0050 — Explicit spawn ownership, client-owned placement
0050 — Explicit spawn ownership, client-owned placement
TL;DR. SPAWN_TERMINAL may name an existing local Terminal as an
ownership address, forcing the server to host the new Terminal in that exact
window. Geometry remains an L3 client concern: headless callers publish the new
leaf through shared LayoutOps without publishing focus. An absent owner keeps
legacy behavior.
Status: Accepted Date: 2026-07-15
Context
A headless phux spawn connection is not attached, so the server previously
placed its Terminal in a recently active session. That heuristic can select a
different session from the target the caller intends to split. A follow-up L3
layout write cannot repair wrong registry ownership: the Terminal already
belongs to the wrong session/window.
Server-tracked focus is not an answer. ADR-0019 makes focus client-local, and layout geometry belongs to the TUI metadata convention rather than L1.
Decision
Add optional SPAWN_TERMINAL.owner_terminal field id 8. When present, the
server resolves that existing local Terminal and creates the new Terminal in
its exact owning window. Resolution failure is handled as SPAWN_FAILED; there
is no heuristic fallback. Ownership targeting is local-only and cannot be
combined with satellite routing.
The field conveys ownership only, never split direction, ratio, or focus. After a successful spawn, a layout-aware caller uses the shared LayoutOps read/mutate/write path to insert the returned leaf. Headless insertion preserves the serialized active-window and focus fields. Layout coordination remains last-write-wins as accepted by ADR-0019; no generic compare-and-set is added. After the spawn reply, a placement caller re-reads authoritative state and verifies that both the owner and new Terminal resolve to the expected exact window/session before publishing layout. This detects an older additive decoder that legally ignored field 8. An absent or mismatched pane is removed synchronously and reported as unsupported/mismatched. If layout publication returns a handled error, the caller likewise removes the known spawned Terminal before returning failure.
owner_terminal = None preserves the existing attached-client / recently
active placement policy for legacy consumers and unplaced CLI calls.
Consequences
An explicit target cannot land in another session or window, while L1 still contains no layout or focus vocabulary. Older senders omit field 8 and retain their behavior; field-tagged decoders skip or default the additive field. Satellite placement remains intentionally unsupported until ownership and L3 layout metadata have a federation-safe addressing model.
Alternatives
A geometry-free spawn followed only by L3 placement was rejected because it cannot change the server registry ownership established at spawn time.
A session id field was rejected because the Terminal target already identifies the exact window and avoids adding another non-federation-routable identity.
Server-side focus tracking or layout execution was rejected by ADR-0019.