diff --git a/Cargo.toml b/Cargo.toml
index 26d7b306260f3..18e8815351255 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -89,7 +89,6 @@ suspicious_operation_groupings = "warn"
 redundant_clone = "warn"
 redundant_pub_crate = "allow" # FIXME
 debug_assert_with_mut_call = "allow" # FIXME
-needless_pass_by_ref_mut = "allow" # FIXME
 # cargo
 cargo = { level = "warn", priority = -1 }
 multiple_crate_versions = "allow"
diff --git a/crates/oxc_isolated_declarations/src/function.rs b/crates/oxc_isolated_declarations/src/function.rs
index 775bbcecd4e98..03a9268b7f49c 100644
--- a/crates/oxc_isolated_declarations/src/function.rs
+++ b/crates/oxc_isolated_declarations/src/function.rs
@@ -13,7 +13,7 @@ use crate::{
 
 impl<'a> IsolatedDeclarations<'a> {
     pub(crate) fn transform_function(
-        &mut self,
+        &self,
         func: &Function<'a>,
         declare: Option<bool>,
     ) -> Box<'a, Function<'a>> {
diff --git a/crates/oxc_isolated_declarations/src/module.rs b/crates/oxc_isolated_declarations/src/module.rs
index 1339999462e82..75462ef1a8b27 100644
--- a/crates/oxc_isolated_declarations/src/module.rs
+++ b/crates/oxc_isolated_declarations/src/module.rs
@@ -21,7 +21,7 @@ impl<'a> IsolatedDeclarations<'a> {
         ))
     }
 
-    pub(crate) fn create_unique_name(&mut self, name: &str) -> Atom<'a> {
+    pub(crate) fn create_unique_name(&self, name: &str) -> Atom<'a> {
         let mut binding = self.ast.atom(name);
         let mut i = 1;
         while self.scope.has_reference(&binding) {
@@ -32,7 +32,7 @@ impl<'a> IsolatedDeclarations<'a> {
     }
 
     pub(crate) fn transform_export_default_declaration(
-        &mut self,
+        &self,
         decl: &ExportDefaultDeclaration<'a>,
     ) -> Option<(Option<Statement<'a>>, Statement<'a>)> {
         let declaration = match &decl.declaration {
@@ -69,7 +69,7 @@ impl<'a> IsolatedDeclarations<'a> {
     }
 
     fn transform_export_expression(
-        &mut self,
+        &self,
         expr: &Expression<'a>,
     ) -> Option<(Option<Statement<'a>>, Expression<'a>)> {
         if matches!(expr, Expression::Identifier(_)) {
@@ -102,7 +102,7 @@ impl<'a> IsolatedDeclarations<'a> {
     }
 
     pub(crate) fn transform_ts_export_assignment(
-        &mut self,
+        &self,
         decl: &TSExportAssignment<'a>,
     ) -> Option<(Option<Statement<'a>>, Statement<'a>)> {
         self.transform_export_expression(&decl.expression).map(|(var_decl, expr)| {
diff --git a/crates/oxc_minifier/src/lib.rs b/crates/oxc_minifier/src/lib.rs
index 3068e77b95781..cf89773a93223 100644
--- a/crates/oxc_minifier/src/lib.rs
+++ b/crates/oxc_minifier/src/lib.rs
@@ -1,5 +1,7 @@
 //! ECMAScript Minifier
 
+#![allow(clippy::needless_pass_by_ref_mut)]
+
 mod compressor;
 mod ctx;
 mod keep_var;
diff --git a/crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs b/crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs
index d8663ad1c3364..ff474ab166c47 100644
--- a/crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs
+++ b/crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs
@@ -1104,7 +1104,7 @@ impl<'a> LatePeepholeOptimizations {
         DELIMITERS.into_iter().find(|&delimiter| strings.clone().all(|s| !s.contains(delimiter)))
     }
 
-    pub fn substitute_catch_clause(&mut self, catch: &mut CatchClause<'a>, ctx: Ctx<'a, '_>) {
+    pub fn substitute_catch_clause(&self, catch: &mut CatchClause<'a>, ctx: Ctx<'a, '_>) {
         if self.target >= ESTarget::ES2019 {
             if let Some(param) = &catch.param {
                 if let BindingPatternKind::BindingIdentifier(ident) = &param.pattern.kind {
diff --git a/crates/oxc_parser/src/cursor.rs b/crates/oxc_parser/src/cursor.rs
index 66d5bf0de31d4..fd207c6590942 100644
--- a/crates/oxc_parser/src/cursor.rs
+++ b/crates/oxc_parser/src/cursor.rs
@@ -188,7 +188,7 @@ impl<'a> ParserImpl<'a> {
     }
 
