feat: refuse a target that is a neighbouring product's configuration home

[rldyourmnd]

Every command here takes an explicit --target because a change aimed at a guessed path is a change aimed at someone else's state. That rule binds this program. It does nothing about a caller who names the wrong place confidently — and Pi has a neighbour close enough to make that easy.

Measured, not inferred from the name

	package	command	home	reads
Pi Coding Agent	@earendil-works/pi-coding-agent	pi	~/.pi/agent	settings.json
Oh My Pi	@oh-my-pi/pi-coding-agent	omp	~/.omp/agent	config.yml, models.yml

Two products descended from the same code — both publish from a directory called packages/coding-agent, both keep configuration one level down under agent, and the two homes are one word apart.

What makes the confusion worth stopping is that it is silent. A Pi setup written into an Oh My Pi home is not rejected by anything downstream — it is ignored, and the directory looks configured. A failure that leaves everything looking right is the one worth refusing before it happens.

$ pi-setup-system install baseline --target ~/.omp/agent
unsupported_native_surface: …/.omp/agent holds config.yml and none of Pi Coding
Agent's own files, which is what Oh My Pi's configuration home looks like. Oh My
Pi keeps its configuration in ~/.omp/agent; this program configures Pi Coding
Agent in ~/.pi/agent. Nothing has been changed. Name the target you meant.

The refusal names both homes, because a stop a caller cannot act on is half an answer.

Three conditions, all required

The cost of a wrong refusal is a caller who cannot configure their own target, so each is asserted rather than assumed:

• the neighbour's marker is present;
• none of this provider's own namespaces are — a home holding settings.json is Pi's whatever else sits beside it;
• the target is not already managed here, which settles it outright.

Six of the seven declare no neighbour

A marker listed without evidence is a refusal waiting to happen, so nothing is listed that was not measured. The empty case — what most of the estate runs — is asserted too.

Observed red both ways

defect reintroduced	failure
check removed	a neighbour's home is planned against
own-files condition removed	a target holding our own file was refused as a neighbour's

A refused plan also leaves no slot and no journal, which the test asserts.

Gate

fmt, clippy -D warnings, 362 tests, conformance 23/23 on all seven.

Sources

• oh-my-pi on npm
• can1357/oh-my-pi
• Getting Started — DeepWiki

https://claude.ai/code/session_012UZkeU7yQhyZqKAaDaQEjA