fix: variable-length Context.headers; lastBlockUtxoRoot as its own context input#889
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mwaddip wants to merge 2 commits into
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fix: variable-length Context.headers; lastBlockUtxoRoot as its own context input#889mwaddip wants to merge 2 commits into
mwaddip wants to merge 2 commits into
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The JVM models lastBlockUtxoRoot as its own ErgoLikeContext input and CContext.LastBlockUtxoRootHash returns it directly; deriving it from headers(0).stateRoot only coincides when headers are non-empty (the JVM requires digest agreement then, ErgoLikeContext.scala:85) and has no value for an empty header chain. Add Context.last_block_utxo_root and return it from the eval; make_context derives it from the newest header, which is exactly the JVM-required relationship. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The JVM models ErgoLikeContext.headers as a variable-length Coll[Header]: empty is explicitly legal, and at block height h <= 10 the window that headerChainBack gathers stops at genesis, so scripts see h - 1 headers. sigma-rust's fixed [Header; 10] cannot represent that; a node bridging it must pad, and a script reading CONTEXT.headers.size or a high index in the first blocks of a chain gets a different answer than the JVM — a silent value fork (practical exposure: testnet from-genesis validation). Context.headers becomes ContextHeaders (BoundedVec 0..=10), and the SDK ErgoStateContext.headers becomes BoundedVec 1..=10 — signing always has a chain tip, and make_context still derives the root from the newest header. The wasm/python/C constructors relax accordingly: every existing caller passing 10 headers keeps working; passing fewer becomes possible. Regression tests drive the two JVM-blessed Context.properties vectors (empty headers -> empty Coll[Header]; LastBlockUtxoRootHash on an empty-headers context -> the standalone root field). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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JVM
ErgoLikeContext.headersis variable-length — empty is legal, and at height h ≤ 10headerChainBackyields h−1 headers — withlastBlockUtxoRootas its own context input (CContextreturns it directly, neverheaders(0)). sigma-rust pinned[Header; 10]and derived the root fromheaders[0]: a node bridging the fixed type must pad, soCONTEXT.headers.size/ high-index reads in a chain's first blocks diverge from the JVM — a silent value fork (exposure: testnet from-genesis validation).Fix:
Context.headers→BoundedVec<Header, 0, 10>+ standaloneContext.last_block_utxo_root; SDK headers →BoundedVec<Header, 1, 10>(signing always has a chain tip); bindings relax==10→1..=10. Regression tests drive JVM-blessed vectors against the truly-empty context.