Add test for ctrlc cancellation after tool execution

Test verifies that sending SIGINT during tool execution stops processing
after that tool completes and prevents subsequent tool calls from running.
Conversation state is preserved in the chat file.

tests/CMakeLists.txt

@@ -20,6 +20,7 @@ add_dr_test(test_tool_list_files)
 add_dr_test(test_tool_grep)
 add_dr_test(test_tool_shell)
 add_dr_test(test_tool_shell_ctrlc)
+add_dr_test(test_ctrlc_after_tool)
 add_dr_test(test_tool_read_multi_modal)
 
 # Add feature validation tests

tests/test_ctrlc_after_tool.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+# test_ctrlc_after_tool.sh - Test ctrlc (SIGINT) handling between tool calls
+
+# Create mock responses: two tool calls followed by a final response
+# First tool sleeps 5 seconds, second tool is instant
+# We send SIGINT during the first tool's execution (at 3s)
+# The new ctrlc check after tool execution should catch it at 5s
+tool_call run_dangerous_shell '{"command":"sleep 5","timeout_seconds":10}' >> mock_ctrlc_between_tools.txt
+tool_call run_dangerous_shell '{"command":"echo second_tool","timeout_seconds":5}' >> mock_ctrlc_between_tools.txt
+be_done 'Final response' >> mock_ctrlc_between_tools.txt
+
+# Run drharness in background
+"${DRHARNESS}" -F chat_ctrlc.json -n -m "Test ctrlc between tools" -t run_dangerous_shell -d < "mock_ctrlc_between_tools.txt" > /dev/null 2>&1 &
+DRHARNESS_PID=$!
+
+# Send SIGINT at 3s - during first tool's sleep
+sleep 3
+kill -SIGINT $DRHARNESS_PID 2>/dev/null || true
+
+# Wait for drharness to complete (first tool finishes at 5s, then ctrlc check catches it)
+wait $DRHARNESS_PID 2>/dev/null || true
+
+# Verify the chat file exists and has the conversation state preserved
+if [ ! -f chat_ctrlc.json ]; then
+    echo "FAIL: chat_ctrlc.json was not created"
+    exit 1
+fi
+
+# Check that we have exactly 3 history entries: user message, assistant tool call, tool result
+# The second tool call should NOT have executed because ctrlc was caught after first tool
+HISTORY_LENGTH=$(history_length chat_ctrlc.json)
+
+if [ "$HISTORY_LENGTH" -ne 3 ]; then
+    echo "FAIL: Expected exactly 3 history entries (user, assistant, tool), got $HISTORY_LENGTH"
+    echo "This indicates the second tool call was not cancelled properly"
+    cat chat_ctrlc.json
+    exit 1
+fi
+
+# Verify user message is present
+USER_ROLE=$(dr_role chat_ctrlc.json 0)
+if [ "$USER_ROLE" != "user" ]; then
+    echo "FAIL: Expected user role at index 0, got $USER_ROLE"
+    exit 1
+fi
+
+# Verify assistant with tool call is present
+ASSISTANT_ROLE=$(dr_role chat_ctrlc.json 1)
+if [ "$ASSISTANT_ROLE" != "assistant" ]; then
+    echo "FAIL: Expected assistant role at index 1, got $ASSISTANT_ROLE"
+    exit 1
+fi
+
+# Verify tool result is present
+TOOL_ROLE=$(dr_role chat_ctrlc.json 2)
+if [ "$TOOL_ROLE" != "tool" ]; then
+    echo "FAIL: Expected tool role at index 2, got $TOOL_ROLE"
+    exit 1
+fi
+
+echo "PASS: ctrlc_after_tool"