     /// # Errors
-    pub(crate) fn expect_without_advance(&mut self, kind: Kind) -> Result<()> {
+    pub(crate) fn expect_without_advance(&self, kind: Kind) -> Result<()> {
         if !self.at(kind) {
             let range = self.cur_token().span();
             return Err(diagnostics::expect_token(kind.to_str(), self.cur_kind().to_str(), range));
diff --git a/crates/oxc_parser/src/js/expression.rs b/crates/oxc_parser/src/js/expression.rs
index 99795601852e4..7d60a3eab74f9 100644
--- a/crates/oxc_parser/src/js/expression.rs
+++ b/crates/oxc_parser/src/js/expression.rs
@@ -437,7 +437,7 @@ impl<'a> ParserImpl<'a> {
     /// Elision :
     ///     ,
     ///    Elision ,
-    pub(crate) fn parse_elision(&mut self) -> ArrayExpressionElement<'a> {
+    pub(crate) fn parse_elision(&self) -> ArrayExpressionElement<'a> {
         self.ast.array_expression_element_elision(self.cur_token().span())
     }
 
diff --git a/crates/oxc_parser/src/modifiers.rs b/crates/oxc_parser/src/modifiers.rs
index 972fa512e9cb8..3cc31c8d42349 100644
--- a/crates/oxc_parser/src/modifiers.rs
+++ b/crates/oxc_parser/src/modifiers.rs
@@ -507,7 +507,7 @@ impl<'a> ParserImpl<'a> {
         self.can_follow_export_modifier()
     }
 
-    fn can_follow_export_modifier(&mut self) -> bool {
+    fn can_follow_export_modifier(&self) -> bool {
         let kind = self.cur_kind();
         kind == Kind::At
             && kind != Kind::Star
@@ -516,7 +516,7 @@ impl<'a> ParserImpl<'a> {
             && self.can_follow_modifier()
     }
 
-    fn can_follow_modifier(&mut self) -> bool {
+    fn can_follow_modifier(&self) -> bool {
         match self.cur_kind() {
             Kind::PrivateIdentifier | Kind::LBrack | Kind::LCurly | Kind::Star | Kind::Dot3 => true,
             kind => kind.is_identifier_or_keyword(),
diff --git a/crates/oxc_parser/src/ts/types.rs b/crates/oxc_parser/src/ts/types.rs
index 3682196866112..f21e08f95516c 100644
--- a/crates/oxc_parser/src/ts/types.rs
+++ b/crates/oxc_parser/src/ts/types.rs
@@ -1367,7 +1367,7 @@ impl<'a> ParserImpl<'a> {
         ))
     }
 
-    fn is_binary_operator(&mut self) -> bool {
+    fn is_binary_operator(&self) -> bool {
         if self.ctx.has_in() && self.at(Kind::In) {
             return false;
         }
diff --git a/crates/oxc_prettier/src/comments/print.rs b/crates/oxc_prettier/src/comments/print.rs
index 317f70c7d1c11..2219b91b5c49a 100644
--- a/crates/oxc_prettier/src/comments/print.rs
+++ b/crates/oxc_prettier/src/comments/print.rs
@@ -8,7 +8,7 @@ use super::{CommentFlags, DanglingCommentsPrintOptions};
 impl<'a> Prettier<'a> {
     #[must_use]
     pub(crate) fn print_comments(
-        &mut self,
+        &self,
         before: Option<Doc<'a>>,
         doc: Doc<'a>,
         after: Option<Doc<'a>>,
@@ -27,28 +27,28 @@ impl<'a> Prettier<'a> {
         doc
     }
 
-    pub(crate) fn has_comment(&mut self, _span: Span, _flags: CommentFlags) -> bool {
+    pub(crate) fn has_comment(&self, _span: Span, _flags: CommentFlags) -> bool {
         false
     }
 
     #[must_use]
-    pub(crate) fn print_leading_comments(&mut self, _span: Span) -> Option<Doc<'a>> {
+    pub(crate) fn print_leading_comments(&self, _span: Span) -> Option<Doc<'a>> {
         None
     }
 
     #[must_use]
-    pub(crate) fn print_trailing_comments(&mut self, _span: Span) -> Option<Doc<'a>> {
+    pub(crate) fn print_trailing_comments(&self, _span: Span) -> Option<Doc<'a>> {
         None
     }
 
     #[must_use]
-    pub(crate) fn print_inner_comment(&mut self, _span: Span) -> Vec<'a, Doc<'a>> {
+    pub(crate) fn print_inner_comment(&self, _span: Span) -> Vec<'a, Doc<'a>> {
         Vec::new_in(self.allocator)
     }
 
