I'm getting this while attempting to import. Not sure where to start with this one......

panic: fatal: An assertion has failed: could not determine index for resource urn:pulumi:cp3-use2::hubspoke::co:aws:ncd:hub$co:aws:ncd:hubvpcattach$aws:ec2transitgateway/vpcAttachment:VpcAttachment::cp3b-attach-vpc-egress-attach

goroutine 92 [running]:
github.com/pulumi/pulumi/sdk/v3/go/common/util/contract.failfast(...)
        github.com/pulumi/pulumi/sdk/v3@v3.198.0/go/common/util/contract/failfast.go:23
github.com/pulumi/pulumi/sdk/v3/go/common/util/contract.Assertf(0x60?, {0x7ff6877cba02?, 0x7ff684e3c101?}, {0xc001a4e8f0?, 0x7ff684e3c3b3?, 0xc001a4e768?})
        github.com/pulumi/pulumi/sdk/v3@v3.198.0/go/common/util/contract/assert.go:35 +0xe8
github.com/pulumi/pulumi/pkg/v3/resource/graph.(*DependencyGraph).DependingOn(0xc001cc03f0, 0xc0033f2700, 0xc001a4ea98, 0x0)
        github.com/pulumi/pulumi/pkg/v3/resource/graph/dependency_graph.go:60 +0x13c
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).calculateDependentReplacements(0xc001ce8240, 0xc0033f2700)
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/step_generator.go:2977 +0x251
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).continueStepsFromDiff(0xc001ce8240, {0x7ff687f328a0, 0xc0032ad110})
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/step_generator.go:1828 +0x109b
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).generateStepsFromDiff(0xc001ce8240, {0x205765002a0, 0xc0028c8300}, {0xc003915d60, 0x9e}, 0xc0033f2700, 0xc0022e4fc0, 0x199?, 0x199?, 0xc001b19110, ...)
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/step_generator.go:1617 +0x4c5
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).continueStepsFromImport(0xc001ce8240, {0x7ff687f356b8, 0xc0028c8300})
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/step_generator.go:1563 +0x1f34
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*stepGenerator).ContinueStepsFromImport(0xc001ce8240, {0x7ff687f356b8?, 0xc0028c8300?})
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/step_generator.go:1050 +0x25
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).handleSingleEvent(0xc001cc1560, {0x7ff687eff280, 0xc0028c8300})
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/deployment_executor.go:563 +0x465
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).Execute.func4(0xc001ca1880, 0xc001cc1560, 0xc002094e30, 0xc001ca1960, {0x7ff687f23f38, 0xc001cadc70}, {0x7ff687f23f00, 0xc001cc09f0})
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/deployment_executor.go:278 +0x2e9
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*deploymentExecutor).Execute(0xc001cc1560, {0x7ff687f23f00, 0xc001cc09f0})
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/deployment_executor.go:343 +0x6be
github.com/pulumi/pulumi/pkg/v3/resource/deploy.(*Deployment).Execute(...)
        github.com/pulumi/pulumi/pkg/v3/resource/deploy/deployment.go:699
github.com/pulumi/pulumi/pkg/v3/engine.(*deployment).run.func1()
        github.com/pulumi/pulumi/pkg/v3/engine/deployment.go:375 +0x88
created by github.com/pulumi/pulumi/pkg/v3/engine.(*deployment).run in goroutine 1
        github.com/pulumi/pulumi/pkg/v3/engine/deployment.go:374 +0x1b8

libraries:

Arpeggio==2.0.2
attrs==24.3.0
debugpy==1.8.12
dill==0.3.9
grpcio==1.75.1
parver==0.5
protobuf==5.29.5
pulumi==3.199.0
pulumi_archive==0.3.4
pulumi_aws==7.7.0
pulumi_aws_native==1.35.0
pulumi_std==2.2.0
PyYAML==6.0.2
semver==3.0.4
setuptools==75.8.0
six==1.17.0
typing_extensions==4.15.0
wheel==0.45.1

Hey, this looks very much like a bug, can you please open an issue in https://github.com/pulumi/pulumi? You could try to upgrade your pulumi version - it might fix it

It seems very similar to this: https://github.com/pulumi/pulumi/issues/20169

It does, can you ping Fraser or Thomas on the issue? If you have a repro, that'd be valuable too