Package pinned native Claude and prove isolated startup

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a0726e-5232-73f2-aaca-2c05ceb62efb

tests/test_runtime_builder.py

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+import hashlib
+import importlib.util
+from pathlib import Path
+
+import pytest
+
+spec = importlib.util.spec_from_file_location(
+    "runtime_builder", Path(__file__).parents[1] / "scripts/build-rein-runtime.py"
+)
+builder = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(builder)
+
+
+def test_claude_copy_is_pinned_and_excludes_home(tmp_path):
+    source = tmp_path / "native"
+    source.write_bytes(b"\x7fELFtest artifact, never executed")
+    (tmp_path / "credentials.json").write_text("must not enter artifact")
+    output = tmp_path / "runtime"
+    (output / "bin").mkdir(parents=True)
+    digest = hashlib.sha256(source.read_bytes()).hexdigest()
+    metadata = builder.install_claude(output, source, digest, "test-version")
+    assert metadata["sha256"] == digest
+    assert metadata["path"] == "/opt/sandboxer/runtime/bin/claude"
+    assert list((output / "bin").iterdir()) == [output / "bin/claude"]
+    assert (output / "bin/claude").read_bytes() == source.read_bytes()
+    assert (output / "bin/claude").stat().st_mode & 0o777 == 0o755
+    assert not (output / "credentials.json").exists()
+    with pytest.raises(FileExistsError):
+        builder.install_claude(output, source, digest, "test-version")
+
+
+def test_changed_binary_and_host_wrapper_refuse(tmp_path):
+    source = tmp_path / "binary"
+    source.write_bytes(b"#!/usr/bin/env node\n")
+    output = tmp_path / "runtime"
+    (output / "bin").mkdir(parents=True)
+    with pytest.raises(ValueError, match="digest mismatch"):
+        builder.install_claude(output, source, "0" * 64, "test-version")
+    digest = hashlib.sha256(source.read_bytes()).hexdigest()
+    with pytest.raises(ValueError, match="native ELF"):
+        builder.install_claude(output, source, digest, "test-version")
+    link = tmp_path / "link"
+    link.symlink_to(source)
+    with pytest.raises(ValueError, match="symlink"):
+        builder.install_claude(output, link, digest, "test-version")
+    assert not (output / "bin/claude").exists()
+
+
+def test_incomplete_claude_pin_refuses_before_build(tmp_path):
+    with pytest.raises(ValueError, match="supplied together"):
+        builder.build(tmp_path / "out", tmp_path, tmp_path, claude_binary=tmp_path / "claude")
+    assert not (tmp_path / "out").exists()