ninemin.lilulab.ai

InstructorRetryException — instructor’s error when a response_model call ends without a validated object

instructor.v2.core.errors.InstructorRetryException: <message>

(Our rendering, with the message left as a placeholder. The module path is where the class is defined at v1.17.0. The message is either one exception’s own text or a block that starts with <failed_attempts>; which one you get is explained under “What str(e) shows” below.)

This error is instructor telling you that a create(...) call with a response_model did not return a validated object. In the retry functions we read, that happens in two ways: the model’s answer failed parsing or validation on the last attempt allowed, or another exception — an error from the API call itself, for one — was raised inside the retry loop, on any attempt, the first included. Every claim about the library below is read off the Python source of 567-labs/instructor at release tag v1.17.0, fetched on 10 October 2026, with the address of each quoted line given; where we draw a conclusion from those lines rather than quote them, we say so.

The class

The class line and the start of its docstring (instructor/v2/core/errors.py, lines 188–291):

class InstructorRetryException(InstructorError): """Exception raised when all retry attempts have been exhausted. This exception is raised after the maximum number of retries has been reached without successfully validating the LLM response.

That is what the docstring says. The code that raises it, below, also wraps errors that are not validation failures; its own comment says so. The constructor (lines 239–255) stores five attributes and passes failed_attempts to the parent:

self.last_completion = last_completion self.messages = messages self.n_attempts = n_attempts self.total_usage = total_usage self.create_kwargs = create_kwargs super().__init__(*args, failed_attempts=failed_attempts, **kwargs)

What each holds, from the raise site at line 434 of retry.py (our reading):

• last_completion — failed_attempts[-1].completion if failed_attempts else None: the raw provider response of the last attempt that failed parsing or validation, or None if none did.
• failed_attempts — a list of FailedAttempt (line 103 of errors.py: attempt_number, exception, completion), one appended per parse or validation failure (retry.py line 363).
• n_attempts — last_attempt_number, set from tenacity’s attempt.retry_state.attempt_number at the start of each attempt (lines 297–298).
• total_usage — the running total that update_total_usage(response=response, total_usage=total_usage) adds each response to (line 331), so it covers the responses received, not a call that raised.
• create_kwargs — kwargs as it stood at the raise. After each validation failure, kwargs is replaced by the reask handler’s result (line 405) before the error is re-raised, the last attempt included, so this can hold a reask that was never sent.
• messages — extract_messages(kwargs); the docstring marks it deprecated in favour of create_kwargs.

The same file defines class TokenBudgetError(InstructorRetryException): (line 258), “Base class for retry termination caused by a token budget.”, which adds budget, and its two subclasses TokenBudgetExceeded (line 286) and TokenUsageUnavailableError (line 290).

To import it, from instructor.core import InstructorRetryException works: instructor/core/__init__.py imports it from .exceptions (lines 4–5), and instructor/core/exceptions.py at this tag is a docstring and one statement, from instructor.v2.core.errors import *. The class itself lives in instructor.v2.core.errors.

What str(e) shows

The parent InstructorError stores failed_attempts in its __init__ and decides the string in __str__ (instructor/v2/core/errors.py, lines 62–100):

if not self.failed_attempts: return super().__str__()

return template.render( last_exception=super().__str__(), failed_attempts=self.failed_attempts

The first argument at the raise site is str(last_exception). So when no attempt failed validation, str(e) is just the text of the exception that ended the loop. Otherwise it is a template: a <failed_attempts> block with one <generation number="{{ attempt.attempt_number }}"> per failed attempt, each holding that attempt’s <exception> and <completion>, then a <last_exception> block with the text of the exception that ended the loop (our reading of lines 71–100).

What reaches line 434

When max_retries is an int (if isinstance(max_retries, int):, line 274), retry_sync_v2 stops after max(max_retries, 0) + 1 attempts, or after timeout seconds when the call’s timeout keyword is a number, and builds its retrier like this (instructor/v2/core/retry.py, lines 274–284):

max_retries_instance = Retrying( stop=stop_condition, retry=retry_if_exception_type(_RETRYABLE_PARSE_ERRORS), reraise=True, )

_RETRYABLE_PARSE_ERRORS (lines 52–57) is ValidationError — Pydantic’s, imported on line 15 — json.JSONDecodeError, AsyncValidationError and ResponseParsingError. Only those are retried. In tenacity at tag 9.1.2, an exception the retry test rejects is raised as it is, and when the stop condition is met with reraise set, the last attempt’s own exception is raised rather than RetryError (our reading of tenacity/__init__.py, lines 398–421, and of RetryError.reraise, lines 185–187):

if not (self.iter_state.is_explicit_retry or self.iter_state.retry_run_result): self._add_action_func(lambda rs: rs.outcome.result())

if self.reraise: raise retry_exc.reraise() raise retry_exc from fut.exception()

