diff --git a/.changeset/effect-sdk-browser-error-noise.md b/.changeset/effect-sdk-browser-error-noise.md
new file mode 100644
index 0000000000..3f743409a3
--- /dev/null
+++ b/.changeset/effect-sdk-browser-error-noise.md
@@ -0,0 +1,5 @@
+---
+"@maple-dev/effect-sdk": patch
+---
+
+The browser client's uncaught-error capture no longer reports errors thrown by browser extensions (an extension's script, or a rejection whose top frame is one) or the benign `ResizeObserver loop` notices, as `@maple/browser` already does.
diff --git a/apps/web/src/page/kit/time-range-picker.scene.test.ts b/apps/web/src/page/kit/time-range-picker.scene.test.ts
index 25a2efc948..6b8c72f765 100644
--- a/apps/web/src/page/kit/time-range-picker.scene.test.ts
+++ b/apps/web/src/page/kit/time-range-picker.scene.test.ts
@@ -213,4 +213,8 @@ describe("time range picker hotkey", () => {
 		expect(isOpenKey(press("D", { shiftKey: true }))).toBe(false)
 		expect(isOpenKey(press("f"))).toBe(false)
 	})
+
+	test("the key-less keydown Chrome fires on autofill opens nothing", () => {
+		expect(isOpenKey({ ...press("d"), key: undefined })).toBe(false)
+	})
 })
diff --git a/apps/web/src/page/kit/time-range-picker.ts b/apps/web/src/page/kit/time-range-picker.ts
index 1159695fb2..14985a9cae 100644
--- a/apps/web/src/page/kit/time-range-picker.ts
+++ b/apps/web/src/page/kit/time-range-picker.ts
@@ -5,7 +5,7 @@ import { parseWarehouseDateTime, relativeRangeSeconds } from "@maple/query-engin
 import { TONE_TEXT } from "@maple/ui/lib/tone"
 import { badgeVariants } from "@maple/ui/styles/ui/badge"
 import { kbdStyles } from "@maple/ui/styles/ui/kbd"
-import { isDialogOpen, isEditableTarget } from "@maple/ui/lib/keyboard"
+import { isDialogOpen, isEditableTarget, pressedKey } from "@maple/ui/lib/keyboard"
 import { Clock, Effect, Option, Schema, type Stream } from "effect"
 import { Command, Dom, Mount, Submodel, type Update } from "foldkit"
 import type { Html, HtmlBuilder } from "foldkit/html"
@@ -503,7 +503,7 @@ export const SelectTimeZone = Command.define("SelectTimeZone", {
 const HOTKEY_ATTRIBUTE = "time-range-hotkey"
 
 type KeyPress = Readonly<{
-	key: string
+	key?: string | undefined
 	metaKey: boolean
 	ctrlKey: boolean
 	altKey: boolean
@@ -512,7 +512,11 @@ type KeyPress = Readonly<{
 
 /** The `time.open` combo: a bare "D" (either case), no modifier held. */
 export const isOpenKey = (event: KeyPress): boolean =>
-	event.key.toLowerCase() === "d" && !event.metaKey && !event.ctrlKey && !event.altKey && !event.shiftKey
+	pressedKey(event).toLowerCase() === "d" &&
+	!event.metaKey &&
+	!event.ctrlKey &&
+	!event.altKey &&
+	!event.shiftKey
 
