feat(conversations,api,ui): rewind takes the last turns of a thread back, the cut session stays in the store

src/beaver_gateway/backends/transcript.py

@@ -20,13 +20,14 @@ except ImportError:  # pragma: no cover
     _cli_version = "2.1.248"
 
 if TYPE_CHECKING:
-    from collections.abc import Iterable
+    from collections.abc import Iterable, Sequence
 
 __all__ = [
     "CLI_VERSION",
     "build_entries",
     "close_open_tool_uses",
     "fingerprint",
+    "last_message_before",
     "messages_from_entries",
     "open_tool_uses",
     "prompt_count",
@@ -35,6 +36,7 @@ __all__ = [
     "spoken_text",
     "strip_tool_entries",
     "text_of",
+    "turn_starts",
     "window_entries",
 ]
 
@@ -438,6 +440,33 @@ def prompt_count(entries: Iterable[Mapping[str, Any]]) -> int:
     return sum(1 for e in entries if _is_prompt_entry(e))
 
 
+def turn_starts(entries: Iterable[Mapping[str, Any]]) -> list[int]:
+    """Where each turn opens: the index of every prompt the SDK was handed.
+
+    The CLI stamps only those with ``promptSource``; what it writes as a
+    user on its own (an interruption note, a skill body) stays inside the
+    turn it belongs to.
+    """
+    return [
+        index
+        for index, entry in enumerate(entries)
+        if entry.get("promptSource") and _is_prompt_entry(entry)
+    ]
+
+
+def last_message_before(entries: Sequence[Mapping[str, Any]], index: int) -> str | None:
+    """Uuid of the last ``user``/``assistant`` entry ahead of ``index``."""
+    for entry in reversed(entries[:index]):
+        uuid = entry.get("uuid")
+        if (
+            entry.get("type") in _PROMPT_TYPES
+            and isinstance(uuid, str)
+            and not entry.get("isSidechain")
+        ):
+            return uuid
+    return None
+
+
 def spoken_text(block: Any, *, thinking_is_progress: bool) -> str:
     """What a content block (dict or model) says to the human.
 

src/beaver_gateway/conversations/questions.py

@@ -7,7 +7,7 @@ import contextlib
 from typing import TYPE_CHECKING, Any, cast
 from uuid import uuid4
 
-from beaver_gateway.conversations.spawning import Spawning
+from beaver_gateway.conversations.rewinding import Rewinding
 from beaver_gateway.conversations.state import Question
 
 if TYPE_CHECKING:
@@ -16,7 +16,7 @@ if TYPE_CHECKING:
 __all__ = ["Questions"]
 
 
-class Questions(Spawning):
+class Questions(Rewinding):
     async def ask(self, key: str, payload: dict[str, Any]) -> str | None:
         """Show the question and wait; ``None`` when nobody answered in time."""
         conv = await self.get(key)

