diff --git a/packages/server/src/filesystem/browser.ts b/packages/server/src/filesystem/browser.ts
index d2a8065d..6643e5b3 100644
--- a/packages/server/src/filesystem/browser.ts
+++ b/packages/server/src/filesystem/browser.ts
@@ -81,6 +81,14 @@ export class FileSystemBrowser {
     return { path: relativePath, absolutePath }
   }
 
+  writeFile(relativePath: string, contents: string): void {
+    if (this.unrestricted) {
+      throw new Error("writeFile is not available in unrestricted mode")
+    }
+    const resolved = this.toRestrictedAbsolute(relativePath)
+    fs.writeFileSync(resolved, contents, "utf-8")
+  }
+
   readFile(relativePath: string): string {
     if (this.unrestricted) {
       throw new Error("readFile is not available in unrestricted mode")
diff --git a/packages/server/src/server/routes/workspaces.ts b/packages/server/src/server/routes/workspaces.ts
index 1541475d..de2afd22 100644
--- a/packages/server/src/server/routes/workspaces.ts
+++ b/packages/server/src/server/routes/workspaces.ts
@@ -19,6 +19,10 @@ const WorkspaceFileContentQuerySchema = z.object({
   path: z.string(),
 })
 
+const WorkspaceFileContentBodySchema = z.object({
+  contents: z.string(),
+})
+
 const WorkspaceFileSearchQuerySchema = z.object({
   q: z.string().trim().min(1, "Query is required"),
   limit: z.coerce.number().int().positive().max(200).optional(),
@@ -100,6 +104,20 @@ export function registerWorkspaceRoutes(app: FastifyInstance, deps: RouteDeps) {
       return handleWorkspaceError(error, reply)
     }
   })
+
+  app.put<{
+    Params: { id: string }
+    Querystring: { path?: string }
+  }>("/api/workspaces/:id/files/content", async (request, reply) => {
+    try {
+      const query = WorkspaceFileContentQuerySchema.parse(request.query ?? {})
+      const body = WorkspaceFileContentBodySchema.parse(request.body ?? {})
+      deps.workspaceManager.writeFile(request.params.id, query.path, body.contents)
+      reply.code(204)
+    } catch (error) {
+      return handleWorkspaceError(error, reply)
+    }
+  })
 }
 
 
diff --git a/packages/server/src/workspaces/manager.ts b/packages/server/src/workspaces/manager.ts
index 602589ee..805b8f95 100644
--- a/packages/server/src/workspaces/manager.ts
+++ b/packages/server/src/workspaces/manager.ts
@@ -83,6 +83,12 @@ export class WorkspaceManager {
     }
   }
 
+  writeFile(workspaceId: string, relativePath: string, contents: string): void {
+    const workspace = this.requireWorkspace(workspaceId)
+    const browser = new FileSystemBrowser({ rootDir: workspace.path })
+    browser.writeFile(relativePath, contents)
+  }
+
   async create(folder: string, name?: string): Promise<WorkspaceDescriptor> {
  
     const id = `${Date.now().toString(36)}`
diff --git a/packages/ui/src/components/alert-dialog.tsx b/packages/ui/src/components/alert-dialog.tsx
index 7ef34570..20c8b989 100644
--- a/packages/ui/src/components/alert-dialog.tsx
+++ b/packages/ui/src/components/alert-dialog.tsx
@@ -108,15 +108,15 @@ const AlertDialog: Component = () => {
             open
             modal
             onOpenChange={(open) => {
-              if (!open) {
+              // Only handle dismiss if dialog is dismissible (default: true)
+              if (!open && payload.dismissible !== false) {
                 dismiss(false, payload)
               }
             }}
           >
             <Dialog.Portal>
-              <Dialog.Overlay class="modal-overlay" />
-               <div class="fixed inset-0 z-50 flex items-center justify-center p-4">
-                 <Dialog.Content class="modal-surface w-full max-w-sm p-6 border border-base shadow-2xl" tabIndex={-1}>
+              <Dialog.Overlay class="modal-overlay z-[60]" />
+              <Dialog.Content class="modal-surface fixed left-1/2 top-1/2 z-[1310] w-full max-w-sm -translate-x-1/2 -translate-y-1/2 p-6 border border-base shadow-2xl" tabIndex={-1}>
                    <div class="flex items-start gap-3">
                      <div
                        class="flex h-12 w-12 shrink-0 items-center justify-center rounded-xl border text-base font-semibold"
@@ -140,10 +140,11 @@ const AlertDialog: Component = () => {
 
