fix(coding-agent): align undici fetch globals

closes #4650

closes #4652

closes #4653

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Fixed JSON parse failures for compressed fetch responses under Node 26.0 by installing undici fetch globals alongside pi's global dispatcher ([#4650](https://github.com/earendil-works/pi/issues/4650), [#4652](https://github.com/earendil-works/pi/issues/4652), [#4653](https://github.com/earendil-works/pi/issues/4653)).
 - Fixed npm-family package commands on Windows to avoid shell argument splitting when install prefixes contain spaces ([#4623](https://github.com/earendil-works/pi/issues/4623)).
 
 ## [0.75.0] - 2026-05-17

packages/coding-agent/src/cli.ts

@@ -5,7 +5,7 @@
  *
  * Test with: npx tsx src/cli-new.ts [args...]
  */
-import { EnvHttpProxyAgent, setGlobalDispatcher } from "undici";
+import { EnvHttpProxyAgent, install as installUndiciGlobals, setGlobalDispatcher } from "undici";
 import { APP_NAME } from "./config.js";
 import { main } from "./main.js";
 
@@ -19,4 +19,9 @@ process.emitWarning = (() => {}) as typeof process.emitWarning;
 // AbortController-based deadlines via retry.provider.timeoutMs.
 setGlobalDispatcher(new EnvHttpProxyAgent({ bodyTimeout: 0, headersTimeout: 0 }));
 
+// Keep fetch and the dispatcher on the same undici implementation. Node 26.0's
+// bundled fetch can otherwise consume compressed responses through npm undici's
+// dispatcher without decompressing them, causing response.json() failures.
+installUndiciGlobals();
+
 main(process.argv.slice(2));