feat(interaction): add scroll-to-element primitive

apps/extension/src/tools/__tests__/scroll.test.ts

@@ -0,0 +1,145 @@
+import { describe, expect, it, vi } from "vitest";
+import { SessionManager } from "@/session-manager/manager";
+import type { CdpRunner } from "@/tools/shared";
+import { handleScrollTo } from "../scroll";
+
+function fakeAgentWindow(ids: number[]) {
+  let i = 0;
+  return {
+    create: vi.fn(async () => {
+      const id = ids[i++];
+      if (id === undefined) throw new Error("ran out of fake ids");
+      return id;
+    }),
+    remove: vi.fn(async () => {}),
+    ensureActiveTab: vi.fn(async () => {}),
+  };
+}
+
+function makeFakeCdp(handlers: Record<string, (params: unknown) => unknown>) {
+  const sent: Array<{ tabId: number; method: string; params?: object }> = [];
+  const sendImpl = async (tabId: number, method: string, params?: object) => {
+    sent.push({ tabId, method, params });
+    const handler = handlers[method];
+    if (!handler && method === "Page.getLayoutMetrics") {
+      return { cssLayoutViewport: { clientWidth: 1280, clientHeight: 720 } };
+    }
+    if (!handler) throw new Error(`unexpected CDP call ${method}`);
+    return handler(params);
+  };
+  const cdp: CdpRunner = {
+    send: vi.fn(sendImpl) as unknown as CdpRunner["send"],
+    trackSessionTab: vi.fn(),
+  };
+  const tabsApi = {
+    get: vi.fn(
+      async (tabId: number) => ({ id: tabId, windowId: 100, active: true }) as chrome.tabs.Tab,
+    ),
+    query: vi.fn(async () => [{ id: 4, windowId: 100, active: true } as chrome.tabs.Tab]),
+  };
+  return { cdp, tabsApi, sent };
+}
+
+describe("handleScrollTo", () => {
+  it("scrolls a ref into view and returns its visible top-viewport bounds", async () => {
+    const manager = new SessionManager({ agentWindow: fakeAgentWindow([100]) });
+    const ctx = await manager.start("aa11");
+    ctx.refStore.set("e3", 1234, { tabId: 4 });
+    const fake = makeFakeCdp({
+      "DOM.scrollIntoViewIfNeeded": () => ({}),
+      "DOM.getContentQuads": () => ({ quads: [[10, 20, 110, 20, 110, 60, 10, 60]] }),
+    });
+
+    const result = await handleScrollTo(
+      manager,
+      { session_id: "aa11", ref: "@e3" },
+      { cdp: fake.cdp, tabsApi: fake.tabsApi },
+    );
+
+    if ("code" in result) throw new Error(`unexpected error: ${JSON.stringify(result)}`);
+    expect(result).toMatchObject({
+      tab_id: 4,
+      used_ref: "e3",
+      x: 10,
+      y: 20,
+      width: 100,
+      height: 40,
+    });
+    expect(fake.sent.map((call) => call.method)).toEqual([
+      "DOM.scrollIntoViewIfNeeded",
+      "DOM.getContentQuads",
+      "Page.getLayoutMetrics",
+    ]);
+  });
+
+  it("scrolls OOPIF refs through their parent frame and CDP session", async () => {
+    const manager = new SessionManager({ agentWindow: fakeAgentWindow([100]) });
+    const ctx = await manager.start("aa11");
+    ctx.refStore.set("e3", 1234, {
+      tabId: 4,
+      frameId: "child-frame",
+      cdpSessionId: "child-session",
+    });
+    const fake = makeFakeCdp({
+      "DOM.scrollIntoViewIfNeeded": () => ({}),
+      "DOM.getBoxModel": () => ({
+        model: { content: [204, 306, 604, 306, 604, 506, 204, 506] },
+      }),
+    });
+    fake.cdp.getFrameGraph = vi.fn(async () => ({
+      rootFrameId: "main",
+      frames: [
+        { frameId: "main", target: { tabId: 4 } },
+        {
+          frameId: "child-frame",
+          parentFrameId: "main",
+          ownerBackendNodeId: 99,
+          target: { tabId: 4, sessionId: "child-session" },
+        },
+      ],
+    }));
+    const targetCalls: Array<{ sessionId?: string; method: string }> = [];
+    fake.cdp.sendToTarget = vi.fn(async (target, method) => {
+      targetCalls.push({ sessionId: target.sessionId, method });
+      if (method === "DOM.scrollIntoViewIfNeeded") return {};
+      if (method === "DOM.getContentQuads") {
+        return { quads: [[10, 20, 110, 20, 110, 60, 10, 60]] };
+      }
+      if (method === "Page.getLayoutMetrics") {
+        return { cssLayoutViewport: { clientWidth: 200, clientHeight: 100 } };
+      }
+      throw new Error(`unexpected child CDP call ${method}`);
+    }) as CdpRunner["sendToTarget"];
+
+    const result = await handleScrollTo(
+      manager,
+      { session_id: "aa11", ref: "@e3" },
+      { cdp: fake.cdp, tabsApi: fake.tabsApi },
+    );
+
+    if ("code" in result) throw new Error(`unexpected error: ${JSON.stringify(result)}`);
+    expect(result).toMatchObject({ x: 224, y: 346, width: 200, height: 80 });
+    expect(targetCalls).toEqual([
+      { sessionId: "child-session", method: "DOM.scrollIntoViewIfNeeded" },
+      { sessionId: "child-session", method: "DOM.getContentQuads" },
+      { sessionId: "child-session", method: "Page.getLayoutMetrics" },
+    ]);
+  });
+
+  it("does not issue CDP calls after an early cancellation", async () => {
+    const manager = new SessionManager({ agentWindow: fakeAgentWindow([100]) });
+    await manager.start("aa11");
+    const abort = new AbortController();
+    abort.abort();
+    const fake = makeFakeCdp({});
+
+    const result = await handleScrollTo(
+      manager,
+      { session_id: "aa11", selector: "#target" },
+      { cdp: fake.cdp, tabsApi: fake.tabsApi, signal: abort.signal },
+    );
+
+    expect(result).toMatchObject({ code: "cancelled" });
+    expect(fake.cdp.send).not.toHaveBeenCalled();
+  });
+});

