Feature Request: Add MTP / speculative decoding support to llama-bench for PR #22673 #22947

Prerequisites

• I am running the latest code. Mention the version if possible as well.
• I carefully followed the README.md.
• I searched using keywords relevant to my issue to make sure that I am creating a new issue that is not already open (or closed).
• I reviewed the Discussions, and have a new and useful enhancement to share.

Feature Description

The draft MTP PR #22673 adds speculative decoding / MTP support to:

llama-cli
llama-server

using flags such as:
--spec-type mtp
--spec-draft-n-max 3
--spec-draft-ngl 99

These flags work correctly in:

llama-cli
llama-server

(have only tested on these two)

but are unrecognized in llama-bench
Example:

./build/bin/llama-bench \
  -m model.gguf \
  --spec-type mtp
 -- spec-draft-n-max 3,4,5
 -- spec-draft-ngl 99,100

returns:

error: invalid parameter for argument: --spec-type

Motivation

Currently MTP benchmarking requires custom scripts or llama-server setups since speculative decoding flags are unavailable in llama-bench.

Adding support directly to llama-bench would make it much easier for users to quickly test and compare speculative decoding configurations such as different n-max values, context depths, throughput scaling, and VRAM tradeoffs using the built-in benchmarking tooling.

Possible Implementation

I did some digging and it looks like llama-bench currently uses its own parser / benchmark loop instead of the shared common argument infrastructure used by llama-cli and llama-server, which is likely why the speculative decoding flags are currently unavailable there.