Release exp-v0.52.175: identical-prompt retry settlement regression (#6631) (#6845)

* test: pin identical-prompt retry settlement

* Release exp-v0.52.175: two-direction regression for identical-prompt retry settlement (#6631)

---------

Co-authored-by: nesquena-hermes <nesquena-hermes@users.noreply.github.com>

CHANGELOG.md

@@ -15,6 +15,8 @@
 
 - **Internal: added regression coverage for the empty-`tool_calls` drop on the metadata-restoration mirror path.** `_api_safe_message_positions()` must apply the same `tool_calls: []` drop as the main API sanitizer (#5737) so metadata restoration never treats a `tool_calls: []` row as a distinct message; a new test pins that empty arrays lose the key while populated tool-call chains (and their tool results) survive untouched. Test-only, no production change. Thanks @webtecnica. (#6803, #6796)
 
+- **Internal: added a two-direction regression for identical-prompt retry settlement.** The active-turn ownership repair that resolves #6571 (settlement materializes the exact pending turn before checking for a terminal assistant answer) had no issue-specific coverage because the original reproduction omitted the runtime turn identity. A new test pins both directions through the real `_merged_transcript_lacks_final_assistant_answer()`: a successful identical-prompt retry keeps its terminal answer (not a `no_response`), while an otherwise-identical retry with no terminal answer still qualifies as a genuine failure. Test-only, no production change (a mutation bite — nulling the merge's `active_turn_identity` provenance — flips the successful case red, confirming the guard is live). (#6631, #6571)
+
 - **The busy-time send behavior is now called "Default message mode," and new installs default to Steer.** The Settings → Preferences control formerly labeled "Busy input mode" is renamed to "Default message mode," and a fresh install now defaults to **Steer** (inject a mid-turn correction without interrupting) instead of Queue. Your existing choice is preserved — if you ever saved settings, your current mode (Queue/Interrupt/Steer) is migrated as-is and unchanged; only never-configured installs pick up the new Steer default. The saved preference still survives a reload or a brief server outage (the localStorage mirror from the previous release is intact). Thanks @rodboev. (#5162, #5145)
 
 ### Added

tests/test_issue6571_identical_retry_settlement.py

@@ -0,0 +1,79 @@
+"""Regression coverage for #6571 identical-prompt retry settlement."""
+
+from __future__ import annotations
+
+from api import streaming
+
+
+PROMPT = "Apply the two requested configuration updates."
+
+
+def _previous_turns():
+    previous_display = [
+        {"role": "user", "content": "Earlier task", "id": 1},
+        {"role": "assistant", "content": "Earlier answer", "id": 2},
+        {"role": "user", "content": PROMPT, "id": 10},
+    ]
+    return previous_display, previous_display[:2]
+
+
+def _active_turn_identity():
+    return {
+        "token": "direct-stream:2",
+        "text": PROMPT,
+        "timestamp": 2.0,
+        "source": "webui",
+        "attachments": [],
+        "current_turn_user_idx": 2,
+        "turn_id": "turn-2",
+    }
+
+
+def _lacks_final_answer(result_messages):
+    previous_display, previous_context = _previous_turns()
+    return streaming._merged_transcript_lacks_final_assistant_answer(
+        previous_display,
+        previous_context,
+        result_messages,
+        PROMPT,
+        source="webui",
+        drop_replayed_assistant=False,
+        active_turn_identity=_active_turn_identity(),
+    )
+
+
+def test_successful_identical_prompt_retry_keeps_terminal_answer():
+    _previous_display, previous_context = _previous_turns()
+    result_messages = previous_context + [
+        {"role": "user", "content": PROMPT, "id": 11},
+        {"role": "assistant", "content": "Working on it.", "id": 12},
+        {
+            "role": "tool",
+            "content": "update succeeded",
+            "tool_call_id": "tool-1",
+            "id": 13,
+        },
+        {
+            "role": "assistant",
+            "content": "Both changes were applied and verified.",
+            "id": 14,
+        },
+    ]
+
+    assert _lacks_final_answer(result_messages) is False
+
+
+def test_failed_identical_prompt_retry_still_lacks_terminal_answer():
+    _previous_display, previous_context = _previous_turns()
+    result_messages = previous_context + [
+        {"role": "user", "content": PROMPT, "id": 11},
+        {"role": "assistant", "content": "Working on it.", "id": 12},
+        {
+            "role": "tool",
+            "content": "update failed",
+            "tool_call_id": "tool-1",
+            "id": 13,
+        },
+    ]
+
+    assert _lacks_final_answer(result_messages) is True