Refactor web build process and update documentation

- Removed Node.js build artifacts from .gitignore and adjusted Makefile to reflect changes in web UI build process, now using server-rendered Go templates instead of React.
- Updated README to clarify the new web UI architecture and output formats, emphasizing the removal of the Node.js build step.
- Added a command to set the number of frames per render task in manager configuration, enhancing user control over rendering settings.
- Improved Gitea workflow by removing unnecessary npm install step, streamlining the CI process.

internal/runner/tasks/encode.go

@@ -12,6 +12,7 @@ import (
 	"regexp"
 	"sort"
 	"strings"
+	"sync"
 
 	"jiggablend/internal/runner/encoding"
 )
@@ -26,6 +27,10 @@ func NewEncodeProcessor() *EncodeProcessor {
 
 // Process executes an encode task.
 func (p *EncodeProcessor) Process(ctx *Context) error {
+	if err := ctx.CheckCancelled(); err != nil {
+		return err
+	}
+
 	ctx.Info(fmt.Sprintf("Starting encode task: job %d", ctx.JobID))
 	log.Printf("Processing encode task %d for job %d", ctx.TaskID, ctx.JobID)
 
@@ -64,23 +69,18 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 		ctx.Info(fmt.Sprintf("File: %s (type: %s, size: %d)", file.FileName, file.FileType, file.FileSize))
 	}
 
-	// Determine source format based on output format
-	sourceFormat := "exr"
+	// Encode from EXR frames only
 	fileExt := ".exr"
-
-	// Find and deduplicate frame files (EXR or PNG)
 	frameFileSet := make(map[string]bool)
 	var frameFilesList []string
 	for _, file := range files {
 		if file.FileType == "output" && strings.HasSuffix(strings.ToLower(file.FileName), fileExt) {
-			// Deduplicate by filename
 			if !frameFileSet[file.FileName] {
 				frameFileSet[file.FileName] = true
 				frameFilesList = append(frameFilesList, file.FileName)
 			}
 		}
 	}
-
 	if len(frameFilesList) == 0 {
 		// Log why no files matched (deduplicate for error reporting)
 		outputFileSet := make(map[string]bool)
@@ -103,37 +103,61 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 				}
 			}
 		}
-		ctx.Error(fmt.Sprintf("no %s frame files found for encode: found %d total files, %d unique output files, %d unique %s files (with other types)", strings.ToUpper(fileExt[1:]), len(files), len(outputFiles), len(frameFilesOtherType), strings.ToUpper(fileExt[1:])))
+		ctx.Error(fmt.Sprintf("no EXR frame files found for encode: found %d total files, %d unique output files, %d unique EXR files (with other types)", len(files), len(outputFiles), len(frameFilesOtherType)))
 		if len(outputFiles) > 0 {
 			ctx.Error(fmt.Sprintf("Output files found: %v", outputFiles))
 		}
 		if len(frameFilesOtherType) > 0 {
-			ctx.Error(fmt.Sprintf("%s files with wrong type: %v", strings.ToUpper(fileExt[1:]), frameFilesOtherType))
+			ctx.Error(fmt.Sprintf("EXR files with wrong type: %v", frameFilesOtherType))
 		}
-		err := fmt.Errorf("no %s frame files found for encode", strings.ToUpper(fileExt[1:]))
+		err := fmt.Errorf("no EXR frame files found for encode")
 		return err
 	}
 
-	ctx.Info(fmt.Sprintf("Found %d %s frames for encode", len(frameFilesList), strings.ToUpper(fileExt[1:])))
+	ctx.Info(fmt.Sprintf("Found %d EXR frames for encode", len(frameFilesList)))
 
