Gemini Antigravity 05-2026 is off: cut over managed agents, tool parsers, and gateway secrets

Introduction

Managed agent IDs age like model IDs. Google announced the 09-2026 Antigravity agent on September 17 with an explicit October 5 shutdown for the May preview. That date is now in the past. Any remaining 05-2026 string is a production incident, not a backlog ticket.

Primary sources: Gemini API deprecations, Gemini API changelog, managed agents, and GitHub secret scanning. Adjacent: Gemini 3.8 Live and governing agent autonomy.

What shut down

Google says remote sandbox runs (`environment: "remote"`) that only read `output_text` or `model_output` need the new agent string and nothing else. That path is the cheap cutover. The expensive path is local tools.

Local tool schema changes

Parameter names moved to PascalCase. Any custom orchestrator that pattern-matches snake_case `function_call` payloads will silently drop actions or write the wrong files. That is the regression to hunt in staging, not in production logs after shutdown.

Secret scanning for agent gateways

GitHub’s October 5 detectors matter because agent stacks leak credentials in `.env` commits, MCP JSON, and prompt dumps. New types include `pydantic_ai_gateway_api_key`, `logfire_token`, `lovable_api_key`, and two Supabase token shapes. Lovable Labs is a partner: public-repo hits can be forwarded for revoke.

• Enable secret scanning on every org that stores agent configs.
• Rotate Pydantic AI gateway keys even if the alert is a historical commit.
• Keep gateway tokens out of Antigravity environment mounts and skill files.
• Treat Logfire tokens as production observability credentials, not demo keys.

What this means for developers

• Grep for `antigravity-preview-05-2026` in repos, Terraform, and CI secrets.
• If you save managed agents, recreate them with `base_agent: "antigravity-preview-09-2026"` and the current `gemini-3.8-flash` (or documented) model.
• Update local tool adapters before flipping traffic. Do not parse 09-2026 calls with 05-2026 schemas.
• Re-run the sandbox-escape checklist on the new file-edit tools. Line-range patches fail differently than full rewrites.

What this means for businesses

• A preview agent ID with a published shutdown date is a calendar risk, not a surprise. Put Gemini managed-agent IDs on the same deprecation board as Copilot models.
• Local-tool agents are a compatibility contract. Budget an integration test, not only an ID rename.
• Pydantic AI and Lovable keys in GitHub are an audit finding. Pair scanning with a rotation SLA.

Cutover checklist

1. 01
   Inventory 05-2026 references

   Code, saved agent IDs, notebooks, and vendor wrappers.
2. 02
   Classify remote vs local

   Remote text-only: ID swap. Local or function_call parsing: schema rewrite first.
3. 03
   Stage 09-2026 on one workflow

   Confirm file edits, grep_search, and MCP tools. Then expand.
4. 04
   Turn on new secret detectors

   Resolve pydantic_ai_gateway, Logfire, Lovable, and Supabase alerts the same week.
5. 05
   Document the next ID

   Treat 09-2026 as preview. Name an owner for the next Antigravity replacement string.

Conclusion

October 5 closed a Gemini managed-agent preview and opened new GitHub detectors for the keys those agents often hold. The work is mechanical: pin 09-2026, rewrite local tool parsers, rotate scanned secrets. Teams that still call 05-2026 are already failing. Teams that only rename the string without touching local schemas will fail on the next file edit.

Sources: ai.google.dev — deprecations ; ai.google.dev — changelog ; ai.google.dev — custom agents ; github.blog