parsers: repair unclosed arg_value tags in GLM tool calls (#14656)

GLM models sometimes omits </arg_value> closing tags in tool call XML, causing xml.Unmarshal to fail with "element <arg_value> closed by </tool_call>".

This is a known issue across the GLM family.

Sanitize the input to fix closing arg_key values so encoding/xml can handle it.

model/parsers/glm46.go

@@ -345,6 +345,47 @@ func escapeGLM46Content(s string) string {
 	return result.String()
 }
 
+// repairUnclosedArgValues inserts missing </arg_value> closing tags.
+// GLM models sometimes omit the closing tag, producing XML like:
+//
+//	<arg_value>value</tool_call>
+//
+// instead of:
+//
+//	<arg_value>value</arg_value></tool_call>
+func repairUnclosedArgValues(s string) string {
+	var result strings.Builder
+	for {
+		openIdx := strings.Index(s, "<arg_value>")
+		if openIdx == -1 {
+			result.WriteString(s)
+			break
+		}
+		afterOpen := openIdx + len("<arg_value>")
+		closeIdx := strings.Index(s[afterOpen:], "</arg_value>")
+		nextKeyIdx := strings.Index(s[afterOpen:], "<arg_key>")
+		// Check if properly closed before the next <arg_key> (or no next key)
+		if closeIdx != -1 && (nextKeyIdx == -1 || closeIdx < nextKeyIdx) {
+			end := afterOpen + closeIdx + len("</arg_value>")
+			result.WriteString(s[:end])
+			s = s[end:]
+			continue
+		}
+		// Unclosed — insert </arg_value> before the next <arg_key> or at end
+		if nextKeyIdx != -1 {
+			insertAt := afterOpen + nextKeyIdx
+			result.WriteString(s[:insertAt])
+			result.WriteString("</arg_value>")
+			s = s[insertAt:]
+		} else {
+			result.WriteString(s)
+			result.WriteString("</arg_value>")
+			break
+		}
+	}
+	return result.String()
+}
+
 func parseGLM46ToolCall(raw glm46EventRawToolCall, tools []api.Tool) (api.ToolCall, error) {
 	// Escape any unescaped entities in text content
 	// We need to escape text between tags, but not the tags themselves
@@ -353,10 +394,14 @@ func parseGLM46ToolCall(raw glm46EventRawToolCall, tools []api.Tool) (api.ToolCa
 	// Wrap the content in a root element to make it valid XML
 	xmlString := "<tool_call>" + escaped + "</tool_call>"
 
-	// Parse XML into struct
+	// Parse XML into struct, retrying once with repaired XML if it fails
 	var parsed GLMToolCallXML
 	if err := xml.Unmarshal([]byte(xmlString), &parsed); err != nil {
-		return api.ToolCall{}, fmt.Errorf("failed to parse XML: %w", err)
+		parsed = GLMToolCallXML{}
+		repaired := "<tool_call>" + repairUnclosedArgValues(escaped) + "</tool_call>"
+		if err2 := xml.Unmarshal([]byte(repaired), &parsed); err2 != nil {
+			return api.ToolCall{}, fmt.Errorf("failed to parse XML: %w", err)
+		}
 	}
 
 	// Extract and trim function name

model/parsers/glm46_test.go

@@ -846,6 +846,47 @@ line3</arg_value>`,
 				},
 			},
 		},
+		{
+			name:  "unclosed arg_value at end",
+			tools: []api.Tool{},
+			rawToolCall: `get-weather
+<arg_key>city</arg_key>
+<arg_value>Paris`,
+			wantToolCall: api.ToolCall{
+				Function: api.ToolCallFunction{
+					Name:      "get-weather",
+					Arguments: args(`{"city": "Paris"}`),
+				},
+			},
+		},
+		{
+			name:  "unclosed arg_value before next arg_key",
+			tools: []api.Tool{},
+			rawToolCall: `get-weather
+<arg_key>city</arg_key>
+<arg_value>Paris<arg_key>unit</arg_key>
+<arg_value>celsius</arg_value>`,
+			wantToolCall: api.ToolCall{
+				Function: api.ToolCallFunction{
+					Name:      "get-weather",
+					Arguments: args(`{"city": "Paris", "unit": "celsius"}`),
+				},
+			},
+		},
+		{
+			name:  "multiple unclosed arg_values",
+			tools: []api.Tool{},
+			rawToolCall: `get-weather
+<arg_key>city</arg_key>
+<arg_value>Paris<arg_key>unit</arg_key>
+<arg_value>celsius`,
+			wantToolCall: api.ToolCall{
+				Function: api.ToolCallFunction{
+					Name:      "get-weather",
+					Arguments: args(`{"city": "Paris", "unit": "celsius"}`),
+				},
+			},
+		},
 	}
 
