diff --git a/interim-server/src/routes/relations_single/get_data_handler.rs b/interim-server/src/routes/relations_single/get_data_handler.rs
index cf3538b..e9c4355 100644
--- a/interim-server/src/routes/relations_single/get_data_handler.rs
+++ b/interim-server/src/routes/relations_single/get_data_handler.rs
@@ -72,7 +72,7 @@ pub(super) async fn get(
     };
 
     let mut sql_raw = format!(
-        "select {0} from {1}.{2}",
+        "select {0} from {1}.{2} order by _id",
         pkey_attrs
             .iter()
             .chain(attrs.iter())
diff --git a/interim-server/src/routes/relations_single/mod.rs b/interim-server/src/routes/relations_single/mod.rs
index 6e93166..bce33fb 100644
--- a/interim-server/src/routes/relations_single/mod.rs
+++ b/interim-server/src/routes/relations_single/mod.rs
@@ -21,7 +21,7 @@ mod update_form_transitions_handler;
 mod update_portal_name_handler;
 mod update_prompts_handler;
 mod update_rel_name_handler;
-mod update_value_handler;
+mod update_values_handler;
 
 pub(super) fn new_router() -> Router<App> {
     Router::<App>::new()
@@ -46,8 +46,8 @@ pub(super) fn new_router() -> Router<App> {
         )
         .route("/p/{portal_id}/insert", post(insert_handler::post))
         .route(
-            "/p/{portal_id}/update-value",
-            post(update_value_handler::post),
+            "/p/{portal_id}/update-values",
+            post(update_values_handler::post),
         )
         .route("/p/{portal_id}/set-filter", post(set_filter_handler::post))
         .route_with_tsr("/p/{portal_id}/form/", get(form_handler::get))
diff --git a/interim-server/src/routes/relations_single/update_value_handler.rs b/interim-server/src/routes/relations_single/update_values_handler.rs
similarity index 70%
rename from interim-server/src/routes/relations_single/update_value_handler.rs
rename to interim-server/src/routes/relations_single/update_values_handler.rs
index 71471f4..7c0278f 100644
--- a/interim-server/src/routes/relations_single/update_value_handler.rs
+++ b/interim-server/src/routes/relations_single/update_values_handler.rs
@@ -5,9 +5,6 @@ use axum::{
     extract::{Path, State},
     response::{IntoResponse as _, Response},
 };
-// [`axum_extra`]'s form extractor is preferred:
-// https://docs.rs/axum-extra/0.10.1/axum_extra/extract/struct.Form.html#differences-from-axumextractform
-use axum_extra::extract::Form;
 use interim_models::{
     datum::Datum,
     portal::Portal,
@@ -17,7 +14,7 @@ use interim_models::{
 use interim_pgtypes::{escape_identifier, pg_attribute::PgAttribute, pg_class::PgClass};
 use serde::Deserialize;
 use serde_json::json;
-use sqlx::{postgres::types::Oid, query};
+use sqlx::{Acquire as _, postgres::types::Oid, query};
 use uuid::Uuid;
 
 use crate::{
@@ -36,12 +33,17 @@ pub(super) struct PathParams {
 
 #[derive(Debug, Deserialize)]
 pub(super) struct FormBody {
+    cells: Vec<CellInfo>,
+}
+
+#[derive(Debug, Deserialize)]
+pub(super) struct CellInfo {
     column: String,
-    pkeys: HashMap<String, Datum>,
+    pkey: HashMap<String, Datum>,
     value: Datum,
 }
 
-/// HTTP POST handler for updating a single value in a backing Postgres table.
+/// HTTP POST handler for updating cell values in a backing Postgres table.
 ///
 /// This handler expects 3 path parameters with the structure described by
 /// [`PathParams`].
@@ -55,7 +57,7 @@ pub(super) async fn post(
         rel_oid,
         workspace_id,
     }): Path<PathParams>,
-    Form(form): Form<FormBody>,
+    Json(form): Json<FormBody>,
 ) -> Result<Response, AppError> {
     // Check workspace authorization.
     let workspace_perms = WorkspaceUserPerm::belonging_to_user(user.id)
@@ -70,7 +72,7 @@ pub(super) async fn post(
     // permission to access/alter both as needed.
 
