diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e023caa
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+node_modules/
+dist/
+plugin/**/*.js
+plugin/**/*.js.map
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..bfdc61b
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,47 @@
+{
+  "name": "prism-facet",
+  "version": "0.1.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "prism-facet",
+      "version": "0.1.0",
+      "devDependencies": {
+        "@types/node": "^25.6.0",
+        "typescript": "^5.5.0"
+      }
+    },
+    "node_modules/@types/node": {
+      "version": "25.6.0",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-25.6.0.tgz",
+      "integrity": "sha512-+qIYRKdNYJwY3vRCZMdJbPLJAtGjQBudzZzdzwQYkEPQd+PJGixUL5QfvCLDaULoLv+RhT3LDkwEfKaAkgSmNQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "undici-types": "~7.19.0"
+      }
+    },
+    "node_modules/typescript": {
+      "version": "5.9.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.9.3.tgz",
+      "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "tsc": "bin/tsc",
+        "tsserver": "bin/tsserver"
+      },
+      "engines": {
+        "node": ">=14.17"
+      }
+    },
+    "node_modules/undici-types": {
+      "version": "7.19.2",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.19.2.tgz",
+      "integrity": "sha512-qYVnV5OEm2AW8cJMCpdV20CDyaN3g0AjDlOGf1OW4iaDEx8MwdtChUp4zu4H0VP3nDRF/8RKWH+IPp9uW0YGZg==",
+      "dev": true,
+      "license": "MIT"
+    }
+  }
+}
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..d17b3bc
--- /dev/null
+++ b/package.json
@@ -0,0 +1,14 @@
+{
+  "name": "prism-facet",
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "build": "tsc --project tsconfig.plugin.json",
+    "install-plugin": "node scripts/install.mjs --install",
+    "uninstall-plugin": "node scripts/install.mjs --uninstall"
+  },
+  "devDependencies": {
+    "@types/node": "^25.6.0",
+    "typescript": "^5.5.0"
+  }
+}
diff --git a/plugin/core/prompt-injector.ts b/plugin/core/prompt-injector.ts
new file mode 100644
index 0000000..d235c2b
--- /dev/null
+++ b/plugin/core/prompt-injector.ts
@@ -0,0 +1,41 @@
+import { readFileSync } from "node:fs";
+import { getRouters } from "./router-loader.js";
+import { getRule } from "./rule-store.js";
+import type { RouterContext } from "./router-loader.js";
+
+export interface InjectionResult {
+  appendSystemContext?: string;
+}
+
+export async function resolveInjection(
+  ctx: RouterContext,
+  log: { info(msg: string): void; warn(msg: string): void }
+): Promise<InjectionResult> {
+  const routers = getRouters();
+  const segments: string[] = [];
+
+  for (const router of routers) {
+    try {
+      const key = await router.module.resolve(ctx);
+      if (!key) continue;
+
+      const promptFile = getRule(router.name, key);
+      if (!promptFile) continue;
+
+      try {
+        const content = readFileSync(promptFile, "utf8").trim();
+        if (content) {
+          segments.push(content);
+          log.info(`[prism-facet] injecting ${router.name}:${key} → ${promptFile}`);
+        }
+      } catch (err) {
+        log.warn(`[prism-facet] cannot read ${promptFile}: ${String(err)}`);
+      }
+    } catch (err) {
+      log.warn(`[prism-facet] router ${router.name} failed: ${String(err)}`);
+    }
+  }
+
+  if (segments.length === 0) return {};
+  return { appendSystemContext: segments.join("\n\n---\n\n") };
+}
diff --git a/plugin/core/router-loader.ts b/plugin/core/router-loader.ts
new file mode 100644
index 0000000..a7bf157
