diff --git a/packages/opencode/script/build.ts b/packages/opencode/script/build.ts
index ce45f770f04..b71391103c6 100755
--- a/packages/opencode/script/build.ts
+++ b/packages/opencode/script/build.ts
@@ -201,6 +201,12 @@ for (const item of targets) {
     },
   })
 
+  // Embedding the bundle invalidates the linker's ad-hoc signature, and macOS 27+
+  // SIGKILLs binaries with invalid pages. Re-sign ad-hoc; release CI re-signs with Developer ID.
+  if (item.os === "darwin" && process.platform === "darwin") {
+    await $`codesign --force --sign - dist/${name}/bin/opencode`
+  }
+
   // Smoke test: only run if binary is for current platform
   if (item.os === process.platform && item.arch === process.arch && !item.abi) {
     const binaryPath = `dist/${name}/bin/opencode`