[IlyasMoutawwakil]

Since DeepSeek-V4 declares ep_dispatch_experts, the Mega MoE override left that rule in place: token dispatch wrapped the Mega MoE experts and called them without a process group, so tp_size=ep_size runs raised on the first forward. The older ep_router + moe_tp_experts plan was never applied either, since the override renamed both styles and the mixin matched neither.

Mega MoE dispatches inside its kernel, so it takes over the experts rule (ep_dispatch_experts -> megamoe_experts), runs on the TP group like masked EP, and requires ep_size == tp_size.

What does this PR do?

Fixes # (issue)

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[ArthurZucker]

lgtm

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: finegrained_fp8

[github-actions]

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CI recap

Dashboard: View test results in Grafana
Latest run: 38892026053:1
Result: failure | Jobs: 15 | Tests: 202,230 | Failures: 2 | Duration: 15h 38m