diff --git a/packages/wordpress-plugin/README.md b/packages/wordpress-plugin/README.md
index ec50e494..e0e34204 100644
--- a/packages/wordpress-plugin/README.md
+++ b/packages/wordpress-plugin/README.md
@@ -331,6 +331,17 @@ an external adapter can consume the verified artifact payload and record adapter
 metadata, PR URL, branch, commit, and artifact digest without WP Codebox calling
 any product-specific apply-back system.
 
+## Agent Context Section
+
+The plugin registers a `wp-codebox` section for the `agents-md` context on the
+upstream context section registry (`WP_Agent_Context_Section_Registry`), so any
+host that composes `AGENTS.md` from registered sections surfaces Codebox routing,
+safety, and discovery guidance to coding agents. Registration is a no-op when the
+registry class is not loaded; no host-specific composer is referenced.
+
+The rendered WP-CLI prefix defaults to `wp --path=<ABSPATH>` and can be adjusted
+through the `wp_codebox_agents_md_wp_cli_cmd` filter.
+
 ## Configuration
 
 Runtime components can be supplied by ability input, the
diff --git a/packages/wordpress-plugin/src/class-wp-codebox-agents-md-section.php b/packages/wordpress-plugin/src/class-wp-codebox-agents-md-section.php
new file mode 100644
index 00000000..59365339
--- /dev/null
+++ b/packages/wordpress-plugin/src/class-wp-codebox-agents-md-section.php
@@ -0,0 +1,104 @@
+<?php
+/**
+ * Composable agent-context section describing WP Codebox.
+ *
+ * Registers a `WP Codebox` section for the `agents-md` context on the
+ * Agents API context section registry so host composers (any consumer of
+ * `WP_Agent_Context_Section_Registry`) surface Codebox routing, safety, and
+ * discovery guidance to coding agents. The plugin owns the surface, so it owns
+ * the guidance; no host-specific composer is referenced here.
+ *
+ * @package WP_Codebox
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+final class WP_Codebox_Agents_Md_Section {
+
+	public const CONTEXT_SLUG = 'agents-md';
+	public const SECTION_SLUG = 'wp-codebox';
+	public const PRIORITY     = 40;
+
+	/**
+	 * Hook the registration onto the Agents API context extension point.
+	 */
+	public static function register(): void {
+		add_action( 'agents_api_context_sections', array( self::class, 'register_section' ) );
+	}
+
+	/**
+	 * Register the section when the substrate registry is loaded.
+	 */
+	public static function register_section(): void {
+		if ( ! class_exists( 'WP_Agent_Context_Section_Registry' ) ) {
+			return;
+		}
+
+		WP_Agent_Context_Section_Registry::register(
+			self::CONTEXT_SLUG,
+			self::SECTION_SLUG,
+			self::PRIORITY,
+			static function (): string {
+				return self::render();
+			},
+			array(
+				'label'       => 'WP Codebox',
+				'description' => 'Disposable WordPress sandbox CLI and abilities.',
+				'meta'        => array(
+					'owner'      => 'wp-codebox',
+					'freshness'  => 'generated',
+					'conditions' => 'Registered when wp-codebox is active and the Agents API context section registry is loaded.',
+				),
+			)
+		);
+	}
+
+	/**
+	 * WP-CLI invocation prefix used in rendered guidance.
+	 *
+	 * Defaults to a path-pinned invocation. Hosts that need a different
+	 * prefix (flags, wrapper binaries, remote routing) adjust it through the
+	 * `wp_codebox_agents_md_wp_cli_cmd` filter.
+	 */
+	public static function wp_cli_cmd(): string {
+		$default = 'wp --path=' . rtrim( (string) ABSPATH, '/\\' );
+
+		$cmd = apply_filters( 'wp_codebox_agents_md_wp_cli_cmd', $default );
+
+		return is_string( $cmd ) && '' !== trim( $cmd ) ? trim( $cmd ) : $default;
+	}
+
+	/**
+	 * Render the section body.
