diff --git a/examples/gallery/pages/devtools/apis.rs b/examples/gallery/pages/devtools/apis.rs
index f3c1063..63e8043 100644
--- a/examples/gallery/pages/devtools/apis.rs
+++ b/examples/gallery/pages/devtools/apis.rs
@@ -156,8 +156,7 @@ pub fn requests(window: &mut Window, cx: &mut App) -> impl IntoElement + use<> {
                     .flex_col()
                     .gap_4()
                     .child(
-                        EnvironmentSelector::new("devtools-environments", environments(), environment)
-                            .on_change(move |key, _, cx| change(&chose, cx, |desk| desk.environment = key.clone())),
+                        EnvironmentSelector::new("devtools-environments", environments(), environment, move |key, _, cx| change(&chose, cx, |desk| desk.environment = key.clone())),
                     )
                     .child(
                         div()
@@ -178,7 +177,11 @@ pub fn requests(window: &mut Window, cx: &mut App) -> impl IntoElement + use<> {
                                         })
                                     })
                                     .on_move(move |key, target, at, _, cx| {
-                                        change(&dragged, cx, |desk| desk.collection = moved(&desk.collection, key, target, at))
+                                        change(&dragged, cx, |desk| {
+                                            if let Some(collection) = moved(&desk.collection, key, target, at) {
+                                                desk.collection = collection;
+                                            }
+                                        })
                                     }),
                             ),
                     ),
@@ -255,8 +258,7 @@ pub fn socket(window: &mut Window, cx: &mut App) -> impl IntoElement + use<> {
     )
     .child(
         div().w(px(620.)).child(
-            WebSocketConsole::new("devtools-socket", "wss://stream.example.com/orders", state, messages, &draft, clock)
-                .on_send(move |text, _, cx| {
+            WebSocketConsole::new("devtools-socket", "wss://stream.example.com/orders", state, messages, &draft, clock, move |text, _, cx| {
                     sent.update(cx, |line, cx| {
                         let at = line.now;
                         line.messages.push(SocketMessage { direction: Direction::Sent, text, at });
@@ -333,8 +335,14 @@ pub fn graphql(window: &mut Window, cx: &mut App) -> impl IntoElement + use<> {
             fields: vec![("OPEN".into(), "".into()), ("SHIPPED".into(), "".into())],
         },
     ];
-    let mut explorer = GraphQLExplorer::new("devtools-graphql", types, &query, &variables, &search)
-        .on_run(move |_, _, _, cx| change(&ran, cx, |graph| graph.answer = Some(ANSWER.into())));
+    let mut explorer = GraphQLExplorer::new(
+        "devtools-graphql",
+        types,
+        &query,
+        &variables,
+        &search,
+        move |_, _, _, cx| change(&ran, cx, |graph| graph.answer = Some(ANSWER.into())),
+    );
     if let Some(answer) = answer {
         explorer = explorer.answer(answer);
     }
diff --git a/examples/gallery/pages/devtools/db.rs b/examples/gallery/pages/devtools/db.rs
index b7909af..04078b0 100644
--- a/examples/gallery/pages/devtools/db.rs
+++ b/examples/gallery/pages/devtools/db.rs
@@ -270,15 +270,12 @@ pub fn structure(window: &mut Window, cx: &mut App) -> impl IntoElement + use<>
             .flex_wrap()
             .gap_6()
             .child(
-                div().w(px(660.)).child(TableStructureEditor::new("devtools-structure", fields)
-                        .on_change(move |next, _, cx| change(&edited, cx, |build| build.fields = next)),
+                div().w(px(660.)).child(TableStructureEditor::new("devtools-structure", fields, move |next, _, cx| change(&edited, cx, |build| build.fields = next)),
                 ),
             )
             .child(
                 div().w(px(300.)).child(
-                    IndexManager::new("devtools-indexes", indexes, names)
-                        .on_drop(move |name, _, cx| change(&dropped, cx, |build| build.indexes.retain(|index| index.name != *name)))
-                        .on_create(move |index, _, cx| change(&created, cx, |build| build.indexes.push(index))),
+                    IndexManager::new("devtools-indexes", indexes, names, move |index, _, cx| change(&created, cx, |build| build.indexes.push(index)), move |name, _, cx| change(&dropped, cx, |build| build.indexes.retain(|index| index.name != *name))),
                 ),
             ),
     )
diff --git a/examples/gallery/pages/devtools/tools.rs b/examples/gallery/pages/devtools/tools.rs
index 7e700eb..2fece13 100644
--- a/examples/gallery/pages/devtools/tools.rs
+++ b/examples/gallery/pages/devtools/tools.rs
@@ -35,8 +35,7 @@ pub fn text(window: &mut Window, cx: &mut App) -> impl IntoElement + use<> {
             .child(div().w(px(380.)).child(Encoder::new("devtools-encoder", "Hello, 世界")))
             .child(
                 div().w(px(360.)).child(
-                    ColorContrastChecker::new("devtools-contrast", fore, back)
-                        .on_change(move |fore, back, _, cx| change(&colors, cx, |colors| *colors = (fore, back))),
+                    ColorContrastChecker::new("devtools-contrast", fore, back, move |fore, back, _, cx| change(&colors, cx, |colors| *colors = (fore, back))),
                 ),
             ),
     )
diff --git a/src/devtools/collection.rs b/src/devtools/collection.rs
index 2b159cc..f06ae50 100644
--- a/src/devtools/collection.rs
+++ b/src/devtools/collection.rs
@@ -85,7 +85,8 @@ fn placed(items: &mut Vec<Saved>, item: Saved, target: &str, at: DropAt) -> Resu
             (DropAt::After, _) => items.insert(ix + 1, item),
             (DropAt::Inside, Saved::Folder { items, .. }) => items.push(item),
             (DropAt::Inside, Saved::Request { key, .. }) => {
-                panic!("collection: {key} is a request, and nothing goes inside it")
+                log::error!("collection: {key} is a request, and nothing goes inside it");
+                return Err(item);
             }
         }
         return Ok(());
@@ -102,15 +103,19 @@ fn placed(items: &mut Vec<Saved>, item: Saved, target: &str, at: DropAt) -> Resu
     Err(item)
 }
 
