feat: pin bwrap rein runtimes and isolate private state

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

scripts/build-rein-runtime.py

@@ -0,0 +1,67 @@
+"""Build a standalone rein-aharness runtime for the fixed bwrap mount path.
+
+Only package installation occurs here. No credentials or model calls are used.
+Run with the sand-boxer Python environment; uv must be available on PATH.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import subprocess
+from pathlib import Path
+
+from sandboxer.extensions.runtime import RUNTIME_MOUNT, runtime_digest
+
+
+def checked(command: list[str]) -> str:
+    result = subprocess.run(command, capture_output=True, text=True, timeout=300)
+    if result.returncode:
+        raise RuntimeError(f"runtime build command failed: {Path(command[0]).name}")
+    return result.stdout.strip()
+
+
+def build(output: Path, rein_source: Path, llm_source: Path) -> dict:
+    revisions = {}
+    for name, source in (("rein-aharness", rein_source), ("llm-connect", llm_source)):
+        if checked(["git", "-C", str(source), "status", "--porcelain"]):
+            raise ValueError(f"{name} source must be committed before building")
+        revisions[name] = checked(["git", "-C", str(source), "rev-parse", "HEAD"])
+    output.mkdir(parents=True, exist_ok=False)
+    checked(["/usr/bin/python3", "-m", "venv", "--copies", "--without-pip", str(output)])
+    checked(["uv", "pip", "install", "--python", str(output / "bin/python3"),
+             str(rein_source), str(llm_source)])
+    # Console entrypoints must reference the in-sandbox mount, not the build host.
+    for path in (output / "bin").iterdir():
+        if not path.is_file() or path.is_symlink():
+            continue
+        with path.open("rb") as stream:
+            first_line = stream.readline(4096)
+        if first_line.startswith(f"#!{output}/bin/python".encode()):
+            body = path.read_bytes().partition(b"\n")[2]
+            path.write_bytes(f"#!{RUNTIME_MOUNT}/bin/python3\n".encode() + body)
+    metadata = json.loads(checked([
+        str(output / "bin/python3"), "-c",
+        "import importlib.metadata,json,platform; "
+        "print(json.dumps({'python':platform.python_version(),'packages':"
+        "{d.metadata['Name']:d.version for d in importlib.metadata.distributions()}}))",
+    ]))
+    metadata["source_revisions"] = revisions
+    (output / "build-info.json").write_text(json.dumps(metadata, indent=2) + "\n")
+    return {"runtime": {"path": str(output), "sha256": runtime_digest(output)},
+            "build": metadata}
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--output", type=Path, required=True)
+    parser.add_argument("--rein-source", type=Path, required=True)
+    parser.add_argument("--llm-source", type=Path, required=True)
+    args = parser.parse_args()
+    result = build(args.output.resolve(), args.rein_source.resolve(), args.llm_source.resolve())
+    print(json.dumps(result, indent=2))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())