diff --git a/CHANGELOG.md b/CHANGELOG.md
index b6bc03b..41d8b9d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## Pending
+
+### Fixed
+
+- `scout traces show` rendered every span's duration ~1000x too small, flattening the bar chart and making the color thresholds and `⚠ slow` warning unreachable. The API reports span durations in seconds despite the `duration_ms` key name; `--json` output is unaffected (#26)
+
 ## [0.5.0] - 2026-09-10
 
 This release rounds out command coverage across the whole Scout API surface
diff --git a/internal/api/types.go b/internal/api/types.go
index b98f207..dee5d71 100644
--- a/internal/api/types.go
+++ b/internal/api/types.go
@@ -232,16 +232,20 @@ type TracesResult struct {
 }
 
 // TraceSpan represents a span in a trace tree.
+//
+// The API populates the duration_ms and exclusive_duration_ms keys with
+// values in seconds, not milliseconds. The JSON tags keep the wire names so
+// --json stays a faithful pass-through; the Go fields carry the real unit.
 type TraceSpan struct {
-	ID                  string      `json:"id"`
-	ParentID            *string     `json:"parent_id"`
-	Operation           string      `json:"operation"`
-	Type                string      `json:"type"`
-	Description         *string     `json:"description"`
-	DurationMs          float64     `json:"duration_ms"`
-	ExclusiveDurationMs float64     `json:"exclusive_duration_ms"`
-	Allocations         int64       `json:"allocations"`
-	Children            []TraceSpan `json:"children,omitempty"`
+	ID                       string      `json:"id"`
+	ParentID                 *string     `json:"parent_id"`
+	Operation                string      `json:"operation"`
+	Type                     string      `json:"type"`
+	Description              *string     `json:"description"`
+	DurationSeconds          float64     `json:"duration_ms"`
+	ExclusiveDurationSeconds float64     `json:"exclusive_duration_ms"`
+	Allocations              int64       `json:"allocations"`
+	Children                 []TraceSpan `json:"children,omitempty"`
 }
 
 // TraceDetail contains full trace information including spans.
diff --git a/internal/output/format_mb_test.go b/internal/output/format_mb_test.go
index 908fff2..e868b2d 100644
--- a/internal/output/format_mb_test.go
+++ b/internal/output/format_mb_test.go
@@ -36,7 +36,7 @@ func TestRenderSpanTreeMemoryFooter(t *testing.T) {
 		DurationInSeconds: 0.5,
 		MemDelta:          2.9296875,
 		Spans: []api.TraceSpan{
-			{ID: "a", Operation: "Controller/users/index", DurationMs: 500},
+			{ID: "a", Operation: "Controller/users/index", DurationSeconds: 0.5},
 		},
 	}
 	out := RenderSpanTree(trace)
diff --git a/internal/output/tree.go b/internal/output/tree.go
index aeac902..4eeb611 100644
--- a/internal/output/tree.go
+++ b/internal/output/tree.go
@@ -70,14 +70,16 @@ func renderSpan(sb *strings.Builder, span api.TraceSpan, totalMs float64, prefix
 		childPrefix = "     "
 	}
 
+	durationMs := span.DurationSeconds * 1000
+
 	// Duration bar
 	barWidth := 20
-	ratio := span.DurationMs / totalMs
+	ratio := durationMs / totalMs
 	if ratio > 1 {
 		ratio = 1
 	}
 	filled := int(ratio * float64(barWidth))
-	if filled < 1 && span.DurationMs > 0 {
+	if filled < 1 && durationMs > 0 {
 		filled = 1
 	}
 	bar := strings.Repeat("█", filled) + strings.Repeat("░", barWidth-filled)
@@ -106,7 +108,7 @@ func renderSpan(sb *strings.Builder, span api.TraceSpan, totalMs float64, prefix
 		prefix,
 		connector,
 		opFormatted,
-		FormatMs(span.DurationMs),
+		FormatMs(durationMs),
 		barColor.Render(bar),
 		warning,
 	)
diff --git a/internal/output/tree_test.go b/internal/output/tree_test.go
new file mode 100644
index 0000000..af1fe13
--- /dev/null
+++ b/internal/output/tree_test.go
@@ -0,0 +1,59 @@
+package output
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/scoutapm/scout/internal/api"
+	"github.com/stretchr/testify/assert"
+)
+
+// spanLine returns the rendered line containing op, with ANSI styling stripped.
+func spanLine(t *testing.T, out, op string) string {
+	t.Helper()
+	for _, line := range strings.Split(out, "\n") {
+		if strings.Contains(line, op) {
+			return line
+		}
+	}
+	t.Fatalf("no rendered line for span %q in:\n%s", op, out)
+	return ""
+}
+
+func TestRenderSpanTreeSpanDurationMatchesTraceDuration(t *testing.T) {
+	trace := api.TraceDetail{
+		ID:                3,
+		MetricName:        "Controller/users/index",
+		DurationInSeconds: 7.9,
+		Spans: []api.TraceSpan{
+			{ID: "a", Operation: "Middleware/Summary", DurationSeconds: 7.9},
+		},
+	}
+	out := RenderSpanTree(trace)
+
+	assert.Contains(t, out, "Trace #3 — Controller/users/index — 7.9s")
+	assert.Contains(t, spanLine(t, out, "Middleware/Summary"), "7.9s")
+}
+
+func TestRenderSpanTreeBarReflectsShareOfTrace(t *testing.T) {
+	trace := api.TraceDetail{
+		ID:                4,
+		MetricName:        "Controller/users/index",
+		DurationInSeconds: 10,
+		Spans: []api.TraceSpan{
+			{ID: "big", Operation: "ActiveRecord/User/find", DurationSeconds: 6},
+			{ID: "small", Operation: "View/users/_row", DurationSeconds: 0.5},
+		},
+	}
+	out := RenderSpanTree(trace)
+
+	big := spanLine(t, out, "ActiveRecord/User/find")
+	assert.Contains(t, big, "⚠ slow")
+	assert.Equal(t, 12, strings.Count(big, "█"))
+	assert.Equal(t, 8, strings.Count(big, "░"))
+
+	small := spanLine(t, out, "View/users/_row")
+	assert.NotContains(t, small, "⚠ slow")
+	assert.Equal(t, 1, strings.Count(small, "█"))
+	assert.Equal(t, 19, strings.Count(small, "░"))
+}