-	// Download frames
-	ctx.Info(fmt.Sprintf("Downloading %d %s frames for encode...", len(frameFilesList), strings.ToUpper(fileExt[1:])))
+	// Download frames with bounded parallelism (8 concurrent downloads)
+	const downloadWorkers = 8
+	ctx.Info(fmt.Sprintf("Downloading %d EXR frames for encode...", len(frameFilesList)))
+
+	type result struct {
+		path string
+		err  error
+	}
+	results := make([]result, len(frameFilesList))
+	var wg sync.WaitGroup
+	sem := make(chan struct{}, downloadWorkers)
+	for i, fileName := range frameFilesList {
+		wg.Add(1)
+		go func(i int, fileName string) {
+			defer wg.Done()
+			sem <- struct{}{}
+			defer func() { <-sem }()
+			framePath := filepath.Join(workDir, fileName)
+			err := ctx.Manager.DownloadFrame(ctx.JobID, fileName, framePath)
+			if err != nil {
+				ctx.Error(fmt.Sprintf("Failed to download EXR frame %s: %v", fileName, err))
+				log.Printf("Failed to download EXR frame for encode %s: %v", fileName, err)
+				results[i] = result{"", err}
+				return
+			}
+			results[i] = result{framePath, nil}
+		}(i, fileName)
+	}
+	wg.Wait()
 
 	var frameFiles []string
-	for i, fileName := range frameFilesList {
-		ctx.Info(fmt.Sprintf("Downloading frame %d/%d: %s", i+1, len(frameFilesList), fileName))
-		framePath := filepath.Join(workDir, fileName)
-		if err := ctx.Manager.DownloadFrame(ctx.JobID, fileName, framePath); err != nil {
-			ctx.Error(fmt.Sprintf("Failed to download %s frame %s: %v", strings.ToUpper(fileExt[1:]), fileName, err))
-			log.Printf("Failed to download %s frame for encode %s: %v", strings.ToUpper(fileExt[1:]), fileName, err)
-			continue
+	for _, r := range results {
+		if r.err == nil && r.path != "" {
+			frameFiles = append(frameFiles, r.path)
 		}
-		ctx.Info(fmt.Sprintf("Successfully downloaded frame %d/%d: %s", i+1, len(frameFilesList), fileName))
-		frameFiles = append(frameFiles, framePath)
+	}
+	if err := ctx.CheckCancelled(); err != nil {
+		return err
 	}
 
 	if len(frameFiles) == 0 {
-		err := fmt.Errorf("failed to download any %s frames for encode", strings.ToUpper(fileExt[1:]))
+		err := fmt.Errorf("failed to download any EXR frames for encode")
 		ctx.Error(err.Error())
 		return err
 	}
@@ -141,11 +165,9 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 	sort.Strings(frameFiles)
 	ctx.Info(fmt.Sprintf("Downloaded %d frames", len(frameFiles)))
 
-	// Check if EXR files have alpha channel and HDR content (only for EXR source format)
+	// Check if EXR files have alpha channel (for encode decision)
 	hasAlpha := false
-	hasHDR := false
-	if sourceFormat == "exr" {
-		// Check first frame for alpha channel and HDR using ffprobe
+	{
 		firstFrame := frameFiles[0]
 		hasAlpha = detectAlphaChannel(ctx, firstFrame)
 		if hasAlpha {
@@ -153,45 +175,28 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 		} else {
 			ctx.Info("No alpha channel detected in EXR files")
 		}
-
-		hasHDR = detectHDR(ctx, firstFrame)
-		if hasHDR {
-			ctx.Info("Detected HDR content in EXR files")
-		} else {
-			ctx.Info("No HDR content detected in EXR files (SDR range)")
-		}
 	}
 
