diff --git a/site/src/api/queries/chats.test.ts b/site/src/api/queries/chats.test.ts
index 5774f549ca208..2c795a97a35a9 100644
--- a/site/src/api/queries/chats.test.ts
+++ b/site/src/api/queries/chats.test.ts
@@ -1,4 +1,4 @@
-import { QueryClient } from "react-query";
+import { QueryClient, QueryObserver } from "react-query";
 import { describe, expect, it, vi } from "vitest";
 import { API } from "#/api/api";
 import type * as TypesGen from "#/api/typesGenerated";
@@ -8,9 +8,13 @@ import {
 	SUCCESS_STATUSES,
 } from "#/pages/AgentsPage/components/RightPanel/DebugPanel/debugPanelUtils";
 import { MockChatMessage } from "#/testHelpers/chatEntities";
+import { createDeferred } from "#/testHelpers/deferred";
 import { buildOptimisticEditedMessage } from "./chatMessageEdits";
 import {
 	addChildToParentInCache,
+	applyChatArchiveStateToCaches,
+	applyWatchedChatArchived,
+	applyWatchedChatCreatedOrUnarchived,
 	archiveChat,
 	type ChatListInput,
 	cancelChatEntity,
@@ -27,6 +31,7 @@ import {
 	chatDebugRunKey,
 	chatDebugRunsKey,
 	chatDiffContentsKey,
+	chatEntitiesFamilyKey,
 	chatEntityKey,
 	chatListFamilyKey,
 	chatListKey,
@@ -63,6 +68,7 @@ import {
 	removeChildFromParentInCache,
 	reorderPinnedChat,
 	replaceChatMessagesHistory,
+	resetUnloadedChatEntity,
 	setChatGroupRole,
 	setChatUserRole,
 	shouldInvalidateChatSearches,
@@ -172,6 +178,34 @@ const createTestQueryClient = (): QueryClient =>
 		},
 	});
 
+const observeChatWithDeferredFirstFetch = (
+	queryClient: QueryClient,
+	staleChat: TypesGen.Chat,
+	durableChat: TypesGen.Chat,
+) => {
+	const firstFetch = createDeferred<TypesGen.Chat>();
+	const durableResult = createDeferred<TypesGen.Chat>();
+	let fetchCount = 0;
+	const observer = new QueryObserver<TypesGen.Chat>(queryClient, {
+		queryKey: chatEntityKey(staleChat.id),
+		queryFn: () => {
+			fetchCount++;
+			return fetchCount === 1 ? firstFetch.promise : durableChat;
+		},
+	});
+	const unsubscribe = observer.subscribe((result) => {
+		if (result.data === durableChat) {
+			durableResult.resolve(result.data);
+		}
+	});
+	return {
+		durableResult,
+		firstFetch,
+		fetchCount: () => fetchCount,
+		unsubscribe,
+	};
+};
+
 describe("advisor config query factories", () => {
 	it("builds the advisor config query and delegates to the API", async () => {
 		const advisorConfig: TypesGen.AdvisorConfig = {
@@ -532,6 +566,25 @@ describe("archiveChat optimistic update", () => {
 		expect(readInfiniteChats(queryClient, { archived: false })).toEqual([]);
 	});
 
+	it("removes loaded search rows after success", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		const unrelatedRow = makeChat("chat-2");
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, [
+			makeChat(chatId, { pin_order: 2 }),
+			unrelatedRow,
+		]);
+
+		const mutation = archiveChat(queryClient);
+		mutation.onSuccess(undefined, chatId);
+
+		const rows = queryClient.getQueryData<TypesGen.Chat[]>(
+			chatSearch({ q: "alpha" }).queryKey,
+		);
+		expect(rows?.find((row) => row.id === chatId)).toBeUndefined();
+		expect(rows?.find((row) => row.id === "chat-2")).toEqual(unrelatedRow);
+	});
+
 	it("rolls back the chats list on error by invalidating", async () => {
 		const queryClient = createTestQueryClient();
 		const chatId = "chat-1";
@@ -694,6 +747,25 @@ describe("unarchiveChat optimistic update", () => {
 		});
 	});
 
+	it("removes loaded search rows after success", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		const unrelatedRow = makeChat("chat-2", { archived: true });
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, [
+			makeChat(chatId, { archived: true }),
+			unrelatedRow,
+		]);
+
+		const mutation = unarchiveChat(queryClient);
+		mutation.onSuccess(undefined, chatId);
+
