Claude Agent Coding Guide

Claude coding agents beyond Claude Code — Cline, OpenCode, Qwen Code and the Claude Agent SDK

Recipes for running Claude Opus 5.5, Opus 5, Sonnet 5 and Fable 5.1 inside open-source coding agents with one API key, and a small test-fixing agent built on the Claude Agent SDK. Every recipe points at the same Anthropic-compatible endpoint, ArgoLink, where these models cost 60% less than Anthropic's list price.

Configuration keys checked 2026-10-07 against docs.cline.bot, opencode.ai/docs, the Qwen Code docs and code.claude.com, and against each tool's source where the docs were silent. Unofficial; not affiliated with Anthropic, Cline, Anomaly or Alibaba.

The setting that breaks most setups: root origin or /v1

Every agent asks for a "base URL", and the right value depends on the HTTP library inside the agent, not on the endpoint:

The wrong value fails in a recognizable way: an AI SDK client without /v1 gets 405 Method Not Allowed from /messages, and an Anthropic SDK client with /v1 gets 404 from /v1/v1/messages.

Cline

VS Code or JetBrains

1. Open Cline's settings (⚙) and choose Anthropic as the API Provider.
2. Paste your key into Anthropic API Key.
3. Tick Use custom base URL and enter https://argolink.io/v1.
4. Pick claude-opus-5-5, claude-opus-5, claude-sonnet-5 or claude-fable-5-1 from the model list.

Cline can keep a different model for Plan and for Act mode: enable Use different models for Plan and Act and pick, for example, Opus 5.5 to plan and Sonnet 5 to edit. Switching modes then switches models.

CLI (configs/cline-cli.sh)

The key and provider are stored in ~/.cline/data/settings/providers.json and shared by the IDE extensions, the CLI and the SDK. --thinking low|medium|high|xhigh sets the effort for a run. For Claude 4.6 and 5.x model IDs Cline sends…