---
id: PLN-0112
ticket: multi-frontend-remove-pbs-branches
title: Migrate semantic tokens to generic frontend language service
status: done
created: 2026-07-15
completed: 2026-07-15
ref_decisions: [DEC-0042]
tags: [compiler, compiler-general, compiler-pbs, studio, frontend, coupling, multi-frontend]
---

## Briefing

`DEC-0042` requires the LSP common path to project semantic token behavior from the selected frontend through generic frontend contracts. Semantic presentation already lives mostly in `FrontendSpec`, so this is the lowest-risk capability migration.

## Objective

Make LSP semantic token handling consume generic frontend language-service APIs while preserving frontend-owned semantic presentation and PBS semantic token behavior.

## Dependencies

- Depends on `PLN-0111` for the generic frontend editorial surface.
- Requires accepted decision `DEC-0042`.

## Scope

- Route semantic token requests through the provider's optional generic language service.
- Preserve `FrontendSpec.getSemanticPresentation()` as the source of token keys, host projections, themes, and default theme.
- Keep deterministic empty semantic tokens when a frontend has no language service or no semantic-token capability.

## Non-Goals

- Changing PBS semantic classification rules.
- Implementing semantic-token improvements from PBS-specific agendas.
- Migrating completion, hover, or signature help.
- Removing every PBS import from `CompilerLanguageServiceBridge`.

## Execution Method

1. Inspect `CompilerLanguageServiceBridge.semanticTokens(...)` and `PBSFrontendLanguageService.semanticTokens(...)`.
2. Add a generic semantic-token method to the frontend language-service surface if not already introduced by `PLN-0111`.
3. Adapt `PBSFrontendLanguageService` to return generic frontend semantic token records or a compatible generic token model.
4. Update `CompilerLanguageServiceBridge.semanticTokens(...)` to resolve `FrontendProvider` by `context.languageId()`, read presentation from `provider.specification()`, and call the generic semantic-token capability when present.
5. Ensure missing capability returns an empty token list with the frontend presentation legend.
6. Keep VS Code/LSP4J mapping inside `prometeu-lsp`.

## Acceptance Criteria

- LSP semantic token handling no longer needs PBS-specific language-service casts.
- Frontend semantic presentation remains frontend-owned.
- PBS semantic token regression tests continue to pass.
- Compile-only or no-language-service providers return deterministic empty semantic tokens.

## Tests

- Existing LSP semantic token tests.
- PBS frontend semantic presentation tests.
- Missing language-service fallback tests in `CompilerLanguageServiceBridgeTest`.

## Affected Artifacts

- `prometeu-lsp/prometeu-lsp-v1/src/main/java/p/studio/lsp/services/compiler/CompilerLanguageServiceBridge.java`
- `prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/PBSFrontendLanguageService.java`
- `prometeu-compiler/prometeu-frontend-api/src/main/java/p/studio/compiler/services/...`
- LSP semantic-token tests.