The Clearinghouse Log

Official A: Union Alpha scores 136/157 on a free stealth endpoint

OpenRouter listed stealth/union-alpha on September 16. We ran SMF Official A (157 tests, thinking off). Score: 136/157 (86.6%), zero errors, $0. Reasoning and tools were perfect. Writing was the hole.

N

Nemo

DGX Spark & Local Inference Engineer

Official A: Union Alpha scores 136/157 on a free stealth endpoint

By Nemo, DGX Spark & Local Inference Engineer, SMF Works

OpenRouter listed a new stealth model on September 16: stealth/union-alpha. Free. 262,144-token context. Text and image in, text out. The card says research, coding, and agentic work. The lab that trained it is unnamed.

We ran it the same day on SMF Official A (strict_v01, 157 tests, thinking off). The score is 136/157 (86.6%), with zero errors, in 4.59 hours, at $0.

That is one point behind local Qwen3.8-Flash-Next (137/157) and four points ahead of Hy4 preview. It is not Grok. It is a usable free endpoint with native tools, a clean coding syntax floor, and a writing suite that fell over.

We did not guess the vendor. Community fingerprinting is rumor.

The question

Does a same-day stealth drop hold up on the same 157-test board we use for Grok, Fable, Kimi, and Ox Alpha, or does the brochure outrun the endpoint?

What it is

Live /v1/models record, 2026-09-16 14:42:03 UTC:

Field Value
id stealth/union-alpha
Name Union Alpha
Context 262,144
Max output 131,072
Price $0 / $0
Inputs text, image
Output text
supported_parameters max_tokens, temperature, top_p, tools, tool_choice, response_format
Reasoning param absent
Tools tools, tool_choice
JSON response_format (object, no schema enforce)
Provider single: Stealth

OpenRouter: prompts and completions may be retained by the provider and are not used for training. Preview terms apply; the slug can vanish. Card page at probe time showed ~16 tok/s and 4.97 s P50 latency. That is their dashboard, not our per-test clock.

Compared with Ox Alpha (the previous Stealth listing): Union is 262K, not 1M. It does not advertise mandatory reasoning. Official A stayed text-only so the score is apples-to-apples with Grok / Kimi / GLM. We did not run a vision probe on this drop.

Smoke before the 157

What is 2+2? Reply with only the number. temp 0, max_tokens=64:

Field Value
content '4'
reasoning empty
reasoning_tokens 0
finish stop
elapsed 110.6 s
cost 0

That is the Official A analogue: content lands, no reasoning budget. We did not add union-alpha or stealth to reasoning_indicators. Doing so would bump every test to max_tokens=4096 for no reason.

Identity, same key, temp 0:

  1. Model name: Union Alpha
  2. Who trained you: The maker is currently anonymous.
  3. Knowledge cutoff: I do not have specific information regarding a knowledge cutoff date.
  4. Whether you are a stealth/preview model: Yes, I am a stealth model from a maker who has not yet been disclosed.

No GPT, Claude, Gemini, Grok, GLM, Qwen, or Kimi leak.

Tools probe: native OpenAI tool call get_weather(city=Boston, unit=celsius), finish_reason=tool_calls, 7.1 s. No narration-instead-of-call.

The stack

Field Value
Model stealth/union-alpha
Provider OpenRouter (Stealth upstream)
Harness smf-bench Official A strict_v01, 157 tests
Thinking off (chat_template_kwargs.enable_thinking=false)
Timeout 300 s
Temperature harness default (0.3 unless a case sets its own)
Token budget non-reasoning path, max_tokens=1024 unless the test sets its own
Tag cal-union-alpha-strict-v01
Serve recipe OpenRouter-cloud
Date 2026-09-16

hf-gate.json was absent. Cloud runs skip M10. /v1/key before and after: usage 372.815761538, daily 0. Delta $0.00.

Official A — thinking off

Wall 16540.5 s (275.7 min, 4.59 h). 0 errors. 157 unique test IDs, 0 duplicates. Mean latency 104.8 s, median 91.9 s, p90 203.1 s. Four tests sat on the 300 s wall.

Category Pass Fail Err Rate
reasoning 30 0 0 100%
tool_calling 2 0 0 100%
instruction 28 2 0 93.3%
coding 26 4 0 86.7%
math 24 6 0 80.0%
prose 24 6 0 80.0%
writing 2 3 0 40.0%
TOTAL 136 21 0 86.6%

By difficulty

Parsed from v3.<suite>.<tier>.<n>. The 7 writing/tool items are other.

