Hardhat error HH602: Artifacts not found after restoring backup without cache

Answer

Hardhat v2.12+ does not automatically trigger a clean compilation when it encounters HH602 “Artifacts not found” after restoring only the artifacts directory. The compiler errors on the missing artifact and leaves the rebuild decision to the user; an explicit hardhat compile (or a task that invokes compilation) is required to regenerate the artifacts and restore consistency.

Confirmed facts

• HH602 is thrown when Hardhat tries to load an artifact JSON that is absent from disk; it does not create or silently regenerate the file.
• The cache directory holds incremental compilation metadata. Without it, the next explicit hardhat compile performs a full rebuild, but compilation is not started automatically on an artifact‑lookup failure.
• Restoring artifacts without cache leaves the build state inconsistent, so the error can appear even when source contracts are unchanged.

Likely explanation

When the backup restores only the artifacts folder, the incremental metadata that tells Hardhat which source files correspond to which artifacts is missing. Before any compile task runs, Hardhat attempts to resolve an artifact (e.g., during a test, deploy script, or hardhat run) and finds the file missing, raising HH602. Because the compiler does not treat a missing artifact as a signal to rebuild, the user must intervene.

Recovery steps for this case

1. Ensure no further commands that rely on the missing artifact are executed until consistency is restored.
2. Remove both the artifacts and cache directories to guarantee a clean state:

rm -rf artifacts cache\nnpx hardhat compile

1. Verify that the previously failing command now succeeds.

Verification

• After recompiling, check that cache/solidity-build-info contains build‑info files matching the newly generated artifacts.
• Re‑run the command that originally produced HH602 (e.g., npx hardhat test) and confirm the error disappears.

Assumptions and uncertainty

Behavior can vary with plugins that maintain their own artifact references (e.g., hardhat-deploy, ethers plugin). In such cases HH602 may surface at different points, but the underlying requirement—manual rebuild—remains the same. Hardhat versions beyond v2.12 may adjust error handling; the described behavior holds for the documented v2.12+ range.

One diagnostic that could change the recommendation: identify whether HH602 is thrown during an explicit hardhat compile call or only during artifact access in another task (tests, scripts, hardhat run). If the error occurs during compile itself, please share the exact compile output; otherwise the clean‑rebuild steps above are sufficient.