[FEATURE] OpenAI Responses server-side compaction #5409

Human Overview

Server-side compaction through OpenAI's API.

SDK Language

Both / Not language-specific

Problem Statement

The OpenAI Responses API compacts server-side and returns an encrypted item with no readable summary. Strands' summarization on that model runs client-side only.

Proposed Solution

Implement compact() for the OpenAI Responses model. Decide whether CompactionBlock can carry both providers' output (0022 open question "Is CompactionBlock provider-neutral?"), and extend #5402 to drop a block with no readable content when switching providers.

Use Case

An agent on an OpenAI reasoning model summarizes without losing its encrypted reasoning.

Additional Context

• Depends on: [FEATURE] Summarize through Anthropic native compaction #5401, [FEATURE] Core: providerData on TextBlock for session restore and model switches #5402
• Design: team/designs/0022-server-side-compaction-support.md (docs(designs): server-side compaction support #5242)