Effect-TS · mattiamanzati · Feb 24, 2026 · Feb 24, 2026 · Feb 24, 2026
diff --git a/.changeset/migrate-effect-v4.md b/.changeset/migrate-effect-v4.md
@@ -0,0 +1,5 @@
+---
+"@effect/language-service": minor
+---
+
+Migrate internal Effect dependency from v3 to v4. This updates all CLI and core modules to use the Effect v4 API while maintaining full backward compatibility with existing functionality.
diff --git a/CLAUDE.md b/CLAUDE.md
@@ -8,7 +8,7 @@ This workflow should be initiated only if asked by the user.
 The following steps can be skipped if no typescript file has been changed in this branch, do not attempt any file change without user consent.
 - run "pnpm lint-fix" to fix code formatting
 - run "pnpm check" to see if you should fix some type errors
-- run "pnpm test" to validate that changes did not broke anything.
+- run "pnpm test" and "pnpm test:v4" to validate that changes did not broke anything.
 
 ### 3. Documentation checks
 - if new diagnostics, completions or refactor are added, ensure they are already mentioned in the README.md. Ensure to read examples and test/__snapshots__ related to the change to ensure full understanding of whats changed

diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/documented.ts.AppLive.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/documented.ts.AppLive.layerinfo
@@ -12,12 +12,12 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[ ] 2. DbConnection[0m
   [0;90m[ ] 3. FileSystem[0m
   [0;90m[x] 4. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const AppLive = UserRepository.Default.pipe([0m
     [0;90mLayer.provide(DbConnection.Default),[0m
     [0;90mLayer.provideMerge(Cache.Default),[0m

diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/documented.ts.CacheLive.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/documented.ts.CacheLive.layerinfo
@@ -11,10 +11,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[ ] 2. FileSystem[0m
-  [0;90m[0m
+
   [0;90mexport const CacheLive = Cache.Default.pipe([0m
     [0;90mLayer.provide(FileSystem.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/duplicated.ts.AppLive.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/duplicated.ts.AppLive.layerinfo
@@ -24,15 +24,15 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Analytics[0m
   [0;90m[x] 2. AppService[0m
   [0;90m[x] 3. Database[0m
   [0;90m[x] 4. EventService[0m
   [0;90m[x] 5. EventsRepository[0m
   [0;90m[x] 6. UserRepository[0m
   [0;90m[x] 7. UserService[0m
-  [0;90m[0m
+
   [0;90mexport const AppLive = AppService.Default.pipe([0m
     [0;90mLayer.provideMerge(EventService.Default),[0m
     [0;90mLayer.provideMerge(UserService.Default),[0m

diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/effect.ts.AppLive.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/effect.ts.AppLive.layerinfo
@@ -9,5 +9,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. DatabaseContext[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/followSymbols.ts.followSymbols.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/followSymbols.ts.followSymbols.layerinfo
@@ -13,10 +13,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. DbConnection[0m
   [0;90m[x] 2. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const followSymbols = simplePipeIn.pipe([0m
     [0;90mLayer.provide(DbConnection.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/followSymbols.ts.moreComplex.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/followSymbols.ts.moreComplex.layerinfo
@@ -14,11 +14,11 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. Cache[0m
   [0;90m[x] 2. DbConnection[0m
   [0;90m[x] 3. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const moreComplex = UserRepository.Default.pipe([0m
     [0;90mLayer.provideMerge(DbConnection.Default),[0m
     [0;90mLayer.provide(cacheWithFs)[0m

diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/generics.ts.NoComment.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/generics.ts.NoComment.layerinfo
@@ -10,5 +10,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. IsGeneric<UserRepository>[0m
diff --git a/...s/harness-effect-v3/__snapshots__/layerinfo/incorrectInference.ts.testInference.layerinfo b/...s/harness-effect-v3/__snapshots__/layerinfo/incorrectInference.ts.testInference.layerinfo
@@ -9,5 +9,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. string[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/multiple.ts.AppLive.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/multiple.ts.AppLive.layerinfo
@@ -24,15 +24,15 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Analytics[0m
   [0;90m[x] 2. AppService[0m
   [0;90m[x] 3. Database[0m
   [0;90m[x] 4. EventService[0m
   [0;90m[x] 5. EventsRepository[0m
   [0;90m[x] 6. UserRepository[0m
   [0;90m[x] 7. UserService[0m
-  [0;90m[0m
+
   [0;90mexport const AppLive = AppService.Default.pipe([0m
     [0;90mLayer.provideMerge(EventService.Default),[0m
     [0;90mLayer.provideMerge(UserService.Default),[0m

diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.cacheWithFs.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.cacheWithFs.layerinfo
@@ -10,10 +10,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[ ] 2. FileSystem[0m
-  [0;90m[0m
+
   [0;90mexport const cacheWithFs = Cache.Default.pipe([0m
     [0;90mLayer.provide(FileSystem.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.expect.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.expect.layerinfo
@@ -14,5 +14,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. UserRepository[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.liveWithPipeable.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.liveWithPipeable.layerinfo
@@ -16,11 +16,11 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[x] 2. DbConnection[0m
   [0;90m[x] 3. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const liveWithPipeable = UserRepository.Default.pipe([0m
     [0;90mLayer.provideMerge(Cache.Default),[0m
     [0;90mLayer.provideMerge(DbConnection.Default)[0m

diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.simplePipeIn.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/simple.ts.simplePipeIn.layerinfo
@@ -14,10 +14,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. Cache[0m
   [0;90m[x] 2. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const simplePipeIn = UserRepository.Default.pipe([0m
     [0;90mLayer.provide(Cache.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v3/__snapshots__/layerinfo/specialChars.ts.NoComment.layerinfo b/packages/harness-effect-v3/__snapshots__/layerinfo/specialChars.ts.NoComment.layerinfo
@@ -10,5 +10,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. IsGeneric<"With<Special>Chars#!">[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/documented.ts.AppLive.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/documented.ts.AppLive.layerinfo
@@ -12,12 +12,12 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[ ] 2. DbConnection[0m
   [0;90m[ ] 3. FileSystem[0m
   [0;90m[x] 4. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const AppLive = UserRepository.Default.pipe([0m
     [0;90mLayer.provide(DbConnection.Default),[0m
     [0;90mLayer.provideMerge(Cache.Default),[0m

diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/documented.ts.CacheLive.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/documented.ts.CacheLive.layerinfo
@@ -11,10 +11,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[ ] 2. FileSystem[0m
-  [0;90m[0m
+
   [0;90mexport const CacheLive = Cache.Default.pipe([0m
     [0;90mLayer.provide(FileSystem.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/duplicated.ts.AppLive.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/duplicated.ts.AppLive.layerinfo
@@ -24,15 +24,15 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Analytics[0m
   [0;90m[x] 2. AppService[0m
   [0;90m[x] 3. Database[0m
   [0;90m[x] 4. EventService[0m
   [0;90m[x] 5. EventsRepository[0m
   [0;90m[x] 6. UserRepository[0m
   [0;90m[x] 7. UserService[0m
-  [0;90m[0m
+
   [0;90mexport const AppLive = AppService.Default.pipe([0m
     [0;90mLayer.provideMerge(EventService.Default),[0m
     [0;90mLayer.provideMerge(UserService.Default),[0m

diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/effect.ts.AppLive.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/effect.ts.AppLive.layerinfo
@@ -9,5 +9,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. DatabaseContext[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/followSymbols.ts.followSymbols.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/followSymbols.ts.followSymbols.layerinfo
@@ -13,10 +13,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. DbConnection[0m
   [0;90m[x] 2. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const followSymbols = simplePipeIn.pipe([0m
     [0;90mLayer.provide(DbConnection.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/followSymbols.ts.moreComplex.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/followSymbols.ts.moreComplex.layerinfo
@@ -14,11 +14,11 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. Cache[0m
   [0;90m[x] 2. DbConnection[0m
   [0;90m[x] 3. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const moreComplex = UserRepository.Default.pipe([0m
     [0;90mLayer.provideMerge(DbConnection.Default),[0m
     [0;90mLayer.provide(cacheWithFs)[0m

diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/multiple.ts.AppLive.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/multiple.ts.AppLive.layerinfo
@@ -24,15 +24,15 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Analytics[0m
   [0;90m[x] 2. AppService[0m
   [0;90m[x] 3. Database[0m
   [0;90m[x] 4. EventService[0m
   [0;90m[x] 5. EventsRepository[0m
   [0;90m[x] 6. UserRepository[0m
   [0;90m[x] 7. UserService[0m
-  [0;90m[0m
+
   [0;90mexport const AppLive = AppService.Default.pipe([0m
     [0;90mLayer.provideMerge(EventService.Default),[0m
     [0;90mLayer.provideMerge(UserService.Default),[0m

diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.cacheWithFs.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.cacheWithFs.layerinfo
@@ -10,10 +10,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[ ] 2. FileSystem[0m
-  [0;90m[0m
+
   [0;90mexport const cacheWithFs = Cache.Default.pipe([0m
     [0;90mLayer.provide(FileSystem.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.expect.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.expect.layerinfo
@@ -14,5 +14,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. UserRepository[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.liveWithPipeable.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.liveWithPipeable.layerinfo
@@ -16,11 +16,11 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. Cache[0m
   [0;90m[x] 2. DbConnection[0m
   [0;90m[x] 3. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const liveWithPipeable = UserRepository.Default.pipe([0m
     [0;90mLayer.provideMerge(Cache.Default),[0m
     [0;90mLayer.provideMerge(DbConnection.Default)[0m

diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.simplePipeIn.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/simple.ts.simplePipeIn.layerinfo
@@ -14,10 +14,10 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[ ] 1. Cache[0m
   [0;90m[x] 2. UserRepository[0m
-  [0;90m[0m
+
   [0;90mexport const simplePipeIn = UserRepository.Default.pipe([0m
     [0;90mLayer.provide(Cache.Default)[0m
   [0;90m)[0m
diff --git a/packages/harness-effect-v4/__snapshots__/layerinfo/specialChars.ts.NoComment.layerinfo b/packages/harness-effect-v4/__snapshots__/layerinfo/specialChars.ts.NoComment.layerinfo
@@ -10,5 +10,5 @@
   [0;90mNot sure you got your composition right? Just write all layers inside a Layer.mergeAll(...)[0m
   [0;90mthen run this command again and use --outputs to select which outputs to include in composition.[0m
   [0;90mExample: --outputs 1,2,3[0m
-  [0;90m[0m
+
   [0;90m[x] 1. IsGeneric<"With<Special>Chars#!">[0m
diff --git a/packages/language-service/package.json b/packages/language-service/package.json
@@ -43,15 +43,9 @@
   "devDependencies": {
     "pako": "^2.1.0",
     "@typescript-eslint/project-service": "^8.52.0",
-    "@effect/cli": "^0.73.0",
-    "@effect/experimental": "^0.58.0",
-    "@effect/platform": "0.94.1",
-    "@effect/platform-node": "0.104.0",
-    "@effect/printer-ansi": "^0.47.0",
-    "@effect/rpc": "^0.73.0",
-    "@effect/sql": "^0.49.0",
+    "@effect/platform-node": "^4.0.0-beta.12",
     "@types/pako": "^2.0.4",
-    "effect": "^3.19.14",
+    "effect": "^4.0.0-beta.12",
     "ts-patch": "^3.3.0"
   }
 }