linear-webhooks-eventsClaude Skill

Linear Webhooks & Events

Overview

Set up and handle Linear webhooks for real-time event notifications.

Prerequisites

• Linear workspace admin access
• Public endpoint for webhook delivery
• Webhook signing secret configured

Available Event Types

Event Type	Description
Issue	Issue created, updated, or removed
IssueComment	Comment added or updated
Project	Project changes
Cycle	Cycle (sprint) changes
Label	Label changes
Reaction	Emoji reactions

Instructions

Step 1: Create Webhook Endpoint

// api/webhooks/linear.ts (Vercel/Next.js style)
import crypto from "crypto";
import type { NextApiRequest, NextApiResponse } from "next";

export const config = {
  api: {
    bodyParser: false, // Need raw body for signature
  },
};

async function getRawBody(req: NextApiRequest): Promise<string> {
  const chunks: Buffer[] = [];
  for await (const chunk of req) {
    chunks.push(chunk);
  }
  return Buffer.concat(chunks).toString("utf8");
}

function verifySignature(payload: string, signature: string): boolean {
  const secret = process.env.LINEAR_WEBHOOK_SECRET!;
  const hmac = crypto.createHmac("sha256", secret);
  const expectedSignature = hmac.update(payload).digest("hex");

  return crypto.timingSafeEqual(
    Buffer.from(signature),
    Buffer.from(expectedSignature)
  );
}

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  if (req.method !== "POST") {
    return res.status(405).json({ error: "Method not allowed" });
  }

  const rawBody = await getRawBody(req);
  const signature = req.headers["linear-signature"] as string;

  if (!signature || !verifySignature(rawBody, signature)) {
    return res.status(401).json({ error: "Invalid signature" });
  }

  const event = JSON.parse(rawBody);

  // Process event
  await processLinearEvent(event);

  return res.status(200).json({ received: true });
}

Step 2: Event Processing Router

// lib/webhook-handlers.ts
interface LinearWebhookPayload {
  action: "create" | "update" | "remove";
  type: string;
  data: Record<string, unknown>;
  createdAt: string;
  organizationId: string;
  webhookTimestamp: number;
  webhookId: string;
}

type EventHandler = (data: Record<string, unknown>, action: string) => Promise<void>;

const handlers: Record<string, EventHandler> = {
  Issue: handleIssueEvent,
  IssueComment: handleCommentEvent,
  Project: handleProjectEvent,
  Cycle: handleCycleEvent,
};

export async function processLinearEvent(payload: LinearWebhookPayload) {
  const handler = handlers[payload.type];

  if (!handler) {
    console.log(`No handler for event type: ${payload.type}`);
    return;
  }

  try {
    await handler(payload.data, payload.action);
  } catch (error) {
    console.error(`Error processing ${payload.type} event:`, error);
    throw error;
  }
}

async function handleIssueEvent(data: Record<string, unknown>, action: string) {
  const issue = data as {
    id: string;
    identifier: string;
    title: string;
    state: { name: string };
    priority: number;
    team: { key: string };
  };

  console.log(`Issue ${action}: ${issue.identifier} - ${issue.title}`);

  switch (action) {
    case "create":
      await onIssueCreated(issue);
      break;
    case "update":
      await onIssueUpdated(issue);
      break;
    case "remove":
      await onIssueRemoved(issue.id);
      break;
  }
}

async function handleCommentEvent(data: Record<string, unknown>, action: string) {
  const comment = data as {
    id: string;
    body: string;
    issue: { identifier: string };
    user: { name: string };
  };

  console.log(`Comment ${action} on ${comment.issue.identifier} by ${comment.user.name}`);
}

async function handleProjectEvent(data: Record<string, unknown>, action: string) {
  console.log(`Project ${action}:`, data);
}

async function handleCycleEvent(data: Record<string, unknown>, action: string) {
  console.log(`Cycle ${action}:`, data);
}

Step 3: Business Logic Handlers

// lib/linear-handlers.ts
import { sendSlackNotification } from "./slack";
import { syncToDatabase } from "./database";

async function onIssueCreated(issue: any) {
  // Sync to local database
  await syncToDatabase("issues", issue.id, issue);

  // Notify Slack for high-priority issues
  if (issue.priority <= 2) {
    await sendSlackNotification({
      channel: "#engineering-alerts",
      text: `New high-priority issue: ${issue.identifier} - ${issue.title}`,
    });
  }
}

async function onIssueUpdated(issue: any) {
  // Update local cache
  await syncToDatabase("issues", issue.id, issue);

  // Check for state changes
  if (issue.state?.name === "Done") {
    await celebrateCompletion(issue);
  }
}

async function onIssueRemoved(issueId: string) {
  await syncToDatabase("issues", issueId, null); // Soft delete
}

async function celebrateCompletion(issue: any) {
  console.log(`Issue completed: ${issue.identifier}`);
}

Step 4: Register Webhook in Linear

# Using Linear UI:
# 1. Go to Settings > API > Webhooks
# 2. Click "Create webhook"
# 3. Enter your endpoint URL
# 4. Select events to receive
# 5. Save and copy the signing secret

// Or via API
import { LinearClient } from "@linear/sdk";

async function createWebhook() {
  const client = new LinearClient({
    apiKey: process.env.LINEAR_API_KEY!,
  });

  const result = await client.createWebhook({
    url: "https://your-domain.com/api/webhooks/linear",
    label: "My Integration Webhook",
    teamId: "your-team-id", // Optional: limit to specific team
    resourceTypes: ["Issue", "IssueComment", "Project"],
  });

  if (result.success) {
    const webhook = await result.webhook;
    console.log("Webhook created:", webhook?.id);
    console.log("Secret (save this!):", webhook?.secret);
  }
}

Step 5: Local Development with ngrok

# Start your local server
npm run dev  # Runs on localhost:3000

# In another terminal, start ngrok
ngrok http 3000

# Copy the https URL and add to Linear webhook settings
# Example: https://abc123.ngrok.io/api/webhooks/linear

Step 6: Idempotent Event Processing

// lib/idempotency.ts
import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL);

export async function processIdempotent(
  webhookId: string,
  processor: () => Promise<void>
): Promise<boolean> {
  const key = `webhook:${webhookId}`;

  // Check if already processed
  const exists = await redis.exists(key);
  if (exists) {
    console.log(`Webhook ${webhookId} already processed, skipping`);
    return false;
  }

  // Mark as processing
  await redis.setex(key, 86400, "processing"); // 24 hour TTL

  try {
    await processor();
    await redis.setex(key, 86400, "completed");
    return true;
  } catch (error) {
    await redis.del(key); // Allow retry
    throw error;
  }
}

// Usage in webhook handler
await processIdempotent(payload.webhookId, async () => {
  await processLinearEvent(payload);
});

Error Handling

Error	Cause	Solution
Invalid signature	Wrong secret or tampering	Verify webhook secret
Timeout	Processing too slow	Use async queue
Duplicate events	Webhook retry	Implement idempotency
Missing data	Partial event	Handle gracefully

Resources

• Linear Webhooks Documentation
• Webhook Events Reference
• ngrok Documentation

Next Steps

Optimize performance with linear-performance-tuning.