refactor: remove /diff-status endpoint, include diff_status in chat payload (#23082)

The `/chats/{chat}/diff-status` endpoint was redundant because:
- The `Chat` type already has a `DiffStatus` field
- Listing chats already resolves and returns `diff_status`
- The `getChat` endpoint was the only one not resolving it (passing
`nil`)

## Changes

**Backend:**
- `getChat` now calls `resolveChatDiffStatus` and includes the result in
the response
- Removed `getChatDiffStatus` handler, route (`GET /diff-status`), and
SDK method
- Tests updated to use `GetChat` instead of `GetChatDiffStatus`

**Frontend:**
- `AgentDetail.tsx`: uses `chatQuery.data?.diff_status` instead of
separate query
- `RemoteDiffPanel.tsx`: accepts `diffStatus` as a prop instead of
fetching internally
- `AgentsPage.tsx`: `diff_status_change` events now invalidate the chat
query
- Removed `chatDiffStatus` query, `chatDiffStatusKey`, and
`getChatDiffStatus` API method

coderd/chats.go

@@ -553,7 +553,16 @@ func (api *API) chatCostUsers(rw http.ResponseWriter, r *http.Request) {
 func (api *API) getChat(rw http.ResponseWriter, r *http.Request) {
 	ctx := r.Context()
 	chat := httpmw.ChatParam(r)
-	httpapi.Write(ctx, rw, http.StatusOK, convertChat(chat, nil))
+
+	diffStatus, err := api.resolveChatDiffStatus(ctx, chat)
+	if err != nil {
+		// Log but don't fail - diff status is supplementary.
+		api.Logger.Error(ctx, "failed to resolve chat diff status",
+			slog.F("chat_id", chat.ID),
+			slog.Error(err),
+		)
+	}
+	httpapi.Write(ctx, rw, http.StatusOK, convertChat(chat, diffStatus))
 }
 
 // EXPERIMENTAL: this endpoint is experimental and is subject to change.
@@ -1299,26 +1308,6 @@ func (api *API) interruptChat(rw http.ResponseWriter, r *http.Request) {
 	httpapi.Write(ctx, rw, http.StatusOK, convertChat(chat, nil))
 }
 
-// EXPERIMENTAL: this endpoint is experimental and is subject to change.
-//
-//nolint:revive // HTTP handler writes to ResponseWriter.
-func (api *API) getChatDiffStatus(rw http.ResponseWriter, r *http.Request) {
-	ctx := r.Context()
-	chat := httpmw.ChatParam(r)
-	chatID := chat.ID
-
-	status, err := api.resolveChatDiffStatus(ctx, chat)
-	if err != nil {
-		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
-			Message: "Failed to get chat diff status.",
-			Detail:  err.Error(),
-		})
-		return
-	}
-
-	httpapi.Write(ctx, rw, http.StatusOK, convertChatDiffStatus(chatID, status))
-}
-
 // EXPERIMENTAL: this endpoint is experimental and is subject to change.
 //
 //nolint:revive // HTTP handler writes to ResponseWriter.

coderd/chats_test.go

@@ -2752,17 +2752,10 @@ func TestGetChatDiffStatus(t *testing.T) {
 		})
 		require.NoError(t, err)
 
-		noCachedStatus, err := client.GetChatDiffStatus(ctx, noCachedStatusChat.ID)
+		noCachedChat, err := client.GetChat(ctx, noCachedStatusChat.ID)
 		require.NoError(t, err)
-		require.Equal(t, noCachedStatusChat.ID, noCachedStatus.ChatID)
-		require.Nil(t, noCachedStatus.URL)
-		require.Nil(t, noCachedStatus.PullRequestState)
-		require.False(t, noCachedStatus.ChangesRequested)
-		require.Zero(t, noCachedStatus.Additions)
-		require.Zero(t, noCachedStatus.Deletions)
-		require.Zero(t, noCachedStatus.ChangedFiles)
-		require.Nil(t, noCachedStatus.RefreshedAt)
-		require.Nil(t, noCachedStatus.StaleAt)
+		require.Equal(t, noCachedStatusChat.ID, noCachedChat.ID)
+		require.Nil(t, noCachedChat.DiffStatus)
 