 	// Generate video
-	// Use alpha if:
-	// 1. User explicitly enabled it OR source has alpha channel AND
-	// 2. Codec supports alpha (AV1 or VP9)
-	preserveAlpha := ctx.ShouldPreserveAlpha()
-	useAlpha := (preserveAlpha || hasAlpha) && (outputFormat == "EXR_AV1_MP4" || outputFormat == "EXR_VP9_WEBM")
-	if (preserveAlpha || hasAlpha) && outputFormat == "EXR_264_MP4" {
-		ctx.Warn("Alpha channel requested/detected but H.264 does not support alpha. Consider using EXR_AV1_MP4 or EXR_VP9_WEBM to preserve alpha.")
-	}
-	if preserveAlpha && !hasAlpha {
-		ctx.Warn("Alpha preservation requested but no alpha channel detected in EXR files.")
+	// Use alpha when source EXR has alpha and codec supports it (AV1 or VP9). H.264 does not support alpha.
+	useAlpha := hasAlpha && (outputFormat == "EXR_AV1_MP4" || outputFormat == "EXR_VP9_WEBM")
+	if hasAlpha && outputFormat == "EXR_264_MP4" {
+		ctx.Warn("Alpha channel detected in EXR but H.264 does not support alpha. Use EXR_AV1_MP4 or EXR_VP9_WEBM to preserve alpha in video.")
 	}
 	if useAlpha {
-		if preserveAlpha && hasAlpha {
-			ctx.Info("Alpha preservation enabled: Using alpha channel encoding")
-		} else if hasAlpha {
-			ctx.Info("Alpha channel detected - automatically enabling alpha encoding")
-		}
+		ctx.Info("Alpha channel detected - encoding with alpha (AV1/VP9)")
 	}
 	var outputExt string
 	switch outputFormat {
 	case "EXR_VP9_WEBM":
 		outputExt = "webm"
-		ctx.Info("Encoding WebM video with VP9 codec (with alpha channel and HDR support)...")
+		ctx.Info("Encoding WebM video with VP9 codec (alpha, HDR)...")
 	case "EXR_AV1_MP4":
 		outputExt = "mp4"
-		ctx.Info("Encoding MP4 video with AV1 codec (with alpha channel)...")
+		ctx.Info("Encoding MP4 video with AV1 codec (alpha, HDR)...")
 	default:
 		outputExt = "mp4"
-		ctx.Info("Encoding MP4 video with H.264 codec...")
+		ctx.Info("Encoding MP4 video with H.264 codec (HDR, HLG)...")
 	}
 
 	outputVideo := filepath.Join(workDir, fmt.Sprintf("output_%d.%s", ctx.JobID, outputExt))
@@ -231,11 +236,6 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 	// Pass 1
 	ctx.Info("Pass 1/2: Analyzing content for optimal encode...")
 	softEncoder := encoder.(*encoding.SoftwareEncoder)
-	// Use HDR if: user explicitly enabled it OR HDR content was detected
-	preserveHDR := (ctx.ShouldPreserveHDR() || hasHDR) && sourceFormat == "exr"
-	if hasHDR && !ctx.ShouldPreserveHDR() {
-		ctx.Info("HDR content detected - automatically enabling HDR preservation")
-	}
 	pass1Cmd := softEncoder.BuildPass1Command(&encoding.EncodeConfig{
 		InputPattern: patternPath,
 		OutputPath:   outputVideo,
@@ -244,8 +244,6 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 		WorkDir:      workDir,
 		UseAlpha:     useAlpha,
 		TwoPass:      true,
-		SourceFormat: sourceFormat,
-		PreserveHDR:  preserveHDR,
 	})
 	if err := pass1Cmd.Run(); err != nil {
 		ctx.Warn(fmt.Sprintf("Pass 1 completed (warnings expected): %v", err))
@@ -254,15 +252,6 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 	// Pass 2
 	ctx.Info("Pass 2/2: Encoding with optimal quality...")
 
-	preserveHDR = (ctx.ShouldPreserveHDR() || hasHDR) && sourceFormat == "exr"
-	if preserveHDR {
-		if hasHDR && !ctx.ShouldPreserveHDR() {
-			ctx.Info("HDR preservation enabled (auto-detected): Using HLG transfer with bt709 primaries")
-		} else {
-			ctx.Info("HDR preservation enabled: Using HLG transfer with bt709 primaries")
-		}
-	}
-
 	config := &encoding.EncodeConfig{
 		InputPattern: patternPath,
 		OutputPath:   outputVideo,
@@ -271,8 +260,6 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 		WorkDir:      workDir,
 		UseAlpha:     useAlpha,
 		TwoPass:      true, // Software encoding always uses 2-pass for quality
-		SourceFormat: sourceFormat,
-		PreserveHDR:  preserveHDR,
 	}
 
 	cmd := encoder.BuildCommand(config)
@@ -294,6 +281,8 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 	if err := cmd.Start(); err != nil {
 		return fmt.Errorf("failed to start encode command: %w", err)
 	}
+	stopMonitor := ctx.StartCancellationMonitor(cmd, "encode")
+	defer stopMonitor()
 
