diff --git a/docs/swarm/ui.md b/docs/swarm/ui.md
index 217fd426..606819a9 100644
--- a/docs/swarm/ui.md
+++ b/docs/swarm/ui.md
@@ -299,14 +299,18 @@ sets the hive's own limits.
 ### Settings at creation
 
 The **+ agent** dialog has two collapsed sections, **resource caps** and
-**inference**, with the same fields as the detail panel's editors. Leave them
-closed or empty and the request is the plain name and hive. Fill them and
-`POST /api/agents` carries them as optional `limits` and `inference` objects,
-the same shapes the two `PUT` routes take. The controller checks them with the
-`PUT` rules before it queues anything, so a bad value gets a refusal with its
-reason and creates no agent. It stores them ahead of the job graph, so they
-are in place before the agent first runs. Creating a name that already exists with no settings
-leaves any stored ones alone.
+**inference**, with the same fields as the detail panel's editors. Leave the
+fields empty and the request is the plain name and hive; collapsing a section doesn't
+withdraw what you typed in it. Fill them and `POST /api/agents` carries them
+as optional `limits` and `inference` objects, the same shapes the two `PUT`
+routes take. The controller checks them with the `PUT` rules before it queues
+anything, so a bad value gets a refusal with its reason and creates no agent.
+
+It stores them ahead of the job graph, before it declares the agent, so they
+are in place before the agent first runs. If the creation then fails, the
+controller puts back what it replaced. Each agent name keys its settings and
+destroying an agent doesn't clear them, so a name set up before keeps its
+stored settings when you leave the fields empty.
 
