diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 8e2c07b03..e43ea1f0f 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -64,6 +64,9 @@
 - Fixed install.sh falsely reporting success on musl-based systems (such as Alpine Linux) when the binary fails to start; the installer now smoke-tests the binary, exits non-zero on failure, and provides remediation steps.
 - Fixed Codex config.toml discovery incorrectly importing MCP servers that are configured with enabled = false.
 - Fixed bash.patterns allow rules rejecting valid commands when quoted arguments contained shell metacharacters (such as Cargo benchmark regex filters).
+### Added
+
+- Added automatic detection of common Ungoogled Chromium Linux installations for the browser tool.
 
 ## [17.2.6] - 2026-08-03
 
diff --git a/packages/coding-agent/src/tools/browser/launch.ts b/packages/coding-agent/src/tools/browser/launch.ts
index a3e7c1f5b..76cccf66b 100644
--- a/packages/coding-agent/src/tools/browser/launch.ts
+++ b/packages/coding-agent/src/tools/browser/launch.ts
@@ -202,10 +202,13 @@ function isExecutableFile(p: string): boolean {
 /** Flatpak application id published by the Ungoogled Chromium project. */
 const UNGOOGLED_CHROMIUM_FLATPAK_ID = "io.github.ungoogled_software.ungoogled_chromium";
 
-function systemChromiumCandidates(): string[] {
-	const home = os.homedir();
+function systemChromiumCandidates(
+	platform: NodeJS.Platform = process.platform,
+	home = os.homedir(),
+	which: (name: string) => string | undefined = $which,
+): string[] {
 	const candidates: string[] = [];
-	switch (process.platform) {
+	switch (platform) {
 		case "darwin": {
 			for (const root of ["/Applications", path.join(home, "Applications")]) {
 				candidates.push(
@@ -220,17 +223,9 @@ function systemChromiumCandidates(): string[] {
 			break;
 		}
 		case "linux": {
-			const names = [
-				"google-chrome-stable",
-				"google-chrome",
-				"chromium",
-				"chromium-browser",
-				"chrome",
-				"ungoogled-chromium",
-				"ungoogled-chromium-browser",
-			];
+			const names = ["google-chrome-stable", "google-chrome", "chromium", "chromium-browser", "chrome"];
 			for (const name of names) {
-				const found = $which(name);
+				const found = which(name);
 				if (found) candidates.push(found);
 			}
 			candidates.push(
@@ -241,13 +236,6 @@ function systemChromiumCandidates(): string[] {
 				"/snap/bin/chromium",
 				"/var/lib/flatpak/exports/bin/com.google.Chrome",
 				"/var/lib/flatpak/exports/bin/org.chromium.Chromium",
-				// Ungoogled Chromium. Distro and AUR packages that keep the plain
-				// `chromium` name are already covered above; these are the paths
-				// unique to it, including the system and per-user Flatpak shims.
-				"/usr/bin/ungoogled-chromium",
-				"/usr/bin/ungoogled-chromium-browser",
-				`/var/lib/flatpak/exports/bin/${UNGOOGLED_CHROMIUM_FLATPAK_ID}`,
-				path.join(home, ".local/share/flatpak/exports/bin", UNGOOGLED_CHROMIUM_FLATPAK_ID),
 			);
 			let onNixos = false;
 			try {
@@ -256,6 +244,19 @@ function systemChromiumCandidates(): string[] {
 			if (onNixos) {
 				candidates.push(path.join(home, ".nix-profile/bin/chromium"), "/run/current-system/sw/bin/chromium");
 			}
+			for (const name of ["ungoogled-chromium", "ungoogled-chromium-browser"]) {
+				const found = which(name);
+				if (found) candidates.push(found);
+			}
+			candidates.push(
+				// Ungoogled Chromium. Distro and AUR packages that keep the plain
+				// `chromium` name are already covered above; these are the paths
+				// unique to it, including the system and per-user Flatpak shims.
+				"/usr/bin/ungoogled-chromium",
+				"/usr/bin/ungoogled-chromium-browser",
+				`/var/lib/flatpak/exports/bin/${UNGOOGLED_CHROMIUM_FLATPAK_ID}`,
+				path.join(home, ".local/share/flatpak/exports/bin", UNGOOGLED_CHROMIUM_FLATPAK_ID),
+			);
 			break;
 		}
 		case "win32": {
@@ -884,9 +885,13 @@ export async function applyStealthPatches(
 	await injectStealthScripts(page);
 }
 
