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Persistence and Blueprint ​

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Two distinct serialization paths exist. Don't confuse them.

MethodWhat it serializesTypical use
execution.save() / execution.load(saved)one execution's runtime state at a moment in timeresume across process restarts, hand off to another worker
flow.save_blueprint() / flow.load_blueprint(blueprint)the flow definition structure (chunks, branches, conditions)distribute or version-control a flow as a config artifact

Execution save / load ​

save() captures everything needed to resume the execution where it stopped:

  • the execution's state
  • lifecycle metadata (status, timestamps, run ids)
  • pending interrupt state (if pause_for(...) was hit)
  • resource_keys — the names of runtime resources expected on resume, but not the live values

What it does not capture:

  • the live runtime_resources themselves (they're not serializable; see State and Resources)
  • in-flight chunks (no execution mid-coroutine; save during a settled state)
python
execution = flow.create_execution(auto_close=False)
await execution.async_start("refund request")

saved_state = execution.save()
# persist saved_state somewhere (Redis, DB, file, etc.)

Restore later (possibly in a different process):

python
restored = flow.create_execution(
    auto_close=False,
    runtime_resources={"db": new_db_client, "logger": new_logger},
)
restored.load(saved_state)

# Continue: emit, continue_with an interrupt, then close
await restored.async_emit("UserFeedback", {"approved": True})
snapshot = await restored.async_close()

The flow definition must be the same flow (or compatible) on both sides — load() doesn't reconstruct the chunk graph from saved_state; it expects the flow to already exist.

Resuming around a pause_for ​

python
execution = flow.create_execution(auto_close=False)
await execution.async_start("topic")

# at this point the flow may have called pause_for(...)
saved = execution.save()

# ... days later, in a different worker ...
restored = flow.create_execution(
    auto_close=False,
    runtime_resources={"search_tool": new_search_function},
)
restored.load(saved)

interrupt_id = next(iter(restored.get_pending_interrupts()))
await restored.async_continue_with(interrupt_id, {"approved": True})
snapshot = await restored.async_close()

get_pending_interrupts() returns ids of interrupts created via pause_for(...). continue_with(id, payload) resolves one interrupt and resumes the graph according to that interrupt's resume_to target.

Flow blueprint save / load ​

A blueprint serializes the structure of the flow — chunk references, branches, conditions — but not the chunk function bodies (those stay in code).

python
def upper(data):
    return str(data.input).upper()

def store(data):
    return data.async_set_state("output", data.input)

source = TriggerFlow(name="source")
source.register_chunk_handler(upper)
source.register_chunk_handler(store)
source.to(upper).to(store)

blueprint = source.save_blueprint()  # dict, can be JSON / YAML serialized

Restore on the other end:

python
restored = TriggerFlow(name="restored")
restored.register_chunk_handler(upper)   # same function bodies must be available
restored.register_chunk_handler(store)
restored.load_blueprint(blueprint)

Key constraint: any chunk used in the blueprint must be registered by the same handler name on the restored side. Without register_chunk_handler(...), the loader can't bind names to functions and the load fails.

For service code, prefer this packaging shape:

  1. Put chunks and conditions in module-level named functions.
  2. Treat the ordinary TriggerFlow(...) object as the flow definition surface.
  3. Inject stable live dependencies with flow.update_runtime_resources(...).
  4. Inject request- or tenant-specific dependencies with per-execution runtime_resources={...}.
  5. Store per-request business data in execution state, not in flow_data.
python
async def analyze(data):
    agent_factory = data.require_resource("agent_factory")
    prompts_path = data.require_resource("prompts_path")
    question = data.input
    data.set_state("question", question)
    agent = agent_factory()
    return agent.load_yaml_prompt(
        prompts_path,
        prompt_key_path="analyze",
        mappings={"question": question},
    ).start()


async def answer(data):
    policy_doc = data.require_resource("policy_doc")
    question = data.get_state("question")
    return f"{policy_doc}\n\nQ: {question}"


def build_policy_flow() -> TriggerFlow:
    flow = TriggerFlow(name="policy")
    flow.update_runtime_resources(
        agent_factory=make_agent,
        prompts_path=PROMPTS_DIR / "policy.yaml",
    )
    flow.to(analyze).to(answer)
    return flow


flow = build_policy_flow()
snapshot = flow.start(
    "travel subsidy?",
    runtime_resources={"policy_doc": tenant_policy_doc},
)

This keeps business modules light while preserving config/blueprint compatibility. Closures are fine for short scripts, but named top-level handlers are the recommended service shape because they are easier to test, register, export, and reload.

Current behavior: TriggerFlow's module-safe definition assembly treats TriggerFlow(...) itself as the planning surface and create_execution(...) / start_execution(...) as the boundary into one run. There is no separate TriggerFlow.define(...) mode. Service modules can replay the same definition assembly safely: named functions keep stable stage identities, and the same function used as two logical stages should be disambiguated with name=....

For model applications that generate a To-Do List or dependency graph at runtime, keep that graph per plan or per request. Reusable templates such as extract / analyze sub-flows belong at module scope; the per-plan executor should use task ids as dynamic stage identities, write task results to execution state, and avoid mutating the main flow definition.

When to use blueprints ​

  • Authoring flows declaratively in YAML / JSON config and loading them at startup.
  • Versioning flow structure separately from handler code.
  • Distributing a flow to multiple workers that already have the chunk implementations.

When not to use blueprints ​

  • For one-off scripts. Just write the flow in Python.
  • For sharing flows with consumers that don't have the handler code. Blueprints are not self-contained.

save vs save_blueprint side-by-side ​

text
Flow definition (chunks, branches, conditions)
        │
        ├── save_blueprint()  →  dict describing graph structure
        │
        ▼
   create_execution()  ────►  one Execution
                                  │
                                  ├── save()  →  dict describing this execution's state
                                  │
                                  ▼
                              async_close() → close snapshot

Both paths return JSON-friendly dicts. Pick storage (Redis, Postgres, S3, file) at the application level — the framework doesn't ship a backend.

Practical patterns ​

Single-server resume

python
saved = execution.save()
redis.set(f"flow:{exec_id}", json.dumps(saved))

# later
saved = json.loads(redis.get(f"flow:{exec_id}"))
restored = flow.create_execution(auto_close=False, runtime_resources={...})
restored.load(saved)

Distributed worker pickup

Pair a blueprint (stored once) with an execution save (stored per execution):

python
blueprint = source_flow.save_blueprint()
db.save("flow_blueprints", blueprint_id, blueprint)

# in worker
flow = TriggerFlow(name="loaded")
register_all_handlers(flow)            # whatever your registration entry is
flow.load_blueprint(db.load("flow_blueprints", blueprint_id))

execution = flow.create_execution(auto_close=False, runtime_resources=...)
execution.load(saved)

See also ​