-/// `items` with `key` moved to `at` of `target`, as a drop in the tree asks.
-pub fn moved(items: &[Saved], key: &str, target: &str, at: DropAt) -> Vec<Saved> {
+/// `items` with `key` moved to `at` of `target`, as a drop in the tree asks; none, logged, when either left the items.
+pub fn moved(items: &[Saved], key: &str, target: &str, at: DropAt) -> Option<Vec<Saved>> {
     let mut items = items.to_vec();
-    let item = taken(&mut items, key).unwrap_or_else(|| panic!("collection: no {key} to move"));
+    let Some(item) = taken(&mut items, key) else {
+        log::error!("collection: no {key} to move");
+        return None;
+    };
     if let Err(item) = placed(&mut items, item, target, at) {
-        panic!("collection: no {target} to move {} beside", item.key());
+        log::error!("collection: no {target} to move {} beside", item.key());
+        return None;
     }
     log::info!("collection: moved {key} {at:?} {target}");
-    items
+    Some(items)
 }
 
 type OnKey = Rc<dyn Fn(&SharedString, &mut Window, &mut App)>;
@@ -236,25 +241,32 @@ mod tests {
             Saved::request("z", "Z", Method::Post),
         ];
         assert_eq!(
-            keys(&moved(&items, "x", "b", DropAt::Inside)),
+            keys(&moved(&items, "x", "b", DropAt::Inside).expect("both are in the items")),
             ["a[y]", "b[x]", "z"]
         );
         assert_eq!(
-            keys(&moved(&items, "z", "a", DropAt::Inside)),
+            keys(&moved(&items, "z", "a", DropAt::Inside).expect("both are in the items")),
             ["a[x,y,z]", "b[]"],
             "a drop inside a folder lands last"
         );
         assert_eq!(
-            keys(&moved(&items, "z", "x", DropAt::Before)),
+            keys(&moved(&items, "z", "x", DropAt::Before).expect("both are in the items")),
             ["a[z,x,y]", "b[]"]
         );
         assert_eq!(
-            keys(&moved(&items, "x", "z", DropAt::After)),
+            keys(&moved(&items, "x", "z", DropAt::After).expect("both are in the items")),
             ["a[y]", "b[]", "z", "x"]
         );
         assert_eq!(
-            keys(&moved(&items, "b", "a", DropAt::Before)),
+            keys(&moved(&items, "b", "a", DropAt::Before).expect("both are in the items")),
             ["b[]", "a[x,y]", "z"]
         );
+        assert_eq!(moved(&items, "gone", "a", DropAt::Before), None);
+        assert_eq!(moved(&items, "x", "gone", DropAt::Before), None);
+        assert_eq!(
+            moved(&items, "x", "z", DropAt::Inside),
+            None,
+            "a request holds nothing"
+        );
     }
 }
diff --git a/src/devtools/contrast.rs b/src/devtools/contrast.rs
index 82cd9a6..98cb65f 100644
--- a/src/devtools/contrast.rs
+++ b/src/devtools/contrast.rs
@@ -64,7 +64,7 @@ pub struct ColorContrastChecker {
     id: ElementId,
     text: Hsla,
     background: Hsla,
-    on_change: Option<OnColors>,
+    on_change: OnColors,
 }
 
