fix(parallel): use truncateUtf16Safe for MCP error JSON truncation (#102592)

Pandah97 · steipete · web-flow · commit c87b9a7cee90 · 2026-07-09T11:25:28.000+01:00
* fix(parallel): use truncateUtf16Safe for MCP error JSON truncation

The extractMcpToolPayload function and error messages use naive
.slice(0, 500) on JSON-serialized errors and results which can split
surrogate pairs. Replace with truncateUtf16Safe().

* test(parallel): cover UTF-16-safe MCP errors

---------

Co-authored-by: Peter Steinberger &lt;steipete@gmail.com&gt;
diff --git a/extensions/parallel/src/parallel-mcp-search.runtime.test.ts b/extensions/parallel/src/parallel-mcp-search.runtime.test.ts
@@ -78,6 +78,28 @@ function headerOf(call: EndpointCall, name: string): string | undefined {
   return (call.init.headers as Record<string, string>)[name];
 }
 
+function boundaryJsonPayload(base: Record<string, unknown>): {
+  payload: Record<string, unknown>;
+  truncatedJson: string;
+} {
+  const empty = { ...base, detail: "" };
+  const jsonPrefix = JSON.stringify(empty).slice(0, -2);
+  const detailPrefix = "x".repeat(499 - jsonPrefix.length);
+  return {
+    payload: { ...base, detail: `${detailPrefix}😀tail` },
+    truncatedJson: `${jsonPrefix}${detailPrefix}`,
+  };
+}
+
+function thrownMessage(run: () => unknown): string {
+  try {
+    run();
+  } catch (error) {
+    return error instanceof Error ? error.message : String(error);
+  }
+  throw new Error("Expected call to throw.");
+}
+
 describe("iterMcpMessages", () => {
   it("parses a single JSON object body", () => {
     expect(iterMcpMessages('{"id":"a","result":{}}')).toEqual([{ id: "a", result: {} }]);
@@ -149,20 +171,26 @@ describe("extractMcpToolPayload", () => {
   });
 
   it("throws on a JSON-RPC error", () => {
-    expect(() => extractMcpToolPayload({ error: { code: -1, message: "boom" } })).toThrow(
-      /Parallel MCP error/,
+    const { payload, truncatedJson } = boundaryJsonPayload({ code: -1, message: "boom" });
+
+    expect(thrownMessage(() => extractMcpToolPayload({ error: payload }))).toBe(
+      `Parallel MCP error: ${truncatedJson}`,
     );
   });
 
   it("throws on a tool-level isError", () => {
-    expect(() =>
-      extractMcpToolPayload({ result: { isError: true, content: [{ type: "text", text: "{}" }] } }),
-    ).toThrow(/Parallel MCP tool error/);
+    const { payload, truncatedJson } = boundaryJsonPayload({ isError: true });
+
+    expect(thrownMessage(() => extractMcpToolPayload({ result: payload }))).toBe(
+      `Parallel MCP tool error: ${truncatedJson}`,
+    );
   });
 
