Blueprint

Blueprint Implementation

You are helping a user work with Blueprint, a system for composing Airflow DAGs from YAML using reusable Python templates. Execute steps in order and prefer the simplest configuration that meets the user's needs.

Package: airflow-blueprint on PyPI Repo: https://github.com/astronomer/blueprint Requires: Python 3.10+, Airflow 2.5+, Blueprint 0.3.0+

Before Starting

Confirm with the user:

1. Airflow version ≥2.5
2. Python version ≥3.10
3. Use case: Blueprint is for standardized, validated templates. If user needs full Airflow flexibility, suggest writing DAGs directly or using DAG Factory instead.

Determine What the User Needs

Project Setup

If the user is starting fresh, guide them through setup:

1. Install the Package

# Add to requirements.txt
airflow-blueprint>=0.3.0

# Or install directly
pip install airflow-blueprint

2. Create the Loader

Create dags/loader.py:

from blueprint import build_all_dags

build_all_dags()

Use build_all_dags, not build_all. The function was renamed in 0.3.0 so the loader's import line contains the substring dag, which Airflow's safe-mode DAG file processor requires — otherwise the file is silently skipped and no DAGs appear. build_all still works as a deprecated alias (emits DeprecationWarning); migrate existing loaders.

DAG-level configuration (schedule, description, tags, default_args, etc.) is handled via YAML fields and BlueprintDagArgs templates — see Customizing DAG-Level Configuration.

3. Verify Installation

uvx --from airflow-blueprint blueprint list

If no blueprints found, user needs to create blueprint classes first.

Provider operators in the CLI. The uvx --from airflow-blueprint environment is isolated and does not include the Airflow provider packages your Astro Runtime project has. If your templates import provider operators (BigQuery, Snowflake, etc.), add --with so the CLI can import them — otherwise list/lint/schema fail with ModuleNotFoundError: No module named 'airflow.providers.X':

uvx --from airflow-blueprint --with apache-airflow-providers-google blueprint list --template-dir dags/templates

Creating Blueprints

When user wants to create a new blueprint template:

Blueprint Structure

# dags/templates/my_blueprints.py
from airflow.operators.bash import BashOperator
from airflow.utils.task_group import TaskGroup
from blueprint import Blueprint, BaseModel, Field

class MyConfig(BaseModel):
    # Required field with description (used in CLI output and JSON schema)
    source_table: str = Field(description="Source table name")
    # Optional field with default and validation
    batch_size: int = Field(default=1000, ge=1)

class MyBlueprint(Blueprint[MyConfig]):
    """Docstring becomes blueprint description."""

    def render(self, config: MyConfig) -> TaskGroup:
        with TaskGroup(group_id=self.step_id) as group:
            BashOperator(
                task_id="my_task",
                bash_command=f"echo '{config.source_table}'"
            )
        return group

Key Rules

Config Field Types Must Be YAML-Compatible

As of 0.3.0, config fields must be single-typed. Multi-type unions like str | int or Union[A, B] are rejected at class-definition time (raises TypeError) because they produce ambiguous YAML parsing and anyOf schemas. The check recurses through nested models, list items, and dict values.

• Allowed: scalars (str, int, float, bool), Literal[...], list[X], dict[str, V], nested BaseModel, and Optional[X] / X | None (the nullable pattern).
• Rejected: str | int, Union[A, B], or any union with more than one non-None arm. Bare Any and dict[str, Any] are rejected for the same reason — use an explicit single type for the value.

Internal Fields Not Settable from YAML

Use Field(default=..., init=False) for fields used inside render() that should not be overridable from YAML. They are excluded from the constructor (always use their default) and omitted from JSON Schema output:

class ExtractConfig(BaseModel):
    source_table: str
    _internal_batch_multiplier: int = Field(default=4, init=False)

Recommend Strict Validation

Suggest adding extra="forbid" to catch YAML typos:

from pydantic import ConfigDict

class MyConfig(BaseModel):
    model_config = ConfigDict(extra="forbid")
    # fields...

Composing Templates

A blueprint can instantiate and render other blueprints inside its render() method, letting you build higher-level templates from lower-level building blocks while exposing a single, flat config to YAML authors.

