diff --git a/agent/model_metadata.py b/agent/model_metadata.py
index 495e0b5384..086f17b3a0 100644
--- a/agent/model_metadata.py
+++ b/agent/model_metadata.py
@@ -380,9 +380,10 @@ DEFAULT_CONTEXT_LENGTHS = {
     "solar-open2": 262144, "solar-pro3": 131072, "solar-pro2": 65536, "solar-mini": 32768,
     # Tencent Hunyuan (262144 = 256 × 1024, aligned with OpenRouter live metadata)
     "hy4-preview": 1_048_576, "hy3-preview": 262144, "hy3": 262144,
-    # "Ox Alpha" stealth model (OpenCode Zen / OpenRouter slugs); NVIDIA Nemotron (128K
+    # "Ox Alpha" stealth model (OpenCode Zen / OpenRouter slugs); "Union Alpha" stealth model
+    # (OpenRouter ``stealth/union-alpha``, 262144 per /api/v1/models); NVIDIA Nemotron (128K
     # except 3.5 Lightning); Poolside Laguna 2.1 (:free / -free slugs); Arcee; OpenRouter.
-    "x-preview-f": 1_048_576, "ox-alpha": 1_048_576,
+    "x-preview-f": 1_048_576, "ox-alpha": 1_048_576, "union-alpha": 262144,
     "nemotron-3.5-lightning": 1_000_000, "nemotron": 131072,
     "laguna-s-2.1": 262144, "laguna-xs-2.1": 262144, "trinity": 262144, "elephant": 262144,
     # Hugging Face Inference Providers — model IDs use org/name format
diff --git a/hermes_cli/models_catalog_static.py b/hermes_cli/models_catalog_static.py
index 9a2c260c3d..3a01aef8a1 100644
--- a/hermes_cli/models_catalog_static.py
+++ b/hermes_cli/models_catalog_static.py
@@ -23,6 +23,7 @@ _OPENROUTER_DESCRIPTIONS = {
     "openai/gpt-6-astra-flex": "0.5x price, flex tier",
     "openai/gpt-6-astra-pro-fast": "2x price, priority tier",
     "openai/gpt-6-astra-pro-flex": "0.5x price, flex tier",
+    "stealth/union-alpha": "free, stealth model",
 }
 OPENROUTER_MODELS: list[tuple[str, str]] = [
     (mid, _OPENROUTER_DESCRIPTIONS.get(mid, "free" if mid.endswith(":free") else ""))
@@ -43,14 +44,16 @@ OPENROUTER_MODELS: list[tuple[str, str]] = [
         "openrouter/pareto-code", "thinkingmachines/inkling:free", "thinkingmachines/inkling-small:free",
         "minimax/minimax-m3:free", "z-ai/glm-5.2:free", "poolside/laguna-s-2.1:free", "poolside/laguna-xs-2.1:free",
         "nvidia/nemotron-3-super-120b-a12b:free", "nvidia/nemotron-3-ultra-550b-a55b:free",
-        "nvidia/nemotron-3.5-lightning:free",
+        "nvidia/nemotron-3.5-lightning:free", "stealth/union-alpha",
     )
 ]
 
-# OpenRouter entries the Nous Portal does not carry (routing/fast variants, free tier).
+# OpenRouter entries the Nous Portal does not carry (routing/fast variants, free tier —
+# ``stealth/union-alpha`` is a $0 stealth SKU without the ``:free`` suffix).
 _OPENROUTER_ONLY = {
     "anthropic/claude-opus-5-fast", "anthropic/claude-opus-4.8-fast", "meta/muse-spark-1.2",
     "meta/muse-spark-1.2-contributor", "meta/muse-spark-1.3", "meta/muse-spark-1.3-contributor", "openrouter/pareto-code",
+    "stealth/union-alpha",
 }
 
 
diff --git a/website/static/api/model-catalog.json b/website/static/api/model-catalog.json
index 31fb4f5b5e..0b34de68c5 100644
--- a/website/static/api/model-catalog.json
+++ b/website/static/api/model-catalog.json
@@ -1,6 +1,6 @@
 {
   "version": 1,
-  "updated_at": "2026-09-10T16:09:08Z",
+  "updated_at": "2026-09-16T16:50:25Z",
   "metadata": {
     "source": "hermes-agent repo",
     "docs": "https://hermes-agent.nousresearch.com/docs/reference/model-catalog"
@@ -244,6 +244,10 @@
         {
           "id": "nvidia/nemotron-3.5-lightning:free",
           "description": "free"
+        },
+        {
+          "id": "stealth/union-alpha",
+          "description": "free, stealth model"
         }
       ]
     },