vibe_preview_start

Start a vibe-preview session: headless Chrome captures the dev server URL at adaptive FPS. The mobile app + web dashboard see the same SSE stream you do. Returns the session metadata.

SERVERYaver SOURCEyaver-cli

High RISK CLASS

Category Execute

Parameters 42 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-kivanccakmak-yaver/vibe-preview-start.md

WHAT IT DOES

What vibe_preview_start does on Yaver

AI agents invoke vibe_preview_start to trigger actions in Yaver. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.

Parameter	Type	Required	Description
`mode`	string	—	Capture cadence; default live
`profile`	string	—	Optional profile override: live-direct \| live-relay-wifi \| live-relay-cell \| change-only \| summary-only
`project`	string	Yes	Project name (used as session key)
`target_url`	string	Yes	Dev server URL to capture (e.g. http://127.0.0.1:3000)

Parameters from the server's own tool schema.

RISK

Why vibe_preview_start is rated High

Starting a headless browser instance and streaming its output is execution of an external process. The effects are not data-read-only (Read) nor simple creation (Write); they involve triggering and controlling a browser session whose behavior and downstream consequences depend on the dev server state.

From the tool's definition 'headless Chrome captures the dev server URL' — spawns a browser process; 'SSE stream' — manages long-lived external I/O. Side effects depend on what runs on the target dev server and what client(s) consume the stream.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs vibe_preview_start safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Yaver, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For vibe_preview_start, this is the rule to start with:

vibe_preview_start Rate-limited

vibe_preview_start stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "vibe_preview_start": {
      "limits": [
        {
          "counter": "vibe_preview_start_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Yaver, apply this rule, and every vibe_preview_start call is checked against it from then on.

FAQ

Questions about vibe_preview_start

What does the vibe_preview_start tool do? +

Start a vibe-preview session: headless Chrome captures the dev server URL at adaptive FPS. The mobile app + web dashboard see the same SSE stream you do. Returns the session metadata. It is categorised as a Execute tool in the Yaver MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

What parameters does vibe_preview_start accept? +

vibe_preview_start accepts 4 parameters: mode, profile, project, target_url. Required: project, target_url. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on vibe_preview_start? +

Register the Yaver MCP server in PolicyLayer and add a rule for vibe_preview_start: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Yaver. Nothing to install.

What risk level is vibe_preview_start? +

vibe_preview_start is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit vibe_preview_start? +

Yes. Add a rate_limit block to the vibe_preview_start rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block vibe_preview_start completely? +

Set action: deny in the PolicyLayer policy for vibe_preview_start. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides vibe_preview_start? +

vibe_preview_start is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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