sgl-project/sglang · warning · DeprecationWarning

attention-backend='nsa' is deprecated; use 'dsa' instead. Th

Error message

attention-backend='nsa' is deprecated; use 'dsa' instead. The alias will be removed in a future release.

What it means

The attention backend name 'nsa' (native sparse attention) is a deprecated alias for what is now called 'dsa'. Selecting it via --attention-backend nsa or AttentionBackendEnum.NSA still works — it creates the DSA backend — but the alias will be removed.

Source

Thrown at python/sglang/srt/layers/attention/attention_registry.py:142

@register_attention_backend("ascend")
def create_ascend_backend(runner):
    from sglang.srt.hardware_backend.npu.attention.ascend_backend import (
        AscendAttnBackend,
    )

    return AscendAttnBackend(runner)


@register_attention_backend("dsa")
def create_dsa_backend(runner):
    from sglang.srt.layers.attention.dsa_backend import DeepseekSparseAttnBackend

    return DeepseekSparseAttnBackend(runner)


@register_attention_backend("nsa")
def _create_nsa_compat(runner):
    warnings.warn(
        "attention-backend='nsa' is deprecated; use 'dsa' instead. "
        "The alias will be removed in a future release.",
        DeprecationWarning,
        stacklevel=2,
    )
    return create_dsa_backend(runner)


@register_attention_backend("dsv4")
def create_dsv4_backend(runner):
    if _is_npu:
        from sglang.srt.hardware_backend.npu.attention.ascend_dsv4_backend import (
            DeepseekV4AscendAttnBackend,
        )

        return DeepseekV4AscendAttnBackend(runner)
    elif _is_hip:
        from sglang.srt.layers.attention.deepseek_v4_backend_hip_radix import (

View on GitHub (pinned to 0132848349)

Solutions

1. Change --attention-backend nsa to --attention-backend dsa in launch commands
2. Update any programmatic registry lookups from 'nsa' to 'dsa'
3. Watch release notes for the removal and migrate before upgrading past it

Example fix

# before
sglang serve --model-path deepseek-ai/DeepSeek-V3 --attention-backend nsa
# after
sglang serve --model-path deepseek-ai/DeepSeek-V3 --attention-backend dsa

assert server_args.attention_backend != "nsa", "use 'dsa'"

When it happens

Trigger: Launching the server with --attention-backend nsa, or setting the attention backend registry key 'nsa' in code, on a DeepSeek-style sparse attention model.

Common situations: Old launch commands/model configs from when the backend was named NSA; scripts pinned to previous sglang versions after upgrading.

Related errors

• sglang.srt.layers.attention.nsa is deprecated; use sglang.sr
• HiSparse supports DSA {label} backend(s) {sorted(allowed_bac
• 'python -m sglang.launch_server' is still supported, but 'sg
• 'data_parallel_rank' is deprecated, use 'routed_dp_rank' ins
• 'data_parallel_rank' is deprecated, use 'routed_dp_rank' ins

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/36aed54d025fc3b2. Report an issue: GitHub.