feat(memory): delegate system prompt section to active memory plugin

Add registerMemoryPromptSection to the plugin API so the active memory
plugin provides its own system prompt builder callback. The built-in
memory-core plugin registers the existing Memory Recall section via
this new API.

When no memory plugin is active (or a plugin does not register a
builder), the memory section is simply omitted from the system prompt.
This lets third-party memory plugins inject their own guidance at the
same position in the prompt.

extensions/lobster/src/lobster-tool.test.ts

@@ -54,6 +54,7 @@ function fakeApi(overrides: Partial<OpenClawPluginApi> = {}): OpenClawPluginApi
     registerHttpRoute() {},
     registerCommand() {},
     registerContextEngine() {},
+    registerMemoryPromptSection() {},
     on() {},
     resolvePath: (p) => p,
     ...overrides,

extensions/memory-core/index.ts

@@ -1,11 +1,35 @@
+import type { MemoryPromptSectionBuilder } from "openclaw/plugin-sdk/memory-core";
 import { definePluginEntry } from "openclaw/plugin-sdk/core";
 
+const buildPromptSection: MemoryPromptSectionBuilder = ({ availableTools, citationsMode }) => {
+  if (!availableTools.has("memory_search") && !availableTools.has("memory_get")) {
+    return [];
+  }
+  const lines = [
+    "## Memory Recall",
+    "Before answering anything about prior work, decisions, dates, people, preferences, or todos: run memory_search on MEMORY.md + memory/*.md; then use memory_get to pull only the needed lines. If low confidence after search, say you checked.",
+  ];
+  if (citationsMode === "off") {
+    lines.push(
+      "Citations are disabled: do not mention file paths or line numbers in replies unless the user explicitly asks.",
+    );
+  } else {
+    lines.push(
+      "Citations: include Source: <path#line> when it helps the user verify memory snippets.",
+    );
+  }
+  lines.push("");
+  return lines;
+};
+
 export default definePluginEntry({
   id: "memory-core",
   name: "Memory (Core)",
   description: "File-backed memory search tools and CLI",
   kind: "memory",
   register(api) {
+    api.registerMemoryPromptSection(buildPromptSection);
+
     api.registerTool(
       (ctx) => {
         const memorySearchTool = api.runtime.tools.createMemorySearchTool({

src/agents/system-prompt.ts

@@ -2,6 +2,7 @@ import { createHmac, createHash } from "node:crypto";
 import type { ReasoningLevel, ThinkLevel } from "../auto-reply/thinking.js";
 import { SILENT_REPLY_TOKEN } from "../auto-reply/tokens.js";
 import type { MemoryCitationsMode } from "../config/types.memory.js";
+import { buildMemoryPromptSection } from "../memory/prompt-section.js";
 import { listDeliverableMessageChannels } from "../utils/message-channel.js";
 import type { ResolvedTimeFormat } from "./date-time.js";
 import type { EmbeddedContextFile } from "./pi-embedded-helpers.js";
@@ -43,24 +44,10 @@ function buildMemorySection(params: {
   if (params.isMinimal) {
     return [];
   }
-  if (!params.availableTools.has("memory_search") && !params.availableTools.has("memory_get")) {
-    return [];
-  }
-  const lines = [
-    "## Memory Recall",
-    "Before answering anything about prior work, decisions, dates, people, preferences, or todos: run memory_search on MEMORY.md + memory/*.md; then use memory_get to pull only the needed lines. If low confidence after search, say you checked.",
-  ];
-  if (params.citationsMode === "off") {
-    lines.push(
-      "Citations are disabled: do not mention file paths or line numbers in replies unless the user explicitly asks.",
-    );
-  } else {
-    lines.push(
-      "Citations: include Source: <path#line> when it helps the user verify memory snippets.",
-    );
-  }
-  lines.push("");
-  return lines;
+  return buildMemoryPromptSection({
+    availableTools: params.availableTools,
+    citationsMode: params.citationsMode,
+  });
 }
 
 function buildUserIdentitySection(ownerLine: string | undefined, isMinimal: boolean) {