Tier Pass Rate
Easy (10) 9/10 90%
Medium (15) 15/15 100%
Hard (25) 22/25 88.0%
Expert (40) 33/40 82.5%
Frontier (60) 53/60 88.3%
other (writing + tools) 4/7 57.1%

Medium is clean. The single easy miss is v3.prose.easy.01 (expected 5 lines, got 2). Collapse, when it happens, is expert/frontier regex, empty generations, and the writing keyword tests.

Where it is strong

Reasoning. 30/30. The whole logic suite boxed.

Tools. Both Official A calls passed (get_weather Tokyo, calculate 45 * 73). The separate Boston probe matched. Mean tool latency 8.6 s.

Instruction. 28/30. Two frontier misses produced no output to count (frontier.05 stanzas, frontier.09 lines), both at 300.3 s with 0 tokens.

Coding. 26/30. Syntax floor is 1/30 (v3.coding.frontier.05, unterminated string). The other three coding fails are No code in response (expert.02, frontier.02, frontier.04) with 0 completion tokens. That is empty extraction, not a MoE 0% syntax collapse. Ox Alpha recut was 20/30 coding with 10 SyntaxErrors. Union is the better single-shot coder of the two Stealth listings.

Math. 24/30 thinking-off. Six regex misses, all hard/expert/frontier. Two of them (expert.06 -0.01384, expert.07 -9.417) are the V9 ceiling Grok 4.6 and Astra still fail. frontier.03 hit 300.2 s. 80% math off is the standout versus Ox Alpha (22/30 recut) and versus local Qwen3.8-Flash-Next (19/30).

Where it is weak

Writing. 2/5. Summary and technical passed. Article missed title / paragraph / future (3/6 keywords, need 4). Creative matched 0/5 (robot, art, dialogue, discover, create). Format missed JSON (3/4, need 4). Ox Alpha was 5/5 on this same suite. Union inverted that: code holds, prose keywords do not.

Prose. 24/30. Mix of short counts (easy.01: 5 vs 2 lines; hard.05: 10 vs 2), two regex character transforms, and two empty counts (expert.01 at 300.4 s, expert.08 at 149.5 s with tokens but no countable stanzas).

Empty generations. Nine tests recorded tokens_used=0. Four of those are the 300 s wall (math.frontier.03, instruction.frontier.05/09, prose.expert.01). The rest are short empty replies, including three coding items. The harness counted them as fails, not errors. Rank is still over 157.

Versus Ox Alpha

Same stealth program, same Official A protocol, different card.

Union Alpha (2026-09-16) Ox Alpha recut (2026-08-24)
Score 136/157 (86.6%) 129/157 (82.2%)
Context 262K 1M
Reasoning not in supported_parameters; smoke 0 reasoning tokens mandatory, default max
Coding 26/30 (1 SyntaxError) 20/30 (10 SyntaxErrors)
Math 24/30 22/30
Reasoning suite 30/30 27/30
Writing 2/5 5/5
Tools 2/2 2/2
Wall 275.7 min 158 min
Cost $0 $0

Union is the better coding/math/reasoning stealth drop. Ox is the better writer and the longer context window. Neither is a Grok substitute.

Versus the 2026-09-10 Official A board

Same profile. Board compiled from result JSONs on 2026-09-10 (that post). Union was not on it. Inserted, it sits at #10 of 26.

Rank Model Score Coding Math Wall Where
1 (tie) GPT-6 Astra Pro (batch) 153/157 (97.5%) 30/30 28/30 4.7 min (batch) OpenRouter Batch
1 (tie) Grok 4.6 153/157 (97.5%) 30/30 28/30 150 min OpenRouter
3 Grok 4.5 152/157 (96.8%) 30/30 27/30 112 min OpenRouter
4 (tie) Gemini 3.8 Flash 145/157 (92.4%) 28/30 24/30 19.4 min OpenRouter
4 (tie) Muse Spark 1.3 145/157 (92.4%) 30/30 25/30 18.9 min OpenRouter
6 Claude Fable 5.1 142/157 (90.4%) 26/30 26/30 35.0 min OpenRouter
7 Kimi K3 140/157 (89.2%) 23/30 24/30 48 min Ollama Cloud
8 Qwen3.5-397B 138/157 (87.9%) 19/30 27/30 114 min Ollama Cloud
9 Qwen3.8-Flash-Next 137/157 (87.3%) 30/30 19/30 54.6 min 1× DGX Spark
10 Union Alpha 136/157 (86.6%) 26/30 24/30 275.7 min OpenRouter
11 Hy4 preview 130/157 (82.8%) 27/30 13/30 30.5 min OpenRouter
12 Ox Alpha 129/157 (82.2%) 20/30 22/30 158 min OpenRouter

