[Models] Cohere Eagle + fix to Cohere MoE

[Terrencezzj]

Purpose

Add Cohere Eagle to vLLM.
Update CohereCommandReasoningParser

Online inference

Terminal 1: start server

MODEL_ID=<model_path>
DRAFT_ID=<draft_path>
SPEC_CONFIG=$(printf '{"method":"eagle","model":"%s","num_speculative_tokens":3,"draft_tensor_parallel_size":2}' "$DRAFT_ID")
vllm serve $MODEL_ID --trust-remote-code --speculative-config "$SPEC_CONFIG"

Terminal 2: run client

curl http://127.0.0.1:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d "{
    \"model\": \"${MODEL_ID}\",
    \"messages\": [
      {\"role\": \"user\", \"content\": \"Hello, what is 2+2?\"}
    ]
  }"

Test Plan

Test Result

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
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• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[gemini-code-assist]

Code Review

This pull request introduces support for the EAGLE speculative decoding draft model for Cohere architectures, including the implementation of EagleCohereForCausalLM and updates to the reasoning parser for handling multiple structural tags. The review feedback highlights several critical improvements: initializing flags to track model-specific weights for the speculative proposer, ensuring the first draft layer correctly disables the input layernorm to align with the original EAGLE implementation, and removing logic that skips loading embeddings to avoid breaking weight-sharing comparisons.

[mergify]

Documentation preview: https://vllm--42078.org.readthedocs.build/en/42078/

[mergify]

Hi @Terrencezzj, the pre-commit checks have failed. Please run:

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