src/beaver_gateway/conversations/rewinding.py

@@ -0,0 +1,114 @@
+"""Taking turns back: the thread moves to a fork that ends before them."""
+
+from __future__ import annotations
+
+import logging
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any, cast
+
+from claude_agent_sdk import fork_session_via_store
+
+from beaver_gateway.backends.transcript import (
+    last_message_before,
+    messages_from_entries,
+    reply_text,
+    text_of,
+    turn_starts,
+)
+from beaver_gateway.conversations.spawning import Spawning
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+
+    from beaver_gateway.storage.models import Conversation
+
+__all__ = ["Rewinding", "Rewound"]
+
+_log = logging.getLogger(__name__)
+
+PREVIEW = 280
+
+
+@dataclass(frozen=True, slots=True)
+class Rewound:
+    conversation: Conversation
+    turns: int
+    previous_session: str
+
+
+class Rewinding(Spawning):
+    async def turns(
+        self, conv: Conversation, *, limit: int = 10
+    ) -> list[dict[str, Any]]:
+        """The latest turns that can be taken back, oldest first; the first stays."""
+        entries = await self.entries(conv)
+        starts = turn_starts(entries)
+        ends = [*starts[1:], len(entries)]
+        spans = list(zip(starts, ends, strict=True))[1:]
+        agent = self._agents.get(conv.agent_name)
+        progress = agent is not None and agent.thinking_is_progress
+        return [
+            self._turn(entries[start:end], thinking_is_progress=progress)
+            for start, end in spans[-limit:]
+        ]
+
+    def _turn(
+        self, entries: Sequence[Any], *, thinking_is_progress: bool
+    ) -> dict[str, Any]:
+        prompt, *rest = messages_from_entries(entries)
+        replies = (
+            reply_text(m["content"], thinking_is_progress=thinking_is_progress)
+            for m in reversed(rest)
+            if m["role"] == "assistant"
+        )
+        return {
+            "id": entries[0].get("uuid"),
+            "ts": entries[0].get("timestamp"),
+            "text": text_of(self._unwrapped(prompt)["content"])[:PREVIEW],
+            "reply": next((text for text in replies if text), "")[:PREVIEW],
+            "failed": any(e.get("isApiErrorMessage") for e in entries),
+        }
+
+    async def rewind(self, conv: Conversation, turn: str) -> Rewound:
+        """Take ``turn`` and every turn after it out of what the model sees.
+
+        Nothing is deleted: the conversation moves to a fork of its session
+        that ends on the message before ``turn``, the cut session stays in
+        the store under its old id.
+        """
+        row_id = cast("int", conv.id)
+        runner = self._runner(row_id)
+        if runner.lock.locked():
+            msg = f"conversation {conv.external_id} is mid-turn; interrupt it first"
+            raise RuntimeError(msg)
+        async with runner.lock:
+            row = await self.get_row(row_id) or conv
+            entries = await self.entries(row)
+            starts = turn_starts(entries)
+            cut = next((i for i in starts[1:] if entries[i].get("uuid") == turn), None)
+            keep = last_message_before(entries, cut) if cut is not None else None
+            if cut is None or keep is None:
+                msg = f"conversation {row.external_id} has no turn {turn} to take back"
+                raise LookupError(msg)
+            previous = cast("str", row.session_id)
+            forked = await fork_session_via_store(
+                self._store,
+                previous,
+                directory=str(self._claude_agent(row.agent_name).cwd),
+                up_to_message_id=keep,
+            )
+            await self._backend(row.agent_name).close(row.external_id)
+
+            async def apply(moved: Conversation) -> None:
+                moved.session_id = forked.session_id
+
+            row = await self._update(row, apply)
+        turns = sum(1 for start in starts if start >= cut)
+        _log.info(
+            "rewound %s by %d turns: session %s -> %s",
+            row.external_id,
+            turns,
+            previous,
+            forked.session_id,
+        )
+        return Rewound(conversation=row, turns=turns, previous_session=previous)

src/beaver_gateway/conversations/service.py

@@ -1,7 +1,7 @@
 """``Conversations`` - the service every frontend, job and gateway tool talks to.
 
 Built as layers, one file each: rows → seeds → turns → messaging →
-spawning → questions → closing; this file adds start, stop and restart
+spawning → rewinding → questions → closing; this file adds start, stop and restart
 recovery. A turn started by a user message streams back to whoever asked;
 a turn started by an inject streams nowhere and can only speak via ``say``.
 """

src/beaver_gateway/conversations/turns.py

@@ -68,14 +68,14 @@ class Turns(Seeds):
         backend = self._backend(conv.agent_name)
         turn_id = turn_id or f"turn_{uuid4().hex[:12]}"
         capture = capture or TurnCapture()
-        resume = session_id if session_id is not None else conv.session_id
         async with runner.lock:
             runner.turn_id = turn_id
             runner.origin = origin
             runner.text = shown if shown is not None else _prompt_preview(messages)
             runner.started_at = datetime.now(UTC)
             runner.tools = {}
-            await self._mark_running(conv, turn_id)
+            row = await self._mark_running(conv, turn_id)
+            resume = session_id if session_id is not None else row.session_id
             before = await self.before_turn(conv)
             self._bus.publish(
                 "turn.start",
@@ -463,12 +463,12 @@ class Turns(Seeds):
         except Exception:  # noqa: BLE001
             _log.exception("rate limit write failed")
 
