5 free Antigravity-powered coding setups for 2026

Google's Antigravity is the most underrated free path to frontier AI coding in 2026. It bundles Gemini 3 Pro Agent, Claude Opus through Vertex, and DeepSeek under one OAuth flow, and a new GCP account gets $300 of credits good for 90 days.

Routed through kRouter, that is several months of agentic coding for $0.

Here are five real setups, ordered from simplest to most powerful.

The anti-ban fix you need to know about

Before we get to the setups: Antigravity has a known account-banning bug that affects third-party integrations. The root cause is a mismatch between string and numeric enums in the loadCodeAssist bootstrap call. When an integration sends "ideType": "VSCODE" instead of "ideType": 9, Google's anti-abuse layer correlates it against the OAuth handshake and flags the account.

kRouter v0.5.46 fixed this at the source. The bootstrap helper now reads from the same getOAuthClientMetadata() function the OAuth call uses, ensuring byte-exact numeric parity. v0.5.47 added a permanent-ban classifier that stops retrying flagged accounts instead of digging the hole deeper.

Every setup below routes through kRouter, which means the anti-ban fix is active by default. You do not need to configure anything. If you skip kRouter and connect Antigravity through another tool, check that it sends numeric enums. We document the full story at /blog/antigravity-verify-account.

Setup 1: Antigravity alone (one provider)

The minimum-viable free setup.

1. Create a Google Cloud account (new accounts get $300 / 90 days)
2. Install kRouter: npm install -g @sifxprime/krouter && krouter -t
3. Dashboard -> Providers -> Antigravity -> OAuth -> sign in
4. Point Claude Code at localhost:20128/v1, model ag/claude-opus-4-6-thinking

Cost: $0 for 90 days, then pay-per-token (cheap).

Catch: Antigravity has a 5-hour usage reset window. If you code intensely for 5 hours straight, you may hit a cooldown. For most developers this is not an issue -- the reset aligns with natural break patterns.

Setup 2: Antigravity + Kiro fallback

Adds free Sonnet 4.5 from Kiro as a backup. Now you have two free providers.

Combo:
1. ag/claude-opus-4-6-thinking   # Antigravity primary
2. kr/claude-sonnet-4.5          # Kiro backup

When Antigravity quota gets tight (or 5h reset cools off), Kiro picks up. You never see an error. The Zenith Score Engine pre-ranks both providers by live latency, so requests go to whichever is faster at that moment.

Setup 3: Antigravity + Vertex direct + Kiro

Vertex AI itself (the underlying platform) is also $300 credits -- but it is a separate billing account from Antigravity. Two GCP accounts = $600 in credits.

1. ag/gemini-pro-agent
2. vertex/gemini-3.1-pro-preview
3. kr/claude-sonnet-4.5

This is the "I want frontier Gemini all day" setup. Pro Agent for agentic flows, Vertex direct for one-shot completions.

Setup 4: The triple-tier all-free stack

Maxes out the free providers:

1. ag/claude-opus-4-6-thinking      # Antigravity (best reasoning)
2. ag/gemini-pro-agent              # Antigravity (best agentic)
3. kr/claude-sonnet-4.5             # Kiro (free Sonnet)
4. oc/<auto>                        # OpenCode Free (no-auth)
5. nvidia/llama-3.3-70b             # NVIDIA NIM (free for devs)

Five providers, all free. Coverage: Opus-tier reasoning, agent loops, Sonnet, OSS fallback, dev tier.

Cost in month 1: $0 (all on Antigravity credits) Cost in month 6 after credits run out: ~$0 (Kiro + OpenCode + NVIDIA still free)

Setup 5: Antigravity + cheap overflow + free safety net

The setup for power users who actually code 6+ hours/day.

1. ag/claude-opus-4-6-thinking
2. glm/glm-5.1                      # $0.6/M overflow
3. minimax/MiniMax-M2.7             # $0.2/M long-context
4. kr/claude-sonnet-4.5             # free safety net

Antigravity is the daily driver. When you hit the 5h reset, GLM/MiniMax pick up at cents-per-million. When even those fail (Chinese provider outages happen), Kiro catches the fallthrough.

Cost: $5-12/month after Antigravity credits expire.

Step-by-step: connecting Antigravity in kRouter

Here is the expanded setup flow:

# 1. Install kRouter
npm install -g @sifxprime/krouter
krouter -t
 
# 2. Open the dashboard
open http://localhost:20128/dashboard
 
# 3. Add Antigravity provider
# Dashboard -> Providers -> Add Provider -> Antigravity
# Click "OAuth Sign-in" -> sign in with your Google account
# kRouter handles the bootstrap call with byte-exact numeric enums
 
# 4. Verify connection
# The dashboard shows available models:
# ag/claude-opus-4-6-thinking
# ag/gemini-pro-agent
# ag/gemini-3-flash
 
# 5. Create a combo
# Dashboard -> Combos -> New Combo
# Add your Antigravity model as tier 1
# Add Kiro as tier 2 (optional free fallback)
 
# 6. Point your IDE
OPENAI_BASE_URL=http://localhost:20128/v1
OPENAI_API_KEY=sk-krouter-local

How to claim the free Vertex credits

If your Google Cloud account does not already show "$300 free credits", you may not have completed the setup. To claim:

1. Go to console.cloud.google.com/billing
2. Create a new billing account (requires a credit card, but it will not be charged)
3. The $300 credit appears immediately
4. Credits valid 90 days

You can claim this credit once per Google account. If you have multiple Google accounts (work, personal, side project), each can claim its own $300.

What about Gemini API directly?

The Gemini API free tier (15 RPM, 1M tokens/day) is also legit free. But it is not the same as Antigravity -- Antigravity routes through Vertex with Pro-tier credits, gets agentic mode (the "Pro Agent" model), and includes Claude. Direct Gemini API is just Gemini.

You can stack both in a combo:

1. ag/gemini-pro-agent
2. gemini/gemini-2.5-pro            # direct API free tier

A real numbers month

A developer using setup 5, coding ~5 hours/day for 30 days:

• Antigravity primary: ~12M tokens, $0 (credits)
• GLM-5.1 overflow: ~3M tokens, $3.60
• MiniMax M2.7 long-context: ~5M tokens, $1.00
• Kiro safety net: ~200k tokens, $0
• Total: $4.60/month

Compare to direct Anthropic API at $3/M input / $15/M output: ~$70/month for the same volume.

The arbitrage is real. kRouter just makes it usable.

Install

npm install -g @sifxprime/krouter
krouter -t

Provider setup at /providers/antigravity. Combo guide at /docs/combos. Changelog at /changelog.

Caveat

Antigravity bans happen if integrations send the wrong OAuth metadata enums. We document why and how to avoid it. Through kRouter you are safe -- but do not pair Antigravity with random other integrations that hit the same Google API endpoints without verifying their enum encoding.