platform-engineering-labs/formae-patch

Patch Infrastructure (Patch Mode)

Use the apply_forma MCP tool in patch mode for urgent targeted changes.

How Patch Works

Patch only applies the changes explicitly specified in the forma file. Other resources are untouched. Use this for:

• Incident response (scaling up during traffic spikes)
• Urgent security fixes
• Quick configuration changes
• Any situation where a full reconcile is inappropriate

Workflow

1. Help the user identify the resource(s) to modify
2. Create or locate a minimal forma file with only the targeted change
3. Always simulate first: call apply_forma with mode: patch, simulate: true
4. Show exactly what will change
5. Ask for explicit confirmation
6. If confirmed: call apply_forma with mode: patch, simulate: false
7. Poll get_command_status to monitor progress:
   • Wait 5 seconds between polls (sleep 5). Do NOT poll in a tight loop.
   • Only report state transitions — do NOT print anything unless a resource changed status since the last poll. Silently poll until something changes.
   • When reporting, summarize what changed rather than dumping the full JSON.
8. Report results

Post-Patch Reminder

After a successful patch, always remind the user:

This patch will appear as drift until you reconcile your IaC code. When the incident is resolved, consider running /formae-fix-code-drift to incorporate this change into your codebase.

Important

• NEVER use pkl eval to evaluate forma files — ALWAYS use formae eval --output-consumer machine. Forma files use formae-specific extensions that only the formae CLI can resolve, and --output-consumer machine ensures parseable output instead of human-formatted text.
• NEVER skip the simulation step
• NEVER apply without user confirmation
• Patches are for urgency. For planned changes, use /formae-apply