fix: fix count tokens for bedrock models#2254
Merged
mehtarac merged 3 commits intostrands-agents:mainfrom May 6, 2026
Merged
Conversation
Codecov Report✅ All modified and coverable lines are covered by tests. 📢 Thoughts on this report? Let us know! |
opieter-aws
approved these changes
May 6, 2026
![github-actions[bot]](https://avatars.githubusercontent.com/in/15368?s=60&v=4){kind=small}
|
Assessment: Comment The fix correctly addresses the root cause — tiktoken's network-dependent encoding download causing hangs in isolated VPCs. The approach of simplifying to a character-based heuristic is sound, since the Bedrock-native Review Details
The change is well-scoped and the test updates correctly validate the new heuristic behavior. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Description
When BedrockModel uses a cross-region inference profile (e.g., us.anthropic.claude-sonnet-4-6), the CountTokens API returns
ValidationException. The SDK then falls back to tiktoken, which attempts to download encoding files from the internet. In isolated VPCs (AgentCore, Lambda in private subnets), this download hangs per model call, blocking all agent invocations and causing pipeline timeouts.The change in this PR modifies the implementation where now the Bedrock token counting fallback path now uses a local heuristic estimator (character-based) instead of tiktoken when the native CountTokens API fails.
Related Issues
Documentation PR
Type of Change
Bug fix
New feature
Breaking change
Documentation update
Other (please describe):
Testing
How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli
hatch run prepareChecklist
By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.