     // Prevent users from modifying Phonograph metadata columns.
-    if form.column.starts_with('_') {
+    if form.cells.iter().any(|cell| cell.column.starts_with('_')) {
         return Err(forbidden!("access denied to update system metadata column"));
     }
 
@@ -91,19 +93,24 @@ pub(super) async fn post(
         .fetch_all(&mut workspace_client)
         .await?;
 
-    // TODO: simplify pkey management
-    form.pkeys
-        .get(&pkey_attrs.first().unwrap().attname)
-        .unwrap()
-        .clone()
-        .bind_onto(form.value.bind_onto(query(&format!(
-            "update {ident} set {value_col} = $1 where {pkey_col} = $2",
-            ident = rel.get_identifier(),
-            value_col = escape_identifier(&form.column),
-            pkey_col = escape_identifier(&pkey_attrs.first().unwrap().attname),
-        ))))
-        .execute(workspace_client.get_conn())
-        .await?;
+    let conn = workspace_client.get_conn();
+    let mut txn = conn.begin().await?;
+    for cell in form.cells {
+        // TODO: simplify pkey management
+        cell.pkey
+            .get(&pkey_attrs.first().unwrap().attname)
+            .unwrap()
+            .clone()
+            .bind_onto(cell.value.bind_onto(query(&format!(
+                "update {ident} set {value_col} = $1 where {pkey_col} = $2",
+                ident = rel.get_identifier(),
+                value_col = escape_identifier(&cell.column),
+                pkey_col = escape_identifier(&pkey_attrs.first().unwrap().attname),
+            ))))
+            .execute(&mut *txn)
+            .await?;
+    }
+    txn.commit().await?;
 
     Ok(Json(json!({ "ok": true })).into_response())
 }
diff --git a/interim-server/templates/portal_table.html b/interim-server/templates/portal_table.html
index 1b72765..da4efa3 100644
--- a/interim-server/templates/portal_table.html
+++ b/interim-server/templates/portal_table.html
@@ -26,6 +26,5 @@
   </main>
 </div>
 <script type="module" src="{{ settings.root_path }}/js_dist/table-viewer.webc.mjs"></script>
-<script type="module" src="{{ settings.root_path }}/js_dist/field-adder.webc.mjs"></script>
 <script type="module" src="{{ settings.root_path }}/js_dist/filter-menu.webc.mjs"></script>
 {% endblock %}
diff --git a/sass/viewer.scss b/sass/viewer.scss
index 63b3a58..adfe201 100644
--- a/sass/viewer.scss
+++ b/sass/viewer.scss
@@ -71,6 +71,7 @@ $table-border-color: #ccc;
     align-items: center;
     display: flex;
     flex: none;
+    user-select: none;
     width: 100%;
 
     &--selected {
@@ -203,18 +204,51 @@ $table-border-color: #ccc;
   }
 }
 
-.datum-editor {
-  align-items: stretch;
+.table-viewer__datum-editor {
   border-top: globals.$default-border;
   display: flex;
   grid-area: editor;
-  height: 12rem;
+  height: 6rem;
+}
 
-  &__input {
-    @include globals.reset_input;
-    padding: 0.75rem 0.5rem;
-    font-family: globals.$font-family-data;
+.datum-editor {
+  &__container {
+    border-left: solid 4px transparent;
+    display: grid;
     flex: 1;
+    grid-template: 'type-selector type-selector' max-content
+      'null-control value-control' max-content
+      'helpers helpers' auto / max-content auto;
+
+    &:has(:focus) {
+      border-left-color: #07f;
+    }
+  
+    &--incomplete {
+      border-left-color: #f33;
+    }
+  }
+
+  &__type-selector {
+    grid-area: type-selector;
+  }
+
+  &__null-control {
+    @include globals.reset_button;
+    align-self: start;
+    grid-area: null-control;
+    padding: 0.75rem;
+
+    &--disabled {
+      opacity: 0.75;
+    }
+  }
+
+  &__text-input {
+    @include globals.reset_input;
+    grid-area: value-control;
+    font-family: globals.$font-family-data;
+    padding: 0.75rem 0.5rem;
   }
 }
 
diff --git a/svelte/src/datum-editor.svelte b/svelte/src/datum-editor.svelte
index ca88cfe..24ecb13 100644
--- a/svelte/src/datum-editor.svelte
+++ b/svelte/src/datum-editor.svelte
@@ -1,23 +1,64 @@
 <script lang="ts">
-  import { type EditorState } from "./editor-state.svelte";
+  import icon_cube_transparent from "../assets/heroicons/20/solid/cube-transparent.svg?raw";
+  import icon_cube from "../assets/heroicons/20/solid/cube.svg?raw";
+  import type { Datum } from "./datum.svelte";
+  import {
+    datum_from_editor_state,
+    editor_state_from_datum,
+    type EditorState,
+  } from "./editor-state.svelte";
   import { type FieldInfo } from "./field.svelte";
 
   type Props = {
+    /**
+     * For use cases in which the user may select between multiple datum types,
+     * such as when embedded in an expression editor, this array represents the
+     * permissible set of field parameters.
+     */
     assignable_fields?: ReadonlyArray<FieldInfo>;
-    editor_state: EditorState;
+
     field_info: FieldInfo;
+
+    on_change?(value?: Datum): void;
+
+    value?: Datum;
   };
 
   let {
     assignable_fields = [],
-    editor_state = $bindable(),
     field_info = $bindable(),
+    on_change,
+    value = $bindable(),
   }: Props = $props();
 
