diff --git a/packages/opencode/script/postinstall.mjs b/packages/opencode/script/postinstall.mjs
index e8b5e995cc..9c9cbd6b00 100644
--- a/packages/opencode/script/postinstall.mjs
+++ b/packages/opencode/script/postinstall.mjs
@@ -1,12 +1,11 @@
 #!/usr/bin/env node
 
 import fs from "fs"
+import crypto from "crypto"
 import path from "path"
 import os from "os"
-import { fileURLToPath } from "url"
 import { createRequire } from "module"
 
-const __dirname = path.dirname(fileURLToPath(import.meta.url))
 const require = createRequire(import.meta.url)
 
 function detectPlatformAndArch() {
@@ -49,60 +48,91 @@ function detectPlatformAndArch() {
 
 function findBinary() {
   const { platform, arch } = detectPlatformAndArch()
-  const packageName = `opencode-${platform}-${arch}`
   const binaryName = platform === "windows" ? "opencode.exe" : "opencode"
 
-  try {
-    // Use require.resolve to find the package
-    const packageJsonPath = require.resolve(`${packageName}/package.json`)
-    const packageDir = path.dirname(packageJsonPath)
-    const binaryPath = path.join(packageDir, "bin", binaryName)
+  // Try modern variant first, then baseline (for CPUs without AVX2)
+  const candidates = [`opencode-${platform}-${arch}`, `opencode-${platform}-${arch}-baseline`]
 
-    if (!fs.existsSync(binaryPath)) {
-      throw new Error(`Binary not found at ${binaryPath}`)
+  for (const packageName of candidates) {
+    try {
+      const packageJsonPath = require.resolve(`${packageName}/package.json`)
+      const packageDir = path.dirname(packageJsonPath)
+      const binaryPath = path.join(packageDir, "bin", binaryName)
+
+      if (fs.existsSync(binaryPath)) {
+        return { binaryPath, binaryName }
+      }
+    } catch {
+      // Package not installed, try next candidate
     }
-
-    return { binaryPath, binaryName }
-  } catch (error) {
-    throw new Error(`Could not find package ${packageName}: ${error.message}`)
   }
+
+  throw new Error(`Could not find platform binary for ${platform}-${arch}`)
 }
 
-function prepareBinDirectory(binaryName) {
-  const binDir = path.join(__dirname, "bin")
-  const targetPath = path.join(binDir, binaryName)
+function findBunShimPath() {
+  // Mirrors Bun's openGlobalBinDir() resolution order from
+  // src/install/PackageManager/PackageManagerOptions.zig:201-233
+  //   1. $BUN_INSTALL_BIN
+  //   2. (bunfig.toml globalBinDir — not accessible from postinstall)
+  //   3. $BUN_INSTALL/bin
+  //   4. $XDG_CACHE_HOME/.bun/bin
+  //   5. $HOME/.bun/bin
+  const candidates = [
+    process.env.BUN_INSTALL_BIN,
+    process.env.BUN_INSTALL && path.join(process.env.BUN_INSTALL, "bin"),
+    process.env.XDG_CACHE_HOME && path.join(process.env.XDG_CACHE_HOME, ".bun", "bin"),
+    path.join(os.homedir(), ".bun", "bin"),
+  ]
 
-  // Ensure bin directory exists
-  if (!fs.existsSync(binDir)) {
-    fs.mkdirSync(binDir, { recursive: true })
+  for (const binDir of candidates) {
+    if (!binDir) continue
+    const shimPath = path.join(binDir, "opencode.exe")
+    if (fs.existsSync(shimPath)) {
+      return shimPath
+    }
   }
-
-  // Remove existing binary/symlink if it exists
-  if (fs.existsSync(targetPath)) {
-    fs.unlinkSync(targetPath)
-  }
-
-  return { binDir, targetPath }
+  return null
 }
 
-function symlinkBinary(sourcePath, binaryName) {
-  const { targetPath } = prepareBinDirectory(binaryName)
-
-  fs.symlinkSync(sourcePath, targetPath)
-  console.log(`opencode binary symlinked: ${targetPath} -> ${sourcePath}`)
-
-  // Verify the file exists after operation
-  if (!fs.existsSync(targetPath)) {
-    throw new Error(`Failed to symlink binary to ${targetPath}`)
+function replaceBunShim(realBinaryPath) {
+  const shimPath = findBunShimPath()
+  if (!shimPath) {
+    console.log("Bun shim not found, skipping replacement")
+    return
   }
+
+  // Check if the shim is already the real binary by comparing file hashes
+  const shimHash = crypto.createHash("sha256").update(fs.readFileSync(shimPath)).digest("hex")
+  const realHash = crypto.createHash("sha256").update(fs.readFileSync(realBinaryPath)).digest("hex")
+  if (shimHash === realHash) {
+    console.log("Bun shim already replaced with real binary")
+    return
+  }
+
+  console.log("Replacing Bun shim with real binary")
+  console.log(`  shim: ${shimPath}`)
+  console.log(`  real: ${realBinaryPath}`)
+  fs.copyFileSync(realBinaryPath, shimPath)
+  console.log("Bun shim replaced successfully")
 }
 
 async function main() {
   try {
     if (os.platform() === "win32") {
-      // On Windows, the .exe is already included in the package and bin field points to it
-      // No postinstall setup needed
-      console.log("Windows detected: binary setup not needed (using packaged .exe)")
+      // On Windows, Bun's global install creates a tiny shim exe (~15KB) that
+      // launches the JS wrapper via spawnSync. This shim receives CTRL_C_EVENT
+      // from the Windows console and dies instantly, killing the real opencode
+      // process before it can handle the signal gracefully.
+      //
+      // Fix: replace the shim with the real compiled binary so Ctrl+C goes
+      // directly to opencode's signal handler (which uses the anomalyco/bun
+      // fork with the SIGINT fix from PR #25876).
+      const agent = (process.env.npm_config_user_agent || "").toLowerCase()
+      if (agent.startsWith("bun")) {
+        const { binaryPath } = findBinary()
+        replaceBunShim(binaryPath)
+      }
       return
     }