-    async def _mark_running(self, conv: Conversation, turn_id: str) -> None:
+    async def _mark_running(self, conv: Conversation, turn_id: str) -> Conversation:
         async def apply(row: Conversation) -> None:
             row.running_turn = turn_id
             row.last_activity_at = datetime.now(UTC)
 
-        await self._update(conv, apply)
+        return await self._update(conv, apply)
 
     async def _mark_done(
         self, conv: Conversation, capture: TurnCapture, *, cut: bool = False

src/beaver_gateway/frontends/api/frontend.py

@@ -79,6 +79,8 @@ MEMORY_MAX_ENTRIES = 5000
 SEARCH_MIN = 2
 GRAPH_LIMIT = 120
 SEARCH_LIMIT = 20
+TURNS_LIMIT = 10
+TURNS_MAX = 50
 SNIPPET_MAX = 160
 
 
@@ -578,6 +580,42 @@ def build_app(  # noqa: PLR0915
             "text": result.text,
         }
 
+    @app.get("/conversations/{public_id}/turns")
+    async def get_turns(public_id: str, request: Request) -> dict[str, Any]:
+        await require_token(request, runtime, scope=SCOPE)
+        conv = await conv_of(public_id)
+        limit = min(query_int(request, "limit", TURNS_LIMIT), TURNS_MAX)
+        return {
+            "id": conv.external_id,
+            "turns": await conversations.turns(conv, limit=limit),
+        }
+
+    @app.post("/conversations/{public_id}/rewind")
+    async def post_rewind(public_id: str, request: Request) -> dict[str, Any]:
+        token = await require_token(request, runtime, scope=ADMIN_SCOPE)
+        conv = await conv_of(public_id)
+        turn = text_of(await body_of(request), "turn")
+        try:
+            result = await conversations.rewind(conv, turn)
+        except LookupError as exc:
+            raise HTTPException(status.HTTP_404_NOT_FOUND, str(exc)) from exc
+        except RuntimeError as exc:
+            raise HTTPException(status.HTTP_409_CONFLICT, str(exc)) from exc
+        out = {
+            "turns": result.turns,
+            "session_id": result.conversation.session_id,
+            "previous_session": result.previous_session,
+        }
+        await audit.log(
+            runtime,
+            actor=f"token:{token}",
+            kind="api_rewind",
+            agent_name=conv.agent_name,
+            conversation=conv.external_id,
+            **out,
+        )
+        return {"id": conv.external_id, **out}
+
     @app.post("/conversations/{public_id}/bind")
     async def post_bind(public_id: str, request: Request) -> dict[str, Any]:
         await require_token(request, runtime, scope=SCOPE)

tests/test_api.py

@@ -16,7 +16,7 @@ from claude_agent_sdk import (
     UserMessage,
 )
 from httpx import ASGITransport, AsyncClient
-from test_conversations import ScriptedClient, World
+from test_conversations import ScriptedClient, World, _three_turns
 
 from beaver_gateway.frontends.markdown.history import rewrite_messages
 from beaver_gateway.security.auth import TokenStore
@@ -444,6 +444,52 @@ async def test_sessions_show_their_processes_and_take_orders(world: World) -> No
     assert kinds == ["session_interrupt", "session_close"]
 
