diff --git a/CHANGELOG.md b/CHANGELOG.md
index f220e82d6..21a5f3178 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,12 @@
 
 ## [Unreleased]
 
+## [v0.51.585] — 2026-06-22 — Release UR (suppress duplicate live process echoes)
+
+### Fixed
+
+- **Live progress text no longer appears twice during streaming.** When the same process prose surfaced through both the visible assistant stream and the live Thinking/interim updates (differing only by paragraph or line-break formatting), it could render duplicated. The server-side visible-output echo detection now ignores all whitespace when comparing, so an `interim_assistant` update that only reformats already-visible token prose is correctly recognized as an echo and suppressed at the source. Thanks @franksong2702. (#4689)
+
 ## [v0.51.584] — 2026-06-22 — Release UQ (freeze /api/sessions cache during streaming)
 
 ### Fixed
diff --git a/api/streaming.py b/api/streaming.py
index 81d2a3dac..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 '')).strip()
-
             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 ea455a13c..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")
@@ -21,3 +23,10 @@ def test_streaming_journals_sse_events_before_queue_delivery():
     assert put_idx < journal_idx < queue_idx
     assert "Failed to append run journal event" in block
     assert "queue_item = (event, data, event_id) if event_id and hasattr(q, \"subscribe_with_snapshot\") else (event, data)" in block
+
+
+def test_visible_process_echo_compare_ignores_all_whitespace():
+    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 _compact_for_echo_compare(token_text) == _compact_for_echo_compare(interim_text)