+		const rows = queryClient.getQueryData<TypesGen.Chat[]>(
+			chatSearch({ q: "alpha" }).queryKey,
+		);
+		expect(rows?.find((row) => row.id === chatId)).toBeUndefined();
+		expect(rows?.find((row) => row.id === "chat-2")).toEqual(unrelatedRow);
+	});
+
 	it("rolls back both caches on error", async () => {
 		const queryClient = createTestQueryClient();
 		const chatId = "chat-1";
@@ -3336,6 +3408,28 @@ describe("semantic cache operations: cancellation", () => {
 		});
 	});
 
+	it("resetUnloadedChatEntity resets exactly when detail data is absent", async () => {
+		const queryClient = createTestQueryClient();
+		const resetSpy = vi.spyOn(queryClient, "resetQueries");
+
+		await resetUnloadedChatEntity(queryClient, "chat-1");
+
+		expect(resetSpy).toHaveBeenCalledWith({
+			queryKey: chatEntityKey("chat-1"),
+			exact: true,
+		});
+	});
+
+	it("resetUnloadedChatEntity is a no-op when detail data exists", async () => {
+		const queryClient = createTestQueryClient();
+		queryClient.setQueryData(chatEntityKey("chat-1"), makeChat("chat-1"));
+		const resetSpy = vi.spyOn(queryClient, "resetQueries");
+
+		await resetUnloadedChatEntity(queryClient, "chat-1");
+
+		expect(resetSpy).not.toHaveBeenCalled();
+	});
+
 	it("cancelChatMessages cancels the exact messages entry", async () => {
 		const queryClient = createTestQueryClient();
 		const cancelSpy = vi.spyOn(queryClient, "cancelQueries");
@@ -3739,3 +3833,344 @@ describe("message upsert fan-out and history replacement", () => {
 		).toBeUndefined();
 	});
 });
+
+describe("chatEntitiesFamilyKey shape", () => {
+	// chatEntityKey builds on this prefix, so every entity detail entry
+	// shares the family root and can be addressed as a group.
+	it("prefixes every chat entity key", () => {
+		expect(chatEntityKey("chat-1")).toEqual([
+			...chatEntitiesFamilyKey,
+			"chat-1",
+		]);
+	});
+});
+
+describe("applyChatArchiveStateToCaches search rows", () => {
+	it("removes matching rows from every cached search and preserves unrelated rows by reference", () => {
+		const queryClient = createTestQueryClient();
+		const unrelatedRow = makeChat("chat-2");
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, [
+			makeChat("chat-1", { pin_order: 2 }),
+			unrelatedRow,
+		]);
+		queryClient.setQueryData(chatSearch({ q: "archived:true" }).queryKey, [
+			makeChat("chat-1", { archived: true }),
+		]);
+
+		applyChatArchiveStateToCaches(queryClient, "chat-1", true);
+
+		expect(
+			queryClient
+				.getQueryData<TypesGen.Chat[]>(chatSearch({ q: "alpha" }).queryKey)
+				?.find((row) => row.id === "chat-1"),
+		).toBeUndefined();
+		expect(
+			queryClient.getQueryData<TypesGen.Chat[]>(
+				chatSearch({ q: "archived:true" }).queryKey,
+			),
+		).toEqual([]);
+		expect(
+			queryClient
+				.getQueryData<TypesGen.Chat[]>(chatSearch({ q: "alpha" }).queryKey)
+				?.find((row) => row.id === "chat-2"),
+		).toEqual(unrelatedRow);
+	});
+
+	it("preserves the previous array reference when the row is not cached", () => {
+		const queryClient = createTestQueryClient();
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, [
+			makeChat("chat-2"),
+		]);
+		const before = queryClient.getQueryData(
+			chatSearch({ q: "alpha" }).queryKey,
+		);
+
+		applyChatArchiveStateToCaches(queryClient, "chat-1", true);
+
+		expect(queryClient.getQueryData(chatSearch({ q: "alpha" }).queryKey)).toBe(
+			before,
+		);
+	});
+
+	it("leaves per-chat sub-resource entries untouched", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		queryClient.setQueryData(chatMessagesKey(chatId), []);
+		queryClient.setQueryData(chatPromptsKey(chatId), { prompts: [] });
+		queryClient.setQueryData(chatACLKey(chatId), {});
+		queryClient.setQueryData(chatDiffContentsKey(chatId), { files: [] });
+
+		applyChatArchiveStateToCaches(queryClient, chatId, true);