 	ctx.Processes.Track(ctx.TaskID, cmd)
 	defer ctx.Processes.Untrack(ctx.TaskID)
@@ -329,6 +318,9 @@ func (p *EncodeProcessor) Process(ctx *Context) error {
 	<-stderrDone
 
 	if err != nil {
+		if cancelled, checkErr := ctx.IsJobCancelled(); checkErr == nil && cancelled {
+			return ErrJobCancelled
+		}
 		var errMsg string
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			if exitErr.ExitCode() == 137 {

internal/runner/tasks/processor.go

@@ -2,12 +2,17 @@
 package tasks
 
 import (
+	"errors"
+	"fmt"
 	"jiggablend/internal/runner/api"
 	"jiggablend/internal/runner/blender"
 	"jiggablend/internal/runner/encoding"
 	"jiggablend/internal/runner/workspace"
 	"jiggablend/pkg/executils"
 	"jiggablend/pkg/types"
+	"os/exec"
+	"sync"
+	"time"
 )
 
 // Processor handles a specific task type.
@@ -20,7 +25,8 @@ type Context struct {
 	TaskID   int64
 	JobID    int64
 	JobName  string
-	Frame    int
+	Frame    int // frame start (inclusive); kept for backward compat
+	FrameEnd int // frame end (inclusive); same as Frame for single-frame
 	TaskType string
 	WorkDir  string
 	JobToken string
@@ -34,11 +40,14 @@ type Context struct {
 	Processes *executils.ProcessTracker
 }
 
-// NewContext creates a new task context.
+// ErrJobCancelled indicates the manager-side job was cancelled during execution.
+var ErrJobCancelled = errors.New("job cancelled")
+
+// NewContext creates a new task context. frameEnd should be >= frame; if 0 or less than frame, it is treated as single-frame (frameEnd = frame).
 func NewContext(
 	taskID, jobID int64,
 	jobName string,
-	frame int,
+	frameStart, frameEnd int,
 	taskType string,
 	workDir string,
 	jobToken string,
@@ -50,11 +59,15 @@ func NewContext(
 	encoder *encoding.Selector,
 	processes *executils.ProcessTracker,
 ) *Context {
+	if frameEnd < frameStart {
+		frameEnd = frameStart
+	}
 	return &Context{
 		TaskID:    taskID,
 		JobID:     jobID,
 		JobName:   jobName,
-		Frame:     frame,
+		Frame:     frameStart,
+		FrameEnd:  frameEnd,
 		TaskType:  taskType,
 		WorkDir:   workDir,
 		JobToken:  jobToken,
@@ -145,12 +158,65 @@ func (c *Context) ShouldEnableExecution() bool {
 	return c.Metadata != nil && c.Metadata.EnableExecution != nil && *c.Metadata.EnableExecution
 }
 
-// ShouldPreserveHDR returns whether to preserve HDR range for EXR encoding.
-func (c *Context) ShouldPreserveHDR() bool {
-	return c.Metadata != nil && c.Metadata.PreserveHDR != nil && *c.Metadata.PreserveHDR
+// IsJobCancelled checks whether the manager marked this job as cancelled.
+func (c *Context) IsJobCancelled() (bool, error) {
+	if c.Manager == nil {
+		return false, nil
+	}
+	status, err := c.Manager.GetJobStatus(c.JobID)
+	if err != nil {
+		return false, err
+	}
+	return status == types.JobStatusCancelled, nil
 }
 
-// ShouldPreserveAlpha returns whether to preserve alpha channel for EXR encoding.
-func (c *Context) ShouldPreserveAlpha() bool {
-	return c.Metadata != nil && c.Metadata.PreserveAlpha != nil && *c.Metadata.PreserveAlpha
+// CheckCancelled returns ErrJobCancelled if the job was cancelled.
+func (c *Context) CheckCancelled() error {
+	cancelled, err := c.IsJobCancelled()
+	if err != nil {
+		return fmt.Errorf("failed to check job status: %w", err)
+	}
+	if cancelled {
+		return ErrJobCancelled
+	}
+	return nil
+}
+
+// StartCancellationMonitor polls manager status and kills cmd if job is cancelled.
+// Caller must invoke returned stop function when cmd exits.
+func (c *Context) StartCancellationMonitor(cmd *exec.Cmd, taskLabel string) func() {
+	stop := make(chan struct{})
+	var once sync.Once
+
+	go func() {
+		ticker := time.NewTicker(2 * time.Second)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-stop:
+				return
+			case <-ticker.C:
+				cancelled, err := c.IsJobCancelled()
+				if err != nil {
+					c.Warn(fmt.Sprintf("Could not check cancellation for %s task: %v", taskLabel, err))
+					continue
+				}
+				if !cancelled {
+					continue
+				}
+				c.Warn(fmt.Sprintf("Job %d was cancelled, stopping %s task early", c.JobID, taskLabel))
+				if cmd != nil && cmd.Process != nil {
+					_ = cmd.Process.Kill()
+				}
+				return
+			}
+		}
+	}()
+
+	return func() {
+		once.Do(func() {
+			close(stop)
+		})
+	}
 }

