---
id: pr-flashinfer-2557
repo: flashinfer-ai/flashinfer
pr: 2557
title: '[Bugfix][comm] Fix FP4 one-shot launch config instability in trtllm_allreduce_fusion'
author: baonudesifeizhai
date: '2026-02-17'
url: https://github.com/flashinfer-ai/flashinfer/pull/2557
source_category: upstream-code
architectures:
- sm100
tags:
- attention_kv
- gemm_quant
- memory_primitives
- moe_routing
- sampling
- scheduler_autotune
techniques:
- autotuning
- fine-grained-quantization
- kernel-fusion
- tile-scheduling
hardware_features:
- blackwell
- fp4
kernel_types:
- attention
- gemm
- memory
- moe
- sampling
- scheduler
languages:
- cuda-cpp
captured_at: '2026-05-16'
status: merged
merge_sha: 432f3438286a20003f8fc568111cad222b6acf4d
inclusion_reason: Separate routing, permutation, top-k, and expert GEMM costs; keep tail-token and expert-layout tests attached to the idea.
changed_paths:
- include/flashinfer/comm/trtllm_allreduce_fusion.cuh
artifact_dir: evidence/pull-bundles/flashinfer/gh-2557
head_ref_oid: 2af67344909169f917462a22e2370ccf500fb090
---
# [Bugfix][comm] Fix FP4 one-shot launch config instability in trtllm_allreduce_fusion

- Repository: `flashinfer-ai/flashinfer`
- PR: [2557](https://github.com/flashinfer-ai/flashinfer/pull/2557)
- Decision: `Separate routing, permutation, top-k, and expert GEMM costs; keep tail-token and expert-layout tests attached to the idea.`
- Reason: Separate routing, permutation, top-k, and expert GEMM costs; keep tail-token and expert-layout tests attached to the idea.

## Changed Paths

- `include/flashinfer/comm/trtllm_allreduce_fusion.cuh`

## Evidence Bundle

`evidence/pull-bundles/flashinfer/gh-2557`
