plan

var (
	// ErrNoMessages is Compact's error for an empty message list.
	ErrNoMessages = errors.New("plan: no messages to compact")
	// ErrEstimateFailed is Compact's error when the token estimator
	// fails.
	ErrEstimateFailed = errors.New("plan: token estimate failed")
	// ErrRetentionOverflow is Compact's error when the retention set
	// alone exceeds the window budget.
	ErrRetentionOverflow = errors.New("plan: retention set alone exceeds the window")
	// ErrNoObjective is Compact's error when no user message exists to
	// retain as the objective.
	ErrNoObjective = errors.New("plan: no user message to retain as objective")
)

var (
	// ErrNoMessagesToSummarize is Summarize's error for an empty message list.
	ErrNoMessagesToSummarize = errors.New("plan: no messages to summarize")
	// ErrInvalidReply is Summarize's error when the reply fails
	// strict parsing or Summary.Validate.
	ErrInvalidReply = errors.New("plan: reply failed strict parsing or validation")
	// ErrCallFailed is Summarize's error when the Completer call
	// itself fails.
	ErrCallFailed = errors.New("plan: summary call failed")
	// ErrSummarySkipped is the sentinel a summarize adapter returns
	// to decline summary injection; the concrete Summarizer never
	// returns it. An adapter may wrap it with a reason, for example
	// fmt.Errorf("%w: %s", ErrSummarySkipped, reason); agentloop's
	// summarizeDropped matches the skip through errors.Is, so a
	// wrapped sentinel still takes the skip path and the wrapping
	// error's own message carries the reason to the caller.
	ErrSummarySkipped = errors.New("plan: summary skipped")
)

var (
	// ErrMaxTokensNotPositive is Validate's error when MaxTokens <= 0.
	// Kept separate from ErrInvalidOptions: agentloop/agentloop_test
	// asserts on this sentinel by name, so it stays a distinct value.
	ErrMaxTokensNotPositive = errors.New("plan: max tokens must be positive")
	// ErrInvalidOptions is the shared sentinel for every other
	// construction-time argument error in this package. Wrap it with
	// fmt.Errorf("%w: %s", ErrInvalidOptions, "<field>: <rule>") and
	// test with errors.Is plus a substring check on the field name.
	ErrInvalidOptions = errors.New("plan: invalid options")
)