diff --git a/pkg/agent/loop.go b/pkg/agent/loop.go
index ef2951365..d7461e76f 100644
--- a/pkg/agent/loop.go
+++ b/pkg/agent/loop.go
@@ -75,6 +75,8 @@ type processOptions struct {
 	SessionKey              string              // Session identifier for history/context
 	Channel                 string              // Target channel for tool execution
 	ChatID                  string              // Target chat ID for tool execution
+	MessageID               string              // Current inbound platform message ID
+	ReplyToMessageID        string              // Current inbound reply target message ID
 	SenderID                string              // Current sender ID for dynamic context
 	SenderDisplayName       string              // Current sender display name for dynamic context
 	UserMessage             string              // User message content (may include prefix)
@@ -104,6 +106,7 @@ const (
 	metadataKeyAccountID       = "account_id"
 	metadataKeyGuildID         = "guild_id"
 	metadataKeyTeamID          = "team_id"
+	metadataKeyReplyToMessage  = "reply_to_message_id"
 	metadataKeyParentPeerKind  = "parent_peer_kind"
 	metadataKeyParentPeerID    = "parent_peer_id"
 )
@@ -222,17 +225,37 @@ func registerSharedTools(
 		// Message tool
 		if cfg.Tools.IsToolEnabled("message") {
 			messageTool := tools.NewMessageTool()
-			messageTool.SetSendCallback(func(channel, chatID, content string) error {
+			messageTool.SetSendCallback(func(channel, chatID, content, replyToMessageID string) error {
 				pubCtx, pubCancel := context.WithTimeout(context.Background(), 5*time.Second)
 				defer pubCancel()
 				return msgBus.PublishOutbound(pubCtx, bus.OutboundMessage{
-					Channel: channel,
-					ChatID:  chatID,
-					Content: content,
+					Channel:          channel,
+					ChatID:           chatID,
+					Content:          content,
+					ReplyToMessageID: replyToMessageID,
 				})
 			})
 			agent.Tools.Register(messageTool)
 		}
+		if cfg.Tools.IsToolEnabled("reaction") {
+			reactionTool := tools.NewReactionTool()
+			reactionTool.SetReactionCallback(func(ctx context.Context, channel, chatID, messageID string) error {
+				if al.channelManager == nil {
+					return fmt.Errorf("channel manager not configured")
+				}
+				ch, ok := al.channelManager.GetChannel(channel)
+				if !ok {
+					return fmt.Errorf("channel %s not found", channel)
+				}
+				rc, ok := ch.(channels.ReactionCapable)
+				if !ok {
+					return fmt.Errorf("channel %s does not support reactions", channel)
+				}
+				_, err := rc.ReactToMessage(ctx, chatID, messageID)
+				return err
+			})
+			agent.Tools.Register(reactionTool)
+		}
 
 		// Send file tool (outbound media via MediaStore — store injected later by SetMediaStore)
 		if cfg.Tools.IsToolEnabled("send_file") {
@@ -1315,6 +1338,8 @@ func (al *AgentLoop) processMessage(ctx context.Context, msg bus.InboundMessage)
 		SessionKey:        sessionKey,
 		Channel:           msg.Channel,
 		ChatID:            msg.ChatID,
+		MessageID:         msg.MessageID,
+		ReplyToMessageID:  inboundMetadata(msg, metadataKeyReplyToMessage),
 		SenderID:          msg.SenderID,
 		SenderDisplayName: msg.Sender.DisplayName,
 		UserMessage:       msg.Content,
@@ -2384,8 +2409,15 @@ turnLoop:
 			}
 