Inside render(), instantiate each child blueprint, set its step_id, call render(...) with a config you construct, and wire the results together inside a parent TaskGroup:

class QualityGateConfig(BaseModel):
    checks: list[str] = Field(default=["nulls", "duplicates"])
    report_channel: str = Field(default="data-alerts")

class QualityGate(Blueprint[QualityGateConfig]):
    """Run checks then send a report — composed from Validate and Report."""

    def render(self, config: QualityGateConfig) -> TaskGroup:
        with TaskGroup(group_id=self.step_id) as group:
            validate = Validate()
            validate.step_id = "validate"
            validate_group = validate.render(ValidateConfig(checks=config.checks))

            report = Report()
            report.step_id = "report"
            report_task = report.render(ReportConfig(channel=config.report_channel))

            validate_group >> report_task
        return group

YAML authors then see a single step with a flat config:

steps:
  quality:
    blueprint: quality_gate
    checks: [nulls, duplicates, freshness]
    report_channel: "#data-alerts"

Composing DAGs in YAML

When user wants to create a DAG from blueprints:

YAML Structure

# dags/my_pipeline.dag.yaml
dag_id: my_pipeline
schedule: "@daily"
description: "My data pipeline"

steps:
  step_one:
    blueprint: my_blueprint
    source_table: raw.customers
    batch_size: 500

  step_two:
    blueprint: another_blueprint
    depends_on: [step_one]
    target: analytics.output

By default, only schedule and description are supported as DAG-level fields (via the built-in DefaultDagArgs). For other fields like tags, default_args, catchup, etc., see Customizing DAG-Level Configuration.

Reserved Keys in Steps

Everything else passes to the blueprint's config.

Trigger Rules (0.3.0)

Use trigger_rule to control when a step runs relative to its upstream dependencies — for example, to run a notification step even if an upstream step failed:

steps:
  analyze:
    blueprint: analyze
    depends_on: [extract]

  notify:
    blueprint: notify
    depends_on: [analyze]
    trigger_rule: all_done   # run regardless of whether analyze succeeded

Valid values are validated dynamically against the installed Airflow's TriggerRule enum (all_success, all_done, one_success, none_failed, etc.). When the step's blueprint renders a TaskGroup, the rule is applied only to the group's root tasks (those with no internal upstream), preserving the blueprint author's internal wiring.

Jinja2 Support

YAML supports Jinja2 templating with access to environment variables, Airflow variables/connections, and runtime context:

dag_id: "{{ env.get('ENV', 'dev') }}_pipeline"
schedule: "{{ var.value.schedule | default('@daily') }}"

steps:
  extract:
    blueprint: extract
    output_path: "/data/{{ context.ds_nodash }}/output.csv"
    run_id: "{{ context.dag_run.run_id }}"

Available template variables:

• env — environment variables
• var — Airflow Variables
• conn — Airflow Connections
• context — proxy that generates Airflow template expressions for runtime macros (e.g. context.ds_nodash, context.dag_run.conf, context.task_instance.xcom_pull(...))

Blueprints in Python DAGs

Blueprints aren't tied to the YAML composition flow. Two patterns (both 0.3.0) let you use them from Python — useful for incremental adoption or data-driven DAG generation.

Inside a Hand-Written DAG

To drop a blueprint-rendered step into an existing Python DAG, instantiate the Blueprint class, set its step_id, call render(), and wire it in with >>:

# dags/hybrid_dag.py
from datetime import datetime

from airflow import DAG
from airflow.operators.bash import BashOperator

from dags.etl_blueprints import Extract, ExtractConfig, Load, LoadConfig

with DAG(dag_id="hybrid_python_dag", start_date=datetime(2024, 1, 1), schedule=None, catchup=False) as dag:
    setup = BashOperator(task_id="setup", bash_command="echo 'setup'")

    extract = Extract()
    extract.step_id = "extract"
    extract_group = extract.render(ExtractConfig(source_table="raw.events", batch_size=100))

    load = Load()
    load.step_id = "load"
    load_task = load.render(LoadConfig(target_table="warehouse.events", mode="append"))

    finalize = BashOperator(task_id="finalize", bash_command="echo 'done'")

    setup >> extract_group >> load_task >> finalize

The step_id you set determines the task_id / group_id the blueprint renders under.