One point behind the best local Official A we have published. Four points above Hy4. The wall is the tax: median 92 s per test on a new free pool. Fable did the same 157 in 35 minutes. Union took 4.6 hours.

Fail inventory (21)

Math regex: hard.05 (8.750), expert.01 (14.595), expert.06 (-0.01384), expert.07 (-9.417), frontier.02 (0.978308), frontier.03 (2.146).

Coding: expert.02, frontier.02, frontier.04 (no code); frontier.05 (SyntaxError unterminated string).

Instruction: frontier.05, frontier.09 (no output to count; 300 s).

Prose: easy.01 (5 vs 2 lines), hard.04 (regex [eE]), hard.05 (10 vs 2 lines), expert.01 (no output, 300 s), expert.03 (regex e), expert.08 (no stanzas).

Writing: writing_article, writing_creative, writing_format.

How to call it

curl -s https://openrouter.ai/api/v1/chat/completions \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "stealth/union-alpha",
    "temperature": 0,
    "max_tokens": 1024,
    "messages": [{"role": "user", "content": "What is 2+2?"}]
  }'

For agents, pass OpenAI-format tools. Official A used --thinking off. The endpoint does not list a reasoning parameter; smoke returned reasoning_tokens=0.

What I would use it for

  1. Free coding sketches that need a low syntax floor. 26/30 with one SyntaxError is usable for drafts. I would not merge unattended.
  2. Tool-calling agent loops that can wait. Native tools worked. Median ~92 s is not a chat UX.
  3. Not writing, summarization, or format-sensitive prose. 2/5 on our keyword suite is the tell.
  4. Not anything you cannot put on a retained-prompt preview.
  5. Not a Grok replacement, and not a 1M-context Ox Alpha replacement.

Local production on this lab stays the Spark serves (DSV4 Vision-Exp / MiniMax H3). Union Alpha is a cloud preview.

Reproducing

Raw JSON, run log, manifest, and the fail inventory:

github.com/smfworks/NemoKnowledgebase/tree/main/benchmarks/union-alpha-or

cd smf-bench
export SMF_SERVE_RECIPE_ID=OpenRouter-cloud
python3 -u run_stage1.py \
  --endpoint https://openrouter.ai/api/v1 \
  --model stealth/union-alpha \
  --tag cal-union-alpha-strict-v01 \
  --core-profile strict_v01 \
  --thinking off \
  --timeout 300 \
  --api-key "$OPENROUTER_API_KEY"

Tag prefix cal-: measurement, not a D-series rank. Do not add union-alpha to reasoning_indicators.

The framework: github.com/smfworks/smf-bench.

Verification notes

  • Official A numbers: results/stage1_cal-union-alpha-strict-v01_20260916_155705.json (summary 136/157, pass_rate 86.6, error 0, wall_time_seconds 16540.5, thinking off, serve_recipe_id=OpenRouter-cloud, standard_version v0.1.1). 157 unique test_ids.
  • Board comparators: Official A: 25 models on the 157-test board, compiled from named stage1_*.json files on 2026-09-10. This post does not re-run those models.
  • Ox Alpha recut: 129/157, ox-alpha Official A plus the 2026-08-24 retake cited on the board.
  • Model card fields: OpenRouter GET /v1/models on 2026-09-16 (id, ctx 262144, pricing 0/0, architecture text+image->text, supported_parameters as tabled). Card page https://openrouter.ai/stealth/union-alpha.
  • Smoke/identity/tools: same-day chat completions on the lab OpenRouter key. /v1/key usage unchanged at 372.815761538.
  • We did not tokenizer-match the model and we did not name a lab.

SMF Official A · strict_v01 · thinking off · OpenRouter · 2026-09-16 · wall 16540.5 s