A Vite context's build retires with its last open environment build

[codecaaron]

Pre-release blocker (teardown audit gap D): a Vite custom buildApp that builds a shared plugin's environments in parallel failed the build. #380 retires the context's Session and engine in closeBundle, and the first environment to close did so while the others still transformed: "[animus-extract] Failed to transform src/Sentinel.ts: v2 transform before analyze — engine instance not initialized". Unreleased (#346 and #380 postdate v0.1.25).

Fix

The context tracks the environments whose build started and has not closed (openBuild in buildStart, closeBuild in closeBundle) and retires its build only when that set empties. A set rather than a count, because the hook pairing is not one-to-one (probe below).

Root's three checks (run-and-discard probe, real Vite 8.2.2, macOS)

Path	Hooks observed	Effect of the set
vite build --watch	each rebuild: buildStart client then closeBundle client	retires after each rebuild and rejoins at the next, as before
parallel build, SSR failing mid-transform	buildStart client, buildStart ssr, closeBundle client, closeBundle ssr ×2	the duplicate close is a no-op; the build still rejects loudly
dev server, client and SSR	buildStart client only; at close closeBundle ssr, closeBundle client	the never-started SSR close leaves client open; the client close retires

Sequential and parallel builds (sharedPlugins on and off) produce identical CSS and SSR/client output, with no raw builder code; with the fix, the slow-SSR parallel build matches them.

Review round (spike-codex P2 at 3adeb4e)

A name-keyed set conflated distinct active builds: a builder reused right after a rejected parallel buildApp (the old SSR build's late close emptied ssr under the new one), and two distinct environments named alike (the first close retired the engine under the second). Both were loud. The context now maps each open build's name to its environment and refuses, in buildStart, a second build of an active environment (a previous build of environment ssr is still running on this plugin instance) and a second environment under an active name; only the environment that opened an entry removes it (bffeeee, 53d81d2). Rows (8674dc4), red at 3adeb4e: 'a second build of a running environment is refused, naming it' and 'two environments under one name are refused, naming it'.

Last round (spike-codex: a refused build owned the active generation's end)

Hook contexts are new objects per call, so they carry no per-attempt token; but Vite ends every build exactly once in buildEnd, failed ones included, while closeBundle can run twice for a failed build (probe). So the refusal is gone: a buildStart for an environment whose build is open (the same object, or one named alike) waits for that build's end and then opens its own generation, and buildEnd ends only the generation its environment opened; the last to end retires the Session and engine (c3e3fca). A dev server's close calls buildEnd only for environments that started. Rows (5abde23), red at 53d81d2: 'a builder reused while an earlier build still runs builds after it' (awaits all four builds: only the planned client failure rejects; the original SSR fulfils) and 'two environments under one name build one after the other'.

Witness

tests/dev-server/build-app.test.ts › the first environment to close leaves the others their Session: a real createBuilder with client and SSR in parallel and SSR transforms delayed; red on main 26a2b51 (the error above), green here.

Checks

macOS at 53d81d2: Vite suite 229/229, lint and fmt clean. Linux CI: runs 38174475316 (3adeb4e), 38175931696 (53d81d2) and 38177357515 (5abde23), every job green.

🤖 Generated with Claude Code

[codecaaron]

Parked by root under the stopping rule after the final round. spike-codex confirmed the reused-builder findings closed (all four builds settle correctly; the original SSR keeps its assets), but the serialise shape introduces a circular wait: a plugin whose transform awaits a nested build of the same environment hangs, because the nested buildStart awaits the outer build's buildEnd (vite-plugin context.ts:517-521 / unplugin core.ts:529-537). The earlier refusal heads fail that case loudly instead. Owner decision pending: ship this head with the nested-build case as a stated limit, ship the refusal head, or leave parallel buildApp unsupported (main fails it loudly).

🤖 Generated with Claude Code