+
+		for (const [label, key] of [
+			["messages", chatMessagesKey(chatId)],
+			["prompts", chatPromptsKey(chatId)],
+			["acl", chatACLKey(chatId)],
+			["diff-contents", chatDiffContentsKey(chatId)],
+		] as const) {
+			expect(
+				queryClient.getQueryData(key),
+				`${label} entry should survive`,
+			).toBeDefined();
+			expect(
+				queryClient.getQueryState(key)?.isInvalidated,
+				`${label} entry should NOT be invalidated`,
+			).not.toBe(true);
+		}
+	});
+});
+
+describe("applyWatchedChatArchived", () => {
+	it("restarts an active initial entity fetch so stale data cannot overwrite archive", async () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		const staleChat = makeChat(chatId, { archived: false });
+		const durableChat = makeChat(chatId, { archived: true });
+		const fetch = observeChatWithDeferredFirstFetch(
+			queryClient,
+			staleChat,
+			durableChat,
+		);
+
+		applyWatchedChatArchived(queryClient, durableChat);
+		fetch.firstFetch.resolve(staleChat);
+		await fetch.durableResult.promise;
+
+		expect(fetch.fetchCount()).toBe(2);
+		expect(
+			queryClient.getQueryData<TypesGen.Chat>(chatEntityKey(chatId))?.archived,
+		).toBe(true);
+		fetch.unsubscribe();
+	});
+
+	it("does not create an entity query when no observer is mounted", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+
+		applyWatchedChatArchived(queryClient, makeChat(chatId, { archived: true }));
+
+		expect(queryClient.getQueryState(chatEntityKey(chatId))).toBeUndefined();
+	});
+
+	it("patches the entity in place instead of removing it", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		queryClient.setQueryData(
+			chatEntityKey(chatId),
+			makeChat(chatId, { pin_order: 2 }),
+		);
+
+		applyWatchedChatArchived(queryClient, makeChat(chatId, { archived: true }));
+
+		expect(
+			queryClient.getQueryData<TypesGen.Chat>(chatEntityKey(chatId)),
+		).toMatchObject({
+			archived: true,
+			pin_order: 0,
+		});
+	});
+
+	it("drops the chat from active lists and patches it in archived lists", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		seedInfiniteChats(queryClient, [makeChat(chatId), makeChat("chat-2")], {
+			archived: false,
+		});
+		seedInfiniteChats(queryClient, [makeChat(chatId, { pin_order: 3 })], {
+			archived: true,
+		});
+
+		applyWatchedChatArchived(queryClient, makeChat(chatId, { archived: true }));
+
+		expect(
+			readInfiniteChats(queryClient, { archived: false })?.map(
+				(chat) => chat.id,
+			),
+		).toEqual(["chat-2"]);
+		expect(
+			readInfiniteChats(queryClient, { archived: true })?.[0],
+		).toMatchObject({
+			id: chatId,
+			archived: true,
+			pin_order: 0,
+		});
+	});
+
+	it("removes search rows and removes the by-workspace mapping", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, [
+			makeChat(chatId),
+		]);
+		queryClient.setQueryData(chatsByWorkspace(["ws-1"]).queryKey, {
+			"ws-1": chatId,
+		});
+
+		applyWatchedChatArchived(queryClient, makeChat(chatId, { archived: true }));
+
+		expect(
+			queryClient.getQueryData<TypesGen.Chat[]>(
+				chatSearch({ q: "alpha" }).queryKey,
+			),
+		).toEqual([]);
+		expect(
+			queryClient.getQueryData(chatsByWorkspace(["ws-1"]).queryKey),
+		).toEqual({});
+	});
+
+	it("invalidates the list, by-workspace, and search families but not per-chat sub-resources", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		seedInfiniteChats(queryClient, [makeChat(chatId)]);
+		queryClient.setQueryData(chatEntityKey(chatId), makeChat(chatId));
+		queryClient.setQueryData(chatMessagesKey(chatId), []);
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, []);
+		queryClient.setQueryData(chatsByWorkspace(["ws-1"]).queryKey, {});
+
+		applyWatchedChatArchived(queryClient, makeChat(chatId, { archived: true }));
