fix(ai,coding-agent): preserve non-vision image placeholders closes #3429

packages/ai/src/providers/anthropic.ts

@@ -783,8 +783,7 @@ function convertMessages(
 						};
 					}
 				});
-				let filteredBlocks = !model?.input.includes("image") ? blocks.filter((b) => b.type !== "image") : blocks;
-				filteredBlocks = filteredBlocks.filter((b) => {
+				const filteredBlocks = blocks.filter((b) => {
 					if (b.type === "text") {
 						return b.text.trim().length > 0;
 					}

packages/ai/src/providers/google-shared.ts

@@ -116,11 +116,10 @@ export function convertMessages<T extends GoogleApiType>(model: Model<T>, contex
 						};
 					}
 				});
-				const filteredParts = !model.input.includes("image") ? parts.filter((p) => p.text !== undefined) : parts;
-				if (filteredParts.length === 0) continue;
+				if (parts.length === 0) continue;
 				contents.push({
 					role: "user",
-					parts: filteredParts,
+					parts,
 				});
 			}
 		} else if (msg.role === "assistant") {

packages/ai/src/providers/openai-completions.ts

@@ -97,8 +97,11 @@ export const streamOpenAICompletions: StreamFunction<"openai-completions", OpenA
 
 		try {
 			const apiKey = options?.apiKey || getEnvApiKey(model.provider) || "";
-			const client = createClient(model, context, apiKey, options?.headers);
-			let params = buildParams(model, context, options);
+			const compat = getCompat(model);
+			const cacheRetention = resolveCacheRetention(options?.cacheRetention);
+			const cacheSessionId = cacheRetention === "none" ? undefined : options?.sessionId;
+			const client = createClient(model, context, apiKey, options?.headers, cacheSessionId, compat);
+			let params = buildParams(model, context, options, compat, cacheRetention);
 			const nextParams = await options?.onPayload?.(params, model);
 			if (nextParams !== undefined) {
 				params = nextParams as OpenAI.Chat.Completions.ChatCompletionCreateParamsStreaming;
@@ -350,6 +353,8 @@ function createClient(
 	context: Context,
 	apiKey?: string,
 	optionsHeaders?: Record<string, string>,
+	sessionId?: string,
+	compat: Required<OpenAICompletionsCompat> = getCompat(model),
 ) {
 	if (!apiKey) {
 		if (!process.env.OPENAI_API_KEY) {
@@ -370,6 +375,12 @@ function createClient(
 		Object.assign(headers, copilotHeaders);
 	}
 
+	if (sessionId && compat.sendSessionAffinityHeaders) {
+		headers.session_id = sessionId;
+		headers["x-client-request-id"] = sessionId;
+		headers["x-session-affinity"] = sessionId;
+	}
+
 	// Merge options headers last so they can override defaults
 	if (optionsHeaders) {
 		Object.assign(headers, optionsHeaders);
@@ -383,12 +394,16 @@ function createClient(
 	});
 }
 
-function buildParams(model: Model<"openai-completions">, context: Context, options?: OpenAICompletionsOptions) {
-	const compat = getCompat(model);
+function buildParams(
+	model: Model<"openai-completions">,
+	context: Context,
+	options?: OpenAICompletionsOptions,
+	compat: Required<OpenAICompletionsCompat> = getCompat(model),
+	cacheRetention: CacheRetention = resolveCacheRetention(options?.cacheRetention),
+) {
 	const messages = convertMessages(model, context, compat);
 	maybeAddOpenRouterAnthropicCacheControl(model, messages);
 
-	const cacheRetention = resolveCacheRetention(options?.cacheRetention);
 	const params: OpenAI.Chat.Completions.ChatCompletionCreateParamsStreaming = {
 		model: model.id,
 		messages,
@@ -580,13 +595,10 @@ export function convertMessages(
 						} satisfies ChatCompletionContentPartImage;
 					}
 				});
-				const filteredContent = !model.input.includes("image")
-					? content.filter((c) => c.type !== "image_url")
-					: content;
-				if (filteredContent.length === 0) continue;
+				if (content.length === 0) continue;
 				params.push({
 					role: "user",
-					content: filteredContent,
+					content,
 				});
 			}
 		} else if (msg.role === "assistant") {
@@ -878,6 +890,7 @@ function detectCompat(model: Model<"openai-completions">): Required<OpenAIComple
 		vercelGatewayRouting: {},
 		zaiToolStream: false,
 		supportsStrictMode: true,
+		sendSessionAffinityHeaders: false,
 	};
 }
 
