Problem

Since #56954, summary compactions reference their kept messages with metadata.firstKeptMessageID and always write recent: "". The field itself was still part of compaction messages and the session.compaction.started / .ended events, so every API reader, client, and plugin saw an empty string that only meant something for compactions saved before that change.

Change

recent is removed from the public contract: schema, OpenAPI, generated clients, plugins.

 CompactionRunning   { status: "running", reason, summary,
-                      recent }
 CompactionCompleted { status: "completed", reason, model?, native?, summary,
-                      recent,
                       providerContext?, cost?, tokens? }
 session.compaction.started { reason, inputID?
-                             recent }
 session.compaction.ended   { reason, model?, native?, providerContext?, text,
-                             recent,
                              cost?, tokens? }

The kept text that replay needs now lives in the compaction's free-form metadata:

new compaction    metadata.firstKeptMessageID ──► history rebuilds the text into metadata.recent (not stored)
old compaction    stored recent: "text"       ──► read as metadata.recent
                                                     │
                                                     ▼
                                        replay: <recent-context>…</recent-context>

• SessionRecentText.kept(message) is the single reader, used by replay and compaction.
• Where the text shows up: /session/:id/context and request hooks see the rebuilt text as metadata.recent, as they saw it in recent before. The message list shows it only for old compactions. Message metadata is never sent to providers.
• Hooks: a compaction hook's free-form metadata is stored as-is, so a hook that sets metadata.recent without a kept-message reference has that text replayed.
• The V1 importer writes the V1 kept tail to metadata.recent instead of recent.

Old data (@opencode/schema/session-legacy)

• Messages: a stored recent with text moves into metadata.recent on read; an empty one is dropped. This applies to stored rows and imported exports.
• Events: recent is dropped from stored compaction.started / .ended events on read. Nothing reads it: messages, not events, are what replay uses. Replay idempotency compares stored events in their upgraded shape, so old events still match.

Downgrades

Nothing writes recent for older versions; this follows the existing pattern of reading old shapes and never writing them. Versions before v2.1 require recent on compaction messages, so they cannot load a session that has a compaction created by this version. Sessions compacted only before the upgrade are unaffected.

Older clients

An older Effect client, or a pinned plugin or SDK built on it, requires recent when it decodes compaction messages and events. It fails against this server, as with any removed required field. Newer clients against an older server ignore the extra field.

Out of scope

• Native compaction's shape (providerContext, the native written by the summary call but never read).

Verification

• New tests:

  • packages/schema/test/session-legacy.test.ts: old recent text moves into metadata, and empty values and event fields are dropped.
  • packages/core/test/session-compaction.test.ts "summaries written before kept-message references keep their stored recent text": inserts a raw old-shape row. It fails without the legacy read.
  • packages/core/test/session-projector.test.ts and session-runner.test.ts: stored compaction rows and events have no recent.
  • packages/core/test/v1-migration.test.ts: the V1 kept tail lands in metadata.recent, with no recent.
  • packages/core/test/bus.test.ts "replays compaction events stored before v2.1 with recent, reading them without it": an old event with kept text replays idempotently and reads back without recent.
  • packages/server/test/session-import.test.ts: an old export's recent text comes back as metadata.recent.

• Tests:

  Package	Command	Result
  core	bun test	6643 pass, 8 fail (shell and preload tests, also failing on v2.1)
  schema	bun test	86 pass
  cli	bun test	331 pass
  server	bun test	85 pass
  client	bun test	229 pass
  tui	bun test test/cli/tui/data.test.tsx test/cli/tui/session-rows.test.ts test/mini/stream-v2.transport.test.ts	144 pass
  session-ui	bun test	251 pass, 21 fail (same count on v2.1)

• Typecheck: bun typecheck passes in schema, protocol, core, client, cli, server, sdk, tui, plugin, app, and session-ui, apart from errors already on v2.1.

• Generated files: check:generated passes in packages/protocol, packages/client, and services/www.