notarius/internal/framework/pipeline/runner_concurrent.go

package pipeline

import (
	"context"
	"errors"
	"fmt"
	"path"
	"sort"
	"strings"
	"sync"
	"time"

	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
)

type laneExtractState struct {
	index      int
	prepared   preparedLaneExecutor
	deps       []CheckpointFingerprint
	decision   CheckpointDecision
	values     []erasedExtractArtifact
	serialized []CheckpointArtifact
	warnings   []contracts.Warning
	rejected   []contracts.RejectedOutput
	results    map[int]extractJobResult
	remaining  int
	failed     bool
	terminal   bool
	output     RunOutput
}

type finalizedExtractResults struct {
	accepted   []erasedExtractArtifact
	serialized []CheckpointArtifact
	warnings   []contracts.Warning
	rejected   []contracts.RejectedOutput
	decision   CheckpointDecision
}

func loadExtract(loader CheckpointLoader, stepID, laneID, moduleKey string, deps []CheckpointFingerprint) (ExtractCheckpoint, CheckpointDecision) {
	if stepAware, ok := loader.(StepCheckpointLoader); ok {
		return stepAware.ExtractForStep(stepID, laneID, moduleKey, deps)
	}
	return loader.Extract(laneID, moduleKey, deps)
}

func recordExtract(recorder CheckpointRecorder, stepID, laneID, moduleKey string, deps []CheckpointFingerprint, outputs []CheckpointArtifact, rejected []contracts.RejectedOutput, warnings []contracts.Warning) error {
	return checkpointExtractSucceeded(recorder, stepID, laneID, moduleKey, deps, outputs, rejected, warnings)
}

type extractJob struct {
	lane  *laneExtractState
	chunk source.Chunk
}

type extractJobResult struct {
	laneIndex  int
	chunkIndex int
	value      erasedExtractArtifact
	serialized CheckpointArtifact
	warnings   []contracts.Warning
	rejected   *contracts.RejectedOutput
	err        error
}

type laneCompletion struct {
	index  int
	output RunOutput
	err    error
}

type orderedRunError struct {
	stage int
	lane  int
	chunk int
	err   error
}

func (r *Runner) runLanes(parent context.Context, input RunInput, step PreparedPipelineStep, checkpoints CheckpointRecorder, loader CheckpointLoader, doc *source.SourceDocument, sourceInput contracts.LLMInputMaterial, sessionID string, chunks []source.Chunk) (RunOutput, error) {
	output := RunOutput{Manifest: manifestFromPipeline(input)}
	states, err := initializeLaneStates(input, step, checkpoints, loader, doc, chunks, &output)
	if err != nil {
		if mergeErr := mergeTerminalLaneStates(&output, states); mergeErr != nil {
			return output, errors.Join(err, mergeErr)
		}
		return output, err
	}
	completedOutputs, runErrors := r.runLaneEngine(parent, laneEngineConfig{
		input: input, checkpoints: checkpoints, loader: loader, doc: doc,
		sourceInput: sourceInput, sessionID: sessionID, chunks: chunks, states: states,
	})
	if err := mergeCompletedLanes(&output, completedOutputs); err != nil {
		return output, err
	}
	if err := selectRunError(parent, runErrors); err != nil {
		return output, err
	}
	return output, nil
}

