core: remove @effect/language-service plugin and optimize hot path type performance

- Removed @effect/language-service from both packages/core and packages/opencode tsconfig files and dependencies

- Wrapped mergeDeep calls in config loading and LLM streaming to avoid expensive remeda conditional merge type instantiations in hot paths

- Narrowed Drizzle migrate() overload signature to avoid expensive variance checks during database initialization

These changes reduce TypeScript type-checking overhead and improve startup and runtime performance for config loading, LLM streaming, and database migrations.

7 files changed, 30 insertions, 37 deletions

diff --git a/bun.lock b/bun.lock
index 64c372661..093bb880a 100644
--- a/bun.lock
+++ b/bun.lock
@@ -456,7 +456,6 @@
       },
       "devDependencies": {
         "@babel/core": "7.28.4",
-        "@effect/language-service": "0.84.2",
         "@octokit/webhooks-types": "7.6.1",
         "@opencode-ai/core": "workspace:*",
         "@opencode-ai/script": "workspace:*",
@@ -1069,8 +1068,6 @@
 
     "@drizzle-team/brocli": ["@drizzle-team/[email protected]", "", {}, "sha512-hD3pekGiPg0WPCCGAZmusBBJsDqGUR66Y452YgQsZOnkdQ7ViEPKuyP4huUGEZQefp8g34RRodXYmJ2TbCH+tg=="],
 
-    "@effect/language-service": ["@effect/[email protected]", "", { "bin": { "effect-language-service": "cli.js" } }, "sha512-l04qNxpiA8rY5yXWckRPJ7Mk5MNerXuNymSFf+IdflfI5i8jgL1bpBNLuP6ijg7wgjdHc/KmTnCj2kT0SCntuA=="],
-
     "@effect/opentelemetry": ["@effect/[email protected]", "", { "peerDependencies": { "@opentelemetry/api": "^1.9", "@opentelemetry/resources": "^2.0.0", "@opentelemetry/sdk-logs": ">=0.203.0 <0.300.0", "@opentelemetry/sdk-metrics": "^2.0.0", "@opentelemetry/sdk-trace-base": "^2.0.0", "@opentelemetry/sdk-trace-node": "^2.0.0", "@opentelemetry/sdk-trace-web": "^2.0.0", "@opentelemetry/semantic-conventions": "^1.33.0", "effect": "^4.0.0-beta.57" }, "optionalPeers": ["@opentelemetry/api", "@opentelemetry/resources", "@opentelemetry/sdk-logs", "@opentelemetry/sdk-metrics", "@opentelemetry/sdk-trace-base", "@opentelemetry/sdk-trace-node", "@opentelemetry/sdk-trace-web"] }, "sha512-gdjZPEP0QQg4qmI1vd+443kheeQZKytrjJIzCJncy6ZEpyk/SfrqeStLqLXdTRcms3IB0ls0vOV7KNq7YmBRVA=="],
 
     "@effect/platform-node": ["@effect/[email protected]", "", { "dependencies": { "@effect/platform-node-shared": "^4.0.0-beta.57", "mime": "^4.1.0", "undici": "^8.0.2" }, "peerDependencies": { "effect": "^4.0.0-beta.57", "ioredis": "^5.7.0" } }, "sha512-la0xxPSAYOsY0d+uVxEBxok3jYB31iPQmIaZZRUj2SNWqcGGHJc6KorKtI8guqSLuv9FGZ255kBWXRbG6hMeeg=="],
diff --git a/packages/core/tsconfig.json b/packages/core/tsconfig.json
index d7745d755..fe5c4d217 100644
--- a/packages/core/tsconfig.json
+++ b/packages/core/tsconfig.json
@@ -2,13 +2,6 @@
   "$schema": "https://json.schemastore.org/tsconfig",
   "extends": "@tsconfig/bun/tsconfig.json",
   "compilerOptions": {
-    "noUncheckedIndexedAccess": false,
-    "plugins": [
-      {
-        "name": "@effect/language-service",
-        "transform": "@effect/language-service/transform",
-        "namespaceImportPackages": ["effect", "@effect/*"]
-      }
-    ]
+    "noUncheckedIndexedAccess": false
   }
 }
diff --git a/packages/opencode/package.json b/packages/opencode/package.json
index 425ddea77..cf2e574f5 100644
--- a/packages/opencode/package.json
+++ b/packages/opencode/package.json
@@ -6,7 +6,6 @@
   "license": "MIT",
   "private": true,
   "scripts": {
-    "prepare": "effect-language-service patch || true",
     "typecheck": "tsgo --noEmit",
     "test": "bun test --timeout 30000",
     "test:ci": "mkdir -p .artifacts/unit && bun test --timeout 30000 --reporter=junit --reporter-outfile=.artifacts/unit/junit.xml",
@@ -42,7 +41,6 @@
   },
   "devDependencies": {
     "@babel/core": "7.28.4",
-    "@effect/language-service": "0.84.2",
     "@octokit/webhooks-types": "7.6.1",
     "@opencode-ai/script": "workspace:*",
     "@opencode-ai/core": "workspace:*",
diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index c79e950e9..44841fe6f 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -3,7 +3,7 @@ import path from "path"
 import { pathToFileURL } from "url"
 import os from "os"
 import z from "zod"
-import { mergeDeep, pipe } from "remeda"
+import { mergeDeep } from "remeda"
 import { Global } from "@opencode-ai/core/global"
 import fsNode from "fs/promises"
 import { NamedError } from "@opencode-ai/core/util/error"
@@ -47,8 +47,13 @@ import { Npm } from "@opencode-ai/core/npm"
 const log = Log.create({ service: "config" })
 
