Node catalog

A3S Flow 1.0 provides 18 nodes that authors can place on a canvas. After choosing a node, you can configure it, connect ports, and validate the full graph in the Playground, or generate the same structure through the CLI. Fields, defaults, ports, runtime bindings, and durable identity rules all come from one manifest catalog.

iteration-start and loop-start are internal container entries. The editor creates them with their container. They do not appear in the node picker and cannot be placed on the top-level canvas.

Node workbench

This workbench uses the public @a3s-lab/flow-ui components. Selecting a node gives the canvas card and configuration panel the same node object. Title, description, and field edits update the preview immediately. Waits, callbacks, batches, child workflows, and containers use dedicated controls.

Canvas previewEdits update the canvas card immediately

Upstream node

Run Step

Handler: task.run

Run one registered task, retry when needed, and save its result.

Next node

Configuration panel

Run Step

Reference

Manifest contract5 fields · 6 ports

Node metadata

Type: flow.step
Category: Task execution · durable-work
Icon: —
Documentation: https://github.com/A3S-Lab/Flow#runtime-model
Manifest version: 1
Owner: host
Role: runtime-command
Runtime binding: schedule_step
Stable ID: graph_node_id
Container start: —
Base classes: A3SFlowNode
Input types: FlowValue
Output types: StepResult · StepError
Flags: Official
Internal: No
Official: Yes
Tool mode: No
Beta: No
Legacy: No

Port contract

Inputs

Inincontrol · FlowControl
Inputinputdata · JsonValue

Outputs

Successsuccesscontrol · FlowControl
Resultresultdata · JsonValue
Recoverable failurefailedcontrol · FlowControl
Recoverable errorerrordata · String

Output definitions

ResultresultStepResult
Recoverable errorerrorStepError

Field contract 5 fields

Step handlerstep_name
Default
textinputRequired
Defaulttask.run
Manifest properties
- _input_typeStrInput
- display_nameStep handler
- infoRegistered task that this step runs.
- namestep_name
- placeholdertool.execute
- requiredtrue
- typestr
- ui_groupexecution
- ui_group_labelExecution
- valuetask.run
Step inputinput
Default
a3s.flow.expressioninput
Default{"apiVersion":"a3s.dev/flow-expression/v1","expression":{"op":"field","path":"input"}}
Manifest properties
- _input_typeA3SFlowExpressionInput
- display_nameStep input
- expression_purposeinput
- infoChoose the workflow data sent to the task.
- input_types["FlowValue"]
- nameinput
- typedict
- ui_groupexecution
- ui_group_labelExecution
- value{"apiVersion":"a3s.dev/flow-expression/v1","expression":{"op":"field","path":"input"}}
Maximum attemptsmax_attempts
Default
numberruntimeRequiredAdvanced
Default3
Manifest properties
- _input_typeIntInput
- advancedtrue
- display_nameMaximum attempts
- infoTotal attempts for this step, including the first execution.
- namemax_attempts
- range_spec{"min":1,"max":100,"step":1}
- requiredtrue
- typeint
- ui_groupretry-policy
- ui_group_labelRetry policy
- value3
Retry delay (ms)retry_delay_ms
Default
numberruntimeRequiredAdvanced
Default0
Manifest properties
- _input_typeIntInput
- advancedtrue
- display_nameRetry delay (ms)
- infoWait time before the next attempt. Use 0 to retry immediately.
- nameretry_delay_ms
- range_spec{"min":0,"max":86400000,"step":100}
- requiredtrue
- typeint
- ui_groupretry-policy
- ui_group_labelRetry policy
- value0
If all attempts failon_exhausted
Default
selectbehaviorRequiredAdvanced
Defaultfail_run
Manifest properties
- _input_typeDropdownInput
- advancedtrue
- display_nameIf all attempts fail
- infoEnd the run, or continue from the failure branch.
- nameon_exhausted
- options[{"label":"End run as failed","value":"fail_run"},{"label":"Continue from failure branch","value":"continue_workflow"}]
- requiredtrue
- typestr
- ui_groupretry-policy
- ui_group_labelRetry policy
- valuefail_run

Six groups

Group	Nodes	Responsibility
Orchestration	Start, Condition	Accept input and choose deterministic control branches
Tasks and tools	Run step, Step batch	Call host tasks and store results, errors, and retry state
Wait and approval	Wait until, Callback and approval, Signal wait	Release workers while waiting for time or external input
Child work	Child operation, Child workflow, Child workflow batch, Continue as new	Track long jobs, own child runs, and continue history
Run state	Progress, Complete, Fail, Cancel, Timeout	Record inspectable state and close run segments
Child-canvas containers	Iteration, Loop	Establish graph scopes and constrain parent, child, and edge relationships

Choose from the task in front of you

Use Run step for one host task after input arrives. Use Step batch when a set of tasks needs per-member results and retry state. Both require a real task handler registered by the host.

Use Wait until for a time boundary, Callback and approval for an approval or one callback, and Signal wait when an existing business channel resumes the run by name. All three release the worker while waiting.

Use Child workflow when a unit of work needs its own history, state, and cancellation policy. Use Iteration to apply one child graph to a collection, and Loop when a condition controls repetition. Ordinary graph edges remain acyclic.

Runtime binding

Nodes with a runtimeBinding compile to durable A3S Flow runtime commands. flow.start and flow.condition execute at the graph layer. iteration and loop define child-canvas structure, while the host decides how each pass compiles into steps or child workflows.

Task and wait nodes normally use the graph node ID as durable identity. Batch nodes also include each member key. Changing those IDs after a run starts prevents replay from matching the original history.

Every individual node page includes the following material.

Intended use and runtime behavior
Every field, default, control, range, option, and visibility condition
Control and data ports
Runtime binding and durable identity rules
Complete node JSON, CLI commands, and a Skill prompt
Recovery, retry, cancellation, and container-scope notes

When configuration validation fails

Start with the reported path and locate the exact node and field. Field errors usually mean a required value is empty, a number is out of range, or a dependent setting no longer matches. Edge errors usually mean incompatible port types, an occupied input, a cross-scope connection, or a cycle.

Do not delete unknown fields merely to silence validation. Check the node page for its current fields and ports, then validate again in the Playground or CLI. Preserve node IDs after runs exist because steps, hooks, progress records, and child runs use those IDs to match committed history.

Verify the catalog with the CLI

The installed catalog ships with the front-end components. Inspect the current version before creating a node.

a3s-flow nodes --pretty
a3s-flow node flow.step --pretty
a3s-flow new flow.step --id charge-order --pretty

After adding nodes to the graph, run validate, compile, and digest. The CLI checks fields, ports, scopes, cycles, and deterministic execution order.

#Node catalog

#Node workbench