feat(chat): /summary slash command for non-destructive session summaries

Typing /summary (optionally with a topic hint) produces a structured
summary as a normal assistant message — without compacting or mutating
session history. Reuses the existing "Start new session from this answer"
button for hand-off.

Prompts are customizable in Settings → Magic Prompts under a new Session
group. Autocomplete shows an 'openchamber' badge to distinguish our
commands from OpenCode-built-in ones.

packages/ui/src/components/chat/ChatInput.tsx

@@ -28,6 +28,7 @@ import * as sessionActions from '@/sync/session-actions';
 import { useUserMessageHistory } from '@/sync/sync-context';
 import { useInlineCommentDraftStore, type InlineCommentDraft } from '@/stores/useInlineCommentDraftStore';
 import { appendInlineComments } from '@/lib/messages/inlineComments';
+import { renderMagicPrompt } from '@/lib/magicPrompts';
 import { AttachedFilesList } from './FileAttachment';
 import { QueuedMessageChips } from './QueuedMessageChips';
 import { FileMentionAutocomplete, type FileMentionHandle } from './FileMentionAutocomplete';
@@ -1533,6 +1534,35 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
                 }
                 return;
             }
+            else if (commandName === 'summary' && currentSessionId) {
+                try {
+                    await sessionActions.waitForConnectionOrThrow();
+                    // Everything after `/summary ` is an optional topic hint
+                    // the user wants the summary focused on.
+                    const topic = normalizedCommand.replace(/^\/summary\b/i, '').trim();
+                    const topicLine = topic ? ` focused on: ${topic}` : '';
+                    const topicBlock = topic
+                        ? `The user asked you to focus this summary on: ${topic}. Prioritize that topic; mention unrelated threads only in passing.`
+                        : '';
+                    const visibleText = await renderMagicPrompt('session.summary.visible', { topic_line: topicLine });
+                    const instructionsText = await renderMagicPrompt('session.summary.instructions', { topic_block: topicBlock });
+                    await sendMessage(
+                        visibleText,
+                        currentProviderId,
+                        currentModelId,
+                        currentAgentName,
+                        [],
+                        agentMentionName,
+                        [{ text: instructionsText, synthetic: true }],
+                        currentVariant,
+                        inputMode,
+                    );
+                    scrollToBottom?.({ instant: true, force: true });
+                } catch (error) {
+                    toast.error(error instanceof Error ? error.message : 'Failed to generate summary');
+                }
+                return;
+            }
         }
 
         // Collect all attachments for error recovery

packages/ui/src/components/chat/CommandAutocomplete.tsx

@@ -13,6 +13,7 @@ interface CommandInfo {
   agent?: string;
   model?: string;
   isBuiltIn?: boolean;
+  isOpenChamber?: boolean;
   isSkill?: boolean;
   scope?: string;
 }
@@ -111,6 +112,10 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
             : []
           ),
           { name: 'compact', description: 'Compress session history using AI to reduce context size', isBuiltIn: true },
+          ...(hasSession
+            ? [{ name: 'summary', description: 'Non-destructive session summary. Optional topic hint after the command.', isOpenChamber: true }]
+            : []
+          ),
         ];
 
         const commandMap = new Map<string, CommandInfo>();
@@ -154,6 +159,10 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
             : []
           ),
           { name: 'compact', description: 'Compress session history using AI to reduce context size', isBuiltIn: true },
+          ...(hasSession
+            ? [{ name: 'summary', description: 'Non-destructive session summary. Optional topic hint after the command.', isOpenChamber: true }]
+            : []
+          ),
         ];
 
         const filtered = (searchQuery
@@ -293,6 +302,7 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
           <div>
             {commands.map((command, index) => {
               const isSystem = command.isBuiltIn;
+              const isOpenChamberBadge = command.isOpenChamber;
               const isProject = command.scope === 'project';
               
               return (
@@ -359,7 +369,18 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
                           skill
                         </span>
                       ) : null}
-                      {isSystem ? (
+                      {isOpenChamberBadge ? (
+                        <span
+                          className="text-[10px] leading-none uppercase font-bold tracking-tight px-1.5 py-1 rounded border flex-shrink-0"
+                          style={{
+                            backgroundColor: 'color-mix(in srgb, var(--primary-base) 14%, transparent)',
+                            color: 'var(--primary-base)',
+                            borderColor: 'color-mix(in srgb, var(--primary-base) 28%, transparent)',
+                          }}
+                        >
+                          openchamber
+                        </span>
+                      ) : isSystem ? (
                         <span className="text-[10px] leading-none uppercase font-bold tracking-tight bg-[var(--status-warning-background)] text-[var(--status-warning)] border-[var(--status-warning-border)] px-1.5 py-1 rounded border flex-shrink-0">
                           system
                         </span>

packages/ui/src/components/sections/magic-prompts/MagicPromptsPage.tsx

@@ -123,6 +123,14 @@ const PROMPT_PAGE_MAP: Record<string, PromptPageConfig> = {
       { id: 'plan.implement.instructions', title: 'Instructions' },
     ],
   },
+  'session.summary': {
+    title: 'Session Summary',
+    description: 'Prompts used by the /summary slash command: visible user message + hidden instructions. Non-destructive — does not compact session history.',
+    blocks: [
+      { id: 'session.summary.visible', title: 'Visible Prompt' },
+      { id: 'session.summary.instructions', title: 'Instructions' },
+    ],
+  },
 };
 
 const hasOwn = (input: Record<string, string>, key: string) => Object.prototype.hasOwnProperty.call(input, key);

packages/ui/src/components/sections/magic-prompts/MagicPromptsSidebar.tsx

@@ -40,6 +40,12 @@ export const MagicPromptsSidebar: React.FC<MagicPromptsSidebarProps> = ({ onItem
           { id: 'plan.implement', title: 'Implement Plan' },
         ],
       },
+      {
+        group: 'Session',
+        items: [
+          { id: 'session.summary', title: 'Session Summary' },
+        ],
+      },
     ] as const;
   }, []);