 impl ColorContrastChecker {
@@ -72,23 +72,15 @@ impl ColorContrastChecker {
         id: impl Into<ElementId>,
         text: impl Into<Hsla>,
         background: impl Into<Hsla>,
+        on_change: impl Fn(Hsla, Hsla, &mut Window, &mut App) + 'static,
     ) -> Self {
         Self {
             id: id.into(),
             text: text.into(),
             background: background.into(),
-            on_change: None,
+            on_change: Rc::new(on_change),
         }
     }
-
-    /// Gets the text's and the background's colors after either changes.
-    pub fn on_change(
-        mut self,
-        handler: impl Fn(Hsla, Hsla, &mut Window, &mut App) + 'static,
-    ) -> Self {
-        self.on_change = Some(Rc::new(handler));
-        self
-    }
 }
 
 impl RenderOnce for ColorContrastChecker {
@@ -99,9 +91,7 @@ impl RenderOnce for ColorContrastChecker {
             ..background
         };
         let ratio = contrast(over(text, solid), solid);
-        let on_change = self
-            .on_change
-            .unwrap_or_else(|| panic!("color contrast checker {:?} has no on_change", self.id));
+        let on_change = self.on_change;
         let theme = cx.theme();
         let well = |name: &'static str, color: Hsla, set: OnColor| {
             div()
diff --git a/src/devtools/environment.rs b/src/devtools/environment.rs
index 8103a68..3d8abe6 100644
--- a/src/devtools/environment.rs
+++ b/src/devtools/environment.rs
@@ -30,7 +30,7 @@ pub struct EnvironmentSelector {
     id: ElementId,
     environments: Vec<Environment>,
     selected: SharedString,
-    on_change: Option<OnKey>,
+    on_change: OnKey,
 }
 
 impl EnvironmentSelector {
@@ -38,22 +38,15 @@ impl EnvironmentSelector {
         id: impl Into<ElementId>,
         environments: impl IntoIterator<Item = Environment>,
         selected: impl Into<SharedString>,
+        on_change: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
     ) -> Self {
         Self {
             id: id.into(),
             environments: environments.into_iter().collect(),
             selected: selected.into(),
-            on_change: None,
+            on_change: Rc::new(on_change),
         }
     }
-
-    pub fn on_change(
-        mut self,
-        handler: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
-    ) -> Self {
-        self.on_change = Some(Rc::new(handler));
-        self
-    }
 }
 
