Blog

Troubleshooting

Structured Outputs 400 Errors: Fix strict JSON Schema Before Retrying

Check endpoint wrappers, required and nullable fields, nested object definitions and common strict JSON Schema errors locally before retrying an API request.

2026-10-13 5

LLM API Editorial Team

Troubleshooting

Tool Call ID Errors: Match Results Across OpenAI and Claude APIs

Trace mismatched tool results across Chat Completions, Responses and Anthropic Messages with synthetic JSON, offline checks and history-trimming diagnostics.

2026-10-13 5

LLM API Editorial Team

Top-Up Support

ChatGPT Top-Up Session Expired? Continue Your Existing Order

Resume a paid ChatGPT top-up through My Orders, handle requested actions, and learn when to contact support—and why passwords and sessions should not be emailed.

2026-10-08 3

LLM API Editorial Team

API Guides

Claude Haiku 5.5 API Guide: Model ID, Setup and Billing Checks

Connect Claude Haiku 5.5 with the exact model ID, choose the correct client URL, and check subscription versus API billing before your first request.

2026-10-08 4

LLM API Editorial Team

API Guides

GPT-6 Astra, Sol, and Luna: Choosing a Model and Using the Responses API

Choose among GPT-6 Astra, Sol, and Luna, then adapt an SDK text or streaming integration without assuming every response has the same output shape.

2026-09-26 3

LLM API Editorial Team

Troubleshooting

API Returns 200 but No Text? A Streaming Troubleshooting Guide

Diagnose empty API answers by checking response events, completion and client parsing. Includes a small Python regression example and a safe support checklist.

2026-09-20 3

LLM API Editorial Team

Engineering

429 Retry-After: Stopping a Rate-Limit Retry Storm

A Mythos V3 engineering case study on adding correct 429 Retry-After headers, separating quota gates, and reducing five-minute application 429s from 1,050 to 7.

2026-08-21 8

Yazhou Hu

Engineering

Node.js Event Loop Blocking: Fixing an O(n²) Prefix-Hash Hot Path

A Mythos V3 engineering note on diagnosing Node.js event loop blocking, replacing quadratic prefix hashing with one linear pass, and proving byte-for-byte equivalence.

2026-08-21 9

Yazhou Hu

Guide

Claude Opus 5 to Opus 5.5: Model ID, Claude Code Setup, and API Migration

Move from Claude Opus 5 to Opus 5.5 with the exact model ID, official breaking changes, copyable Claude Code setup, and llmapi.pro availability checks.

2026-08-14 6

LLM API Editorial Team

Comparison

Claude Opus 5 vs Fable 5: Which to Use in 2026

Claude Opus 5 vs Fable 5: same 1M context and 128K output, but Fable costs 2x at list. A decision table for picking the right Claude model in 2026.

2026-08-11 7

Yazhou Hu

Guide

Claude API Pay-As-You-Go: Costs, Billing and Setup

Understand metered Claude API costs, compare billing options, check model access, and connect the right endpoint and key before making your first request.

2026-06-30 6

LLM API Editorial Team

Guide

DeepSeek and Qwen in Claude Code: Setup and Compatibility Checks

Check the base URL, model ID, account access and billing before using DeepSeek or Qwen in Claude Code. Follow a small-task test and troubleshoot the first error.

2026-06-30 4

LLM API Editorial Team

Guide

Anthropic API Rate Limits & Usage Tiers Explained (2026)

How Claude API rate limits work in 2026: RPM, ITPM, and OTPM; the four spend-based usage tiers and how you advance; why cached reads don't count; and how to handle 429s.

2026-06-29 8

Yazhou Hu

Tutorial

ANTHROPIC_BASE_URL: Claude Code Setup and /v1 Fixes

Set ANTHROPIC_BASE_URL correctly for Claude Code on Windows, macOS and Linux. Compare base URLs with request endpoints and diagnose 404, authentication and quota errors.

2026-06-28 5

LLM API Editorial Team

Comparison

Cheap Claude API Access in 2026: The Legit Ways to Pay Less

The real ways to get cheaper Claude API access in 2026 — right-sizing the model, prompt caching, batch, subscription vs pay-as-you-go, and relays — with an honest look at the trade-offs of each.

2026-06-27 8

Yazhou Hu

Guide

Claude Code Token Cost: Why It Climbs and How to Cut It

Claude Code token cost grows super-linearly because context is re-sent every turn. Here's why long sessions get expensive and the concrete levers to cut spend.

2026-06-23 7

Yazhou Hu

Guide

What Is a Claude-Compatible API Relay? A Plain Explainer

A claude compatible api relay speaks the same endpoints Claude Code already uses. Here's how relays work, why your CLI can't tell, and whether to trust one.

2026-06-16 7

Yazhou Hu

Comparison

Claude Sonnet 4.6 vs Opus 4.8 in Claude Code: Which to Run

Claude Sonnet 4.6 vs Opus 4.8 for Claude Code: Sonnet is cheaper and faster for daily coding; Opus 4.8 wins hard refactors and architecture. Task-by-task picks, token cost, and the in-session /model switch.

2026-06-09 7

Yazhou Hu

Comparison

Claude Code vs Codex CLI in 2026: An Honest Head-to-Head

Claude Code vs Codex CLI compared on workflow, protocol, and config — run both agentic coding CLIs off one sk-relay key because we expose both protocols.

2026-06-06 8

Yazhou Hu

Guide

Claude Opus 4.8 in Claude Code: Setup, the 1M Context Window, and What It Costs

Run Claude Opus 4.8 in Claude Code: exact model IDs, the ANTHROPIC_BASE_URL setup, whether the 1M-token context window is still available, and how to keep the bill down.

2026-06-06 7

Yazhou Hu