func initializeLaneStates(input RunInput, step PreparedPipelineStep, checkpoints CheckpointRecorder, loader CheckpointLoader, doc *source.SourceDocument, chunks []source.Chunk, output *RunOutput) ([]*laneExtractState, error) {
	states := make([]*laneExtractState, len(step.lanes))
	for i, prepared := range step.lanes {
		if prepared.typed == nil {
			return states, fmt.Errorf("typed lane %q executor is not prepared", prepared.resolved.ID)
		}
		if err := setTypedLaneManifestMetadata(output, prepared.resolved.ID, prepared.typed.extractor, prepared.typed.merger, prepared.typed.normalizer); err != nil {
			return states, err
		}
		if input.CheckpointPolicy.requiresReusable(input.stepID, prepared.resolved.ID) && !input.CheckpointPolicy.forced(input.stepID, prepared.resolved.ID) {
			state, err := hydrateRequiredLane(input, loader, doc, i, prepared)
			states[i] = state
			if err != nil {
				return states, err
			}
			continue
		}
		state, err := prepareLaneExtract(input, loader, doc, chunks, i, prepared, output)
		if err != nil {
			return states, err
		}
		if !state.decision.Reused {
			if err := checkpointExtractRunning(checkpoints, input.stepID, prepared.resolved.ID, prepared.resolved.Extract.Module, state.deps); err != nil {
				return states, fmt.Errorf("write extract checkpoint for lane %q: %w", prepared.resolved.ID, err)
			}
		} else if err := finalizeLaneExtract(checkpoints, input.stepID, state); err != nil {
			return states, err
		}
		states[i] = state
	}
	return states, nil
}

type laneEngineConfig struct {
	input       RunInput
	checkpoints CheckpointRecorder
	loader      CheckpointLoader
	doc         *source.SourceDocument
	sourceInput contracts.LLMInputMaterial
	sessionID   string
	chunks      []source.Chunk
	states      []*laneExtractState
}

type laneEngine struct {
	runner *Runner
	laneEngineConfig
	ctx                 context.Context
	cancel              context.CancelFunc
	workerCount         int
	jobs                chan extractJob
	results             chan extractJobResult
	completions         chan laneCompletion
	continuations       chan *laneExtractState
	continuationWorkers sync.WaitGroup
	pending             []*laneExtractState
	completedOutputs    []RunOutput
	runErrors           []orderedRunError
	launched            int
	completed           int
}

func (r *Runner) runLaneEngine(parent context.Context, config laneEngineConfig) ([]RunOutput, []orderedRunError) {
	engine := newLaneEngine(r, parent, config)
	return engine.run()
}

func newLaneEngine(r *Runner, parent context.Context, config laneEngineConfig) *laneEngine {
	workerCount := config.input.ExtractWorkers
	if workerCount < 1 {
		workerCount = 1
	}
	ctx, cancel := context.WithCancel(parent)
	return &laneEngine{
		runner: r, laneEngineConfig: config, ctx: ctx, cancel: cancel, workerCount: workerCount,
		jobs: make(chan extractJob, workerCount), results: make(chan extractJobResult, workerCount),
		completions: make(chan laneCompletion, len(config.states)), continuations: make(chan *laneExtractState, workerCount),
		completedOutputs: make([]RunOutput, len(config.states)),
	}
}

func (e *laneEngine) run() ([]RunOutput, []orderedRunError) {
	defer e.cancel()
	e.initializeCollection()
	e.startExtractWorkers()
	e.startContinuationWorkers()
	e.collect()
	close(e.continuations)
	e.continuationWorkers.Wait()
	return e.completedOutputs, e.runErrors
}

func (e *laneEngine) initializeCollection() {
	for _, state := range e.states {
		if state.terminal {
			e.completedOutputs[state.index] = state.output
		} else if state.decision.Reused {
			e.pending = append(e.pending, state)
		}
	}
}

func (e *laneEngine) startExtractWorkers() {
	var workers sync.WaitGroup
	for i := 0; i < e.workerCount; i++ {
		workers.Add(1)
		go func() {
			defer workers.Done()
			for job := range e.jobs {
				if e.ctx.Err() != nil {
					continue
				}
				e.results <- e.runner.runExtractJob(e.ctx, e.input, e.doc, e.sourceInput, e.sessionID, job)
			}
		}()
	}
	go e.dispatchExtractJobs()
	go func() { workers.Wait(); close(e.results) }()
}

