test(827): capture Gate0 runtime evidence

docs/compaction-refresh/probes/p6_claude_hook.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+"""Claude SessionStart additionalContext producer for P6 observation."""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import os
+import sys
+from pathlib import Path
+
+BLOCK = "\n".join(
+    [
+        "GATE0_CLAUDE_ATOMIC_BEGIN",
+        "segment-01=alpha-2d11",
+        "segment-02=middle-8e22",
+        "segment-03=omega-4f33",
+        "GATE0_CLAUDE_ATOMIC_END",
+    ]
+)
+
+
+def starttime(pid: int) -> int:
+    text = Path(f"/proc/{pid}/stat").read_text()
+    return int(text[text.rfind(")") + 2 :].split()[19])
+
+
+def main() -> None:
+    hook_input = json.load(sys.stdin)
+    log = Path(os.environ["GATE0_CLAUDE_HOOK_LOG"])
+    record = {
+        "hook_event_name": hook_input.get("hook_event_name"),
+        "pid": os.getpid(),
+        "ppid": os.getppid(),
+        "starttime_ticks": starttime(os.getpid()),
+        "block_length": len(BLOCK.encode()),
+        "block_sha256": hashlib.sha256(BLOCK.encode()).hexdigest(),
+        "emission": "one hookSpecificOutput.additionalContext string field",
+    }
+    log.write_text(json.dumps(record, sort_keys=True) + "\n")
+    print(
+        json.dumps(
+            {
+                "hookSpecificOutput": {
+                    "hookEventName": "SessionStart",
+                    "additionalContext": BLOCK,
+                }
+            }
+        )
+    )
+
+
+if __name__ == "__main__":
+    main()