diff --git a/http/server.go b/http/server.go
index 2af501a..a28d662 100644
--- a/http/server.go
+++ b/http/server.go
@@ -188,13 +188,19 @@ func (s *Server) handleLuaRoute(ctx *fasthttp.RequestCtx, bytecode []byte, scrip
 	}()
 
 	session := s.sessionManager.GetSessionFromRequest(ctx)
+
+	// Advance flash data (move current flash to old, clear old)
+	session.AdvanceFlash()
+
 	sessionMap["id"] = session.ID
 
-	// Only get session data if not empty
+	// Get session data and flash data
 	if !session.IsEmpty() {
-		sessionMap["data"] = session.GetAll()
+		sessionMap["data"] = session.GetAll() // This now includes flash data
+		sessionMap["flash"] = session.GetAllFlash()
 	} else {
 		sessionMap["data"] = emptyMap
+		sessionMap["flash"] = emptyMap
 	}
 
 	// Set basic context
@@ -250,10 +256,11 @@ func (s *Server) handleLuaRoute(ctx *fasthttp.RequestCtx, bytecode []byte, scrip
 		return
 	}
 
-	// Handle session updates
+	// Handle session updates including flash data
 	if len(response.SessionData) > 0 {
 		if _, clearAll := response.SessionData["__clear_all"]; clearAll {
 			session.Clear()
+			session.ClearFlash() // Also clear flash data
 			delete(response.SessionData, "__clear_all")
 		}
 
@@ -266,6 +273,16 @@ func (s *Server) handleLuaRoute(ctx *fasthttp.RequestCtx, bytecode []byte, scrip
 		}
 	}
 
+	// Handle flash data from response
+	if flashData, ok := response.Metadata["flash"].(map[string]any); ok {
+		for k, v := range flashData {
+			if err := session.FlashSafe(k, v); err != nil && s.debugMode {
+				logger.Warnf("Error setting flash data %s: %v", k, err)
+			}
+		}
+		delete(response.Metadata, "flash") // Remove from metadata after processing
+	}
+
 	s.sessionManager.ApplySessionCookie(ctx, session)
 	runner.ApplyResponse(response, ctx)
 	runner.ReleaseResponse(response)
diff --git a/runner/lua/sandbox.lua b/runner/lua/sandbox.lua
index fb65982..dfd61d6 100644
--- a/runner/lua/sandbox.lua
+++ b/runner/lua/sandbox.lua
@@ -233,17 +233,23 @@ end
 
 -- Template processing with code execution
 function render(template_str, env)
-	local function get_line(s, ln)
-		for line in s:gmatch("([^\n]*)\n?") do
-			if ln == 1 then return line end
-			ln = ln - 1
-		end
-	end
-
-	local function pos_to_line(s, pos)
-		local line = 1
-		for _ in s:sub(1, pos):gmatch("\n") do line = line + 1 end
-		return line
+	local function is_control_structure(code)
+		-- Check if code is a control structure that doesn't produce output
+		local trimmed = code:match("^%s*(.-)%s*$")
+		return trimmed == "else" or
+		       trimmed == "end" or
+		       trimmed:match("^if%s") or
+		       trimmed:match("^elseif%s") or
+		       trimmed:match("^for%s") or
+		       trimmed:match("^while%s") or
+		       trimmed:match("^repeat%s*$") or
+		       trimmed:match("^until%s") or
+		       trimmed:match("^do%s*$") or
+		       trimmed:match("^local%s") or
+		       trimmed:match("^function%s") or
+		       trimmed:match(".*=%s*function%s*%(") or
+		       trimmed:match(".*then%s*$") or
+		       trimmed:match(".*do%s*$")
 	end
 
 	local pos, chunks = 1, {}
@@ -273,11 +279,9 @@ function render(template_str, env)
 		end
 
 		local code = template_str:sub(pos, close_start-1):match("^%s*(.-)%s*$")
+		local is_control = is_control_structure(code)
 
-		-- Check if it's a simple variable name for escaped output
-		local is_simple_var = tag_type == "=" and code:match("^[%w_]+$")
-
-		table.insert(chunks, {tag_type, code, pos, is_simple_var})
+		table.insert(chunks, {tag_type, code, pos, is_control})
 		pos = close_stop + 1
 	end
 
