{"record":{"id":"ccb77fd9bd5d7e17","repo":"unslothai/unsloth","slug":"apply-chat-template-for-generation-no-attempt-pro","errorCode":null,"errorMessage":"apply_chat_template_for_generation: no attempt produced a result","messagePattern":"apply_chat_template_for_generation: no attempt produced a result","errorType":"exception","errorClass":"RuntimeError","httpStatus":null,"severity":"error","filePath":"studio/backend/core/inference/chat_template_helpers.py","lineNumber":2555,"sourceCode":"        boundary = _boundary_kwargs if boundary is None else boundary\n        last_exc: Optional[Exception] = None\n        for kwargs in attempts:\n            try:\n                return tokenizer.apply_chat_template(\n                    _swept_for(kwargs, msgs),\n                    tokenize = False,\n                    **boundary,\n                    **kwargs,\n                )\n            except TypeError as e:\n                last_exc = e\n                continue\n            except Exception as e:\n                last_exc = e\n                break\n        if last_exc is not None:\n            raise last_exc\n        raise RuntimeError(\"apply_chat_template_for_generation: no attempt produced a result\")\n\n    def _render_continuation_manually(msgs: list) -> str:\n        \"\"\"For tokenizers predating ``continue_final_message`` (TypeError above).\n\n        Prefix and partial come from the SAME swept copy: an attempt that drops the tools\n        kwarg re-sweeps for the default template, whose markup would otherwise survive raw.\n        \"\"\"\n        for kwargs in attempts:\n            swept = _swept_for(kwargs, msgs)\n            try:\n                prefix = tokenizer.apply_chat_template(\n                    swept[:-1], tokenize = False, add_generation_prompt = True, **kwargs\n                )\n            except TypeError:\n                continue\n            partial = trailing_assistant_text(swept) or _continue_text\n            return f\"{strip_open_reasoning_prefill(prefix)}{partial}\"\n        raise TypeError(\"no attempt rendered the continuation prefix\")","sourceCodeStart":2537,"sourceCodeEnd":2573,"githubUrl":"https://github.com/unslothai/unsloth/blob/203007d19051dcd2ae33876786d117c99f6b0368/studio/backend/core/inference/chat_template_helpers.py#L2537-L2573","documentation":"Raised by apply_chat_template_for_generation when its loop of candidate kwarg attempts (tools on/off, continue_final_message variants, etc.) produced no result AND no exception was recorded — every attempt was skipped via `continue` on TypeError without any call succeeding. It is a defensive invariant: the attempt list was empty or all attempts failed with TypeError.","triggerScenarios":"A tokenizer whose apply_chat_template signature is incompatible with every attempt (very old transformers); an attempts list built empty because the swept message/kwarg combinations deduplicated to nothing; TypeError raised on the first attempt short-circuiting the loop via `break` with last_exc set is re-raised instead — this specific message means the no-exception no-result branch.","commonSituations":"transformers version far older/newer than the supported range so all kwarg combinations raise TypeError; a tokenizer class overriding apply_chat_template with an incompatible signature; none of the model card's template variants being applicable.","solutions":["Check the transformers version in use; upgrade/downgrade to a version whose apply_chat_template accepts add_generation_prompt and the swept kwargs","Log each attempt's kwargs and the TypeError to see which signature mismatch repeats, then add a compatible attempt","As a caller, fall back to rendering the prompt manually (join message contents with the tokenizer's known template) when this RuntimeError fires"],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"try:\n    prompt = apply_chat_template_for_generation(tokenizer, messages)\nexcept RuntimeError as e:\n    if \"no attempt produced a result\" in str(e):\n        prompt = manual_prompt_render(messages)  # known-format fallback","preventionTips":["Pin a transformers version compatible with the models in use","Smoke-test apply_chat_template once at startup, not per request","Log each attempt's kwargs to extend the attempt list for new tokenizer signatures"],"tags":["chat-template","tokenizer","transformers","compatibility"],"backgroundTag":null,"analyzedSha":"203007d19051dcd2ae33876786d117c99f6b0368","analyzedAt":"2026-08-15T02:48:39.846Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}