func (e *laneEngine) dispatchExtractJobs() {
	defer close(e.jobs)
	for chunkIndex := range e.chunks {
		for laneIndex := range e.states {
			state := e.states[laneIndex]
			if state.terminal || state.decision.Reused {
				continue
			}
			select {
			case e.jobs <- extractJob{lane: state, chunk: e.chunks[chunkIndex]}:
			case <-e.ctx.Done():
				return
			}
		}
	}
}

func (e *laneEngine) startContinuationWorkers() {
	for i := 0; i < e.workerCount; i++ {
		e.continuationWorkers.Add(1)
		go func() {
			defer e.continuationWorkers.Done()
			for state := range e.continuations {
				if err := e.ctx.Err(); err != nil {
					e.completions <- laneCompletion{index: state.index, err: err}
					continue
				}
				laneOutput, err := e.runner.continueLane(e.ctx, e.input, e.checkpoints, e.loader, e.doc, e.sourceInput, e.sessionID, e.chunks, state)
				e.completions <- laneCompletion{index: state.index, output: laneOutput, err: err}
			}
		}()
	}
}

func (e *laneEngine) collect() {
	resultChannel := (<-chan extractJobResult)(e.results)
	for resultChannel != nil || len(e.pending) > 0 || e.completed < e.launched {
		var continuationChannel chan<- *laneExtractState
		var nextContinuation *laneExtractState
		if len(e.pending) > 0 && e.ctx.Err() == nil {
			continuationChannel = e.continuations
			nextContinuation = e.pending[0]
		} else if e.ctx.Err() != nil {
			e.pending = nil
		}
		select {
		case continuationChannel <- nextContinuation:
			e.pending = e.pending[1:]
			e.launched++
		case result, ok := <-resultChannel:
			if !ok {
				resultChannel = nil
				continue
			}
			e.handleExtractResult(result)
		case completion := <-e.completions:
			e.handleCompletion(completion)
		}
	}
}

func (e *laneEngine) handleExtractResult(result extractJobResult) {
	state := e.states[result.laneIndex]
	state.remaining--
	if result.err != nil {
		state.failed = true
		e.runErrors = append(e.runErrors, orderedRunError{stage: 0, lane: state.index, chunk: result.chunkIndex, err: result.err})
		_ = checkpointExtractFailed(e.checkpoints, e.input.stepID, state.prepared.resolved.ID, state.prepared.resolved.Extract.Module, state.deps, result.err)
		e.cancel()
	} else {
		state.results[result.chunkIndex] = result
	}
	if state.remaining != 0 || state.failed || e.ctx.Err() != nil {
		return
	}
	if err := finalizeLaneExtract(e.checkpoints, e.input.stepID, state); err != nil {
		state.failed = true
		e.runErrors = append(e.runErrors, orderedRunError{stage: 0, lane: state.index, chunk: len(e.chunks), err: err})
		e.cancel()
		return
	}
	e.pending = append(e.pending, state)
}

func (e *laneEngine) handleCompletion(completion laneCompletion) {
	e.completed++
	e.completedOutputs[completion.index] = completion.output
	if completion.err != nil {
		e.runErrors = append(e.runErrors, classifyLaneError(completion.index, len(e.chunks), completion.err))
		e.cancel()
	}
}