 			toolStart := time.Now()
-			toolResult := ts.agent.Tools.ExecuteWithContext(
+			execCtx := tools.WithToolInboundContext(
 				turnCtx,
+				ts.channel,
+				ts.chatID,
+				ts.opts.MessageID,
+				ts.opts.ReplyToMessageID,
+			)
+			toolResult := ts.agent.Tools.ExecuteWithContext(
+				execCtx,
 				toolName,
 				toolArgs,
 				ts.channel,
diff --git a/pkg/agent/loop_test.go b/pkg/agent/loop_test.go
index 25d20c689..58149f92c 100644
--- a/pkg/agent/loop_test.go
+++ b/pkg/agent/loop_test.go
@@ -531,6 +531,20 @@ func TestToolContext_Updates(t *testing.T) {
 	if got := tools.ToolChannel(context.Background()); got != "" {
 		t.Errorf("expected empty channel from bare context, got %q", got)
 	}
+
+	inboundCtx := tools.WithToolInboundContext(
+		context.Background(),
+		"telegram",
+		"chat-42",
+		"msg-123",
+		"msg-100",
+	)
+	if got := tools.ToolMessageID(inboundCtx); got != "msg-123" {
+		t.Errorf("expected messageID 'msg-123', got %q", got)
+	}
+	if got := tools.ToolReplyToMessageID(inboundCtx); got != "msg-100" {
+		t.Errorf("expected replyToMessageID 'msg-100', got %q", got)
+	}
 }
 
 // TestToolRegistry_GetDefinitions verifies tool definitions can be retrieved
diff --git a/pkg/tools/base.go b/pkg/tools/base.go
index ec743e164..afee95692 100644
--- a/pkg/tools/base.go
+++ b/pkg/tools/base.go
@@ -21,8 +21,10 @@ type Tool interface {
 type toolCtxKey struct{ name string }
 
 var (
-	ctxKeyChannel = &toolCtxKey{"channel"}
-	ctxKeyChatID  = &toolCtxKey{"chatID"}
+	ctxKeyChannel          = &toolCtxKey{"channel"}
+	ctxKeyChatID           = &toolCtxKey{"chatID"}
+	ctxKeyMessageID        = &toolCtxKey{"messageID"}
+	ctxKeyReplyToMessageID = &toolCtxKey{"replyToMessageID"}
 )
 
 // WithToolContext returns a child context carrying channel and chatID.
@@ -32,6 +34,23 @@ func WithToolContext(ctx context.Context, channel, chatID string) context.Contex
 	return ctx
 }
 
+// WithToolMessageContext returns a child context carrying inbound message IDs.
+func WithToolMessageContext(ctx context.Context, messageID, replyToMessageID string) context.Context {
+	ctx = context.WithValue(ctx, ctxKeyMessageID, messageID)
+	ctx = context.WithValue(ctx, ctxKeyReplyToMessageID, replyToMessageID)
+	return ctx
+}
+
+// WithToolInboundContext returns a child context carrying channel/chat and inbound IDs.
+func WithToolInboundContext(
+	ctx context.Context,
+	channel, chatID, messageID, replyToMessageID string,
+) context.Context {
+	ctx = WithToolContext(ctx, channel, chatID)
+	ctx = WithToolMessageContext(ctx, messageID, replyToMessageID)
+	return ctx
+}
+
 // ToolChannel extracts the channel from ctx, or "" if unset.
 func ToolChannel(ctx context.Context) string {
 	v, _ := ctx.Value(ctxKeyChannel).(string)
@@ -44,6 +63,18 @@ func ToolChatID(ctx context.Context) string {
 	return v
 }
 
+// ToolMessageID extracts the current inbound message ID from ctx, or "" if unset.
+func ToolMessageID(ctx context.Context) string {
+	v, _ := ctx.Value(ctxKeyMessageID).(string)
+	return v
+}
+
+// ToolReplyToMessageID extracts the current inbound reply target from ctx, or "" if unset.
+func ToolReplyToMessageID(ctx context.Context) string {
+	v, _ := ctx.Value(ctxKeyReplyToMessageID).(string)
+	return v
+}
+
 // AsyncCallback is a function type that async tools use to notify completion.
 // When an async tool finishes its work, it calls this callback with the result.
 //
diff --git a/pkg/tools/message.go b/pkg/tools/message.go
index 438ceeddd..064065a38 100644
--- a/pkg/tools/message.go
+++ b/pkg/tools/message.go
@@ -6,7 +6,7 @@ import (
 	"sync/atomic"
 )
 
