certora

Declare contract functions in a methods block, capture state before a call, execute the function with an env argument, then assert the postcondition. Use @withrevert with lastReverted to check revert conditions, and mathint for overflow-free spec arithmetic.

Slither runs fast static analysis for quick vulnerability scans, Foundry fuzzing samples random inputs for property testing, and Certora exhaustively proves properties for all inputs via SMT solving. Use Certora when you need mathematical certainty for critical invariants like token accounting.

A vacuous pass means over-constrained require statements exclude all valid executions, so the assert is never reached. Enable rule_sanity basic or advanced, add a satisfy true reachability check, and remove require statements one at a time to find the conflict.

Yes, the Prover runs on Certora's cloud infrastructure and requires a CERTORAKEY environment variable. Keys are available at certora.com/signup, with free access for academic and open-source projects.

Increase smt_timeout in the config, split complex rules into smaller ones, bound large values with require, and enable optimistic_loop with a loop_iter of 3-5. Running a single rule with --rule also reduces memory pressure.

Include all contracts in the files array, link storage references with the link config option, and declare external contracts in CVL using the using keyword. For unknown external call targets, use DISPATCHER or NONDET summaries in the methods block.