diff --git a/crates/brk_bindgen/src/analysis/positions.rs b/crates/brk_bindgen/src/analysis/positions.rs
index 626eaec56..5368be6a1 100644
--- a/crates/brk_bindgen/src/analysis/positions.rs
+++ b/crates/brk_bindgen/src/analysis/positions.rs
@@ -43,27 +43,48 @@ pub fn analyze_pattern_modes(
 ) -> BTreeMap<String, PatternBaseResult> {
     // Collect analyses from all instances, keyed by pattern name
     let mut all_analyses: BTreeMap<String, Vec<InstanceAnalysis>> = BTreeMap::new();
-    // Also collect base results for each node, keyed by tree path
+    // Base results for each node, keyed by tree path
     let mut node_bases: BTreeMap<String, PatternBaseResult> = BTreeMap::new();
+    // Track which tree path belongs to which pattern (avoids re-traversal)
+    let mut path_to_pattern: BTreeMap<String, String> = BTreeMap::new();
 
-    // Bottom-up traversal
-    collect_instance_analyses(tree, "", pattern_lookup, &mut all_analyses, &mut node_bases);
+    // Pass 1: bottom-up traversal
+    collect_instance_analyses(
+        tree,
+        "",
+        pattern_lookup,
+        &mut all_analyses,
+        &mut node_bases,
+        &mut path_to_pattern,
+    );
 
-    // For each pattern, determine mode from collected instances
+    // Determine initial modes
     for pattern in patterns.iter_mut() {
         if let Some(analyses) = all_analyses.get(&pattern.name) {
             pattern.mode = determine_pattern_mode(analyses, &pattern.fields);
         }
     }
 
-    // Second pass: fill mixed-empty field_parts now that pattern modes are known.
+    // Pass 2: fill mixed-empty field_parts now that pattern modes are known
     fill_mixed_empty_field_parts(tree, "", pattern_lookup, patterns, &mut node_bases);
 
-    // Re-collect analyses from updated node_bases and re-determine pattern modes
-    let mut all_analyses2: BTreeMap<String, Vec<InstanceAnalysis>> = BTreeMap::new();
-    collect_updated_analyses(tree, "", pattern_lookup, &node_bases, &mut all_analyses2);
+    // Re-determine modes from updated node_bases (no tree re-traversal needed)
+    let mut updated_analyses: BTreeMap<String, Vec<InstanceAnalysis>> = BTreeMap::new();
+    for (path, pattern_name) in &path_to_pattern {
+        if let Some(br) = node_bases.get(path) {
+            updated_analyses
+                .entry(pattern_name.clone())
+                .or_default()
+                .push(InstanceAnalysis {
+                    base: br.base.clone(),
+                    field_parts: br.field_parts.clone(),
+                    is_suffix_mode: br.is_suffix_mode,
+                    has_outlier: br.has_outlier,
+                });
+        }
+    }
     for pattern in patterns.iter_mut() {
-        if let Some(analyses) = all_analyses2.get(&pattern.name) {
+        if let Some(analyses) = updated_analyses.get(&pattern.name) {
             pattern.mode = determine_pattern_mode(analyses, &pattern.fields);
         }
     }
@@ -71,39 +92,6 @@ pub fn analyze_pattern_modes(
     node_bases
 }
 
