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1. Overview

OpenCode is an open-source AI coding assistant supporting 75+ models and local deployment. With LeapX API, you can use mainstream and latest models (e.g. GPT, Claude, Gemini) in OpenCode and configure custom providers and models. Download: https://opencode.ai/

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2. Quick setup (LeapX API)

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2.1 Get an API key

Create and copy your API key from the LeapX API console.

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2.2 Configure a custom provider in OpenCode

  1. Open OpenCode and go to Server / Provider settings.
  2. Add a custom provider (Configure an OpenAI compatible provider).
  3. Fill in:
    • Provider ID: e.g. leapx (lowercase, digits, hyphens or underscores)
    • Display name: e.g. LeapX API
    • Base URL: https://api.leapx-hub.com/v1 (must end with /v1)
    • API key: paste your LeapX API key
  4. Under Models, add the models you need (e.g. gpt-4o, claude-sonnet-4-20250514). Model IDs must match the LeapX model list.
  5. After saving, use providerID/modelID in the model selector (e.g. leapx/gpt-4o).
OpenCode custom provider setup Configuration reference (matching the screenshots above):
  • Base URL: https://api.leapx-hub.com/v1
  • API key: from LeapX console (e.g. sk-xxxxxxxxxxxxx)
  • Models: choose from LeapX model list and enter the model ID
OpenCode provider and API config OpenCode model config

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2.3 Switching models

In the chat or settings, select the configured provider and model (e.g. leapx/gpt-4o) to switch. OpenCode switch model
  • For self-hosted or backup LeapX, set Base URL to that address, e.g. http://your-server:3003/v1.
  • Default model can be set in project or global opencode.json with "model": "leapx/modelID".

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3. Some models require the Responses API (important)

Some models use a different API than standard Chat Completions and require the Responses API. If you see an error like this when using such a model in OpenCode: Some Azure / OpenAI models only support the Responses API and do not support the traditional Chat Completions endpoint. Example error:
The chatCompletion operation does not work with the specified model, gpt-5.1-codex. Please choose different model and try again.
The screenshot below shows how this error appears in the UI: Error when using gpt-5.1-codex with Chat Completions This means the request was sent as Chat Completions while the model only exposes Responses API on the server. You need to configure OpenCode to use the correct API.

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3.1 Models that require the Responses API (typical)

For the full and up-to-date list, see Azure / vendor documentation, e.g.: You can make OpenCode use the Responses API for a given model by adding the apiCompatibility parameter for that model in the config file. No code changes are required. 1. Locate the config file
  • Windows: C:\Users\<username>\.config\opencode\opencode.jsonc
  • macOS / Linux: ~/.config/opencode/opencode.jsonc
    You can also use opencode.json or opencode.jsonc in your project directory.
2. Add the parameter to the model config under your custom provider In your existing provider (e.g. custom provider pointing to LeapX or your own API), add "apiCompatibility": "responses" for models that need the Responses API (e.g. gpt-5.1-codex). Example: Responses API requirement for some models opencode.jsonc: apiCompatibility responses for gpt-5.1-codex
After saving, when you select that provider’s gpt-5.1-codex in OpenCode (e.g. backup_leapx/gpt-5.1-codex), requests will be sent to that baseURL in Responses API format. 3. Success example The screenshot below shows a normal chat in OpenCode using a correctly configured model (e.g. backup_v1/gpt-5.1-chat). OpenCode chat after successful config

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3.3 Summary

See the LeapX model list for available models and IDs.

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Success example

The screenshot below shows a normal chat in OpenCode using LeapX API. OpenCode success with LeapX API

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5. References