--- /dev/null
+++ b/plugin/core/router-loader.ts
@@ -0,0 +1,77 @@
+import { readdirSync } from "node:fs";
+import path from "node:path";
+
+export interface RouterContext {
+  agentId: string;
+}
+
+export interface RouterModule {
+  resolve(ctx: RouterContext): string | Promise<string>;
+}
+
+export interface LoadedRouter {
+  name: string;
+  filePath: string;
+  module: RouterModule;
+}
+
+const _G = globalThis as Record<string, unknown>;
+const ROUTERS_KEY = "_prismFacetRouters";
+const LOAD_COUNTER_KEY = "_prismFacetLoadCounter";
+
+function getRouterMap(): Map<string, LoadedRouter> {
+  if (!(_G[ROUTERS_KEY] instanceof Map)) {
+    _G[ROUTERS_KEY] = new Map<string, LoadedRouter>();
+  }
+  return _G[ROUTERS_KEY] as Map<string, LoadedRouter>;
+}
+
+function routerNameFromFile(filename: string): string {
+  return filename.replace(/\.(ts|js|mjs)$/, "");
+}
+
+export async function loadRouters(
+  routersDir: string,
+  log: { info(msg: string): void; warn(msg: string): void }
+): Promise<void> {
+  const map = getRouterMap();
+  map.clear();
+
+  if (typeof _G[LOAD_COUNTER_KEY] !== "number") _G[LOAD_COUNTER_KEY] = 0;
+  (_G[LOAD_COUNTER_KEY] as number)++;
+  const counter = _G[LOAD_COUNTER_KEY] as number;
+
+  let files: string[];
+  try {
+    files = readdirSync(routersDir).filter(
+      (f) => /\.(ts|js|mjs)$/.test(f) && !f.startsWith(".")
+    );
+  } catch {
+    log.warn(`[prism-facet] routers directory not found: ${routersDir}`);
+    return;
+  }
+
+  for (const file of files) {
+    const name = routerNameFromFile(file);
+    const filePath = path.resolve(routersDir, file);
+    try {
+      const mod = (await import(`${filePath}?v=${counter}`)) as RouterModule;
+      if (typeof mod.resolve !== "function") {
+        log.warn(`[prism-facet] router ${name}: no resolve() export, skipping`);
+        continue;
+      }
+      map.set(name, { name, filePath, module: mod });
+      log.info(`[prism-facet] router loaded: ${name}`);
+    } catch (err) {
+      log.warn(`[prism-facet] router ${name}: failed to load — ${String(err)}`);
+    }
+  }
+}
+
+export function getRouters(): LoadedRouter[] {
+  return Array.from(getRouterMap().values());
+}
+
+export function getRouterNames(): string[] {
+  return Array.from(getRouterMap().keys());
+}
diff --git a/plugin/core/rule-store.ts b/plugin/core/rule-store.ts
new file mode 100644
index 0000000..1e1bb9b
--- /dev/null
+++ b/plugin/core/rule-store.ts
@@ -0,0 +1,56 @@
+import { readFileSync, writeFileSync } from "node:fs";
+
+export type RuleStore = Record<string, string>; // "router:key" → prompt file path
+
+const _G = globalThis as Record<string, unknown>;
+const RULES_KEY = "_prismFacetRules";
+const RULES_PATH_KEY = "_prismFacetRulesPath";
+
+function getRules(): RuleStore {
+  if (!_G[RULES_KEY] || typeof _G[RULES_KEY] !== "object") {
+    _G[RULES_KEY] = {};
+  }
+  return _G[RULES_KEY] as RuleStore;
+}
+
+function getRulesPath(): string {
+  return (_G[RULES_PATH_KEY] as string) || "";
+}
+
+function save(): void {
+  const p = getRulesPath();
+  if (!p) return;
+  writeFileSync(p, JSON.stringify(getRules(), null, 2) + "\n", "utf8");
+}
+
+export function initRuleStore(filePath: string): void {
+  _G[RULES_PATH_KEY] = filePath;
+  try {
+    const raw = readFileSync(filePath, "utf8");
+    _G[RULES_KEY] = JSON.parse(raw) as RuleStore;
+  } catch {
+    _G[RULES_KEY] = {};
+  }
+}
+
+export function addRule(router: string, key: string, promptFile: string): void {
+  getRules()[`${router}:${key}`] = promptFile;
+  save();
+}
+