+  let editor_state = $state<EditorState | undefined>();
   let type_selector_menu_button_element = $state<
     HTMLButtonElement | undefined
   >();
   let type_selector_popover_element = $state<HTMLDivElement | undefined>();
+  let text_input_element = $state<HTMLInputElement | undefined>();
+
+  $effect(() => {
+    if (value) {
+      editor_state = editor_state_from_datum(value);
+    }
+  });
+
+  export function focus() {
+    text_input_element?.focus();
+  }
+
+  function handle_input() {
+    if (!editor_state) {
+      console.warn("preconditions for handle_input() not met");
+      return;
+    }
+    value = datum_from_editor_state(
+      editor_state,
+      field_info.field.presentation,
+    );
+    on_change?.(value);
+  }
 
   function handle_type_selector_menu_button_click() {
     type_selector_popover_element?.togglePopover();
@@ -30,40 +71,76 @@
   }
 </script>
 
-<div class="datum-editor__container">
-  {#if assignable_fields.length > 0}
-    <div class="datum-editor__type-selector">
-      <button
-        bind:this={type_selector_menu_button_element}
-        class="datum-editor__type-selector-menu-button"
-        onclick={handle_type_selector_menu_button_click}
-        type="button"
-      >
-        {field_info.field.presentation.t}
-      </button>
-      <div
-        bind:this={type_selector_popover_element}
-        class="datum-editor__type-selector-popover"
-        popover="auto"
-      >
-        {#each assignable_fields as assignable_field_info}
-          <button
-            onclick={() =>
-              handle_type_selector_field_button_click(assignable_field_info)}
-            type="button"
-          >
-            {assignable_field_info.field.presentation.t}
-          </button>
-        {/each}
+<div
+  class="datum-editor__container"
+  class:datum-editor__container--incomplete={!value}
+>
+  {#if editor_state}
+    {#if assignable_fields?.length > 0}
+      <div class="datum-editor__type-selector">
+        <button
+          bind:this={type_selector_menu_button_element}
+          class="datum-editor__type-selector-menu-button"
+          onclick={handle_type_selector_menu_button_click}
+          type="button"
+        >
+          {field_info.field.presentation.t}
+        </button>
+        <div
+          bind:this={type_selector_popover_element}
+          class="datum-editor__type-selector-popover"
+          popover="auto"
+        >
+          {#each assignable_fields as assignable_field_info}
+            <button
+              onclick={() =>
+                handle_type_selector_field_button_click(assignable_field_info)}
+              type="button"
+            >
+              {assignable_field_info.field.presentation.t}
+            </button>
+          {/each}
+        </div>
       </div>
-    </div>
-  {/if}
-  <div class="datum-editor__content">
-    {#if field_info.field.presentation.t === "Text" || field_info.field.presentation.t === "Uuid"}
-      <input bind:value={editor_state.text_value} type="text" />
-    {:else if field_info.field.presentation.t === "Timestamp"}
-      <input bind:value={editor_state.date_value} type="date" />
-      <input bind:value={editor_state.time_value} type="time" />
     {/if}
-  </div>
+    <button
+      type="button"
+      class="datum-editor__null-control"
+      class:datum-editor__null-control--disabled={editor_state.text_value !==
+        ""}
+      disabled={editor_state.text_value !== ""}
+      onclick={() => {
+        if (!editor_state) {
+          console.warn("null control onclick() preconditions not met");
+          return;
+        }
+        editor_state.is_null = !editor_state.is_null;
+        handle_input();
+      }}
+    >
+      {#if editor_state.is_null}
+        {@html icon_cube_transparent}
+      {:else}
+        {@html icon_cube}
+      {/if}
+    </button>
+    {#if field_info.field.presentation.t === "Text" || field_info.field.presentation.t === "Uuid"}
+      <input
+        bind:this={text_input_element}
+        value={editor_state.text_value}
+        oninput={({ currentTarget: { value } }) => {
+          if (editor_state) {
+            editor_state.text_value = value;
+            handle_input();
+          }
+        }}
+        class="datum-editor__text-input"
+        type="text"
+      />
+    {:else if field_info.field.presentation.t === "Timestamp"}
+      <input value={editor_state.date_value} type="date" />
+      <input value={editor_state.time_value} type="time" />
+    {/if}
+    <div class="datum-editor__helpers"></div>
+  {/if}
 </div>
diff --git a/svelte/src/editor-state.svelte.ts b/svelte/src/editor-state.svelte.ts
index 358a617..ab15e3d 100644
--- a/svelte/src/editor-state.svelte.ts
+++ b/svelte/src/editor-state.svelte.ts
@@ -57,8 +57,11 @@ export function datum_from_editor_state(
   value: EditorState,
   presentation: Presentation,
 ): Datum | undefined {
+  if (presentation.t === "Dropdown") {
+    return { t: "Text", c: value.is_null ? undefined : value.text_value };
+  }
   if (presentation.t === "Text") {
-    return { t: "Text", c: value.text_value };
+    return { t: "Text", c: value.is_null ? undefined : value.text_value };
   }
   if (presentation.t === "Timestamp") {
     // FIXME
@@ -66,7 +69,12 @@ export function datum_from_editor_state(
   }
   if (presentation.t === "Uuid") {
     try {
-      return { t: "Uuid", c: uuid.stringify(uuid.parse(value.text_value)) };
+      return {
+        t: "Uuid",
+        c: value.is_null
+          ? undefined
+          : uuid.stringify(uuid.parse(value.text_value)),
+      };
     } catch {
       // uuid.parse() throws a TypeError if unsuccessful.
       return undefined;
diff --git a/svelte/src/expression-editor.webc.svelte b/svelte/src/expression-editor.webc.svelte
index 16083d8..612c571 100644
--- a/svelte/src/expression-editor.webc.svelte
+++ b/svelte/src/expression-editor.webc.svelte
@@ -14,14 +14,9 @@
   import ExpressionSelector from "./expression-selector.svelte";
   import { type PgExpressionAny } from "./expression.svelte";
   import ExpressionEditor from "./expression-editor.webc.svelte";
-  import {
-    DEFAULT_EDITOR_STATE,
-    editor_state_from_datum,
-    type EditorState,
-    datum_from_editor_state,
-  } from "./editor-state.svelte";
   import { type FieldInfo } from "./field.svelte";
   import { type Presentation } from "./presentation.svelte";
+  import type { Datum } from "./datum.svelte";
 
