diff --git a/codex-rs/tools/src/file_ref.rs b/codex-rs/tools/src/file_ref.rs
new file mode 100644
index 0000000000..26bf4b30d6
--- /dev/null
+++ b/codex-rs/tools/src/file_ref.rs
@@ -0,0 +1,134 @@
+use std::fmt;
+
+/// Fully qualified reference to a file-like asset known to Code Mode.
+///
+/// The scheme tells the file broker which provider owns the asset. The broker
+/// should keep provider-specific credentials and bytes out of model-visible
+/// arguments while still letting Code Mode pass stable refs between tools.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct FileRef {
+    raw: String,
+    scheme: FileScheme,
+    body: String,
+}
+
+impl FileRef {
+    pub fn parse(raw: impl Into<String>) -> Result<Self, FileRefParseError> {
+        let raw = raw.into();
+        let Some((scheme, body)) = raw.split_once("://") else {
+            return Err(FileRefParseError::MissingScheme);
+        };
+        if body.is_empty() {
+            return Err(FileRefParseError::MissingBody);
+        }
+        let scheme = FileScheme::parse(scheme)?;
+        let body = body.to_string();
+        Ok(Self { raw, scheme, body })
+    }
+
+    pub fn raw(&self) -> &str {
+        &self.raw
+    }
+
+    pub fn scheme(&self) -> FileScheme {
+        self.scheme
+    }
+
+    pub fn body(&self) -> &str {
+        &self.body
+    }
+}
+
+/// Provider family that owns a file ref.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum FileScheme {
+    Env,
+    Library,
+    Connector,
+    Other,
+}
+
+impl FileScheme {
+    fn parse(scheme: &str) -> Result<Self, FileRefParseError> {
+        if scheme.is_empty() {
+            return Err(FileRefParseError::MissingScheme);
+        }
+        if !scheme
+            .chars()
+            .all(|ch| ch.is_ascii_lowercase() || ch.is_ascii_digit() || ch == '_' || ch == '-')
+        {
+            return Err(FileRefParseError::InvalidScheme(scheme.to_string()));
+        }
+        Ok(match scheme {
+            "env" => Self::Env,
+            "oai_library" => Self::Library,
+            "connector" => Self::Connector,
+            _ => Self::Other,
+        })
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum FileRefParseError {
+    MissingScheme,
+    InvalidScheme(String),
+    MissingBody,
+}
+
+impl fmt::Display for FileRefParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::MissingScheme => write!(f, "file ref must start with a provider scheme"),
+            Self::InvalidScheme(scheme) => write!(f, "invalid file ref scheme `{scheme}`"),
+            Self::MissingBody => write!(f, "file ref must include a provider-owned path or id"),
+        }
+    }
+}
+
+impl std::error::Error for FileRefParseError {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn parses_env_file_ref() {
+        assert_eq!(
+            FileRef::parse("env://current/work/report.pdf"),
+            Ok(FileRef {
+                raw: "env://current/work/report.pdf".to_string(),
+                scheme: FileScheme::Env,
+                body: "current/work/report.pdf".to_string(),
+            })
+        );
+    }
+
+    #[test]
+    fn classifies_known_provider_schemes() {
+        assert_eq!(
+            FileRef::parse("oai_library://file_123")
+                .expect("library ref should parse")
+                .scheme(),
+            FileScheme::Library
+        );
+        assert_eq!(
+            FileRef::parse("connector://google_drive/file_123")
+                .expect("connector ref should parse")
+                .scheme(),
+            FileScheme::Connector
+        );
+    }
+
+    #[test]
+    fn rejects_ambiguous_refs() {
+        assert_eq!(
+            FileRef::parse("report.pdf"),
+            Err(FileRefParseError::MissingScheme)
+        );
+        assert_eq!(
+            FileRef::parse("env://"),
+            Err(FileRefParseError::MissingBody)
+        );
+    }
+}
diff --git a/codex-rs/tools/src/lib.rs b/codex-rs/tools/src/lib.rs
index 2a87ba35d7..3441d6192e 100644
--- a/codex-rs/tools/src/lib.rs
+++ b/codex-rs/tools/src/lib.rs
@@ -3,6 +3,7 @@
 
 mod code_mode;
 mod dynamic_tool;
+mod file_ref;
 mod function_call_error;
 mod image_detail;
 mod json_schema;
@@ -25,6 +26,9 @@ pub use code_mode::collect_code_mode_tool_definitions;
 pub use code_mode::tool_spec_to_code_mode_tool_definition;
 pub use codex_protocol::ToolName;
 pub use dynamic_tool::parse_dynamic_tool;
+pub use file_ref::FileRef;
+pub use file_ref::FileRefParseError;
+pub use file_ref::FileScheme;
 pub use function_call_error::FunctionCallError;
 pub use image_detail::can_request_original_image_detail;
 pub use image_detail::normalize_output_image_detail;