 ### Linking external accounts
 
diff --git a/frontend/packages/swarm-ui/src/agent/detail/AgentInference.tsx b/frontend/packages/swarm-ui/src/agent/detail/AgentInference.tsx
index 08e5a7f7..4bea9102 100644
--- a/frontend/packages/swarm-ui/src/agent/detail/AgentInference.tsx
+++ b/frontend/packages/swarm-ui/src/agent/detail/AgentInference.tsx
@@ -141,36 +141,40 @@ export function draftBody(d: InferenceDraft): Settings {
 export function InferenceFields({
   draft,
   onChange,
+  idPrefix = "inference",
 }: {
   draft: InferenceDraft;
   onChange: (d: InferenceDraft) => void;
+  // Ids must be unique on the page, and the agents page can hold the editor
+  // and the create dialog at once.
+  idPrefix?: string;
 }) {
   const problem = draftProblem(draft);
   return (
     <>
       <TextField
-        id="inference-model"
+        id={`${idPrefix}-model`}
         label="model"
         value={draft.model}
         placeholder="e.g. opus"
         onInput={(model) => onChange({ ...draft, model })}
       />
       <SelectField
-        id="inference-effort"
+        id={`${idPrefix}-effort`}
         label="effort"
         value={draft.effort}
         options={EFFORT_OPTIONS}
         onChange={(effort) => onChange({ ...draft, effort })}
       />
       <TextField
-        id="inference-subagent-models"
+        id={`${idPrefix}-subagent-models`}
         label="subagent models"
         value={draft.subagents}
         placeholder="e.g. haiku, sonnet"
         onInput={(subagents) => onChange({ ...draft, subagents })}
       />
       <TextField
-        id="inference-max-subagents"
+        id={`${idPrefix}-max-subagents`}
         label="max subagents"
         value={draft.maxSubagents}
         placeholder="empty for no cap"
diff --git a/frontend/packages/swarm-ui/src/agent/detail/AgentLimits.tsx b/frontend/packages/swarm-ui/src/agent/detail/AgentLimits.tsx
index 2089411d..da7fb392 100644
--- a/frontend/packages/swarm-ui/src/agent/detail/AgentLimits.tsx
+++ b/frontend/packages/swarm-ui/src/agent/detail/AgentLimits.tsx
@@ -50,16 +50,20 @@ export function LimitsFields({
   memory,
   onCpu,
   onMemory,
+  idPrefix = "limits",
 }: {
   cpu: string;
   memory: string;
   onCpu: (v: string) => void;
   onMemory: (v: string) => void;
+  // Ids must be unique on the page, and the agents page can hold the editor
+  // and the create dialog at once.
+  idPrefix?: string;
 }) {
   return (
     <>
       <TextField
-        id="limits-cpu-quota"
+        id={`${idPrefix}-cpu-quota`}
         label="cpu quota"
         value={cpu}
         placeholder="e.g. 400%"
@@ -69,7 +73,7 @@ export function LimitsFields({
         A percentage of one core: 100% is one core, 400% is four.
       </p>
       <TextField
-        id="limits-memory-max"
+        id={`${idPrefix}-memory-max`}
         label="memory max"
         value={memory}
         placeholder="e.g. 8G"
diff --git a/frontend/packages/swarm-ui/src/pages/CreateAgentForm.tsx b/frontend/packages/swarm-ui/src/pages/CreateAgentForm.tsx
index 8041e23d..e7b2f0ca 100644
--- a/frontend/packages/swarm-ui/src/pages/CreateAgentForm.tsx
+++ b/frontend/packages/swarm-ui/src/pages/CreateAgentForm.tsx
@@ -167,8 +167,8 @@ export function CreateAgentForm({
           <p class="create-agent-intro">
             Create a new agent's swarm-level identity. This only queues the job
             — check <Link href="/jobs">jobs</Link> to watch it settle. Resource
-            caps and inference are optional; leave them closed to keep the
-            defaults.
+            caps and inference are optional; leave them empty to set nothing. A
+            name set up before keeps the settings stored for it.
           </p>
           {hivesError && (
             <ApiErrorPanel
@@ -206,6 +206,7 @@ export function CreateAgentForm({
               <summary>resource caps</summary>
               <div class="create-agent-section-body">
                 <LimitsFields
+                  idPrefix="create-limits"
                   cpu={cpu}
                   memory={memory}
                   onCpu={setCpu}
@@ -216,7 +217,11 @@ export function CreateAgentForm({
             <details class="create-agent-section">
               <summary>inference</summary>
               <div class="create-agent-section-body">
-                <InferenceFields draft={inference} onChange={setInference} />
+                <InferenceFields
+                  idPrefix="create-inference"
+                  draft={inference}
+                  onChange={setInference}
+                />
               </div>
             </details>
             <Button
diff --git a/swarm-controller/src/agent_limits.rs b/swarm-controller/src/agent_limits.rs
index 9aabd3f3..06563bff 100644
--- a/swarm-controller/src/agent_limits.rs
+++ b/swarm-controller/src/agent_limits.rs
@@ -257,24 +257,28 @@ pub(crate) async fn put_agent_limits(
     Ok(Json(value.into()))
 }
 
+/// What [`store`] replaced: the caps that were stored, or `None` for no key.
+pub(crate) struct Replaced(Option<AgentCaps>);
+
 /// Replace `agent`'s stored caps with `value`.
 pub(crate) async fn store(
     client: &async_nats::Client,
     agent: &str,
     value: &AgentCaps,
-) -> Result<(), ProblemDetails> {
+) -> Result<Replaced, ProblemDetails> {
     let store = open_or_create(client).await?;
     for _ in 0..MAX_ATTEMPTS {
         let (current, revision, undecodable) = read_or_default::<AgentCaps>(&store, agent)
             .await
             .map_err(|e| queue_problem(&e))?;
+        let replaced = Replaced(revision.map(|_| current.clone()));
         if (current == *value && !undecodable)
             || write(&store, agent, value, revision)
                 .await
                 .map_err(|e| queue_problem(&e))?
         {
             tracing::info!(%agent, ?value, "set agent limits");
-            return Ok(());
+            return Ok(replaced);
         }
     }
     Err(queue_problem(&anyhow::anyhow!(
@@ -282,6 +286,24 @@ pub(crate) async fn store(
     )))
 }
 