apps/extension/src/tools/dispatcher.ts

@@ -26,6 +26,7 @@ import type {
   ResponseFrame,
   RpcError,
   ScreenshotParams,
+  ScrollToParams,
   SelectParams,
   SnapshotParams,
   WaitForNavigationParams,
@@ -52,6 +53,7 @@ import {
   handleSnapshot,
 } from "./observation";
 import { handleRecordAwait, handleRecordStart, handleRecordStop } from "./record";
+import { handleScrollTo } from "./scroll";
 import {
   handleSessionStart,
   handleSessionStop,
@@ -471,6 +473,17 @@ export class ToolDispatcher {
         );
         return this.rememberHover((req.params as HoverParams).session_id, result);
       }
+      case "tool.scroll_to":
+        return this.withHoverReleaseForRequest(
+          req.params as ScrollToParams,
+          () =>
+            handleScrollTo(
+              this.sessions,
+              req.params as ScrollToParams,
+              this.cdp ? { cdp: this.cdp, tabsApi: chromeTabsApi, signal } : undefined,
+            ),
+          signal,
+        );
       case "tool.fill":
         return this.withHoverReleaseForRequest(
           req.params as FillParams,
@@ -718,6 +731,7 @@ function sessionIdForBrowserControlMethod(req: RequestFrame): string | null {
     case "tool.reload":
     case "tool.click":
     case "tool.hover":
+    case "tool.scroll_to":
     case "tool.fill":
     case "tool.press":
     case "tool.select":

apps/extension/src/tools/interaction.ts

@@ -128,7 +128,7 @@ async function wait(ms: number, signal?: AbortSignal): Promise<void> {
  * `RpcError` if the caller supplied neither (or both), or if neither
  * lookup matched.
  */
-async function resolveBackendNode(
+export async function resolveBackendNode(
   cdp: CdpRunner,
   ctx: SessionContext,
   target: { tabId: number },

