From 55be6ec8409c6e0c2e9533058ab0409ee8226f29 Mon Sep 17 00:00:00 2001
From: "Tommy D. Rossi" <beats.by.morse@gmail.com>
Date: Mon, 16 Feb 2026 20:03:36 +0100
Subject: [PATCH] fix: sanitize Buffer and long string output in CLI/MCP
 logging

Buffer instances (from screenshots, PDFs, responses) were dumping hundreds of
chars of hex bytes via util.inspect. Long strings nested in objects (base64,
HTML) also wasted context window space.

- Add Buffer.prototype[util.inspect.custom] in all entry points (cli, mcp,
  cdp-relay) so Buffers display as '<Buffer N bytes>' instead of hex dumps
- Add maxStringLength: 1000 to all util.inspect calls so strings inside
  inspected objects get capped (top-level strings are untouched, the existing
  10k char overall truncation handles those)
---
 playwriter/src/cdp-relay.ts     | 7 +++++++
 playwriter/src/cli.ts           | 6 ++++++
 playwriter/src/create-logger.ts | 2 +-
 playwriter/src/executor.ts      | 4 ++--
 playwriter/src/mcp.ts           | 8 ++++++++
 5 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/playwriter/src/cdp-relay.ts b/playwriter/src/cdp-relay.ts
index e308a60..1391497 100644
--- a/playwriter/src/cdp-relay.ts
+++ b/playwriter/src/cdp-relay.ts
@@ -17,6 +17,13 @@ import type {
   IsRecordingParams,
 } from './protocol.js'
 import pc from 'picocolors'
+import util from 'node:util'
+
+// Prevent Buffers from dumping hex bytes in util.inspect output.
+Buffer.prototype[util.inspect.custom] = function () {
+  return `<Buffer ${this.length} bytes>`
+}
+
 import { EventEmitter } from 'node:events'
 import { VERSION, EXTENSION_IDS } from './utils.js'
 import { createCdpLogger, type CdpLogEntry, type CdpLogger } from './cdp-log.js'
diff --git a/playwriter/src/cli.ts b/playwriter/src/cli.ts
index e345406..ce2e52b 100644
--- a/playwriter/src/cli.ts
+++ b/playwriter/src/cli.ts
@@ -2,8 +2,14 @@
 
 import fs from 'node:fs'
 import path from 'node:path'
+import util from 'node:util'
 import { fileURLToPath } from 'node:url'
 import { cac } from '@xmorse/cac'
+
+// Prevent Buffers from dumping hex bytes in util.inspect output.
+Buffer.prototype[util.inspect.custom] = function () {
+  return `<Buffer ${this.length} bytes>`
+}
 import { killPortProcess } from './kill-port.js'
 import { VERSION, LOG_FILE_PATH, LOG_CDP_FILE_PATH, parseRelayHost } from './utils.js'
 import { ensureRelayServer, RELAY_PORT, waitForExtension, getExtensionOutdatedWarning, getExtensionStatus } from './relay-client.js'
diff --git a/playwriter/src/create-logger.ts b/playwriter/src/create-logger.ts
index 387d1f5..675be18 100644
--- a/playwriter/src/create-logger.ts
+++ b/playwriter/src/create-logger.ts
@@ -22,7 +22,7 @@ export function createFileLogger({ logFilePath }: { logFilePath?: string } = {})
 
   const log = (...args: unknown[]): Promise<void> => {
     const message = args.map(arg =>
-      typeof arg === 'string' ? arg : util.inspect(arg, { depth: null, colors: false })
+      typeof arg === 'string' ? arg : util.inspect(arg, { depth: null, colors: false, maxStringLength: 1000 })
     ).join(' ')
     queue = queue.then(() => fs.promises.appendFile(resolvedLogFilePath, stripAnsi(message) + '\n'))
     return queue
diff --git a/playwriter/src/executor.ts b/playwriter/src/executor.ts
index be8e39a..0cc8907 100644
--- a/playwriter/src/executor.ts
+++ b/playwriter/src/executor.ts
@@ -514,7 +514,7 @@ export class PlaywrightExecutor {
         const formattedArgs = args
           .map((arg) => {
             if (typeof arg === 'string') return arg
-            return util.inspect(arg, { depth: 4, colors: false, maxArrayLength: 100, breakLength: 80 })
+            return util.inspect(arg, { depth: 4, colors: false, maxArrayLength: 100, maxStringLength: 1000, breakLength: 80 })
           })
           .join(' ')
         text += `[${method}] ${formattedArgs}\n`
@@ -853,7 +853,7 @@ export class PlaywrightExecutor {
           const formatted =
             typeof resolvedResult === 'string'
               ? resolvedResult
-              : util.inspect(resolvedResult, { depth: 4, colors: false, maxArrayLength: 100, breakLength: 80 })
+              : util.inspect(resolvedResult, { depth: 4, colors: false, maxArrayLength: 100, maxStringLength: 1000, breakLength: 80 })
           if (formatted.trim()) {
             responseText += `[return value] ${formatted}\n`
           }
diff --git a/playwriter/src/mcp.ts b/playwriter/src/mcp.ts
index 7a50d89..55b520f 100644
--- a/playwriter/src/mcp.ts
+++ b/playwriter/src/mcp.ts
@@ -3,8 +3,16 @@ import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js'
 import { z } from 'zod'
 import fs from 'node:fs'
 import path from 'node:path'
+import util from 'node:util'
 import { fileURLToPath } from 'node:url'
 import { createRequire } from 'node:module'
+
+// Prevent Buffers from dumping hex bytes in util.inspect output.
+// Without this, returning a screenshot Buffer would log ~400+ chars of useless hex.
+Buffer.prototype[util.inspect.custom] = function () {
+  return `<Buffer ${this.length} bytes>`
+}
+
 import dedent from 'string-dedent'
 import { LOG_FILE_PATH, VERSION, parseRelayHost } from './utils.js'
 import { ensureRelayServer, RELAY_PORT } from './relay-client.js'