 /// What a row shows for a value: dots for a secret until it is opened.
@@ -84,71 +77,71 @@ impl RenderOnce for EnvironmentSelector {
             .environments
             .iter()
             .find(|environment| environment.key == self.selected)
-            .unwrap_or_else(|| {
-                panic!(
-                    "environment selector {id:?}: no environment {}",
-                    self.selected
-                )
-            })
-            .clone();
+            .cloned();
+        if chosen.is_none() {
+            log::error!(
+                "environment selector {id:?}: no environment {}; none chosen",
+                self.selected
+            );
+        }
         let shown = window.use_keyed_state((id.clone(), "shown"), cx, |_, _| Vec::<Secret>::new());
         let theme = cx.theme();
-        let on_change = self
-            .on_change
-            .unwrap_or_else(|| panic!("environment selector {id:?} has no on_change"));
-        let rows = chosen.variables.iter().map(|(name, value)| {
-            let secret = chosen.secrets.contains(name);
-            let key: Secret = (chosen.key.clone(), name.clone());
-            let open = shown.read(cx).contains(&key);
-            let flip = shown.clone();
-            let seen = format!(
-                "environment-{}-{name}-{}",
-                chosen.key,
-                if secret && !open { "masked" } else { "shown" }
-            );
-            div()
-                .flex()
-                .items_center()
-                .gap_2()
-                .py_1()
-                .child(
-                    div()
-                        .flex_none()
-                        .w(theme.label_width())
-                        .font_family(theme.mono_family.clone())
-                        .text_size(theme.text_size(TextSize::Sm))
-                        .child(Ellipsis::new(format!("{{{{{name}}}}}"))),
-                )
-                .child(
-                    div()
-                        .flex_1()
-                        .min_w_0()
-                        .text_size(theme.text_size(TextSize::Sm))
-                        .text_color(theme.colors.fg_muted)
-                        .debug_selector(move || seen)
-                        .child(Ellipsis::new(shown_value(value, secret, open))),
-                )
-                .children(secret.then(|| {
-                    IconButton::new(
-                        (id.clone(), format!("reveal-{name}")),
-                        if open {
-                            IconName::EyeOff
-                        } else {
-                            IconName::Eye
-                        },
+        let on_change = self.on_change;
+        let rows = chosen.iter().flat_map(|chosen| {
+            chosen.variables.iter().map(|(name, value)| {
+                let secret = chosen.secrets.contains(name);
+                let key: Secret = (chosen.key.clone(), name.clone());
+                let open = shown.read(cx).contains(&key);
+                let flip = shown.clone();
+                let seen = format!(
+                    "environment-{}-{name}-{}",
+                    chosen.key,
+                    if secret && !open { "masked" } else { "shown" }
+                );
+                div()
+                    .flex()
+                    .items_center()
+                    .gap_2()
+                    .py_1()
+                    .child(
+                        div()
+                            .flex_none()
+                            .w(theme.label_width())
+                            .font_family(theme.mono_family.clone())
+                            .text_size(theme.text_size(TextSize::Sm))
+                            .child(Ellipsis::new(format!("{{{{{name}}}}}"))),
                     )
-                    .tooltip(if open {
-                        "Hide the value"
-                    } else {
-                        "Show the value"
-                    })
-                    .on_click(move |_, _, cx| {
-                        flip.update(cx, |shown, cx| {
-                            flipped(shown, &key);
-                            cx.notify();
+                    .child(
+                        div()
+                            .flex_1()
+                            .min_w_0()
+                            .text_size(theme.text_size(TextSize::Sm))
+                            .text_color(theme.colors.fg_muted)
+                            .debug_selector(move || seen)
+                            .child(Ellipsis::new(shown_value(value, secret, open))),
+                    )
+                    .children(secret.then(|| {
+                        IconButton::new(
+                            (id.clone(), format!("reveal-{name}")),
+                            if open {
+                                IconName::EyeOff
+                            } else {
+                                IconName::Eye
+                            },
+                        )
+                        .tooltip(if open {
+                            "Hide the value"
+                        } else {
+                            "Show the value"
                         })
-                    })
-                }))
+                        .on_click(move |_, _, cx| {
+                            flip.update(cx, |shown, cx| {
+                                flipped(shown, &key);
+                                cx.notify();
+                            })
+                        })
+                    }))
+            })
         });
         div()
             .flex()
@@ -161,7 +154,7 @@ impl RenderOnce for EnvironmentSelector {
                         Choice::new(environment.key.clone(), environment.name.clone())
                     }),
                 )
-                .selected(chosen.key.clone())
+                .selected(self.selected.clone())
                 .on_change(move |key, window, cx| {
                     log::info!("environment selector: {key}");
                     on_change(key, window, cx);
@@ -172,7 +165,10 @@ impl RenderOnce for EnvironmentSelector {
                     .text_size(theme.text_size(TextSize::Xs))
                     .text_color(theme.colors.fg_subtle)
                     .font_weight(FontWeight::MEDIUM)
-                    .child(format!("{} variables", chosen.variables.len())),
+                    .child(match &chosen {
+                        Some(chosen) => format!("{} variables", chosen.variables.len()),
+                        None => "No environment chosen".into(),
+                    }),
             )
             .child(div().flex().flex_col().children(rows))
     }
diff --git a/src/devtools/graphql.rs b/src/devtools/graphql.rs
index 1fc33f9..218ec63 100644
--- a/src/devtools/graphql.rs
+++ b/src/devtools/graphql.rs
@@ -57,7 +57,7 @@ pub struct GraphQLExplorer {
     answer: Option<SharedString>,
     search: Entity<TextInput>,
     running: bool,
-    on_run: Option<OnRun>,
+    on_run: OnRun,
     on_pick: Option<OnKey>,
 }
 
