diff --git a/crates/ide-host/src/ops/lsp.rs b/crates/ide-host/src/ops/lsp.rs
index 67f31cb4..a0105b87 100644
--- a/crates/ide-host/src/ops/lsp.rs
+++ b/crates/ide-host/src/ops/lsp.rs
@@ -76,9 +76,17 @@ async fn plugin_call<T: Send + 'static>(f: impl FnOnce() -> T + Send + 'static)
     tokio::task::spawn_blocking(f).await.ok()
 }
 
-/// Items from plugins carry no server (resolve and commands don't apply).
+/// Items from plugins carry no server: commands don't apply, and a code
+/// action is resolved by the plugin named in its `data` ([`PluginActionRef`]).
 const PLUGIN_SERVER: ServerId = ServerId(0);
 
+/// `data` of a plugin's code action whose edits it computes when picked.
+#[derive(serde::Serialize, serde::Deserialize)]
+struct PluginActionRef {
+    plugin: String,
+    data: String,
+}
+
 /// A plugin's `completion-item.kind` (wit/providers.wit lists them).
 fn plugin_completion_kind(kind: &str) -> Option<CompletionKind> {
     Some(match kind {
@@ -120,14 +128,14 @@ fn plugin_completion(item: ide_plugin::CompletionItem) -> CompletionItem {
         kind,
         documentation: item.documentation.map(|value| Markup { kind: "markdown".into(), value }),
         sort_text: item.sort_text,
-        filter_text: None,
+        filter_text: item.filter_text,
         preselect: false,
         deprecated: false,
         insert_text: item.insert_text,
-        is_snippet: false,
+        is_snippet: item.snippet,
         replace_range: item.replace,
         replace_range_tab: None,
-        additional_edits: Vec::new(),
+        additional_edits: item.additional_edits,
         commit_characters: Vec::new(),
         command: None,
         data: None,
@@ -314,7 +322,7 @@ pub async fn lsp_code_actions(
     };
     let plugin_actions: Vec<CodeAction> = plugin_actions
         .into_iter()
-        .map(|(_, a)| plugin_code_action(a))
+        .map(|(plugin, a)| plugin_code_action(&plugin, a))
         .filter(|a| {
             only.is_empty()
                 || a.kind.as_ref().is_some_and(|k| only.iter().any(|o| k == o || k.starts_with(&format!("{o}."))))
@@ -330,24 +338,53 @@ pub async fn lsp_code_actions(
     prepare_actions(project, doc, version, actions).await
 }
 
-fn plugin_code_action(a: ide_plugin::CodeAction) -> CodeAction {
-    let files = a
+fn plugin_code_action(plugin: &str, a: ide_plugin::CodeAction) -> CodeAction {
+    // With `data` and no edits, the plugin computes them when the action is picked.
+    let lazy = a.edits.is_empty() && a.data.is_some();
+    let files: Vec<_> = a
         .edits
         .into_iter()
         .map(|(path, edits)| ide_core::FileEdit::Edit { path: path.into(), edits, version: None })
         .collect();
+    let data = a
+        .data
+        .filter(|_| lazy)
+        .and_then(|data| serde_json::to_value(PluginActionRef { plugin: plugin.to_owned(), data }).ok());
     CodeAction {
         title: a.title,
         kind: a.kind,
         is_preferred: a.preferred,
         disabled_reason: None,
-        edit: Some(WorkspaceEdit { files, preconditions: Vec::new() }),
+        edit: (!lazy).then(|| WorkspaceEdit { files, preconditions: Vec::new() }),
         command: None,
-        data: None,
+        data,
         server: PLUGIN_SERVER,
     }
 }
 
+/// A code action resolved by whoever offered it: its language server, or
+/// the plugin its `data` names.
+async fn resolve_action(host: &Host, window: &str, doc: DocId, action: CodeAction) -> IdeResult<CodeAction> {
+    if action.server != PLUGIN_SERVER {
+        return host.project(window)?.lsp.resolve_code_action(doc, action).await;
+    }
+    let Some(r) = action.data.clone().and_then(|d| serde_json::from_value::<PluginActionRef>(d).ok()) else {
+        return Ok(action);
+    };
+    let (plugins, d) = plugin_providers(host, window, doc, ProviderKind::CodeActions)
+        .ok_or_else(|| ide_core::IdeError::unavailable("the plugin that offered this action is gone"))?;
+    let pending = ide_plugin::CodeAction {
+        title: action.title.clone(),
+        kind: action.kind.clone(),
+        preferred: action.is_preferred,
+        edits: Vec::new(),
+        data: Some(r.data),
+    };
+    let plugin = r.plugin.clone();
+    let resolved = blocking(move || plugins.resolve_code_action(&plugin, &d, pending)).await?;
+    Ok(plugin_code_action(&r.plugin, ide_plugin::CodeAction { data: None, ..resolved }))
+}
+
 /// Cancellable code actions with the kinds the servers advertise (Refactor This, refactoring availability).
 pub async fn lsp_code_action_query(
     host: &Host,
@@ -381,7 +418,7 @@ pub async fn lsp_resolve_code_action(
     let project = host.project(window)?;
     let documents = project.documents.clone();
     let version = blocking(move || documents.version(doc)).await?;
-    let action = project.lsp.resolve_code_action(doc, action).await?;
+    let action = resolve_action(host, window, doc, action).await?;
     Ok(prepare_actions(project, doc, version, vec![action]).await?.remove(0))
 }
 
@@ -391,7 +428,7 @@ pub async fn lsp_apply_code_action(host: &Host, window: &str, doc: DocId, action
     let action = if action.edit.is_none() && action.command.is_none() {
         let documents = project.documents.clone();
         let version = blocking(move || documents.version(doc)).await?;
-        let action = project.lsp.resolve_code_action(doc, action).await?;
+        let action = resolve_action(host, window, doc, action).await?;
         prepare_actions(project.clone(), doc, version, vec![action]).await?.remove(0)
     } else {
         action
@@ -801,6 +838,25 @@ pub(crate) fn register(d: &mut Dispatcher) {
 mod tests {
     use super::*;
 
+    #[test]
+    fn a_plugin_action_with_data_and_no_edits_is_resolved_by_its_plugin() {
+        let action = |edits: Vec<(std::path::PathBuf, Vec<TextEdit>)>, data: Option<&str>| ide_plugin::CodeAction {
+            title: "Fix".into(),
+            kind: None,
+            preferred: false,
+            edits,
+            data: data.map(str::to_owned),
+        };
+        let lazy = plugin_code_action("acme.x", action(Vec::new(), Some("ref")));
+        assert!(lazy.edit.is_none());
+        let r: PluginActionRef = serde_json::from_value(lazy.data.unwrap()).unwrap();
+        assert_eq!((r.plugin.as_str(), r.data.as_str()), ("acme.x", "ref"));
+        // With edits, `data` is the plugin's business: applied as is.
+        let edit = TextEdit { range: Range::default(), new_text: "x".into() };
+        let eager = plugin_code_action("acme.x", action(vec![("/a".into(), vec![edit])], Some("ref")));
+        assert!(eager.edit.is_some() && eager.data.is_none());
+    }
+
     #[test]
     fn every_completion_kind_the_plugin_api_documents_is_understood() {
         let wit = include_str!("../../../../wit/providers.wit");
diff --git a/crates/ide-host/src/plugins/providers.rs b/crates/ide-host/src/plugins/providers.rs
index d60b806a..b37c12e1 100644
--- a/crates/ide-host/src/plugins/providers.rs
+++ b/crates/ide-host/src/plugins/providers.rs
@@ -292,6 +292,21 @@ impl PluginHost {
         .collect()
     }
 
+    /// The edits of an action `plugin_id` returned with `data`, now that the
+    /// user picked it: a call with the command budget, not the edit path's.
+    pub fn resolve_code_action(
+        &self,
+        plugin_id: &str,
+        doc: &ProviderDocument,
+        action: CodeAction,
+    ) -> ide_core::IdeResult<CodeAction> {
+        let d = Arc::new(doc.clone());
+        let timeout = self.limits.timeout;
+        self.code_call(plugin_id, ide_plugin::Invocation::default(), "resolving the code action", move |rt, _| {
+            rt.resolve_code_action(&d, &action, timeout)
+        })
+    }
+
     pub fn provide_definition(&self, doc: &ProviderDocument, at: ide_core::Pos) -> Vec<Location> {
         let d = Arc::new(doc.clone());
         self.edit_calls(ProviderKind::Definition, &doc.language, move |rt, timeout| {
diff --git a/crates/ide-host/tests/plugins.rs b/crates/ide-host/tests/plugins.rs
index 1b8eb466..fb592967 100644
--- a/crates/ide-host/tests/plugins.rs
+++ b/crates/ide-host/tests/plugins.rs
@@ -635,7 +635,7 @@ fn idle_instances_are_reclaimed_and_schedules_reactivate() {
     assert_eq!(f.host.instances(), 0);
     let info = f.host.info_of("misbehave").unwrap();
     assert_eq!((info.status, info.stats.reclaims), (PluginStatus::Inactive, 1));
-    assert_eq!(f.command_titles("misbehave").len(), 8, "contributions stay");
+    assert_eq!(f.command_titles("misbehave").len(), 10, "contributions stay");
     assert_eq!(f.run("misbehave", "echo", Some("y")).unwrap().as_deref(), Some("y"));
     assert_eq!(f.host.info_of("misbehave").unwrap().stats.activations, 2);
 
