diff --git a/internal/uploads/worker_duration_test.go b/internal/uploads/worker_duration_test.go
new file mode 100644
index 0000000..a1c94d4
--- /dev/null
+++ b/internal/uploads/worker_duration_test.go
@@ -0,0 +1,116 @@
+package uploads_test
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"git.d-ma.be/mathias/tapir/internal/domain"
+	"git.d-ma.be/mathias/tapir/internal/uploads"
+)
+
+// The duration limit is a claim in the file's header. The worker measures what was
+// really converted and refuses both a recording that is longer than the limit (the
+// header lied low) and one that ends far earlier than the file claimed (it was truncated
+// and would otherwise yield a partial transcript with no warning) -- adversarial review F2.
+
+// sizedConverter writes a (sparse) 16 kHz mono PCM WAV of the given length, without
+// actually allocating it: 32,000 bytes per second plus a 44-byte header.
+type sizedConverter struct{ seconds float64 }
+
+func (c sizedConverter) ToWAV(_ context.Context, _, dst string) error {
+	f, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+	return f.Truncate(44 + int64(c.seconds*32000))
+}
+
+func durationWorker(t *testing.T, r *wrig, wavSeconds float64, max time.Duration) *uploads.Worker {
+	t.Helper()
+	opts := []uploads.WorkerOption{}
+	if max > 0 {
+		opts = append(opts, uploads.WithMaxDuration(max))
+	}
+	return uploads.NewWorker(r.st, sizedConverter{seconds: wavSeconds}, r.tr, r.tmp, time.Minute, opts...)
+}
+
+func jobWith(r *wrig, t *testing.T, claimed time.Duration) uploads.Job {
+	j := r.spool(t, "a")
+	j.Duration = claimed
+	return j
+}
+
+func TestWorkerDuration_AConvertedLengthOverTheLimitFailsTheJobBeforeAnyEngineSeesIt(t *testing.T) {
+	r := newWRig(t, time.Minute)
+	w := durationWorker(t, r, 100*60, 90*time.Minute)
+
+	w.Process(context.Background(), jobWith(r, t, 10*time.Second))
+
+	_, failed := r.st.snapshot()
+	assert.Equal(t, domain.UploadErrTooLong, failed["a"], "a header that claimed 10 s must not let 100 minutes through")
+	assert.Empty(t, r.tr.paths, "no engine may be sent audio that is over the limit")
+	assert.Empty(t, r.leftovers(t), "the audio is still deleted")
+}
+
+func TestWorkerDuration_JustOverTheLimitWithinTheSlackStillTranscribes(t *testing.T) {
+	r := newWRig(t, time.Minute)
+	w := durationWorker(t, r, 90*60+20, 90*time.Minute)
+
+	w.Process(context.Background(), jobWith(r, t, 90*time.Minute))
+
+	completed, failed := r.st.snapshot()
+	assert.Empty(t, failed)
+	assert.Contains(t, completed, "a", "ffmpeg rounds: 20 s over a 90-minute limit is not a lie")
+}
+
+func TestWorkerDuration_AFileThatEndsFarEarlierThanItClaimedIsRefusedNotHalfTranscribed(t *testing.T) {
+	r := newWRig(t, time.Minute)
+	w := durationWorker(t, r, 20*60, 90*time.Minute)
+
+	w.Process(context.Background(), jobWith(r, t, 60*time.Minute))
+
+	_, failed := r.st.snapshot()
+	assert.Equal(t, domain.UploadErrIncomplete, failed["a"], "a recording truncated at a third must not return a third of a transcript with no warning")
+	assert.Empty(t, r.tr.paths)
+}
+
+func TestWorkerDuration_AnEstimateThatIsMerelyALittleOffIsNotTruncation(t *testing.T) {
+	tests := []struct {
+		name    string
+		claimed time.Duration
+		wav     float64
+	}{
+		{"five percent short", 60 * time.Minute, 57 * 60},
+		{"under two minutes short of a long file", 60 * time.Minute, 59 * 60},
+		{"unknown claimed length", 0, 20 * 60},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := newWRig(t, time.Minute)
+			w := durationWorker(t, r, tt.wav, 90*time.Minute)
+
+			w.Process(context.Background(), jobWith(r, t, tt.claimed))
+
+			completed, failed := r.st.snapshot()
+			assert.Empty(t, failed)
+			assert.Contains(t, completed, "a")
+		})
+	}
+}
+
+func TestWorkerDuration_WithNoMaximumConfiguredNothingIsMeasured(t *testing.T) {
+	r := newWRig(t, time.Minute)
+	w := durationWorker(t, r, 100*60, 0)
+
+	w.Process(context.Background(), jobWith(r, t, 0))
+
+	completed, _ := r.st.snapshot()
+	assert.Contains(t, completed, "a")
+	require.NotNil(t, w)
+}