   it("throws when there is no parseable content", () => {
-    expect(() => extractMcpToolPayload({ result: { content: [] } })).toThrow(
-      /no parseable content/,
+    const { payload, truncatedJson } = boundaryJsonPayload({ content: [] });
+
+    expect(thrownMessage(() => extractMcpToolPayload({ result: payload }))).toBe(
+      `Parallel MCP returned no parseable content: ${truncatedJson}`,
     );
   });
 });
diff --git a/extensions/parallel/src/parallel-mcp-search.runtime.ts b/extensions/parallel/src/parallel-mcp-search.runtime.ts
@@ -7,6 +7,7 @@ import {
 } from "openclaw/plugin-sdk/provider-http";
 import { withTrustedWebSearchEndpoint } from "openclaw/plugin-sdk/provider-web-search";
 import { isRecord } from "openclaw/plugin-sdk/string-coerce-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 
 // Free hosted Search MCP. This keyless transport is used only after the user
 // explicitly selects the `parallel-free` web_search provider. Docs:
@@ -154,11 +155,13 @@ export function selectMcpEnvelope(text: string, requestId: string): JsonRpcMessa
  */
 export function extractMcpToolPayload(envelope: JsonRpcMessage): McpToolPayload {
   if ("error" in envelope) {
-    throw new Error(`Parallel MCP error: ${JSON.stringify(envelope.error).slice(0, 500)}`);
+    throw new Error(
+      `Parallel MCP error: ${truncateUtf16Safe(JSON.stringify(envelope.error), 500)}`,
+    );
   }
   const result = isRecord(envelope.result) ? envelope.result : {};
   if (result.isError) {
-    throw new Error(`Parallel MCP tool error: ${JSON.stringify(result).slice(0, 500)}`);
+    throw new Error(`Parallel MCP tool error: ${truncateUtf16Safe(JSON.stringify(result), 500)}`);
   }
   if (isRecord(result.structuredContent)) {
     return result.structuredContent;
@@ -177,7 +180,7 @@ export function extractMcpToolPayload(envelope: JsonRpcMessage): McpToolPayload
     }
   }
   throw new Error(
-    `Parallel MCP returned no parseable content: ${JSON.stringify(result).slice(0, 500)}`,
+    `Parallel MCP returned no parseable content: ${truncateUtf16Safe(JSON.stringify(result), 500)}`,
   );
 }
 

Original file line number	Diff line number	Diff line change
`@@ -7,6 +7,7 @@ import {`
`7`	`7`	`} from "openclaw/plugin-sdk/provider-http";`
`8`	`8`	`import { withTrustedWebSearchEndpoint } from "openclaw/plugin-sdk/provider-web-search";`
`9`	`9`	`import { isRecord } from "openclaw/plugin-sdk/string-coerce-runtime";`
	`10`	`+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";`
`10`	`11`
`11`	`12`	`// Free hosted Search MCP. This keyless transport is used only after the user`
`12`	`13`	// explicitly selects the `parallel-free` web_search provider. Docs:
`@@ -154,11 +155,13 @@ export function selectMcpEnvelope(text: string, requestId: string): JsonRpcMessa`
`154`	`155`	`*/`
`155`	`156`	`export function extractMcpToolPayload(envelope: JsonRpcMessage): McpToolPayload {`
`156`	`157`	`if ("error" in envelope) {`
`157`		- throw new Error(`Parallel MCP error: ${JSON.stringify(envelope.error).slice(0, 500)}`);
	`158`	`+ throw new Error(`
	`159`	+ `Parallel MCP error: ${truncateUtf16Safe(JSON.stringify(envelope.error), 500)}`,
	`160`	`+ );`
`158`	`161`	`}`
`159`	`162`	`const result = isRecord(envelope.result) ? envelope.result : {};`
`160`	`163`	`if (result.isError) {`
`161`		- throw new Error(`Parallel MCP tool error: ${JSON.stringify(result).slice(0, 500)}`);
	`164`	+ throw new Error(`Parallel MCP tool error: ${truncateUtf16Safe(JSON.stringify(result), 500)}`);
`162`	`165`	`}`
`163`	`166`	`if (isRecord(result.structuredContent)) {`
`164`	`167`	`return result.structuredContent;`
`@@ -177,7 +180,7 @@ export function extractMcpToolPayload(envelope: JsonRpcMessage): McpToolPayload`
`177`	`180`	`}`
`178`	`181`	`}`
`179`	`182`	`throw new Error(`
`180`		- `Parallel MCP returned no parseable content: ${JSON.stringify(result).slice(0, 500)}`,
	`183`	+ `Parallel MCP returned no parseable content: ${truncateUtf16Safe(JSON.stringify(result), 500)}`,
`181`	`184`	`);`
`182`	`185`	`}`
`183`	`186`