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Mistral tool parser: ignore missing beginning of tools token #3751

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Merged
merged 6 commits into from
Nov 3, 2025
Merged

Mistral tool parser: ignore missing beginning of tools token #3751

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dkalinowski Oct 30, 2025
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dkalinowski Oct 30, 2025
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Merge remote-tracking branch 'origin/main' into mistral-ignore-bot
dkalinowski Oct 31, 2025
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Merge remote-tracking branch 'origin/main' into mistral-ignore-bot
dkalinowski Oct 31, 2025
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Merge remote-tracking branch 'origin/main' into mistral-ignore-bot
dkalinowski Oct 31, 2025
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Merge branch 'main' into mistral-ignore-bot
dkalinowski Nov 3, 2025
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8 changes: 6 additions & 2 deletions src/llm/io_processing/mistral/tool_parser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -38,8 +38,12 @@ void MistralToolParser::parse(ParsedOutput& parsedOutput, const std::vector<int6
// In regular parsing, the parser will consume entire model output only if the first generated token is the beginning of tools token.
// In immediate parsing, the parser will consume entire model output regardless of the first token.
if (generatedTokens[0] != this->botTokenId && !immediateParsingEnabled) {
SPDLOG_LOGGER_DEBUG(llm_calculator_logger, "Begin of tools token has not been found in the model output. Exiting parser.");
return;
if (parsedOutput.content.size() >= 2 && parsedOutput.content[0] == '[' && parsedOutput.content[1] == '{') {
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@mzegla mzegla Oct 30, 2025

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Can't we rely on generatedTokens? We already base on checking it in condition above, so why not keep it continuous?

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@dkalinowski dkalinowski Oct 31, 2025

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I don't think its good idea, [{ is regular text (non special token)
Do you want me to handle all cases where:

  • [ and { are separate tokens? x, y
  • [{ is glued together into 1 token? x

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@mzegla mzegla Nov 3, 2025

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No, in that case I think it's fine.

SPDLOG_LOGGER_DEBUG(llm_calculator_logger, "Model output starts with '[{' but begin of tools token is missing. Proceeding with parsing.");
} else {
SPDLOG_LOGGER_DEBUG(llm_calculator_logger, "Begin of tools token or '[{' has not been found in the model output. Exiting parser.");
return;
}
}

rapidjson::Document toolsDoc;
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13 changes: 13 additions & 0 deletions src/test/llm/output_parsers/mistral_output_parser_test.cpp
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Expand Up @@ -79,6 +79,19 @@ TEST_F(MistralOutputParserTest, ParseToolCallOutputWithSingleToolCall) {
}
}

TEST_F(MistralOutputParserTest, ParseToolCallOutputWithSingleToolCall_MissingToolCallStartTag) {
std::string testInput = "[{\"name\": \"example_tool\", \"arguments\": {\"arg1\": \"value1\", \"arg2\": 42}}]</s>";
auto generatedTensor = mistralTokenizer->encode(testInput, ov::genai::add_special_tokens(false)).input_ids;
std::vector<int64_t> generatedTokens(generatedTensor.data<int64_t>(), generatedTensor.data<int64_t>() + generatedTensor.get_size());
ParsedOutput parsedOutput = outputParserWithRegularToolParsing->parse(generatedTokens, true);
EXPECT_EQ(parsedOutput.content, "");
EXPECT_EQ(parsedOutput.reasoning, "");
ASSERT_EQ(parsedOutput.toolCalls.size(), 1);
EXPECT_EQ(parsedOutput.toolCalls[0].name, "example_tool");
EXPECT_EQ(parsedOutput.toolCalls[0].arguments, "{\"arg1\":\"value1\",\"arg2\":42}");
EXPECT_EQ(parsedOutput.toolCalls[0].id.empty(), false);
}

TEST_F(MistralOutputParserTest, ParseToolCallOutputWithThreeToolCalls) {
std::string input = "[TOOL_CALLS][{\"name\": \"example_tool\", \"arguments\": {\"arg1\": \"value1\", \"arg2\": 42}},"
"{\"name\": \"another_tool\", \"arguments\": {\"param1\": \"data\", \"param2\": true}},"
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