Browser MCP for logged-in tasks. Uses your Chrome — credentials stay local. Zero-token replay.
io.github.LeonTing1010/tap — Browser MCP for logged-in tasks
This MCP server provides a browser “action layer” for tasks in a user’s own logged-in Chrome environment. It is described as using locally kept credentials, targeting exception-heavy and compliance-critical workflows that are not covered by clean APIs.
🛠️ Key Features
Browser MCP for logged-in tasks
Uses “your Chrome” (browser-based automation)
Credentials “stay local”
“Zero-token replay” and “compiled once, replayed forever”
The action layer your agent drives in your own logged-in browser — for the exception-heavy, compliance-critical last 20% that clean APIs can't reach. Compiled once, replayed forever at zero LLM tokens.
Your agent's closed-loop action layer for the browser — the login-gated, exception-heavy, compliance-critical last 20% that clean APIs and cloud agents can't reach. Driven in your own Chrome, captured once, replayed forever at zero LLM tokens.
As APIs get walled off and metered, the work that survives lives behind logins, OTP walls, and human-gesture gates — the exceptions, approvals, and compliance steps a cloud agent architecturally can't touch. Taprun is the action layer for exactly that: your agent drives your real, already-logged-in Chrome, closes the loop (act → verify the effect → re-run on drift), and hands you a deterministic replay you own.
Every other browser agent re-runs a live LLM — and re-burns tokens — on every execution. Taprun's AI agent inspects the page once and emits a deterministic .flow.json program; every replay after that is pure data dispatch — same result every call, $0 in tokens, no agent in the loop. It runs in your real Chrome, so cookies and login sessions stay on your machine by architecture. tap verify catches breakage before your data goes stale.
Works with Claude Code, CodeBuddy, Cursor, Cline, Windsurf, and any MCP host — install straight from the chat window. Forge a tap from any URL on demand — no catalog needed.
code
Capture: AI inspects the site → compiles a .flow.json program (one-time cost)
Run: The program executes instantly, same result every time ($0, zero AI)
Verify: tap verify checks the snapshot equivalence predicate (catches drift)
Repair: re-run capture against the same site/name; the next (only when needed)
verify rebaselines after human review
How Taprun Compares
Taprun
AI Browser Agents
Traditional Scrapers
AI cost per run
$0 (compile once)
Tokens every run
Free
Accuracy
Deterministic
Varies per run
Deterministic
Silent failure detection
Per-tap CEL snapshot_equivalent predicate + 4-arm verdict
None
None
Breakage diagnostics
tap verify — exact diff of what changed
None
Manual spot checks
Detection risk
Low (real browser sessions)
High
High
Runtimes
2 (Chrome extension + Playwright)
1
1
Code inspectable
.flow.json — bare JSON, 18-op closed vocabulary, git diff
Black box / ephemeral
Fragile scripts
MCP native
Yes (authoring layer only — execution is zero tokens)
No
No
Get Started
1. Attach to your agent — from the chat window
Claude Code / CodeBuddy — paste two lines into the chat, nothing else:
That installs the Taprun MCP server plus the skills that teach your agent when to use it and the hook that routes walled fetches to Taprun — no terminal, no config file. (CodeBuddy wires plugin MCP servers at startup only, so fully restart it once after installing; Claude Code picks them up with /reload-plugins.)
Any other MCP host (Cursor · VS Code · Claude Desktop) — one command writes the config for you:
The binary self-copies to ~/.tap/bin and your agent's MCP config is written. Re-check anytime with tap embed --verify.
Using a coding agent that isn't in that list?tap embed targets are data, not code: drop a row into ~/.tap/embed-targets.json and the new agent works immediately — no engine release. Each row names one of four install kinds (cc-plugin for Claude-Code-plugin hosts, cli-mcp-add for CLIs with a <cli> mcp add, ide-deeplink, desktop-bundle), e.g. [{"id":"kode","kind":"cc-plugin","display":"Kode CLI","tier":1,"cli":"kode"}]. Same doctrine as the rest of Taprun — the engine stays closed and mechanical; you extend it in local data.
Now pick your runtime — the extension is only needed to reuse your live logged-in Chrome:
Public pages / open APIs / CI — nothing more to install. The MCP server runs over npx; you're done. Append --no-extension for a fully in-chat Playwright runtime with its own isolated profile (no browser gesture, no click).
Logged-in sites (your bank / internal dashboard / Xiaohongshu / Zhihu) — just tell your agent "set up tap for logged-in sites" right in the chat. The tap-setup skill drives the whole bridge from the chat: it materializes the stable binary (from the engine npx already downloaded — no second download) and registers the native-messaging manifest, then opens the extension page. The single Add to Chrome click is the only step that isn't a chat action — it is the trust gate that lets Taprun reuse your existing login, and the in-flight call resumes automatically once it lands.
Claude Desktop: download tap.mcpb and double-click.
Other install paths (brew · curl · manual MCP JSON · raw binaries)
"state": "committed" plus today's trending repos at zero tokens = your install works and the claim holds.
3. Forge your own
bash
tap capture https://news.ycombinator.com hn/front --intent "front-page stories with points"
tap hn/front # replay forever, $0
Or just ask your AI agent:
code
You: What's trending on GitHub today?
Agent: Here are today's top repos — React compiler hit 734 stars...
You: Capture a tap for Douban top 250 movies
Agent: Done. Run `tap douban/top250` anytime — $0 per run.