+
+		for (const [label, key] of [
+			["chat list", infiniteChatsTestKey],
+			["chat search", chatSearch({ q: "alpha" }).queryKey],
+			["by-workspace", chatsByWorkspace(["ws-1"]).queryKey],
+		] as const) {
+			expect(
+				queryClient.getQueryState(key)?.isInvalidated,
+				`${label} entry should be invalidated`,
+			).toBe(true);
+		}
+		expect(
+			queryClient.getQueryData(chatMessagesKey(chatId)),
+			"messages entry should survive",
+		).toBeDefined();
+		expect(
+			queryClient.getQueryState(chatMessagesKey(chatId))?.isInvalidated,
+			"messages entry should NOT be invalidated",
+		).not.toBe(true);
+		expect(
+			queryClient.getQueryData(chatEntityKey(chatId)),
+			"entity entry should survive",
+		).toBeDefined();
+	});
+});
+
+describe("applyWatchedChatCreatedOrUnarchived", () => {
+	it("restarts an active initial entity fetch so stale data cannot overwrite unarchive", async () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		const staleChat = makeChat(chatId, { archived: true });
+		const durableChat = makeChat(chatId, { archived: false });
+		const fetch = observeChatWithDeferredFirstFetch(
+			queryClient,
+			staleChat,
+			durableChat,
+		);
+
+		applyWatchedChatCreatedOrUnarchived(queryClient, durableChat);
+		fetch.firstFetch.resolve(staleChat);
+		await fetch.durableResult.promise;
+
+		expect(fetch.fetchCount()).toBe(2);
+		expect(
+			queryClient.getQueryData<TypesGen.Chat>(chatEntityKey(chatId))?.archived,
+		).toBe(false);
+		fetch.unsubscribe();
+	});
+
+	it("restarts an active initial fetch for a genuinely new chat", async () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-new";
+		const staleChat = makeChat(chatId, { title: "stale" });
+		const durableChat = makeChat(chatId, { title: "durable" });
+		const fetch = observeChatWithDeferredFirstFetch(
+			queryClient,
+			staleChat,
+			durableChat,
+		);
+
+		applyWatchedChatCreatedOrUnarchived(queryClient, durableChat);
+		fetch.firstFetch.resolve(staleChat);
+		await fetch.durableResult.promise;
+
+		expect(fetch.fetchCount()).toBe(2);
+		expect(
+			queryClient.getQueryData<TypesGen.Chat>(chatEntityKey(chatId))?.title,
+		).toBe("durable");
+		fetch.unsubscribe();
+	});
+
+	it("flips a cached archived entity back to active and repairs list rows", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		queryClient.setQueryData(
+			chatEntityKey(chatId),
+			makeChat(chatId, { archived: true }),
+		);
+		seedInfiniteChats(queryClient, [makeChat(chatId, { archived: true })], {
+			archived: true,
+		});
+		seedInfiniteChats(queryClient, [makeChat(chatId, { archived: true })], {
+			archived: false,
+		});
+
+		applyWatchedChatCreatedOrUnarchived(queryClient, makeChat(chatId));
+
+		expect(
+			queryClient.getQueryData<TypesGen.Chat>(chatEntityKey(chatId))?.archived,
+		).toBe(false);
+		expect(readInfiniteChats(queryClient, { archived: true })).toEqual([]);
+		expect(
+			readInfiniteChats(queryClient, { archived: false })?.[0].archived,
+		).toBe(false);
+	});
+
+	it("only invalidates the collection families for a truly new chat", () => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-new";
+		seedInfiniteChats(queryClient, [makeChat("chat-2")]);
+		queryClient.setQueryData(chatSearch({ q: "alpha" }).queryKey, []);
+		queryClient.setQueryData(chatsByWorkspace(["ws-1"]).queryKey, {});
+
+		applyWatchedChatCreatedOrUnarchived(queryClient, makeChat(chatId));
+
+		expect(queryClient.getQueryData(chatEntityKey(chatId))).toBeUndefined();
+		expect(queryClient.getQueryState(chatEntityKey(chatId))).toBeUndefined();
+		for (const [label, key] of [
+			["chat list", infiniteChatsTestKey],
+			["chat search", chatSearch({ q: "alpha" }).queryKey],
+			["by-workspace", chatsByWorkspace(["ws-1"]).queryKey],
+		] as const) {
