feat: add --express flag to sam deploy and sam sync#9106
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…n Express mode
CloudFormation Express mode completes stack operations ~4x faster by
returning once resource configuration is applied rather than waiting for
full stabilization. This adds --express/--no-express to both commands:
- sam deploy --express (opt-in, default false)
- sam sync --express (opt-in by default, default true)
When enabled, passes DeploymentConfig={"Mode":"EXPRESS","DisableRollback":...}
to CreateChangeSet/CreateStack/UpdateStack. The DisableRollback value inside
DeploymentConfig is controlled by the existing --disable-rollback flag.
Requires boto3/botocore >= 1.43.38 (PR #9084).
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https://github.com/aws/aws-sam-cli/actions/runs/28536766808 |
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After sync infra completes in express mode, log a warning that resources may still be stabilizing. The watch loop already handles transient errors gracefully (logs and continues), so users can re-save to retry.
Default express to false for sync (same as deploy) until public announcement. Added TODO to flip default after announcement. Also add express to sync help text grouping.
seshubaws
reviewed
Jul 1, 2026
| ) | ||
| kwargs = {"ChangeSetName": changeset_id, "StackName": stack_name} | ||
| if not express: | ||
| kwargs["DisableRollback"] = disable_rollback |
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does setting this explicitly overwrite what the user passes in for --on-failure?
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express has a new way to set DisableRollback, this is to keep DisableRollback for non express behavior, the new 394-397 is equal to old 381-383 behavior on non-express
seshubaws
approved these changes
Jul 1, 2026
vicheey
approved these changes
Jul 1, 2026
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PR description needs update to reflect that |
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updated, thanks |
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Which issue(s) does this change fix?
Adds support for CloudFormation Express mode in SAM CLI.
Why is this change necessary?
CloudFormation Express mode (announced Jun 30, 2026) completes stack operations ~4x faster by returning once resource configuration is applied, without waiting for full stabilization (traffic readiness, edge propagation, resource cleanup). SAM CLI should expose this capability to developers for faster iteration cycles.
How does it address the issue?
--express/--no-expressflag tosam deploy(default: off) andsam sync(default: off)DeploymentConfig={"Mode": "EXPRESS", "DisableRollback": <value>}to CloudFormation APIs (CreateChangeSet,CreateStack,UpdateStack)DisableRollbackinsideDeploymentConfigis controlled by the existing--disable-rollbackflagDisableRollback/OnFailurekwargs (CFN rejects them alongsideDeploymentConfig)--save-params(express = true/false)What side effects does this change have?
--expresswith an older botocore, CFN returns anInvalidParameterValueerror (self-explanatory) -> this is rare, if user install from pip or from our installer it will come with correct botocore version.Mandatory Checklist
PRs will only be reviewed after checklist is complete
make prpassesmake update-reproducible-reqsif dependencies were changedBy submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.