FlashAttention (legacy)

FlashAttention is the legacy boolean toggle for flash attention. It predates the more granular FlashAttentionMode enum. Prefer FlashAttentionMode for new code.

Quick reference
Type bool?
Default null (use model default)
Category Attention (legacy)
Field on ContextParameters.FlashAttention

What it does

  • null — no explicit override; runtime / model default applies.
  • true — request flash attention (equivalent to FlashAttentionMode = Enabled).
  • false — disable flash attention (equivalent to FlashAttentionMode = Disabled).

FlashAttentionMode supersedes this field. When both are set, consult SDK behavior — to avoid ambiguity, set only one.

When to change it

Scenario Value
Default — prefer FlashAttentionMode instead null
Legacy code using this field Keep for backwards compatibility

For new code, use FlashAttentionMode which offers the three-way Auto / Disabled / Enabled choice.

Example

// Legacy style (kept for compatibility):
preset.ContextParameters.FlashAttention = true;

// Preferred (modern):
preset.ContextParameters.FlashAttentionMode = FlashAttentionType.Enabled;

Interactions

What’s next

FlashAttentionMode PoolingType