Test the compute-honesty spot-check (challenge.py); defer endpoint bindings#43
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shard/challenge.py is the primitive that actually catches a node getting paid without running its block's real matmuls — the gap the receipt hash-chain can't close (a chain proves byte-continuity, never out == block(in)). A verifier draws a seeded input both sides derive identically, the suspect and a trusted replica run the same block, and outputs are compared by cosine + relative norm with a tolerance (honest heterogeneous hardware drifts a few ULPs -> cosine ~1; garbage/wrong/skipped block -> cosine ~0). It had ZERO tests. 13 CPU tests (pure discriminators direct; challenge_block with synthetic blocks, block_forward stubbed): derive_challenge deterministic + seed-varying; sketch deterministic; compare passes identical + ULP drift, fails garbage / scaled-magnitude (rel-norm guard) / partial-direction, works on sketches; challenge_block passes an honest recompute and fails a lazy-constant / wrong block, feeding both sides the same seeded input. Test-only. Suite 189 green.
…al lever Worked the endpoint-binding trust model and decided against building it. Under the coordinator-trusted model a tok_in_root/tok_out_root is theater: the tail root is a tautology (the coordinator already observes+uses the reply tokens), and the head root only proves a node saw the tokens it was handed — the coordinator can already bit-exactly recompute the head's in_root from embedding(token_ids) (a gather, hardware-independent). Neither proves compute. Compute honesty is challenge.py's redundant-recompute spot-check (now tested), and a (prompt, answer) receipt-of-service belongs in the c0mpute layer, not the engine's activation chain. Record the decision + revisit condition.
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Two things:
1. Adversarial tests for
shard/challenge.py(had zero) — the layer-block spot-check that catches a node getting paid without running its block's real matmuls (the gap the receipt hash-chain can't close). 13 CPU tests:comparepasses identical + honest ULP drift, fails garbage / wrong-magnitude (rel-norm guard) / partial-direction;challenge_blockpasses an honest recompute and fails a lazy-constant / wrong block, with both sides fed the same seeded input;derive_challenge/sketchdeterminism.2. Decision: defer receipt endpoint bindings. Under coordinator-trusted-challenge a
tok_in_root/tok_out_rootis security theater — the tail root is a tautology (the coordinator already observes the reply tokens), the head root only proves a node saw the tokens (and the coordinator can already bit-exactly recompute the head'sin_rootfromembedding(token_ids)). Neither proves compute — that'schallenge.py's job. A (prompt, answer) receipt-of-service belongs in the c0mpute layer. Recorded in the living state with the revisit condition.Test + doc only, no production change. Suite 189 green.