diff --git a/packages/ui/src/components/chat/ChatMessage.tsx b/packages/ui/src/components/chat/ChatMessage.tsx
index 320031eb..b3a577a2 100644
--- a/packages/ui/src/components/chat/ChatMessage.tsx
+++ b/packages/ui/src/components/chat/ChatMessage.tsx
@@ -31,6 +31,12 @@ import { FadeInOnReveal } from './message/FadeInOnReveal';
 import { streamPerfCount } from '@/stores/utils/streamDebug';
 import { areOptionalRenderRelevantMessagesEqual, areRenderRelevantMessagesEqual, areRelevantTurnGroupingContextsEqual } from './message/renderCompare';
 import type { ReviewTransferDirection } from '@/lib/reviewFlow';
+import { toast } from 'sonner';
+import { useI18n } from '@/lib/i18n';
+import { useGlobalSessionsStore } from '@/stores/useGlobalSessionsStore';
+import { getContextObligatoryMessages } from '@/lib/contextObligatoryMessages';
+import { setContextObligatoryMessage } from '@/sync/session-actions';
+import { isVSCodeRuntime } from '@/lib/desktop';
 
 const ToolOutputDialog = lazyWithChunkRecovery(() => import('./message/ToolOutputDialog'));
 
@@ -150,8 +156,10 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
     onUserAnimationConsumed,
     reviewTransferDirection = null,
 }) => {
+    const { t } = useI18n();
     const { isMobile, isTablet, hasTouchInput } = useDeviceInfo();
     const alwaysShowMessageActions = isMobile || isTablet;
+    const canPinIntoContext = !isVSCodeRuntime();
     const { currentTheme } = useThemeSystem();
     const messageContainerRef = React.useRef<HTMLDivElement | null>(null);
 
@@ -402,6 +410,29 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
         const timeInfo = message.info.time as { created?: number } | undefined;
         return typeof timeInfo?.created === 'number' ? timeInfo.created : null;
     }, [message.info.time]);
+    const isPinnedIntoContext = useGlobalSessionsStore((state) => {
+        const session = state.activeSessions.find((candidate) => candidate.id === sessionId)
+            ?? state.archivedSessions.find((candidate) => candidate.id === sessionId);
+        return getContextObligatoryMessages(session).some((entry) => entry.id === message.info.id);
+    });
+    const [pinPending, setPinPending] = React.useState(false);
+    const handleToggleContextPin = React.useCallback(async () => {
+        if (!sessionId || !messageCreatedAt || pinPending) return;
+        setPinPending(true);
+        try {
+            const directory = useSessionUIStore.getState().getDirectoryForSession(sessionId);
+            await setContextObligatoryMessage(sessionId, directory, {
+                id: message.info.id,
+                createdAt: messageCreatedAt,
+                role: isUser ? 'user' : 'assistant',
+            }, !isPinnedIntoContext);
+        } catch (error) {
+            console.error('[chat-message] failed to update context pin', error);
+            toast.error(t('chat.messageBody.actions.contextPinFailed'));
+        } finally {
+            setPinPending(false);
+        }
+    }, [isPinnedIntoContext, isUser, message.info.id, messageCreatedAt, pinPending, sessionId, t]);
 
     const isMessageCompleted = React.useMemo(() => {
         if (isUser) return true;
@@ -1038,6 +1069,9 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
                                                 agentMention={agentMention}
                                                 onRevert={handleRevert}
                                                 onFork={isUser ? handleFork : undefined}
+                                                contextPinned={isPinnedIntoContext}
+                                                contextPinPending={pinPending}
+                                                onToggleContextPin={canPinIntoContext && messageCreatedAt ? handleToggleContextPin : undefined}
                                                 errorMessage={assistantErrorText}
                                                 errorVariant={assistantErrorVariant}
                                                 userActionsMode={useExternalUserActionsRow ? 'external-content' : 'inline'}
@@ -1072,6 +1106,9 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
                                                 agentMention={agentMention}
                                                 onRevert={handleRevert}
                                                 onFork={isUser ? handleFork : undefined}
+                                                contextPinned={isPinnedIntoContext}
+                                                contextPinPending={pinPending}
+                                                onToggleContextPin={canPinIntoContext && messageCreatedAt ? handleToggleContextPin : undefined}
                                                 errorMessage={assistantErrorText}
                                                 errorVariant={assistantErrorVariant}
                                                 userActionsMode="external-actions"