+export function removeRule(router: string, key: string): boolean {
+  const rules = getRules();
+  const ruleKey = `${router}:${key}`;
+  if (!(ruleKey in rules)) return false;
+  delete rules[ruleKey];
+  save();
+  return true;
+}
+
+export function getRule(router: string, key: string): string | undefined {
+  return getRules()[`${router}:${key}`];
+}
+
+export function listRules(): Record<string, string> {
+  return { ...getRules() };
+}
diff --git a/plugin/hooks/before-prompt-build.ts b/plugin/hooks/before-prompt-build.ts
new file mode 100644
index 0000000..5f23c50
--- /dev/null
+++ b/plugin/hooks/before-prompt-build.ts
@@ -0,0 +1,25 @@
+import { resolveInjection } from "../core/prompt-injector.js";
+
+const _G = globalThis as Record<string, unknown>;
+const DEDUP_KEY = "_prismFacetBPBDedup";
+
+export function registerBeforePromptBuild(api: {
+  on(hook: string, handler: (...args: any[]) => any): void;
+  logger: { info(msg: string): void; warn(msg: string): void };
+}): void {
+  if (!(_G[DEDUP_KEY] instanceof WeakSet)) _G[DEDUP_KEY] = new WeakSet<object>();
+  const dedup = _G[DEDUP_KEY] as WeakSet<object>;
+
+  api.on("before_prompt_build", async (event: unknown, ctx: { agentId?: string }) => {
+    if (dedup.has(event as object)) return;
+    dedup.add(event as object);
+
+    const agentId = ctx.agentId || "";
+    if (!agentId) return;
+
+    const result = await resolveInjection({ agentId }, api.logger);
+    if (result.appendSystemContext) {
+      return { appendSystemContext: result.appendSystemContext };
+    }
+  });
+}
diff --git a/plugin/index.ts b/plugin/index.ts
new file mode 100644
index 0000000..aa0a28d
--- /dev/null
+++ b/plugin/index.ts
@@ -0,0 +1,66 @@
+import path from "node:path";
+import { loadRouters } from "./core/router-loader.js";
+import { initRuleStore } from "./core/rule-store.js";
+import { registerBeforePromptBuild } from "./hooks/before-prompt-build.js";
+import { registerPromptRulesTool } from "./tools/prompt-rules.js";
+
+interface PluginConfig {
+  routersDir?: string;
+  rulesFile?: string;
+}
+
+interface OpenClawPluginApi {
+  logger: {
+    info(msg: string): void;
+    warn(msg: string): void;
+    error(msg: string): void;
+  };
+  on(hook: string, handler: (...args: any[]) => any): void;
+  registerTool(def: any): void;
+  config?: PluginConfig;
+}
+
+const _G = globalThis as Record<string, unknown>;
+const LIFECYCLE_KEY = "_prismFacetGatewayLifecycleRegistered";
+
+function normalizeConfig(api: OpenClawPluginApi): PluginConfig {
+  const raw = (api as any).config ?? {};
+  return {
+    routersDir: typeof raw.routersDir === "string" ? raw.routersDir : undefined,
+    rulesFile: typeof raw.rulesFile === "string" ? raw.rulesFile : undefined,
+  };
+}
+
+export default {
+  id: "prism-facet",
+  name: "PrismFacet",
+
+  register(api: OpenClawPluginApi) {
+    const config = normalizeConfig(api);
+    const pluginDir = path.dirname(new URL(import.meta.url).pathname);
+    const routersDir = config.routersDir || path.resolve(pluginDir, "routers");
+    const rulesFile = config.rulesFile || path.resolve(pluginDir, "rules.json");
+
+    // Gateway lifecycle: init once
+    if (!_G[LIFECYCLE_KEY]) {
+      _G[LIFECYCLE_KEY] = true;
+
+      initRuleStore(rulesFile);
+      loadRouters(routersDir, api.logger).catch((err) => {
+        api.logger.error(`[prism-facet] failed to load routers: ${String(err)}`);
+      });
+
+      api.on("gateway_stop", () => {
+        _G[LIFECYCLE_KEY] = false;
+      });
+    }
+
+    // Agent session hooks: register every time (dedup inside handler)
