## Summary
- `create_notebook`/`update_notebook` now validate every
`database_cell`'s `database_identifier` against the project's real
database list (`getReadReplicas`) before writing, throwing an
assistant-actionable `NotebookToolError` (same pattern as the existing
`expected_updated_at` mismatch check) when it doesn't match.
- Only fetches the database list when a cell actually sets
`database_identifier` — no added cost for the common case.
- `update_notebook` validates only the cells its own operations
introduce (`insert_cell`/`replace_cell`), not the whole resulting
notebook — otherwise an unrelated, untouched pre-existing cell whose
replica was removed after the fact would block updates that never touch
it.
Part 4/6 of the stack for FE-4225 (expose valid database identifiers to
the notebook AI agent). Stacked on #49332. This closes the gap that PR 3
reopened: a model can no longer invent an identifier that silently
breaks a cell — it now gets a retryable error naming `list_databases`
(added in #49328) as the way to find a real one.
## Test plan
- [x] `create_notebook`/`update_notebook` reject an unknown
`database_identifier` with `NotebookToolError` + `exposeToAssistant:
true`
- [x] Both succeed when the identifier matches a real database
- [x] `create_notebook` never calls the databases endpoint when no cell
sets `database_identifier`
- [x] `update_notebook` succeeds without validating or fetching
databases when no operation introduces a database_cell, even if an
untouched existing cell carries a now-invalid identifier
- [x] `pnpm --filter studio exec tsc --noEmit` passes
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added a database-listing tool that provides database identifiers and
metadata, including primary-database status.
* Database results now return only the relevant fields.
* **Bug Fixes**
* Added validation to prevent notebooks from referencing unknown
databases.
* Create and update actions now provide clear errors for invalid
database identifiers.
* Updates validate newly added or replaced cells while preserving
existing, untouched cells.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Charis
ee59d28240