add prependSystemContext and appendSystemContext to before_prompt_build (fixes #35131) (#35177)

Merged via squash.

Prepared head SHA: d9a2869ad6
Co-authored-by: maweibin <18023423+maweibin@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

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

@@ -1,6 +1,7 @@
 import { describe, expect, it, vi } from "vitest";
 import type { OpenClawConfig } from "../../../config/config.js";
 import {
+  composeSystemPromptWithHookContext,
   isOllamaCompatProvider,
   resolveAttemptFsWorkspaceOnly,
   resolveOllamaBaseUrlForRun,
@@ -54,6 +55,8 @@ describe("resolvePromptBuildHookResult", () => {
     expect(result).toEqual({
       prependContext: "from-cache",
       systemPrompt: "legacy-system",
+      prependSystemContext: undefined,
+      appendSystemContext: undefined,
     });
   });
 
@@ -71,6 +74,58 @@ describe("resolvePromptBuildHookResult", () => {
     expect(hookRunner.runBeforeAgentStart).toHaveBeenCalledWith({ prompt: "hello", messages }, {});
     expect(result.prependContext).toBe("from-hook");
   });
+
+  it("merges prompt-build and legacy context fields in deterministic order", async () => {
+    const hookRunner = {
+      hasHooks: vi.fn(() => true),
+      runBeforePromptBuild: vi.fn(async () => ({
+        prependContext: "prompt context",
+        prependSystemContext: "prompt prepend",
+        appendSystemContext: "prompt append",
+      })),
+      runBeforeAgentStart: vi.fn(async () => ({
+        prependContext: "legacy context",
+        prependSystemContext: "legacy prepend",
+        appendSystemContext: "legacy append",
+      })),
+    };
+
+    const result = await resolvePromptBuildHookResult({
+      prompt: "hello",
+      messages: [],
+      hookCtx: {},
+      hookRunner,
+    });
+
+    expect(result.prependContext).toBe("prompt context\n\nlegacy context");
+    expect(result.prependSystemContext).toBe("prompt prepend\n\nlegacy prepend");
+    expect(result.appendSystemContext).toBe("prompt append\n\nlegacy append");
+  });
+});
+
+describe("composeSystemPromptWithHookContext", () => {
+  it("returns undefined when no hook system context is provided", () => {
+    expect(composeSystemPromptWithHookContext({ baseSystemPrompt: "base" })).toBeUndefined();
+  });
+
+  it("builds prepend/base/append system prompt order", () => {
+    expect(
+      composeSystemPromptWithHookContext({
+        baseSystemPrompt: "  base system  ",
+        prependSystemContext: "  prepend  ",
+        appendSystemContext: "  append  ",
+      }),
+    ).toBe("prepend\n\nbase system\n\nappend");
+  });
+
+  it("avoids blank separators when base system prompt is empty", () => {
+    expect(
+      composeSystemPromptWithHookContext({
+        baseSystemPrompt: "   ",
+        appendSystemContext: "  append only  ",
+      }),
+    ).toBe("append only");
+  });
 });
 
 describe("resolvePromptModeForSession", () => {

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

@@ -19,6 +19,7 @@ import type {
   PluginHookBeforePromptBuildResult,
 } from "../../../plugins/types.js";
 import { isSubagentSessionKey } from "../../../routing/session-key.js";
+import { joinPresentTextSegments } from "../../../shared/text/join-segments.js";
 import { resolveSignalReactionLevel } from "../../../signal/reaction-level.js";
 import { resolveTelegramInlineButtonsScope } from "../../../telegram/inline-buttons.js";
 import { resolveTelegramReactionLevel } from "../../../telegram/reaction-level.js";
@@ -567,12 +568,37 @@ export async function resolvePromptBuildHookResult(params: {
       : undefined);
   return {
     systemPrompt: promptBuildResult?.systemPrompt ?? legacyResult?.systemPrompt,
-    prependContext: [promptBuildResult?.prependContext, legacyResult?.prependContext]
-      .filter((value): value is string => Boolean(value))
-      .join("\n\n"),
+    prependContext: joinPresentTextSegments([
+      promptBuildResult?.prependContext,
+      legacyResult?.prependContext,
+    ]),
+    prependSystemContext: joinPresentTextSegments([
+      promptBuildResult?.prependSystemContext,
+      legacyResult?.prependSystemContext,
+    ]),
+    appendSystemContext: joinPresentTextSegments([
+      promptBuildResult?.appendSystemContext,
+      legacyResult?.appendSystemContext,
+    ]),
   };
 }
 
+export function composeSystemPromptWithHookContext(params: {
+  baseSystemPrompt?: string;
+  prependSystemContext?: string;
+  appendSystemContext?: string;
+}): string | undefined {
+  const prependSystem = params.prependSystemContext?.trim();
+  const appendSystem = params.appendSystemContext?.trim();
+  if (!prependSystem && !appendSystem) {
+    return undefined;
+  }
+  return joinPresentTextSegments(
+    [params.prependSystemContext, params.baseSystemPrompt, params.appendSystemContext],
+    { trim: true },
+  );
+}
+
 export function resolvePromptModeForSession(sessionKey?: string): "minimal" | "full" {
   if (!sessionKey) {
     return "full";
@@ -1522,6 +1548,20 @@ export async function runEmbeddedAttempt(
             systemPromptText = legacySystemPrompt;
             log.debug(`hooks: applied systemPrompt override (${legacySystemPrompt.length} chars)`);
           }
+          const prependedOrAppendedSystemPrompt = composeSystemPromptWithHookContext({
+            baseSystemPrompt: systemPromptText,
+            prependSystemContext: hookResult?.prependSystemContext,
+            appendSystemContext: hookResult?.appendSystemContext,
+          });
+          if (prependedOrAppendedSystemPrompt) {
+            const prependSystemLen = hookResult?.prependSystemContext?.trim().length ?? 0;
+            const appendSystemLen = hookResult?.appendSystemContext?.trim().length ?? 0;
+            applySystemPromptOverrideToSession(activeSession, prependedOrAppendedSystemPrompt);
+            systemPromptText = prependedOrAppendedSystemPrompt;
+            log.debug(
+              `hooks: applied prependSystemContext/appendSystemContext (${prependSystemLen}+${appendSystemLen} chars)`,
+            );
+          }
         }
 
         log.debug(`embedded run prompt start: runId=${params.runId} sessionId=${params.sessionId}`);