fix: preserve reasoning_details shape to prevent malformed responses

Follow-up to #10285.

- Preserve the original reasoning_details array structure from the API
  to prevent malformed responses when sending back to providers
- Strip 'id' field from openai-responses-v1 blocks because OpenAI's
  Responses API requires 'store: true' to persist reasoning blocks
  (we manage conversation state client-side)
- Preserve 'id' field for other formats like xai-responses-v1
- Handle reasoning_details on string-content messages that were
  previously losing this data during transformation
- Add comprehensive test coverage for reasoning_details handling

Author: hannesrudolph

src/api/providers/openrouter.ts

@@ -361,7 +361,8 @@ export class OpenRouterHandler extends BaseProvider implements SingleCompletionH
 		}
 
 		let lastUsage: CompletionUsage | undefined = undefined
-		// Accumulator for reasoning_details: accumulate text by type-index key
+		// Accumulator for reasoning_details FROM the API.
+		// We preserve the original shape of reasoning_details to prevent malformed responses.
 		const reasoningDetailsAccumulator = new Map<
 			string,
 			{
@@ -376,6 +377,11 @@ export class OpenRouterHandler extends BaseProvider implements SingleCompletionH
 			}
 		>()
 
+		// Track whether we've yielded displayable text from reasoning_details.
+		// When reasoning_details has displayable content (reasoning.text or reasoning.summary),
+		// we skip yielding the top-level reasoning field to avoid duplicate display.
+		let hasYieldedReasoningFromDetails = false
+
 		for await (const chunk of stream) {
 			// OpenRouter returns an error object instead of the OpenAI SDK throwing an error.
 			if ("error" in chunk) {
@@ -438,22 +444,28 @@ export class OpenRouterHandler extends BaseProvider implements SingleCompletionH
 						}
 
 						// Yield text for display (still fragmented for live streaming)
+						// Only reasoning.text and reasoning.summary have displayable content
+						// reasoning.encrypted is intentionally skipped as it contains redacted content
 						let reasoningText: string | undefined
 						if (detail.type === "reasoning.text" && typeof detail.text === "string") {
 							reasoningText = detail.text
 						} else if (detail.type === "reasoning.summary" && typeof detail.summary === "string") {
 							reasoningText = detail.summary
 						}
-						// Note: reasoning.encrypted types are intentionally skipped as they contain redacted content
 
 						if (reasoningText) {
+							hasYieldedReasoningFromDetails = true
 							yield { type: "reasoning", text: reasoningText }
 						}
 					}
-				} else if ("reasoning" in delta && delta.reasoning && typeof delta.reasoning === "string") {
-					// Handle legacy reasoning format - only if reasoning_details is not present
-					// See: https://openrouter.ai/docs/use-cases/reasoning-tokens
-					yield { type: "reasoning", text: delta.reasoning }
+				}
+
+				// Handle top-level reasoning field for UI display.
+				// Skip if we've already yielded from reasoning_details to avoid duplicate display.
+				if ("reasoning" in delta && delta.reasoning && typeof delta.reasoning === "string") {
+					if (!hasYieldedReasoningFromDetails) {
+						yield { type: "reasoning", text: delta.reasoning }
+					}
 				}
 
 				// Emit raw tool call chunks - NativeToolCallParser handles state management
@@ -488,7 +500,7 @@ export class OpenRouterHandler extends BaseProvider implements SingleCompletionH
 			}
 		}
 
-		// After streaming completes, store the accumulated reasoning_details
+		// After streaming completes, store ONLY the reasoning_details we received from the API.
 		if (reasoningDetailsAccumulator.size > 0) {
 			this.currentReasoningDetails = Array.from(reasoningDetailsAccumulator.values())
 		}

src/api/providers/roo.ts

@@ -146,7 +146,8 @@ export class RooHandler extends BaseOpenAiCompatibleProvider<string> {
 			const stream = await this.createStream(systemPrompt, messages, metadata, { headers })
 
 			let lastUsage: RooUsage | undefined = undefined
-			// Accumulator for reasoning_details: accumulate text by type-index key
+			// Accumulator for reasoning_details FROM the API.
+			// We preserve the original shape of reasoning_details to prevent malformed responses.
 			const reasoningDetailsAccumulator = new Map<
 				string,
 				{
@@ -161,6 +162,11 @@ export class RooHandler extends BaseOpenAiCompatibleProvider<string> {
 				}
 			>()
 
+			// Track whether we've yielded displayable text from reasoning_details.
+			// When reasoning_details has displayable content (reasoning.text or reasoning.summary),
+			// we skip yielding the top-level reasoning field to avoid duplicate display.
+			let hasYieldedReasoningFromDetails = false
+
 			for await (const chunk of stream) {
 				const delta = chunk.choices[0]?.delta
 				const finishReason = chunk.choices[0]?.finish_reason
@@ -223,29 +229,32 @@ export class RooHandler extends BaseOpenAiCompatibleProvider<string> {
 							}
 
 							// Yield text for display (still fragmented for live streaming)
+							// Only reasoning.text and reasoning.summary have displayable content
+							// reasoning.encrypted is intentionally skipped as it contains redacted content
 							let reasoningText: string | undefined
 							if (detail.type === "reasoning.text" && typeof detail.text === "string") {
 								reasoningText = detail.text
 							} else if (detail.type === "reasoning.summary" && typeof detail.summary === "string") {
 								reasoningText = detail.summary
 							}
-							// Note: reasoning.encrypted types are intentionally skipped as they contain redacted content
 
 							if (reasoningText) {
+								hasYieldedReasoningFromDetails = true
 								yield { type: "reasoning", text: reasoningText }
 							}
 						}
-					} else if ("reasoning" in delta && delta.reasoning && typeof delta.reasoning === "string") {
-						// Handle legacy reasoning format - only if reasoning_details is not present
-						yield {
-							type: "reasoning",
-							text: delta.reasoning,
+					}
+
+					// Handle top-level reasoning field for UI display.
+					// Skip if we've already yielded from reasoning_details to avoid duplicate display.
+					if ("reasoning" in delta && delta.reasoning && typeof delta.reasoning === "string") {
+						if (!hasYieldedReasoningFromDetails) {
+							yield { type: "reasoning", text: delta.reasoning }
 						}
 					} else if ("reasoning_content" in delta && typeof delta.reasoning_content === "string") {
 						// Also check for reasoning_content for backward compatibility
-						yield {
-							type: "reasoning",
-							text: delta.reasoning_content,
+						if (!hasYieldedReasoningFromDetails) {
+							yield { type: "reasoning", text: delta.reasoning_content }
 						}
 					}
 
@@ -282,7 +291,7 @@ export class RooHandler extends BaseOpenAiCompatibleProvider<string> {
 				}
 			}
 
-			// After streaming completes, store the accumulated reasoning_details
+			// After streaming completes, store ONLY the reasoning_details we received from the API.
 			if (reasoningDetailsAccumulator.size > 0) {
 				this.currentReasoningDetails = Array.from(reasoningDetailsAccumulator.values())
 			}