apps/extension/src/tools/scroll.ts

@@ -0,0 +1,69 @@
+import { ChromiumCdp } from "@/browser-driver/chromium-cdp";
+import type { SessionManager } from "@/session-manager/manager";
+import type { RpcError, ScrollToParams, ScrollToResult } from "@/transport/types";
+import { attachDialogs, markDialogCursor } from "./dialogs";
+import { resolveNodeGeometry } from "./frame-geometry";
+import { resolveBackendNode } from "./interaction";
+import {
+  type CdpRunner,
+  type ChromeTabsApi,
+  chromeTabsApi,
+  enforceAgentWindow,
+  isRpcError,
+  lookupSession,
+  resolveTargetTab,
+} from "./shared";
+
+export interface ScrollToDeps {
+  cdp: CdpRunner;
+  tabsApi: ChromeTabsApi;
+  signal?: AbortSignal;
+}
+
+let defaultDeps: { cdp: ChromiumCdp; tabsApi: ChromeTabsApi } | null = null;
+function getDefaultDeps(): { cdp: ChromiumCdp; tabsApi: ChromeTabsApi } {
+  if (!defaultDeps) defaultDeps = { cdp: new ChromiumCdp(), tabsApi: chromeTabsApi };
+  return defaultDeps;
+}
+
+export async function handleScrollTo(
+  manager: SessionManager,
+  params: ScrollToParams,
+  deps: ScrollToDeps = getDefaultDeps(),
+): Promise<ScrollToResult | RpcError> {
+  const ctxOrErr = lookupSession(manager, params, "scroll-to");
+  if (isRpcError(ctxOrErr)) return ctxOrErr;
+  const ctx = ctxOrErr;
+  if (deps.signal?.aborted) return { code: "cancelled", message: "scroll-to aborted" };
+  const target = await resolveTargetTab(manager, ctx, params.tab_id, deps.tabsApi);
+  if (isRpcError(target)) return target;
+  const denied = enforceAgentWindow(ctx, target, "scroll-to");
+  if (denied) return denied;
+  const dialogCursor = markDialogCursor(deps.cdp, target.tabId);
+  const node = await resolveBackendNode(deps.cdp, ctx, target, params, "scroll-to");
+  if (isRpcError(node)) return node;
+  if (deps.signal?.aborted) return { code: "cancelled", message: "scroll-to aborted" };
+
+  deps.cdp.trackSessionTab?.(ctx.sessionId, target.tabId);
+  const geometry = await resolveNodeGeometry(
+    deps.cdp,
+    target.tabId,
+    {
+      target: node.cdpTarget,
+      backendNodeId: node.backendNodeId,
+      ...(node.frameId ? { frameId: node.frameId } : {}),
+    },
+    { scrollIntoView: true },
+  );
+  if (isRpcError(geometry)) return geometry;
+
+  return attachDialogs(deps.cdp, target.tabId, dialogCursor, {
+    tab_id: target.tabId,
+    used_ref: node.usedRef,
+    used_selector: node.usedSelector,
+    x: geometry.topBounds.x,
+    y: geometry.topBounds.y,
+    width: geometry.topBounds.width,
+    height: geometry.topBounds.height,
+  });
+}

apps/extension/src/transport/types.ts

@@ -444,6 +444,25 @@ export interface HoverResult {
   dialogs?: JavaScriptDialogInfo[];
 }
 
