plamentsv/external-precondition-audit

EXTERNAL_PRECONDITION_AUDIT Skill

Trigger Pattern: Any external contract interaction detected in attack_surface.md Inject Into: Breadth agents (merged via M7 hierarchy) Constraint: Interface-level inference only -- no production fetch required

For every external contract the protocol interacts with:

1. Interface-Level Requirement Inference

From the interface/import used by the protocol, infer what the external contract requires:

| External Function Called | Parameters Passed | Likely Preconditions (from interface) | Our Protocol Validates? | |-------------------------|-------------------|---------------------------------------|------------------------|

Inference method: Read the function signature, parameter names, NatSpec comments (if any), and common patterns for that function type. Example: IVault.swap(FundManagement memory funds) -> infer that funds.sender must be authorized, funds.recipient determines where output goes.

2. Return Value Consumption

| External Call | Return Type | How Protocol Uses Return | Failure Mode if Return Unexpected | |--------------|-------------|-------------------------|----------------------------------|

For each return value: what happens if it returns 0? What happens if it returns MAX? What happens if the external call reverts?

• For each external data structure received (Vec, array, Map, list): (a) What ordering/uniqueness does the consuming code assume? (b) Does the external contract's spec guarantee that ordering? (c) What happens if the assumption is violated (unsorted, duplicates, gaps)?

3. State Dependency Mapping

| Protocol State | Depends on External State | External State Can Change Without Our Knowledge? | |---------------|--------------------------|--------------------------------------------------|

For each dependency: model what happens when the external state changes between our protocol's read and use.

Step Execution Checklist

| Section | Required | Completed? | |---------|----------|------------| | 1. Interface-Level Requirement Inference | YES | Y/N/? | | 2. Return Value Consumption | YES | Y/N/? | | 3. State Dependency Mapping | YES | Y/N/? |