orchflow 0.4.0

A lightweight Python framework for readable multi-agent pipelines.

Orchflow

Orchflow is a lightweight Python framework for readable multi-agent pipelines. It gives you sequential, parallel, conditional, retryable, and observable orchestration, with lightweight human review and JSON resume, without forcing every workflow into a heavy graph runtime.

pip install orchflow

from orchflow import Flow, StepContext, step


@step
async def research(input: str, context: StepContext) -> str:
    return f"research about {input}"


@step
async def write(input: str, context: StepContext) -> str:
    return f"draft based on {context.previous}"


result = await Flow([research, write]).run("agent orchestration")
print(result.output)

Why Orchflow Exists

Plain Python function chaining is easy to read, but it becomes fragile as soon as a workflow needs retries, parallel work, branching, shared state, or traces. Large graph frameworks are powerful, but they can add more abstraction than a small agent pipeline needs.

Orchflow sits in the middle: the user writes normal Python functions, while the framework handles orchestration mechanics that should be reliable and inspectable.

flowchart LR
    A["flow.run(input)"] --> B["Step: research"]
    B --> C{"Parallel group"}
    C --> D["Step: web_research"]
    C --> E["Step: docs_research"]
    D --> F["Merge outputs"]
    E --> F
    F --> G{"Condition"}
    G --> H["technical_writer"]
    G --> I["general_writer"]
    H --> J["FlowResult + traces"]
    I --> J

What It Demonstrates

Orchflow is intentionally small, but it is built like a real package:

• Async-first execution with sync-step support through worker threads
• Sequential pipelines, parallel fan-out, and conditional routing
• Retry policy at both flow and step level
• Shared run state with explicit StepContext
• Flat StepTrace records for every attempt, including failures
• Live lifecycle events with Flow.events(...)
• Lightweight human input gates with callback or stdin providers
• JSON checkpoints and resume for practical long-running workflows
• Optional LiteLLM-backed Agent without making LiteLLM a core dependency
• Offline test helpers under orchflow.testing
• Typed package metadata, CI, TestPyPI/PyPI release workflows, and tag releases

Core Concepts

Orchflow keeps the public model deliberately small.

Concept	Purpose
Agent	Stateless role-based LLM helper with optional LiteLLM support
@step	Decorator for a unit of workflow work
StepContext	Carries previous output, original input, metadata, and shared state
Flow	Orchestrates sequential, parallel, and conditional execution
FlowResult	Final output, traces, state, timing, and failure details
FlowEvent	Live lifecycle event emitted while a flow runs
human_input	Step helper for pausing a flow and collecting reviewer text
JsonCheckpointStore	Local JSON checkpoint store for resume

Sequential Flow

from orchflow import Flow, StepContext, step


@step(name="research", retry=2)
async def research(input: str, context: StepContext) -> str:
    return f"notes about {input}"


@step(name="draft")
async def draft(input: str, context: StepContext) -> str:
    return f"article based on {context.previous}"


result = await Flow([research, draft], name="content-pipeline").run(
    "AI agent orchestration"
)

print(result.output)
print([trace.step_name for trace in result.traces])

Important data-flow rule: the first input argument is always the original flow.run(...) input. Previous step output is available as context.previous.

Parallel Flow

Wrap independent steps in a list to run them concurrently.

flow = Flow([
    plan,
    [web_research, docs_research],
    synthesize,
])

result = await flow.run("workflow frameworks")

The next step receives a dictionary keyed by step name:

{
    "web_research": "...",
    "docs_research": "..."
}

Parallel steps produce separate flat trace entries with the same parallel_group_id.

Conditional Flow

from orchflow import Flow, condition

flow = Flow([
    classify,
    condition(
        when=lambda ctx: ctx.previous == "technical",
        then=technical_writer,
        otherwise=general_writer,
    ),
])

The predicate receives the current StepContext, so routing can use context.previous, shared state, or run metadata.

