fix(M2-005,M2-006): enforce user ownership at repo level for conversations and agents (#293)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/brain/src/agents.ts

@@ -1,4 +1,4 @@
-import { eq, or, type Db, agents } from '@mosaic/db';
+import { eq, and, or, type Db, agents } from '@mosaic/db';
 
 export type Agent = typeof agents.$inferSelect;
 export type NewAgent = typeof agents.$inferInsert;
@@ -27,6 +27,10 @@ export function createAgentsRepo(db: Db) {
       return db.select().from(agents).where(eq(agents.isSystem, true));
     },
 
+    /**
+     * Return only agents the user may access: their own agents plus all system agents.
+     * Never returns other users' private agents.
+     */
     async findAccessible(ownerId: string): Promise<Agent[]> {
       return db
         .select()
@@ -39,17 +43,44 @@ export function createAgentsRepo(db: Db) {
       return rows[0]!;
     },
 
-    async update(id: string, data: Partial<NewAgent>): Promise<Agent | undefined> {
+    /**
+     * Update an agent.
+     *
+     * For user-owned agents pass `ownerId` — the WHERE clause will enforce ownership so that
+     * one user cannot overwrite another user's agent.  For system agents the caller must
+     * omit `ownerId` (admin-only path) and the WHERE clause only matches on `id`.
+     *
+     * Returns undefined when no row was matched (not found or ownership mismatch).
+     */
+    async update(
+      id: string,
+      data: Partial<NewAgent>,
+      ownerId?: string,
+    ): Promise<Agent | undefined> {
+      const condition =
+        ownerId !== undefined
+          ? and(eq(agents.id, id), eq(agents.ownerId, ownerId))
+          : eq(agents.id, id);
+
       const rows = await db
         .update(agents)
         .set({ ...data, updatedAt: new Date() })
-        .where(eq(agents.id, id))
+        .where(condition)
         .returning();
       return rows[0];
     },
 
-    async remove(id: string): Promise<boolean> {
-      const rows = await db.delete(agents).where(eq(agents.id, id)).returning();
+    /**
+     * Delete a user-owned agent, scoped to the given owner.
+     * Will not match system agents even if the id is correct, because system agents have
+     * `ownerId = null` which cannot equal a real user id.
+     * Returns false when no row was matched (not found, wrong owner, or system agent).
+     */
+    async remove(id: string, ownerId: string): Promise<boolean> {
+      const rows = await db
+        .delete(agents)
+        .where(and(eq(agents.id, id), eq(agents.ownerId, ownerId)))
+        .returning();
       return rows.length > 0;
     },
   };