+/// Put back what [`store`] replaced. Best effort: a failure is logged, since
+/// the caller is already on its way to an error of its own.
+pub(crate) async fn restore(client: &async_nats::Client, agent: &str, replaced: Replaced) {
+    let put_back = match replaced.0 {
+        Some(previous) => store(client, agent, &previous).await.map(|_| ()),
+        None => match open_or_create(client).await {
+            Ok(store) => store
+                .delete(agent)
+                .await
+                .map_err(|e| queue_problem(&anyhow::Error::new(e))),
+            Err(e) => Err(e),
+        },
+    };
+    if let Err(e) = put_back {
+        tracing::warn!(%agent, error = ?e, "could not put back the agent's limits");
+    }
+}
+
 #[utoipa::path(
     delete,
     path = "/api/agents/{name}/limits",
@@ -441,7 +463,7 @@ pub(crate) mod tests {
     }
 
     /// One hive, `pr1ma`, on `client`.
-    fn state(client: &async_nats::Client) -> crate::AppState {
+    pub(crate) fn state(client: &async_nats::Client) -> crate::AppState {
         crate::AppState {
             hives: Arc::new(vec![crate::HiveEntry {
                 name: "pr1ma".to_owned(),
@@ -512,7 +534,7 @@ pub(crate) mod tests {
 
     /// The raw value a hive reads for `agent`, or `None` for no key or a
     /// deleted one.
-    async fn published(client: &async_nats::Client, agent: &str) -> Option<String> {
+    pub(crate) async fn published(client: &async_nats::Client, agent: &str) -> Option<String> {
         let store = swarm_queue_client::agent_limits::open_or_create(client)
             .await
             .expect("bucket");
@@ -735,4 +757,33 @@ pub(crate) mod tests {
         assert_eq!(answer.0, Caps::default());
         assert_eq!(published(&client, "atlas").await.as_deref(), Some("{}"));
     }
+
+    /// `restore` puts back the caps a `store` replaced, or takes the key out
+    /// again when there was none.
+    #[tokio::test]
+    async fn restore_undoes_a_store() {
+        let nats = TestNats::start();
+        let client = nats.client().await;
+        let caps = |json: &str| {
+            serde_json::from_str::<Caps>(json)
+                .expect("caps")
+                .into_stored()
+                .expect("valid")
+        };
+
+        let first = super::store(&client, "atlas", &caps(CAPPED))
+            .await
+            .expect("stored");
+        super::restore(&client, "atlas", first).await;
+        assert_eq!(published(&client, "atlas").await, None);
+
+        super::store(&client, "atlas", &caps(CAPPED))
+            .await
+            .expect("stored");
+        let second = super::store(&client, "atlas", &caps(r#"{"cpu_quota":"100%"}"#))
+            .await
+            .expect("replaced");
+        super::restore(&client, "atlas", second).await;
+        assert_eq!(published(&client, "atlas").await.as_deref(), Some(CAPPED));
+    }
 }
diff --git a/swarm-controller/src/inference.rs b/swarm-controller/src/inference.rs
index 63e3c4bd..99f21fff 100644
--- a/swarm-controller/src/inference.rs
+++ b/swarm-controller/src/inference.rs
@@ -317,24 +317,29 @@ pub(crate) async fn put_agent_inference(
     Ok(Json(value.into()))
 }
 
