VTSTech · Oct 9, 2026 · Oct 9, 2026
diff --git a/agentkthx/cli/commands/config.py b/agentkthx/cli/commands/config.py
@@ -26,6 +26,8 @@
     "cf": "Cloudflare",
     "siliconflow": "SiliconFlow",
     "sf": "SiliconFlow",
+    "duckduckgo": "DuckDuckGo",
+    "ddg": "DuckDuckGo",
 }
 
 
@@ -244,6 +246,24 @@
         "RESERVED for a future free tier — unused today (no free models; "
         "default: Qwen/Qwen3-8B)",
     ),
+    # ── DuckDuckGo AI Chat ──
+    (
+        "DUCKDUCKGO_BASE_URL",
+        "DuckDuckGo AI Chat URL (default: https://duckduckgo.com — the "
+        "protocol lives under /duckchat/v1)",
+    ),
+    (
+        "DUCKDUCKGO_USER_AGENT",
+        "Browser User-Agent override — DDG 403s non-browser UAs; empty = "
+        "built-in Chrome 120 UA (only set if DDG rejects the built-in one)",
+    ),
+    (
+        "DUCKDUCKGO_DEFAULT_MODEL",
+        "Default model (default: gpt-4o-mini; catalog: gpt-4o-mini, "
+        "claude-3-haiku-20240307, meta-llama/Llama-3.3-70B-Instruct-Turbo, "
+        "mistralai/Mistral-Small-24B-Instruct-2501, o3-mini — no API key "
+        "needed, the backend is keyless and anonymous)",
+    ),
     # ── ACP / TurboQuant ──
     ("ACP_BASE_URL", "ACP server URL"),
     ("ACP_USER", "ACP username (default: admin)"),
@@ -286,6 +306,9 @@ def cmd_config(args: argparse.Namespace) -> int:
         CLOUDFLARE_FREE_ONLY,
         DEBUG,
         DEFAULT_MODEL,
+        DUCKDUCKGO_BASE_URL,
+        DUCKDUCKGO_DEFAULT_MODEL,
+        DUCKDUCKGO_USER_AGENT,
         GEMINI_API_KEY,
         GEMINI_BASE_URL,
         GEMINI_DEFAULT_MODEL,
@@ -374,6 +397,7 @@ def cmd_config(args: argparse.Namespace) -> int:
             ("NVIDIA_BASE_URL", NVIDIA_BASE_URL),
             ("CLOUDFLARE_BASE_URL", CLOUDFLARE_BASE_URL or "(built from CLOUDFLARE_ACCOUNT_ID)"),
             ("SILICONFLOW_BASE_URL", SILICONFLOW_BASE_URL),
+            ("DUCKDUCKGO_BASE_URL", DUCKDUCKGO_BASE_URL),
             ("ACP_BASE_URL", ACP_BASE_URL),
         ]
         for name, val in urls:
@@ -400,6 +424,7 @@ def cmd_config(args: argparse.Namespace) -> int:
                 ("MISTRAL_BASE_URL", MISTRAL_BASE_URL),
                 ("ORCAROUTER_BASE_URL", ORCAROUTER_BASE_URL),
                 ("POLLINATIONS_BASE_URL", POLLINATIONS_BASE_URL),
+                ("DUCKDUCKGO_BASE_URL", DUCKDUCKGO_BASE_URL),
                 ("ACP_BASE_URL", ACP_BASE_URL),
             ],
             "OpenRouter": [
@@ -480,6 +505,14 @@ def cmd_config(args: argparse.Namespace) -> int:
                 ("SILICONFLOW_FREE_ONLY", str(SILICONFLOW_FREE_ONLY)),
                 ("SILICONFLOW_FREE_FALLBACK_MODEL", SILICONFLOW_FREE_FALLBACK_MODEL),
             ],
+            "DuckDuckGo": [
+                ("DUCKDUCKGO_BASE_URL", DUCKDUCKGO_BASE_URL),
+                ("DUCKDUCKGO_DEFAULT_MODEL", DUCKDUCKGO_DEFAULT_MODEL),
+                (
+                    "DUCKDUCKGO_USER_AGENT",
+                    DUCKDUCKGO_USER_AGENT or "(built-in browser UA)",
+                ),
+            ],
             "ACP": [
                 ("ACP_USER", ACP_USER),
                 ("ACP_PASS", _mask_key(ACP_PASS)),
@@ -544,6 +577,7 @@ def cmd_config(args: argparse.Namespace) -> int:
             "Cloudflare": CLOUDFLARE_BASE_URL
             or f"https://api.cloudflare.com/client/v4/accounts/{CLOUDFLARE_ACCOUNT_ID or '<ID>'}/ai/v1",
             "SiliconFlow": SILICONFLOW_BASE_URL,
+            "DuckDuckGo": DUCKDUCKGO_BASE_URL,
             "ACP": ACP_BASE_URL,
         },
         acp_user=ACP_USER,