 
+async def test_rewind_lists_turns_and_needs_admin_scope(world: World) -> None:
+    api = Api(world)
+    api.store.grant("api-only", "weak", scope="api")
+    weak = {"Authorization": "Bearer weak"}
+    sid, entries = await _three_turns(world)
+    conv = await world.conversations.create(
+        kind="master", agent="a", origin="test", session_id=sid
+    )
+    path = f"/conversations/{conv.external_id}"
+
+    listed = (await api.http.get(f"{path}/turns", headers=weak)).json()
+    assert [t["text"] for t in listed["turns"]] == ["two", "three"]
+    assert (await api.get(f"{path}/turns", {"limit": 1}))["turns"] == [
+        listed["turns"][1]
+    ]
+    body = {"turn": listed["turns"][0]["id"]}
+    denied = await api.http.post(f"{path}/rewind", json=body, headers=weak)
+    assert denied.status_code == 403
+    missing = await api.http.post(
+        f"{path}/rewind", json={"turn": entries[0]["uuid"]}, headers=HEADERS
+    )
+    assert missing.status_code == 404
+
+    done = await api.http.post(f"{path}/rewind", json=body, headers=HEADERS)
+    assert done.status_code == 200, done.text
+    out = done.json()
+    assert out["turns"] == 2 and out["previous_session"] == sid
+    assert (await api.get(path))["session_id"] == out["session_id"] != sid
+    assert (await api.get(f"{path}/turns"))["turns"] == []
+    messages = (await api.get(f"{path}/history"))["messages"]
+    assert [m["content"] for m in messages] == [
+        "one",
+        [{"type": "text", "text": "done one"}],
+    ]
+    (record,) = (await api.get("/audit"))["records"]
+    assert record["kind"] == "api_rewind"
+    assert record["detail"]["previous_session"] == sid
+
+    ScriptedClient.hold = asyncio.Event()
+    await world.conversations.post(conv, "busy")
+    await asyncio.sleep(0.2)
+    busy = await api.http.post(f"{path}/rewind", json=body, headers=HEADERS)
+    assert busy.status_code == 409
+    ScriptedClient.hold.set()
+
+
 async def test_tokens_and_audit_need_admin_scope(world: World) -> None:
     api = Api(world)
     api.store.grant("api-only", "weak", scope="api")

tests/test_conversations.py

@@ -504,6 +504,105 @@ async def test_copy_seed_forks_parent_with_window(world: World) -> None:
     assert (await world.conversations.get(child.external_id)).flags["seed"] is None
 
 
+async def _three_turns(world: World) -> tuple[str, list[dict[str, Any]]]:
+    sid = str(uuid.uuid4())
+    history = [
+        {"role": "user", "content": "one"},
+        {"role": "assistant", "content": "done one"},
+        {"role": "user", "content": "two"},
+        {
+            "role": "assistant",
+            "content": [{"type": "tool_use", "id": "t1", "name": "Read", "input": {}}],
+        },
+        {
+            "role": "user",
+            "content": [{"type": "tool_result", "tool_use_id": "t1", "content": "x"}],
+        },
+        {"role": "assistant", "content": "done two"},
+        {"role": "user", "content": "three"},
+        {"role": "assistant", "content": "refused"},
+    ]
+    entries = build_entries(history, session_id=sid, cwd=str(world.root), model="m")
+    entries[-1]["isApiErrorMessage"] = True
+    note = {
+        **entries[2],
+        "uuid": str(uuid.uuid4()),
+        "message": {
+            "role": "user",
+            "content": [{"type": "text", "text": "[Request interrupted by user]"}],
+        },
+    }
+    del note["promptSource"]
+    entries.insert(6, note)
+    await world.store.append(world.key(sid), entries)
+    return sid, entries
+
+
+async def test_rewind_moves_the_thread_to_a_fork_that_ends_before_the_turn(
+    world: World,
+) -> None:
+    sid, entries = await _three_turns(world)
+    conv = await world.conversations.create(
+        kind="master", agent="a", origin="test", session_id=sid
+    )
+    await world.conversations.post(conv, "live")
+    await world.settle(conv, 1)
+    assert world.pool.get(conv.external_id) is not None
+
+    turns = await world.conversations.turns(conv)
+    assert [(t["text"], t["reply"], t["failed"]) for t in turns] == [
+        ("two", "done two", False),
+        ("three", "refused", True),
+    ]
+    assert [t["id"] for t in turns] == [entries[2]["uuid"], entries[7]["uuid"]]
+
+    result = await world.conversations.rewind(conv, turns[1]["id"])
+
+    assert result.turns == 1 and result.previous_session == sid
+    moved = result.conversation.session_id
+    assert moved != sid
+    assert (await world.conversations.get(conv.external_id)).session_id == moved
+    assert await world.store.load(world.key(sid)) == entries
+    kept = [
+        e["message"]["content"]
+        for e in await world.store.load(world.key(moved))
+        if e["type"] in ("user", "assistant")
+    ]
+    assert len(kept) == 7 and kept[0] == "one"
+    assert kept[-1] == [{"type": "text", "text": "[Request interrupted by user]"}]
+    assert world.pool.get(conv.external_id) is None
+
+    await world.conversations.run_text_turn(conv, "after", origin="user")
+    assert conv.session_id == sid
+    assert ScriptedClient.instances[-1].options.resume == moved
+
+    (two,) = await world.conversations.turns(result.conversation)
+    assert two["text"] == "two"
+    again = await world.conversations.rewind(conv, two["id"])
+    assert again.turns == 1 and again.previous_session == moved
+    assert await world.conversations.turns(again.conversation) == []
+    first = (await world.store.load(world.key(again.conversation.session_id)))[0]
+    with pytest.raises(LookupError):
+        await world.conversations.rewind(conv, first["uuid"])
+    with pytest.raises(LookupError):
+        await world.conversations.rewind(conv, str(uuid.uuid4()))
+
+
+async def test_rewind_waits_for_no_turn(world: World) -> None:
+    sid, entries = await _three_turns(world)
+    conv = await world.conversations.create(
+        kind="master", agent="a", origin="test", session_id=sid
+    )
+    ScriptedClient.hold = asyncio.Event()
+    await world.conversations.post(conv, "busy")
+    await asyncio.sleep(0.2)
+    with pytest.raises(RuntimeError, match="mid-turn"):
+        await world.conversations.rewind(conv, entries[7]["uuid"])
+    ScriptedClient.hold.set()
+    await world.settle(conv, 1)
+    assert (await world.conversations.get(conv.external_id)).session_id == sid
+
+
 async def test_merge_injects_summary_into_parent(world: World) -> None:
     sid = str(uuid.uuid4())
     await world.store.append(

