audit-contract-drift

name	audit-contract-drift
description	Find places where documented API contracts and the implementation diverge
context	fork
agent	auditor
disable-model-invocation	true

Most audits read code; this one reads documentation first and then traces each promise to every implementation path that should honor it. The bugs caught here are not concurrency or arithmetic defects — they are quiet contradictions between what the javadoc promises and what the code does.

Build a list of behavioral promises from public API docs, then trace each one to every code path that should honor it.

Sources of contracts to enumerate:

• Caffeine.java — every <b>Note:</b> and <b>Warning:</b> block in a builder method's javadoc. Pay particular attention to:
  • weakKeys, weakValues, softValues — equality semantics flip to identity (==) for the configured strength
  • expireAfter*, refreshAfterWrite — duration constraints, what "expired" means at boundaries
  • maximumSize, maximumWeight — eviction triggering and amortization
  • removalListener, evictionListener — when and how notifications fire
• Cache.java, LoadingCache.java, AsyncCache.java, AsyncLoadingCache.java — javadoc of every method, especially "must", "will", "guarantees", "for any reason" language.
• Policy.java — every method's documented behavior.
• Weigher.java, Expiry.java, RemovalListener.java, RemovalCause.java — user-facing contracts referenced by the cache.

For each contract, record the exact wording, the configurations that activate it, and the set of operations affected.

Then trace each promise through every code path that should honor it:

• Direct API calls on Cache / LoadingCache / AsyncCache
• asMap() view methods (size, isEmpty, containsKey, containsValue, get, put, remove(k), remove(k,v), replace, compute*, merge, equals, hashCode)
• asMap().keySet() / values() / entrySet() — contains, remove, removeAll, retainAll, removeIf, iterator, spliterator
• Bulk operations (putAll, getAll, getAllPresent, invalidateAll)
• AsyncCache.synchronous() round-trip — does the sync view honor the same contract as the async cache?
• Serialization round-trip — does the deserialized cache honor the same promises about expiration durations, loader presence, etc.?

A path that uses a different equivalence, ordering, or visibility from what the contract promises is a contract drift finding. So is a path that silently downgrades a configuration on round-trip.

Common drift patterns to check explicitly:

• Identity vs. equals on weak/soft caches: weakKeys/weakValues/ softValues promise identity, but view collections that use o.equals(value) or Collection.contains(value) may apply the user's equality semantics instead.
• Cardinality vs. presence asymmetry: methods documented as treating in-flight async values as absent must align with size, isEmpty, equals, hashCode, and iterators on the same view.
• Notification "for any reason": removalListener documented to fire for any cause, but async paths may drop notifications for null or exceptional completions.
• Cross-version serialization: serialized fields renamed or defaulted differently across versions can silently lose configuration or throw on round-trip.
• Same-instance return semantics: e.g., compute(k, (k,v) -> v) is documented one way but updates timestamps/weight regardless.
• size() documented as estimate: this is an explicit out — verify it is actually documented as an estimate everywhere it diverges from logical presence.
• Synchronous vs. asynchronous view divergence: the synchronous() view's asMap() may treat in-flight entries inconsistently across query, mutation, and cardinality methods.

Each finding should anchor both sides of the drift — the source of the contract (file + javadoc snippet) and the divergent implementation (file + method) — and include a minimal user-observable scenario where the docs and the code disagree.