diff --git a/services/hermes/agent-deployment.yaml b/services/hermes/agent-deployment.yaml
index 77228b6e6..4e94c9671 100644
--- a/services/hermes/agent-deployment.yaml
+++ b/services/hermes/agent-deployment.yaml
@@ -25,7 +25,7 @@ spec:
         ai.bstein.dev/execution: Hermes Kanban with durable direct Codex and Claude Code CLI workers
         ai.bstein.dev/model-policy: Jetson-assisted AUTO routing, low through xhigh, cross-provider fallback
         ai.bstein.dev/placement: rpi5 preferred; Jetson deferred until state storage is available
-        ai.bstein.dev/config-rev: "20260812-stream-tool-failover"
+        ai.bstein.dev/config-rev: "20260812-deduplicate-tool-stream"
         vault.hashicorp.com/agent-inject: "true"
         vault.hashicorp.com/role: hermes-agent
         vault.hashicorp.com/agent-inject-secret-anthropic-token: kv/data/atlas/hermes/agent-tokens
diff --git a/services/hermes/scripts/codex_broker.py b/services/hermes/scripts/codex_broker.py
index 6f34c4520..2d950547b 100644
--- a/services/hermes/scripts/codex_broker.py
+++ b/services/hermes/scripts/codex_broker.py
@@ -273,17 +273,35 @@ def _normalized_stream(body: bytes, completed: dict[str, Any]) -> bytes:
     """Return Responses SSE with the reconstructed terminal response attached."""
     normalized: list[str] = []
     replaced_terminal = False
+    skip_event_data = False
     for line in body.decode("utf-8", errors="replace").splitlines():
+        if line == "event: response.function_call_arguments.done":
+            # Switchyard translates both the argument deltas and this terminal
+            # snapshot into Chat Completions deltas.  That duplicates the JSON
+            # object and Hermes mistakes the result for provider truncation.
+            # The preceding deltas are complete and already validated by
+            # ``_completed_response``; suppress only the redundant snapshot.
+            skip_event_data = True
+            continue
         if line.startswith("data:"):
             value = line[5:].strip()
             try:
                 event = json.loads(value)
             except (TypeError, ValueError, json.JSONDecodeError):
                 event = None
+            if (
+                skip_event_data
+                or isinstance(event, dict)
+                and event.get("type") == "response.function_call_arguments.done"
+            ):
+                skip_event_data = False
+                continue
             if isinstance(event, dict) and event.get("type") == "response.completed":
                 event["response"] = completed
                 line = "data: " + json.dumps(event, separators=(",", ":"))
                 replaced_terminal = True
+        elif line:
+            skip_event_data = False
         normalized.append(line)
     if not replaced_terminal:
         raise RuntimeError("Codex stream ended without a completed event")
diff --git a/testing/tests/test_hermes_chat_quality.py b/testing/tests/test_hermes_chat_quality.py
index 2532d6333..c85d06866 100644
--- a/testing/tests/test_hermes_chat_quality.py
+++ b/testing/tests/test_hermes_chat_quality.py
@@ -684,6 +684,23 @@ def test_codex_broker_auth_and_request_contract(tmp_path: Path, monkeypatch):
         "output"
     ] == [completed_item]
     assert normalized.endswith("\n\n")
+    streamed_function_body = (
+        "event: response.function_call_arguments.delta\n"
+        'data: {"type":"response.function_call_arguments.delta",'
+        '"item_id":"call_1","delta":"{\\"path\\":\\"/tmp\\"}"}\n\n'
+        "event: response.function_call_arguments.done\n"
+        'data: {"type":"response.function_call_arguments.done",'
+        '"item_id":"call_1","arguments":"{\\"path\\":\\"/tmp\\"}"}\n\n'
+        "event: response.completed\n"
+        "data: "
+        + json.dumps({"type": "response.completed", "response": completed})
+        + "\n\n"
+    ).encode()
+    normalized_function_stream = module._normalized_stream(
+        streamed_function_body, completed
+    ).decode()
+    assert "response.function_call_arguments.delta" in normalized_function_stream
+    assert "response.function_call_arguments.done" not in normalized_function_stream
     with pytest.raises(RuntimeError, match="retryable incomplete response"):
         module._completed_response(
             [