diff --git a/apps/desktop/src/main/lib/browser-mcp-bridge/server.ts b/apps/desktop/src/main/lib/browser-mcp-bridge/server.ts
index 56418bcdcaa..f16eab3cbd7 100644
--- a/apps/desktop/src/main/lib/browser-mcp-bridge/server.ts
+++ b/apps/desktop/src/main/lib/browser-mcp-bridge/server.ts
@@ -37,15 +37,6 @@ import { getBoundPaneForSession, resolvePpidToSession } from "./pane-resolver";
 
 const RUNTIME_INFO_PATH = join(SUPERSET_HOME_DIR, "browser-mcp.json");
 
-const MAX_JSON_BODY_BYTES = 8 * 1024 * 1024;
-
-class PayloadTooLargeError extends Error {
-	readonly status = 413;
-	constructor() {
-		super(`request body exceeds ${MAX_JSON_BODY_BYTES} bytes`);
-	}
-}
-
 async function resolvePaneFromRequest(
 	req: IncomingMessage,
 ): Promise<
@@ -75,21 +66,6 @@ async function resolvePaneFromRequest(
 	return { paneId, sessionId: resolved.sessionId };
 }
 
-async function _readJson<T>(req: IncomingMessage): Promise<T> {
-	const chunks: Buffer[] = [];
-	let total = 0;
-	for await (const chunk of req) {
-		const buf = chunk as Buffer;
-		total += buf.length;
-		if (total > MAX_JSON_BODY_BYTES) throw new PayloadTooLargeError();
-		chunks.push(buf);
-	}
-	const raw = Buffer.concat(chunks).toString("utf8");
-	return raw ? (JSON.parse(raw) as T) : ({} as T);
-}
-// Kept for follow-up endpoints that accept bodies; silences unused hint.
-void _readJson;
-
 function send(res: ServerResponse, status: number, body: unknown): void {
 	res.statusCode = status;
 	res.setHeader("content-type", "application/json");
@@ -206,9 +182,6 @@ export async function startBrowserMcpBridge(): Promise<BridgeHandle> {
 
 			return send(res, 404, { error: "not found" });
 		} catch (error) {
-			if (error instanceof PayloadTooLargeError) {
-				return send(res, 413, { error: error.message });
-			}
 			console.error("[browser-mcp-bridge]", error);
 			return send(res, 500, {
 				error: error instanceof Error ? error.message : String(error),
diff --git a/packages/superset-browser-mcp/README.md b/packages/superset-browser-mcp/README.md
new file mode 100644
index 00000000000..e9124791f9d
--- /dev/null
+++ b/packages/superset-browser-mcp/README.md
@@ -0,0 +1,73 @@
+# @superset/superset-browser-mcp
+
+Small stdio MCP server that bridges an LLM session to a Superset desktop app
+browser pane. Superset ships the compiled binary at
+`<app>/Contents/Resources/resources/superset-browser-mcp/superset-browser-mcp`;
+`claude mcp add superset-browser -s user -- <that path>` registers it into
+Claude Code, `codex mcp add superset-browser -- <that path>` into Codex.
+
+## What it does (and what it doesn't)
+
+Actual browser automation — click, navigate, screenshot, DOM inspection — is
+delegated to mature external CDP (Chrome DevTools Protocol) MCPs:
+
+- [`chrome-devtools-mcp`](https://github.com/ChromeDevTools/chrome-devtools-mcp)
+- [`browser-use`](https://github.com/browser-use/browser-use)
+- [`playwright-mcp`](https://github.com/microsoft/playwright-mcp)
+
+This MCP's only job is **binding routing**: give the LLM a URL that scopes
+CDP down to the one Superset pane that the user attached to the session.
+
+Tools:
+
+- `get_cdp_endpoint` — returns `{ webSocketDebuggerUrl, httpBase, targetId, … }`
+  for the pane currently bound to this LLM session. Plug those into any
+  external CDP MCP and it only sees that pane.
+- `get_connected_pane` — returns `{ bound, paneId, url, title, sessionId }`
+  as a sanity check before handing the endpoint to another tool.
+
+## Architecture
+
+```
+Claude / Codex session
+        │  (stdio tool call: get_cdp_endpoint)
+        ▼
+packages/superset-browser-mcp  (this package)
+        │  HTTP over loopback, ~/.superset/browser-mcp.json
+        ▼
+apps/desktop main process
+  ├── session resolver (PPID → terminal pane → LLM session)
+  ├── binding store (sessionId ↔ paneId)
+  └── CDP filter proxy
+        │  ws(s)://…/cdp/<token>/devtools/page/<targetId>
+        ▼
+Chromium --remote-debugging-port   (random port)
+        │  filter: only the bound pane's target is visible
+        ▼
+External CDP MCP (chrome-devtools-mcp / browser-use / …)
+```
+
+## Flow
+
+1. User opens a browser pane in Superset and hits **Connect**, binding it to
+   their running Claude / Codex terminal session. The binding is persisted in
+   Superset's local DB so it survives restarts.
+2. Claude / Codex spawns this MCP. It talks to the Superset bridge over the
+   loopback port written to `~/.superset/browser-mcp.json` (workspace-scoped
+   via `SUPERSET_HOME_DIR`).
+3. `get_cdp_endpoint` returns a per-session-token URL pointing at the filter
+   proxy. The LLM uses it to configure chrome-devtools-mcp / browser-use /
+   etc. from the same session.
+4. The external CDP client sees exactly one page target — the bound pane —
+   via `/json/list`. Sibling panes and the workspace shell are invisible.
+5. Re-binding in the UI re-routes the filtered endpoint to the new pane; the
+   next CDP connection picks up the swap automatically.
+
+## Dev notes
+
+Source lives at `src/bin.ts`; tools at `src/tools/index.ts`. The binary is
+produced by `bun build --compile` and copied into the Electron app via
+`extraResources` — see the desktop app's `electron-builder.ts`.
+
+For the full roadmap (including the PRs that shipped this stack) see
+`plan.md` at the repo root.
diff --git a/packages/superset-browser-mcp/src/tools/index.ts b/packages/superset-browser-mcp/src/tools/index.ts
index 8c20b770c17..8bae76f1b4c 100644
--- a/packages/superset-browser-mcp/src/tools/index.ts
+++ b/packages/superset-browser-mcp/src/tools/index.ts
@@ -22,12 +22,13 @@ interface CdpEndpointResponse {
 }
 
