diff --git a/engine/Cargo.lock b/engine/Cargo.lock
index e5b499628..d25fe03d1 100644
--- a/engine/Cargo.lock
+++ b/engine/Cargo.lock
@@ -2775,6 +2775,8 @@ dependencies = [
  "pest",
  "pest_derive",
  "pretty",
+ "pretty_assertions",
+ "regex",
  "serde",
  "serde_json",
  "test-log",
@@ -3745,9 +3747,9 @@ dependencies = [
 
 [[package]]
 name = "pretty_assertions"
-version = "1.4.0"
+version = "1.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af7cee1a6c8a5b9208b3cb1061f10c0cb689087b3d8ce85fb9d2dd7a29b6ba66"
+checksum = "3ae130e2f271fbc2ac3a40fb1d07180839cdbbe443c7a27e1e3c13c5cac0116d"
 dependencies = [
  "diff",
  "yansi",
@@ -5793,9 +5795,9 @@ checksum = "66fee0b777b0f5ac1c69bb06d361268faafa61cd4682ae064a171c16c433e9e4"
 
 [[package]]
 name = "yansi"
-version = "0.5.1"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09041cd90cf85f7f8b2df60c646f853b7f535ce68f85244eb6731cf89fa498ec"
+checksum = "cfe53a6657fd280eaa890a3bc59152892ffa3e30101319d168b781ed6529b049"
 
 [[package]]
 name = "zerocopy"
diff --git a/engine/Cargo.toml b/engine/Cargo.toml
index 5d09c649d..3abd8ee0f 100644
--- a/engine/Cargo.toml
+++ b/engine/Cargo.toml
@@ -67,7 +67,7 @@ minijinja = { version = "1.0.16", default-features = false, features = [
   # loader
   #
 ] }
-pretty_assertions = "1.4.0"
+pretty_assertions = "1.4.1"
 rand = "0.8.5"
 regex = "1.10.4"
 reqwest = { version = "0.12.5", features = [
diff --git a/engine/baml-lib/schema-ast/Cargo.toml b/engine/baml-lib/schema-ast/Cargo.toml
index fe64fbffc..445e85992 100644
--- a/engine/baml-lib/schema-ast/Cargo.toml
+++ b/engine/baml-lib/schema-ast/Cargo.toml
@@ -25,8 +25,10 @@ pest_derive = "2.1.0"
 either = "1.8.1"
 test-log = "0.2.16"
 pretty = "0.12.3"
+regex.workspace = true
 
 [dev-dependencies]
+pretty_assertions.workspace = true
 unindent = "0.2.3"
 
 [features]
diff --git a/engine/baml-lib/schema-ast/src/formatter/mod.rs b/engine/baml-lib/schema-ast/src/formatter/mod.rs
index 716946d2e..b42e2fc86 100644
--- a/engine/baml-lib/schema-ast/src/formatter/mod.rs
+++ b/engine/baml-lib/schema-ast/src/formatter/mod.rs
@@ -1,3 +1,6 @@
+#[cfg(test)]
+mod tests;
+
 use std::{
     borrow::BorrowMut,
     cell::{RefCell, RefMut},
@@ -6,12 +9,13 @@ use std::{
 };
 
 use crate::parser::{BAMLParser, Rule};
-use anyhow::{anyhow, Result};
+use anyhow::{anyhow, Context, Result};
 use pest::{
     iterators::{Pair, Pairs},
     Parser,
 };
 use pretty::RcDoc;
+use regex::Regex;
 
 pub struct FormatOptions {
     pub indent_width: isize,
@@ -19,6 +23,11 @@ pub struct FormatOptions {
 }
 
 pub fn format_schema(source: &str, format_options: FormatOptions) -> Result<String> {
+    let ignore_directive_regex = Regex::new(r"(?i)baml-format\s*:\s*ignore")?;
+    if ignore_directive_regex.is_match(source) {
+        return Ok(source.to_string());
+    }
+
     let mut schema = BAMLParser::parse(Rule::schema, source)?;
     let schema_pair = schema.next().ok_or(anyhow!("Expected a schema"))?;
     if schema_pair.as_rule() != Rule::schema {
@@ -39,22 +48,28 @@ pub fn format_schema(source: &str, format_options: FormatOptions) -> Result<Stri
 
 macro_rules! next_pair {
     ($pairs:ident, $rule:expr) => {{
-        match $pairs.peek() {
-            Some(pair) => {
-                if pair.as_rule() != $rule {
-                    Err(anyhow!(
-                        "Expected a {:?}, got a {:?} ({}:{})",
-                        $rule,
-                        pair.as_rule(),
-                        file!(),
-                        line!()
-                    ))
-                } else {
-                    $pairs.next();
-                    Ok(pair)
+        loop {
+            match $pairs.peek() {
+                Some(pair) => {
+                    if pair.as_rule() == Rule::NEWLINE {
+                        $pairs.next();
+                        continue;
+                    }
+                    if pair.as_rule() != $rule {
+                        break Err(anyhow!(
+                            "Expected a {:?}, got a {:?} ({}:{})",
+                            $rule,
+                            pair.as_rule(),
+                            file!(),
+                            line!()
+                        ));
+                    } else {
+                        $pairs.next();
+                        break Ok(pair);
+                    }
                 }
+                None => break Err(anyhow!("Expected a {}", stringify!($rule))),
             }
-            None => Err(anyhow!("Expected a {}", stringify!($rule))),
         }
     }};
 
@@ -72,23 +87,77 @@ macro_rules! next_pair {
     }};
 }
 
+trait ToDoc {
+    type DocType;
+
+    fn to_doc(&self) -> Self::DocType;
+}
+
+impl<'a> ToDoc for Pair<'a, Rule> {
+    type DocType = RcDoc<'a, ()>;
+
+    /// Embed the exact contents of the corresponding source in the output.
+    ///
+    /// This is our formatting "bail-out" effectively, where if we don't know
+    /// how to format something, we just emit the original source.
+    ///
+    /// NB: according to the `RcDoc::text` docs, this is an API violation,
+    /// because we call `to_doc()` on many Pest pairs that contain newlines
+    /// within them. I suspect that this is less of a "the 'pretty' crate will
+    /// break catastrophically in unexpected ways if text symbols contain
+    /// newlines" problem, and more of a "having newlines in text symbols may
+    /// produce surprising formatting" issue. It would be pretty bizarre for
+    /// the 'pretty' crate to inspect tokens for newlines (but not unreasonable!)
+    /// given how Wadler pretty prints work, but we need to rely on this
+    /// property to be able to incrementally implement our formatter.
+    fn to_doc(&self) -> Self::DocType {
+        if self.as_rule() == Rule::empty_lines {
+            // If we're formatting empty lines, superfluous whitespace should get stripped.
+            let newline_count = self.as_str().matches('\n').count();
+            return RcDoc::concat(std::iter::repeat(RcDoc::hardline()).take(newline_count));
+        }
+        RcDoc::text(self.as_str())
+    }
+}
+
 struct Formatter {
     indent_width: isize,
     fail_on_unhandled_rule: bool,
 }
 
 impl Formatter {
+    /// The number of spaces to add before an inline trailing comment.
+    /// Here, "trailing comment" does not refer to the trailing_comment Pest rule, but rather just
+    /// a comment in this style:
+    ///    
+    ///   class Foo {
+    ///       field string   // comment
+    ///                   ^^^------------ This is what will get replaced with SPACES_BEFORE_TRAILING_COMMENT
+    ///   }
+    const SPACES_BEFORE_TRAILING_COMMENT: &'static str = "  ";
+
     fn schema_to_doc<'a>(&self, mut pairs: Pairs<'a, Rule>) -> Result<RcDoc<'a, ()>> {
         let mut doc = RcDoc::nil();
 
         for pair in &mut pairs {
             match pair.as_rule() {
                 Rule::type_expression_block => {
-                    doc = doc.append(self.type_expression_block_to_doc(pair.into_inner())?);
+                    match self.type_expression_block_to_doc(pair.clone().into_inner()) {
+                        Ok(pair_doc) => {
+                            doc = doc.append(pair_doc.group());
+                        }
+                        Err(e) => {
+                            log::debug!("Error formatting type_expression_block: {:#?}", e);
+                            doc = doc.append(pair.to_doc());
+                        }
+                    }
                 }
                 Rule::EOI => {
                     // skip
                 }
+                Rule::value_expression_block | Rule::empty_lines => {
+                    doc = doc.append(pair.to_doc());
+                }
                 _ => {
                     doc = doc.append(self.unhandled_rule_to_doc(pair)?);
                 }
@@ -129,9 +198,13 @@ impl Formatter {
         let mut content_docs = vec![];
 
         for pair in &mut pairs {
+            let error_context = format!("type_expression: {:#?}", pair);
             match pair.as_rule() {
                 Rule::type_expression => {
-                    content_docs.push(self.type_expression_to_doc(pair.into_inner())?);
+                    content_docs.push(
+                        self.type_expression_to_doc(pair.into_inner())
+                            .context(error_context)?,
+                    );
                 }
                 Rule::block_attribute => {
                     content_docs.push(pair_to_doc_text(pair));
@@ -167,8 +240,17 @@ impl Formatter {
 
         let mut doc = RcDoc::nil()
             .append(pair_to_doc_text(ident))
-            .append(RcDoc::space())
-            .append(self.field_type_chain_to_doc(field_type_chain.into_inner())?);
+            .append(RcDoc::space());
+
+        // Since our compiler currently doesn't allow newlines in type expressions, we can't
+        // put comments in the middle of a type expression, so we can rely on this hack to
+        // cascade comments all the way out of a type expression.
+        let (field_type_chain_doc, field_type_chain_comments) =
+            self.field_type_chain_to_doc(field_type_chain.into_inner())?;
+        doc = doc.append(field_type_chain_doc);
+        if let Some(field_type_chain_comments) = field_type_chain_comments {
+            doc = doc.append(field_type_chain_comments);
+        }
 
         for pair in pairs {
             match pair.as_rule() {
@@ -190,13 +272,22 @@ impl Formatter {
         Ok(doc)
     }
 
