From 73444b7b5623f5bc569277c8c7dc809843312d11 Mon Sep 17 00:00:00 2001
From: Julien Denize <40604584+juliendenize@users.noreply.github.com>
Date: Sun, 2 Nov 2025 09:48:33 +0100
Subject: [PATCH] Performance fix MistralTokenizer: cache special ids and
 tokens (#27925)

Signed-off-by: Julien Denize <julien.denize@mistral.ai>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
---
 vllm/transformers_utils/tokenizers/mistral.py | 66 +++++++++----------
 1 file changed, 32 insertions(+), 34 deletions(-)

diff --git a/vllm/transformers_utils/tokenizers/mistral.py b/vllm/transformers_utils/tokenizers/mistral.py
index 6f710bf23..703352322 100644
--- a/vllm/transformers_utils/tokenizers/mistral.py
+++ b/vllm/transformers_utils/tokenizers/mistral.py
@@ -191,6 +191,12 @@ class MistralTokenizer(TokenizerBase):
         # Sort the dict for convenience
         self._vocab_dict = dict(sorted(self._vocab_dict.items(), key=lambda x: x[1]))
 
+        # Cache special tokens for faster access.
+        self._special_token_ids = self._get_special_token_ids()
+        self._special_token_ids_set = set(self._special_token_ids)
+        self._special_tokens = self._get_special_tokens(self._special_token_ids)
+        self._special_tokens_set = set(self._special_tokens)
+
         # Vocab sorted by token id.
         self._vocab = self.tokenizer._vocab
         self._max_token_id = self.vocab_size - 1
@@ -210,23 +216,7 @@ class MistralTokenizer(TokenizerBase):
             )
         )
 
-    # the following attributes are set to fit vLLM's design and are used
-    # by the structured output backends.
-    @property
-    def all_special_tokens_extended(self) -> list[str]:
-        return self.all_special_tokens
-
-    @property
-    def all_special_tokens(self) -> list[str]:
-        from mistral_common.tokens.tokenizers.base import SpecialTokenPolicy
-
-        return [
-            self.tokenizer.decode([i], special_token_policy=SpecialTokenPolicy.KEEP)
-            for i in self.all_special_ids
-        ]
-
-    @property
-    def all_special_ids(self) -> list[int]:
+    def _get_special_token_ids(self) -> list[int]:
         from mistral_common.tokens.tokenizers.sentencepiece import (
             SentencePieceTokenizer,
         )
@@ -244,6 +234,28 @@ class MistralTokenizer(TokenizerBase):
             raise ValueError(f"Unknown tokenizer type: {type(self.tokenizer)}")
         return sorted(special_ids)
 
+    def _get_special_tokens(self, all_special_ids: list[int]) -> list[str]:
+        from mistral_common.tokens.tokenizers.base import SpecialTokenPolicy
+
+        return [
+            self.tokenizer.decode([i], special_token_policy=SpecialTokenPolicy.KEEP)
+            for i in all_special_ids
+        ]
+
+    # the following attributes are set to fit vLLM's design and are used
+    # by the structured output backends.
+    @property
+    def all_special_tokens_extended(self) -> list[str]:
+        return self.all_special_tokens
+
+    @property
+    def all_special_tokens(self) -> list[str]:
+        return self._special_tokens
+
+    @property
+    def all_special_ids(self) -> list[int]:
+        return self._special_token_ids
+
     @property
     def bos_token_id(self) -> int:
         return self.tokenizer.bos_id
@@ -277,21 +289,7 @@ class MistralTokenizer(TokenizerBase):
         raise NotImplementedError()
 
     def _is_special_token_id(self, token_id: int) -> bool:
-        from mistral_common.tokens.tokenizers.sentencepiece import (
-            SentencePieceTokenizer,
-        )
-        from mistral_common.tokens.tokenizers.tekken import Tekkenizer
-
-        if self.is_spm:
-            assert isinstance(self.tokenizer, SentencePieceTokenizer), type(
-                self.tokenizer
-            )
-            return token_id in self.tokenizer._control_tokens
-        if self.is_tekken:
-            assert isinstance(self.tokenizer, Tekkenizer), type(self.tokenizer)
-            return token_id < self.tokenizer.num_special_tokens
-        else:
-            raise ValueError(f"Unknown tokenizer type: {type(self.tokenizer)}")
+        return token_id in self._special_token_ids_set
 
     def __len__(self) -> int:
         return self.vocab_size
@@ -405,7 +403,7 @@ class MistralTokenizer(TokenizerBase):
             tokens = [
                 t
                 for t in tokens
-                if (t in to_decode_special_tokens or t not in self.all_special_tokens)
+                if (t in to_decode_special_tokens or t not in self._special_tokens_set)
             ]
 
             if any(isinstance(t, bytes) for t in tokens):
@@ -489,7 +487,7 @@ class MistralTokenizer(TokenizerBase):
             # We filtered unwanted special tokens so we can decode the rest.
             tokens = [
                 self.tokenizer.id_to_byte_piece(token_id, SpecialTokenPolicy.KEEP)
-                if token_id not in self.all_special_ids
+                if token_id not in self._special_token_ids_set
                 else self.tokenizer.decode([token_id], SpecialTokenPolicy.KEEP)
                 for token_id in ids_kept
             ]