From 09bdf9ddafffc72398b2f70bea22fe1afc5ecdab Mon Sep 17 00:00:00 2001
From: Simon <10131203+gaomeng1900@users.noreply.github.com>
Date: Wed, 4 Mar 2026 18:53:24 +0800
Subject: [PATCH] feat(core): experimental support for llms.txt (#157)

* feat(core): experimental support for llms.txt

* docs: experimentalLlmsTxt
---
 docs/CHANGELOG.md                             |  3 ++-
 packages/core/src/PageAgentCore.ts            | 19 +++++++++-----
 packages/core/src/config/index.ts             |  8 ++++++
 packages/core/src/utils/index.ts              | 25 +++++++++++++++++++
 .../docs/advanced/page-agent-core/page.tsx    |  9 +++++++
 5 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 07f0611..b9bd8c5 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -122,9 +122,10 @@ PageAgent is now ready for production use. The API is stable and breaking change
 - **Ask User Tool** - Agent can ask users for clarification
 - **i18n Support** - English and Chinese localization
 
-### Configuration
+### Configuration 
 
 ```typescript
+// Version 1.0.0
 interface PageAgentConfig {
     // LLM Configuration (required)
     baseURL: string
diff --git a/packages/core/src/PageAgentCore.ts b/packages/core/src/PageAgentCore.ts
index 04f88f2..2571d67 100644
--- a/packages/core/src/PageAgentCore.ts
+++ b/packages/core/src/PageAgentCore.ts
@@ -21,7 +21,7 @@ import type {
 	MacroToolInput,
 	MacroToolResult,
 } from './types'
-import { assert, normalizeResponse, uid, waitFor } from './utils'
+import { assert, fetchLlmsTxt, normalizeResponse, uid, waitFor } from './utils'
 
 export { type PageAgentConfig }
 export type { SupportedLanguage }
@@ -222,6 +222,7 @@ export class PageAgentCore extends EventTarget {
 		this.history = []
 		this.#setStatus('running')
 		this.#emitHistoryChange()
+		this.#observations = []
 
 		// Reset internal states
 		this.#states = { totalWaitTime: 0, lastURL: '', browserState: null }
@@ -462,14 +463,13 @@ export class PageAgentCore extends EventTarget {
 	 * Get instructions from config
 	 */
 	async #getInstructions(): Promise<string> {
-		const { instructions } = this.config
-		if (!instructions) return ''
+		const { instructions, experimentalLlmsTxt } = this.config
 
-		const systemInstructions = instructions.system?.trim()
+		const systemInstructions = instructions?.system?.trim()
 		let pageInstructions: string | undefined
 
 		const url = this.#states.browserState?.url || ''
-		if (instructions.getPageInstructions && url) {
+		if (instructions?.getPageInstructions && url) {
 			try {
 				pageInstructions = instructions.getPageInstructions(url)?.trim()
 			} catch (error) {
@@ -479,7 +479,10 @@ export class PageAgentCore extends EventTarget {
 				)
 			}
 		}
-		if (!systemInstructions && !pageInstructions) return ''
+
+		const llmsTxt = experimentalLlmsTxt && url ? await fetchLlmsTxt(url) : undefined
+
+		if (!systemInstructions && !pageInstructions && !llmsTxt) return ''
 
 		let result = '<instructions>\n'
 
@@ -491,6 +494,10 @@ export class PageAgentCore extends EventTarget {
 			result += `<page_instructions>\n${pageInstructions}\n</page_instructions>\n`
 		}
 
+		if (llmsTxt) {
+			result += `<llms_txt>\n${llmsTxt}\n</llms_txt>\n`
+		}
+
 		result += '</instructions>\n\n'
 
 		return result
diff --git a/packages/core/src/config/index.ts b/packages/core/src/config/index.ts
index 9db66b1..0ad553c 100644
--- a/packages/core/src/config/index.ts
+++ b/packages/core/src/config/index.ts
@@ -126,6 +126,14 @@ export interface AgentConfig {
 	 */
 	experimentalScriptExecutionTool?: boolean
 
+	/**
+	 * @experimental
+	 * Fetch /llms.txt from current site origin and include as context.
+	 * Only fetched once per origin per task.
+	 * @default false
+	 */
+	experimentalLlmsTxt?: boolean
+
 	/**
 	 * Transform page content before sending to LLM.
 	 * Called after DOM extraction and simplification, before LLM invocation.
diff --git a/packages/core/src/utils/index.ts b/packages/core/src/utils/index.ts
index 7644849..e62d819 100644
--- a/packages/core/src/utils/index.ts
+++ b/packages/core/src/utils/index.ts
@@ -57,6 +57,31 @@ export function uid() {
 	return id
 }
 
+const llmsTxtCache = new Map<string, string | null>()
+
+/** Fetch /llms.txt for a URL's origin. Cached per origin, `null` = tried and not found. */
+export async function fetchLlmsTxt(url: string): Promise<string | null> {
+	const origin = new URL(url).origin
+	if (llmsTxtCache.has(origin)) return llmsTxtCache.get(origin)!
+
+	const endpoint = `${origin}/llms.txt`
+	let result: string | null = null
+	try {
+		console.log(chalk.gray(`[llms.txt] Fetching ${endpoint}`))
+		const res = await fetch(endpoint, { signal: AbortSignal.timeout(3000) })
+		if (res.ok) {
+			result = await res.text()
+			console.log(chalk.green(`[llms.txt] Found (${result.length} chars)`))
+		} else {
+			console.log(chalk.gray(`[llms.txt] ${res.status} for ${endpoint}`))
+		}
+	} catch (e) {
+		console.log(chalk.gray(`[llms.txt] Failed for ${endpoint}`), e)
+	}
+	llmsTxtCache.set(origin, result)
+	return result
+}
+
 /**
  * Simple assertion function that throws an error if the condition is falsy
  * @param condition - The condition to assert
diff --git a/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx b/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx
index 9476041..7f41371 100644
--- a/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx
+++ b/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx
@@ -185,6 +185,15 @@ const result = await agent.execute('Fill in the form with test data')`}
 								? '启用实验性 JavaScript 执行工具'
 								: 'Enable experimental JavaScript execution tool',
 						},
+						{
+							name: 'experimentalLlmsTxt',
+							type: 'boolean',
+							defaultValue: 'false',
+							status: 'experimental',
+							description: isZh
+								? '从当前站点根目录获取 /llms.txt 并作为上下文提供给 LLM，每个 origin 仅请求一次'
+								: 'Fetch /llms.txt from site origin and include as LLM context, fetched once per origin',
+						},
 					]}
 				/>