@@ -2410,3 +2410,56 @@ fn uninstalling_deletes_the_plugins_secrets() {
     f.host.uninstall("openidea.ai-completion").unwrap();
     assert!(keychain.0.lock().is_empty(), "{:?}", keychain.0.lock().keys().collect::<Vec<_>>());
 }
+
+/// Plugin API 1.0 leaves room to grow: event kinds are names, and the editor
+/// providers carry snippets, imports, lazily computed quick fixes and tagged
+/// problems.
+#[test]
+fn completion_quick_fixes_problems_and_event_kinds_of_api_1() {
+    let f = fixture(Limits::default());
+    let pkg = f._tmp.path().join("misbehave-providers");
+    copy_dir(&misbehave_pkg(), &pkg);
+    let manifest = std::fs::read_to_string(pkg.join("plugin.toml")).unwrap();
+    std::fs::write(
+        pkg.join("plugin.toml"),
+        format!("{manifest}\n[[contributes.providers]]\nkinds = [\"completion\", \"code-actions\"]\nlanguages = [\"text\"]\n"),
+    )
+    .unwrap();
+    f.install(&pkg);
+    let doc = |text: &str| ide_plugin::ProviderDocument {
+        path: f.project.join("a.txt"),
+        language: "text".into(),
+        version: 1,
+        text: text.into(),
+    };
+    let at = ide_core::Pos::new(0, 0);
+
+    let items = f.host.provide_completion(&doc("rich"), at, None);
+    let item = &items[0].1;
+    assert_eq!(
+        (item.insert_text.as_str(), item.snippet, item.filter_text.as_deref()),
+        ("f(${1:x})$0", true, Some("fun"))
+    );
+    assert_eq!(item.additional_edits[0].new_text, "use f;\n");
+
+    // Offered without edits; computed when picked.
+    let actions = f.host.provide_code_actions(&doc("lazy"), ide_core::Range::default());
+    let (plugin, action) = actions.into_iter().next().expect("offered");
+    assert!(action.edits.is_empty() && action.data.as_deref() == Some("fix"));
+    let resolved = f.host.resolve_code_action(&plugin, &doc("lazy"), action.clone()).unwrap();
+    assert_eq!(resolved.edits[0].1[0].new_text, "fixed ");
+    let foreign = ide_plugin::CodeAction { data: Some("other".into()), ..action };
+    assert!(f.host.resolve_code_action(&plugin, &doc("lazy"), foreign).is_err());
+
+    // A kind this IDE doesn't know is refused, not a trap.
+    let err = f.host.run_command("misbehave", "subscribe", Some("file-deleted"), f.inv()).unwrap_err();
+    assert!(err.message.contains("no event kind"), "{}", err.message);
+    let err = f.host.run_command("misbehave", "subscribe", Some("file-saved"), f.inv()).unwrap_err();
+    assert!(err.message.contains("events"), "known, but not granted: {}", err.message);
+
+    // Tags the IDE knows, the tool that found it.
+    let path = f.project.join("a.txt");
+    f.host.run_command("misbehave", "diagnose", Some(&path.to_string_lossy()), f.inv()).unwrap();
+    let d = f.workspace.diagnostics.lock().get(&("misbehave".into(), path)).cloned().unwrap();
+    assert_eq!((d[0].unnecessary, d[0].deprecated, d[0].source.as_deref()), (true, false, Some("lint")));
+}
diff --git a/crates/ide-plugin/src/runtime.rs b/crates/ide-plugin/src/runtime.rs
index fdb48019..bd5a9975 100644
--- a/crates/ide-plugin/src/runtime.rs
+++ b/crates/ide-plugin/src/runtime.rs
@@ -467,7 +467,6 @@ const MAX_SYNTAX_ITEMS: usize = 200_000;
 const MAX_BATCH: usize = 1000;
 
 fn event_to_wit(e: WorkbenchEvent) -> wit_events::Event {
-    use crate::types::ActionSource as S;
     match e {
         WorkbenchEvent::FileOpened(p) => wit_events::Event::FileOpened(p),
         WorkbenchEvent::FileSaved(p) => wit_events::Event::FileSaved(p),
@@ -477,14 +476,7 @@ fn event_to_wit(e: WorkbenchEvent) -> wit_events::Event {
         WorkbenchEvent::ActionPerformed(a) => wit_events::Event::ActionPerformed(wit_events::ActionPerformed {
             action: a.action,
             title: a.title,
-            source: match a.source {
-                S::Keyboard => wit_events::ActionSource::Keyboard,
-                S::Menu => wit_events::ActionSource::Menu,
-                S::Toolbar => wit_events::ActionSource::Toolbar,
-                S::ContextMenu => wit_events::ActionSource::ContextMenu,
-                S::Search => wit_events::ActionSource::Search,
-                S::Other => wit_events::ActionSource::Other,
-            },
+            source: a.source.name().to_owned(),
             shortcut: a.shortcut,
         }),
     }
@@ -670,9 +662,17 @@ impl Runtime {
                 detail: i.detail.map(|d| clip(d, MAX_TITLE)),
                 kind: i.kind.map(|k| clip(k, 32)),
                 insert_text: clip(i.insert_text, 64 << 10),
+                snippet: i.snippet,
                 replace: i.replace.map(range_from_wit),
                 sort_text: i.sort_text.map(|t| clip(t, 64)),
+                filter_text: i.filter_text.map(|t| clip(t, MAX_TITLE)),
                 documentation: i.documentation.map(|d| clip(d, 16 << 10)),
+                additional_edits: i
+                    .additional_edits
+                    .into_iter()
+                    .take(MAX_ADDITIONAL_EDITS)
+                    .map(edit_from_wit)
+                    .collect(),
             })
             .collect())
     }
@@ -699,27 +699,20 @@ impl Runtime {
     ) -> Result<Vec<CodeAction>, CallError> {
         let d = doc_to_wit(doc);
         let actions = self.provider_call(timeout, |p, s| p.call_code_actions(s, &d, range_to_wit(selection)))?;
-        Ok(actions
-            .into_iter()
-            .take(MAX_PROVIDER_ITEMS)
-            .map(|a| CodeAction {
-                title: clip(a.title, MAX_TITLE),
-                kind: a.kind.map(|k| clip(k, 64)),
-                preferred: a.preferred,
-                edits: a
-                    .edits
-                    .into_iter()
-                    .map(|f| {
-                        let edits = f
-                            .edits
-                            .into_iter()
-                            .map(|e| ide_core::TextEdit { range: range_from_wit(e.range), new_text: e.text })
-                            .collect();
-                        (std::path::PathBuf::from(f.path), edits)
-                    })
-                    .collect(),
-            })
-            .collect())
+        Ok(actions.into_iter().take(MAX_PROVIDER_ITEMS).map(code_action_from_wit).collect())
+    }
+
+    /// The edits of an action `provide_code_actions` returned with `data`.
+    pub fn resolve_code_action(
+        &mut self,
+        doc: &ProviderDocument,
+        action: &CodeAction,
+        timeout: Duration,
+    ) -> Result<CodeAction, CallError> {
+        let d = doc_to_wit(doc);
+        let a = code_action_to_wit(action);
+        let resolved = self.provider_call(timeout, |p, s| p.call_resolve_code_action(s, &d, &a))?;
+        resolved.map(code_action_from_wit).map_err(|e| CallError::Guest(e.into()))
     }
 
     pub fn provide_definition(
@@ -968,6 +961,47 @@ const MAX_VIEW_ITEMS: usize = 20_000;
 const MAX_CELL: usize = 64 << 10;
 const MAX_HTML: usize = 4 << 20;
 
+/// Most additional edits of a completion item.
+const MAX_ADDITIONAL_EDITS: usize = 100;
+
+fn edit_from_wit(e: wit_types::TextEdit) -> ide_core::TextEdit {
+    ide_core::TextEdit { range: range_from_wit(e.range), new_text: e.text }
+}
+
+fn code_action_from_wit(a: wit_prov::CodeAction) -> CodeAction {
+    CodeAction {
+        title: clip(a.title, MAX_TITLE),
+        kind: a.kind.map(|k| clip(k, 64)),
+        preferred: a.preferred,
+        edits: a
+            .edits
+            .into_iter()
+            .map(|f| (std::path::PathBuf::from(f.path), f.edits.into_iter().map(edit_from_wit).collect()))
+            .collect(),
+        data: a.data.map(|d| clip(d, 64 << 10)),
+    }
+}
+
+fn code_action_to_wit(a: &CodeAction) -> wit_prov::CodeAction {
+    wit_prov::CodeAction {
+        title: a.title.clone(),
+        kind: a.kind.clone(),
+        preferred: a.preferred,
+        edits: a
+            .edits
+            .iter()
+            .map(|(path, edits)| wit_prov::FileEdit {
+                path: path.to_string_lossy().into_owned(),
+                edits: edits
+                    .iter()
+                    .map(|e| wit_types::TextEdit { range: range_to_wit(e.range), text: e.new_text.clone() })
+                    .collect(),
+            })
+            .collect(),
+        data: a.data.clone(),
+    }
+}
+
 fn opt_clip(s: Option<String>, max: usize) -> Option<String> {
     s.map(|s| clip(s, max))
 }
@@ -975,6 +1009,9 @@ fn opt_clip(s: Option<String>, max: usize) -> Option<String> {
 fn view_from_wit(v: wit_vt::View) -> View {
     let body = match v.body {
         wit_vt::Body::Message(m) => ViewBody::Message(clip(m, 16 << 10)),
+        wit_vt::Body::Other(e) => {
+            ViewBody::Message(format!("This view needs a newer version of OpenIDEA ({}).", clip(e.kind, 64)))
+        }
         wit_vt::Body::Tree(items) => ViewBody::Tree(
             items
                 .into_iter()
@@ -1006,10 +1043,8 @@ fn view_from_wit(v: wit_vt::View) -> View {
             fields
                 .into_iter()
                 .take(MAX_VIEW_ITEMS)
-                .map(|f| ViewField {
-                    key: clip(f.key, 128),
-                    label: clip(f.label, MAX_TITLE),
-                    value: match f.value {
+                .filter_map(|f| {
+                    let value = match f.value {
                         wit_vt::FieldValue::Text(t) => FieldValue::Text(clip(t, MAX_CELL)),
                         wit_vt::FieldValue::Multiline(t) => FieldValue::Multiline(clip(t, 1 << 20)),
                         wit_vt::FieldValue::Checkbox(b) => FieldValue::Checkbox(b),
@@ -1017,7 +1052,10 @@ fn view_from_wit(v: wit_vt::View) -> View {
                             options: options.into_iter().take(1000).map(|o| clip(o, MAX_TITLE)).collect(),
                             selected: clip(selected, MAX_TITLE),
                         },
-                    },
+                        // A field type of a newer API: left out.
+                        wit_vt::FieldValue::Other(_) => return None,
+                    };
+                    Some(ViewField { key: clip(f.key, 128), label: clip(f.label, MAX_TITLE), value })
                 })
                 .collect(),
         ),
@@ -1067,3 +1105,26 @@ fn event_to_wit_view(e: ViewEvent) -> wit_vt::ViewEvent {
         ViewEvent::Message { text } => W::Message(text),
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn ext(kind: &str) -> wit_types::Extension {
+        wit_types::Extension { kind: kind.into(), data: "{}".into() }
+    }
+
+    #[test]
+    fn bodies_and_fields_of_a_newer_api_degrade() {
+        let view = |body| wit_vt::View { toolbar: Vec::new(), body, status: None };
+        let shown = view_from_wit(view(wit_vt::Body::Other(ext("markdown"))));
+        assert_eq!(shown.body, ViewBody::Message("This view needs a newer version of OpenIDEA (markdown).".into()));
+        let field = |key: &str, value| wit_vt::Field { key: key.into(), label: key.into(), value };
+        let form = view_from_wit(view(wit_vt::Body::Form(vec![
+            field("color", wit_vt::FieldValue::Other(ext("color"))),
+            field("name", wit_vt::FieldValue::Text("n".into())),
+        ])));
+        let ViewBody::Form(fields) = form.body else { panic!("a form") };
+        assert_eq!(fields.iter().map(|f| f.key.as_str()).collect::<Vec<_>>(), ["name"], "unknown fields are left out");
+    }
+}
diff --git a/crates/ide-plugin/src/types.rs b/crates/ide-plugin/src/types.rs
index dbd80edb..b1d7b215 100644
--- a/crates/ide-plugin/src/types.rs
+++ b/crates/ide-plugin/src/types.rs
@@ -126,6 +126,20 @@ pub enum ActionSource {
     Other,
 }
 
