diff --git a/CHANGELOG.md b/CHANGELOG.md
index 64456af..e015860 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
## [Unreleased]
+### Added
+- **DuckDuckGo anomaly challenge detection.** Detect DuckDuckGo anomaly challenge walls (`//duckduckgo.com/anomaly.js`, `anomaly-modal`) in Tier 1 and the MITM proxy, escalating requests to the browser tiers rather than treating the challenge page as successful content (#119).
+
## [1.5.0] - 2026-09-04
### Changed
diff --git a/apps/api/src/proxy/__tests__/directForward.test.ts b/apps/api/src/proxy/__tests__/directForward.test.ts
index 660d453..bb2fbb8 100644
--- a/apps/api/src/proxy/__tests__/directForward.test.ts
+++ b/apps/api/src/proxy/__tests__/directForward.test.ts
@@ -49,6 +49,11 @@ const fetchFixture = (req: Request): Response => {
return new Response('', {
headers: { "Content-Type": "text/html; charset=utf-8" },
})
+ if (pathname === "/duckduckgo-challenge")
+ return new Response(
+ '',
+ { status: 202, headers: { "Content-Type": "text/html; charset=utf-8" } },
+ )
if (pathname === "/video")
return new Response(chunked(Buffer.from([0, 1, 2, 3]), Buffer.from([4, 5, 6, 7])), {
headers: { "Content-Type": "video/mp4" },
@@ -297,6 +302,20 @@ describe("directForwardHttp — buffered by default", () => {
expect(result.body.toString()).toContain("Just a moment")
})
+ test("detects a 202 DuckDuckGo anomaly challenge", async () => {
+ const result = await directForwardHttp({
+ url: `${baseUrl}/duckduckgo-challenge`,
+ method: "POST",
+ headers: {},
+ })
+
+ expect(result.mode).toBe("buffer")
+ if (result.mode !== "buffer") return
+ expect(result.status).toBe(202)
+ expect(result.challengeDetected).toBe(true)
+ expect(result.body.toString()).toContain("anomaly-modal")
+ })
+
test("detects a challenge in a compressed HTML response", async () => {
const result = await directForwardHttp({
url: `${baseUrl}/gzip-challenge`,
diff --git a/apps/api/src/proxy/directForward.ts b/apps/api/src/proxy/directForward.ts
index a8505b2..820c981 100644
--- a/apps/api/src/proxy/directForward.ts
+++ b/apps/api/src/proxy/directForward.ts
@@ -346,7 +346,7 @@ async function readHttpResponse(
// Challenge detection on the buffered body. Bounded preview keeps this cheap.
const previewText = decodeForInspection(body.subarray(0, offset), headers["content-encoding"])
- const challengeType = detectChallengeType(previewText, headers)
+ const challengeType = detectChallengeType(previewText, headers, status)
const challengeDetected = !skipChallengeDetection && isChallengeWall(status, body.length, challengeType)
return {
diff --git a/packages/tiers/src/index.ts b/packages/tiers/src/index.ts
index b85646e..f392871 100644
--- a/packages/tiers/src/index.ts
+++ b/packages/tiers/src/index.ts
@@ -17,6 +17,7 @@ export {
hasDataDomeCaptcha,
hasDataDomeChallenge,
hasDdosGuardChallenge,
+ hasDuckDuckGoChallenge,
hasHcaptcha,
hasImpervaChallenge,
hasRecaptcha,
diff --git a/packages/tiers/src/tiers/1.ts b/packages/tiers/src/tiers/1.ts
index 15aa76a..56ecad9 100644
--- a/packages/tiers/src/tiers/1.ts
+++ b/packages/tiers/src/tiers/1.ts
@@ -7,6 +7,7 @@ import {
hasAkamaiChallenge,
hasAwsWafCaptcha,
hasAwsWafChallenge,
+ hasDuckDuckGoChallenge,
hasHcaptcha,
hasRecaptcha,
hasTurnstile,
@@ -142,6 +143,20 @@ export async function runTier1(
}
}
+ if (hasDuckDuckGoChallenge(previewText, responseHeaders)) {
+ return {
+ tier: 1,
+ status: "needs-js",
+ durationMs: Date.now() - start,
+ reason: "duckduckgo-anomaly-challenge",
+ challenge: "duckduckgo",
+ responseHeaders,
+ contentType,
+ body: rawBytes,
+ statusCode: res.status,
+ }
+ }
+
// JS-only challenges: the page's static HTML is just a shell that loads the
// captcha widget via