diff --git a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
index d5298518700..395b62e8691 100644
--- a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
@@ -126,6 +126,7 @@ export function Session() {
   const [showDetails, setShowDetails] = createSignal(kv.get("tool_details_visibility", true))
   const [showScrollbar, setShowScrollbar] = createSignal(kv.get("scrollbar_visible", false))
   const [userMessageMarkdown, setUserMessageMarkdown] = createSignal(kv.get("user_message_markdown", true))
+  const [sidebarOverlayEnabled, setSidebarOverlayEnabled] = createSignal(kv.get("sidebar_overlay", true))
   const [diffWrapMode, setDiffWrapMode] = createSignal<"word" | "none">("word")
   const [animationsEnabled, setAnimationsEnabled] = createSignal(kv.get("animations_enabled", true))
 
@@ -136,7 +137,11 @@ export function Session() {
     if (sidebar() === "auto" && wide()) return true
     return false
   })
-  const contentWidth = createMemo(() => dimensions().width - (sidebarVisible() ? 42 : 0) - 4)
+  const sidebarOverlay = createMemo(() => {
+    if (!sidebarOverlayEnabled()) return false
+    return sidebarVisible() && !wide()
+  })
+  const contentWidth = createMemo(() => dimensions().width - (sidebarVisible() && !sidebarOverlay() ? 42 : 0) - 4)
 
   const scrollAcceleration = createMemo(() => {
     const tui = sync.data.config.tui
@@ -486,6 +491,20 @@ export function Session() {
         dialog.clear()
       },
     },
+    {
+      title: sidebarOverlayEnabled() ? "Disable sidebar overlay" : "Enable sidebar overlay",
+      value: "sidebar_overlay",
+      keybind: "sidebar_overlay_toggle",
+      category: "System",
+      onSelect: (dialog) => {
+        setSidebarOverlayEnabled((prev) => {
+          const next = !prev
+          kv.set("sidebar_overlay", next)
+          return next
+        })
+        dialog.clear()
+      },
+    },
     {
       title: usernameVisible() ? "Hide username" : "Show username",
       value: "session.username_visible.toggle",
diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index 807cd46fd26..bbf259c2676 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -477,6 +477,7 @@ export namespace Config {
         .default("<leader>h")
         .describe("Toggle code block concealment in messages"),
       tool_details: z.string().optional().default("none").describe("Toggle tool details visibility"),
+      sidebar_overlay_toggle: z.string().optional().default("none").describe("Toggle sidebar overlay mode"),
       model_list: z.string().optional().default("<leader>m").describe("List available models"),
       model_cycle_recent: z.string().optional().default("f2").describe("Next recently used model"),
       model_cycle_recent_reverse: z.string().optional().default("shift+f2").describe("Previous recently used model"),