diff --git a/src-tauri/src/acp/connection.rs b/src-tauri/src/acp/connection.rs
index a1106f5..e4659c7 100644
--- a/src-tauri/src/acp/connection.rs
+++ b/src-tauri/src/acp/connection.rs
@@ -640,6 +640,15 @@ async fn run_connection(
                 init_resp.agent_capabilities.load_session, supports_fork
             );
 
+            // Emit fork support capability
+            let _ = handle.emit(
+                "acp://event",
+                AcpEvent::ForkSupported {
+                    connection_id: conn_id.clone(),
+                    supported: supports_fork,
+                },
+            );
+
             // Emit connected status
             let _ = handle.emit(
                 "acp://event",
diff --git a/src-tauri/src/acp/types.rs b/src-tauri/src/acp/types.rs
index 7027301..b9084dd 100644
--- a/src-tauri/src/acp/types.rs
+++ b/src-tauri/src/acp/types.rs
@@ -105,6 +105,11 @@ pub enum AcpEvent {
         connection_id: String,
         prompt_capabilities: PromptCapabilitiesInfo,
     },
+    /// Whether the agent supports session/fork
+    ForkSupported {
+        connection_id: String,
+        supported: bool,
+    },
     /// Current session mode changed
     ModeChanged {
         connection_id: String,
diff --git a/src/components/conversations/conversation-detail-panel.tsx b/src/components/conversations/conversation-detail-panel.tsx
index ad143fe..0139669 100644
--- a/src/components/conversations/conversation-detail-panel.tsx
+++ b/src/components/conversations/conversation-detail-panel.tsx
@@ -826,7 +826,9 @@ const ConversationTabView = memo(function ConversationTabView({
       onSaveQueueEdit={handleSaveQueueEdit}
       onCancelQueueEdit={handleQueueCancelEdit}
       onForkSend={
-        connStatus === "connected" && hasPersistedConversation
+        connStatus === "connected" &&
+        hasPersistedConversation &&
+        conn.supportsFork
           ? handleForkSend
           : undefined
       }
diff --git a/src/contexts/acp-connections-context.tsx b/src/contexts/acp-connections-context.tsx
index f2c9255..9fbfc0d 100644
--- a/src/contexts/acp-connections-context.tsx
+++ b/src/contexts/acp-connections-context.tsx
@@ -90,6 +90,7 @@ export interface ConnectionState {
   agentType: AgentType
   status: ConnectionStatus
   promptCapabilities: PromptCapabilitiesInfo
+  supportsFork: boolean
   selectorsReady: boolean
   sessionId: string | null
   modes: SessionModeStateInfo | null
@@ -180,6 +181,11 @@ type Action =
       contextKey: string
       promptCapabilities: PromptCapabilitiesInfo
     }
+  | {
+      type: "FORK_SUPPORTED"
+      contextKey: string
+      supported: boolean
+    }
   | { type: "MODE_CHANGED"; contextKey: string; modeId: string }
   | {
       type: "PLAN_UPDATE"
@@ -500,6 +506,7 @@ function connectionsReducer(
           audio: false,
           embedded_context: false,
         },
+        supportsFork: false,
         selectorsReady: false,
         sessionId: null,
         modes: null,
@@ -889,6 +896,18 @@ function connectionsReducer(
       return next
     }
 
+    case "FORK_SUPPORTED": {
+      const conn = state.get(action.contextKey)
+      if (!conn) return state
+      if (conn.supportsFork === action.supported) return state
+      const next = new Map(state)
+      next.set(action.contextKey, {
+        ...conn,
+        supportsFork: action.supported,
+      })
+      return next
+    }
+
     case "MODE_CHANGED": {
       const conn = state.get(action.contextKey)
       if (!conn?.modes) return state
@@ -1469,6 +1488,14 @@ export function AcpConnectionsProvider({ children }: { children: ReactNode }) {
             promptCapabilities: e.prompt_capabilities,
           })
           break
+        case "fork_supported":
+          flushStreamingQueue()
+          dispatch({
+            type: "FORK_SUPPORTED",
+            contextKey,
+            supported: e.supported,
+          })
+          break
         case "mode_changed":
           flushStreamingQueue()
           dispatch({
diff --git a/src/hooks/use-connection.ts b/src/hooks/use-connection.ts
index c31c604..18c8f39 100644
--- a/src/hooks/use-connection.ts
+++ b/src/hooks/use-connection.ts
@@ -30,6 +30,7 @@ export interface UseConnectionReturn {
   connectionId: string | null
   status: ConnectionStatus | null
   promptCapabilities: PromptCapabilitiesInfo
+  supportsFork: boolean
   selectorsReady: boolean
   sessionId: string | null
   modes: SessionModeStateInfo | null
@@ -76,6 +77,7 @@ export function useConnection(contextKey: string): UseConnectionReturn {
   const status = connection?.status ?? null
   const promptCapabilities =
     connection?.promptCapabilities ?? DEFAULT_PROMPT_CAPABILITIES
+  const supportsFork = connection?.supportsFork ?? false
   const selectorsReady = connection?.selectorsReady ?? false
   const sessionId = connection?.sessionId ?? null
   const modes = connection?.modes ?? null
@@ -133,6 +135,7 @@ export function useConnection(contextKey: string): UseConnectionReturn {
       connectionId,
       status,
       promptCapabilities,
+      supportsFork,
       selectorsReady,
       sessionId,
       modes,
@@ -154,6 +157,7 @@ export function useConnection(contextKey: string): UseConnectionReturn {
       connectionId,
       status,
       promptCapabilities,
+      supportsFork,
       selectorsReady,
       sessionId,
       modes,
diff --git a/src/lib/types.ts b/src/lib/types.ts
index d618c3e..ecc1dbf 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -463,6 +463,11 @@ export type AcpEvent =
       connection_id: string
       prompt_capabilities: PromptCapabilitiesInfo
     }
+  | {
+      type: "fork_supported"
+      connection_id: string
+      supported: boolean
+    }
   | {
       type: "mode_changed"
       connection_id: string