                     <Show when={isPrompt}>
                       <div class="mt-4">
-                        <label class="text-sm font-medium text-secondary">
+                        <label for="prompt-input" class="text-sm font-medium text-secondary">
                           {payload.inputLabel || t("alertDialog.prompt.inputLabel")}
                         </label>
                         <input
+                          id="prompt-input"
                           ref={(el) => {
                             promptInputRef = el
                           }}
@@ -184,11 +185,10 @@ const AlertDialog: Component = () => {
                      >
                        {confirmLabel}
                      </button>
-                   </div>
-                 </Dialog.Content>
-               </div>
-             </Dialog.Portal>
-           </Dialog>
+                    </div>
+                  </Dialog.Content>
+                </Dialog.Portal>
+              </Dialog>
          )
        }}
      </Show>
diff --git a/packages/ui/src/components/file-viewer/monaco-file-viewer.tsx b/packages/ui/src/components/file-viewer/monaco-file-viewer.tsx
index cffecf2d..4816f225 100644
--- a/packages/ui/src/components/file-viewer/monaco-file-viewer.tsx
+++ b/packages/ui/src/components/file-viewer/monaco-file-viewer.tsx
@@ -9,6 +9,8 @@ interface MonacoFileViewerProps {
   scopeKey: string
   path: string
   content: string
+  onSave?: (content: string) => void
+  onContentChange?: (content: string) => void
 }
 
 export function MonacoFileViewer(props: MonacoFileViewerProps) {
@@ -33,6 +35,11 @@ export function MonacoFileViewer(props: MonacoFileViewerProps) {
     editor = null
   }
 
+  const saveContent = () => {
+    if (!editor || !props.onSave) return
+    props.onSave(editor.getValue())
+  }
+
   onMount(() => {
     let cancelled = false
     void (async () => {
@@ -44,7 +51,7 @@ export function MonacoFileViewer(props: MonacoFileViewerProps) {
       editor = monaco.editor.create(host, {
         value: "",
         language: "plaintext",
-        readOnly: true,
+        readOnly: false,
         automaticLayout: true,
         lineNumbers: "on",
         minimap: { enabled: false },
@@ -54,6 +61,14 @@ export function MonacoFileViewer(props: MonacoFileViewerProps) {
         fontSize: 13,
       })
 
+      editor.addCommand(monaco.KeyMod.CtrlCmd | monaco.KeyCode.KeyS, saveContent)
+
+      editor.onDidChangeModelContent(() => {
+        if (props.onContentChange) {
+          props.onContentChange(editor.getValue())
+        }
+      })
+
       setReady(true)
     })()
 
diff --git a/packages/ui/src/components/instance-info.tsx b/packages/ui/src/components/instance-info.tsx
index 31684cbe..8f9c893c 100644
--- a/packages/ui/src/components/instance-info.tsx
+++ b/packages/ui/src/components/instance-info.tsx
@@ -44,6 +44,7 @@ const InstanceInfo: Component<InstanceInfoProps> = (props) => {
       variant: "warning",
       confirmLabel: t("infoView.dispose.confirm.confirmLabel"),
       cancelLabel: t("infoView.dispose.confirm.cancelLabel"),
+      dismissible: false,
     })
 
     if (!confirmed) return
diff --git a/packages/ui/src/components/instance/instance-shell2.tsx b/packages/ui/src/components/instance/instance-shell2.tsx
index 750e15f8..bf10cc54 100644
--- a/packages/ui/src/components/instance/instance-shell2.tsx
+++ b/packages/ui/src/components/instance/instance-shell2.tsx
@@ -420,6 +420,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
         onClose={closeLeftDrawer}
         ModalProps={modalProps}
         sx={{
+          zIndex: 60,
           "& .MuiDrawer-paper": {
             width: isPhoneLayout() ? "100vw" : `${sessionSidebarWidth()}px`,
             boxSizing: "border-box",
@@ -530,6 +531,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
         onClose={closeRightDrawer}
         ModalProps={modalProps}
         sx={{
+          zIndex: 60,
           "& .MuiDrawer-paper": {
             width: isPhoneLayout() ? "100vw" : `${rightDrawerWidth()}px`,
             boxSizing: "border-box",
diff --git a/packages/ui/src/components/instance/shell/right-panel/RightPanel.tsx b/packages/ui/src/components/instance/shell/right-panel/RightPanel.tsx
index a57d11ed..8226105f 100644
--- a/packages/ui/src/components/instance/shell/right-panel/RightPanel.tsx
+++ b/packages/ui/src/components/instance/shell/right-panel/RightPanel.tsx
@@ -24,6 +24,9 @@ import type { DiffContextMode, DiffViewMode, DiffWordWrapMode, RightPanelTab } f
 
