diff --git a/packages/opencode/src/cli/cmd/run.ts b/packages/opencode/src/cli/cmd/run.ts
index a05b273e4489..56c406f6850f 100644
--- a/packages/opencode/src/cli/cmd/run.ts
+++ b/packages/opencode/src/cli/cmd/run.ts
@@ -333,7 +333,7 @@ export const RunCommand = effectCmd({
             process.exit(1)
           }
 
-          const mime = (await Filesystem.isDir(resolvedPath)) ? "application/x-directory" : "text/plain"
+          const mime = (await Filesystem.isDir(resolvedPath)) ? "application/x-directory" : await Filesystem.mimeType(resolvedPath)
 
           files.push({
             type: "file",