@@ -288,24 +292,43 @@ function render(template_str, env)
 			table.insert(buffer, "_b_i = _b_i + 1\n")
 			table.insert(buffer, "_b[_b_i] = " .. string.format("%q", chunk) .. "\n")
 		else
-			t = chunk[1]
-			if t == "=" then
-				if chunk[4] then -- is_simple_var
+			local tag_type, code, pos, is_control = chunk[1], chunk[2], chunk[3], chunk[4]
+
+			if is_control then
+				-- Control structure - just insert as raw Lua code
+				table.insert(buffer, "--[[" .. pos .. "]] " .. code .. "\n")
+			elseif tag_type == "=" then
+				-- Simple variable check
+				if code:match("^[%w_]+$") then
 					table.insert(buffer, "_b_i = _b_i + 1\n")
-					table.insert(buffer, "--[[" .. chunk[3] .. "]] _b[_b_i] = _escape(_tostring(" .. chunk[2] .. "))\n")
+					table.insert(buffer, "--[[" .. pos .. "]] _b[_b_i] = _escape(_tostring(" .. code .. "))\n")
 				else
-					table.insert(buffer, "--[[" .. chunk[3] .. "]] " .. chunk[2] .. "\n")
+					-- Expression output with escaping
+					table.insert(buffer, "_b_i = _b_i + 1\n")
+					table.insert(buffer, "--[[" .. pos .. "]] _b[_b_i] = _escape(_tostring(" .. code .. "))\n")
 				end
-			elseif t == "-" then
+			elseif tag_type == "-" then
+				-- Unescaped output
 				table.insert(buffer, "_b_i = _b_i + 1\n")
-				table.insert(buffer, "--[[" .. chunk[3] .. "]] _b[_b_i] = _tostring(" .. chunk[2] .. ")\n")
+				table.insert(buffer, "--[[" .. pos .. "]] _b[_b_i] = _tostring(" .. code .. ")\n")
 			end
 		end
 	end
 	table.insert(buffer, "return _b")
 
-	local fn, err = loadstring(table.concat(buffer))
-	if not fn then error(err) end
+	local generated_code = table.concat(buffer)
+
+	-- DEBUG: Uncomment to see generated code
+	-- print("Generated Lua code:")
+	-- print(generated_code)
+	-- print("---")
+
+	local fn, err = loadstring(generated_code)
+	if not fn then
+		print("Generated code that failed to compile:")
+		print(generated_code)
+		error(err)
+	end
 
 	env = env or {}
 	local runtime_env = setmetatable({}, {__index = function(_, k) return env[k] or _G[k] end})
@@ -428,3 +451,142 @@ function password_verify(plain_password, hash_string)
 
 	return __password_verify(plain_password, hash_string)
 end
+
+-- ======================================================================
+-- SESSION FLASH FUNCTIONS
+-- ======================================================================
+
+function session_flash(key, value)
+	__response.flash = __response.flash or {}
+	__response.flash[key] = value
+end
+
+function session_get_flash(key)
+	-- Check current flash data first
+	if __response.flash and __response.flash[key] ~= nil then
+		return __response.flash[key]
+	end
+
+	-- Check session flash data
+	if __ctx.session and __ctx.session.flash and __ctx.session.flash[key] ~= nil then
+		return __ctx.session.flash[key]
+	end
+
+	return nil
+end
+
+function session_has_flash(key)
+	-- Check current flash
+	if __response.flash and __response.flash[key] ~= nil then
+		return true
+	end
+
+	-- Check session flash
+	if __ctx.session and __ctx.session.flash and __ctx.session.flash[key] ~= nil then
+		return true
+	end
+
+	return false
+end
+
+function session_get_all_flash()
+	local flash = {}
+
+	-- Add session flash data first
+	if __ctx.session and __ctx.session.flash then
+		for k, v in pairs(__ctx.session.flash) do
+			flash[k] = v
+		end
+	end
+
+	-- Add current response flash (overwrites session flash if same key)
+	if __response.flash then
+		for k, v in pairs(__response.flash) do
+			flash[k] = v
+		end
+	end
+
+	return flash
+end
+
+function session_flash_now(key, value)
+	-- Flash for current request only (not persisted)
+	_G._current_flash = _G._current_flash or {}
+	_G._current_flash[key] = value
+end
+
+function session_get_flash_now(key)
+	return _G._current_flash and _G._current_flash[key]
+end
+
+-- ======================================================================
+-- FLASH HELPER FUNCTIONS
+-- ======================================================================
+
+function flash_success(message)
+	session_flash("success", message)
+end
+
+function flash_error(message)
+	session_flash("error", message)
+end
+
+function flash_warning(message)
+	session_flash("warning", message)
+end
+
+function flash_info(message)
+	session_flash("info", message)
+end
+
+function flash_message(type, message)
+	session_flash(type, message)
+end
+
+-- Get flash messages by type
+function get_flash_success()
+	return session_get_flash("success")
+end
+
+function get_flash_error()
+	return session_get_flash("error")
+end
+
+function get_flash_warning()
+	return session_get_flash("warning")
+end
+
+function get_flash_info()
+	return session_get_flash("info")
+end
+
+-- Check if flash messages exist
+function has_flash_success()
+	return session_has_flash("success")
+end
+
+function has_flash_error()
+	return session_has_flash("error")
+end
+
+function has_flash_warning()
+	return session_has_flash("warning")
+end
+
+function has_flash_info()
+	return session_has_flash("info")
+end
+
+-- Convenience function for redirects with flash
+function redirect_with_flash(url, type, message, status)
+	session_flash(type or "info", message)
+	http_redirect(url, status)
+end
+
+function redirect_with_success(url, message, status)
+	redirect_with_flash(url, "success", message, status)
+end
+
+function redirect_with_error(url, message, status)
+	redirect_with_flash(url, "error", message, status)
+end
diff --git a/runner/sandbox.go b/runner/sandbox.go
index e48762c..ff33d8c 100644
--- a/runner/sandbox.go
+++ b/runner/sandbox.go
@@ -68,6 +68,7 @@ func (s *Sandbox) Execute(state *luajit.State, bytecode []byte, ctx *Context) (*
 		"cookies":  []any{},
 		"metadata": make(map[string]any),
 		"session":  make(map[string]any),
+		"flash":    make(map[string]any),
 	}
 
