feat: add configurable prompt Enter behavior

.changeset/mobile-enter-newline.md

@@ -2,4 +2,4 @@
 "@jmfederico/pi-web": patch
 ---
 
-Add a Keyboard shortcuts setting for choosing whether Enter sends chat messages or inserts new lines in this browser, while preserving the desktop-vs-mobile default (desktop Enter sends; mobile/coarse/narrow Enter inserts a new line).
+Add a Keyboard shortcuts setting for choosing whether Enter sends chat messages or inserts new lines in this browser, with Shift+Enter performing the opposite action when supported, while preserving the desktop-vs-mobile default (desktop Enter sends; mobile/coarse/narrow Enter inserts a new line).

src/client/src/components/PromptEditor.ts

@@ -13,7 +13,7 @@ import { machineSessionKey } from "../machineKeys";
 import { detectPromptCompletionTrigger, fileCompletionInsertText, type PromptCompletionTrigger } from "../promptCompletions";
 import { clearDraft, loadDraft, saveDraft } from "../promptDraftStorage";
 import { loadAttachmentDelivery, saveAttachmentDelivery } from "../attachmentPreferences";
-import { createMobilePromptEnterMedia, readPromptEnterPreference, shouldSendPromptOnEnter } from "../promptEnterBehavior";
+import { createMobilePromptEnterMedia, readPromptEnterPreference, shouldSendPromptOnEnterShortcut, shouldUsePromptEnterShiftShortcut } from "../promptEnterBehavior";
 import { promptEditorStyles, type CompletionItem } from "./shared";
 import { renderAttachIcon, renderSendIcon, renderQueueIcon, renderSteerIcon, renderStopIcon, renderThinkingGauge } from "./promptEditorIcons";
 import { thinkingGauge, thinkingLevelLabel } from "../../../shared/thinkingLevels";
@@ -61,6 +61,7 @@ export class PromptEditor extends LitElement {
   private readonly editableCompartment = new Compartment();
   private readonly readOnlyCompartment = new Compartment();
   private readonly mobilePromptEnterMedia = createMobilePromptEnterMedia();
+  private explicitShiftKeyActive = false;
 
   protected override willUpdate(changed: PropertyValues<this>) {
     if (!changed.has("sessionId") && !changed.has("machineId")) return;
@@ -230,6 +231,10 @@ export class PromptEditor extends LitElement {
           syntaxHighlighting(defaultHighlightStyle, { fallback: true }),
           EditorView.lineWrapping,
           EditorView.contentAttributes.of((view) => inputAssistanceContentAttributes(view.state.sliceDoc(0, view.state.selection.main.head))),
+          EditorView.domEventHandlers({
+            keyup: (event) => this.handleEditorKeyUp(event),
+            blur: () => this.resetEditorModifierState(),
+          }),
           placeholder("Message pi... Use / for commands, @ for tracked files, @ space for all files"),
           this.editableCompartment.of(EditorView.editable.of(!this.disabled)),
           this.readOnlyCompartment.of(EditorState.readOnly.of(this.disabled)),
@@ -237,11 +242,10 @@ export class PromptEditor extends LitElement {
             if (update.docChanged) this.updateDraft(update.state.doc.toString());
           }),
           keymap.of([
+            { any: (view, event) => this.handleEditorKeyDown(event, view) },
             { key: "ArrowDown", run: () => this.moveCompletion(1) },
             { key: "ArrowUp", run: () => this.moveCompletion(-1) },
             { key: "Escape", run: () => this.closeCompletions() },
-            { key: "Enter", run: (view) => this.handleEditorEnter(view) },
-            { key: "Shift-Enter", run: (view) => insertNewlineContinueMarkup(view) || insertNewlineAndIndent(view) },
             { key: "Tab", run: (view) => this.handleEditorTab(view) },
             { key: "Shift-Tab", run: (view) => indentWithTab.shift?.(view) ?? false },
             { key: "Backspace", run: (view) => deleteMarkupBackward(view) },
@@ -337,13 +341,39 @@ export class PromptEditor extends LitElement {
     return true;
   }
 
-  private handleEditorEnter(view: EditorView): boolean {
+  private handleEditorKeyDown(event: KeyboardEvent, view: EditorView): boolean {
-    if (this.completions.length) {
+    if (event.key === "Shift") {
+      this.explicitShiftKeyActive = true;
+      return false;
+    }
+    if (event.key !== "Enter") {
+      this.explicitShiftKeyActive = false;
+      return false;
+    }
+    if (event.defaultPrevented || event.isComposing || view.composing) return false;
+
+    const shiftKey = shouldUsePromptEnterShiftShortcut(event.shiftKey, this.explicitShiftKeyActive, this.mobilePromptEnterMedia);
+    this.explicitShiftKeyActive = false;
+    return this.handleEditorEnter(view, shiftKey);
+  }
+
+  private handleEditorKeyUp(event: KeyboardEvent): boolean {
+    if (event.key === "Shift") this.explicitShiftKeyActive = false;
+    return false;
+  }
+
+  private resetEditorModifierState(): boolean {
+    this.explicitShiftKeyActive = false;
+    return false;
+  }
+
+  private handleEditorEnter(view: EditorView, shiftKey: boolean): boolean {
+    if (!shiftKey && this.completions.length) {
       const completion = this.completions[this.selectedIndex];
       if (completion !== undefined) this.pick(completion);
       return true;
     }
-    if (!shouldSendPromptOnEnter(this.mobilePromptEnterMedia, readPromptEnterPreference())) {
+    if (!shouldSendPromptOnEnterShortcut(shiftKey, this.mobilePromptEnterMedia, readPromptEnterPreference())) {
       return insertNewlineContinueMarkup(view) || insertNewlineAndIndent(view);
     }
     this.send(this.canSteer || this.isCompacting ? "followUp" : undefined);

