Azure Deployment Preflight Validation

Validate ARM template deployments before execution by running what-if analysis, checking permissions, and generating a structured preflight report.

Adapted from github/awesome-copilot azure-deployment-preflight skill.

When to Use

• Before deploying infrastructure to Azure
• To preview what changes a deployment will make
• To verify permissions are sufficient for deployment
• As part of the template generation workflow (invoked by template generator)

Procedure

Step 1: Locate Template Files

Find the ARM template and parameters to validate:

# From deployment artifacts
DEPLOYMENT_ID="deploy-20260218-193500"
TEMPLATE=".azure/deployments/$DEPLOYMENT_ID/template.json"
PARAMETERS=".azure/deployments/$DEPLOYMENT_ID/parameters.json"

# Or from user-provided path
TEMPLATE="path/to/template.json"

Verify files exist before proceeding.

Step 1.5: Resource Availability Gate

Invoke /azure-resource-availability skill to validate all resources in the template before running what-if.

This catches issues that az deployment sub validate and what-if do NOT catch — such as:

• VM SKU restrictions per subscription/region
• Deprecated or LTS-only service versions (e.g., Kubernetes)
• API version incompatibilities (fields that don't exist in the chosen version)
• Quota limits that would be exceeded

# Parse template for resources to check
# For each resource: extract type, apiVersion, SKU, service version, region
# Pass to /azure-resource-availability

Gate behavior:

• ✅ PASSED → continue to Step 2
• ⚠️ WARNINGS → continue but include warnings in preflight report
• ❌ BLOCKED → STOP. Report blocking issues with alternatives. Do not proceed to what-if.

Save the availability report to .azure/deployments/$DEPLOYMENT_ID/availability-report.md.

Step 2: Validate Template Syntax

Check the ARM template is valid JSON and follows schema:

# Validate template syntax
az deployment sub validate \
  --location {location} \
  --template-file "$TEMPLATE" \
  --parameters @"$PARAMETERS" \
  --output json 2>&1

What to capture:

• Syntax errors with details
• Schema validation warnings
• Parameter validation issues

Step 3: Run What-If Analysis

Run what-if to preview resource changes without deploying:

# For subscription-level deployments (Git-Ape default)
az deployment sub what-if \
  --location {location} \
  --template-file "$TEMPLATE" \
  --parameters @"$PARAMETERS" \
  --result-format FullResourcePayloads \
  --output json 2>&1

Fallback: If permission errors occur, retry without RBAC validation:

az deployment sub what-if \
  --location {location} \
  --template-file "$TEMPLATE" \
  --parameters @"$PARAMETERS" \
  --result-format FullResourcePayloads \
  --no-prompt \
  --output json 2>&1

Note the fallback in the report.

Step 4: Parse What-If Results

Categorize resource changes from the what-if output:

Change Type	Symbol	Meaning
Create	➕	New resource will be created
Delete	➖	Resource will be deleted
Modify	✏️	Resource properties will change
NoChange	✅	Resource unchanged
Ignore	⏭️	Resource not analyzed
Deploy	🚀	Resource will be deployed (changes unknown)

For modified resources, capture the specific property changes:

Resource: Microsoft.Storage/storageAccounts/starnwkdhk
  ~ properties.minimumTlsVersion: "TLS1_0" → "TLS1_2"
  ~ tags.Environment: "staging" → "dev"

Step 5: Generate Preflight Report

Create a structured report saved to .azure/deployments/$DEPLOYMENT_ID/preflight-report.md:

# Preflight Validation Report

**Deployment ID:** {deployment-id}
**Validated:** {timestamp}
**Template:** {template-path}
**Scope:** Subscription-level

## Summary

| Check | Status |
|-------|--------|
| Template Syntax | ✅ Valid |
| Schema Compliance | ✅ Valid |
| What-If Analysis | ✅ Completed |
| Permission Check | ✅ Sufficient |

## What-If Results

### Resources to Create ({count})
| Resource Type | Name | Location |
|---------------|------|----------|
| Microsoft.Resources/resourceGroups | rg-xxx | eastus |
| Microsoft.Storage/storageAccounts | stxxx | eastus |

### Resources to Modify ({count})
| Resource | Property | Current | New |
|----------|----------|---------|-----|
| stxxx | minimumTlsVersion | TLS1_0 | TLS1_2 |

### Resources to Delete ({count})
{list or "None"}

### Resources Unchanged ({count})
{count resources with no changes}

## Issues Found

### Errors
{any blocking errors}

### Warnings
{any non-blocking warnings}

## Recommendations
- {actionable suggestions}

Step 6: Return Results

Return the preflight report to the calling agent. If any errors were found, recommend the user address them before deploying.

Save report to .azure/deployments/$DEPLOYMENT_ID/preflight-report.md.

Error Handling

Error Type	Action
Not logged in	Note in report, suggest az login
Permission denied	Fall back to no-RBAC validation, note in report
Template syntax error	Include all errors, mark as blocking
Resource group not found	Note in report (RG may be created by template)
API version issues	Note in report, suggest updating

Key principle: Continue validation even when errors occur. Capture all issues in the final report.

Integration

Called by template generator after generating ARM template:

Template Generator → /azure-deployment-preflight → Preflight Report → User Confirmation

Manual invocation:

User: /azure-deployment-preflight --deployment-id deploy-20260218-193500

Agent: Running preflight validation...
[Validates template, runs what-if, generates report]