internal/runner/tasks/render.go

@@ -27,9 +27,19 @@ func NewRenderProcessor() *RenderProcessor {
 
 // Process executes a render task.
 func (p *RenderProcessor) Process(ctx *Context) error {
-	ctx.Info(fmt.Sprintf("Starting task: job %d, frame %d, format: %s",
-		ctx.JobID, ctx.Frame, ctx.GetOutputFormat()))
-	log.Printf("Processing task %d: job %d, frame %d", ctx.TaskID, ctx.JobID, ctx.Frame)
+	if err := ctx.CheckCancelled(); err != nil {
+		return err
+	}
+
+	if ctx.FrameEnd > ctx.Frame {
+		ctx.Info(fmt.Sprintf("Starting task: job %d, frames %d-%d, format: %s",
+			ctx.JobID, ctx.Frame, ctx.FrameEnd, ctx.GetOutputFormat()))
+		log.Printf("Processing task %d: job %d, frames %d-%d", ctx.TaskID, ctx.JobID, ctx.Frame, ctx.FrameEnd)
+	} else {
+		ctx.Info(fmt.Sprintf("Starting task: job %d, frame %d, format: %s",
+			ctx.JobID, ctx.Frame, ctx.GetOutputFormat()))
+		log.Printf("Processing task %d: job %d, frame %d", ctx.TaskID, ctx.JobID, ctx.Frame)
+	}
 
 	// Find .blend file
 	blendFile, err := workspace.FindFirstBlendFile(ctx.WorkDir)
@@ -64,12 +74,8 @@ func (p *RenderProcessor) Process(ctx *Context) error {
 		return fmt.Errorf("failed to create Blender home directory: %w", err)
 	}
 
-	// Determine render format
-	outputFormat := ctx.GetOutputFormat()
-	renderFormat := outputFormat
-	if outputFormat == "EXR_264_MP4" || outputFormat == "EXR_AV1_MP4" || outputFormat == "EXR_VP9_WEBM" {
-		renderFormat = "EXR" // Use EXR for maximum quality
-	}
+	// We always render EXR (linear) for VFX accuracy; job output_format is the deliverable (EXR sequence or video).
+	renderFormat := "EXR"
 
 	// Create render script
 	if err := p.createRenderScript(ctx, renderFormat); err != nil {
@@ -77,18 +83,30 @@ func (p *RenderProcessor) Process(ctx *Context) error {
 	}
 
 	// Render
-	ctx.Info(fmt.Sprintf("Starting Blender render for frame %d...", ctx.Frame))
+	if ctx.FrameEnd > ctx.Frame {
+		ctx.Info(fmt.Sprintf("Starting Blender render for frames %d-%d...", ctx.Frame, ctx.FrameEnd))
+	} else {
+		ctx.Info(fmt.Sprintf("Starting Blender render for frame %d...", ctx.Frame))
+	}
 	if err := p.runBlender(ctx, blenderBinary, blendFile, outputDir, renderFormat, blenderHome); err != nil {
+		if errors.Is(err, ErrJobCancelled) {
+			ctx.Warn("Render stopped because job was cancelled")
+			return err
+		}
 		ctx.Error(fmt.Sprintf("Blender render failed: %v", err))
 		return err
 	}
 
