fix: don't drop a tool call whose id an earlier round already used

The tool loop builds `output` once per request but runs many rounds inside it,
and each round skips a function_call whose id appears anywhere in `output` -
including rounds already completed. Results are rebuilt per round and appended
regardless, so an id a later round reuses loses its call and keeps its result.

The turn then holds function_call_output items with no function_call, and the
next request fails at the provider with "tool message tool_call_id '...' does
not match any tool call in the preceding assistant messages". The malformed turn
is persisted, so retrying cannot succeed and every later message in that chat
fails the same way.

Renaming a reused id restores the pairing. Scoped to ids that are already
answered, so the case the dedup exists for - Responses API items already in
`output` and still awaiting a result - is untouched.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/open_webui/utils/middleware.py

@@ -4920,6 +4920,15 @@ async def streaming_chat_response_handler(response, ctx):
 
                     response_tool_calls = tool_calls.pop(0)
 
+                    # Some providers restart tool-call numbering each round, so a later round can reuse an id an
+                    # earlier one already answered - the dedup below would then drop the call but keep its result.
+                    answered_call_ids = {
+                        item.get('call_id') for item in output if item.get('type') == 'function_call_output'
+                    }
+                    for tc in response_tool_calls:
+                        if tc.get('id') in answered_call_ids:
+                            tc['id'] = f'{tc.get("id")}-r{tool_call_iterations}'
+
                     # Append function_call items for each tool call
                     # (Responses API already has them from streaming, so skip duplicates)
                     existing_call_ids = {item.get('call_id') for item in output if item.get('type') == 'function_call'}