Effect-TS · mattiamanzati · Feb 4, 2026 · Feb 4, 2026
diff --git a/.changeset/effect-v4-completions.md b/.changeset/effect-v4-completions.md
@@ -0,0 +1,10 @@
+---
+"@effect/language-service": minor
+---
+
+Add Effect v4 completions support
+
+- Detect installed Effect version (v3 or v4) and conditionally enable version-specific completions
+- Add `Schema.ErrorClass` and `Schema.RequestClass` completions for Effect v4
+- Disable v3-only completions (`Effect.Service`, `Effect.Tag`, `Schema.TaggedError`, `Schema.TaggedClass`, `Schema.TaggedRequest`, `Context.Tag` self, `Rpc.make` classes, `Schema.brand`, `Model.Class`) when Effect v4 is detected
+- Support lowercase `taggedEnum` in addition to `TaggedEnum` for v4 API compatibility
diff --git a/packages/harness-effect-v4/__snapshots__/completions.test.ts.snap b/packages/harness-effect-v4/__snapshots__/completions.test.ts.snap
@@ -1,5 +1,145 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
+exports[`Completion contextSelfInClasses > contextSelfInClasses.ts at 4:40 1`] = `
+[
+  {
+    "insertText": "Context.Tag("@effect/harness-effect-v4/MyService")<MyService, \${0}>(){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "Tag("MyService")",
+    "replacementSpan": {
+      "length": 8,
+      "start": 144,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
+exports[`Completion contextSelfInClasses > contextSelfInClasses_directImportTag.ts at 4:35 1`] = `[]`;
+
+exports[`Completion contextSelfInClasses > contextSelfInClasses_identifierKey.ts at 5:40 1`] = `
+[
+  {
+    "insertText": "Context.Tag("@effect/harness-effect-v4/MyService")<MyService, \${0}>(){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "Tag("MyService")",
+    "replacementSpan": {
+      "length": 8,
+      "start": 240,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
+exports[`Completion durationInput > durationInput.ts at 4:38 1`] = `
+[
+  {
+    "insertText": "\${0} nanos",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "nanos",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} micros",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "micros",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} millis",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "millis",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} seconds",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "seconds",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} minutes",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "minutes",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} hours",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "hours",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} days",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "days",
+    "sortText": "11",
+  },
+  {
+    "insertText": "\${0} weeks",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "weeks",
+    "sortText": "11",
+  },
+]
+`;
+
+exports[`Completion durationInput > durationInput_props.ts at 5:14 1`] = `[]`;
+
+exports[`Completion effectCodegensComment > effectCodegensComment.ts at 2:5 1`] = `
+[
+  {
+    "insertText": "@effect-codegens \${1|accessors,annotate,typeToSchema|} $0",
+    "isSnippet": true,
+    "kind": "string",
+    "name": "@effect-codegens",
+    "replacementSpan": {
+      "length": 1,
+      "start": 73,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
+exports[`Completion effectDataClasses > effectDataClasses.ts at 4:35 1`] = `
+[
+  {
+    "insertText": "Data.TaggedError("MyError")<{\${0}}>{}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "TaggedError("MyError")",
+    "replacementSpan": {
+      "length": 5,
+      "start": 133,
+    },
+    "sortText": "11",
+  },
+  {
+    "insertText": "Data.TaggedClass("MyError")<{\${0}}>{}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "TaggedClass("MyError")",
+    "replacementSpan": {
+      "length": 5,
+      "start": 133,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
 exports[`Completion effectDiagnosticsComment > effectDiagnosticsComment.ts at 2:5 1`] = `
 [
   {
@@ -43,6 +183,98 @@ exports[`Completion effectJsdocComment > effectJsdocComment.ts at 2:6 1`] = `
 ]
 `;
 
+exports[`Completion effectSchemaSelfInClasses > effectSchemaSelfInClasses_directImportClass.ts at 4:35 1`] = `
+[
+  {
+    "insertText": "Class<MyClass>("MyClass")({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "Class<MyClass>",
+    "replacementSpan": {
+      "length": 5,
+      "start": 143,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
+exports[`Completion effectSchemaSelfInClasses > effectSchemaSelfInClasses_dotToken.ts at 4:22 1`] = `
+[
+  {
+    "insertText": "S.Class<Test>("Test")({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "Class<Test>",
+    "replacementSpan": {
+      "length": 2,
+      "start": 130,
+    },
+    "sortText": "11",
+  },
+  {
+    "insertText": "S.ErrorClass<Test>()({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "ErrorClass<Test>",
+    "replacementSpan": {
+      "length": 2,
+      "start": 130,
+    },
+    "sortText": "11",
+  },
+  {
+    "insertText": "S.RequestClass<Test>("Test")({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "RequestClass<Test>",
+    "replacementSpan": {
+      "length": 2,
+      "start": 130,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
+exports[`Completion effectSchemaSelfInClasses > effectSchemaSelfInClasses_tagg.ts at 4:25 1`] = `
+[
+  {
+    "insertText": "S.Class<Test>("Test")({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "Class<Test>",
+    "replacementSpan": {
+      "length": 5,
+      "start": 130,
+    },
+    "sortText": "11",
+  },
+  {
+    "insertText": "S.ErrorClass<Test>()({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "ErrorClass<Test>",
+    "replacementSpan": {
+      "length": 5,
+      "start": 130,
+    },
+    "sortText": "11",
+  },
+  {
+    "insertText": "S.RequestClass<Test>("Test")({\${0}}){}",
+    "isSnippet": true,
+    "kind": "const",
+    "name": "RequestClass<Test>",
+    "replacementSpan": {
+      "length": 5,
+      "start": 130,
+    },
+    "sortText": "11",
+  },
+]
+`;
+
 exports[`Completion fnFunctionStar > fnFunctionStar.ts at 4:24 1`] = `
 [
   {

