fix(dashboard-agent): merge the step breakpoint into the message's anthropic options

Setting the breakpoint replaced the whole `anthropic` provider-options object on
the last message, dropping any other Anthropic option it carried.

Author: kathiekiwi

internal-packages/dashboard-agent/src/step-cache.test.ts

@@ -97,6 +97,21 @@ describe("the step cache breakpoint", () => {
     expect(ttlOf(marked.at(-1))).toBe("5m");
   });
 
+  it("keeps the marked message's other anthropic options when it sets the breakpoint", () => {
+    const marked = markStepCacheBreakpoint([
+      turnHistory(),
+      {
+        ...toolResult(MIN_STEP_CACHE_CHARS),
+        providerOptions: { anthropic: { anotherOption: "keep" }, openai: { store: false } },
+      },
+    ]);
+
+    expect(marked.at(-1)!.providerOptions).toEqual({
+      anthropic: { anotherOption: "keep", cacheControl: STEP_CACHE_CONTROL },
+      openai: { store: false },
+    });
+  });
+
   it("leaves no empty anthropic object behind", () => {
     const marked = markStepCacheBreakpoint([
       stepBreakpointWith({}),
@@ -133,6 +148,24 @@ describe("wrapping the SDK's prepareStep", () => {
     expect(ttlOf(prepared!.messages!.at(-1) as Message)).toBe("5m");
   });
 
+  it("keeps the last message's other anthropic options", async () => {
+    const inner = () => ({
+      messages: [
+        turnHistory(),
+        {
+          ...toolResult(MIN_STEP_CACHE_CHARS),
+          providerOptions: { anthropic: { anotherOption: "keep" } },
+        },
+      ],
+    });
+
+    const prepared = await withStepCacheBreakpoint(inner as never)({ messages: [] } as never);
+
+    expect((prepared!.messages!.at(-1) as Message).providerOptions).toEqual({
+      anthropic: { anotherOption: "keep", cacheControl: STEP_CACHE_CONTROL },
+    });
+  });
+
   it("keeps the rest of the inner result", async () => {
     const inner = () => ({ toolChoice: "none", messages: [turnHistory()] });
     const prepared = (await withStepCacheBreakpoint(inner as never)({

internal-packages/dashboard-agent/src/step-cache.ts

@@ -30,6 +30,13 @@ function cacheControlTtl(message: MaybeCached): string | undefined {
   return typeof ttl === "string" ? ttl : undefined;
 }
 
+function anthropicOptions(message: MaybeCached): Record<string, unknown> {
+  const anthropic = message.providerOptions?.anthropic;
+  return typeof anthropic === "object" && anthropic !== null
+    ? (anthropic as Record<string, unknown>)
+    : {};
+}
+
 function withoutStepBreakpoint<T extends MaybeCached>(message: T): T {
   if (cacheControlTtl(message) !== STEP_CACHE_CONTROL.ttl) return message;
   const { anthropic, ...rest } = message.providerOptions as Record<string, unknown>;
@@ -63,7 +70,7 @@ export function markStepCacheBreakpoint<T extends MaybeCached>(messages: T[]): T
       ...last,
       providerOptions: {
         ...last.providerOptions,
-        anthropic: { cacheControl: STEP_CACHE_CONTROL },
+        anthropic: { ...anthropicOptions(last), cacheControl: STEP_CACHE_CONTROL },
       },
     },
   ];