 	for i, tc := range cases {
@@ -860,3 +901,45 @@ line3</arg_value>`,
 		})
 	}
 }
+
+func TestRepairUnclosedArgValues(t *testing.T) {
+	cases := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{
+			name:  "already valid",
+			input: `<arg_key>k</arg_key><arg_value>v</arg_value>`,
+			want:  `<arg_key>k</arg_key><arg_value>v</arg_value>`,
+		},
+		{
+			name:  "unclosed at end",
+			input: `<arg_key>k</arg_key><arg_value>v`,
+			want:  `<arg_key>k</arg_key><arg_value>v</arg_value>`,
+		},
+		{
+			name:  "unclosed before next arg_key",
+			input: `<arg_key>a</arg_key><arg_value>1<arg_key>b</arg_key><arg_value>2</arg_value>`,
+			want:  `<arg_key>a</arg_key><arg_value>1</arg_value><arg_key>b</arg_key><arg_value>2</arg_value>`,
+		},
+		{
+			name:  "no arg_value tags",
+			input: `just plain text`,
+			want:  `just plain text`,
+		},
+		{
+			name:  "multiple unclosed",
+			input: `<arg_key>a</arg_key><arg_value>1<arg_key>b</arg_key><arg_value>2`,
+			want:  `<arg_key>a</arg_key><arg_value>1</arg_value><arg_key>b</arg_key><arg_value>2</arg_value>`,
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := repairUnclosedArgValues(tc.input)
+			if got != tc.want {
+				t.Errorf("got %q, want %q", got, tc.want)
+			}
+		})
+	}
+}

x/models/glm4_moe_lite/parser.go

@@ -369,6 +369,45 @@ func escapeContent(s string) string {
 	return result.String()
 }
 
+// repairUnclosedArgValues inserts missing </arg_value> closing tags.
+// GLM models sometimes omit the closing tag, producing XML like:
+//
+//	<arg_value>value</tool_call>
+//
+// instead of:
+//
+//	<arg_value>value</arg_value></tool_call>
+func repairUnclosedArgValues(s string) string {
+	var result strings.Builder
+	for {
+		openIdx := strings.Index(s, "<arg_value>")
+		if openIdx == -1 {
+			result.WriteString(s)
+			break
+		}
+		afterOpen := openIdx + len("<arg_value>")
+		closeIdx := strings.Index(s[afterOpen:], "</arg_value>")
+		nextKeyIdx := strings.Index(s[afterOpen:], "<arg_key>")
+		if closeIdx != -1 && (nextKeyIdx == -1 || closeIdx < nextKeyIdx) {
+			end := afterOpen + closeIdx + len("</arg_value>")
+			result.WriteString(s[:end])
+			s = s[end:]
+			continue
+		}
+		if nextKeyIdx != -1 {
+			insertAt := afterOpen + nextKeyIdx
+			result.WriteString(s[:insertAt])
+			result.WriteString("</arg_value>")
+			s = s[insertAt:]
+		} else {
+			result.WriteString(s)
+			result.WriteString("</arg_value>")
+			break
+		}
+	}
+	return result.String()
+}
+
 func parseToolCall(raw eventRawToolCall, tools []api.Tool) (api.ToolCall, error) {
 	// Escape any unescaped entities in text content
 	escaped := escapeContent(raw.raw)
@@ -376,10 +415,14 @@ func parseToolCall(raw eventRawToolCall, tools []api.Tool) (api.ToolCall, error)
 	// Wrap the content in a root element to make it valid XML
 	xmlString := "<tool_call>" + escaped + "</tool_call>"
 
-	// Parse XML into struct
+	// Parse XML into struct, retrying once with repaired XML if it fails
 	var parsed ToolCallXML
 	if err := xml.Unmarshal([]byte(xmlString), &parsed); err != nil {
-		return api.ToolCall{}, fmt.Errorf("failed to parse XML: %w", err)
+		parsed = ToolCallXML{}
+		repaired := "<tool_call>" + repairUnclosedArgValues(escaped) + "</tool_call>"
+		if err2 := xml.Unmarshal([]byte(repaired), &parsed); err2 != nil {
+			return api.ToolCall{}, fmt.Errorf("failed to parse XML: %w", err)
+		}
 	}
 
 	// Extract and trim function name