[VLM][Bugfix] Enable specifying prompt target via index (#14038)

vllm/model_executor/models/molmo.py

@@ -46,8 +46,8 @@ from vllm.multimodal.inputs import (MultiModalFieldConfig, MultiModalKwargs,
 from vllm.multimodal.parse import (ImageProcessorItems, ImageSize,
                                    MultiModalDataItems)
 from vllm.multimodal.processing import (BaseMultiModalProcessor,
-                                        BaseProcessingInfo, PromptInsertion,
-                                        PromptUpdate)
+                                        BaseProcessingInfo, PromptIndexTargets,
+                                        PromptInsertion, PromptUpdate)
 from vllm.multimodal.profiling import BaseDummyInputsBuilder, ProcessorInputs
 from vllm.sequence import IntermediateTensors
 from vllm.utils import JSONTree, json_map_leaves
@@ -1371,7 +1371,7 @@ class MolmoMultiModalProcessor(BaseMultiModalProcessor[MolmoProcessingInfo]):
         return [
             PromptInsertion(
                 modality="image",
-                target="<|endoftext|>",
+                target=PromptIndexTargets.prefix("<|endoftext|>"),
                 insertion=get_insertion_molmo,
             )
         ]