@@ -69,6 +69,7 @@ impl GraphQLExplorer {
         query: &Entity<CodeEditor>,
         variables: &Entity<CodeEditor>,
         search: &Entity<TextInput>,
+        on_run: impl Fn(String, String, &mut Window, &mut App) + 'static,
     ) -> Self {
         Self {
             id: id.into(),
@@ -78,7 +79,7 @@ impl GraphQLExplorer {
             answer: None,
             search: search.clone(),
             running: false,
-            on_run: None,
+            on_run: Rc::new(on_run),
             on_pick: None,
         }
     }
@@ -94,14 +95,6 @@ impl GraphQLExplorer {
         self
     }
 
-    pub fn on_run(
-        mut self,
-        handler: impl Fn(String, String, &mut Window, &mut App) + 'static,
-    ) -> Self {
-        self.on_run = Some(Rc::new(handler));
-        self
-    }
-
     pub fn on_pick(
         mut self,
         handler: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
@@ -149,9 +142,7 @@ impl RenderOnce for GraphQLExplorer {
                 .child(text)
         };
         let tall = theme.list_max_height();
-        let on_run = self
-            .on_run
-            .unwrap_or_else(|| panic!("graphql explorer {id:?} has no on_run"));
+        let on_run = self.on_run;
         let (query, variables) = (self.query.clone(), self.variables.clone());
         let typed = variables.read(cx).text().to_string();
         let unread = (!typed.trim().is_empty())
diff --git a/src/devtools/schema.rs b/src/devtools/schema.rs
index 3b0c44d..c017820 100644
--- a/src/devtools/schema.rs
+++ b/src/devtools/schema.rs
@@ -245,19 +245,19 @@ pub(crate) fn diagram(
 ) -> (Vec<Node>, Vec<Edge>) {
     let nodes = tables
         .iter()
-        .map(|table| {
-            let at = places
-                .iter()
-                .find(|(name, _)| *name == table.name)
-                .unwrap_or_else(|| panic!("ER diagram: no place for {}", table.name))
-                .1;
-            table.fields.iter().fold(
+        .filter_map(|table| {
+            let Some((_, at)) = places.iter().find(|(name, _)| *name == table.name) else {
+                log::error!("ER diagram: no place for {}; left out", table.name);
+                return None;
+            };
+            let at = *at;
+            Some(table.fields.iter().fold(
                 Node::new(table.name.clone(), table.name.clone(), at),
                 |node, field| {
                     node.input(Port::new(field.name.clone(), field.name.clone(), "field"))
                         .output(Port::new(field.name.clone(), field.typed(), "field"))
                 },
-            )
+            ))
         })
         .collect();
     let edges = tables
@@ -337,8 +337,8 @@ mod tests {
     }
 
     #[test]
-    #[should_panic(expected = "no place for orders")]
-    fn a_table_without_a_place_fails_loud() {
-        diagram(&[DbTable::new("orders", [])], &[]);
+    fn a_table_without_a_place_is_left_out() {
+        let (nodes, edges) = diagram(&[DbTable::new("orders", [])], &[]);
+        assert!(nodes.is_empty() && edges.is_empty());
     }
 }
diff --git a/src/devtools/socket.rs b/src/devtools/socket.rs
index 3cc6375..8eaa4f5 100644
--- a/src/devtools/socket.rs
+++ b/src/devtools/socket.rs
@@ -53,7 +53,7 @@ pub struct WebSocketConsole {
     messages: Vec<SocketMessage>,
     draft: Entity<TextInput>,
     now: Timestamp,
-    on_send: Option<OnText>,
+    on_send: OnText,
     on_toggle: Option<Run>,
 }
 
@@ -66,6 +66,7 @@ impl WebSocketConsole {
         messages: impl IntoIterator<Item = SocketMessage>,
         draft: &Entity<TextInput>,
         now: Timestamp,
+        on_send: impl Fn(SharedString, &mut Window, &mut App) + 'static,
     ) -> Self {
         Self {
             id: id.into(),
@@ -74,20 +75,11 @@ impl WebSocketConsole {
             messages: messages.into_iter().collect(),
             draft: draft.clone(),
             now,
-            on_send: None,
+            on_send: Rc::new(on_send),
             on_toggle: None,
         }
     }
 
