diff --git a/deepseek-recipe/src/stream/output_parser.rs b/deepseek-recipe/src/stream/output_parser.rs
index 99a3491..ed0fe43 100644
--- a/deepseek-recipe/src/stream/output_parser.rs
+++ b/deepseek-recipe/src/stream/output_parser.rs
@@ -161,11 +161,11 @@ pub(super) enum InvalidTokenKind {
 /// two distinct actions to produce both of its quotes.
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub(super) enum ArgumentsLabel {
-    /// `{` before the first argument.
+    /// `{"` before the first argument name.
     ObjectOpen,
-    /// `, ` before each later argument.
+    /// `, "` before each later argument name.
     ArgumentSeparator,
-    /// `: ` between an argument name and its value.
+    /// `": ` between an argument name and its value.
     KeyValueSeparator,
     /// `"` before a string value.
     StringOpen,
@@ -176,9 +176,9 @@ pub(super) enum ArgumentsLabel {
 impl ArgumentsLabel {
     pub(super) fn as_str(self) -> &'static str {
         match self {
-            Self::ObjectOpen => "{",
-            Self::ArgumentSeparator => ", ",
-            Self::KeyValueSeparator => ": ",
+            Self::ObjectOpen => "{\"",
+            Self::ArgumentSeparator => ", \"",
+            Self::KeyValueSeparator => "\": ",
             Self::StringOpen | Self::StringClose => "\"",
         }
     }
@@ -247,7 +247,7 @@ enum Stage {
     /// Inside an `invoke` tag, before a `parameter` tag or the closing tag.
     /// `is_first_argument` holds until the first argument is written.
     ToolCallArguments { is_first_argument: bool },
-    /// The quoted argument name of a `parameter` tag.
+    /// The argument name of a `parameter` tag, up to its closing quote.
     ToolCallArgumentName,
     /// The `string="true|false">` attribute of a `parameter` tag.
     ToolCallArgumentStringAttribute,
@@ -504,7 +504,7 @@ impl State {
             }
             Stage::ToolCallArguments { is_first_argument } => {
                 match_branches.add_literal_branch(
-                    "parameter name=",
+                    "parameter name=\"",
                     Stage::ToolCallArgumentName,
                     if is_first_argument {
                         ActionOnMatched::LabelToolCallArguments(ArgumentsLabel::ObjectOpen)
@@ -525,7 +525,7 @@ impl State {
             }
             Stage::ToolCallArgumentName => {
                 match_branches.add_literal_branch(
-                    " ",
+                    "\"",
                     Stage::ToolCallArgumentStringAttribute,
                     ActionOnMatched::LabelToolCallArguments(ArgumentsLabel::KeyValueSeparator),
                 );
diff --git a/deepseek-recipe/src/stream/processor.rs b/deepseek-recipe/src/stream/processor.rs
index 870a419..4b3aa9c 100644
--- a/deepseek-recipe/src/stream/processor.rs
+++ b/deepseek-recipe/src/stream/processor.rs
@@ -748,6 +748,44 @@ mod tests {
         assert_eq!(finish_chunk(&chunks).0, FinishReason::ToolCalls);
     }
 
+    #[tokio::test]
+    async fn argument_names_keep_their_spaces() {
+        // Names with and without spaces, as first and later arguments, with
+        // string and raw values; an empty name ends the second call.
+        let block = r#"<｜DSML｜tool_calls>
+<｜DSML｜invoke name="book_trip">
+<｜DSML｜parameter name="start date" string="true">2026-10-22</｜DSML｜parameter>
+<｜DSML｜parameter name="city" string="true">Tokyo</｜DSML｜parameter>
+<｜DSML｜parameter name="party size" string="false">2</｜DSML｜parameter>
+<｜DSML｜parameter name="nights" string="false">3</｜DSML｜parameter>
+</｜DSML｜invoke>
+<｜DSML｜invoke name="book_trip">
+<｜DSML｜parameter name="room count" string="false">1</｜DSML｜parameter>
+<｜DSML｜parameter name="guest name" string="true">Ada Lovelace</｜DSML｜parameter>
+<｜DSML｜parameter name="" string="true">empty</｜DSML｜parameter>
+</｜DSML｜invoke>
+</｜DSML｜tool_calls>"#;
+        let expected = [
+            (
+                "book_trip",
+                r#"{"start date": "2026-10-22", "city": "Tokyo", "party size": 2, "nights": 3}"#,
+            ),
+            (
+                "book_trip",
+                r#"{"room count": 1, "guest name": "Ada Lovelace", "": "empty"}"#,
+            ),
+        ];
+        let output = format!("{PREAMBLE}\n\n{block}");
+        for chunks in [
+            parse_characters(&output, ParsingOptions::default()).await,
+            parse_texts(&[&output], ParsingOptions::default()).await,
+        ] {
+            assert_eq!(content(&chunks), PREAMBLE);
+            assert_tool_calls(&chunks, &expected);
+            assert_eq!(finish_chunk(&chunks).0, FinishReason::ToolCalls);
+        }
+    }
+
     #[tokio::test]
     async fn json_text_in_a_string_value_is_escaped() {
         let output = format!("{PREAMBLE}\n\n{TOOL_CALLS}");