SAM Doctor

ERROR REFERENCE

Character sets beyond ASCII are not supported

A resource handler rejected a property value because it contains a character outside ASCII - an em dash, an arrow, or a smart quote that looks completely ordinary in an editor. The template is syntactically valid; one character in one value is not.

WHAT IT MEANS

What this error means

The evidence line names the rejected parameter or property, for example Value (Pre-deploy Lambda → RDS plus VPC endpoints) for parameter GroupDescription is invalid. Character sets beyond ASCII are not supported. That property's documented character set does not include the pasted character, even though it can be invisible on screen - copied from a design document, a word processor, or a chat message. This is a different failure from a value that is merely too long or otherwise malformed; those keep producing the generic resource-failure finding instead.

FIX

How to fix it

  1. Identify the rejected property named in the evidence line, and find the exact template or generated source (including any Fn::Sub or parameter input) that produced the value. If a SAM build artifact was deployed, check .aws-sam/build/template.yaml too.
  2. Find the character instead of retyping the value blind: 
    python -c "from pathlib import Path; p=Path('template.yaml'); print([n for n,s in enumerate(p.read_text(encoding='utf-8').splitlines(),1) if not s.isascii()])"
  3. Replace the character with wording the property's documented character set allows - use to, not →, rather than deleting the value.
  4. Confirm the failed resource before changing the template: 
    aws cloudformation describe-stack-events --stack-name my-app

AUTOMATE THE TRIAGE

Diagnose this automatically

SAM Doctor recognizes the non-ASCII rejection (high confidence) and hands every other resource failure in the same log to the generic CREATE_FAILED / UPDATE_FAILED finding instead. Runs locally; no AWS access, no log upload. 

python -m pip install sam-doctor
sam-doctor diagnose deployment.log --format markdown

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