You are building a customer support resolution agent using the Claude Agent SDK.

Option D separates durable case history from volatile operational data. The new session receives a compact, structured summary describing the billing dispute, the customer’s objective, actions previously taken, and the unresolved status. It does not inherit outdated backend observations as though they were still authoritative. Fresh tool calls then retrieve the current refund or order state before the agent responds.

Agent SDK sessions preserve conversation history, including earlier tool calls and tool results. Resuming the complete transcript therefore reintroduces stale system data into the active context, even though the external backend may have changed substantially during the four-hour gap. Conversation persistence must not be confused with persistence of external-system truth.

Option A performs unnecessary calls to every previously used tool, including tools unrelated to the returning customer’s current question. Option B relies on prompt compliance while retaining contradictory historical evidence in context. Option C manually removes tool results from an existing transcript and may damage the logical relationship between prior tool_use and tool_result blocks while still retaining a long, unstructured conversation.

A structured summary should preserve stable identifiers, previous actions, customer commitments, and unresolved issues. Time-sensitive fields such as refund status, delivery state, account balance, or expected resolution should always be refreshed through authoritative tools.

Official references/topics: Session persistence, stale tool-result management, context compaction, fresh-data retrieval.