 /**
  * `useAppHotkey("time.open", () => setOpen(true))`: "D" outside fields and dialogs, unmodified,
diff --git a/apps/web/src/shell/subscription.ts b/apps/web/src/shell/subscription.ts
index 7a0ff6a59e..ebbbfcc8dd 100644
--- a/apps/web/src/shell/subscription.ts
+++ b/apps/web/src/shell/subscription.ts
@@ -1,4 +1,4 @@
-import { isDialogOpen, isEditableTarget } from "@maple/ui/lib/keyboard"
+import { isDialogOpen, isEditableTarget, pressedKey } from "@maple/ui/lib/keyboard"
 import { Option, Stream } from "effect"
 import { Dom } from "foldkit"
 import { DASHBOARD_FAVORITES_EVENT, readDashboardFavorites } from "./favorites"
@@ -47,7 +47,7 @@ export const globalShortcuts: Stream.Stream<Message> = Dom.streamFromEventFilter
 	target: () => document,
 	type: "keydown",
 	filterMapEvent: (event): Option.Option<Message> => {
-		const key = event.key.toLowerCase()
+		const key = pressedKey(event).toLowerCase()
 		if ((event.metaKey || event.ctrlKey) && key === "k") {
 			event.preventDefault()
 			return Option.some(Message.PressedPaletteShortcut())
diff --git a/bun.lock b/bun.lock
index 97a4bf669f..a3d0bbc71c 100644
--- a/bun.lock
+++ b/bun.lock
@@ -712,6 +712,7 @@
       "devDependencies": {
         "@effect/vitest": "catalog:effect",
         "@maple/browser-session": "workspace:*",
+        "@maple/sdk-core": "workspace:*",
         "@types/node": "catalog:tooling",
         "effect": "catalog:effect",
         "tsdown": "^0.23.0",
diff --git a/packages/effect-sdk/package.json b/packages/effect-sdk/package.json
index 793c4cb1c6..42390077b9 100644
--- a/packages/effect-sdk/package.json
+++ b/packages/effect-sdk/package.json
@@ -68,6 +68,7 @@
 	"devDependencies": {
 		"@effect/vitest": "catalog:effect",
 		"@maple/browser-session": "workspace:*",
+		"@maple/sdk-core": "workspace:*",
 		"@types/node": "catalog:tooling",
 		"effect": "catalog:effect",
 		"tsdown": "^0.23.0",
diff --git a/packages/effect-sdk/src/client/error-noise.test.ts b/packages/effect-sdk/src/client/error-noise.test.ts
new file mode 100644
index 0000000000..7a9ea810f5
--- /dev/null
+++ b/packages/effect-sdk/src/client/error-noise.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest"
+import { isBrowserNoise } from "./error-noise.js"
+
+const withStack = (message: string, stack: string): Error => {
+	const error = new Error(message)
+	error.stack = stack
+	return error
+}
+
+describe("isBrowserNoise", () => {
+	it("drops the ResizeObserver loop notices", () => {
+		expect(
+			isBrowserNoise(
+				new Error("ResizeObserver loop completed with undelivered notifications."),
+				"window.onerror",
+				"https://app.maple.dev/",
+			),
+		).toBe(true)
+		expect(isBrowserNoise(new Error("ResizeObserver loop limit exceeded"), "window.onerror")).toBe(true)
+	})
+
