Web applications commonly rely on widely deployed defenses such as tokens, headers, andserver-side validation logic to mitigate request forgery, tampering, and replay. While effectiveagainst many threats, these mechanisms primarily establish authenticity and coarse integrity,and do not formally enforce the precise structure and single-use semantic intent of individualstateful actions.This paper introduces AACL, a language-theoretic control framework in which the serverdynamically issues an ephemeral, intent-bound grammar for each sensitive action instance. Eachrequest is treated as a short-lived language instance and validated through formal recognition(e.g., DFA-driven parsing) before execution. Grammars are state-bound and invalidated after useor expiry, enforcing structural conformance and single-use semantics under explicit threat-modelassumptions.We formalize the AACL model, describe its integration into a web application architecture,and present a prototype demonstrating how ephemeral grammars reduce replay and structuralmutation attacks. AACL complements existing authentication and authorization mechanisms byintroducing a state-aware, language-level enforcement layer for web interactions.