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Proposed prerequisites surfaced while evaluating the GQA fused-attention ADR against the actual kernbench tl/sim_engine implementation: - ADR-0061 tl.broadcast: data-faithful GQA head reuse (fixes the MemoryStore nbytes check that forces h_q==h_kv==1 today). - ADR-0062 tl.load_async: non-blocking HBM tile load for KV prefetch (KV-load-bound decode/long-context overlap). - ADR-0063 tl.scratch_scope: per-tile scratch recycling (removes the 1 MiB bump-allocator ceiling that caps context at S=16). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>