ui/src/lib/api/client.ts

@@ -16,6 +16,7 @@ import type {
   SearchResponse,
   SessionsResponse,
   TokenRow,
+  TurnSummary,
   UsageGroup,
   UsageResponse,
   VaultGraph,
@@ -187,6 +188,14 @@ export class ApiClient {
     return this.get(`/api/conversations/${id}/history`);
   }
 
+  turns(id: string, limit: number): Promise<{ turns: TurnSummary[] }> {
+    return this.get(`/api/conversations/${id}/turns`, { limit });
+  }
+
+  rewind(id: string, turn: string): Promise<{ turns: number }> {
+    return this.post(`/api/conversations/${id}/rewind`, { turn });
+  }
+
   context(id: string, prompt = false): Promise<ContextResponse> {
     return this.get(`/api/conversations/${id}/context`, {
       prompt: prompt ? 1 : undefined,

ui/src/lib/api/types.ts

@@ -113,6 +113,14 @@ export interface HistoryMessage {
   ts?: string | null;
 }
 
+export interface TurnSummary {
+  failed: boolean;
+  id: string;
+  reply: string;
+  text: string;
+  ts: string | null;
+}
+
 export interface EntriesPage {
   entries: Record<string, unknown>[];
   id: string;

ui/src/lib/format.ts

@@ -109,6 +109,13 @@ export function fmtTime(iso: string | null | undefined): string {
     : "–";
 }
 
+export function fmtMinute(iso: string | null | undefined): string {
+  const date = parseDate(iso);
+  return date
+    ? date.toLocaleTimeString(undefined, { hour: "2-digit", minute: "2-digit" })
+    : "–";
+}
+
 export function fmtDateTime(iso: string | null | undefined): string {
   const date = parseDate(iso);
   return date

ui/src/lib/panel/actions.svelte.ts

@@ -9,6 +9,7 @@ import FileTextIcon from "@lucide/svelte/icons/file-text";
 import GitBranchIcon from "@lucide/svelte/icons/git-branch";
 import GitMergeIcon from "@lucide/svelte/icons/git-merge";
 import PencilIcon from "@lucide/svelte/icons/pencil";
+import RewindIcon from "@lucide/svelte/icons/rewind";
 import RotateCcwIcon from "@lucide/svelte/icons/rotate-ccw";
 import SendIcon from "@lucide/svelte/icons/send";
 import type { Component } from "svelte";
@@ -38,6 +39,7 @@ export interface ActionScope {
   onChanged: () => void;
   onOpen: (id: string) => void;
   onRename: () => void;
+  onRewind: () => void;
 }
 
