Bedrock vs. the direct Anthropic API
Calling Claude through Bedrock differs from Anthropic's client SDKs in several concrete ways, all sourced from Anthropic's own Bedrock doc and AWS's documentation:
Authentication
The direct Anthropic API uses a single portable ANTHROPIC_API_KEY bearer header. Bedrock's primary auth path is AWS SigV4 request signing via standard AWS credential resolution (~/.aws/credentials, AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY, or temporary session-token credentials). Bedrock also supports bearer-token auth as an alternative (via AWS_BEARER_TOKEN_BEDROCK), useful in corporate environments that want to avoid managing full IAM credentials -- but bearer-token auth is only supported in the C#, Go, and Java SDKs; the PHP, Python, TypeScript, and Ruby SDKs use SigV4 signing only.
Model IDs
Bedrock uses provider-prefixed, and in many cases date-versioned, model ID strings such as anthropic.claude-opus-4-5-20251101-v1:0, rather than the direct API's short public names. The newest releases (Opus 4.6, Sonnet 4.6) have dropped the ARN version suffix (anthropic.claude-opus-4-6-v1, anthropic.claude-sonnet-4-6), and Claude Opus 4.7 has no ARN-versioned ID at all, served instead through the same infrastructure as the Messages-API Bedrock endpoint.
Regions and endpoint types
Starting with Sonnet 4.5 and later, Bedrock offers global endpoints (dynamic routing, no premium) and regional/CRIS endpoints (guaranteed routing through US/EU/Japan/Australia, 10% pricing premium) -- a distinction that has no equivalent on the direct API. See cross-region inference.
Guardrails and Provisioned Throughput
Amazon Bedrock Guardrails (content filters, PII detection, topic restrictions) and Provisioned Throughput (dedicated Model-Unit capacity, hourly-billed) are both AWS infrastructure-level features layered on top of the model, with no direct-API equivalent.
Source: platform.claude.com/docs/en/build-with-claude/claude-on-amazon-bedrock, live-fetched 2026-07-01/07-02. See also the full fact catalog for every cited claim.