Output Error Http Client

---
name: output-error-http-client
description: Fix HTTP client misuse in Output SDK steps. Use when seeing untraced requests, missing error details, axios-related errors, HTTP calls aren't being properly logged and retried, or paid API costs are missing from cost reports.
allowed-tools: [Bash, Read]
---

# Fix HTTP Client Misuse

## Overview

This skill helps diagnose and fix issues caused by using axios, fetch, or other HTTP clients directly instead of Output SDK's `createKyClient` from `@outputai/http`. The Output SDK client provides tracing, automatic retries, and better error handling.

## When to Use This Skill

You're seeing:
- Untraced HTTP requests (not appearing in workflow traces)
- Missing error details for failed requests
- axios-related errors or import issues
- Retries not working for HTTP failures
- Inconsistent timeout behavior

## Root Cause

Using axios, fetch, or other HTTP clients directly bypasses Output SDK's:
- **Request/response tracing**: Calls aren't logged in workflow traces
- **Automatic retries**: Failed requests aren't retried
- **Error standardization**: Error formats may be inconsistent
- **Timeout handling**: Timeouts may not integrate with step timeouts

## Symptoms

### Using axios Directly

```typescript
// WRONG: Using axios
import axios from 'axios';

export const fetchData = step( {
  name: 'fetchData',
  fn: async input => {
    const response = await axios.get( 'https://api.example.com/data' );
    return response.data;
  }
} );
```

### Using fetch Directly

```typescript
// WRONG: Using fetch
export const fetchData = step( {
  name: 'fetchData',
  fn: async input => {
    const response = await fetch( 'https://api.example.com/data' );
    return response.json();
  }
} );
```

## Solution

Use `createKyClient` from `@outputai/http`:

### Basic Usage

```typescript
import { z, step } from '@outputai/core';
import { createKyClient } from '@outputai/http';

export const fetchData = step( {
  name: 'fetchData',
  inputSchema: z.object( {
    endpoint: z.string()
  } ),
  outputSchema: z.object( {
    data: z.unknown()
  } ),
  fn: async input => {
    const client = createKyClient( {
      prefix: 'https://api.example.com'
    } );

    const data = await client.get( input.endpoint ).json();
    return { data };
  }
} );
```

### With Full Configuration

```typescript
import { createKyClient } from '@outputai/http';

const client = createKyClient( {
  prefix: 'https://api.example.com',
  timeout: 30000,  // 30 second timeout
  retry: {
    limit: 3,      // Retry up to 3 times
    methods: [ 'GET', 'POST' ],  // Which methods to retry
    statusCodes: [ 408, 500, 502, 503, 504 ]  // Which status codes trigger retry
  },
  headers: {
    'Authorization': `Bearer ${apiKey}`,
    'Content-Type': 'application/json'
  }
} );
```

## HTTP Methods

### GET Request

```typescript
const data = await client.get( 'users/123' ).json();
```

### POST Request

```typescript
const result = await client.post( 'users', {
  json: {
    name: 'John',
    email: 'john@example.com'
  }
} ).json();
```

### PUT Request

```typescript
const updated = await client.put( 'users/123', {
  json: {
    name: 'John Updated'
  }
} ).json();
```

### DELETE Request

```typescript
await client.delete( 'users/123' );
```

### With Query Parameters

```typescript
const data = await client.get( 'search', {
  searchParams: {
    q: 'query',
    limit: 10
  }
} ).json();
```

### Metadata-Only Responses

When code only reads metadata from a non-`HEAD` response, such as `response.url`, `response.status`, or headers, cancel the
unused body. Reading a body with `.json()`, `.text()`, etc. already consumes it.

```typescript
const response = await client.get( url );

try {
  return response.url;
} finally {
  await response.body?.cancel();
}
```

## Complete Migration Example

### Before (Wrong - using axios)

```typescript
import axios from 'axios';
import { step } from '@outputai/core';

export const createUser = step( {
  name: 'createUser',
  fn: async input => {
    try {
      const response = await axios.post(
        'https://api.example.com/users',
        { name: input.name, email: input.email },
        {
          headers: { 'Authorization': `Bearer ${process.env.API_KEY}` },
          timeout: 30000
        }
      );
      return response.data;
    } catch ( error ) {
      if ( axios.isAxiosError( error ) ) {
        throw new Error( `API Error: ${error.response?.data?.message}` );
      }
      throw error;
    }
  }
} );
```

