binder: snapshot

crates/brk_binder/src/javascript.rs

@@ -8,8 +8,9 @@ use brk_types::{Index, TreeNode};
 use serde_json::Value;
 
 use crate::{
-    ClientMetadata, Endpoint, IndexSetPattern, PatternField, StructuralPattern, TypeSchemas,
-    get_node_fields, to_camel_case, to_pascal_case,
+    ClientMetadata, Endpoint, FieldNamePosition, IndexSetPattern, PatternField, StructuralPattern,
+    TypeSchemas, get_first_leaf_name, get_node_fields, get_pattern_instance_base, to_camel_case,
+    to_pascal_case,
 };
 
 /// Generate JavaScript + JSDoc client from metadata and OpenAPI endpoints
@@ -330,6 +331,9 @@ fn generate_structural_patterns(
     writeln!(output, "// Reusable structural pattern factories\n").unwrap();
 
     for pattern in patterns {
+        // Check if this pattern is parameterizable (has field positions detected)
+        let is_parameterizable = pattern.is_parameterizable();
+
         // Generate JSDoc typedef
         writeln!(output, "/**").unwrap();
         writeln!(output, " * @typedef {{Object}} {}", pattern.name).unwrap();
@@ -349,13 +353,19 @@ fn generate_structural_patterns(
         writeln!(output, "/**").unwrap();
         writeln!(output, " * Create a {} pattern node", pattern.name).unwrap();
         writeln!(output, " * @param {{BrkClientBase}} client").unwrap();
-        writeln!(output, " * @param {{string}} basePath").unwrap();
+        if is_parameterizable {
+            writeln!(output, " * @param {{string}} acc - Accumulated metric name").unwrap();
+        } else {
+            writeln!(output, " * @param {{string}} basePath").unwrap();
+        }
         writeln!(output, " * @returns {{{}}}", pattern.name).unwrap();
         writeln!(output, " */").unwrap();
+
+        let param_name = if is_parameterizable { "acc" } else { "basePath" };
         writeln!(
             output,
-            "function create{}(client, basePath) {{",
-            pattern.name
+            "function create{}(client, {}) {{",
+            pattern.name, param_name
         )
         .unwrap();
         writeln!(output, "  return {{").unwrap();
@@ -366,36 +376,11 @@ fn generate_structural_patterns(
             } else {
                 ""
             };
-            if metadata.is_pattern_type(&field.rust_type) {
-                writeln!(
-                    output,
-                    "    {}: create{}(client, `${{basePath}}/{}`){}",
-                    to_camel_case(&field.name),
-                    field.rust_type,
-                    field.name,
-                    comma
-                )
-                .unwrap();
-            } else if field_uses_accessor(field, metadata) {
-                let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
-                writeln!(
-                    output,
-                    "    {}: create{}(client, `${{basePath}}/{}`){}",
-                    to_camel_case(&field.name),
-                    accessor.name,
-                    field.name,
-                    comma
-                )
-                .unwrap();
+
+            if is_parameterizable {
+                generate_parameterized_field(output, field, pattern, metadata, comma);
             } else {
-                writeln!(
-                    output,
-                    "    {}: new MetricNode(client, `${{basePath}}/{}`){}",
-                    to_camel_case(&field.name),
-                    field.name,
-                    comma
-                )
-                .unwrap();
+                generate_tree_path_field(output, field, metadata, comma);
             }
         }
 
@@ -404,6 +389,105 @@ fn generate_structural_patterns(
     }
 }
 
+/// Generate a field using parameterized (prepend/append) metric name construction
+fn generate_parameterized_field(
+    output: &mut String,
+    field: &PatternField,
+    pattern: &StructuralPattern,
+    metadata: &ClientMetadata,
+    comma: &str,
+) {
+    let field_name_js = to_camel_case(&field.name);
+
+    // For branch fields, pass the accumulated name to nested pattern
+    if metadata.is_pattern_type(&field.rust_type) {
+        // Get the field position to determine how to transform the accumulated name
+        let child_acc = if let Some(pos) = pattern.get_field_position(&field.name) {
+            match pos {
+                FieldNamePosition::Append(suffix) => format!("`${{acc}}{}`", suffix),
+                FieldNamePosition::Prepend(prefix) => format!("`{}{}`", prefix, "${acc}"),
+                FieldNamePosition::Identity => "acc".to_string(),
+                FieldNamePosition::SetBase(base) => format!("'{}'", base),
+            }
+        } else {
+            // Fallback: append field name
+            format!("`${{acc}}_{}`", field.name)
+        };
+
+        writeln!(
+            output,
+            "    {}: create{}(client, {}){}",
+            field_name_js, field.rust_type, child_acc, comma
+        )
+        .unwrap();
+        return;
+    }
+
+    // For leaf fields, construct the metric path based on position
+    let metric_expr = if let Some(pos) = pattern.get_field_position(&field.name) {
+        match pos {
+            FieldNamePosition::Append(suffix) => format!("`/${{acc}}{suffix}`"),
+            FieldNamePosition::Prepend(prefix) => format!("`/{prefix}${{acc}}`"),
+            FieldNamePosition::Identity => "`/${acc}`".to_string(),
+            FieldNamePosition::SetBase(base) => format!("'/{base}'"),
+        }
+    } else {
+        // Fallback: use field name appended
+        format!("`/${{acc}}_{}`", field.name)
+    };
+
+    if field_uses_accessor(field, metadata) {
+        let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
+        writeln!(
+            output,
+            "    {}: create{}(client, {}){}",
+            field_name_js, accessor.name, metric_expr, comma
+        )
+        .unwrap();
+    } else {
+        writeln!(
+            output,
+            "    {}: new MetricNode(client, {}){}",
+            field_name_js, metric_expr, comma
+        )
+        .unwrap();
+    }
+}
+
+/// Generate a field using tree path construction (fallback for non-parameterizable patterns)
+fn generate_tree_path_field(
+    output: &mut String,
+    field: &PatternField,
+    metadata: &ClientMetadata,
+    comma: &str,
+) {
+    let field_name_js = to_camel_case(&field.name);
+
+    if metadata.is_pattern_type(&field.rust_type) {
+        writeln!(
+            output,
+            "    {}: create{}(client, `${{basePath}}/{}`){}",
+            field_name_js, field.rust_type, field.name, comma
+        )
+        .unwrap();
+    } else if field_uses_accessor(field, metadata) {
+        let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
+        writeln!(
+            output,
+            "    {}: create{}(client, `${{basePath}}/{}`){}",
+            field_name_js, accessor.name, field.name, comma
+        )
+        .unwrap();
+    } else {
+        writeln!(
+            output,
+            "    {}: new MetricNode(client, `${{basePath}}/{}`){}",
+            field_name_js, field.name, comma
+        )
+        .unwrap();
+    }
+}
+
 /// Convert pattern field to JavaScript/JSDoc type
 fn field_to_js_type(field: &PatternField, metadata: &ClientMetadata) -> String {
     if metadata.is_pattern_type(&field.rust_type) {
@@ -556,7 +640,7 @@ fn generate_main_client(
 fn generate_tree_initializer(
     output: &mut String,
     node: &TreeNode,
-    path: &str,
+    accumulated_name: &str,
     indent: usize,
     pattern_lookup: &std::collections::HashMap<Vec<PatternField>, String>,
     metadata: &ClientMetadata,
@@ -566,12 +650,6 @@ fn generate_tree_initializer(
     if let TreeNode::Branch(children) = node {
         for (i, (child_name, child_node)) in children.iter().enumerate() {
             let field_name = to_camel_case(child_name);
-            let child_path = if path.is_empty() {
-                format!("/{}", child_name)
-            } else {
-                format!("{}/{}", path, child_name)
-            };
-
             let comma = if i < children.len() - 1 { "," } else { "" };
 
