Fix OpenAI reasoning item error in Responses API #59
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OpenAI Responses API was failing with error: 'Item rs_* of type reasoning was provided without its required following item' This occurred when using reasoning models (gpt-5, o3, o4-mini) with tool calls in multi-turn conversations. Root cause: When using reasoning models with tool calls, OpenAI requires including 'reasoning.encrypted_content' in the include option to properly preserve reasoning context across conversation steps. Solution: Add include: ['reasoning.encrypted_content'] to OpenAI provider options when reasoningEffort is configured. Refs: https://sdk.vercel.ai/providers/ai-sdk-providers/openai#responses-models
ammario
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Oct 7, 2025
## Problem After merging PR #59, the OpenAI reasoning error still occurred: ``` Item 'rs_01e84f5b161f6bce0068e480e7778481a3a2c3b6234d6bb7c6' of type 'reasoning' was provided without its required following item. ``` ## Root Cause Analysis **The issue was OpenAI-specific.** Anthropic reasoning and OpenAI reasoning work differently: ### Anthropic - Uses **text-based reasoning parts** in message content - These **SHOULD be sent back** to the API (via `sendReasoning: true` option, which defaults to true) - The model uses historical reasoning context to improve responses ### OpenAI - Uses **encrypted reasoning items** with IDs (e.g., `rs_*`) - These are managed automatically via `previous_response_id` - Sending Anthropic-style text reasoning parts creates **orphaned reasoning items** that cause API errors - Per OpenAI docs: "In typical multi-turn conversations, you don't need to include reasoning items or tokens—the model is trained to produce the best output without them" ## Solution **Strip reasoning parts ONLY for OpenAI**, before converting CmuxMessages to ModelMessages. - Added `stripReasoningForOpenAI()` function for OpenAI-specific processing - Apply it conditionally based on provider in `aiService.ts` - Keeps Anthropic behavior intact (reasoning sent via `sendReasoning`) ## Changes 1. **New function**: `stripReasoningForOpenAI()` in `modelMessageTransform.ts` 2. **Updated `aiService.ts`**: Apply reasoning stripping only for OpenAI provider 3. **Reverted previous change**: `filterEmptyAssistantMessages()` no longer strips all reasoning 4. **Added detailed comments** explaining provider-specific differences This ensures: - ✅ OpenAI doesn't get orphaned reasoning items - ✅ Anthropic still receives reasoning context - ✅ Provider-specific behavior is clearly documented
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Problem
OpenAI Responses API was intermittently failing with error:
This occurred when using reasoning models (gpt-5, o3, o4-mini) with tool calls in multi-turn conversations.
Root Cause
From the Vercel AI SDK documentation:
Even though we're using the default
store: trueandpreviousResponseIdfor persistence, we still need to explicitly include reasoning encrypted content when tool calls are involved. The reasoning items have IDs (likers_*) that must be properly linked to their following items.Solution
Added
include: ['reasoning.encrypted_content']to OpenAI provider options whenreasoningEffortis configured (meaning reasoning is enabled).This ensures reasoning context is properly preserved across multi-turn conversations with tool calls.
Changes
buildProviderOptions()insrc/utils/ai/providerOptions.tsincludewhen reasoning is actually enabledTesting
Not adding automated tests as the error was intermittent and difficult to reliably reproduce. The fix is based directly on OpenAI/Vercel SDK documentation requirements.