+export interface ScrollToParams {
+  session_id: string;
+  ref?: string;
+  selector?: string;
+  tab_id?: number;
+  timeout_ms?: number;
+}
+
+export interface ScrollToResult {
+  tab_id: number;
+  used_ref?: string;
+  used_selector?: string;
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+  dialogs?: JavaScriptDialogInfo[];
+}
+
 export interface FillParams {
   session_id: string;
   value: string;

crates/bsk-cli/skill/SKILL.md

@@ -202,6 +202,7 @@ Both capture from the moment the tab is attached and read a bounded per-tab buff
 |---------|---------|
 | `bsk click <ref-or-selector>` | Click element (`--button`, `--click-count`, `--modifiers`) |
 | `bsk hover <ref-or-selector>` | Move the mouse to an element and wait for hover UI to settle (`--settle`, `--modifiers`) |
+| `bsk scroll-to <ref-or-selector>` | Scroll an element and its frame owners into the visible viewport |
 | `bsk fill <ref-or-selector> --value <text>` | Clear and type into input |
 | `bsk select <ref-or-selector> --value <v>` | Set `<select>` option(s) by `value` (repeat `--value` for multi-select) |
 | `bsk press <key>` | Key/combo (`Enter`, `Ctrl+A`, …; optional `--ref` to focus first) |

crates/bsk-cli/src/cli/mod.rs

@@ -25,6 +25,7 @@ pub mod record;
 pub mod record_state;
 pub mod render_error;
 pub mod screenshot;
+pub mod scroll;
 pub mod session;
 pub mod snapshot;
 pub mod status;
@@ -48,6 +49,7 @@ use crate::cli::network::NetworkArgs;
 use crate::cli::observe::ObserveArgs;
 use crate::cli::record::RecordCmd;
 use crate::cli::screenshot::ScreenshotArgs;
+use crate::cli::scroll::ScrollToArgs;
 use crate::cli::session::SessionCmd;
 use crate::cli::snapshot::SnapshotArgs;
 use crate::cli::tab::TabCmd;
@@ -167,6 +169,10 @@ pub enum Command {
     /// Hover a snapshot ref or CSS selector.
     Hover(HoverArgs),
 
+    /// Scroll a snapshot ref or CSS selector into the visible viewport.
+    #[command(name = "scroll-to")]
+    ScrollTo(ScrollToArgs),
+
     /// Fill an input / textarea / contenteditable.
     Fill(FillArgs),
 

