fix: implement shadow copying for native binaries on Windows

src/plugin/pty/manager.ts

@@ -1,8 +1,9 @@
-import { spawn, type IPty } from "bun-pty";
+import type { IPty } from "bun-pty";
 import type { OpencodeClient } from "@opencode-ai/sdk";
 import { RingBuffer } from "./buffer.ts";
 import type { PTYSession, PTYSessionInfo, SpawnOptions, ReadResult, SearchResult } from "./types.ts";
 import { createLogger } from "../logger.ts";
+import { prepareShadowPty } from "./shadow.ts";
 
 const log = createLogger("manager");
 
@@ -21,8 +22,17 @@ function generateId(): string {
 
 class PTYManager {
   private sessions: Map<string, PTYSession> = new Map();
+  private ptyModule: typeof import("bun-pty") | null = null;
 
-  spawn(opts: SpawnOptions): PTYSessionInfo {
+  private async ensureLoaded() {
+    if (this.ptyModule) return this.ptyModule;
+    await prepareShadowPty();
+    this.ptyModule = await import("bun-pty");
+    return this.ptyModule;
+  }
+
+  async spawn(opts: SpawnOptions): Promise<PTYSessionInfo> {
+    const { spawn } = await this.ensureLoaded();
     const id = generateId();
     const args = opts.args ?? [];
     const workdir = opts.workdir ?? process.cwd();

src/plugin/pty/shadow.ts

@@ -0,0 +1,53 @@
+import fs from "node:fs";
+import path from "node:path";
+import os from "node:os";
+import crypto from "node:crypto";
+
+/**
+ * Prepares a shadow copy of the bun-pty native binary on Windows.
+ * This prevents file locking issues when multiple OpenCode instances are running.
+ */
+export async function prepareShadowPty() {
+  if (process.platform !== "win32") {
+    return;
+  }
+
+  if (process.env.BUN_PTY_LIB) {
+    return;
+  }
+
+  try {
+    // Resolve the bun-pty package location
+    const entryPath = await Bun.resolve("bun-pty", import.meta.dir);
+    const packageRoot = path.dirname(path.dirname(entryPath));
+
+    const dllPath = path.join(packageRoot, "rust-pty", "target", "release", "rust_pty.dll");
+
+    if (!fs.existsSync(dllPath)) {
+      return;
+    }
+
+    const tempDir = path.join(os.tmpdir(), "opencode-pty", crypto.randomUUID());
+    fs.mkdirSync(tempDir, { recursive: true });
+
+    const targetDllPath = path.join(tempDir, "rust_pty.dll");
+    fs.copyFileSync(dllPath, targetDllPath);
+
+    // Set the environment variable that bun-pty uses to find its native library
+    process.env.BUN_PTY_LIB = targetDllPath;
+
+    // Ensure we clean up on exit
+    process.on("exit", () => {
+      try {
+        fs.rmSync(tempDir, { recursive: true, force: true });
+      } catch {
+        // Ignore cleanup errors
+      }
+    });
+  } catch (err) {
+    // Fail silently but log if in dev
+    if (process.env.NODE_ENV === "development") {
+      console.error("[opencode-pty] Failed to shadow copy native binary:", err);
+    }
+  }
+}

src/plugin/pty/tools/spawn.ts

@@ -22,7 +22,7 @@ export const ptySpawn = tool({
     }
 
     const sessionId = ctx.sessionID;
-    const info = manager.spawn({
+    const info = await manager.spawn({
       command: args.command,
       args: args.args,
       workdir: args.workdir,