diff --git a/control_plane/src/emit/asapquery_backend.rs b/control_plane/src/emit/asapquery_backend.rs
index d306f351..27c63930 100644
--- a/control_plane/src/emit/asapquery_backend.rs
+++ b/control_plane/src/emit/asapquery_backend.rs
@@ -166,8 +166,8 @@ fn _type_check(_: &AgentCollectorConfig) {}
 mod tests {
     use super::*;
     use crate::types::{
-        AgentDataSink, BackendCollectorConfig, CollectionPlan, DeltaDecision,
-        GatewayCollectorConfig, OutputMode, ProcessorMode, SketchParams, TransmissionCostSummary,
+        AgentDataSink, CollectionPlan, DeltaDecision, GatewayCollectorConfig, OutputMode,
+        ProcessorMode, SketchParams, TransmissionCostSummary,
     };
     use std::time::Duration;
 
@@ -191,10 +191,6 @@ mod tests {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: sketch_type,
-                group_by: vec![],
-            },
             precompute: vec![],
             valid_until: chrono::Utc::now() + chrono::Duration::seconds(300),
             delta_decision: DeltaDecision::default(),
diff --git a/control_plane/src/metrics_exposer.rs b/control_plane/src/metrics_exposer.rs
index 94e332df..72d33730 100644
--- a/control_plane/src/metrics_exposer.rs
+++ b/control_plane/src/metrics_exposer.rs
@@ -206,16 +206,15 @@ impl MetricsRegistry {
             // a label value, doesn't need to be cryptographic.
             let mut hasher = DefaultHasher::new();
             // Cover the fields the planner actually changes per
-            // re-plan: agent sketch+mode+delta, backend merge+group_by,
-            // and valid_until (to catch refresh-only re-plans).
+            // re-plan: agent sketch+mode+delta+grouping, and valid_until
+            // (to catch refresh-only re-plans).
             format!(
-                "{:?}|{:?}|{:?}|{:?}|{:?}|{:?}|{:?}",
+                "{:?}|{:?}|{:?}|{:?}|{:?}|{:?}",
                 plan.agent_config.sketch_type,
                 plan.agent_config.mode,
                 plan.agent_config.delta_transmission,
                 plan.agent_config.window_duration,
-                plan.backend_config.merge_sketch_type,
-                plan.backend_config.group_by,
+                plan.agent_config.aggregate_by,
                 plan.valid_until,
             )
             .hash(&mut hasher);
@@ -451,10 +450,6 @@ mod tests {
                     data_sink: AgentDataSink::default(),
                 },
                 gateway_config: GatewayCollectorConfig { passthrough: true },
-                backend_config: BackendCollectorConfig {
-                    merge_sketch_type: sketch,
-                    group_by: vec![],
-                },
                 precompute: vec![],
                 valid_until: Utc::now() + chrono::Duration::seconds(valid_secs),
                 delta_decision: Default::default(),
diff --git a/control_plane/src/optimizer/cost/delta.rs b/control_plane/src/optimizer/cost/delta.rs
index 09c37fbe..10025c56 100644
--- a/control_plane/src/optimizer/cost/delta.rs
+++ b/control_plane/src/optimizer/cost/delta.rs
@@ -516,10 +516,6 @@ mod tests {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: st,
-                group_by: vec![],
-            },
             precompute: vec![],
             valid_until: Utc::now(),
             delta_decision: DeltaDecision::default(),
diff --git a/control_plane/src/optimizer/cost/mod.rs b/control_plane/src/optimizer/cost/mod.rs
index 3d5bc898..e8322f0a 100644
--- a/control_plane/src/optimizer/cost/mod.rs
+++ b/control_plane/src/optimizer/cost/mod.rs
@@ -248,7 +248,6 @@ impl CostModelPlanner {
             plan.agent_config.sketch_params = params;
             plan.agent_config.mode = mode;
             plan.agent_config.window_duration = window_duration;
-            plan.backend_config.merge_sketch_type = st.clone();
             apply_delta_decision_with(&mut plan, w, wc, &table);
             return plan;
         }
@@ -269,7 +268,6 @@ impl CostModelPlanner {
             trial.agent_config.sketch_params = params;
             trial.agent_config.mode = mode;
             trial.agent_config.window_duration = window_duration;
-            trial.backend_config.merge_sketch_type = st;
 