diff --git a/agentkthx/config.py b/agentkthx/config.py
@@ -435,6 +435,34 @@
 SILICONFLOW_FREE_FALLBACK_MODEL = os.environ.get("SILICONFLOW_FREE_FALLBACK_MODEL", "Qwen/Qwen3-8B")
 
 
+# ═══════════════════════════════════════════════════════════════════════════════
+# DuckDuckGo plugin (agentkthx/plugins/duckduckgo/)
+# DuckDuckGo AI Chat (duck.ai) — the keyless, anonymous, zero-cost LLM
+# surface via the NON-OpenAI /duckchat/v1 protocol. NO API KEY EXISTS —
+# "authentication" is the x-vqd-hash-1 CHALLENGE PROOF (the retired
+# x-vqd-4 opaque token is gone): GET /status issues an obfuscated JS
+# challenge, the bundled Node solver executes it against a clean-browser
+# environment, and the solved result rides the X-Vqd-Hash-1 request
+# header. Each /chat response carries the NEXT challenge (per-turn
+# rotation). Held in-memory per backend instance, never persisted. See
+# docs/api/DUCKDUCKGO_API_TECHNICAL_REFERENCE.md.
+# ═══════════════════════════════════════════════════════════════════════════════
+DUCKDUCKGO_BASE_URL = os.environ.get("DUCKDUCKGO_BASE_URL", "https://duck.ai")
+# Browser User-Agent — DDG's anti-bot layer returns 403 for
+# non-browser UAs. Empty string falls back to the backend's built-in
+# Chrome 136 UA (the default). The challenge solver is fed the SAME
+# UA (a mismatch invalidates the proof). Only set this if DDG starts
+# rejecting the built-in one (UA rotation is an anti-fingerprinting
+# last resort, not a routine knob).
+DUCKDUCKGO_USER_AGENT = os.environ.get("DUCKDUCKGO_USER_AGENT", "")
+# Default model — gpt-6-luna is DuckDuckGo's own default pick. The
+# catalog: gpt-6-luna, gpt-5.6-luna, gpt-5.4-nano, gpt-5.4-mini,
+# claude-haiku-4-5, mistral-small-2603, tinfoil/gpt-oss-120b,
+# tinfoil/gemma4-31b (legacy aliases gpt-4o-mini, claude-3-haiku,
+# llama, mixtral, o3-mini resolve forward to their successors).
+DUCKDUCKGO_DEFAULT_MODEL = os.environ.get("DUCKDUCKGO_DEFAULT_MODEL", "gpt-6-luna")
+
+
 # ═══════════════════════════════════════════════════════════════════════════════
 # BACKEND SELECTION
 # ═══════════════════════════════════════════════════════════════════════════════

diff --git a/agentkthx/core/types.py b/agentkthx/core/types.py
@@ -199,6 +199,20 @@ class BackendType(Enum):
     # docs/api/SILICONFLOW_API_TECHNICAL_REFERENCE.md.
     SILICONFLOW = "siliconflow"
 