+impl ActionSource {
+    /// As plugins see it.
+    pub fn name(self) -> &'static str {
+        match self {
+            Self::Keyboard => "keyboard",
+            Self::Menu => "menu",
+            Self::Toolbar => "toolbar",
+            Self::ContextMenu => "context-menu",
+            Self::Search => "search",
+            Self::Other => "other",
+        }
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Type)]
 #[serde(rename_all = "camelCase")]
 pub struct ActionPerformed {
@@ -348,9 +362,14 @@ pub struct CompletionItem {
     /// WIT `completion-kind` name (`method`, `keyword`, …).
     pub kind: Option<String>,
     pub insert_text: String,
+    /// `insert_text` has tab stops and placeholders.
+    pub snippet: bool,
     pub replace: Option<ide_core::Range>,
     pub sort_text: Option<String>,
+    pub filter_text: Option<String>,
     pub documentation: Option<String>,
+    /// Applied with the item elsewhere in the document (an import).
+    pub additional_edits: Vec<ide_core::TextEdit>,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -365,6 +384,8 @@ pub struct CodeAction {
     pub kind: Option<String>,
     pub preferred: bool,
     pub edits: Vec<(PathBuf, Vec<ide_core::TextEdit>)>,
+    /// The plugin's reference: the edits come from `resolve_code_action`.
+    pub data: Option<String>,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
diff --git a/crates/ide-plugin/src/wit_host.rs b/crates/ide-plugin/src/wit_host.rs
index 265f992a..0a2bbe36 100644
--- a/crates/ide-plugin/src/wit_host.rs
+++ b/crates/ide-plugin/src/wit_host.rs
@@ -440,20 +440,11 @@ impl vcs::Host for StoreData {
     }
 }
 
-fn kind_from_wit(k: events::EventKind) -> EventKind {
-    match k {
-        events::EventKind::FileOpened => EventKind::FileOpened,
-        events::EventKind::FileSaved => EventKind::FileSaved,
-        events::EventKind::EditorFocused => EventKind::EditorFocused,
-        events::EventKind::ActionPerformed => EventKind::ActionPerformed,
-        events::EventKind::VcsChanged => EventKind::VcsChanged,
-        events::EventKind::Scheduled => EventKind::Scheduled,
-    }
-}
-
 impl events::Host for StoreData {
-    fn subscribe(&mut self, kind: events::EventKind) -> Fallible<()> {
-        let kind = kind_from_wit(kind);
+    fn subscribe(&mut self, kind: String) -> Fallible<()> {
+        let Some(kind) = EventKind::parse(&kind) else {
+            return Ok(Err(wit::Error::Invalid(format!("no event kind {kind:?} in this OpenIDEA"))));
+        };
         if let Some(cap) = kind.capability()
             && let Err(e) = self.require(cap)
         {
@@ -463,8 +454,10 @@ impl events::Host for StoreData {
         Ok(Ok(()))
     }
 
-    fn unsubscribe(&mut self, kind: events::EventKind) -> wasmtime::Result<()> {
-        self.host.subscribe(kind_from_wit(kind), false);
+    fn unsubscribe(&mut self, kind: String) -> wasmtime::Result<()> {
+        if let Some(kind) = EventKind::parse(&kind) {
+            self.host.subscribe(kind, false);
+        }
         Ok(())
     }
 }
@@ -542,10 +535,10 @@ impl diagnostics::Host for StoreData {
                     diagnostics::Severity::Hint => ide_core::Severity::Hint,
                 },
                 message: clip(d.message, 4096),
-                source: Some(source.clone()),
+                source: Some(d.source.map_or_else(|| source.clone(), |s| clip(s, 128))),
                 code: d.code.map(|c| clip(c, 128)),
-                unnecessary: false,
-                deprecated: false,
+                unnecessary: d.tags.iter().any(|t| t == "unnecessary"),
+                deprecated: d.tags.iter().any(|t| t == "deprecated"),
                 server: Some(source.clone()),
             })
             .collect();
diff --git a/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm b/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm
index b0c8caee..b55671ab 100644
Binary files a/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm and b/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm differ
diff --git a/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm.sources b/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm.sources
index 2edfa822..707df000 100644
--- a/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm.sources
+++ b/crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm.sources
@@ -1 +1 @@
-86dfe70a30ab1f7955a16e96c1b32c8be663456b871cc4d3bed7dc6052c062da
+c9acbc021f3840649823cb7680e13907d429c6fda8271fdb0ae6e5ea89ed15ee
diff --git a/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm b/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm
index aaa324d9..d15e5082 100644
Binary files a/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm and b/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm differ
diff --git a/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm.sources b/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm.sources
index 61e1857b..695b65da 100644
--- a/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm.sources
+++ b/crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm.sources
@@ -1 +1 @@
-0dacb82ac35c1f132dc66e85dbf0663b729f818279d3b32cd06403e502fbf880
+2fb6aa879562733bf5b7f11dabe8fc6a415c9ef695868fe7845417a4245d2dc8
diff --git a/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm b/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm
index d6018357..37db117e 100644
Binary files a/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm and b/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm differ
diff --git a/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm.sources b/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm.sources
index 1c5ed64f..59546337 100644
--- a/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm.sources
+++ b/crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm.sources
@@ -1 +1 @@
-0ad2e4c6977a576b7eb27fc1e535fd056dd9da64bdfe6cfda9ca9f57537d0384
+25b0f419a68a3b1651d3c2774d834b05e40ede52bc5ed8c0eba6d27a204efe82
diff --git a/crates/ide-plugin/tests/fixtures/misbehave/plugin.toml b/crates/ide-plugin/tests/fixtures/misbehave/plugin.toml
index 29dba7d6..1eae84d2 100644
--- a/crates/ide-plugin/tests/fixtures/misbehave/plugin.toml
+++ b/crates/ide-plugin/tests/fixtures/misbehave/plugin.toml
@@ -40,3 +40,11 @@ title = "insert"
 [[contributes.commands]]
 id = "cancel"
 title = "cancel"
+
+[[contributes.commands]]
+id = "subscribe"
+title = "subscribe"
+
+[[contributes.commands]]
+id = "diagnose"
+title = "diagnose"
diff --git a/crates/ide-plugin/tests/fixtures/misbehave/src/lib.rs b/crates/ide-plugin/tests/fixtures/misbehave/src/lib.rs
index cd6d6511..890bf845 100644
--- a/crates/ide-plugin/tests/fixtures/misbehave/src/lib.rs
+++ b/crates/ide-plugin/tests/fixtures/misbehave/src/lib.rs
@@ -14,7 +14,9 @@ wit_bindgen::generate!({
     generate_all,
 });
 
-use exports::openidea::plugin::providers::{self, CodeAction, CompletionItem, Document, InlineSuggestion, LineMarker};
+use exports::openidea::plugin::providers::{
+    self, CodeAction, CompletionItem, Document, FileEdit, InlineSuggestion, LineMarker,
+};
 use exports::openidea::plugin::syntax_provider::{self, Fold, Symbol, Token};
 use exports::openidea::plugin::{commands, event_handler, lifecycle};
 use openidea::plugin::{invocation::Invocation, types};
@@ -67,6 +69,23 @@ impl commands::Guest for Misbehave {
             }
             // The user gave up: not the plugin failing.
             "cancel" => Err(types::Error::Cancelled),
+            // Event kinds are names: one this IDE doesn't know is refused.
+            "subscribe" => openidea::plugin::events::subscribe(&arg.unwrap_or_default()).map(|()| None),
+            // Tagged problems from another tool on the line 0 of `arg`.
+            "diagnose" => {
+                use openidea::plugin::diagnostics::{self, Diagnostic, Severity};
+                let start = types::Position { line: 0, character: 0 };
+                let d = Diagnostic {
+                    range: types::Range { start, end: start },
+                    severity: Severity::Warning,
+                    message: "unused".into(),
+                    code: None,
+                    source: Some("lint".into()),
+                    tags: vec!["unnecessary".into(), "glowing".into()],
+                    related: Vec::new(),
+                };
+                diagnostics::publish(&arg.unwrap_or_default(), &[d]).map(|()| None)
+            }
             other => Err(types::Error::NotFound(format!("command {other}"))),
         }
     }
@@ -113,14 +132,24 @@ impl syntax_provider::Guest for Misbehave {
 impl providers::Guest for Misbehave {
     fn completion(doc: Document, _at: types::Position, _trigger: Option<String>) -> Vec<CompletionItem> {
         behave(&doc.text);
+        // `rich`: a snippet that also adds an import.
+        let rich = doc.text == "rich";
+        let start = types::Position { line: 0, character: 0 };
         vec![CompletionItem {
             label: doc.path.clone(),
             detail: None,
             kind: Some("keyword".into()),
-            insert_text: doc.path,
+            insert_text: if rich { "f(${1:x})$0".into() } else { doc.path },
+            snippet: rich,
             replace: None,
             sort_text: None,
+            filter_text: rich.then(|| "fun".into()),
             documentation: None,
+            additional_edits: if rich {
+                vec![types::TextEdit { range: types::Range { start, end: start }, text: "use f;\n".into() }]
+            } else {
+                Vec::new()
+            },
         }]
     }
 
@@ -128,8 +157,27 @@ impl providers::Guest for Misbehave {
         None
     }
 
-    fn code_actions(_doc: Document, _selection: types::Range) -> Vec<CodeAction> {
-        Vec::new()
+    /// `lazy`: one action whose edits come from `resolve-code-action`.
+    fn code_actions(doc: Document, _selection: types::Range) -> Vec<CodeAction> {
+        if doc.text != "lazy" {
+            return Vec::new();
+        }
+        vec![CodeAction {
+            title: "Fix later".into(),
+            kind: Some("quickfix".into()),
+            preferred: false,
+            edits: Vec::new(),
+            data: Some("fix".into()),
+        }]
+    }
+
+    fn resolve_code_action(doc: Document, action: CodeAction) -> Result<CodeAction, types::Error> {
+        if action.data.as_deref() != Some("fix") {
+            return Err(types::Error::Invalid("not one of mine".into()));
+        }
+        let start = types::Position { line: 0, character: 0 };
+        let edit = types::TextEdit { range: types::Range { start, end: start }, text: "fixed ".into() };
+        Ok(CodeAction { edits: vec![FileEdit { path: doc.path, edits: vec![edit] }], ..action })
     }
 
     fn definition(_doc: Document, _at: types::Position) -> Vec<types::Location> {
diff --git a/plugins/README.md b/plugins/README.md
index ae53436b..a579afb6 100644
--- a/plugins/README.md
+++ b/plugins/README.md
@@ -321,6 +321,11 @@ Events are batched: a running plugin gets them within a fraction of a second,
 an idle one collects them for 2 s before it is woken, so frequent events
 (Key Promoter's actions) don't keep it alive.
 
