docs: clarify Transformers checkpoint CTC capability boundary

README.md

@@ -32,6 +32,10 @@ This is the Hugging Face Transformers-compatible version of [Fun-ASR-Nano-2512](
 
 Fun-ASR-Nano is an end-to-end speech recognition model by [FunAudioLLM](https://github.com/FunAudioLLM), trained on tens of millions of hours of real speech data. This checkpoint supports Chinese, English, and Japanese; its Chinese coverage includes 7 dialect groups and 26 regional accents. For 31-language recognition, use the separate [Fun-ASR-MLT-Nano-2512](https://huggingface.co/FunAudioLLM/Fun-ASR-MLT-Nano-2512) checkpoint.
 
+## Capability boundary
+
+This Transformers checkpoint is for generation-based transcription. It does not include the native CTC branch, so it does not provide CTC-dependent timestamps or speaker diarization. For those capabilities, use the [original checkpoint](https://huggingface.co/FunAudioLLM/Fun-ASR-Nano-2512) through [FunASR](https://github.com/modelscope/FunASR) or its native vLLM integration.
+
 ## Transformers quickstart
 
 Fun-ASR-Nano support is being added to Transformers in [huggingface/transformers#46180](https://github.com/huggingface/transformers/pull/46180). Until it is included in a Transformers release, use a build containing that PR.