diff --git a/crates/criterion_compat/Cargo.toml b/crates/criterion_compat/Cargo.toml
index 0044814c..b6ff74fa 100644
--- a/crates/criterion_compat/Cargo.toml
+++ b/crates/criterion_compat/Cargo.toml
@@ -56,3 +56,7 @@ harness = false
 [[bench]]
 name = "test_benches"
 harness = false
+
+[[bench]]
+name = "repro_custom_main"
+harness = false
diff --git a/crates/criterion_compat/benches/repro_custom_main.rs b/crates/criterion_compat/benches/repro_custom_main.rs
new file mode 100644
index 00000000..f50488f4
--- /dev/null
+++ b/crates/criterion_compat/benches/repro_custom_main.rs
@@ -0,0 +1,30 @@
+/// Reproducer for COD-2324: URI formatting issues when users bypass criterion_group!/criterion_main!
+/// and use a custom main function (like the rtmalloc project does).
+use codspeed_criterion_compat::{criterion_group, BenchmarkId, Criterion};
+
+fn bench_with_group(c: &mut Criterion) {
+    let mut group = c.benchmark_group("my_group");
+    group.bench_function("my_bench", |b| b.iter(|| 2 + 2));
+    group.bench_function(BenchmarkId::new("parameterized", 42), |b| b.iter(|| 2 + 2));
+    group.finish();
+}
+
+criterion_group!(benches, bench_with_group);
+
+#[cfg(codspeed)]
+fn main() {
+    // Pattern A: Using new_instrumented() but calling bench functions directly (not through criterion_group!)
+    let mut criterion = Criterion::new_instrumented();
+    bench_with_group(&mut criterion);
+
+    // Pattern B: Calling through criterion_group!-generated function (should work correctly)
+    let mut criterion2 = Criterion::new_instrumented();
+    benches(&mut criterion2);
+}
+
+#[cfg(not(codspeed))]
+fn main() {
+    // Without codspeed, just run through upstream criterion directly
+    let mut criterion = Criterion::default().configure_from_args();
+    bench_with_group(&mut criterion);
+}
diff --git a/crates/criterion_compat/src/compat/criterion.rs b/crates/criterion_compat/src/compat/criterion.rs
index a8b85c1a..a388b529 100644
--- a/crates/criterion_compat/src/compat/criterion.rs
+++ b/crates/criterion_compat/src/compat/criterion.rs
@@ -92,6 +92,7 @@ impl<M: Measurement> Criterion<M> {
         self.macro_group = macro_group.into();
     }
 
+    #[track_caller]
     pub fn bench_function<F>(&mut self, id: &str, f: F) -> &mut Criterion<M>
     where
         F: FnMut(&mut Bencher),
@@ -101,6 +102,7 @@ impl<M: Measurement> Criterion<M> {
         self
     }
 
+    #[track_caller]
     pub fn bench_with_input<F, I>(&mut self, id: BenchmarkId, input: &I, f: F) -> &mut Criterion<M>
     where
         F: FnMut(&mut Bencher, &I),
@@ -118,9 +120,28 @@ impl<M: Measurement> Criterion<M> {
         self
     }
 
+    #[track_caller]
     pub fn benchmark_group<S: Into<String>>(&mut self, group_name: S) -> BenchmarkGroup<M> {
+        self.fill_missing_file_from_caller();
         BenchmarkGroup::<M>::new(self, group_name.into())
     }
+
+    /// When `current_file` wasn't set by `criterion_group!`, derive it from the caller location.
+    #[track_caller]
+    fn fill_missing_file_from_caller(&mut self) {
+        if !self.current_file.is_empty() {
+            return;
+        }
+        let caller = std::panic::Location::caller();
+        if let Ok(workspace_root) = std::env::var("CODSPEED_CARGO_WORKSPACE_ROOT") {
+            self.current_file = std::path::PathBuf::from(workspace_root)
+                .join(caller.file())
+                .to_string_lossy()
+                .into_owned();
+        } else {
+            self.current_file = caller.file().to_string();
+        }
+    }
 }
 
 // Dummy methods
diff --git a/crates/criterion_compat/src/compat/group.rs b/crates/criterion_compat/src/compat/group.rs
index 90e52877..b0aaf85d 100644
--- a/crates/criterion_compat/src/compat/group.rs
+++ b/crates/criterion_compat/src/compat/group.rs
@@ -62,13 +62,25 @@ impl<'a, M: Measurement> BenchmarkGroup<'a, M> {
         F: FnMut(&mut Bencher, &I),
         I: ?Sized,
     {
-        let git_relative_file_path = get_git_relative_path(&self.current_file);
-        let mut uri = format!(
-            "{}::{}::{}",
-            git_relative_file_path.to_string_lossy(),
-            self.macro_group,
-            self.group_name,
-        );
+        let mut uri = String::new();
+
+        if !self.current_file.is_empty() {
+            let git_relative_file_path = get_git_relative_path(&self.current_file);
+            let file_str = git_relative_file_path.to_string_lossy();
+            if !file_str.is_empty() {
+                uri.push_str(&file_str);
+            }
+        }
+        if !self.macro_group.is_empty() {
+            if !uri.is_empty() {
+                uri.push_str("::");
+            }
+            uri.push_str(&self.macro_group);
+        }
+        if !uri.is_empty() {
+            uri.push_str("::");
+        }
+        uri.push_str(&self.group_name);
         if let Some(function_name) = id.function_name {
             uri = format!("{uri}::{function_name}");
         }