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Your coding agent can't fix what it can't see.

Replay captures the full browser runtime — every DOM change, network request, and state update — and turns it into a root cause and a specific fix. No manual debugging.

Trusted by top engineering teams

Your agent reads code.
It can't read the runtime.

A test fails. A user hits a bug. Your agent takes a guess at the fix, pushes it, and the same test fails again. Without runtime context, agents are stuck in a loop — guessing, patching, retrying.

The problem isn't the agent. It's that the agent has no way to see what actually happened in the browser. No DOM state, no network timing, no component re-renders. It's debugging blind.

You end up pulling the agent aside, opening DevTools yourself, and spending an hour doing the work manually. The whole point of the agent was to save you that time.

That's why we built Replay

Give your agent
the power of time-travel

Replay captures a deterministic recording — every DOM change, network request, JS execution frame, and state update. Using Replay MCP, your coding agent can analyze the recording, trace the exact causal chain from failure to root cause, and deliver the root cause and a suggested fix. No guessing. No manual debugging. No human required.

You might be thinking “how is this different than the monitoring tools I'm already using?” We made this video for you.

Three ways to Replay

Replay's time-travel debugging works wherever your tests run and wherever your agent works. Most teams use all three.

In your CI pipeline

Replay CI Agent posting a root-cause analysis on a GitHub PR

Test fails. Fix lands on your PR.

The Replay CI Agent installs as a GitHub bot. It records every Playwright run on every PR. When a test fails, Replay analyzes the recording and posts root cause plus a suggested fix as a PR comment — automatically.

Set up the CI Agent

In your IDE

Replay MCP letting a coding agent time-travel through a recording inside an IDE

Your agent time-travels through the recording.

Replay MCP connects to Cursor, Claude Code, Codex, Copilot, or Windsurf in one command. Your coding agent can step through any recorded execution, inspect state at any point in time, and identify root causes — right inside your IDE.

Set up Replay MCP

In your browser

Replay Chrome extension capturing a deterministic recording of a browser bug

Record any bug, anywhere.

The Replay Chrome extension lets engineers and QA capture a deterministic recording of any bug — on localhost, a staging environment, or production. Record it once, hand it to your agent or step through it yourself. No reproduction required.

Install the extension

From bug to fix — without touching DevTools

See how Replay MCP lets your agent dive in and explain the problem.

Button doesn't work

Creating a new task does nothing

Chat transcript with Replay MCP

The form to add a new task isn't doing anything

I'll investigate why the form to add a new task isn't working. Let me start by exploring the recording to understand what's happening.

Let me look at the CreateTaskModal component more closely to understand its implementation, especially the form submission logic.

I can see the form submission logic. Line 53-54 shows handleSubmit was called once, but let me check where the onSave callback leads to. Let me look at TasksListPage to see how the modal's onSave is handled.

I found the issue! Looking at handleCreateTask (lines 73-93):

  1. Line 83 shows the function was called once (hit count: 1)
  2. Lines 84-90 build the payload object
  3. Line 92 closes the modal with setCreateModalOpen(false) (hit count: 1)
  4. But there's no fetch call to actually save the task!

The function closes the modal at the end, but it never makes a network request to persist the new task. The payload is built but never sent to the server.

Root Cause

The handleCreateTask function in TasksListPage.tsx is missing the API call to create the task. It:

  1. Builds the payload object ✓
  2. Closes the modal ✓
  3. Does NOT call fetch to POST the task to the backend

Compare this to line 65-70 where fetch is used to load deals - a similar pattern should exist after building the payload on line 92, but it's missing. The function just closes the modal without actually saving anything.

What your agent gets from Replay

Three things Replay delivers on every bug.

Root-cause analysis, automated

Replay doesn't just report the error. It traces through the recording to find the exact cause — the state change, the failed request, the bad render — and explains why it happened.

Detailed fixes, not vague suggestions

Your agent receives a specific, implementation-ready fix with full context — which file, which function, what to change, and why. No more trial-and-error loops.

Works with any coding agent

Replay MCP connects to Claude Code, Codex, Cursor, Copilot, Windsurf, and any agent that supports MCP. Add it once and every agent in your workflow gets full runtime visibility.

Claude CodeClaude CodeCodexCodexCursorCursorCopilotCopilotWindsurfWindsurf

Case Studies

Hear from Replay teams directly

Testimonials

See what time travelers are saying

“Next.js App Router is now stable in 13.4. Wouldn’t have been possible without Replay, we investigated so many (over 20) super complicated bugs that using traditional debugging would have cost us days to investigate.”

Tim Neutkins

@Co-author of Next.js

“I think Replay has a very good chance of creating a new category around collaborative debugging”

Guillermo Rauch

@Founder of Vercel

“When I see a hard-to-reproduce issue in GitHub, I ask for a replay.”

JJ Kasper

@Co-author of Next.js

“If I don't immediately know the answer to a bug, I immediately reach for Replay.io. It's like HMR for repros.”

Sebastian Markbåge

@React Maintainer

“Replay.io is galaxy brain tooling. Real gamechanger.”

Dan Abramov

@React Maintainer

Built for teams shipping with agents

Wherever your agent gets stuck on a bug it can't see, Replay closes the gap.

Agent-assisted development

Your coding agent hits a failing test or runtime error. Instead of looping, it sends the recording to Replay and gets a precise fix back — then implements it.

Flaky tests in CI

Record every test run. When a test flakes, Replay analyzes the recording and delivers the root cause and fix to your agent — no manual investigation needed.

Bug triage on autopilot

A user reports a bug. Replay captures the session, generates the diagnosis and fix. Your agent applies it. You review the PR.

Unblocking stuck agents

When your agent loops on a problem — retrying the same patch, failing the same test — Replay gives it the runtime context it needs to break out.

Replay vs. the old way

Without Replay

  • Agent guesses at the fix, fails, retries in a loop
  • You step in to debug manually with DevTools
  • Flaky tests get retried and ignored
  • Bug reports sit in the backlog waiting for someone to reproduce them
  • Agents write code fast but can't debug what they break

With Replay

  • Agent gets a detailed fix from the recording on the first try
  • You review the PR instead of opening DevTools
  • Flaky tests get diagnosed and fixed automatically
  • Bug reports get a recording, analysis, and fix in minutes
  • Agents ship fixes as fast as they ship features

Common questions

Replay MCP is a Model Context Protocol server that connects Replay's recording and analysis engine to your coding agent. When your agent encounters a bug, Replay MCP provides the root cause and a detailed fix — drawn from a deterministic browser recording — so the agent can implement the fix directly.

Stop debugging for your agent. Give it time-travel.

Free to get started. No credit card required.