Pinned sessions can be lost when multiple TUI instances write session.json #44736

Description

Each TUI reads the global session.json pin list once and keeps a private in-memory copy. Pinning, unpinning, or handling session.deleted rewrites the entire file without locking, rereading, merging, or serializing writes. A stale TUI can therefore erase pins added by another TUI.

Reproduction

1. Start TUI A and TUI B with the same pin list.
2. In B, pin a session. B writes the updated list.
3. In stale A, pin/unpin another session or delete a session.
4. Restart OpenCode.

The pin added in B is gone because A replaced the complete file with its stale snapshot.

Expected

Concurrent TUI instances should not erase unrelated pin updates.

Cause

createSession() loads the file once and each save() passes the full in-memory array to a fire-and-forget writeJsonAtomic() call:

• opencode/packages/tui/src/context/local.tsx

  Lines 411 to 493 in 826d9ad

  	function createSession() {
  	const [sessionStore, setSessionStore] = createStore<{
  	ready: boolean
  	pinned: string[]
  	}>({
  	ready: false,
  	pinned: [],
  	})
  	const filePath = path.join(paths.state, "session.json")
  	const state = {
  	pending: false,
  	}
  	function save() {
  	if (!sessionStore.ready) {
  	state.pending = true
  	return
  	}
  	state.pending = false
  	void writeJsonAtomic(filePath, {
  	pinned: sessionStore.pinned,
  	})
  	}
  	readJson<unknown>(filePath)
  	.then((x) => {
  	if (!x || typeof x !== "object") return
  	const pinned = (x as Record<string, unknown>).pinned
  	if (Array.isArray(pinned))
  	setSessionStore(
  	"pinned",
  	pinned.filter((item): item is string => typeof item === "string"),
  	)
  	})
  	.catch(() => {})
  	.finally(() => {
  	setSessionStore("ready", true)
  	if (state.pending) save()
  	})
  	const slots = createMemo(() => {
  	const existing = new Set(sync.data.session.filter((x) => x.parentID === undefined).map((x) => x.id))
  	return sessionStore.pinned.filter((id) => existing.has(id)).slice(0, 9)
  	})
  	function prune(sessionID: string) {
  	batch(() => {
  	if (sessionStore.pinned.includes(sessionID)) {
  	setSessionStore(
  	"pinned",
  	sessionStore.pinned.filter((x) => x !== sessionID),
  	)
  	}
  	save()
  	})
  	}
  	event.on("session.deleted", (evt) => {
  	prune(evt.properties.info.id)
  	})
  	return {
  	get ready() {
  	return sessionStore.ready
  	},
  	pinned() {
  	return sessionStore.pinned
  	},
  	slots,
  	isPinned(sessionID: string) {
  	return sessionStore.pinned.includes(sessionID)
  	},
  	togglePin(sessionID: string) {
  	batch(() => {
  	const exists = sessionStore.pinned.includes(sessionID)
  	const next = exists
  	? sessionStore.pinned.filter((x) => x !== sessionID)
  	: [...sessionStore.pinned, sessionID]
  	setSessionStore("pinned", next)
  	save()
  	})
  	},

• opencode/packages/tui/src/util/persistence.ts

  Lines 22 to 33 in 826d9ad

  	export async function writeJsonAtomic(filePath: string, value: unknown) {
  	await mkdir(path.dirname(filePath), { recursive: true })
  	const temporary = `${filePath}.${process.pid}.${crypto.randomUUID()}.tmp`
  	await Bun.write(temporary, JSON.stringify(value)).catch(async (error) => {
  	await rm(temporary, { force: true }).catch(() => undefined)
  	throw error
  	})
  	await rename(temporary, filePath).catch(async (error) => {
  	await rm(temporary, { force: true }).catch(() => undefined)
  	throw error
  	})
  	}

Atomic rename prevents partial files but does not prevent stale writers. There is also no file watcher or close-time merge. Closing a TUI alone does not save; the last completed save wins.

I verified that the relevant persistence code is identical in v1.18.18, v1.18.19, v1.18.20, v1.18.21, and current dev.

Environment

• macOS
• Multiple OpenCode TUIs in WebStorm and system terminals
• OpenCode v1.18.18 through v1.18.21