fix(agent): retry malformed anthropic stream parser errors — port to extracted modules

Original commit 9c304a7f5 by helix4u targeted _flatten_exception_chain,
_summarize_api_error, and the _call streaming retry loop in pre-refactor
run_agent.py. Re-applied to:

  - New _is_provider_stream_parse_error helper → run_agent.py (next
    to _flatten_exception_chain in the AIAgent class)
  - _summarize_api_error early-return for the malformed-streaming
    ValueError → run_agent.py (kept method body)
  - _call streaming retry: _is_stream_parse_err flag wired into
    _is_transient AND the post-exhaustion branch + dedicated
    malformed-streaming user-status string → agent/chat_completion_helpers.py
    (the _call body now lives there)

Co-authored-by: helix4u <4317663+helix4u@users.noreply.github.com>

agent/chat_completion_helpers.py

@@ -1632,6 +1632,7 @@ def interruptible_streaming_api_call(agent, api_kwargs: dict, *, on_first_delta=
                     _is_conn_err = isinstance(
                         e, (_httpx.ConnectError, _httpx.RemoteProtocolError, ConnectionError)
                     )
+                    _is_stream_parse_err = agent._is_provider_stream_parse_error(e)
 
                     # If the stream died AFTER some tokens were delivered:
                     # normally we don't retry (the user already saw text,
@@ -1671,7 +1672,10 @@ def interruptible_streaming_api_call(agent, api_kwargs: dict, *, on_first_delta=
                                     for phrase in _SSE_PREVIEW_PHRASES
                                 )
                         _is_transient = (
-                            _is_timeout or _is_conn_err or _is_sse_conn_err_preview
+                            _is_timeout
+                            or _is_conn_err
+                            or _is_sse_conn_err_preview
+                            or _is_stream_parse_err
                         )
                         _can_silent_retry = (
                             _partial_tool_in_flight
@@ -1769,7 +1773,7 @@ def interruptible_streaming_api_call(agent, api_kwargs: dict, *, on_first_delta=
                                 for phrase in _SSE_CONN_PHRASES
                             )
 
-                    if _is_timeout or _is_conn_err or _is_sse_conn_err:
+                    if _is_timeout or _is_conn_err or _is_sse_conn_err or _is_stream_parse_err:
                         # Transient network / timeout error. Retry the
                         # streaming request with a fresh connection first.
                         if _stream_attempt < _max_stream_retries:
@@ -1811,6 +1815,11 @@ def interruptible_streaming_api_call(agent, api_kwargs: dict, *, on_first_delta=
                             diag=request_client_holder.get("diag"),
                         )
                         agent._emit_status(
+                            "❌ Provider returned malformed streaming data after "
+                            f"{_max_stream_retries + 1} attempts. "
+                            "The provider may be experiencing issues — "
+                            "try again in a moment."
+                            if _is_stream_parse_err else
                             "❌ Connection to provider failed after "
                             f"{_max_stream_retries + 1} attempts. "
                             "The provider may be experiencing issues — "

run_agent.py

@@ -700,6 +700,24 @@ class AIAgent:
         from agent.stream_diag import flatten_exception_chain
         return flatten_exception_chain(error)
 
+    def _is_provider_stream_parse_error(self, error: BaseException) -> bool:
+        """Return True for malformed provider streaming data from SDK parsers.
+
+        Some Anthropic-compatible streaming providers can send a malformed
+        event-stream frame.  The Anthropic SDK surfaces that as a plain
+        ``ValueError`` such as ``expected ident at line 1 column 149``.  That
+        is provider wire-format trouble, not local request validation, so it
+        should follow the same retry path as a truncated JSON body.
+        """
+        if getattr(self, "api_mode", None) != "anthropic_messages":
+            return False
+        if not isinstance(error, ValueError):
+            return False
+        if isinstance(error, (UnicodeEncodeError, json.JSONDecodeError)):
+            return False
+        message = str(error).strip().lower()
+        return "expected ident at line" in message
+
     def _log_stream_retry(
         self,
         *,
@@ -1335,6 +1353,12 @@ class AIAgent:
         """
         raw = str(error)
 
+        if (
+            isinstance(error, ValueError)
+            and "expected ident at line" in raw.lower()
+        ):
+            return f"Malformed provider streaming response: {raw[:300]}"
+
         # Cloudflare / proxy HTML pages: grab the <title> for a clean summary
         if "<!DOCTYPE" in raw or "<html" in raw:
             m = re.search(r"<title[^>]*>([^<]+)</title>", raw, re.IGNORECASE)