fix(core): respect disabled Plan agent config (#44761)

Co-authored-by: rekram1-node <63023139+rekram1-node@users.noreply.github.com>

packages/core/src/plugin/internal.ts

@@ -236,6 +236,7 @@ const pre = [
   MCPCodeModeExclusionPlugin.Plugin,
   WellKnownPlugin.Plugin,
   AgentPlugin.Plugin,
+  PlanPlugin.Plugin,
   CommandPlugin.Plugin,
   SkillPlugin.Plugin,
   ...SystemPromptPlugin.Plugins,
@@ -274,7 +275,6 @@ const post = [
   ConfigWebSearchPlugin.Plugin,
   VariantPlugin.Plugin,
   ConfigPolicyPlugin.Plugin,
-  PlanPlugin.Plugin,
 ] as const satisfies readonly InternalPlugin[]
 
 export const list = Effect.fn("PluginInternal.list")(function* () {

packages/core/test/config/plugin.test.ts

@@ -52,6 +52,17 @@ describe("PluginSupervisor config", () => {
     ),
   )
 
+  it.live("allows the built-in Plan agent to be disabled", () =>
+    withLocation(
+      { agents: { plan: { disabled: true } } },
+      Effect.gen(function* () {
+        yield* ready()
+        const agents = yield* Agent.Service
+        expect(yield* agents.get(Agent.ID.make("plan"))).toBeUndefined()
+      }),
+    ),
+  )
+
   it.live("loads configured Promise plugins with options", () =>
     withLocation(
       {