+    registerBeforePromptBuild(api);
+
+    // Tools
+    registerPromptRulesTool(api, routersDir);
+
+    api.logger.info("[prism-facet] plugin registered");
+  },
+};
diff --git a/plugin/openclaw.plugin.json b/plugin/openclaw.plugin.json
new file mode 100644
index 0000000..7e7ec2e
--- /dev/null
+++ b/plugin/openclaw.plugin.json
@@ -0,0 +1,21 @@
+{
+  "id": "prism-facet",
+  "name": "PrismFacet",
+  "version": "0.1.0",
+  "description": "Dynamic system prompt injection via routers and rules",
+  "main": "index.js",
+  "configSchema": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {
+      "routersDir": {
+        "type": "string",
+        "description": "Directory containing router .ts/.js files (default: {pluginDir}/routers)"
+      },
+      "rulesFile": {
+        "type": "string",
+        "description": "Path to rules.json (default: {pluginDir}/rules.json)"
+      }
+    }
+  }
+}
diff --git a/plugin/package.json b/plugin/package.json
new file mode 100644
index 0000000..d702479
--- /dev/null
+++ b/plugin/package.json
@@ -0,0 +1,6 @@
+{
+  "name": "prism-facet",
+  "version": "0.1.0",
+  "type": "module",
+  "main": "index.js"
+}
diff --git a/plugin/tools/prompt-rules.ts b/plugin/tools/prompt-rules.ts
new file mode 100644
index 0000000..5897a6e
--- /dev/null
+++ b/plugin/tools/prompt-rules.ts
@@ -0,0 +1,100 @@
+import { addRule, removeRule, listRules } from "../core/rule-store.js";
+import { loadRouters, getRouterNames } from "../core/router-loader.js";
+import { resolveInjection } from "../core/prompt-injector.js";
+
+export function registerPromptRulesTool(
+  api: {
+    registerTool(def: any): void;
+    logger: { info(msg: string): void; warn(msg: string): void };
+  },
+  routersDir: string
+): void {
+  api.registerTool({
+    name: "prompt_rules",
+    description:
+      "Manage PrismFacet prompt injection rules. " +
+      "Actions: add (register a rule mapping router:key to a prompt file), " +
+      "remove (delete a rule), list (show all rules), " +
+      "test (preview which prompts would be injected for an agent), " +
+      "reload-routers (hot-reload all router functions), " +
+      "list-routers (show loaded routers).",
+    parameters: {
+      type: "object",
+      properties: {
+        action: {
+          type: "string",
+          enum: ["add", "remove", "list", "test", "reload-routers", "list-routers"],
+          description: "The action to perform",
+        },
+        router: {
+          type: "string",
+          description: "Router name (for add/remove)",
+        },
+        key: {
+          type: "string",
+          description: "Rule key (for add/remove)",
+        },
+        file: {
+          type: "string",
+          description: "Absolute path to prompt file (for add)",
+        },
+        agent: {
+          type: "string",
+          description: "Agent ID to test (for test)",
+        },
+      },
+      required: ["action"],
+    },
+    execute: async (_toolCallId: string, params: Record<string, unknown>) => {
+      const action = params.action as string;
+      const router = params.router as string | undefined;
+      const key = params.key as string | undefined;
+      const file = params.file as string | undefined;
+      const agent = params.agent as string | undefined;
+
+      switch (action) {
+        case "add": {
+          if (!router || !key || !file) {
+            return { content: [{ type: "text", text: "Error: add requires router, key, and file" }] };
+          }
+          addRule(router, key, file);
