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query() offers two model-selection modes:
  • Fixed model (default): the entire session uses one model.
  • Dynamic selection: a callback is called before every LLM request to return the model. You can route by purpose (main conversation, sub-agent, context compaction, etc.) or return a BYOK credential to use your own API key.
The two modes are mutually exclusive: passing the callback switches to dynamic-selection mode and the fixed-model setting is ignored.

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Fixed model

Specify it via the model option; omit to use the account default: 
import { qodercliAuth, query } from '@qoder-ai/qoder-agent-sdk';

const q = query({
  prompt: 'Analyze this code',
  options: {
    auth: qodercliAuth(),
    model: 'performance',
  },
});

​
Dynamic selection

Provide a callback function that is invoked before every LLM request: 
import { qodercliAuth, query, type ModelPolicyProvider } from '@qoder-ai/qoder-agent-sdk';

const resolveModel: ModelPolicyProvider = (context) => {
  return { model: 'performance' };
};

const q = query({
  prompt: 'Analyze this code',
  options: {
    auth: qodercliAuth(),
    resolveModel,
  },
});
The callback receives the request’s purpose, session info, and the list of currently available models.

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Routing by purpose

Use a different model per purpose: 
const resolveModel: ModelPolicyProvider = (context) => {
  switch (context.purpose) {
    case 'main':       return { model: 'performance' };
    case 'subagent':   return { model: 'efficient' };
    case 'compact':    return { model: 'lite' };
    default:           return { model: 'auto' };
  }
};
Purposes cover scenarios like main conversation, sub-agent, context compaction, WebFetch, and image generation. For the full list, see SDK References.

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Timeout

The callback has a default timeout (in milliseconds). Increase it when the callback performs remote I/O: 
{ resolveModel, resolveModelTimeoutMs: 800 }

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BYOK: use your own API key

The callback can also return a BYOK credential object — that request will be routed to a third-party provider: 
const resolveModel: ModelPolicyProvider = () => ({
  model: {
    provider: 'bailian',
    model: 'qwen3.5-plus-cp',
    api_key: process.env.MY_API_KEY!,
  },
});
The available provider/model catalog can be fetched at runtime, so the front-end can render selectors and an API-key input. Before using a user-supplied BYOK credential in resolveModel, you can validate the provider / model / API-key combination through the CLI: 
const q = query({
  prompt: 'Validate BYOK configuration',
  options: { auth: qodercliAuth() },
});

const ok = await q.validateByokModel({
  provider: 'openai',
  model: 'gpt-4o',
  api_key: process.env.MY_API_KEY!,
  url: 'https://api.openai.com/v1',
  style: 'openai',
});

if (ok === false) {
  throw new Error('Invalid BYOK configuration');
}
The method returns null when the running CLI does not support BYOK validation.

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Runtime operations

While a session is running you can fetch the account’s currently available model list: 
import { qodercliAuth, query } from '@qoder-ai/qoder-agent-sdk';

const q = query({
  prompt: '...',
  options: { auth: qodercliAuth() },
});

const models = await q.getAvailableModels();
for (const m of models) {
  console.log(`${m.value}\t${m.displayName}\t${m.description}`);
}
ModelInfo also carries availability flags and rich metadata such as context_config and thinking_config when the backend provides them. You can also switch the current model in fixed-model mode, fetch the BYOK provider catalog, or validate a BYOK model configuration. For specific method signatures, see SDK References.

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Error handling

Dynamic-selection mode has no automatic fallback — a callback that times out, throws, or returns an empty model causes the query to fail. Handle errors inside the callback: 
const resolveModel: ModelPolicyProvider = async (context) => {
  try {
    const policy = await fetchRemotePolicy(context);
    return { model: policy.model };
  } catch {
    return { model: 'auto' };   // fallback, must be non-empty
  }
};
For full field and type definitions, see SDK References.