 import { getDefaultWorktreeSlug, getOrCreateWorktreeClient, getWorktreeSlugForSession } from "../../../../stores/worktrees"
 import { requestData } from "../../../../lib/opencode-api"
+import { serverApi } from "../../../../lib/api-client"
+import { showConfirmDialog } from "../../../../stores/alerts"
+import { showToastNotification } from "../../../../lib/notifications"
 import { buildUnifiedDiffFromSdkPatch, tryReverseApplyUnifiedDiff } from "../../../../lib/unified-diff-reverse"
 import { useGlobalPointerDrag } from "../useGlobalPointerDrag"
 import {
@@ -102,6 +105,9 @@ const RightPanel: Component<RightPanelProps> = (props) => {
   const [browserSelectedContent, setBrowserSelectedContent] = createSignal<string | null>(null)
   const [browserSelectedLoading, setBrowserSelectedLoading] = createSignal(false)
   const [browserSelectedError, setBrowserSelectedError] = createSignal<string | null>(null)
+  const [browserSelectedDirty, setBrowserSelectedDirty] = createSignal(false)
+  const [browserSelectedSaving, setBrowserSelectedSaving] = createSignal(false)
+  const [browserSelectedOriginalContent, setBrowserSelectedOriginalContent] = createSignal<string | null>(null)
 
   const [diffViewMode, setDiffViewMode] = createSignal<DiffViewMode>(
     readStoredEnum(RIGHT_PANEL_CHANGES_DIFF_VIEW_MODE_KEY, ["split", "unified"] as const) ?? "unified",
@@ -539,6 +545,8 @@ const RightPanel: Component<RightPanelProps> = (props) => {
     setBrowserSelectedLoading(true)
     setBrowserSelectedError(null)
     setBrowserSelectedContent(null)
+    setBrowserSelectedDirty(false)
+    setBrowserSelectedOriginalContent(null)
 
     // Phone: treat file selection as a commit action and close the overlay.
     if (props.isPhoneLayout()) {
@@ -559,6 +567,7 @@ const RightPanel: Component<RightPanelProps> = (props) => {
         throw new Error("Unsupported file type")
       }
       setBrowserSelectedContent(text)
+      setBrowserSelectedOriginalContent(text) // Track original content for conflict detection
     } catch (error) {
       setBrowserSelectedError(error instanceof Error ? error.message : "Failed to read file")
     } finally {
@@ -566,6 +575,95 @@ const RightPanel: Component<RightPanelProps> = (props) => {
     }
   }
 
+  const saveBrowserFile = async (content: string): Promise<boolean> => {
+    const path = browserSelectedPath()
+    if (!path) return false
+
+    // Check for conflict: agent edited file while user was editing
+    const originalContent = browserSelectedOriginalContent()
+    if (originalContent !== null) {
+      try {
+        const currentDiskContent = await requestData<FileContent>(
+          browserClient().file.read({ path }),
+          "file.read",
+        )
+        const diskContent = (currentDiskContent as any)?.content
+
+        // If disk content differs from what we originally loaded (agent edit)
+        // AND differs from user's current edits, we have a conflict
+        if (diskContent !== originalContent && diskContent !== content) {
+          const confirmed = await showConfirmDialog(
+            props.t("instanceShell.rightPanel.actions.conflict.message", { path }),
+            {
+              variant: "warning",
+              confirmLabel: props.t("instanceShell.rightPanel.actions.conflict.confirmLabel"),
+              cancelLabel: props.t("instanceShell.rightPanel.actions.conflict.cancelLabel"),
+              dismissible: false,
+            },
+          )
+          if (!confirmed) {
+            return false
+          }
+          // User chose to overwrite, proceed with save
+        }
+      } catch {
+        // If we can't check for conflict, proceed with save
+      }
+    }
+
+    setBrowserSelectedSaving(true)
+    try {
+      await serverApi.writeWorkspaceFile(props.instanceId, path, content)
+      setBrowserSelectedContent(content)
+      setBrowserSelectedOriginalContent(content) // Update original to match saved
+      setBrowserSelectedDirty(false)
+      showToastNotification({
+        message: props.t("instanceShell.rightPanel.toast.saveSuccess"),
+        variant: "success",
+      })
+      return true
+    } catch (error) {
+      setBrowserSelectedError(error instanceof Error ? error.message : "Failed to save file")
+      showToastNotification({
+        message: props.t("instanceShell.rightPanel.toast.saveError"),
+        variant: "error",
+      })
+      return false
+    } finally {
+      setBrowserSelectedSaving(false)
+    }
+  }
+
+  const handleBrowserFileChange = (content: string) => {
+    setBrowserSelectedContent(content)
+    setBrowserSelectedDirty(true)
+  }
+
+  const handleOpenBrowserFileRequest = async (path: string) => {
+    if (browserSelectedDirty()) {
+      const confirmed = await showConfirmDialog(
+        props.t("instanceShell.rightPanel.actions.saveConfirm.message", { path: browserSelectedPath() || "" }),
+        {
+          variant: "warning",
+          confirmLabel: props.t("instanceShell.rightPanel.actions.saveConfirm.confirmLabel"),
+          cancelLabel: props.t("instanceShell.rightPanel.actions.saveConfirm.cancelLabel"),
+          dismissible: false,
+        },
+      )
+      if (confirmed) {
+        const saveSuccess = await saveBrowserFile(browserSelectedContent() || "")
+        if (!saveSuccess) {
+          // Save failed - stay on current file, error toast already shown
+          return
+        }
+      } else {
+        // User chose not to save - clear dirty state and discard edits
+        setBrowserSelectedDirty(false)
+      }
+    }
+    await openBrowserFile(path)
+  }
+
   createEffect(() => {
     if (rightPanelTab() !== "files") return
     if (browserLoading()) return
@@ -578,6 +676,7 @@ const RightPanel: Component<RightPanelProps> = (props) => {
     setBrowserSelectedContent(null)
     setBrowserSelectedLoading(false)
     setBrowserSelectedError(null)
+    setBrowserSelectedDirty(false)
   })
 