@@ -905,5 +918,6 @@ function getCompat(model: Model<"openai-completions">): Required<OpenAICompletio
 		vercelGatewayRouting: model.compat.vercelGatewayRouting ?? detected.vercelGatewayRouting,
 		zaiToolStream: model.compat.zaiToolStream ?? detected.zaiToolStream,
 		supportsStrictMode: model.compat.supportsStrictMode ?? detected.supportsStrictMode,
+		sendSessionAffinityHeaders: model.compat.sendSessionAffinityHeaders ?? detected.sendSessionAffinityHeaders,
 	};
 }

packages/ai/src/providers/openai-responses-shared.ts

@@ -153,13 +153,10 @@ export function convertResponsesMessages<TApi extends Api>(
 						image_url: `data:${item.mimeType};base64,${item.data}`,
 					} satisfies ResponseInputImage;
 				});
-				const filteredContent = !model.input.includes("image")
-					? content.filter((c) => c.type !== "input_image")
-					: content;
-				if (filteredContent.length === 0) continue;
+				if (content.length === 0) continue;
 				messages.push({
 					role: "user",
-					content: filteredContent,
+					content,
 				});
 			}
 		} else if (msg.role === "assistant") {

packages/ai/src/providers/transform-messages.ts

@@ -1,4 +1,60 @@
-import type { Api, AssistantMessage, Message, Model, ToolCall, ToolResultMessage } from "../types.js";
+import type {
+	Api,
+	AssistantMessage,
+	ImageContent,
+	Message,
+	Model,
+	TextContent,
+	ToolCall,
+	ToolResultMessage,
+} from "../types.js";
+
+const NON_VISION_USER_IMAGE_PLACEHOLDER = "(image omitted: model does not support images)";
+const NON_VISION_TOOL_IMAGE_PLACEHOLDER = "(tool image omitted: model does not support images)";
+
+function replaceImagesWithPlaceholder(content: (TextContent | ImageContent)[], placeholder: string): TextContent[] {
+	const result: TextContent[] = [];
+	let previousWasPlaceholder = false;
+
+	for (const block of content) {
+		if (block.type === "image") {
+			if (!previousWasPlaceholder) {
+				result.push({ type: "text", text: placeholder });
+			}
+			previousWasPlaceholder = true;
+			continue;
+		}
+
+		result.push(block);
+		previousWasPlaceholder = block.text === placeholder;
+	}
+
+	return result;
+}
+
+function downgradeUnsupportedImages<TApi extends Api>(messages: Message[], model: Model<TApi>): Message[] {
+	if (model.input.includes("image")) {
+		return messages;
+	}
+
+	return messages.map((msg) => {
+		if (msg.role === "user" && Array.isArray(msg.content)) {
+			return {
+				...msg,
+				content: replaceImagesWithPlaceholder(msg.content, NON_VISION_USER_IMAGE_PLACEHOLDER),
+			};
+		}
+
+		if (msg.role === "toolResult") {
+			return {
+				...msg,
+				content: replaceImagesWithPlaceholder(msg.content, NON_VISION_TOOL_IMAGE_PLACEHOLDER),
+			};
+		}
+
+		return msg;
+	});
+}
 
 /**
  * Normalize tool call ID for cross-provider compatibility.
@@ -12,9 +68,10 @@ export function transformMessages<TApi extends Api>(
 ): Message[] {
 	// Build a map of original tool call IDs to normalized IDs
 	const toolCallIdMap = new Map<string, string>();
+	const imageAwareMessages = downgradeUnsupportedImages(messages, model);
 
-	// First pass: transform messages (thinking blocks, tool call ID normalization)
-	const transformed = messages.map((msg) => {
+	// First pass: transform messages (unsupported image downgrade, thinking blocks, tool call ID normalization)
+	const transformed = imageAwareMessages.map((msg) => {
 		// User messages pass through unchanged
 		if (msg.role === "user") {
 			return msg;