[Compute] Surface VMSS VM capacity reservation details

[Priyal-Saxena]

Preconditions

• No need to upgrade Python SDK or the Python SDK is ready.

Related command

az vmss create / az vmss update
  --disable-capacity-reservation-assignment

az vmss show --resource-group <resource-group> --name <vmss-name> --instance-id <instance-id>
  (surface capacityReservation.capacityReservationGroup.id)

az vmss get-instance-view --resource-group <resource-group> --name <vmss-name> --instance-id <instance-id>
  (surface capacityReservationType)

Resource Provider

Microsoft.Compute/virtualMachineScaleSets,
Microsoft.Compute/virtualMachineScaleSets/virtualMachines

Description of Feature or Work Requested

Add Azure CLI support for VM Scale Set capacity reservation assignment and VMSS VM capacity reservation outputs introduced in Compute API version 2026-04-01:

• Add --disable-capacity-reservation-assignment to az vmss create and az vmss update. This sets virtualMachineProfile.capacityReservation.disableCapacityReservationAssignment on the parent VMSS so its VM instances are explicitly opted out of implicit or explicit capacity reservation assignment and consume publicly available capacity. This is the opt-out counterpart to the existing --capacity-reservation-group option.
• Surface capacityReservation.capacityReservationGroup.id from the individual VMSS VM model-view response through az vmss show --instance-id. The group is inherited from the parent VMSS and cannot be changed on the individual VMSS VM.
• Surface capacityReservationType from the individual VMSS VM instance-view response through az vmss get-instance-view --instance-id. This indicates whether the instance consumes Targeted, Open, or Block reserved capacity, is NotEligible, or is explicitly Disabled.

This extends the Open Capacity Reservation work tracked in #33769 from standalone VMs to VMSS configuration and individual VMSS VM responses.

Minimum API Version Required

2026-04-01

Swagger PR link / SDK link

• Compute 2026-04-01: add capacityReservation to VirtualMachineScaleSetVM response azure-rest-api-specs#44684
• Compute 2026-04-01: add capacityReservationType to VMSS VM instance view azure-rest-api-specs#44682
• [OCR] Add Open Capacity Reservation SDK support azure-rest-api-specs#44376

Request Example

• VMSS VM model view with capacity reservation:
  https://github.com/Azure/azure-rest-api-specs/blob/compute-2026-04-01/specification/compute/resource-manager/Microsoft.Compute/Compute/stable/2026-04-01/examples/virtualMachineScaleSetExamples/VirtualMachineScaleSetVM_Get_WithCapacityReservation.json
• VMSS VM instance view with capacity reservation type:
  https://github.com/Azure/azure-rest-api-specs/blob/compute-2026-04-01/specification/compute/resource-manager/Microsoft.Compute/Compute/stable/2026-04-01/examples/virtualMachineScaleSetExamples/VirtualMachineScaleSetVM_Get_InstanceViewWithCapacityReservationType.json
• Shared capacity reservation profile with disableCapacityReservationAssignment:
  [OCR] Add Open Capacity Reservation SDK support azure-rest-api-specs#44376

Target Date

2026-08-15

PM Contact

N/A / TBD

Engineer Contact

Priyal Saxena (Priyal Saxena (@Priyal-Saxena))

Additional context

The REST API specification changes are merged into the compute-2026-04-01 feature branch and are pending promotion to main.

disableCapacityReservationAssignment and capacityReservationGroup represent opposing intents and should not be used together. For VMSS update scenarios, existing VMSS rollout behavior applies (for example, az vmss update-instances when required by the upgrade policy).

Feature flag for testing: Microsoft.Compute/OpenCapacityReservation.

[yonzhan]

Thank you for opening this issue, we will look into it.

[william051200]

Hi Priyal Saxena (@Priyal-Saxena) , I will be working on this feature. However, we noticed that the feature has not yet been merged into the main branch. To minimize development risk, we’ll begin implementation once it has been merged.

cc Julie Zhu (@yanzhudd)