Configuration¶

a2akit reads settings from environment variables prefixed with A2AKIT_. Every setting has a sensible default; explicit constructor parameters always take priority.

Environment Variables¶

Variable	Default	Description
`A2AKIT_BLOCKING_TIMEOUT`	`30.0`	Seconds `message:send` blocks for a result
`A2AKIT_CANCEL_FORCE_TIMEOUT`	`60.0`	Seconds before force-cancel kicks in
`A2AKIT_MAX_CONCURRENT_TASKS`	(none)	Worker parallelism (`None` = unlimited)
`A2AKIT_MAX_RETRIES`	`3`	Broker retry attempts on worker crash
`A2AKIT_BROKER_BUFFER`	`1000`	InMemoryBroker queue depth
`A2AKIT_EVENT_BUFFER`	`200`	InMemoryEventBus fan-out buffer per task
`A2AKIT_LOG_LEVEL`	(unset)	Root `a2akit` logger level (e.g. `DEBUG`)
`A2AKIT_PUSH_MAX_RETRIES`	`3`	Max webhook delivery attempts
`A2AKIT_PUSH_RETRY_DELAY`	`1.0`	Base delay between retries (exponential backoff)
`A2AKIT_PUSH_TIMEOUT`	`10.0`	HTTP timeout for webhook delivery
`A2AKIT_PUSH_MAX_CONCURRENT`	`50`	Max concurrent webhook deliveries
`A2AKIT_PUSH_ALLOW_HTTP`	`False`	Allow HTTP webhook URLs (dev only)

Redis Settings¶

These settings apply when using the Redis broker, event bus, or cancel registry (pip install a2akit[redis]).

Variable	Default	Description
`A2AKIT_REDIS_URL`	`redis://localhost:6379/0`	Default Redis connection URL
`A2AKIT_REDIS_KEY_PREFIX`	`a2akit:`	Key prefix for multi-tenant isolation
`A2AKIT_REDIS_BROKER_STREAM`	`tasks`	Stream name for the broker queue
`A2AKIT_REDIS_BROKER_GROUP`	`workers`	Consumer group name
`A2AKIT_REDIS_BROKER_CONSUMER_PREFIX`	`worker`	Consumer name prefix (hostname+PID appended)
`A2AKIT_REDIS_BROKER_BLOCK_MS`	`5000`	XREADGROUP block timeout (ms)
`A2AKIT_REDIS_BROKER_CLAIM_TIMEOUT_MS`	`60000`	XAUTOCLAIM idle threshold (ms)
`A2AKIT_REDIS_EVENT_BUS_CHANNEL_PREFIX`	`events:`	Pub/Sub channel prefix
`A2AKIT_REDIS_EVENT_BUS_STREAM_PREFIX`	`eventlog:`	Replay stream prefix
`A2AKIT_REDIS_EVENT_BUS_STREAM_MAXLEN`	`1000`	Max replay stream length per task
`A2AKIT_REDIS_CANCEL_KEY_PREFIX`	`cancel:`	Cancel flag key prefix
`A2AKIT_REDIS_CANCEL_TTL_S`	`86400`	Cancel key TTL in seconds (24h)

Priority¶

Settings are resolved in this order (highest priority first):

Constructor parameter — explicit values passed to A2AServer()
Environment variable — A2AKIT_* prefix
Built-in default — hardcoded in Settings

Constructor > Env-Var > Default

Example¶

Set environment variables:

export A2AKIT_BLOCKING_TIMEOUT=10
export A2AKIT_LOG_LEVEL=DEBUG
export A2AKIT_MAX_CONCURRENT_TASKS=4

Programmatic Override¶

Use Settings() to override defaults programmatically:

from a2akit import A2AServer, Settings

custom = Settings(blocking_timeout=5.0, max_retries=5)
server = A2AServer(worker=..., agent_card=..., settings=custom)

Settings Class¶

from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    model_config = SettingsConfigDict(env_prefix="A2AKIT_")

    blocking_timeout: float = 30.0
    cancel_force_timeout: float = 60.0
    max_concurrent_tasks: int | None = None
    max_retries: int = 3
    broker_buffer: int = 1000
    event_buffer: int = 200
    log_level: str | None = None

    # Redis
    redis_url: str = "redis://localhost:6379/0"
    redis_key_prefix: str = "a2akit:"
    redis_broker_stream: str = "tasks"
    redis_broker_group: str = "workers"
    redis_broker_consumer_prefix: str = "worker"
    redis_broker_block_ms: int = 5000
    redis_broker_claim_timeout_ms: int = 60000
    redis_event_bus_channel_prefix: str = "events:"
    redis_event_bus_stream_prefix: str = "eventlog:"
    redis_event_bus_stream_maxlen: int = 1000
    redis_cancel_key_prefix: str = "cancel:"
    redis_cancel_ttl_s: int = 86400  # 24h

    # Push notification settings
    push_max_retries: int = 3
    push_retry_delay: float = 1.0
    push_timeout: float = 10.0
    push_max_concurrent: int = 50
    push_allow_http: bool = False
    push_idle_timeout: float = 300.0

The Settings class uses pydantic-settings for automatic environment variable binding.

A2AServer Constructor Parameters¶

These constructor parameters override Settings values:

Parameter	Settings Field	Description
`blocking_timeout_s`	`blocking_timeout`	Blocking timeout in seconds
`cancel_force_timeout_s`	`cancel_force_timeout`	Force-cancel timeout
`max_concurrent_tasks`	`max_concurrent_tasks`	Worker parallelism
`push_max_retries`	`push_max_retries`	Webhook delivery retries
`push_retry_delay`	`push_retry_delay`	Retry base delay
`push_timeout`	`push_timeout`	Webhook HTTP timeout
`push_max_concurrent`	`push_max_concurrent`	Concurrent delivery limit
`push_allow_http`	`push_allow_http`	Allow HTTP webhook URLs
`push_idle_timeout`	`push_idle_timeout`	Idle timeout for delivery queues
`push_allowed_hosts`	—	Hostname allowlist (constructor only)
`push_blocked_hosts`	—	Hostname blocklist (constructor only)

Development vs. Production

For development, the defaults work well. For production, consider:

Setting A2AKIT_MAX_CONCURRENT_TASKS to limit resource usage
Reducing A2AKIT_BLOCKING_TIMEOUT for faster client feedback
Setting A2AKIT_LOG_LEVEL=INFO for structured logging