Gemma 3 4B Instruct is the smallest Gemma 3 instruct model in the Amazon Bedrock catalog, at $0.04 per Mtok input and $0.08 per Mtok output. With 4B parameters and a 4,096 token output cap it is a classification and triage model, not a builder. Inside Atlas that means one correct placement: the small_model slot, never the primary model. The upside is that $0.04 per Mtok against a 128K context is cheap enough to scan an entire codebase for routing decisions, and the 4B weights fit comfortably in 8GB of VRAM if you self-host instead.
What is Gemma 3 4B Instruct actually good for in Atlas?
Gemma 3 4B Instruct is good for classification, triage, and routing inside Atlas. At $0.04 per Mtok input against a 128K context, gemma-3-4b-it is cheap enough to scan an entire codebase to decide where work should go, and its non-reasoning path returns answers with low latency.
Atlas makes a steady stream of calls that do not need a strong model: session titles, short summaries, and the classification steps that decide which file or which subagent handles a request. Atlas fans out work to subagents that can run in the foreground or in parallel background sessions, and a fan-out of triage questions is exactly the workload Gemma 3 4B Instruct is priced for. Non-reasoning and low latency is what you want for Atlas's title and summary calls, where speed beats depth.
Why can Gemma 3 4B Instruct not write meaningful diffs?
Gemma 3 4B Instruct has a 4,096 token max output, half the 8,192 of the 12B and 27B Gemma 3 variants, so it cannot write meaningful diffs. Atlas computes a unified diff for every file edit, and a real diff on real code does not fit in 4,096 tokens.
Output ceiling is a hard physical limit, not a quality judgment. Even if Gemma 3 4B Instruct produced a perfect change, a 4,096 token budget truncates the unified diff before it is complete, and a truncated diff is not applicable. Layer on the fact that 4B dense parameters are too small to drive Atlas's build agent reliably on anything beyond trivial edits, and the conclusion is clear: Gemma 3 4B Instruct reads, summarizes, and classifies. Something else writes.
How do you stop Gemma 3 4B Instruct from editing files in Atlas?
Deny write tools for Gemma 3 4B Instruct in the Atlas permission config so it can read and summarize but not edit. Every Atlas tool call is permission-gated against allow, ask, and deny rules before it runs, so a deny rule on write tools is enforced before the call executes.
Permission gating turns a policy into a guarantee. Rather than trusting that a 4B model with a 4,096 token output cap will not attempt an edit, put write tools behind a deny rule and the attempt never reaches the filesystem. Combine that with using Gemma 3 4B Instruct only in the "small_model" slot of atlas.json, never as "model", and the model is structurally confined to the work it can actually do. Atlas also snapshots file changes as git patches so edits can be diffed and rolled back, which is the backstop if a rule is ever too loose.
How do you set up Gemma 3 4B Instruct on Amazon Bedrock for Atlas?
Configure AWS auth with AWS_PROFILE, or the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY pair, and set AWS_REGION. Grant Bedrock model access to Gemma 3 4B in your region, then run `atlas models amazon-bedrock` and look for google.gemma-3-4b-it.
Bedrock entitlements are per region, so granting model access to Gemma 3 4B in one AWS_REGION does not grant it in another, and a missing grant looks like a missing model rather than a permission error. Once google.gemma-3-4b-it appears in `atlas models amazon-bedrock`, use it only in the "small_model" slot of atlas.json, never as "model". That single placement rule is the difference between a cheap, useful helper and a build agent that cannot finish a diff.
Can you self-host Gemma 3 4B Instruct instead of using Bedrock?
Gemma 3 4B Instruct has 4B dense parameters, which means it fits comfortably in 8GB of VRAM if you self-host the open weights instead of renting it on Bedrock at $0.04 per Mtok input. That is the lowest hardware bar of any Gemma 3 instruct model.
An 8GB VRAM footprint puts Gemma 3 4B Instruct on ordinary developer hardware, not on a server. Paired with Atlas's ability to build its code index with local Ollama embeddings, keeping code off third-party servers, a self-hosted Gemma 3 4B Instruct can handle local triage without any request leaving the laptop. The limits do not change when you self-host: the 4,096 token output cap and the non-reasoning path travel with the weights, so it is still a triage model.
When should you pick a different model than Gemma 3 4B Instruct?
Pick a different model than Gemma 3 4B Instruct for any work that writes code. Gemma 3 4B Instruct is too small to drive Atlas's build agent reliably beyond trivial edits, and its 4,096 token output cap is half the 8,192 tokens the 12B and 27B Gemma 3 variants allow.
The nearest step up is Gemma 3 12B Instruct at $0.05 per Mtok input with an 8,192 token output ceiling, which is a small price increase for double the output headroom. Atlas lets you switch the active model and provider on the fly with favorites and recents, so testing the difference on a real task is quick. Keep Gemma 3 4B Instruct for what it genuinely owns: reading a lot of code at $0.04 per Mtok input to make a routing decision fast.
Setup
- 01Configure AWS auth (AWS_PROFILE or the AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY pair) and set AWS_REGION.
- 02Grant Bedrock model access to Gemma 3 4B in your region.
- 03Run `atlas models amazon-bedrock` and look for google.gemma-3-4b-it.
- 04Use it only in the "small_model" slot of atlas.json, never as "model".
- 05Deny write tools for this model in the Atlas permission config so it can read and summarize but not edit.
Frequently asked questions
- how much does gemma 3 4b cost on amazon bedrock
- Gemma 3 4B Instruct costs $0.04 per Mtok input and $0.08 per Mtok output on Amazon Bedrock, making it the cheapest Gemma 3 instruct model in the catalog.
- what is the output limit of gemma 3 4b instruct
- Gemma 3 4B Instruct caps output at 4,096 tokens, half the 8,192 tokens the 12B and 27B Gemma 3 variants allow. That ceiling means it cannot write meaningful unified diffs.
- can gemma 3 4b run on 8gb vram
- Yes. Gemma 3 4B Instruct has 4B dense parameters and fits comfortably in 8GB of VRAM if you self-host the open weights instead of renting it on Bedrock.
- how do i prevent a small model from editing my code in atlas
- Deny write tools for that model in the Atlas permission config. Every Atlas tool call is permission-gated against allow, ask, and deny rules before it runs, so a denied write tool never reaches the filesystem.
- should gemma 3 4b be my main atlas model
- No. Gemma 3 4B Instruct is too small to drive Atlas's build agent reliably beyond trivial edits. Use it only in the "small_model" slot of atlas.json, never as "model".
- what is the cheapest model for code triage and classification
- Gemma 3 4B Instruct at $0.04 per Mtok input against a 128K context is cheap enough to scan an entire codebase for routing decisions, and its non-reasoning low latency path suits title and summary calls.
- how do i find google.gemma-3-4b-it in atlas
- Configure AWS auth with AWS_PROFILE or the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY pair, set AWS_REGION, grant Bedrock model access to Gemma 3 4B in that region, then run `atlas models amazon-bedrock`.
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