test(managed-agent): parse only complete rows in the wedge driver wire (#14496)

* test(managed-agent): parse only complete rows in the wedge driver wire

* test(managed-agent): pin the wire reader to complete rows

The blocked-wedge driver's wire reader had no executable coverage: the
driver cannot be imported (it parses argv and boots a daemon at load),
and the Java gates that spawn it are skipped on PR events. Extract the
parse into a side-effect-free helper so a unit test can exercise it, and
pin the mutants that matter with two complete rows plus an unterminated
tail.

---------

Co-authored-by: 易良 <1204183885@qq.com>

integration-tests/helpers/hosted-recovery-blocked-wedge-driver.ts

@@ -34,6 +34,7 @@ import { LISTENING_LINE_RE, stopDaemon } from './daemon-process.js';
 import { HOSTED_HOME_PREFIX } from '../scratch-dir.js';
 import { relayUpstream } from './hosted-relay-headers.js';
 import { waitUntil } from './hosted-harness-process.js';
+import { parseWireRows, type WireRow } from './wire-rows.js';
 
 const config = JSON.parse(await readFile(process.argv[2], 'utf8')) as {
   tenantId: string;
@@ -544,25 +545,9 @@ const model = await startFakeOpenAIServer(({ body }) => {
 
 const daemon = await new WedgeDaemon().start(model.baseUrl);
 
-interface WireRow {
-  kind?: string;
-  requestId?: number;
-  at?: number;
-  method?: string;
-  url?: string;
-  operation?: string;
-  status?: number;
-  requestSnippet?: string;
-  responseSnippet?: string;
-  replied?: string;
-}
-
 async function readWire(): Promise<WireRow[]> {
   try {
-    return (await readFile(config.wireFile, 'utf8'))
-      .split('\n')
-      .filter(Boolean)
-      .map((line) => JSON.parse(line) as WireRow);
+    return parseWireRows(await readFile(config.wireFile, 'utf8'));
   } catch (cause) {
     if ((cause as NodeJS.ErrnoException)?.code === 'ENOENT') return [];
     throw cause;

integration-tests/helpers/wire-rows.test.ts

@@ -0,0 +1,41 @@
+/**
+ * @license
+ * Copyright 2026 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, expect, it } from 'vitest';
+import { parseWireRows } from './wire-rows.js';
+
+describe('parseWireRows', () => {
+  it('returns no rows for an empty buffer', () => {
+    expect(parseWireRows('')).toEqual([]);
+  });
+
+  it('returns no rows when the only row has no trailing newline yet', () => {
+    expect(parseWireRows('{"kind":"a"}')).toEqual([]);
+  });
+
+  it('drops an unterminated tail and keeps the complete rows', () => {
+    // Two complete rows keep lastIndexOf -> indexOf observable; with a single
+    // complete row that mutant survives.
+    expect(parseWireRows('{"kind":"a"}\n{"kind":"b"}\n{"kind":"c"')).toEqual([
+      { kind: 'a' },
+      { kind: 'b' },
+    ]);
+  });
+
+  it('returns one row for a single terminated row', () => {
+    expect(parseWireRows('{"kind":"a"}\n')).toEqual([{ kind: 'a' }]);
+  });
+
+  it('returns no rows for a buffer that is only a newline', () => {
+    expect(parseWireRows('\n')).toEqual([]);
+  });
+
+  it('still throws on a malformed complete row', () => {
+    expect(() => parseWireRows('{"kind":"a"}\n{"kind":\n')).toThrow(
+      SyntaxError,
+    );
+  });
+});

integration-tests/helpers/wire-rows.ts

@@ -0,0 +1,31 @@
+/**
+ * @license
+ * Copyright 2026 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export interface WireRow {
+  kind?: string;
+  requestId?: number;
+  at?: number;
+  method?: string;
+  url?: string;
+  operation?: string;
+  status?: number;
+  requestSnippet?: string;
+  responseSnippet?: string;
+  replied?: string;
+}
+
+// The blocked-wedge driver appends each row with one appendFile of
+// JSON.stringify(row) + '\n', and polls the same file from the same process,
+// so a read can land mid-append. Parse only complete rows: an unterminated
+// tail is the row still being written, and the next poll reads it whole. A
+// complete-but-malformed row still reaches JSON.parse and throws.
+export function parseWireRows(text: string): WireRow[] {
+  return text
+    .slice(0, text.lastIndexOf('\n') + 1)
+    .split('\n')
+    .filter(Boolean)
+    .map((line) => JSON.parse(line) as WireRow);
+}