feat(timeline): apply conversation rewinds without replacing history

Rewinding a prompt used to rotate the timeline epoch, so every open
client refetched and remounted the whole chat. A rewind is now a
retirement: the daemon keeps the rewound turn stored but outside the
conversation, and capable clients remove the rows that started in
[retireFromSeq, seq) in place. Catch-up pages carry the retirements in
their span. Clients without the timeline_rewind_operations capability
get the old replacement shape.

The daemon retires only what the provider actually removed. Providers
report the boundary they kept. A failure known to change nothing keeps
the conversation. Any other failure leaves the rewind open and refuses
prompts until reloading the agent proves the outcome from the
provider's replayed prompts. A recorded cut whose save failed is
committed by the next prompt or the reload, which resumes the rewound
session.

Plugin providers complete session.revert without saying what they
removed. Paseo then reloads the session itself and judges the outcome
from the replay, so a no-op completion is not taken as a cut.

The app anchors each row at the seq it started at, because a late
update moves a row's latest seq into the rewound range. The app also
refuses pages served before the newest retirement it has seen, then
refetches them.

Known limits:
- The automatic plugin settle shows the agent as restoring briefly.
- An empty or mismatched plugin replay leaves the rewind unresolved.
  Fork the chat to recover.
- A plugin's failed revert still needs a manual reload.
- An open rewind lives in memory, so a daemon restart drops it.

packages/client/src/connection.test.ts

@@ -209,6 +209,37 @@ test("SDK subscribers receive timeline replacement instead of silently losing hi
   }
 });
 
+test("SDK subscribers receive a conversation rewind as a retired range", async () => {
+  const { createPaseoApi } = await import("./index");
+  const h = connection();
+  const received: unknown[] = [];
+  try {
+    const ready = h.client.connect();
+    h.open();
+    await ready;
+    const off = createPaseoApi(h.client)
+      .agents.ref("agent")
+      .timeline.subscribe((event) => received.push(event));
+    await off.ready;
+    h.receive({
+      type: "agent.timeline.rewind",
+      payload: {
+        agentId: "agent",
+        epoch: "epoch-1",
+        seq: 12,
+        retireFromSeq: 7,
+        subscriptionId: off.subscriptionId,
+      },
+    });
+    expect(received).toEqual([
+      { agentId: "agent", event: { type: "rewind", epoch: "epoch-1", seq: 12, retireFromSeq: 7 } },
+    ]);
+    off();
+  } finally {
+    await h.client.close();
+  }
+});
+
 test("local listeners create no demand before or after reconnect", async () => {
   const h = connection();
   try {

packages/client/src/connection/index.ts

@@ -140,6 +140,7 @@ export const DEFAULT_CLIENT_CAPABILITIES = {
   [CLIENT_CAPS.compactProviderSnapshots]: true,
   [CLIENT_CAPS.providerSnapshotReferences]: true,
   [CLIENT_CAPS.timelineReplacementInvalidation]: true,
+  [CLIENT_CAPS.timelineRewindOperations]: true,
   [CLIENT_CAPS.timelineNotifications]: true,
   [CLIENT_CAPS.pluginTimelineItems]: true,
   [CLIENT_CAPS.workspaceSetupBlocked]: true,

packages/client/src/connection/legacy.ts

@@ -246,7 +246,9 @@ export class LegacySubscriptions {
         );
       case "agent.timeline.set_subscription.request":
         return (
-          (message.type === "agent_stream" || message.type === "agent.timeline.replacement") &&
+          (message.type === "agent_stream" ||
+            message.type === "agent.timeline.replacement" ||
+            message.type === "agent.timeline.rewind") &&
           (query.agentIds as string[]).includes(message.payload.agentId)
         );
       case "session.events.set_subscription.request":

packages/client/src/index.ts

@@ -317,6 +317,14 @@ export type PaseoAgentTimelineEvent =
       agentId: string;
       event: { type: "replacement"; epoch: string };
     }
+  | {
+      /**
+       * A conversation rewind removed the rows anchored in `[retireFromSeq, seq)` from the active
+       * history. Rows after `seq` belong to the rewound conversation.
+       */
+      agentId: string;
+      event: { type: "rewind"; epoch: string; seq: number; retireFromSeq: number };
+    }
   | {
       agentId: string;
       subscriptionId: string;
@@ -338,7 +346,9 @@ export interface PaseoAgentTimelineHandle {
    * Delivers live events only. After reconnect, subscription_restored precedes
    * subsequent updates. History may have been missed; use refetch() to request
    * the range you need. No history is fetched automatically. A replacement event
-   * invalidates the previous epoch. Subscription errors release this observation.
+   * invalidates the previous epoch. A rewind event removes `[retireFromSeq, seq)`
+   * from the active history without changing the epoch. Subscription errors
+   * release this observation.
    * Await the returned unsubscribe function's `ready` promise before starting
    * work that must be observed. It rejects if establishment fails.
    */
@@ -942,6 +952,16 @@ function createAgentHandleFactory(
                   agentId: id,
                   event: { type: "replacement", epoch: message.payload.epoch },
                 });
+              case "agent.timeline.rewind":
+                return handler({
+                  agentId: id,
+                  event: {
+                    type: "rewind",
+                    epoch: message.payload.epoch,
+                    seq: message.payload.seq,
+                    retireFromSeq: message.payload.retireFromSeq,
+                  },
+                });
             }
           }),
       },

packages/client/src/timeline-subscription/index.ts

@@ -3,7 +3,7 @@ import type { OwnedSubscription, TimelineSubscription } from "../connection/inde
 
 type TimelineUpdate = Extract<
   SessionOutboundMessage,
-  { type: "agent_stream" | "agent.timeline.replacement" }
+  { type: "agent_stream" | "agent.timeline.replacement" | "agent.timeline.rewind" }
 >;
 
 /** Local SDK lifecycle messages; these are not additional wire RPCs. */
@@ -59,7 +59,11 @@ export function subscribeTimeline(
       });
     },
     update: (message) => {
-      if (message.type === "agent_stream" || message.type === "agent.timeline.replacement")
+      if (
+        message.type === "agent_stream" ||
+        message.type === "agent.timeline.replacement" ||
+        message.type === "agent.timeline.rewind"
+      )
         notify(message);
     },
     error: fail,