Programmatic Building with Builder / DAGConfig

For data-driven DAG generation (one DAG per region, tenant, etc.), build DAGs in a loop with Builder and DAGConfig, then register each in globals() so Airflow discovers them:

from blueprint import Builder, DAGConfig

builder = Builder()

for region in ["us", "eu", "apac"]:
    config = DAGConfig(
        dag_id=f"pipeline_{region}",
        schedule="@hourly",
        steps={
            "extract": {"blueprint": "extract", "source_table": f"raw.{region}"},
            "load": {"blueprint": "load", "depends_on": ["extract"], "target_table": f"out.{region}"},
        },
    )
    dag = builder.build(config)
    globals()[dag.dag_id] = dag

DAGConfig accepts the same fields you would write in YAML (dag_id, steps, plus any fields your BlueprintDagArgs consumes). Builder, DAGConfig, and StepConfig are all exported from blueprint. See examples/advanced/dags/programmatic_dags.py in the repo.

Customizing DAG-Level Configuration

By default, Blueprint supports schedule and description as DAG-level YAML fields. To use other DAG constructor arguments (tags, default_args, catchup, etc.), define a BlueprintDagArgs subclass.

When to Use

• User wants tags, default_args, catchup, start_date, or any other DAG kwargs in YAML
• User wants to derive DAG properties from config (e.g. team name → owner, tier → retries)

Defining a BlueprintDagArgs Subclass

# dags/templates/my_dag_args.py
from pydantic import BaseModel
from blueprint import BlueprintDagArgs

class MyDagArgsConfig(BaseModel):
    schedule: str | None = None
    description: str | None = None
    tags: list[str] = []
    owner: str = "data-team"
    retries: int = 2

class MyDagArgs(BlueprintDagArgs[MyDagArgsConfig]):
    def render(self, config: MyDagArgsConfig) -> dict[str, Any]:
        return {
            "schedule": config.schedule,
            "description": config.description,
            "tags": config.tags,
            "default_args": {
                "owner": config.owner,
                "retries": config.retries,
            },
        }

Then in YAML, the extra fields are validated by the config model:

dag_id: my_pipeline
schedule: "@daily"
tags: [etl, production]
owner: data-team
retries: 3

steps:
  extract:
    blueprint: extract
    source_table: raw.data

Rules

• Only one BlueprintDagArgs subclass per project (raises MultipleDagArgsError if more than one exists)
• The render() method returns a dict of kwargs passed to the Airflow DAG() constructor
• If no custom subclass exists, the built-in DefaultDagArgs is used (supports only schedule and description)

Runtime Parameter Overrides

Blueprint config fields can be overridden at DAG trigger time using Airflow params. This enables users to customize behavior when manually triggering DAGs from the Airflow UI.

Opt In with supports_params = True

A blueprint must set the class attribute supports_params = True for its config fields to register as Airflow params (namespaced as {step}__{field}). Without it, self.param() / self.resolve_config() do nothing and no fields appear in the trigger form. Only opt in for blueprints that actually use those methods — otherwise dead params clutter the form with no effect.

Using self.param() in Template Fields

Use self.param("field") in operator template fields to make a config field overridable at runtime. Airflow renders the actual value at execution time:

class ExtractConfig(BaseModel):
    query: str = Field(description="SQL query to run")
    batch_size: int = Field(default=1000, ge=1)

class Extract(Blueprint[ExtractConfig]):
    supports_params = True

    def render(self, config: ExtractConfig) -> TaskGroup:
        with TaskGroup(group_id=self.step_id) as group:
            BashOperator(
                task_id="run_query",
                bash_command=f"run-etl --query {self.param('query')} --batch {self.param('batch_size')}"
            )
        return group

Using self.resolve_config() in Python Callables

For @task or PythonOperator callables, use self.resolve_config() to merge runtime params into config. It returns a new validated config instance:

class Extract(Blueprint[ExtractConfig]):
    supports_params = True

    def render(self, config: ExtractConfig) -> TaskGroup:
        bp = self  # capture reference for closure

        @task(task_id="run_query")
        def run_query(**context):
            resolved = bp.resolve_config(config, context)
            # resolved.query has the runtime override if one was provided
            execute(resolved.query, resolved.batch_size)

        with TaskGroup(group_id=self.step_id) as group:
            run_query()
        return group

Use self.param() for operators with template fields and self.resolve_config() for Python logic in @task functions; both can be combined in one blueprint.