   createEffect(() => {
@@ -630,6 +729,22 @@ const RightPanel: Component<RightPanelProps> = (props) => {
   }
 
   const refreshFilesTab = async () => {
+    // Prompt for confirmation if file has unsaved changes
+    if (browserSelectedDirty()) {
+      const confirmed = await showConfirmDialog(
+        props.t("instanceShell.rightPanel.actions.refreshDirty.message"),
+        {
+          variant: "warning",
+          confirmLabel: props.t("instanceShell.rightPanel.actions.refreshDirty.confirmLabel"),
+          cancelLabel: props.t("instanceShell.rightPanel.actions.refreshDirty.cancelLabel"),
+          dismissible: false,
+        },
+      )
+      if (!confirmed) {
+        return
+      }
+    }
+
     void loadBrowserEntries(browserPath())
     const selected = browserSelectedPath()
     if (selected) {
@@ -651,6 +766,8 @@ const RightPanel: Component<RightPanelProps> = (props) => {
           throw new Error("Unsupported file type")
         }
         setBrowserSelectedContent(text)
+        setBrowserSelectedOriginalContent(text) // Update original content after refresh
+        setBrowserSelectedDirty(false) // Clear dirty after refresh
       } catch (error) {
         setBrowserSelectedError(error instanceof Error ? error.message : "Failed to read file")
       } finally {
@@ -830,11 +947,15 @@ const RightPanel: Component<RightPanelProps> = (props) => {
               browserSelectedContent={browserSelectedContent}
               browserSelectedLoading={browserSelectedLoading}
               browserSelectedError={browserSelectedError}
+              browserSelectedDirty={browserSelectedDirty}
+              browserSelectedSaving={browserSelectedSaving}
               parentPath={browserParentPath}
               scopeKey={browserScopeKey}
               onLoadEntries={(path: string) => void loadBrowserEntries(path)}
-              onOpenFile={(path: string) => void openBrowserFile(path)}
+              onRequestOpenFile={(path: string) => void handleOpenBrowserFileRequest(path)}
               onRefresh={() => void refreshFilesTab()}
+              onSave={(content: string) => void saveBrowserFile(content)}
+              onContentChange={(content: string) => handleBrowserFileChange(content)}
               listOpen={filesListOpen}
               onToggleList={toggleFilesList}
               splitWidth={filesSplitWidth}
diff --git a/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx b/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx
index 976d1431..1cb4f68e 100644
--- a/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx
+++ b/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx
@@ -1,7 +1,7 @@
 import { For, Show, Suspense, lazy, type Accessor, type Component, type JSX } from "solid-js"
 import type { FileNode } from "@opencode-ai/sdk/v2/client"
 
-import { RefreshCw } from "lucide-solid"
+import { RefreshCw, Save } from "lucide-solid"
 
 import SplitFilePanel from "../components/SplitFilePanel"
 