-    fn field_type_chain_to_doc<'a>(&self, pairs: Pairs<'a, Rule>) -> Result<RcDoc<'a, ()>> {
+    fn field_type_chain_to_doc<'a>(
+        &self,
+        pairs: Pairs<'a, Rule>,
+    ) -> Result<(RcDoc<'a, ()>, Option<RcDoc<'a, ()>>)> {
         let mut docs = vec![];
+        let mut comments = vec![];
 
         for pair in pairs {
             match pair.as_rule() {
                 Rule::field_type_with_attr => {
-                    docs.push(self.field_type_with_attr_to_doc(pair.into_inner())?);
+                    let (field_type_doc, field_type_comments) =
+                        self.field_type_with_attr_to_doc(pair.into_inner())?;
+                    docs.push(field_type_doc);
+                    if let Some(field_type_comments) = field_type_comments {
+                        comments.push(field_type_comments);
+                    }
                 }
                 Rule::field_operator => {
                     docs.push(RcDoc::text("|"));
@@ -207,31 +298,69 @@ impl Formatter {
             }
         }
 
-        Ok(RcDoc::intersperse(docs, RcDoc::space())
-            .nest(self.indent_width)
-            .group())
+        Ok((
+            RcDoc::intersperse(docs, RcDoc::space())
+                .nest(self.indent_width)
+                .group(),
+            if comments.is_empty() {
+                None
+            } else {
+                Some(RcDoc::concat(comments).group())
+            },
+        ))
     }
 
-    fn field_type_with_attr_to_doc<'a>(&self, mut pairs: Pairs<'a, Rule>) -> Result<RcDoc<'a, ()>> {
+    fn field_type_with_attr_to_doc<'a>(
+        &self,
+        mut pairs: Pairs<'a, Rule>,
+    ) -> Result<(RcDoc<'a, ()>, Option<RcDoc<'a, ()>>)> {
         let mut docs = vec![];
+        // This is a hack: we cascade comments all the way out of a type
+        // expression, relying on the (current) limitation that our users can't
+        // have newlines in a type expression today.
+        //
+        // The correct way to handle this is to either (1) make our lexer understand that
+        // trailing comments are not actually a part of a type expression or (2) teach the
+        // formatter how to push comments to the correct context.
+        //
+        // Arguably we're currently using (2), and just implementing it in a naive way,
+        // because we just push all comments to the context of the type expression, rather
+        // than, say, an operand of the type expression.
+        let mut comments = vec![];
 
         for pair in &mut pairs {
             match pair.as_rule() {
                 Rule::field_type => {
                     docs.push(self.field_type_to_doc(pair.into_inner())?);
                 }
-                Rule::field_attribute | Rule::trailing_comment => {
+                Rule::field_attribute => {
                     docs.push(pair_to_doc_text(pair));
                 }
+                Rule::trailing_comment => {
+                    if comments.is_empty() {
+                        comments.push(RcDoc::text(Self::SPACES_BEFORE_TRAILING_COMMENT));
+                    }
+                    comments.push(pair_to_doc_text(pair));
+                }
+                Rule::NEWLINE => {
+                    comments.push(RcDoc::hardline());
+                }
                 _ => {
                     docs.push(self.unhandled_rule_to_doc(pair)?);
                 }
             }
         }
 
-        Ok(RcDoc::intersperse(docs, RcDoc::space())
-            .nest(self.indent_width)
-            .group())
+        Ok((
+            RcDoc::intersperse(docs, RcDoc::space())
+                .nest(self.indent_width)
+                .group(),
+            if comments.is_empty() {
+                None
+            } else {
+                Some(RcDoc::concat(comments).group())
+            },
+        ))
     }
 
     fn field_type_to_doc<'a>(&self, pairs: Pairs<'a, Rule>) -> Result<RcDoc<'a, ()>> {
@@ -283,75 +412,3 @@ impl Formatter {
 fn pair_to_doc_text<'a>(pair: Pair<'a, Rule>) -> RcDoc<'a, ()> {
     RcDoc::text(pair.as_str().trim())
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use unindent::Unindent as _;
-
-    #[track_caller]
-    fn assert_format_eq(schema: &str, expected: &str) -> Result<()> {
-        let formatted = format_schema(
-            &schema.unindent().trim_end(),
-            FormatOptions {
-                indent_width: 4,
-                fail_on_unhandled_rule: true,
-            },
-        )?;
-        assert_eq!(expected.unindent().trim_end(), formatted);
-        Ok(())
-    }
-
-    #[test]
-    fn test_format_schema() -> anyhow::Result<()> {
-        assert_format_eq(
-            r#"
-                class Foo {
-                }
-            "#,
-            r#"
-                class Foo {}
-            "#,
-        )?;
-
-        assert_format_eq(
-            r#"
-                class Foo { field1 string }
-            "#,
-            r#"
-                class Foo {
-                    field1 string
-                }
-            "#,
-        )?;
-
-        assert_format_eq(
-            r#"
-                class Foo {
-
-                    field1 string
-                }
-            "#,
-            r#"
-                class Foo {
-                    field1 string
-                }
-            "#,
-        )?;
-
-        assert_format_eq(
-            r#"
-                class Foo {
-                    field1   string|int
-                }
-            "#,
-            r#"
-                class Foo {
-                    field1 string | int
-                }
-            "#,
-        )?;
-
-        Ok(())
-    }
-}
diff --git a/engine/baml-lib/schema-ast/src/formatter/tests.rs b/engine/baml-lib/schema-ast/src/formatter/tests.rs
new file mode 100644
index 000000000..0312d1c69
--- /dev/null
+++ b/engine/baml-lib/schema-ast/src/formatter/tests.rs
@@ -0,0 +1,222 @@
+use super::*;
+use pretty_assertions::assert_eq;
+use unindent::Unindent as _;
+
+#[track_caller]
+fn assert_format_eq(schema: &str, expected: &str) -> Result<()> {
+    let formatted = format_schema(
+        &schema,
+        FormatOptions {
+            indent_width: 2,
+            fail_on_unhandled_rule: true,
+        },
+    )?;
+    assert_eq!(formatted, expected);
+
+    Ok(())
+}
+
+#[test]
+fn class_containing_whitespace() -> anyhow::Result<()> {
+    let actual = r#"
+          class Foo {
+          }
+
+          class Foo { field1 string }
+
+          class Foo {
+
+            field1 string
+          }
+
+          class Foo {
+              field1   string|int
+          }
+        "#
+    .unindent()
+    .trim_end()
+    .to_string();
+
+    let expected = r#"
+          class Foo {}
+
+          class Foo {
+            field1 string
+          }
+
+          class Foo {
+            field1 string
+          }
+
+          class Foo {
+            field1 string | int
+          }
+        "#
+    .unindent()
+    .trim_end()
+    .to_string();
+
+    assert_format_eq(&actual, &expected)?;
+    assert_format_eq(&expected, &expected)
+}
+
+#[test]
+fn class_with_assorted_comment_styles() -> anyhow::Result<()> {
+    let actual = r#"
+    class Foo0 {
+      lorem string    // trailing comments should be separated by two spaces
+      ipsum string
+    }
+
+    class Foo1 {
+       lorem string
+      ipsum string
+        // dolor string
+    }
+
+    class Foo2 {
+
+        // "lorem" is a latin word
+        lorem string
+
+        // "ipsum" is a latin word
+        ipsum string
+
+    }
+
+    class Foo3 {
+      lorem string
+      ipsum string
+                    // Lorem ipsum dolor sit amet
+      // Consectetur adipiscing elit
+            // Sed do eiusmod tempor incididunt
+      // Ut labore et dolore magna aliqua
+        // Ut enim ad minim veniam
+    }
+        "#
+    .unindent()
+    .trim_end()
+    .to_string();
+
+    let expected = r#"
+    class Foo0 {
+      lorem string  // trailing comments should be separated by two spaces
+      ipsum string
+    }
+
+    class Foo1 {
+      lorem string
+      ipsum string
+      // dolor string
+    }
+
+    class Foo2 {
+      // "lorem" is a latin word
+      lorem string
+      // "ipsum" is a latin word
+      ipsum string
+    }
+
+    class Foo3 {
+      lorem string
+      ipsum string
+      // Lorem ipsum dolor sit amet
+      // Consectetur adipiscing elit
+      // Sed do eiusmod tempor incididunt
+      // Ut labore et dolore magna aliqua
+      // Ut enim ad minim veniam
+    }
+        "#
+    .unindent()
+    .trim_end()
+    .to_string();
+
+    assert_format_eq(&actual, &expected)?;
+    assert_format_eq(&expected, &expected)
+}
+
+#[test]
+fn baml_format_escape_directive_works() -> anyhow::Result<()> {
+    let expected = r#"
+    // baml-format: ignore
+    class BadlyFormatted0 {
+        lorem string    // trailing comments should be separated by two spaces
+  ipsum string
+    }
+
+    class BadlyFormatted1 {
+      lorem string
+      ipsum string
+                    // Lorem ipsum dolor sit amet
+      // Consectetur adipiscing elit
+            // Sed do eiusmod tempor incididunt
+      // Ut labore et dolore magna aliqua
+        // Ut enim ad minim veniam
+    }
+        "#
+    .unindent()
+    .trim_end()
+    .to_string();
+
+    assert_format_eq(&expected, &expected)
+}
+
+/// We have not yet implemented formatting for functions or enums,
+/// so those should be preserved as-is.
+#[test]
+fn class_formatting_is_resilient_to_unhandled_rules() -> anyhow::Result<()> {
+    let actual = r##"
+    function      LlmConvert(input: string) -> string {
+    client    "openai/gpt-4o"
+            prompt #"
+              Extract this info from the email in JSON format:
+              {{ ctx.output_format }}
+            "#
+    }
+
+    enum Latin {
+                    Lorem
+    Ipsum
+    }
+
+    class Foo {
+          lorem     "alpha" | "bravo"
+    ipsum "charlie"|"delta"
+    }
+    "##
+    .unindent()
+    .trim_end()
+    .to_string();
+    let expected = r##"
+    function      LlmConvert(input: string) -> string {
+    client    "openai/gpt-4o"
+            prompt #"
+              Extract this info from the email in JSON format:
+              {{ ctx.output_format }}
+            "#
+    }
+
+    enum Latin {
+                    Lorem
+    Ipsum
+    }
+
+    class Foo {
+      lorem "alpha" | "bravo"
+      ipsum "charlie" | "delta"
+    }
+        "##
+    .unindent()
+    .trim_end()
+    .to_string();
+
+    assert_format_eq(&actual, &expected)
+}
+
+#[test]
+fn newlines_with_only_spaces_are_stripped() -> anyhow::Result<()> {
+    let actual = "class Foo {}\n     \n     \nclass Bar {}\n";
+    let expected = "class Foo {}\n\n\nclass Bar {}\n";
+
+    assert_format_eq(&actual, &expected)
+}
diff --git a/engine/baml-lib/schema-ast/src/parser/datamodel.pest b/engine/baml-lib/schema-ast/src/parser/datamodel.pest
index 7fe6ec60e..623b746ad 100644
--- a/engine/baml-lib/schema-ast/src/parser/datamodel.pest
+++ b/engine/baml-lib/schema-ast/src/parser/datamodel.pest
@@ -162,7 +162,7 @@ doc_content      = @{ (!NEWLINE ~ ANY)* }
 // Shared Building Blocks and Comments
 // ######################################
 WHITESPACE  = _{ " " | "\t" }
-NEWLINE     = _{ "\n" | "\r\n" | "\r" }
+NEWLINE     = { "\n" | "\r\n" | "\r" }
 empty_lines = @{ (WHITESPACE* ~ NEWLINE)+ }
 
