chore(dev): run backend with air

.gitignore

@@ -1,2 +1,3 @@
 data
 .opencode
+.env

AGENTS.md

@@ -22,7 +22,7 @@ The frontend builds to `frontend/public/dist/`, then `make frontend` copies the
 make all        # Build frontend + backend
 make frontend   # Build frontend, copy to backend/web/static/
 make backend    # Build Go binary (requires frontend assets)
-make dev        # Run both with hot-reload
+make dev        # Run frontend watcher + backend hot reload via air
 make tests      # Run Go tests
 make docker     # Build Docker image
 ```

Makefile

@@ -27,7 +27,7 @@ clean:
 dev:
 	rm -rf frontend/public/dist
 	cd frontend && bun run build
-	cd backend && AETHERA_STATIC_DIR=../frontend/public go run ./cmd --listen 0.0.0.0 & \
+	cd backend && AETHERA_STATIC_DIR=../frontend/public air & \
 	backend_pid=$$!; \
 	trap 'kill $$backend_pid' INT TERM EXIT; \
 	cd frontend && bun run dev

backend/.air.toml

@@ -0,0 +1,30 @@
+root = "."
+tmp_dir = "tmp"
+
+[build]
+cmd = "go build -o ./tmp/aethera ./cmd"
+bin = "./tmp/aethera"
+full_bin = "./tmp/aethera --listen 0.0.0.0"
+delay = 1000
+exclude_dir = ["data", "dist", "tmp", "web/static"]
+exclude_file = []
+exclude_regex = ["_test.go"]
+include_dir = []
+include_ext = ["go", "mod", "sum"]
+kill_delay = "500ms"
+log = "build-errors.log"
+send_interrupt = true
+stop_on_error = true
+
+[color]
+app = ""
+build = "yellow"
+main = "magenta"
+runner = "green"
+watcher = "cyan"
+
+[log]
+time = false
+
+[misc]
+clean_on_exit = true

backend/AGENTS.md

@@ -3,6 +3,7 @@
 ## Stack
 
 - **Go 1.25.5** (`reichard.io/aethera`)
+- **air** (backend hot reload for `make dev`)
 - **cobra** (CLI framework)
 - **logrus** (structured logging)
 - **openai-go/v3** (OpenAI API client)
@@ -66,6 +67,7 @@ web/                    # Embedded static assets (embed.go)
 | POST     | `/api/chats/{chatId}`         | PostChatMessage    |
 | DELETE   | `/api/chats/{chatId}`         | DeleteChat         |
 | GET      | `/api/chats/{chatId}/stream`  | GetChatStream      |
+| POST     | `/api/chats/{chatId}/stop`    | StopChatGeneration |
 
 ## Testing
 

backend/internal/api/generation.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"context"
 	"errors"
 	"slices"
 	"sync"
@@ -19,6 +20,8 @@ type generationManager struct {
 
 type generation struct {
 	mu          sync.RWMutex
+	ctx         context.Context
+	cancel      context.CancelFunc
 	subscribers map[chan *MessageChunk]struct{}
 	done        chan struct{}
 	closed      bool
@@ -36,7 +39,10 @@ func (m *generationManager) start(chatID uuid.UUID, prepare func(*generation) er
 	}
 
 	// Reserve Generation
+	ctx, cancel := context.WithCancel(context.Background())
 	gen := &generation{
+		ctx:         ctx,
+		cancel:      cancel,
 		subscribers: make(map[chan *MessageChunk]struct{}),
 		done:        make(chan struct{}),
 	}
@@ -79,6 +85,19 @@ func (m *generationManager) subscribe(chatID uuid.UUID) (<-chan *MessageChunk, f
 	return ch, func() { gen.unsubscribe(ch) }, true
 }
 
+func (m *generationManager) stop(chatID uuid.UUID) bool {
+	m.mu.RLock()
+	gen, found := m.generations[chatID]
+	m.mu.RUnlock()
+	if !found {
+		return false
+	}
+
+	// Cancel Generation
+	gen.cancel()
+	return true
+}
+
 func (g *generation) subscribe() chan *MessageChunk {
 	ch := make(chan *MessageChunk, 64)
 
@@ -126,6 +145,7 @@ func (g *generation) close() {
 		return
 	}
 	g.closed = true
+	g.cancel()
 	close(g.done)
 	for subscriber := range g.subscribers {
 		close(subscriber)

backend/internal/api/handlers.go

@@ -449,6 +449,32 @@ func (a *API) GetChatStream(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func (a *API) StopChatGeneration(w http.ResponseWriter, r *http.Request) {
+	log := a.logger.WithField("handler", "StopChatGenerationHandler")
+
