diff --git a/AGENTS.md b/AGENTS.md
index 52600b56..194b4b85 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -51,3 +51,24 @@ The project is a client daemon (`loopd`) that connects to a user's `lnd` node an
 *   **Cryptography:** Extensively uses Taproot and MuSig2 for efficiency, privacy, and complex spending conditions, especially in the `instantout` and `staticaddr` features.
 *   **Labeling (`labels/`):** A utility to create and validate labels for swaps, which helps distinguish between user-initiated and automated swaps (e.g., `[reserved]: autoloop-out`).
 *   **Assets (`assets/`):** Contains logic for interacting with `tapd` (Taproot Assets Protocol Daemon), allowing Loop to facilitate swaps involving assets other than Bitcoin.
+
+**5. Minimum `lnd` Version (`loopd/run.go`):**
+
+`loopd` enforces a minimum `lnd` version at startup through
+`LoopMinRequiredLndVersion` in `loopd/run.go` (handed to `lndclient` as
+`CheckVersion`). This is a hard gate: loopd refuses to start against an older
+`lnd` node.
+
+**Maintenance rule:** whenever you start using an `lnd` gRPC method or message
+field that does not exist in older `lnd`, bump `LoopMinRequiredLndVersion` to the
+`lnd` release that introduced that API, and record which API drove the bump in the
+comment above the variable. Pin it to the *real* floor of the APIs the client uses
+— do **not** just track the `go.mod` dependency. Historically this value only
+tracked `go.mod` and drifted out of sync with the APIs actually called (it sat at
+0.17.0 while the client already depended on 0.18.4 APIs). To find the introducing
+release, grep the field/method across `lnd` version tags, e.g.
+`git grep <field> <tag> -- <proto-file>`. As of the current floor (**v0.18.4-beta**)
+the binding dependencies are the asset loop-out fields
+`routerrpc.SendPaymentRequest.first_hop_custom_records` and
+`lnrpc.Route.custom_channel_data` (lnd v0.18.4-beta), plus the sweep-batcher fee
+floor `walletrpc.EstimateFeeResponse.min_relay_fee_sat_per_kw` (lnd v0.18.3-beta).
diff --git a/loopd/run.go b/loopd/run.go
index 0735d29a..e33fea8e 100644
--- a/loopd/run.go
+++ b/loopd/run.go
@@ -24,10 +24,24 @@ var (
 	// LoopMinRequiredLndVersion is the minimum required version of lnd that
 	// is compatible with the current version of the loop client. Also all
 	// listed build tags/subservers need to be enabled.
+	//
+	// IMPORTANT: bump this whenever the client starts using an lnd RPC
+	// method or message field that does not exist in older lnd, to the lnd
+	// release that introduced that API (see the maintenance note in
+	// AGENTS.md). The current floor of v0.18.4-beta is set by the highest
+	// such dependency the client has today:
+	//   - routerrpc.SendPaymentRequest.first_hop_custom_records and
+	//     lnrpc.Route.custom_channel_data, used by asset loop outs
+	//     (loopout.go): both added in lnd v0.18.4-beta.
+	//   - walletrpc.EstimateFeeResponse.min_relay_fee_sat_per_kw, read by
+	//     the sweep batcher fee floor via lndclient WalletKit.MinRelayFee
+	//     (sweepbatcher/, loopd/sweep_htlc.go): added in lnd v0.18.3-beta.
+	//     On older lnd this field silently decodes to 0, disabling the
+	//     sweeper's min-relay fee floor.
 	LoopMinRequiredLndVersion = &verrpc.Version{
 		AppMajor: 0,
-		AppMinor: 17,
-		AppPatch: 0,
+		AppMinor: 18,
+		AppPatch: 4,
 		BuildTags: []string{
 			"signrpc", "walletrpc", "chainrpc", "invoicesrpc",
 		},