+    # DuckDuckGo AI Chat — the keyless, anonymous, zero-cost LLM
+    # surface at duckduckgo.com/duckchat/v1 (fronting duck.ai). NOT
+    # OpenAI-compatible: custom x-vqd-4 header-token handshake
+    # (bootstrap via GET /status, rotate on every /chat response),
+    # own SSE shape, no /models endpoint, no sampling params, tools
+    # stripped (ReAct only), ~20-turn conversation limit. Catalog:
+    # GPT-4o mini, o3-mini, Claude Haiku, Llama 3.3 70B, Mistral
+    # Small 3 24B — the upstream frontier set, IP-stripped by DDG's
+    # privacy layer. The ONLY cloud backend that subclasses
+    # BaseBackend directly instead of CloudBackend.
+    # See agentkthx/plugins/duckduckgo/ and
+    # docs/api/DUCKDUCKGO_API_TECHNICAL_REFERENCE.md.
+    DUCKDUCKGO = "duckduckgo"
+
 
 class ApiMode(Enum):
     """API mode for backend communication.

diff --git a/agentkthx/data/model_seed.json b/agentkthx/data/model_seed.json
@@ -1923,5 +1923,79 @@
       "default_temperature": 0.7,
       "default_max_tokens": 8192
     }
+  },
+  "duckduckgo": {
+    "gpt-6-luna": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 16384,
+      "family": "gpt",
+      "free_tier": true,
+      "upstream": "OpenAI GPT-6 Luna (via DDG proxy)",
+      "note": "DuckDuckGo's own default model ('Best for everyday use'); verified against the live dropdown + benoitpetit/duckduckgo-chat-cli models.go, 2026-10-09"
+    },
+    "gpt-5.6-luna": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 16384,
+      "family": "gpt",
+      "free_tier": true,
+      "upstream": "OpenAI GPT-5.6 Luna (via DDG proxy)",
+      "note": "Previous Luna model; legacy alias gpt-4o-mini resolves here (duckduckgo-chat-cli compat map)"
+    },
+    "gpt-5.4-nano": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 16384,
+      "family": "gpt",
+      "free_tier": true,
+      "upstream": "OpenAI GPT-5.4 Nano (via DDG proxy)",
+      "note": "Fast, lightweight tier; alias 'nano' resolves here"
+    },
+    "gpt-5.4-mini": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 16384,
+      "family": "gpt",
+      "free_tier": true,
+      "upstream": "OpenAI GPT-5.4 Mini (via DDG proxy)",
+      "note": "'Solid but hits limits sooner'; legacy aliases o3-mini / o4mini resolve here"
+    },
+    "claude-haiku-4-5": {
+      "context_length": 200000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 8192,
+      "family": "claude",
+      "free_tier": true,
+      "upstream": "Anthropic Claude Haiku 4.5",
+      "note": "Alias 'claude' resolves here; legacy claude-3-haiku / claude-3-haiku-20240307 IDs rotated out (now 404 ERR_MODEL_UNAVAILABLE)"
+    },
+    "mistral-small-2603": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 8192,
+      "family": "mistral",
+      "free_tier": true,
+      "upstream": "Mistral Small 4",
+      "note": "Display name 'Mistral Small 4'; wire ID is mistral-small-2603 (NOT mistral-small-4); alias 'mixtral' resolves here"
+    },
+    "tinfoil/gpt-oss-120b": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 16384,
+      "family": "gpt-oss",
+      "free_tier": true,
+      "upstream": "OpenAI gpt-oss-120b on Tinfoil (zero provider visibility)",
+      "note": "Open-weight reasoning model served with reasoningEffort 'low'; alias 'llama' resolves here (the open-weights slot)"
+    },
+    "tinfoil/gemma4-31b": {
+      "context_length": 128000,
+      "default_temperature": 0.7,