 // ######################################
diff --git a/engine/baml-lib/schema-ast/src/parser/helpers.rs b/engine/baml-lib/schema-ast/src/parser/helpers.rs
index 91c8bb8d5..2251dcb52 100644
--- a/engine/baml-lib/schema-ast/src/parser/helpers.rs
+++ b/engine/baml-lib/schema-ast/src/parser/helpers.rs
@@ -9,7 +9,8 @@ pub fn parsing_catch_all(token: Pair<'_>, kind: &str) {
         | Rule::trailing_comment
         | Rule::comment_block
         | Rule::block_comment
-        | Rule::SPACER_TEXT => {}
+        | Rule::SPACER_TEXT
+        | Rule::NEWLINE => {}
         x => unreachable!(
             "Encountered impossible {} during parsing: {:?} {:?}",
             kind,
diff --git a/engine/cli/src/format.rs b/engine/cli/src/format.rs
index 974604c24..8e9c99878 100644
--- a/engine/cli/src/format.rs
+++ b/engine/cli/src/format.rs
@@ -1,13 +1,14 @@
 use std::{fs, path::PathBuf};
 
 use anyhow::Result;
-use baml_runtime::{baml_src_files, BamlRuntime};
+use baml_runtime::baml_src_files;
 use clap::Args;
 use internal_baml_core::internal_baml_schema_ast::{format_schema, FormatOptions};
 
 #[derive(Args, Debug)]
 pub struct FormatArgs {
-    #[arg(long, help = "path/to/baml_src", default_value = "./baml_src")]
+    // default_value for --from is _usually_ the baml_src directory, but not for baml-cli fmt!
+    #[arg(long, help = "path/to/baml_src", default_value = ".")]
     pub from: PathBuf,
 
     #[arg(
@@ -30,8 +31,8 @@ impl FormatArgs {
             // Usually this is done in commands.rs, but fmt is a special case
             // because it doesn't need to actually load the BAML runtime to parse
             // BAML files.
-            let from = BamlRuntime::parse_baml_src_path(&self.from)?;
-            baml_src_files(&from)?
+            // let from = BamlRuntime::parse_baml_src_path(&self.from)?;
+            baml_src_files(&self.from)?
         } else {
             self.paths.clone()
         };
@@ -53,7 +54,7 @@ impl FormatArgs {
                     }
                 }
                 Err(e) => {
-                    log::error!("Failed to format {}: {}", path.display(), e);
+                    log::error!("Failed to format {}: {:?}", path.display(), e);
                 }
             }
         }
diff --git a/fern/03-reference/baml-cli/fmt.mdx b/fern/03-reference/baml-cli/fmt.mdx
new file mode 100644
index 000000000..bc3509268
--- /dev/null
+++ b/fern/03-reference/baml-cli/fmt.mdx
@@ -0,0 +1,25 @@
+The `fmt` command will format your BAML files.
+
+<Warning>
+  **Warning: Beta Feature**
+  
+  This feature is still in-progress, and does not yet support all BAML syntax.
+</Warning>
+
+## Usage
+
+```
+baml-cli fmt [OPTIONS] [file.baml] [file2.baml] [file3.baml] ...
+```
+
+## Details
+
+To disable the formatter in a file, you can add
+
+```baml
+// baml-format: ignore
+```
+
+anywhere in the file.
+
+Formatting is done in-place and non-configurable.
\ No newline at end of file
diff --git a/integ-tests/baml_src/formatter/test-comments.baml b/integ-tests/baml_src/formatter/test-comments.baml
new file mode 100644
index 000000000..550dfb8fc
--- /dev/null
+++ b/integ-tests/baml_src/formatter/test-comments.baml
@@ -0,0 +1,27 @@
+class FormatterTest0 {
+  lorem string  // trailing comments should be preserved
+  ipsum string
+}
+
+class FormatterTest1 {
+  lorem string
+  ipsum string
+  // dolor string
+}
+
+class FormatterTest2 {
+  // "lorem" is a latin word
+  lorem string
+  // "ipsum" is a latin word
+  ipsum string
+}
+
+class FormatterTest3 {
+  lorem string
+  ipsum string
+  // Lorem ipsum dolor sit amet
+  // Consectetur adipiscing elit
+  // Sed do eiusmod tempor incididunt
+  // Ut labore et dolore magna aliqua
+  // Ut enim ad minim veniam
+}
\ No newline at end of file
diff --git a/integ-tests/python/baml_client/inlinedbaml.py b/integ-tests/python/baml_client/inlinedbaml.py
index b1b088470..50c14023d 100644
--- a/integ-tests/python/baml_client/inlinedbaml.py
+++ b/integ-tests/python/baml_client/inlinedbaml.py
@@ -25,6 +25,7 @@
     "fiddle-examples/extract-receipt-info.baml": "class ReceiptItem {\n  name string\n  description string?\n  quantity int\n  price float\n}\n\nclass ReceiptInfo {\n    items ReceiptItem[]\n    total_cost float?\n    venue \"barisa\" | \"ox_burger\"\n}\n\nfunction ExtractReceiptInfo(email: string, reason: \"curiosity\" | \"personal_finance\") -> ReceiptInfo {\n  client GPT4o\n  prompt #\"\n    Given the receipt below:\n\n    ```\n    {{email}}\n    ```\n\n    {{ ctx.output_format }}\n  \"#\n}\n\n",
     "fiddle-examples/images/image.baml": "function DescribeImage(img: image) -> string {\n  client GPT4o\n  prompt #\"\n    {{ _.role(\"user\") }}\n\n\n    Describe the image below in 20 words:\n    {{ img }}\n  \"#\n\n}\n\nclass FakeImage {\n  url string\n}\n\nclass ClassWithImage {\n  myImage image\n  param2 string\n  fake_image FakeImage\n}\n\n// chat role user present\nfunction DescribeImage2(classWithImage: ClassWithImage, img2: image) -> string { \n  client GPT4Turbo\n  prompt #\"\n    {{ _.role(\"user\") }}\n    You should return 2 answers that answer the following commands.\n\n    1. Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    2. Also tell me what's happening here in one sentence:\n    {{ img2 }}\n  \"#\n}\n\n// no chat role\nfunction DescribeImage3(classWithImage: ClassWithImage, img2: image) -> string {\n  client GPT4Turbo\n  prompt #\"\n    Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    Tell me also what's happening here in one sentence and relate it to the word {{ classWithImage.param2 }}:\n    {{ img2 }}\n  \"#\n}\n\n\n// system prompt and chat prompt\nfunction DescribeImage4(classWithImage: ClassWithImage, img2: image) -> string {\n  client GPT4Turbo\n  prompt #\"\n    {{ _.role(\"system\")}}\n\n    Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    Tell me also what's happening here in one sentence and relate it to the word {{ classWithImage.param2 }}:\n    {{ img2 }}\n  \"#\n}\n\ntest TestName {\n  functions [DescribeImage]\n  args {\n    img { url \"https://imgs.xkcd.com/comics/standards.png\"}\n  }\n}\n",
     "fiddle-examples/symbol-tuning.baml": "enum Category3 {\n    Refund @alias(\"k1\")\n    @description(\"Customer wants to refund a product\")\n\n    CancelOrder @alias(\"k2\")\n    @description(\"Customer wants to cancel an order\")\n\n    TechnicalSupport @alias(\"k3\")\n    @description(\"Customer needs help with a technical issue unrelated to account creation or login\")\n\n    AccountIssue @alias(\"k4\")\n    @description(\"Specifically relates to account-login or account-creation\")\n\n    Question @alias(\"k5\")\n    @description(\"Customer has a question\")\n}\n\nfunction ClassifyMessage3(input: string) -> Category {\n  client GPT4\n\n  prompt #\"\n    Classify the following INPUT into ONE\n    of the following categories:\n\n    INPUT: {{ input }}\n\n    {{ ctx.output_format }}\n\n    Response:\n  \"#\n}",
+    "formatter/test-comments.baml": "class FormatterTest0 {\n  lorem string  // trailing comments should be preserved\n  ipsum string\n}\n\nclass FormatterTest1 {\n  lorem string\n  ipsum string\n  // dolor string\n}\n\nclass FormatterTest2 {\n  // \"lorem\" is a latin word\n  lorem string\n  // \"ipsum\" is a latin word\n  ipsum string\n}\n\nclass FormatterTest3 {\n  lorem string\n  ipsum string\n  // Lorem ipsum dolor sit amet\n  // Consectetur adipiscing elit\n  // Sed do eiusmod tempor incididunt\n  // Ut labore et dolore magna aliqua\n  // Ut enim ad minim veniam\n}",
     "generators.baml": "generator lang_python {\n  output_type python/pydantic\n  output_dir \"../python\"\n  version \"0.71.1\"\n}\n\ngenerator lang_typescript {\n  output_type typescript\n  output_dir \"../typescript\"\n  version \"0.71.1\"\n}\n\ngenerator lang_ruby {\n  output_type ruby/sorbet\n  output_dir \"../ruby\"\n  version \"0.71.1\"\n}\n\n// generator openapi {\n//   output_type rest/openapi\n//   output_dir \"../openapi\"\n//   version \"0.71.1\"\n//   on_generate \"rm .gitignore\"\n// }\n",
     "test-files/aliases/aliased-inputs.baml": "\nclass InputClass {\n  key string @alias(\"color\")\n  key2 string\n}\n\n\nclass InputClassNested {\n  key string\n  nested InputClass @alias(\"interesting-key\")\n}\n \n\nfunction AliasedInputClass(input: InputClass) -> string {\n  client GPT35\n  prompt #\"\n\n    {{input}}\n\n    This is a test. What's the name of the first json key above? Remember, tell me the key, not value.\n  \"#\n}\n \nfunction AliasedInputClass2(input: InputClass) -> string {\n  client GPT35\n  prompt #\"\n\n    {# making sure we can still access the original key #}\n    {%if input.key == \"tiger\"%}\n      Repeat this value back to me, and nothing else: {{input.key}}\n    {%endif%}\n  \"#\n}\n \n function AliasedInputClassNested(input: InputClassNested) -> string {\n  client GPT35\n  prompt #\"\n    {{ _.role(\"user\")}}\n\n    {{input}}\n\n    This is a test. What's the name of the second json key above? Remember, tell me the key, not value.\n  \"#\n }\n\n\nenum AliasedEnum {\n  KEY_ONE @alias(\"tiger\")\n  KEY_TWO\n}\n\nfunction AliasedInputEnum(input: AliasedEnum) -> string {\n  client GPT4o\n  prompt #\"\n    {{ _.role(\"user\")}}\n\n\n    Write out this word only in your response, in lowercase:\n    ---\n    {{input}}\n    ---\n    Answer:\n  \"#\n}\n\n\nfunction AliasedInputList(input: AliasedEnum[]) -> string {\n  client GPT35\n  prompt #\"\n    {{ _.role(\"user\")}}\n    Given this array:\n    ---\n    {{input}}\n    ---\n\n    Return the first element in the array:\n  \"#\n}\n\n",
     "test-files/aliases/classes.baml": "class TestClassAlias {\n  key string @alias(\"key-dash\") @description(#\"\n    This is a description for key\n    af asdf\n  \"#)\n  key2 string @alias(\"key21\")\n  key3 string @alias(\"key with space\")\n  key4 string //unaliased\n  key5 string @alias(\"key.with.punctuation/123\")\n}\n\nfunction FnTestClassAlias(input: string) -> TestClassAlias {\n  client GPT35\n  prompt #\"\n    {{ctx.output_format}}\n  \"#\n}\n\ntest FnTestClassAlias {\n  functions [FnTestClassAlias]\n  args {\n    input \"example input\"\n  }\n}\n",
diff --git a/integ-tests/python/baml_client/partial_types.py b/integ-tests/python/baml_client/partial_types.py
index 9ce8a02c0..a80af5e9c 100644
--- a/integ-tests/python/baml_client/partial_types.py
+++ b/integ-tests/python/baml_client/partial_types.py
@@ -149,6 +149,22 @@ class FooAny(BaseModel):
 class Forest(BaseModel):
     trees: List["Tree"]
 
