backend new models check - gemini - 2026-09-16

Files checked: `src/backend/drivers/ai-chat/providers/gemini/models.ts`, `src/backend/drivers/ai-image/providers/gemini/models.ts`, `src/backend/drivers/ai-video/providers/gemini/models.ts`, `src/backend/drivers/ai-tts/providers/gemini/costs.ts`

**chat (7)**
- `gemini-3.1-pro-preview-customtools` | aliases: none | context: 1048576 | created: n/a | price: see provider pricing page
Notes: custom-tools variant of already-covered `gemini-3.1-pro-preview`; not a dated snapshot so not auto-collapsed.
- `gemini-omni-flash-preview` | aliases: none | context: 131072 | created: n/a | price: see provider pricing page
- `gemini-omni-1.1-flash` | aliases: none | context: 131072 | created: n/a | price: see provider pricing page
- `gemini-robotics-er-2-preview` | aliases: none | context: 131072 | created: n/a | price: see provider pricing page
Notes: modality? — embodied-reasoning/robotics-specialized model, not a general chat model; verify relevance before adding.
- `antigravity-preview-05-2026` | aliases: none | context: 1048576 | created: n/a (May-2026 per name) | price: see provider pricing page
Notes: modality? — specialized coding-agent preview; superseded by `antigravity-preview-09-2026` below (same family).
- `antigravity-preview-09-2026` | aliases: none | context: 1048576 | created: n/a (Sep-2026 per name) | price: see provider pricing page
Notes: modality? — likely the current pointer of the Antigravity agent family.
- `deep-research-max-preview-04-2026` | aliases: none | context: 131072 | created: n/a (Apr-2026 per name) | price: see provider pricing page
Notes: modality? — specialized deep-research agent, not a general chat model.
- `deep-research-preview-04-2026` | aliases: none | context: 131072 | created: n/a (Apr-2026 per name) | price: see provider pricing page
Notes: modality? — same family as above.

**image (1)**
- `nano-banana-pro-preview` | aliases: none | context: 131072 | created: n/a | price: see provider pricing page
Notes: same displayName/specs as backend's `gemini-3-pro-image-preview` (which already aliases "nano-banana-pro") — very likely just another alias for that same model rather than a distinct new model; recommend adding as an alias instead of a new entry.

skipped (unsupported modality): 18 — examples: `gemini-3.5-transcribe`, `lyria-3-clip-preview`, `lyria-3.5`, `gemini-embedding-001`, `aqa`, `gemini-3.8-live`, `lyria-realtime-exp`
legacy upstream models not in backend (verify intent): `gemini-2.5-computer-use-preview-10-2025`, `deep-research-pro-preview-12-2025`

Start with the four listed Gemini files under src/backend/drivers and compare their existing model entries with the candidates in this issue. Verify model modality, family aliases, and provider pricing before updating the supported entries; done means appropriate models and aliases are represented without adding unsupported modalities or superseded variants.

Written by the indexing model from the issue text.