diff --git a/packages/pi-fff/src/index.ts b/packages/pi-fff/src/index.ts
index 649aaca2..115927e1 100644
--- a/packages/pi-fff/src/index.ts
+++ b/packages/pi-fff/src/index.ts
@@ -6,11 +6,16 @@
  */
 
 import nodePath from "node:path";
-import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
+import {
+  type ExtensionAPI,
+  keyHint,
+} from "@earendil-works/pi-coding-agent";
 import {
   type AutocompleteItem,
   type AutocompleteProvider,
+  type Component,
   Text,
+  truncateToWidth,
 } from "@earendil-works/pi-tui";
 import type {
   FileFinderApi,
@@ -35,6 +40,7 @@ const DEFAULT_GREP_LIMIT = 20;
 const DEFAULT_FIND_LIMIT = 30;
 const GREP_MAX_LINE_LENGTH = 500;
 const MENTION_MAX_RESULTS = 20;
+const COLLAPSED_TOOL_OUTPUT_LINES = 5;
 
 type FffMode = "tools-and-ui" | "tools-only" | "override";
 
@@ -573,30 +579,28 @@ export default function fffExtension(pi: ExtensionAPI) {
     options: { expanded?: boolean },
     theme: any,
     context: any,
-    maxLines = 15,
   ) => {
     const text =
-      (context.lastComponent as Text | undefined) ?? new Text("", 0, 0);
+      (context.lastComponent as CollapsibleToolOutput | undefined) ??
+      new CollapsibleToolOutput();
     const output =
       result.content?.find((c) => c.type === "text")?.text?.trim() ?? "";
     if (!output) {
       text.setText(theme.fg("muted", "No output"));
+      text.setCollapsed(undefined, "");
       return text;
     }
 
-    const lines = output.split("\n");
-    const displayLines = lines.slice(
-      0,
-      options.expanded ? lines.length : maxLines,
+    text.setText(
+      output
+        .split("\n")
+        .map((line: string) => theme.fg("toolOutput", line))
+        .join("\n"),
+    );
+    text.setCollapsed(
+      options.expanded ? undefined : COLLAPSED_TOOL_OUTPUT_LINES,
+      theme.fg("muted", `... (${keyHint("app.tools.expand", "to expand")})`),
     );
-    let content = `\n${displayLines.map((line: string) => theme.fg("toolOutput", line)).join("\n")}`;
-    if (lines.length > displayLines.length) {
-      content += theme.fg(
-        "muted",
-        `\n... (${lines.length - displayLines.length} more lines)`,
-      );
-    }
-    text.setText(content);
     return text;
   };
 
@@ -783,7 +787,7 @@ export default function fffExtension(pi: ExtensionAPI) {
     },
 
     renderResult(result, options, theme, context) {
-      return renderTextResult(result, options, theme, context, 15);
+      return renderTextResult(result, options, theme, context);
     },
   });
 
@@ -933,7 +937,7 @@ export default function fffExtension(pi: ExtensionAPI) {
     },
 
     renderResult(result, options, theme, context) {
-      return renderTextResult(result, options, theme, context, 20);
+      return renderTextResult(result, options, theme, context);
     },
   });
 
@@ -1033,7 +1037,7 @@ export default function fffExtension(pi: ExtensionAPI) {
       },
 