@@ -1104,6 +1141,9 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
                                 messageFinish={messageFinish}
                                 messageCompletedAt={messageCompletedAt ?? undefined}
                                 messageCreatedAt={messageCreatedAt ?? undefined}
+                                contextPinned={isPinnedIntoContext}
+                                contextPinPending={pinPending}
+                                onToggleContextPin={canPinIntoContext && messageCreatedAt ? handleToggleContextPin : undefined}
                                  isMobile={isMobile}
                                  alwaysShowActions={alwaysShowMessageActions}
                                  hasTouchInput={hasTouchInput}
diff --git a/packages/ui/src/components/chat/message/MessageBody.tsx b/packages/ui/src/components/chat/message/MessageBody.tsx
index 6563375f..e985e64f 100644
--- a/packages/ui/src/components/chat/message/MessageBody.tsx
+++ b/packages/ui/src/components/chat/message/MessageBody.tsx
@@ -434,6 +434,9 @@ interface MessageBodyProps {
     userActionsMode?: 'inline' | 'external-content' | 'external-actions';
     stickyUserHeaderEnabled?: boolean;
     reviewTransferDirection?: ReviewTransferDirection | null;
+    contextPinned?: boolean;
+    contextPinPending?: boolean;
+    onToggleContextPin?: () => void;
 }
 
 const TOOL_REVEAL_CACHE_MAX = 200;
@@ -454,7 +457,7 @@ const writeRevealedToolIds = (messageId: string, value: Set<string>): void => {
     revealedToolIdsByMessage.set(messageId, new Set(value));
 };
 
-const UserMessageBody = React.memo(({ messageId, parts, messageCreatedAt, isMobile, alwaysShowActions = isMobile, hasTouchInput, hasTextContent, onCopyMessage, copiedMessage, onShowPopup, agentMention, onRevert, onFork, userActionsMode = 'inline', stickyUserHeaderEnabled = true }: {
+const UserMessageBody = React.memo(({ messageId, parts, messageCreatedAt, isMobile, alwaysShowActions = isMobile, hasTouchInput, hasTextContent, onCopyMessage, copiedMessage, onShowPopup, agentMention, onRevert, onFork, contextPinned, contextPinPending, onToggleContextPin, userActionsMode = 'inline', stickyUserHeaderEnabled = true }: {
     messageId: string;
     parts: Part[];
     messageCreatedAt?: number | null;
@@ -468,6 +471,9 @@ const UserMessageBody = React.memo(({ messageId, parts, messageCreatedAt, isMobi
     agentMention?: AgentMentionInfo;
     onRevert?: () => void;
     onFork?: () => void;
+    contextPinned?: boolean;
+    contextPinPending?: boolean;
+    onToggleContextPin?: () => void;
     userActionsMode?: 'inline' | 'external-content' | 'external-actions';
     stickyUserHeaderEnabled?: boolean;
 }) => {
@@ -554,7 +560,7 @@ const UserMessageBody = React.memo(({ messageId, parts, messageCreatedAt, isMobi
         const formatted = formatTimestampForDisplay(messageCreatedAt, timeFormatPreference);
         return formatted.length > 0 ? formatted : null;
     }, [locale, messageCreatedAt, timeFormatPreference]);
-    const actionsBlock = ((canCopyMessage && hasCopyableText) || onRevert || effectiveOnFork) && showUserActions ? (
+    const actionsBlock = ((canCopyMessage && hasCopyableText) || onRevert || effectiveOnFork || onToggleContextPin) && showUserActions ? (
         <div className={cn(
             'group/user-actions',
             isMobile
@@ -638,6 +644,29 @@ const UserMessageBody = React.memo(({ messageId, parts, messageCreatedAt, isMobi
                         <TooltipContent sideOffset={6}>{t('chat.messageBody.actions.fork')}</TooltipContent>
                     </Tooltip>
                 )}
+                {onToggleContextPin && hasCopyableText && (
+                    <Tooltip>
+                        <TooltipTrigger asChild>
+                            <Button
+                                type="button"
+                                variant="ghost"
+                                size="icon"
+                                className={cn(
+                                    'h-6 w-6 bg-transparent hover:text-foreground hover:!bg-transparent active:!bg-transparent focus-visible:!bg-transparent focus-visible:ring-2 focus-visible:ring-primary/50',
+                                    contextPinned ? 'text-[color:var(--status-info)]' : 'text-muted-foreground',
+                                )}
+                                disabled={contextPinPending}
+                                aria-pressed={contextPinned}
+                                aria-label={t(contextPinned ? 'chat.messageBody.actions.unpinContext' : 'chat.messageBody.actions.pinContext')}
+                                onPointerDown={(event) => event.stopPropagation()}
+                                onClick={(event) => { event.stopPropagation(); onToggleContextPin(); }}
+                            >
+                                <Icon name={contextPinned ? 'pushpin-2-fill' : 'pushpin-2'} className="h-3 w-3" />
+                            </Button>
+                        </TooltipTrigger>
