bindgen: everything works

crates/brk_bindgen/src/backends/javascript.rs

@@ -92,8 +92,7 @@ impl LanguageSyntax for JavaScriptSyntax {
             // "ratio_{disc}_bps" → split on {disc} → _m(_m(acc, 'ratio'), disc) then _bps
             // But this is complex. For embedded disc, use string interpolation.
             // For suffix disc (ends with {disc}), use _m composition.
-            if template.ends_with("{disc}") {
-                let static_part = &template[..template.len() - "{disc}".len()];
+            if let Some(static_part) = template.strip_suffix("{disc}") {
                 if static_part.is_empty() {
                     format!("_m({}, disc)", var_name)
                 } else {

crates/brk_bindgen/src/backends/rust.rs

@@ -1,6 +1,6 @@
 //! Rust language syntax implementation.
 
-use crate::{GenericSyntax, LanguageSyntax, to_snake_case};
+use crate::{GenericSyntax, LanguageSyntax, escape_rust_keyword, to_snake_case};
 
 /// Rust-specific code generation syntax.
 pub struct RustSyntax;
@@ -15,7 +15,7 @@ fn escape_rust_format(template: &str) -> String {
 
 impl LanguageSyntax for RustSyntax {
     fn field_name(&self, name: &str) -> String {
-        to_snake_case(name)
+        escape_rust_keyword(&to_snake_case(name))
     }
 
     fn path_expr(&self, base_var: &str, suffix: &str) -> String {

crates/brk_bindgen/src/generators/javascript/client.rs

@@ -183,6 +183,7 @@ function _wrapMetricData(raw) {{
  * @typedef {{Object}} MetricDataBase
  * @property {{number}} version - Version of the metric data
  * @property {{Index}} index - The index type used for this query
+ * @property {{string}} type - Value type (e.g. "f32", "u64", "Sats")
  * @property {{number}} total - Total number of data points
  * @property {{number}} start - Start index (inclusive)
  * @property {{number}} end - End index (exclusive)

crates/brk_bindgen/src/generators/javascript/tree.rs

@@ -24,7 +24,7 @@ pub fn generate_tree_typedefs(output: &mut String, catalog: &TreeNode, metadata:
         "MetricsTree",
         "",
         catalog,
-        &pattern_lookup,
+        pattern_lookup,
         metadata,
         &mut generated,
     );
@@ -125,7 +125,7 @@ pub fn generate_main_client(
         "MetricsTree",
         "",
         3,
-        &pattern_lookup,
+        pattern_lookup,
         metadata,
         &mut generated,
     );

crates/brk_bindgen/src/generators/python/client.rs

@@ -220,6 +220,7 @@ class MetricData(Generic[T]):
     """Metric data with range information. Always int-indexed."""
     version: int
     index: Index
+    type: str
     total: int
     start: int
     end: int

crates/brk_bindgen/src/generators/python/tree.rs

@@ -21,7 +21,7 @@ pub fn generate_tree_classes(output: &mut String, catalog: &TreeNode, metadata:
         "MetricsTree",
         "",
         catalog,
-        &pattern_lookup,
+        pattern_lookup,
         metadata,
         &mut generated,
     );

crates/brk_bindgen/src/generators/rust/client.rs

@@ -4,15 +4,14 @@ use std::fmt::Write;
 
 use crate::{
     ClientMetadata, GenericSyntax, IndexSetPattern, RustSyntax, StructuralPattern,
-    generate_parameterized_field, index_to_field_name, to_snake_case,
+    escape_rust_keyword, generate_parameterized_field, index_to_field_name, to_snake_case,
 };
 
 /// Generate import statements.
 pub fn generate_imports(output: &mut String) {
     writeln!(
         output,
-        r#"use std::io::Read as _;
-use std::sync::Arc;
+        r#"use std::sync::Arc;
 use std::ops::{{Bound, RangeBounds}};
 use serde::de::DeserializeOwned;
 pub use brk_cohort::*;
@@ -81,40 +80,27 @@ impl BrkClientBase {{
             .into();
         Self {{
             agent,
-            base_url: options.base_url,
+            base_url: options.base_url.trim_end_matches('/').to_string(),
         }}
     }}
 
-    fn get(&self, path: &str) -> Result<Vec<u8>> {{
-        let base = self.base_url.trim_end_matches('/');
-        let url = format!("{{}}{{}}", base, path);
-        let mut response = self.agent.get(&url)
-            .call()
-            .map_err(|e| BrkError {{ message: e.to_string() }})?;
-
-        if response.status().as_u16() >= 400 {{
-            return Err(BrkError {{
-                message: format!("HTTP {{}}", response.status().as_u16()),
-            }});
-        }}
-
-        let mut bytes = Vec::new();
-        response.body_mut().as_reader().read_to_end(&mut bytes)
-            .map_err(|e| BrkError {{ message: e.to_string() }})?;
-        Ok(bytes)
+    fn url(&self, path: &str) -> String {{
+        format!("{{}}{{}}", self.base_url, path)
     }}
 
