StableEdge: Certifying Early Workflow Routes from Structured Agent Streams

Agent workflows increasingly branch on structured model output while bytes are still arriving. At a partial JSON prefix, a route chosen by an ordinary predicate can change under a valid continuation, producing wrong or duplicate workflow dispatch. We formalize safe early admission as completion-invariant routing: a prefix may be acted upon only if every schema-valid completion selects the same ordered route. StableEdge decides this condition by computing a conservative route image over a bounded policy profile with required route discriminators, certifying singleton images, and binding each certificate to a grammar-attested stream contract, a digest-bound commit envelope, a durable ledger, and an idempotent receiver. On 1,616 matched final-valid traces from BFCL v4 and AgentDojo, StableEdge makes exactly one correct admission per trace with zero observed wrong or duplicate dispatches, reaching admission a median 1,340 ms of recorded generation time before the final message and certifying 19.9 percentage points more traces early than a safe closed-field policy. Byte-prefix law audits, trust negative controls, crash and concurrency conditions, a structural grid, and three native runtimes locate when this gain is available and when it collapses.