Definition: Plan diff
A plan diff is the preview kernstack plan produces before any deploy: the creates, updates, and deletes the new stack.json would cause — with deletes listed under “Will delete” and refused until a person passes --confirm-destructive. It is also available as kernstack plan --json.
What the plan shows
The plan compares the declared stack against the live environment and names the consequences in platform language: this route is new, this function changed, this table will be deleted. Creates and updates apply before deletes, so a rename reads as a rename instead of a loss. Nothing applies at plan time; the command is read-only by design and safe to run anywhere, including an agent’s terminal.
Why the diff is the governance object
Code review shows what changed in files; the plan shows what changes in the world. That second artifact is the one reviewers approve, the one agents can assert against (“no deletes in this change”), and the one a deploy gate can require to come from review-approved source. When an incident asks “who let this happen”, the plan attached to the change is the honest answer.
Frequently asked questions
No. It is a read-only comparison of the declared stack against the live environment. Only kernstack deploy applies a plan, and destructive entries additionally need --confirm-destructive from a human.
Yes — kernstack plan --json returns the change set structurally. Agents use it to verify their own work against instructions; CI can assert policies like “no deletes” before anyone is paged for approval.
Projects can set min_source_assurance so deploys require review-approved source. The approved plan — the exact change set a person saw — is then what the deploy is allowed to apply.
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