Revert "fix: keep OpenAI reasoning responses stateful" (#4571)

Reverts #4557

Author: KyleAMathews

.changeset/openai-reasoning-store-true.md

@@ -267,11 +267,6 @@ function withProviderPayloadDefaults(
 
       return {
         ...body,
-        // OpenAI Responses reasoning/tool-call continuations replay rs_*
-        // reasoning items. With store:false, OpenAI does not persist those
-        // items server-side, which can make follow-up requests fail with
-        // "Item with id ... not found". Keep Responses stateful for built-ins.
-        store: true,
         reasoning: {
           ...existingReasoning,
           effort,

packages/agents/src/model-catalog.ts

@@ -126,7 +126,6 @@ describe(`model catalog`, () => {
     )
 
     expect(payload).toEqual({
-      store: true,
       reasoning: { effort: `minimal` },
     })
   })
@@ -146,51 +145,10 @@ describe(`model catalog`, () => {
     )
 
     expect(payload).toEqual({
-      store: true,
       reasoning: { effort: `high` },
     })
   })
 
-  it(`forces store true only for OpenAI reasoning model payloads`, async () => {
-    const openAiCatalog = await createBuiltinModelCatalog()
-    const openAiConfig = resolveBuiltinModelConfig(openAiCatalog!, {
-      model: `openai:gpt-5`,
-    })
-
-    expect(
-      openAiConfig.onPayload!(
-        { store: false, reasoning: { effort: `none` } },
-        {} as any
-      )
-    ).toEqual({
-      store: true,
-      reasoning: { effort: `minimal` },
-    })
-
-    delete process.env.OPENAI_API_KEY
-    process.env.DEEPSEEK_API_KEY = `test-deepseek-key`
-    vi.stubGlobal(
-      `fetch`,
-      vi.fn(async (url: string) => {
-        if (String(url).includes(`deepseek.com`)) {
-          return {
-            ok: true,
-            status: 200,
-            json: async () => ({ data: [{ id: `deepseek-v4-flash` }] }),
-          }
-        }
-        return { ok: false, status: 401, json: async () => ({}) }
-      })
-    )
-
-    const deepseekCatalog = await createBuiltinModelCatalog()
-    const deepseekConfig = resolveBuiltinModelConfig(deepseekCatalog!, {
-      model: `deepseek:deepseek-v4-flash`,
-    })
-
-    expect(deepseekConfig.onPayload).toBeUndefined()
-  })
-
   it(`does not expose providers whose keys are rejected`, async () => {
     vi.stubGlobal(
       `fetch`,