   const ASSIGNABLE_PRESENTATIONS: Presentation[] = [
     { t: "Text", c: { input_mode: { t: "MultiLine", c: {} } } },
@@ -49,23 +44,12 @@
 
   let { identifier_hints = [], value = $bindable() }: Props = $props();
 
-  let editor_state = $state<EditorState>(
-    value?.t === "Literal"
-      ? editor_state_from_datum(value.c)
-      : DEFAULT_EDITOR_STATE,
-  );
+  // Dynamic state to bind to datum editor.
+  let editor_value = $state<Datum | undefined>();
   let editor_field_info = $state<FieldInfo>(ASSIGNABLE_FIELDS[0]);
 
   $effect(() => {
-    if (value?.t === "Literal" && editor_field_info) {
-      const datum_value = datum_from_editor_state(
-        editor_state,
-        editor_field_info.field.presentation,
-      );
-      if (datum_value) {
-        value.c = datum_value;
-      }
-    }
+    editor_value = value?.t === "Literal" ? value.c : undefined;
   });
 
   function handle_identifier_selector_change(
@@ -75,6 +59,12 @@
       value.c.parts_raw = [ev.currentTarget.value];
     }
   }
+
+  function handle_editor_change(datum_value: Datum) {
+    if (value?.t === "Literal") {
+      value.c = datum_value;
+    }
+  }
 </script>
 
 <div class="expression-editor__container">
@@ -102,9 +92,10 @@
           </select>
         {:else if value.t === "Literal"}
           <DatumEditor
-            bind:editor_state
             bind:field_info={editor_field_info}
+            bind:value={editor_value}
             assignable_fields={ASSIGNABLE_FIELDS}
+            on_change={handle_editor_change}
           />
         {/if}
       </div>
diff --git a/svelte/src/table-viewer.webc.svelte b/svelte/src/table-viewer.webc.svelte
index c00071b..93437f2 100644
--- a/svelte/src/table-viewer.webc.svelte
+++ b/svelte/src/table-viewer.webc.svelte
@@ -17,11 +17,6 @@
   import icon_sparkles from "../assets/heroicons/20/solid/sparkles.svg?raw";
   import { type Datum, datum_schema } from "./datum.svelte";
   import DatumEditor from "./datum-editor.svelte";
-  import {
-    DEFAULT_EDITOR_STATE,
-    datum_from_editor_state,
-    type EditorState,
-  } from "./editor-state.svelte";
   import {
     type Coords,
     type Row,
@@ -42,15 +37,18 @@
 
   let { columns = [] }: Props = $props();
 