@@ -21,13 +21,17 @@ interface FilesTabProps {
   browserSelectedContent: Accessor<string | null>
   browserSelectedLoading: Accessor<boolean>
   browserSelectedError: Accessor<string | null>
+  browserSelectedDirty: Accessor<boolean>
+  browserSelectedSaving: Accessor<boolean>
 
   parentPath: Accessor<string | null>
   scopeKey: Accessor<string>
 
   onLoadEntries: (path: string) => void
-  onOpenFile: (path: string) => void
+  onRequestOpenFile: (path: string) => void
   onRefresh: () => void
+  onSave: (content: string) => void
+  onContentChange: (content: string) => void
 
   listOpen: Accessor<boolean>
   onToggleList: () => void
@@ -38,6 +42,13 @@ interface FilesTabProps {
 }
 
 const FilesTab: Component<FilesTabProps> = (props) => {
+  const handleSave = () => {
+    const content = props.browserSelectedContent()
+    if (content !== undefined && content !== null) {
+      props.onSave(content)
+    }
+  }
+
   const renderContent = (): JSX.Element => {
     const entriesValue = props.browserEntries()
     const entries = entriesValue || []
@@ -86,7 +97,13 @@ const FilesTab: Component<FilesTabProps> = (props) => {
                           </div>
                         }
                       >
-                        <LazyMonacoFileViewer scopeKey={props.scopeKey()} path={payload().path} content={payload().content} />
+                        <LazyMonacoFileViewer
+                          scopeKey={props.scopeKey()}
+                          path={payload().path}
+                          content={payload().content}
+                          onSave={props.onSave}
+                          onContentChange={props.onContentChange}
+                        />
                       </Suspense>
                     )}
                   </Show>
@@ -135,7 +152,7 @@ const FilesTab: Component<FilesTabProps> = (props) => {
                   props.onLoadEntries(item.path)
                   return
                 }
-                props.onOpenFile(item.path)
+                props.onRequestOpenFile(item.path)
               }}
               title={item.path}
             >
@@ -168,14 +185,25 @@ const FilesTab: Component<FilesTabProps> = (props) => {
               </Show>
               <Show when={props.browserError()}>{(err) => <span class="text-error">{err()}</span>}</Show>
             </div>
-
+            <button
+              type="button"
+              class="files-header-icon-button"
+              title={props.t("instanceShell.rightPanel.actions.save") || "Save (Ctrl+S)"}
+              aria-label={props.t("instanceShell.rightPanel.actions.save") || "Save"}
+              disabled={props.browserSelectedSaving() || !props.browserSelectedDirty()}
+              style={{ "margin-inline-start": "auto" }}
+              onClick={handleSave}
+            >
+              <Show when={props.browserSelectedSaving()} fallback={<Save class="h-4 w-4" />}>
+                <RefreshCw class="h-4 w-4 animate-spin" />
+              </Show>
+            </button>
             <button
               type="button"
               class="files-header-icon-button"
               title={props.t("instanceShell.rightPanel.actions.refresh")}
               aria-label={props.t("instanceShell.rightPanel.actions.refresh")}
               disabled={props.browserLoading()}
-              style={{ "margin-inline-start": "auto" }}
               onClick={() => props.onRefresh()}
             >
               <RefreshCw class={`h-4 w-4${props.browserLoading() ? " animate-spin" : ""}`} />
@@ -198,4 +226,4 @@ const FilesTab: Component<FilesTabProps> = (props) => {
   return <>{renderContent()}</>
 }
 
-export default FilesTab
+export default FilesTab
\ No newline at end of file
diff --git a/packages/ui/src/components/remote-access-overlay.tsx b/packages/ui/src/components/remote-access-overlay.tsx
index 6bcf53cf..da8ef383 100644
--- a/packages/ui/src/components/remote-access-overlay.tsx
+++ b/packages/ui/src/components/remote-access-overlay.tsx
@@ -98,6 +98,7 @@ export function RemoteAccessOverlay(props: RemoteAccessOverlayProps) {
       variant: "warning",
       confirmLabel: t("remoteAccess.listeningMode.restartConfirm.confirmLabel"),
       cancelLabel: t("remoteAccess.listeningMode.restartConfirm.cancelLabel"),
+      dismissible: false,
     })
 
     if (!confirmed) {
diff --git a/packages/ui/src/components/session-list.tsx b/packages/ui/src/components/session-list.tsx
index 2e2bcb59..74bc0cfc 100644
--- a/packages/ui/src/components/session-list.tsx
+++ b/packages/ui/src/components/session-list.tsx
@@ -157,6 +157,7 @@ const SessionList: Component<SessionListProps> = (props) => {
         variant: "warning",
         confirmLabel: t("sessionList.delete.confirmLabel"),
         cancelLabel: t("sessionList.delete.cancelLabel"),
+        dismissible: false,
       },
     )
     if (!confirmed) return
@@ -285,6 +286,7 @@ const SessionList: Component<SessionListProps> = (props) => {
         variant: "warning",
         confirmLabel: t("sessionList.bulkDelete.confirmLabel"),
         cancelLabel: t("sessionList.bulkDelete.cancelLabel"),
+        dismissible: false,
       },
     )
 
