feat: add support for attachments in message tool

pkg/agent/loop.go

@@ -95,11 +95,12 @@ func createToolRegistry(workspace string, restrict bool, cfg *config.Config, msg
 	// Message tool - available to both agent and subagent
 	// Subagent uses it to communicate directly with user
 	messageTool := tools.NewMessageTool()
-	messageTool.SetSendCallback(func(channel, chatID, content string) error {
+	messageTool.SetSendCallback(func(channel, chatID, content string, attachments []string) error {
 		msgBus.PublishOutbound(bus.OutboundMessage{
 			Channel: channel,
 			ChatID:  chatID,
 			Content: content,
+			Media:   attachments,
 		})
 		return nil
 	})

pkg/bus/types.go

@@ -11,9 +11,10 @@ type InboundMessage struct {
 }
 
 type OutboundMessage struct {
-	Channel string `json:"channel"`
+	Channel string   `json:"channel"`
-	ChatID  string `json:"chat_id"`
+	ChatID  string   `json:"chat_id"`
-	Content string `json:"content"`
+	Content string   `json:"content"`
+	Media   []string `json:"media,omitempty"`
 }
 
 type MessageHandler func(InboundMessage) error

pkg/channels/discord.go

@@ -101,12 +101,24 @@ func (c *DiscordChannel) Send(ctx context.Context, msg bus.OutboundMessage) erro
 		return fmt.Errorf("channel ID is empty")
 	}
 
+	for _, mediaPath := range msg.Media {
+		file, err := os.Open(mediaPath)
+		if err != nil {
+			return fmt.Errorf("failed to open media file %s: %w", mediaPath, err)
+		}
+		_, err = c.session.ChannelFileSend(channelID, mediaPath, file)
+		file.Close()
+		if err != nil {
+			return fmt.Errorf("failed to send media file %s: %w", mediaPath, err)
+		}
+	}
+
 	runes := []rune(msg.Content)
 	if len(runes) == 0 {
 		return nil
 	}
 
-	chunks := splitMessage(msg.Content, 1500) // Discord has a limit of 2000 characters per message, leave 500 for natural split e.g. code blocks
+	chunks := splitMessage(msg.Content, 1500)
 
 	for _, chunk := range chunks {
 		if err := c.sendChunk(ctx, channelID, chunk); err != nil {
@@ -253,7 +265,19 @@ func (c *DiscordChannel) sendChunk(ctx context.Context, channelID, content strin
 
 	done := make(chan error, 1)
 	go func() {
-		_, err := c.session.ChannelMessageSend(channelID, content)
+		var err error
+		if strings.HasPrefix(content, "file://") {
+			filePath := strings.TrimPrefix(content, "file://")
+			file, fErr := os.Open(filePath)
+			if fErr != nil {
+				done <- fErr
+				return
+			}
+			defer file.Close()
+			_, err = c.session.ChannelFileSend(channelID, filePath, file)
+		} else {
+			_, err = c.session.ChannelMessageSend(channelID, content)
+		}
 		done <- err
 	}()
 

pkg/tools/message.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 )
 
-type SendCallback func(channel, chatID, content string) error
+type SendCallback func(channel, chatID, content string, attachments []string) error
 
 type MessageTool struct {
 	sendCallback   SendCallback
@@ -42,6 +42,11 @@ func (t *MessageTool) Parameters() map[string]interface{} {
 				"type":        "string",
 				"description": "Optional: target chat/user ID",
 			},
+			"attachments": map[string]interface{}{
+				"type":        "array",
+				"items":       map[string]interface{}{"type": "string"},
+				"description": "Optional: list of local file paths or URLs to attach",
+			},
 		},
 		"required": []string{"content"},
 	}
@@ -70,6 +75,13 @@ func (t *MessageTool) Execute(ctx context.Context, args map[string]interface{})
 
 	channel, _ := args["channel"].(string)
 	chatID, _ := args["chat_id"].(string)
+	attachmentsRaw, _ := args["attachments"].([]interface{})
+	var attachments []string
+	for _, a := range attachmentsRaw {
+		if s, ok := a.(string); ok {
+			attachments = append(attachments, s)
+		}
+	}
 
 	if channel == "" {
 		channel = t.defaultChannel
@@ -86,7 +98,7 @@ func (t *MessageTool) Execute(ctx context.Context, args map[string]interface{})
 		return &ToolResult{ForLLM: "Message sending not configured", IsError: true}
 	}
 
-	if err := t.sendCallback(channel, chatID, content); err != nil {
+	if err := t.sendCallback(channel, chatID, content, attachments); err != nil {
 		return &ToolResult{
 			ForLLM:  fmt.Sprintf("sending message: %v", err),
 			IsError: true,

pkg/tools/message_test.go

@@ -11,10 +11,12 @@ func TestMessageTool_Execute_Success(t *testing.T) {
 	tool.SetContext("test-channel", "test-chat-id")
 
 	var sentChannel, sentChatID, sentContent string
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	var sentAttachments []string
+	tool.SetSendCallback(func(channel, chatID, content string, attachments []string) error {
 		sentChannel = channel
 		sentChatID = chatID
 		sentContent = content
+		sentAttachments = attachments
 		return nil
 	})
 
@@ -35,6 +37,9 @@ func TestMessageTool_Execute_Success(t *testing.T) {
 	if sentContent != "Hello, world!" {
 		t.Errorf("Expected content 'Hello, world!', got '%s'", sentContent)
 	}
+	if len(sentAttachments) != 0 {
+		t.Errorf("Expected 0 attachments, got %d", len(sentAttachments))
+	}
 
 	// Verify ToolResult meets US-011 criteria:
 	// - Send success returns SilentResult (Silent=true)
@@ -63,7 +68,7 @@ func TestMessageTool_Execute_WithCustomChannel(t *testing.T) {
 	tool.SetContext("default-channel", "default-chat-id")
 
 	var sentChannel, sentChatID string
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content string, attachments []string) error {
 		sentChannel = channel
 		sentChatID = chatID
 		return nil
@@ -99,7 +104,7 @@ func TestMessageTool_Execute_SendFailure(t *testing.T) {
 	tool.SetContext("test-channel", "test-chat-id")
 
 	sendErr := errors.New("network error")
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content string, attachments []string) error {
 		return sendErr
 	})
 
@@ -153,7 +158,7 @@ func TestMessageTool_Execute_NoTargetChannel(t *testing.T) {
 	tool := NewMessageTool()
 	// No SetContext called, so defaultChannel and defaultChatID are empty
 
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content string, attachments []string) error {
 		return nil
 	})