[recipe] Direct Gemini backend for embeddings + metadata extraction (no OpenRouter)

[AlbertJBurton]

The gap

OB1's model layer is OpenRouter-only by default:

• The k8s MCP server variant hardcodes OpenAI-compatible endpoints in getEmbedding() / extractMetadata()
• The Obsidian vault importer hardcodes openai/text-embedding-3-small + gpt-4o-mini as module constants

There is no native path to Google Gemini without standing up a LiteLLM shim or staying on OpenRouter.

Why it matters

• Usage-based billing with no middleman — fits self-hosted / paywall-averse stacks (the same reasoning as Recipe: Local embeddings via Ollama (remove cloud API dependency) #31)
• gemini-embedding-001 supports outputDimensionality (768 / 1536 / 3072), so dims can match an existing schema exactly — no migration
• gemini-2.5-flash handles the JSON metadata extraction just fine
• OpenRouter fragility is already tracked in response_format json_object is a no-op on the default OpenRouter model #468 / agent-memory-api: OPENROUTER_BASE hardcoded — same generalization argument as entity-extraction-worker #315 — one less dependency is one less failure mode

Verified solution (working fork)

We patched both call sites to call Gemini REST directly — ~40 lines: two functions (getEmbedding, extractMetadata) plus the config block on the server, same surgery on the importer (which we also pointed at direct Postgres, since we're fully self-hosted).

Reference implementation: github.com/ScottichPhDLass/OB1 @ branch iris/gemini-direct (commits ff5c5cf server, a5db7f9 importer).

Proven in production use: a 198-thought vault import + query battery (semantic retrieval and hybrid vector+metadata-filter queries) all passing against gemini-embedding-001 @ 768 dims and gemini-2.5-flash.

Offer

Happy to convert this into a recipe PR in the style of #31 / #266, or leave the fork as a reference implementation. Also worth noting: Google exposes an OpenAI-compatible endpoint, so an alternative path is a provider-abstraction that accepts either — but the direct REST patch is the smallest, dependency-free option we tested.

Related: #75 (opposite direction — Gemini CLI as an MCP client to OB1), #315 (hardcoded OPENROUTER_BASE generalization argument).

[github-actions]

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