 	// Call __execute(script_func, ctx, response)
@@ -170,6 +171,11 @@ func (s *Sandbox) buildResponse(luaResp map[string]any, body any) *Response {
 		maps.Copy(resp.SessionData, session)
 	}
 
+	// Extract flash data and add to metadata for processing by server
+	if flash, ok := luaResp["flash"].(map[string]any); ok && len(flash) > 0 {
+		resp.Metadata["flash"] = flash
+	}
+
 	return resp
 }
 
diff --git a/sessions/session.go b/sessions/session.go
index 28c8a47..daabb88 100644
--- a/sessions/session.go
+++ b/sessions/session.go
@@ -13,6 +13,8 @@ import (
 type Session struct {
 	ID        string
 	Data      map[string]any
+	FlashData map[string]any // Flash data for next request
+	OldFlash  map[string]any // Flash data from previous request (to be cleared)
 	CreatedAt time.Time
 	UpdatedAt time.Time
 	LastUsed  time.Time
@@ -23,7 +25,11 @@ type Session struct {
 var (
 	sessionPool = sync.Pool{
 		New: func() any {
-			return &Session{Data: make(map[string]any, 8)}
+			return &Session{
+				Data:      make(map[string]any, 8),
+				FlashData: make(map[string]any, 4),
+				OldFlash:  make(map[string]any, 4),
+			}
 		},
 	}
 	bufPool = benc.NewBufPool(benc.WithBufferSize(4096))
@@ -35,7 +41,9 @@ func NewSession(id string, maxAge int) *Session {
 	now := time.Now()
 	*s = Session{
 		ID:        id,
-		Data:      s.Data, // Reuse map
+		Data:      s.Data, // Reuse maps
+		FlashData: s.FlashData,
+		OldFlash:  s.OldFlash,
 		CreatedAt: now,
 		UpdatedAt: now,
 		LastUsed:  now,
@@ -49,6 +57,12 @@ func (s *Session) Release() {
 	for k := range s.Data {
 		delete(s.Data, k)
 	}
+	for k := range s.FlashData {
+		delete(s.FlashData, k)
+	}
+	for k := range s.OldFlash {
+		delete(s.OldFlash, k)
+	}
 	sessionPool.Put(s)
 }
 
@@ -70,12 +84,22 @@ func (s *Session) GetTable(key string) map[string]any {
 	return nil
 }
 
-// GetAll returns a deep copy of all session data
+// GetAll returns a deep copy of all session data including flash data
 func (s *Session) GetAll() map[string]any {
-	copy := make(map[string]any, len(s.Data))
+	copy := make(map[string]any, len(s.Data)+len(s.FlashData)+len(s.OldFlash))
 	for k, v := range s.Data {
 		copy[k] = deepCopy(v)
 	}
+	// Include current flash data
+	for k, v := range s.FlashData {
+		copy[k] = deepCopy(v)
+	}
+	// Include old flash data (still available this request)
+	for k, v := range s.OldFlash {
+		if _, exists := copy[k]; !exists { // Don't override new flash
+			copy[k] = deepCopy(v)
+		}
+	}
 	return copy
 }
 
@@ -103,6 +127,77 @@ func (s *Session) SetTable(key string, table map[string]any) error {
 	return s.SetSafe(key, table)
 }
 