(We read tenacity at that tag; we did not check which tenacity version your instructor install resolves to.) The loop that runs inside this retrier starts at line 294 and its handlers follow (instructor/v2/core/retry.py, lines 414–454):

except (IncompleteOutputException, TokenBudgetError): raise except Exception as e: # Max retries exceeded or non-validation error occurred last_exception = e

So, with an int max_retries, line 416 receives (our reading of lines 294–416 and the tenacity lines above):

• A parse or validation error on the last attempt — one of the four retryable types, after the stop condition is met; when it came from parsing the response, it was appended to failed_attempts first.
• An error from the API call itself, on any attempt: it is logged as API call failed on attempt {attempt_number}: {e} (line 308) and re-raised, and unless it is IncompleteOutputException (re-raised at line 306, before that log) or one of the four retryable types, it is not retried.
• Any other exception raised in the loop that is not one of the four retryable types, IncompleteOutputException or a TokenBudgetError.

A TokenBudgetError is raised at line 403 (raise budget_error from e) only when _budget_error returns one, and that function returns None when token_budget is None (lines 158–159), the parameter’s default. It reaches your code unwrapped through line 414, and it is still an InstructorRetryException by inheritance. If you pass your own Retrying as max_retries, its retry and reraise settings decide instead; without reraise, tenacity raises RetryError (line 421) and that is what line 416 wraps (our reading).

The raise itself:

raise InstructorRetryException( str(last_exception), last_completion=failed_attempts[-1].completion if failed_attempts else None, n_attempts=last_attempt_number, total_usage=total_usage, messages=extract_messages(kwargs), create_kwargs=kwargs, failed_attempts=failed_attempts, ) from last_exception

Because of from last_exception, the original exception is e.__cause__. The other raise in the function, line 446, comes after the comment # Should never reach here (line 444), uses str(last_exception) if last_exception else "Unknown error" as its message and has no from. In retry_async_v2 (line 517) the same code repeats with AsyncRetrying (lines 575–579, the same three arguments): the handlers are at lines 710 and 712, the raise at line 730 with ) from last_exception at line 738, and the fallthrough raise at line 742. Those four, 434, 446, 730 and 742, are every raise InstructorRetryException( line in retry.py; we searched no other instructor module for raises.

In the field

A Ragas report shows the second case, an API error on the first attempt, with no failed validation in front of it, to judge by its message, which has no <failed_attempts> block (our reading; vibrantlabsai/ragas#3031; line cut by us):

instructor.v2.core.errors.InstructorRetryException: Error code: 400 - {'error': {'code': 'unsupported_parameter',

The same block in the report has the line API call failed on attempt 1: Error code: 400 above it, the log message from line 308. An instructor report shows the template form, opening with the first failed generation (567-labs/instructor#2654):

InstructorRetryException: <failed_attempts> <generation number="1"> <exception> 'list' object has no attribute 'find' </exception>

Its traceback runs through an older instructor/core/retry.py that shows 310 except RetryError as e:, not the v1.17.0 code above; the string format is the same template.

What to do

from instructor.core import InstructorRetryException, TokenBudgetError def explain(e: InstructorRetryException) -> str: if isinstance(e, TokenBudgetError): return f'stopped by token_budget after {e.n_attempts} attempts' if not e.failed_attempts: return f'no attempt failed validation; cause: {e.__cause__!r}' last = e.failed_attempts[-1] return f'attempt {last.attempt_number} failed validation: {last.exception}'

(Our sketch. Call it from an except InstructorRetryException as e: block. Since TokenBudgetError is a subclass, test for it first.)

• If failed_attempts is empty, it was not validation. Read e.__cause__: an API error such as the 400 above is not one of the retryable types, so it was not retried, and more retries will not change it; fix the request (our reading).
• If failed_attempts has entries, read them. Each exception says what failed validation and each completion is what the model returned; e.last_completion is the last of them. Then change the response_model, the prompt or the model. The docstring’s own “Common Causes” list starts with Response model too strict for the LLM's capabilities.
• Raising max_retries is a choice, not a fix. Each extra attempt is another call added to total_usage; if the same field fails every time, more attempts fail the same way (our inference).
• If it is a TokenBudgetError, a token budget stopped the retries (the token_budget parameter of retry_sync_v2, documented as Positive cumulative token budget for validation retries, line 247), not the max_retries count.

The thing worth keeping even if you never see this class again: at v1.17.0 this name does not only mean “validation failed too often” — any exception inside the retry loop, other than IncompleteOutputException and TokenBudgetError, comes out wearing it, with the original attached as __cause__ (our reading).

What is behind this site

The short version: InstructorRetryException is what instructor’s retry_sync_v2 and retry_async_v2 raise when a response_model call ends without a validated object. With an int max_retries that is the last attempt’s validation error, or any other exception from the retry loop except IncompleteOutputException and TokenBudgetError — an API error included, on the first attempt as well — raised from the original, which is __cause__. str(e) is that exception’s text, or a <failed_attempts> block when attempts failed validation. TokenBudgetError is a subclass. Read failed_attempts and __cause__ before raising max_retries.

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