func hydrateRequiredLane(input RunInput, loader CheckpointLoader, doc *source.SourceDocument, index int, prepared preparedLaneExecutor) (*laneExtractState, error) {
	lane, typed := prepared.resolved, prepared.typed
	local := RunOutput{Manifest: manifestFromPipeline(input)}
	checkpoint, decision := loader.AcceptedNormalize(input.stepID, lane.ID, lane.Normalize.Module)
	if decision.Reused {
		decision = checkpointDecision(CheckpointDecisionReused, CheckpointReasonAcceptedArtifactReused)
		if checkpoint.Output.LaneID != lane.ID || checkpoint.Output.ModuleKey != lane.Normalize.Module || checkpoint.Output.SourceID != doc.ID {
			decision = checkpointDecision(CheckpointDecisionExecuted, CheckpointReasonArtifactPayloadInvalid)
		}
	}
	resolution, err := resolveCheckpointDecision(&local, loader, input.CheckpointPolicy, StageNormalize, input.stepID, lane.ID, lane.Normalize.Module, decision, typed.codec, []CheckpointArtifact{checkpoint.Output})
	decision = resolution.decision
	state := &laneExtractState{index: index, prepared: prepared, decision: decision, terminal: true, output: local}
	if err != nil {
		return state, err
	}
	hydrated := resolution.artifacts[0]
	local.Warnings = append(local.Warnings, cloneWarnings(checkpoint.Warnings)...)
	local.NormalizeOutputs = append(local.NormalizeOutputs, contracts.SerializedOutput{
		StepID:        input.stepID,
		LaneID:        lane.ID,
		NormalizerKey: lane.Normalize.Module,
		SourceID:      doc.ID,
		Artifact:      contracts.CloneSerializedArtifact(hydrated.Artifact),
	})
	state.output = local
	return state, nil
}

func mergeTerminalLaneStates(output *RunOutput, states []*laneExtractState) error {
	for _, state := range states {
		if state == nil || !state.terminal {
			continue
		}
		if err := mergeLaneOutput(output, state.output); err != nil {
			return err
		}
	}
	return nil
}

func mergeCompletedLanes(output *RunOutput, completedOutputs []RunOutput) error {
	for i := range completedOutputs {
		if err := mergeLaneOutput(output, completedOutputs[i]); err != nil {
			return err
		}
	}
	return nil
}

func prepareLaneExtract(input RunInput, loader CheckpointLoader, doc *source.SourceDocument, chunks []source.Chunk, index int, prepared preparedLaneExecutor, output *RunOutput) (*laneExtractState, error) {
	lane, typed := prepared.resolved, prepared.typed
	digest, err := joinedChunkDigest(chunks)
	if err != nil {
		return nil, fmt.Errorf("digest chunks for lane %q: %w", lane.ID, err)
	}
	extractReferences := operationReferenceSet(input, lane.ExtractReferences)
	deps := append(digestFingerprints("chunks", digest), generatedReferenceDependencies(extractReferences)...)
	state := &laneExtractState{index: index, prepared: prepared, deps: normalizeCheckpointFingerprints(deps), remaining: len(chunks), results: make(map[int]extractJobResult, len(chunks))}
	cp, decision := loadExtract(loader, input.stepID, lane.ID, lane.Extract.Module, state.deps)
	resolution, err := resolveCheckpointDecision(output, loader, input.CheckpointPolicy, StageExtract, input.stepID, lane.ID, lane.Extract.Module, decision, typed.codec, cp.Outputs)
	if err != nil {
		return nil, err
	}
	decision = resolution.decision
	state.decision = decision
	if decision.Reused {
		state.remaining = 0
		for i, stored := range resolution.artifacts {
			value := resolution.values[i]
			artifact := erasedExtractArtifact{LaneID: lane.ID, ExtractorKey: lane.Extract.Module, SourceID: doc.ID, ChunkID: stored.ChunkID, ChunkIndex: stored.ChunkIndex, ChunkRef: stored.ChunkRef, Value: value}
			if stored.ChunkIndex >= 0 && stored.ChunkIndex < len(chunks) && artifact.ChunkRef == (source.SourceRef{}) {
				artifact.ChunkRef = chunks[stored.ChunkIndex].Ref
			}
			state.values = append(state.values, artifact)
			state.serialized = append(state.serialized, cloneCheckpointArtifact(stored))
		}
		state.warnings, state.rejected = cloneWarnings(cp.Warnings), cloneRejectedOutputs(cp.Rejected)
	}
	return state, nil
}