-    /// Gets the text to send; the field empties after.
-    pub fn on_send(
-        mut self,
-        handler: impl Fn(SharedString, &mut Window, &mut App) + 'static,
-    ) -> Self {
-        self.on_send = Some(Rc::new(handler));
-        self
-    }
-
     /// Asked to connect while closed, or to disconnect while open.
     pub fn on_toggle(mut self, handler: impl Fn(&mut Window, &mut App) + 'static) -> Self {
         self.on_toggle = Some(Rc::new(handler));
@@ -159,9 +151,7 @@ impl RenderOnce for WebSocketConsole {
         };
         let open = self.state == SocketState::Open;
         let (messages, now) = (Rc::new(self.messages), self.now);
-        let on_send = self
-            .on_send
-            .unwrap_or_else(|| panic!("websocket console {:?} has no on_send", self.id));
+        let on_send = self.on_send;
         let draft = self.draft.clone();
         let ready = open && !draft.read(cx).text().trim().is_empty();
         let send = Rc::new(move |window: &mut Window, cx: &mut App| {
diff --git a/src/devtools/structure.rs b/src/devtools/structure.rs
index 7e14f68..3fd13ce 100644
--- a/src/devtools/structure.rs
+++ b/src/devtools/structure.rs
@@ -100,32 +100,26 @@ struct Room(f32);
 pub struct TableStructureEditor {
     id: ElementId,
     fields: Vec<Field>,
-    on_change: Option<OnEdit<Vec<Field>>>,
+    on_change: OnEdit<Vec<Field>>,
 }
 
 impl TableStructureEditor {
-    pub fn new(id: impl Into<ElementId>, fields: impl IntoIterator<Item = Field>) -> Self {
+    pub fn new(
+        id: impl Into<ElementId>,
+        fields: impl IntoIterator<Item = Field>,
+        on_change: impl Fn(Vec<Field>, &mut Window, &mut App) + 'static,
+    ) -> Self {
         Self {
             id: id.into(),
             fields: fields.into_iter().collect(),
-            on_change: None,
+            on_change: Rc::new(on_change),
         }
     }
-
-    pub fn on_change(
-        mut self,
-        handler: impl Fn(Vec<Field>, &mut Window, &mut App) + 'static,
-    ) -> Self {
-        self.on_change = Some(Rc::new(handler));
-        self
-    }
 }
 
 impl RenderOnce for TableStructureEditor {
     fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
-        let on_change = self
-            .on_change
-            .unwrap_or_else(|| panic!("table structure editor {:?} has no on_change", self.id));
+        let on_change = self.on_change;
         let (id, fields, on_change) = (self.id, self.fields, &on_change);
         let room = window.use_keyed_state((id.clone(), "room"), cx, |_, _| Room::default());
         let rem = window.rem_size();
@@ -303,8 +297,8 @@ pub struct IndexManager {
     id: ElementId,
     indexes: Vec<Index>,
     fields: Vec<SharedString>,
-    on_drop: Option<OnName>,
-    on_create: Option<OnIndex>,
+    on_drop: OnName,
+    on_create: OnIndex,
 }
 
 impl IndexManager {
@@ -313,34 +307,23 @@ impl IndexManager {
         id: impl Into<ElementId>,
         indexes: impl IntoIterator<Item = Index>,
         fields: impl IntoIterator<Item = impl Into<SharedString>>,
+        on_create: impl Fn(Index, &mut Window, &mut App) + 'static,
+        on_drop: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
     ) -> Self {
         Self {
             id: id.into(),
             indexes: indexes.into_iter().collect(),
             fields: fields.into_iter().map(Into::into).collect(),
-            on_drop: None,
-            on_create: None,
+            on_drop: Rc::new(on_drop),
+            on_create: Rc::new(on_create),
         }
     }
-
-    pub fn on_drop(
-        mut self,
-        handler: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
-    ) -> Self {
-        self.on_drop = Some(Rc::new(handler));
-        self
-    }
-
-    pub fn on_create(mut self, handler: impl Fn(Index, &mut Window, &mut App) + 'static) -> Self {
-        self.on_create = Some(Rc::new(handler));
-        self
-    }
 }
 
 impl RenderOnce for IndexManager {
     fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
-        let on_create = self.on_create.expect("an index manager needs on_create");
-        let on_drop = self.on_drop.expect("an index manager needs on_drop");
+        let on_create = self.on_create;
+        let on_drop = self.on_drop;
         let id = self.id;
         let draft = window.use_keyed_state((id.clone(), "draft"), cx, |window, cx| Draft {
             name: cx.new(|cx| TextInput::new(window, cx).placeholder("Index name")),
diff --git a/src/devtools/tests/api.rs b/src/devtools/tests/api.rs
index 1c69f9e..200806a 100644
--- a/src/devtools/tests/api.rs
+++ b/src/devtools/tests/api.rs
@@ -100,10 +100,17 @@ fn console(bench: &Bench, window: &mut Window, cx: &mut App, owner: Entity<Bench
         _ => SocketState::Closed,
     };
     let toggled = owner.clone();
-    WebSocketConsole::new("socket", "wss://example.com", state, [], &draft, now)
-        .on_send(move |text, _, cx| say(&owner, format!("send {text}"), cx))
-        .on_toggle(move |_, cx| say(&toggled, "toggle".into(), cx))
-        .into_any_element()
+    WebSocketConsole::new(
+        "socket",
+        "wss://example.com",
+        state,
+        [],
+        &draft,
+        now,
+        move |text, _, cx| say(&owner, format!("send {text}"), cx),
+    )
+    .on_toggle(move |_, cx| say(&toggled, "toggle".into(), cx))
+    .into_any_element()
 }
 
