The interface lives at `lsp/lsp/`. The seam exposes exactly four semantic operations — `goToDefinition`, `findReferences`, `goToImplementation`, `hover` — and no generic JSON-RPC escape hatch, so a provider swap does not change how the model asks for navigation and no protocol payload or unreviewed mutation reaches the model contract. Providers register **capabilities**, not tools; `tool-lsp` is the only owner of the model-facing name, schema, prompt guidance, and presentation.
See the [LSP capability seam Agent Note](../../.agents/notes/implemented/architecture/2026-07-15-lsp-capability-seam.md) for the design rationale, including why documents open transiently per query, why the local host reads through Node APIs rather than `ctx.fs`, and why extension ownership is exclusive within one runtime.