+                        <TooltipContent sideOffset={6}>{t(contextPinned ? 'chat.messageBody.actions.unpinContext' : 'chat.messageBody.actions.pinContext')}</TooltipContent>
+                    </Tooltip>
+                )}
                 {canCopyMessage && hasCopyableText && (
                     <Tooltip>
                         <TooltipTrigger asChild>
@@ -1057,6 +1086,9 @@ const AssistantMessageBody = React.memo(({
     errorMessage,
     errorVariant = 'error',
     reviewTransferDirection = null,
+    contextPinned,
+    contextPinPending,
+    onToggleContextPin,
 }: Omit<MessageBodyProps, 'isUser'>) => {
     const { t, locale } = useI18n();
     const chatSurfaceMode = useChatSurfaceMode();
@@ -2003,6 +2035,29 @@ const AssistantMessageBody = React.memo(({
                     <TooltipContent sideOffset={6}>{t('chat.messageBody.actions.saveAsPlan')}</TooltipContent>
                 </Tooltip>
             ) : null}
+            {onToggleContextPin && hasCopyableText ? (
+                <Tooltip>
+                    <TooltipTrigger asChild>
+                        <Button
+                            type="button"
+                            variant="ghost"
+                            size="icon"
+                            className={cn(
+                                'h-8 w-8 bg-transparent hover:text-foreground hover:!bg-transparent active:!bg-transparent focus-visible:!bg-transparent focus-visible:ring-2 focus-visible:ring-primary/50',
+                                contextPinned ? 'text-[color:var(--status-info)]' : 'text-muted-foreground',
+                            )}
+                            disabled={contextPinPending}
+                            aria-pressed={contextPinned}
+                            aria-label={t(contextPinned ? 'chat.messageBody.actions.unpinContext' : 'chat.messageBody.actions.pinContext')}
+                            onPointerDown={(event) => event.stopPropagation()}
+                            onClick={(event) => { event.stopPropagation(); onToggleContextPin(); }}
+                        >
+                            <Icon name={contextPinned ? 'pushpin-2-fill' : 'pushpin-2'} className="h-3.5 w-3.5" />
+                        </Button>
+                    </TooltipTrigger>
+                    <TooltipContent sideOffset={6}>{t(contextPinned ? 'chat.messageBody.actions.unpinContext' : 'chat.messageBody.actions.pinContext')}</TooltipContent>
+                </Tooltip>
+            ) : null}
             {!isMiniChatSurface && !isReviewSessionView ? <Tooltip>
                 <TooltipTrigger asChild>
                     <Button
@@ -2176,6 +2231,9 @@ const MessageBody = React.memo(({ isUser, ...props }: MessageBodyProps) => {
                 agentMention={props.agentMention}
                 onRevert={props.onRevert}
                 onFork={props.onFork}
+                contextPinned={props.contextPinned}
+                contextPinPending={props.contextPinPending}
+                onToggleContextPin={props.onToggleContextPin}
                 userActionsMode={props.userActionsMode}
                 stickyUserHeaderEnabled={props.stickyUserHeaderEnabled}
             />
diff --git a/packages/ui/src/lib/contextObligatoryMessages.test.ts b/packages/ui/src/lib/contextObligatoryMessages.test.ts
new file mode 100644
index 00000000..24d23043
--- /dev/null
+++ b/packages/ui/src/lib/contextObligatoryMessages.test.ts
@@ -0,0 +1,20 @@
+import { describe, expect, test } from 'bun:test';
+
+import { getContextObligatoryMessages, withContextObligatoryMessage } from './contextObligatoryMessages';
+
+describe('context obligatory message metadata', () => {
+  test('preserves sibling metadata while pinning and unpinning without duplicates', () => {
+    const message = { id: 'msg_1', createdAt: 10, role: 'user' as const };
+    const initial = { openchamber: { goal: { id: 'goal_1' } }, external: true };
+    const pinned = withContextObligatoryMessage(initial, message, true);
+    const repinned = withContextObligatoryMessage(pinned, message, true);
+    const session = { metadata: repinned } as never;
+
+    expect(getContextObligatoryMessages(session)).toEqual([message]);
+    expect((repinned.openchamber as Record<string, unknown>).goal).toEqual({ id: 'goal_1' });
+    expect(withContextObligatoryMessage(repinned, message, false)).toEqual({
+      external: true,
+      openchamber: { goal: { id: 'goal_1' }, context_obligatory_messages: [] },
+    });
+  });
+});
diff --git a/packages/ui/src/lib/contextObligatoryMessages.ts b/packages/ui/src/lib/contextObligatoryMessages.ts
new file mode 100644
index 00000000..982d7e88
--- /dev/null
+++ b/packages/ui/src/lib/contextObligatoryMessages.ts
@@ -0,0 +1,48 @@
+import type { Session } from '@opencode-ai/sdk/v2';
+
+import { getSessionMetadata, type SessionMetadataRecord } from './sessionReviewMetadata';
+
+export type ContextObligatoryMessage = {
+  id: string;
+  createdAt: number;
+  role: 'user' | 'assistant';
+};
+
