diff --git a/letta/orm/agent.py b/letta/orm/agent.py
index e6b14987..781ab383 100644
--- a/letta/orm/agent.py
+++ b/letta/orm/agent.py
@@ -70,7 +70,14 @@ class Agent(SqlalchemyBase, OrganizationMixin):
     )
     tools: Mapped[List["Tool"]] = relationship("Tool", secondary="tools_agents", lazy="selectin", passive_deletes=True)
     sources: Mapped[List["Source"]] = relationship("Source", secondary="sources_agents", lazy="selectin")
-    core_memory: Mapped[List["Block"]] = relationship("Block", secondary="blocks_agents", lazy="selectin")
+    core_memory: Mapped[List["Block"]] = relationship(
+        "Block",
+        secondary="blocks_agents",
+        lazy="selectin",
+        passive_deletes=True,  # Ensures SQLAlchemy doesn't fetch blocks_agents rows before deleting
+        back_populates="agents",
+        doc="Blocks forming the core memory of the agent.",
+    )
     messages: Mapped[List["Message"]] = relationship(
         "Message",
         back_populates="agent",
diff --git a/letta/orm/block.py b/letta/orm/block.py
index ecfa6fe1..3e8c8006 100644
--- a/letta/orm/block.py
+++ b/letta/orm/block.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Optional, Type
+from typing import TYPE_CHECKING, List, Optional, Type
 
 from sqlalchemy import JSON, BigInteger, Index, Integer, UniqueConstraint, event
 from sqlalchemy.orm import Mapped, attributes, mapped_column, relationship
@@ -39,6 +39,14 @@ class Block(OrganizationMixin, SqlalchemyBase):
 
     # relationships
     organization: Mapped[Optional["Organization"]] = relationship("Organization")
+    agents: Mapped[List["Agent"]] = relationship(
+        "Agent",
+        secondary="blocks_agents",
+        lazy="selectin",
+        passive_deletes=True,  # Ensures SQLAlchemy doesn't fetch blocks_agents rows before deleting
+        back_populates="core_memory",
+        doc="Agents associated with this block.",
+    )
 
     def to_pydantic(self) -> Type:
         match self.label:
diff --git a/tests/test_managers.py b/tests/test_managers.py
index 28ad057a..fe6280d5 100644
--- a/tests/test_managers.py
+++ b/tests/test_managers.py
@@ -1155,6 +1155,10 @@ def test_detach_block(server: SyncServer, sarah_agent, default_block, default_us
     agent = server.agent_manager.get_agent_by_id(sarah_agent.id, actor=default_user)
     assert len(agent.memory.blocks) == 0
 
+    # Check that block still exists
+    block = server.block_manager.get_block_by_id(block_id=default_block.id, actor=default_user)
+    assert block
+
 
 def test_detach_nonexistent_block(server: SyncServer, sarah_agent, default_user):
     """Test detaching a block that isn't attached."""
@@ -2080,6 +2084,26 @@ def test_delete_block(server: SyncServer, default_user):
     assert len(blocks) == 0
 
 
+def test_delete_block_detaches_from_agent(server: SyncServer, sarah_agent, default_user):
+    # Create and delete a block
+    block = server.block_manager.create_or_update_block(PydanticBlock(label="human", value="Sample content"), actor=default_user)
+    agent_state = server.agent_manager.attach_block(agent_id=sarah_agent.id, block_id=block.id, actor=default_user)
+
+    # Check that block has been attached
+    assert block.id in [b.id for b in agent_state.memory.blocks]
+
+    # Now attempt to delete the block
+    server.block_manager.delete_block(block_id=block.id, actor=default_user)
+
+    # Verify that the block was deleted
+    blocks = server.block_manager.get_blocks(actor=default_user)
+    assert len(blocks) == 0
+
+    # Check that block has been detached too
+    agent_state = server.agent_manager.get_agent_by_id(agent_id=sarah_agent.id, actor=default_user)
+    assert not (block.id in [b.id for b in agent_state.memory.blocks])
+
+
 # ======================================================================================================================
 # SourceManager Tests - Sources
 # ======================================================================================================================