Revert JSON mode — incompatible with non-strict tool schemas

abossard · Copilot · abossard · commit 5069ca7aae1f · 2026-03-04T13:58:02.000+01:00
OpenAI's response_format: json_object requires all tools to have strict schemas. Our tools (from @operation decorator) don't set strict=True, causing: 'csv_search_tickets is not strict. Only strict function tools can be auto-parsed'. Reverting to prompt-only JSON enforcement, which tested at 3/3 reliability with gpt-5-nano. The frontend fallback (wraps non-JSON as {message: raw_text}) provides additional safety. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
diff --git a/backend/agent_builder/engine/react_runner.py b/backend/agent_builder/engine/react_runner.py
@@ -41,7 +41,6 @@ def build_llm(
         "api_key": api_key,
         "base_url": base_url or None,
         "temperature": temperature,
-        "model_kwargs": {"response_format": {"type": "json_object"}},
     }
     if max_tokens > 0:
         kwargs["max_tokens"] = max_tokens

Original file line number	Diff line number	Diff line change
`@@ -41,7 +41,6 @@ def build_llm(`
`41`	`41`	`"api_key": api_key,`
`42`	`42`	`"base_url": base_url or None,`
`43`	`43`	`"temperature": temperature,`
`44`		`- "model_kwargs": {"response_format": {"type": "json_object"}},`
`45`	`44`	`}`
`46`	`45`	`if max_tokens > 0:`
`47`	`46`	`kwargs["max_tokens"] = max_tokens`