### After (Correct - using createKyClient)

```typescript
import { z, step } from '@outputai/core';
import { createKyClient } from '@outputai/http';
import { credentials } from '@outputai/core/credentials';

export const createUser = step( {
  name: 'createUser',
  inputSchema: z.object( {
    name: z.string(),
    email: z.string().email()
  } ),
  outputSchema: z.object( {
    id: z.string(),
    name: z.string(),
    email: z.string()
  } ),
  fn: async input => {
    const client = createKyClient( {
      prefix: 'https://api.example.com',
      timeout: 30000,
      retry: { limit: 3 },
      headers: {
        'Authorization': `Bearer ${credentials.require( 'service.api_key' )}`
      }
    } );

    const user = await client.post( 'users', {
      json: {
        name: input.name,
        email: input.email
      }
    } ).json();

    return user;
  }
} );
```

## Error Handling

The Ky client provides structured error handling:

```typescript
import { createKyClient, ky } from '@outputai/http';

export const fetchData = step( {
  name: 'fetchData',
  fn: async input => {
    const client = createKyClient( { prefix: 'https://api.example.com' } );

    try {
      return await client.get( 'data' ).json();
    } catch ( error ) {
      if ( error instanceof ky.HTTPError ) {
        // Access response details
        const status = error.response.status;
        const body = await error.response.json();
        throw new Error( `API returned ${status}: ${body.message}` );
      }
      throw error;
    }
  }
} );
```

## Missing Cost Tracking for Paid APIs

### Symptom

A client wraps a paid third-party API, but its calls never show up in the `API Costs` section of `npx output workflow cost` — they're traced (so tracing works), but their cost is always $0 or absent from the report.

### Root Cause

`npx output workflow cost` only knows about HTTP spend that was explicitly attached with `addRequestCost` from `@outputai/http`. Tracing a request is automatic; costing it is not — a client that never calls `addRequestCost` will trace correctly and cost nothing, which is expected for free/internal services but a bug for paid ones.

### Solution

Attach cost inside an `afterResponse` hook on the client so every call is costed automatically, rather than at each call site. See `output-dev-http-client-create` (section "Attaching Request Cost (Paid APIs)") for the metered-response and flat-rate patterns, and `output-dev-cost-hooks` for forwarding those costs to an external observability system.

```typescript
// WRONG: paid API, no cost tracking
const client = createKyClient( { prefix: 'https://api.service.com' } );

// CORRECT: cost attached automatically for every call
import { addRequestCost, createKyClient } from '@outputai/http';

const client = createKyClient( {
  prefix: 'https://api.service.com',
  hooks: {
    afterResponse: [
      ( _request, _options, response ) => {
        if ( !response.ok ) return;
        addRequestCost( response, 0.005 );
      }
    ]
  }
} );
```

## Finding axios/fetch Usage

Search your codebase:

```bash
# Find axios imports
grep -rn "from 'axios'\|from \"axios\"" src/

# Find fetch calls
grep -rn "await fetch(" src/

# Find other HTTP libraries
grep -rn "got\|node-fetch\|request\|superagent" src/
```

## Benefits of createKyClient

1. **Tracing**: Requests appear in workflow traces with timing
2. **Automatic Retries**: Configurable retry logic for transient failures
3. **Consistent Errors**: Standardized error format across all requests
4. **Timeout Integration**: Works with step and workflow timeouts
5. **Type Safety**: Full TypeScript support

## Configuration Options

| Option | Description | Default |
|--------|-------------|---------|
| `prefix` | Base URL for all requests | (required) |
| `timeout` | Request timeout in ms | 10000 |
| `retry.limit` | Max retry attempts | 2 |
| `retry.methods` | HTTP methods to retry | ['GET', 'PUT', 'HEAD', 'DELETE', 'OPTIONS', 'TRACE'] |
| `retry.statusCodes` | Status codes to retry | [408, 413, 429, 500, 502, 503, 504] |
| `headers` | Default headers | {} |

## Verification

After migrating to createKyClient:

1. **Run the workflow**: `npx output workflow run <name> --input '<input>'`
2. **Check the trace**: `npx output workflow debug <id> --json`
3. **Verify tracing**: HTTP requests should appear in the step trace
4. **Test retries**: Simulate failures to verify retry behavior

## Related Issues

- For I/O in workflow functions, see `output-error-direct-io`
- For connection issues, see `output-services-check`
- For encrypted secrets management, see `output-dev-credentials`
- For attaching and forwarding request cost, see `output-dev-http-client-create` and `output-dev-cost-hooks`