diff --git a/cmd/tapir/uploads.go b/cmd/tapir/uploads.go
index 13f7d02..bda8a19 100644
--- a/cmd/tapir/uploads.go
+++ b/cmd/tapir/uploads.go
@@ -55,8 +55,8 @@ func buildUploads(ctx context.Context, cfg config.Config, st uploadsStore, log *
 		log.Warn("uploads: marked interrupted by a restart (audio is not retained; they must be re-uploaded)", "count", n)
 	}
 
-	worker := uploads.NewWorker(st, &audio.FFmpeg{Bin: cfg.FFmpegBin}, buildTranscriber(cfg),
-		cfg.UploadTmpDir, cfg.TranscribeTimeout)
+	worker := uploads.NewWorker(st, newConverter(cfg), buildTranscriber(cfg),
+		cfg.UploadTmpDir, cfg.TranscribeTimeout, uploads.WithMaxDuration(cfg.UploadMaxDuration))
 	intake := uploads.NewIntake(st, &audio.FFprobe{Bin: cfg.FFprobeBin}, worker,
 		uploadLimits(cfg), cfg.UploadTmpDir)
 	return intake, worker, nil
@@ -94,6 +94,12 @@ func wireUploads(app *web.App, cfg config.Config, in *uploads.Intake) {
 	app.UploadChatModels = uploadChatModels(cfg)
 }
 
+// newConverter is the ffmpeg adapter capped at the configured maximum duration, so a file
+// whose header lies about its length cannot become hours of WAV (ADR-035 review).
+func newConverter(cfg config.Config) *audio.FFmpeg {
+	return &audio.FFmpeg{Bin: cfg.FFmpegBin, MaxSeconds: int(cfg.UploadMaxDuration.Seconds())}
+}
+
 // adjudicatorTimeout bounds one adjudication call. A call takes ~2 s on gemma4-26b and ~10 s
 // on 31b; this is the wait before an unresponsive model is counted as an error.
 const adjudicatorTimeout = 2 * time.Minute