 /// Stops: Disconnect, the message field, then Send once it holds words.
@@ -179,9 +186,15 @@ fn graph(bench: &Bench, window: &mut Window, cx: &mut App, owner: Entity<Bench>)
         return div().into_any_element();
     };
     let search = window.use_keyed_state("search", cx, TextInput::new);
-    GraphQLExplorer::new("graph", [], &query, &variables, &search)
-        .on_run(move |query, variables, _, cx| say(&owner, format!("{query} {variables}"), cx))
-        .into_any_element()
+    GraphQLExplorer::new(
+        "graph",
+        [],
+        &query,
+        &variables,
+        &search,
+        move |query, variables, _, cx| say(&owner, format!("{query} {variables}"), cx),
+    )
+    .into_any_element()
 }
 
 /// Stops: the schema, the query, the variables, then Run while they read.
@@ -216,10 +229,10 @@ fn environments(bench: &Bench, _: &mut Window, _: &mut App, _: Entity<Bench>) ->
         variables: vec![("token".into(), token.to_string().into())],
         secrets: vec!["token".into()],
     };
-    let selected = if bench.choice == 0 {
-        "staging"
-    } else {
-        "production"
+    let selected = match bench.choice {
+        0 => "staging",
+        1 => "production",
+        _ => "gone",
     };
     EnvironmentSelector::new(
         "environments",
@@ -228,8 +241,8 @@ fn environments(bench: &Bench, _: &mut Window, _: &mut App, _: Entity<Bench>) ->
             env("production", "sk_live_9999"),
         ],
         selected,
+        |_, _, _| {},
     )
-    .on_change(|_, _, _| {})
     .into_any_element()
 }
 
@@ -265,10 +278,16 @@ fn schema(_: &Bench, window: &mut Window, cx: &mut App, owner: Entity<Bench>) ->
         kind: TypeKind::Object,
         fields: vec![("id".into(), "ID!".into())],
     };
-    GraphQLExplorer::new("graph", [order], &query, &variables, &search)
-        .on_run(|_, _, _, _| {})
-        .on_pick(move |path, _, cx| say(&owner, path.to_string(), cx))
-        .into_any_element()
+    GraphQLExplorer::new(
+        "graph",
+        [order],
+        &query,
+        &variables,
+        &search,
+        |_, _, _, _| {},
+    )
+    .on_pick(move |path, _, cx| say(&owner, path.to_string(), cx))
+    .into_any_element()
 }
 
 /// Stops: the schema first, its cursor on Order.
@@ -297,8 +316,8 @@ fn log(_: &Bench, window: &mut Window, cx: &mut App, owner: Entity<Bench>) -> An
         messages,
         &draft,
         now,
+        move |text, _, cx| say(&owner, format!("send {text}"), cx),
     )
-    .on_send(move |text, _, cx| say(&owner, format!("send {text}"), cx))
     .into_any_element()
 }
 
@@ -314,3 +333,21 @@ fn the_log_holds_at_its_newest_message(cx: &mut TestAppContext) {
         "the newest message lies inside the log: {newest:?} in {log:?}"
     );
 }
+
+#[gpui::test]
+fn an_environment_that_left_shows_none_chosen(cx: &mut TestAppContext) {
+    let (host, cx) = bench(environments, cx);
+    host.update(cx, |bench, cx| {
+        bench.choice = 2;
+        cx.notify();
+    });
+    settle(cx);
+    assert!(
+        cx.debug_bounds("environment-staging-token-masked")
+            .is_none()
+    );
+    assert!(
+        cx.debug_bounds("environment-production-token-masked")
+            .is_none()
+    );
+}
diff --git a/src/devtools/tests/mod.rs b/src/devtools/tests/mod.rs
index f7695f0..e75e6b0 100644
--- a/src/devtools/tests/mod.rs
+++ b/src/devtools/tests/mod.rs
@@ -107,15 +107,18 @@ fn enter_opens_a_connection_and_a_rows_button_leaves_the_row_alone(cx: &mut Test
 }
 