func (r *Runner) runExtractJob(ctx context.Context, input RunInput, doc *source.SourceDocument, sourceInput contracts.LLMInputMaterial, sessionID string, job extractJob) extractJobResult {
	state := job.lane
	chunk, cloneErr := cloneSourceChunk(job.chunk)
	lane, typed := state.prepared.resolved, state.prepared.typed
	result := extractJobResult{laneIndex: state.index, chunkIndex: job.chunk.Index}
	if cloneErr != nil {
		result.err = fmt.Errorf("clone chunk %q for extraction: %w", job.chunk.ID, cloneErr)
		return result
	}
	var accepted erasedExtractArtifact
	var serialized CheckpointArtifact
	var acceptedWarnings []contracts.Warning
	ok, rejection, err := runWithRetry(ctx, lane.Extract.Retries, func(attempt int) (bool, *contracts.RejectedOutput, error) {
		started := time.Now().UTC()
		attemptPath := path.Join("extract", debugPathComponent(lane.ID), fmt.Sprintf("chunk-%06d", chunk.Index+1), fmt.Sprintf("attempt-%02d", attempt))
		attemptCtx, llmScope := withDebugLLMScope(ctx, attemptPath)
		terminal := newAttemptTerminalRecorder(input.Debug, attemptPath, "extract", llmScope, debugTimedEnvelope{Stage: string(StageExtract), StepID: input.stepID, LaneID: lane.ID, ModuleKey: lane.Extract.Module, Attempt: attempt, StartedAt: started})
		requestMetadata, metadataErr := cloneMetadata(input.Metadata)
		if metadataErr != nil {
			return false, nil, terminal.record(nil, fmt.Errorf("clone extract request metadata: %w", metadataErr))
		}
		extractReferences := operationReferenceSet(input, lane.ExtractReferences)
		extracted, callErr := typed.extract(attemptCtx, typed.extractor, contracts.TypedExtractionRequest{Source: doc, Chunk: &chunk, SourceInput: chunkInputMaterial(sourceInput, chunk), SessionID: sessionID, References: CloneReferenceSet(extractReferences), LLMProfile: lane.Extract.LLMProfile, Metadata: requestMetadata})
		if callErr != nil {
			attemptErr := fmt.Errorf("extract lane %q chunk %q with extractor %q: %w", lane.ID, chunk.ID, lane.Extract.Module, callErr)
			return false, nil, terminal.record(nil, attemptErr)
		}
		artifact := erasedExtractArtifact{LaneID: lane.ID, ExtractorKey: lane.Extract.Module, SourceID: doc.ID, ChunkID: chunk.ID, ChunkIndex: chunk.Index, ChunkRef: chunk.Ref, Value: extracted.Value}
		attemptWarnings := cloneWarnings(extracted.Warnings)
		serializedCandidate, encodeErr := serializeCandidateArtifact(typed.codec, artifact.LaneID, artifact.ExtractorKey, artifact.SourceID, artifact.Value)
		if encodeErr != nil {
			attemptErr := fmt.Errorf("serialize extract candidate for lane %q chunk %q: %w", lane.ID, chunk.ID, encodeErr)
			payload := map[string]any{"warnings": debugWarningEnvelopes(attemptWarnings)}
			return false, nil, terminal.record(payload, attemptErr)
		}
		serializedCandidate.ChunkID, serializedCandidate.ChunkIndex, serializedCandidate.ChunkRef = artifact.ChunkID, artifact.ChunkIndex, artifact.ChunkRef
		warnings, rejected, validateErr := r.validateTypedArtifact(attemptCtx, typed.codec, typedValidationTarget{stage: StageExtract, stepID: input.stepID, laneID: lane.ID, moduleKey: lane.Extract.Module, source: doc, sourceID: doc.ID, sourceInput: chunkInputMaterial(sourceInput, chunk), sessionID: sessionID, references: extractReferences, metadata: input.Metadata, chunk: &chunk, ref: chunk.Ref, value: extracted.Value, candidate: &serializedCandidate}, state.prepared.extractValidators, attempt, input.Debug)
		attemptWarnings = append(attemptWarnings, warnings...)
		payload := map[string]any{"output": debugCheckpointArtifact(serializedCandidate), "warnings": debugWarningEnvelopes(attemptWarnings), "rejection": debugRejectedOutputPtr(rejected)}
		if validateErr != nil || rejected != nil {
			return false, rejected, terminal.record(payload, validateErr)
		}
		stored, encodeErr := checkpointArtifact(typed.codec, artifact.LaneID, artifact.ExtractorKey, artifact.SourceID, artifact.Value)
		if encodeErr != nil {
			attemptErr := fmt.Errorf("serialize accepted extract output for lane %q chunk %q: %w", lane.ID, chunk.ID, encodeErr)
			return false, nil, terminal.record(payload, attemptErr)
		}
		stored.ChunkID, stored.ChunkIndex, stored.ChunkRef = artifact.ChunkID, artifact.ChunkIndex, artifact.ChunkRef
		accepted, serialized = artifact, stored
		acceptedWarnings = attemptWarnings
		if debugErr := terminal.record(payload, nil); debugErr != nil {
			return false, nil, debugErr
		}
		return true, nil, nil
	})
	result.err = err
	if err == nil && !ok {
		result.rejected = rejection
		return result
	}
	result.value, result.serialized, result.warnings = accepted, serialized, acceptedWarnings
	return result
}