crates/bsk-cli/src/cli/scroll.rs

@@ -0,0 +1,117 @@
+//! `bsk scroll-to` — bring a target element into the visible viewport.
+
+use std::time::Duration;
+
+use anyhow::Context;
+use bsk_protocol::Method;
+use bsk_protocol::tools::{ScrollToParams, ScrollToResult};
+use clap::Args;
+
+use crate::cli::ensure_daemon::ensure_daemon;
+use crate::cli::error::{CliError, Format};
+use crate::cli::interaction::looks_like_ref;
+use crate::cli::navigate::parse_timeout_ms;
+
+#[derive(Debug, Clone, Args)]
+pub struct ScrollToArgs {
+    /// Snapshot ref (`@e3`, `e3`) or CSS selector. Optional when `--ref`/`--selector` is used.
+    pub target: Option<String>,
+
+    #[arg(long = "ref")]
+    pub ref_: Option<String>,
+
+    #[arg(long = "selector")]
+    pub selector: Option<String>,
+
+    #[arg(long)]
+    pub session: String,
+
+    #[arg(long = "tab-id")]
+    pub tab_id: Option<i64>,
+
+    #[arg(long, default_value = "30s", value_parser = parse_timeout_ms)]
+    pub timeout: u32,
+}
+
+pub fn dispatch(args: ScrollToArgs, format: Format) -> Result<(), CliError> {
+    let info = ensure_daemon().context("ensure daemon is running")?;
+    let (ref_, selector) = split_target(args.target, args.ref_, args.selector)?;
+    let params = ScrollToParams {
+        session_id: args.session,
+        ref_,
+        selector,
+        tab_id: args.tab_id,
+        timeout_ms: Some(args.timeout),
+    };
+    let reply: ScrollToResult = crate::cli::business_rpc::call(
+        info.sock_path,
+        "scroll-to-1",
+        Method::ToolScrollTo,
+        Some(params),
+        ipc_timeout(args.timeout),
+    )?;
+    match format {
+        Format::Json => println!(
+            "{}",
+            serde_json::to_string_pretty(&reply)
+                .map_err(|e| CliError::Local(anyhow::anyhow!(e)))?
+        ),
+        Format::Human => {
+            let target =
+                format_used_target(reply.used_ref.as_deref(), reply.used_selector.as_deref());
+            println!(
+                "scroll-to ok tab={} target={target} bounds=({}, {}, {}, {})",
+                reply.tab_id, reply.x, reply.y, reply.width, reply.height
+            );
+        }
+    }
+    Ok(())
+}
+
+fn split_target(
+    positional: Option<String>,
+    explicit_ref: Option<String>,
+    explicit_selector: Option<String>,
+) -> Result<(Option<String>, Option<String>), CliError> {
+    match (positional, explicit_ref, explicit_selector) {
+        (None, None, None) => Err(CliError::Local(anyhow::anyhow!(
+            "missing target: pass <ref-or-selector>, --ref @eN, or --selector <css>"
+        ))),
+        (None, Some(r), None) => Ok((Some(r), None)),
+        (None, None, Some(s)) => Ok((None, Some(s))),
+        (Some(target), None, None) if looks_like_ref(&target) => Ok((Some(target), None)),
+        (Some(target), None, None) => Ok((None, Some(target))),
+        _ => Err(CliError::Local(anyhow::anyhow!(
+            "pass exactly one of: <target>, --ref, or --selector"
+        ))),
+    }
+}
+
+fn format_used_target(used_ref: Option<&str>, used_selector: Option<&str>) -> String {
+    used_ref
+        .map(|r| format!("@{r}"))
+        .or_else(|| used_selector.map(str::to_string))
+        .unwrap_or_else(|| "?".into())
+}
+
+fn ipc_timeout(timeout_ms: u32) -> Duration {
+    Duration::from_millis(u64::from(timeout_ms))
+        .checked_add(Duration::from_secs(15))
+        .unwrap_or(Duration::from_secs(u64::from(timeout_ms / 1_000) + 15))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn split_target_detects_refs_and_selectors() {
+        let (ref_, selector) = split_target(Some("@e3".into()), None, None).unwrap();
+        assert_eq!(ref_.as_deref(), Some("@e3"));
+        assert!(selector.is_none());
+
+        let (ref_, selector) = split_target(Some("#target".into()), None, None).unwrap();
+        assert!(ref_.is_none());
+        assert_eq!(selector.as_deref(), Some("#target"));
+    }
+}

crates/bsk-cli/src/daemon/ipc.rs

@@ -243,6 +243,7 @@ pub fn full_handler(status: DaemonStatus, state: Arc<DaemonState>) -> RpcHandler
                 | Method::ToolReload
                 | Method::ToolClick
                 | Method::ToolHover
+                | Method::ToolScrollTo
                 | Method::ToolFill
                 | Method::ToolPress
                 | Method::ToolSelect

crates/bsk-cli/src/main.rs

@@ -94,6 +94,7 @@ fn dispatch(cli: Cli, format: Format) -> Result<(), CliError> {
         Command::Reload(args) => cli::navigate::dispatch_reload(args, format),
         Command::Click(args) => cli::interaction::dispatch_click(args, format),
         Command::Hover(args) => cli::interaction::dispatch_hover(args, format),
+        Command::ScrollTo(args) => cli::scroll::dispatch(args, format),
         Command::Fill(args) => cli::interaction::dispatch_fill(args, format),
         Command::Press(args) => cli::interaction::dispatch_press(args, format),
         Command::Select(args) => cli::interaction::dispatch_select(args, format),

crates/bsk-cli/tests/cli_parse.rs

@@ -206,6 +206,15 @@ fn parses_hover_with_settle() {
     assert_eq!(args.settle, 300);
 }
 