+	 */
+	public static function render(): string {
+		$wp = self::wp_cli_cmd();
+
+		$lines = array(
+			'## WP Codebox',
+			'',
+			'WP Codebox launches disposable, isolated WordPress sandboxes for coding-agent tasks, runtime workloads, and fuzzing. Sandboxes cannot touch the host site; they produce artifact bundles (changed files, patches, evidence) that the host reviews and applies back explicitly. Abilities live under `wp-codebox/*`; the CLI mirrors the same PHP service layer.',
+			'',
+			'**Default routing**',
+			'- Run a bounded coding task in a sandbox: `' . $wp . ' codebox run-agent-task --goal=\'...\' --format=json`',
+			'- Independent task waves: `' . $wp . ' codebox run-agent-task-batch --input-file=<batch.json>` or `' . $wp . ' codebox run-agent-task-fanout --input-file=<fanout.json>`',
+			'- Run a runtime task or WordPress workload: `' . $wp . ' codebox run-runtime-task --input-json=\'{...}\'` or `' . $wp . ' codebox run-wordpress-workload --input-file=<workload.json>`',
+			'- Check runtime/provider readiness before dispatch: `' . $wp . ' codebox resolve-runtime-requirements --format=json`',
+			'- Review what a sandbox produced: `' . $wp . ' codebox artifacts list --format=json`, then `' . $wp . ' codebox artifacts inspect <artifact_id> --format=json`',
+			'- Apply reviewed changes to the host: `' . $wp . ' codebox artifacts preflight-apply <artifact_id>` → `' . $wp . ' codebox artifacts stage-apply <artifact_id> --approved-files=...` → `' . $wp . ' codebox artifacts apply <artifact_id> --approved-files=...`',
+			'- Browser-executed Playground session: `' . $wp . ' codebox browser-session create --goal=\'...\' --format=json`',
+			'',
+			'**Safety**',
+			'- `artifacts apply` mutates the host through the configured apply-back adapter. Always `preflight-apply` and review `inspect` output first; pass only the files you approved via `--approved-files`.',
+			'- Provider credentials reach sandboxes through `secret_env` names. Never print secret values in prompts, task payloads, logs, or artifacts.',
+			'- WP-CLI runs in trusted operator context and bypasses ability permission callbacks; shell access is the permission boundary.',
+			'',
+			'**Discovery**',
+			'Use `' . $wp . ' codebox --help` and `' . $wp . ' codebox <command> --help` for the live command contract; `--input-json` / `--input-file` carry complex payloads and CLI flags override payload fields. Inspect `' . $wp . ' codebox runtime descriptor --format=json` for the registered runtime profile. Live `--help` output is authoritative.',
+		);
+
+		return implode( "\n", $lines ) . "\n";
+	}
+}
diff --git a/packages/wordpress-plugin/wp-codebox.php b/packages/wordpress-plugin/wp-codebox.php
index 9062c8ea..8ae0c42e 100644
--- a/packages/wordpress-plugin/wp-codebox.php
+++ b/packages/wordpress-plugin/wp-codebox.php
@@ -77,6 +77,7 @@
 require_once __DIR__ . '/src/class-wp-codebox-runtime-package-executor.php';
 require_once __DIR__ . '/src/class-wp-codebox-api.php';
 require_once __DIR__ . '/src/class-wp-codebox-abilities.php';
+require_once __DIR__ . '/src/class-wp-codebox-agents-md-section.php';
 
 if ( defined( 'WP_CLI' ) && WP_CLI ) {
 	require_once __DIR__ . '/src/class-wp-codebox-cli-command.php';
@@ -94,6 +95,7 @@
 add_action( 'plugins_loaded', array( WP_Codebox_Php_Ai_Client_Browser_Provider_Adapter::class, 'register' ), 20 );
 new WP_Codebox_Abilities();
 WP_Codebox_Browser_Provider_Bridge::register();
+WP_Codebox_Agents_Md_Section::register();
 
 if ( defined( 'WP_CLI' ) && WP_CLI ) {
 	WP_Codebox_CLI_Command::register();
diff --git a/tests/php-agents-md-section.test.ts b/tests/php-agents-md-section.test.ts
new file mode 100644
index 00000000..f8da89cf
--- /dev/null
+++ b/tests/php-agents-md-section.test.ts
@@ -0,0 +1,103 @@
+import assert from "node:assert/strict"
+import { execFileSync } from "node:child_process"
+
+// Proves the plugin registers its own `agents-md` context section on a
+// minimal stand-in for WP_Agent_Context_Section_Registry (the Agents API
+// substrate), that the render body carries routing/safety/discovery guidance
+// with the host-filtered WP-CLI prefix, and that registration is a no-op
+// when the substrate class is absent.
