The depth of a smart contract audit is determined by several technical and business factors, including:

Contract complexity and size, as larger and more advanced logic requires deeper analysis

Value at risk, meaning contracts handling significant funds demand more rigorous review

Use case and functionality, such as DeFi, IDO launchpads, or governance systems

External integrations, including oracles, third-party protocols, and cross-chain components

Upgradeability and architecture, especially when proxy patterns are involved

Code maturity and documentation quality, which affect audit efficiency and coverage

Regulatory, compliance, and security expectations of stakeholders and investors

A thorough audit depth is chosen to balance risk exposure, project goals, and security requirements, ensuring the contract is safe before deployment.
More to know: https://www.blockchainappfactory.com/smart-contract-audit