+          return { content: [{ type: "text", text: `Rule added: ${router}:${key} → ${file}` }] };
+        }
+        case "remove": {
+          if (!router || !key) {
+            return { content: [{ type: "text", text: "Error: remove requires router and key" }] };
+          }
+          const removed = removeRule(router, key);
+          const msg = removed ? `Rule removed: ${router}:${key}` : `Rule not found: ${router}:${key}`;
+          return { content: [{ type: "text", text: msg }] };
+        }
+        case "list": {
+          const rules = listRules();
+          const entries = Object.entries(rules);
+          if (entries.length === 0) return { content: [{ type: "text", text: "No rules registered." }] };
+          return { content: [{ type: "text", text: entries.map(([k, v]) => `${k} → ${v}`).join("\n") }] };
+        }
+        case "test": {
+          if (!agent) return { content: [{ type: "text", text: "Error: test requires agent" }] };
+          const result = await resolveInjection({ agentId: agent }, api.logger);
+          if (!result.appendSystemContext) {
+            return { content: [{ type: "text", text: `No prompts matched for agent: ${agent}` }] };
+          }
+          return { content: [{ type: "text", text: `Matched prompts for ${agent}:\n\n${result.appendSystemContext}` }] };
+        }
+        case "reload-routers": {
+          await loadRouters(routersDir, api.logger);
+          const names = getRouterNames();
+          return { content: [{ type: "text", text: `Routers reloaded: ${names.join(", ") || "(none)"}` }] };
+        }
+        case "list-routers": {
+          const names = getRouterNames();
+          const msg = names.length > 0 ? `Loaded routers: ${names.join(", ")}` : "No routers loaded.";
+          return { content: [{ type: "text", text: msg }] };
+        }
+        default:
+          return { content: [{ type: "text", text: `Unknown action: ${action}` }] };
+      }
+    },
+  });
+}
diff --git a/rules.json b/rules.json
new file mode 100644
index 0000000..9e26dfe
--- /dev/null
+++ b/rules.json
@@ -0,0 +1 @@
+{}
\ No newline at end of file
diff --git a/scripts/install.mjs b/scripts/install.mjs
new file mode 100644
index 0000000..3723d91
--- /dev/null
+++ b/scripts/install.mjs
@@ -0,0 +1,143 @@
+#!/usr/bin/env node
+import fs from "node:fs";
+import path from "node:path";
+import { execSync } from "node:child_process";
+import { fileURLToPath } from "node:url";
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const projRoot = path.resolve(__dirname, "..");
+const pluginSrcDir = path.join(projRoot, "plugin");
+const routersSrcDir = path.join(projRoot, "routers");
+
+const PLUGIN_ID = "prism-facet";
+const ocDir = path.join(process.env.HOME || "~", ".openclaw");
+const pluginsDir = path.join(ocDir, "plugins");
+const installDir = path.join(pluginsDir, PLUGIN_ID);
+const configPath = path.join(ocDir, "openclaw.json");
+
+const args = process.argv.slice(2);
+const action = args[0];
+
+if (!action || !["--install", "--uninstall", "--update"].includes(action)) {
+  console.log("Usage: node scripts/install.mjs --install | --uninstall | --update");
+  process.exit(1);
+}
+
+function readConfig() {
+  return JSON.parse(fs.readFileSync(configPath, "utf8"));
+}
+
+function writeConfig(cfg) {
+  fs.writeFileSync(configPath, JSON.stringify(cfg, null, 2) + "\n", "utf8");
+}
+
+function setIfMissing(obj, key, value) {
+  if (obj[key] === undefined || obj[key] === null) {
+    obj[key] = value;
+  }
+}
+
+function buildPlugin() {