+Kinds are names (`subscribe` takes a string), so later IDEs add kinds without
+a new API: an IDE refuses a kind it doesn't know with `invalid`, and a kind
+newer than the plugin's SDK arrives as `Event::Other { kind, data }` (JSON).
+The SDK's event enums are `#[non_exhaustive]`; match them with a `_` arm.
+
 ### Providers
 
 Declare what the plugin provides in the editor; only plugins whose
@@ -338,7 +343,14 @@ Then `register_plugin!(MyPlugin, providers)` and implement
 the document (path, language, version, text). Results join the language
 servers' (completion lists, ⌥⏎ quick fixes, ⌘B, gutter icons; a code action
 carries edits for any files, applied as one change). A completion item's
-`kind` (`CompletionKind` in the SDK, a string in the WIT) picks its icon.
+`kind` (`CompletionKind` in the SDK, a string in the WIT) picks its icon; it
+can be a `snippet` (`$1`, `${1:name}`, `$0`), match on `filter_text` instead
+of its label, and bring `additional_edits` elsewhere in the document (an
+import). A code action can leave `edits` empty and set `data`: its edits are
+then computed by `resolve_code_action` when the user picks it, under the
+command budget instead of the 50 ms. Problems (`publish_diagnostics`) can name
+the tool that found them (`source`) and be `unnecessary` (faded) or
+`deprecated` (struck through).
 Editor providers run under the edit-path budget: 50 ms, after which the
 result is dropped, and an interruption at 500 ms. Every plugin providing a
 kind is asked at the same time, so each has the whole budget.
@@ -393,6 +405,9 @@ collapse of items, form fields, table cells, inserted and deleted rows, and
 `html` messages. A tree is a flat list whose items name their `parent`; an
 `expandable` item gets its children when it is expanded. A table gets only
 the rows it shows (`viewport`): report `total_rows` and return those.
+Bodies, field types and view events added by later APIs travel as `Other {
+kind, data }`: an IDE that doesn't know a body says it needs updating, and
+leaves out a field type it doesn't know.
 
 Showing a view activates the plugin (`on-view:<id>`). `views` become tool
 windows; a `customEditors` file (`priority = "default"`) opens in the
@@ -890,7 +905,10 @@ only grows:
    Extend with new types and new functions (or interfaces). `types.error` is
    used everywhere and is no exception; new situations use `failed(string)`
    or `invalid(string)`. Sets that keep growing (completion, token, symbol and
-   fold kinds, icons) are strings for this reason.
+   fold kinds, icons, event kinds, action sources, diagnostic tags) are
+   strings for this reason, and variants that grow (`event`, view `body`,
+   `view-event`, `field-value`) have an `other(extension)` case, a kind and
+   JSON data, that carries later cases to older plugins and IDEs.
 2. **Host interfaces (imports) may gain functions and interfaces**: older
    components don't import them.
 3. **Plugin interfaces (exports) never gain functions** once released: the
@@ -902,6 +920,11 @@ only grows:
    minor with a message that says to update the IDE or rebuild with the SDK.
 5. **One version number**: the `wit/` package version, `ENGINE_VERSION` and
    `API_VERSION` agree, and the SDK's `wit/` copy is identical to `wit/`.
+6. **1.x calls are synchronous and pass documents whole.** Host calls block
+   the plugin's instance, and providers get the document's text with each
+   call. WASI 0.3 async components come with 2.0, behind an adapter in the
+   host that keeps 1.x plugins running; incremental document sync, if
+   needed, is a new interface.
 
 Checked automatically:
 
diff --git a/plugins/official/ai-completion/dist/plugin.wasm b/plugins/official/ai-completion/dist/plugin.wasm
index c51a0c67..b163d582 100644
Binary files a/plugins/official/ai-completion/dist/plugin.wasm and b/plugins/official/ai-completion/dist/plugin.wasm differ
diff --git a/plugins/official/ai-completion/dist/plugin.wasm.sources b/plugins/official/ai-completion/dist/plugin.wasm.sources
index 8baa3d1f..e5251dd3 100644
--- a/plugins/official/ai-completion/dist/plugin.wasm.sources
+++ b/plugins/official/ai-completion/dist/plugin.wasm.sources
@@ -1 +1 @@
-aa09a92c0ba9d85a01c56bbf4455e40ae44f005b443ce1002bbe8011408ff975
+28e4bf10a41bdda011111b0e150ebe96205c57f410bad98c19eea3f1286349d6
diff --git a/plugins/official/checkstyle/dist/plugin.wasm b/plugins/official/checkstyle/dist/plugin.wasm
index 98fccd27..e4ffd3c2 100644
Binary files a/plugins/official/checkstyle/dist/plugin.wasm and b/plugins/official/checkstyle/dist/plugin.wasm differ
diff --git a/plugins/official/checkstyle/dist/plugin.wasm.sources b/plugins/official/checkstyle/dist/plugin.wasm.sources
index 1c46bf44..66dca89d 100644
--- a/plugins/official/checkstyle/dist/plugin.wasm.sources
+++ b/plugins/official/checkstyle/dist/plugin.wasm.sources
@@ -1 +1 @@
-908c2fd177ad2bb9a8a8492505151c3b81579191156c5ec53f705127f50a8ee9
+7e015486cc916f5edbac542863373fd7204f5bcd534f6c408d5f9d2b72913862
diff --git a/plugins/official/checkstyle/src/lib.rs b/plugins/official/checkstyle/src/lib.rs
index 74f17cc4..aebf998e 100644
--- a/plugins/official/checkstyle/src/lib.rs
+++ b/plugins/official/checkstyle/src/lib.rs
@@ -97,12 +97,8 @@ fn diagnostic(p: &Problem, text: &str) -> Diagnostic {
     let line_len = text.split('\n').nth(p.line as usize).map_or(0, |l| l.encode_utf16().count() as u32);
     let start = p.column.unwrap_or(0).min(line_len);
     let end = if p.column.is_some() && start < line_len { start + 1 } else { line_len };
-    Diagnostic {
-        range: Range::new(Position::new(p.line, start), Position::new(p.line, end.max(start))),
-        severity: p.severity,
-        message: p.message.clone(),
-        code: Some(p.check.clone()),
-    }
+    let range = Range::new(Position::new(p.line, start), Position::new(p.line, end.max(start)));
+    Diagnostic::new(range, p.severity, p.message.clone()).code(p.check.clone())
 }
 
