From 9e80e42b4dcb81b4e5bf64d14ed9ba72e6b95f20 Mon Sep 17 00:00:00 2001
From: Dmitriy Kovalenko <dmtr.kovalenko@outlook.com>
Date: Sun, 23 Aug 2026 21:22:49 -0700
Subject: [PATCH] refactor(fff-mcp): match multi_grep context rounding

---
 crates/fff-mcp/src/server.rs | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/crates/fff-mcp/src/server.rs b/crates/fff-mcp/src/server.rs
index fed78683a..cd2cacfb1 100644
--- a/crates/fff-mcp/src/server.rs
+++ b/crates/fff-mcp/src/server.rs
@@ -13,6 +13,8 @@ use std::time::{SystemTime, UNIX_EPOCH};
 
 const SCAN_READY_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(30);
 
+const MAX_CONTEXT_LINES: usize = 100;
+
 fn normalize_max_results(raw: Option<f64>, default: usize) -> usize {
     match raw {
         None => default,
@@ -21,6 +23,15 @@ fn normalize_max_results(raw: Option<f64>, default: usize) -> usize {
     }
 }
 
+// Context lines are copied per match, so a bogus float must not saturate to usize::MAX.
+fn normalize_context(raw: Option<f64>) -> Option<usize> {
+    let v = raw?;
+    if !v.is_finite() || v < 0.0 {
+        return None;
+    }
+    Some((v.round() as usize).min(MAX_CONTEXT_LINES))
+}
+
 fn cleanup_fuzzy_query(s: &str) -> String {
     let mut out = String::with_capacity(s.len());
     for c in s.chars() {
@@ -101,6 +112,8 @@ pub struct GrepParams {
     pub cursor: Option<String>,
     /// Output format (default 'content').
     pub output_mode: Option<String>,
+    /// Context lines before/after each match.
+    pub context: Option<f64>,
 }
 
 fn deserialize_patterns<'de, D>(deserializer: D) -> Result<Vec<String>, D::Error>
@@ -572,7 +585,7 @@ impl FffServer {
             max_results,
             params.cursor.as_deref(),
             output_mode,
-            None,
+            normalize_context(params.context),
         )?;
         self.maybe_append_update_notice(&mut result);
         Ok(result)
@@ -605,7 +618,7 @@ impl FffServer {
 impl FffServer {
     fn multi_grep_inner(&self, params: MultiGrepParams) -> Result<CallToolResult, ErrorData> {
         let max_results = normalize_max_results(params.max_results, 20);
-        let context = params.context.map(|v| v.round() as usize);
+        let context = normalize_context(params.context);
         let output_mode = OutputMode::new(params.output_mode.as_deref());
 
         let file_offset = params
@@ -720,6 +733,22 @@ mod tests {
         assert_eq!(via_pattern.query, "foo");
     }
 
+    #[test]
+    fn normalize_context_rejects_bogus_and_caps() {
+        assert_eq!(normalize_context(None), None);
+        assert_eq!(normalize_context(Some(3.4)), Some(3));
+        assert_eq!(normalize_context(Some(-1.0)), None);
+        assert_eq!(normalize_context(Some(f64::NAN)), None);
+        assert_eq!(normalize_context(Some(1e308)), Some(MAX_CONTEXT_LINES));
+    }
+
+    #[test]
+    fn grep_params_parses_context() {
+        let params: GrepParams =
+            serde_json::from_str(r#"{"query":"foo","context":3}"#).expect("context field");
+        assert_eq!(params.context, Some(3.0));
+    }
+
     #[test]
     fn find_files_params_accepts_pattern_alias() {
         let via_query: FindFilesParams =