-/** Exposes the resolved executable candidate list for detection tests. */
-export function systemChromiumCandidatesForTest(): string[] {
-	return systemChromiumCandidates();
+/** Exposes executable candidates for detection tests. */
+export function systemChromiumCandidatesForTest(
+	platform: NodeJS.Platform = process.platform,
+	home?: string,
+	which?: (name: string) => string | undefined,
+): string[] {
+	return systemChromiumCandidates(platform, home, which);
 }
 
 export function stealthIgnoreDefaultArgsForTest(executablePath: string | undefined): string[] {
diff --git a/packages/coding-agent/test/tools/browser-launch.test.ts b/packages/coding-agent/test/tools/browser-launch.test.ts
index f7e0948e4..c545fed31 100644
--- a/packages/coding-agent/test/tools/browser-launch.test.ts
+++ b/packages/coding-agent/test/tools/browser-launch.test.ts
@@ -45,24 +45,23 @@ describe("browser launch stealth defaults", () => {
 
 const UNGOOGLED_CHROMIUM_FLATPAK_ID = "io.github.ungoogled_software.ungoogled_chromium";
 
-describe("system Chromium candidates on Linux", () => {
-	it("offers Ungoogled Chromium executables", () => {
-		if (process.platform !== "linux") return;
-		const candidates = systemChromiumCandidatesForTest();
+describe("system Chromium candidates", () => {
+	const linuxCandidates = (which: (name: string) => string | undefined = () => undefined) =>
+		systemChromiumCandidatesForTest("linux", "/home/test", which);
+
+	it("offers Ungoogled Chromium executables on Linux", () => {
+		const candidates = linuxCandidates();
 
 		expect(candidates).toContain("/usr/bin/ungoogled-chromium");
 		expect(candidates).toContain("/usr/bin/ungoogled-chromium-browser");
 		expect(candidates).toContain(`/var/lib/flatpak/exports/bin/${UNGOOGLED_CHROMIUM_FLATPAK_ID}`);
-
-		const perUserFlatpak = candidates.find(candidate =>
-			candidate.endsWith(`/.local/share/flatpak/exports/bin/${UNGOOGLED_CHROMIUM_FLATPAK_ID}`),
+		expect(candidates).toContain(
+			`/home/test/.local/share/flatpak/exports/bin/${UNGOOGLED_CHROMIUM_FLATPAK_ID}`,
 		);
-		expect(perUserFlatpak).toBeDefined();
 	});
 
-	it("keeps the previously supported executables", () => {
-		if (process.platform !== "linux") return;
-		const candidates = systemChromiumCandidatesForTest();
+	it("keeps the previously supported Linux executables", () => {
+		const candidates = linuxCandidates();
 
 		for (const executablePath of [
 			"/usr/bin/google-chrome-stable",
@@ -77,10 +76,10 @@ describe("system Chromium candidates on Linux", () => {
 		}
 	});
 
-	it("ranks Ungoogled Chromium below the stock builds", () => {
-		if (process.platform !== "linux") return;
-		const candidates = systemChromiumCandidatesForTest();
-		const ungoogled = candidates.indexOf("/usr/bin/ungoogled-chromium");
+	it("ranks PATH-resolved Ungoogled Chromium below stock builds", () => {
+		const ungoogledPath = "/custom/bin/ungoogled-chromium";
+		const candidates = linuxCandidates(name => (name === "ungoogled-chromium" ? ungoogledPath : undefined));
+		const ungoogled = candidates.indexOf(ungoogledPath);
 
 		for (const executablePath of [
 			"/usr/bin/google-chrome-stable",
@@ -91,6 +90,13 @@ describe("system Chromium candidates on Linux", () => {
 			expect(ungoogled).toBeGreaterThan(candidates.indexOf(executablePath));
 		}
 	});
+
+	it("does not add Ungoogled Chromium candidates on macOS or Windows", () => {
+		for (const platform of ["darwin", "win32"] as const) {
+			const candidates = systemChromiumCandidatesForTest(platform, "/home/test", () => "/custom/ungoogled");
+			expect(candidates.some(candidate => candidate.toLowerCase().includes("ungoogled"))).toBeFalse();
+		}
+	});
 });
 
 describe("browser executable selection", () => {