+			expect(
+				queryClient.getQueryState(key)?.isInvalidated,
+				`${label} entry should be invalidated`,
+			).toBe(true);
+		}
+	});
+});
+
+describe("archive mutation entity retention", () => {
+	it.each([
+		{ name: "archiveChat", factory: archiveChat, archived: true },
+		{ name: "unarchiveChat", factory: unarchiveChat, archived: false },
+	])("$name onSuccess never removes the entity family", ({
+		factory,
+		archived,
+	}) => {
+		const queryClient = createTestQueryClient();
+		const chatId = "chat-1";
+		queryClient.setQueryData(
+			chatEntityKey(chatId),
+			makeChat(chatId, { archived: !archived }),
+		);
+		queryClient.setQueryData(chatMessagesKey(chatId), []);
+
+		const mutation = factory(queryClient);
+		mutation.onSuccess(undefined, chatId);
+		mutation.onSettled(undefined, undefined, chatId);
+
+		expect(
+			queryClient.getQueryData<TypesGen.Chat>(chatEntityKey(chatId)),
+		).toMatchObject({ archived });
+		expect(queryClient.getQueryData(chatMessagesKey(chatId))).toBeDefined();
+	});
+});
diff --git a/site/src/api/queries/chats.ts b/site/src/api/queries/chats.ts
index 83e031392bd93..94c7752b7614e 100644
--- a/site/src/api/queries/chats.ts
+++ b/site/src/api/queries/chats.ts
@@ -28,8 +28,10 @@ const chatsByWorkspaceFamilyKey = [
 	"by-workspace",
 ] as const;
 
+export const chatEntitiesFamilyKey = ["chats", "entities"] as const;
+
 export const chatEntityKey = (chatId: string) =>
-	["chats", "entities", chatId] as const;
+	[...chatEntitiesFamilyKey, chatId] as const;
 
 export const chatFilesKey = ["chats", "files"] as const;
 
@@ -131,15 +133,23 @@ export const updateInfiniteChatsCache = (
  * in the cache, but only if the chat doesn't already exist in any
  * page. This avoids the per-page duplication that would occur if
  * a prepend updater were passed to updateInfiniteChatsCache, which
- * runs independently on each page.
+ * runs independently on each page. Lists whose archived filter
+ * conflicts with the chat's archive state are skipped, so an active
+ * chat is never inserted into an archived-only list.
  */
 export const prependToInfiniteChatsCache = (
 	queryClient: QueryClient,
 	chat: TypesGen.Chat,
 ) => {
-	queryClient.setQueriesData<InfiniteChatsCacheData>(
-		{ queryKey: chatListFamilyKey },
-		(prev) => {
+	const queries = queryClient.getQueriesData<InfiniteChatsCacheData>({
+		queryKey: chatListFamilyKey,
+	});
+	for (const [queryKey] of queries) {
+		const archivedFilter = archivedFilterForChatListKey(queryKey);
+		if (archivedFilter !== undefined && archivedFilter !== chat.archived) {
+			continue;
+		}
+		queryClient.setQueryData<InfiniteChatsCacheData>(queryKey, (prev) => {
 			if (!prev?.pages) return prev;
 			// Check across ALL pages to avoid duplicates.
 			const exists = prev.pages.some((page) =>
@@ -151,8 +161,8 @@ export const prependToInfiniteChatsCache = (
 				i === 0 ? [chat, ...page] : page,
 			);
 			return { ...prev, pages: nextPages };
-		},
-	);
+		});
+	}
 };
 
 /**
@@ -298,9 +308,15 @@ const patchChatArchiveState = (
 };
 
 /**
- * Applies an accepted archive state to loaded sidebar and detail caches.
- * Removes the chat from any filtered list whose archived filter conflicts
- * with the new state, and resets pin_order to 0 when archiving.
+ * Applies an accepted archive state to loaded sidebar, search, and
+ * detail caches. Removes the chat from any filtered list whose archived
+ * filter conflicts with the new state, and resets pin_order to 0 when
+ * archiving.
+ *
+ * Search rows are removed rather than patched: a cached row matched its
+ * query's archived filter before the change, so after the change it
+ * belongs to a different result set. Search invalidations issued by the
+ * callers repopulate any result set that still matches.
