fix(coding-agent): ignore Node's own worker messages in image resize

Under `node --watch`, Node 24.19+ and 26.x post `{ "watch:require": [...] }`
on the worker message channel (nodejs/node#65044). The image resize code
treated the first message as the worker's reply, resolved it to `null`, and
dropped the image as "could not be resized below the inline image size limit".

Worker replies now carry a `type` marker, and the main thread ignores any
message without it. The reply type is now either a result or an error.

fixes #10527

packages/coding-agent/CHANGELOG.md

@@ -23,6 +23,7 @@
 - Fixed the codemode description not marking `searchTools()`, `describeTool()`, and `describeNamespace()` as async, which led models to serialize the unawaited promise as `{}` ([#10555](https://github.com/earendil-works/pi/issues/10555))
 - Fixed codemode output items running together, so models could not tell where one `text()` or `console.log()` output ended and the next began. With several text items, each now starts with a `==> text N/M <==` line, and `console` calls follow the other output in one `<console_output>` block with one line per call
 - Fixed `/mcp` waiting for all servers to connect before opening; the manager now updates live and remains usable while enabling, reconnecting, or disabling servers ([#10562](https://github.com/earendil-works/pi/issues/10562))
+- Fixed images being dropped as "could not be resized" when running under `node --watch` on Node 24.19+ and 26.x, where Node posts its own messages on the image resize worker channel ([#10527](https://github.com/earendil-works/pi/issues/10527))
 
 ## [1.0.4] - 2026-10-05
 

packages/coding-agent/src/utils/image-resize-core.ts

@@ -18,6 +18,16 @@ export interface ResizedImage {
 	wasResized: boolean;
 }
 
+/**
+ * Tag on image resize worker replies. Node can post its own messages on the worker channel
+ * (for example `{ "watch:require": [...] }` under `node --watch`), so replies must be identifiable.
+ */
+export const IMAGE_RESIZE_WORKER_RESPONSE_TYPE = "pi:image-resize-response";
+
+export type ResizeImageWorkerResponse =
+	| { type: typeof IMAGE_RESIZE_WORKER_RESPONSE_TYPE; result: ResizedImage | null }
+	| { type: typeof IMAGE_RESIZE_WORKER_RESPONSE_TYPE; error: string };
+
 // 4.5MB of base64 payload. Provides headroom below Anthropic's 5MB limit.
 const DEFAULT_MAX_BYTES = 4.5 * 1024 * 1024;
 

packages/coding-agent/src/utils/image-resize-worker.ts

@@ -1,5 +1,10 @@
 import { parentPort } from "node:worker_threads";
-import { type ImageResizeOptions, type ResizedImage, resizeImageInProcess } from "./image-resize-core.ts";
+import {
+	IMAGE_RESIZE_WORKER_RESPONSE_TYPE,
+	type ImageResizeOptions,
+	type ResizeImageWorkerResponse,
+	resizeImageInProcess,
+} from "./image-resize-core.ts";
 
 interface ResizeImageWorkerRequest {
 	inputBytes: Uint8Array;
@@ -7,11 +12,6 @@ interface ResizeImageWorkerRequest {
 	options?: ImageResizeOptions;
 }
 
-interface ResizeImageWorkerResponse {
-	result?: ResizedImage | null;
-	error?: string;
-}
-
 function isResizeImageWorkerRequest(value: unknown): value is ResizeImageWorkerRequest {
 	if (!value || typeof value !== "object") return false;
 	const record = value as Record<string, unknown>;
@@ -30,10 +30,11 @@ port.once("message", (message: unknown) => {
 				throw new Error("Invalid image resize worker request");
 			}
 			const result = await resizeImageInProcess(message.inputBytes, message.mimeType, message.options);
-			const response: ResizeImageWorkerResponse = { result };
+			const response: ResizeImageWorkerResponse = { type: IMAGE_RESIZE_WORKER_RESPONSE_TYPE, result };
 			port.postMessage(response);
 		} catch (error) {
 			const response: ResizeImageWorkerResponse = {
+				type: IMAGE_RESIZE_WORKER_RESPONSE_TYPE,
 				error: error instanceof Error ? error.message : String(error),
 			};
 			port.postMessage(response);

packages/coding-agent/src/utils/image-resize.ts

@@ -1,13 +1,14 @@
 import { Worker } from "node:worker_threads";
-import { type ImageResizeOptions, type ResizedImage, resizeImageInProcess } from "./image-resize-core.ts";
+import {
+	IMAGE_RESIZE_WORKER_RESPONSE_TYPE,
+	type ImageResizeOptions,
+	type ResizedImage,
+	type ResizeImageWorkerResponse,
+	resizeImageInProcess,
+} from "./image-resize-core.ts";
 
 export type { ImageResizeOptions, ResizedImage } from "./image-resize-core.ts";
 
-interface ResizeImageWorkerResponse {
-	result?: ResizedImage | null;
-	error?: string;
-}
-
 function toTransferableBytes(input: Uint8Array): Uint8Array<ArrayBuffer> {
 	// Transfer detaches the buffer, so transfer a worker-owned copy and leave the
 	// caller's bytes intact.
@@ -15,7 +16,9 @@ function toTransferableBytes(input: Uint8Array): Uint8Array<ArrayBuffer> {
 }
 
 function isResizeImageWorkerResponse(value: unknown): value is ResizeImageWorkerResponse {
-	return value !== null && typeof value === "object";
+	return (
+		value !== null && typeof value === "object" && "type" in value && value.type === IMAGE_RESIZE_WORKER_RESPONSE_TYPE
+	);
 }
 
 function createResizeWorker(workerSpecifier: string | URL): Worker {
@@ -44,16 +47,12 @@ async function resizeImageInWorker(
 				reject(error);
 			};
 
-			worker.once("message", (message: unknown) => {
-				if (!isResizeImageWorkerResponse(message)) {
-					fail(new Error("Invalid image resize worker response"));
-					return;
-				}
-				if (message.error) {
-					fail(new Error(message.error));
-					return;
-				}
-				settle(message.result ?? null);
+			worker.on("message", (message: unknown) => {
+				// Ignore messages Node posts on the worker channel itself, such as
+				// `{ "watch:require": [...] }` under `node --watch` (nodejs/node#65044).
+				if (!isResizeImageWorkerResponse(message)) return;
+				if ("error" in message) fail(new Error(message.error));
+				else settle(message.result);
 			});
 			worker.once("error", fail);
 			worker.once("exit", (code) => {