             match child_node {
@@ -597,18 +675,44 @@ fn generate_tree_initializer(
                 TreeNode::Branch(grandchildren) => {
                     let child_fields = get_node_fields(grandchildren, pattern_lookup);
                     if let Some(pattern_name) = pattern_lookup.get(&child_fields) {
+                        // For parameterized patterns, derive accumulated metric name from first leaf
+                        let pattern = metadata
+                            .structural_patterns
+                            .iter()
+                            .find(|p| &p.name == pattern_name);
+                        let is_parameterizable =
+                            pattern.map(|p| p.is_parameterizable()).unwrap_or(false);
+
+                        let arg = if is_parameterizable {
+                            // Get the metric base from the first leaf descendant
+                            get_pattern_instance_base(child_node, child_name)
+                        } else {
+                            // Fallback to tree path for non-parameterizable patterns
+                            if accumulated_name.is_empty() {
+                                format!("/{}", child_name)
+                            } else {
+                                format!("{}/{}", accumulated_name, child_name)
+                            }
+                        };
+
                         writeln!(
                             output,
                             "{}{}: create{}(this, '{}'){}",
-                            indent_str, field_name, pattern_name, child_path, comma
+                            indent_str, field_name, pattern_name, arg, comma
                         )
                         .unwrap();
                     } else {
+                        // Not a pattern - recurse with accumulated name
+                        let child_acc = infer_child_accumulated_name(
+                            child_node,
+                            accumulated_name,
+                            child_name,
+                        );
                         writeln!(output, "{}{}: {{", indent_str, field_name).unwrap();
                         generate_tree_initializer(
                             output,
                             child_node,
-                            &child_path,
+                            &child_acc,
                             indent + 1,
                             pattern_lookup,
                             metadata,
@@ -621,6 +725,34 @@ fn generate_tree_initializer(
     }
 }
 
+/// Infer the accumulated metric name for a child node
+fn infer_child_accumulated_name(node: &TreeNode, parent_acc: &str, field_name: &str) -> String {
+    // Try to infer from first leaf descendant
+    if let Some(leaf_name) = get_first_leaf_name(node) {
+        // Look for field_name in the leaf metric name
+        if let Some(pos) = leaf_name.find(field_name) {
+            // The field_name appears in the metric - use it as base
+            if pos == 0 {
+                // At start - this is the base
+                return field_name.to_string();
+            } else if leaf_name.chars().nth(pos - 1) == Some('_') {
+                // After underscore - likely an append pattern
+                if parent_acc.is_empty() {
+                    return field_name.to_string();
+                }
+                return format!("{}_{}", parent_acc, field_name);
+            }
+        }
+    }
+
+    // Fallback: append field name
+    if parent_acc.is_empty() {
+        field_name.to_string()
+    } else {
+        format!("{}_{}", parent_acc, field_name)
+    }
+}
+
 /// Generate API methods
 fn generate_api_methods(output: &mut String, endpoints: &[Endpoint]) {
     for endpoint in endpoints {

crates/brk_binder/src/lib.rs

@@ -1,5 +1,9 @@
-mod js;
+use std::{fs::create_dir_all, io, path::Path};
+
+use brk_query::Vecs;
+
 mod javascript;
+mod js;
 mod openapi;
 mod python;
 mod rust;
@@ -12,10 +16,6 @@ pub use python::*;
 pub use rust::*;
 pub use types::*;
 
-use brk_query::Vecs;
-use std::io;
-use std::path::Path;
-
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");
 
 /// Generate all client libraries from the query vecs and OpenAPI JSON
@@ -29,17 +29,17 @@ pub fn generate_clients(vecs: &Vecs, openapi_json: &str, output_dir: &Path) -> i
 
