AgentLab

Universal record-and-replay for LLM agents.

Status: pre-alpha, APIs will change.

AgentLab captures model calls, tools, state transitions, and timing into a trace you can replay without hitting the network. It is built around a framework-agnostic core and an HTTP capture layer that works with any SDK that routes requests through httpx.

Overhead

Per-LLM-call cost of running inside agentlab.record():

Measured against an in-process loopback HTTP server with a 10 ms upstream delay (eliminates network jitter so the delta isolates SDK overhead: HTTP capture, span emit, JSONL write+fsync, matcher, LLMSpan build). Real LLM calls land in the 100 ms – 2000 ms range, so this works out to under 1% wall-clock overhead in practice.

Reproduce with:

uv run python scripts/bench_record_overhead.py --calls 200 --runs 5

Installation

pip install agentic-lab           # minimal SDK
pip install 'agentic-lab[ui]'     # + Starlette UI server

The PyPI distribution is agentic-lab; the importable Python module is agentlab:

import agentlab as al

For local development, this repo is uv-managed:

git clone https://github.com/ambuj-krishna-agrawal/agentlab.git
cd agentlab
uv sync --all-extras --frozen

Use --frozen by default so your environment matches uv.lock and CI.

Documentation

• Quickstart — five minutes from install to a replayable trace.
• Provider coverage — every supported LLM provider + how to add custom ones.
• Error reference — every AGL-… code with a remediation sentence (auto-generated from src/agentlab/errors.py).
• Changelog — version history.
• AGENTS.md — invariants and quality gates contributors must respect.
• CONTRIBUTING.md — human-contributor process.

Configuration

• Secrets live in .env (git-ignored). Copy .env.example and set the provider keys you use.
• Non-secret defaults live in src/agentlab/_defaults.toml and can be overridden by AGENTLAB_* environment variables.
• Full typed config lives in src/agentlab/config.py.

Quickstart

Five minutes from pip install to a trace you can replay without an API key. The full runnable script ships in the wheel at agentlab.examples.quickstart; the inline version:

import os
import openai
import agentlab as al

client = openai.OpenAI(
    api_key=os.environ["OPENROUTER_API_KEY"],
    base_url="https://openrouter.ai/api/v1",
)

# 1. Record.
with (
    al.record(agent_name="quickstart") as recording,
    al.agent(name="quickstart", version="0"),
    al.step(role=al.StepRole.EXECUTE),
):
    response = client.chat.completions.create(
        model="openai/gpt-4o-mini",
        messages=[{"role": "user", "content": "Reply with the single word 'ok'."}],
        max_tokens=16,
    )
print("model said:", response.choices[0].message.content)
print("trace at:  ", recording.directory)

# 2. Replay — no network, no key.
with al.replay(str(recording.directory)) as session:
    replay = client.chat.completions.create(
        model="openai/gpt-4o-mini",
        messages=[{"role": "user", "content": "Reply with the single word 'ok'."}],
        max_tokens=16,
    )
print("replay said:", replay.choices[0].message.content)
print("cache hits: ", session.cache_hits)

pip install 'agentic-lab[ui]' openai
export OPENROUTER_API_KEY=sk-or-...
python -m agentlab.examples.quickstart
agentlab serve --root ~/.agentlab/traces
# → http://127.0.0.1:7861/

The with al.agent(...) and al.step(...) envelopes give the auto-emitted LLMSpan a typed parent (the V4 schema forbids LLM under bare RUN). Production agents normally establish these once near their entrypoints and don't repeat them per-call — see agentlab.examples.workflows for that shape.

Larger example agents

Reference agents under agentlab.examples cover the Anthropic building-effective-agents shapes:

All three use OpenRouter via langchain-openai, real (or realistic) tools, and can write traces into a local example_traces/ directory that agentlab serve can browse.