+	// Parse Chat ID
+	rawChatID := r.PathValue("chatId")
+	if rawChatID == "" {
+		log.Error("missing chat ID parameter")
+		http.Error(w, "Chat ID is required", http.StatusBadRequest)
+		return
+	}
+	chatID, err := uuid.Parse(rawChatID)
+	if err != nil {
+		log.WithError(err).Error("invalid chat ID format")
+		http.Error(w, "Invalid chat ID format", http.StatusBadRequest)
+		return
+	}
+
+	// Stop Generation
+	if !a.generationManager.stop(chatID) {
+		http.Error(w, "Chat generation is not active", http.StatusNotFound)
+		return
+	}
+
+	w.WriteHeader(http.StatusNoContent)
+}
+
 func (a *API) PostChatMessage(w http.ResponseWriter, r *http.Request) {
 	log := a.logger.WithField("handler", "PostChatMessageHandler")
 
@@ -563,7 +589,7 @@ func (a *API) startMessageGeneration(chatID uuid.UUID, chatModel, userMessage st
 
 func (a *API) runMessageGeneration(apiClient *client.Client, chat *store.Chat, assistantMsg *store.Message, chatModel string, gen *generation) {
 	// Create Generation Context
-	ctx, cancel := context.WithTimeout(context.Background(), time.Minute*5)
+	ctx, cancel := context.WithTimeout(gen.ctx, time.Minute*5)
 	defer cancel()
 
 	// Send Message
@@ -593,15 +619,37 @@ func (a *API) runMessageGeneration(apiClient *client.Client, chat *store.Chat, a
 
 		return nil
 	}); err != nil {
-		assistantMsg.Status = store.MessageStatusFailed
+		// Handle Stopped Generation
+		if errors.Is(gen.ctx.Err(), context.Canceled) {
+			assistantMsg.Status = store.MessageStatusStopped
 			if saveErr := a.store.SaveChatMessage(assistantMsg); saveErr != nil {
-			a.logger.WithError(saveErr).WithField("chat_id", chat.ID).Error("failed to save failed assistant message")
+				a.logger.WithError(saveErr).WithField("chat_id", chat.ID).Error("failed to save stopped assistant message")
+			}
+			gen.broadcast(&MessageChunk{AssistantMessage: assistantMsg})
+			return
+		}
+
+		// Handle Error Generation
+		assistantMsg.Status = store.MessageStatusError
+		if saveErr := a.store.SaveChatMessage(assistantMsg); saveErr != nil {
+			a.logger.WithError(saveErr).WithField("chat_id", chat.ID).Error("failed to save errored assistant message")
 		}
 		gen.broadcast(&MessageChunk{AssistantMessage: assistantMsg})
 		a.logger.WithError(err).WithField("chat_id", chat.ID).Error("failed to generate text stream")
 		return
 	}
 
+	// Handle Stopped Generation
+	if errors.Is(gen.ctx.Err(), context.Canceled) {
+		assistantMsg.Status = store.MessageStatusStopped
+		if err := a.store.SaveChatMessage(assistantMsg); err != nil {
+			a.logger.WithError(err).WithField("chat_id", chat.ID).Error("failed to save stopped assistant message")
+			return
+		}
+		gen.broadcast(&MessageChunk{AssistantMessage: assistantMsg})
+		return
+	}
+
 	// Summarize & Update Chat Title
 	if chat.Title == "" {
 		var err error

backend/internal/server/server.go

@@ -49,6 +49,7 @@ func StartServer(settingsStore store.Store, dataDir, staticDir, listenAddress st
 	mux.HandleFunc("POST /api/chats", api.PostChat)
 	mux.HandleFunc("GET /api/chats/{chatId}", api.GetChat)
 	mux.HandleFunc("GET /api/chats/{chatId}/stream", api.GetChatStream)
+	mux.HandleFunc("POST /api/chats/{chatId}/stop", api.StopChatGeneration)
 	mux.HandleFunc("POST /api/chats/{chatId}", api.PostChatMessage)
 	mux.HandleFunc("DELETE /api/chats/{chatId}", api.DeleteChat)
 

backend/internal/store/types.go

@@ -33,7 +33,8 @@ type MessageStatus string
 const (
 	MessageStatusStreaming MessageStatus = "streaming"
 	MessageStatusComplete  MessageStatus = "complete"
-	MessageStatusFailed    MessageStatus = "failed"
+	MessageStatusStopped   MessageStatus = "stopped"
+	MessageStatusError     MessageStatus = "error"
 )
 
 type Message struct {

flake.nix

@@ -26,6 +26,7 @@
         devShells.default = pkgs.mkShell {
