diff --git a/replays/register.go b/replays/register.go
index eac93cb..dd5cea9 100644
--- a/replays/register.go
+++ b/replays/register.go
@@ -430,6 +430,19 @@ var Register = []Replay{
 		Package: "./cmd/mesh-controller", Test: "TestReplay201ThePlansSend",
 		Files: []string{"cmd/mesh-controller/replay201_test.go"},
 		Home:  "mesh-controller", HomeRef: "45a1783ba9a43fd466a518ee85673c701223b517"},
+	// A requirement could not be optional (issue 166): every soft dependency had become a hard requirement, so a
+	// manifest could not say grafana runs without a data source — a mesh without influxdb could not register it,
+	// and with influxdb only in the catalogue, assigning grafana installed influxdb for it. A test of its own in
+	// the controller, written with only what it had before — ParseManifest, Resolve, the resolve tests' helpers —
+	// laid over the commit before. Fix is the merge of its pull request (mesh-controller #281); Home is the commit
+	// that added the replay (mesh-controller #287), reachable once that pull request merges.
+	{ID: "R166", Issue: 166, Kind: InRepository, Repository: "mesh-controller", Fix: "4473bc7d7315bb462dcce7d6a8927bff37ecdc59",
+		What: "a manifest could not say a requirement is optional: grafana, which runs without a data source, could " +
+			"not be assigned on a mesh without influxdb, and influxdb only in the catalogue was installed for it",
+		Asserts: "a requirement marked optional parses; with no provider running, assigning its consumer is not refused " +
+			"and installs nothing for it; with a provider running elsewhere it binds",
+		Package: "./internal/catalogue", Test: "TestReplay166", Files: []string{"internal/catalogue/replay166_test.go"},
+		Home: "mesh-controller", HomeRef: "b1baa8d8baf0289b76e8082b3b95d146af6a973e"},
 }
 
 // Find is the replay of that id, or of that issue.