Refactor: single collection with shared/private visibility

Breaking change: per-agent collections replaced by a single 'memories'
collection with metadata-based access control.

- All memories live in one collection
- 'agent' metadata tracks the creator
- 'private' (bool, default False) controls visibility
- Query returns: shared (private=False) + own private (agent=asker)
- Save endpoint accepts optional 'private' field
- Version bumped to 0.2.0

main.py

@@ -2,8 +2,10 @@
 
 Endpoints
 ---------
-- ``POST /api/{agent_name}/save``   — Save a memory
-- ``POST /api/{agent_name}/query``  — Query memories by semantic similarity
+- ``POST /api/{agent_name}/save``   — Save a memory (shared by default,
+                                       or private if ``private: true``)
+- ``POST /api/{agent_name}/query``  — Query memories visible to the agent
+                                       (all shared + its own private ones)
 - ``GET  /health``                   — Health check
 """
 
@@ -25,8 +27,9 @@ from store import MemoryStore
 app = FastAPI(
     title="Vector Memory Server",
     description="Semantic memory retrieval via REST. "
-    "Per-agent collections, powered by ChromaDB + all-MiniLM-L6-v2.",
-    version="0.1.0",
+    "Shared-by-default, private-opt-in. "
+    "ChromaDB + all-MiniLM-L6-v2.",
+    version="0.2.0",
 )
 
 store = MemoryStore(Config.DATA_DIR)
@@ -38,6 +41,7 @@ store = MemoryStore(Config.DATA_DIR)
 
 class SaveRequest(BaseModel):
     text: str
+    private: bool = False
     type: Optional[str] = "fact"
     tags: Optional[list[str]] = None
     date: Optional[str] = None
@@ -63,9 +67,15 @@ class QueryResponse(BaseModel):
 
 @app.post("/api/{agent_name}/save", response_model=SaveResponse)
 async def save_memory(agent_name: str, request: SaveRequest) -> SaveResponse:
-    """Embed and store a memory for the given agent."""
+    """Embed and store a memory for *agent_name*.
+
+    By default the memory is **shared** (visible to all agents).
+    Set ``private: true`` to restrict visibility to *agent_name* only.
+    """
     try:
-        metadata: dict = {}
+        metadata: dict = {
+            "private": request.private,
+        }
         if request.type:
             metadata["type"] = request.type
         if request.tags:
@@ -83,7 +93,11 @@ async def save_memory(agent_name: str, request: SaveRequest) -> SaveResponse:
 async def query_memory(
     agent_name: str, request: QueryRequest
 ) -> QueryResponse:
-    """Retrieve semantically similar memories for the given agent."""
+    """Retrieve memories visible to *agent_name*.
+
+    Returns all **shared** memories from any agent, plus **private**
+    memories owned by *agent_name*.
+    """
     try:
         results = store.query(agent_name, request.query, request.top_n)
         return QueryResponse(results=results)

store.py

@@ -1,4 +1,22 @@
-"""ChromaDB-backed memory store with per-agent collections."""
+"""ChromaDB-backed memory store with shared/private visibility.
+
+All memories live in a single collection. Each memory has two key
+metadata fields:
+
+- ``agent`` (str) — the agent that created it
+- ``private`` (bool) — ``False`` by default (visible to all agents)
+
+When querying, the store returns:
+
+1. **All shared memories** (``private=False``) — every agent sees these.
+2. **Only the querying agent's own private memories** (``private=True``
+   and ``agent=<asker>``).
+
+This gives a clean hierarchy: shared knowledge by default, with an
+opt-in privacy mechanism for per-agent internal notes.
+"""
+
+from __future__ import annotations
 
 import uuid
 
@@ -7,12 +25,14 @@ from chromadb.config import Settings
 
 from embedder import Embedder
 
+COLLECTION_NAME = "memories"
+
 
 class MemoryStore:
     """Persistent vector store using ChromaDB.
 
-    Each agent gets its own collection (``agent_{name}``) so memories
-    are cleanly separated and can be queried independently.
+    … with an optional ``private`` flag (default ``False``) so agents
+    can keep sensitive memories to themselves.
     """
 
     def __init__(self, data_dir: str) -> None:
@@ -26,11 +46,11 @@ class MemoryStore:
     # Internal helpers
     # ------------------------------------------------------------------
 
-    def _get_collection(self, agent_name: str):
-        """Get or create a ChromaDB collection for *agent_name*."""
+    def _collection(self):
+        """Return the single shared collection (create if missing)."""
         return self.client.get_or_create_collection(
-            name=f"agent_{agent_name}",
-            metadata={"agent": agent_name},
+            name=COLLECTION_NAME,
+            metadata={"description": "Shared + private agent memories"},
         )
 
     # ------------------------------------------------------------------
@@ -43,18 +63,36 @@ class MemoryStore:
         text: str,
         metadata: dict | None = None,
     ) -> str:
-        """Embed *text* and store it in the agent's collection.
+        """Embed and store *text*.
 
-        Returns the auto-generated memory ID.
+        Parameters
+        ----------
+        agent_name
+            The agent creating this memory (stored in metadata).
+        text
+            The memory content.
+        metadata
+            Optional extra fields.  If it contains a ``private`` key
+            that will be passed to ChromaDB as-is; otherwise ``private``
+            defaults to ``False``.  The ``agent`` key is always
+            overwritten with *agent_name*.
+
+        Returns
+        -------
+        The auto-generated memory UUID.
         """
-        collection = self._get_collection(agent_name)
+        collection = self._collection()
         memory_id = str(uuid.uuid4())
         embedding = self.embedder.embed(text)
 
+        meta: dict = dict(metadata or {})
+        meta.setdefault("private", False)
+        meta["agent"] = agent_name
+
         collection.add(
             embeddings=[embedding],
             documents=[text],
-            metadatas=[metadata or {}],
+            metadatas=[meta],
             ids=[memory_id],
         )
         return memory_id
@@ -65,20 +103,36 @@ class MemoryStore:
         query_text: str,
         top_n: int = 5,
     ) -> list[dict]:
-        """Return the *top_n* most semantically similar memories as text.
+        """Return semantically similar memories visible to *agent_name*.
 
-        Each result dict contains:
-            - ``text`` – the stored memory text
-            - ``metadata`` – any additional metadata (original ``text``
-              field in metadata is stripped)
-            - ``distance`` – cosine distance from the query
+        Visibility rules
+        ----------------
+        - All non‑private memories (``private=False``) are returned
+          regardless of which agent created them.
+        - Private memories (``private=True``) are only returned for the
+          agent that owns them (``agent == agent_name``).
+
+        Each result dict contains
+        - ``text`` — the stored memory text
+        - ``metadata`` — metadata (minus the raw ``text`` field)
+        - ``distance`` — cosine distance from the query
         """
-        collection = self._get_collection(agent_name)
+        collection = self._collection()
         query_embedding = self.embedder.embed(query_text)
 
+        # ── ChromaDB where filter ──────────────────────────────────
+        # Show shared memories + the asking agent's own private ones.
+        where_filter = {
+            "$or": [
+                {"private": {"$eq": False}},
+                {"agent": {"$eq": agent_name}},
+            ]
+        }
+
         results = collection.query(
             query_embeddings=[query_embedding],
             n_results=top_n,
+            where=where_filter,
         )
 
         formatted: list[dict] = []
@@ -94,8 +148,6 @@ class MemoryStore:
                     if results.get("metadatas")
                     else {}
                 )
-                # Don't return the raw document text in metadata (it's
-                # already the top-level "text" field).
                 meta.pop("text", None)
 
                 formatted.append({