diff --git a/policy/memory-action.go b/policy/memory-action.go
index 5d20282..6e52845 100644
--- a/policy/memory-action.go
+++ b/policy/memory-action.go
@@ -50,9 +50,15 @@ const (
 	// MemoryListSecretsAction - list the secrets in a cortex.
 	MemoryListSecretsAction MemoryAction = "memory:ListSecrets"
 
-	// MemoryPutAgentAction - write an agent record in a cortex.
+	// MemoryPutAgentAction - create an agent record, or write a memory beneath
+	// it. Create-only, so it is safe to grant alongside a memory write.
 	MemoryPutAgentAction MemoryAction = "memory:PutAgent"
 
+	// MemoryUpdateAgentAction - modify an existing agent record in a cortex. Separate
+	// from MemoryPutAgentAction, which only creates: an update re-derives the agent's
+	// IAM policy from its mounts, so it must be grantable without granting creation.
+	MemoryUpdateAgentAction MemoryAction = "memory:UpdateAgent"
+
 	// MemoryGetAgentAction - read an agent record from a cortex.
 	MemoryGetAgentAction MemoryAction = "memory:GetAgent"
 
@@ -84,6 +90,7 @@ var SupportedMemoryActions = map[MemoryAction]struct{}{
 	MemoryDeleteSecretAction: {},
 	MemoryListSecretsAction:  {},
 	MemoryPutAgentAction:     {},
+	MemoryUpdateAgentAction:  {},
 	MemoryGetAgentAction:     {},
 	MemoryDeleteAgentAction:  {},
 	MemoryListAgentsAction:   {},
diff --git a/policy/memory-action_test.go b/policy/memory-action_test.go
index a41c641..a261d4a 100644
--- a/policy/memory-action_test.go
+++ b/policy/memory-action_test.go
@@ -35,6 +35,7 @@ func TestMemoryActionIsValid(t *testing.T) {
 		{MemoryDeleteSecretAction, true},
 		{MemoryListSecretsAction, true},
 		{MemoryPutAgentAction, true},
+		{MemoryUpdateAgentAction, true},
 		{MemoryGetAgentAction, true},
 		{MemoryDeleteAgentAction, true},
 		{MemoryListAgentsAction, true},
diff --git a/policy/memory-resource_test.go b/policy/memory-resource_test.go
index 6514bbd..96bf7f4 100644
--- a/policy/memory-resource_test.go
+++ b/policy/memory-resource_test.go
@@ -791,7 +791,10 @@ func TestStarPrefixedResourceParses(t *testing.T) {
 // both actions against one resource would leak names without any cue.
 func TestMemoryEnumerationConditionKeys(t *testing.T) {
 	listActions := []string{"memory:ListAgents", "memory:ListSecrets", "memory:ListCortexes"}
-	pointActions := []string{"memory:GetAgent", "memory:PutAgent", "memory:DeleteAgent", "memory:GetSecret"}
+	pointActions := []string{
+		"memory:GetAgent", "memory:PutAgent", "memory:DeleteAgent", "memory:GetSecret",
+		"memory:UpdateAgent",
+	}
 
 	for _, action := range listActions {
 		keys, ok := MemoryActionConditionKeyMap[Action(action)]
@@ -809,8 +812,10 @@ func TestMemoryEnumerationConditionKeys(t *testing.T) {
 	// let a policy look scoped while constraining nothing.
 	for _, action := range pointActions {
 		keys := MemoryActionConditionKeyMap[Action(action)]
-		if keys.Match(condition.MemoryPrefix.ToKey()) {
-			t.Errorf("%s must not accept %s", action, condition.MemoryPrefix)
+		for _, key := range []condition.KeyName{condition.MemoryPrefix, condition.MemoryMaxKeys} {
+			if keys.Match(key.ToKey()) {
+				t.Errorf("%s must not accept %s", action, key)
+			}
 		}
 	}