diff --git a/console/src/main.ts b/console/src/main.ts
index 401339f..5df8a73 100644
--- a/console/src/main.ts
+++ b/console/src/main.ts
@@ -455,10 +455,12 @@ function selectFleet(name: string): void {
   activeFleet = name;
   activeMembers = fleet.members;
   if (fleet.runtime === "k8s") {
-    // No ECS cluster for a k8s fleet — reads now go by the `fleet` name
-    // instead (oab-mcp resolves the bound context/namespace itself,
-    // studio#146 slices 2-3); `activeCluster` stays a plain "" sentinel,
-    // never read on this path.
+    // No ECS cluster for a k8s fleet — reads and scale/start/stop now go by
+    // the `fleet` name instead (oab-mcp resolves the bound context/namespace
+    // itself, studio#146 + the deploy_scale k8s dispatch fix). `activeCluster`
+    // stays a plain "" sentinel: still sent alongside `fleet` on every call
+    // for back-compat with the ECS path, but every k8s-aware tool checks
+    // `fleet`'s runtime before ever looking at it.
     activeCluster = "";
     const where = `${fleet.context ?? "current-context"}/${fleet.namespace ?? "default"}`;
     if (clusterLabel) clusterLabel.textContent = `${activeFleet} · ${where}`;
@@ -920,7 +922,11 @@ async function scale(
   );
   repaintRoster(); // disable the button immediately
   try {
-    await source.scaleDeployment(name, size, namespace, activeCluster);
+    // `activeCluster` is the "" sentinel for a k8s-runtime fleet (see
+    // `selectFleet`) — `fleet` carries the same (context, namespace)
+    // resolution `listDeployments`/`runtimeContext` already rely on, so
+    // oab-mcp can dispatch by runtime instead of falling through to ECS.
+    await source.scaleDeployment(name, size, namespace, activeCluster, activeFleet ?? undefined);
     note("info", `roster: ${action === "start" ? "started" : "stopped"} ${namespace}/${name}`);
     // tick() observes the new desiredCount and prunes the guard when it flips.
     await tick();
diff --git a/console/src/source.ts b/console/src/source.ts
index d980511..117defe 100644
--- a/console/src/source.ts
+++ b/console/src/source.ts
@@ -39,12 +39,16 @@ export interface Source {
   // Scale a deployment on (size 1) or off (size 0) — the start/stop action.
   // Reversible: ECS keeps the Spec at desiredCount 0, so no state store is
   // needed. `namespace` is required (the service is `oab-{namespace}-{name}`);
-  // the managing credential is resolved per-cluster from `cluster`.
+  // the managing credential is resolved per-cluster from `cluster`. `fleet`
+  // (same rule as `listDeployments`/`runtimeContext`) is required to reach a
+  // k8s-runtime fleet — pass it whenever a fleet is active, alongside
+  // `cluster`, so oab-mcp can dispatch by runtime without a cluster fallback.
   scaleDeployment(
     name: string,
     size: 0 | 1,
     namespace: string,
     cluster?: string,
+    fleet?: string,
   ): Promise<void>;
   // The remote reverse-MCP connection (Part B): the management endpoint's parsed
   // url + live status for the panel. The editor now edits the registry
@@ -181,12 +185,14 @@ export class TauriSource implements Source {
     size: 0 | 1,
     namespace: string,
     cluster?: string,
+    fleet?: string,
   ): Promise<void> {
     await this.invoke()<unknown>("deploy_scale", {
       name,
       size,
       namespace,
       cluster,
+      fleet,
     });
   }
   async remoteConfig(): Promise<RemoteConfig> {
diff --git a/crates/oab-mcp/src/lib.rs b/crates/oab-mcp/src/lib.rs
index 1ccc5d0..6469f57 100644
--- a/crates/oab-mcp/src/lib.rs
+++ b/crates/oab-mcp/src/lib.rs
@@ -146,15 +146,15 @@ pub fn tools() -> Vec<Tool> {
         ),
         Tool::new(
             "deploy_scale",
-            "Scale an OAB service on or off. OAB services run a single bot token, so size must be 0 (off) or 1 (on).",
+            "Scale an OAB service on or off. OAB services run a single bot token, so size must be 0 (off) or 1 (on). Works for both ECS and k8s-runtime fleets (pass `fleet` for k8s — required, since a k8s-runtime fleet has no ECS cluster to fall back to).",
             as_map(json!({
                 "type": "object",
                 "properties": {
                     "name": { "type": "string", "description": "Agent / service name (service = oab-{namespace}-{name})." },
                     "size": { "type": "integer", "enum": [0, 1], "description": "0 = off, 1 = on." },
-                    "fleet": { "type": "string", "description": "Fleet name (see fleet_config): targets the fleet's cluster and managing credential; a write to a service outside the fleet's members is refused. Overrides the cluster arg." },
-                    "cluster": { "type": "string", "description": "ECS cluster (defaults to the server's configured cluster)." },
-                    "namespace": { "type": "string", "description": "Namespace (default \"default\")." }
+                    "fleet": { "type": "string", "description": "Fleet name (see fleet_config): targets the fleet's cluster/context and managing credential; a write to a service outside the fleet's members is refused. Overrides the cluster arg. Required for a k8s-runtime fleet." },
+                    "cluster": { "type": "string", "description": "ECS cluster (defaults to the server's configured cluster). Ignored for a k8s-runtime fleet." },
+                    "namespace": { "type": "string", "description": "Namespace (default \"default\"). Ignored for a k8s-runtime fleet — the fleet binding's own namespace is used." }
                 },
                 "required": ["name", "size"]
             })),
@@ -918,8 +918,6 @@ impl OabMcp {
     }
 
     async fn t_scale(&self, args: &Map<String, Value>) -> Result<Value> {
-        let t = self.target(args)?;
-        let cluster = t.cluster.clone();
         let namespace = args
             .get("namespace")
             .and_then(Value::as_str)
@@ -932,10 +930,27 @@ impl OabMcp {
             args.get("size")
                 .and_then(Value::as_i64)
                 .ok_or_else(|| anyhow::anyhow!("missing or invalid arg: size"))? as i32;
+        let service_name = format!("oab-{namespace}-{name}");
+        if let Some(b) = self.named_fleet(args)? {
+            if b.runtime == scp::FleetRuntime::K8s {
+                // Guard: a fleet handle only operates its own members — same
+                // reasoning as the ECS path below.