-	// Verify output
-	if _, err := p.findOutputFile(ctx, outputDir, renderFormat); err != nil {
+	// Verify output (range or single frame)
+	if err := p.verifyOutputRange(ctx, outputDir, renderFormat); err != nil {
 		ctx.Error(fmt.Sprintf("Output verification failed: %v", err))
 		return err
 	}
-	ctx.Info(fmt.Sprintf("Blender render completed for frame %d", ctx.Frame))
+	if ctx.FrameEnd > ctx.Frame {
+		ctx.Info(fmt.Sprintf("Blender render completed for frames %d-%d", ctx.Frame, ctx.FrameEnd))
+	} else {
+		ctx.Info(fmt.Sprintf("Blender render completed for frame %d", ctx.Frame))
+	}
 
 	return nil
 }
@@ -116,10 +134,9 @@ func (p *RenderProcessor) createRenderScript(ctx *Context, renderFormat string)
 		return errors.New(errMsg)
 	}
 
-	// Write output format
-	outputFormat := ctx.GetOutputFormat()
-	ctx.Info(fmt.Sprintf("Writing output format '%s' to format file", outputFormat))
-	if err := os.WriteFile(formatFilePath, []byte(outputFormat), 0644); err != nil {
+	// Write EXR to format file so Blender script sets OPEN_EXR (job output_format is for downstream deliverable only).
+	ctx.Info("Writing output format 'EXR' to format file")
+	if err := os.WriteFile(formatFilePath, []byte("EXR"), 0644); err != nil {
 		errMsg := fmt.Sprintf("failed to create format file: %v", err)
 		ctx.Error(errMsg)
 		return errors.New(errMsg)
@@ -151,7 +168,12 @@ func (p *RenderProcessor) runBlender(ctx *Context, blenderBinary, blendFile, out
 	outputAbsPattern, _ := filepath.Abs(outputPattern)
 	args = append(args, "-o", outputAbsPattern)
 
-	args = append(args, "-f", fmt.Sprintf("%d", ctx.Frame))
+	// Render single frame or range: -f N for one frame, -s start -e end -a for range
+	if ctx.FrameEnd > ctx.Frame {
+		args = append(args, "-s", fmt.Sprintf("%d", ctx.Frame), "-e", fmt.Sprintf("%d", ctx.FrameEnd), "-a")
+	} else {
+		args = append(args, "-f", fmt.Sprintf("%d", ctx.Frame))
+	}
 
 	// Wrap with xvfb-run
 	xvfbArgs := []string{"-a", "-s", "-screen 0 800x600x24", blenderBinary}
@@ -185,6 +207,8 @@ func (p *RenderProcessor) runBlender(ctx *Context, blenderBinary, blendFile, out
 	if err := cmd.Start(); err != nil {
 		return fmt.Errorf("failed to start blender: %w", err)
 	}
+	stopMonitor := ctx.StartCancellationMonitor(cmd, "render")
+	defer stopMonitor()
 
 	// Track process
 	ctx.Processes.Track(ctx.TaskID, cmd)
@@ -231,6 +255,9 @@ func (p *RenderProcessor) runBlender(ctx *Context, blenderBinary, blendFile, out
 	<-stderrDone
 
 	if err != nil {
+		if cancelled, checkErr := ctx.IsJobCancelled(); checkErr == nil && cancelled {
+			return ErrJobCancelled
+		}
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			if exitErr.ExitCode() == 137 {
 				return errors.New("Blender was killed due to excessive memory usage (OOM)")
@@ -242,60 +269,64 @@ func (p *RenderProcessor) runBlender(ctx *Context, blenderBinary, blendFile, out
 	return nil
 }
 
-func (p *RenderProcessor) findOutputFile(ctx *Context, outputDir, renderFormat string) (string, error) {
+// verifyOutputRange checks that output files exist for the task's frame range (first and last at minimum).
+func (p *RenderProcessor) verifyOutputRange(ctx *Context, outputDir, renderFormat string) error {
 	entries, err := os.ReadDir(outputDir)
 	if err != nil {
-		return "", fmt.Errorf("failed to read output directory: %w", err)
+		return fmt.Errorf("failed to read output directory: %w", err)
 	}
 
 	ctx.Info("Checking output directory for files...")
+	ext := strings.ToLower(renderFormat)
 