How It Works

• Params are auto-generated from Pydantic config models and namespaced per step (e.g. step_name__field)
• YAML values become param defaults; Pydantic metadata (description, constraints, enum values) flows through to the Airflow trigger form
• Invalid overrides raise ValidationError at execution time

Trigger Form Customization

Pydantic field schema flows through to Airflow's trigger form. Control how each field renders with json_schema_extra:

class LoadConfig(BaseModel):
    query: str = Field(description="SQL to execute", json_schema_extra={"format": "multiline"})
    schedule_date: str = Field(default="2024-01-01", json_schema_extra={"format": "date"})

Supported format values include "multiline" (textarea), "date", "date-time", and "time" (pickers). Also usable: examples (dropdown with free text), values_display (human-readable labels for enum/example values), and description_md (Markdown descriptions).

Validation nuance: only Field constraints that map to JSON Schema (ge, le, pattern, min_length, max_length, Literal enums) are enforced in the trigger form. Custom @field_validator / @model_validator logic does not map to JSON Schema, so it runs only at build time and inside resolve_config() — not in the form. If custom validators enforce important constraints, call self.resolve_config() in your @task function so they run on overridden values.

Triggering with Overrides

Override params via the Airflow UI trigger form, or via the API using conf with the namespaced names:

curl -X POST /api/v2/dags/customer_pipeline/dagRuns \
  -d '{"conf": {"load__target_table": "staging.customers", "load__mode": "append"}}'

Post-Build Callbacks

Use on_dag_built to post-process DAGs after they are constructed. This is useful for adding tags, access controls, audit metadata, or any cross-cutting concern.

from pathlib import Path
from blueprint import build_all_dags

def add_audit_tags(dag, yaml_path: Path) -> None:
    dag.tags.append("managed-by-blueprint")
    dag.tags.append(f"source:{yaml_path.name}")

build_all_dags(on_dag_built=add_audit_tags)

The callback receives:

• dag — the constructed Airflow DAG object (mutable)
• yaml_path — the Path to the YAML file that defined the DAG

Validation Commands

Run CLI commands with uvx:

uvx --from airflow-blueprint blueprint <command>

Validation Workflow

# Check all YAML files
uvx --from airflow-blueprint blueprint lint

# Expected output for valid files:
# PASS customer_pipeline.dag.yaml (dag_id=customer_pipeline)

Versioning

When user needs to version blueprints for backwards compatibility:

Version Naming Convention

• v1: MyBlueprint (no suffix)
• v2: MyBlueprintV2
• v3: MyBlueprintV3

# v1 - original
class ExtractConfig(BaseModel):
    source_table: str

class Extract(Blueprint[ExtractConfig]):
    def render(self, config): ...

# v2 - breaking changes, new class
class ExtractV2Config(BaseModel):
    sources: list[dict]  # Different schema

class ExtractV2(Blueprint[ExtractV2Config]):
    def render(self, config): ...

Explicit Name and Version

As an alternative to the class name convention, blueprints can set name and version directly:

class MyCustomExtractor(Blueprint[ExtractV3Config]):
    name = "extract"
    version = 3

    def render(self, config): ...

This is useful when the class name doesn't follow the NameV{N} convention or when you want clearer control.

Using Versions in YAML

steps:
  # Pin to v1
  legacy_extract:
    blueprint: extract
    version: 1
    source_table: raw.data

  # Use latest (v2)
  new_extract:
    blueprint: extract
    sources: [{table: orders}]

Version Rules

• A blueprint's discovered versions must form a contiguous 1..N sequence. A gap (e.g. v1 and v3 with no v2) raises NonContiguousVersionError during discovery.
• Pinning a version that doesn't exist in YAML raises InvalidVersionError.

Schema Generation

Generate JSON schemas for editor autocompletion or external tooling:

# Generate schema for a blueprint (step template)
uvx --from airflow-blueprint blueprint schema extract -o extract.schema.json

# Generate schema for DAG-level YAML fields (dag_id, steps, + custom BlueprintDagArgs fields)
uvx --from airflow-blueprint blueprint schema --dag-args -o dag-args.schema.json

Use --dag-args (with no blueprint name) to generate the schema for DAG-level YAML fields — dag_id, steps, and any fields your custom BlueprintDagArgs exposes — rather than a single step template's config.