-type SendCallback func(channel, chatID, content string) error
+type SendCallback func(channel, chatID, content, replyToMessageID string) error
 
 type MessageTool struct {
 	sendCallback SendCallback
@@ -41,6 +41,10 @@ func (t *MessageTool) Parameters() map[string]any {
 				"type":        "string",
 				"description": "Optional: target chat/user ID",
 			},
+			"reply_to_message_id": map[string]any{
+				"type":        "string",
+				"description": "Optional: reply target message ID for channels that support threaded replies",
+			},
 		},
 		"required": []string{"content"},
 	}
@@ -69,6 +73,7 @@ func (t *MessageTool) Execute(ctx context.Context, args map[string]any) *ToolRes
 
 	channel, _ := args["channel"].(string)
 	chatID, _ := args["chat_id"].(string)
+	replyToMessageID, _ := args["reply_to_message_id"].(string)
 
 	if channel == "" {
 		channel = ToolChannel(ctx)
@@ -85,7 +90,7 @@ func (t *MessageTool) Execute(ctx context.Context, args map[string]any) *ToolRes
 		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, replyToMessageID); err != nil {
 		return &ToolResult{
 			ForLLM:  fmt.Sprintf("sending message: %v", err),
 			IsError: true,
diff --git a/pkg/tools/message_test.go b/pkg/tools/message_test.go
index 05630972e..93a611ee0 100644
--- a/pkg/tools/message_test.go
+++ b/pkg/tools/message_test.go
@@ -10,7 +10,7 @@ func TestMessageTool_Execute_Success(t *testing.T) {
 	tool := NewMessageTool()
 
 	var sentChannel, sentChatID, sentContent string
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content, replyToMessageID string) error {
 		sentChannel = channel
 		sentChatID = chatID
 		sentContent = content
@@ -61,7 +61,7 @@ func TestMessageTool_Execute_WithCustomChannel(t *testing.T) {
 	tool := NewMessageTool()
 
 	var sentChannel, sentChatID string
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content, replyToMessageID string) error {
 		sentChannel = channel
 		sentChatID = chatID
 		return nil
@@ -96,7 +96,7 @@ func TestMessageTool_Execute_SendFailure(t *testing.T) {
 	tool := NewMessageTool()
 
 	sendErr := errors.New("network error")
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content, replyToMessageID string) error {
 		return sendErr
 	})
 
@@ -149,7 +149,7 @@ func TestMessageTool_Execute_NoTargetChannel(t *testing.T) {
 	tool := NewMessageTool()
 	// No WithToolContext — channel/chatID are empty
 
-	tool.SetSendCallback(func(channel, chatID, content string) error {
+	tool.SetSendCallback(func(channel, chatID, content, replyToMessageID string) error {
 		return nil
 	})
 