       renderResult(result, options, theme, context) {
-        return renderTextResult(result, options, theme, context, 15);
+        return renderTextResult(result, options, theme, context);
       },
     });
   } // end if (enableMultiGrep)
@@ -1129,3 +1133,32 @@ export default function fffExtension(pi: ExtensionAPI) {
     },
   });
 }
+
+class CollapsibleToolOutput implements Component {
+  private readonly text = new Text("", 0, 0);
+  private maxLines: number | undefined;
+  private overflowHint = "";
+
+  setText(value: string): void {
+    this.text.setText(value);
+  }
+
+  setCollapsed(maxLines: number | undefined, overflowHint: string): void {
+    this.maxLines = maxLines;
+    this.overflowHint = overflowHint;
+  }
+
+  render(width: number): string[] {
+    const lines = this.text.render(width);
+    if (this.maxLines === undefined || lines.length <= this.maxLines) return lines;
+
+    return [
+      ...lines.slice(0, Math.max(0, this.maxLines - 1)),
+      truncateToWidth(this.overflowHint, width),
+    ];
+  }
+
+  invalidate(): void {
+    this.text.invalidate();
+  }
+}
diff --git a/packages/pi-fff/test/extension.test.ts b/packages/pi-fff/test/extension.test.ts
index c0d351c6..8788da32 100644
--- a/packages/pi-fff/test/extension.test.ts
+++ b/packages/pi-fff/test/extension.test.ts
@@ -48,6 +48,10 @@ const finderModule = {
 mock.module("@ff-labs/fff-node", () => finderModule);
 mock.module("@ff-labs/fff-bun", () => finderModule);
 
+mock.module("@earendil-works/pi-coding-agent", () => ({
+  keyHint: (_keybinding: string, description: string) => `Ctrl+O ${description}`,
+}));
+
 mock.module("@earendil-works/pi-tui", () => ({
   Text: class Text {
     text: string;
@@ -57,7 +61,20 @@ mock.module("@earendil-works/pi-tui", () => ({
     setText(text: string) {
       this.text = text;
     }
+    render(width: number) {
+      return this.text
+        .split("\n")
+        .flatMap((line) =>
+          line.length === 0
+            ? [""]
+            : Array.from({ length: Math.ceil(line.length / width) }, (_, index) =>
+                line.slice(index * width, (index + 1) * width),
+              ),
+        );
+    }
+    invalidate() {}
   },
+  truncateToWidth: (text: string, width: number) => text.slice(0, width),
 }));
 
 const schema = (type: string) => (options?: unknown) => ({ type, options });
@@ -85,6 +102,7 @@ type EventHandler = (...args: any[]) => unknown;
 function createPi(mode?: string) {
   const events = new Map<string, EventHandler>();
   const commands = new Map<string, any>();
+  const tools = new Map<string, any>();
 
   const pi = {
     getFlag: mock((name: string) => (name === "fff-mode" ? mode : undefined)),
@@ -95,11 +113,13 @@ function createPi(mode?: string) {
       commands.set(name, command);
     }),
     registerFlag: mock(() => undefined),
-    registerTool: mock(() => undefined),
+    registerTool: mock((tool: any) => {
+      tools.set(tool.name, tool);
+    }),
     appendEntry: mock(() => undefined),
   };
 
-  return { pi, events, commands };
+  return { pi, events, commands, tools };
 }
 
 function createContext() {
@@ -146,6 +166,40 @@ beforeEach(() => {
   delete process.env.PI_FFF_MODE;
 });
 
+describe("pi-fff tool output rendering", () => {
+  test("caps collapsed output at five rendered lines and expands with Ctrl+O", async () => {
+    const { tools } = await start("override");
+    const grep = tools.get("grep");
+    const theme = { fg: (_color: string, text: string) => text };
+    const result = {
+      content: [
+        {
+          type: "text",
+          text: `${"a".repeat(90)}\n${"b".repeat(90)}\n${"c".repeat(90)}`,
+        },
+      ],
+    };
+
+    const collapsed = grep.renderResult(result, { expanded: false }, theme, {
+      lastComponent: undefined,
+    });
+    expect(collapsed.render(40)).toEqual([
+      "a".repeat(40),
+      "a".repeat(40),
+      "a".repeat(10),
+      "b".repeat(40),
+      "... (Ctrl+O to expand)",
+    ]);
+
+    const expanded = grep.renderResult(result, { expanded: true }, theme, {
+      lastComponent: collapsed,
+    });
+    expect(expanded).toBe(collapsed);
+    expect(expanded.render(40)).toHaveLength(9);
+    expect(expanded.render(40)).not.toContain("... (Ctrl+O to expand)");
+  });
+});
+
 describe("pi-fff autocomplete registration", () => {
   test("session_start registers a provider without replacing the editor", async () => {
     const { ctx } = await start();