diff --git a/tools/mypy.sh b/tools/mypy.sh
index 2454ff9fde466..bf95e4c526fd1 100755
--- a/tools/mypy.sh
+++ b/tools/mypy.sh
@@ -23,6 +23,7 @@ run_mypy vllm/compilation
 run_mypy vllm/distributed
 run_mypy vllm/engine
 run_mypy vllm/executor
+run_mypy vllm/inputs
 run_mypy vllm/lora
 run_mypy vllm/model_executor
 run_mypy vllm/plugins
diff --git a/vllm/inputs/data.py b/vllm/inputs/data.py
index d54cbb5c37819..cdaf6dd76eaa1 100644
--- a/vllm/inputs/data.py
+++ b/vllm/inputs/data.py
@@ -250,7 +250,7 @@ def prompt(self) -> Optional[str]:
         if inputs["type"] == "token" or inputs["type"] == "multimodal":
             return inputs.get("prompt")
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def prompt_token_ids(self) -> List[int]:
@@ -259,7 +259,7 @@ def prompt_token_ids(self) -> List[int]:
         if inputs["type"] == "token" or inputs["type"] == "multimodal":
             return inputs.get("prompt_token_ids", [])
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def token_type_ids(self) -> List[int]:
@@ -268,7 +268,7 @@ def token_type_ids(self) -> List[int]:
         if inputs["type"] == "token" or inputs["type"] == "multimodal":
             return inputs.get("token_type_ids", [])
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def prompt_embeds(self) -> Optional[torch.Tensor]:
@@ -277,7 +277,7 @@ def prompt_embeds(self) -> Optional[torch.Tensor]:
         if inputs["type"] == "token" or inputs["type"] == "multimodal":
             return None
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def multi_modal_data(self) -> "MultiModalDataDict":
@@ -289,7 +289,7 @@ def multi_modal_data(self) -> "MultiModalDataDict":
         if inputs["type"] == "multimodal":
             return inputs.get("mm_kwargs", {})
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def multi_modal_inputs(self) -> Union[Dict, "MultiModalKwargs"]:
@@ -301,7 +301,7 @@ def multi_modal_inputs(self) -> Union[Dict, "MultiModalKwargs"]:
         if inputs["type"] == "multimodal":
             return inputs.get("mm_kwargs", {})
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def multi_modal_hashes(self) -> List[str]:
@@ -311,9 +311,10 @@ def multi_modal_hashes(self) -> List[str]:
             return inputs.get("multi_modal_hashes", [])
 
         if inputs["type"] == "multimodal":
-            return inputs.get("mm_hashes", [])
+            # only the case when we use MultiModalInputsV2
+            return inputs.get("mm_hashes", [])  # type: ignore[return-value]
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def multi_modal_placeholders(self) -> "MultiModalPlaceholderDict":
@@ -325,7 +326,7 @@ def multi_modal_placeholders(self) -> "MultiModalPlaceholderDict":
         if inputs["type"] == "multimodal":
             return inputs.get("mm_placeholders", {})
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
     @cached_property
     def mm_processor_kwargs(self) -> Dict[str, Any]:
@@ -337,7 +338,7 @@ def mm_processor_kwargs(self) -> Dict[str, Any]:
         if inputs["type"] == "multimodal":
             return {}
 
-        assert_never(inputs)
+        assert_never(inputs)  # type: ignore[arg-type]
 
 
 ProcessorInputs = Union[DecoderOnlyInputs, EncoderDecoderInputs]
diff --git a/vllm/inputs/preprocess.py b/vllm/inputs/preprocess.py
index 3d606817e90aa..aaa10d278ddb0 100644
--- a/vllm/inputs/preprocess.py
+++ b/vllm/inputs/preprocess.py
@@ -436,7 +436,7 @@ def _build_enc_dec_llm_inputs(
                 or encoder_inputs["type"] == "multimodal"):
             pass
         else:
-            assert_never(encoder_inputs)
+            assert_never(encoder_inputs)  # type: ignore[arg-type]
 
         if decoder_inputs is None:
             dec_token_ids = self._prepare_decoder_input_ids_for_generation(
@@ -452,7 +452,7 @@ def _build_enc_dec_llm_inputs(
                 raise ValueError("Multi-modal decoder inputs of encoder-"
                                  "decoder models are not supported yet")
         else:
-            assert_never(encoder_inputs)
+            assert_never(encoder_inputs)  # type: ignore[arg-type]
 
         return EncoderDecoderInputs(
             encoder=encoder_inputs,
@@ -569,7 +569,7 @@ def _build_decoder_only_llm_inputs(
                 prompt_adapter_request=prompt_adapter_request,
             )
         else:
-            assert_never(prompt_inputs)
+            assert_never(prompt_inputs)  # type: ignore[arg-type]
 
         return prompt_inputs
 
diff --git a/vllm/inputs/registry.py b/vllm/inputs/registry.py
index 090347706ca93..2d9d024e03e80 100644
--- a/vllm/inputs/registry.py
+++ b/vllm/inputs/registry.py
@@ -419,7 +419,7 @@ def _ensure_mm_kwargs(
             # Be more strict in V2
             assert "mm_kwargs" in inputs
         else:
-            assert_never(inputs["type"])
+            assert_never(inputs["type"])  # type: ignore[arg-type]
 
     def process_input(self, model_config: "ModelConfig",
                       inputs: ProcessorInputs) -> ProcessorInputs: