Stop a closed terminal from crashing the desktop app through its own logging

apps/desktop/main/index.ts

@@ -123,8 +123,14 @@ import {
 } from "./services/secure-storage-policy";
 import type { ServiceSupervisor } from "./services/supervisor";
 import { TransportBridge } from "./transport-bridge";
+import { installStdioResilience } from "./stdio-resilience";
 import { createMainWindow } from "./window";
 
+// FIRST, before anything can log. The CLI spawns this process with
+// `stdio: "inherit"`, so the window outlives the terminal that launched it and
+// a closed terminal turns the next console.* into an uncaught EPIPE.
+installStdioResilience();
+
 applyBrandIdentity(app, { platform: process.platform });
 
 const bootTimingStartedAt = process.hrtime.bigint();

apps/desktop/main/stdio-resilience.test.ts

@@ -0,0 +1,74 @@
+import { PassThrough } from "node:stream";
+import { describe, expect, it } from "vitest";
+
+import { installStdioResilience } from "./stdio-resilience";
+
+/**
+ * The bug these pin: the app is spawned `stdio: "inherit"` from the `copilot`
+ * CLI, so closing the launching terminal leaves the GUI writing to a dead
+ * pipe, and an unguarded `console.error` then crashes the main process.
+ *
+ * Note what makes this testable at all: the assertion is about whether the
+ * stream THROWS, so each case emits a real `error` event rather than checking
+ * that a listener was registered. "A listener exists" is exactly the shape of
+ * assertion that passes over a listener which re-throws everything.
+ */
+describe("installStdioResilience", () => {
+  const epipe = (): Error =>
+    Object.assign(new Error("write EPIPE"), { code: "EPIPE" });
+
+  it("swallows EPIPE so a dead pipe cannot crash the process", () => {
+    const stream = new PassThrough();
+    const dispose = installStdioResilience([stream]);
+
+    expect(() => stream.emit("error", epipe())).not.toThrow();
+
+    dispose();
+  });
+
+  it("re-throws anything that is not EPIPE", () => {
+    const stream = new PassThrough();
+    const dispose = installStdioResilience([stream]);
+    const enospc = Object.assign(new Error("no space left"), {
+      code: "ENOSPC",
+    });
+
+    // A full disk is a real failure. Swallowing every stream error to fix
+    // EPIPE is how the next one goes unnoticed.
+    expect(() => stream.emit("error", enospc)).toThrow("no space left");
+
+    dispose();
+  });
+
+  it("guards every stream it is given, not just the first", () => {
+    const out = new PassThrough();
+    const err = new PassThrough();
+    const dispose = installStdioResilience([out, err]);
+
+    expect(() => out.emit("error", epipe())).not.toThrow();
+    expect(() => err.emit("error", epipe())).not.toThrow();
+
+    dispose();
+  });
+
+  it("removes only its own listeners when disposed", () => {
+    const stream = new PassThrough();
+    const before = stream.listenerCount("error");
+    const dispose = installStdioResilience([stream]);
+    expect(stream.listenerCount("error")).toBe(before + 1);
+
+    dispose();
+
+    expect(stream.listenerCount("error")).toBe(before);
+  });
+
+  it("leaves the stream unguarded again after disposal", () => {
+    const stream = new PassThrough();
+    installStdioResilience([stream])();
+
+    // With no listener, Node's EventEmitter throws an emitted 'error'. This is
+    // the control case: it proves the passing case above is the guard working
+    // and not PassThrough being tolerant on its own.
+    expect(() => stream.emit("error", epipe())).toThrow("write EPIPE");
+  });
+});

apps/desktop/main/stdio-resilience.ts

@@ -0,0 +1,68 @@
+/**
+ * Keep a broken stdout/stderr pipe from killing the app.
+ *
+ * WHY THIS EXISTS, because it looks like defensive noise until you know the
+ * launch shape. `tools/cli/bin/copilot.mjs` spawns the app with
+ * `stdio: "inherit"`, so the GUI process writes straight to the terminal that
+ * ran `copilot`. That terminal is not the app's lifetime — the window outlives
+ * it. Close the terminal (or end the ssh session, or quit the shell) and the
+ * app keeps running with stdout pointing at a pipe whose reader is gone.
+ *
+ * The next `console.error` in the main process then raises `EPIPE`, and with no
+ * listener on the stream Node turns it into an uncaught exception that takes
+ * down the whole app. Observed exactly that way:
+ *
+ *     Uncaught Exception:
+ *     Error: write EPIPE
+ *         at afterWriteDispatched (node:internal/stream_base_commons:159:15)
+ *         ...
+ *         at console.error (node:internal/console/constructor:444:26)
+ *         at replyWithError (node:electron/js2c/browser_init)
+ *
+ * Read that trace bottom-up: the main process was REPORTING an IPC error, and
+ * the reporting killed it. A failure in the error path is the worst place to
+ * have one, because it converts a handled problem into a crash.
+ *
+ * There are ~30 `console.*` call sites in `main/`, so guarding them one by one
+ * is not the fix; attaching a listener to the stream is. A stream with an
+ * `error` listener no longer throws, and EPIPE genuinely has nothing to do
+ * about it — the reader is gone and there is nowhere to log the fact that
+ * there is nowhere to log. Anything that is NOT EPIPE is re-thrown, because a
+ * disk-full or permission error on stderr is a real failure and swallowing
+ * every stream error to fix one of them is how you lose the next one.
+ */
+
+import type { Writable } from "node:stream";
+
+/** The one error code that means "the reader went away, and that is fine". */
+const BROKEN_PIPE = "EPIPE";
+
+/**
+ * Attach EPIPE-tolerant error handling to the process's output streams.
+ *
+ * Call this as early in main as possible — before any logging, because the
+ * write it protects can be the first one. Returns a disposer so a test can
+ * remove the listeners it added rather than leaking them across cases.
+ */
+export function installStdioResilience(
+  streams: readonly Writable[] = [process.stdout, process.stderr],
+): () => void {
+  const attached: Array<[Writable, (error: Error) => void]> = [];
+
+  for (const stream of streams) {
+    const onError = (error: Error): void => {
+      if ((error as NodeJS.ErrnoException).code === BROKEN_PIPE) {
+        return;
+      }
+      throw error;
+    };
+    stream.on("error", onError);
+    attached.push([stream, onError]);
+  }
+
+  return () => {
+    for (const [stream, onError] of attached) {
+      stream.off("error", onError);
+    }
+  };
+}