+#[test]
+fn parses_scroll_to_target() {
+    let cli = parse(&["bsk", "scroll-to", "@e2", "--session", "s1"]);
+    let Command::ScrollTo(args) = cli.command else {
+        panic!("expected scroll-to command");
+    };
+    assert_eq!(args.target.as_deref(), Some("@e2"));
+}
+
 #[test]
 fn rejects_zero_click_count() {
     assert!(

crates/bsk-cli/tests/tools_m7_ipc.rs

@@ -1,5 +1,4 @@
-//! M7 integration: drive the 7 new tool RPCs (navigate /
-//! navigate_back / navigate_forward / reload / click / fill / press)
+//! M7 integration: drive interaction and navigation tool RPCs
 //! through the IPC + per-session queue + fake extension and assert
 //! the wire shapes line up. The extension stub mirrors each method's
 //! `*Result` so we exercise the daemon's serialise → forward →
@@ -15,8 +14,8 @@ use bsk_protocol::system::{HandshakeParams, HandshakeResult};
 use bsk_protocol::tools::{
     ClickParams, ClickResult, FillParams, FillResult, KeyModifier, MouseButton, NavigateBackParams,
     NavigateBackResult, NavigateForwardParams, NavigateForwardResult, NavigateParams,
-    NavigateResult, PressParams, PressResult, ReloadParams, ReloadResult, SelectParams,
-    SelectResult, SessionStartParams, SessionStartResult, WaitUntil,
+    NavigateResult, PressParams, PressResult, ReloadParams, ReloadResult, ScrollToParams,
+    ScrollToResult, SelectParams, SelectResult, SessionStartParams, SessionStartResult, WaitUntil,
 };
 use bsk_protocol::{
     BrowserPeerInfo, ErrorCode, Frame, Method, RequestFrame, ResponseBody, ResponseFrame, RpcError,
@@ -382,6 +381,51 @@ async fn click_round_trips_ref_and_modifiers() {
     handle.shutdown().await;
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn scroll_to_round_trips_visible_bounds() {
+    let (handle, sock) = spawn_daemon().await;
+    let mut ws = connect_ext(handle.ws_addr()).await;
+    let _ = do_handshake(&mut ws).await;
+
+    run_extension(ws, |req| {
+        assert_eq!(req.method, Method::ToolScrollTo);
+        let params = req.params.clone().unwrap();
+        let parsed: ScrollToParams = serde_json::from_value(params).unwrap();
+        assert_eq!(parsed.ref_.as_deref(), Some("@e3"));
+        ResponseBody::Ok(
+            serde_json::to_value(ScrollToResult {
+                tab_id: 9,
+                used_ref: Some("e3".into()),
+                used_selector: None,
+                x: 10.0,
+                y: 20.0,
+                width: 100.0,
+                height: 40.0,
+                dialogs: vec![],
+            })
+            .unwrap(),
+        )
+    });
+
+    let session_id = ipc_session_start(&sock).await;
+    let result: ScrollToResult = ipc_tool_call(
+        &sock,
+        Method::ToolScrollTo,
+        ScrollToParams {
+            session_id,
+            ref_: Some("@e3".into()),
+            selector: None,
+            tab_id: None,
+            timeout_ms: Some(5_000),
+        },
+    )
+    .await
+    .expect("scroll-to ok");
+    assert_eq!(result.used_ref.as_deref(), Some("e3"));
+    assert_eq!(result.width, 100.0);
+    handle.shutdown().await;
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn fill_round_trips_clear_before_default() {
     let (handle, sock) = spawn_daemon().await;

crates/bsk-protocol/schema/tool_scroll_to_params.json

@@ -0,0 +1,42 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "ScrollToParams",
+  "type": "object",
+  "required": [
+    "session_id"
+  ],
+  "properties": {
+    "ref": {
+      "description": "Optional `@e<N>` ref allocated by the last observation. Mutually exclusive with `selector`.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "selector": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "session_id": {
+      "type": "string"
+    },
+    "tab_id": {
+      "description": "Target tab. Defaults to the Agent Window's active tab.",
+      "type": [
+        "integer",
+        "null"
+      ],
+      "format": "int64"
+    },
+    "timeout_ms": {
+      "type": [
+        "integer",
+        "null"
+      ],
+      "format": "uint32",
+      "minimum": 1.0
+    }
+  }
+}