             let s = score_with(&trial, w, &table);
             if !s.meets_sla {
@@ -1041,10 +1039,6 @@ mod tests {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: st,
-                group_by: vec![],
-            },
             precompute: vec![],
             valid_until: Utc::now(),
             delta_decision: DeltaDecision::default(),
diff --git a/control_plane/src/optimizer/cost/pareto.rs b/control_plane/src/optimizer/cost/pareto.rs
index 2c1d1e3c..80624aa4 100644
--- a/control_plane/src/optimizer/cost/pareto.rs
+++ b/control_plane/src/optimizer/cost/pareto.rs
@@ -116,7 +116,6 @@ pub fn pareto_frontier(
         plan.agent_config.sketch_params = params;
         plan.agent_config.mode = mode;
         plan.agent_config.window_duration = window_duration;
-        plan.backend_config.merge_sketch_type = st.clone();
 
         // Apply delta decision using the cost table.
         apply_delta(st.clone(), &mut plan, workload, wc, &table);
diff --git a/control_plane/src/optimizer/rules/mod.rs b/control_plane/src/optimizer/rules/mod.rs
index 89306fa9..543f24dd 100644
--- a/control_plane/src/optimizer/rules/mod.rs
+++ b/control_plane/src/optimizer/rules/mod.rs
@@ -344,9 +344,6 @@ impl RulesPlanner {
             .collect();
         label_matchers.sort();
 
-        let backend_sketch = sketch_type.clone();
-        let group_by = aggregate_by.clone();
-
         let valid_until = Utc::now() + chrono::Duration::seconds(self.valid_for.as_secs() as i64);
 
         CollectionPlan {
@@ -371,10 +368,6 @@ impl RulesPlanner {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: backend_sketch,
-                group_by,
-            },
             precompute: vec![],
             valid_until,
             delta_decision: DeltaDecision::default(),
@@ -414,10 +407,6 @@ impl RulesPlanner {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: SketchType::DDSketch,
-                group_by: vec![],
-            },
             precompute: vec![],
             valid_until,
             delta_decision: DeltaDecision::default(),
@@ -583,15 +572,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn backend_config_matches_sketch_type() {
-        let plan = RulesPlanner::new().plan(&workload(vec![AggType::Quantile]));
-        assert_eq!(
-            plan.backend_config.merge_sketch_type,
-            plan.agent_config.sketch_type
-        );
-    }
-
     #[test]
     fn gateway_passthrough() {
         let plan = RulesPlanner::new().plan(&workload(vec![AggType::Quantile]));
diff --git a/control_plane/src/replan.rs b/control_plane/src/replan.rs
index e77e911a..070a4801 100644
--- a/control_plane/src/replan.rs
+++ b/control_plane/src/replan.rs
@@ -509,10 +509,6 @@ mod tests {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: SketchType::DDSketch,
-                group_by: vec![],
-            },
             precompute: vec![],
             valid_until: Utc::now() + chrono::Duration::seconds(3600),
             delta_decision: DeltaDecision::default(),
diff --git a/control_plane/src/store/mod.rs b/control_plane/src/store/mod.rs
index 140185a1..bf292f18 100644
--- a/control_plane/src/store/mod.rs
+++ b/control_plane/src/store/mod.rs
@@ -177,10 +177,6 @@ mod tests {
                 data_sink: AgentDataSink::default(),
             },
             gateway_config: GatewayCollectorConfig { passthrough: true },
-            backend_config: BackendCollectorConfig {
-                merge_sketch_type: SketchType::DDSketch,
-                group_by: vec![],
-            },
             precompute: vec![],
             valid_until,
             delta_decision: DeltaDecision::default(),
diff --git a/control_plane/src/types.rs b/control_plane/src/types.rs
index c20523d0..dd67ff62 100644
--- a/control_plane/src/types.rs
+++ b/control_plane/src/types.rs
@@ -518,12 +518,6 @@ pub struct GatewayCollectorConfig {
     pub passthrough: bool,
 }
 
-#[derive(Debug, Clone)]
-pub struct BackendCollectorConfig {
-    pub merge_sketch_type: SketchType,
-    pub group_by: Vec<String>,
-}
-
 #[derive(Debug, Clone)]
 pub struct PrecomputeJob {
     pub query_expr: String,
@@ -570,7 +564,6 @@ impl StageResourceBudgets {
 pub struct CollectionPlan {
     pub agent_config: AgentCollectorConfig,
     pub gateway_config: GatewayCollectorConfig,
-    pub backend_config: BackendCollectorConfig,
     pub precompute: Vec<PrecomputeJob>,
     pub valid_until: DateTime<Utc>,
     /// Resolved delta transmission decision and rationale.