           packages = with pkgs; [
             # Backend
+            air
             go
             gopls
             golangci-lint
@@ -38,6 +39,8 @@
 
           shellHook = ''
             export LD_LIBRARY_PATH=${pkgs.stdenv.cc.cc.lib}/lib:$LD_LIBRARY_PATH
+
+            . .env
           '';
         };
       }

frontend/public/pages/chats.html

@@ -68,12 +68,18 @@
             x-html="renderMarkdown(message.content)"
           ></div>
 
-          <!-- Timestamp -->
+          <!-- Message Metadata -->
           <div class="flex items-center justify-between gap-2 mt-2">
             <div
               class="text-[10px] opacity-60"
               x-text="new Date(message.created_at).toLocaleTimeString()"
             ></div>
+            <div
+              x-show="message.role === 'assistant' && ['stopped', 'error', 'failed'].includes(message.status)"
+              :class="message.status === 'stopped' ? 'bg-primary-300/50 text-primary-700' : 'bg-tertiary-100 text-tertiary-700'"
+              class="px-2 py-0.5 rounded-full text-[10px] font-medium"
+              x-text="message.status === 'stopped' ? 'Stopped' : 'Error'"
+            ></div>
           </div>
         </div>
 
@@ -279,6 +285,26 @@
               </svg>
             </template>
           </button>
+
+          <button
+            x-show="loading"
+            type="button"
+            @click="stopResponse()"
+            :disabled="!activeStreamChatID"
+            :class="!activeStreamChatID ? 'opacity-50 cursor-not-allowed' : 'hover:shadow-md hover:scale-105'"
+            class="self-stretch w-[44px] bg-tertiary-600 text-white rounded-xl transition-all flex items-center justify-center flex-shrink-0"
+            title="Stop response"
+            aria-label="Stop response"
+          >
+            <svg
+              class="h-4 w-4"
+              fill="currentColor"
+              viewBox="0 0 24 24"
+              aria-hidden="true"
+            >
+              <path d="M6 6h12v12H6z" />
+            </svg>
+          </button>
         </form>
 
         <!-- Error Message -->

frontend/src/client.ts

@@ -124,6 +124,17 @@ export async function streamChatUpdates(
   return streamMessage(response, onChunk);
 }
 
+export async function stopChatGeneration(chatId: string): Promise<void> {
+  const response = await fetch(`/api/chats/${chatId}/stop`, {
+    method: 'POST',
+  });
+
+  if (!response.ok) {
+    const errorData = await response.json().catch(() => ({}));
+    throw new Error(readError(errorData) || `HTTP ${response.status}`);
+  }
+}
+
 export async function getChatMessages(chatId: string): Promise<Chat> {
   const response = await fetch(`/api/chats/${chatId}`);
   const data = await response.json().catch(() => ({}));

frontend/src/components/chatManager.ts

@@ -7,6 +7,7 @@ import {
   getModels,
   sendMessage,
   streamChatUpdates,
+  stopChatGeneration,
   getChatMessages,
   listChats,
   deleteChat,
@@ -87,6 +88,18 @@ Alpine.data('chatManager', () => ({
     }
   },
 
+  async stopResponse() {
+    if (!this.activeStreamChatID) return;
+
+    // Stop Active Generation
+    try {
+      await stopChatGeneration(this.activeStreamChatID);
+    } catch (err) {
+      console.error('Error stopping response:', err);
+      this.error = parseError(err);
+    }
+  },
+
   async sendMessage() {
     const message = this.inputMessage.trim();
     if ((!message && this.selectedImages.length === 0) || this.loading) return;

frontend/src/types/index.ts

@@ -7,7 +7,7 @@ export interface Chat {
   messages: Message[];
 }
 
-export type MessageStatus = 'streaming' | 'complete' | 'failed';
+export type MessageStatus = 'streaming' | 'complete' | 'stopped' | 'error' | 'failed';
 
 export interface Message {
   id: string;