+class FormatterTest0(BaseModel):
+    lorem: Optional[str] = None
+    ipsum: Optional[str] = None
+
+class FormatterTest1(BaseModel):
+    lorem: Optional[str] = None
+    ipsum: Optional[str] = None
+
+class FormatterTest2(BaseModel):
+    lorem: Optional[str] = None
+    ipsum: Optional[str] = None
+
+class FormatterTest3(BaseModel):
+    lorem: Optional[str] = None
+    ipsum: Optional[str] = None
+
 class GroceryReceipt(BaseModel):
     receiptId: Optional[str] = None
     storeName: Optional[str] = None
diff --git a/integ-tests/python/baml_client/type_builder.py b/integ-tests/python/baml_client/type_builder.py
index 741999408..3b30598a0 100644
--- a/integ-tests/python/baml_client/type_builder.py
+++ b/integ-tests/python/baml_client/type_builder.py
@@ -20,7 +20,7 @@
 class TypeBuilder(_TypeBuilder):
     def __init__(self):
         super().__init__(classes=set(
-          ["BigNumbers","BinaryNode","Blah","BlockConstraint","BlockConstraintForParam","BookOrder","ClassOptionalOutput","ClassOptionalOutput2","ClassToRecAlias","ClassWithImage","CompoundBigNumbers","ContactInfo","CustomTaskResult","DummyOutput","DynInputOutput","DynamicClassOne","DynamicClassTwo","DynamicOutput","Earthling","Education","Email","EmailAddress","Event","FakeImage","FlightConfirmation","FooAny","Forest","GroceryReceipt","InnerClass","InnerClass2","InputClass","InputClassNested","LinkedList","LinkedListAliasNode","LiteralClassHello","LiteralClassOne","LiteralClassTwo","MalformedConstraints","MalformedConstraints2","Martian","MergeAttrs","NamedArgsSingleClass","Nested","Nested2","NestedBlockConstraint","NestedBlockConstraintForParam","Node","NodeWithAliasIndirection","OptionalListAndMap","OptionalTest_Prop1","OptionalTest_ReturnType","OrderInfo","OriginalA","OriginalB","Person","PhoneNumber","Quantity","RaysData","ReceiptInfo","ReceiptItem","Recipe","Resume","Schema","SearchParams","SomeClassNestedDynamic","StringToClassEntry","TestClassAlias","TestClassNested","TestClassWithEnum","TestOutputClass","Tree","TwoStoriesOneTitle","UnionTest_ReturnType","WithReasoning",]
+          ["BigNumbers","BinaryNode","Blah","BlockConstraint","BlockConstraintForParam","BookOrder","ClassOptionalOutput","ClassOptionalOutput2","ClassToRecAlias","ClassWithImage","CompoundBigNumbers","ContactInfo","CustomTaskResult","DummyOutput","DynInputOutput","DynamicClassOne","DynamicClassTwo","DynamicOutput","Earthling","Education","Email","EmailAddress","Event","FakeImage","FlightConfirmation","FooAny","Forest","FormatterTest0","FormatterTest1","FormatterTest2","FormatterTest3","GroceryReceipt","InnerClass","InnerClass2","InputClass","InputClassNested","LinkedList","LinkedListAliasNode","LiteralClassHello","LiteralClassOne","LiteralClassTwo","MalformedConstraints","MalformedConstraints2","Martian","MergeAttrs","NamedArgsSingleClass","Nested","Nested2","NestedBlockConstraint","NestedBlockConstraintForParam","Node","NodeWithAliasIndirection","OptionalListAndMap","OptionalTest_Prop1","OptionalTest_ReturnType","OrderInfo","OriginalA","OriginalB","Person","PhoneNumber","Quantity","RaysData","ReceiptInfo","ReceiptItem","Recipe","Resume","Schema","SearchParams","SomeClassNestedDynamic","StringToClassEntry","TestClassAlias","TestClassNested","TestClassWithEnum","TestOutputClass","Tree","TwoStoriesOneTitle","UnionTest_ReturnType","WithReasoning",]
         ), enums=set(
           ["AliasedEnum","Category","Category2","Category3","Color","DataType","DynEnumOne","DynEnumTwo","EnumInClass","EnumOutput","Hobby","MapKey","NamedArgsSingleEnum","NamedArgsSingleEnumList","OptionalTest_CategoryType","OrderStatus","Tag","TestEnum",]
         ))
diff --git a/integ-tests/python/baml_client/types.py b/integ-tests/python/baml_client/types.py
index 6a68f8efd..de43ade95 100644
--- a/integ-tests/python/baml_client/types.py
+++ b/integ-tests/python/baml_client/types.py
@@ -274,6 +274,22 @@ class FooAny(BaseModel):
 class Forest(BaseModel):
     trees: List["Tree"]
 