  */
 export const applyChatArchiveStateToCaches = (
 	queryClient: QueryClient,
@@ -367,6 +383,68 @@ export const applyChatArchiveStateToCaches = (
 			return changed ? { ...prev, pages } : prev;
 		});
 	}
+
+	const searchQueries = queryClient.getQueriesData<TypesGen.Chat[]>({
+		queryKey: chatSearchFamilyKey,
+	});
+	for (const [queryKey] of searchQueries) {
+		queryClient.setQueryData<TypesGen.Chat[]>(queryKey, (prev) => {
+			if (!prev) {
+				return prev;
+			}
+			const next = prev.filter((row) => row.id !== chatId);
+			return next.length === prev.length ? prev : next;
+		});
+	}
+};
+
+/**
+ * Watch-event effect for the `deleted` kind, which the server publishes
+ * once per family member when a chat family is archived. Archive is a
+ * patch, never an eviction: the entity and its sub-resources stay
+ * cached so an open route flips to the archived read-only state without
+ * a loading flash or a zombie render.
+ */
+export const applyWatchedChatArchived = (
+	queryClient: QueryClient,
+	chat: TypesGen.Chat,
+) => {
+	void cancelChatListRefetches(queryClient);
+	if (queryClient.getQueryData(chatEntityKey(chat.id)) === undefined) {
+		void resetUnloadedChatEntity(queryClient, chat.id);
+	} else {
+		void cancelLoadedChatEntityRefetch(queryClient, chat.id);
+	}
+	applyChatArchiveStateToCaches(queryClient, chat.id, true);
+	removeChatFromChatsByWorkspace(queryClient, chat.id);
+	void invalidateChatListQueries(queryClient);
+	void invalidateChatsByWorkspace(queryClient);
+	void invalidateChatSearches(queryClient);
+};
+
+/**
+ * Watch-event effect for a root `created` event, which the server
+ * publishes both for new chats and for unarchive transitions (one event
+ * per family member). A cached entity marked archived identifies the
+ * unarchive case; a truly new chat only needs the family invalidations
+ * and never gets a speculative entity entry. The caller remains
+ * responsible for list prepend and child insertion.
+ */
+export const applyWatchedChatCreatedOrUnarchived = (
+	queryClient: QueryClient,
+	chat: TypesGen.Chat,
+) => {
+	const cachedChat = queryClient.getQueryData<TypesGen.Chat>(
+		chatEntityKey(chat.id),
+	);
+	if (cachedChat === undefined) {
+		void resetUnloadedChatEntity(queryClient, chat.id);
+	} else if (cachedChat.archived) {
+		applyChatArchiveStateToCaches(queryClient, chat.id, false);
+	}
+	void invalidateChatListQueries(queryClient);
+	void invalidateChatsByWorkspace(queryClient);
+	void invalidateChatSearches(queryClient);
 };
 
 const parseUpdatedAtInstant = (updatedAt: string) => {
@@ -765,6 +843,23 @@ export const cancelLoadedChatEntityRefetch = (
 	});
 };
 
+/**
+ * Restarts an active first-time fetch after a durable watch transition.
+ * Invalidation reuses the stale initial promise when no data is loaded.
+ */
+export const resetUnloadedChatEntity = (
+	queryClient: QueryClient,
+	chatId: string,
+) => {
+	if (queryClient.getQueryData(chatEntityKey(chatId)) !== undefined) {
+		return;
+	}
+	return queryClient.resetQueries({
+		queryKey: chatEntityKey(chatId),
+		exact: true,
+	});
+};
+
 export const cancelChatMessages = (queryClient: QueryClient, chatId: string) =>
 	queryClient.cancelQueries({
 		queryKey: chatMessagesKey(chatId),
diff --git a/site/src/pages/AgentsPage/AgentsPageLayout.stories.tsx b/site/src/pages/AgentsPage/AgentsPageLayout.stories.tsx
index 8e77cfe51356a..c452dd94aea35 100644
--- a/site/src/pages/AgentsPage/AgentsPageLayout.stories.tsx
+++ b/site/src/pages/AgentsPage/AgentsPageLayout.stories.tsx
@@ -13,6 +13,12 @@ import {
 } from "storybook/test";
 import { reactRouterParameters } from "storybook-addon-remix-react-router";
 import { API } from "#/api/api";
+import { getAuthorizationKey } from "#/api/queries/authCheck";
+import {
+	chatEntityKey,
+	chatMessagesKey,
+	chatPromptsKey,
+} from "#/api/queries/chats";
 import type * as TypesGen from "#/api/typesGenerated";
 import type { Chat } from "#/api/typesGenerated";
 import { DeleteDialog } from "#/components/Dialog/DeleteDialog/DeleteDialog";
@@ -25,9 +31,11 @@ import {
 import {
 	withAuthProvider,
 	withDashboardProvider,
+	withProxyProvider,
 	withWebSocket,
 } from "#/testHelpers/storybook";
 import { CoderAgentsPageView } from "../AISettingsPage/CoderAgentsPage/CoderAgentsPageView";
+import AgentChatPage, { RIGHT_PANEL_OPEN_KEY } from "./AgentChatPage";
 import AgentCreatePage from "./AgentCreatePage";
 import AgentSettingsCompactionPage from "./AgentSettingsCompactionPage";
 import AgentSettingsGeneralPage from "./AgentSettingsGeneralPage";
@@ -932,6 +940,139 @@ export const WithAgentSelected: Story = {
 	},
 };
 
+// ---------------------------------------------------------------------------
+// Watch-event archive semantics: these stories mount the real AgentChatPage
+// under the layout's :agentId route so the layout's chat-watch socket drives
+// the page through the production watch path.