@@ -251,4 +251,37 @@ func TestMessageTool_Parameters(t *testing.T) {
 	if chatIDProp["type"] != "string" {
 		t.Error("Expected chat_id type to be 'string'")
 	}
+
+	// Check reply_to_message_id property (optional)
+	replyToProp, ok := props["reply_to_message_id"].(map[string]any)
+	if !ok {
+		t.Error("Expected 'reply_to_message_id' property")
+	}
+	if replyToProp["type"] != "string" {
+		t.Error("Expected reply_to_message_id type to be 'string'")
+	}
+}
+
+func TestMessageTool_Execute_WithReplyToMessageID(t *testing.T) {
+	tool := NewMessageTool()
+
+	var sentReplyTo string
+	tool.SetSendCallback(func(channel, chatID, content, replyToMessageID string) error {
+		sentReplyTo = replyToMessageID
+		return nil
+	})
+
+	ctx := WithToolContext(context.Background(), "test-channel", "test-chat-id")
+	args := map[string]any{
+		"content":             "Reply test",
+		"reply_to_message_id": "msg-123",
+	}
+
+	result := tool.Execute(ctx, args)
+	if result.IsError {
+		t.Fatalf("expected success, got error: %s", result.ForLLM)
+	}
+	if sentReplyTo != "msg-123" {
+		t.Fatalf("expected reply_to_message_id msg-123, got %q", sentReplyTo)
+	}
 }
diff --git a/pkg/tools/reaction.go b/pkg/tools/reaction.go
new file mode 100644
index 000000000..3455b07a9
--- /dev/null
+++ b/pkg/tools/reaction.go
@@ -0,0 +1,87 @@
+package tools
+
+import (
+	"context"
+	"fmt"
+)
+
+type ReactionCallback func(ctx context.Context, channel, chatID, messageID string) error
+
+type ReactionTool struct {
+	reactionCallback ReactionCallback
+}
+
+func NewReactionTool() *ReactionTool {
+	return &ReactionTool{}
+}
+
+func (t *ReactionTool) Name() string {
+	return "reaction"
+}
+
+func (t *ReactionTool) Description() string {
+	return "Add a reaction to a message. Defaults to the current inbound message when message_id is omitted."
+}
+
+func (t *ReactionTool) Parameters() map[string]any {
+	return map[string]any{
+		"type": "object",
+		"properties": map[string]any{
+			"message_id": map[string]any{
+				"type":        "string",
+				"description": "Optional: target message ID; defaults to the current inbound message",
+			},
+			"channel": map[string]any{
+				"type":        "string",
+				"description": "Optional: target channel (telegram, whatsapp, etc.)",
+			},
+			"chat_id": map[string]any{
+				"type":        "string",
+				"description": "Optional: target chat/user ID",
+			},
+		},
+	}
+}
+
+func (t *ReactionTool) SetReactionCallback(callback ReactionCallback) {
+	t.reactionCallback = callback
+}
+
+func (t *ReactionTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
+	channel, _ := args["channel"].(string)
+	chatID, _ := args["chat_id"].(string)
+	messageID, _ := args["message_id"].(string)
+
+	if channel == "" {
+		channel = ToolChannel(ctx)
+	}
+	if chatID == "" {
+		chatID = ToolChatID(ctx)
+	}
+	if messageID == "" {
+		messageID = ToolMessageID(ctx)
+	}
+
+	if channel == "" || chatID == "" {
+		return &ToolResult{ForLLM: "No target channel/chat specified", IsError: true}
+	}
+	if messageID == "" {
+		return &ToolResult{ForLLM: "message_id is required", IsError: true}
+	}
+	if t.reactionCallback == nil {
+		return &ToolResult{ForLLM: "Reaction not configured", IsError: true}
+	}
+
+	if err := t.reactionCallback(ctx, channel, chatID, messageID); err != nil {
+		return &ToolResult{
+			ForLLM:  fmt.Sprintf("adding reaction: %v", err),
+			IsError: true,
+			Err:     err,
+		}
+	}
+
+	return &ToolResult{
+		ForLLM: fmt.Sprintf("Reaction added to %s:%s message %s", channel, chatID, messageID),
+		Silent: true,
+	}
+}
diff --git a/pkg/tools/reaction_test.go b/pkg/tools/reaction_test.go
new file mode 100644
index 000000000..6fc90445a
--- /dev/null
+++ b/pkg/tools/reaction_test.go
@@ -0,0 +1,96 @@
+package tools
+
+import (
+	"context"
+	"errors"
+	"testing"
+)
+
+func TestReactionTool_Execute_UsesContextMessageIDByDefault(t *testing.T) {
+	tool := NewReactionTool()
+
+	var gotChannel, gotChatID, gotMessageID string
+	tool.SetReactionCallback(func(ctx context.Context, channel, chatID, messageID string) error {
+		gotChannel = channel
+		gotChatID = chatID
+		gotMessageID = messageID
+		return nil
+	})
+
+	ctx := WithToolInboundContext(context.Background(), "telegram", "chat-1", "msg-100", "")
+	result := tool.Execute(ctx, map[string]any{})
+	if result.IsError {
+		t.Fatalf("expected success, got error: %s", result.ForLLM)
+	}
+	if gotChannel != "telegram" || gotChatID != "chat-1" || gotMessageID != "msg-100" {
+		t.Fatalf("unexpected callback args: channel=%q chatID=%q messageID=%q", gotChannel, gotChatID, gotMessageID)
+	}
+}
+
+func TestReactionTool_Execute_AllowsExplicitMessageIDOverride(t *testing.T) {
+	tool := NewReactionTool()
+
+	var gotMessageID string
+	tool.SetReactionCallback(func(ctx context.Context, channel, chatID, messageID string) error {
+		gotMessageID = messageID
+		return nil
+	})
+
+	ctx := WithToolInboundContext(context.Background(), "telegram", "chat-1", "msg-context", "")
+	result := tool.Execute(ctx, map[string]any{"message_id": "msg-explicit"})
+	if result.IsError {
+		t.Fatalf("expected success, got error: %s", result.ForLLM)
+	}
+	if gotMessageID != "msg-explicit" {
+		t.Fatalf("expected explicit message id, got %q", gotMessageID)
+	}
+}
+
+func TestReactionTool_Execute_MissingMessageID(t *testing.T) {
+	tool := NewReactionTool()
+	tool.SetReactionCallback(func(ctx context.Context, channel, chatID, messageID string) error { return nil })
+
+	ctx := WithToolContext(context.Background(), "telegram", "chat-1")
+	result := tool.Execute(ctx, map[string]any{})
+	if !result.IsError {
+		t.Fatal("expected error")
+	}
+	if result.ForLLM != "message_id is required" {
+		t.Fatalf("unexpected error message: %q", result.ForLLM)
+	}
+}
+
+func TestReactionTool_Execute_CallbackError(t *testing.T) {
+	tool := NewReactionTool()
+	tool.SetReactionCallback(func(ctx context.Context, channel, chatID, messageID string) error {
+		return errors.New("unsupported")
+	})
+
+	ctx := WithToolInboundContext(context.Background(), "telegram", "chat-1", "msg-100", "")
+	result := tool.Execute(ctx, map[string]any{})
+	if !result.IsError {
+		t.Fatal("expected error")
+	}
+	if result.Err == nil {
+		t.Fatal("expected wrapped error")
+	}
+}
+
+func TestReactionTool_Parameters(t *testing.T) {
+	tool := NewReactionTool()
+	params := tool.Parameters()
+
+	props, ok := params["properties"].(map[string]any)
+	if !ok {
+		t.Fatal("expected properties map")
+	}
+	if _, ok := props["message_id"]; !ok {
+		t.Fatal("expected message_id parameter")
+	}
+	if _, ok := props["channel"]; !ok {
+		t.Fatal("expected channel parameter")
+	}
+	if _, ok := props["chat_id"]; !ok {
+		t.Fatal("expected chat_id parameter")
+	}
+}
diff --git a/pkg/tools/registry_test.go b/pkg/tools/registry_test.go
index db52749f6..16bd30928 100644
--- a/pkg/tools/registry_test.go
+++ b/pkg/tools/registry_test.go
@@ -190,6 +190,33 @@ func TestToolRegistry_ExecuteWithContext_EmptyContext(t *testing.T) {
 	}
 }
 
