feat(backends,storage,core,markdown,infra): claude agent sdk backend, session store, transcript seeding, runner isolation

src/beaver_gateway/core/prompt.py

@@ -0,0 +1,34 @@
+"""System prompt assembly from a list of source files.
+
+The gateway holds no prompt text: an agent names its granules (paths from
+``config.py``) and :func:`assemble` concatenates them in that order, so the
+result is byte-for-byte identical for every session of the same agent as
+long as the files are. Each granule's hash is logged at assembly so a
+drifted prompt can be traced to the file that changed.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import logging
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from collections.abc import Iterable
+
+__all__ = ["assemble"]
+
+_log = logging.getLogger("beaver_gateway.core.prompt")
+
+
+def assemble(sources: Iterable[str | Path]) -> str:
+    parts: list[str] = []
+    for source in sources:
+        path = Path(source)
+        text = path.read_text(encoding="utf-8").strip()
+        digest = hashlib.sha256(text.encode("utf-8")).hexdigest()[:12]
+        _log.info("prompt granule %s sha=%s bytes=%d", path, digest, len(text))
+        if text:
+            parts.append(text)
+    return "\n\n".join(parts) + "\n"