7 files changed, 84 insertions, 6 deletions
diff --git a/src/cdp/discovery.ts b/src/cdp/discovery.ts
index f33adc6..60fb14f 100644
--- a/src/cdp/discovery.ts
+++ b/src/cdp/discovery.ts
@@ -101,7 +101,16 @@ type Candidate = {
   readonly userDataDir: string;
 };
 
+// Read here rather than in the client: the daemon owns the only socket to Chrome, so an override the daemon cannot see has no effect.
+export const endpointFromEnv = (env: NodeJS.ProcessEnv = process.env): CdpEndpoint | undefined => {
+  const wsUrl = env["BU_CDP_WS"]?.trim();
+  return wsUrl ? { wsUrl } : undefined;
+};
+
 export const discoverEndpoint = async (): Promise<Result<CdpEndpoint, CdpError>> => {
+  const override = endpointFromEnv();
+  if (override) return ok(override);
+
   const dirs = userDataDirCandidates();
 
   const candidates: Candidate[] = [];
diff --git a/src/client.ts b/src/client.ts
index 84a98ee..5367489 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -140,12 +140,9 @@ export const createBrowserClient = (opts: BrowserClientOptions): BrowserClient =
 
   const start = async (): Promise<Result<void, CdpError>> => {
     if (transport.state() === "open" && session.current()) return ok(undefined);
-    const envUrl = process.env["BU_CDP_WS"];
     let wsUrl: string;
     if (remote?.cdpUrl) {
       wsUrl = remote.cdpUrl;
-    } else if (envUrl) {
-      wsUrl = envUrl;
     } else {
       const discovered = await discoverEndpoint();
       if (!discovered.success) return discovered;
diff --git a/src/domains/click.ts b/src/domains/click.ts
index cb4b007..41c3024 100644
--- a/src/domains/click.ts
+++ b/src/domains/click.ts
@@ -3,6 +3,7 @@ import { Text } from "@mariozechner/pi-tui";
 import type { BrowserClient } from "../client";
 import { Coords, MouseButton } from "../schemas/common";
 import { type Result, ok } from "../util/result";
+import { debugClicksEnabled } from "../util/debug";
 import { defineBrowserTool, type ToolErr } from "../util/tool";
 import { cdpCall } from "./cdp-call";
 import { captureWithCrosshair } from "./screenshot";
@@ -62,7 +63,7 @@ export const clickTool = defineBrowserTool({
     "A 'ref is stale' error means the page changed — re-run browser_snapshot to get fresh refs.",
     "After clicking, read the appended page-changes diff to confirm the action landed before moving on (no separate snapshot needed for a quick check).",
     "Coordinates are viewport CSS pixels (not device pixels). Compositor-level clicks pass through iframes, shadow DOM, and cross-origin content.",
-    "If a click doesn't register, set BH_DEBUG_CLICKS=1 to get annotated screenshots (debug only). For React/Vue components ignoring clicks, try browser_dispatch_key.",
+    "If a click doesn't register, run pi with --browser-debug-clicks (or set BH_DEBUG_CLICKS=1) to get annotated screenshots. For React/Vue components ignoring clicks, try browser_dispatch_key.",
   ],
   parameters: ClickArgs,
   concurrency: "serialized",
@@ -79,7 +80,7 @@ export const clickTool = defineBrowserTool({
     if (!clicked.success) return clicked;
 
     const diff = await interactiveDiff(client);
-    if (process.env["BH_DEBUG_CLICKS"]) {
+    if (debugClicksEnabled()) {
       const debug = await captureWithCrosshair(client, { x, y });
       if (debug.success) {
         return ok({
diff --git a/src/index.ts b/src/index.ts
index 1573605..6097881 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,7 +8,8 @@ import { type BrowserState, defaultState, persistState, restoreState } from "./s
 import { registerAllTools } from "./registry";
 import { cleanupTempDirs } from "./util/truncate";
 import { createDaemonTransport } from "./cdp/daemon-transport";
-import { asString } from "./util/guards";
+import { setDebugClicks } from "./util/debug";
+import { asBoolean, asString } from "./util/guards";
 
 export default function browserHarnessExtension(pi: ExtensionAPI): void {
   const flagNs = asString(pi.getFlag("browser-namespace"));
@@ -82,6 +83,7 @@ export default function browserHarnessExtension(pi: ExtensionAPI): void {
 
   pi.on("session_start", async (_event, ctx) => {
     state = restoreState(ctx, state.namespace);
+    setDebugClicks(asBoolean(pi.getFlag("browser-debug-clicks")) ?? false);
 
