Package pinned native Claude and prove isolated startup

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

scripts/build-rein-runtime.py

@@ -7,7 +7,9 @@ Run with the sand-boxer Python environment; uv must be available on PATH.
 from __future__ import annotations
 
 import argparse
+import hashlib
 import json
+import re
 import subprocess
 from pathlib import Path
 
@@ -21,7 +23,31 @@ def checked(command: list[str]) -> str:
     return result.stdout.strip()
 
 
-def build(output: Path, rein_source: Path, llm_source: Path) -> dict:
+def install_claude(output: Path, source: Path, sha256: str, version: str) -> dict:
+    """Copy only an explicitly pinned native executable, never an interactive HOME."""
+    if not re.fullmatch(r"[0-9a-f]{64}", sha256) or not version.strip():
+        raise ValueError("Claude requires an exact SHA-256 and expected version")
+    if source.is_symlink() or not source.is_file():
+        raise ValueError("Claude source must be a regular file, not a symlink")
+    content = source.read_bytes()
+    if hashlib.sha256(content).hexdigest() != sha256:
+        raise ValueError("Claude executable digest mismatch")
+    if not content.startswith(b"\x7fELF"):
+        raise ValueError("Claude executable must be native ELF, not a host wrapper")
+    destination = output / "bin/claude"
+    with destination.open("xb") as stream:
+        stream.write(content)
+    destination.chmod(0o755)
+    return {"path": f"{RUNTIME_MOUNT}/bin/claude", "sha256": sha256,
+            "expected_version": version, "source": str(source)}
+
+
+def build(output: Path, rein_source: Path, llm_source: Path,
+          claude_binary: Path | None = None, claude_sha256: str | None = None,
+          claude_version: str | None = None) -> dict:
+    supplied = (claude_binary, claude_sha256, claude_version)
+    if any(x is not None for x in supplied) and not all(x is not None for x in supplied):
+        raise ValueError("Claude binary, SHA-256 and expected version must be supplied together")
     revisions = {}
     for name, source in (("rein-aharness", rein_source), ("llm-connect", llm_source)):
         if checked(["git", "-C", str(source), "status", "--porcelain"]):
@@ -46,6 +72,8 @@ def build(output: Path, rein_source: Path, llm_source: Path) -> dict:
         "print(json.dumps({'python':platform.python_version(),'packages':"
         "{d.metadata['Name']:d.version for d in importlib.metadata.distributions()}}))",
     ]))
+    if claude_binary is not None:
+        metadata["claude"] = install_claude(output, claude_binary, claude_sha256, claude_version)
     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)},
@@ -57,8 +85,12 @@ def main() -> int:
     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)
+    parser.add_argument("--claude-binary", type=Path)
+    parser.add_argument("--claude-sha256")
+    parser.add_argument("--claude-version")
     args = parser.parse_args()
-    result = build(args.output.resolve(), args.rein_source.resolve(), args.llm_source.resolve())
+    result = build(args.output.resolve(), args.rein_source.resolve(), args.llm_source.resolve(),
+                   args.claude_binary, args.claude_sha256, args.claude_version)
     print(json.dumps(result, indent=2))
     return 0