Errata Replay

The driver says success. The wire disagrees. Errata Replay turns documented chip defects into executable firmware regressions. A test can pass in an ideal emulator while missing a defect described for the developer's chip revision. We connect that prose to a repeatable comparison: nominal behavior, the documented exception, and a vendor workaround. Our main demonstration compiles unmodified, hash-pinned Nordic nrfx v2.11.0 drivers with a small ARM application. In Renode, identical ELF bytes return NRFX_SUCCESS in both the nominal and affected SPIM models, yet an independent simulated SPI target receives one byte versus two. A separate legacy-SPI workaround ELF restores one byte. Direct guest-RAM return-value observations, three boundary controls, and reproducible builds make the result inspectable. Meta's Muse Spark extracts revision/build scope, trigger conditions, effects, remedies, and exact quotations into a typed contract. A separately reviewed gate validates that contract before trusted adapters execute actual Cortex-M4 firmware. The model's answer and the execution observations remain separate evidence. The visual replay pauses at the first recorded divergence and shows the extra byte as unspecified. Evidence bundles retain exact ELF inputs, observations, source/model hashes, and trusted-adapter replay instructions. The local workbench supports document/ARM ELF uploads, queued execution, cancellation, history, and comparisons. Reviewers can explore saved results in a read-only showcase without an API key. The prototype covers three reviewed nRF52832 revision-3 behaviors: extra SPIM bytes, RAM power-status aliasing, and false I2S events after STOP. Its contribution is a revision-scoped errata-to-regression workflow that helps firmware engineers preserve documented exceptions across software changes. It requires no board, and complements later hardware validation. These are behavioral emulation results from synthetic applications using real drivers, not physical-silicon, customer-use, cycle-accuracy, or arbitrary-chip claims. Interactive replay: https://errata.6r33n.kr