+class FormatterTest0(BaseModel):
+    lorem: str
+    ipsum: str
+
+class FormatterTest1(BaseModel):
+    lorem: str
+    ipsum: str
+
+class FormatterTest2(BaseModel):
+    lorem: str
+    ipsum: str
+
+class FormatterTest3(BaseModel):
+    lorem: str
+    ipsum: str
+
 class GroceryReceipt(BaseModel):
     receiptId: str
     storeName: str
diff --git a/integ-tests/ruby/baml_client/inlined.rb b/integ-tests/ruby/baml_client/inlined.rb
index aafa0086c..97b329398 100644
--- a/integ-tests/ruby/baml_client/inlined.rb
+++ b/integ-tests/ruby/baml_client/inlined.rb
@@ -25,6 +25,7 @@ module Inlined
         "fiddle-examples/extract-receipt-info.baml" => "class ReceiptItem {\n  name string\n  description string?\n  quantity int\n  price float\n}\n\nclass ReceiptInfo {\n    items ReceiptItem[]\n    total_cost float?\n    venue \"barisa\" | \"ox_burger\"\n}\n\nfunction ExtractReceiptInfo(email: string, reason: \"curiosity\" | \"personal_finance\") -> ReceiptInfo {\n  client GPT4o\n  prompt #\"\n    Given the receipt below:\n\n    ```\n    {{email}}\n    ```\n\n    {{ ctx.output_format }}\n  \"#\n}\n\n",
         "fiddle-examples/images/image.baml" => "function DescribeImage(img: image) -> string {\n  client GPT4o\n  prompt #\"\n    {{ _.role(\"user\") }}\n\n\n    Describe the image below in 20 words:\n    {{ img }}\n  \"#\n\n}\n\nclass FakeImage {\n  url string\n}\n\nclass ClassWithImage {\n  myImage image\n  param2 string\n  fake_image FakeImage\n}\n\n// chat role user present\nfunction DescribeImage2(classWithImage: ClassWithImage, img2: image) -> string { \n  client GPT4Turbo\n  prompt #\"\n    {{ _.role(\"user\") }}\n    You should return 2 answers that answer the following commands.\n\n    1. Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    2. Also tell me what's happening here in one sentence:\n    {{ img2 }}\n  \"#\n}\n\n// no chat role\nfunction DescribeImage3(classWithImage: ClassWithImage, img2: image) -> string {\n  client GPT4Turbo\n  prompt #\"\n    Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    Tell me also what's happening here in one sentence and relate it to the word {{ classWithImage.param2 }}:\n    {{ img2 }}\n  \"#\n}\n\n\n// system prompt and chat prompt\nfunction DescribeImage4(classWithImage: ClassWithImage, img2: image) -> string {\n  client GPT4Turbo\n  prompt #\"\n    {{ _.role(\"system\")}}\n\n    Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    Tell me also what's happening here in one sentence and relate it to the word {{ classWithImage.param2 }}:\n    {{ img2 }}\n  \"#\n}\n\ntest TestName {\n  functions [DescribeImage]\n  args {\n    img { url \"https://imgs.xkcd.com/comics/standards.png\"}\n  }\n}\n",
         "fiddle-examples/symbol-tuning.baml" => "enum Category3 {\n    Refund @alias(\"k1\")\n    @description(\"Customer wants to refund a product\")\n\n    CancelOrder @alias(\"k2\")\n    @description(\"Customer wants to cancel an order\")\n\n    TechnicalSupport @alias(\"k3\")\n    @description(\"Customer needs help with a technical issue unrelated to account creation or login\")\n\n    AccountIssue @alias(\"k4\")\n    @description(\"Specifically relates to account-login or account-creation\")\n\n    Question @alias(\"k5\")\n    @description(\"Customer has a question\")\n}\n\nfunction ClassifyMessage3(input: string) -> Category {\n  client GPT4\n\n  prompt #\"\n    Classify the following INPUT into ONE\n    of the following categories:\n\n    INPUT: {{ input }}\n\n    {{ ctx.output_format }}\n\n    Response:\n  \"#\n}",
+        "formatter/test-comments.baml" => "class FormatterTest0 {\n  lorem string  // trailing comments should be preserved\n  ipsum string\n}\n\nclass FormatterTest1 {\n  lorem string\n  ipsum string\n  // dolor string\n}\n\nclass FormatterTest2 {\n  // \"lorem\" is a latin word\n  lorem string\n  // \"ipsum\" is a latin word\n  ipsum string\n}\n\nclass FormatterTest3 {\n  lorem string\n  ipsum string\n  // Lorem ipsum dolor sit amet\n  // Consectetur adipiscing elit\n  // Sed do eiusmod tempor incididunt\n  // Ut labore et dolore magna aliqua\n  // Ut enim ad minim veniam\n}",
         "generators.baml" => "generator lang_python {\n  output_type python/pydantic\n  output_dir \"../python\"\n  version \"0.71.1\"\n}\n\ngenerator lang_typescript {\n  output_type typescript\n  output_dir \"../typescript\"\n  version \"0.71.1\"\n}\n\ngenerator lang_ruby {\n  output_type ruby/sorbet\n  output_dir \"../ruby\"\n  version \"0.71.1\"\n}\n\n// generator openapi {\n//   output_type rest/openapi\n//   output_dir \"../openapi\"\n//   version \"0.71.1\"\n//   on_generate \"rm .gitignore\"\n// }\n",
         "test-files/aliases/aliased-inputs.baml" => "\nclass InputClass {\n  key string @alias(\"color\")\n  key2 string\n}\n\n\nclass InputClassNested {\n  key string\n  nested InputClass @alias(\"interesting-key\")\n}\n \n\nfunction AliasedInputClass(input: InputClass) -> string {\n  client GPT35\n  prompt #\"\n\n    {{input}}\n\n    This is a test. What's the name of the first json key above? Remember, tell me the key, not value.\n  \"#\n}\n \nfunction AliasedInputClass2(input: InputClass) -> string {\n  client GPT35\n  prompt #\"\n\n    {# making sure we can still access the original key #}\n    {%if input.key == \"tiger\"%}\n      Repeat this value back to me, and nothing else: {{input.key}}\n    {%endif%}\n  \"#\n}\n \n function AliasedInputClassNested(input: InputClassNested) -> string {\n  client GPT35\n  prompt #\"\n    {{ _.role(\"user\")}}\n\n    {{input}}\n\n    This is a test. What's the name of the second json key above? Remember, tell me the key, not value.\n  \"#\n }\n\n\nenum AliasedEnum {\n  KEY_ONE @alias(\"tiger\")\n  KEY_TWO\n}\n\nfunction AliasedInputEnum(input: AliasedEnum) -> string {\n  client GPT4o\n  prompt #\"\n    {{ _.role(\"user\")}}\n\n\n    Write out this word only in your response, in lowercase:\n    ---\n    {{input}}\n    ---\n    Answer:\n  \"#\n}\n\n\nfunction AliasedInputList(input: AliasedEnum[]) -> string {\n  client GPT35\n  prompt #\"\n    {{ _.role(\"user\")}}\n    Given this array:\n    ---\n    {{input}}\n    ---\n\n    Return the first element in the array:\n  \"#\n}\n\n",
         "test-files/aliases/classes.baml" => "class TestClassAlias {\n  key string @alias(\"key-dash\") @description(#\"\n    This is a description for key\n    af asdf\n  \"#)\n  key2 string @alias(\"key21\")\n  key3 string @alias(\"key with space\")\n  key4 string //unaliased\n  key5 string @alias(\"key.with.punctuation/123\")\n}\n\nfunction FnTestClassAlias(input: string) -> TestClassAlias {\n  client GPT35\n  prompt #\"\n    {{ctx.output_format}}\n  \"#\n}\n\ntest FnTestClassAlias {\n  functions [FnTestClassAlias]\n  args {\n    input \"example input\"\n  }\n}\n",
diff --git a/integ-tests/ruby/baml_client/partial-types.rb b/integ-tests/ruby/baml_client/partial-types.rb
index 438593d7f..ecbda8c40 100644
--- a/integ-tests/ruby/baml_client/partial-types.rb
+++ b/integ-tests/ruby/baml_client/partial-types.rb
@@ -47,6 +47,10 @@ class FakeImage < T::Struct; end
     class FlightConfirmation < T::Struct; end
     class FooAny < T::Struct; end
     class Forest < T::Struct; end
+    class FormatterTest0 < T::Struct; end
+    class FormatterTest1 < T::Struct; end
+    class FormatterTest2 < T::Struct; end
+    class FormatterTest3 < T::Struct; end
     class GroceryReceipt < T::Struct; end
     class InnerClass < T::Struct; end
     class InnerClass2 < T::Struct; end
@@ -486,6 +490,62 @@ def initialize(props)
         @props = props
       end
     end
+    class FormatterTest0 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, T.nilable(String)
+      const :ipsum, T.nilable(String)
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
+    class FormatterTest1 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, T.nilable(String)
+      const :ipsum, T.nilable(String)
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
+    class FormatterTest2 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, T.nilable(String)
+      const :ipsum, T.nilable(String)
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
+    class FormatterTest3 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, T.nilable(String)
+      const :ipsum, T.nilable(String)
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
     class GroceryReceipt < T::Struct
       include Baml::Sorbet::Struct
       const :receiptId, T.nilable(String)
diff --git a/integ-tests/ruby/baml_client/type-registry.rb b/integ-tests/ruby/baml_client/type-registry.rb
index 3095f25e9..b9cdec85d 100644
--- a/integ-tests/ruby/baml_client/type-registry.rb
+++ b/integ-tests/ruby/baml_client/type-registry.rb
@@ -18,7 +18,7 @@ module Baml
     class TypeBuilder
         def initialize
             @registry = Baml::Ffi::TypeBuilder.new
-            @classes = Set[ "BigNumbers",  "BinaryNode",  "Blah",  "BlockConstraint",  "BlockConstraintForParam",  "BookOrder",  "ClassOptionalOutput",  "ClassOptionalOutput2",  "ClassToRecAlias",  "ClassWithImage",  "CompoundBigNumbers",  "ContactInfo",  "CustomTaskResult",  "DummyOutput",  "DynInputOutput",  "DynamicClassOne",  "DynamicClassTwo",  "DynamicOutput",  "Earthling",  "Education",  "Email",  "EmailAddress",  "Event",  "FakeImage",  "FlightConfirmation",  "FooAny",  "Forest",  "GroceryReceipt",  "InnerClass",  "InnerClass2",  "InputClass",  "InputClassNested",  "LinkedList",  "LinkedListAliasNode",  "LiteralClassHello",  "LiteralClassOne",  "LiteralClassTwo",  "MalformedConstraints",  "MalformedConstraints2",  "Martian",  "MergeAttrs",  "NamedArgsSingleClass",  "Nested",  "Nested2",  "NestedBlockConstraint",  "NestedBlockConstraintForParam",  "Node",  "NodeWithAliasIndirection",  "OptionalListAndMap",  "OptionalTest_Prop1",  "OptionalTest_ReturnType",  "OrderInfo",  "OriginalA",  "OriginalB",  "Person",  "PhoneNumber",  "Quantity",  "RaysData",  "ReceiptInfo",  "ReceiptItem",  "Recipe",  "Resume",  "Schema",  "SearchParams",  "SomeClassNestedDynamic",  "StringToClassEntry",  "TestClassAlias",  "TestClassNested",  "TestClassWithEnum",  "TestOutputClass",  "Tree",  "TwoStoriesOneTitle",  "UnionTest_ReturnType",  "WithReasoning", ]
+            @classes = Set[ "BigNumbers",  "BinaryNode",  "Blah",  "BlockConstraint",  "BlockConstraintForParam",  "BookOrder",  "ClassOptionalOutput",  "ClassOptionalOutput2",  "ClassToRecAlias",  "ClassWithImage",  "CompoundBigNumbers",  "ContactInfo",  "CustomTaskResult",  "DummyOutput",  "DynInputOutput",  "DynamicClassOne",  "DynamicClassTwo",  "DynamicOutput",  "Earthling",  "Education",  "Email",  "EmailAddress",  "Event",  "FakeImage",  "FlightConfirmation",  "FooAny",  "Forest",  "FormatterTest0",  "FormatterTest1",  "FormatterTest2",  "FormatterTest3",  "GroceryReceipt",  "InnerClass",  "InnerClass2",  "InputClass",  "InputClassNested",  "LinkedList",  "LinkedListAliasNode",  "LiteralClassHello",  "LiteralClassOne",  "LiteralClassTwo",  "MalformedConstraints",  "MalformedConstraints2",  "Martian",  "MergeAttrs",  "NamedArgsSingleClass",  "Nested",  "Nested2",  "NestedBlockConstraint",  "NestedBlockConstraintForParam",  "Node",  "NodeWithAliasIndirection",  "OptionalListAndMap",  "OptionalTest_Prop1",  "OptionalTest_ReturnType",  "OrderInfo",  "OriginalA",  "OriginalB",  "Person",  "PhoneNumber",  "Quantity",  "RaysData",  "ReceiptInfo",  "ReceiptItem",  "Recipe",  "Resume",  "Schema",  "SearchParams",  "SomeClassNestedDynamic",  "StringToClassEntry",  "TestClassAlias",  "TestClassNested",  "TestClassWithEnum",  "TestOutputClass",  "Tree",  "TwoStoriesOneTitle",  "UnionTest_ReturnType",  "WithReasoning", ]
             @enums = Set[ "AliasedEnum",  "Category",  "Category2",  "Category3",  "Color",  "DataType",  "DynEnumOne",  "DynEnumTwo",  "EnumInClass",  "EnumOutput",  "Hobby",  "MapKey",  "NamedArgsSingleEnum",  "NamedArgsSingleEnumList",  "OptionalTest_CategoryType",  "OrderStatus",  "Tag",  "TestEnum", ]
         end
 