+// ---------------------------------------------------------------------------
+
+const agentsWithAgentChatPageRouting = {
+	...agentsRouting,
+	children: agentsRouting.children.map((route) =>
+		"path" in route && route.path === ":agentId"
+			? { ...route, element: <AgentChatPage /> }
+			: route,
+	),
+};
+
+const WATCHED_CHAT_ID = "chat-watched";
+
+// MockChat is owned by MockUserOwner, so the page renders the owner view
+// (composer enabled unless archived) instead of the other-user banner.
+const watchedChat = (overrides: Partial<Chat> = {}): Chat => ({
+	...MockChat,
+	id: WATCHED_CHAT_ID,
+	title: "Watched agent",
+	last_model_config_id: defaultModelConfigID,
+	created_at: oneWeekAgo,
+	updated_at: oneWeekAgo,
+	...overrides,
+});
+
+const watchedChatQueries = (chat: Chat) => [
+	{ key: chatEntityKey(chat.id), data: chat },
+	{
+		key: chatMessagesKey(chat.id),
+		data: {
+			pages: [{ messages: [], queued_messages: [], has_more: false }],
+			pageParams: [undefined],
+		},
+	},
+	{ key: chatPromptsKey(chat.id), data: { prompts: [] } },
+	{
+		key: getAuthorizationKey({
+			checks: {
+				canShareChat: {
+					object: {
+						resource_type: "chat",
+						owner_id: chat.owner_id,
+						organization_id: chat.organization_id,
+					},
+					action: "share",
+				},
+			},
+		}),
+		data: { canShareChat: true },
+	},
+];
+
+const chatWatchEvent = (kind: TypesGen.ChatWatchEventKind, chat: Chat) => ({
+	event: "message" as const,
+	data: JSON.stringify({ kind, chat } satisfies TypesGen.ChatWatchEvent),
+});
+
+const watchedChatPageParameters = (
+	chat: Chat,
+	watchEvents: readonly ReturnType<typeof chatWatchEvent>[],
+) => ({
+	queries: watchedChatQueries(chat),
+	webSocket: {
+		"/chats/watch": [...watchEvents],
+	},
+	reactRouter: reactRouterParameters({
+		location: {
+			path: `/agents/${WATCHED_CHAT_ID}`,
+			pathParams: { agentId: WATCHED_CHAT_ID },
+		},
+		routing: [agentsWithAgentChatPageRouting, aiSettingsRouting],
+	}),
+});
+
+const mockAgentChatPageAPIs = () => {
+	localStorage.removeItem(RIGHT_PANEL_OPEN_KEY);
+	spyOn(API, "getApiKey").mockRejectedValue(new Error("missing API key"));
+	spyOn(API.experimental, "updateChat").mockResolvedValue();
+	return () => localStorage.removeItem(RIGHT_PANEL_OPEN_KEY);
+};
+
+export const ArchiveWatchEventKeepsOpenChatMounted: Story = {
+	decorators: [withProxyProvider()],
+	beforeEach: () => {
+		mockChats([watchedChat()]);
+		return mockAgentChatPageAPIs();
+	},
+	parameters: watchedChatPageParameters(watchedChat(), [
+		chatWatchEvent("deleted", watchedChat({ archived: true })),
+	]),
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		expect(
+			await canvas.findByText("This agent has been archived and is read-only."),
+		).toBeVisible();
+		await waitFor(() => {
+			expect(canvas.getByRole("textbox")).toHaveAttribute(
+				"aria-disabled",
+				"true",
+			);
+		});
+		expect(canvas.queryByText("Chat not found")).not.toBeInTheDocument();
+	},
+};
+
+export const UnarchiveWatchEventRecoversArchivedChat: Story = {
+	decorators: [withProxyProvider()],
+	beforeEach: () => {
+		mockChats([watchedChat({ archived: true })]);
+		return mockAgentChatPageAPIs();
+	},
+	parameters: watchedChatPageParameters(watchedChat({ archived: true }), [
+		chatWatchEvent("created", watchedChat({ archived: false })),
+	]),
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		await waitFor(() => {
+			expect(canvas.getByRole("textbox")).not.toHaveAttribute(
+				"aria-disabled",
+				"true",
+			);
+		});
+		expect(
+			canvas.queryByText("This agent has been archived and is read-only."),
+		).not.toBeInTheDocument();
+		expect(canvas.queryByText("Chat not found")).not.toBeInTheDocument();
+	},
+};
+
 // Error reasons surface via each chat's last_error, which the
 // layout turns into sidebar error badges.