     // Generate Rust client (uses real brk_types, no schema conversion needed)
     let rust_path = output_dir.join("rust");
-    std::fs::create_dir_all(&rust_path)?;
+    create_dir_all(&rust_path)?;
     generate_rust_client(&metadata, &endpoints, &rust_path)?;
 
     // Generate JavaScript client (needs schemas for type definitions)
     let js_path = output_dir.join("javascript");
-    std::fs::create_dir_all(&js_path)?;
+    create_dir_all(&js_path)?;
     generate_javascript_client(&metadata, &endpoints, &schemas, &js_path)?;
 
     // Generate Python client (needs schemas for type definitions)
     let python_path = output_dir.join("python");
-    std::fs::create_dir_all(&python_path)?;
+    create_dir_all(&python_path)?;
     generate_python_client(&metadata, &endpoints, &schemas, &python_path)?;
 
     Ok(())

crates/brk_binder/src/python.rs

@@ -8,8 +8,8 @@ use brk_types::{Index, TreeNode};
 use serde_json::Value;
 
 use crate::{
-    ClientMetadata, Endpoint, IndexSetPattern, PatternField, StructuralPattern, TypeSchemas,
-    get_node_fields, to_pascal_case, to_snake_case,
+    ClientMetadata, Endpoint, FieldNamePosition, IndexSetPattern, PatternField, StructuralPattern,
+    TypeSchemas, get_node_fields, get_pattern_instance_base, to_pascal_case, to_snake_case,
 };
 
 /// Generate Python client from metadata and OpenAPI endpoints
@@ -253,6 +253,8 @@ fn generate_structural_patterns(
     writeln!(output, "# Reusable structural pattern classes\n").unwrap();
 
     for pattern in patterns {
+        let is_parameterizable = pattern.is_parameterizable();
+
         writeln!(output, "class {}:", pattern.name).unwrap();
         writeln!(
             output,
@@ -260,44 +262,27 @@ fn generate_structural_patterns(
         )
         .unwrap();
         writeln!(output, "    ").unwrap();
-        writeln!(
-            output,
-            "    def __init__(self, client: BrkClientBase, base_path: str):"
-        )
-        .unwrap();
+
+        if is_parameterizable {
+            writeln!(
+                output,
+                "    def __init__(self, client: BrkClientBase, acc: str):"
+            )
+            .unwrap();
+            writeln!(output, "        \"\"\"Create pattern node with accumulated metric name.\"\"\"").unwrap();
+        } else {
+            writeln!(
+                output,
+                "    def __init__(self, client: BrkClientBase, base_path: str):"
+            )
+            .unwrap();
+        }
 
         for field in &pattern.fields {
-            let py_type = field_to_python_type(field, metadata);
-            if metadata.is_pattern_type(&field.rust_type) {
-                writeln!(
-                    output,
-                    "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
-                    to_snake_case(&field.name),
-                    py_type,
-                    field.rust_type,
-                    field.name
-                )
-                .unwrap();
-            } else if field_uses_accessor(field, metadata) {
-                let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
-                writeln!(
-                    output,
-                    "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
-                    to_snake_case(&field.name),
-                    py_type,
-                    accessor.name,
-                    field.name
-                )
-                .unwrap();
+            if is_parameterizable {
+                generate_parameterized_python_field(output, field, pattern, metadata);
             } else {
-                writeln!(
-                    output,
-                    "        self.{}: {} = MetricNode(client, f'{{base_path}}/{}')",
-                    to_snake_case(&field.name),
-                    py_type,
-                    field.name
-                )
-                .unwrap();
+                generate_tree_path_python_field(output, field, metadata);
             }
         }
 
@@ -305,6 +290,102 @@ fn generate_structural_patterns(
     }
 }
 
+/// Generate a field using parameterized (prepend/append) metric name construction
+fn generate_parameterized_python_field(
+    output: &mut String,
+    field: &PatternField,
+    pattern: &StructuralPattern,
+    metadata: &ClientMetadata,
+) {
+    let field_name = to_snake_case(&field.name);
+    let py_type = field_to_python_type(field, metadata);
+
+    // For branch fields, pass the accumulated name to nested pattern
+    if metadata.is_pattern_type(&field.rust_type) {
+        let child_acc = if let Some(pos) = pattern.get_field_position(&field.name) {
+            match pos {
+                FieldNamePosition::Append(suffix) => format!("f'{{acc}}{}'", suffix),
+                FieldNamePosition::Prepend(prefix) => format!("f'{}{{acc}}'", prefix),
+                FieldNamePosition::Identity => "acc".to_string(),
+                FieldNamePosition::SetBase(base) => format!("'{}'", base),
+            }
+        } else {
+            format!("f'{{acc}}_{}'", field.name)
+        };
+
+        writeln!(
+            output,
+            "        self.{}: {} = {}(client, {})",
+            field_name, py_type, field.rust_type, child_acc
+        )
+        .unwrap();
+        return;
+    }
+
+    // For leaf fields, construct the metric path based on position
+    let metric_expr = if let Some(pos) = pattern.get_field_position(&field.name) {
+        match pos {
+            FieldNamePosition::Append(suffix) => format!("f'/{{acc}}{}'", suffix),
+            FieldNamePosition::Prepend(prefix) => format!("f'/{}{{acc}}'", prefix),
+            FieldNamePosition::Identity => "f'/{acc}'".to_string(),
+            FieldNamePosition::SetBase(base) => format!("'/{}'", base),
+        }
+    } else {
+        format!("f'/{{acc}}_{}'", field.name)
+    };
+
+    if field_uses_accessor(field, metadata) {
+        let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
+        writeln!(
+            output,
+            "        self.{}: {} = {}(client, {})",
+            field_name, py_type, accessor.name, metric_expr
+        )
+        .unwrap();
+    } else {
+        writeln!(
+            output,
+            "        self.{}: {} = MetricNode(client, {})",
+            field_name, py_type, metric_expr
+        )
+        .unwrap();
+    }
+}
+
+/// Generate a field using tree path construction (fallback for non-parameterizable patterns)
+fn generate_tree_path_python_field(
+    output: &mut String,
+    field: &PatternField,
+    metadata: &ClientMetadata,
+) {
+    let field_name = to_snake_case(&field.name);
+    let py_type = field_to_python_type(field, metadata);
+
+    if metadata.is_pattern_type(&field.rust_type) {
+        writeln!(
+            output,
+            "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
+            field_name, py_type, field.rust_type, field.name
+        )
+        .unwrap();
+    } else if field_uses_accessor(field, metadata) {
+        let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
+        writeln!(
+            output,
+            "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
+            field_name, py_type, accessor.name, field.name
+        )
+        .unwrap();
+    } else {
+        writeln!(
+            output,
+            "        self.{}: {} = MetricNode(client, f'{{base_path}}/{}')",
+            field_name, py_type, field.name
+        )
+        .unwrap();
+    }
+}
+
 /// Convert pattern field to Python type annotation
 fn field_to_python_type(field: &PatternField, metadata: &ClientMetadata) -> String {
     if metadata.is_pattern_type(&field.rust_type) {
@@ -374,38 +455,80 @@ fn generate_tree_class(
         )
         .unwrap();
 