diff --git a/packages/ui/src/components/settings/remote-access-settings-section.tsx b/packages/ui/src/components/settings/remote-access-settings-section.tsx
index 049036dd..52dd65fc 100644
--- a/packages/ui/src/components/settings/remote-access-settings-section.tsx
+++ b/packages/ui/src/components/settings/remote-access-settings-section.tsx
@@ -86,6 +86,7 @@ export const RemoteAccessSettingsSection: Component = () => {
       variant: "warning",
       confirmLabel: t("remoteAccess.listeningMode.restartConfirm.confirmLabel"),
       cancelLabel: t("remoteAccess.listeningMode.restartConfirm.cancelLabel"),
+      dismissible: false,
     })
 
     if (!confirmed) return
diff --git a/packages/ui/src/lib/api-client.ts b/packages/ui/src/lib/api-client.ts
index 9ed896ff..e733bf7d 100644
--- a/packages/ui/src/lib/api-client.ts
+++ b/packages/ui/src/lib/api-client.ts
@@ -234,6 +234,16 @@ export const serverApi = {
       `/api/workspaces/${encodeURIComponent(id)}/files/content?${params.toString()}`,
     )
   },
+  writeWorkspaceFile(id: string, relativePath: string, contents: string): Promise<void> {
+    const params = new URLSearchParams({ path: relativePath })
+    return request(
+      `/api/workspaces/${encodeURIComponent(id)}/files/content?${params.toString()}`,
+      {
+        method: "PUT",
+        body: JSON.stringify({ contents }),
+      },
+    )
+  },
 