+const isRecord = (value: unknown): value is Record<string, unknown> =>
+  Boolean(value && typeof value === 'object' && !Array.isArray(value));
+
+export const getContextObligatoryMessages = (
+  session: Session | null | undefined,
+): ContextObligatoryMessage[] => {
+  const openchamber = getSessionMetadata(session).openchamber;
+  if (!isRecord(openchamber) || !Array.isArray(openchamber.context_obligatory_messages)) return [];
+
+  return openchamber.context_obligatory_messages.filter((value): value is ContextObligatoryMessage =>
+    isRecord(value)
+    && typeof value.id === 'string'
+    && typeof value.createdAt === 'number'
+    && Number.isFinite(value.createdAt)
+    && (value.role === 'user' || value.role === 'assistant'));
+};
+
+export const withContextObligatoryMessage = (
+  metadata: SessionMetadataRecord,
+  message: ContextObligatoryMessage,
+  pinned: boolean,
+): SessionMetadataRecord => {
+  const openchamber = isRecord(metadata.openchamber) ? metadata.openchamber : {};
+  const current = Array.isArray(openchamber.context_obligatory_messages)
+    ? openchamber.context_obligatory_messages.filter((value): value is ContextObligatoryMessage =>
+      isRecord(value) && typeof value.id === 'string')
+    : [];
+  const withoutMessage = current.filter((value) => value.id !== message.id);
+  const nextMessages = pinned ? [...withoutMessage, message] : withoutMessage;
+
+  return {
+    ...metadata,
+    openchamber: {
+      ...openchamber,
+      context_obligatory_messages: nextMessages,
+    },
+  };
+};
diff --git a/packages/ui/src/lib/i18n/messages/en.ts b/packages/ui/src/lib/i18n/messages/en.ts
index 12e193ca..afba87bb 100644
--- a/packages/ui/src/lib/i18n/messages/en.ts
+++ b/packages/ui/src/lib/i18n/messages/en.ts
@@ -1886,6 +1886,9 @@ export const dict = {
   'chat.messageBody.actions.fork': 'Fork from here',
   'chat.messageBody.actions.copyMessageAria': 'Copy message text',
   'chat.messageBody.actions.copyMessage': 'Copy message',
+  'chat.messageBody.actions.pinContext': 'Pin into context (survives compaction)',
+  'chat.messageBody.actions.unpinContext': 'Unpin from context (will not survive compaction)',
+  'chat.messageBody.actions.contextPinFailed': 'Could not update the context pin',
   'chat.messageBody.actions.openPreviewAria': 'Open preview',
   'chat.messageBody.actions.openPreview': 'Open preview',
   'chat.messageBody.actions.copyAnswer': 'Copy answer',
diff --git a/packages/ui/src/lib/i18n/messages/es.ts b/packages/ui/src/lib/i18n/messages/es.ts
index 0f1f84dd..b1e68764 100644
--- a/packages/ui/src/lib/i18n/messages/es.ts
+++ b/packages/ui/src/lib/i18n/messages/es.ts
@@ -1864,6 +1864,9 @@ export const dict: Record<I18nKey, string> = {
   "chat.messageBody.actions.fork": "Bifurcar desde aquí",
   "chat.messageBody.actions.copyMessageAria": "Copiar texto del mensaje",
   "chat.messageBody.actions.copyMessage": "Copiar mensaje",
+  "chat.messageBody.actions.pinContext": "Fijar en el contexto (se conserva tras la compactación)",
+  "chat.messageBody.actions.unpinContext": "Quitar del contexto (no se conservará tras la compactación)",
+  "chat.messageBody.actions.contextPinFailed": "No se pudo actualizar el mensaje fijado en el contexto",
   "chat.messageBody.actions.openPreviewAria": "Abrir vista previa",
   "chat.messageBody.actions.openPreview": "Abrir vista previa",
   "chat.messageBody.actions.copyAnswer": "Copiar respuesta",
diff --git a/packages/ui/src/lib/i18n/messages/fr.ts b/packages/ui/src/lib/i18n/messages/fr.ts
index f82a4063..e4ce8184 100644
--- a/packages/ui/src/lib/i18n/messages/fr.ts
+++ b/packages/ui/src/lib/i18n/messages/fr.ts
@@ -1679,6 +1679,9 @@ export const dict = {
   'chat.messageBody.actions.fork': 'Fourche d\'ici',
   'chat.messageBody.actions.copyMessageAria': 'Copier le texte du message',
   'chat.messageBody.actions.copyMessage': 'Copier le message',
+  'chat.messageBody.actions.pinContext': 'Épingler dans le contexte (conservé après compactage)',
+  'chat.messageBody.actions.unpinContext': 'Désépingler du contexte (non conservé après compactage)',
+  'chat.messageBody.actions.contextPinFailed': 'Impossible de modifier l’épinglage dans le contexte',
   'chat.messageBody.actions.openPreviewAria': 'Ouvrir l\'aperçu',
   'chat.messageBody.actions.openPreview': 'Ouvrir l\'aperçu',
   'chat.messageBody.actions.copyAnswer': 'Copier la réponse',
diff --git a/packages/ui/src/lib/i18n/messages/ja.ts b/packages/ui/src/lib/i18n/messages/ja.ts
index a105dd50..36fcd376 100644
--- a/packages/ui/src/lib/i18n/messages/ja.ts
+++ b/packages/ui/src/lib/i18n/messages/ja.ts
@@ -1882,6 +1882,9 @@ export const dict: Record<I18nKey, string> = {
   'chat.messageBody.actions.fork': 'ここからフォーク',
   'chat.messageBody.actions.copyMessageAria': 'メッセージテキストをコピー',
   'chat.messageBody.actions.copyMessage': 'メッセージをコピー',
+  'chat.messageBody.actions.pinContext': 'コンテキストに固定（圧縮後も保持）',
+  'chat.messageBody.actions.unpinContext': 'コンテキストから固定解除（圧縮後は保持されません）',
+  'chat.messageBody.actions.contextPinFailed': 'コンテキストの固定を更新できませんでした',
