AI and models
Free OpenCode Zen models, ranked
The top free OpenCode Zen models for building with Bricklayer, with picks for coding, debugging, and quick edits.
Seven free Zen models to try with OpenCode on your Bricklayer project. Muse Spark 1.3 leads S tier for building full features. Reach for Nemotron 3 Ultra for hard bugs, or MiMo-V2.6-Flash for everyday coding.
Checked October 10, 2026 · 7 min read
How the ranking works.
This is an editorial shortlist based on published capabilities and fit for building Roblox games. We have not run a head-to-head Bricklayer benchmark. S is where we would start for complex work, A offers useful alternatives, and B suits focused edits and experiments. Numbers show our suggested order within that shortlist.Tap a model for when to use it, when to skip it, and its exact OpenCode ID.
Check the free route before starting.
These IDs are listed as free in Zen’s pricing table as of the date above. Availability can change. Select the exact ID; a similarly named paid model is a separate route.S Whole features and hard problems
Our first picks for work that needs several steps: understand the project, make a change, and check the result.
1. Meta Muse Spark 1.3 Contributor Free
opencode/muse-spark-1.3-contributor-freeMeta builds Muse Spark 1.3 for long coding workflows, reliable tool calls, and reasoning across a project. It takes our top S-tier spot for turning a feature brief into a sequence of code changes and checks.
Reach for it when
You are building a feature across several scripts and want the agent to keep the goal, earlier edits, and test results in view.
Skip it when
You cannot allow your prompts and completions to be used for model training. The free Zen entry uses Meta’s Contributor variant.
How to use it: Describe the intended gameplay, ask it to inspect the project and propose milestones, then implement and playtest one milestone at a time.
Model details: Meta’s Muse Spark 1.3 overview
2. NVIDIA Nemotron 3 Ultra Free
opencode/nemotron-3-ultra-freeNVIDIA positions Ultra for complex agent work, including planning, tool use, and code generation. That makes it our first pick for tracing a stubborn bug or working out how several game systems should fit together.
Reach for it when
A purchase fires twice, a save system loses progress, or you need to reason about how client and server code interact.
Skip it when
You already know the fix and only need a tiny edit. Try Lightning for the focused implementation.
How to use it: Give it the relevant scripts and the exact steps that reproduce the bug. Ask for a diagnosis, a small fix, and a way to test it.
Model details: NVIDIA’s model overview
3. Xiaomi MiMo-V2.6-Flash Free
opencode/mimo-v2.6-flash-freeXiaomi documents reasoning, tool calls, and structured output, with a focus on everyday agent workflows. We would start here for a clear feature request, then switch to Ultra if the problem needs deeper diagnosis.
Reach for it when
You have a concrete goal, such as adding a checkpoint system, changing a shop interaction, or wiring up a small UI.
Skip it when
You have not decided what the feature should do. Write down the behavior and success criteria before asking for an implementation.
How to use it: Ask it to inspect the existing code, implement one milestone, and explain what to check in Studio before continuing.
Model details: Xiaomi’s MiMo-V2.6-Flash overview
A Visual work and useful alternatives
Good alternatives when a screenshot is part of the task or you want another approach to the same problem.
4. LongCat 2.5 Preview Free
opencode/longcat-2.5-preview-freeOpenCode’s model catalog describes LongCat 2.5 Preview as a reasoning model for coding and agent tasks with image understanding. We would try it when the visible result matters as much as the script that produced it.
Reach for it when
A HUD is clipped, a menu overlaps another element, or a layout looks wrong and you can provide a screenshot plus the relevant code.
Skip it when
Your current model connection cannot accept image attachments, or a text-only error message already explains the problem.
How to use it: Attach one clear screenshot, explain the intended layout, and ask for the smallest change that fixes the mismatch.
Model details: OpenCode’s LongCat model metadata
5. Xiaomi MiMo-V2.5 Free
opencode/mimo-v2.5-freeMiMo-V2.5 supports multimodal understanding, reasoning, and tool calls. It is a useful alternative for discussing a scene or interface and reviewing a proposed change; our preference for V2.6-Flash above is an editorial starting point, not a measured win on Roblox tasks.
Reach for it when
You want a second explanation of a confusing script or feedback on how a UI should behave before making another edit.
Skip it when
You are expecting the base model’s advertised media support to guarantee that every attachment type works through Zen. Check the model picker first.
How to use it: Provide the relevant code and, if supported by your connection, a screenshot. Ask for a short explanation and one concrete next step.
Model details: Xiaomi’s MiMo-V2.5 overview
B Small edits and experiments
Keep the request narrow. These are picks for a focused task or a comparison, rather than the first choice for a large feature.
6. NVIDIA Nemotron 3.5 Lightning Free
opencode/nemotron-3.5-lightning-freeNVIDIA designs Lightning for fast, specialized task execution, reserving more complex planning for larger models. We would use it after the plan is clear, for a small script change or a tightly scoped question.
Reach for it when
You need a single function explained, a label changed, or a small implementation step completed from a clear specification.
Skip it when
The request spans several systems or asks the model to decide the architecture while implementing it.
How to use it: Name the file, describe the exact behavior to change, and give one acceptance check. Free endpoint load can still affect response time.
Model details: NVIDIA’s Lightning overview
7. Big Pickle
opencode/big-pickleOpenCode lists Big Pickle as a free stealth model. With less public information about its identity and capabilities, we rank it below the documented models and suggest comparing it on a small task first.
Reach for it when
You want another candidate answer for a throwaway prototype or a simple script you can test immediately.
Skip it when
You need a documented model family or predictable behavior for a large change.
How to use it: Give it the same small prompt as another model and compare correctness in Studio before committing to a longer session.
Model details: OpenCode’s Big Pickle listing
Use OpenCode with your Bricklayer project
Open your game in Bricklayer and keep Studio connected. OpenCode can work in that same local project folder; Bricklayer syncs its script edits into Studio. See advanced setup for how the folder workflow fits together. This guide is for the OpenCode agent; Bricklayer’s built-in OpenRouter chat uses the OpenRouter model guide.
In OpenCode, use /models to choose a Zen model. If prompted to connect, use /connect and follow the Zen connection instructions.
If a model is missing, refresh the catalog with the OpenCode models command, then reopen the picker:
opencode models opencode --refreshGive the agent one small milestone, review the changes, and press Play in Studio. If it gets stuck, pass the next model the original goal and the current error so it can start from the evidence.
Free model notes
Muse Spark’s free Zen route is the Contributor variant: prompts and completions can be used to train future Meta models. See Meta’s Contributor terms. Choose the exact free Zen ID above; Meta’s direct API and standard Muse Spark routes have their own pricing.
Zen describes these free offers as temporary. MiMo and Big Pickle may use collected data for model improvement; NVIDIA’s free routes are trials with logging and restrictions on confidential data. LongCat’s preview currently has a zero-retention policy. Read Zen’s privacy notes before sending project content.
This shortlist leaves out newer stealth and preview entries where we have less evidence to recommend a role. Jev is designed for structured decisions rather than a normal coding conversation. For the complete current lineup, check Zen’s model list.
A simple way to pick
Building a feature?
Chasing a hard bug?
One small edit?
More ways to build for free