 export const WithErrorReasons: Story = {
diff --git a/site/src/pages/AgentsPage/AgentsPageLayout.tsx b/site/src/pages/AgentsPage/AgentsPageLayout.tsx
index 16f66ca937a73..41f79d6b280cd 100644
--- a/site/src/pages/AgentsPage/AgentsPageLayout.tsx
+++ b/site/src/pages/AgentsPage/AgentsPageLayout.tsx
@@ -18,6 +18,8 @@ import { getErrorMessage } from "#/api/errors";
 import {
 	addChildToParentInCache,
 	applyChatArchiveStateToCaches,
+	applyWatchedChatArchived,
+	applyWatchedChatCreatedOrUnarchived,
 	archiveChat,
 	cancelChatListRefetches,
 	cancelLoadedChatEntityRefetch,
@@ -36,9 +38,7 @@ import {
 	prependToInfiniteChatsCache,
 	proposeChatTitle,
 	readInfiniteChatsCache,
-	removeChatEntity,
 	removeChatFromChatsByWorkspace,
-	removeChildFromParentInCache,
 	reorderPinnedChat,
 	shouldInvalidateChatSearches,
 	shouldInvalidateChatsByWorkspace,
@@ -611,20 +611,12 @@ const AgentsPageLayout: FC = () => {
 					}
 
 					if (chatEvent.kind === "deleted") {
-						// Drop the chat from the flat root list (root or
-						// cascade via root_chat_id) and from any parent's
-						// embedded children (individual child archive).
-						updateInfiniteChatsCache(queryClient, (chats) =>
-							chats.filter(
-								(c) =>
-									c.id !== updatedChat.id && c.root_chat_id !== updatedChat.id,
-							),
-						);
-						removeChildFromParentInCache(queryClient, updatedChat.id);
-						removeChatEntity(queryClient, updatedChat.id);
-						removeChatFromChatsByWorkspace(queryClient, updatedChat.id);
-						void invalidateChatsByWorkspace(queryClient);
-						void invalidateChatSearches(queryClient);
+						// The server publishes `deleted` when a chat is
+						// archived (one event per family member); there is
+						// no hard-delete wire event. Patch archive state in
+						// place so an open route stays mounted and flips to
+						// its read-only state.
+						applyWatchedChatArchived(queryClient, updatedChat);
 						return;
 					}
 					if (chatEvent.kind === "diff_status_change") {
@@ -657,11 +649,23 @@ const AgentsPageLayout: FC = () => {
 								updatedChat,
 								updatedChat.parent_chat_id,
 							);
+							// A family unarchive and a new sub-agent with a
+							// mounted initial fetch both need entity recovery.
+							const cachedChat = queryClient.getQueryData<TypesGen.Chat>(
+								chatEntityKey(updatedChat.id),
+							);
+							if (
+								cachedChat?.archived ||
+								(cachedChat === undefined &&
+									queryClient.getQueryState(chatEntityKey(updatedChat.id)) !==
+										undefined)
+							) {
+								applyWatchedChatCreatedOrUnarchived(queryClient, updatedChat);
+							}
 						} else {
+							// `created` also fires for unarchive transitions.
+							applyWatchedChatCreatedOrUnarchived(queryClient, updatedChat);
 							prependToInfiniteChatsCache(queryClient, updatedChat);
-							void invalidateChatListQueries(queryClient);
-							void invalidateChatsByWorkspace(queryClient);
-							void invalidateChatSearches(queryClient);
 						}
 					} else {
 						mergeWatchedChatIntoCaches(queryClient, updatedChat, {