diff --git a/integ-tests/ruby/baml_client/types.rb b/integ-tests/ruby/baml_client/types.rb
index 320f35062..33c5e3734 100644
--- a/integ-tests/ruby/baml_client/types.rb
+++ b/integ-tests/ruby/baml_client/types.rb
@@ -172,6 +172,10 @@ class FakeImage < T::Struct; end
     class FlightConfirmation < T::Struct; end
     class FooAny < T::Struct; end
     class Forest < T::Struct; end
+    class FormatterTest0 < T::Struct; end
+    class FormatterTest1 < T::Struct; end
+    class FormatterTest2 < T::Struct; end
+    class FormatterTest3 < T::Struct; end
     class GroceryReceipt < T::Struct; end
     class InnerClass < T::Struct; end
     class InnerClass2 < T::Struct; end
@@ -611,6 +615,62 @@ def initialize(props)
         @props = props
       end
     end
+    class FormatterTest0 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, String
+      const :ipsum, String
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
+    class FormatterTest1 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, String
+      const :ipsum, String
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
+    class FormatterTest2 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, String
+      const :ipsum, String
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
+    class FormatterTest3 < T::Struct
+      include Baml::Sorbet::Struct
+      const :lorem, String
+      const :ipsum, String
+
+      def initialize(props)
+        super(
+          lorem: props[:lorem],
+          ipsum: props[:ipsum],
+        )
+
+        @props = props
+      end
+    end
     class GroceryReceipt < T::Struct
       include Baml::Sorbet::Struct
       const :receiptId, String
diff --git a/integ-tests/typescript/baml_client/async_client.ts b/integ-tests/typescript/baml_client/async_client.ts
index 91b7ed5d1..17c98f3b9 100644
--- a/integ-tests/typescript/baml_client/async_client.ts
+++ b/integ-tests/typescript/baml_client/async_client.ts
@@ -17,7 +17,7 @@ $ pnpm add @boundaryml/baml
 // biome-ignore format: autogenerated code
 import { BamlRuntime, FunctionResult, BamlCtxManager, BamlStream, Image, ClientRegistry, BamlValidationError, createBamlValidationError } from "@boundaryml/baml"
 import { Checked, Check } from "./types"
-import {BigNumbers, BinaryNode, Blah, BlockConstraint, BlockConstraintForParam, BookOrder, ClassOptionalOutput, ClassOptionalOutput2, ClassToRecAlias, ClassWithImage, CompoundBigNumbers, ContactInfo, CustomTaskResult, DummyOutput, DynInputOutput, DynamicClassOne, DynamicClassTwo, DynamicOutput, Earthling, Education, Email, EmailAddress, Event, FakeImage, FlightConfirmation, FooAny, Forest, GroceryReceipt, InnerClass, InnerClass2, InputClass, InputClassNested, LinkedList, LinkedListAliasNode, LiteralClassHello, LiteralClassOne, LiteralClassTwo, MalformedConstraints, MalformedConstraints2, Martian, MergeAttrs, NamedArgsSingleClass, Nested, Nested2, NestedBlockConstraint, NestedBlockConstraintForParam, Node, NodeWithAliasIndirection, OptionalListAndMap, OptionalTest_Prop1, OptionalTest_ReturnType, OrderInfo, OriginalA, OriginalB, Person, PhoneNumber, Quantity, RaysData, ReceiptInfo, ReceiptItem, Recipe, Resume, Schema, SearchParams, SomeClassNestedDynamic, StringToClassEntry, TestClassAlias, TestClassNested, TestClassWithEnum, TestOutputClass, Tree, TwoStoriesOneTitle, UnionTest_ReturnType, WithReasoning, AliasedEnum, Category, Category2, Category3, Color, DataType, DynEnumOne, DynEnumTwo, EnumInClass, EnumOutput, Hobby, MapKey, NamedArgsSingleEnum, NamedArgsSingleEnumList, OptionalTest_CategoryType, OrderStatus, Tag, TestEnum} from "./types"
+import {BigNumbers, BinaryNode, Blah, BlockConstraint, BlockConstraintForParam, BookOrder, ClassOptionalOutput, ClassOptionalOutput2, ClassToRecAlias, ClassWithImage, CompoundBigNumbers, ContactInfo, CustomTaskResult, DummyOutput, DynInputOutput, DynamicClassOne, DynamicClassTwo, DynamicOutput, Earthling, Education, Email, EmailAddress, Event, FakeImage, FlightConfirmation, FooAny, Forest, FormatterTest0, FormatterTest1, FormatterTest2, FormatterTest3, GroceryReceipt, InnerClass, InnerClass2, InputClass, InputClassNested, LinkedList, LinkedListAliasNode, LiteralClassHello, LiteralClassOne, LiteralClassTwo, MalformedConstraints, MalformedConstraints2, Martian, MergeAttrs, NamedArgsSingleClass, Nested, Nested2, NestedBlockConstraint, NestedBlockConstraintForParam, Node, NodeWithAliasIndirection, OptionalListAndMap, OptionalTest_Prop1, OptionalTest_ReturnType, OrderInfo, OriginalA, OriginalB, Person, PhoneNumber, Quantity, RaysData, ReceiptInfo, ReceiptItem, Recipe, Resume, Schema, SearchParams, SomeClassNestedDynamic, StringToClassEntry, TestClassAlias, TestClassNested, TestClassWithEnum, TestOutputClass, Tree, TwoStoriesOneTitle, UnionTest_ReturnType, WithReasoning, AliasedEnum, Category, Category2, Category3, Color, DataType, DynEnumOne, DynEnumTwo, EnumInClass, EnumOutput, Hobby, MapKey, NamedArgsSingleEnum, NamedArgsSingleEnumList, OptionalTest_CategoryType, OrderStatus, Tag, TestEnum} from "./types"
 import TypeBuilder from "./type_builder"
 import { DO_NOT_USE_DIRECTLY_UNLESS_YOU_KNOW_WHAT_YOURE_DOING_CTX, DO_NOT_USE_DIRECTLY_UNLESS_YOU_KNOW_WHAT_YOURE_DOING_RUNTIME } from "./globals"
 