     // Re-read the on-disk profile pin every session start: another pi session may have changed it since this client was created.
     const profilePin = await readPin();
diff --git a/src/util/debug.ts b/src/util/debug.ts
new file mode 100644
index 0000000..e3b3a62
--- /dev/null
+++ b/src/util/debug.ts
@@ -0,0 +1,8 @@
+let flagEnabled = false;
+
+export const setDebugClicks = (on: boolean): void => {
+  flagEnabled = on;
+};
+
+export const debugClicksEnabled = (env: NodeJS.ProcessEnv = process.env): boolean =>
+  flagEnabled || Boolean(env["BH_DEBUG_CLICKS"]);
diff --git a/test/cdp/discovery-test.ts b/test/cdp/discovery-test.ts
new file mode 100644
index 0000000..7fc18fb
--- /dev/null
+++ b/test/cdp/discovery-test.ts
@@ -0,0 +1,29 @@
+import { test, describe } from "node:test";
+import assert from "node:assert/strict";
+import { endpointFromEnv } from "../../src/cdp/discovery";
+
+describe("BU_CDP_WS endpoint override", () => {
+  test("an unset variable leaves discovery to run normally", () => {
+    assert.equal(endpointFromEnv({}), undefined);
+  });
+
+  test("a set variable becomes the endpoint", () => {
+    const e = endpointFromEnv({ BU_CDP_WS: "ws://127.0.0.1:9333/devtools/browser/abc" });
+    assert.equal(e?.wsUrl, "ws://127.0.0.1:9333/devtools/browser/abc");
+  });
+
+  test("no userDataDir is claimed for a remote endpoint", () => {
+    const e = endpointFromEnv({ BU_CDP_WS: "ws://example.test/x" });
+    assert.equal(e?.userDataDir, undefined);
+  });
+
+  test("surrounding whitespace is trimmed", () => {
+    const e = endpointFromEnv({ BU_CDP_WS: "  ws://127.0.0.1:9222/x  " });
+    assert.equal(e?.wsUrl, "ws://127.0.0.1:9222/x");
+  });
+
+  test("an empty or whitespace-only variable is ignored, not treated as an endpoint", () => {
+    assert.equal(endpointFromEnv({ BU_CDP_WS: "" }), undefined);
+    assert.equal(endpointFromEnv({ BU_CDP_WS: "   " }), undefined);
+  });
+});
diff --git a/test/util/debug-test.ts b/test/util/debug-test.ts
new file mode 100644
index 0000000..08236dd
--- /dev/null
+++ b/test/util/debug-test.ts
@@ -0,0 +1,32 @@
+import { test, describe, afterEach } from "node:test";
+import assert from "node:assert/strict";
+import { debugClicksEnabled, setDebugClicks } from "../../src/util/debug";
+
+describe("debug click overlay switch", () => {
+  afterEach(() => {
+    setDebugClicks(false);
+  });
+
+  test("off when neither the flag nor the env var is set", () => {
+    assert.equal(debugClicksEnabled({}), false);
+  });
+
+  test("the --browser-debug-clicks flag turns it on", () => {
+    setDebugClicks(true);
+    assert.equal(debugClicksEnabled({}), true);
+  });
+
+  test("BH_DEBUG_CLICKS still turns it on without the flag", () => {
+    assert.equal(debugClicksEnabled({ BH_DEBUG_CLICKS: "1" }), true);
+  });
+
+  test("an empty BH_DEBUG_CLICKS does not turn it on", () => {
+    assert.equal(debugClicksEnabled({ BH_DEBUG_CLICKS: "" }), false);
+  });
+
+  test("the flag can be turned back off", () => {
+    setDebugClicks(true);
+    setDebugClicks(false);
+    assert.equal(debugClicksEnabled({}), false);
+  });
+});