feat: add strict tool message ordering setting for OpenAI-compatible providers

Adds a new setting `openAiStrictToolMessageOrdering` for OpenAI-compatible providers
that, when enabled, merges text content after tool results into the last tool message
instead of creating a separate user message.

This fixes the "Unexpected role user after role tool" error that occurs with
providers like NVIDIA NIM and Devstral that enforce strict message ordering rules.

Fixes #10540

packages/types/src/provider-settings.ts

@@ -250,7 +250,7 @@ const openAiSchema = baseProviderSettingsSchema.extend({
 	openAiStreamingEnabled: z.boolean().optional(),
 	openAiHostHeader: z.string().optional(), // Keep temporarily for backward compatibility during migration.
 	openAiHeaders: z.record(z.string(), z.string()).optional(),
-	openAiStrictToolMessageOrdering: z.boolean().optional(), // Merge text after tool results to avoid "user after tool" errors.
+	openAiStrictToolMessageOrdering: z.boolean().optional(), // For providers that don't allow user messages after tool messages.
 })
 
 const ollamaSchema = baseProviderSettingsSchema.extend({

src/api/providers/openai.ts

@@ -102,6 +102,11 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 			content: systemPrompt,
 		}
 
+		// When strict tool message ordering is enabled, merge text content after tool_results
+		// into the last tool message instead of creating a separate user message.
+		// This is required for providers like NVIDIA NIM that don't allow user messages after tool messages.
+		const strictToolMessageOrdering = this.options.openAiStrictToolMessageOrdering ?? false
+
 		if (this.options.openAiStreamingEnabled ?? true) {
 			let convertedMessages
 
@@ -122,11 +127,10 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 					}
 				}
 
-				// When openAiStrictToolMessageOrdering is enabled, merge text content after tool results
-				// into the last tool message. This fixes "user after tool" errors with NVIDIA NIM,
-				// OpenRouter, and other strict OpenAI-compatible APIs.
-				const mergeToolResultText = this.options.openAiStrictToolMessageOrdering ?? false
-				convertedMessages = [systemMessage, ...convertToOpenAiMessages(messages, { mergeToolResultText })]
+				convertedMessages = [
+					systemMessage,
+					...convertToOpenAiMessages(messages, { mergeToolResultText: strictToolMessageOrdering }),
+				]
 
 				if (modelInfo.supportsPromptCache) {
 					// Note: the following logic is copied from openrouter:
@@ -228,15 +232,14 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 				yield this.processUsageMetrics(lastUsage, modelInfo)
 			}
 		} else {
-			// When openAiStrictToolMessageOrdering is enabled, merge text content after tool results
-			// into the last tool message. This fixes "user after tool" errors with NVIDIA NIM,
-			// OpenRouter, and other strict OpenAI-compatible APIs.
-			const mergeToolResultText = this.options.openAiStrictToolMessageOrdering ?? false
 			const requestOptions: OpenAI.Chat.Completions.ChatCompletionCreateParamsNonStreaming = {
 				model: modelId,
 				messages: deepseekReasoner
 					? convertToR1Format([{ role: "user", content: systemPrompt }, ...messages])
-					: [systemMessage, ...convertToOpenAiMessages(messages, { mergeToolResultText })],
+					: [
+							systemMessage,
+							...convertToOpenAiMessages(messages, { mergeToolResultText: strictToolMessageOrdering }),
+						],
 				...(metadata?.tools && { tools: this.convertToolsForOpenAI(metadata.tools) }),
 				...(metadata?.tool_choice && { tool_choice: metadata.tool_choice }),
 				...(metadata?.toolProtocol === "native" && {
@@ -346,14 +349,11 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 	): ApiStream {
 		const modelInfo = this.getModel().info
 		const methodIsAzureAiInference = this._isAzureAiInference(this.options.openAiBaseUrl)
+		const strictToolMessageOrdering = this.options.openAiStrictToolMessageOrdering ?? false
 
 		if (this.options.openAiStreamingEnabled ?? true) {
 			const isGrokXAI = this._isGrokXAI(this.options.openAiBaseUrl)
 
-			// When openAiStrictToolMessageOrdering is enabled, merge text content after tool results
-			// into the last tool message. This fixes "user after tool" errors with NVIDIA NIM,
-			// OpenRouter, and other strict OpenAI-compatible APIs.
-			const mergeToolResultText = this.options.openAiStrictToolMessageOrdering ?? false
 			const requestOptions: OpenAI.Chat.Completions.ChatCompletionCreateParamsStreaming = {
 				model: modelId,
 				messages: [
@@ -361,7 +361,7 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 						role: "developer",
 						content: `Formatting re-enabled\n${systemPrompt}`,
 					},
-					...convertToOpenAiMessages(messages, { mergeToolResultText }),
+					...convertToOpenAiMessages(messages, { mergeToolResultText: strictToolMessageOrdering }),
 				],
 				stream: true,
 				...(isGrokXAI ? {} : { stream_options: { include_usage: true } }),
@@ -391,10 +391,6 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 
 			yield* this.handleStreamResponse(stream)
 		} else {
-			// When openAiStrictToolMessageOrdering is enabled, merge text content after tool results
-			// into the last tool message. This fixes "user after tool" errors with NVIDIA NIM,
-			// OpenRouter, and other strict OpenAI-compatible APIs.
-			const mergeToolResultText = this.options.openAiStrictToolMessageOrdering ?? false
 			const requestOptions: OpenAI.Chat.Completions.ChatCompletionCreateParamsNonStreaming = {
 				model: modelId,
 				messages: [
@@ -402,7 +398,7 @@ export class OpenAiHandler extends BaseProvider implements SingleCompletionHandl
 						role: "developer",
 						content: `Formatting re-enabled\n${systemPrompt}`,
 					},
-					...convertToOpenAiMessages(messages, { mergeToolResultText }),
+					...convertToOpenAiMessages(messages, { mergeToolResultText: strictToolMessageOrdering }),
 				],
 				reasoning_effort: modelInfo.reasoningEffort as "low" | "medium" | "high" | undefined,
 				temperature: undefined,

webview-ui/src/components/settings/providers/OpenAICompatible.tsx

@@ -162,10 +162,10 @@ export const OpenAICompatible = ({
 				<Checkbox
 					checked={apiConfiguration?.openAiStrictToolMessageOrdering ?? false}
 					onChange={handleInputChange("openAiStrictToolMessageOrdering", noTransform)}>
-					{t("settings:providers.openAiStrictToolMessageOrdering")}
+					{t("settings:providers.openAiStrictToolMessageOrdering.label")}
 				</Checkbox>
 				<div className="text-sm text-vscode-descriptionForeground ml-6">
-					{t("settings:providers.openAiStrictToolMessageOrderingDescription")}
+					{t("settings:providers.openAiStrictToolMessageOrdering.description")}
 				</div>
 			</div>
 			<div>

webview-ui/src/i18n/locales/en/settings.json

@@ -498,6 +498,10 @@
 			},
 			"resetDefaults": "Reset to Defaults"
 		},
+		"openAiStrictToolMessageOrdering": {
+			"label": "Strict tool message ordering",
+			"description": "Enable for providers like NVIDIA NIM and Devstral that require strict message ordering. When enabled, text content after tool results is merged into the last tool message instead of creating a separate user message."
+		},
 		"rateLimitSeconds": {
 			"label": "Rate limit",
 			"description": "Minimum time between API requests."