+/// What [`store`] replaced: the settings that were stored, or `None` for no
+/// key.
+pub(crate) struct Replaced(Option<AgentInference>);
+
 /// Replace `agent`'s stored inference settings with `value`.
 pub(crate) async fn store(
     client: &async_nats::Client,
     agent: &str,
     value: &AgentInference,
-) -> Result<(), ProblemDetails> {
+) -> Result<Replaced, ProblemDetails> {
     let store = open(client).await?;
     for _ in 0..MAX_ATTEMPTS {
         let (current, revision, undecodable) = read_or_default::<AgentInference>(&store, agent)
             .await
             .map_err(|e| queue_problem(&e))?;
+        let replaced = Replaced(revision.map(|_| current.clone()));
         if (current == *value && !undecodable)
             || write(&store, agent, value, revision)
                 .await
                 .map_err(|e| queue_problem(&e))?
         {
             tracing::info!(%agent, ?value, "set inference settings");
-            return Ok(());
+            return Ok(replaced);
         }
     }
     Err(queue_problem(&anyhow::anyhow!(
@@ -343,6 +348,24 @@ pub(crate) async fn store(
     )))
 }
 
+/// Put back what [`store`] replaced. Best effort: a failure is logged, since
+/// the caller is already on its way to an error of its own.
+pub(crate) async fn restore(client: &async_nats::Client, agent: &str, replaced: Replaced) {
+    let put_back = match replaced.0 {
+        Some(previous) => store(client, agent, &previous).await.map(|_| ()),
+        None => match open(client).await {
+            Ok(store) => store
+                .delete(agent)
+                .await
+                .map_err(|e| queue_problem(&anyhow::Error::new(e))),
+            Err(e) => Err(e),
+        },
+    };
+    if let Err(e) = put_back {
+        tracing::warn!(%agent, error = ?e, "could not put back the agent's inference settings");
+    }
+}
+
 #[utoipa::path(
     delete,
     path = "/api/agents/{name}/inference",
@@ -587,4 +610,32 @@ mod tests {
         let entry = store.get("atlas").await.expect("read").expect("a value");
         assert_eq!(&entry[..], b"{}");
     }
+
+    /// `restore` puts back the settings a `store` replaced, or takes the key
+    /// out again when there was none.
+    #[tokio::test]
+    async fn restore_undoes_a_store() {
+        let nats = crate::test_nats::TestNats::start();
+        let client = nats.client().await;
+        let bucket = agent_inference::open_or_create(&client)
+            .await
+            .expect("bucket");
+        let value = |json: &str| settings(json).unwrap().into_stored().unwrap();
+
+        let first = store(&client, "atlas", &value(r#"{"model":"opus"}"#))
+            .await
+            .expect("stored");
+        restore(&client, "atlas", first).await;
+        assert!(bucket.get("atlas").await.expect("read").is_none());
+
+        store(&client, "atlas", &value(r#"{"model":"opus"}"#))
+            .await
+            .expect("stored");
+        let second = store(&client, "atlas", &value(r#"{"model":"haiku"}"#))
+            .await
+            .expect("replaced");
+        restore(&client, "atlas", second).await;
+        let entry = bucket.get("atlas").await.expect("read").expect("a value");
+        assert_eq!(&entry[..], br#"{"model":"opus"}"#);
+    }
 }
diff --git a/swarm-controller/src/main.rs b/swarm-controller/src/main.rs
index da6233be..9c3502a9 100644
--- a/swarm-controller/src/main.rs
+++ b/swarm-controller/src/main.rs
@@ -1791,6 +1791,7 @@ struct CreateAgentResponse {
         (status = 200, description = "job chain queued", body = CreateAgentResponse),
         (status = 400, description = "`name` or `hive` is not a valid identifier, `name` is new and reserved or refused by the forge, `hive` is not in this swarm, or `limits` or `inference` holds a value the matching `PUT` refuses (problem+json)", body = String),
         (status = 409, description = "the swarm has already placed `name` on a different hive (problem+json)", body = String),
+        (status = 422, description = "an unknown field in the body, in `limits`, or in `inference`, or an `effort` that is not one of the five levels"),
         (status = 503, description = "the swarm queue is not connected, so whether `name` is placed on another hive is unknown, or `limits` or `inference` is set and cannot be stored (problem+json)", body = String),
         (status = 500, description = "the job chain could not be queued, or another hive's wanted state could not be read (problem+json)", body = String),
     ),
@@ -1816,11 +1817,6 @@ async fn create_agent(
         .map(inference::InferenceSettings::into_stored)
         .transpose()
         .map_err(|why| error_problem(axum::http::StatusCode::BAD_REQUEST, &why))?;
-    let settings_queue = if limits.is_some() || inference.is_some() {
-        Some(schedules::queue(&state).map_err(schedules::refused)?)
-    } else {
-        None
-    };
 