-  type CommittedChange = {
-    coords_initial: Coords;
-    // This will be identical to coords_initial, unless the change altered a
-    // primary key.
-    coords_updated: Coords;
+  type CellDelta = {
+    // Assumes that primary keys are immutable and that rows are only added or
+    // removed upon a refresh.
+    coords: Coords;
     value_initial: Datum;
     value_updated: Datum;
   };
 
+  type Delta = {
+    cells: CellDelta[];
+  };
+
   type LazyData = {
     rows: Row[];
     fields: FieldInfo[];
@@ -62,14 +60,27 @@
     original_value: Datum;
   };
 
-  type ParsedPkey = Record<string, Datum>;
-
   let selections = $state<Selection[]>([]);
-  let editing = $state(false);
-  let editor_state = $state<EditorState>(DEFAULT_EDITOR_STATE);
-  let committed_changes = $state<CommittedChange[][]>([]);
-  let reverted_changes = $state<CommittedChange[][]>([]);
-  let editor_input_element = $state<HTMLInputElement | undefined>();
+  // While the datum editor is focused and while updated values are being pushed
+  // to the server, other actions such as changing the set of selected cells are
+  // restricted.
+  let editor_value = $state<Datum | undefined>(undefined);
+  let deltas = $state<{
+    commit_queued: Delta[];
+    commit_pending: Delta[];
+    committed: Delta[];
+    revert_queued: Delta[];
+    revert_pending: Delta[];
+    reverted: Delta[];
+  }>({
+    commit_queued: [],
+    commit_pending: [],
+    committed: [],
+    revert_queued: [],
+    revert_pending: [],
+    reverted: [],
+  });
+  let datum_editor = $state<DatumEditor | undefined>();
   let table_element = $state<HTMLDivElement | undefined>();
   let inserter_rows = $state<Row[]>([]);
   let lazy_data = $state<LazyData | undefined>();
@@ -117,120 +128,103 @@
       } else if (sel.region === "inserter") {
         cell_data = inserter_rows[sel.coords[0]].data[sel.coords[1]];
       }
-      if (cell_data?.t === "Text" || cell_data?.t === "Uuid") {
-        editor_state.text_value = cell_data.c ?? "";
-      } else {
-        editor_state.text_value = "";
-      }
+      editor_value = cell_data;
     } else {
-      editor_state.text_value = "";
+      editor_value = undefined;
     }
   }
 