 /// The project containing `path`.
@@ -188,6 +184,7 @@ impl Providers for Checkstyle {
                     kind: Some("quickfix".into()),
                     preferred: true,
                     edits: vec![(doc.path.clone(), vec![edit])],
+                    data: None,
                 });
             }
         }
diff --git a/plugins/official/csv-editor/dist/plugin.wasm b/plugins/official/csv-editor/dist/plugin.wasm
index f3529166..5e29e582 100644
Binary files a/plugins/official/csv-editor/dist/plugin.wasm and b/plugins/official/csv-editor/dist/plugin.wasm differ
diff --git a/plugins/official/csv-editor/dist/plugin.wasm.sources b/plugins/official/csv-editor/dist/plugin.wasm.sources
index fcd50761..3a0d19f0 100644
--- a/plugins/official/csv-editor/dist/plugin.wasm.sources
+++ b/plugins/official/csv-editor/dist/plugin.wasm.sources
@@ -1 +1 @@
-64270fa0f5b3084c78764f09b8ce161742fdbff9c28fb90590da39594e558db1
+a6cf59e74595e13908e2cbf1752c58665c6963de258413c9d7332d2a7dd9cbd0
diff --git a/plugins/official/git-toolbox/dist/plugin.wasm b/plugins/official/git-toolbox/dist/plugin.wasm
index c7d8ad40..936c901a 100644
Binary files a/plugins/official/git-toolbox/dist/plugin.wasm and b/plugins/official/git-toolbox/dist/plugin.wasm differ
diff --git a/plugins/official/git-toolbox/dist/plugin.wasm.sources b/plugins/official/git-toolbox/dist/plugin.wasm.sources
index 0bcb7925..13c47727 100644
--- a/plugins/official/git-toolbox/dist/plugin.wasm.sources
+++ b/plugins/official/git-toolbox/dist/plugin.wasm.sources
@@ -1 +1 @@
-22876f842f727a2b9aa292986df3393f5b5f30c5c34319f5665f7d2701c8accf
+b8dde206a74b222b93e61056d4cbe403617ae240d142e01e91420a2aacdb2da4
diff --git a/plugins/official/graphviz/dist/plugin.wasm b/plugins/official/graphviz/dist/plugin.wasm
index 337a9781..172e8708 100644
Binary files a/plugins/official/graphviz/dist/plugin.wasm and b/plugins/official/graphviz/dist/plugin.wasm differ
diff --git a/plugins/official/graphviz/dist/plugin.wasm.sources b/plugins/official/graphviz/dist/plugin.wasm.sources
index f750b77c..8bdfeeb8 100644
--- a/plugins/official/graphviz/dist/plugin.wasm.sources
+++ b/plugins/official/graphviz/dist/plugin.wasm.sources
@@ -1 +1 @@
-14c60782eca79a25cf2c38d58c05be0eb97c4afc607d4cc83302d1445d094aab
+a681c2abd4a65d6aeb62efd514e9b170f4fca52b0c14d2d380a3b04be0a3fbc6
diff --git a/plugins/official/graphviz/src/lib.rs b/plugins/official/graphviz/src/lib.rs
index cd76c651..c8ab1210 100644
--- a/plugins/official/graphviz/src/lib.rs
+++ b/plugins/official/graphviz/src/lib.rs
@@ -52,12 +52,9 @@ pub fn diagnostics(text: &str, reports: &[Report]) -> Vec<Diagnostic> {
         .map(|r| {
             let line = r.line.map_or(0, |l| l.saturating_sub(1)).min(lines.len().saturating_sub(1) as u32);
             let len = lines.get(line as usize).map_or(0, |l| l.encode_utf16().count() as u32);
-            Diagnostic {
-                range: Range::new(Position::new(line, 0), Position::new(line, len)),
-                severity: if r.error { Severity::Error } else { Severity::Warning },
-                message: r.message.clone(),
-                code: Some("graphviz".into()),
-            }
+            let range = Range::new(Position::new(line, 0), Position::new(line, len));
+            let severity = if r.error { Severity::Error } else { Severity::Warning };
+            Diagnostic::new(range, severity, r.message.clone()).code("graphviz")
         })
         .collect()
 }
diff --git a/plugins/official/key-promoter/dist/plugin.wasm b/plugins/official/key-promoter/dist/plugin.wasm
index 9ef9e3d0..4a092d36 100644
Binary files a/plugins/official/key-promoter/dist/plugin.wasm and b/plugins/official/key-promoter/dist/plugin.wasm differ
diff --git a/plugins/official/key-promoter/dist/plugin.wasm.sources b/plugins/official/key-promoter/dist/plugin.wasm.sources
index 069068aa..23ac06dc 100644
--- a/plugins/official/key-promoter/dist/plugin.wasm.sources
+++ b/plugins/official/key-promoter/dist/plugin.wasm.sources
@@ -1 +1 @@
-7f5aacde2b8a8bcee5365c8cbda91045195688899c6537dc2159037cca74a672
+3c83bc9559df54457e19e650cdd21bab9d609e22daaa1fc4f596910b70834a34
diff --git a/plugins/official/license-header/dist/plugin.wasm b/plugins/official/license-header/dist/plugin.wasm
index 1c82e278..6672d2bd 100644
Binary files a/plugins/official/license-header/dist/plugin.wasm and b/plugins/official/license-header/dist/plugin.wasm differ
diff --git a/plugins/official/license-header/dist/plugin.wasm.sources b/plugins/official/license-header/dist/plugin.wasm.sources
index 7dc3c5ab..a70c551b 100644
--- a/plugins/official/license-header/dist/plugin.wasm.sources
+++ b/plugins/official/license-header/dist/plugin.wasm.sources
@@ -1 +1 @@
-45a7ee993b5c234b0d25e5b05ef60e714fa3edf63d6bd0d6a29b13587c8d09ce
+63f1bbdf6eca5a4642cd3453ae384ff3f876de0373c12008b757a63852164b71
diff --git a/plugins/official/license-header/src/lib.rs b/plugins/official/license-header/src/lib.rs
index 7fd5d789..1da3c9e1 100644
--- a/plugins/official/license-header/src/lib.rs
+++ b/plugins/official/license-header/src/lib.rs
@@ -129,12 +129,8 @@ pub fn header_edit(path: &str, text: &str, year: i64, owner: &str, license: &str
 fn missing(text: &str) -> Diagnostic {
     let line = insert_line(text);
     let len = text.lines().nth(line as usize).map_or(0, |l| l.encode_utf16().count() as u32);
-    Diagnostic {
-        range: Range::new(Position::new(line, 0), Position::new(line, len)),
-        severity: Severity::Info,
-        message: "No license header".into(),
-        code: Some(CODE.into()),
-    }
+    Diagnostic::new(Range::new(Position::new(line, 0), Position::new(line, len)), Severity::Info, "No license header")
+        .code(CODE)
 }
 
 /// Reports `path` when it takes a header and has none, clears it otherwise.
@@ -274,6 +270,7 @@ impl Providers for LicenseHeader {
             kind: Some("quickfix".into()),
             preferred: true,
             edits: vec![(doc.path.clone(), vec![edit])],
+            data: None,
         }]
     }
 }
diff --git a/plugins/official/mybatis/dist/plugin.wasm b/plugins/official/mybatis/dist/plugin.wasm
index ca729516..1fe1055f 100644
Binary files a/plugins/official/mybatis/dist/plugin.wasm and b/plugins/official/mybatis/dist/plugin.wasm differ
diff --git a/plugins/official/mybatis/dist/plugin.wasm.sources b/plugins/official/mybatis/dist/plugin.wasm.sources
index 758553fc..532aada7 100644
--- a/plugins/official/mybatis/dist/plugin.wasm.sources
+++ b/plugins/official/mybatis/dist/plugin.wasm.sources
@@ -1 +1 @@
-d5cf81455ae8b2b0fd6d1402d8775913bd7999db62b9bdf87675890ce52b1e80
+0db5cb24c358651d0e728ab3efb52286290c1a38ec379435225c935d4165ad6a
diff --git a/plugins/official/regex-tester/dist/plugin.wasm b/plugins/official/regex-tester/dist/plugin.wasm
index 1d39d764..d2740781 100644
Binary files a/plugins/official/regex-tester/dist/plugin.wasm and b/plugins/official/regex-tester/dist/plugin.wasm differ
diff --git a/plugins/official/regex-tester/dist/plugin.wasm.sources b/plugins/official/regex-tester/dist/plugin.wasm.sources
index 013089c4..845c9957 100644
--- a/plugins/official/regex-tester/dist/plugin.wasm.sources
+++ b/plugins/official/regex-tester/dist/plugin.wasm.sources
@@ -1 +1 @@
-227c8150c6ad7a5a20236764f149c876cbbc3b082763bf2e7fc05de99726b740
+257478b050ea360c55e904f2a89c6069293139ff0d97ba860de3f29dac927787
diff --git a/plugins/official/solidity/dist/plugin.wasm b/plugins/official/solidity/dist/plugin.wasm
index 4fd185f6..e1a8d32d 100644
Binary files a/plugins/official/solidity/dist/plugin.wasm and b/plugins/official/solidity/dist/plugin.wasm differ
diff --git a/plugins/official/solidity/dist/plugin.wasm.sources b/plugins/official/solidity/dist/plugin.wasm.sources
index 20e8de03..681447c6 100644
--- a/plugins/official/solidity/dist/plugin.wasm.sources
+++ b/plugins/official/solidity/dist/plugin.wasm.sources
@@ -1 +1 @@
-bbadcaa7a86a3e0a3f8be6d86aed2229d5cdfd128fda3435b4d64c7e19ad1df2
+21e7510d6a3712bf0f21d53a5c8d652e3c2787d89a1fc25998cde96efe124207
diff --git a/plugins/official/string-tools/dist/plugin.wasm b/plugins/official/string-tools/dist/plugin.wasm
index b38c2f9c..b38b7db6 100644
Binary files a/plugins/official/string-tools/dist/plugin.wasm and b/plugins/official/string-tools/dist/plugin.wasm differ
diff --git a/plugins/official/string-tools/dist/plugin.wasm.sources b/plugins/official/string-tools/dist/plugin.wasm.sources
index 7c78b969..56d78c0a 100644
--- a/plugins/official/string-tools/dist/plugin.wasm.sources
+++ b/plugins/official/string-tools/dist/plugin.wasm.sources
@@ -1 +1 @@
-09cc92e8e731f8f59f3857a71f9a30cc3d9e04a1c32092920f573b0f26592855
+04844bfbfbcb1770f4f4742658944c592922b037b2387e9340de58ef0d9baacc
diff --git a/sdk/rust/openidea-plugin/src/host.rs b/sdk/rust/openidea-plugin/src/host.rs
index 187c5f8b..760c6d30 100644
--- a/sdk/rust/openidea-plugin/src/host.rs
+++ b/sdk/rust/openidea-plugin/src/host.rs
@@ -152,24 +152,12 @@ mod imp {
         wit::vcs::fetch(p).map_err(error)
     }
 
-    fn kind(k: EventKind) -> wit::events::EventKind {
-        use wit::events::EventKind as K;
-        match k {
-            EventKind::FileOpened => K::FileOpened,
-            EventKind::FileSaved => K::FileSaved,
-            EventKind::EditorFocused => K::EditorFocused,
-            EventKind::ActionPerformed => K::ActionPerformed,
-            EventKind::VcsChanged => K::VcsChanged,
-            EventKind::Scheduled => K::Scheduled,
-        }
-    }
-
     pub fn subscribe(k: EventKind) -> Result<(), Error> {
-        wit::events::subscribe(kind(k)).map_err(error)
+        wit::events::subscribe(k.name()).map_err(error)
     }
 
     pub fn unsubscribe(k: EventKind) {
-        wit::events::unsubscribe(kind(k))
+        wit::events::unsubscribe(k.name())
     }
 
     pub fn begin_task(title: &str, cancellable: bool) -> TaskRes {
@@ -189,7 +177,7 @@ mod imp {
     }
 
     pub fn publish_diagnostics(path: &str, items: &[Diagnostic]) -> Result<(), Error> {
-        use wit::diagnostics::{Diagnostic as D, Severity as S};
+        use wit::diagnostics::{Diagnostic as D, RelatedInformation as R, Severity as S};
         let items: Vec<D> = items
             .iter()
             .map(|d| D {
@@ -202,6 +190,23 @@ mod imp {
                 },
                 message: d.message.clone(),
                 code: d.code.clone(),
+                source: d.source.clone(),
+                tags: [(d.unnecessary, "unnecessary"), (d.deprecated, "deprecated")]
+                    .into_iter()
+                    .filter(|(on, _)| *on)
+                    .map(|(_, tag)| tag.to_owned())
+                    .collect(),
+                related: d
+                    .related
+                    .iter()
+                    .map(|r| R {
+                        location: wit::types::Location {
+                            path: r.location.path.clone(),
+                            range: range_out(r.location.range),
+                        },
+                        message: r.message.clone(),
+                    })
+                    .collect(),
             })
             .collect();
         wit::diagnostics::publish(path, &items).map_err(error)
@@ -264,7 +269,7 @@ mod imp {
     }
 
     pub fn event(e: wit::events::Event) -> Event {
-        use wit::events::{ActionSource as S, Event as E};
+        use wit::events::Event as E;
         match e {
             E::FileOpened(p) => Event::FileOpened(p),
             E::FileSaved(p) => Event::FileSaved(p),
@@ -274,16 +279,10 @@ mod imp {
             E::ActionPerformed(a) => Event::ActionPerformed(ActionPerformed {
                 action: a.action,
                 title: a.title,
-                source: match a.source {
-                    S::Keyboard => ActionSource::Keyboard,
-                    S::Menu => ActionSource::Menu,
-                    S::Toolbar => ActionSource::Toolbar,
-                    S::ContextMenu => ActionSource::ContextMenu,
-                    S::Search => ActionSource::Search,
-                    S::Other => ActionSource::Other,
-                },
+                source: ActionSource::parse(&a.source),
                 shortcut: a.shortcut,
             }),
+            E::Other(x) => Event::Other { kind: x.kind, data: x.data },
         }
     }
 }
diff --git a/sdk/rust/openidea-plugin/src/lib.rs b/sdk/rust/openidea-plugin/src/lib.rs
index f59d728c..57aebe86 100644
--- a/sdk/rust/openidea-plugin/src/lib.rs
+++ b/sdk/rust/openidea-plugin/src/lib.rs
@@ -255,6 +255,16 @@ macro_rules! __providers_exports {
                 $crate::__rt::code_actions::<$plugin>(doc, selection)
             }
 
