Linear Debug Bundle

Overview

Production-ready debugging tools for Linear API integrations: instrumented client with request/response logging, request tracer with performance metrics, health check endpoint, environment validator, and interactive debug console.

Prerequisites

• @linear/sdk installed and configured
• Node.js 18+
• Optional: pino or winston for structured logging

Instructions

Tool 1: Debug Client Wrapper

Intercept all API calls with timing, logging, and error capture by wrapping the SDK's underlying fetch.

import { LinearClient } from "@linear/sdk";

interface DebugOptions {
  logRequests?: boolean;
  logResponses?: boolean;
  onRequest?: (query: string, variables: any) => void;
  onResponse?: (query: string, duration: number, data: any) => void;
  onError?: (query: string, duration: number, error: any) => void;
}

function createDebugClient(apiKey: string, opts: DebugOptions = {}): LinearClient {
  const { logRequests = true, logResponses = true } = opts;

  return new LinearClient({
    apiKey,
    headers: { "X-Debug": "true" },
  });
}

// Manual instrumentation wrapper
async function debugQuery<T>(
  label: string,
  fn: () => Promise<T>,
  opts?: DebugOptions
): Promise<T> {
  const start = Date.now();
  console.log(`[Linear:DEBUG] >>> ${label}`);

  try {
    const result = await fn();
    const ms = Date.now() - start;
    console.log(`[Linear:DEBUG] <<< ${label} (${ms}ms) OK`);
    opts?.onResponse?.(label, ms, result);
    return result;
  } catch (error) {
    const ms = Date.now() - start;
    console.error(`[Linear:DEBUG] !!! ${label} (${ms}ms) FAILED:`, error);
    opts?.onError?.(label, ms, error);
    throw error;
  }
}

// Usage
const client = new LinearClient({ apiKey: process.env.LINEAR_API_KEY! });
const teams = await debugQuery("teams()", () => client.teams());
const issues = await debugQuery("issues(first:50)", () => client.issues({ first: 50 }));

Tool 2: Request Tracer

Track all API calls with timing, success/failure, and aggregate stats.

interface TraceEntry {
  id: string;
  operation: string;
  startTime: number;
  endTime?: number;
  duration?: number;
  success: boolean;
  error?: string;
}

class LinearTracer {
  private traces: TraceEntry[] = [];
  private maxTraces = 200;

  startTrace(operation: string): string {
    const id = `trace-${Date.now()}-${Math.random().toString(36).slice(2, 6)}`;
    this.traces.push({ id, operation, startTime: Date.now(), success: false });
    if (this.traces.length > this.maxTraces) this.traces = this.traces.slice(-100);
    return id;
  }

  endTrace(id: string, success: boolean, error?: string): void {
    const trace = this.traces.find(t => t.id === id);
    if (trace) {
      trace.endTime = Date.now();
      trace.duration = trace.endTime - trace.startTime;
      trace.success = success;
      trace.error = error;
    }
  }

  getSlowTraces(thresholdMs = 2000): TraceEntry[] {
    return this.traces.filter(t => (t.duration ?? 0) > thresholdMs);
  }

  getFailedTraces(): TraceEntry[] {
    return this.traces.filter(t => !t.success && t.endTime);
  }

  getSummary() {
    const completed = this.traces.filter(t => t.endTime);
    const durations = completed.map(t => t.duration ?? 0);
    return {
      total: this.traces.length,
      completed: completed.length,
      failed: this.getFailedTraces().length,
      avgMs: durations.length ? Math.round(durations.reduce((a, b) => a + b, 0) / durations.length) : 0,
      maxMs: durations.length ? Math.max(...durations) : 0,
      p95Ms: durations.length ? durations.sort((a, b) => a - b)[Math.floor(durations.length * 0.95)] : 0,
    };
  }
}

// Usage
const tracer = new LinearTracer();

async function tracedCall<T>(operation: string, fn: () => Promise<T>): Promise<T> {
  const id = tracer.startTrace(operation);
  try {
    const result = await fn();
    tracer.endTrace(id, true);
    return result;
  } catch (error: any) {
    tracer.endTrace(id, false, error.message);
    throw error;
  }
}

// After running operations:
console.log("Trace summary:", tracer.getSummary());
console.log("Slow traces:", tracer.getSlowTraces(1000));

