Hermes-agent

acp_adapter/provenance.py

@@ -0,0 +1,127 @@
+"""Derive ACP session-provenance metadata from the existing compression chain.
+
+This is an additive Hermes extension surfaced under ACP ``_meta.hermes`` so
+existing ACP clients ignore it. It carries no new persisted state: everything
+is derived on demand from the ``sessions`` table (``parent_session_id`` /
+``end_reason``), which already models compression-continuation chains.
+
+The ACP/editor ``session_id`` stays the stable public handle. When context
+compression rotates the internal Hermes head, ``build_session_provenance`` lets
+a client see the previous/current internal ids and the lineage root without
+parsing status text, guessing from token drops, or reading ``state.db``.
+"""
+
+from __future__ import annotations
+
+from typing import Any, Dict, Optional
+
+# Bound defensive walks; compression chains this deep are pathological.
+_MAX_WALK = 100
+
+
+def build_session_provenance(
+    db: Any,
+    acp_session_id: str,
+    current_hermes_session_id: str,
+    *,
+    previous_hermes_session_id: Optional[str] = None,
+) -> Optional[Dict[str, Any]]:
+    """Build ``_meta.hermes.sessionProvenance`` for an ACP session.
+
+    Args:
+        db: A ``SessionDB`` (must expose ``get_session``).
+        acp_session_id: The stable ACP/editor-facing session handle.
+        current_hermes_session_id: The live internal Hermes DB session id
+            (``state.agent.session_id``).
+        previous_hermes_session_id: The internal id from before the most recent
+            turn, when known. Supplied by ``prompt()`` to flag a rotation.
+
+    Returns:
+        A dict suitable for ``{"hermes": {"sessionProvenance": <dict>}}`` under
+        ACP ``_meta``, or ``None`` if the session can't be read.
+    """
+    try:
+        row = db.get_session(current_hermes_session_id)
+    except Exception:
+        return None
+    if not row:
+        return None
+
+    parent_id = row.get("parent_session_id")
+    end_reason = row.get("end_reason")
+
+    # Walk parents to the lineage root and count compression depth. Only
+    # compression-split parents (parent.end_reason == 'compression') count
+    # toward depth — delegate/branch children share the parent_session_id
+    # column but are not compaction boundaries.
+    root_id = current_hermes_session_id
+    compression_depth = 0
+    cursor_parent = parent_id
+    seen = {current_hermes_session_id}
+    for _ in range(_MAX_WALK):
+        if not cursor_parent or cursor_parent in seen:
+            break
+        seen.add(cursor_parent)
+        try:
+            prow = db.get_session(cursor_parent)
+        except Exception:
+            prow = None
+        if not prow:
+            break
+        root_id = cursor_parent
+        if prow.get("end_reason") == "compression":
+            compression_depth += 1
+        cursor_parent = prow.get("parent_session_id")
+
+    # A session is a compression continuation when its parent was ended with
+    # end_reason='compression'. Determine that from the immediate parent.
+    is_continuation = False
+    if parent_id:
+        try:
+            immediate_parent = db.get_session(parent_id)
+        except Exception:
+            immediate_parent = None
+        if immediate_parent and immediate_parent.get("end_reason") == "compression":
+            is_continuation = True
+
+    rotated = bool(
+        previous_hermes_session_id
+        and previous_hermes_session_id != current_hermes_session_id
+    )
+
+    provenance: Dict[str, Any] = {
+        "acpSessionId": acp_session_id,
+        "currentHermesSessionId": current_hermes_session_id,
+        "rootHermesSessionId": root_id,
+        "parentHermesSessionId": parent_id,
+        "sessionKind": "continuation" if is_continuation else "root",
+        "compressionDepth": compression_depth,
+    }
+    if previous_hermes_session_id:
+        provenance["previousHermesSessionId"] = previous_hermes_session_id
+    if rotated:
+        # The head moved during the last turn. The only mechanism that rotates
+        # the internal id mid-turn is compression-driven session splitting.
+        provenance["reason"] = "compression"
+        provenance["creatorKind"] = "compression"
+
+    return provenance
+
+
+def session_provenance_meta(
+    db: Any,
+    acp_session_id: str,
+    current_hermes_session_id: str,
+    *,
+    previous_hermes_session_id: Optional[str] = None,
+) -> Optional[Dict[str, Any]]:
+    """Return a ready ``_meta`` payload: ``{"hermes": {"sessionProvenance": ...}}``."""
+    prov = build_session_provenance(
+        db,
+        acp_session_id,
+        current_hermes_session_id,
+        previous_hermes_session_id=previous_hermes_session_id,
+    )
+    if prov is None:
+        return None
+    return {"hermes": {"sessionProvenance": prov}}