+// Flash stores a value that will be available for the next request only
+func (s *Session) Flash(key string, value any) {
+	s.FlashData[key] = value
+	s.UpdatedAt = time.Now()
+	s.dirty = true
+}
+
+// FlashSafe stores a flash value with validation
+func (s *Session) FlashSafe(key string, value any) error {
+	if err := validate(value); err != nil {
+		return fmt.Errorf("session.FlashSafe: %w", err)
+	}
+	s.Flash(key, value)
+	return nil
+}
+
+// GetFlash returns a flash value (from either current or old flash)
+func (s *Session) GetFlash(key string) any {
+	// Check current flash first
+	if v, ok := s.FlashData[key]; ok {
+		return deepCopy(v)
+	}
+	// Check old flash
+	if v, ok := s.OldFlash[key]; ok {
+		return deepCopy(v)
+	}
+	return nil
+}
+
+// HasFlash checks if a flash key exists
+func (s *Session) HasFlash(key string) bool {
+	_, inNew := s.FlashData[key]
+	_, inOld := s.OldFlash[key]
+	return inNew || inOld
+}
+
+// GetAllFlash returns all flash data (both current and old)
+func (s *Session) GetAllFlash() map[string]any {
+	flash := make(map[string]any, len(s.FlashData)+len(s.OldFlash))
+	// Add old flash first
+	for k, v := range s.OldFlash {
+		flash[k] = deepCopy(v)
+	}
+	// Add current flash (overwrites old if same key)
+	for k, v := range s.FlashData {
+		flash[k] = deepCopy(v)
+	}
+	return flash
+}
+
+// AdvanceFlash moves current flash to old flash and clears old flash
+// This should be called at the start of each request
+func (s *Session) AdvanceFlash() {
+	// Clear old flash
+	for k := range s.OldFlash {
+		delete(s.OldFlash, k)
+	}
+
+	// Move current flash to old flash
+	if len(s.FlashData) > 0 {
+		for k, v := range s.FlashData {
+			s.OldFlash[k] = v
+		}
+		// Clear current flash
+		for k := range s.FlashData {
+			delete(s.FlashData, k)
+		}
+		s.dirty = true
+	}
+}
+
 // Delete removes a value from the session
 func (s *Session) Delete(key string) {
 	delete(s.Data, key)
@@ -117,6 +212,15 @@ func (s *Session) Clear() {
 	s.dirty = true
 }
 
+// ClearFlash removes all flash data
+func (s *Session) ClearFlash() {
+	if len(s.FlashData) > 0 || len(s.OldFlash) > 0 {
+		s.FlashData = make(map[string]any, 4)
+		s.OldFlash = make(map[string]any, 4)
+		s.dirty = true
+	}
+}
+
 // IsExpired checks if the session has expired
 func (s *Session) IsExpired() bool {
 	return time.Now().After(s.Expiry)
@@ -144,6 +248,8 @@ func (s *Session) ResetDirty() {
 func (s *Session) SizePlain() int {
 	return bstd.SizeString(s.ID) +
 		bstd.SizeMap(s.Data, bstd.SizeString, sizeAny) +
+		bstd.SizeMap(s.FlashData, bstd.SizeString, sizeAny) +
+		bstd.SizeMap(s.OldFlash, bstd.SizeString, sizeAny) +
 		bstd.SizeInt64()*4
 }
 
@@ -151,6 +257,8 @@ func (s *Session) SizePlain() int {
 func (s *Session) MarshalPlain(n int, b []byte) int {
 	n = bstd.MarshalString(n, b, s.ID)
 	n = bstd.MarshalMap(n, b, s.Data, bstd.MarshalString, marshalAny)
+	n = bstd.MarshalMap(n, b, s.FlashData, bstd.MarshalString, marshalAny)
+	n = bstd.MarshalMap(n, b, s.OldFlash, bstd.MarshalString, marshalAny)
 	n = bstd.MarshalInt64(n, b, s.CreatedAt.Unix())
 	n = bstd.MarshalInt64(n, b, s.UpdatedAt.Unix())
 	n = bstd.MarshalInt64(n, b, s.LastUsed.Unix())
@@ -170,6 +278,16 @@ func (s *Session) UnmarshalPlain(n int, b []byte) (int, error) {
 		return n, err
 	}
 
+	n, s.FlashData, err = bstd.UnmarshalMap[string, any](n, b, bstd.UnmarshalString, unmarshalAny)
+	if err != nil {
+		return n, err
+	}
+
+	n, s.OldFlash, err = bstd.UnmarshalMap[string, any](n, b, bstd.UnmarshalString, unmarshalAny)
+	if err != nil {
+		return n, err
+	}
+
 	var ts int64
 	for _, t := range []*time.Time{&s.CreatedAt, &s.UpdatedAt, &s.LastUsed, &s.Expiry} {
 		n, ts, err = bstd.UnmarshalInt64(n, b)
@@ -430,5 +548,5 @@ func deepEqual(a, b any) bool {
 
 // IsEmpty returns true if the session has no data
 func (s *Session) IsEmpty() bool {
-	return len(s.Data) == 0
+	return len(s.Data) == 0 && len(s.FlashData) == 0 && len(s.OldFlash) == 0
 }