crates/bsk-protocol/schema/tool_scroll_to_result.json

@@ -0,0 +1,123 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "ScrollToResult",
+  "type": "object",
+  "required": [
+    "height",
+    "tab_id",
+    "width",
+    "x",
+    "y"
+  ],
+  "properties": {
+    "dialogs": {
+      "type": "array",
+      "items": {
+        "$ref": "#/definitions/JavaScriptDialogInfo"
+      }
+    },
+    "height": {
+      "type": "number",
+      "format": "double"
+    },
+    "tab_id": {
+      "type": "integer",
+      "format": "int64"
+    },
+    "used_ref": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "used_selector": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "width": {
+      "type": "number",
+      "format": "double"
+    },
+    "x": {
+      "description": "Visible target bounds in top-level viewport CSS pixels.",
+      "type": "number",
+      "format": "double"
+    },
+    "y": {
+      "type": "number",
+      "format": "double"
+    }
+  },
+  "definitions": {
+    "JavaScriptDialogHandledAction": {
+      "description": "How the extension resolved the dialog so CDP could continue.",
+      "type": "string",
+      "enum": [
+        "accepted",
+        "dismissed"
+      ]
+    },
+    "JavaScriptDialogInfo": {
+      "description": "One observed + handled JavaScript dialog during a tool call.",
+      "type": "object",
+      "required": [
+        "handled",
+        "message",
+        "sequence",
+        "tab_id",
+        "type"
+      ],
+      "properties": {
+        "default_prompt": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "handled": {
+          "$ref": "#/definitions/JavaScriptDialogHandledAction"
+        },
+        "has_browser_handler": {
+          "type": [
+            "boolean",
+            "null"
+          ]
+        },
+        "message": {
+          "type": "string"
+        },
+        "sequence": {
+          "description": "Monotonic per-tab sequence for ordering within a session.",
+          "type": "integer",
+          "format": "uint64",
+          "minimum": 0.0
+        },
+        "tab_id": {
+          "type": "integer",
+          "format": "int64"
+        },
+        "type": {
+          "$ref": "#/definitions/JavaScriptDialogType"
+        },
+        "url": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      }
+    },
+    "JavaScriptDialogType": {
+      "description": "Native JS dialog kind reported by CDP.",
+      "type": "string",
+      "enum": [
+        "alert",
+        "confirm",
+        "prompt",
+        "beforeunload"
+      ]
+    }
+  }
+}

crates/bsk-protocol/src/bin/dump-schema.rs

@@ -79,6 +79,8 @@ fn main() {
     dump!(ClickResult, "tool_click_result");
     dump!(HoverParams, "tool_hover_params");
     dump!(HoverResult, "tool_hover_result");
+    dump!(ScrollToParams, "tool_scroll_to_params");
+    dump!(ScrollToResult, "tool_scroll_to_result");
     dump!(FillParams, "tool_fill_params");
     dump!(FillResult, "tool_fill_result");
     dump!(PressParams, "tool_press_params");

crates/bsk-protocol/src/method.rs

@@ -72,6 +72,8 @@ pub enum Method {
     ToolClick,
     #[serde(rename = "tool.hover")]
     ToolHover,
+    #[serde(rename = "tool.scroll_to")]
+    ToolScrollTo,
     #[serde(rename = "tool.fill")]
     ToolFill,
     #[serde(rename = "tool.press")]
@@ -153,6 +155,7 @@ impl Method {
             | Method::ToolNavigateForward
             | Method::ToolReload
             | Method::ToolClick
+            | Method::ToolScrollTo
             | Method::ToolFill
             | Method::ToolPress
             | Method::ToolSelect
@@ -283,6 +286,7 @@ mod tests {
         assert!(Method::ToolNavigateForward.is_mutating());
         assert!(Method::ToolReload.is_mutating());
         assert!(Method::ToolClick.is_mutating());
+        assert!(Method::ToolScrollTo.is_mutating());
         assert!(Method::ToolFill.is_mutating());
         assert!(Method::ToolPress.is_mutating());
         assert!(Method::ToolSelect.is_mutating());
@@ -327,6 +331,7 @@ mod tests {
         assert_eq!(Method::ToolHover.effect(), MethodEffect::TransientInput);
         assert_eq!(Method::ToolObserve.effect(), MethodEffect::TransientInput);
         assert_eq!(Method::ToolClick.effect(), MethodEffect::BrowserMutation);
+        assert_eq!(Method::ToolScrollTo.effect(), MethodEffect::BrowserMutation);
         assert_eq!(Method::Cancel.effect(), MethodEffect::ControlPlane);
     }
 
