Agentic Travel Transaction Safety

AI agents can re-plan, retry tools or invoke the same intent through different execution paths. Agentic transaction safety therefore depends on idempotency plus explicit side-effect guards.

Side-effect boundary

Separate read tools such as search/retrieve/quote/status from write tools such as book/capture/cancel/refund/exchange/modify. Write tools require stronger guards.

Idempotency key

Use purchaseIntentId + operation + version. Persist it across agent retries and map it to provider-native idempotency where available.

Agent retry rule

A tool error must not automatically trigger another write. Treat authoritative failure differently from UNKNOWN outcome; reconcile UNKNOWN before repeating side effects.

Duplicate transaction prevention

Use persistent idempotency, unique constraints, provider-key mapping, one active attempt, UNKNOWN retry blocking, request hashes and audited manual overrides.

Payment/booking separation

Do not let the agent translate "payment captured" into "trip booked". Transaction completion requires the relevant booking, payment and document states to agree.

Replacement booking guard

When the first booking remains UNKNOWN, require authoritative lookup, a human checkpoint, explicit duplicate-risk handling and a new purchase intent/version before creating a replacement.

Tool contract

Write tool responses should include operationId, status, terminal flag, provider reference, retrySafe and reconciliationRequired.

Failure modes

Duplicate LLM tool calls, orchestration retries after timeout, lost success responses, provider success with failed local persistence, payment/booking divergence and replayed plans using stale authorization.

Observability

Track blocked duplicate side effects, UNKNOWN write attempts, repeated tool calls, idempotency conflicts, reconciliation-required outcomes and plan replays.

Production checklist

Classify read/write tools, persist idempotency, make retries UNKNOWN-aware, return terminal metadata, expose reconciliation tools, separate payment/booking state, require HITL for replacements and audit every write attempt.