diff --git a/integ-tests/typescript/baml_client/inlinedbaml.ts b/integ-tests/typescript/baml_client/inlinedbaml.ts
index 68c3cbd1a..d9ca6330a 100644
--- a/integ-tests/typescript/baml_client/inlinedbaml.ts
+++ b/integ-tests/typescript/baml_client/inlinedbaml.ts
@@ -26,6 +26,7 @@ const fileMap = {
   "fiddle-examples/extract-receipt-info.baml": "class ReceiptItem {\n  name string\n  description string?\n  quantity int\n  price float\n}\n\nclass ReceiptInfo {\n    items ReceiptItem[]\n    total_cost float?\n    venue \"barisa\" | \"ox_burger\"\n}\n\nfunction ExtractReceiptInfo(email: string, reason: \"curiosity\" | \"personal_finance\") -> ReceiptInfo {\n  client GPT4o\n  prompt #\"\n    Given the receipt below:\n\n    ```\n    {{email}}\n    ```\n\n    {{ ctx.output_format }}\n  \"#\n}\n\n",
   "fiddle-examples/images/image.baml": "function DescribeImage(img: image) -> string {\n  client GPT4o\n  prompt #\"\n    {{ _.role(\"user\") }}\n\n\n    Describe the image below in 20 words:\n    {{ img }}\n  \"#\n\n}\n\nclass FakeImage {\n  url string\n}\n\nclass ClassWithImage {\n  myImage image\n  param2 string\n  fake_image FakeImage\n}\n\n// chat role user present\nfunction DescribeImage2(classWithImage: ClassWithImage, img2: image) -> string { \n  client GPT4Turbo\n  prompt #\"\n    {{ _.role(\"user\") }}\n    You should return 2 answers that answer the following commands.\n\n    1. Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    2. Also tell me what's happening here in one sentence:\n    {{ img2 }}\n  \"#\n}\n\n// no chat role\nfunction DescribeImage3(classWithImage: ClassWithImage, img2: image) -> string {\n  client GPT4Turbo\n  prompt #\"\n    Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    Tell me also what's happening here in one sentence and relate it to the word {{ classWithImage.param2 }}:\n    {{ img2 }}\n  \"#\n}\n\n\n// system prompt and chat prompt\nfunction DescribeImage4(classWithImage: ClassWithImage, img2: image) -> string {\n  client GPT4Turbo\n  prompt #\"\n    {{ _.role(\"system\")}}\n\n    Describe this in 5 words:\n    {{ classWithImage.myImage }}\n\n    Tell me also what's happening here in one sentence and relate it to the word {{ classWithImage.param2 }}:\n    {{ img2 }}\n  \"#\n}\n\ntest TestName {\n  functions [DescribeImage]\n  args {\n    img { url \"https://imgs.xkcd.com/comics/standards.png\"}\n  }\n}\n",
   "fiddle-examples/symbol-tuning.baml": "enum Category3 {\n    Refund @alias(\"k1\")\n    @description(\"Customer wants to refund a product\")\n\n    CancelOrder @alias(\"k2\")\n    @description(\"Customer wants to cancel an order\")\n\n    TechnicalSupport @alias(\"k3\")\n    @description(\"Customer needs help with a technical issue unrelated to account creation or login\")\n\n    AccountIssue @alias(\"k4\")\n    @description(\"Specifically relates to account-login or account-creation\")\n\n    Question @alias(\"k5\")\n    @description(\"Customer has a question\")\n}\n\nfunction ClassifyMessage3(input: string) -> Category {\n  client GPT4\n\n  prompt #\"\n    Classify the following INPUT into ONE\n    of the following categories:\n\n    INPUT: {{ input }}\n\n    {{ ctx.output_format }}\n\n    Response:\n  \"#\n}",
+  "formatter/test-comments.baml": "class FormatterTest0 {\n  lorem string  // trailing comments should be preserved\n  ipsum string\n}\n\nclass FormatterTest1 {\n  lorem string\n  ipsum string\n  // dolor string\n}\n\nclass FormatterTest2 {\n  // \"lorem\" is a latin word\n  lorem string\n  // \"ipsum\" is a latin word\n  ipsum string\n}\n\nclass FormatterTest3 {\n  lorem string\n  ipsum string\n  // Lorem ipsum dolor sit amet\n  // Consectetur adipiscing elit\n  // Sed do eiusmod tempor incididunt\n  // Ut labore et dolore magna aliqua\n  // Ut enim ad minim veniam\n}",
   "generators.baml": "generator lang_python {\n  output_type python/pydantic\n  output_dir \"../python\"\n  version \"0.71.1\"\n}\n\ngenerator lang_typescript {\n  output_type typescript\n  output_dir \"../typescript\"\n  version \"0.71.1\"\n}\n\ngenerator lang_ruby {\n  output_type ruby/sorbet\n  output_dir \"../ruby\"\n  version \"0.71.1\"\n}\n\n// generator openapi {\n//   output_type rest/openapi\n//   output_dir \"../openapi\"\n//   version \"0.71.1\"\n//   on_generate \"rm .gitignore\"\n// }\n",
   "test-files/aliases/aliased-inputs.baml": "\nclass InputClass {\n  key string @alias(\"color\")\n  key2 string\n}\n\n\nclass InputClassNested {\n  key string\n  nested InputClass @alias(\"interesting-key\")\n}\n \n\nfunction AliasedInputClass(input: InputClass) -> string {\n  client GPT35\n  prompt #\"\n\n    {{input}}\n\n    This is a test. What's the name of the first json key above? Remember, tell me the key, not value.\n  \"#\n}\n \nfunction AliasedInputClass2(input: InputClass) -> string {\n  client GPT35\n  prompt #\"\n\n    {# making sure we can still access the original key #}\n    {%if input.key == \"tiger\"%}\n      Repeat this value back to me, and nothing else: {{input.key}}\n    {%endif%}\n  \"#\n}\n \n function AliasedInputClassNested(input: InputClassNested) -> string {\n  client GPT35\n  prompt #\"\n    {{ _.role(\"user\")}}\n\n    {{input}}\n\n    This is a test. What's the name of the second json key above? Remember, tell me the key, not value.\n  \"#\n }\n\n\nenum AliasedEnum {\n  KEY_ONE @alias(\"tiger\")\n  KEY_TWO\n}\n\nfunction AliasedInputEnum(input: AliasedEnum) -> string {\n  client GPT4o\n  prompt #\"\n    {{ _.role(\"user\")}}\n\n\n    Write out this word only in your response, in lowercase:\n    ---\n    {{input}}\n    ---\n    Answer:\n  \"#\n}\n\n\nfunction AliasedInputList(input: AliasedEnum[]) -> string {\n  client GPT35\n  prompt #\"\n    {{ _.role(\"user\")}}\n    Given this array:\n    ---\n    {{input}}\n    ---\n\n    Return the first element in the array:\n  \"#\n}\n\n",
   "test-files/aliases/classes.baml": "class TestClassAlias {\n  key string @alias(\"key-dash\") @description(#\"\n    This is a description for key\n    af asdf\n  \"#)\n  key2 string @alias(\"key21\")\n  key3 string @alias(\"key with space\")\n  key4 string //unaliased\n  key5 string @alias(\"key.with.punctuation/123\")\n}\n\nfunction FnTestClassAlias(input: string) -> TestClassAlias {\n  client GPT35\n  prompt #\"\n    {{ctx.output_format}}\n  \"#\n}\n\ntest FnTestClassAlias {\n  functions [FnTestClassAlias]\n  args {\n    input \"example input\"\n  }\n}\n",
diff --git a/integ-tests/typescript/baml_client/sync_client.ts b/integ-tests/typescript/baml_client/sync_client.ts
index 67709fc70..ed6484a89 100644
--- a/integ-tests/typescript/baml_client/sync_client.ts
+++ b/integ-tests/typescript/baml_client/sync_client.ts
@@ -17,7 +17,7 @@ $ pnpm add @boundaryml/baml
 // biome-ignore format: autogenerated code
 import { BamlRuntime, FunctionResult, BamlCtxManager, BamlSyncStream, Image, ClientRegistry, createBamlValidationError, BamlValidationError } from "@boundaryml/baml"
 import { Checked, Check } from "./types"
-import {BigNumbers, BinaryNode, Blah, BlockConstraint, BlockConstraintForParam, BookOrder, ClassOptionalOutput, ClassOptionalOutput2, ClassToRecAlias, ClassWithImage, CompoundBigNumbers, ContactInfo, CustomTaskResult, DummyOutput, DynInputOutput, DynamicClassOne, DynamicClassTwo, DynamicOutput, Earthling, Education, Email, EmailAddress, Event, FakeImage, FlightConfirmation, FooAny, Forest, GroceryReceipt, InnerClass, InnerClass2, InputClass, InputClassNested, LinkedList, LinkedListAliasNode, LiteralClassHello, LiteralClassOne, LiteralClassTwo, MalformedConstraints, MalformedConstraints2, Martian, MergeAttrs, NamedArgsSingleClass, Nested, Nested2, NestedBlockConstraint, NestedBlockConstraintForParam, Node, NodeWithAliasIndirection, OptionalListAndMap, OptionalTest_Prop1, OptionalTest_ReturnType, OrderInfo, OriginalA, OriginalB, Person, PhoneNumber, Quantity, RaysData, ReceiptInfo, ReceiptItem, Recipe, Resume, Schema, SearchParams, SomeClassNestedDynamic, StringToClassEntry, TestClassAlias, TestClassNested, TestClassWithEnum, TestOutputClass, Tree, TwoStoriesOneTitle, UnionTest_ReturnType, WithReasoning, AliasedEnum, Category, Category2, Category3, Color, DataType, DynEnumOne, DynEnumTwo, EnumInClass, EnumOutput, Hobby, MapKey, NamedArgsSingleEnum, NamedArgsSingleEnumList, OptionalTest_CategoryType, OrderStatus, Tag, TestEnum} from "./types"
+import {BigNumbers, BinaryNode, Blah, BlockConstraint, BlockConstraintForParam, BookOrder, ClassOptionalOutput, ClassOptionalOutput2, ClassToRecAlias, ClassWithImage, CompoundBigNumbers, ContactInfo, CustomTaskResult, DummyOutput, DynInputOutput, DynamicClassOne, DynamicClassTwo, DynamicOutput, Earthling, Education, Email, EmailAddress, Event, FakeImage, FlightConfirmation, FooAny, Forest, FormatterTest0, FormatterTest1, FormatterTest2, FormatterTest3, GroceryReceipt, InnerClass, InnerClass2, InputClass, InputClassNested, LinkedList, LinkedListAliasNode, LiteralClassHello, LiteralClassOne, LiteralClassTwo, MalformedConstraints, MalformedConstraints2, Martian, MergeAttrs, NamedArgsSingleClass, Nested, Nested2, NestedBlockConstraint, NestedBlockConstraintForParam, Node, NodeWithAliasIndirection, OptionalListAndMap, OptionalTest_Prop1, OptionalTest_ReturnType, OrderInfo, OriginalA, OriginalB, Person, PhoneNumber, Quantity, RaysData, ReceiptInfo, ReceiptItem, Recipe, Resume, Schema, SearchParams, SomeClassNestedDynamic, StringToClassEntry, TestClassAlias, TestClassNested, TestClassWithEnum, TestOutputClass, Tree, TwoStoriesOneTitle, UnionTest_ReturnType, WithReasoning, AliasedEnum, Category, Category2, Category3, Color, DataType, DynEnumOne, DynEnumTwo, EnumInClass, EnumOutput, Hobby, MapKey, NamedArgsSingleEnum, NamedArgsSingleEnumList, OptionalTest_CategoryType, OrderStatus, Tag, TestEnum} from "./types"
 import TypeBuilder from "./type_builder"
 import { DO_NOT_USE_DIRECTLY_UNLESS_YOU_KNOW_WHAT_YOURE_DOING_CTX, DO_NOT_USE_DIRECTLY_UNLESS_YOU_KNOW_WHAT_YOURE_DOING_RUNTIME } from "./globals"
 