@@ -336,6 +341,7 @@ mod tests {
         assert!(Method::ToolHover.requires_interrupt_gate());
         assert!(Method::ToolObserve.requires_interrupt_gate());
         assert!(Method::ToolClick.requires_interrupt_gate());
+        assert!(Method::ToolScrollTo.requires_interrupt_gate());
         assert!(!Method::Cancel.requires_interrupt_gate());
     }
 }

crates/bsk-protocol/src/tools/mod.rs

@@ -10,6 +10,7 @@ pub mod network;
 pub mod observation;
 pub mod record;
 pub mod script;
+pub mod scroll;
 pub mod session;
 pub mod tabs;
 pub mod waits;
@@ -25,6 +26,7 @@ pub use network::*;
 pub use observation::*;
 pub use record::*;
 pub use script::*;
+pub use scroll::*;
 pub use session::*;
 pub use tabs::*;
 pub use waits::*;

crates/bsk-protocol/src/tools/scroll.rs

@@ -0,0 +1,65 @@
+//! Element scrolling primitive (`tool.scroll_to`).
+
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+use super::JavaScriptDialogInfo;
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, JsonSchema)]
+pub struct ScrollToParams {
+    pub session_id: String,
+    /// Optional `@e<N>` ref allocated by the last observation.
+    /// Mutually exclusive with `selector`.
+    #[serde(
+        rename = "ref",
+        alias = "ref_",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
+    pub ref_: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub selector: Option<String>,
+    /// Target tab. Defaults to the Agent Window's active tab.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub tab_id: Option<i64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[schemars(range(min = 1))]
+    pub timeout_ms: Option<u32>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, JsonSchema)]
+pub struct ScrollToResult {
+    pub tab_id: i64,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub used_ref: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub used_selector: Option<String>,
+    /// Visible target bounds in top-level viewport CSS pixels.
+    pub x: f64,
+    pub y: f64,
+    pub width: f64,
+    pub height: f64,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub dialogs: Vec<JavaScriptDialogInfo>,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn params_serialise_ref_field_name() {
+        let params = ScrollToParams {
+            session_id: "abcd".into(),
+            ref_: Some("@e3".into()),
+            selector: None,
+            tab_id: Some(42),
+            timeout_ms: Some(5_000),
+        };
+        let value = serde_json::to_value(&params).unwrap();
+        assert_eq!(value.get("ref").and_then(|v| v.as_str()), Some("@e3"));
+        assert!(value.get("ref_").is_none());
+        let round: ScrollToParams = serde_json::from_value(value).unwrap();
+        assert_eq!(round, params);
+    }
+}

skill/SKILL.md

@@ -202,6 +202,7 @@ Both capture from the moment the tab is attached and read a bounded per-tab buff
 |---------|---------|
 | `bsk click <ref-or-selector>` | Click element (`--button`, `--click-count`, `--modifiers`) |
 | `bsk hover <ref-or-selector>` | Move the mouse to an element and wait for hover UI to settle (`--settle`, `--modifiers`) |
+| `bsk scroll-to <ref-or-selector>` | Scroll an element and its frame owners into the visible viewport |
 | `bsk fill <ref-or-selector> --value <text>` | Clear and type into input |
 | `bsk select <ref-or-selector> --value <v>` | Set `<select>` option(s) by `value` (repeat `--value` for multi-select) |
 | `bsk press <key>` | Key/combo (`Enter`, `Ctrl+A`, …; optional `--ref` to focus first) |