Provider coverage

Inside an agentlab.record() block AgentLab patches httpx transport methods, so every SDK that routes through httpx (which is most modern Python LLM SDKs) lands its raw exchange in http.jsonl. That file is the source of truth for replay; the typed LLMSpan is a best-effort view layered on top.

The built-in matchers turn recognised exchanges into typed LLMSpans out of the box:

Adding a custom or self-hosted provider

OpenAI-compatible hosts (vLLM, Ollama, your private gateway) need one line:

import agentlab as al
from agentlab.llm.matchers.openai import HostPathMatcher

al.register_llm_provider(HostPathMatcher(
    name="my-vllm",
    host_suffix="llm.internal.example.com",
    path_prefix="/v1/chat/completions",
))

For wholly different body shapes, subclass agentlab.llm.LLMProviderMatcher.

Pricing

The SDK is token-only by default — LLMSpan.cost.usd stays at 0.0 and the span is annotated with agentlab.llm.pricing.unknown=True. Provider list-prices change too often to bake into the SDK. Operators who want USD computed on every span install their own table:

from agentlab.llm.pricing import PriceRow, StaticPriceTable, set_price_table

set_price_table(StaticPriceTable(rows=(
    PriceRow("openai", "gpt-4o", 2.50, 10.00),
    PriceRow("anthropic", "claude-3-5-sonnet*", 3.00, 15.00),
)))

Strict mode for unrecognised exchanges

By default, exchanges that don't match any provider matcher log a warning (one per (trace, host)) and the raw exchange remains in http.jsonl. Power users can opt into stricter behaviour:

with al.record(strict_unknown_provider="raise"):  # or "emit_op"
    ...

"raise" surfaces the gap as UnknownLLMProviderError; "emit_op" records the call as a typed OpSpan so the trace tree is complete even without a matcher.

UI and examples

Generate traces with the bundled examples (they ship inside the wheel), then run the backend UI server against that local trace directory:

uv run python -m agentlab.examples.workflows.research_assistant --traces example_traces
uv run agentlab --root example_traces serve --port 7861

Optional frontend dev server with HMR:

cd frontend
npm install
npm run dev

The bundled runnable agents live in agentlab.examples and are available from the Agents page when the server starts successfully.

UI walkthrough

Dashboard

Traces list

Trace detail

Agents

Settings

Development

Run the local quality gate:

bash scripts/check.sh

Equivalent commands:

uv run ruff check .
uv run ruff format --check .
uv run mypy
uv run pytest tests/unit tests/integration -n auto --dist=worksteal

Testing

Current test tiers:

• tests/unit/: hermetic unit tests (no real network).
• tests/integration/: in-process integration tests with mocked HTTP where needed.

For live-provider smoke runs, use the runnable examples in example/ through their CLIs or the UI Agents page.

Project layout

agentlab/
├── src/agentlab/
│   ├── __init__.py          # public API surface
│   ├── cli.py               # `agentlab` console entry point
│   ├── config.py            # typed settings
│   ├── recorder.py          # public `record()` context manager
│   ├── _defaults.toml       # bundled non-secret defaults
│   ├── _proto/              # generated protobuf bindings (private)
│   ├── bridges/             # export bridges (e.g. OTel GenAI)
│   ├── core/                # recording primitives
│   ├── examples/            # bundled runnable agent seeds (shipped in wheel)
│   ├── io/                  # trace IO + HTTP capture
│   ├── integrations/        # framework adapters
│   ├── llm/                 # provider-agnostic LLM client
│   ├── replay/              # deterministic replay engine
│   ├── storage/             # JSONL + protobuf stores
│   ├── ui/                  # Starlette UI server + DTO mapping
│   ├── pytest.py            # pytest plugin
│   └── promote.py           # replay-test scaffold generator
├── frontend/                # React SPA for the UI server
├── proto/agentlab/v1/trace.proto
├── scripts/                 # check, proto regen, UI screenshot helpers
├── tests/{unit,integration}/
└── uv.lock

License

Apache 2.0 — see LICENSE.