diff --git a/api/streaming.py b/api/streaming.py
index 8251c2e42..c31883d16 100644
--- a/api/streaming.py
+++ b/api/streaming.py
@@ -74,6 +74,11 @@ def _session_payload_with_full_messages(session, *, tool_calls=None):
     return raw
 
 
+def _compact_for_echo_compare(value: str) -> str:
+    """Normalize visible stream text for duplicate echo detection."""
+    return re.sub(r'\s+', '', str(value or ''))
+
+
 # Global lock for os.environ writes. Per-session locks (_agent_lock) prevent
 # concurrent runs of the SAME session, but two DIFFERENT sessions can still
 # interleave their os.environ writes. This global lock serializes the env
@@ -6347,9 +6352,6 @@ def _run_agent_streaming(
                 stats.setdefault('estimated', False)
                 put('metering', stats)
 
-            def _compact_for_echo_compare(value: str) -> str:
-                return re.sub(r'\s+', '', str(value or ''))
-
             def _is_visible_output_echo(text: str) -> bool:
                 candidate = _compact_for_echo_compare(text)
                 if not candidate:
diff --git a/tests/test_run_journal_streaming_static.py b/tests/test_run_journal_streaming_static.py
index 6ab50d89c..a25421715 100644
--- a/tests/test_run_journal_streaming_static.py
+++ b/tests/test_run_journal_streaming_static.py
@@ -1,5 +1,7 @@
 from pathlib import Path
 
+from api.streaming import _compact_for_echo_compare
+
 
 def test_streaming_initializes_one_run_journal_writer_per_stream():
     src = Path("api/streaming.py").read_text(encoding="utf-8")
@@ -24,12 +26,7 @@ def test_streaming_journals_sse_events_before_queue_delivery():
 
 
 def test_visible_process_echo_compare_ignores_all_whitespace():
-    src = Path("api/streaming.py").read_text(encoding="utf-8")
-    helper_idx = src.index("def _compact_for_echo_compare(value: str) -> str:")
-    helper = src[helper_idx:src.index("def _is_visible_output_echo", helper_idx)]
+    token_text = "先把 issue 4249 拉下来\n\n先看正文和评论"
+    interim_text = "先把 issue 4249 拉下来先看正文和评论"
 
-    assert "re.sub(r'\\s+', '', str(value or ''))" in helper, (
-        "Visible process-prose echo detection must ignore paragraph and line-break "
-        "formatting so interim_assistant does not duplicate token prose that only "
-        "differs by whitespace."
-    )
+    assert _compact_for_echo_compare(token_text) == _compact_for_echo_compare(interim_text)