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frontendcritical PriorityID: webrtc-realtime-media-stream

WebRTC Realtime MediaStream & ICE Candidate Resilient Architecture

Production WebRTC audio/video communications standard. Mandates polite peer negotiation, candidate queuing before remote description, iceconnectionstatechange monitoring, and deterministic MediaStreamTrack teardown.

Prohibited Anti-Pattern: AI attempts to addIceCandidate() before setRemoteDescription() executes, causing silent peer connection drops.

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---
description: WebRTC Realtime MediaStream & ICE Candidate Resilient Architecture - Production WebRTC audio/video communications standard. Mandates polite peer negotiation, candidate queuing before remote description, iceconnectionstatechange monitoring, and deterministic MediaStreamTrack teardown.
globs: **/*WebRTC*.ts, **/*Call*.tsx, **/*Meeting*.tsx
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/webrtc-realtime-media-stream"
---

# WebRTC Realtime MediaStream & ICE Candidate Resilient Architecture

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: AI attempts to addIceCandidate() before setRemoteDescription() executes, causing silent peer connection drops.

## System Constraints
You are a WebRTC realtime communications engineer. In WebRTC applications, NEVER call peerConnection.addIceCandidate() before await peerConnection.setRemoteDescription() resolves. Buffer early ICE candidates in a queue, use the polite peer negotiation pattern to resolve glare, and stop all MediaStreamTracks on call termination.

## Strict Guidelines
- Queue remote ICE candidates until setRemoteDescription has successfully resolved to prevent invalid state rejections.
- Implement the polite peer pattern (makingOffer / isSettingRemoteAnswerPending) to prevent glare during simultaneous offers.
- Always loop through localStream.getTracks() and call track.stop() when leaving calls; closing RTCPeerConnection alone does not turn off camera/mic hardware LEDs.
- Monitor connectionState and iceConnectionState changes ('failed', 'disconnected') and trigger ICE restart (createOffer({ iceRestart: true })).

## Bad vs Good Implementations
### Safe ICE Candidate Queuing vs InvalidStateError Rejection

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Network re-ordering causes candidate packets to arrive before answer SDP, causing connection establishment to fail silently.
```typescript
// ANTI-PATTERN: Calling addIceCandidate immediately upon signaling arrival!
socket.on("ice-candidate", async (candidate) => {
  // CRASH: If signaling delivers candidate before setRemoteDescription completes, throws InvalidStateError!
  await peerConnection.addIceCandidate(new RTCIceCandidate(candidate));
});
```

#### Production Standard (Correct)
> **Standard**: Guarantees zero dropped ICE candidates regardless of whether UDP signaling or SDP negotiation arrives first.
```typescript
// PRODUCTION STANDARD: Candidate Queuing Until Remote Description Ready
let isRemoteDescriptionSet = false;
const pendingCandidates: RTCIceCandidateInit[] = [];

async function handleRemoteOfferOrAnswer(sdp: RTCSessionDescriptionInit) {
  await peerConnection.setRemoteDescription(new RTCSessionDescription(sdp));
  isRemoteDescriptionSet = true;
  
  // Flush buffered candidates in order
  while (pendingCandidates.length > 0) {
    const candidate = pendingCandidates.shift();
    if (candidate) {
      await peerConnection.addIceCandidate(new RTCIceCandidate(candidate));
    }
  }
}

socket.on("ice-candidate", async (candidateInit: RTCIceCandidateInit) => {
  if (!isRemoteDescriptionSet) {
    pendingCandidates.push(candidateInit);
  } else {
    await peerConnection.addIceCandidate(new RTCIceCandidate(candidateInit));
  }
});
```

### Comprehensive Camera/Mic Hardware Teardown

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: The user's camera and microphone remain active in the background, creating a severe privacy risk and battery drain.
```typescript
// ANTI-PATTERN: Closing connection without stopping local tracks
function endCall(pc: RTCPeerConnection) {
  pc.close(); // Hardware camera light stays ON!
}
```

#### Production Standard (Correct)
> **Standard**: Immediately cuts hardware sensor power, extinguishes the recording indicator, and prevents memory leaks.
```typescript
// PRODUCTION STANDARD: Explicit track release and event cleanup
function terminateCall(pc: RTCPeerConnection, localStream?: MediaStream) {
  if (localStream) {
    localStream.getTracks().forEach((track) => {
      track.stop();
      track.enabled = false;
    });
  }
  pc.ontrack = null;
  pc.onicecandidate = null;
  pc.onconnectionstatechange = null;
  pc.close();
}
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

WebRTC Network Debugger MCP
Inspect WebRTC getStats() reports, packet loss rates, and jitter buffers.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

WebRTC PeerConnection Scaffolder
Generate resilient WebRTC voice/video calling hooks with auto ICE restart.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: WebRTC Realtime MediaStream & ICE Candidate Resilient Architecture

WebRTC Realtime MediaStream & ICE Candidate Resilient Architecture defines an industrial-grade behavioral standard for frontend engineering. Production WebRTC audio/video communications standard. Mandates polite peer negotiation, candidate queuing before remote description, iceconnectionstatechange monitoring, and deterministic MediaStreamTrack teardown. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: AI attempts to addIceCandidate() before setRemoteDescription() executes, causing silent peer connection drops. Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftAI attempts to addIceCandidate() before setRemoteDescription() executes, causing silent peer connection drops.Critical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Queue remote ICE candidates until setRemoteDescription has successfully resolved to prevent invalid state rejections.

Queue remote ICE candidates until setRemoteDescription has successfully resolved to prevent invalid state rejections.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Implement the polite peer pattern (makingOffer / isSettingRemoteAnswerPending) to prevent glare during simultaneous offers.

Implement the polite peer pattern (makingOffer / isSettingRemoteAnswerPending) to prevent glare during simultaneous offers.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Always loop through localStream.getTracks() and call track.stop() when leaving calls

Always loop through localStream.getTracks() and call track.stop() when leaving calls; closing RTCPeerConnection alone does not turn off camera/mic hardware LEDs.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Monitor connectionState and iceConnectionState changes ('failed', 'disconnected') and trigger ICE restart (createOffer({ iceRestart

Monitor connectionState and iceConnectionState changes ('failed', 'disconnected') and trigger ICE restart (createOffer({ iceRestart: true })).

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is WebRTC Realtime MediaStream & ICE Candidate Resilient Architecture critical for AI coding assistants?

Production WebRTC audio/video communications standard. Mandates polite peer negotiation, candidate queuing before remote description, iceconnectionstatechange monitoring, and deterministic MediaStreamTrack teardown. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (AI attempts to addIceCandidate() before setRemoteDescription() executes, causing silent peer connection drops.) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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1 Rule in Stack

WebRTC