v1.11: opencode-style compaction port

- compaction.ts: usable/isOverflow/estimate/turns/select/buildPrompt/process
- compaction-prompt.ts: SUMMARY_TEMPLATE verbatim from opencode
- schema: messages.{compacted_at,summary,tail_start_id} + chats.needs_compaction
- inference: auto-trigger on overflow, pre-fetch compaction before next turn
- /compact slash command rewired to new path
- WS: chat_status working/idle around compaction + compacted frame
- frontend: SummaryCard + sonner toast on compacted
- 24 unit tests for pure functions

apps/web/src/api/client.ts

@@ -168,8 +168,11 @@ export const api = {
       request<void>(`/api/chats/${chatId}`, { method: 'DELETE' }),
     messages: (chatId: string) =>
       request<Message[]>(`/api/chats/${chatId}/messages`),
+    // v1.11: anchored-rolling compaction. POST awaits the LLM call inside
+    // the route's lifecycle; the new summary row arrives via the 'compacted'
+    // WS frame (useSessionStream refetches + toasts).
     compact: (chatId: string) =>
-      request<{ compact_message_id: string }>(`/api/chats/${chatId}/compact`, { method: 'POST' }),
+      request<{ ok: true }>(`/api/chats/${chatId}/compact`, { method: 'POST' }),
     stop: (chatId: string) =>
       request<{ stopped: boolean }>(`/api/chats/${chatId}/stop`, { method: 'POST' }),
     forceSend: (chatId: string, content: string) =>

apps/web/src/api/types.ts

@@ -145,6 +145,19 @@ export interface Message {
   // v1.8.2: per-message metadata; see MessageMetadata. null for the vast
   // majority of messages.
   metadata: MessageMetadata | null;
+  // v1.11: anchored rolling compaction fields. Optional on the wire so that
+  // older API responses (or test fixtures) parse without explicit nulls.
+  //   summary       — true on the assistant row that holds the active
+  //                   anchored summary. Render via SummaryCard.
+  //   tail_start_id — first preserved tail message the summary covers up to
+  //                   (exclusive). Diagnostic only on the client.
+  //   compacted_at  — set on rows that are "behind the curtain" of the
+  //                   current summary. Returned by the GET endpoint so the
+  //                   UI can show history, but the server-side inference
+  //                   assembly filters these out.
+  summary?: boolean;
+  tail_start_id?: string | null;
+  compacted_at?: string | null;
 }
 
 export interface ModelInfo {
@@ -305,6 +318,11 @@ export type WsFrame =
     }
   | { type: 'messages_deleted'; message_ids: string[]; chat_id?: string }
   | { type: 'chat_renamed'; chat_id: string; name: string }
+  // v1.11: published by services/compaction.ts after the new anchored
+  // summary row lands. Carries the new summary row id for diagnostics; the
+  // session-stream handler ignores the id and re-fetches the full message
+  // list (the cohort of compacted_at-stamped rows changed too).
+  | { type: 'compacted'; session_id: string; chat_id: string; summary_message_id: string }
   // v1.8.2: `reason` discriminates structured failures (the UI prefers it
   // over `error` text when present).
   | { type: 'error'; message_id?: string; chat_id?: string; error: string; reason?: ErrorReason };