diff --git a/crates/g3-core/tests/streaming_parser_stuttering_test.rs b/crates/g3-core/tests/streaming_parser_stuttering_test.rs
new file mode 100644
index 0000000..4e3fc8a
--- /dev/null
+++ b/crates/g3-core/tests/streaming_parser_stuttering_test.rs
@@ -0,0 +1,240 @@
+//! Integration tests for streaming parser stuttering bug fix (fa3c920)
+//!
+//! BEHAVIOR PROTECTED:
+//! When an LLM "stutters" and emits incomplete tool call fragments followed by
+//! complete tool calls, the parser should:
+//! 1. Not get stuck waiting for the incomplete fragment to complete
+//! 2. Successfully parse complete tool calls that appear after the fragment
+//!
+//! SURFACE TARGETED:
+//! StreamingToolParser - the public API for processing streaming chunks
+//!
+//! INTENTIONALLY NOT ASSERTED:
+//! - Internal parser state transitions
+//! - Specific invalidation mechanism details
+//! - Order of internal operations
+//! - Behavior of patterns that don't match the actual bug scenario
+
+use g3_core::StreamingToolParser;
+use g3_providers::CompletionChunk;
+
+/// Helper to create a completion chunk
+fn chunk(content: &str, finished: bool) -> CompletionChunk {
+    CompletionChunk {
+        content: content.to_string(),
+        finished,
+        tool_calls: None,
+        usage: None,
+        stop_reason: None,
+        tool_call_streaming: None,
+    }
+}
+
+// =============================================================================
+// CHARACTERIZATION: The exact stuttering pattern from the bug report
+// =============================================================================
+
+/// Test the exact pattern observed in butler session butler_c6ab59af2e4f991c
+/// where the LLM emitted: complete -> incomplete fragment -> complete
+///
+/// This is the critical bug fix test - before the fix, the parser would get
+/// stuck on the incomplete fragment and return zero tool calls.
+#[test]
+fn test_stuttering_complete_incomplete_complete() {
+    let mut parser = StreamingToolParser::new();
+
+    // This is the exact pattern that caused the bug:
+    // 1. Complete tool call
+    // 2. Incomplete fragment (just {"tool":)
+    // 3. Complete tool call again
+    let content = r#"{"tool": "shell", "args": {"command": "ls"}}
+
+{"tool":
+
+{"tool": "shell", "args": {"command": "pwd"}}"#;
+
+    let tools = parser.process_chunk(&chunk(content, true));
+
+    // CRITICAL: We must get at least one valid tool call
+    // Before the fix, the parser would get stuck on the incomplete fragment
+    // and return zero tool calls
+    assert!(
+        !tools.is_empty(),
+        "Parser must not get stuck on incomplete fragment. Expected tool calls, got none."
+    );
+
+    // Verify we got valid tool calls (at least one should be "shell")
+    assert!(
+        tools.iter().any(|t| t.tool == "shell"),
+        "Expected at least one 'shell' tool call"
+    );
+}
+
+/// Verify the parser finds at least one complete tool call even with stuttering
+#[test]
+fn test_stuttering_finds_at_least_one_complete_call() {
+    let mut parser = StreamingToolParser::new();
+
+    // Complete -> incomplete -> complete with different commands
+    let content = r#"{"tool": "shell", "args": {"command": "first"}}
+
+{"tool":
+
+{"tool": "shell", "args": {"command": "second"}}"#;
+
+    let tools = parser.process_chunk(&chunk(content, true));
+
+    // CHARACTERIZATION: The parser finds at least one complete tool call.
+    // The exact number depends on implementation details (streaming vs batch parsing).
+    // The critical behavior is that it doesn't return zero (the original bug).
