fix: support us-gov. and other multi-character Bedrock geo prefixes #3645

Leundai · 2025-12-04T18:06:41Z

Summary

The BedrockProvider.model_profile method previously only handled 2-character regional prefixes (e.g., us., eu.), causing issues with models using longer prefixes like us-gov. (AWS GovCloud) and global..

Problem

When using extended thinking with us-gov.anthropic.* models via Bedrock, the model_profile method doesn't recognize the us-gov. prefix because it only strips 2-character prefixes:

# Previous implementation:
parts = model_name.split('.', 2)
if len(parts) > 2 and len(parts[0]) == 2:
    parts = parts[1:]

This causes bedrock_send_back_thinking_parts to stay at its default False value. As a result, ThinkingPart blocks from previous conversation turns are converted to text blocks with thinking tags instead of reasoningContent, causing Bedrock to reject the request with:

Expected `thinking` or `redacted_thinking`, but found `text`

Solution

Added _strip_geo_prefix() helper function that properly handles all known geo prefixes including us-gov. and global.
Updated _AWS_BEDROCK_INFERENCE_GEO_PREFIXES constant to include us-gov. (the comment in the code already suggested this)
Added comprehensive parametrized tests for all 8 geo prefixes

Affected Models

us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0
us-gov.anthropic.claude-3-7-sonnet-20250219-v1:0
global.anthropic.claude-opus-4-5-20251101-v1:0
And any other cross-region inference profile using multi-character prefixes

Testing

All existing tests pass, plus new parametrized tests for all geo prefixes

The BedrockProvider.model_profile method previously only handled 2-character regional prefixes (e.g., 'us.', 'eu.'), causing issues with models using longer prefixes like 'us-gov.' (AWS GovCloud) and 'global.'. This caused extended thinking to fail in multi-turn conversations because bedrock_send_back_thinking_parts stayed at its default False value for these models. ThinkingPart blocks from previous turns were converted to text blocks instead of reasoningContent, causing Bedrock to reject requests with: 'Expected thinking or redacted_thinking, but found text' Changes: - Add _strip_geo_prefix() helper function to properly handle all known geo prefixes including us-gov. and global. - Update _AWS_BEDROCK_INFERENCE_GEO_PREFIXES to include us-gov. - Add comprehensive tests for all geo prefixes Fixes cross-region inference for AWS GovCloud environments.

Leundai · 2025-12-04T18:14:08Z

pydantic_ai_slim/pydantic_ai/providers/bedrock.py



+# Known geo prefixes for cross-region inference profile IDs
+_BEDROCK_GEO_PREFIXES: tuple[str, ...] = ('us.', 'eu.', 'apac.', 'jp.', 'au.', 'ca.', 'global.', 'us-gov.')


I think at some point it might be worth unifying this and the other private constant in models/bedrock.py

But this just extends it to support govcloud and global. Its been a real issue since Claude 4.5 came out and AWS doing cross-region inferencing

I think you should definitely not duplicate it, since we're already importing the BedrockModelProfile in models/bedrock.py we should make this public and import it there.

pydantic-ai/pydantic_ai_slim/pydantic_ai/models/bedrock.py

Line 46 in 8d111fe

from pydantic_ai.providers.bedrock import BedrockModelProfile

@DouweM do you agree?

dsfaccini

thank you for the PR @Leundai ! I've requested a couple changes, let me know if you have any questions.

dsfaccini · 2025-12-05T22:31:51Z

pydantic_ai_slim/pydantic_ai/providers/bedrock.py



+# Known geo prefixes for cross-region inference profile IDs
+_BEDROCK_GEO_PREFIXES: tuple[str, ...] = ('us.', 'eu.', 'apac.', 'jp.', 'au.', 'ca.', 'global.', 'us-gov.')


