[mcp-server] Expose fuzzy file search in MCP (#2677)

## Summary
Expose a simple fuzzy file search implementation for mcp clients to work
with

## Testing
- [x] Tested locally

codex-rs/mcp-server/tests/common/mcp_process.rs

@@ -357,6 +357,23 @@ impl McpProcess {
         self.send_request("logoutChatGpt", None).await
     }
 
+    /// Send a `fuzzyFileSearch` JSON-RPC request.
+    pub async fn send_fuzzy_file_search_request(
+        &mut self,
+        query: &str,
+        roots: Vec<String>,
+        cancellation_token: Option<String>,
+    ) -> anyhow::Result<i64> {
+        let mut params = serde_json::json!({
+            "query": query,
+            "roots": roots,
+        });
+        if let Some(token) = cancellation_token {
+            params["cancellationToken"] = serde_json::json!(token);
+        }
+        self.send_request("fuzzyFileSearch", Some(params)).await
+    }
+
     async fn send_request(
         &mut self,
         method: &str,

codex-rs/mcp-server/tests/suite/fuzzy_file_search.rs

@@ -0,0 +1,104 @@
+use mcp_test_support::McpProcess;
+use mcp_types::JSONRPCResponse;
+use mcp_types::RequestId;
+use pretty_assertions::assert_eq;
+use serde_json::json;
+use tempfile::TempDir;
+use tokio::time::timeout;
+
+const DEFAULT_READ_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(10);
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_fuzzy_file_search_sorts_and_includes_indices() {
+    // Prepare a temporary Codex home and a separate root with test files.
+    let codex_home = TempDir::new().expect("create temp codex home");
+    let root = TempDir::new().expect("create temp search root");
+
+    // Create files designed to have deterministic ordering for query "abc".
+    std::fs::write(root.path().join("abc"), "x").expect("write file abc");
+    std::fs::write(root.path().join("abcde"), "x").expect("write file abcx");
+    std::fs::write(root.path().join("abexy"), "x").expect("write file abcx");
+    std::fs::write(root.path().join("zzz.txt"), "x").expect("write file zzz");
+
+    // Start MCP server and initialize.
+    let mut mcp = McpProcess::new(codex_home.path()).await.expect("spawn mcp");
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize())
+        .await
+        .expect("init timeout")
+        .expect("init failed");
+
+    let root_path = root.path().to_string_lossy().to_string();
+    // Send fuzzyFileSearch request.
+    let request_id = mcp
+        .send_fuzzy_file_search_request("abe", vec![root_path.clone()], None)
+        .await
+        .expect("send fuzzyFileSearch");
+
+    // Read response and verify shape and ordering.
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await
+    .expect("fuzzyFileSearch timeout")
+    .expect("fuzzyFileSearch resp");
+
+    let value = resp.result;
+    assert_eq!(
+        value,
+        json!({
+            "files": [
+                { "root": root_path.clone(), "path": "abexy", "score": 88, "indices": [0, 1, 2] },
+                { "root": root_path.clone(), "path": "abcde", "score": 74, "indices": [0, 1, 4] },
+            ]
+        })
+    );
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_fuzzy_file_search_accepts_cancellation_token() {
+    let codex_home = TempDir::new().expect("create temp codex home");
+    let root = TempDir::new().expect("create temp search root");
+
+    std::fs::write(root.path().join("alpha.txt"), "contents").expect("write alpha");
+
+    let mut mcp = McpProcess::new(codex_home.path()).await.expect("spawn mcp");
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize())
+        .await
+        .expect("init timeout")
+        .expect("init failed");
+
+    let root_path = root.path().to_string_lossy().to_string();
+    let request_id = mcp
+        .send_fuzzy_file_search_request("alp", vec![root_path.clone()], None)
+        .await
+        .expect("send fuzzyFileSearch");
+
+    let request_id_2 = mcp
+        .send_fuzzy_file_search_request(
+            "alp",
+            vec![root_path.clone()],
+            Some(request_id.to_string()),
+        )
+        .await
+        .expect("send fuzzyFileSearch");
+
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id_2)),
+    )
+    .await
+    .expect("fuzzyFileSearch timeout")
+    .expect("fuzzyFileSearch resp");
+
+    let files = resp
+        .result
+        .get("files")
+        .and_then(|value| value.as_array())
+        .cloned()
+        .expect("files array");
+
+    assert_eq!(files.len(), 1);
+    assert_eq!(files[0]["root"], root_path);
+    assert_eq!(files[0]["path"], "alpha.txt");
+}

codex-rs/mcp-server/tests/suite/mod.rs

@@ -5,6 +5,7 @@ mod codex_message_processor_flow;
 mod codex_tool;
 mod config;
 mod create_conversation;
+mod fuzzy_file_search;
 mod interrupt;
 mod list_resume;
 mod login;