bedrockstack

Low-level Python ergonomics for AWS Bedrock + Anthropic Claude. Three primitives every team building on Bedrock ends up rewriting from scratch:

1. RetryPolicy — Bedrock-aware backoff that knows the difference between a ThrottlingException (retry), a ModelNotReadyException (wait longer), and a ValidationException (never retry).
2. Ledger — thread-safe cost tracking with scope tags, grouped totals, and Anthropic-on-Bedrock pricing baked in (override per Ledger(prices=...)).
3. wrap_stream() — normalize the streaming-error parity gap between AnthropicBedrock and the native Anthropic client into a single exception hierarchy.

This is the layer above boto3.client('bedrock-runtime'), not a replacement. Sibling library: bedrockcache for prompt-caching audits.

Install

pip install bedrockstack

Zero runtime dependencies. Works alongside whatever Bedrock client you already use (boto3, AnthropicBedrock, LiteLLM, Strands).

Retries

import boto3
from bedrockstack import bedrock_default

bedrock = boto3.client("bedrock-runtime", region_name="us-east-1")
policy = bedrock_default()  # 6 attempts, 0.5s..30s exponential w/ jitter

response = policy.call(
    lambda: bedrock.converse(modelId="anthropic.claude-sonnet-4-5-v1:0", ...)
)

What it does and doesn't retry:

Retries	Never retries
ThrottlingException	ValidationException
ServiceUnavailableException	AccessDeniedException
InternalServerException	ResourceNotFoundException
ModelNotReadyException (with longer initial delay)	InvalidRequestException
ModelTimeoutException	ModelErrorException
ModelStreamErrorException	(anything else not in the retryable list)
ServiceQuotaExceededException
Connection / read timeouts (matched by class name)

Cost ledger

from bedrockstack import Ledger, Usage

led = Ledger()

with led.scope(user_id="abc", feature="rag"):
    led.record(
        model="anthropic.claude-sonnet-4-5-v1:0",
        usage=Usage(input_tokens=10_000, output_tokens=2_000,
                    cache_read_input_tokens=8_000),
    )

print(led.dollars(user_id="abc"))             # 0.027
print(led.dollars(feature="rag"))             # 0.027
print(led.totals(group_by="model"))           # {'anthropic.claude-sonnet-4-5-v1:0': 0.027}

Inference-profile model IDs (us.anthropic.claude-...) and LiteLLM-style prefixes (bedrock/anthropic.claude-...) are normalized automatically.

To override prices when AWS rebases:

from bedrockstack import Ledger, ModelPrice
led = Ledger(prices={
    "anthropic.claude-sonnet-4-5-v1:0": ModelPrice(0.0025, 0.0125, 0.00025, 0.003125),
})

Streaming-error normalization

from anthropic import AnthropicBedrock
from bedrockstack import wrap_stream, StreamOverloadedError, StreamRateLimitError

client = AnthropicBedrock()
stream = client.messages.create(model="anthropic.claude-sonnet-4-5-v1:0",
                                stream=True, messages=[...])

try:
    for event in wrap_stream(stream):
        ...
except StreamOverloadedError:
    # 529 mid-stream — back off long
    ...
except StreamRateLimitError:
    # 429 mid-stream — back off short
    ...

The same wrap_stream() works against the native Anthropic client and AnthropicBedrock. You handle one set of exceptions instead of two.

What it explicitly is not

• Not an agent framework. Use Strands or pydantic-ai for that.
• Not a router. LiteLLM exists.
• Not a prompt-caching auditor — that's bedrockcache.
• Bedrock + Anthropic-only. No OpenAI / Vertex / Azure surface.

Sibling libraries

Three independent libraries that compose around Anthropic-on-Bedrock:

• bedrockcache — static auditor for prompt caching.
• bedrockstack (this) — retry policy, cost ledger, streaming-error normalization.
• ragvitals — 5-dim drift detection for the RAG pipelines these models live inside.

Roadmap

• v0.2: ToolRunner with AnthropicBedrock parity (matches the native client's messages.tool_runner).
• v0.3: BedrockClient wrapper that bundles retry + ledger + streaming around a boto3 client.
• v0.4: region failover for inference-profile model IDs.
• v0.5: SageMaker Async Inference helper.

Develop

pip install -e ".[dev]"
pytest -v

License

MIT