-/// Re-collect instance analyses from updated node_bases for pattern mode redetermination.
-fn collect_updated_analyses(
-    node: &TreeNode,
-    path: &str,
-    pattern_lookup: &BTreeMap<Vec<PatternField>, String>,
-    node_bases: &BTreeMap<String, PatternBaseResult>,
-    all_analyses: &mut BTreeMap<String, Vec<InstanceAnalysis>>,
-) {
-    let TreeNode::Branch(children) = node else {
-        return;
-    };
-
-    for (field_name, child_node) in children {
-        let child_path = build_child_path(path, field_name);
-        collect_updated_analyses(child_node, &child_path, pattern_lookup, node_bases, all_analyses);
-    }
-
-    let fields = get_node_fields(children, pattern_lookup);
-    if let Some(pattern_name) = pattern_lookup.get(&fields) {
-        if let Some(base_result) = node_bases.get(path) {
-            all_analyses
-                .entry(pattern_name.clone())
-                .or_default()
-                .push(InstanceAnalysis {
-                    base: base_result.base.clone(),
-                    field_parts: base_result.field_parts.clone(),
-                    is_suffix_mode: base_result.is_suffix_mode,
-                    has_outlier: base_result.has_outlier,
-                });
-        }
-    }
-}
-
 /// Second pass: fill empty field_parts for nodes that have a mix of empty and
 /// non-empty parts, using shortest leaf names for children that need disc.
 fn fill_mixed_empty_field_parts(
@@ -187,6 +175,7 @@ fn collect_instance_analyses(
     pattern_lookup: &BTreeMap<Vec<PatternField>, String>,
     all_analyses: &mut BTreeMap<String, Vec<InstanceAnalysis>>,
     node_bases: &mut BTreeMap<String, PatternBaseResult>,
+    path_to_pattern: &mut BTreeMap<String, String>,
 ) -> Option<String> {
     match node {
         TreeNode::Leaf(leaf) => {
@@ -204,6 +193,7 @@ fn collect_instance_analyses(
                     pattern_lookup,
                     all_analyses,
                     node_bases,
+                    path_to_pattern,
                 ) {
                     child_bases.insert(field_name.clone(), base);
                 }
@@ -272,6 +262,7 @@ fn collect_instance_analyses(
             // Get the pattern name for this node (if any)
             let fields = get_node_fields(children, pattern_lookup);
             if let Some(pattern_name) = pattern_lookup.get(&fields) {
+                path_to_pattern.insert(path.to_string(), pattern_name.clone());
                 all_analyses
                     .entry(pattern_name.clone())
                     .or_default()
@@ -1107,6 +1098,7 @@ mod tests {
 
         let mut all_analyses = BTreeMap::new();
         let mut node_bases = BTreeMap::new();
+        let mut path_to_pattern = BTreeMap::new();
         let pattern_lookup = BTreeMap::new();
 
         collect_instance_analyses(
@@ -1115,6 +1107,7 @@ mod tests {
             &pattern_lookup,
             &mut all_analyses,
             &mut node_bases,
+            &mut path_to_pattern,
         );
 
         let result = node_bases.get("test").expect("should have node_bases entry");
diff --git a/crates/brk_bindgen/src/generate/fields.rs b/crates/brk_bindgen/src/generate/fields.rs
index 9dd2ec32d..f05118ec4 100644
--- a/crates/brk_bindgen/src/generate/fields.rs
+++ b/crates/brk_bindgen/src/generate/fields.rs
@@ -8,7 +8,7 @@ use std::fmt::Write;
 
 use brk_types::MetricLeafWithSchema;
 
-use crate::{ClientMetadata, LanguageSyntax, PatternField, StructuralPattern};
+use crate::{ClientMetadata, LanguageSyntax, PatternBaseResult, PatternField, StructuralPattern};
 
 /// Create a path suffix from a name.
 /// Adds `_` prefix only if the name doesn't already start with `_`.
@@ -102,10 +102,11 @@ pub fn generate_parameterized_field<S: LanguageSyntax>(
     .unwrap();
 }
 
-/// Generate a tree node field with a specific child node for pattern instance base detection.
+/// Generate a tree node field using pre-computed base results.
 ///
-/// This is used when generating tree nodes where we need to detect the pattern instance
-/// base from descendant leaf names.
+/// Handles pattern fields (both templated and non-templated), leaf fields,
+/// and non-pattern branch fields. For templated patterns, extracts the
+/// discriminator from the base result's field_parts.
 pub fn generate_tree_node_field<S: LanguageSyntax>(
     output: &mut String,
     syntax: &S,
@@ -113,36 +114,69 @@ pub fn generate_tree_node_field<S: LanguageSyntax>(
     metadata: &ClientMetadata,
     indent: &str,
     child_name: &str,
-    pattern_base: Option<&str>,
+    client_expr: &str,
+    base_result: Option<&PatternBaseResult>,
 ) {
     let field_name = syntax.field_name(&field.name);
     let type_ann = metadata.field_type_annotation(field, false, None, syntax.generic_syntax());
 
     let value = if metadata.is_pattern_type(&field.rust_type) {
-        // Use metric base only for parameterizable patterns
-        let use_base = metadata
-            .find_pattern(&field.rust_type)
-            .is_some_and(|p| p.is_parameterizable())
-            && pattern_base.is_some();
+        let pattern = metadata.find_pattern(&field.rust_type);
+        let use_base = pattern.is_some_and(|p| p.is_parameterizable()) && base_result.is_some();
 
