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From 76398ed1a6ff4a08036e5bf5095ce9be0907cdec Mon Sep 17 00:00:00 2001
From: Ewout van Mansom <ewout@vanmansom.name>
Date: Wed, 8 Apr 2026 14:27:53 +0200
Subject: [PATCH 1/6] chat : use AST-only path for Gemma 4 tool call parsing
Ensure the Gemma 4 PEG mapper handles all tool-related AST nodes
directly via gemma4_to_json, without falling back to the base mapper's
normalize_container_value / normalize_gemma4_to_json character-scanning
heuristics. This fixes incorrect parsing of tool call arguments
containing braces inside string values (e.g. JSON strings in tool args).
Also adds whitespace-only reasoning cleanup and defaults empty tool
arguments to "{}" for consistency.
Fixes #21384
---
common/chat-peg-parser.cpp | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/common/chat-peg-parser.cpp b/common/chat-peg-parser.cpp
index 624dee22f..5ceec7309 100644
--- a/common/chat-peg-parser.cpp
+++ b/common/chat-peg-parser.cpp
@@ -866,10 +866,24 @@ common_peg_parser common_chat_peg_builder::standard_json_tools(
return force_tool_calls ? section : optional(section);
}
-void common_chat_peg_gemma4_mapper::from_ast(const common_peg_ast_arena & arena, const common_peg_parse_result & result) {
- for (const auto & node : result.nodes) {
+void common_chat_peg_gemma4_mapper::from_ast(const common_peg_ast_arena & arena, const common_peg_parse_result & parse_result_arg) {
+ for (const auto & node : parse_result_arg.nodes) {
visit(arena, node);
}
+
+ // Discard whitespace-only reasoning content (e.g. from empty thinking blocks)
+ if (!result.reasoning_content.empty()) {
+ bool all_whitespace = true;
+ for (char c : result.reasoning_content) {
+ if (c != ' ' && c != '\n' && c != '\r' && c != '\t') {
+ all_whitespace = false;
+ break;
+ }
+ }
+ if (all_whitespace) {
+ result.reasoning_content.clear();
+ }
+ }
}
static std::string gemma4_to_json(const common_peg_ast_arena & arena, common_peg_ast_id id) {
@@ -984,15 +998,21 @@ void common_chat_peg_gemma4_mapper::visit(const common_peg_ast_arena & arena, co
auto name_id = arena.find_by_tag(node, "tool-name");
auto args_id = arena.find_by_tag(node, "tool-args");
- if (name_id != COMMON_PEG_INVALID_AST_ID && args_id != COMMON_PEG_INVALID_AST_ID) {
+ if (name_id != COMMON_PEG_INVALID_AST_ID) {
const auto & name_node = arena.get(name_id);
- const auto & args_node = arena.get(args_id);
if (!name_node.is_partial) {
common_chat_tool_call call;
call.name = std::string(name_node.text);
- if (!args_node.children.empty()) {
- call.arguments = gemma4_to_json(arena, args_node.children[0]);
+ if (args_id != COMMON_PEG_INVALID_AST_ID) {
+ const auto & args_node = arena.get(args_id);
+ if (!args_node.children.empty()) {
+ call.arguments = gemma4_to_json(arena, args_node.children[0]);
+ } else {
+ call.arguments = "{}";
+ }
+ } else {
+ call.arguments = "{}";
}
result.tool_calls.push_back(call);
}
--
2.53.0
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