   'chat.messageBody.actions.openPreviewAria': 'プレビューを開く',
   'chat.messageBody.actions.openPreview': 'プレビューを開く',
   'chat.messageBody.actions.copyAnswer': '回答をコピー',
diff --git a/packages/ui/src/lib/i18n/messages/ko.ts b/packages/ui/src/lib/i18n/messages/ko.ts
index 0ab296d4..5c66223a 100644
--- a/packages/ui/src/lib/i18n/messages/ko.ts
+++ b/packages/ui/src/lib/i18n/messages/ko.ts
@@ -1888,6 +1888,9 @@ export const dict: Record<I18nKey, string> = {
   'chat.messageBody.actions.fork': '여기서 분기 시작',
   'chat.messageBody.actions.copyMessageAria': '메시지 텍스트 복사',
   'chat.messageBody.actions.copyMessage': '메시지 복사',
+  'chat.messageBody.actions.pinContext': '컨텍스트에 고정(압축 후에도 유지)',
+  'chat.messageBody.actions.unpinContext': '컨텍스트에서 고정 해제(압축 후 유지되지 않음)',
+  'chat.messageBody.actions.contextPinFailed': '컨텍스트 고정을 업데이트하지 못했습니다',
   'chat.messageBody.actions.copyAnswer': '답변 복사',
   'chat.messageBody.actions.savingImage': '이미지 저장 중…',
   'chat.messageBody.actions.saveAsImage': '이미지로 저장',
diff --git a/packages/ui/src/lib/i18n/messages/pl.ts b/packages/ui/src/lib/i18n/messages/pl.ts
index d2d03be1..40675f8a 100644
--- a/packages/ui/src/lib/i18n/messages/pl.ts
+++ b/packages/ui/src/lib/i18n/messages/pl.ts
@@ -777,6 +777,9 @@ export const dict: Record<I18nKey, string> = {
   'chat.messageBody.actions.fork': 'Rozwidl od tego miejsca',
   'chat.messageBody.actions.copyMessageAria': 'Kopiuj tekst wiadomości',
   'chat.messageBody.actions.copyMessage': 'Kopiuj wiadomość',
+  'chat.messageBody.actions.pinContext': 'Przypnij do kontekstu (przetrwa kompakcję)',
+  'chat.messageBody.actions.unpinContext': 'Odepnij od kontekstu (nie przetrwa kompakcji)',
+  'chat.messageBody.actions.contextPinFailed': 'Nie udało się zaktualizować przypięcia w kontekście',
   'chat.messageBody.actions.openPreviewAria': 'Otwórz podgląd',
   'chat.messageBody.actions.openPreview': 'Otwórz podgląd',
   'chat.messageBody.actions.copyAnswer': 'Kopiuj odpowiedź',
diff --git a/packages/ui/src/lib/i18n/messages/pt-BR.ts b/packages/ui/src/lib/i18n/messages/pt-BR.ts
index 5343dc02..06466d8a 100644
--- a/packages/ui/src/lib/i18n/messages/pt-BR.ts
+++ b/packages/ui/src/lib/i18n/messages/pt-BR.ts
@@ -1864,6 +1864,9 @@ export const dict: Record<I18nKey, string> = {
   "chat.messageBody.actions.fork": "Bifurcar daqui",
   "chat.messageBody.actions.copyMessageAria": "Copiar texto da mensagem",
   "chat.messageBody.actions.copyMessage": "Copiar mensagem",
+  "chat.messageBody.actions.pinContext": "Fixar no contexto (permanece após a compactação)",
+  "chat.messageBody.actions.unpinContext": "Desafixar do contexto (não permanece após a compactação)",
+  "chat.messageBody.actions.contextPinFailed": "Não foi possível atualizar a fixação no contexto",
   "chat.messageBody.actions.openPreviewAria": "Abrir visualização",
   "chat.messageBody.actions.openPreview": "Abrir visualização",
   "chat.messageBody.actions.copyAnswer": "Copiar resposta",
diff --git a/packages/ui/src/lib/i18n/messages/uk.ts b/packages/ui/src/lib/i18n/messages/uk.ts
index d044c2d0..ee377998 100644
--- a/packages/ui/src/lib/i18n/messages/uk.ts
+++ b/packages/ui/src/lib/i18n/messages/uk.ts
@@ -1864,6 +1864,9 @@ export const dict: Record<I18nKey, string> = {
   "chat.messageBody.actions.fork": "Відгалузити звідси",
   "chat.messageBody.actions.copyMessageAria": "Копіювати текст повідомлення",
   "chat.messageBody.actions.copyMessage": "Копіювати повідомлення",
+  "chat.messageBody.actions.pinContext": "Закріпити в контексті (збережеться після стиснення)",
+  "chat.messageBody.actions.unpinContext": "Відкріпити від контексту (не збережеться після стиснення)",
+  "chat.messageBody.actions.contextPinFailed": "Не вдалося оновити закріплення в контексті",
   "chat.messageBody.actions.openPreviewAria": "Відкрити попередній перегляд",
   "chat.messageBody.actions.openPreview": "Відкрити попередній перегляд",
   "chat.messageBody.actions.copyAnswer": "Скопіювати відповідь",
diff --git a/packages/ui/src/lib/i18n/messages/zh-CN.ts b/packages/ui/src/lib/i18n/messages/zh-CN.ts
index 49fe02ea..bf06b39f 100644
--- a/packages/ui/src/lib/i18n/messages/zh-CN.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-CN.ts
@@ -1852,6 +1852,9 @@ export const dict: Record<I18nKey, string> = {
   'chat.messageBody.actions.fork': '从此处分叉',
   'chat.messageBody.actions.copyMessageAria': '复制消息文本',
   'chat.messageBody.actions.copyMessage': '复制消息',
+  'chat.messageBody.actions.pinContext': '固定到上下文（压缩后仍保留）',
+  'chat.messageBody.actions.unpinContext': '从上下文取消固定（压缩后不再保留）',
+  'chat.messageBody.actions.contextPinFailed': '无法更新上下文固定状态',
   'chat.messageBody.actions.openPreviewAria': '打开预览',
   'chat.messageBody.actions.openPreview': '打开预览',
   'chat.messageBody.actions.copyAnswer': '复制回答',
diff --git a/packages/ui/src/lib/i18n/messages/zh-TW.ts b/packages/ui/src/lib/i18n/messages/zh-TW.ts
index a169b976..64ed8d1c 100644
--- a/packages/ui/src/lib/i18n/messages/zh-TW.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-TW.ts