-        let path_arg = if use_base {
-            syntax.string_literal(pattern_base.unwrap())
+        if use_base {
+            let br = base_result.unwrap();
+            let base_arg = syntax.string_literal(&br.base);
+            if let Some(pat) = pattern
+                && pat.is_templated()
+            {
+                let disc = pat
+                    .extract_disc_from_instance(&br.field_parts)
+                    .unwrap_or_default();
+                let disc_arg = syntax.string_literal(&disc);
+                format!(
+                    "{}({}, {}, {})",
+                    syntax.constructor_name(&field.rust_type),
+                    client_expr,
+                    base_arg,
+                    disc_arg
+                )
+            } else {
+                format!(
+                    "{}({}, {})",
+                    syntax.constructor_name(&field.rust_type),
+                    client_expr,
+                    base_arg
+                )
+            }
         } else {
-            syntax.path_expr("base_path", &path_suffix(child_name))
-        };
-        syntax.constructor(&field.rust_type, &path_arg)
+            let path_arg = syntax.path_expr("base_path", &path_suffix(child_name));
+            format!(
+                "{}({}, {})",
+                syntax.constructor_name(&field.rust_type),
+                client_expr,
+                path_arg
+            )
+        }
     } else if let Some(accessor) = metadata.find_index_set_pattern(&field.indexes) {
-        // Leaf field - use metric name if provided, else tree path
-        let path_arg = pattern_base
-            .map(|name| syntax.string_literal(name))
+        let path_arg = base_result
+            .map(|br| syntax.string_literal(&br.base))
             .unwrap_or_else(|| syntax.path_expr("base_path", &path_suffix(child_name)));
-        syntax.constructor(&accessor.name, &path_arg)
+        format!(
+            "{}({}, {})",
+            syntax.constructor_name(&accessor.name),
+            client_expr,
+            path_arg
+        )
     } else if field.is_branch() {
-        // Non-pattern branch - instantiate the nested struct
         let path_expr = syntax.path_expr("base_path", &path_suffix(child_name));
-        syntax.constructor(&field.rust_type, &path_expr)
+        format!(
+            "{}({}, {})",
+            syntax.constructor_name(&field.rust_type),
+            client_expr,
+            path_expr
+        )
     } else {
-        // All metrics must be indexed
         panic!(
             "Field '{}' is a leaf with no index accessor. All metrics must be indexed.",
             field.name
diff --git a/crates/brk_bindgen/src/generators/javascript/tree.rs b/crates/brk_bindgen/src/generators/javascript/tree.rs
index 33670b556..d657167c9 100644
--- a/crates/brk_bindgen/src/generators/javascript/tree.rs
+++ b/crates/brk_bindgen/src/generators/javascript/tree.rs
@@ -7,7 +7,7 @@ use brk_types::TreeNode;
 
 use crate::{
     ClientMetadata, Endpoint, GenericSyntax, JavaScriptSyntax, PatternField, build_child_path,
-    generate_leaf_field, prepare_tree_node, to_camel_case,
+    generate_leaf_field, generate_tree_node_field, prepare_tree_node, to_camel_case,
 };
 
 use super::api::generate_api_methods;
@@ -220,29 +220,16 @@ fn generate_tree_initializer(
             );
             writeln!(output, "{}}},", indent_str).unwrap();
         } else {
-            // Use pattern factory
-            let pattern = metadata.find_pattern(&child.field.rust_type);
-            if let Some(pat) = pattern
-                && pat.is_templated()
-            {
-                // Templated: extract discriminator using the pattern's templates
-                let disc = pat
-                    .extract_disc_from_instance(&child.base_result.field_parts)
-                    .unwrap_or_default();
-                writeln!(
-                    output,
-                    "{}{}: create{}(this, '{}', '{}'),",
-                    indent_str, field_name, child.field.rust_type, child.base_result.base, disc
-                )
-                .unwrap();
-            } else {
-                writeln!(
-                    output,
-                    "{}{}: create{}(this, '{}'),",
-                    indent_str, field_name, child.field.rust_type, child.base_result.base
-                )
-                .unwrap();
-            }
+            generate_tree_node_field(
+                output,
+                &syntax,
+                &child.field,
+                metadata,
+                &indent_str,
+                child.name,
+                "this",
+                Some(&child.base_result),
+            );
         }
     }
 }
diff --git a/crates/brk_bindgen/src/generators/python/tree.rs b/crates/brk_bindgen/src/generators/python/tree.rs
index 019089073..cddadcc6c 100644
--- a/crates/brk_bindgen/src/generators/python/tree.rs
+++ b/crates/brk_bindgen/src/generators/python/tree.rs
@@ -6,8 +6,8 @@ use std::fmt::Write;
 use brk_types::TreeNode;
 
