feat: add chat panel location setting

package.json

@@ -327,6 +327,21 @@
           "type": "boolean",
           "default": false,
           "description": "Automatically reveal a new Pi chat tab when the extension activates. Previously open Pi session tabs are always restored."
+        },
+        "pi-on-code.chatPanelLocation": {
+          "type": "string",
+          "default": "splitPanel",
+          "enum": [
+            "panel",
+            "splitPanel",
+            "secondarySideBar"
+          ],
+          "enumDescriptions": [
+            "Open new chats as tabs in the active editor group without splitting the editor area.",
+            "Open new chats in an editor group split to the right of the active group (default).",
+            "Keep chats in the right-most chat editor group: split once, then stack further chats there (right-hand chat rail)."
+          ],
+          "description": "Where new Pi chat panels are placed: editor tab (Panel), right split (SplitPanel), or the right chat rail (SecondarySideBar)."
         }
       }
     },

src/chat-panel-location.ts

@@ -0,0 +1,41 @@
+/**
+ * Where a newly created Pi chat panel is placed inside the VS Code window.
+ *
+ * - `"panel"` — the chat opens as a tab in the active editor group; the editor
+ *   area is never split for it.
+ * - `"splitPanel"` — the chat opens in a new editor group split to the right
+ *   of the active group (historical default behavior).
+ * - `"secondarySideBar"` — chats live in the right-most chat editor group:
+ *   the first chat splits to the right once and later chats are stacked into
+ *   the same far-right group, approximating a right-hand chat rail without
+ *   multiplying editor columns.
+ */
+export type ChatPanelLocation = "panel" | "splitPanel" | "secondarySideBar";
+
+export const DEFAULT_CHAT_PANEL_LOCATION: ChatPanelLocation = "splitPanel";
+
+export function parseChatPanelLocation(raw: unknown): ChatPanelLocation {
+  return raw === "panel" || raw === "splitPanel" || raw === "secondarySideBar"
+    ? raw
+    : DEFAULT_CHAT_PANEL_LOCATION;
+}
+
+export type ChatColumnTarget =
+  | { kind: "active" }
+  | { kind: "beside" }
+  | { kind: "column"; column: number };
+
+/** Choose the editor column a new chat panel should open in. */
+export function resolveChatColumnTarget(
+  location: ChatPanelLocation,
+  openChatColumns: ReadonlyArray<number>,
+): ChatColumnTarget {
+  if (location === "panel") { return { kind: "active" }; }
+  if (location === "secondarySideBar") {
+    if (openChatColumns.length > 0) {
+      return { kind: "column", column: Math.max(...openChatColumns) };
+    }
+    return { kind: "beside" };
+  }
+  return { kind: "beside" };
+}

src/extension.ts

@@ -21,6 +21,10 @@ import { extractSessionId } from "./session-reference.js";
 import { shouldRevealSessionPanel } from "./session-startup.js";
 import { findReusableDraft, shouldPromoteDraft } from "./session-draft.js";
 import { normalizeSessionRename } from "./session-rename.js";
+import {
+  parseChatPanelLocation,
+  resolveChatColumnTarget,
+} from "./chat-panel-location.js";
 import {
   emptySessionListPreferences,
   isSessionArchived,
@@ -1604,7 +1608,19 @@ function addSession(context: vscode.ExtensionContext, cwd = getWorkspaceCwd()):
     void saveOpenSessionPaths();
   };
   setActiveSession(sw);
-  void sw.webviewPanel.show();
+  const location = parseChatPanelLocation(
+    vscode.workspace.getConfiguration("pi-on-code").get("chatPanelLocation"),
+  );
+  const openChatColumns = sessions
+    .map((session) => session.webviewPanel.viewColumn)
+    .filter((column): column is number => typeof column === "number");
+  const target = resolveChatColumnTarget(location, openChatColumns);
+  const viewColumn = target.kind === "active"
+    ? vscode.ViewColumn.Active
+    : target.kind === "beside"
+      ? vscode.ViewColumn.Beside
+      : target.column;
+  void sw.webviewPanel.show(viewColumn);
   void initSessionInBackground(context, sw, { fresh: true });
 }
 