+    assert!(
+        !tools.is_empty(),
+        "Expected at least 1 tool call, got none"
+    );
+}
+
+// =============================================================================
+// CHARACTERIZATION: Edge cases that should NOT trigger invalidation
+// =============================================================================
+
+/// Tool call patterns inside JSON strings should not cause invalidation
+#[test]
+fn test_tool_pattern_in_string_value_not_invalidated() {
+    let mut parser = StreamingToolParser::new();
+
+    // Writing example code that contains a tool call pattern
+    let content = r#"{"tool": "write_file", "args": {"file_path": "example.md", "content": "Example:\n{\"tool\": \"shell\"}"}}"#;
+
+    let tools = parser.process_chunk(&chunk(content, true));
+
+    // Should parse the outer tool call correctly
+    assert_eq!(tools.len(), 1);
+    assert_eq!(tools[0].tool, "write_file");
+    // The inner pattern should be part of the content, not a separate tool call
+    assert!(tools[0].args["content"]
+        .as_str()
+        .unwrap()
+        .contains("{\"tool\""));
+}
+
+/// Nested JSON objects should not trigger false invalidation
+#[test]
+fn test_nested_json_not_invalidated() {
+    let mut parser = StreamingToolParser::new();
+
+    // Tool call with nested JSON in args
+    let content = r#"{"tool": "shell", "args": {"command": "echo '{\"nested\": true}'"}}"#;
+
+    let tools = parser.process_chunk(&chunk(content, true));
+
+    assert_eq!(tools.len(), 1);
+    assert_eq!(tools[0].tool, "shell");
+}
+
+// =============================================================================
+// CHARACTERIZATION: Recovery behavior
+// =============================================================================
+
+/// Parser should work correctly after reset
+#[test]
+fn test_parser_reset_clears_state() {
+    let mut parser = StreamingToolParser::new();
+
+    // First: process content with stuttering
+    let content1 = r#"{"tool": "shell", "args": {"command": "ls"}}
+
+{"tool":
+
+{"tool": "shell", "args": {"command": "pwd"}}"#;
+    let _tools1 = parser.process_chunk(&chunk(content1, true));
+
+    // Reset for new message
+    parser.reset();
+
+    // Second message should work normally
+    let content2 = r#"{"tool": "read_file", "args": {"file_path": "test.txt"}}"#;
+    let tools2 = parser.process_chunk(&chunk(content2, true));
+
+    assert_eq!(tools2.len(), 1);
+    assert_eq!(tools2[0].tool, "read_file");
+}
+
+/// Incomplete tool call detection works
+#[test]
+fn test_incomplete_detection() {
+    let mut parser = StreamingToolParser::new();
+
+    // Incomplete fragment
+    parser.process_chunk(&chunk("{\"tool\":", false));
+    assert!(
+        parser.has_incomplete_tool_call(),
+        "Should detect incomplete tool call"
+    );
+}
+
+// =============================================================================
+// CHARACTERIZATION: Multiple complete tool calls (no stuttering)
+// =============================================================================
+
+/// Multiple complete tool calls should all be found
+#[test]
+fn test_multiple_complete_tool_calls() {
+    let mut parser = StreamingToolParser::new();
+
+    let content = r#"{"tool": "shell", "args": {"command": "ls"}}
+
+{"tool": "read_file", "args": {"file_path": "test.txt"}}"#;
+
+    let tools = parser.process_chunk(&chunk(content, true));
+
+    assert_eq!(tools.len(), 2, "Should find both tool calls");
+    assert_eq!(tools[0].tool, "shell");
+    assert_eq!(tools[1].tool, "read_file");
+}
+
+// =============================================================================
+// CHARACTERIZATION: Boundary conditions
+// =============================================================================
+
+/// Minimal stutter pattern with complete call first
+#[test]
+fn test_minimal_stutter_with_complete_first() {
+    let mut parser = StreamingToolParser::new();
+
+    // Complete call, then incomplete, then complete
+    let content = r#"{"tool": "shell", "args": {}}
+{"tool":
+{"tool": "shell", "args": {}}"#;
+
+    let tools = parser.process_chunk(&chunk(content, true));
+
+    assert!(!tools.is_empty(), "Should find at least one complete tool call");
+}
+
+/// Stutter at chunk boundary - incomplete in one chunk, complete in next
+#[test]
+fn test_stutter_split_across_chunk_boundary() {
+    let mut parser = StreamingToolParser::new();
+
+    // First chunk: complete tool call
+    let tools1 = parser.process_chunk(&chunk(
+        r#"{"tool": "shell", "args": {"command": "ls"}}"#,
+        false,
+    ));
+    assert_eq!(tools1.len(), 1, "First complete tool call should be detected");
+
+    // Mark as consumed
+    parser.mark_tool_calls_consumed();
+
+    // Second chunk: incomplete fragment
+    parser.process_chunk(&chunk("\n{\"tool\":", false));
+
+    // Third chunk: new complete tool call (finished)
+    let tools3 = parser.process_chunk(&chunk(
+        "\n{\"tool\": \"read_file\", \"args\": {\"file_path\": \"test.txt\"}}",
+        true,
+    ));
+
+    // Should find the complete tool call at stream end
+    assert!(!tools3.is_empty(), "Should find complete tool call at stream end");
+}