 const TELEGRAM = "telegram";
@@ -103,6 +105,12 @@ export function conversationActions(
     label: "Branch…",
     run: scope.onBranch,
   });
+  actions.push({
+    disabled: !info.session_id,
+    icon: RewindIcon,
+    label: "Rewind…",
+    run: scope.onRewind,
+  });
   actions.push({
     checked: remembers,
     gap: true,

ui/src/lib/panel/conversation-menu.svelte

@@ -13,6 +13,7 @@
   import { usePanelHost } from "./host";
   import MenuItems, { type MenuKit } from "./menu-items.svelte";
   import RenameDialog from "./rename-dialog.svelte";
+  import RewindDialog from "./rewind-dialog.svelte";
 
   let {
     client,
@@ -47,6 +48,7 @@
   let failure = $state<string | null>(null);
   let branchOpen = $state(false);
   let renameOpen = $state(false);
+  let rewindOpen = $state(false);
 
   const loaded = $derived(info ?? fetched);
 
@@ -77,6 +79,9 @@
     onRename: () => {
       renameOpen = true;
     },
+    onRewind: () => {
+      rewindOpen = true;
+    },
   });
   const actions = $derived(loaded ? conversationActions(loaded, scope) : []);
 </script>
@@ -141,4 +146,5 @@
     bind:open={branchOpen}
   />
   <RenameDialog {client} info={loaded} {onChanged} bind:open={renameOpen} />
+  <RewindDialog {client} info={loaded} {onChanged} bind:open={rewindOpen} />
 {/if}