-  function try_move_selection(direction: "Down" | "Left" | "Right" | "Up") {
-    if (lazy_data && !editing && selections.length > 0) {
-      const last_selection = selections[selections.length - 1];
-      if (
-        direction === "Right" &&
-        last_selection.coords[1] < lazy_data.fields.length - 1
-      ) {
-        set_selections([
-          {
-            region: last_selection.region,
-            coords: [last_selection.coords[0], last_selection.coords[1] + 1],
-          },
-        ]);
-      } else if (direction === "Left" && last_selection.coords[1] > 0) {
-        set_selections([
-          {
-            region: last_selection.region,
-            coords: [last_selection.coords[0], last_selection.coords[1] - 1],
-          },
-        ]);
-      } else if (direction === "Down") {
-        if (last_selection.region === "main") {
-          if (last_selection.coords[0] < lazy_data.rows.length - 1) {
-            set_selections([
-              {
-                region: "main",
-                coords: [
-                  last_selection.coords[0] + 1,
-                  last_selection.coords[1],
-                ],
-              },
-            ]);
-          } else {
-            // At bottom of main table.
-            set_selections([
-              {
-                region: "inserter",
-                coords: [0, last_selection.coords[1]],
-              },
-            ]);
-          }
-        } else if (last_selection.region === "inserter") {
-          if (last_selection.coords[0] < inserter_rows.length - 1) {
-            set_selections([
-              {
-                region: "inserter",
-                coords: [
-                  last_selection.coords[0] + 1,
-                  last_selection.coords[1],
-                ],
-              },
-            ]);
-          }
+  function move_selection(direction: "Down" | "Left" | "Right" | "Up") {
+    if (!lazy_data || selections.length === 0) {
+      console.warn("move_selection() preconditions not met");
+      return;
+    }
+
+    const last_selection = selections[selections.length - 1];
+    if (
+      direction === "Right" &&
+      last_selection.coords[1] < lazy_data.fields.length - 1
+    ) {
+      set_selections([
+        {
+          region: last_selection.region,
+          coords: [last_selection.coords[0], last_selection.coords[1] + 1],
+        },
+      ]);
+    } else if (direction === "Left" && last_selection.coords[1] > 0) {
+      set_selections([
+        {
+          region: last_selection.region,
+          coords: [last_selection.coords[0], last_selection.coords[1] - 1],
+        },
+      ]);
+    } else if (direction === "Down") {
+      if (last_selection.region === "main") {
+        if (last_selection.coords[0] < lazy_data.rows.length - 1) {
+          set_selections([
+            {
+              region: "main",
+              coords: [last_selection.coords[0] + 1, last_selection.coords[1]],
+            },
+          ]);
+        } else {
+          // At bottom of main table.
+          set_selections([
+            {
+              region: "inserter",
+              coords: [0, last_selection.coords[1]],
+            },
+          ]);
         }
-      } else if (direction === "Up") {
-        if (last_selection.region === "main") {
-          if (last_selection.coords[0] > 0) {
-            set_selections([
-              {
-                region: "main",
-                coords: [
-                  last_selection.coords[0] - 1,
-                  last_selection.coords[1],
-                ],
-              },
-            ]);
-          }
-        } else if (last_selection.region === "inserter") {
-          if (last_selection.coords[0] > 0) {
-            set_selections([
-              {
-                region: "inserter",
-                coords: [
-                  last_selection.coords[0] - 1,
-                  last_selection.coords[1],
-                ],
-              },
-            ]);
-          } else {
-            // At top of inserter table.
-            set_selections([
-              {
-                region: "main",
-                coords: [lazy_data.rows.length - 1, last_selection.coords[1]],
-              },
-            ]);
-          }
+      } else if (last_selection.region === "inserter") {
+        if (last_selection.coords[0] < inserter_rows.length - 1) {
+          set_selections([
+            {
+              region: "inserter",
+              coords: [last_selection.coords[0] + 1, last_selection.coords[1]],
+            },
+          ]);
+        }
+      }
+    } else if (direction === "Up") {
+      if (last_selection.region === "main") {
+        if (last_selection.coords[0] > 0) {
+          set_selections([
+            {
+              region: "main",
+              coords: [last_selection.coords[0] - 1, last_selection.coords[1]],
+            },
+          ]);
+        }
+      } else if (last_selection.region === "inserter") {
+        if (last_selection.coords[0] > 0) {
+          set_selections([
+            {
+              region: "inserter",
+              coords: [last_selection.coords[0] - 1, last_selection.coords[1]],
+            },
+          ]);
+        } else {
+          // At top of inserter table.
+          set_selections([
+            {
+              region: "main",
+              coords: [lazy_data.rows.length - 1, last_selection.coords[1]],
+            },
+          ]);
         }
       }
     }
   }
 
   function try_sync_edit_to_cells() {
-    if (lazy_data && editing && selections.length === 1) {
+    if (lazy_data && selections.length === 1) {
       const [sel] = selections;
-      const parsed = datum_from_editor_state(
-        editor_state,
-        lazy_data.fields[sel.coords[1]].field.presentation,
-      );
-      if (parsed !== undefined) {
+      if (editor_value !== undefined) {
         if (sel.region === "main") {
-          lazy_data.rows[sel.coords[0]].data[sel.coords[1]] = parsed;
+          lazy_data.rows[sel.coords[0]].data[sel.coords[1]] = editor_value;
         } else if (sel.region === "inserter") {
-          inserter_rows[sel.coords[0]].data[sel.coords[1]] = parsed;
+          inserter_rows[sel.coords[0]].data[sel.coords[1]] = editor_value;
         } else {
           throw new Error("Unknown region");
         }
@@ -238,65 +232,70 @@
     }
   }
 
-  function try_start_edit() {
-    if (!editing) {
-      editing = true;
-      editor_input_element?.focus();
+  function try_queue_delta() {
+    // Copy `editor_value` so that it can be used intuitively within closures.
+    const editor_value_scoped = editor_value;
+    if (editor_value_scoped === undefined) {
+      cancel_edit();
+    } else {
+      if (selections.length > 0) {
+        deltas.commit_queued = [
+          ...deltas.commit_queued,
+          {
+            cells: selections
+              .filter(({ region }) => region === "main")
+              .map((sel) => ({
+                coords: sel.coords,
+                value_initial: sel.original_value,
+                value_updated: editor_value_scoped,
+              })),
+          },
+        ];
+        selections = selections.map((sel) => ({
+          ...sel,
+          original_value: editor_value_scoped,
+        }));
+      }
     }
   }
 