+            fn resolve_code_action(
+                doc: $crate::providers_bindings::exports::openidea::plugin::providers::Document,
+                action: $crate::providers_bindings::exports::openidea::plugin::providers::CodeAction,
+            ) -> ::core::result::Result<
+                $crate::providers_bindings::exports::openidea::plugin::providers::CodeAction,
+                $crate::bindings::openidea::plugin::types::Error,
+            > {
+                $crate::__rt::resolve_code_action::<$plugin>(doc, action)
+            }
+
             fn definition(
                 doc: $crate::providers_bindings::exports::openidea::plugin::providers::Document,
                 at: $crate::bindings::openidea::plugin::types::Position,
@@ -420,9 +430,12 @@ pub mod __rt {
                 detail: i.detail,
                 kind: i.kind.map(|k| k.as_str().to_owned()),
                 insert_text: i.insert_text,
+                snippet: i.snippet,
                 replace: i.replace.map(crate::host::__range_to),
                 sort_text: i.sort_text,
+                filter_text: i.filter_text,
                 documentation: i.documentation,
+                additional_edits: i.additional_edits.into_iter().map(edit_out).collect(),
             })
             .collect()
     }
@@ -443,25 +456,54 @@ pub mod __rt {
         sel: b::types::Range,
     ) -> Vec<w::CodeAction> {
         let d = doc(d);
-        with::<T, _>(|x| x.code_actions(&d, crate::host::__range_from(sel)))
-            .into_iter()
-            .map(|a| w::CodeAction {
-                title: a.title,
-                kind: a.kind,
-                preferred: a.preferred,
-                edits: a
-                    .edits
-                    .into_iter()
-                    .map(|(path, edits)| w::FileEdit {
-                        path,
-                        edits: edits
-                            .into_iter()
-                            .map(|e| b::types::TextEdit { range: crate::host::__range_to(e.range), text: e.text })
-                            .collect(),
-                    })
-                    .collect(),
-            })
-            .collect()
+        with::<T, _>(|x| x.code_actions(&d, crate::host::__range_from(sel))).into_iter().map(action_out).collect()
+    }
+
+    pub fn resolve_code_action<T: Plugin + p::Providers + Default>(
+        d: w::Document,
+        action: w::CodeAction,
+    ) -> Result<w::CodeAction, b::types::Error> {
+        let d = doc(d);
+        with::<T, _>(|x| x.resolve_code_action(&d, action_in(action))).map(action_out).map_err(error_out)
+    }
+
+    fn edit_out(e: crate::TextEdit) -> b::types::TextEdit {
+        b::types::TextEdit { range: crate::host::__range_to(e.range), text: e.text }
+    }
+
+    fn action_out(a: p::CodeAction) -> w::CodeAction {
+        w::CodeAction {
+            title: a.title,
+            kind: a.kind,
+            preferred: a.preferred,
+            edits: a
+                .edits
+                .into_iter()
+                .map(|(path, edits)| w::FileEdit { path, edits: edits.into_iter().map(edit_out).collect() })
+                .collect(),
+            data: a.data,
+        }
+    }
+
+    fn action_in(a: w::CodeAction) -> p::CodeAction {
+        p::CodeAction {
+            title: a.title,
+            kind: a.kind,
+            preferred: a.preferred,
+            edits: a
+                .edits
+                .into_iter()
+                .map(|f| {
+                    let edits = f
+                        .edits
+                        .into_iter()
+                        .map(|e| crate::TextEdit { range: crate::host::__range_from(e.range), text: e.text })
+                        .collect();
+                    (f.path, edits)
+                })
+                .collect(),
+            data: a.data,
+        }
     }
 
     pub fn definition<T: Plugin + p::Providers + Default>(
@@ -531,6 +573,9 @@ pub mod __rt {
                             v::FieldValue::Multiline(t) => vt::FieldValue::Multiline(t),
                             v::FieldValue::Checkbox(c) => vt::FieldValue::Checkbox(c),
                             v::FieldValue::Choice(o, s) => vt::FieldValue::Choice((o, s)),
+                            v::FieldValue::Other { kind, data } => {
+                                vt::FieldValue::Other(b::types::Extension { kind, data })
+                            }
                         },
                     })
                     .collect(),
@@ -543,6 +588,7 @@ pub mod __rt {
                 editable: t.editable,
             }),
             v::Body::Html(h) => vt::Body::Html(h),
+            v::Body::Other { kind, data } => vt::Body::Other(b::types::Extension { kind, data }),
         };
         vt::View {
             toolbar: view
@@ -582,6 +628,7 @@ pub mod __rt {
             vt::ViewEvent::InsertRow(r) => v::ViewEvent::InsertRow(r),
             vt::ViewEvent::DeleteRows(r) => v::ViewEvent::DeleteRows(r),
             vt::ViewEvent::Message(m) => v::ViewEvent::Message(m),
+            vt::ViewEvent::Other(x) => v::ViewEvent::Other { kind: x.kind, data: x.data },
         };
         with::<T, _>(|p| p.handle(&view, event, &ctx)).map_err(error_out)
     }
diff --git a/sdk/rust/openidea-plugin/src/mock.rs b/sdk/rust/openidea-plugin/src/mock.rs
index 33ce121d..66f38eb7 100644
--- a/sdk/rust/openidea-plugin/src/mock.rs
+++ b/sdk/rust/openidea-plugin/src/mock.rs
@@ -722,11 +722,8 @@ mod tests {
         let out = mock.invocation().project().unwrap().run_process("java", &["-version".into()], None).unwrap();
         assert_eq!(out.stdout, "-version");
         assert_eq!(mock.process_runs()[0].cwd.as_deref(), Some("/project"));
-        host::publish_diagnostics(
-            "/project/a.java",
-            &[Diagnostic { range: Range::default(), severity: Severity::Warning, message: "m".into(), code: None }],
-        )
-        .unwrap();
+        host::publish_diagnostics("/project/a.java", &[Diagnostic::new(Range::default(), Severity::Warning, "m")])
+            .unwrap();
         assert_eq!(mock.diagnostics()["/project/a.java"].len(), 1);
     }
 }
diff --git a/sdk/rust/openidea-plugin/src/providers.rs b/sdk/rust/openidea-plugin/src/providers.rs
index c10f75cf..2cf80850 100644
--- a/sdk/rust/openidea-plugin/src/providers.rs
+++ b/sdk/rust/openidea-plugin/src/providers.rs
@@ -92,12 +92,18 @@ pub struct CompletionItem {
     pub label: String,
     pub detail: Option<String>,
     pub kind: Option<CompletionKind>,
+    /// With `snippet`, tab stops and placeholders (`$1`, `${1:name}`, `$0`).
     pub insert_text: String,
+    pub snippet: bool,
     /// Replaced on accept; `None`: the word at the caret.
     pub replace: Option<Range>,
     pub sort_text: Option<String>,
+    /// Matched against what was typed instead of `label`.
+    pub filter_text: Option<String>,
     /// Markdown.
     pub documentation: Option<String>,
+    /// Applied with the item elsewhere in the document (an import).
+    pub additional_edits: Vec<TextEdit>,
 }
 
 impl CompletionItem {
@@ -107,9 +113,12 @@ impl CompletionItem {
             detail: None,
             kind: Some(kind),
             insert_text: label.into(),
+            snippet: false,
             replace: None,
             sort_text: None,
+            filter_text: None,
             documentation: None,
+            additional_edits: Vec::new(),
         }
     }
 }
@@ -129,6 +138,9 @@ pub struct CodeAction {
     pub preferred: bool,
     /// (absolute path, edits) per file.
     pub edits: Vec<(String, Vec<TextEdit>)>,
+    /// The plugin's own reference: with it and no `edits`, the edits come
+    /// from [`Providers::resolve_code_action`] once the user picks the action.
+    pub data: Option<String>,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -157,6 +169,12 @@ pub trait Providers {
         Vec::new()
     }
 
+    /// The edits of an action [`Providers::code_actions`] returned with
+    /// `data`, when the user picks it (the command budget applies, not 50 ms).
+    fn resolve_code_action(&mut self, _doc: &Document, action: CodeAction) -> Result<CodeAction, crate::Error> {
+        Ok(action)
+    }
+
     fn definition(&mut self, _doc: &Document, _at: Position) -> Vec<Location> {
         Vec::new()
     }
diff --git a/sdk/rust/openidea-plugin/src/types.rs b/sdk/rust/openidea-plugin/src/types.rs
index 5a74f67d..6a6fbd7a 100644
--- a/sdk/rust/openidea-plugin/src/types.rs
+++ b/sdk/rust/openidea-plugin/src/types.rs
@@ -143,7 +143,9 @@ pub struct StatusItem {
     pub command: Option<String>,
 }
 
+/// Kinds of workbench events; later SDKs add more.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[non_exhaustive]
 pub enum EventKind {
     FileOpened,
     FileSaved,
@@ -154,17 +156,46 @@ pub enum EventKind {
     Scheduled,
 }
 