+func TestToolRegistry_ExecuteWithContext_PreservesMessageContext(t *testing.T) {
+	r := NewToolRegistry()
+	ct := &mockContextAwareTool{
+		mockRegistryTool: *newMockTool("ctx_tool", "needs context"),
+	}
+	r.Register(ct)
+
+	baseCtx := WithToolMessageContext(context.Background(), "msg-123", "msg-100")
+	r.ExecuteWithContext(baseCtx, "ctx_tool", nil, "telegram", "chat-42", nil)
+
+	if ct.lastCtx == nil {
+		t.Fatal("expected Execute to be called")
+	}
+	if got := ToolChannel(ct.lastCtx); got != "telegram" {
+		t.Errorf("expected channel 'telegram', got %q", got)
+	}
+	if got := ToolChatID(ct.lastCtx); got != "chat-42" {
+		t.Errorf("expected chatID 'chat-42', got %q", got)
+	}
+	if got := ToolMessageID(ct.lastCtx); got != "msg-123" {
+		t.Errorf("expected messageID 'msg-123', got %q", got)
+	}
+	if got := ToolReplyToMessageID(ct.lastCtx); got != "msg-100" {
+		t.Errorf("expected replyToMessageID 'msg-100', got %q", got)
+	}
+}
+
 func TestToolRegistry_ExecuteWithContext_AsyncCallback(t *testing.T) {
 	r := NewToolRegistry()
 	at := &mockAsyncRegistryTool{