fix(ssh): agent signing failures no longer trigger password prompts

packages/ssh/src/auth.ts

@@ -205,6 +205,10 @@ export const buildSshChildEnvironment = Effect.fn("ssh/auth.buildSshChildEnviron
 export function isSshAuthFailure(error: unknown): boolean {
   const message = error instanceof Error ? error.message : String(error);
   const normalized = message.toLowerCase();
+  // Surface the agent signing error instead of hiding it behind a password prompt.
+  if (/(?:^|\n)sign_and_send_pubkey: signing failed [^\n]* from agent: /u.test(normalized)) {
+    return false;
+  }
   return (
     /permission denied \((?:publickey|password|keyboard-interactive|hostbased|gssapi-with-mic)[^)]*\)/u.test(
       normalized,

packages/ssh/src/tunnel.test.ts

@@ -260,6 +260,102 @@ describe("ssh tunnel scripts", () => {
     }),
   );
 
+  it.effect.each([
+    {
+      name: "agent signing failure",
+      stderr:
+        'sign_and_send_pubkey: signing failed for ED25519 "/tmp/key" from agent: agent refused operation\nubuntu@127.0.0.1: Permission denied (publickey,password,keyboard-interactive).',
+      expectedPrompts: 0,
+    },
+    {
+      name: "agent communication failure while signing",
+      stderr:
+        'sign_and_send_pubkey: signing failed for ED25519 "/tmp/key" from agent: communication with agent failed\r\nubuntu@127.0.0.1: Permission denied (publickey,password).',
+      expectedPrompts: 0,
+    },
+    {
+      name: "agent unreachable before any key is offered",
+      stderr:
+        "error fetching identities: communication with agent failed\nubuntu@127.0.0.1: Permission denied (publickey,password).",
+      expectedPrompts: 1,
+    },
+    {
+      name: "agent signing failure on a key-only server",
+      stderr:
+        'sign_and_send_pubkey: signing failed for ED25519 "/tmp/key" from agent: agent refused operation\nubuntu@127.0.0.1: Permission denied (publickey).',
+      expectedPrompts: 0,
+    },
+    {
+      name: "publickey-only denial",
+      stderr: "ubuntu@127.0.0.1: Permission denied (publickey).",
+      expectedPrompts: 1,
+    },
+    {
+      name: "password denial",
+      stderr: "ubuntu@127.0.0.1: Permission denied (publickey,password).",
+      expectedPrompts: 1,
+    },
+    {
+      name: "keyboard-interactive denial",
+      stderr: "ubuntu@127.0.0.1: Permission denied (publickey,keyboard-interactive).",
+      expectedPrompts: 1,
+    },
+  ])(
+    "prompts for a password unless the agent failed to sign: $name",
+    ({ stderr, expectedPrompts }) =>
+      Effect.gen(function* () {
+        let prompts = 0;
+        const spawner = ChildProcessSpawner.make((command) =>
+          Effect.succeed(
+            commandArgs(command).includes("-G")
+              ? makeSuccessfulProcess("")
+              : {
+                  ...makeSuccessfulProcess(""),
+                  exitCode: Effect.succeed(ChildProcessSpawner.ExitCode(255)),
+                  stderr: Stream.make(new TextEncoder().encode(stderr)),
+                },
+          ),
+        );
+        const layer = Layer.mergeAll(
+          NodeServices.layer,
+          Layer.succeed(ChildProcessSpawner.ChildProcessSpawner, spawner),
+          Layer.succeed(HttpClient.HttpClient, hangingHttpClient),
+          Layer.succeed(NetService.NetService, testNetService),
+          Layer.succeed(
+            SshAuth.SshPasswordPrompt,
+            SshAuth.SshPasswordPrompt.of({
+              isAvailable: true,
+              request: () =>
+                Effect.sync(() => {
+                  prompts++;
+                  return null;
+                }),
+            }),
+          ),
+          SshTunnel.SshEnvironmentManager.layer({ resolveCliRunner: Effect.succeed(ARCHIVE) }),
+        );
+        yield* Effect.gen(function* () {
+          const manager = yield* SshTunnel.SshEnvironmentManager;
+          const result = yield* Effect.result(
+            manager.ensureEnvironment({
+              alias: "devbox",
+              hostname: "127.0.0.1",
+              username: "ubuntu",
+              port: null,
+            }),
+          );
+          assert.isTrue(Result.isFailure(result));
+          assert.equal(prompts, expectedPrompts);
+          if (expectedPrompts === 0 && Result.isFailure(result)) {
+            assert.instanceOf(result.failure, SshCommandError);
+            if (result.failure instanceof SshCommandError) {
+              assert.equal(result.failure.stderr, stderr);
+            }
+          }
+        }).pipe(Effect.provide(layer), Effect.scoped);
+      }),
+  );
+
   it.effect.each(["local tunnel", "remote server"] as const)(
     "waits for %s shutdown before reconnecting the same target",
     (stalledStep) =>