diff --git a/repos/spack_repo/builtin/packages/opencode/package.py b/repos/spack_repo/builtin/packages/opencode/package.py
new file mode 100644
index 00000000000..b4af39784b9
--- /dev/null
+++ b/repos/spack_repo/builtin/packages/opencode/package.py
@@ -0,0 +1,56 @@
+# Copyright Spack Project Developers. See COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import platform
+
+from spack_repo.builtin.build_systems.generic import Package
+
+from spack.package import *
+
+# Upstream ships a self-contained (Bun single-file) binary per platform.
+# The npm wrapper package (opencode-ai) resolves its platform binary in a
+# postinstall script via optionalDependencies, which does not work in an
+# offline spack install phase — so install the GitHub release binary instead
+# (same pattern as the builtin cudnn-style per-platform version tables).
+_versions = {
+    "1.18.3": {
+        "Linux-x86_64": "60f27b2679f00a511b6539f97e02448afaf58d9c66e2448285ea0c517ca84583",
+        "Linux-aarch64": "da0a631174eba380b2a1d51f9d364fa3812da433e72743c72471d4b5da59c69d",
+    }
+}
+
+_arch_map = {"x86_64": "x64", "aarch64": "arm64"}
+
+
+class Opencode(Package):
+    """opencode — an open-source AI coding agent for the terminal.
+
+    Runs as a TUI or headless CLI against MCP servers and LLM providers, so
+    agentic workflows work on machines without a graphical client (farm
+    nodes, CI reproducers, ...)."""
+
+    homepage = "https://opencode.ai"
+    url = (
+        "https://github.com/anomalyco/opencode/releases/download/v1.18.3/opencode-linux-x64.tar.gz"
+    )
+
+    maintainers("aprozo")
+
+    license("MIT", checked_by="aprozo")
+
+    for _ver, _shas in _versions.items():
+        _key = f"{platform.system()}-{platform.machine()}"
+        if _key in _shas:
+            _arch = _arch_map[platform.machine()]
+            version(
+                _ver,
+                sha256=_shas[_key],
+                url=f"https://github.com/anomalyco/opencode/releases/download/v{_ver}/opencode-linux-{_arch}.tar.gz",
+            )
+
+    def install(self, spec, prefix):
+        # The tarball contains the single `opencode` binary at its root.
+        mkdirp(prefix.bin)
+        install("opencode", join_path(prefix.bin, "opencode"))
+        set_executable(join_path(prefix.bin, "opencode"))