diff --git a/src/comfydv/_llm/chat.py b/src/comfydv/_llm/chat.py
index b45283c..dca8bef 100644
--- a/src/comfydv/_llm/chat.py
+++ b/src/comfydv/_llm/chat.py
@@ -136,7 +136,26 @@ async def chat_structured(
             # top-level "seed" param, which works against both Ollama's and
             # llama-server's OpenAI-compatible endpoints) and give it a beat
             # via RETRY_BACKOFF_SECS in case it's still finishing loading.
-            attempt_settings["seed"] = next_seed(options, attempt)
+            seed = next_seed(options, attempt)
+            attempt_settings["seed"] = seed
+            if "extra_body" in attempt_settings:
+                # beacon-reviewer caught this: if a caller pinned options["seed"],
+                # it's also sitting in extra_body.options.seed (the Ollama-native
+                # passthrough). Left untouched, a backend that honors that nested
+                # field over the top-level OpenAI "seed" above would keep sending
+                # the same old seed on every retry — silently defeating this fix
+                # for exactly the pinned-seed case. Copy rather than mutate in
+                # place: extra_body/options here are the caller's own dicts,
+                # shared across every attempt (and possibly other calls).
+                # ModelSettings declares extra_body as `object` (it's an
+                # opaque passthrough field), so a plain dict() call on it
+                # doesn't type-check — cast first, this module always builds
+                # it as a dict (see model_settings above).
+                extra_body = dict(cast(dict, attempt_settings["extra_body"]))
+                nested_options = dict(extra_body.get("options") or {})
+                nested_options["seed"] = seed
+                extra_body["options"] = nested_options
+                attempt_settings["extra_body"] = extra_body
         try:
             result = await agent.run(
                 prompt,
diff --git a/tests/test_llm_chat_structured.py b/tests/test_llm_chat_structured.py
index b9f2ce2..ea57ed6 100644
--- a/tests/test_llm_chat_structured.py
+++ b/tests/test_llm_chat_structured.py
@@ -244,7 +244,33 @@ def test_chat_structured_retry_seed_starts_from_pinned_base(monkeypatch):
 
     assert fake.calls[0][2] == {"extra_body": {"options": {"seed": 42}}}
     assert fake.calls[1][2]["seed"] == 43  # base(42) + (attempt 2 - 1)
-    assert fake.calls[1][2]["extra_body"] == {"options": {"seed": 42}}
+    # The nested Ollama-native options.seed must track the same retry seed as
+    # the top-level one — a backend that honors the nested field over the
+    # top-level OpenAI "seed" must not keep seeing the stale pinned value.
+    assert fake.calls[1][2]["extra_body"] == {"options": {"seed": 43}}
+
+
+def test_chat_structured_retry_does_not_mutate_callers_options_dict(monkeypatch):
+    """Regression guard for the fix above: syncing the nested seed must copy,
+    not mutate, the caller's options dict — otherwise a second call reusing
+    the same options object would start from the wrong base seed."""
+    bad = ValidationError.from_exception_data("Widget", [])
+    fake = _FakeAgent([bad, _Widget(name="c", count=3)])
+    monkeypatch.setattr(chat_mod, "_build_agent", lambda **kw: fake)
+
+    caller_options = {"seed": 42}
+    _run_async(
+        chat_mod.chat_structured(
+            base_url="http://localhost:11434/v1",
+            model="llama3",
+            messages=_messages(),
+            schema=_Widget,
+            options=caller_options,
+            max_retries=2,
+        )
+    )
+
+    assert caller_options == {"seed": 42}
 
 
 def test_chat_structured_retry_sleeps_between_attempts(monkeypatch):