Human Review

Use human_input(...) when a pipeline needs a lightweight review point without adding checkpointing, queues, or a separate UI.

from orchflow import Flow, StepContext, condition, human_input, step


@step
async def draft(input: str, context: StepContext) -> str:
    text = f"Draft about {input}"
    context.state["draft"] = text
    return text


review = human_input(
    lambda ctx: f"Review this draft:\n{ctx.previous}\n\nDecision: ",
    name="human_review",
)


@step
async def publish(input: str, context: StepContext) -> str:
    return f"Published: {context.state['draft']}"


@step
async def revise(input: str, context: StepContext) -> str:
    return f"Revision requested: {context.previous}"


flow = Flow([
    draft,
    review,
    condition(
        when=lambda ctx: str(ctx.previous).strip().lower() == "approve",
        then=publish,
        otherwise=revise,
    ),
])

By default, human_input(...) reads from stdin. Applications and tests can pass a sync or async provider(prompt, context) callback instead. The human response is normal step output, so it is available as context.previous to the next step.

Checkpoint And Resume

Use JsonCheckpointStore when a flow should survive a transient failure without rerunning completed top-level work.

from orchflow import Flow, JsonCheckpointStore

store = JsonCheckpointStore("orchflow-checkpoint.json")
flow = Flow([collect, draft, publish], name="checkpointed-pipeline")

first = await flow.run(
    "AI agent orchestration",
    checkpoint=store,
    raise_on_error=False,
)

if not first.success:
    resumed = await flow.resume(store)
    print(resumed.output)

Checkpoints are plain JSON and are saved after each completed top-level item: single steps, selected condition branches, or complete parallel groups. A failed parallel group resumes by rerunning the whole group. Successful flows keep the checkpoint file and mark it completed for inspection.

Live Events

Flow.events(...) lets applications observe a workflow while it runs.

async for event in flow.events("agent observability"):
    print(event.type, event.step_name, event.attempt)

Event types:

• flow_started
• step_started
• step_completed
• step_failed
• retry_scheduled
• flow_completed
• flow_failed
• checkpoint_saved
• checkpoint_loaded

Events are orchestration lifecycle events, not token streaming. The final flow_completed or flow_failed event carries a FlowResult.

Trace Output

Every step attempt creates a flat StepTrace.

result = await flow.run("topic")

for trace in result.traces:
    print(trace.to_dict())

Example shape:

{
    "step_name": "draft",
    "input": "topic",
    "output": "article...",
    "error": None,
    "attempt": 1,
    "parallel_group_id": None,
    "duration_seconds": 0.42,
    "started_at": "2026-05-10T03:13:48.994932+00:00",
    "ended_at": "2026-05-10T03:13:49.414932+00:00",
    "success": True,
}

Optional LLM Agent

Core Orchflow has no runtime dependencies. The public Agent uses LiteLLM only when you install the optional extra:

pip install "orchflow[litellm]"

from orchflow import Agent

writer = Agent(
    name="writer",
    role="You write concise technical explanations.",
    model="gpt-4o-mini",
)

text = await writer.run("Explain lightweight orchestration")

Tool-calling loops, memory, and durable agent state are intentionally outside the current scope. Orchflow focuses on orchestration first.

Examples

uv run python examples/basic_sequential.py
uv run python examples/parallel_steps.py
uv run python examples/conditional_flow.py
uv run python examples/live_events.py
uv run python examples/human_review.py
uv run python examples/checkpoint_resume.py

Docs:

• Quickstart
• Concepts
• API reference
• Examples
• Publishing
• Roadmap

Development

uv sync --extra dev
uv run pytest
uv run ruff check
uv run ruff format --check
uv run pyright
uv build

Release Process

TestPyPI publishing is manual through .github/workflows/publish-testpypi.yml. Real PyPI publishing is tag-based through .github/workflows/publish-pypi.yml.

git tag -a v0.4.0 -m "Release v0.4.0"
git push origin v0.4.0

The release workflow verifies that the Git tag matches pyproject.toml, uploads to PyPI through trusted publishing, and creates a GitHub Release.

Roadmap

• 0.4.x: checkpoint/resume polish and docs improvements
• 0.5.0: richer optional agent adapters

Source Of Truth

Project decisions live in AGENTS.md. Implementation follows that document.