+const output = execFileSync(
+  "php",
+  [
+    "-r",
+    String.raw`
+define('ABSPATH', '/srv/site/');
+
+$GLOBALS['actions'] = array();
+$GLOBALS['filters'] = array();
+function add_action(string $hook, callable $cb, int $priority = 10, int $accepted_args = 1): void { $GLOBALS['actions'][$hook][] = $cb; }
+function do_action(string $hook, ...$args): void { foreach ($GLOBALS['actions'][$hook] ?? array() as $cb) { $cb(); } }
+function add_filter(string $hook, callable $cb, int $priority = 10, int $accepted_args = 1): void { $GLOBALS['filters'][$hook][] = $cb; }
+function apply_filters(string $hook, $value, ...$args) { foreach ($GLOBALS['filters'][$hook] ?? array() as $cb) { $value = $cb($value); } return $value; }
+
+require __DIR__ . '/packages/wordpress-plugin/src/class-wp-codebox-agents-md-section.php';
+
+// 1. Without the substrate class, firing the hook registers nothing and does not fatal.
+WP_Codebox_Agents_Md_Section::register();
+do_action('agents_api_context_sections');
+$without_substrate_ok = true;
+
+$registered_before_substrate = isset($GLOBALS['registered']) ? count($GLOBALS['registered']) : 0;
+
+// 2. With a minimal substrate stand-in, the section registers with the expected shape.
+// Declared inside a block so PHP does not hoist it above step 1.
+if (true) {
+	final class WP_Agent_Context_Section_Registry {
+		public static array $registered = array();
+		public static function register(string $context, string $slug, int $priority, callable $callback, array $args = array()) {
+			self::$registered[] = compact('context', 'slug', 'priority', 'callback', 'args');
+			return self::$registered[count(self::$registered) - 1];
+		}
+	}
+}
+do_action('agents_api_context_sections');
+
+add_filter('wp_codebox_agents_md_wp_cli_cmd', static function ($cmd) { return 'wp --allow-root --path=/srv/site'; });
+
+$reg = WP_Agent_Context_Section_Registry::$registered[0] ?? null;
+$rendered = $reg ? ($reg['callback'])(array(), array()) : '';
+
+echo json_encode(array(
+	'without_substrate_ok' => $without_substrate_ok && 0 === $registered_before_substrate,
+	'count' => count(WP_Agent_Context_Section_Registry::$registered),
+	'context' => $reg['context'] ?? null,
+	'slug' => $reg['slug'] ?? null,
+	'priority' => $reg['priority'] ?? null,
+	'label' => $reg['args']['label'] ?? null,
+	'owner' => $reg['args']['meta']['owner'] ?? null,
+	'freshness' => $reg['args']['meta']['freshness'] ?? null,
+	'default_cmd' => 'wp --path=/srv/site',
+	'rendered' => $rendered,
+), JSON_UNESCAPED_SLASHES);
+`,
+  ],
+  { cwd: new URL("..", import.meta.url), encoding: "utf8" }
+)
+
+const result = JSON.parse(output)
+
+assert.equal(result.without_substrate_ok, true)
+assert.equal(result.count, 1, "registers exactly one section")
+assert.equal(result.context, "agents-md")
+assert.equal(result.slug, "wp-codebox")
+assert.equal(result.priority, 40)
+assert.equal(result.label, "WP Codebox")
+assert.equal(result.owner, "wp-codebox")
+assert.equal(result.freshness, "generated")
+
+const rendered: string = result.rendered
+assert.ok(rendered.startsWith("## WP Codebox\n"), "section starts with its heading")
+for (const heading of ["**Default routing**", "**Safety**", "**Discovery**"]) {
+  assert.ok(rendered.includes(heading), `contains ${heading}`)
+}
+for (const verb of [
+  "codebox run-agent-task",
+  "codebox run-agent-task-fanout",
+  "codebox run-wordpress-workload",
+  "codebox resolve-runtime-requirements",
+  "codebox artifacts inspect",
+  "codebox artifacts preflight-apply",
+  "codebox artifacts apply",
+  "codebox browser-session create",
+  "codebox --help",
+]) {
+  assert.ok(rendered.includes(verb), `routes to ${verb}`)
+}
+assert.ok(
+  rendered.includes("wp --allow-root --path=/srv/site codebox"),
+  "uses the host-filtered WP-CLI prefix"
+)
+assert.ok(!rendered.includes(result.default_cmd + " codebox"), "filtered prefix replaces the default")
+assert.ok(!/datamachine|DataMachine/.test(rendered), "no host composer names leak into generic guidance")
+
+console.log("php-agents-md-section: OK")