-        for field in &fields {
+        for (field, (child_name, child_node)) in fields.iter().zip(children.iter()) {
             let py_type = field_to_python_type(field, metadata);
+            let field_name_py = to_snake_case(&field.name);
+
             if metadata.is_pattern_type(&field.rust_type) {
-                writeln!(
-                    output,
-                    "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
-                    to_snake_case(&field.name),
-                    py_type,
-                    field.rust_type,
-                    field.name
-                )
-                .unwrap();
+                // Check if the pattern is parameterizable
+                let pattern = metadata
+                    .structural_patterns
+                    .iter()
+                    .find(|p| p.name == field.rust_type);
+                let is_parameterizable = pattern.map(|p| p.is_parameterizable()).unwrap_or(false);
+
+                if is_parameterizable {
+                    // Get the metric base from the first leaf descendant
+                    let metric_base = get_pattern_instance_base(child_node, child_name);
+                    writeln!(
+                        output,
+                        "        self.{}: {} = {}(client, '{}')",
+                        field_name_py, py_type, field.rust_type, metric_base
+                    )
+                    .unwrap();
+                } else {
+                    writeln!(
+                        output,
+                        "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
+                        field_name_py, py_type, field.rust_type, field.name
+                    )
+                    .unwrap();
+                }
             } else if field_uses_accessor(field, metadata) {
+                // Leaf with accessor - get actual metric path from leaf
+                let metric_path = if let TreeNode::Leaf(leaf) = child_node {
+                    format!("/{}", leaf.name())
+                } else {
+                    format!("{{base_path}}/{}", field.name)
+                };
                 let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
-                writeln!(
-                    output,
-                    "        self.{}: {} = {}(client, f'{{base_path}}/{}')",
-                    to_snake_case(&field.name),
-                    py_type,
-                    accessor.name,
-                    field.name
-                )
-                .unwrap();
+                if metric_path.contains("{base_path}") {
+                    writeln!(
+                        output,
+                        "        self.{}: {} = {}(client, f'{}')",
+                        field_name_py, py_type, accessor.name, metric_path
+                    )
+                    .unwrap();
+                } else {
+                    writeln!(
+                        output,
+                        "        self.{}: {} = {}(client, '{}')",
+                        field_name_py, py_type, accessor.name, metric_path
+                    )
+                    .unwrap();
+                }
             } else {
-                writeln!(
-                    output,
-                    "        self.{}: {} = MetricNode(client, f'{{base_path}}/{}')",
-                    to_snake_case(&field.name),
-                    py_type,
-                    field.name
-                )
-                .unwrap();
+                // Leaf without accessor - get actual metric path from leaf
+                let metric_path = if let TreeNode::Leaf(leaf) = child_node {
+                    format!("/{}", leaf.name())
+                } else {
+                    format!("{{base_path}}/{}", field.name)
+                };
+                if metric_path.contains("{base_path}") {
+                    writeln!(
+                        output,
+                        "        self.{}: {} = MetricNode(client, f'{}')",
+                        field_name_py, py_type, metric_path
+                    )
+                    .unwrap();
+                } else {
+                    writeln!(
+                        output,
+                        "        self.{}: {} = MetricNode(client, '{}')",
+                        field_name_py, py_type, metric_path
+                    )
+                    .unwrap();
+                }
             }
         }
 

crates/brk_binder/src/rust.rs

@@ -6,7 +6,7 @@ use std::path::Path;
 
 use brk_types::{Index, TreeNode};
 
-use crate::{ClientMetadata, Endpoint, IndexSetPattern, PatternField, StructuralPattern, get_node_fields, to_pascal_case, to_snake_case};
+use crate::{ClientMetadata, Endpoint, FieldNamePosition, IndexSetPattern, PatternField, StructuralPattern, get_node_fields, get_pattern_instance_base, to_pascal_case, to_snake_case};
 
 /// Generate Rust client from metadata and OpenAPI endpoints
 pub fn generate_rust_client(
@@ -232,6 +232,8 @@ fn generate_pattern_structs(output: &mut String, patterns: &[StructuralPattern],
     writeln!(output, "// Reusable pattern structs\n").unwrap();
 
     for pattern in patterns {
+        let is_parameterizable = pattern.is_parameterizable();
+
         writeln!(output, "/// Pattern struct for repeated tree structure.").unwrap();
         writeln!(output, "pub struct {}<'a> {{", pattern.name).unwrap();
 
@@ -245,30 +247,20 @@ fn generate_pattern_structs(output: &mut String, patterns: &[StructuralPattern],
 
