diff --git a/packages/opencode/src/provider/provider.ts b/packages/opencode/src/provider/provider.ts
index 6e116fe41e..d643f25373 100644
--- a/packages/opencode/src/provider/provider.ts
+++ b/packages/opencode/src/provider/provider.ts
@@ -19,6 +19,7 @@ import { zod } from "@/util/effect-zod"
 import { iife } from "@/util/iife"
 import { Global } from "../global"
 import path from "path"
+import { pathToFileURL } from "url"
 import { Effect, Layer, Context, Schema, Types } from "effect"
 import { EffectBridge } from "@/effect"
 import { InstanceState } from "@/effect"
@@ -1506,7 +1507,10 @@ const layer: Layer.Layer<
           installedPath = model.api.npm
         }
 
-        const mod = await import(installedPath)
+        // `installedPath` is a local entry path or an existing `file://` URL. Normalize
+        // only path inputs so Node on Windows accepts the dynamic import.
+        const importSpec = installedPath.startsWith("file://") ? installedPath : pathToFileURL(installedPath).href
+        const mod = await import(importSpec)
 
         const fn = mod[Object.keys(mod).find((key) => key.startsWith("create"))!]
         const loaded = fn({
diff --git a/packages/opencode/src/tool/registry.ts b/packages/opencode/src/tool/registry.ts
index e27593e597..0211e33bcb 100644
--- a/packages/opencode/src/tool/registry.ts
+++ b/packages/opencode/src/tool/registry.ts
@@ -157,9 +157,9 @@ export const layer: Layer.Layer<
         if (matches.length) yield* config.waitForDependencies()
         for (const match of matches) {
           const namespace = path.basename(match, path.extname(match))
-          const mod = yield* Effect.promise(
-            () => import(process.platform === "win32" ? match : pathToFileURL(match).href),
-          )
+          // `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)) {
             custom.push(fromPlugin(id === "default" ? namespace : `${namespace}_${id}`, def))
           }