+                if !b.includes(&service_name, name) {
+                    anyhow::bail!("service {service_name:?} is not a member of the named fleet");
+                }
+                let namespace = b.namespace.clone().unwrap_or_else(|| namespace.to_string());
+                scp::scale_k8s_deployment(b.context.as_deref(), &namespace, name, size).await?;
+                return Ok(json!({
+                    "ok": true, "cluster": null, "context": b.context, "namespace": namespace,
+                    "name": name, "size": size,
+                }));
+            }
+        }
+        let t = self.target(args)?;
+        let cluster = t.cluster.clone();
         // Guard: a fleet handle only operates its own members — refuse to scale a
         // service outside the named fleet (a no-op for unscoped or whole-cluster
         // calls). Stops a fleet-scoped call from reaching a co-located non-member.
-        let service_name = format!("oab-{namespace}-{name}");
         if !t.includes(&service_name, name) {
             anyhow::bail!("service {service_name:?} is not a member of the named fleet");
         }
diff --git a/crates/studio-cp/src/lib.rs b/crates/studio-cp/src/lib.rs
index 88b9f5c..b35d885 100644
--- a/crates/studio-cp/src/lib.rs
+++ b/crates/studio-cp/src/lib.rs
@@ -2448,6 +2448,22 @@ pub async fn scale_deployment(
     oabctl::studio_api::scale(aws_config, cluster, namespace, name, size).await
 }
 
+/// Scale a k8s-runtime OAB service to `size` replicas (0 = off, 1 = on) — the
+/// k8s counterpart to [`scale_deployment`]. `deploy_scale`/`t_scale` never
+/// had a k8s branch (studio#146 only made the *read* path — list/get/
+/// runtime_context — k8s-aware); this closes that gap so a k8s-runtime
+/// fleet's start/stop action reaches `K8sDriver::scale` instead of silently
+/// falling through to the ECS path with an empty cluster string.
+pub async fn scale_k8s_deployment(
+    context: Option<&str>,
+    namespace: &str,
+    name: &str,
+    size: i32,
+) -> anyhow::Result<()> {
+    use oabctl::ProvisionDriver;
+    oabctl::K8sDriver::from_context(context).await?.scale(namespace, name, size).await
+}
+
 /// Delete a control-plane resource (e.g. an `OABService`).
 ///
 /// The control-plane bucket is resolved from the environment / account, not
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 0f47aed..3600262 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -569,6 +569,9 @@ async fn list_service_accounts(
 /// Spec is kept by ECS, so it's reversible). An OAB service runs a single bot
 /// token, so size is 0/1 only; `namespace` is required upstream to resolve the
 /// service (`oab-{namespace}-{name}`) and the managing credential is per-cluster.
+/// `fleet` (same rule as `deploy_list`/`runtime_context`) is required to reach a
+/// k8s-runtime fleet — without it this silently fell through to the ECS path
+/// with an empty cluster string.
 #[tauri::command]
 async fn deploy_scale(
     core: tauri::State<'_, Core>,
@@ -576,6 +579,7 @@ async fn deploy_scale(
     size: i64,
     namespace: Option<String>,
     cluster: Option<String>,
+    fleet: Option<String>,
 ) -> Result<Value, String> {
     let cluster = cluster.unwrap_or_else(default_cluster);
     let client = {
@@ -589,6 +593,9 @@ async fn deploy_scale(
     if let Some(ns) = namespace {
         params["namespace"] = json!(ns);
     }
+    if let Some(f) = fleet {
+        params["fleet"] = json!(f);
+    }
     match client.call_tool("deploy_scale", params).await {
         Ok(v) => Ok(v),
         Err(e) => {