         // Generate impl block with constructor
         writeln!(output, "impl<'a> {}<'a> {{", pattern.name).unwrap();
-        writeln!(output, "    pub fn new(client: &'a BrkClientBase, base_path: &str) -> Self {{").unwrap();
+
+        if is_parameterizable {
+            writeln!(output, "    /// Create a new pattern node with accumulated metric name.").unwrap();
+            writeln!(output, "    pub fn new(client: &'a BrkClientBase, acc: &str) -> Self {{").unwrap();
+        } else {
+            writeln!(output, "    pub fn new(client: &'a BrkClientBase, base_path: &str) -> Self {{").unwrap();
+        }
         writeln!(output, "        Self {{").unwrap();
 
         for field in &pattern.fields {
-            let field_name = to_snake_case(&field.name);
-            if metadata.is_pattern_type(&field.rust_type) {
-                writeln!(
-                    output,
-                    "            {}: {}::new(client, &format!(\"{{base_path}}/{}\"))," ,
-                    field_name, field.rust_type, field.name
-                ).unwrap();
-            } else if field_uses_accessor(field, metadata) {
-                let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
-                writeln!(
-                    output,
-                    "            {}: {}::new(client, &format!(\"{{base_path}}/{}\"))," ,
-                    field_name, accessor.name, field.name
-                ).unwrap();
+            if is_parameterizable {
+                generate_parameterized_rust_field(output, field, pattern, metadata);
             } else {
-                writeln!(
-                    output,
-                    "            {}: MetricNode::new(client, format!(\"{{base_path}}/{}\"))," ,
-                    field_name, field.name
-                ).unwrap();
+                generate_tree_path_rust_field(output, field, metadata);
             }
         }
 
@@ -278,6 +270,94 @@ fn generate_pattern_structs(output: &mut String, patterns: &[StructuralPattern],
     }
 }
 
+/// Generate a field using parameterized (prepend/append) metric name construction
+fn generate_parameterized_rust_field(
+    output: &mut String,
+    field: &PatternField,
+    pattern: &StructuralPattern,
+    metadata: &ClientMetadata,
+) {
+    let field_name = to_snake_case(&field.name);
+
+    // For branch fields, pass the accumulated name to nested pattern
+    if metadata.is_pattern_type(&field.rust_type) {
+        let child_acc = if let Some(pos) = pattern.get_field_position(&field.name) {
+            match pos {
+                FieldNamePosition::Append(suffix) => format!("&format!(\"{{acc}}{}\")", suffix),
+                FieldNamePosition::Prepend(prefix) => format!("&format!(\"{}{{acc}}\")", prefix),
+                FieldNamePosition::Identity => "acc".to_string(),
+                FieldNamePosition::SetBase(base) => format!("\"{}\"", base),
+            }
+        } else {
+            format!("&format!(\"{{acc}}_{}\")", field.name)
+        };
+
+        writeln!(
+            output,
+            "            {}: {}::new(client, {}),",
+            field_name, field.rust_type, child_acc
+        ).unwrap();
+        return;
+    }
+
+    // For leaf fields, construct the metric path based on position
+    let metric_expr = if let Some(pos) = pattern.get_field_position(&field.name) {
+        match pos {
+            FieldNamePosition::Append(suffix) => format!("format!(\"/{{acc}}{}\")", suffix),
+            FieldNamePosition::Prepend(prefix) => format!("format!(\"/{}{{acc}}\")", prefix),
+            FieldNamePosition::Identity => "format!(\"/{acc}\")".to_string(),
+            FieldNamePosition::SetBase(base) => format!("\"/{}\".to_string()", base),
+        }
+    } else {
+        format!("format!(\"/{{acc}}_{}\")", field.name)
+    };
+
+    if field_uses_accessor(field, metadata) {
+        let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
+        writeln!(
+            output,
+            "            {}: {}::new(client, &{}),",
+            field_name, accessor.name, metric_expr
+        ).unwrap();
+    } else {
+        writeln!(
+            output,
+            "            {}: MetricNode::new(client, {}),",
+            field_name, metric_expr
+        ).unwrap();
+    }
+}
+
+/// Generate a field using tree path construction (fallback for non-parameterizable patterns)
+fn generate_tree_path_rust_field(
+    output: &mut String,
+    field: &PatternField,
+    metadata: &ClientMetadata,
+) {
+    let field_name = to_snake_case(&field.name);
+
+    if metadata.is_pattern_type(&field.rust_type) {
+        writeln!(
+            output,
+            "            {}: {}::new(client, &format!(\"{{base_path}}/{}\")),",
+            field_name, field.rust_type, field.name
+        ).unwrap();
+    } else if field_uses_accessor(field, metadata) {
+        let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
+        writeln!(
+            output,
+            "            {}: {}::new(client, &format!(\"{{base_path}}/{}\")),",
+            field_name, accessor.name, field.name
+        ).unwrap();
+    } else {
+        writeln!(
+            output,
+            "            {}: MetricNode::new(client, format!(\"{{base_path}}/{}\")),",
+            field_name, field.name
+        ).unwrap();
+    }
+}
+
 /// Convert a PatternField to the full type annotation
 fn field_to_type_annotation(field: &PatternField, metadata: &ClientMetadata) -> String {
     if metadata.is_pattern_type(&field.rust_type) {
@@ -380,27 +460,72 @@ fn generate_tree_node(
         writeln!(output, "    pub fn new(client: &'a BrkClientBase, base_path: &str) -> Self {{").unwrap();
         writeln!(output, "        Self {{").unwrap();
 