src/test/chat-panel-location.test.ts

@@ -0,0 +1,88 @@
+import * as assert from "node:assert";
+import { readFileSync } from "node:fs";
+import {
+  DEFAULT_CHAT_PANEL_LOCATION,
+  parseChatPanelLocation,
+  resolveChatColumnTarget,
+} from "../chat-panel-location.js";
+
+suite("Chat panel location", () => {
+  test("defaults to splitPanel for missing or invalid values", () => {
+    assert.strictEqual(DEFAULT_CHAT_PANEL_LOCATION, "splitPanel");
+    assert.strictEqual(parseChatPanelLocation(undefined), "splitPanel");
+    assert.strictEqual(parseChatPanelLocation("sidebar-left"), "splitPanel");
+    assert.strictEqual(parseChatPanelLocation(42), "splitPanel");
+  });
+
+  test("accepts the three documented locations", () => {
+    assert.strictEqual(parseChatPanelLocation("panel"), "panel");
+    assert.strictEqual(parseChatPanelLocation("splitPanel"), "splitPanel");
+    assert.strictEqual(parseChatPanelLocation("secondarySideBar"), "secondarySideBar");
+  });
+
+  test("panel mode opens in the active editor group without splitting", () => {
+    assert.deepStrictEqual(
+      resolveChatColumnTarget("panel", [1, 2]),
+      { kind: "active" },
+    );
+  });
+
+  test("splitPanel mode always splits to the right of the active group", () => {
+    assert.deepStrictEqual(
+      resolveChatColumnTarget("splitPanel", [1, 2, 3]),
+      { kind: "beside" },
+    );
+  });
+
+  test("secondarySideBar stacks new chats into the right-most chat column", () => {
+    assert.deepStrictEqual(
+      resolveChatColumnTarget("secondarySideBar", [1, 3]),
+      { kind: "column", column: 3 },
+    );
+  });
+
+  test("secondarySideBar splits once when no chat column exists yet", () => {
+    assert.deepStrictEqual(
+      resolveChatColumnTarget("secondarySideBar", []),
+      { kind: "beside" },
+    );
+  });
+
+  test("publishes a matching configuration property", () => {
+    const manifest = JSON.parse(
+      readFileSync(new URL("../../package.json", import.meta.url), "utf8"),
+    ) as {
+      contributes: {
+        configuration: {
+          properties: Record<string, {
+            default: unknown;
+            enum?: unknown[];
+            enumDescriptions?: unknown[];
+          }>;
+        };
+      };
+    };
+    const property = manifest.contributes.configuration.properties["pi-on-code.chatPanelLocation"];
+    assert.ok(property, "pi-on-code.chatPanelLocation property is missing");
+    assert.strictEqual(property.default, "splitPanel");
+    assert.deepStrictEqual(property.enum, ["panel", "splitPanel", "secondarySideBar"]);
+    assert.strictEqual(property.enumDescriptions?.length, 3);
+  });
+
+  test("new-session creation consults the setting and panel column", () => {
+    const extension = readFileSync(
+      new URL("../../src/extension.ts", import.meta.url),
+      "utf8",
+    );
+    assert.match(extension, /parseChatPanelLocation\(/);
+    assert.match(extension, /getConfiguration\("pi-on-code"\)\.get\("chatPanelLocation"\)/);
+    assert.match(extension, /resolveChatColumnTarget\(location, openChatColumns\)/);
+    assert.match(extension, /sw\.webviewPanel\.show\(viewColumn\)/);
+    const panel = readFileSync(
+      new URL("../../src/webview-panel.ts", import.meta.url),
+      "utf8",
+    );
+    assert.match(panel, /async show\(column\?: vscode\.ViewColumn\)/);
+    assert.match(panel, /column \?\? vscode\.ViewColumn\.Two/);
+  });
+});

src/webview-panel.ts

@@ -89,8 +89,9 @@ export class PiWebviewPanel {
   set onActivate(cb: (() => void) | null) { this._onActivateCb = cb; }
   private _onActivateCb: (() => void) | null = null;
   get isActive(): boolean { return this.panel?.active === true; }
+  get viewColumn(): vscode.ViewColumn | undefined { return this.panel?.viewColumn; }
 
-  async show(): Promise<void> {
+  async show(column?: vscode.ViewColumn): Promise<void> {
     if (this.panel) {
       this.panel.reveal();
       // Retained webviews can keep the compositor surface from the size they
@@ -107,7 +108,7 @@ export class PiWebviewPanel {
     this.panel = vscode.window.createWebviewPanel(
       "pi-chat-" + randomId,
       "Pi on Code",
-      vscode.ViewColumn.Two,
+      column ?? vscode.ViewColumn.Two,
       {
         enableScripts: true,
         retainContextWhenHidden: true,