Optional: Drive the binary from your own code (TypeScript / Python)
Skip MCP — call the tap binary from your own loop:
bash
tap capture <url> hackernews/top --intent "front-page top stories"
tap hackernews/top --args '{}'# JSON-on-stdout, exit 0 on success
tap verify hackernews/top # 3-arm verdict (live / drifted / unreachable)
The CLI emits ToolResult<T> envelopes as JSON — same shape the MCP surface returns — so any language with a subprocess library can drive it. See tap --help for the full verb list.
Have an existing Playwright / Puppeteer / Stagehand script?
Don't rewrite. Convert with one of the open-source adapters — drop your existing source in, get a Taprun-compatible .flow.json plan out:
bash
# Existing Playwright script (47M weekly npm downloads — most likely the one you have)
npm install @taprun/from-playwright @taprun/spec
node -e "import('@taprun/from-playwright').then(m => console.log(m.playwrightToTap(require('fs').readFileSync('tests/login.spec.ts','utf8'), {site:'example', name:'login'})))"# Or scaffold a new starter from scratch
npx create-tap-script github/trending https://github.com/trending
Generates a starter .flow.json envelope from <site>/<name> <url>
The format itself is documented at @taprun/spec — the public protocol surface package: TypeScript types for the v2 Plan (18-op closed union + discriminated read/write Plan union) + JSON Schema 2020-12 with $id resolvable at taprun.dev/spec/plan-v1/schema.json, bidirectionally drift-guarded against the TS types. Third-party tooling (IDE $schema autocomplete, ajv-equivalent validators in Python/Ruby/Go, governance layers, alternative runtimes, MCP hosts with plan-aware permission scoping) builds against this package without depending on the proprietary Taprun engine. Plan-v1 reference: taprun.dev/spec/plan-v1. Source for all five packages: packages/ (see packages/README.md for the workspace overview).
What Can You Do?
Read — Extract data from any website
bash
tap reddit/hot # Reddit front page
tap bilibili/trending # Bilibili trending
tap arxiv/search --keyword "LLM"# arXiv papers
Write — Operate any website
bash
tap xiaohongshu/publish --title "My Note" --images photo.jpg
tap zhihu/publish --title "My Article" --content "..."
Watch — Monitor changes
bash
tap verify github/trending # spot drift; schedule via cron / launchd
Compose — Chain like Unix pipes
bash
tap github/trending | tap filter --field stars --gt 500 | tap table
Forge — Create new automations with AI
bash
tap capture https://news.ycombinator.com hackernews/hot --intent "top stories"# API detected — compiled without AI
tap capture https://example.com mysite/home --intent "..."# BYOK Claude / GPT for the long tail
Bring your own model — works with Claude, OpenAI, DeepSeek, or any
OpenAI-compatible endpoint including local Ollama / LM Studio for
fully offline forge:
bash
tap config set ai.baseUrl http://localhost:11434/v1
tap config set ai.key ollama
tap config set ai.model llama3.1
tap capture https://arxiv.org/list/cs.AI/recent arxiv/recent --intent "recent papers"# 0 bytes leave your machine
How It Works
code
┌─ Chrome extension (your real browser sessions)
You → AI → Taprun ──────┤
capture └─ Playwright (headless, server, CI/CD)
You describe what you want (URL × natural-language intent)
AI compiles it into a .flow.json program — bare JSON, 18-op closed vocabulary, version-controlled
Taprun runs the program on either runtime — forever, at $0
Every successful compilation makes the next one faster. Need a tap for a new site? Your agent forges one on demand with capture — no catalog required.
Verified Claims
tap-skills is no longer a skills catalog — it's a claims ledger: dated, falsifiable claims about the live web, each vendoring its own deterministic plan, re-verified nightly by CI at zero LLM tokens. A claim that drifts flips to 🟡 publicly, the same night.
Verify the first claim yourself (~2 minutes, no login, no browser):
You get the exact verification the nightly CI gets — deterministic replay, same result. The 140-skill v1 catalog is preserved untouched on the v1-archive branch; pre-built catalogs only rot, so plans are forged on demand with capture instead.
bash
tap verify <site>/<name> # Snapshot equivalence — catches silent failures before your data goes stale
tap list # See everything available
tap show <site>/<name> # Print the saved tap's plan as JSON
Local-first by architecture
Zero-token replay is the headline; local-first is the guarantee underneath it. Taprun runs in your browser — the Chrome extension reuses your live login sessions, so cookies, auth tokens, and credentials never leave your machine. A structural choice, not a marketing claim:
Concern
Cloud-first browser SDKs
Taprun (local-first)
Where do logged-in cookies live?
On the cloud vendor's servers
Only in your local browser
What does the AI see?
The full session + your data
Only the page DOM during forge time
Compliance with noindex / robots.txt / TOS
Vendor signs ToS for you
Your account, your terms
Internal / intranet sites
Need VPN tunneling
Just open the page
Decommission risk
Vendor goes down → your scrapers stop
Local code keeps running
Layer
Protection
Sandbox
Programs run with zero permissions — no file, network, or system access
Static Analysis
CI blocks dangerous patterns before they reach users
Local-only
Your data, sessions, and API keys never leave your machine — architecturally
Taprun is local-first by architecture. It drives your own browser on your own machine — credentials, cookies, and page data never leave it. The engine ships no telemetry and makes no outbound network calls except the ones your own saved taps explicitly direct (op:fetch). Saved taps, secrets, and traces live under ~/.tap/ on your machine only.