-        for field in &fields {
+        for (field, (child_name, child_node)) in fields.iter().zip(children.iter()) {
             let field_name = to_snake_case(&field.name);
             if metadata.is_pattern_type(&field.rust_type) {
-                writeln!(
-                    output,
-                    "            {}: {}::new(client, &format!(\"{{base_path}}/{}\"))," ,
-                    field_name, field.rust_type, field.name
-                ).unwrap();
+                // Check if the pattern is parameterizable
+                let pattern = metadata
+                    .structural_patterns
+                    .iter()
+                    .find(|p| p.name == field.rust_type);
+                let is_parameterizable = pattern.map(|p| p.is_parameterizable()).unwrap_or(false);
+
+                if is_parameterizable {
+                    // Get the metric base from the first leaf descendant
+                    let metric_base = get_pattern_instance_base(child_node, child_name);
+                    writeln!(
+                        output,
+                        "            {}: {}::new(client, \"{}\"),",
+                        field_name, field.rust_type, metric_base
+                    ).unwrap();
+                } else {
+                    writeln!(
+                        output,
+                        "            {}: {}::new(client, &format!(\"{{base_path}}/{}\"))," ,
+                        field_name, field.rust_type, field.name
+                    ).unwrap();
+                }
             } else if field_uses_accessor(field, metadata) {
+                // Leaf with accessor - get actual metric path from leaf
+                let metric_path = if let TreeNode::Leaf(leaf) = child_node {
+                    format!("/{}", leaf.name())
+                } else {
+                    format!("{{base_path}}/{}", field.name)
+                };
                 let accessor = metadata.find_index_set_pattern(&field.indexes).unwrap();
-                writeln!(
-                    output,
-                    "            {}: {}::new(client, &format!(\"{{base_path}}/{}\"))," ,
-                    field_name, accessor.name, field.name
-                ).unwrap();
+                if metric_path.contains("{base_path}") {
+                    writeln!(
+                        output,
+                        "            {}: {}::new(client, &format!(\"{}\")),",
+                        field_name, accessor.name, metric_path
+                    ).unwrap();
+                } else {
+                    writeln!(
+                        output,
+                        "            {}: {}::new(client, \"{}\"),",
+                        field_name, accessor.name, metric_path
+                    ).unwrap();
+                }
             } else {
-                writeln!(
-                    output,
-                    "            {}: MetricNode::new(client, format!(\"{{base_path}}/{}\"))," ,
-                    field_name, field.name
-                ).unwrap();
+                // Leaf without accessor - get actual metric path from leaf
+                let metric_path = if let TreeNode::Leaf(leaf) = child_node {
+                    format!("/{}", leaf.name())
+                } else {
+                    format!("{{base_path}}/{}", field.name)
+                };
+                if metric_path.contains("{base_path}") {
+                    writeln!(
+                        output,
+                        "            {}: MetricNode::new(client, format!(\"{}\")),",
+                        field_name, metric_path
+                    ).unwrap();
+                } else {
+                    writeln!(
+                        output,
+                        "            {}: MetricNode::new(client, \"{}\".to_string()),",
+                        field_name, metric_path
+                    ).unwrap();
+                }
             }
         }
 

crates/brk_binder/src/types.rs

@@ -1,9 +1,22 @@
-use std::collections::{BTreeSet, HashMap};
+use std::collections::{BTreeMap, BTreeSet, HashMap};
 use std::hash::{Hash, Hasher};
 
 use brk_query::Vecs;
 use brk_types::{Index, TreeNode};
 
+/// How a field modifies the accumulated metric name
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum FieldNamePosition {
+    /// Field prepends a prefix: leaf.name() = prefix + accumulated
+    Prepend(String),
+    /// Field appends a suffix: leaf.name() = accumulated + suffix
+    Append(String),
+    /// Field IS the accumulated name (no modification)
+    Identity,
+    /// Field sets a new base name (used at pattern entry points)
+    SetBase(String),
+}
+
 /// Metadata extracted from brk_query for client generation
 #[derive(Debug)]
 pub struct ClientMetadata {
@@ -33,6 +46,8 @@ pub struct StructuralPattern {
     pub name: String,
     /// Ordered list of child fields (sorted by field name)
     pub fields: Vec<PatternField>,
+    /// How each field modifies the accumulated name (field_name -> position)
+    pub field_positions: HashMap<String, FieldNamePosition>,
 }
 
 impl StructuralPattern {
@@ -41,6 +56,21 @@ impl StructuralPattern {
     pub fn contains_leaves(&self) -> bool {
         self.fields.iter().any(|f| !f.indexes.is_empty())
     }
+
+    /// Returns true if all leaf fields have consistent name transformations.
+    /// A pattern is parameterizable if we can detect prepend/append patterns.
+    pub fn is_parameterizable(&self) -> bool {
+        !self.field_positions.is_empty()
+            && self.fields.iter().all(|f| {
+                // Branch fields are always OK (they delegate to nested patterns)
+                f.indexes.is_empty() || self.field_positions.contains_key(&f.name)
+            })
+    }
+
+    /// Get the field position for a given field name
+    pub fn get_field_position(&self, field_name: &str) -> Option<&FieldNamePosition> {
+        self.field_positions.get(field_name)
+    }
 }
 
 /// A field in a structural pattern
@@ -126,19 +156,255 @@ fn detect_structural_patterns(tree: &TreeNode) -> Vec<StructuralPattern> {
     // Process tree bottom-up to resolve all branch types
     resolve_branch_patterns(tree, &mut signature_to_pattern, &mut signature_counts);
 
-    // Build final list of patterns (only those appearing 2+ times)
+    // Build initial list of patterns (only those appearing 2+ times)
     let mut patterns: Vec<StructuralPattern> = signature_to_pattern
-        .into_iter()
-        .filter(|(sig, _)| signature_counts.get(sig).copied().unwrap_or(0) >= 2)
-        .map(|(fields, name)| StructuralPattern { name, fields })
+        .iter()
+        .filter(|(sig, _)| signature_counts.get(*sig).copied().unwrap_or(0) >= 2)
+        .map(|(fields, name)| StructuralPattern {
+            name: name.clone(),
+            fields: fields.clone(),
+            field_positions: HashMap::new(),
+        })
         .collect();
 