+	it("drops a rejection thrown from an extension's injected script", () => {
+		const metaMask = withStack(
+			"Failed to connect to MetaMask",
+			"i: Failed to connect to MetaMask\n    at Object.connect (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/scripts/inpage.js:12:4822)",
+		)
+		expect(isBrowserNoise(metaMask, "unhandledrejection")).toBe(true)
+		expect(
+			isBrowserNoise(withStack("x", "connect@moz-extension://abc/inpage.js:1:2"), "unhandledrejection"),
+		).toBe(true)
+	})
+
+	it("drops an uncaught error whose script is an extension's", () => {
+		expect(
+			isBrowserNoise(
+				new Error("boom"),
+				"window.onerror",
+				"chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/backendManager.js",
+			),
+		).toBe(true)
+	})
+
+	it("keeps the app's own errors, even when an extension frame sits further down the stack", () => {
+		const own = withStack(
+			"Cannot read properties of undefined (reading 'toLowerCase')",
+			"TypeError: Cannot read properties of undefined (reading 'toLowerCase')\n    at isOpenKey (https://app.maple.dev/assets/time-range-picker.js:1:2)\n    at chrome-extension://abc/content.js:3:4",
+		)
+		expect(isBrowserNoise(own, "unhandledrejection")).toBe(false)
+		expect(
+			isBrowserNoise(
+				withStack(
+					"mail a@b.co failed",
+					"Error: mail a@b.co failed\n    at send (https://app.test/a.js:1:1)",
+				),
+				"window.onerror",
+			),
+		).toBe(false)
+		expect(isBrowserNoise("plain rejection", "unhandledrejection")).toBe(false)
+	})
+})
diff --git a/packages/effect-sdk/src/client/error-noise.ts b/packages/effect-sdk/src/client/error-noise.ts
new file mode 100644
index 0000000000..ccff6eb6af
--- /dev/null
+++ b/packages/effect-sdk/src/client/error-noise.ts
@@ -0,0 +1,10 @@
+// Uncaught errors that are not the app's: a browser extension's own failures and
+// the benign `ResizeObserver loop` notice. The patterns are `@maple/sdk-core`'s
+// default filters, the same ones `@maple/browser` applies.
+import { asError, type ErrorSource, makeErrorFilter } from "@maple/sdk-core"
+
+const defaultFilters = makeErrorFilter()
+
+/** True for an error the page's own code did not throw. `filename` is `ErrorEvent.filename`. */
+export const isBrowserNoise = (error: unknown, source: ErrorSource, filename?: string): boolean =>
+	!defaultFilters(asError(error), { source, originalError: error }, filename || undefined)
diff --git a/packages/effect-sdk/src/client/flushable.test.ts b/packages/effect-sdk/src/client/flushable.test.ts
index 7de5366b97..1f25164daf 100644
--- a/packages/effect-sdk/src/client/flushable.test.ts
+++ b/packages/effect-sdk/src/client/flushable.test.ts
@@ -79,6 +79,9 @@ const spanNames = (calls: ReadonlyArray<FetchCall>): Array<string> =>
 		).resourceSpans[0].scopeSpans[0].spans.map((span) => span.name),
 	)
 
