Trait LayerCapabilities 

pub trait LayerCapabilities {
    // Provided methods
    fn uses_local_mla_prefill(&self) -> bool { ... }
    fn fp8_calibration_frozen(&self) -> Option<bool> { ... }
    fn decode_graph_unsupported(&self) -> bool { ... }
    fn decode_multi_seq_unsupported(&self) -> bool { ... }
    fn decode_rollback_unsupported(&self) -> bool { ... }
    fn decode_verify_multi_unsupported(&self) -> bool { ... }
    fn graph_stale_on_new_sequence(&self) -> bool { ... }
    fn is_ssm_layer(&self) -> bool { ... }
    fn uses_ssm_pool(&self) -> bool { ... }
    fn supports_replay_tail_split(&self) -> bool { ... }
}

2026-09-26: A supertrait of TransformerLayer; see the module header.

Provided Methods

fn uses_local_mla_prefill(&self) -> bool

2026-09-25: True when this layer’s prefill attends only over the tokens it is handed, so skipping a cached prefix would hide it from attention. The Qwen3 attention layer returns true when it runs MLA; the prefix lookup then matches nothing unless METRALE_MLA_PREFIX_SKIP=1 (mla_prefill_needs_full_recompute).

fn fp8_calibration_frozen(&self) -> Option<bool>

2026-09-25: Whether this layer’s online FP8-KV calibration has frozen its scale; None when the layer runs no online calibration (the default). The model lifts its CUDA-graph suppression once no layer reports Some(false) (graphs_ready_after_fp8_kv_cal).

fn decode_graph_unsupported(&self) -> bool

2026-09-25: True when this layer’s decode cannot run inside a CUDA graph, such as the QSA indexer’s host top-k. The model ORs it across layers into decode_graph_veto when it is built.

fn decode_multi_seq_unsupported(&self) -> bool

2026-09-25: True when this layer cannot serve a batched multi-sequence decode step. The batched decode ORs it across layers into hc_perseq (decode_a2.rs) and then runs each sequence through decode; the single-GPU fused decode+prefill ORs it into hc_qsa_perseq (decode_b.rs) and then runs the batched decode and the prefill separately.

fn decode_rollback_unsupported(&self) -> bool

2026-09-25: True when this layer keeps per-sequence state that lowering the sequence’s KV cursor does not rewind, such as a monotonic cache count or an n-gram history. The model ORs it across layers, and the scheduler’s rollback_to_boundary then declines the rollback (LayerStateNotRewindable).

fn decode_verify_multi_unsupported(&self) -> bool

2026-09-25: True when this layer cannot serve a batched multi-sequence verify (decode_verify_multi); can_batch_verify_dispatch then refuses the batch. It is separate from Self::decode_multi_seq_unsupported because the answers can differ.

fn graph_stale_on_new_sequence(&self) -> bool

2026-09-25: True when a captured decode graph goes stale once a new sequence takes this slot. Decode graphs are keyed by slot_idx, which is safe only while every per-sequence address a capture bakes lives in the slot-addressed SSM pool. A layer that allocates its own per-sequence buffers (GLM-5.3’s DSA indexer cache) returns true, and free_sequence_dispatch then drops that slot’s graphs, except for a slot index past the SSM pool’s max_slots.

fn is_ssm_layer(&self) -> bool

2026-09-25: True for an SSM layer. The model’s split prefill then runs prefill_phase1, prefill_gdn_full and prefill_phase3 instead of prefill.

fn uses_ssm_pool(&self) -> bool

2026-09-25: Whether this layer’s recurrent state lives in the shared SSM pool. When true (the default), sequence setup hands a linear-attention layer an SsmLayerState with pool addresses and never calls its alloc_state. A linear-attention layer with its own state type returns false; the Kimi K3 layer (kimi_k3/bound.rs) does, and downcasts its state to K3CpuFallbackState.

fn supports_replay_tail_split(&self) -> bool

2026-10-01: True when this layer’s prefill honours a replay-tail capture (ForwardContext::midchunk_capture with replay_tail) on every build: the rows from cap_local on get the bits a prefill pass starting at cap_local gives them (an SSM layer splits its conv and recurrence there and copies its state into the plan’s slots; an attention layer runs those rows as their own paged call). The model plans a replay-tail capture only when every layer says so (TransformerModel::inpass_cut_capture_supported); otherwise it keeps the two-pass tail split.

Implementors

impl LayerCapabilities for Qwen3AttentionLayer

impl LayerCapabilities for Qwen3SsmLayer