diff --git a/src/hippocampus/store/ops.rs b/src/hippocampus/store/ops.rs
index 67d5a7f..463ec2e 100644
--- a/src/hippocampus/store/ops.rs
+++ b/src/hippocampus/store/ops.rs
@@ -359,7 +359,16 @@ impl Store {
             }
         }
         if !found {
-            return Err(format!("no link between {} and {}", source, target));
+            // Upsert: create the link if it doesn't exist
+            self.add_link(source, target, "link_set")?;
+            // Set the strength on the newly created link
+            for rel in self.relations.iter_mut().rev() {
+                if !rel.deleted && rel.source_key == source && rel.target_key == target {
+                    rel.strength = strength;
+                    break;
+                }
+            }
+            return Ok(0.0);
         }
         Ok(old)
     }