As of 0.3.0, each emitted schema includes a top-level templateType field — "blueprint" for a step template, "dag_args" for DAG-level fields — so consumers can tell them apart. The command emits raw JSON when piped or written via -o/--output (and pretty, syntax-highlighted JSON when run interactively), so > redirection produces valid JSON.

Astro Project Auto-Detection

After creating or modifying a blueprint, automatically check if the project is an Astro project by looking for a .astro/ directory (created by astro dev init).

If the project is an Astro project, automatically regenerate schemas without prompting:

mkdir -p blueprint/generated-schemas
# For each name from `blueprint list`:
#   uvx --from airflow-blueprint blueprint schema NAME -o blueprint/generated-schemas/NAME.schema.json
# Also emit the DAG-level args schema:
#   uvx --from airflow-blueprint blueprint schema --dag-args -o blueprint/generated-schemas/dag-args.schema.json

The Astro IDE reads blueprint/generated-schemas/ to render configuration forms. Keeping schemas in sync ensures the visual builder always reflects the latest blueprint configs.

If you cannot determine whether the project is an Astro project, ask the user once and remember for the rest of the session.

Troubleshooting

"Blueprint not found"

Cause: Blueprint class not in Python path.

Fix: Check template directory or use --template-dir:

uvx --from airflow-blueprint blueprint list --template-dir dags/templates/

"Extra inputs are not permitted"

Cause: YAML field name typo with extra="forbid" enabled.

Fix: Run uvx --from airflow-blueprint blueprint describe <name> to see valid field names.

DAG not appearing in Airflow

Cause: Missing or broken loader — including a loader that imports the deprecated build_all, which Airflow safe-mode may skip.

Fix: Ensure dags/loader.py exists and calls build_all_dags():

from blueprint import build_all_dags
build_all_dags()

"ModuleNotFoundError: No module named 'airflow.providers.X'" from blueprint list/lint/schema

Cause: The standalone uvx --from airflow-blueprint CLI environment doesn't include Airflow provider packages that your Astro Runtime project has. A template importing provider operators can't be imported by the CLI. This is the CLI's isolated environment, not your project.

Fix: Add --with apache-airflow-providers-X to the uvx invocation (common: apache-airflow-providers-standard, -google, -snowflake):

uvx --from airflow-blueprint --with apache-airflow-providers-snowflake blueprint lint

Validation errors shown as Airflow import errors

As of v0.2.0, Pydantic validation errors are surfaced as Airflow import errors with actionable messages instead of being silently swallowed. The error message includes details on missing fields, unexpected fields, and type mismatches, along with guidance to run blueprint lint or blueprint describe.

"Cyclic dependency detected"

Cause: Circular depends_on references.

Fix: Review step dependencies and remove cycles.

"MultipleDagArgsError"

Cause: More than one BlueprintDagArgs subclass discovered in the project.

Fix: Only one BlueprintDagArgs subclass is allowed. Remove or merge duplicates.

"NonContiguousVersionError" / "InvalidVersionError"

Cause: A blueprint's versions don't form a contiguous 1..N sequence (NonContiguousVersionError), or YAML pins a version that doesn't exist (InvalidVersionError).

Fix: Ensure versions increment by one with no gaps; run uvx --from airflow-blueprint blueprint list to see available versions.

"non-YAML-compatible fields" (TypeError at import)

Cause: A config field uses a type Blueprint rejects since 0.3.0 — a multi-type union (e.g. str | int), bare Any, or dict[str, Any].

Fix: Use a single, explicit type. Optional[X] / X | None is still allowed. See Creating Blueprints → Config Field Types Must Be YAML-Compatible.

Debugging in Airflow UI

Every Blueprint task has extra fields in Rendered Template:

• blueprint_step_config - resolved YAML config
• blueprint_step_code - Python source of blueprint

Verification Checklist

Before finishing, verify with user:

• blueprint list shows their templates
• blueprint lint passes (run it bare to scan all *.dag.yaml recursively, or pass a specific file — passing a directory path fails with Is a directory)
• dags/loader.py exists with build_all_dags()
• DAG appears in Airflow UI without parse errors

Reference

• GitHub: https://github.com/astronomer/blueprint
• PyPI: https://pypi.org/project/airflow-blueprint/

Astro IDE

• Astro IDE Blueprint docs: https://docs.astronomer.io/astro/ide-blueprint