func finalizeLaneExtract(checkpoints CheckpointRecorder, stepID string, state *laneExtractState) error {
	lane := state.prepared.resolved
	indexes := make([]int, 0, len(state.results))
	for index := range state.results {
		indexes = append(indexes, index)
	}
	sort.Ints(indexes)
	for _, index := range indexes {
		result := state.results[index]
		if result.rejected != nil {
			state.rejected = append(state.rejected, *result.rejected)
			continue
		}
		state.values = append(state.values, result.value)
		state.serialized = append(state.serialized, result.serialized)
		state.warnings = append(state.warnings, result.warnings...)
	}
	sort.SliceStable(state.values, func(i, j int) bool { return state.values[i].ChunkIndex < state.values[j].ChunkIndex })
	sort.SliceStable(state.serialized, func(i, j int) bool { return state.serialized[i].ChunkIndex < state.serialized[j].ChunkIndex })
	sort.SliceStable(state.rejected, func(i, j int) bool { return state.rejected[i].ChunkIndex < state.rejected[j].ChunkIndex })
	if !state.decision.Reused {
		if err := recordExtract(checkpoints, stepID, lane.ID, lane.Extract.Module, state.deps, state.serialized, state.rejected, state.warnings); err != nil {
			return fmt.Errorf("write extract checkpoint for lane %q: %w", lane.ID, err)
		}
	}
	return nil
}

func (r *Runner) continueLane(ctx context.Context, input RunInput, checkpoints CheckpointRecorder, loader CheckpointLoader, doc *source.SourceDocument, sourceInput contracts.LLMInputMaterial, sessionID string, chunks []source.Chunk, state *laneExtractState) (RunOutput, error) {
	lane := state.prepared.resolved
	local := RunOutput{Manifest: manifestFromPipeline(input)}
	results := finalizedExtractResults{
		accepted:   state.values,
		serialized: state.serialized,
		warnings:   state.warnings,
		rejected:   state.rejected,
		decision:   state.decision,
	}
	local.Warnings = append(local.Warnings, cloneWarnings(results.warnings)...)
	local.Rejected = append(local.Rejected, cloneRejectedOutputs(results.rejected)...)
	if err := writeDebugTimed(input.Debug, path.Join("extract", debugPathComponent(lane.ID), "input.json"), debugTimedEnvelope{Stage: string(StageExtract), StepID: input.stepID, LaneID: lane.ID, ModuleKey: lane.Extract.Module, StartedAt: time.Now().UTC(), Payload: map[string]any{"reused": results.decision.Reused, "decision": results.decision, "source": debugSourceDocumentEnvelope(doc), "chunks": debugSourceChunkEnvelopes(chunks), "options": redactSensitiveMap(lane.Extract.Options), "metadata": redactSensitiveMap(input.Metadata)}}); err != nil {
		return local, &laneRunError{stage: StageExtract, err: err}
	}
	if err := writeDebugTimed(input.Debug, path.Join("extract", debugPathComponent(lane.ID), "output.json"), debugTimedEnvelope{Stage: string(StageExtract), StepID: input.stepID, LaneID: lane.ID, ModuleKey: lane.Extract.Module, StartedAt: time.Now().UTC(), Payload: map[string]any{"reused": results.decision.Reused, "outputs": debugCheckpointArtifacts(results.serialized), "rejected": debugRejectedOutputEnvelopes(results.rejected), "warnings": debugWarningEnvelopes(results.warnings)}}); err != nil {
		return local, &laneRunError{stage: StageExtract, err: err}
	}
	if len(results.accepted) == 0 {
		return local, nil
	}
	err := r.continueTypedLane(ctx, input, checkpoints, loader, doc, sourceInput, sessionID, state.prepared, results, &local)
	return local, err
}