I think you should definitely not duplicate it, since we're already importing the BedrockModelProfile in models/bedrock.py we should make this public and import it there.

pydantic-ai/pydantic_ai_slim/pydantic_ai/models/bedrock.py

Line 46 in 8d111fe

from pydantic_ai.providers.bedrock import BedrockModelProfile

@DouweM do you agree?

dsfaccini · 2025-12-05T22:32:58Z

pydantic_ai_slim/pydantic_ai/providers/bedrock.py

-        # Handle regional prefixes (e.g. "us.")
-        if len(parts) > 2 and len(parts[0]) == 2:
-            parts = parts[1:]
+        # Strip regional/geo prefix if present (e.g. "us.", "eu.", "us-gov.", "global.")


you can remove this comment

dsfaccini · 2025-12-05T22:33:25Z

tests/providers/test_bedrock.py

    assert unknown_model is None
+
+
+@pytest.mark.parametrize('prefix', ['us.', 'eu.', 'apac.', 'jp.', 'au.', 'ca.', 'global.', 'us-gov.'])


can we use the BEDROCK_GEO_PREFIXES you defined above here?

dsfaccini · 2025-12-05T22:34:28Z

tests/providers/test_bedrock.py

+    assert isinstance(profile, BedrockModelProfile)
+    assert profile.bedrock_supports_tool_choice is True
+    assert profile.bedrock_send_back_thinking_parts is True


if these don't vary across models we don't need to test them, right? the test just tests that all prefixes are hadnled properly

dsfaccini · 2025-12-05T22:36:24Z

tests/providers/test_bedrock.py

+def test_bedrock_provider_model_profile_us_gov_anthropic(env: TestEnv, mocker: MockerFixture):
+    """Test that us-gov. prefixed Anthropic models get the correct profile.
+
+    This specifically tests the us-gov. prefix which was previously broken
+    because the provider only handled 2-character prefixes.
+    """
+    env.set('AWS_DEFAULT_REGION', 'us-east-1')
+    provider = BedrockProvider()
+
+    ns = 'pydantic_ai.providers.bedrock'
+    anthropic_model_profile_mock = mocker.patch(f'{ns}.anthropic_model_profile', wraps=anthropic_model_profile)
+
+    # Test us-gov. prefix (AWS GovCloud cross-region inference)
+    profile = provider.model_profile('us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0')
+    anthropic_model_profile_mock.assert_called_with('claude-sonnet-4-5-20250929')
+    assert isinstance(profile, BedrockModelProfile)
+    assert profile.bedrock_supports_tool_choice is True
+    assert profile.bedrock_send_back_thinking_parts is True
+
+    # Test global. prefix
+    profile = provider.model_profile('global.anthropic.claude-opus-4-5-20251101-v1:0')
+    anthropic_model_profile_mock.assert_called_with('claude-opus-4-5-20251101')
+    assert isinstance(profile, BedrockModelProfile)
+    assert profile.bedrock_supports_tool_choice is True
+    assert profile.bedrock_send_back_thinking_parts is True


we're already testing this above, aren't we?

let's add a test to check that we don't have any bedrock shorthand in KnownModelName with a geo prefix that we haven't added in the BEDROCK_GEO_PREFIXES

Leundai commented Dec 4, 2025

View reviewed changes

chore: trigger CI

5e4bf13

dsfaccini suggested changes Dec 5, 2025

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fix: support us-gov. and other multi-character Bedrock geo prefixes #3645

fix: support us-gov. and other multi-character Bedrock geo prefixes #3645

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		# Known geo prefixes for cross-region inference profile IDs
		_BEDROCK_GEO_PREFIXES: tuple[str, ...] = ('us.', 'eu.', 'apac.', 'jp.', 'au.', 'ca.', 'global.', 'us-gov.')

		assert unknown_model is None


		@pytest.mark.parametrize('prefix', ['us.', 'eu.', 'apac.', 'jp.', 'au.', 'ca.', 'global.', 'us-gov.'])

fix: support us-gov. and other multi-character Bedrock geo prefixes #3645

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fix: support us-gov. and other multi-character Bedrock geo prefixes #3645

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Leundai commented Dec 4, 2025 •

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