 		cachedStatusChat, err := db.InsertChat(dbauthz.AsSystemRestricted(ctx), database.InsertChatParams{
 			OwnerID:           user.UserID,
@@ -2804,8 +2797,11 @@ func TestGetChatDiffStatus(t *testing.T) {
 		)
 		require.NoError(t, err)
 
-		cachedStatus, err := client.GetChatDiffStatus(ctx, cachedStatusChat.ID)
+		cachedChat, err := client.GetChat(ctx, cachedStatusChat.ID)
 		require.NoError(t, err)
+		require.Equal(t, cachedStatusChat.ID, cachedChat.ID)
+		require.NotNil(t, cachedChat.DiffStatus)
+		cachedStatus := cachedChat.DiffStatus
 		require.Equal(t, cachedStatusChat.ID, cachedStatus.ChatID)
 		require.NotNil(t, cachedStatus.URL)
 		require.Equal(t, "https://github.com/coder/coder/tree/feature/diff-status", *cachedStatus.URL)
@@ -2840,11 +2836,11 @@ func TestGetChatDiffStatus(t *testing.T) {
 		require.NoError(t, err)
 
 		otherClient, _ := coderdtest.CreateAnotherUser(t, client, firstUser.OrganizationID)
-		_, err = otherClient.GetChatDiffStatus(ctx, createdChat.ID)
+		_, err = otherClient.GetChat(ctx, createdChat.ID)
 		requireSDKError(t, err, http.StatusNotFound)
 	})
 
-	// Integration test: exercises the full HTTP handler refresh
+	// Integration test: exercises the full GetChat handler refresh
 	// path with a real DB, dbauthz, a mock GitHub API, and an
 	// external-auth-linked user. Verifies that a stale chat diff
 	// status is refreshed end-to-end via the gitsync worker's
@@ -2943,8 +2939,9 @@ func TestGetChatDiffStatus(t *testing.T) {
 		)
 		require.NoError(t, err)
 
-		// Call the HTTP endpoint. This exercises the full code
-		// path: resolveChatDiffStatus -> RefreshChat (with
+		// Call GetChat which now resolves diff status inline.
+		// This exercises the full code path:
+		// resolveChatDiffStatus -> RefreshChat (with
 		// AsSystemRestricted) -> Refresher.Refresh ->
 		// resolveChatGitAccessToken (GetExternalAuthLink with
 		// AsSystemRestricted) -> FetchPullRequestStatus (mock).
@@ -2953,8 +2950,10 @@ func TestGetChatDiffStatus(t *testing.T) {
 		// would fail under the chatd RBAC context (missing
 		// ActionReadPersonal), causing ErrNoTokenAvailable and a
 		// refresh failure that silently returns stale data.
-		status, err := client.GetChatDiffStatus(ctx, chat.ID)
+		result, err := client.GetChat(ctx, chat.ID)
 		require.NoError(t, err)
+		require.NotNil(t, result.DiffStatus)
+		status := result.DiffStatus
 
 		// The mock GitHub API returned PR #42 with 25 additions,
 		// 7 deletions, 4 changed files, state "open".

coderd/coderd.go

@@ -1187,7 +1187,6 @@ func New(options *Options) *API {
 				r.Patch("/messages/{message}", api.patchChatMessage)
 				r.Get("/stream", api.streamChat)
 				r.Post("/interrupt", api.interruptChat)
-				r.Get("/diff-status", api.getChatDiffStatus)
 				r.Get("/diff", api.getChatDiffContents)
 				r.Route("/queue/{queuedMessage}", func(r chi.Router) {
 					r.Delete("/", api.deleteChatQueuedMessage)