diff --git a/packages/opencode/src/tool/glob.ts b/packages/opencode/src/tool/glob.ts
index a2611246c66..1dbb5cfee79 100644
--- a/packages/opencode/src/tool/glob.ts
+++ b/packages/opencode/src/tool/glob.ts
@@ -31,6 +31,13 @@ export const GlobTool = Tool.define("glob", {
 
     let search = params.path ?? Instance.directory
     search = path.isAbsolute(search) ? search : path.resolve(Instance.directory, search)
+
+    // Prevent searching root directory
+    const parsed = path.parse(search)
+    if (search === parsed.root) {
+      throw new Error(`Searching root directory is not allowed: ${search}`)
+    }
+
     await assertExternalDirectory(ctx, search, { kind: "directory" })
 
     const limit = 100
diff --git a/packages/opencode/src/tool/grep.ts b/packages/opencode/src/tool/grep.ts
index 82e7ac1667e..e818dbfe15c 100644
--- a/packages/opencode/src/tool/grep.ts
+++ b/packages/opencode/src/tool/grep.ts
@@ -37,6 +37,13 @@ export const GrepTool = Tool.define("grep", {
 
     let searchPath = params.path ?? Instance.directory
     searchPath = path.isAbsolute(searchPath) ? searchPath : path.resolve(Instance.directory, searchPath)
+
+    // Prevent searching root directory
+    const parsed = path.parse(searchPath)
+    if (searchPath === parsed.root) {
+      throw new Error(`Searching root directory is not allowed: ${searchPath}`)
+    }
+
     await assertExternalDirectory(ctx, searchPath, { kind: "directory" })
 
     const rgPath = await Ripgrep.filepath()