From 34ed5bb399980bb8b9392fd7eebb465180a98d6d Mon Sep 17 00:00:00 2001
From: Kit Langton <kit.langton@gmail.com>
Date: Fri, 24 Jul 2026 13:01:51 -0400
Subject: [PATCH] refactor(core): simplify prompt cache diagnostics

---
 .../src/session/prompt-cache-diagnostics.ts   |  4 +--
 .../test/prompt-cache-diagnostics.test.ts     | 30 ++++---------------
 2 files changed, 8 insertions(+), 26 deletions(-)

diff --git a/packages/core/src/session/prompt-cache-diagnostics.ts b/packages/core/src/session/prompt-cache-diagnostics.ts
index 81397668c3..99ab54576a 100644
--- a/packages/core/src/session/prompt-cache-diagnostics.ts
+++ b/packages/core/src/session/prompt-cache-diagnostics.ts
@@ -1,7 +1,7 @@
 export * as PromptCacheDiagnostics from "./prompt-cache-diagnostics"
 
-import { createHash } from "node:crypto"
 import type { LLMRequest } from "@opencode-ai/ai"
+import { Hash } from "@opencode-ai/util/hash"
 
 interface Entry {
   readonly label: string
@@ -26,7 +26,7 @@ export type Comparison =
       readonly label: string
     }
 
-const hash = (value: unknown) => createHash("sha256").update(JSON.stringify(value)).digest("hex").slice(0, 16)
+const hash = (value: unknown) => Hash.sha256(JSON.stringify(value)).slice(0, 16)
 
 export function snapshot(request: LLMRequest): Snapshot {
   return {
diff --git a/packages/core/test/prompt-cache-diagnostics.test.ts b/packages/core/test/prompt-cache-diagnostics.test.ts
index 104878ca7a..4049c99465 100644
--- a/packages/core/test/prompt-cache-diagnostics.test.ts
+++ b/packages/core/test/prompt-cache-diagnostics.test.ts
@@ -16,6 +16,8 @@ const request = LLM.request({
   prompt: "First",
   tools: [tool],
 })
+const compare = (current: LLMRequest) =>
+  PromptCacheDiagnostics.compare(PromptCacheDiagnostics.snapshot(request), PromptCacheDiagnostics.snapshot(current))
 
 describe("PromptCacheDiagnostics", () => {
   test("distinguishes initial and stable requests", () => {
@@ -26,33 +28,18 @@ describe("PromptCacheDiagnostics", () => {
 
   test("recognizes append-only history", () => {
     const current = LLMRequest.update(request, { messages: [...request.messages, Message.assistant("Second")] })
-    expect(
-      PromptCacheDiagnostics.compare(
-        PromptCacheDiagnostics.snapshot(request),
-        PromptCacheDiagnostics.snapshot(current),
-      ),
-    ).toEqual({ status: "append-only", previousMessages: 1, currentMessages: 2 })
+    expect(compare(current)).toEqual({ status: "append-only", previousMessages: 1, currentMessages: 2 })
   })
 
   test("detects cache-sensitive setting changes", () => {
     const current = LLMRequest.update(request, { generation: GenerationOptions.make({ temperature: 0.5 }) })
-    expect(
-      PromptCacheDiagnostics.compare(
-        PromptCacheDiagnostics.snapshot(request),
-        PromptCacheDiagnostics.snapshot(current),
-      ),
-    ).toEqual({ status: "changed", component: "settings", index: 0, label: "model settings" })
+    expect(compare(current)).toEqual({ status: "changed", component: "settings", index: 0, label: "model settings" })
   })
 
   test("finds the first changed prefix component", () => {
     const changedTool = ToolDefinition.make({ ...tool, description: "Read one file" })
     const current = LLMRequest.update(request, { tools: [changedTool] })
-    expect(
-      PromptCacheDiagnostics.compare(
-        PromptCacheDiagnostics.snapshot(request),
-        PromptCacheDiagnostics.snapshot(current),
-      ),
-    ).toMatchObject({ status: "changed", component: "tools", index: 0, label: "read" })
+    expect(compare(current)).toEqual({ status: "changed", component: "tools", index: 0, label: "read" })
   })
 
   test("treats appended tools as a prefix change", () => {
@@ -62,11 +49,6 @@ describe("PromptCacheDiagnostics", () => {
       inputSchema: { type: "object", properties: {} },
     })
     const current = LLMRequest.update(request, { tools: [...request.tools, write] })
-    expect(
-      PromptCacheDiagnostics.compare(
-        PromptCacheDiagnostics.snapshot(request),
-        PromptCacheDiagnostics.snapshot(current),
-      ),
-    ).toMatchObject({ status: "changed", component: "tools", index: 1, label: "write" })
+    expect(compare(current)).toEqual({ status: "changed", component: "tools", index: 1, label: "write" })
   })
 })