diff --git a/packages/coding-agent/docs/extensions.md b/packages/coding-agent/docs/extensions.md
index 332ce755..09cae0a8 100644
--- a/packages/coding-agent/docs/extensions.md
+++ b/packages/coding-agent/docs/extensions.md
@@ -1556,6 +1556,9 @@ ctx.ui.setTitle("pi - my-project");
 ctx.ui.setEditorText("Prefill text");
 const current = ctx.ui.getEditorText();
 
+// Paste into editor (triggers paste handling, including collapse for large content)
+ctx.ui.pasteToEditor("pasted content");
+
 // Tool output expansion
 const wasExpanded = ctx.ui.getToolsExpanded();
 ctx.ui.setToolsExpanded(true);
diff --git a/packages/coding-agent/src/core/extensions/runner.ts b/packages/coding-agent/src/core/extensions/runner.ts
index 4b69c6eb..44bb323e 100644
--- a/packages/coding-agent/src/core/extensions/runner.ts
+++ b/packages/coding-agent/src/core/extensions/runner.ts
@@ -175,6 +175,7 @@ const noOpUIContext: ExtensionUIContext = {
 	setHeader: () => {},
 	setTitle: () => {},
 	custom: async () => undefined as never,
+	pasteToEditor: () => {},
 	setEditorText: () => {},
 	getEditorText: () => "",
 	editor: async () => undefined,
diff --git a/packages/coding-agent/src/core/extensions/types.ts b/packages/coding-agent/src/core/extensions/types.ts
index 45bf4806..4362b6af 100644
--- a/packages/coding-agent/src/core/extensions/types.ts
+++ b/packages/coding-agent/src/core/extensions/types.ts
@@ -162,6 +162,9 @@ export interface ExtensionUIContext {
 		},
 	): Promise<T>;
 
+	/** Paste text into the editor, triggering paste handling (collapse for large content). */
+	pasteToEditor(text: string): void;
+
 	/** Set the text in the core input editor. */
 	setEditorText(text: string): void;
 
diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
index 2d7207f1..b325c59e 100644
--- a/packages/coding-agent/src/modes/interactive/interactive-mode.ts
+++ b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
@@ -1383,6 +1383,7 @@ export class InteractiveMode {
 			setHeader: (factory) => this.setExtensionHeader(factory),
 			setTitle: (title) => this.ui.terminal.setTitle(title),
 			custom: (factory, options) => this.showExtensionCustom(factory, options),
+			pasteToEditor: (text) => this.editor.handleInput(`\x1b[200~${text}\x1b[201~`),
 			setEditorText: (text) => this.editor.setText(text),
 			getEditorText: () => this.editor.getText(),
 			editor: (title, prefill) => this.showExtensionEditor(title, prefill),
diff --git a/packages/coding-agent/src/modes/rpc/rpc-mode.ts b/packages/coding-agent/src/modes/rpc/rpc-mode.ts
index 78b9849e..4ab920ce 100644
--- a/packages/coding-agent/src/modes/rpc/rpc-mode.ts
+++ b/packages/coding-agent/src/modes/rpc/rpc-mode.ts
@@ -197,6 +197,11 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 			return undefined as never;
 		},
 
+		pasteToEditor(text: string): void {
+			// Paste handling not supported in RPC mode - falls back to setEditorText
+			this.setEditorText(text);
+		},
+
 		setEditorText(text: string): void {
 			// Fire and forget - host can implement editor control
 			output({
diff --git a/packages/tui/src/editor-component.ts b/packages/tui/src/editor-component.ts
index 87ec9581..c6b6c43d 100644
--- a/packages/tui/src/editor-component.ts
+++ b/packages/tui/src/editor-component.ts
@@ -19,6 +19,9 @@ export interface EditorComponent extends Component {
 	/** Set the text content */
 	setText(text: string): void;
 
+	/** Handle raw terminal input (key presses, paste sequences, etc.) */
+	handleInput(data: string): void;
+
 	// =========================================================================
 	// Callbacks (required)
 	// =========================================================================