Agent Loop docs

Providers

Agent.from_env() selects and builds a provider client from the mapping you give it. With LLM_PROVIDER=openai and OPENAI_API_KEY configured as in Hello World:

import os

from agentloop import Agent

with Agent.from_env(os.environ, tools=[]) as agent:
    print(agent.run("Say hello in one word."))

Output:

Hello

Each built-in provider implements the same LLMClient interface and converts requests, responses, usage, stop reasons, and errors into shared types. Agent.from_env() uses Settings.from_env() and build_client() internally; build_client() also applies the configured retry policy. See configuration if you need to validate settings separately.

Provider-specific clients

Use a provider builder when you need options that Settings does not expose. For example, the OpenAI builder accepts an organization or project header and lets you choose an API:

import os

from agentloop.providers.openai import build_openai_client

with build_openai_client(api_key=os.environ["OPENAI_API_KEY"]) as client:
    print(client.name, client.model, client.api)

Output:

openai gpt-5.1 responses

The builder returns a direct provider client. Wrap it in RetryingClient if you need retries; build_client() and Agent.from_env() do that for you.

HTTP client, trust, and proxy settings

Pass an HTTP client you configured when you need a custom trust store, proxy, transport, or timeout. OpenAI, OpenRouter, and Modal use httpx.Client. Anthropic uses the HTTP client type required by the installed Anthropic SDK (httpx2.Client in the version used here).

The supplied HTTP client stays yours to close. This example gives OpenAI a 30-second HTTP timeout and checks that leaving the agent's context did not close the shared client:

import os

import httpx

from agentloop import Agent

with httpx.Client(timeout=30.0) as http:
    with Agent.from_env(os.environ, tools=[], http_client=http) as agent:
        print(agent.run("Reply with the word ready."))
    print(f"HTTP client closed by agent: {http.is_closed}")

Output:

ready
HTTP client closed by agent: False

For a corporate trust store or proxy, configure httpx.Client(verify=..., proxy=...) in the same place. The adapter supplies its own URL and credentials for each request; your client needs no base_url or default authorization header. If LLM_TIMEOUT_SECONDS is set, that explicit per-call timeout overrides the HTTP client's timeout.

The same http_client= parameter is available on build_client() and provider builders. Passing a client of the wrong HTTP package raises ConfigurationError. A TLS, DNS, or proxy failure raises non-retryable ProviderUnreachable; a transient connection error may be retried. OpenAI-compatible clients created by the library do not follow redirects and report a 3xx as UnexpectedRedirect. Anthropic's SDK follows redirects by default; supply a client with follow_redirects=False if you want it to report them instead.

Chat Completions or Responses

OpenAI uses the Responses API by default. Set OPENAI_API=completions (or Settings.openai_api="completions") only when you need Chat Completions compatibility. OpenRouter and Modal always use Chat Completions.

Responses requests send store: false and the full transcript. The adapter strips output item IDs on replay, so a continued conversation does not depend on the provider retaining server-side state.

See the provider reference or implement a custom provider.