     #[must_use]
     pub(crate) fn print_dangling_comments(
-        &mut self,
+        &self,
         _span: Span,
         _dangling_options: Option<&DanglingCommentsPrintOptions>,
     ) -> Option<Doc<'a>> {
diff --git a/crates/oxc_prettier/src/format/print/arrow_function.rs b/crates/oxc_prettier/src/format/print/arrow_function.rs
index b7891eb12f090..aba6cfa898503 100644
--- a/crates/oxc_prettier/src/format/print/arrow_function.rs
+++ b/crates/oxc_prettier/src/format/print/arrow_function.rs
@@ -43,7 +43,7 @@ pub fn print_arrow_function<'a>(
 }
 
 pub fn should_print_params_without_parens<'a>(
-    p: &mut Prettier<'a>,
+    p: &Prettier<'a>,
     expr: &ArrowFunctionExpression<'a>,
 ) -> bool {
     match p.options.arrow_parens {
diff --git a/crates/oxc_prettier/src/format/print/class.rs b/crates/oxc_prettier/src/format/print/class.rs
index da3a8518e30a6..9cac541176ab8 100644
--- a/crates/oxc_prettier/src/format/print/class.rs
+++ b/crates/oxc_prettier/src/format/print/class.rs
@@ -229,7 +229,7 @@ impl<'a> ClassPropertyLike<'a, '_> {
         }
     }
 
-    fn format_accessibility(&self, p: &mut Prettier<'a>) -> Option<Doc<'a>> {
+    fn format_accessibility(&self, p: &Prettier<'a>) -> Option<Doc<'a>> {
         match self {
             ClassPropertyLike::AccessorProperty(def) => {
                 def.accessibility.map(|v| text!(v.as_str()))
diff --git a/crates/oxc_prettier/src/format/print/function_parameters.rs b/crates/oxc_prettier/src/format/print/function_parameters.rs
index ddcd47cbb1a19..23f8626329430 100644
--- a/crates/oxc_prettier/src/format/print/function_parameters.rs
+++ b/crates/oxc_prettier/src/format/print/function_parameters.rs
@@ -7,7 +7,7 @@ use crate::{
 };
 
 pub fn should_hug_the_only_function_parameter(
-    p: &mut Prettier<'_>,
+    p: &Prettier<'_>,
     params: &FormalParameters<'_>,
 ) -> bool {
     if params.parameters_count() != 1 {
diff --git a/crates/oxc_prettier/src/format/print/object.rs b/crates/oxc_prettier/src/format/print/object.rs
index 9ed082668fbf9..0712d5375f98f 100644
--- a/crates/oxc_prettier/src/format/print/object.rs
+++ b/crates/oxc_prettier/src/format/print/object.rs
@@ -300,7 +300,7 @@ pub fn print_object<'a>(p: &mut Prettier<'a>, obj: &ObjectLike<'a, '_>) -> Doc<'
     group!(p, parts, should_break, None)
 }
 
-fn should_hug_the_only_parameter(p: &mut Prettier<'_>, kind: AstKind<'_>) -> bool {
+fn should_hug_the_only_parameter(p: &Prettier<'_>, kind: AstKind<'_>) -> bool {
     match kind {
         AstKind::FormalParameters(params) => {
             function_parameters::should_hug_the_only_function_parameter(p, params)
diff --git a/crates/oxc_regular_expression/src/parser/reader/string_literal_parser/parser_impl.rs b/crates/oxc_regular_expression/src/parser/reader/string_literal_parser/parser_impl.rs
index 94e104cd3d609..2eb3750f2c5eb 100644
--- a/crates/oxc_regular_expression/src/parser/reader/string_literal_parser/parser_impl.rs
+++ b/crates/oxc_regular_expression/src/parser/reader/string_literal_parser/parser_impl.rs
@@ -517,16 +517,16 @@ impl Parser {
         self.offset
     }
 
-    fn peek_nth(&mut self, n: usize) -> Option<char> {
+    fn peek_nth(&self, n: usize) -> Option<char> {
         let nth = self.index + n;
         self.chars.get(nth).copied()
     }
 
-    fn peek(&mut self) -> Option<char> {
+    fn peek(&self) -> Option<char> {
         self.peek_nth(0)
     }
 
-    fn peek2(&mut self) -> Option<char> {
+    fn peek2(&self) -> Option<char> {
         self.peek_nth(1)
     }
 }
diff --git a/crates/oxc_transformer/src/lib.rs b/crates/oxc_transformer/src/lib.rs
index f4fb1d86dde22..57755a3345870 100644
--- a/crates/oxc_transformer/src/lib.rs
+++ b/crates/oxc_transformer/src/lib.rs
@@ -5,6 +5,8 @@
 //! * <https://babel.dev/docs/presets>
 //! * <https://github.com/microsoft/TypeScript/blob/v5.6.3/src/compiler/transformer.ts>
 