     // Two checks, and the second is the one that makes the field worth
     // having: `Ident::parse` says the string is *shaped* like a hive name,
@@ -1881,6 +1877,13 @@ async fn create_agent(
         let detail = format!("hive {hive:?} is not in this swarm — known hives: {known}");
         return Err(error_problem(axum::http::StatusCode::BAD_REQUEST, &detail));
     }
+    // Checked after the roster, so a mistyped hive stays a 400 while the queue
+    // is down.
+    let settings_queue = if limits.is_some() || inference.is_some() {
+        Some(schedules::queue(&state).map_err(schedules::refused)?)
+    } else {
+        None
+    };
 
     // Agent names are one swarm-wide namespace: identity, forge user, store
     // path and matrix id all carry the bare name. The same name on the same
@@ -1901,28 +1904,35 @@ async fn create_agent(
         );
         return Err(error_problem(axum::http::StatusCode::CONFLICT, &detail));
     }
-    // Stored ahead of the job graph: the hive reads these by agent name when it
-    // runs the agent, and a failed write here leaves nothing created.
-    if let Some(client) = &settings_queue {
-        if let Some(limits) = &limits {
-            agent_limits::store(client, &agent, limits).await?;
+    // Stored ahead of the job graph, not once the agent is declared: the hive
+    // reads these by agent name when it first runs the agent. A failure from
+    // here on puts back what was stored, so a refused creation leaves no
+    // settings behind for the name.
+    let stored = match &settings_queue {
+        Some(client) => {
+            StoredSettings::store(client, &agent, limits.as_ref(), inference.as_ref()).await?
         }
-        if let Some(inference) = &inference {
-            inference::store(client, &agent, inference).await?;
-        }
-    }
-    let mut sched = state
-        .jobq
-        .lock()
-        .unwrap_or_else(std::sync::PoisonError::into_inner);
-    let ids = sched
-        .insert_job(None, |b| declare_agent_job(b, &agent, &hive))
-        .map_err(|e| {
-            error_problem(
+        None => StoredSettings::default(),
+    };
+    let queued = {
+        let mut sched = state
+            .jobq
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner);
+        sched.insert_job(None, |b| declare_agent_job(b, &agent, &hive))
+    };
+    let ids = match queued {
+        Ok(ids) => ids,
+        Err(e) => {
+            if let Some(client) = &settings_queue {
+                stored.roll_back(client, &agent).await;
+            }
+            return Err(error_problem(
                 axum::http::StatusCode::INTERNAL_SERVER_ERROR,
                 &e.to_string(),
-            )
-        })?;
+            ));
+        }
+    };
     let [id] = ids[..] else {
         unreachable!("exactly one handle was asked for");
     };
@@ -1932,6 +1942,49 @@ async fn create_agent(
     }))
 }
 