-/// How the user started an action.
+impl EventKind {
+    /// The name the IDE knows it by.
+    pub fn name(self) -> &'static str {
+        match self {
+            Self::FileOpened => "file-opened",
+            Self::FileSaved => "file-saved",
+            Self::EditorFocused => "editor-focused",
+            Self::ActionPerformed => "action-performed",
+            Self::VcsChanged => "vcs-changed",
+            Self::Scheduled => "scheduled",
+        }
+    }
+}
+
+/// How the user started an action; later IDEs may report more.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum ActionSource {
     Keyboard,
     Menu,
     Toolbar,
     ContextMenu,
     Search,
+    /// Anything else, including sources this SDK doesn't know.
     Other,
 }
 
+impl ActionSource {
+    pub fn parse(name: &str) -> Self {
+        match name {
+            "keyboard" => Self::Keyboard,
+            "menu" => Self::Menu,
+            "toolbar" => Self::Toolbar,
+            "context-menu" => Self::ContextMenu,
+            "search" => Self::Search,
+            _ => Self::Other,
+        }
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct ActionPerformed {
     /// Action id (`editor.duplicate-line`).
@@ -177,6 +208,7 @@ pub struct ActionPerformed {
 
 /// A workbench event (see [`crate::host::subscribe`]).
 #[derive(Clone, Debug, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum Event {
     FileOpened(String),
     FileSaved(String),
@@ -186,6 +218,11 @@ pub enum Event {
     VcsChanged(String),
     /// The `on-schedule` period elapsed.
     Scheduled,
+    /// A kind this SDK doesn't know: its name and JSON data.
+    Other {
+        kind: String,
+        data: String,
+    },
 }
 
 /// The repository containing a project.
@@ -227,6 +264,41 @@ pub struct Diagnostic {
     pub message: String,
     /// Rule or check id.
     pub code: Option<String>,
+    /// The tool that found it, when not the plugin itself.
+    pub source: Option<String>,
+    /// Code that does nothing (shown faded).
+    pub unnecessary: bool,
+    /// Use of something deprecated (struck through).
+    pub deprecated: bool,
+    /// Other places that explain it.
+    pub related: Vec<RelatedInformation>,
+}
+
+impl Diagnostic {
+    pub fn new(range: Range, severity: Severity, message: impl Into<String>) -> Self {
+        Self {
+            range,
+            severity,
+            message: message.into(),
+            code: None,
+            source: None,
+            unnecessary: false,
+            deprecated: false,
+            related: Vec::new(),
+        }
+    }
+
+    pub fn code(mut self, code: impl Into<String>) -> Self {
+        self.code = Some(code.into());
+        self
+    }
+}
+
+/// Another place that explains a diagnostic.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RelatedInformation {
+    pub location: Location,
+    pub message: String,
 }
 
 /// An HTTP request (see [`crate::host::fetch`]).
@@ -276,3 +348,17 @@ pub struct ProcessOutput {
     pub stdout: String,
     pub stderr: String,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn names_the_ide_uses() {
+        assert_eq!(EventKind::ActionPerformed.name(), "action-performed");
+        assert_eq!(ActionSource::parse("context-menu"), ActionSource::ContextMenu);
+        assert_eq!(ActionSource::parse("pen"), ActionSource::Other, "a source of a newer IDE");
+        let d = Diagnostic::new(Range::default(), Severity::Hint, "m").code("c");
+        assert_eq!((d.code.as_deref(), d.unnecessary, d.related.len()), (Some("c"), false, 0));
+    }
+}
diff --git a/sdk/rust/openidea-plugin/src/views.rs b/sdk/rust/openidea-plugin/src/views.rs
index 3da8e506..b8a693d5 100644
--- a/sdk/rust/openidea-plugin/src/views.rs
+++ b/sdk/rust/openidea-plugin/src/views.rs
@@ -110,12 +110,19 @@ impl ListItem {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum FieldValue {
     Text(String),
     Multiline(String),
     Checkbox(bool),
     /// Options and the chosen one.
     Choice(Vec<String>, String),
+    /// A field type of a newer plugin API: its kind and JSON data (IDEs that
+    /// don't know it leave the field out).
+    Other {
+        kind: String,
+        data: String,
+    },
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -142,6 +149,7 @@ pub struct Table {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum Body {
     Message(String),
     Tree(Vec<TreeItem>),
@@ -151,6 +159,12 @@ pub enum Body {
     /// Shown in a sandboxed frame; its script talks to the plugin with
     /// `openidea.postMessage(text)` and `openidea.onMessage(fn)`.
     Html(String),
+    /// A body of a newer plugin API: its kind and JSON data (IDEs that don't
+    /// know it say they need updating).
+    Other {
+        kind: String,
+        data: String,
+    },
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -197,6 +211,7 @@ impl Viewport {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum ViewEvent {
     Button(String),
     Activate(String),
@@ -213,6 +228,11 @@ pub enum ViewEvent {
     InsertRow(u32),
     DeleteRows(Vec<u32>),
     Message(String),
+    /// An event this SDK doesn't know: its kind and JSON data.
+    Other {
+        kind: String,
+        data: String,
+    },
 }
 
 /// Content of the plugin's declared views and custom editors.
diff --git a/sdk/rust/openidea-plugin/wit/events.wit b/sdk/rust/openidea-plugin/wit/events.wit
index 8470c298..2d118d81 100644
--- a/sdk/rust/openidea-plugin/wit/events.wit
+++ b/sdk/rust/openidea-plugin/wit/events.wit
@@ -2,36 +2,15 @@ package openidea:plugin@1.0.0;
 
 /// Workbench events, delivered in batches to `event-handler.handle`.
 interface events {
-    use types.{error};
-
-    enum event-kind {
-        file-opened,
-        file-saved,
-        /// The focused editor changed.
-        editor-focused,
-        /// An IDE action ran. Requires `events.input`.
-        action-performed,
-        /// A repository's state changed (commit, checkout, fetch, …).
-        vcs-changed,
-        /// The plugin's `on-schedule` period elapsed.
-        scheduled,
-    }
-
-    /// How the user started an action.
-    enum action-source {
-        keyboard,
-        menu,
-        toolbar,
-        context-menu,
-        search,
-        other,
-    }
+    use types.{error, extension};
 
     record action-performed {
         /// Action id (`editor.duplicate-line`).
         action: string,
         title: string,
-        source: action-source,
+        /// How the user started it: `keyboard`, `menu`, `toolbar`,
+        /// `context-menu`, `search` or `other` (more may be added).
+        source: string,
         /// Its keyboard shortcut, when it has one (`Ctrl+D`).
         shortcut: option<string>,
     }
@@ -43,14 +22,21 @@ interface events {
         action-performed(action-performed),
         vcs-changed(string),
         scheduled,
+        /// A kind added after 1.0 (subscribed to by its name).
+        other(extension),
     }
 
     /// Delivers `kind` events from now on, for the rest of the session (also
     /// across idle reclaim: an event activates the plugin again). Declare
     /// `activation = ["on-event:<kind>"]` to get them before first use.
+    /// Kinds: `file-opened`, `file-saved`, `editor-focused` (the focused editor
+    /// changed), `vcs-changed` (a repository's state changed: commit,
+    /// checkout, fetch…), `action-performed` (an IDE action ran) and
+    /// `scheduled` (the `on-schedule` period elapsed); later IDEs add more,
+    /// and an IDE that doesn't know one fails with `invalid`.
     /// Requires `events` (`events.input` for `action-performed`).
-    subscribe: func(kind: event-kind) -> result<_, error>;
-    unsubscribe: func(kind: event-kind);
+    subscribe: func(kind: string) -> result<_, error>;
+    unsubscribe: func(kind: string);
 }
 
 /// Long-running work with a progress indicator. While a task is open, the
diff --git a/sdk/rust/openidea-plugin/wit/io.wit b/sdk/rust/openidea-plugin/wit/io.wit
index a1aeb849..f1fe634a 100644
--- a/sdk/rust/openidea-plugin/wit/io.wit
+++ b/sdk/rust/openidea-plugin/wit/io.wit
@@ -2,7 +2,7 @@ package openidea:plugin@1.0.0;
 
 /// Problems in files, shown in the editor and the Problems view.
 interface diagnostics {
-    use types.{error, range};
+    use types.{error, range, location};
 
     enum severity {
         error,
@@ -11,12 +11,23 @@ interface diagnostics {
         hint,
     }
 
+    /// Another place that explains a diagnostic (the earlier declaration, say).
+    record related-information {
+        location: location,
+        message: string,
+    }
+
     record diagnostic {
         range: range,
         severity: severity,
         message: string,
         /// Rule or check id (`LineLength`).
         code: option<string>,
+        /// The tool that found it, when not the plugin itself (`checkstyle`).
+        source: option<string>,
+        /// `unnecessary` (shown faded) and `deprecated` (struck through); unknown ones are ignored.
+        tags: list<string>,
+        related: list<related-information>,
     }
 
     /// Replaces the plugin's diagnostics for the file at `path` (absolute, in
diff --git a/sdk/rust/openidea-plugin/wit/providers.wit b/sdk/rust/openidea-plugin/wit/providers.wit
index cfca6560..97dd4c7a 100644
--- a/sdk/rust/openidea-plugin/wit/providers.wit
+++ b/sdk/rust/openidea-plugin/wit/providers.wit
@@ -5,7 +5,7 @@ package openidea:plugin@1.0.0;
 /// on the editing path: a result later than ~50 ms is dropped, a call still
 /// running at 500 ms is interrupted.
 interface providers {
-    use types.{position, range, text-edit, location};
+    use types.{error, position, range, text-edit, location};
 
     /// The document a request is about.
     record document {
@@ -24,11 +24,17 @@ interface providers {
         /// constant, struct, event, operator or type-parameter. Unknown kinds
         /// show no icon.
         kind: option<string>,
+        /// With `snippet`, tab stops and placeholders (`$1`, `${1:name}`, `$0`).
         insert-text: string,
+        snippet: bool,
         /// Replaced on accept; `none`: the word at the caret.
         replace: option<range>,
         sort-text: option<string>,
+        /// Matched against what was typed instead of `label`.
+        filter-text: option<string>,
         documentation: option<string>,
+        /// Applied with the item elsewhere in the document (an import).
+        additional-edits: list<text-edit>,
     }
 
     record inline-suggestion {
@@ -48,6 +54,9 @@ interface providers {
         kind: option<string>,
         preferred: bool,
         edits: list<file-edit>,
+        /// The plugin's own reference: with it and no `edits`, the edits are
+        /// computed by `resolve-code-action` once the user picks the action.
+        data: option<string>,
     }
 
     record line-marker {
@@ -64,6 +73,9 @@ interface providers {
     inline-completion: func(doc: document, at: position) -> option<inline-suggestion>;
     /// Actions for `selection` (quick fixes for the plugin's own diagnostics).
     code-actions: func(doc: document, selection: range) -> list<code-action>;
+    /// The edits of an action `code-actions` returned with `data`, when the
+    /// user picks it (the command budget applies, not the editor's 50 ms).
+    resolve-code-action: func(doc: document, action: code-action) -> result<code-action, error>;
     definition: func(doc: document, at: position) -> list<location>;
     line-markers: func(doc: document) -> list<line-marker>;
 }
diff --git a/sdk/rust/openidea-plugin/wit/types.wit b/sdk/rust/openidea-plugin/wit/types.wit
index 5c4f237e..2e2b48f7 100644
--- a/sdk/rust/openidea-plugin/wit/types.wit
+++ b/sdk/rust/openidea-plugin/wit/types.wit
@@ -52,6 +52,15 @@ interface types {
         range: range,
     }
 