+#![allow(clippy::needless_pass_by_ref_mut)]
+
 use std::path::Path;
 
 use oxc_allocator::{Allocator, Vec as ArenaVec};
diff --git a/crates/oxc_traverse/src/context/scoping.rs b/crates/oxc_traverse/src/context/scoping.rs
index a11a7a8e6e9c2..708fc092a1d65 100644
--- a/crates/oxc_traverse/src/context/scoping.rs
+++ b/crates/oxc_traverse/src/context/scoping.rs
@@ -425,7 +425,7 @@ impl TraverseScoping {
     ///
     /// Once this set is created, generating a UID is a relatively quick operation, rather than
     /// iterating over all symbols and unresolved references every time generate a UID.
-    fn get_uid_names(&mut self) -> FxHashSet<CompactStr> {
+    fn get_uid_names(&self) -> FxHashSet<CompactStr> {
         self.scopes
             .root_unresolved_references()
             .keys()
diff --git a/crates/oxc_wasm/src/lib.rs b/crates/oxc_wasm/src/lib.rs
index 2c69f2ba0ca32..5494fbedd4d22 100644
--- a/crates/oxc_wasm/src/lib.rs
+++ b/crates/oxc_wasm/src/lib.rs
@@ -311,7 +311,7 @@ impl Oxc {
     }
 
     fn run_linter(
-        &mut self,
+        &self,
         run_options: &OxcRunOptions,
         path: &Path,
         program: &Program,
diff --git a/tasks/ast_tools/src/parse/parse.rs b/tasks/ast_tools/src/parse/parse.rs
index d64f8d9f7f24e..c7cdb8a3cd214 100644
--- a/tasks/ast_tools/src/parse/parse.rs
+++ b/tasks/ast_tools/src/parse/parse.rs
@@ -167,7 +167,7 @@ impl<'c> Parser<'c> {
     }
 
     /// Get type name for a [`TypeId`].
-    fn type_name(&mut self, type_id: TypeId) -> &str {
+    fn type_name(&self, type_id: TypeId) -> &str {
         &self.type_names[type_id.index()]
     }
 
@@ -516,7 +516,7 @@ impl<'c> Parser<'c> {
     ///
     /// [`Derive`]: crate::Derive
     /// [`Generator`]: crate::Generator
-    fn parse_type_attrs(&mut self, type_def: &mut TypeDef, attrs: &[Attribute]) {
+    fn parse_type_attrs(&self, type_def: &mut TypeDef, attrs: &[Attribute]) {
         for attr in attrs {
             if !matches!(attr.style, AttrStyle::Outer) {
                 continue;
@@ -600,7 +600,7 @@ impl<'c> Parser<'c> {
     ///
     /// [`Derive`]: crate::Derive
     /// [`Generator`]: crate::Generator
-    fn parse_ast_attr(&mut self, type_def: &mut TypeDef, attr: &Attribute) {
+    fn parse_ast_attr(&self, type_def: &mut TypeDef, attr: &Attribute) {
         let parts = match &attr.meta {
             Meta::Path(_) => return,
             Meta::List(meta_list) => meta_list
@@ -687,7 +687,7 @@ impl<'c> Parser<'c> {
     }
 
     /// Parse [`Skeleton`] to yield a [`MetaType`].
-    fn parse_meta_type(&mut self, meta_id: MetaId, skeleton: Skeleton) -> MetaType {
+    fn parse_meta_type(&self, meta_id: MetaId, skeleton: Skeleton) -> MetaType {
         let (type_name, file_id, attrs) = match skeleton {
             Skeleton::Struct(skeleton) => (skeleton.name, skeleton.file_id, skeleton.item.attrs),
             Skeleton::Enum(skeleton) => (skeleton.name, skeleton.file_id, skeleton.item.attrs),
diff --git a/tasks/transform_conformance/src/test_case.rs b/tasks/transform_conformance/src/test_case.rs
index 06aad91f5edfc..69ef7c67bb866 100644
--- a/tasks/transform_conformance/src/test_case.rs
+++ b/tasks/transform_conformance/src/test_case.rs
@@ -389,7 +389,7 @@ impl TestCase {
         }
     }
 
-    fn test_exec(&mut self, filtered: bool) {
+    fn test_exec(&self, filtered: bool) {
         if filtered {
             println!("input_path: {:?}", &self.path);
             println!("Input:\n{}\n", fs::read_to_string(&self.path).unwrap());