From d8381e201cb1407a939b496642a0803aec58a47d Mon Sep 17 00:00:00 2001
From: Adam Malczewski <github@tradam.dev>
Date: Sat, 10 Oct 2026 00:54:47 +0900
Subject: feat(turn-metrics): per-step cache hit badge on each step-metrics row

---
 src/features/chat/ui.test.ts         | 28 ++++++++++++++++++++++++++++
 src/features/chat/ui/ChatView.svelte | 21 +++++++++++++++------
 2 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/src/features/chat/ui.test.ts b/src/features/chat/ui.test.ts
index bea5e77..189be2e 100644
--- a/src/features/chat/ui.test.ts
+++ b/src/features/chat/ui.test.ts
@@ -378,6 +378,34 @@ describe("ChatView", () => {
     expect(screen.getByText(/1\.2s/)).toBeInTheDocument();
   });
 
+  it("renders a per-step cache hit badge coloured by level", () => {
+    const step = {
+      stepId: "t1#0" as StepId,
+      usage: { inputTokens: 1000, outputTokens: 10, cacheReadTokens: 750 },
+      decodeMs: 100,
+    };
+    const chunks: RenderedChunk[] = [
+      { seq: 1, role: "user", chunk: { type: "text", text: "Hi" }, provisional: false },
+      {
+        seq: 2,
+        role: "assistant",
+        chunk: {
+          type: "tool-call",
+          toolCallId: "tc1",
+          toolName: "t",
+          input: {},
+          stepId: step.stepId,
+        },
+        provisional: false,
+      },
+    ];
+    const turnMetrics: TurnMetricsEntry[] = [{ turnId: "t1", steps: [step], total: null }];
+    render(ChatView, { props: { chunks, turnMetrics } });
+    const badge = screen.getByTestId("step-cache-badge");
+    expect(badge).toHaveTextContent("75%");
+    expect(badge).toHaveClass("badge-success");
+  });
+
   it("renders cache hit-rate badges (Last turn + Chat Total) coloured by level", () => {
     const chunks: RenderedChunk[] = [
       { seq: 1, role: "user", chunk: { type: "text", text: "Hi" }, provisional: false },
diff --git a/src/features/chat/ui/ChatView.svelte b/src/features/chat/ui/ChatView.svelte
index 182b3d6..8f153bf 100644
--- a/src/features/chat/ui/ChatView.svelte
+++ b/src/features/chat/ui/ChatView.svelte
@@ -248,14 +248,23 @@
   {#each keyedRows as { row, key } (key)}
     {#if row.kind === "step-metrics"}
       {@const sv = viewStepMetrics(row.step, row.index)}
+      {@const stepCache = viewCacheRate(row.step.usage)}
       <div class="chat chat-start">
         <div class="chat-bubble w-full max-w-5xl bg-transparent p-0">
-          <div class="text-xs opacity-70">
-            {sv.label} · {sv.tokensLabel}
-            {#if sv.tps}
-              · {sv.tps}{/if}
-            {#if sv.ttft}
-              · {sv.ttft} to first token{/if}
+          <div class="flex flex-wrap items-center gap-x-1 text-xs">
+            <span class="opacity-70">
+              {sv.label} · {sv.tokensLabel}
+              {#if sv.tps}
+                · {sv.tps}{/if}
+              {#if sv.ttft}
+                · {sv.ttft} to first token{/if}
+              ·
+            </span>
+            <span class="opacity-70">cache:</span>
+            <span
+              class="badge badge-xs {badgeClass[stepCache.level]}"
+              data-testid="step-cache-badge">{stepCache.pct}%</span
+            >
           </div>
         </div>
       </div>
-- 
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