From 7a012cac08c0e198bbffb48dcfd75a4f908d75e7 Mon Sep 17 00:00:00 2001
From: Dax Raad <d@ironbay.co>
Date: Thu, 14 May 2026 23:36:28 -0400
Subject: [PATCH] fix(tool): ignore invalid custom tool exports

---
 packages/opencode/src/tool/registry.ts       |  7 ++++-
 packages/opencode/test/tool/registry.test.ts | 27 ++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/packages/opencode/src/tool/registry.ts b/packages/opencode/src/tool/registry.ts
index 56df754afe..5869b50a2a 100644
--- a/packages/opencode/src/tool/registry.ts
+++ b/packages/opencode/src/tool/registry.ts
@@ -201,7 +201,8 @@ export const layer: Layer.Layer<
           // `match` is an absolute filesystem path from `Glob.scanSync(..., { absolute: true })`.
           // Import it as `file://` so Node on Windows accepts the dynamic import.
           const mod = yield* Effect.promise(() => import(pathToFileURL(match).href))
-          for (const [id, def] of Object.entries<ToolDefinition>(mod)) {
+          for (const [id, def] of Object.entries(mod)) {
+            if (!isPluginTool(def)) continue
             custom.push(fromPlugin(id === "default" ? namespace : `${namespace}_${id}`, def))
           }
         }
@@ -396,6 +397,10 @@ function isZodType(value: unknown): value is z.ZodType {
   return typeof value === "object" && value !== null && "_zod" in value
 }
 
+function isPluginTool(value: unknown): value is ToolDefinition {
+  return typeof value === "object" && value !== null && "args" in value && "description" in value && "execute" in value
+}
+
 function isJsonSchemaDefinition(value: unknown): value is JSONSchema7Definition {
   return typeof value === "boolean" || (typeof value === "object" && value !== null && !Array.isArray(value))
 }
diff --git a/packages/opencode/test/tool/registry.test.ts b/packages/opencode/test/tool/registry.test.ts
index 3239855ca5..0a96a689cd 100644
--- a/packages/opencode/test/tool/registry.test.ts
+++ b/packages/opencode/test/tool/registry.test.ts
@@ -158,6 +158,33 @@ describe("tool.registry", () => {
     }),
   )
 
+  it.instance("ignores non-tool exports in .opencode/tool files", () =>
+    Effect.gen(function* () {
+      const test = yield* TestInstance
+      const tool = path.join(test.directory, ".opencode", "tool")
+      yield* Effect.promise(() => fs.mkdir(tool, { recursive: true }))
+      yield* Effect.promise(() =>
+        Bun.write(
+          path.join(tool, "mixed.ts"),
+          [
+            "export const helper = 'not a tool'",
+            "export default {",
+            "  description: 'mixed tool',",
+            "  args: {},",
+            "  execute: async () => 'ok',",
+            "}",
+            "",
+          ].join("\n"),
+        ),
+      )
+
+      const registry = yield* ToolRegistry.Service
+      const ids = yield* registry.ids()
+      expect(ids).toContain("mixed")
+      expect(ids).not.toContain("mixed_helper")
+    }),
+  )
+
   it.instance("loads tools from .opencode/tools (plural)", () =>
     Effect.gen(function* () {
       const test = yield* TestInstance