 use crate::{
-    ClientMetadata, GenericSyntax, PatternField, PythonSyntax, build_child_path,
-    escape_python_keyword, generate_leaf_field, prepare_tree_node, to_snake_case,
+    ClientMetadata, LanguageSyntax, PatternField, PythonSyntax, build_child_path,
+    generate_leaf_field, generate_tree_node_field, prepare_tree_node,
 };
 
 /// Generate tree classes
@@ -70,8 +70,6 @@ fn generate_tree_class(
 
     let syntax = PythonSyntax;
     for child in &ctx.children {
-        let field_name_py = escape_python_keyword(&to_snake_case(child.name));
-
         if child.is_leaf {
             if let TreeNode::Leaf(leaf) = child.node {
                 generate_leaf_field(
@@ -79,43 +77,24 @@ fn generate_tree_class(
                 );
             }
         } else if child.should_inline {
-            // Inline class
+            let field_name = syntax.field_name(child.name);
             writeln!(
                 output,
                 "        self.{}: {} = {}(client)",
-                field_name_py, child.inline_type_name, child.inline_type_name
+                field_name, child.inline_type_name, child.inline_type_name
             )
             .unwrap();
         } else {
-            // Use pattern class with metric base
-            let py_type = metadata.resolve_tree_field_type(
+            generate_tree_node_field(
+                output,
+                &syntax,
                 &child.field,
-                child.child_fields.as_deref(),
-                name,
+                metadata,
+                "        ",
                 child.name,
-                GenericSyntax::PYTHON,
+                "client",
+                Some(&child.base_result),
             );
-            let pattern = metadata.find_pattern(&child.field.rust_type);
-            if let Some(pat) = pattern
-                && pat.is_templated()
-            {
-                let disc = pat
-                    .extract_disc_from_instance(&child.base_result.field_parts)
-                    .unwrap_or_default();
-                writeln!(
-                    output,
-                    "        self.{}: {} = {}(client, '{}', '{}')",
-                    field_name_py, py_type, child.field.rust_type, child.base_result.base, disc
-                )
-                .unwrap();
-            } else {
-                writeln!(
-                    output,
-                    "        self.{}: {} = {}(client, '{}')",
-                    field_name_py, py_type, child.field.rust_type, child.base_result.base
-                )
-                .unwrap();
-            }
         }
     }
 
diff --git a/crates/brk_bindgen/src/generators/rust/tree.rs b/crates/brk_bindgen/src/generators/rust/tree.rs
index 6d611d391..2edc276ac 100644
--- a/crates/brk_bindgen/src/generators/rust/tree.rs
+++ b/crates/brk_bindgen/src/generators/rust/tree.rs
@@ -97,34 +97,16 @@ fn generate_tree_node(
             )
             .unwrap();
         } else {
-            // Pattern type - use ::new() constructor
-            let pattern = metadata.find_pattern(&child.field.rust_type);
-            if let Some(pat) = pattern
-                && pat.is_templated()
-            {
-                let disc = pat
-                    .extract_disc_from_instance(&child.base_result.field_parts)
-                    .unwrap_or_default();
-                writeln!(
-                    output,
-                    "            {}: {}::new(client.clone(), {}, {}.to_string()),",
-                    field_name,
-                    child.field.rust_type,
-                    syntax.string_literal(&child.base_result.base),
-                    syntax.string_literal(&disc),
-                )
-                .unwrap();
-            } else {
-                generate_tree_node_field(
-                    output,
-                    &syntax,
-                    &child.field,
-                    metadata,
-                    "            ",
-                    child.name,
-                    Some(&child.base_result.base),
-                );
-            }
+            generate_tree_node_field(
+                output,
+                &syntax,
+                &child.field,
+                metadata,
+                "            ",
+                child.name,
+                "client.clone()",
+                Some(&child.base_result),
+            );
         }
     }