ok this is new.. pulumi dies while previewing an update

panic: fatal: An assertion has failed

goroutine 144 [running]:
<http://github.com/pulumi/pulumi/sdk/v3/go/common/util/contract.failfast(...)|github.com/pulumi/pulumi/sdk/v3/go/common/util/contract.failfast(...)>
        /Users/runner/work/pulumi/pulumi/sdk/go/common/util/contract/failfast.go:23
<http://github.com/pulumi/pulumi/sdk/v3/go/common/util/contract.Assert(...)|github.com/pulumi/pulumi/sdk/v3/go/common/util/contract.Assert(...)>
        /Users/runner/work/pulumi/pulumi/sdk/go/common/util/contract/assert.go:26
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.NewDeleteReplacementStep|github.com/pulumi/pulumi/pkg/v3/resource/deploy.NewDeleteReplacementStep>(0xc0004116b0, 0xc001058ea0, 0x80)
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/step.go:306 +0x16c
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).generateStepsFromDiff(0xc000647320|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).generateStepsFromDiff(0xc000647320>, {0x7f17ebbb5258, 0xc001f7cdf0}, {0xc002a3c870, 0x0}, 0xc000cb77a0, 0xc0005e9b00, 0xc0009763c0, 0xc0019d6480, 0xc001aa9f80, ...)
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/step_generator.go:835 +0x1445
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).generateSteps(0xc000647320|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).generateSteps(0xc000647320>, {0x7f17ebbb5258, 0xc001f7cdf0})
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/step_generator.go:622 +0x1cf2
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).GenerateSteps(0xc000647320|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).GenerateSteps(0xc000647320>, {0x7f17ebbb5258, 0xc001f7cdf0})
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/step_generator.go:190 +0x46
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).handleSingleEvent(0xc0006292a8|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).handleSingleEvent(0xc0006292a8>, {0x2205760, 0xc001f7cdf0})
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/deployment_executor.go:447 +0xe5
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).Execute.func3(0xc00067d800|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).Execute.func3(0xc00067d800>, 0xc0006292a8, 0xc001e4c080, {0x2242b50, 0xc001e2e400}, 0x0, 0x0, {0x2242bf8, 0xc001a46420})
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/deployment_executor.go:284 +0x273
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).Execute(0xc0006292a8|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).Execute(0xc0006292a8>, {0x2242bf8, 0xc001a46420}, {{0x7f17eb8e7180, 0xc000fc11e0}, 0x7fffffff, 0x0, 0x0, {0x3230378, 0x0, ...}, ...}, ...)
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/deployment_executor.go:300 +0x99f
<http://github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*Deployment).Execute(0xc0004116b0|github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*Deployment).Execute(0xc0004116b0>, {0x2242bf8, 0xc001a46420}, {{0x7f17eb8e7180, 0xc000fc11e0}, 0x7fffffff, 0x0, 0x0, {0x3230378, 0x0, ...}, ...}, ...)
        /Users/runner/work/pulumi/pulumi/pkg/resource/deploy/deployment.go:432 +0xd0
<http://github.com/pulumi/pulumi/pkg/v3/engine.(*deployment).run.func1()|github.com/pulumi/pulumi/pkg/v3/engine.(*deployment).run.func1()>
        /Users/runner/work/pulumi/pulumi/pkg/engine/deployment.go:269 +0x250
created by <http://github.com/pulumi/pulumi/pkg/v3/engine.(*deployment).run|github.com/pulumi/pulumi/pkg/v3/engine.(*deployment).run>
        /Users/runner/work/pulumi/pulumi/pkg/engine/deployment.go:252 +0x365