diff --git a/packages/core/src/plugin/system-prompt.ts b/packages/core/src/plugin/system-prompt.ts
index a07b3917e57..aba4599e0ac 100644
--- a/packages/core/src/plugin/system-prompt.ts
+++ b/packages/core/src/plugin/system-prompt.ts
@@ -54,7 +54,7 @@ function make(
           const prompt = getPrompt(`${model?.modelID ?? event.model.id} ${model?.family ?? ""}`.toLowerCase())
           if (!prompt) return
           if (options.operation === "append") {
-            event.system.push(SystemPart.make(prompt))
+            event.system.splice(1, 0, SystemPart.make(prompt))
             return
           }
           event.system[0] = { ...system, text: prompt }
diff --git a/packages/core/test/session-runner.test.ts b/packages/core/test/session-runner.test.ts
index 55a9cced3b7..b24c2de52ba 100644
--- a/packages/core/test/session-runner.test.ts
+++ b/packages/core/test/session-runner.test.ts
@@ -1590,8 +1590,8 @@ describe("SessionRunnerLLM", () => {
 
     expect(s.requests.at(-1)?.system.map((part) => part.text)).toEqual([
       defaultSystem,
-      "Initial context",
       expect.stringContaining("# Delegation"),
+      "Initial context",
     ])
   })
 
@@ -1611,8 +1611,8 @@ describe("SessionRunnerLLM", () => {
 
     expect(s.requests.at(-1)?.system.map((part) => part.text)).toEqual([
       defaultSystem,
-      "Initial context",
       expect.stringContaining("# Delegation"),
+      "Initial context",
     ])
   })