 fn structure(_: &Bench, _: &mut Window, _: &mut App, owner: Entity<Bench>) -> AnyElement {
-    TableStructureEditor::new("structure", [Field::new("id", "int").primary()])
-        .on_change(move |fields, _, cx| {
+    TableStructureEditor::new(
+        "structure",
+        [Field::new("id", "int").primary()],
+        move |fields, _, cx| {
             let names: Vec<String> = fields
                 .iter()
                 .map(|field| format!("{}:{}", field.name, field.ty))
                 .collect();
             say(&owner, names.join(" "), cx)
-        })
-        .into_any_element()
+        },
+    )
+    .into_any_element()
 }
 
 /// A row's stops: name, type, empty, key, default and remove; Add field comes after.
@@ -204,16 +207,14 @@ fn another_engine_brings_its_port(cx: &mut TestAppContext) {
 fn narrow(_: &Bench, _: &mut Window, _: &mut App, _: Entity<Bench>) -> AnyElement {
     div()
         .w(px(280.0))
-        .child(
-            TableStructureEditor::new(
-                "structure",
-                [
-                    Field::new("user_id", "timestamptz"),
-                    Field::new("total", "numeric"),
-                ],
-            )
-            .on_change(|_, _, _| {}),
-        )
+        .child(TableStructureEditor::new(
+            "structure",
+            [
+                Field::new("user_id", "timestamptz"),
+                Field::new("total", "numeric"),
+            ],
+            |_, _, _| {},
+        ))
         .into_any_element()
 }
 
diff --git a/tasks/panics.md b/tasks/panics.md
index 49e8ccf..3668e95 100644
--- a/tasks/panics.md
+++ b/tasks/panics.md
@@ -47,7 +47,7 @@ Each item reads every site in its folders, fixes what the rules name, updates ca
 - [x] P30 Calendar — `src/calendar`
 - [x] P31 Project — `src/project`
 - [x] P32 Canvas & Design — `src/canvas`
-- [ ] P33 DB & Dev Tools — `src/devtools`
+- [x] P33 DB & Dev Tools — `src/devtools`
 - [ ] P34 Dashboard — `src/dashboard`
 - [ ] P35 Settings — `src/settings`
 - [ ] P36 Account — `src/account`
@@ -98,3 +98,4 @@ One line per item: what changed, what stayed and why, review rounds.
 - P30: calendar views step only within jiff's range less a year at each end (`calendar::within`, `stepped`), so every grid around a day fits, and a step past logs and stays; recurrences end where jiff's range ends; the year view's marks stop at an event's last day; the event editor refuses moves, ends, all-day starts and switches to timed that leave jiff's range or a stale painted kind, each with a log; a backward timed draft's days are its first day. Kept: owner dates at jiff's far edges, one list's uniqueness, an event's own order, one organizer, working hours, slots, reminder offsets, constant patterns, picks that always name a value. Review: 2 rounds.
 - P31: a gone assignee logs and shows nobody; a milestone past its count fills, the text real; a roadmap past jiff's range ends inclusively on its last day; the database timeline leaves out and counts tasks due before they start and counts months in `i32`, and its calendar keeps to days `calendar::within` holds; the board's drag and drop take only columns, cards and places this frame holds. Kept: one list's uniqueness, an initiative's and a milestone's own order, shares, month counts, pomodoro lengths, issue keys, lookups over the components' own tables. Review: 3 rounds.
 - P32: the eight design panels take their handlers in `new` (AGENTS.md says so); edges, links, wires, links in progress, resizes, restacks, topics and whiteboard edits that name a node, port, shape, layer or topic gone from this frame log and change nothing; a wire's release fits its source as it now stands; `Topic::adding`, `removing` and `renaming` return `Option`; a mind map's selection, a palette's tool and a history position no longer held mark none. Kept: one-value contracts (alignment counts, frames, zoom, polygon sides, brush hues and type weights among the theme's tables), lookups over the panels' own option tables, button-gated expects. Review: 2 rounds.
+- P33: six devtools take their handlers in `new` (contrast checker, environment selector, GraphQL explorer, WebSocket console, structure editor, index manager); `collection::moved` returns `Option` for a gone key or target or a drop into a request; a gone environment shows none chosen; an ER table without a place stays out. Kept: readings, costs, lookups over the components' own tables, button-gated expects, JSON that read writes back. Review: 1 round.