ui/src/lib/panel/rewind-dialog.svelte

@@ -0,0 +1,210 @@
+<script lang="ts">
+  import { tick, untrack } from "svelte";
+  import { toast } from "svelte-sonner";
+  import type { ApiClient } from "$lib/api/client";
+  import type { ConversationSummary, TurnSummary } from "$lib/api/types";
+  import EmptyState from "$lib/components/empty-state.svelte";
+  import ErrorNote from "$lib/components/error-note.svelte";
+  import { Button } from "$lib/components/ui/button";
+  import * as Dialog from "$lib/components/ui/dialog";
+  import { Skeleton } from "$lib/components/ui/skeleton";
+  import { clip, fmtDateTime, fmtMinute, shortId } from "$lib/format";
+  import { cn } from "$lib/utils";
+
+  let {
+    client,
+    info,
+    open = $bindable(false),
+    onChanged,
+  }: {
+    client: ApiClient;
+    info: Pick<ConversationSummary, "id" | "kind" | "running_turn" | "title">;
+    open?: boolean;
+    onChanged: () => void;
+  } = $props();
+
+  const LIMIT = 30;
+  const LINE = 160;
+
+  let turns = $state<TurnSummary[] | null>(null);
+  let failure = $state<string | null>(null);
+  let picked = $state<number | null>(null);
+  let busy = $state(false);
+  let list = $state<HTMLDivElement | null>(null);
+
+  const name = $derived(info.title || `${info.kind} ${shortId(info.id)}`);
+  const count = $derived(
+    turns === null || picked === null ? 0 : turns.length - picked
+  );
+
+  function plural(n: number): string {
+    return n === 1 ? "1 turn" : `${n} turns`;
+  }
+
+  function brokenTail(rows: TurnSummary[]): number | null {
+    let at = rows.length;
+    while (at > 0 && rows[at - 1].failed) {
+      at -= 1;
+    }
+    return at < rows.length ? at : null;
+  }
+
+  async function load() {
+    turns = null;
+    failure = null;
+    picked = null;
+    try {
+      ({ turns } = await client.turns(info.id, LIMIT));
+      picked = brokenTail(turns);
+      await tick();
+      if (list) {
+        list.scrollTop = list.scrollHeight;
+        list
+          .querySelector(":checked")
+          ?.closest("label")
+          ?.scrollIntoView({ block: "nearest" });
+      }
+    } catch (error) {
+      failure = error instanceof Error ? error.message : String(error);
+    }
+  }
+
+  async function rewind() {
+    const turn = turns?.[picked ?? -1];
+    if (!turn) {
+      return;
+    }
+    busy = true;
+    try {
+      const result = await client.rewind(info.id, turn.id);
+      open = false;
+      toast.success(`Cut ${plural(result.turns)}`);
+      onChanged();
+    } catch (error) {
+      toast.error(error instanceof Error ? error.message : String(error));
+    } finally {
+      busy = false;
+    }
+  }
+
+  $effect(() => {
+    if (open) {
+      untrack(() => load());
+    }
+  });
+</script>
+
+<Dialog.Root bind:open>
+  <Dialog.Content>
+    <Dialog.Header>
+      <Dialog.Title>Rewind {name}</Dialog.Title>
+      <Dialog.Description>
+        Pick the turn to cut from. The model forgets it and every turn after it.
+        The old session stays in the database.
+      </Dialog.Description>
+    </Dialog.Header>
+    <div class="flex min-w-0 flex-col gap-3">
+      {#if failure}
+        <ErrorNote message={failure} retry={load} />
+      {:else if turns === null}
+        <div class="flex flex-col gap-3 py-2">
+          {#each [0, 1, 2] as row (row)}
+            <div class="flex flex-col gap-1.5">
+              <Skeleton class="h-3.5 w-3/5" />
+              <Skeleton class="h-3 w-4/5" />
+            </div>
+          {/each}
+        </div>
+      {:else if turns.length === 0}
+        <EmptyState
+          hint="The first turn of a thread stays, and this thread has no other."
+          title="Nothing to cut"
+        />
+      {:else}
+        <div
+          aria-label="Turn to cut from"
+          class="-mx-2 grid max-h-[min(22rem,50dvh)] grid-cols-[auto_minmax(0,1fr)] gap-x-3 overflow-y-auto rounded-md pt-2"
+          role="radiogroup"
+          bind:this={list}
+        >
+          {#each turns as turn, index (turn.id)}
+            {@const gone = picked !== null && index >= picked}
+            <label
+              class={cn(
+                "relative col-span-2 grid cursor-pointer grid-cols-subgrid items-baseline border-t px-2 py-2 first:border-t-transparent has-focus-visible:ring-1 has-focus-visible:ring-ring has-focus-visible:ring-inset",
+                gone ? "bg-destructive/5" : "row-hover",
+                index === picked &&
+                  "border-t-destructive/40 first:border-t-destructive/40"
+              )}
+            >
+              <input
+                checked={index === picked}
+                class="sr-only"
+                name="rewind-turn"
+                onchange={() => {
+                  picked = index;
+                }}
+                type="radio"
+              >
+              <span
+                class="tabular text-muted-foreground text-xs"
+                title={fmtDateTime(turn.ts)}
+              >
+                {fmtMinute(turn.ts)}
+              </span>
+              <span class="flex min-w-0 flex-col">
+                <span
+                  class={cn(
+                    "truncate font-medium",
+                    gone && "text-muted-foreground"
+                  )}
+                >
+                  {clip(turn.text, LINE) || "empty prompt"}
+                </span>
+                <span
+                  class={cn(
+                    "truncate text-xs",
+                    turn.failed ? "text-destructive" : "text-muted-foreground"
+                  )}
+                >
+                  {clip(turn.reply, LINE) ||
+                    (turn.failed ? "failed" : "no reply")}
+                </span>
+              </span>
+              {#if index === picked}
+                <span
+                  class="-top-2 absolute right-2 rounded-md bg-[color-mix(in_oklab,var(--destructive)_12%,var(--popover))] px-1.5 font-medium text-destructive text-xs leading-4"
+                >
+                  cut from here
+                </span>
+              {/if}
+            </label>
+          {/each}
+        </div>
+      {/if}
+      {#if info.running_turn}
+        <p class="text-warn text-xs">A turn is running. Interrupt it first.</p>
+      {/if}
+    </div>
+    <Dialog.Footer>
+      <Button
+        onclick={() => {
+          // biome-ignore lint/suspicious/noGlobalAssign: bindable prop, not window.open
+          open = false;
+        }}
+        variant="ghost"
+      >
+        Cancel
+      </Button>
+      {#if turns?.length}
+        <Button
+          disabled={busy || count === 0 || Boolean(info.running_turn)}
+          onclick={rewind}
+          variant="destructive"
+        >
+          {count === 0 ? "Cut" : `Cut ${plural(count)}`}
+        </Button>
+      {/if}
+    </Dialog.Footer>
+  </Dialog.Content>
+</Dialog.Root>