@@ -1856,6 +1856,9 @@ export const dict: Record<I18nKey, string> = {
   'chat.messageBody.actions.fork': '從此處分支',
   'chat.messageBody.actions.copyMessageAria': '複製訊息文字',
   'chat.messageBody.actions.copyMessage': '複製訊息',
+  'chat.messageBody.actions.pinContext': '釘選到內容脈絡（壓縮後仍保留）',
+  'chat.messageBody.actions.unpinContext': '從內容脈絡取消釘選（壓縮後不再保留）',
+  'chat.messageBody.actions.contextPinFailed': '無法更新內容脈絡釘選狀態',
   'chat.messageBody.actions.openPreviewAria': '開啟預覽',
   'chat.messageBody.actions.openPreview': '開啟預覽',
   'chat.messageBody.actions.copyAnswer': '複製回答',
diff --git a/packages/ui/src/sync/session-actions.ts b/packages/ui/src/sync/session-actions.ts
index dee72102..e3c661ef 100644
--- a/packages/ui/src/sync/session-actions.ts
+++ b/packages/ui/src/sync/session-actions.ts
@@ -27,6 +27,7 @@ import {
   withoutReviewSessionLink,
   type SessionMetadataRecord,
 } from "@/lib/sessionReviewMetadata"
+import { withContextObligatoryMessage, type ContextObligatoryMessage } from "@/lib/contextObligatoryMessages"
 
 const MESSAGE_REFETCH_LIMIT = 100
 const SEND_CONFIRMATION_REFETCH_LIMIT = 30
@@ -472,6 +473,19 @@ export async function patchSessionMetadata(
   return updated
 }
 
+export async function setContextObligatoryMessage(
+  sessionId: string,
+  directory: string | null | undefined,
+  message: ContextObligatoryMessage,
+  pinned: boolean,
+): Promise<Session> {
+  const updated = await patchSessionMetadata(sessionId, directory, (metadata) =>
+    withContextObligatoryMessage(metadata, message, pinned))
+  const sessionDirectory = (updated as Session & { directory?: string | null }).directory ?? directory ?? undefined
+  mirrorSessionIntoLiveStores(updated, sessionDirectory ?? undefined)
+  return updated
+}
+
 async function cleanupReviewMetadataBeforeDelete(sessionId: string, directory?: string | null): Promise<void> {
   let session: Session
   try {
diff --git a/packages/web/server/index.js b/packages/web/server/index.js
index a74f6295..be2f5ef5 100644
--- a/packages/web/server/index.js
+++ b/packages/web/server/index.js
@@ -74,6 +74,7 @@ import { createSessionRuntime } from './lib/opencode/session-runtime.js';
 import { createOpenCodeWatcherRuntime } from './lib/opencode/watcher.js';
 import { createSessionAssistRuntime } from './lib/session-assist/runtime.js';
 import { createSessionGoalRuntime } from './lib/session-goal/runtime.js';
+import { createContextObligatoryRuntime } from './lib/context-obligatory/runtime.js';
 import { createScheduledTasksRuntime } from './lib/scheduled-tasks/runtime.js';
 import { createServerStartupRuntime } from './lib/opencode/server-startup-runtime.js';
 import { createTunnelWiringRuntime } from './lib/opencode/tunnel-wiring-runtime.js';
@@ -768,6 +769,10 @@ const sessionGoalRuntime = createSessionGoalRuntime({
     });
   },
 });
+const contextObligatoryRuntime = createContextObligatoryRuntime({
+  buildOpenCodeUrl,
+  getOpenCodeAuthHeaders,
+});
 
 const globalMessageStreamHub = createGlobalMessageStreamHub({
   buildOpenCodeUrl,
@@ -813,6 +818,7 @@ globalMessageStreamHub.subscribeEvent((event) => {
     : '';
   sessionAssistRuntime.processPayload(payload, directory);
   sessionGoalRuntime.processPayload(payload, directory);
+  contextObligatoryRuntime.processPayload(payload, directory);
 });
 
 const processForwardedEventPayload = (payload, emitSyntheticEvent) => {
@@ -1130,6 +1136,7 @@ const gracefulShutdownRuntime = createGracefulShutdownRuntime({
   openCodeWatcherRuntime,
   sessionAssistRuntime,
   sessionGoalRuntime,
+  contextObligatoryRuntime,
   sessionRuntime,
   getHealthCheckInterval: () => healthCheckInterval,
   clearHealthCheckInterval: (value) => clearInterval(value),
diff --git a/packages/web/server/lib/context-obligatory/DOCUMENTATION.md b/packages/web/server/lib/context-obligatory/DOCUMENTATION.md
new file mode 100644
index 00000000..368ff8f3
--- /dev/null
+++ b/packages/web/server/lib/context-obligatory/DOCUMENTATION.md
@@ -0,0 +1,19 @@
+# Context Obligatory Messages
+
+Messages explicitly pinned by the user are stored under
+`session.metadata.openchamber.context_obligatory_messages` as `{ id, createdAt,
+role }`. The UI uses a fresh-read metadata merge when pinning or unpinning.
+
+The server runtime listens for OpenCode's dedicated `session.compacted` event.
+It fetches every pinned message by ID, keeps non-empty text parts, sorts them
+by the stored creation time, and immediately sends one synthetic user part
+through `prompt_async`. OpenCode's session runner serializes this with its own
+post-compaction continuation. Missing individual messages are skipped without
+discarding the remaining context. Ordinary idle events perform no work and
+make no requests.
+
+After a successful send, the runtime merge-writes
+`context_obligatory_last_compaction_message_id`. This cursor prevents a
+replayed compaction event from reinjecting the same summary. The runtime is
+owned by the OpenChamber web backend and therefore is not available in
+extension-only VS Code mode.