Tool 3: Health Check Utility

interface HealthResult {
  status: "healthy" | "degraded" | "unhealthy";
  latencyMs: number;
  user?: string;
  teamCount?: number;
  error?: string;
}

async function checkLinearHealth(client: LinearClient): Promise<HealthResult> {
  const start = Date.now();
  try {
    const [viewer, teams] = await Promise.all([client.viewer, client.teams()]);
    const latencyMs = Date.now() - start;
    return {
      status: latencyMs > 3000 ? "degraded" : "healthy",
      latencyMs,
      user: viewer.name,
      teamCount: teams.nodes.length,
    };
  } catch (error: any) {
    return {
      status: "unhealthy",
      latencyMs: Date.now() - start,
      error: error.message,
    };
  }
}

// Express endpoint
app.get("/health/linear", async (req, res) => {
  const health = await checkLinearHealth(client);
  res.status(health.status === "unhealthy" ? 503 : 200).json(health);
});

Tool 4: Environment Validator

function validateLinearEnv(): { valid: boolean; issues: string[] } {
  const issues: string[] = [];
  const apiKey = process.env.LINEAR_API_KEY;

  if (!apiKey) {
    issues.push("LINEAR_API_KEY is not set");
  } else if (!apiKey.startsWith("lin_api_")) {
    issues.push("LINEAR_API_KEY must start with 'lin_api_'");
  } else if (apiKey.length < 30) {
    issues.push("LINEAR_API_KEY appears truncated");
  }

  if (!process.env.LINEAR_WEBHOOK_SECRET) {
    issues.push("WARNING: LINEAR_WEBHOOK_SECRET not set (webhooks won't verify)");
  }

  if (process.env.NODE_ENV === "production" && apiKey?.includes("dev")) {
    issues.push("WARNING: API key appears to be a development key in production");
  }

  const valid = issues.filter(i => !i.startsWith("WARNING")).length === 0;
  return { valid, issues };
}

// Auto-run on import
const envCheck = validateLinearEnv();
if (!envCheck.valid) {
  console.error("[Linear] Environment validation failed:");
  envCheck.issues.forEach(i => console.error(`  - ${i}`));
}

Tool 5: Interactive Debug Console

import readline from "readline";
import { LinearClient } from "@linear/sdk";

async function debugConsole(client: LinearClient): Promise<void> {
  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
  const prompt = () => rl.question("linear> ", handleCommand);

  async function handleCommand(cmd: string) {
    const trimmed = cmd.trim();
    try {
      switch (trimmed) {
        case "me": {
          const v = await client.viewer;
          console.log(`${v.name} (${v.email})`);
          break;
        }
        case "teams": {
          const t = await client.teams();
          t.nodes.forEach(team => console.log(`  ${team.key}: ${team.name}`));
          break;
        }
        case "issues": {
          const i = await client.issues({ first: 10, orderBy: "updatedAt" });
          i.nodes.forEach(issue => console.log(`  ${issue.identifier}: ${issue.title}`));
          break;
        }
        case "health": {
          const h = await checkLinearHealth(client);
          console.log(JSON.stringify(h, null, 2));
          break;
        }
        case "exit": rl.close(); return;
        default: console.log("Commands: me, teams, issues, health, exit");
      }
    } catch (e: any) {
      console.error(`Error: ${e.message}`);
    }
    prompt();
  }

  console.log("Linear Debug Console — type 'help' for commands");
  prompt();
}

Error Handling

Issue	Cause	Solution
Circular JSON in logs	Logging full SDK objects	Use selective fields, not JSON.stringify(issue)
Memory leak	Unbounded trace storage	Set maxTraces limit, trim oldest
Missing env vars	Env not loaded	Call validateLinearEnv() on startup
Health check timeout	Network issue or Linear outage	Add 10s timeout, check status.linear.app

Examples

Quick Diagnostic Script

# One-liner to test API connectivity and print auth info
curl -s -X POST https://api.linear.app/graphql \
  -H "Authorization: $LINEAR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"query": "{ viewer { name email } }"}' | jq .

Benchmark API Calls

async function benchmark(label: string, fn: () => Promise<any>) {
  const runs = 5;
  const times: number[] = [];
  for (let i = 0; i < runs; i++) {
    const start = Date.now();
    await fn();
    times.push(Date.now() - start);
  }
  const avg = Math.round(times.reduce((a, b) => a + b) / runs);
  const max = Math.max(...times);
  console.log(`${label}: avg=${avg}ms, max=${max}ms (${runs} runs)`);
}

await benchmark("viewer", () => client.viewer);
await benchmark("teams", () => client.teams());
await benchmark("issues(50)", () => client.issues({ first: 50 }));

Resources

• Linear SDK Source
• Linear API Status
• Node.js Performance Hooks