Gemma-4 12B Coder vs Claude Fable 5

What I tested — same prompt, two models

I run the same fixed prompt set through every new model the day it drops — same string, one shot, single HTML file out — and I score the result 0–10 on whether it ran, how close it hit the brief, and how good it looked. Below is what came out when I gave the exact same prompts to Gemma-4 12B Coder and Claude Fable 5, side by side, on 0 shared tasks inside the Agent Operating System.

Both models were given identical prompts inside the Agent Operating System — no help, no iteration, no "best of N" tricks. I run each prompt once, save the HTML file the model produces, and score it 0–10 on whether it ran, how close it hit the brief, and how good it looked. The scoring is mine. The verdicts below are pulled from my source comparison guides at agentos.guide where I publish every score and the reasoning behind it.

Gemma-4 12B Coder · Wired into the Agent OS local engine (Local chat + Local Hermes Engine + Agent Kanban) as the free, offline coder. Scored by Claude judge against the same one-shot prompts every other model ran.

Claude Fable 5 · Selected from Agent OS for the highest-stakes one-shot work — replacing Opus 4.8 as the safety net on hard prompts. Bench scoring pending.

Strengths & weaknesses I logged

Pricing & context — the spec sheet

The verdict — which should you pick?

Not enough scored shared tasks yet for a head-to-head average. The live demos for both are on the matrix above — play them and form your own opinion.

If you only run one of these inside your stack, the head-to-head average above is the call. If you can run both, my honest play is to wire Gemma-4 12B Coder and Claude Fable 5 both into the Agent Operating System and dispatch each from the kanban by task type — free, private, offline coding where nothing can leave your machine → Gemma-4 12B Coder, mission-critical one-shot builds where you want anthropic's newest reasoning → Claude Fable 5. That's the same setup I run for the 3,600+ founders inside the AI Profit Boardroom.

FAQ — Gemma-4 12B Coder vs Claude Fable 5

Which is better, Gemma-4 12B Coder or Claude Fable 5?

On Goldie Bench, Gemma-4 12B Coder averages no scored verdicts yet across the shared tasks, with 0 gold, 0 silver, 0 bronze overall. Claude Fable 5 averages no scored verdicts yet, with 0 gold, 0 silver, 0 bronze. Not enough scored shared tasks yet to call a winner.

How much does Gemma-4 12B Coder cost vs Claude Fable 5?

Gemma-4 12B Coder: A community fine-tune of Google's Gemma-4 12B (xentriom/gemma-4-12B-coder-fable5-composer2.5-v1), Apache-2.0. Free to download and run 100% offline on your own Mac via Ollama — no API, no per-token bill. The Q4_K_M build is 7.4GB. Claude Fable 5: Released alongside Mythos 5 on June 9, 2026 as the publicly-available member of the new Mythos class. Premium per-token pricing on the Anthropic API; available everywhere Opus 4.8 ships.

What's the context window for Gemma-4 12B Coder vs Claude Fable 5?

Gemma-4 12B Coder has a 256,000 tokens context window. Claude Fable 5 has a 200,000 tokens (1M with extended thinking) context window.

When should I pick Gemma-4 12B Coder over Claude Fable 5?

Pick Gemma-4 12B Coder for: Free, private, offline coding where nothing can leave your machine; Landing pages, simple canvas builds, and code you'll review before shipping; Anyone who wants a $0 local coder wired into their Agent OS. The trade-off is the weaknesses we logged on the bench: Half its one-shots shipped broken on the bench — a missing canvas append, a missing render loop, and an uncompiled WebGL shader; Far below frontier models on complex 3D / WebGL / games — strongest on pages and simple canvas work, not simulations.

When should I pick Claude Fable 5 over Gemma-4 12B Coder?

Pick Claude Fable 5 for: Mission-critical one-shot builds where you want Anthropic's newest reasoning; Long-context work using extended thinking up to 1M tokens; Plan-heavy multi-step tasks where intelligence in the plan matters more than the build. The trade-off is the weaknesses we logged on the bench: No goldiebench per-task scores yet — bench rank pending a published head-to-head guide; Premium pricing; Fusion premium panel reportedly out-scores it at half the API cost.

How does Goldie Bench score Gemma-4 12B Coder vs Claude Fable 5?

Every demo on this page was built by Julian Goldie inside the Agent Operating System — same fixed prompt for both models, one shot, single HTML file out. Each result gets a 0–10 score on whether it ran, how close it hit the brief, and how good it looked. The highest score on each task gets gold; second gets silver; third gets bronze. See methodology for full provenance.

Related comparisons

Other head-to-heads using the same scoring system:

Full model pages: Gemma-4 12B Coder · Claude Fable 5 · back to the leaderboard