+      "default_max_tokens": 8192,
+      "family": "gemma",
+      "free_tier": true,
+      "upstream": "Google Gemma 4 31B on Tinfoil (zero provider visibility)",
+      "note": "BETA in the dropdown; served with reasoningEffort 'low'; alias 'gemma' resolves here"
+    }
   }
 }
diff --git a/agentkthx/plugins/duckduckgo/__init__.py b/agentkthx/plugins/duckduckgo/__init__.py
@@ -0,0 +1,38 @@
+"""
+AgentKthx Plugin — DuckDuckGo AI Chat Backend
+
+DuckDuckGo AI Chat (duck.ai) backend — the keyless, anonymous,
+zero-cost LLM surface: no API key, no signup, no quota. Current
+lineup (GPT-6 Luna, GPT-5.6 Luna, GPT-5.4 Nano/Mini, Claude
+Haiku 4.5, Mistral Small 4, and the Tinfoil-hosted gpt-oss-120b /
+Gemma 4 31B) proxied through DuckDuckGo's privacy layer via the
+NON-OpenAI /duckchat/v1 protocol — now CHALLENGE-BASED (the
+x-vqd-hash-1 JS proof replaced the retired x-vqd-4 token; solved
+by the bundled Node helper).
+
+The only AgentKthx cloud backend that subclasses BaseBackend
+directly instead of CloudBackend — see duckduckgo.py for the
+protocol rationale.
+
+See docs/api/DUCKDUCKGO_API_TECHNICAL_REFERENCE.md for full details.
+
+Written by VTSTech — https://www.vts-tech.org
+"""
+
+from __future__ import annotations
+
+
+def register(manager) -> None:
+    """Register the DuckDuckGo backend with the plugin manager."""
+    from .duckduckgo import DuckDuckGoBackend
+
+    manager.register_backend("duckduckgo", DuckDuckGoBackend)
+    # Alias for convenience — `--backend duckduckgo` and `--backend ddg`
+    # both work. Mirrors the SiliconFlow `sf` alias pattern.
+    manager.register_backend("ddg", DuckDuckGoBackend)
+
+
+def unregister(manager) -> None:
+    """Unregister the DuckDuckGo backend from the plugin manager."""
+    manager.unregister_backend("duckduckgo")
+    manager.unregister_backend("ddg")
diff --git a/agentkthx/plugins/duckduckgo/ddg_durable.js b/agentkthx/plugins/duckduckgo/ddg_durable.js
@@ -0,0 +1,40 @@
+#!/usr/bin/env node
+// ═══════════════════════════════════════════════════════════════════════
+// ddg_durable.js — durableStream RSA keypair generator for duck.ai
+//
+// The duck.ai POST /duckchat/v1/chat body now carries a `durableStream`
+// object: {messageId, conversationId, publicKey}. The publicKey is a
+// client-generated RSA-2048 JWK (the web client persists its pair in
+// localStorage under `duckaiStreamsTestCredentials`; the server uses it
+// to encrypt stream-resume payloads). Python stdlib has no RSA, so we
+// mint the keypair here — Node crypto is built in.
+//
+// Prints one JSON object on stdout:
+//   {"publicJwk":  {alg,e,ext,key_ops,kty,n,use},
+//    "privateJwk": {…full RSA private JWK…}}
+//
+// Usage: node ddg_durable.js
+// ═══════════════════════════════════════════════════════════════════════
+'use strict';
+
+const { generateKeyPairSync } = require('crypto');
+
+const { publicKey, privateKey } = generateKeyPairSync('rsa', {
+  modulusLength: 2048,
+  publicKeyEncoding: { format: 'jwk' },
+  privateKeyEncoding: { format: 'jwk' },
+});
+
+// Normalize to the exact shape the duck.ai frontend sends (captured live):
+// alg RSA-OAEP-256, key_ops ["encrypt"], use "enc", ext true.
+const publicJwk = {
+  alg: 'RSA-OAEP-256',
+  e: publicKey.e,
+  ext: true,
+  key_ops: ['encrypt'],
+  kty: publicKey.kty,
+  n: publicKey.n,
+  use: 'enc',
+};
+
+process.stdout.write(JSON.stringify({ publicJwk, privateJwk: privateKey }));