diff --git a/packages/harness-effect-v4/examples/completions/contextSelfInClasses.ts b/packages/harness-effect-v4/examples/completions/contextSelfInClasses.ts
@@ -0,0 +1,4 @@
+// 4:40
+import * as Context from "effect/Context"
+
+export class MyService extends Context.
diff --git a/packages/harness-effect-v4/examples/completions/contextSelfInClasses_directImportTag.ts b/packages/harness-effect-v4/examples/completions/contextSelfInClasses_directImportTag.ts
@@ -0,0 +1,4 @@
+// 4:35
+import { Tag } from "effect/Context"
+
+export class MyService extends Tag
diff --git a/packages/harness-effect-v4/examples/completions/contextSelfInClasses_identifierKey.ts b/packages/harness-effect-v4/examples/completions/contextSelfInClasses_identifierKey.ts
@@ -0,0 +1,5 @@
+// 5:40
+// @test-config { "keyPatterns": [ { "pattern": "package-identifier", "target": "service" } ] }
+import * as Context from "effect/Context"
+
+export class MyService extends Context.
diff --git a/packages/harness-effect-v4/examples/completions/durationInput.ts b/packages/harness-effect-v4/examples/completions/durationInput.ts
@@ -0,0 +1,4 @@
+// 4:38
+import * as Effect from "effect/Effect"
+
+export const program = Effect.sleep("")
diff --git a/packages/harness-effect-v4/examples/completions/durationInput_props.ts b/packages/harness-effect-v4/examples/completions/durationInput_props.ts
@@ -0,0 +1,6 @@
+// 5:14
+import * as Effect from "effect/Effect"
+
+export const program = Effect.timeoutFail(Effect.never, {
+  duration: ""
+})
diff --git a/packages/harness-effect-v4/examples/completions/effectCodegensComment copy.ts b/packages/harness-effect-v4/examples/completions/effectCodegensComment copy.ts
@@ -0,0 +1,2 @@
+// 2:5
+// @
diff --git a/packages/harness-effect-v4/examples/completions/effectCodegensComment.ts b/packages/harness-effect-v4/examples/completions/effectCodegensComment.ts
@@ -0,0 +1,2 @@
+// 2:5
+// @
diff --git a/packages/harness-effect-v4/examples/completions/effectDataClasses.ts b/packages/harness-effect-v4/examples/completions/effectDataClasses.ts
@@ -0,0 +1,4 @@
+// 4:35
+import * as Data from "effect/Data"
+
+export class MyError extends Data.
diff --git a/...ges/harness-effect-v4/examples/completions/effectSchemaSelfInClasses_directImportClass.ts b/...ges/harness-effect-v4/examples/completions/effectSchemaSelfInClasses_directImportClass.ts
@@ -0,0 +1,4 @@
+// 4:35
+import { Class } from "effect/Schema"
+
+export class MyClass extends Class
diff --git a/packages/harness-effect-v4/examples/completions/effectSchemaSelfInClasses_dotToken.ts b/packages/harness-effect-v4/examples/completions/effectSchemaSelfInClasses_dotToken.ts
@@ -0,0 +1,4 @@
+// 4:22
+import * as S from "effect/Schema"
+
+class Test extends S.
diff --git a/packages/harness-effect-v4/examples/completions/effectSchemaSelfInClasses_tagg.ts b/packages/harness-effect-v4/examples/completions/effectSchemaSelfInClasses_tagg.ts
@@ -0,0 +1,4 @@
+// 4:25
+import * as S from "effect/Schema"
+
+class Test extends S.tag
diff --git a/packages/language-service/src/completions/contextSelfInClasses.ts b/packages/language-service/src/completions/contextSelfInClasses.ts
@@ -13,6 +13,7 @@ export const contextSelfInClasses = LSP.createCompletion({
     const ts = yield* Nano.service(TypeScriptApi.TypeScriptApi)
     const tsUtils = yield* Nano.service(TypeScriptUtils.TypeScriptUtils)
     const typeParser = yield* Nano.service(TypeParser.TypeParser)
+    if (typeParser.supportedEffect() === "v4") return []
 
     const maybeInfos = tsUtils.parseDataForExtendsClassCompletion(sourceFile, position)
     if (!maybeInfos) return []