Testing the Resumed "Claude Fable 5" on Amazon Bedrock
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Introduction
On June 12, 2026, access to Claude Fable 5 and Mythos 5 was suspended due to U.S. government export controls. After an interruption of about three weeks, the export controls were lifted on June 30, and service resumed on July 1.
According to Anthropic's official blog, the circumstances of the suspension were as follows. Amazon researchers reported a technique for bypassing Fable 5's safeguards, and the U.S. government applied export controls. After consulting with the government, Anthropic trained a new safety classifier and improved it to block the reported technique in more than 99% of cases.
In this article, we verify the behavior on Amazon Bedrock after service resumption and check how the region rollout has changed since the previous article (as of 2026-06-10).
Changes since the previous article (6/10)
| Item | Previous article (6/10) | Current (7/1) |
|---|---|---|
| Model status | ACTIVE → suspended on 6/12 | ACTIVE |
| Model-providing regions (ACTIVE) | us-east-1, eu-north-1 | us-east-1, us-east-2, us-west-2, eu-west-1, ap-northeast-1 |
| US inference profile routing destinations | Not verified | us-east-1, us-east-2, us-west-2 |
| Mantle support | Out of scope for verification | Cannot be invoked within the scope of verification (404 in all regions) |
| Safeguards | Initial version | New safety classifier added (blocks the reported technique at 99%+) |
Verification details
The verification environment is as follows.
- Regions: us-east-1 (Converse API), ap-northeast-1 (Global profile attempt)
- Model ID:
us.anthropic.claude-fable-5(US cross-region inference profile) - Verification date and time: 2026-07-01 15:50 JST
- Prerequisites: Agreement / Data Retention were already configured in the previous article
Checking the region rollout
I used list-foundation-models to check whether the model exists in each region. The following is an example run in us-east-1. I switched --region and ran it in each region.
aws bedrock list-foundation-models \
--query "modelSummaries[?contains(modelId, 'fable')].{modelId:modelId,status:modelLifecycle.status}" \
--output table \
--region us-east-1
In the previous article, there were only two regions, us-east-1 and eu-north-1, but the model was now ACTIVE in five regions.
| Region | Status |
|---|---|
| us-east-1 | ACTIVE |
| us-east-2 | ACTIVE |
| us-west-2 | ACTIVE |
| eu-west-1 | ACTIVE |
| ap-northeast-1 | ACTIVE |
I also checked the routing destinations of the US inference profile.
aws bedrock list-inference-profiles \
--query "inferenceProfileSummaries[?contains(inferenceProfileId, 'fable')]" \
--region us-east-1
The US profile (us.anthropic.claude-fable-5) routes to three regions: us-east-1, us-east-2, and us-west-2. A Global profile (global.anthropic.claude-fable-5) also exists, but as described below, I could not confirm that it worked at the time of verification.
Running inference with the Converse API
US profile (success)
aws bedrock-runtime converse \
--model-id "us.anthropic.claude-fable-5" \
--messages '[{"content":[{"text":"Hello! Reply with exactly one sentence confirming your model name."}],"role":"user"}]' \
--inference-config '{"maxTokens":100}' \
--region us-east-1
Full response
{
"output": {
"message": {
"role": "assistant",
"content": [
{
"reasoningContent": {
"reasoningText": {
"text": "",
"signature": "CAISiAIKYAgPEAEYAipA..."
}
}
},
{
"text": "I am Claude, an AI assistant made by Anthropic."
}
]
}
},
"stopReason": "end_turn",
"usage": {
"inputTokens": 28,
"outputTokens": 49,
"totalTokens": 77,
"cacheReadInputTokens": 0
},
"metrics": {
"latencyMs": 2534
}
}
The Converse API call with the US profile succeeded. As in the previous article, the response contained reasoningContent and text. The latency was 2,534 ms and outputTokens was 49 (the count is higher than the visible text because it includes tokens for reasoningContent).
Global profile (success could not be confirmed at the time of verification)
I encountered two kinds of errors with the Global profile.
When invoked from us-east-1:
An error occurred (InternalServerException) when calling the Converse operation (reached max retries: 2):
The system encountered an unexpected error during processing. Try your request again.
I tried three times in total (including the SDK's automatic retries), and all returned the same InternalServerException.
When invoked from ap-northeast-1:
An error occurred (ValidationException) when calling the Converse operation:
The model returned the following errors: data retention mode 'default' is not available for this model
Regarding the InternalServerException, I tried three times under the same conditions and none succeeded, so I could not isolate the cause at the time of verification. The ValidationException is an error related to the Data Retention setting, but this verification alone was not enough to identify the cause.
Mantle (Anthropic-compatible endpoint)
I checked invocation via Bedrock Mantle (/anthropic/v1/messages), which was out of scope in the previous article.
from anthropic import AnthropicBedrockMantle
client = AnthropicBedrockMantle(aws_region='us-east-1')
response = client.messages.create(
model='anthropic.claude-fable-5',
max_tokens=64,
messages=[{'role': 'user', 'content': 'Hello! Reply in one sentence.'}]
)
anthropic.NotFoundError: Error code: 404 -
{'type': 'error', 'error': {'type': 'not_found_error',
'message': "The model 'anthropic.claude-fable-5' does not exist"}}
I tried the following regions and model ID patterns, and all returned 404.
| Region | Result |
|---|---|
| us-east-1 | 404 |
| us-west-2 | 404 |
| us-east-2 | 404 |
| eu-west-1 | 404 |
| ap-northeast-1 | 404 |
Model IDs tried: anthropic.claude-fable-5, claude-fable-5, us.anthropic.claude-fable-5, global.anthropic.claude-fable-5
At the time of verification, Fable 5 could not be invoked from Bedrock Mantle with the combinations of regions and model IDs I tried. You need to use it via the Converse API (bedrock-runtime).
Summary
I confirmed that Claude Fable 5 is available again on Amazon Bedrock. Via the US inference profile (us.anthropic.claude-fable-5), inference with the Converse API from us-east-1 succeeded.
According to list-foundation-models, the region rollout had expanded from the two regions in the previous article to five regions. I was also able to confirm that the US inference profile's routing destinations are the three regions us-east-1, us-east-2, and us-west-2.
On the other hand, although the Global profile exists, I could not confirm that it worked in this verification, and Bedrock Mantle returned 404 within the range I tried. At present, the only method confirmed to work in this verification is invoking the US inference profile with the Converse API from us-east-1.
