Round 5 review: one P1, a frontend scope hole, and three P2s.
**1. A fallback that SPAWNS and then dies retried forever.** The
once-per-buffer guard bounds calls to `_attach_buffer`, not the server
those calls produce. `ensure_server` still never forwards `cfg.restart`,
so the fallback inherits `OnCrash`; an executable that exits before
`initialize` is respawned by the manager with no attempt ceiling —
silently, because `latched` has already disabled the primary's failure
poll. The fallback now gets its own one-shot die-before-initialize
watch, which retires it (ending the respawn loop) and reports.
The prior failing-fallback test used a NONEXISTENT executable, so it
only ever exercised synchronous ENOENT. To reach "spawned, then died"
the fixture has to actually spawn.
**2. Simultaneous frontends.** Both repair triggers read the ambient
`pmacs.window.buffer()`, and the daemon restores `active_frontend` to
the last-dispatched frontend before `tick_processes` — so a Lean buffer
active in ANOTHER frontend receives no `buffer.after-switch` here and
stays stale after its server is globally retired.
Fixed at the seam that is frontend-agnostic: **make consumption safe.**
`attached_for_active` now rebuilds rather than returning a record whose
server is dead, and `attachment_for_request` reports none (it must not
perturb LSP state, so it cannot rebuild). Whichever frontend runs a
command is the active one while it runs, so healing at the point of use
reaches every buffer no eager sweep can. This also closes the half where
a dead attachment was handed to a command and the request vanished.
**3. The retirement sweep stopped user-managed servers.** Selecting on
`language_id == "lean4"` also names servers the user spawned from
`init.lua`, which are not derived from `pmacs.lsp.config.lean4`. It now
keys on the `default-lean4` label `ensure_server` stamps — the
derivation discriminator.
**4. Repair ran even when no swap occurred.** `swap_to_fallback()`
returning false left `latched` true, so the next tick retried the
UNCHANGED configuration and reported it as a fallback failure. Split
into `probe.fallback_installed`: repair exists to apply a swap, so no
swap means nothing to apply.
**5. The once-per-buffer assertion counted table keys**, which cannot
distinguish "once per buffer" from "every tick for one buffer" —
cardinality stays 1 either way. Replaced with a numeric attempt counter;
the bite reports 174 attempts against the expected 1.
Five bites, each against 7c37bdc: no fallback watch -> attempt reaches
4; retire by language_id -> the user's server is stopped; gate repair on
`latched` -> a repair is attempted with no swap; drop the
once-per-buffer guard -> 174 vs 1; hand back a dead attachment -> a
command receives a `stopped` server.
Two more vacuity shapes recorded in the ledger (8 and 9): counting
distinct keys cannot bound repeated work, and a nonexistent executable
cannot reach any post-spawn failure.
Levi Neuwirth
19f48d46c0