fix: preserve subagent task overrides (#78356)

Co-authored-by: Alex Knight <15041791+amknight@users.noreply.github.com>

CHANGELOG.md

@@ -128,6 +128,7 @@ Docs: https://docs.openclaw.ai
 - Control UI/sessions: fire the documented `/new` command and lifecycle hooks only for explicit Control UI session creation, restoring session-memory and custom hook capture without changing SDK parent-session creates. Fixes #76957. Thanks @BunsDev.
 - Exec approvals: fall back to a guarded copy when Windows rejects rename-overwrite for `exec-approvals.json`, while preserving symlink, hard-link, and owner-only permission safeguards. Fixes #77785. (#77907) Thanks @Alex-Alaniz and @MilleniumGenAI.
 - Slack: preserve Socket Mode SDK error context and structured Slack API fields in reconnect logs, so startup failures no longer collapse to a bare `unknown error`.
+- Agents/subagents: preserve the delegated task prompt when a spawned target agent uses `systemPromptOverride`, so `sessions_spawn(mode: "run")` child runs still see their assigned task. Fixes #77950. Thanks @amknight.
 - iOS pairing: allow setup-code and manual `ws://` connects for private LAN and `.local` gateways while keeping Tailscale/public routes on `wss://`, and prefer explicit gateway passwords over stale bootstrap tokens in mixed-auth reconnects. Fixes #47887; carries forward #65185. Thanks @draix and @BunsDev.
 - Node/Windows: fall back to the Startup-folder launcher when Spanish-localized `schtasks` reports `Acceso denegado`, matching the existing access-denied fallback path. Fixes #77993. Thanks @jackonedev.
 - Plugins/diagnostics: make source-only TypeScript package warnings actionable by explaining that missing compiled runtime output is a publisher packaging issue and pointing users to update/reinstall or disable/uninstall the plugin. Fixes #77835. Thanks @googlerest.

src/agents/pi-embedded-runner/run/attempt-system-prompt.test.ts

@@ -68,6 +68,38 @@ describe("buildAttemptSystemPrompt", () => {
     expect(result.systemPrompt).not.toContain("USER.md");
   });
 
+  it("preserves runtime extra system prompt context when a system prompt override is configured", () => {
+    const result = buildAttemptSystemPrompt({
+      isRawModelRun: false,
+      systemPromptOverrideText: "Custom override prompt.",
+      transformProviderSystemPrompt,
+      embeddedSystemPrompt: {
+        workspaceDir: "/tmp/openclaw",
+        reasoningTagHint: false,
+        runtimeInfo: {
+          host: "test-host",
+          os: "Darwin",
+          arch: "arm64",
+          node: "v22.0.0",
+          model: "openai/gpt-5.5",
+        },
+        tools: [],
+        modelAliasLines: [],
+        userTimezone: "UTC",
+        promptMode: "minimal",
+        extraSystemPrompt:
+          "# Subagent Context\n\n## Your Role\n- You were created to handle: RUN_MODE_TASK_77950",
+        bootstrapMode: "full",
+        contextFiles: [],
+      },
+      providerTransform: baseProviderTransform,
+    });
+
+    expect(result.systemPrompt).toContain("Custom override prompt.");
+    expect(result.systemPrompt).toContain("## Subagent Context");
+    expect(result.systemPrompt).toContain("RUN_MODE_TASK_77950");
+  });
+
   it("omits system prompts for raw model probes", () => {
     const result = buildAttemptSystemPrompt({
       isRawModelRun: true,

src/agents/pi-embedded-runner/run/attempt-system-prompt.ts

@@ -30,15 +30,33 @@ export type AttemptSystemPrompt = {
   systemPromptOverride: (defaultPrompt?: string) => string;
 };
 
+function appendRuntimeExtraSystemPrompt(params: {
+  systemPrompt: string;
+  extraSystemPrompt?: string;
+  promptMode?: EmbeddedSystemPromptParams["promptMode"];
+}): string {
+  const extraSystemPrompt = params.extraSystemPrompt?.trim();
+  if (!extraSystemPrompt || params.promptMode === "none") {
+    return params.systemPrompt;
+  }
+  const contextHeader =
+    params.promptMode === "minimal" ? "## Subagent Context" : "## Group Chat Context";
+  return `${params.systemPrompt.trimEnd()}\n\n${contextHeader}\n${extraSystemPrompt}\n`;
+}
+
 export function buildAttemptSystemPrompt(
   params: BuildAttemptSystemPromptParams,
 ): AttemptSystemPrompt {
   const baseSystemPrompt = params.systemPromptOverrideText
-    ? appendAgentBootstrapSystemPromptSupplement({
-        systemPrompt: params.systemPromptOverrideText,
-        bootstrapMode: params.embeddedSystemPrompt.bootstrapMode,
-        bootstrapTruncationNotice: params.embeddedSystemPrompt.bootstrapTruncationNotice,
-        contextFiles: params.embeddedSystemPrompt.contextFiles,
+    ? appendRuntimeExtraSystemPrompt({
+        systemPrompt: appendAgentBootstrapSystemPromptSupplement({
+          systemPrompt: params.systemPromptOverrideText,
+          bootstrapMode: params.embeddedSystemPrompt.bootstrapMode,
+          bootstrapTruncationNotice: params.embeddedSystemPrompt.bootstrapTruncationNotice,
+          contextFiles: params.embeddedSystemPrompt.contextFiles,
+        }),
+        extraSystemPrompt: params.embeddedSystemPrompt.extraSystemPrompt,
+        promptMode: params.embeddedSystemPrompt.promptMode,
       })
     : buildEmbeddedSystemPrompt(params.embeddedSystemPrompt);