Compare rebuilt bytes and explain every difference

Choose the actual release artifacts under examination: a native wheel, an inference executable, a filesystem image, or another explicit payload. Build logs and external signatures may be outside that comparison if the claim says so. Do not quietly exclude a differing executable because its tests pass. Record the source revision, build instructions, target, toolchain, dependencies, and relevant configuration. A comparison across different declared targets can legitimately differ, but then it is not evidence that one fixed target was reconstructed. The scope must be precise enough for another builder to attempt the same reconstruction.

Compare complete specified bytes directly or through an appropriate cryptographic digest with a trusted expected value. Digest equality is practical content-identity evidence under the algorithm's assumptions; a digest copied from the same untrusted download does not independently approve anything. Preserve comparison results and identities alongside the input record. If one output differs, locate its structure and producer before assigning a cause. An archive header, code section, embedded path, or model table points to different next checks. A single aggregate match percentage cannot authorize an unexplained difference in a critical output.

Timestamps, archive ordering, filesystem enumeration, absolute build paths, locale, and random choices can change bytes without an intended source change. A documented timestamp convention such as SOURCE_DATE_EPOCH can help only when the relevant tools actually honor it. Check which generator or packaging stage emitted each variable field. Fix the producing process and rebuild both outputs, rather than merely deleting inconvenient differences after comparison. If normalization is intentionally part of artifact production, make it a versioned build step with a declared scope, so the compared artifact remains the artifact distributed to users.

Reproducible outputs can still be wrong in exactly the same way. A deterministic parser defect or harmful source modification will reproduce if both builders use it. Independent rebuilders offer stronger evidence about correspondence when they do not simply reuse the original output or share every compromised authority. Yet two organizations using the same corrupted compiler can agree perfectly. Separate the question of byte correspondence from source review, toolchain trust, behavioral tests, and isolation. Record the common inputs and trust boundaries instead of calling two matching executions independent just because they ran on different hosts.

An output cache may speed normal development while providing no new reconstruction evidence: returning yesterday's stored artifact will naturally return yesterday's bytes. Force the relevant actions to execute in a controlled fresh environment when testing the reconstruction claim. Check that caches are keyed by complete influencing inputs and that their content integrity and writers are governed. In an AI toolchain, a cached generated kernel can mask an undeclared toolkit dependency. Retain enough logs and input identities to distinguish a genuine rebuild from retrieval, and investigate discrepancies before issuing the release's verification statement.

The cache lab makes reuse visible without pretending to compile software. For each separate run, Reset, set both capacity C and stride s, predict the initial hit and miss counts, then inspect. At C=4, s=4 the sixteen requests repeat four addresses: four misses are followed by twelve hits. At C=2, s=4 none of those requests hit. These are exact results for one empty fully associative LRU cache and its synthetic address stream. They illustrate that successful reuse and freshly executing an action answer different questions; they do not measure a build cache or establish reproducibility.