---
id: PLN-0109
ticket: multi-frontend-compiler-vs-language-services
title: Make LSP editorial calls capability aware
status: done
created: 2026-07-15
ref_decisions: [DEC-0041]
tags: [compiler, compiler-general, studio, lsp, editor, frontend, multi-frontend]
---

## Briefing

`DEC-0041` requires LSP and Studio consumers to query editorial capability availability before invoking editor-specific behavior. The current LSP bridge still contains PBS-specific editorial logic. This plan migrates LSP editorial calls to capability-aware provider lookup and graceful fallbacks.

## Objective

Make LSP completion, hover, signature help, semantic tokens, and future editorial calls resolve the active frontend provider, consult optional language-service capabilities, and return deterministic neutral responses when capabilities are absent.

## Dependencies

- Accepted decision: `DEC-0041`.
- `PLN-0108` should expose PBS editor assistance through `FrontendProvider.languageService()`.
- Existing `FrontendRegistryService` frontend lookup.
- Existing LSP baseline messages and tests.

## Scope

- Update LSP bridge code to resolve frontend providers rather than hard-coding PBS editorial paths.
- Add fallback behavior for absent completion, hover, signature help, and semantic token capability.
- Preserve compiler-backed diagnostics through analyze/build paths.
- Keep PBS editorial behavior stable when its language service is present.
- Document or encode unsupported/neutral responses according to existing LSP baseline message shapes.

## Non-Goals

- Add new LSP features.
- Change VSCode extension behavior beyond consuming existing baseline responses.
- Remove all PBS-specific code in one step if adapter compatibility still requires local mapping.
- Make semantic presentation metadata optional; only live semantic token production is optional.

## Execution Method

1. Inspect `prometeu-lsp/prometeu-lsp-v1/src/main/java/p/studio/lsp/services/compiler/CompilerLanguageServiceBridge.java` and identify all direct PBS editorial calls.
2. Add a provider-resolution path using `FrontendRegistryService` or the existing registry abstraction for `context.languageId()`.
3. For each editorial endpoint, query `provider.languageService()` and then the relevant capability before invoking implementation behavior.
4. Return neutral fallbacks when absent:
   - completion: incomplete `false` with empty items;
   - hover: absent/neutral hover content according to current baseline message constraints;
   - signature help: empty signatures with stable active indices;
   - semantic tokens: frontend legend/presentation where available and empty token list when live tokenization is absent.
5. Keep `analyzeDocument` compiler-diagnostic behavior on the compiler pipeline and do not require `languageService()`.
6. Update tests to cover both PBS-present and capability-absent frontends.

## Acceptance Criteria

- LSP editorial endpoints do not assume every compiler frontend has editor assistance.
- Absent editorial capabilities produce deterministic empty or neutral responses, not compiler failures.
- Compiler diagnostics still work without a language service.
- PBS editor assistance remains unchanged when PBS language service is available.
- Any remaining PBS-specific code is adapter-local and documented as temporary if not removed.

## Tests

- Add LSP tests for a compile-only frontend or stub provider with no language service.
- Preserve existing `CompilerLanguageServiceBridgeTest` coverage for PBS completion, hover, signature help, and semantic tokens.
- Add regression coverage that `analyzeDocument` returns compiler diagnostics independently of editorial services.
- Run targeted LSP module tests.

## Affected Artifacts

- `prometeu-lsp/prometeu-lsp-v1/src/main/java/p/studio/lsp/services/compiler/CompilerLanguageServiceBridge.java`
- `prometeu-lsp/prometeu-lsp-v1/src/test/java/p/studio/lsp/services/compiler/CompilerLanguageServiceBridgeTest.java`
- LSP baseline message types only if neutral response representation is currently insufficient.
- Frontend registry integration points used by LSP.