Current limits - Averta

The Anthropic wrapper intentionally fails closed for unsupported inputs. That is not a nice-to-have; silently skipping a checkpoint would be a security bug.

Supported

Capability	Status
`client.messages.create(...)`	Supported for non-streaming calls.
Request preflight	Supported for latest user text and supported base64 images.
User-defined client tools	Supported when tools have a stable `name`.
Tool exposure filtering	Supported through request decisions and `restrict_tools`.
Tool-call checks	Supported for returned `tool_use` blocks.
Tool-result checks	Supported for pure tool-result continuation turns.
Output checks and rewrites	Supported for non-streaming final text.

Not Supported Yet

Input or API	Behavior
`messages.create({ stream: true })`	Fails closed before Anthropic is called.
`messages.stream(...)`	Fails closed before Anthropic is called.
URL image sources	Fails closed.
GIF images	Fails closed.
Document blocks	Fails closed.
Non-text tool-result blocks	Fails closed.
Mixed tool-result continuation turns	Fails closed.
Server-hosted Anthropic tools	Fails closed in the current wrapper.
Bedrock or Vertex Anthropic clients	Not covered by the current JavaScript wrapper docs.

Rich Media Rules

Supported image blocks must use:

{
  type: "image",
  source: {
    type: "base64",
    media_type: "image/jpeg", // or image/png, image/webp
    data: imageBase64,
  },
}

Any other media shape is rejected before request preflight.

Error Handling

Unsupported inputs and blocked checkpoints throw AvertaSdkError from @averta-security/sdk-core.

import { AvertaSdkError } from "@averta-security/sdk-core";

try {
  await client.messages.create({
    model: process.env.ANTHROPIC_MODEL ?? "claude-sonnet-4-5",
    max_tokens: 512,
    stream: true,
    messages: [{ role: "user", content: "Hello" }],
  });
} catch (error) {
  if (error instanceof AvertaSdkError) {
    console.error(error.code);
  }
}

Use non-streaming messages.create(...) when you need Averta request, tool, tool-result, and output checks around Anthropic today.