src/memory/prompt-section.test.ts

@@ -0,0 +1,52 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import {
+  registerMemoryPromptSection,
+  buildMemoryPromptSection,
+  _resetMemoryPromptSection,
+} from "./prompt-section.js";
+
+describe("memory prompt section registry", () => {
+  beforeEach(() => {
+    _resetMemoryPromptSection();
+  });
+
+  it("returns empty array when no builder is registered", () => {
+    const result = buildMemoryPromptSection({
+      availableTools: new Set(["memory_search", "memory_get"]),
+    });
+    expect(result).toEqual([]);
+  });
+
+  it("delegates to the registered builder", () => {
+    registerMemoryPromptSection(({ availableTools }) => {
+      if (!availableTools.has("memory_search")) return [];
+      return ["## Custom Memory", "Use custom memory tools.", ""];
+    });
+
+    const result = buildMemoryPromptSection({
+      availableTools: new Set(["memory_search"]),
+    });
+    expect(result).toEqual(["## Custom Memory", "Use custom memory tools.", ""]);
+  });
+
+  it("passes citationsMode to the builder", () => {
+    registerMemoryPromptSection(({ citationsMode }) => {
+      return [`citations: ${citationsMode ?? "default"}`];
+    });
+
+    expect(
+      buildMemoryPromptSection({
+        availableTools: new Set(),
+        citationsMode: "off",
+      }),
+    ).toEqual(["citations: off"]);
+  });
+
+  it("last registration wins", () => {
+    registerMemoryPromptSection(() => ["first"]);
+    registerMemoryPromptSection(() => ["second"]);
+
+    const result = buildMemoryPromptSection({ availableTools: new Set() });
+    expect(result).toEqual(["second"]);
+  });
+});

src/memory/prompt-section.ts

@@ -0,0 +1,29 @@
+import type { MemoryCitationsMode } from "../config/types.memory.js";
+
+/**
+ * Callback that the active memory plugin provides to build
+ * its section of the agent system prompt.
+ */
+export type MemoryPromptSectionBuilder = (params: {
+  availableTools: Set<string>;
+  citationsMode?: MemoryCitationsMode;
+}) => string[];
+
+// Module-level singleton — only one memory plugin can be active (exclusive slot).
+let _builder: MemoryPromptSectionBuilder | undefined;
+
+export function registerMemoryPromptSection(builder: MemoryPromptSectionBuilder): void {
+  _builder = builder;
+}
+
+export function buildMemoryPromptSection(params: {
+  availableTools: Set<string>;
+  citationsMode?: MemoryCitationsMode;
+}): string[] {
+  return _builder?.(params) ?? [];
+}
+
+/** Reset state (for tests). */
+export function _resetMemoryPromptSection(): void {
+  _builder = undefined;
+}

src/plugin-sdk/memory-core.ts

@@ -2,4 +2,5 @@
 // Keep this list additive and scoped to symbols used under extensions/memory-core.
 
 export { emptyPluginConfigSchema } from "../plugins/config-schema.js";
+export type { MemoryPromptSectionBuilder } from "../memory/prompt-section.js";
 export type { OpenClawPluginApi } from "../plugins/types.js";

src/plugins/types.ts

@@ -1341,6 +1341,10 @@ export type OpenClawPluginApi = {
     id: string,
     factory: import("../context-engine/registry.js").ContextEngineFactory,
   ) => void;
+  /** Register the system prompt section builder for this memory plugin (exclusive slot). */
+  registerMemoryPromptSection: (
+    builder: import("../memory/prompt-section.js").MemoryPromptSectionBuilder,
+  ) => void;
   resolvePath: (input: string) => string;
   /** Register a lifecycle hook handler */
   on: <K extends PluginHookName>(

test/helpers/extensions/plugin-api.ts

@@ -23,6 +23,7 @@ export function createTestPluginApi(api: TestPluginApiInput): OpenClawPluginApi
     onConversationBindingResolved() {},
     registerCommand() {},
     registerContextEngine() {},
+    registerMemoryPromptSection() {},
     resolvePath(input: string) {
       return input;
     },