   fetchConfigOwner<T extends Record<string, any> = Record<string, any>>(owner: string): Promise<T> {
     return request<T>(`/api/storage/config/${encodeURIComponent(owner)}`)
diff --git a/packages/ui/src/lib/i18n/messages/en/instance.ts b/packages/ui/src/lib/i18n/messages/en/instance.ts
index 1ee49f45..0c6e5bee 100644
--- a/packages/ui/src/lib/i18n/messages/en/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/en/instance.ts
@@ -95,6 +95,18 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.status": "Status",
   "instanceShell.rightPanel.tabs.ariaLabel": "Right panel tabs",
   "instanceShell.rightPanel.actions.refresh": "Refresh",
+  "instanceShell.rightPanel.actions.save": "Save (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "Do you want to save changes to \"{path}\" before switching?",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "Save",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "Discard Changes",
+  "instanceShell.rightPanel.actions.conflict.message": "File was modified by the agent. Overwrite agent's changes?",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "Overwrite",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "Cancel",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "File has unsaved changes. Refresh will discard your edits. Continue?",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "Refresh",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "Cancel",
+  "instanceShell.rightPanel.toast.saveSuccess": "File saved successfully",
+  "instanceShell.rightPanel.toast.saveError": "Failed to save file",
   "instanceShell.rightPanel.sections.sessionChanges": "Session Changes",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "Files modified in the current session. Shows additions and deletions for each file.",
   "instanceShell.rightPanel.sections.plan": "Plan",
diff --git a/packages/ui/src/lib/i18n/messages/es/instance.ts b/packages/ui/src/lib/i18n/messages/es/instance.ts
index 42836ff9..abc05827 100644
--- a/packages/ui/src/lib/i18n/messages/es/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/es/instance.ts
@@ -94,6 +94,19 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.files": "Archivos",
   "instanceShell.rightPanel.tabs.status": "Estado",
   "instanceShell.rightPanel.tabs.ariaLabel": "Pestañas del panel derecho",
+  "instanceShell.rightPanel.actions.refresh": "Actualizar",
+  "instanceShell.rightPanel.actions.save": "Guardar (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "¿Deseas guardar los cambios en \"{path}\" antes de cambiar?",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "Guardar",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "Descartar cambios",
+  "instanceShell.rightPanel.actions.conflict.message": "El archivo fue modificado por el agente. ¿Sobrescribir los cambios del agente?",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "Sobrescribir",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "Cancelar",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "El archivo tiene cambios sin guardar. Actualizar discardará tus ediciones. ¿Continuar?",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "Actualizar",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "Cancelar",
+  "instanceShell.rightPanel.toast.saveSuccess": "Archivo guardado exitosamente",
+  "instanceShell.rightPanel.toast.saveError": "Error al guardar el archivo",
   "instanceShell.rightPanel.sections.sessionChanges": "Cambios de sesión",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "Archivos modificados en la sesión actual. Muestra las adiciones y eliminaciones de cada archivo.",
   "instanceShell.rightPanel.sections.plan": "Plan",
diff --git a/packages/ui/src/lib/i18n/messages/fr/instance.ts b/packages/ui/src/lib/i18n/messages/fr/instance.ts
index e0427f6a..25f250b2 100644
--- a/packages/ui/src/lib/i18n/messages/fr/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/fr/instance.ts
@@ -94,6 +94,19 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.files": "Fichiers",
   "instanceShell.rightPanel.tabs.status": "Statut",
   "instanceShell.rightPanel.tabs.ariaLabel": "Onglets du panneau droit",
+  "instanceShell.rightPanel.actions.refresh": "Actualiser",
+  "instanceShell.rightPanel.actions.save": "Enregistrer (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "Voulez-vous enregistrer les modifications de \"{path}\" avant de changer ?",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "Enregistrer",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "Annuler les modifications",
+  "instanceShell.rightPanel.actions.conflict.message": "Le fichier a été modifié par l'agent. Écraser les modifications de l'agent ?",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "Écraser",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "Annuler",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "Le fichier a des modifications non enregistrées. Actualiser supprimera vos modifications. Continuer ?",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "Actualiser",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "Annuler",
+  "instanceShell.rightPanel.toast.saveSuccess": "Fichier enregistré avec succès",
+  "instanceShell.rightPanel.toast.saveError": "Échec de l'enregistrement du fichier",
   "instanceShell.rightPanel.sections.sessionChanges": "Changements de session",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "Fichiers modifiés dans la session actuelle. Affiche les ajouts et suppressions pour chaque fichier.",
   "instanceShell.rightPanel.sections.plan": "Plan",
diff --git a/packages/ui/src/lib/i18n/messages/he/instance.ts b/packages/ui/src/lib/i18n/messages/he/instance.ts
index 6c8345fe..1288d356 100644
--- a/packages/ui/src/lib/i18n/messages/he/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/he/instance.ts
@@ -95,6 +95,18 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.status": "סטטוס",
   "instanceShell.rightPanel.tabs.ariaLabel": "לשוניות לוח ימני",
   "instanceShell.rightPanel.actions.refresh": "רענן",
+  "instanceShell.rightPanel.actions.save": "שמור (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "האם ברצונך לשמור את השינויים לפני המעבר?",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "שמור",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "בטל שינויים",
+  "instanceShell.rightPanel.actions.conflict.message": "הקובץ שונה על ידי הסוכן. לדרוס את שינויי הסוכן?",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "דרוס",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "בטל",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "לקובץ יש שינויים שלא נשמרו. רענון יבטל את העריכות שלך. להמשיך?",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "רענן",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "בטל",