 /**
- * This MCP is intentionally kept minimal. The plan (see ./plan.md in
- * the repo root) is to expose the bound pane as a filtered CDP endpoint
- * so users can drive it with mature external browser MCPs
- * (chrome-devtools-mcp, browser-use, playwright-mcp). The tools here
- * are only the metadata shim LLMs need to verify the binding; the CDP
- * endpoint itself ships in follow-up PRs.
+ * This MCP is intentionally kept minimal. Browser automation primitives
+ * (click / navigate / screenshot / DOM inspection) are delegated to
+ * mature external CDP-speaking MCPs — chrome-devtools-mcp, browser-use,
+ * playwright-mcp, etc. — connected to the bound pane via the filtered
+ * CDP endpoint that `get_cdp_endpoint` returns. The two tools here are
+ * the handoff: `get_cdp_endpoint` for the URL, `get_connected_pane` as
+ * a metadata sanity check.
  */
 export function registerTools(server: McpServer, client: BridgeClient): void {
 	server.registerTool(
diff --git a/plan.md b/plan.md
index e4e4c100efb..ea4e120180e 100644
--- a/plan.md
+++ b/plan.md
@@ -43,6 +43,9 @@
 
 ## Phase B PR ロードマップ
 
+> **Status (2026-04-21):** PR1 / PR2 / PR3 マージ済。PR4 (本 PR) で
+> プラン上の last-mile クリーンアップを行い、Phase B 完了。
+
 ### PR1: CDP エンドポイント公開（pane → Chromium targetId 解決）
 
 - Superset 起動時に `--remote-debugging-port=0` (ランダム port) を有効化
@@ -98,7 +101,7 @@
 - Connect 後の pane 情報画面 (ReadyPanel) にも「この pane の CDP endpoint」
   リンクを常設し、別の LLM クライアントから直接叩けるように
 
-### PR4: 古い自作 tools の整理
+### PR4: 古い自作 tools の整理 (本 PR)
 
 - PR1〜3 で代替が整い次第、以下の MCP tools を deprecated にするか削除:
   - `navigate` / `screenshot` / `evaluate_js` / `get_console_logs`