> ## Documentation Index
> Fetch the complete documentation index at: https://docs.instructorphp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# V1.21.0

## Highlights

* StepResult pattern across Agent, Chat, ToolUse, and Collaboration with immutable steps and explicit continuation outcomes.
* Continuation evaluation is unified around `ContinuationEvaluation` and `ContinuationOutcome`, with clearer stop reasons.
* Retry policy handling is explicit for Inference and Embeddings (no more `retryPolicy` inside options).
* Hub status persistence now tolerates malformed UTF-8 output instead of failing to write status data.

## Breaking Changes

* Continuation interfaces `CanDecideToContinue`, `CanExplainContinuation`, and `CanProvideStopReason` were removed. Custom criteria must implement `CanEvaluateContinuation` and return `ContinuationEvaluation`.
* Error handling classes moved from `Cognesy\Addons\StepByStep\Continuation` to `Cognesy\Addons\StepByStep\ErrorHandling`.
* `retryPolicy` is no longer accepted in `options` or `LLMConfig` options. Use explicit retry policy objects.
* Continuation outcomes are no longer stored on step objects. Use `StepResult` or state accessors instead.

## Agent, Chat, ToolUse, Collaboration

* States now store `StepResult` collections and serialize them.
* `canContinue()` reads from the last step result; mismatches between steps and step results now raise a logic error.
* Message compilation supports `summary` and `buffer` sections for inference context.
* Token usage is accumulated before continuation evaluation so usage limits are accurate.

## StepByStep / Continuation

* `ContinuationCriteria` composes `CanEvaluateContinuation` criteria and exposes `evaluateAll()` with aggregated outcomes.
* Criteria classes return richer `ContinuationEvaluation` objects with explicit decisions and stop reasons.
* New outcome helpers provide derived decision, resolver, and stop reason from evaluations.

## Polyglot / Inference and Embeddings

* `InferenceRequest` and `EmbeddingsRequest` now carry retry policies explicitly.
* `InferenceRequestBuilder` and request builder traits expose `withRetryPolicy()`.
* `PendingInference` and `PendingEmbeddings` pull retry policies from requests rather than `options`.

## Hub

* Status JSON encoding now substitutes invalid UTF-8 bytes to avoid failures when saving example output.

## Migration from v1.20.0

* Update custom continuation criteria to implement `CanEvaluateContinuation` and return `ContinuationEvaluation` (replace `CanDecideToContinue`, `CanExplainContinuation`, `CanProvideStopReason`).
* Update imports to the new error handling namespace: `Cognesy\Addons\StepByStep\ErrorHandling\*`.
* Remove `retryPolicy` from LLM or request options. Use `withRetryPolicy()` on inference/embeddings builders or requests.
* Replace any step-level continuation outcome access with `state->continuationOutcome()` or `state->lastStepResult()`.