func classifyLaneError(lane, sentinel int, err error) orderedRunError {
	stage := 1
	var laneErr *laneRunError
	if errors.As(err, &laneErr) {
		switch laneErr.stage {
		case StageExtract:
			stage = 0
		case StageNormalize:
			stage = 2
		}
	} else if strings.Contains(strings.ToLower(err.Error()), "normalize") {
		stage = 2
	}
	return orderedRunError{stage: stage, lane: lane, chunk: sentinel, err: err}
}

func selectRunError(parent context.Context, values []orderedRunError) error {
	if err := parent.Err(); err != nil {
		return err
	}
	if len(values) == 0 {
		return nil
	}
	hasReal := false
	for _, value := range values {
		if !errors.Is(value.err, context.Canceled) && !errors.Is(value.err, context.DeadlineExceeded) {
			hasReal = true
			break
		}
	}
	filtered := values[:0]
	for _, value := range values {
		if hasReal && (errors.Is(value.err, context.Canceled) || errors.Is(value.err, context.DeadlineExceeded)) {
			continue
		}
		filtered = append(filtered, value)
	}
	sort.SliceStable(filtered, func(i, j int) bool {
		if filtered[i].stage != filtered[j].stage {
			return filtered[i].stage < filtered[j].stage
		}
		if filtered[i].lane != filtered[j].lane {
			return filtered[i].lane < filtered[j].lane
		}
		return filtered[i].chunk < filtered[j].chunk
	})
	return filtered[0].err
}

func mergeLaneOutput(dst *RunOutput, src RunOutput) error {
	if dst == nil {
		return nil
	}
	dst.NormalizeOutputs = append(dst.NormalizeOutputs, cloneSerializedOutputs(src.NormalizeOutputs)...)
	dst.Rejected = append(dst.Rejected, cloneRejectedOutputs(src.Rejected)...)
	dst.Warnings = append(dst.Warnings, cloneWarnings(src.Warnings)...)
	dst.CheckpointEvents = append(dst.CheckpointEvents, src.CheckpointEvents...)
	for i := range dst.Manifest.ArtifactLanes {
		for j := range src.Manifest.ArtifactLanes {
			if dst.Manifest.ArtifactLanes[i].ID == src.Manifest.ArtifactLanes[j].ID && dst.Manifest.ArtifactLanes[i].StepID == src.Manifest.ArtifactLanes[j].StepID && src.Manifest.ArtifactLanes[j].Metadata != nil {
				metadata, err := cloneMetadata(src.Manifest.ArtifactLanes[j].Metadata)
				if err != nil {
					return fmt.Errorf("clone lane %q manifest metadata: %w", dst.Manifest.ArtifactLanes[i].ID, err)
				}
				dst.Manifest.ArtifactLanes[i].Metadata = metadata
			}
		}
	}
	return nil
}