diff --git a/datafusion-tracing/src/planner.rs b/datafusion-tracing/src/planner.rs
index f7d30ab..c6e49f7 100644
--- a/datafusion-tracing/src/planner.rs
+++ b/datafusion-tracing/src/planner.rs
@@ -20,8 +20,7 @@
 use async_trait::async_trait;
 use datafusion::catalog::Session;
 use datafusion::common::Result;
-use datafusion::execution::SessionStateBuilder;
-use datafusion::execution::context::{QueryPlanner, SessionState};
+use datafusion::execution::context::QueryPlanner;
 use datafusion::logical_expr::LogicalPlan;
 use datafusion::physical_plan::{ExecutionPlan, displayable};
 use std::sync::Arc;
@@ -54,26 +53,10 @@ pub(crate) struct TracingQueryPlanner {
 }
 
 impl TracingQueryPlanner {
-    /// Create a new `TracingQueryPlanner` that wraps the provided inner planner at a specific level.
-    fn new_with_level(inner: Arc<dyn QueryPlanner + Send + Sync>, level: Level) -> Self {
+    /// Wrap the session's query planner with tracing at the specified level.
+    pub(crate) fn new(inner: Arc<dyn QueryPlanner + Send + Sync>, level: Level) -> Self {
         Self { inner, level }
     }
-
-    /// Wraps the query planner of an existing `SessionState` with tracing instrumentation at a specific level.
-    ///
-    /// This preserves any custom `QueryPlanner` that may already be configured in the state,
-    /// ensuring that tracing is added as a layer on top of existing functionality.
-    pub(crate) fn instrument_state_with_level(
-        state: SessionState,
-        level: Level,
-    ) -> SessionState {
-        let current_planner = state.query_planner().clone();
-        let wrapped_planner = Arc::new(Self::new_with_level(current_planner, level));
-
-        SessionStateBuilder::from(state)
-            .with_query_planner(wrapped_planner)
-            .build()
-    }
 }
 
 #[async_trait]
diff --git a/datafusion-tracing/src/rule_instrumentation.rs b/datafusion-tracing/src/rule_instrumentation.rs
index ce652f6..36e2ade 100644
--- a/datafusion-tracing/src/rule_instrumentation.rs
+++ b/datafusion-tracing/src/rule_instrumentation.rs
@@ -977,18 +977,20 @@ pub fn instrument_session_state(
     );
 
     // Rebuild SessionState with instrumented rules
-    let state = SessionStateBuilder::from(state)
-        .with_analyzer_rules(analyzers)
+    let planner = Arc::clone(state.query_planner());
+    let mut builder = SessionStateBuilder::from(state)
         .with_optimizer_rules(optimizers)
-        .with_physical_optimizer_rules(physical_optimizers)
-        .build();
+        .with_physical_optimizer_rules(physical_optimizers);
+    // Keep the existing analyzer's function rewrites.
+    builder.analyzer().get_or_insert_default().rules = analyzers;
 
     // Automatically instrument the query planner when physical optimizer is enabled
     if options.physical_optimizer.phase_span_enabled() {
-        TracingQueryPlanner::instrument_state_with_level(state, span_level)
-    } else {
-        state
+        builder = builder
+            .with_query_planner(Arc::new(TracingQueryPlanner::new(planner, span_level)));
     }
+
+    builder.build()
 }
 
 /// Instruments analyzer rules with phase sentinel and optional rule-level spans.
@@ -1126,8 +1128,10 @@ fn instrument_physical_optimizer_rules(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use datafusion::common::DataFusionError;
+    use datafusion::common::{DFSchema, DataFusionError};
     use datafusion::execution::SessionStateBuilder;
+    use datafusion::logical_expr::Expr;
+    use datafusion::logical_expr::expr_rewriter::FunctionRewrite;
     use datafusion::prelude::{SessionConfig, SessionContext};
     use std::fmt;
     use std::sync::atomic::{AtomicBool, Ordering};
@@ -1400,6 +1404,40 @@ mod tests {
         Ok(())
     }
 
+    #[derive(Debug)]
+    struct NoOpFunctionRewrite;
+
+    impl FunctionRewrite for NoOpFunctionRewrite {
+        fn name(&self) -> &str {
+            "retained_function_rewrite"
+        }
+
+        fn rewrite(
+            &self,
+            expr: Expr,
+            _: &DFSchema,
+            _: &ConfigOptions,
+        ) -> Result<Transformed<Expr>> {
+            Ok(Transformed::no(expr))
+        }
+    }
+
+    #[test]
+    fn instrumentation_preserves_analyzer_function_rewrites() {
+        let mut builder = SessionStateBuilder::new();
+        builder
+            .analyzer()
+            .get_or_insert_default()
+            .add_function_rewrite(Arc::new(NoOpFunctionRewrite));
+
+        let state = crate::instrument_rules_with_info_spans!(
+            options: RuleInstrumentationOptions::full(),
+            state: builder.build()
+        );
+
+        assert_eq!(state.analyzer().function_rewrites.len(), 1);
+    }
+
     // -----------------------------------------------------------------------
     // Tests
     // -----------------------------------------------------------------------