diff --git a/src/lean_spec/subspecs/forkchoice/store.py b/src/lean_spec/subspecs/forkchoice/store.py
index 764e7ba3..5b333553 100644
--- a/src/lean_spec/subspecs/forkchoice/store.py
+++ b/src/lean_spec/subspecs/forkchoice/store.py
@@ -210,18 +210,21 @@ def from_anchor(
         # Read the slot at which the anchor block was proposed.
         anchor_slot = anchor_block.slot
 
-        # Initialize checkpoints from this state.
+        # Seed both checkpoints from the anchor block itself.
         #
-        # We explicitly set the root to the anchor block root.
-        # The state internally might have zero-hash checkpoints (if genesis),
-        # but the Store must treat the anchor block as the justified/finalized point.
+        # The store treats the anchor as the new "genesis" for fork choice:
+        # all history below it is pruned. The justified and finalized checkpoints
+        # therefore point at the anchor block with the anchor's own slot,
+        # regardless of what the anchor state's embedded checkpoints say.
+        anchor_checkpoint = Checkpoint(root=anchor_root, slot=anchor_slot)
+
         return cls(
             time=Interval.from_slot(anchor_slot),
             config=state.config,
             head=anchor_root,
             safe_target=anchor_root,
-            latest_justified=state.latest_justified.model_copy(update={"root": anchor_root}),
-            latest_finalized=state.latest_finalized.model_copy(update={"root": anchor_root}),
+            latest_justified=anchor_checkpoint,
+            latest_finalized=anchor_checkpoint,
             blocks={anchor_root: anchor_block},
             states={anchor_root: state},
             validator_id=validator_id,
@@ -515,8 +518,8 @@ def on_block(
             # Keep the checkpoint with the higher slot.
             # On slot ties, prefer the store's own checkpoint.
             #
-            # The store's checkpoint is pinned to the anchor block root at init.
-            # The anchor state may hold a pre-anchor root.
+            # The store's checkpoint is pinned to the anchor at init and only
+            # moves forward via real justification/finalization events.
             # On ties the store's view is authoritative.
             latest_justified = max(
                 self.latest_justified, post_state.latest_justified, key=lambda c: c.slot
diff --git a/tests/consensus/devnet/fc/test_checkpoint_sync.py b/tests/consensus/devnet/fc/test_checkpoint_sync.py
index 15c07a90..c9657fb5 100644
--- a/tests/consensus/devnet/fc/test_checkpoint_sync.py
+++ b/tests/consensus/devnet/fc/test_checkpoint_sync.py
@@ -47,7 +47,8 @@ def test_store_init_from_non_genesis_anchor(
     -----------------------------
 
     - Head points to the anchor block.
-    - Latest justified and latest finalized both reference the anchor root.
+    - Latest justified and latest finalized both reference the anchor root
+      at the anchor's own slot (beacon-chain seeding convention).
     - Store clock is at the anchor slot (no pre-anchor intervals tracked).
     - The anchor block is the only entry in the store's block map.
 
@@ -78,9 +79,12 @@ def test_store_init_from_non_genesis_anchor(
                     time=anchor_time_intervals,
                     head_slot=ANCHOR_SLOT,
                     head_root_label="genesis",
-                    latest_justified_slot=anchor_state.latest_justified.slot,
+                    # Both checkpoints are seeded from the anchor itself:
+                    # slot = anchor.slot, root = anchor_root. The anchor
+                    # state's embedded checkpoint slots are intentionally ignored.
+                    latest_justified_slot=ANCHOR_SLOT,
                     latest_justified_root_label="genesis",
-                    latest_finalized_slot=anchor_state.latest_finalized.slot,
+                    latest_finalized_slot=ANCHOR_SLOT,
                     latest_finalized_root_label="genesis",
                     safe_target_root_label="genesis",
                     labels_in_store=["genesis"],
@@ -135,9 +139,11 @@ def test_extend_chain_from_non_genesis_anchor(
                 checks=StoreChecks(
                     head_slot=Slot(11),
                     head_root_label="block_11",
-                    latest_justified_slot=anchor_state.latest_justified.slot,
+                    # Empty blocks carry no attestations, so neither checkpoint
+                    # advances past the anchor seeding.
+                    latest_justified_slot=ANCHOR_SLOT,
                     latest_justified_root_label="genesis",
-                    latest_finalized_slot=anchor_state.latest_finalized.slot,
+                    latest_finalized_slot=ANCHOR_SLOT,
                     latest_finalized_root_label="genesis",
                     labels_in_store=["genesis", "block_11"],
                 ),
@@ -151,7 +157,9 @@ def test_extend_chain_from_non_genesis_anchor(
                 checks=StoreChecks(
                     head_slot=Slot(12),
                     head_root_label="block_12",
+                    latest_justified_slot=ANCHOR_SLOT,
                     latest_justified_root_label="genesis",
+                    latest_finalized_slot=ANCHOR_SLOT,
                     latest_finalized_root_label="genesis",
                     labels_in_store=["genesis", "block_11", "block_12"],
                 ),
@@ -165,7 +173,9 @@ def test_extend_chain_from_non_genesis_anchor(
                 checks=StoreChecks(
                     head_slot=Slot(13),
                     head_root_label="block_13",
+                    latest_justified_slot=ANCHOR_SLOT,
                     latest_justified_root_label="genesis",
+                    latest_finalized_slot=ANCHOR_SLOT,
                     latest_finalized_root_label="genesis",
                     labels_in_store=["genesis", "block_11", "block_12", "block_13"],
                 ),
@@ -238,9 +248,9 @@ def test_fork_off_non_genesis_anchor(
             # unambiguously heavier.
             #
             # Source is pinned to the anchor block because the store
-            # only knows about blocks at or after the anchor. The
-            # anchor state's internal justified root still points to
-            # pre-anchor history that was discarded on checkpoint sync.
+            # only knows about blocks at or after the anchor, and the
+            # store's latest_justified checkpoint is seeded at
+            # (anchor.slot, anchor_root).
             BlockStep(
                 block=BlockSpec(
                     slot=Slot(12),