diff --git a/packages/web/server/lib/context-obligatory/runtime.js b/packages/web/server/lib/context-obligatory/runtime.js
new file mode 100644
index 00000000..2552ac2e
--- /dev/null
+++ b/packages/web/server/lib/context-obligatory/runtime.js
@@ -0,0 +1,140 @@
+const FETCH_TIMEOUT_MS = 15_000;
+const MESSAGE_FETCH_LIMIT = 20;
+
+const isRecord = (value) => Boolean(value && typeof value === 'object' && !Array.isArray(value));
+
+const readContextState = (session) => {
+  const metadata = isRecord(session?.metadata) ? session.metadata : {};
+  const openchamber = isRecord(metadata.openchamber) ? metadata.openchamber : {};
+  const messages = Array.isArray(openchamber.context_obligatory_messages)
+    ? openchamber.context_obligatory_messages.filter((item) =>
+      isRecord(item)
+      && typeof item.id === 'string'
+      && typeof item.createdAt === 'number'
+      && (item.role === 'user' || item.role === 'assistant'))
+    : [];
+  return { metadata, openchamber, messages };
+};
+
+const buildContextPrompt = (entries) => {
+  const timeline = entries.map(({ pinned, text }) => {
+    const timestamp = new Date(pinned.createdAt).toISOString();
+    return `## ${pinned.role} — ${timestamp}\n\n${text}`;
+  }).join('\n\n---\n\n');
+  return [
+    'The following messages are from the compacted conversation. The user explicitly marked them as important and required in your context. Pay close attention to them; they may have been sent by either the user or you before compaction.',
+    'Use them while continuing the pre-compaction work. Do not treat this context restoration as a new standalone task.',
+    'If any tasks or next steps remain, do not acknowledge, summarize, or mention this restored context in a separate response. Simply continue the work and use it silently as background context. Do not append a recap of it after completing those tasks. Only if no tasks or next steps remain, give the user a very brief summary of the important restored context in no more than one short paragraph, without lists or a detailed recap.',
+    '',
+    timeline,
+  ].join('\n');
+};
+
+export const createContextObligatoryRuntime = ({
+  buildOpenCodeUrl,
+  getOpenCodeAuthHeaders,
+}) => {
+  const inflight = new Set();
+  let stopped = false;
+
+  const openCodeFetch = async (fetchPath, { directory, method = 'GET', body, query } = {}) => {
+    const params = new URLSearchParams(query || {});
+    if (directory) params.set('directory', directory);
+    const search = params.toString();
+    const response = await fetch(`${buildOpenCodeUrl(fetchPath, '')}${search ? `?${search}` : ''}`, {
+      method,
+      headers: {
+        Accept: 'application/json',
+        ...(body ? { 'Content-Type': 'application/json' } : {}),
+        ...getOpenCodeAuthHeaders(),
+      },
+      ...(body ? { body: JSON.stringify(body) } : {}),
+      signal: AbortSignal.timeout(FETCH_TIMEOUT_MS),
+    });
+    if (!response.ok) throw new Error(`OpenCode ${method} ${fetchPath} failed with ${response.status}`);
+    return response.json().catch(() => null);
+  };
+
+  const tick = async (sessionId, directory) => {
+    const session = await openCodeFetch(`/session/${encodeURIComponent(sessionId)}`, { directory });
+    if (session?.parentID) return;
+    const state = readContextState(session);
+    if (state.messages.length === 0) return;
+
+    const recent = await openCodeFetch(`/session/${encodeURIComponent(sessionId)}/message`, {
+      directory,
+      query: { limit: String(MESSAGE_FETCH_LIMIT) },
+    });
+    if (!Array.isArray(recent) || recent.length === 0) return;
+    const summary = recent.toReversed().find((message) =>
+      message?.info?.role === 'assistant' && message.info.summary === true)?.info;
+    if (!summary?.id || !summary?.time?.completed) return;
+    if (state.openchamber.context_obligatory_last_compaction_message_id === summary.id) return;
+
+    const fetched = await Promise.allSettled(state.messages.map(async (pinned) => {
+      const message = await openCodeFetch(
+        `/session/${encodeURIComponent(sessionId)}/message/${encodeURIComponent(pinned.id)}`,
+        { directory },
+      );
+      const text = Array.isArray(message?.parts)
+        ? message.parts.filter((part) => part?.type === 'text' && typeof part.text === 'string')
+          .map((part) => part.text.trim()).filter(Boolean).join('\n\n')
+        : '';
+      return { pinned, text };
+    }));
+    const entries = fetched
+      .filter((result) => result.status === 'fulfilled' && result.value.text)
+      .map((result) => result.value)
+      .sort((left, right) => left.pinned.createdAt - right.pinned.createdAt);
+    if (entries.length === 0) return;
+
+    const executionInfo = recent.toReversed().find((message) =>
+      message?.info?.role === 'assistant' && message.info.summary !== true)?.info;
+    const providerID = typeof executionInfo?.providerID === 'string' ? executionInfo.providerID : '';
+    const modelID = typeof executionInfo?.modelID === 'string' ? executionInfo.modelID : '';
+    if (!providerID || !modelID) throw new Error('no pre-compaction assistant provider/model');
+    const agent = typeof executionInfo.agent === 'string' ? executionInfo.agent : executionInfo.mode;
+    await openCodeFetch(`/session/${encodeURIComponent(sessionId)}/prompt_async`, {
+      directory,
+      method: 'POST',
+      body: {
+        model: { providerID, modelID },
+        ...(typeof agent === 'string' && agent ? { agent } : {}),
+        parts: [{ type: 'text', text: buildContextPrompt(entries), synthetic: true }],
+      },
+    });
+
+    const fresh = await openCodeFetch(`/session/${encodeURIComponent(sessionId)}`, { directory });
+    const freshState = readContextState(fresh);
+    await openCodeFetch(`/session/${encodeURIComponent(sessionId)}`, {
