deepseek-harness/docs/rfc/proposed/2026-06-20-drop-acp-session-load.md

RFC: Drop ACP session/load until resume has a product shape

Status: proposed

Problem

ACP advertises loadSession: true and implements session/load by injecting persistence into the bridge, validating cwd against stored metadata, reconstructing an agent from the persisted log, and replaying prior transcript updates to the client. That path has its own race handling, loading-id guard, replay presenter logic, and tests. It also depends on the canonical log retaining enough UI data to reconstruct old chunks and tool presentations.

Durable persistence remains foundational, but editor-visible resume is not yet a designed product flow. There is no session picker, no title/preview metadata, and no clear UX for failed or partial loads. The bridge is paying complexity for a feature that is mostly exercised by tests and documentation.

Proposal

For now, ACP starts fresh sessions only. initialize advertises loadSession: false or omits the capability, and session/load is unsupported. Persistence remains available to the agent loop and tests; resume can still exist as a lower-level factory if another consumer needs it. The editor bridge should reintroduce session/load alongside a real session-selection UX and a stable load transcript contract.

Acceptance criteria

• ACP no longer injects sessionPersistence solely for session/load.
• initialize does not advertise load support.
• The session/load handler, loading-id tracking, cwd preflight for loaded sessions, and load replay tests are removed.
• Snapshot fixtures no longer rely on load replay presentation.
• ACP docs describe fresh-session support only.

What we give up

An editor cannot reopen a prior persisted session through ACP. That is a real product feature, but the current implementation is ahead of the UX and ties the bridge to token-level log replay. Keeping persistence while dropping editor load narrows the bridge to the workflow it can currently present cleanly.