ZK: Proving infrastructure & economics

Epic for proving infrastructure and economics — the project's biggest unknown. Covers local/mock proving, fallback prover, token management, and proving metrics.

Start by reading this epic and breaking its four named areas—local/mock proving, fallback proving, token management, and proving metrics—into separate scoped issues. No files, tests, or entry points are identified, and completion criteria are not defined, so the work is not yet ready for a newcomer to begin.

Written by the indexing model from the issue text.