-  function try_commit_edit() {
-    (async function () {
-      if (lazy_data && editing && editor_state && selections.length === 1) {
-        const [sel] = selections;
-        const field = lazy_data.fields[sel.coords[1]];
-        const parsed = datum_from_editor_state(
-          editor_state,
-          field.field.presentation,
-        );
-        if (parsed !== undefined) {
-          if (sel.region === "main") {
-            const pkey = JSON.parse(
-              lazy_data.rows[sel.coords[0]].key as string,
-            ) as ParsedPkey;
-            const resp = await fetch("update-value", {
-              method: "post",
-              headers: { "Content-Type": "application/json" },
-              body: JSON.stringify({
-                column: field.field.name,
-                pkeys: pkey,
-                value: parsed,
-              }),
-            });
-            if (resp.status >= 200 && resp.status < 300) {
-              committed_changes.push([
-                {
-                  coords_initial: sel.coords,
-                  coords_updated: sel.coords, // TODO: this assumes no inserted/deleted rows
-                  value_initial: sel.original_value,
-                  value_updated: parsed,
-                },
-              ]);
-              editing = false;
-              selections = [{ ...sel, original_value: parsed }];
-              table_element?.focus();
-            } else {
-              // TODO display feedback to user
-              console.error(resp);
-              console.error(await resp.text());
-            }
-          } else if (sel.region === "inserter") {
-            table_element?.focus();
-            editing = false;
-            selections = [{ ...sel, original_value: parsed }];
-          } else {
-            throw new Error("Unknown region");
-          }
-        } else {
-          // TODO
-        }
-      }
-    })().catch(console.error);
+  async function commit_delta(delta: Delta) {
+    // Copy `lazy_data` so that it can be used intuitively within closures.
+    const lazy_data_scoped = lazy_data;
+    if (!lazy_data_scoped) {
+      console.warn("sync_delta() preconditions not met");
+      return;
+    }
+    deltas.commit_pending = [...deltas.commit_pending, delta];
+    const resp = await fetch("update-values", {
+      method: "post",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        cells: delta.cells.map((cell) => ({
+          pkey: JSON.parse(lazy_data_scoped.rows[cell.coords[0]].key as string),
+          column: lazy_data_scoped.fields[cell.coords[1]].field.name,
+          value: cell.value_updated,
+        })),
+      }),
+    });
+    if (resp.status >= 200 && resp.status < 300) {
+      deltas.commit_pending = deltas.commit_pending.filter((x) => x !== delta);
+      deltas.committed = [...deltas.committed, delta];
+    } else {
+      // TODO display feedback to user
+      console.error(resp);
+      console.error(await resp.text());
+    }
+  }
+
+  function tick_delta_queue() {
+    const front_of_queue: Delta | undefined = deltas.commit_queued[0];
+    if (front_of_queue) {
+      deltas.commit_queued = deltas.commit_queued.filter(
+        (x) => x !== front_of_queue,
+      );
+      commit_delta(front_of_queue).catch(console.error);
+    }
   }
 
   function cancel_edit() {
@@ -313,7 +312,6 @@
     });
     // Reset editor input value
     set_selections(selections);
-    editing = false;
     table_element?.focus();
   }
 
@@ -323,7 +321,7 @@
     if (lazy_data) {
       const arrow_direction = arrow_key_direction(ev.key);
       if (arrow_direction) {
-        try_move_selection(arrow_direction);
+        move_selection(arrow_direction);
         ev.preventDefault();
       }
       if (ev.key === "Enter") {
@@ -347,69 +345,33 @@
             ];
           }
         } else {
-          try_start_edit();
+          datum_editor?.focus();
         }
       }
     }
   }
 
-  function handle_table_cell_dblclick(_: Coords) {
-    try_start_edit();
-  }
-
-  function handle_table_focus() {
-    if (selections.length === 0 && (lazy_data?.rows[0]?.data.length ?? 0) > 0) {
-      set_selections([{ region: "main", coords: [0, 0] }]);
-    }
-  }
-
   // -------- Event Handlers: Main Table -------- //
 
   function handle_main_cell_click(ev: MouseEvent, coords: Coords) {
-    if (!editing) {
-      if (ev.metaKey || ev.ctrlKey) {
-        // TODO
-        // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
-        // editor_input_value = "";
-      } else {
-        set_selections([{ region: "main", coords }]);
-      }
+    if (ev.metaKey || ev.ctrlKey) {
+      // TODO
+      // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
+      // editor_input_value = "";
+    } else {
+      set_selections([{ region: "main", coords }]);
     }
   }
 