+      directory,
+      method: 'PATCH',
+      body: {
+        metadata: {
+          ...freshState.metadata,
+          openchamber: {
+            ...freshState.openchamber,
+            context_obligatory_last_compaction_message_id: summary.id,
+          },
+        },
+      },
+    });
+  };
+
+  const processPayload = (payload, directoryHint = '') => {
+    if (stopped || payload?.type !== 'session.compacted') return;
+    const sessionId = payload?.properties?.sessionID;
+    if (typeof sessionId !== 'string' || inflight.has(sessionId)) return;
+    const directory = payload?.properties?.directory || directoryHint;
+    inflight.add(sessionId);
+    return tick(sessionId, directory)
+      .catch((error) => console.warn('[context-obligatory] injection failed:', error?.message || error))
+      .finally(() => inflight.delete(sessionId));
+  };
+
+  const stop = () => {
+    stopped = true;
+  };
+
+  return { processPayload, stop };
+};
diff --git a/packages/web/server/lib/context-obligatory/runtime.test.js b/packages/web/server/lib/context-obligatory/runtime.test.js
new file mode 100644
index 00000000..abc67eb9
--- /dev/null
+++ b/packages/web/server/lib/context-obligatory/runtime.test.js
@@ -0,0 +1,77 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { createContextObligatoryRuntime } from './runtime.js';
+
+const json = (body) => new Response(JSON.stringify(body), {
+  status: 200,
+  headers: { 'Content-Type': 'application/json' },
+});
+
+describe('context obligatory runtime', () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it('injects pinned text in chronological order after compaction and records the summary cursor', async () => {
+    const requests = [];
+    let sessionReads = 0;
+    vi.stubGlobal('fetch', vi.fn(async (input, init = {}) => {
+      const url = new URL(typeof input === 'string' ? input : input.url);
+      requests.push({ path: url.pathname, method: init.method ?? 'GET', body: init.body });
+      if (url.pathname === '/session/ses_1' && init.method === 'PATCH') return json({});
+      if (url.pathname === '/session/ses_1') {
+        sessionReads += 1;
+        return json({
+          id: 'ses_1',
+          metadata: { openchamber: { context_obligatory_messages: [
+            { id: 'msg_2', createdAt: 20, role: 'assistant' },
+            { id: 'msg_1', createdAt: 10, role: 'user' },
+          ] } },
+        });
+      }
+      if (url.pathname === '/session/ses_1/message') return json([
+        { info: { id: 'msg_agent', role: 'assistant', providerID: 'provider', modelID: 'model', agent: 'build' } },
+        { info: { id: 'msg_summary', role: 'assistant', summary: true, time: { completed: 30 } } },
+      ]);
+      if (url.pathname === '/session/ses_1/message/msg_1') return json({ parts: [{ type: 'text', text: 'First' }] });
+      if (url.pathname === '/session/ses_1/message/msg_2') return json({ parts: [{ type: 'text', text: 'Second' }] });
+      if (url.pathname === '/session/ses_1/prompt_async') return json({});
+      throw new Error(`Unexpected ${url.pathname}`);
+    }));
+    const runtime = createContextObligatoryRuntime({
+      buildOpenCodeUrl: (path) => `http://opencode.test${path}`,
+      getOpenCodeAuthHeaders: () => ({}),
+    });
+
+    await runtime.processPayload({ type: 'session.compacted', properties: { sessionID: 'ses_1' } });
+
+    const prompt = requests.find((request) => request.path.endsWith('/prompt_async'));
+    const payload = JSON.parse(prompt.body);
+    expect(payload).toMatchObject({
+      model: { providerID: 'provider', modelID: 'model' },
+      agent: 'build',
+      parts: [{ type: 'text', synthetic: true }],
+    });
+    expect(payload.parts[0].text.indexOf('First')).toBeLessThan(payload.parts[0].text.indexOf('Second'));
+    expect(payload.parts[0].text).toContain('continuing the pre-compaction work');
+    expect(payload.parts[0].text).toContain('use it silently as background context');
+    expect(payload.parts[0].text).toContain('Only if no tasks or next steps remain');
+    expect(payload.parts[0].text).toContain('no more than one short paragraph');
+    const patch = requests.find((request) => request.method === 'PATCH');
+    expect(JSON.parse(patch.body).metadata.openchamber.context_obligatory_last_compaction_message_id).toBe('msg_summary');
+    expect(sessionReads).toBe(2);
+    runtime.stop();
+  });
+
+  it('ignores ordinary idle events without making requests', async () => {
+    const fetchImpl = vi.fn();
+    vi.stubGlobal('fetch', fetchImpl);
+    const runtime = createContextObligatoryRuntime({
+      buildOpenCodeUrl: (path) => `http://opencode.test${path}`,
+      getOpenCodeAuthHeaders: () => ({}),
+    });
+    await runtime.processPayload({ type: 'session.status', properties: { sessionID: 'ses_1', status: { type: 'idle' } } });
+    expect(fetchImpl).not.toHaveBeenCalled();
+    runtime.stop();
+  });
+});
diff --git a/packages/web/server/lib/opencode/shutdown-runtime.js b/packages/web/server/lib/opencode/shutdown-runtime.js
index 189c2c08..63b555a2 100644
--- a/packages/web/server/lib/opencode/shutdown-runtime.js
+++ b/packages/web/server/lib/opencode/shutdown-runtime.js
@@ -10,6 +10,7 @@ export const createGracefulShutdownRuntime = (dependencies) => {
     sessionRuntime,
     sessionAssistRuntime,
     sessionGoalRuntime,
+    contextObligatoryRuntime,
     scheduledTasksRuntime,
     getHealthCheckInterval,
     clearHealthCheckInterval,
@@ -45,6 +46,7 @@ export const createGracefulShutdownRuntime = (dependencies) => {
     sessionRuntime.dispose();
     sessionAssistRuntime?.stop?.();
     sessionGoalRuntime?.stop?.();
+    contextObligatoryRuntime?.stop?.();
     scheduledTasksRuntime?.stop?.();
 
     const healthCheckInterval = getHealthCheckInterval();