+/** The `ErrorEvent` / `PromiseRejectionEvent` fields the global error handlers read. */
+type ShimEvent = Readonly<{ error?: Error | null; message?: string; filename?: string; reason?: Error }>
+
 // Minimal DOM event shim — vitest runs in node, where globalThis isn't an
 // EventTarget. Lets us drive `pagehide` / `visibilitychange` without jsdom.
 const setupDom = () => {
@@ -101,6 +104,9 @@ const setupDom = () => {
 		fire: (type: string) => {
 			for (const fn of listeners[type] ?? []) (fn as () => void)()
 		},
+		dispatch: (type: string, event: ShimEvent) => {
+			for (const fn of listeners[type] ?? []) (fn as (event: ShimEvent) => void)(event)
+		},
 		// A browser runs a microtask checkpoint after each listener; `fire` does not.
 		fireWithCheckpoints: async (type: string) => {
 			for (const fn of listeners[type] ?? []) {
@@ -414,6 +420,33 @@ describe("MapleFlush.make (client)", () => {
 		expect(dom.listenerCount("visibilitychange")).toBe(0)
 	})
 
+	it("reports the app's uncaught errors and drops extension and ResizeObserver noise", async () => {
+		const { calls, restore: rf } = setupFetch()
+		const dom = setupDom()
+		restore = () => {
+			rf()
+			dom.restore()
+		}
+		const telemetry = make(baseConfig)
+		const extensionFrame = new Error("Failed to connect to MetaMask")
+		extensionFrame.stack =
+			"i: Failed to connect to MetaMask\n    at Object.connect (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/scripts/inpage.js:12:4822)"
+
+		dom.dispatch("error", {
+			error: null,
+			message: "ResizeObserver loop completed with undelivered notifications.",
+			filename: "https://app.test/",
+		})
+		dom.dispatch("error", { error: new Error("boom"), filename: "chrome-extension://abc/content.js" })
+		dom.dispatch("unhandledrejection", { reason: extensionFrame })
+		dom.dispatch("error", { error: new TypeError("app bug"), filename: "https://app.test/assets/app.js" })
+		dom.dispatch("unhandledrejection", { reason: new Error("app rejection") })
+		await telemetry.flush()
+
+		expect(spanNames(calls)).toEqual(["browser.uncaught_error", "browser.unhandled_rejection"])
+		await telemetry.dispose()
+	})
+
 	it("auto-flushes on the interval, and dispose() stops the timer", async () => {
 		vi.useFakeTimers()
 		const { calls, restore: r } = setupFetch()
diff --git a/packages/effect-sdk/src/client/flushable.ts b/packages/effect-sdk/src/client/flushable.ts
index a5cfbeb838..8a78df902a 100644
--- a/packages/effect-sdk/src/client/flushable.ts
+++ b/packages/effect-sdk/src/client/flushable.ts
@@ -32,6 +32,7 @@ import { makeMetricBuffer } from "../shared/flushable-metrics.js"
 import { type CaptureExceptionOptions, makeSpanBuffer, type SpanBuffer } from "../shared/flushable-tracer.js"
 import type { MapleSpanOptions } from "../shared/span-options.js"
 import { browserDocument, browserNavigator, browserResourceAttributes } from "./browser-globals.js"
+import { isBrowserNoise } from "./error-noise.js"
 import { type ClientReplayConfig, startClientSession } from "./replay-loader.js"
 import { withSessionLink } from "./session-link.js"
 import type { PrivacyOptions } from "./track.js"
@@ -359,7 +360,7 @@ export const make = (config: MapleClientFlushableConfig): FlushableTelemetry =>
 		// louder error tracker.
 		const error: unknown =
 			event.error ?? (event.message && event.filename ? new Error(event.message) : undefined)
-		if (error === undefined) return
+		if (error === undefined || isBrowserNoise(error, "window.onerror", event.filename)) return
 		captureException(error, {
 			name: "browser.uncaught_error",
 			attributes: {
@@ -375,6 +376,7 @@ export const make = (config: MapleClientFlushableConfig): FlushableTelemetry =>
 	}
 
 	const onUnhandledRejection = (event: PromiseRejectionEvent): void => {
+		if (isBrowserNoise(event.reason, "unhandledrejection")) return
 		captureException(event.reason, {
 			name: "browser.unhandled_rejection",
 			attributes: { "maple.exception.source": "unhandledrejection" },
diff --git a/packages/tsconfig.effect-sdk.dts.json b/packages/tsconfig.effect-sdk.dts.json
index 442a507b2c..d1a7a1ccd2 100644
--- a/packages/tsconfig.effect-sdk.dts.json
+++ b/packages/tsconfig.effect-sdk.dts.json
@@ -1,7 +1,7 @@
 {
 	// Declaration emit for effect-sdk's tsdown build only. It lives here so tsgo's
-	// rootDir covers @maple/browser-session, whose types the SDK bundles.
+	// rootDir covers @maple/browser-session and @maple/sdk-core, whose types the SDK bundles.
 	"extends": "./effect-sdk/tsconfig.json",
-	"include": ["./effect-sdk/src/**/*.ts", "./browser-session/src/**/*.ts"],
+	"include": ["./effect-sdk/src/**/*.ts", "./browser-session/src/**/*.ts", "./sdk-core/src/**/*.ts"],
 	"exclude": ["**/*.test.ts", "**/*.bench.ts"]
 }
diff --git a/packages/ui/src/lib/keyboard.ts b/packages/ui/src/lib/keyboard.ts
index 4ded726931..4dd84f0814 100644
--- a/packages/ui/src/lib/keyboard.ts
+++ b/packages/ui/src/lib/keyboard.ts
@@ -3,6 +3,9 @@
 
 const EDITABLE_TAGS = new Set(["INPUT", "TEXTAREA", "SELECT"])
 
+/** `event.key`, or "" for the key-less `keydown` Chrome fires when it autofills a form. */
+export const pressedKey = (event: { readonly key?: string | undefined }): string => event.key ?? ""
+
 /** True when the event target is a text field / contentEditable — skip shortcuts there. */
 export function isEditableTarget(target: EventTarget | null): boolean {
 	if (!(target instanceof HTMLElement)) return false