   // -------- Event Handlers: Inserter Table -------- //
 
   function handle_inserter_cell_click(ev: MouseEvent, coords: Coords) {
-    if (!editing) {
-      if (ev.metaKey || ev.ctrlKey) {
-        // TODO
-        // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
-        // editor_input_value = "";
-      } else {
-        set_selections([{ region: "inserter", coords }]);
-      }
-    }
-  }
-
-  // -------- Event Handlers: Editor -------- //
-
-  function handle_editor_blur() {
-    try_commit_edit();
-  }
-
-  function handle_editor_focus() {
-    try_start_edit();
-  }
-
-  function handle_editor_input() {
-    try_sync_edit_to_cells();
-  }
-
-  function handle_editor_keydown(ev: KeyboardEvent) {
-    if (ev.key === "Enter") {
-      try_commit_edit();
-    } else if (ev.key === "Escape") {
-      cancel_edit();
+    if (ev.metaKey || ev.ctrlKey) {
+      // TODO
+      // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
+      // editor_input_value = "";
+    } else {
+      set_selections([{ region: "inserter", coords }]);
     }
   }
 
@@ -440,6 +402,8 @@
       },
     ];
   })().catch(console.error);
+
+  setInterval(tick_delta_queue, 500);
 </script>
 
 {#snippet table_region({
@@ -474,24 +438,21 @@
             aria-selected={cell_selected}
             class="lens-table__cell"
             onmousedown={(ev) => on_cell_click(ev, cell_coords)}
-            ondblclick={() => handle_table_cell_dblclick(cell_coords)}
+            ondblclick={() => {
+              datum_editor?.focus();
+            }}
             role="gridcell"
             style:width={`${field.field.table_width_px}px`}
             tabindex="-1"
           >
             <div
-              class={[
-                "lens-cell__container",
-                cell_selected && "lens-cell__container--selected",
-              ]}
+              class="lens-cell__container"
+              class:lens-cell__container--selected={cell_selected}
             >
               {#if cell_data.t === "Text"}
                 <div
-                  class={[
-                    "lens-cell__content",
-                    "lens-cell__content--text",
-                    cell_data.c === undefined && "lens-cell__content--null",
-                  ]}
+                  class="lens-cell__content lens-cell__content--text"
+                  class:lens-cell__content--null={cell_data.c === undefined}
                 >
                   {#if cell_data.c === undefined}
                     {@html null_value_html}
@@ -501,11 +462,8 @@
                 </div>
               {:else if cell_data.t === "Uuid"}
                 <div
-                  class={[
-                    "lens-cell__content",
-                    "lens-cell__content--uuid",
-                    cell_data.c === undefined && "lens-cell__content--null",
-                  ]}
+                  class="lens-cell__content lens-cell__content--uuid"
+                  class:lens-cell__content--null={cell_data.c === undefined}
                 >
                   {#if cell_data.c === undefined}
                     {@html null_value_html}
@@ -514,9 +472,7 @@
                   {/if}
                 </div>
               {:else}
-                <div
-                  class={["lens-cell__content", "lens-cell__content--unknown"]}
-                >
+                <div class="lens-cell__content lens-cell__content--unknown">
                   <div>UNKNOWN</div>
                 </div>
               {/if}
@@ -538,7 +494,9 @@
     <div
       bind:this={table_element}
       class="lens-table"
-      onfocus={handle_table_focus}
+      onfocus={() => {
+        try_queue_delta();
+      }}
       onkeydown={handle_table_keydown}
       role="grid"
       tabindex="0"
@@ -593,28 +551,17 @@
         {/each}
       </form>
     </div>
-    <div class="datum-editor">
-      {#if selections.length === 1 && editor_state}
+    <div class="table-viewer__datum-editor">
+      {#if selections.length === 1}
         <DatumEditor
-          bind:editor_state
+          bind:this={datum_editor}
+          bind:value={editor_value}
           field_info={lazy_data.fields[selections[0].coords[1]]}
+          on_change={() => {
+            try_sync_edit_to_cells();
+          }}
         />
       {/if}
-      <!--
-      <input
-        bind:this={editor_input_element}
-        bind:value={editor_input_value}
-        class={[
-          "lens-editor__input",
-          selections.length !== 1 && "lens-editor__input--hidden",
-        ]}
-        onblur={handle_editor_blur}
-        onfocus={handle_editor_focus}
-        oninput={handle_editor_input}
-        onkeydown={handle_editor_keydown}
-        tabindex="-1"
-      />
-      -->
     </div>
   {/if}
 </div>