From b18f2e2afa86137b5f30991229907c92f950e19b Mon Sep 17 00:00:00 2001
From: Linus Schlumberger <linus.schlumberger@siemens.com>
Date: Tue, 17 Mar 2026 16:58:06 +0100
Subject: [PATCH] feat(app): add fork and revert functionality

Close #8885
---
 packages/app/src/pages/session.tsx            | 10 +++++
 .../src/pages/session/message-timeline.tsx    |  4 ++
 packages/ui/src/components/session-turn.css   | 45 +++++++++++++++++++
 packages/ui/src/components/session-turn.tsx   | 44 +++++++++++++++++-
 4 files changed, 102 insertions(+), 1 deletion(-)

diff --git a/packages/app/src/pages/session.tsx b/packages/app/src/pages/session.tsx
index 6d29170081ab..197c55ada703 100644
--- a/packages/app/src/pages/session.tsx
+++ b/packages/app/src/pages/session.tsx
@@ -1732,6 +1732,16 @@ export default function Page() {
                     }}
                     renderedUserMessages={historyWindow.renderedUserMessages()}
                     anchor={anchor}
+                    onRevert={(messageID) => {
+                      const sessionID = params.id
+                      if (!sessionID) return
+                      void revert({ sessionID, messageID })
+                    }}
+                    onFork={(messageID) => {
+                      const sessionID = params.id
+                      if (!sessionID) return
+                      void fork({ sessionID, messageID })
+                    }}
                   />
                 </Show>
               </Match>
diff --git a/packages/app/src/pages/session/message-timeline.tsx b/packages/app/src/pages/session/message-timeline.tsx
index 74f2e8c2c12d..a98712263b8c 100644
--- a/packages/app/src/pages/session/message-timeline.tsx
+++ b/packages/app/src/pages/session/message-timeline.tsx
@@ -216,6 +216,8 @@ export function MessageTimeline(props: {
   onLoadEarlier: () => void
   renderedUserMessages: UserMessage[]
   anchor: (id: string) => string
+  onRevert?: (messageID: string) => void
+  onFork?: (messageID: string) => void
 }) {
   let touchGesture: number | undefined
 
@@ -1007,6 +1009,8 @@ export function MessageTimeline(props: {
                         showReasoningSummaries={settings.general.showReasoningSummaries()}
                         shellToolDefaultOpen={settings.general.shellToolPartsExpanded()}
                         editToolDefaultOpen={settings.general.editToolPartsExpanded()}
+                        onRevert={props.onRevert ? () => props.onRevert!(messageID) : undefined}
+                        onFork={props.onFork ? () => props.onFork!(messageID) : undefined}
                         classes={{
                           root: "min-w-0 w-full relative",
                           content: "flex flex-col justify-between !overflow-visible",
diff --git a/packages/ui/src/components/session-turn.css b/packages/ui/src/components/session-turn.css
index 26d918050d7f..47f641b6400c 100644
--- a/packages/ui/src/components/session-turn.css
+++ b/packages/ui/src/components/session-turn.css
@@ -28,6 +28,51 @@
     min-width: 0;
     gap: 18px;
     overflow-anchor: none;
+    position: relative;
+
+    [data-slot="session-turn-header"] {
+      position: absolute;
+      right: 0;
+      display: flex;
+      gap: 8px;
+      align-items: center;
+      padding-left: 16px;
+      background: linear-gradient(to right, transparent, var(--background-stronger) 12px);
+      opacity: 0;
+      transition: opacity 0.15s ease;
+      pointer-events: none;
+    }
+
+    &:hover [data-slot="session-turn-header"] {
+      opacity: 1;
+      pointer-events: auto;
+    }
+
+    [data-slot="session-turn-badge"] {
+      display: inline-flex;
+      align-items: center;
+      padding: 2px 6px;
+      border-radius: 4px;
+      font-family: var(--font-family-mono);
+      font-size: var(--font-size-x-small);
+      font-weight: var(--font-weight-medium);
+      line-height: var(--line-height-normal);
+      white-space: nowrap;
+      color: var(--text-base);
+      background: var(--surface-raised-base);
+    }
+  }
+
+  [data-slot="session-turn-user-badges"] {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    padding-left: 16px;
+  }
+
+  [data-slot="session-turn-message-actions"] {
+    display: flex;
+    gap: 4px;
   }
 
   [data-slot="session-turn-message-content"] {
diff --git a/packages/ui/src/components/session-turn.tsx b/packages/ui/src/components/session-turn.tsx
index 8c9c1ffe4030..e4afaea42bce 100644
--- a/packages/ui/src/components/session-turn.tsx
+++ b/packages/ui/src/components/session-turn.tsx
@@ -1,4 +1,10 @@
-import { AssistantMessage, type FileDiff, Message as MessageType, Part as PartType } from "@opencode-ai/sdk/v2/client"
+import {
+  AssistantMessage,
+  type FileDiff,
+  Message as MessageType,
+  Part as PartType,
+  UserMessage,
+} from "@opencode-ai/sdk/v2/client"
 import type { SessionStatus } from "@opencode-ai/sdk/v2"
 import { useData } from "../context"
 import { useFileComponent } from "../context/file"
@@ -18,6 +24,10 @@ import { Icon } from "./icon"
 import { TextShimmer } from "./text-shimmer"
 import { SessionRetry } from "./session-retry"
 import { TextReveal } from "./text-reveal"
+import { ProviderIcon } from "./provider-icon"
+import type { IconName } from "./provider-icons/types"
+import { Tooltip } from "./tooltip"
+import { IconButton } from "./icon-button"
 import { createAutoScroll } from "../hooks"
 import { useI18n } from "../context/i18n"
 
@@ -149,6 +159,8 @@ export function SessionTurn(
     active?: boolean
     status?: SessionStatus
     onUserInteracted?: () => void
+    onRevert?: () => void
+    onFork?: () => void
     classes?: {
       root?: string
       content?: string
@@ -393,6 +405,36 @@ export function SessionTurn(
               data-slot="session-turn-message-container"
               class={props.classes?.container}
             >
+              <Show when={props.onRevert || props.onFork}>
+                <div data-slot="session-turn-header">
+                  <div data-slot="session-turn-message-actions">
+                    <Show when={props.onRevert}>
+                      <Tooltip value="Revert to this message" placement="top" gutter={8}>
+                        <IconButton icon="arrow-left" variant="secondary" onClick={props.onRevert} />
+                      </Tooltip>
+                    </Show>
+                    <Show when={props.onFork}>
+                      <Tooltip value="Fork from this message" placement="top" gutter={8}>
+                        <IconButton icon="branch" variant="secondary" onClick={props.onFork} />
+                      </Tooltip>
+                    </Show>
+                  </div>
+                  <div data-slot="session-turn-user-badges">
+                    <Show when={(message()! as UserMessage).agent}>
+                      <span data-slot="session-turn-badge">{(message()! as UserMessage).agent}</span>
+                    </Show>
+                    <Show when={(message()! as UserMessage).model?.modelID}>
+                      <span data-slot="session-turn-badge" class="inline-flex items-center gap-1">
+                        <ProviderIcon
+                          id={(message()! as UserMessage).model!.providerID as IconName}
+                          class="size-3.5 shrink-0"
+                        />
+                        {(message()! as UserMessage).model?.modelID}
+                      </span>
+                    </Show>
+                  </div>
+                </div>
+              </Show>
               <div data-slot="session-turn-message-content" aria-live="off">
                 <Message message={message()!} parts={parts()} actions={props.actions} />
               </div>