fix: prevent tool_rounds cross-cascade contamination causing hangs

Root cause: proxy.rs eagerly pushed tool rounds via push_tool_round_calls
when intercepting Google's functionCall response. These stale rounds leaked
into LS follow-up requests, producing malformed history that Google timed
out on (60s 'no upstream response').

Changes:
- Remove push_tool_round_calls from proxy.rs response interception
- proxy.rs: use get_tool_rounds (non-destructive) instead of take_tool_rounds
  so accumulated rounds persist across multiple LS requests per cascade
- responses.rs/gemini.rs: build rounds via take+push+set pattern — each
  handler accumulates its own rounds from get_last_function_calls + results
- completions.rs: unchanged (set_tool_rounds replaces from messages)
- clear_tools: also clears tool_rounds to prevent stale data between sessions
- store.rs: add get_tool_rounds (non-destructive clone) method

src/api/gemini.rs

@@ -229,14 +229,19 @@ pub(crate) async fn handle_gemini(
             }
         }
         if !pending.is_empty() {
-            state
-                .mitm_store
-                .attach_tool_round_results(pending)
-                .await;
+            // Build a ToolRound from captured function calls + client results.
+            // Accumulate with existing rounds for multi-round history rewriting.
+            let last_calls = state.mitm_store.get_last_function_calls().await;
+            let mut rounds = state.mitm_store.take_tool_rounds().await;
+            rounds.push(crate::mitm::store::ToolRound {
+                calls: last_calls,
+                results: pending,
+            });
+            state.mitm_store.set_tool_rounds(rounds).await;
         }
         info!(
             count = results.len(),
-            "Stored Gemini-native tool results for MITM injection (attached to tool round)"
+            "Stored Gemini-native tool results for MITM injection (built tool round)"
         );
     }
 

src/api/responses.rs

@@ -269,14 +269,19 @@ pub(crate) async fn handle_responses(
                 result: result_value,
             });
         }
-        // Attach results to the latest open ToolRound (pushed by proxy.rs)
-        state
-            .mitm_store
-            .attach_tool_round_results(pending)
-            .await;
+        // Build a ToolRound from the MITM-captured function calls + client results.
+        // get_last_function_calls() has the calls from Google's previous response.
+        // We take existing accumulated rounds and append this new round.
+        let last_calls = state.mitm_store.get_last_function_calls().await;
+        let mut rounds = state.mitm_store.take_tool_rounds().await;
+        rounds.push(crate::mitm::store::ToolRound {
+            calls: last_calls,
+            results: pending,
+        });
+        state.mitm_store.set_tool_rounds(rounds).await;
         info!(
             count = tool_results.len(),
-            "Stored tool results for MITM injection (attached to tool round)"
+            "Stored tool results for MITM injection (built tool round)"
         );
     }
 

src/mitm/proxy.rs

@@ -602,7 +602,7 @@ async fn handle_http_over_tls(
                     let last_calls = store.get_last_function_calls().await;
                     let generation_params = store.get_generation_params().await;
                     let pending_image = store.take_pending_image().await;
-                    let tool_rounds = store.take_tool_rounds().await;
+                    let tool_rounds = store.get_tool_rounds().await;
 
                     let tool_ctx = if tools.is_some()
                         || !pending_results.is_empty()
@@ -826,7 +826,6 @@ async fn handle_http_over_tls(
                                         .await;
                                 }
                                 store.set_last_function_calls(calls.clone()).await;
-                                store.push_tool_round_calls(calls.clone()).await;
                                 info!(
                                     "MITM: stored {} function call(s) from initial body",
                                     calls.len()
@@ -903,7 +902,6 @@ async fn handle_http_over_tls(
                                 .await;
                         }
                         store.set_last_function_calls(calls.clone()).await;
-                        store.push_tool_round_calls(calls.clone()).await;
                         info!(
                             "MITM: stored {} function call(s) from body chunk",
                             calls.len()

src/mitm/store.rs

@@ -484,6 +484,8 @@ impl MitmStore {
     pub async fn clear_tools(&self) {
         *self.active_tools.write().await = None;
         *self.active_tool_config.write().await = None;
+        // Also clear accumulated tool rounds to prevent stale data
+        self.tool_rounds.write().await.clear();
     }
 
     /// Set active tool config (Gemini toolConfig format).
@@ -537,6 +539,13 @@ impl MitmStore {
         std::mem::take(&mut *self.tool_rounds.write().await)
     }
 
+    /// Get (non-destructive clone) multi-round tool call history.
+    /// Used by proxy.rs to read rounds without consuming them, so they
+    /// persist across multiple LS requests in the same cascade.
+    pub async fn get_tool_rounds(&self) -> Vec<ToolRound> {
+        self.tool_rounds.read().await.clone()
+    }
+
     /// Push a new tool round from Google's response (calls only, results empty).
     /// Called by proxy.rs when the MITM intercepts functionCall parts.
     pub async fn push_tool_round_calls(&self, calls: Vec<CapturedFunctionCall>) {