+    // Build lookup for second pass
+    let pattern_lookup: HashMap<Vec<PatternField>, String> = signature_to_pattern;
+
+    // Second pass: analyze field positions by traversing tree instances
+    analyze_pattern_field_positions(tree, &mut patterns, &pattern_lookup);
+
     // Sort by number of fields descending (larger patterns first)
     patterns.sort_by(|a, b| b.fields.len().cmp(&a.fields.len()));
 
     patterns
 }
 
+/// Analyze field positions for all patterns by traversing tree instances.
+/// For each pattern instance, we compare parent accumulated name with child leaf names.
+fn analyze_pattern_field_positions(
+    tree: &TreeNode,
+    patterns: &mut [StructuralPattern],
+    pattern_lookup: &HashMap<Vec<PatternField>, String>,
+) {
+    // Collect instances: pattern_name -> vec of (accumulated_name, field_name, leaf_name)
+    let mut instances: HashMap<String, Vec<(String, String, String)>> = HashMap::new();
+
+    // Traverse tree and collect instances
+    collect_pattern_instances(tree, "", &mut instances, pattern_lookup);
+
+    // For each pattern, analyze field positions from instances
+    for pattern in patterns.iter_mut() {
+        if let Some(pattern_instances) = instances.get(&pattern.name) {
+            pattern.field_positions = analyze_field_positions_from_instances(pattern_instances);
+        }
+    }
+}
+
+/// Recursively traverse tree and collect pattern instances with accumulated metric names.
+fn collect_pattern_instances(
+    node: &TreeNode,
+    accumulated_name: &str,
+    instances: &mut HashMap<String, Vec<(String, String, String)>>,
+    pattern_lookup: &HashMap<Vec<PatternField>, String>,
+) {
+    if let TreeNode::Branch(children) = node {
+        // Check if this branch matches a pattern
+        let fields = get_node_fields_for_analysis(children, pattern_lookup);
+        if let Some(pattern_name) = pattern_lookup.get(&fields) {
+            // Collect instances for this pattern
+            for (field_name, child_node) in children {
+                if let TreeNode::Leaf(leaf) = child_node {
+                    instances
+                        .entry(pattern_name.clone())
+                        .or_default()
+                        .push((accumulated_name.to_string(), field_name.clone(), leaf.name().to_string()));
+                }
+            }
+        }
+
+        // Continue traversing children
+        for (field_name, child_node) in children {
+            let child_accumulated = match child_node {
+                TreeNode::Leaf(leaf) => leaf.name().to_string(),
+                TreeNode::Branch(_) => {
+                    // For branches, we need to infer the accumulated name
+                    // If there's a leaf descendant, use its name as the basis
+                    if let Some(desc_leaf_name) = get_descendant_leaf_name(child_node) {
+                        // Try to extract what this level contributes
+                        infer_accumulated_name(accumulated_name, field_name, &desc_leaf_name)
+                    } else {
+                        // No descendants - use field name as base
+                        if accumulated_name.is_empty() {
+                            field_name.clone()
+                        } else {
+                            format!("{}_{}", accumulated_name, field_name)
+                        }
+                    }
+                }
+            };
+            collect_pattern_instances(child_node, &child_accumulated, instances, pattern_lookup);
+        }
+    }
+}
+
+/// Get a descendant leaf name from a branch node (first one found)
+fn get_descendant_leaf_name(node: &TreeNode) -> Option<String> {
+    match node {
+        TreeNode::Leaf(leaf) => Some(leaf.name().to_string()),
+        TreeNode::Branch(children) => {
+            for child in children.values() {
+                if let Some(name) = get_descendant_leaf_name(child) {
+                    return Some(name);
+                }
+            }
+            None
+        }
+    }
+}
+
+/// Infer the accumulated name at this level by analyzing what part of the descendant's name
+/// comes from the current field.
+fn infer_accumulated_name(parent_acc: &str, field_name: &str, descendant_leaf: &str) -> String {
+    // Try to find field_name in the descendant's metric name
+    if let Some(pos) = descendant_leaf.find(field_name) {
+        // Extract the part that corresponds to this level
+        if pos == 0 {
+            // Field is at the start
+            field_name.to_string()
+        } else if pos > 0 && descendant_leaf.chars().nth(pos - 1) == Some('_') {
+            // Field appears after underscore - this is likely an append
+            if parent_acc.is_empty() {
+                field_name.to_string()
+            } else {
+                format!("{}_{}", parent_acc, field_name)
+            }
+        } else {
+            field_name.to_string()
+        }
+    } else {
+        // Field name not directly found - use as is
+        if parent_acc.is_empty() {
+            field_name.to_string()
+        } else {
+            format!("{}_{}", parent_acc, field_name)
+        }
+    }
+}
+
+/// Analyze instances to determine field positions (prepend/append/identity).
+fn analyze_field_positions_from_instances(
+    instances: &[(String, String, String)],
+) -> HashMap<String, FieldNamePosition> {
+    // Group by field name
+    let mut field_instances: HashMap<String, Vec<(String, String)>> = HashMap::new();
+    for (acc, field, leaf) in instances {
+        field_instances
+            .entry(field.clone())
+            .or_default()
+            .push((acc.clone(), leaf.clone()));
+    }
+
+    let mut positions = HashMap::new();
+
+    for (field_name, field_data) in field_instances {
+        if let Some(position) = detect_field_position(&field_data) {
+            positions.insert(field_name, position);
+        }
+    }
+
+    positions
+}
+
+/// Detect the position transformation for a field based on (accumulated, leaf_name) pairs.
+fn detect_field_position(data: &[(String, String)]) -> Option<FieldNamePosition> {
+    if data.is_empty() {
+        return None;
+    }
+
+    // Try to detect pattern from first instance, then validate against others
+    let (first_acc, first_leaf) = &data[0];
+
+    // Case 1: Identity - leaf == accumulated
+    if first_acc == first_leaf {
+        return Some(FieldNamePosition::Identity);
+    }
+
+    // Case 2: Append - leaf = acc + suffix
+    if let Some(suffix) = first_leaf.strip_prefix(first_acc.as_str()) {
+        let suffix = suffix.to_string();
+        // Validate this pattern holds for all instances
+        if data.iter().all(|(acc, leaf)| {
+            if acc.is_empty() {
+                // When acc is empty, leaf should equal suffix (without leading _)
+                leaf == suffix.trim_start_matches('_')
+            } else {
+                leaf.strip_prefix(acc.as_str()) == Some(&suffix)
+            }
+        }) {
+            return Some(FieldNamePosition::Append(suffix));
+        }
+    }
+
+    // Case 3: Prepend - leaf = prefix + acc
+    if let Some(prefix) = first_leaf.strip_suffix(first_acc.as_str()) {
+        let prefix = prefix.to_string();
+        // Validate this pattern holds for all instances
+        if data.iter().all(|(acc, leaf)| {
+            if acc.is_empty() {
+                // When acc is empty, leaf should equal prefix (without trailing _)
+                leaf == prefix.trim_end_matches('_')
+            } else {
+                leaf.strip_suffix(acc.as_str()) == Some(&prefix)
+            }
+        }) {
+            return Some(FieldNamePosition::Prepend(prefix));
+        }
+    }
+
+    // Case 4: SetBase - the field name IS the metric base
+    // This happens at entry points where accumulated is empty
+    if first_acc.is_empty() {
+        return Some(FieldNamePosition::SetBase(first_leaf.clone()));
+    }
+
+    None
+}
+
+/// Get node fields for pattern matching during analysis
+fn get_node_fields_for_analysis(
+    children: &BTreeMap<String, TreeNode>,
+    pattern_lookup: &HashMap<Vec<PatternField>, String>,
+) -> Vec<PatternField> {
+    let mut fields: Vec<PatternField> = children
+        .iter()
+        .map(|(name, node)| {
+            let (rust_type, json_type, indexes) = match node {
+                TreeNode::Leaf(leaf) => (
+                    leaf.value_type().to_string(),
+                    schema_to_json_type(&leaf.schema),
+                    leaf.indexes().clone(),
+                ),
+                TreeNode::Branch(grandchildren) => {
+                    let child_fields = get_node_fields_for_analysis(grandchildren, pattern_lookup);
+                    let pattern_name = pattern_lookup
+                        .get(&child_fields)
+                        .cloned()
+                        .unwrap_or_else(|| "Unknown".to_string());
+                    (pattern_name.clone(), pattern_name, BTreeSet::new())
+                }
+            };
+            PatternField {
+                name: name.clone(),
+                rust_type,
+                json_type,
+                indexes,
+            }
+        })
+        .collect();
+    fields.sort_by(|a, b| a.name.cmp(&b.name));
+    fields
+}
+
 /// Recursively resolve branch patterns bottom-up.
 /// Returns the pattern name for this node if it's a branch, or None if it's a leaf.
 fn resolve_branch_patterns(
@@ -301,6 +567,35 @@ pub fn to_camel_case(s: &str) -> String {
     }
 }
 