+  console.log("Building plugin...");
+  // Compile TypeScript from plugin/ to plugin/ (in-place, JS output)
+  execSync("npx tsc --project tsconfig.plugin.json", { cwd: projRoot, stdio: "inherit" });
+}
+
+function install() {
+  // 1. Build
+  buildPlugin();
+
+  // 2. Clean and copy plugin to install dir
+  if (fs.existsSync(installDir)) {
+    fs.rmSync(installDir, { recursive: true });
+  }
+  fs.mkdirSync(installDir, { recursive: true });
+
+  // Copy compiled plugin files
+  copyDirRecursive(pluginSrcDir, installDir, [".ts"]);
+
+  // Copy routers alongside plugin
+  const routersInstallDir = path.join(installDir, "routers");
+  if (fs.existsSync(routersSrcDir)) {
+    fs.mkdirSync(routersInstallDir, { recursive: true });
+    copyDirRecursive(routersSrcDir, routersInstallDir);
+  }
+
+  // Create empty rules.json if not exists
+  const rulesPath = path.join(installDir, "rules.json");
+  if (!fs.existsSync(rulesPath)) {
+    fs.writeFileSync(rulesPath, "{}\n", "utf8");
+  }
+
+  // 3. Update openclaw.json
+  const cfg = readConfig();
+  const plugins = cfg.plugins ??= {};
+  const allow = plugins.allow ??= [];
+  const loadPaths = (plugins.load ??= {}).paths ??= [];
+  const entries = plugins.entries ??= {};
+
+  if (!allow.includes(PLUGIN_ID)) allow.push(PLUGIN_ID);
+  if (!loadPaths.includes(installDir)) loadPaths.push(installDir);
+
+  const entry = entries[PLUGIN_ID] ??= {};
+  setIfMissing(entry, "enabled", true);
+  const hooks = entry.hooks ??= {};
+  setIfMissing(hooks, "allowPromptInjection", true);
+
+  writeConfig(cfg);
+  console.log(`Installed ${PLUGIN_ID} to ${installDir}`);
+  console.log("Restart gateway: openclaw gateway restart");
+}
+
+function uninstall() {
+  const cfg = readConfig();
+  const plugins = cfg.plugins ?? {};
+
+  // Remove from allow
+  if (Array.isArray(plugins.allow)) {
+    plugins.allow = plugins.allow.filter((id) => id !== PLUGIN_ID);
+  }
+
+  // Remove entry
+  if (plugins.entries) delete plugins.entries[PLUGIN_ID];
+
+  // Remove load path
+  if (plugins.load?.paths) {
+    plugins.load.paths = plugins.load.paths.filter((p) => !p.includes(PLUGIN_ID));
+  }
+
+  writeConfig(cfg);
+
+  // Remove install dir
+  if (fs.existsSync(installDir)) {
+    fs.rmSync(installDir, { recursive: true });
+    console.log(`Removed ${installDir}`);
+  }
+
+  console.log(`Uninstalled ${PLUGIN_ID}`);
+}
+
+function copyDirRecursive(src, dest, excludeExts = []) {
+  if (!fs.existsSync(dest)) fs.mkdirSync(dest, { recursive: true });
+  for (const entry of fs.readdirSync(src, { withFileTypes: true })) {
+    const srcPath = path.join(src, entry.name);
+    const destPath = path.join(dest, entry.name);
+    if (entry.isDirectory()) {
+      if (entry.name === "node_modules") continue;
+      copyDirRecursive(srcPath, destPath, excludeExts);
+    } else {
+      if (excludeExts.some((ext) => entry.name.endsWith(ext))) continue;
+      fs.copyFileSync(srcPath, destPath);
+    }
+  }
+}
+
+switch (action) {
+  case "--install":
+  case "--update":
+    install();
+    break;
+  case "--uninstall":
+    uninstall();
+    break;
+}
diff --git a/tsconfig.plugin.json b/tsconfig.plugin.json
new file mode 100644
index 0000000..0489d26
--- /dev/null
+++ b/tsconfig.plugin.json
@@ -0,0 +1,18 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "outDir": "plugin",
+    "rootDir": "plugin",
+    "declaration": false,
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "allowJs": true,
+    "emitDeclarationOnly": false
+  },
+  "include": ["plugin/**/*.ts"],
+  "exclude": ["plugin/**/*.js"]
+}