diff --git a/packages/opencode/src/cli/cmd/tui/app.tsx b/packages/opencode/src/cli/cmd/tui/app.tsx
index 4b177e292cf..309595ac127 100644
--- a/packages/opencode/src/cli/cmd/tui/app.tsx
+++ b/packages/opencode/src/cli/cmd/tui/app.tsx
@@ -51,7 +51,7 @@ async function getTerminalBackgroundColor(): Promise<"dark" | "light"> {
     }
 
     const handler = (data: Buffer) => {
-      const str = data.toString()
+      const str = data.toString("utf8")
       const match = str.match(/\x1b]11;([^\x07\x1b]+)/)
       if (match) {
         cleanup()
diff --git a/packages/opencode/src/cli/cmd/tui/util/terminal.ts b/packages/opencode/src/cli/cmd/tui/util/terminal.ts
index 2b81068b3f9..638ee164281 100644
--- a/packages/opencode/src/cli/cmd/tui/util/terminal.ts
+++ b/packages/opencode/src/cli/cmd/tui/util/terminal.ts
@@ -52,7 +52,7 @@ export namespace Terminal {
       }
 
       const handler = (data: Buffer) => {
-        const str = data.toString()
+        const str = data.toString("utf8")
 
         // Match OSC 11 (background color)
         const bgMatch = str.match(/\x1b]11;([^\x07\x1b]+)/)