+/// Get the first leaf name from a tree node (used across all generators)
+pub fn get_first_leaf_name(node: &TreeNode) -> Option<String> {
+    match node {
+        TreeNode::Leaf(leaf) => Some(leaf.name().to_string()),
+        TreeNode::Branch(children) => {
+            for child in children.values() {
+                if let Some(name) = get_first_leaf_name(child) {
+                    return Some(name);
+                }
+            }
+            None
+        }
+    }
+}
+
+/// Get the metric base for a pattern instance by analyzing the first leaf descendant.
+/// This extracts the common base that all leaves in this pattern instance share.
+pub fn get_pattern_instance_base(node: &TreeNode, field_name: &str) -> String {
+    if let Some(leaf_name) = get_first_leaf_name(node) {
+        // Look for field_name in the leaf metric name
+        if leaf_name.contains(field_name) {
+            // The field name is part of the metric - use it as base
+            return field_name.to_string();
+        }
+    }
+    // Fallback: use field name
+    field_name.to_string()
+}
+
 /// Detect index patterns - collect all indexes and find sets that appear 2+ times
 fn detect_index_patterns(tree: &TreeNode) -> (BTreeSet<Index>, Vec<IndexSetPattern>) {
     let mut used_indexes: BTreeSet<Index> = BTreeSet::new();

crates/brk_server/src/lib.rs

@@ -1,6 +1,6 @@
 #![doc = include_str!("../README.md")]
 
-use std::{path::PathBuf, sync::Arc, time::Duration};
+use std::{panic, path::PathBuf, sync::Arc, time::Duration};
 
 use aide::axum::ApiRouter;
 use axum::{
@@ -143,10 +143,14 @@ impl Server {
             .join("clients");
         if clients_path.exists() {
             let openapi_json = serde_json::to_string(&openapi).unwrap();
-            if let Err(e) = brk_binder::generate_clients(vecs, &openapi_json, &clients_path) {
-                error!("Failed to generate clients: {e}");
-            } else {
-                info!("Generated clients at {}", clients_path.display());
+            let result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+                brk_binder::generate_clients(vecs, &openapi_json, &clients_path)
+            }));
+
+            match result {
+                Ok(Ok(())) => info!("Generated clients at {}", clients_path.display()),
+                Ok(Err(e)) => error!("Failed to generate clients: {e}"),
+                Err(_) => error!("Client generation panicked"),
             }
         }