+  "instanceShell.rightPanel.toast.saveSuccess": "הקובץ נשמר בהצלחה",
+  "instanceShell.rightPanel.toast.saveError": "כשלון בשמירת הקובץ",
   "instanceShell.rightPanel.sections.sessionChanges": "שינויי סשן",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "קבצים שהשתנו בסשן הנוכחי. מציג הוספות ומחיקות לכל קובץ.",
   "instanceShell.rightPanel.sections.plan": "תוכנית",
diff --git a/packages/ui/src/lib/i18n/messages/ja/instance.ts b/packages/ui/src/lib/i18n/messages/ja/instance.ts
index c17cad4a..7fbb21d0 100644
--- a/packages/ui/src/lib/i18n/messages/ja/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/ja/instance.ts
@@ -94,6 +94,19 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.files": "ファイル",
   "instanceShell.rightPanel.tabs.status": "ステータス",
   "instanceShell.rightPanel.tabs.ariaLabel": "右パネルのタブ",
+  "instanceShell.rightPanel.actions.refresh": "更新",
+  "instanceShell.rightPanel.actions.save": "保存 (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "「{path}」への変更を切り替え前に保存しますか？",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "保存",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "変更を破棄",
+  "instanceShell.rightPanel.actions.conflict.message": "ファイルはエージェントによって変更されました。上書きしますか？",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "上書き",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "キャンセル",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "ファイルには未保存の変更があります。更新すると編集が破棄されます。続行しますか？",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "更新",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "キャンセル",
+  "instanceShell.rightPanel.toast.saveSuccess": "ファイルを保存しました",
+  "instanceShell.rightPanel.toast.saveError": "ファイルの保存に失敗しました",
   "instanceShell.rightPanel.sections.sessionChanges": "セッション変更",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "現在のセッションで変更されたファイル。各ファイルの追加と削除を表示します。",
   "instanceShell.rightPanel.sections.plan": "計画",
diff --git a/packages/ui/src/lib/i18n/messages/ru/instance.ts b/packages/ui/src/lib/i18n/messages/ru/instance.ts
index 490cfce7..3d160f7c 100644
--- a/packages/ui/src/lib/i18n/messages/ru/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/ru/instance.ts
@@ -94,6 +94,19 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.files": "Файлы",
   "instanceShell.rightPanel.tabs.status": "Статус",
   "instanceShell.rightPanel.tabs.ariaLabel": "Вкладки правой панели",
+  "instanceShell.rightPanel.actions.refresh": "Обновить",
+  "instanceShell.rightPanel.actions.save": "Сохранить (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "Сохранить изменения в \"{path}\" перед переключением?",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "Сохранить",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "Отменить изменения",
+  "instanceShell.rightPanel.actions.conflict.message": "Файл был изменён агентом. Перезаписать изменения агента?",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "Перезаписать",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "Отмена",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "Файл имеет несохранённые изменения. Обновление отменит ваши правки. Продолжить?",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "Обновить",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "Отмена",
+  "instanceShell.rightPanel.toast.saveSuccess": "Файл успешно сохранён",
+  "instanceShell.rightPanel.toast.saveError": "Не удалось сохранить файл",
   "instanceShell.rightPanel.sections.sessionChanges": "Изменения сессии",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "Файлы, измененные в текущей сессии. Показывает добавления и удаления для каждого файла.",
   "instanceShell.rightPanel.sections.plan": "План",
diff --git a/packages/ui/src/lib/i18n/messages/zh-Hans/instance.ts b/packages/ui/src/lib/i18n/messages/zh-Hans/instance.ts
index 012c9024..424e1fe0 100644
--- a/packages/ui/src/lib/i18n/messages/zh-Hans/instance.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-Hans/instance.ts
@@ -94,6 +94,19 @@ export const instanceMessages = {
   "instanceShell.rightPanel.tabs.files": "文件",
   "instanceShell.rightPanel.tabs.status": "状态",
   "instanceShell.rightPanel.tabs.ariaLabel": "右侧面板标签页",
+  "instanceShell.rightPanel.actions.refresh": "刷新",
+  "instanceShell.rightPanel.actions.save": "保存 (Ctrl+S)",
+  "instanceShell.rightPanel.actions.saveConfirm.message": "切换前是否保存对 \"{path}\" 的更改？",
+  "instanceShell.rightPanel.actions.saveConfirm.confirmLabel": "保存",
+  "instanceShell.rightPanel.actions.saveConfirm.cancelLabel": "放弃更改",
+  "instanceShell.rightPanel.actions.conflict.message": "文件已被代理修改。是否覆盖代理的更改？",
+  "instanceShell.rightPanel.actions.conflict.confirmLabel": "覆盖",
+  "instanceShell.rightPanel.actions.conflict.cancelLabel": "取消",
+  "instanceShell.rightPanel.actions.refreshDirty.message": "文件有未保存的更改。刷新将放弃您的编辑。继续？",
+  "instanceShell.rightPanel.actions.refreshDirty.confirmLabel": "刷新",
+  "instanceShell.rightPanel.actions.refreshDirty.cancelLabel": "取消",
+  "instanceShell.rightPanel.toast.saveSuccess": "文件保存成功",
+  "instanceShell.rightPanel.toast.saveError": "保存文件失败",
   "instanceShell.rightPanel.sections.sessionChanges": "会话更改",
   "instanceShell.rightPanel.sections.sessionChanges.tooltip": "当前会话中修改的文件。显示每个文件的添加和删除。",
   "instanceShell.rightPanel.sections.plan": "计划",
diff --git a/packages/ui/src/stores/alerts.ts b/packages/ui/src/stores/alerts.ts
index 720e0208..18071520 100644
--- a/packages/ui/src/stores/alerts.ts
+++ b/packages/ui/src/stores/alerts.ts
@@ -10,6 +10,8 @@ export type AlertDialogState = {
   variant?: AlertVariant
   confirmLabel?: string
   cancelLabel?: string
+  /** When false, prevents dismissal via Escape key or backdrop click. Default: true */
+  dismissible?: boolean
   onConfirm?: () => void
   onCancel?: () => void
 
diff --git a/packages/ui/src/stores/session-state.ts b/packages/ui/src/stores/session-state.ts
index d0e57c37..aa0c67d0 100644
--- a/packages/ui/src/stores/session-state.ts
+++ b/packages/ui/src/stores/session-state.ts
@@ -673,6 +673,7 @@ async function cleanupBlankSessions(instanceId: string, excludeSessionId?: strin
         detail: tGlobal("sessionState.cleanup.deepConfirm.detail"),
         confirmLabel: tGlobal("sessionState.cleanup.deepConfirm.confirmLabel"),
         cancelLabel: tGlobal("sessionState.cleanup.deepConfirm.cancelLabel"),
+        dismissible: false,
       }
     )
     if (!confirmed) return