diff --git a/internal/lsp/server.go b/internal/lsp/server.go
index 0642ddd..522425a 100644
--- a/internal/lsp/server.go
+++ b/internal/lsp/server.go
@@ -268,11 +268,13 @@ func handleDidOpen(params DidOpenTextDocumentParams) {
 	documents[params.TextDocument.URI] = params.TextDocument.Text
 	p := parser.NewParser(params.TextDocument.Text)
 	config, err := p.Parse()
-	if err == nil {
-		tree.AddFile(path, config)
-		tree.ResolveReferences()
-		runValidation(params.TextDocument.URI)
+	if err != nil {
+		publishParserError(params.TextDocument.URI, err)
+		return
 	}
+	tree.AddFile(path, config)
+	tree.ResolveReferences()
+	runValidation(params.TextDocument.URI)
 }
 
 func handleDidChange(params DidChangeTextDocumentParams) {
@@ -284,11 +286,13 @@ func handleDidChange(params DidChangeTextDocumentParams) {
 	path := uriToPath(params.TextDocument.URI)
 	p := parser.NewParser(text)
 	config, err := p.Parse()
-	if err == nil {
-		tree.AddFile(path, config)
-		tree.ResolveReferences()
-		runValidation(params.TextDocument.URI)
+	if err != nil {
+		publishParserError(params.TextDocument.URI, err)
+		return
 	}
+	tree.AddFile(path, config)
+	tree.ResolveReferences()
+	runValidation(params.TextDocument.URI)
 }
 
 func handleFormatting(params DocumentFormattingParams) []TextEdit {
@@ -378,6 +382,44 @@ func runValidation(uri string) {
 	}
 }
 
+func publishParserError(uri string, err error) {
+	var line, col int
+	var msg string
+	// Try parsing "line:col: message"
+	n, _ := fmt.Sscanf(err.Error(), "%d:%d: ", &line, &col)
+	if n == 2 {
+		parts := strings.SplitN(err.Error(), ": ", 2)
+		if len(parts) == 2 {
+			msg = parts[1]
+		}
+	} else {
+		// Fallback
+		line = 1
+		col = 1
+		msg = err.Error()
+	}
+
+	diag := LSPDiagnostic{
+		Range: Range{
+			Start: Position{Line: line - 1, Character: col - 1},
+			End:   Position{Line: line - 1, Character: col},
+		},
+		Severity: 1, // Error
+		Message:  msg,
+		Source:   "mdt-parser",
+	}
+
+	notification := JsonRpcMessage{
+		Jsonrpc: "2.0",
+		Method:  "textDocument/publishDiagnostics",
+		Params:  mustMarshal(PublishDiagnosticsParams{
+			URI:         uri,
+			Diagnostics: []LSPDiagnostic{diag},
+		}),
+	}
+	send(notification)
+}
+
 func collectFiles(node *index.ProjectNode, files map[string]bool) {
 	for _, frag := range node.Fragments {
 		files[frag.File] = true
diff --git a/internal/parser/lexer.go b/internal/parser/lexer.go
index 84bb052..c8afc3f 100644
--- a/internal/parser/lexer.go
+++ b/internal/parser/lexer.go
@@ -22,6 +22,7 @@ const (
 	TokenPragma
 	TokenComment
 	TokenDocstring
+	TokenComma
 )
 
 type Token struct {
@@ -109,7 +110,7 @@ func (l *Lexer) NextToken() Token {
 			return l.emit(TokenEOF)
 		}
 
-		if unicode.IsSpace(r) || r == ',' {
+		if unicode.IsSpace(r) {
 			l.ignore()
 			continue
 		}
@@ -121,6 +122,8 @@ func (l *Lexer) NextToken() Token {
 			return l.emit(TokenLBrace)
 		case '}':
 			return l.emit(TokenRBrace)
+		case ',':
+			return l.emit(TokenComma)
 		case '"':
 			return l.lexString()
 		case '/':
diff --git a/internal/parser/parser.go b/internal/parser/parser.go
index 2a11217..a097098 100644
--- a/internal/parser/parser.go
+++ b/internal/parser/parser.go
@@ -235,6 +235,10 @@ func (p *Parser) parseValue() (Value, error) {
 				arr.EndPosition = endTok.Position
 				break
 			}
+			if t.Type == TokenComma {
+				p.next()
+				continue
+			}
 			val, err := p.parseValue()
 			if err != nil {
 				return nil, err
diff --git a/mdt b/mdt
index 652da78..11ff859 100755
Binary files a/mdt and b/mdt differ
diff --git a/specification.md b/specification.md
index 2c86e3a..2e52149 100644
--- a/specification.md
+++ b/specification.md
@@ -90,6 +90,7 @@ The LSP server should provide the following capabilities:
   - `//!allow(WARNING_TYPE): REASON` - Global suppression for a specific warning type across the whole project (supported: `unused`, `implicit`).
   - `//!cast(DEF_TYPE, CUR_TYPE): REASON` - Suppress "Type Inconsistency" errors if types match.
 - **Structure**: A configuration is composed by one or more definitions.
+- **Strictness**: Any content that is not a valid comment (or pragma/docstring) or a valid definition (Field, Node, or Object) is **not allowed** and must generate a parsing error.
 
 ### Core MARTe Classes