diff --git a/crates/oxc_diagnostics/src/service.rs b/crates/oxc_diagnostics/src/service.rs
index 4ef7387068f1d..e2422de582b71 100644
--- a/crates/oxc_diagnostics/src/service.rs
+++ b/crates/oxc_diagnostics/src/service.rs
@@ -6,7 +6,6 @@ use std::{
 };
 
 use cow_utils::CowUtils;
-use miette::LabeledSpan;
 use percent_encoding::AsciiSet;
 #[cfg(not(windows))]
 use std::fs::canonicalize as strict_canonicalize;
@@ -122,7 +121,6 @@ impl DiagnosticService {
         cwd: C,
         path: P,
         source_text: &str,
-        source_start: u32,
         diagnostics: Vec<OxcDiagnostic>,
     ) -> Vec<Error> {
         // TODO: This causes snapshots to fail when running tests through a JetBrains terminal.
@@ -141,29 +139,7 @@ impl DiagnosticService {
         let source = Arc::new(NamedSource::new(path_display, source_text.to_owned()));
         diagnostics
             .into_iter()
-            .map(|diagnostic| {
-                if source_start == 0 {
-                    return diagnostic.with_source_code(Arc::clone(&source));
-                }
-
-                match &diagnostic.labels {
-                    None => diagnostic.with_source_code(Arc::clone(&source)),
-                    Some(labels) => {
-                        let new_labels = labels
-                            .iter()
-                            .map(|labeled_span| {
-                                LabeledSpan::new(
-                                    labeled_span.label().map(std::string::ToString::to_string),
-                                    labeled_span.offset() + source_start as usize,
-                                    labeled_span.len(),
-                                )
-                            })
-                            .collect::<Vec<_>>();
-
-                        diagnostic.with_labels(new_labels).with_source_code(Arc::clone(&source))
-                    }
-                }
-            })
+            .map(|diagnostic| diagnostic.with_source_code(Arc::clone(&source)))
             .collect()
     }
 
diff --git a/crates/oxc_linter/src/service/runtime.rs b/crates/oxc_linter/src/service/runtime.rs
index b52355a6f6d68..a221384aa4649 100644
--- a/crates/oxc_linter/src/service/runtime.rs
+++ b/crates/oxc_linter/src/service/runtime.rs
@@ -494,7 +494,7 @@ impl Runtime {
 
     // clippy: the source field is checked and assumed to be less than 4GB, and
     // we assume that the fix offset will not exceed 2GB in either direction
-    #[expect(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
+    #[expect(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
     pub(super) fn run(&mut self, tx_error: &DiagnosticSender) {
         rayon::scope(|scope| {
             self.resolve_modules(scope, true, tx_error, |me, mut module_to_lint| {
@@ -532,13 +532,19 @@ impl Runtime {
                                 .collect(),
                         };
 
+                        // adjust offset for multiple source text in a single file
+                        if section.source.start != 0 {
+                            for message in &mut messages {
+                                message.move_offset(section.source.start);
+                            }
+                        }
+
                         let source_text = section.source.source_text;
                         if me.linter.options().fix.is_some() {
                             let fix_result = Fixer::new(source_text, messages).fix();
                             if fix_result.fixed {
                                 // write to file, replacing only the changed part
-                                let start =
-                                    section.source.start.saturating_add_signed(fix_offset) as usize;
+                                let start = fix_offset as usize;
                                 let end = start + source_text.len();
                                 new_source_text
                                     .to_mut()
@@ -557,7 +563,6 @@ impl Runtime {
                                 &me.cwd,
                                 path,
                                 dep.source_text,
-                                section.source.start,
                                 errors,
                             );
                             tx_error.send((path.to_path_buf(), diagnostics)).unwrap();