What a semantic patch can honestly prove about WebAssembly output

When a coding agent changes a systems program, a source diff is only the beginning of the question. The more useful question is: what exact machine-facing artifacts would this semantic change produce, and can another process independently verify that relationship? That is one of the research problems we are exploring in SEMAPRAX , an Apache-2.0 agent-native systems programming language built at Wavect GmbH. SEMAPRAX is currently v0.2 pre-alpha experimental research software . It is not production-ready. The narrow mechanism described here is useful precisely because its claims are bounded. From a patch to target projections SEMAPRAX has a read-only command: semaprax target-evidence <file> <patch.spatch> The command takes a verified source snapshot and a semantic patch. It independently rebuilds both the base program and the patched candidate, then derives several deterministic compiler-owned projections: semantic Graph JSON an explicit capability manifest Native C11 source a structurally validated WebAssembly Core module For every projection, the report records a domain-separated digest and byte length. It also classifies the projection as changed or unchanged. That sounds simple, but the distinction matters. A source edit can leave one projection unchanged while altering another. A documentation-level identity change, a capability change, and a runtime-behavior change should not all be flattened into the same “some bytes changed” signal. The target report therefore binds the proposed semantic change to the compiler artifacts it actually affects. Why deterministic output is the prerequisite Evidence over compiler output is only useful when the output is reproducible. SEMAPRAX treats source formatting, semantic graph data, diagnostics, semantic patches, and target artifacts as deterministic projections. The same admitted input must produce the same bytes. Otherwise a digest says little: a second verifier could not distinguish a meaningful change from nondeterministic