fix(agent): allow cross-provider creation for modeless providers (#2000)

* fix: 允许无模式 Provider 创建子 Agent

* test: 补充无模式 Provider 继承场景

packages/server/src/server/agent/create-agent-mode.test.ts

@@ -96,6 +96,32 @@ describe("resolveAndValidateCreateAgentMode", () => {
     );
   });
 
+  it("uses the provider default when the cross-provider target has no modes", () => {
+    const resolved = resolveAndValidateCreateAgentMode({
+      requestedMode: undefined,
+      targetProvider: "pi",
+      parent: agentParent("codex", "auto"),
+      unattended: false,
+      availableModes: [],
+      targetUnattendedMode: undefined,
+    });
+
+    expect(resolved).toBeUndefined();
+  });
+
+  it("uses the provider default when an unattended parent targets a provider with no modes", () => {
+    const resolved = resolveAndValidateCreateAgentMode({
+      requestedMode: undefined,
+      targetProvider: "pi",
+      parent: agentParent("claude", "bypassPermissions", true),
+      unattended: false,
+      availableModes: [],
+      targetUnattendedMode: undefined,
+    });
+
+    expect(resolved).toBeUndefined();
+  });
+
   it("passes through an explicit mode when the target provider's modes are unknown", () => {
     const resolved = resolveAndValidateCreateAgentMode({
       requestedMode: "default",

packages/server/src/server/agent/create-agent-mode.ts

@@ -14,6 +14,7 @@ export interface ResolveCreateAgentModeInput {
   unattended: boolean;
   // `undefined` = target provider's modes unknown: explicit modes pass through
   // unvalidated, but cross-provider inheritance is still refused.
+  // `[]` = target provider explicitly has no modes: use its default behavior.
   availableModes: string[] | undefined;
   // Target provider's own unattended mode id, if it has one. Used to bridge
   // unattended parents into unattended children across providers.
@@ -71,6 +72,10 @@ export function resolveAndValidateCreateAgentMode(
     return input.targetUnattendedMode;
   }
 
+  if (availableModes?.length === 0) {
+    return undefined;
+  }
+
   throw new Error(
     `cannot inherit mode '${formatCreateConfigParentMode(parent)}' from ${formatCreateConfigParentSource(parent)} for new agent (provider '${targetProvider}'). Pass an explicit mode. Available modes for '${targetProvider}': ${listModes(availableModes)}`,
   );