+    /// A case added after 1.0, carried by the `other` case of a variant that
+    /// grows (events, view bodies, view events, form fields): its kind and its
+    /// data as JSON. Whoever doesn't know the kind ignores it or shows a
+    /// fallback; the SDKs decode the kinds they know.
+    record extension {
+        kind: string,
+        data: string,
+    }
+
     /// Passed to `lifecycle.activate`.
     record context {
         plugin-id: string,
diff --git a/sdk/rust/openidea-plugin/wit/views.wit b/sdk/rust/openidea-plugin/wit/views.wit
index de1ae780..dcc806dc 100644
--- a/sdk/rust/openidea-plugin/wit/views.wit
+++ b/sdk/rust/openidea-plugin/wit/views.wit
@@ -8,6 +8,8 @@ package openidea:plugin@1.0.0;
 /// runs in the WebView, except a `html` body, which is shown in a sandboxed
 /// frame that can only exchange messages with the plugin.
 interface view-types {
+    use types.{extension};
+
     record button {
         id: string,
         label: string,
@@ -43,6 +45,8 @@ interface view-types {
         checkbox(bool),
         /// The options and the chosen one.
         choice(tuple<list<string>, string>),
+        /// A field type added after 1.0 (an IDE that doesn't know it leaves it out).
+        other(extension),
     }
 
     record field {
@@ -72,6 +76,8 @@ interface view-types {
         /// network, no IDE API. Its script talks to the plugin with
         /// `openidea.postMessage(text)` / `openidea.onMessage(fn)`.
         html(string),
+        /// A body added after 1.0; an IDE that doesn't know it says it needs updating.
+        other(extension),
     }
 
     record view {
@@ -109,6 +115,8 @@ interface view-types {
         delete-rows(list<u32>),
         /// From the `html` body's script.
         message(string),
+        /// An event added after 1.0, from a body or field added after 1.0.
+        other(extension),
     }
 }
 
diff --git a/wit/events.wit b/wit/events.wit
index 8470c298..2d118d81 100644
--- a/wit/events.wit
+++ b/wit/events.wit
@@ -2,36 +2,15 @@ package openidea:plugin@1.0.0;
 
 /// Workbench events, delivered in batches to `event-handler.handle`.
 interface events {
-    use types.{error};
-
-    enum event-kind {
-        file-opened,
-        file-saved,
-        /// The focused editor changed.
-        editor-focused,
-        /// An IDE action ran. Requires `events.input`.
-        action-performed,
-        /// A repository's state changed (commit, checkout, fetch, …).
-        vcs-changed,
-        /// The plugin's `on-schedule` period elapsed.
-        scheduled,
-    }
-
-    /// How the user started an action.
-    enum action-source {
-        keyboard,
-        menu,
-        toolbar,
-        context-menu,
-        search,
-        other,
-    }
+    use types.{error, extension};
 
     record action-performed {
         /// Action id (`editor.duplicate-line`).
         action: string,
         title: string,
-        source: action-source,
+        /// How the user started it: `keyboard`, `menu`, `toolbar`,
+        /// `context-menu`, `search` or `other` (more may be added).
+        source: string,
         /// Its keyboard shortcut, when it has one (`Ctrl+D`).
         shortcut: option<string>,
     }
@@ -43,14 +22,21 @@ interface events {
         action-performed(action-performed),
         vcs-changed(string),
         scheduled,
+        /// A kind added after 1.0 (subscribed to by its name).
+        other(extension),
     }
 
     /// Delivers `kind` events from now on, for the rest of the session (also
     /// across idle reclaim: an event activates the plugin again). Declare
     /// `activation = ["on-event:<kind>"]` to get them before first use.
+    /// Kinds: `file-opened`, `file-saved`, `editor-focused` (the focused editor
+    /// changed), `vcs-changed` (a repository's state changed: commit,
+    /// checkout, fetch…), `action-performed` (an IDE action ran) and
+    /// `scheduled` (the `on-schedule` period elapsed); later IDEs add more,
+    /// and an IDE that doesn't know one fails with `invalid`.
     /// Requires `events` (`events.input` for `action-performed`).
-    subscribe: func(kind: event-kind) -> result<_, error>;
-    unsubscribe: func(kind: event-kind);
+    subscribe: func(kind: string) -> result<_, error>;
+    unsubscribe: func(kind: string);
 }
 
 /// Long-running work with a progress indicator. While a task is open, the
diff --git a/wit/io.wit b/wit/io.wit
index a1aeb849..f1fe634a 100644
--- a/wit/io.wit
+++ b/wit/io.wit
@@ -2,7 +2,7 @@ package openidea:plugin@1.0.0;
 
 /// Problems in files, shown in the editor and the Problems view.
 interface diagnostics {
-    use types.{error, range};
+    use types.{error, range, location};
 
     enum severity {
         error,
@@ -11,12 +11,23 @@ interface diagnostics {
         hint,
     }
 
+    /// Another place that explains a diagnostic (the earlier declaration, say).
+    record related-information {
+        location: location,
+        message: string,
+    }
+
     record diagnostic {
         range: range,
         severity: severity,
         message: string,
         /// Rule or check id (`LineLength`).
         code: option<string>,
+        /// The tool that found it, when not the plugin itself (`checkstyle`).
+        source: option<string>,
+        /// `unnecessary` (shown faded) and `deprecated` (struck through); unknown ones are ignored.
+        tags: list<string>,
+        related: list<related-information>,
     }
 
     /// Replaces the plugin's diagnostics for the file at `path` (absolute, in
diff --git a/wit/providers.wit b/wit/providers.wit
index cfca6560..97dd4c7a 100644
--- a/wit/providers.wit
+++ b/wit/providers.wit
@@ -5,7 +5,7 @@ package openidea:plugin@1.0.0;
 /// on the editing path: a result later than ~50 ms is dropped, a call still
 /// running at 500 ms is interrupted.
 interface providers {
-    use types.{position, range, text-edit, location};
+    use types.{error, position, range, text-edit, location};
 
     /// The document a request is about.
     record document {
@@ -24,11 +24,17 @@ interface providers {
         /// constant, struct, event, operator or type-parameter. Unknown kinds
         /// show no icon.
         kind: option<string>,
+        /// With `snippet`, tab stops and placeholders (`$1`, `${1:name}`, `$0`).
         insert-text: string,
+        snippet: bool,
         /// Replaced on accept; `none`: the word at the caret.
         replace: option<range>,
         sort-text: option<string>,
+        /// Matched against what was typed instead of `label`.
+        filter-text: option<string>,
         documentation: option<string>,
+        /// Applied with the item elsewhere in the document (an import).
+        additional-edits: list<text-edit>,
     }
 
     record inline-suggestion {
@@ -48,6 +54,9 @@ interface providers {
         kind: option<string>,
         preferred: bool,
         edits: list<file-edit>,
+        /// The plugin's own reference: with it and no `edits`, the edits are
+        /// computed by `resolve-code-action` once the user picks the action.
+        data: option<string>,
     }
 
     record line-marker {
@@ -64,6 +73,9 @@ interface providers {
     inline-completion: func(doc: document, at: position) -> option<inline-suggestion>;
     /// Actions for `selection` (quick fixes for the plugin's own diagnostics).
     code-actions: func(doc: document, selection: range) -> list<code-action>;
+    /// The edits of an action `code-actions` returned with `data`, when the
+    /// user picks it (the command budget applies, not the editor's 50 ms).
+    resolve-code-action: func(doc: document, action: code-action) -> result<code-action, error>;
     definition: func(doc: document, at: position) -> list<location>;
     line-markers: func(doc: document) -> list<line-marker>;
 }
diff --git a/wit/types.wit b/wit/types.wit
index 5c4f237e..2e2b48f7 100644
--- a/wit/types.wit
+++ b/wit/types.wit
@@ -52,6 +52,15 @@ interface types {
         range: range,
     }
 
+    /// A case added after 1.0, carried by the `other` case of a variant that
+    /// grows (events, view bodies, view events, form fields): its kind and its
+    /// data as JSON. Whoever doesn't know the kind ignores it or shows a
+    /// fallback; the SDKs decode the kinds they know.
+    record extension {
+        kind: string,
+        data: string,
+    }
+
     /// Passed to `lifecycle.activate`.
     record context {
         plugin-id: string,
diff --git a/wit/views.wit b/wit/views.wit
index de1ae780..dcc806dc 100644
--- a/wit/views.wit
+++ b/wit/views.wit
@@ -8,6 +8,8 @@ package openidea:plugin@1.0.0;
 /// runs in the WebView, except a `html` body, which is shown in a sandboxed
 /// frame that can only exchange messages with the plugin.
 interface view-types {
+    use types.{extension};
+
     record button {
         id: string,
         label: string,
@@ -43,6 +45,8 @@ interface view-types {
         checkbox(bool),
         /// The options and the chosen one.
         choice(tuple<list<string>, string>),
+        /// A field type added after 1.0 (an IDE that doesn't know it leaves it out).
+        other(extension),
     }
 
     record field {
@@ -72,6 +76,8 @@ interface view-types {
         /// network, no IDE API. Its script talks to the plugin with
         /// `openidea.postMessage(text)` / `openidea.onMessage(fn)`.
         html(string),
+        /// A body added after 1.0; an IDE that doesn't know it says it needs updating.
+        other(extension),
     }
 
     record view {
@@ -109,6 +115,8 @@ interface view-types {
         delete-rows(list<u32>),
         /// From the `html` body's script.
         message(string),
+        /// An event added after 1.0, from a body or field added after 1.0.
+        other(extension),
     }
 }