src/client/src/components/settings/SettingsShortcutsPanel.ts

@@ -16,12 +16,12 @@ const PROMPT_ENTER_OPTIONS: readonly { value: PromptEnterPreference; label: stri
   {
     value: "send",
     label: "Enter sends message",
-    description: "Plain Enter sends the chat message from this browser.",
+    description: "Enter sends the chat message; Shift+Enter adds a new line when supported.",
   },
   {
     value: "newline",
     label: "Enter inserts new line",
-    description: "Plain Enter adds a line break; use the send button to send.",
+    description: "Enter adds a line break; Shift+Enter sends the chat message when supported.",
   },
 ];
 
@@ -127,9 +127,9 @@ export class SettingsShortcutsPanel extends LitElement {
         <div class="prompt-enter-copy">
           <span class="card-eyebrow">Chat composer</span>
           <h3 id="prompt-enter-preference-title">Enter key behavior</h3>
-          <p>Choose what plain Enter does in this browser.</p>
+          <p>Choose what Enter does in this browser. Shift+Enter does the opposite when supported; automatic touch-keyboard capitalization is ignored to avoid accidental sends.</p>
         </div>
-        <div class="prompt-enter-options" role="radiogroup" aria-label="Plain Enter behavior in the chat composer">
+        <div class="prompt-enter-options" role="radiogroup" aria-label="Enter and Shift Enter behavior in the chat composer">
           ${PROMPT_ENTER_OPTIONS.map((option) => html`
             <label class="prompt-enter-option">
               <input

src/client/src/promptEnterBehavior.test.ts

@@ -5,6 +5,8 @@ import {
   PROMPT_ENTER_PREFERENCE_STORAGE_KEY,
   readPromptEnterPreference,
   shouldSendPromptOnEnter,
+  shouldSendPromptOnEnterShortcut,
+  shouldUsePromptEnterShiftShortcut,
   writePromptEnterPreference,
   type PromptEnterMedia,
 } from "./promptEnterBehavior";
@@ -26,6 +28,23 @@ describe("promptEnterBehavior", () => {
     expect(shouldSendPromptOnEnter(undefined, "newline")).toBe(false);
   });
 
+  it("swaps Shift+Enter with the plain Enter behavior", () => {
+    expect(shouldSendPromptOnEnterShortcut(false, { matches: false } satisfies PromptEnterMedia, "auto")).toBe(true);
+    expect(shouldSendPromptOnEnterShortcut(true, { matches: false } satisfies PromptEnterMedia, "auto")).toBe(false);
+    expect(shouldSendPromptOnEnterShortcut(false, { matches: true } satisfies PromptEnterMedia, "auto")).toBe(false);
+    expect(shouldSendPromptOnEnterShortcut(true, { matches: true } satisfies PromptEnterMedia, "auto")).toBe(true);
+    expect(shouldSendPromptOnEnterShortcut(true, undefined, "send")).toBe(false);
+    expect(shouldSendPromptOnEnterShortcut(true, undefined, "newline")).toBe(true);
+  });
+
+  it("ignores implicit Shift state on mobile-like keyboards", () => {
+    expect(shouldUsePromptEnterShiftShortcut(false, true, { matches: true } satisfies PromptEnterMedia)).toBe(false);
+    expect(shouldUsePromptEnterShiftShortcut(true, false, { matches: true } satisfies PromptEnterMedia)).toBe(false);
+    expect(shouldUsePromptEnterShiftShortcut(true, true, { matches: true } satisfies PromptEnterMedia)).toBe(true);
+    expect(shouldUsePromptEnterShiftShortcut(true, false, { matches: false } satisfies PromptEnterMedia)).toBe(true);
+    expect(shouldUsePromptEnterShiftShortcut(true, false, undefined)).toBe(true);
+  });
+
   it("parses local storage preference values", () => {
     expect(parsePromptEnterPreference("auto")).toBe("auto");
     expect(parsePromptEnterPreference("send")).toBe("send");

src/client/src/promptEnterBehavior.ts

@@ -38,6 +38,19 @@ export function shouldSendPromptOnEnter(media = createMobilePromptEnterMedia(),
   return media?.matches !== true;
 }
 
+export function shouldUsePromptEnterShiftShortcut(shiftKey: boolean, explicitShiftKeyActive: boolean, media = createMobilePromptEnterMedia()): boolean {
+  // Touch keyboards can report autocapitalization as Shift on Enter after a line break.
+  // On mobile-like screens, only trust Shift when the editor saw an explicit Shift keydown.
+  if (!shiftKey) return false;
+  if (media?.matches === true) return explicitShiftKeyActive;
+  return true;
+}
+
+export function shouldSendPromptOnEnterShortcut(shiftKey: boolean, media = createMobilePromptEnterMedia(), preference = readPromptEnterPreference()): boolean {
+  const plainEnterSends = shouldSendPromptOnEnter(media, preference);
+  return shiftKey ? !plainEnterSends : plainEnterSends;
+}
+
 function browserStorage(): PromptEnterPreferenceStorage | undefined {
   if (typeof window === "undefined") return undefined;
   try {