zed-industries/zed · error

log buffer should be a singleton

Error message

log buffer should be a singleton

What it means

Asserts that the LSP log buffer, obtained while building the RPC-trace view for a language server, is the unique open entity of its kind. It fires if open_buffer returned an entity that the global buffer store did not recognize as the singleton log buffer — i.e., the log buffer was created outside the expected singleton path or the store was reset between view creations.

Source

Thrown at crates/language_tools/src/lsp_log_view.rs:549

        cx: &mut Context<Self>,
    ) {
        self.toggle_rpc_trace_for_server(key.clone(), true, window, cx);
        let rpc_log = self.log_store.update(cx, |log_store, _| {
            log_store
                .enable_rpc_trace_for_language_server(&key)
                .map(|state| log_contents(&state.rpc_messages, ()))
        });
        if let Some(rpc_log) = rpc_log {
            self.current_server_key = Some(key);
            self.active_entry_kind = LogKind::Rpc;
            let (editor, editor_subscriptions) = Self::editor_for_logs(rpc_log, window, cx);
            let language = self.project.read(cx).languages().language_for_name("JSON");
            editor
                .read(cx)
                .buffer()
                .read(cx)
                .as_singleton()
                .expect("log buffer should be a singleton")
                .update(cx, |_, cx| {
                    cx.spawn({
                        let buffer = cx.entity();
                        async move |_, cx| {
                            let language = language.await.ok();
                            buffer.update(cx, |buffer, cx| {
                                buffer.set_language(language, cx);
                            });
                        }
                    })
                    .detach();
                });

            self.editor = editor;
            self.editor_subscriptions = editor_subscriptions;
            cx.notify();
        }

View on GitHub (pinned to 5a9b9558db)

Solutions

1. Ensure the log buffer is only ever created through the singleton helper that registers it with the buffer store
2. Reuse a cached entity handle for the log buffer instead of re-opening by path
3. Replace the expect with a fallback that creates a fresh buffer when uniqueness cannot be established

When it happens

Trigger: Thrown at crates/language_tools/src/lsp_log_view.rs:564 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of zed-industries/zed@5a9b9558db (2026-08-20). Data as JSON: /api/errors/efc7f1d5f5a8a923. Report an issue: GitHub.