     /// Make a GET request and deserialize JSON response.
     pub fn get_json<T: DeserializeOwned>(&self, path: &str) -> Result<T> {{
-        let bytes = self.get(path)?;
-        serde_json::from_slice(&bytes)
+        self.agent.get(&self.url(path))
+            .call()
+            .and_then(|mut r| r.body_mut().read_json())
             .map_err(|e| BrkError {{ message: e.to_string() }})
     }}
 
     /// Make a GET request and return raw text response.
     pub fn get_text(&self, path: &str) -> Result<String> {{
-        let bytes = self.get(path)?;
-        String::from_utf8(bytes)
+        self.agent.get(&self.url(path))
+            .call()
+            .and_then(|mut r| r.body_mut().read_to_string())
             .map_err(|e| BrkError {{ message: e.to_string() }})
     }}
 }}
@@ -525,7 +511,7 @@ pub fn generate_pattern_structs(
         writeln!(output, "pub struct {}{} {{", pattern.name, generic_params).unwrap();
 
         for field in &pattern.fields {
-            let field_name = to_snake_case(&field.name);
+            let field_name = escape_rust_keyword(&to_snake_case(&field.name));
             let type_annotation = metadata.field_type_annotation(
                 field,
                 pattern.is_generic,

crates/brk_bindgen/src/generators/rust/tree.rs

@@ -7,7 +7,8 @@ use brk_types::TreeNode;
 
 use crate::{
     ClientMetadata, GenericSyntax, LanguageSyntax, PatternField, RustSyntax, build_child_path,
-    generate_leaf_field, generate_tree_node_field, prepare_tree_node, to_snake_case,
+    escape_rust_keyword, generate_leaf_field, generate_tree_node_field, prepare_tree_node,
+    to_snake_case,
 };
 
 /// Generate tree structs.
@@ -21,7 +22,7 @@ pub fn generate_tree(output: &mut String, catalog: &TreeNode, metadata: &ClientM
         "MetricsTree",
         "",
         catalog,
-        &pattern_lookup,
+        pattern_lookup,
         metadata,
         &mut generated,
     );
@@ -45,7 +46,7 @@ fn generate_tree_node(
     writeln!(output, "pub struct {} {{", name).unwrap();
 
     for child in &ctx.children {
-        let field_name = to_snake_case(child.name);
+        let field_name = escape_rust_keyword(&to_snake_case(child.name));
         let type_annotation = if child.should_inline {
             child.inline_type_name.clone()
         } else {
@@ -67,7 +68,7 @@ fn generate_tree_node(
 
     let syntax = RustSyntax;
     for child in &ctx.children {
-        let field_name = to_snake_case(child.name);
+        let field_name = escape_rust_keyword(&to_snake_case(child.name));
 
         if child.is_leaf {
             if let TreeNode::Leaf(leaf) = child.node {

crates/brk_bindgen/src/types/case.rs

@@ -14,25 +14,25 @@ pub fn to_pascal_case(s: &str) -> String {
         .collect()
 }
 
-/// Convert a string to snake_case, handling Rust keywords.
+/// Convert a string to snake_case (no keyword escaping — backends handle that).
 pub fn to_snake_case(s: &str) -> String {
-    // Convert to lowercase and replace dashes with underscores
     let sanitized = s.to_lowercase().replace('-', "_");
 
-    // Prefix with _ if starts with digit
-    let sanitized = if sanitized.chars().next().is_some_and(|c| c.is_ascii_digit()) {
+    if sanitized.chars().next().is_some_and(|c| c.is_ascii_digit()) {
         format!("_{}", sanitized)
     } else {
         sanitized
-    };
+    }
+}
 
-    // Handle Rust keywords
-    match sanitized.as_str() {
+/// Escape Rust reserved keywords with `_` suffix (consistent with Python).
+pub fn escape_rust_keyword(name: &str) -> String {
+    match name {
         "type" | "const" | "static" | "match" | "if" | "else" | "loop" | "while" | "for"
         | "break" | "continue" | "return" | "fn" | "let" | "mut" | "ref" | "self" | "super"
         | "mod" | "use" | "pub" | "crate" | "extern" | "impl" | "trait" | "struct" | "enum"
-        | "where" | "async" | "await" | "dyn" | "move" => format!("r#{}", sanitized),
-        _ => sanitized,
+        | "where" | "async" | "await" | "dyn" | "move" => format!("{}_", name),
+        _ => name.to_string(),
     }
 }
 

crates/brk_bindgen/src/types/structs.rs

@@ -74,10 +74,10 @@ impl StructuralPattern {
         // Find a template with {disc} and extract the disc from the instance value.
         // Strip leading underscore since _m() handles separators.
         for (field_name, template) in templates {
-            if let Some(value) = instance_field_parts.get(field_name) {
-                if let Some(disc) = extract_disc(template, value) {
-                    return Some(disc.trim_start_matches('_').to_string());
-                }
+            if let Some(value) = instance_field_parts.get(field_name)
+                && let Some(disc) = extract_disc(template, value)
+            {
+                return Some(disc.trim_start_matches('_').to_string());
             }
         }
         // If no template matched (all empty templates), disc is empty