fix: add get_channel_messages MCP tool and fix search to include channel messages

Agents could send channel messages but had no MCP tool to read them.
Also, search_messages only searched DMs (to/from agent), missing channel
messages entirely. Now SearchMessages includes channel messages where
the agent is a member.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/channels/service.go

@@ -332,6 +332,11 @@ func (s *Service) GetChannel(ctx context.Context, id int64) (*Channel, error) {
 	return s.store.GetChannel(ctx, id)
 }
 
+// IsMember checks if an agent is a member of a channel.
+func (s *Service) IsMember(ctx context.Context, channelID int64, agentName string) (bool, error) {
+	return s.store.IsMember(ctx, channelID, agentName)
+}
+
 // GetChannelByName returns a channel by name.
 func (s *Service) GetChannelByName(ctx context.Context, name string) (*Channel, error) {
 	return s.store.GetChannelByName(ctx, NormalizeChannelName(name))

internal/mcp/channel_tools.go

@@ -8,17 +8,20 @@ import (
 	"github.com/mark3labs/mcp-go/server"
 
 	"github.com/synapbus/synapbus/internal/channels"
+	"github.com/synapbus/synapbus/internal/messaging"
 )
 
 // ChannelToolRegistrar registers channel MCP tools on the server.
 type ChannelToolRegistrar struct {
 	channelService *channels.Service
+	msgService     *messaging.MessagingService
 }
 
 // NewChannelToolRegistrar creates a new channel tool registrar.
-func NewChannelToolRegistrar(channelService *channels.Service) *ChannelToolRegistrar {
+func NewChannelToolRegistrar(channelService *channels.Service, msgService *messaging.MessagingService) *ChannelToolRegistrar {
 	return &ChannelToolRegistrar{
 		channelService: channelService,
+		msgService:     msgService,
 	}
 }
 
@@ -30,6 +33,7 @@ func (ctr *ChannelToolRegistrar) RegisterAll(s *server.MCPServer) {
 	s.AddTool(ctr.listChannelsTool(), ctr.handleListChannels)
 	s.AddTool(ctr.inviteToChannelTool(), ctr.handleInviteToChannel)
 	s.AddTool(ctr.kickFromChannelTool(), ctr.handleKickFromChannel)
+	s.AddTool(ctr.getChannelMessagesTool(), ctr.handleGetChannelMessages)
 	s.AddTool(ctr.sendChannelMessageTool(), ctr.handleSendChannelMessage)
 	s.AddTool(ctr.updateChannelTool(), ctr.handleUpdateChannel)
 }
@@ -87,6 +91,15 @@ func (ctr *ChannelToolRegistrar) kickFromChannelTool() mcp.Tool {
 	)
 }
 
+func (ctr *ChannelToolRegistrar) getChannelMessagesTool() mcp.Tool {
+	return mcp.NewTool("get_channel_messages",
+		mcp.WithDescription("Get recent messages from a channel you are a member of"),
+		mcp.WithNumber("channel_id", mcp.Description("ID of the channel")),
+		mcp.WithString("channel_name", mcp.Description("Name of the channel (alternative to channel_id)")),
+		mcp.WithNumber("limit", mcp.Description("Max number of messages to return (default 50, max 200)")),
+	)
+}
+
 func (ctr *ChannelToolRegistrar) sendChannelMessageTool() mcp.Tool {
 	return mcp.NewTool("send_channel_message",
 		mcp.WithDescription("Send a message to all members of a channel"),
@@ -281,6 +294,58 @@ func (ctr *ChannelToolRegistrar) handleKickFromChannel(ctx context.Context, req
 	})
 }
 
+func (ctr *ChannelToolRegistrar) handleGetChannelMessages(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	agentName, ok := extractAgentName(ctx)
+	if !ok {
+		return mcp.NewToolResultError("authentication required"), nil
+	}
+
+	channelID, err := ctr.resolveChannelID(ctx, req)
+	if err != nil {
+		return mcp.NewToolResultError(fmt.Sprintf("get_channel_messages failed: %s", err)), nil
+	}
+
+	// Verify the agent is a member of the channel
+	isMember, err := ctr.channelService.IsMember(ctx, channelID, agentName)
+	if err != nil {
+		return mcp.NewToolResultError(fmt.Sprintf("get_channel_messages failed: %s", err)), nil
+	}
+	if !isMember {
+		return mcp.NewToolResultError("you are not a member of this channel"), nil
+	}
+
+	limit := req.GetInt("limit", 50)
+	if limit > 200 {
+		limit = 200
+	}
+
+	messages, err := ctr.msgService.GetChannelMessages(ctx, channelID, limit)
+	if err != nil {
+		return mcp.NewToolResultError(fmt.Sprintf("get_channel_messages failed: %s", err)), nil
+	}
+
+	result := make([]map[string]any, len(messages))
+	for i, msg := range messages {
+		result[i] = map[string]any{
+			"id":         msg.ID,
+			"from":       msg.FromAgent,
+			"body":       msg.Body,
+			"priority":   msg.Priority,
+			"status":     msg.Status,
+			"created_at": msg.CreatedAt,
+		}
+		if len(msg.Metadata) > 0 {
+			result[i]["metadata"] = msg.Metadata
+		}
+	}
+
+	return resultJSON(map[string]any{
+		"channel_id": channelID,
+		"messages":   result,
+		"count":      len(result),
+	})
+}
+
 func (ctr *ChannelToolRegistrar) handleSendChannelMessage(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 	agentName, ok := extractAgentName(ctx)
 	if !ok {

internal/mcp/channel_tools_test.go

@@ -31,7 +31,7 @@ func newTestChannelRegistrar(t *testing.T) (*ChannelToolRegistrar, *channels.Ser
 	db.Exec(`INSERT OR IGNORE INTO agents (name, display_name, type, capabilities, owner_id, api_key_hash, status) VALUES ('agent-b', 'Agent B', 'ai', '{}', 1, 'hash', 'active')`)
 	db.Exec(`INSERT OR IGNORE INTO agents (name, display_name, type, capabilities, owner_id, api_key_hash, status) VALUES ('agent-c', 'Agent C', 'ai', '{}', 1, 'hash', 'active')`)
 
-	registrar := NewChannelToolRegistrar(channelService)
+	registrar := NewChannelToolRegistrar(channelService, msgService)
 	return registrar, channelService
 }
 

internal/mcp/server.go

@@ -146,7 +146,7 @@ func NewMCPServer(
 
 	// Register channel tools
 	if channelService != nil {
-		channelRegistrar := NewChannelToolRegistrar(channelService)
+		channelRegistrar := NewChannelToolRegistrar(channelService, msgService)
 		channelRegistrar.RegisterAll(mcpSrv)
 	}
 

internal/messaging/store.go

@@ -332,9 +332,11 @@ func (s *SQLiteMessageStore) SearchMessages(ctx context.Context, agentName, quer
 	var conditions []string
 	var args []any
 
-	// Scope to messages accessible by this agent
-	conditions = append(conditions, "(m.to_agent = ? OR m.from_agent = ?)")
-	args = append(args, agentName, agentName)
+	// Scope to messages accessible by this agent:
+	// - DMs where agent is sender or recipient
+	// - Channel messages where agent is a member
+	conditions = append(conditions, "(m.to_agent = ? OR m.from_agent = ? OR (m.channel_id IS NOT NULL AND m.to_agent = '' AND EXISTS (SELECT 1 FROM channel_members cm WHERE cm.channel_id = m.channel_id AND cm.agent_name = ?)))")
+	args = append(args, agentName, agentName, agentName)
 
 	var joinClause string
 	var orderClause string