diff --git a/integ-tests/typescript/baml_client/type_builder.ts b/integ-tests/typescript/baml_client/type_builder.ts
index 2d40ca5d8..56a984f5b 100644
--- a/integ-tests/typescript/baml_client/type_builder.ts
+++ b/integ-tests/typescript/baml_client/type_builder.ts
@@ -50,7 +50,7 @@ export default class TypeBuilder {
     constructor() {
         this.tb = new _TypeBuilder({
           classes: new Set([
-            "BigNumbers","BinaryNode","Blah","BlockConstraint","BlockConstraintForParam","BookOrder","ClassOptionalOutput","ClassOptionalOutput2","ClassToRecAlias","ClassWithImage","CompoundBigNumbers","ContactInfo","CustomTaskResult","DummyOutput","DynInputOutput","DynamicClassOne","DynamicClassTwo","DynamicOutput","Earthling","Education","Email","EmailAddress","Event","FakeImage","FlightConfirmation","FooAny","Forest","GroceryReceipt","InnerClass","InnerClass2","InputClass","InputClassNested","LinkedList","LinkedListAliasNode","LiteralClassHello","LiteralClassOne","LiteralClassTwo","MalformedConstraints","MalformedConstraints2","Martian","MergeAttrs","NamedArgsSingleClass","Nested","Nested2","NestedBlockConstraint","NestedBlockConstraintForParam","Node","NodeWithAliasIndirection","OptionalListAndMap","OptionalTest_Prop1","OptionalTest_ReturnType","OrderInfo","OriginalA","OriginalB","Person","PhoneNumber","Quantity","RaysData","ReceiptInfo","ReceiptItem","Recipe","Resume","Schema","SearchParams","SomeClassNestedDynamic","StringToClassEntry","TestClassAlias","TestClassNested","TestClassWithEnum","TestOutputClass","Tree","TwoStoriesOneTitle","UnionTest_ReturnType","WithReasoning",
+            "BigNumbers","BinaryNode","Blah","BlockConstraint","BlockConstraintForParam","BookOrder","ClassOptionalOutput","ClassOptionalOutput2","ClassToRecAlias","ClassWithImage","CompoundBigNumbers","ContactInfo","CustomTaskResult","DummyOutput","DynInputOutput","DynamicClassOne","DynamicClassTwo","DynamicOutput","Earthling","Education","Email","EmailAddress","Event","FakeImage","FlightConfirmation","FooAny","Forest","FormatterTest0","FormatterTest1","FormatterTest2","FormatterTest3","GroceryReceipt","InnerClass","InnerClass2","InputClass","InputClassNested","LinkedList","LinkedListAliasNode","LiteralClassHello","LiteralClassOne","LiteralClassTwo","MalformedConstraints","MalformedConstraints2","Martian","MergeAttrs","NamedArgsSingleClass","Nested","Nested2","NestedBlockConstraint","NestedBlockConstraintForParam","Node","NodeWithAliasIndirection","OptionalListAndMap","OptionalTest_Prop1","OptionalTest_ReturnType","OrderInfo","OriginalA","OriginalB","Person","PhoneNumber","Quantity","RaysData","ReceiptInfo","ReceiptItem","Recipe","Resume","Schema","SearchParams","SomeClassNestedDynamic","StringToClassEntry","TestClassAlias","TestClassNested","TestClassWithEnum","TestOutputClass","Tree","TwoStoriesOneTitle","UnionTest_ReturnType","WithReasoning",
           ]),
           enums: new Set([
             "AliasedEnum","Category","Category2","Category3","Color","DataType","DynEnumOne","DynEnumTwo","EnumInClass","EnumOutput","Hobby","MapKey","NamedArgsSingleEnum","NamedArgsSingleEnumList","OptionalTest_CategoryType","OrderStatus","Tag","TestEnum",
diff --git a/integ-tests/typescript/baml_client/types.ts b/integ-tests/typescript/baml_client/types.ts
index fae4be644..ae8dfea30 100644
--- a/integ-tests/typescript/baml_client/types.ts
+++ b/integ-tests/typescript/baml_client/types.ts
@@ -330,6 +330,30 @@ export interface Forest {
   
 }
 
+export interface FormatterTest0 {
+  lorem: string
+  ipsum: string
+  
+}
+
+export interface FormatterTest1 {
+  lorem: string
+  ipsum: string
+  
+}
+
+export interface FormatterTest2 {
+  lorem: string
+  ipsum: string
+  
+}
+
+export interface FormatterTest3 {
+  lorem: string
+  ipsum: string
+  
+}
+
 export interface GroceryReceipt {
   receiptId: string
   storeName: string
diff --git a/tools/build b/tools/build
index 2402b8781..e92be8d43 100755
--- a/tools/build
+++ b/tools/build
@@ -166,6 +166,26 @@ case "$_path" in
     fi
     ;;
 
+  /integ-tests/baml_src | /integ-tests/baml_src/* )
+    command="cd ${_repo_root}/engine"
+    command="${command} && git checkout -- ${_repo_root}/integ-tests/baml_src/formatter/test-comments.baml"
+    command="${command} && cargo run --bin baml-cli fmt ${_repo_root}/integ-tests/baml_src/formatter/test-comments.baml"
+    command="${command} && git difftool --extcmd icdiff -y -- ${_repo_root}/integ-tests/baml_src/formatter/test-comments.baml"
+    if [ "$_watch_mode" -eq 1 ]; then
+      npx nodemon \
+        --ext py,pyi,rs,j2,toml \
+        --watch "${_repo_root}/engine" \
+        --watch . \
+        --ignore 'baml_client/**' \
+        --ignore 'target/**' \
+        --ignore .pytest_cache \
+        --exec "${command}"
+    else
+      eval "${command}"
+      date
+    fi
+    ;;
+
   /integ-tests/python | /integ-tests/python/* )
     command="true"
     command="env -u CONDA_PREFIX poetry run maturin develop --manifest-path ${_repo_root}/engine/language_client_python/Cargo.toml"