntityRefs();
+    expect(refs.workspace("a:b", "c").key).not.toBe(refs.workspace("a", "b:c").key);
+    expect(createEntityRefs().workspace("host", "entity")).not.toBe(
+      refs.workspace("host", "entity"),
+    );
+  });
+});
diff --git a/packages/plugin/src/client/refs.ts b/packages/plugin/src/client/refs.ts
new file mode 100644
index 0000000000..0dbdd69428
--- /dev/null
+++ b/packages/plugin/src/client/refs.ts
@@ -0,0 +1,26 @@
+import type { AgentRef, ProjectRef, TerminalRef, WorkspaceRef } from "../refs.js";
+
+/** Owned by the app session, shared by every plugin installation. */
+export function createEntityRefs() {
+  function intern<Kind extends string>(kind: Kind) {
+    const references = new Map<
+      string,
+      Readonly<{ kind: Kind; key: string; hostId: string; id: string }>
+    >();
+    return function reference(hostId: string, id: string) {
+      const key = JSON.stringify([hostId, id]);
+      let ref = references.get(key);
+      if (!ref) {
+        ref = Object.freeze({ kind, key, hostId, id });
+        references.set(key, ref);
+      }
+      return ref;
+    };
+  }
+  return {
+    workspace: intern("workspace") satisfies (hostId: string, id: string) => WorkspaceRef,
+    agent: intern("agent") satisfies (hostId: string, id: string) => AgentRef,
+    project: intern("project") satisfies (hostId: string, id: string) => ProjectRef,
+    terminal: intern("terminal") satisfies (hostId: string, id: string) => TerminalRef,
+  };
+}
diff --git a/packages/plugin/src/contracts.ts b/packages/plugin/src/contracts.ts
index 7e71cb22c5..17c14a7edf 100644
--- a/packages/plugin/src/contracts.ts
+++ b/packages/plugin/src/contracts.ts
@@ -1,3 +1,4 @@
+import type { WorkspaceRef, AgentRef, ProjectRef, TerminalRef } from "./refs.js";
 import type { PluginText } from "./text.js";
 import type { JsonValue } from "@getpaseo/protocol/agent-types";
 import type { PluginSerializableIcon } from "./icons.js";
@@ -19,7 +20,22 @@ export interface PluginTheme {
   };
 }
 
+export type WorkspaceIndicator = "needs_input" | "failed" | "running" | "attention" | "done";
+
 export interface PluginWorkspaceSnapshot {
+  readonly ref: WorkspaceRef;
+  readonly hostId: string;
+  readonly project: ProjectRef;
+  readonly pinnedAt: string | null;
+  readonly labels: readonly string[];
+  readonly background: boolean;
+  readonly branch: string | null;
+  /** Null when an older host has not supplied the workspace creation time. */
+  readonly createdAt: string | null;
+  readonly lastPromptAt: string | null;
+  readonly parentAgent: AgentRef | null;
+  readonly indicator: WorkspaceIndicator;
+  readonly indicatorLabel: string | null;
   readonly id: string;
   readonly projectId: string;
   readonly projectDisplayName: string;
@@ -29,6 +45,7 @@ export interface PluginWorkspaceSnapshot {
   readonly kind: "directory" | "local_checkout" | "checkout" | "worktree";
   readonly name: string;
   readonly title: string | null;
+  /** Raw daemon status; prefer indicator for presentation. */
   readonly status: "needs_input" | "failed" | "running" | "attention" | "done";
   readonly statusEnteredAt: string | null;
   readonly archivingAt: string | null;
@@ -36,6 +53,10 @@ export interface PluginWorkspaceSnapshot {
 }
 
 export interface PluginAgentSnapshot {
+  readonly ref: AgentRef;
+  readonly hostId: string;
+  readonly workspace: WorkspaceRef;
+  readonly parentAgent: AgentRef | null;
   readonly id: string;
   readonly workspaceId: string;
   readonly provider: string;
@@ -96,3 +117,21 @@ export interface PluginTimelineTransformResult {
 }
 
 export type PluginCleanup = () => void | Promise<void>;
+
+export interface PluginProjectSnapshot {
+  readonly ref: ProjectRef;
+  readonly hostId: string;
+  readonly displayName: string;
+  readonly rootPath: string;
+  readonly kind: PluginWorkspaceSnapshot["projectKind"];
+  readonly iconRevision: string | null;
+}
+
+export interface PluginTerminalSnapshot {
+  readonly ref: TerminalRef;
+  readonly hostId: string;
+  readonly workspace: WorkspaceRef;
+  readonly title: string;
+  readonly isScript: boolean;
+  readonly createdAt: string;
+}
diff --git a/packages/plugin/src/index.ts b/packages/plugin/src/index.ts
index 839b5003df..8680ae949f 100644
--- a/packages/plugin/src/index.ts
+++ b/packages/plugin/src/index.ts
@@ -3,6 +3,9 @@ export type {
   PluginTheme,
   PluginWorkspaceSnapshot,
   PluginAgentSnapshot,
+  PluginProjectSnapshot,
+  PluginTerminalSnapshot,
+  WorkspaceIndicator,
   PluginThemeColors,
   PluginThemeContribution,
   PluginAttachmentSourceContribution,
diff --git a/packages/plugin/src/refs.ts b/packages/plugin/src/refs.ts
new file mode 100644
index 0000000000..e0293bfe09
--- /dev/null
+++ b/packages/plugin/src/refs.ts
@@ -0,0 +1,11 @@
+interface EntityRef<Kind extends string> {
+  readonly kind: Kind;
+  readonly key: string;
+  readonly hostId: string;
+  readonly id: string;
+}
+
+export interface WorkspaceRef extends EntityRef<"workspace"> {}
+export interface AgentRef extends EntityRef<"agent"> {}
+export interface ProjectRef extends EntityRef<"project"> {}
+export interface TerminalRef extends EntityRef<"terminal"> {}