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USAGE.md

@@ -229,7 +229,9 @@ Two independent decode-bandwidth levers:
 - **Block-selector** (`--sparse-attn on`): per-block min/max key
   bounds give an upper bound on each block's attention mass; decode
   visits only the top-K blocks (+ sinks + recent). Flags:
-  `--sparse-attn-block-size` (128), `--sparse-attn-topk` (0 = auto),
+  `--sparse-attn-block-size` (128), `--sparse-attn-topk` (default 0 =
+  visit **all** blocks, i.e. no skipping; pass `auto` for adaptive
+  max(64, n_blocks/4), or an explicit block count),
   `--sparse-attn-recent`, `--sparse-attn-sink` (1),
   `--sparse-attn-refresh` (8 — re-select every N decode steps),
   `--sparse-attn-mode` (0). Default **off**.