+/// What `create_agent` replaced in the settings stores, to put back if the
+/// creation is refused after the write.
+#[derive(Default)]
+struct StoredSettings {
+    limits: Option<agent_limits::Replaced>,
+    inference: Option<inference::Replaced>,
+}
+
+impl StoredSettings {
+    /// Store whichever of `limits` and `inference` are given. A failure on
+    /// the second puts back the first.
+    async fn store(
+        client: &async_nats::Client,
+        agent: &str,
+        limits: Option<&swarm_queue_client::agent_limits::AgentCaps>,
+        inference: Option<&swarm_queue_client::agent_inference::AgentInference>,
+    ) -> Result<Self, problem_details::ProblemDetails> {
+        let mut stored = Self::default();
+        if let Some(limits) = limits {
+            stored.limits = Some(agent_limits::store(client, agent, limits).await?);
+        }
+        if let Some(inference) = inference {
+            match inference::store(client, agent, inference).await {
+                Ok(replaced) => stored.inference = Some(replaced),
+                Err(e) => {
+                    stored.roll_back(client, agent).await;
+                    return Err(e);
+                }
+            }
+        }
+        Ok(stored)
+    }
+
+    async fn roll_back(self, client: &async_nats::Client, agent: &str) {
+        if let Some(replaced) = self.limits {
+            agent_limits::restore(client, agent, replaced).await;
+        }
+        if let Some(replaced) = self.inference {
+            inference::restore(client, agent, replaced).await;
+        }
+    }
+}
+
 /// [`placed_elsewhere`] over a snapshot of the queued placements and a read
 /// of the published ones, **in that order**.
 ///
@@ -3817,6 +3870,75 @@ mod tests {
         assert_eq!(node_count(&sched), 0, "nothing may be queued");
     }
 
+    /// Through the real handler and a real `nats-server`: both settings land
+    /// under the agent's key as the hive reads them, and the graph is queued.
+    #[tokio::test]
+    async fn a_creation_with_settings_stores_them_and_queues_the_graph() {
+        let nats = crate::test_nats::TestNats::start();
+        let client = nats.client().await;
+        let state = crate::agent_limits::tests::state(&client);
+        let req: super::CreateAgentRequest = serde_json::from_str(
+            r#"{"name":"atlas","hive":"pr1ma","limits":{"cpu_quota":"400%"},
+                "inference":{"model":"opus","max_subagents":3}}"#,
+        )
+        .expect("body parses");
+        let _queued = super::create_agent(axum::extract::State(state.clone()), axum::Json(req))
+            .await
+            .expect("a valid creation with settings goes through");
+
+        assert_eq!(
+            crate::agent_limits::tests::published(&client, "atlas")
+                .await
+                .as_deref(),
+            Some(r#"{"cpu_quota":"400%"}"#)
+        );
+        let inference = swarm_queue_client::agent_inference::open_or_create(&client)
+            .await
+            .expect("bucket")
+            .get("atlas")
+            .await
+            .expect("read")
+            .expect("a value");
+        assert_eq!(&inference[..], br#"{"model":"opus","max_subagents":3}"#);
+        assert!(
+            state
+                .jobq
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner)
+                .graph()
+                .nodes()
+                .count()
+                > 0,
+            "the graph must be queued"
+        );
+    }
+
+    /// A valid cap beside an invalid model stores neither and queues nothing,
+    /// on a server that could have stored the cap.
+    #[tokio::test]
+    async fn a_bad_setting_stores_none_of_them() {
+        let nats = crate::test_nats::TestNats::start();
+        let client = nats.client().await;
+        let state = crate::agent_limits::tests::state(&client);
+        let req: super::CreateAgentRequest = serde_json::from_str(
+            r#"{"name":"atlas","hive":"pr1ma","limits":{"cpu_quota":"400%"},
+                "inference":{"model":"-opus"}}"#,
+        )
+        .expect("body parses");
+        let err = super::create_agent(axum::extract::State(state.clone()), axum::Json(req))
+            .await
+            .expect_err("a bad model must be refused");
+        assert_eq!(
+            axum::response::IntoResponse::into_response(err).status(),
+            axum::http::StatusCode::BAD_REQUEST
+        );
+        assert_eq!(
+            crate::agent_limits::tests::published(&client, "atlas").await,
+            None
+        );
+        assert_eq!(node_count(&state.jobq), 0, "nothing may be queued");
+    }
+
     /// `state_with_roster` with a second hive, `sec0nd`.
     fn state_with_two_hives() -> (super::AppState, SharedSched) {
         let (state, sched) = state_with_roster();