-	// Try exact match first
-	expectedFile := filepath.Join(outputDir, fmt.Sprintf("frame_%04d.%s", ctx.Frame, strings.ToLower(renderFormat)))
-	if _, err := os.Stat(expectedFile); err == nil {
-		ctx.Info(fmt.Sprintf("Found output file: %s", filepath.Base(expectedFile)))
-		return expectedFile, nil
+	// Check first and last frame in range (minimum required for range; single frame = one check)
+	framesToCheck := []int{ctx.Frame}
+	if ctx.FrameEnd > ctx.Frame {
+		framesToCheck = append(framesToCheck, ctx.FrameEnd)
 	}
-
-	// Try without zero padding
-	altFile := filepath.Join(outputDir, fmt.Sprintf("frame_%d.%s", ctx.Frame, strings.ToLower(renderFormat)))
-	if _, err := os.Stat(altFile); err == nil {
-		ctx.Info(fmt.Sprintf("Found output file: %s", filepath.Base(altFile)))
-		return altFile, nil
-	}
-
-	// Try just frame number
-	altFile2 := filepath.Join(outputDir, fmt.Sprintf("%04d.%s", ctx.Frame, strings.ToLower(renderFormat)))
-	if _, err := os.Stat(altFile2); err == nil {
-		ctx.Info(fmt.Sprintf("Found output file: %s", filepath.Base(altFile2)))
-		return altFile2, nil
-	}
-
-	// Search through all files
-	for _, entry := range entries {
-		if !entry.IsDir() {
-			fileName := entry.Name()
-			if strings.Contains(fileName, "%04d") || strings.Contains(fileName, "%d") {
-				ctx.Warn(fmt.Sprintf("Skipping file with literal pattern: %s", fileName))
-				continue
-			}
-			frameStr := fmt.Sprintf("%d", ctx.Frame)
-			frameStrPadded := fmt.Sprintf("%04d", ctx.Frame)
-			if strings.Contains(fileName, frameStrPadded) ||
-				(strings.Contains(fileName, frameStr) && strings.HasSuffix(strings.ToLower(fileName), strings.ToLower(renderFormat))) {
-				outputFile := filepath.Join(outputDir, fileName)
-				ctx.Info(fmt.Sprintf("Found output file: %s", fileName))
-				return outputFile, nil
+	for _, frame := range framesToCheck {
+		found := false
+		// Try frame_0001.ext, frame_1.ext, 0001.ext
+		for _, name := range []string{
+			fmt.Sprintf("frame_%04d.%s", frame, ext),
+			fmt.Sprintf("frame_%d.%s", frame, ext),
+			fmt.Sprintf("%04d.%s", frame, ext),
+		} {
+			if _, err := os.Stat(filepath.Join(outputDir, name)); err == nil {
+				found = true
+				ctx.Info(fmt.Sprintf("Found output file: %s", name))
+				break
 			}
 		}
-	}
-
-	// Not found
-	fileList := []string{}
-	for _, entry := range entries {
-		if !entry.IsDir() {
-			fileList = append(fileList, entry.Name())
+		if !found {
+			// Search entries for this frame number
+			frameStr := fmt.Sprintf("%d", frame)
+			frameStrPadded := fmt.Sprintf("%04d", frame)
+			for _, entry := range entries {
+				if entry.IsDir() {
+					continue
+				}
+				fileName := entry.Name()
+				if strings.Contains(fileName, "%04d") || strings.Contains(fileName, "%d") {
+					continue
+				}
+				if (strings.Contains(fileName, frameStrPadded) ||
+					strings.Contains(fileName, frameStr)) && strings.HasSuffix(strings.ToLower(fileName), ext) {
+					found = true
+					ctx.Info(fmt.Sprintf("Found output file: %s", fileName))
+					break
+				}
+			}
+		}
+		if !found {
+			fileList := []string{}
+			for _, e := range entries {
+				if !e.IsDir() {
+					fileList = append(fileList, e.Name())
+				}
+			}
+			return fmt.Errorf("output file for frame %d not found; files in output directory: %v", frame, fileList)
 		}
 	}
-	return "", fmt.Errorf("output file not found: %s\nFiles in output directory: %v", expectedFile, fileList)
+	return nil
 }