 // Custom merge function that concatenates array fields instead of replacing them
+// Keep remeda's deep conditional merge type out of hot config-loading paths; TS profiling showed it dominates here.
+function mergeConfig(target: Info, source: Info): Info {
+  return mergeDeep(target, source) as Info
+}
+
 function mergeConfigConcatArrays(target: Info, source: Info): Info {
-  const merged = mergeDeep(target, source)
+  const merged = mergeConfig(target, source)
   if (target.instructions && source.instructions) {
     merged.instructions = Array.from(new Set([...target.instructions, ...source.instructions]))
   }
@@ -387,12 +392,10 @@ export const layer = Layer.effect(
     })
 
     const loadGlobal = Effect.fnUntraced(function* () {
-      let result: Info = pipe(
-        {},
-        mergeDeep(yield* loadFile(path.join(Global.Path.config, "config.json"))),
-        mergeDeep(yield* loadFile(path.join(Global.Path.config, "opencode.json"))),
-        mergeDeep(yield* loadFile(path.join(Global.Path.config, "opencode.jsonc"))),
-      )
+      let result: Info = {}
+      result = mergeConfig(result, yield* loadFile(path.join(Global.Path.config, "config.json")))
+      result = mergeConfig(result, yield* loadFile(path.join(Global.Path.config, "opencode.json")))
+      result = mergeConfig(result, yield* loadFile(path.join(Global.Path.config, "opencode.jsonc")))
 
       const legacy = path.join(Global.Path.config, "config")
       if (existsSync(legacy)) {
@@ -402,7 +405,7 @@ export const layer = Layer.effect(
               const { provider, model, ...rest } = mod.default
               if (provider && model) result.model = `${provider}/${model}`
               result["$schema"] = "https://opencode.ai/config.json"
-              result = mergeDeep(result, rest)
+              result = mergeConfig(result, rest)
               await fsNode.writeFile(path.join(Global.Path.config, "config.json"), JSON.stringify(result, null, 2))
               await fsNode.unlink(legacy)
             })
diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index 58677debc..69b0b27c3 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -3,7 +3,7 @@ import * as Log from "@opencode-ai/core/util/log"
 import { Context, Effect, Layer, Record } from "effect"
 import * as Stream from "effect/Stream"
 import { streamText, wrapLanguageModel, type ModelMessage, type Tool, tool, jsonSchema } from "ai"
-import { mergeDeep, pipe } from "remeda"
+import { mergeDeep } from "remeda"
 import { GitLabWorkflowLanguageModel } from "gitlab-ai-provider"
 import { ProviderTransform } from "@/provider/transform"
 import { Config } from "@/config/config"
@@ -29,6 +29,10 @@ const log = Log.create({ service: "llm" })
 export const OUTPUT_TOKEN_MAX = ProviderTransform.OUTPUT_TOKEN_MAX
 type Result = Awaited<ReturnType<typeof streamText>>
 
+// Avoid re-instantiating remeda's deep merge types in this hot LLM path; the runtime behavior is still mergeDeep.
+const mergeOptions = (target: Record<string, any>, source: Record<string, any> | undefined): Record<string, any> =>
+  mergeDeep(target, source ?? {}) as Record<string, any>
+
 export type StreamInput = {
   user: MessageV2.User
   sessionID: string
@@ -134,11 +138,9 @@ const live: Layer.Layer<
             sessionID: input.sessionID,
             providerOptions: item.options,
           })
-      const options: Record<string, any> = pipe(
-        base,
-        mergeDeep(input.model.options),
-        mergeDeep(input.agent.options),
-        mergeDeep(variant),
+      const options = mergeOptions(
+        mergeOptions(mergeOptions(base, input.model.options), input.agent.options),
+        variant,
       )
       if (isOpenaiOauth) {
         options.instructions = system.join("\n")
diff --git a/packages/opencode/src/storage/db.ts b/packages/opencode/src/storage/db.ts
index 95bb568bd..de4683b75 100644
--- a/packages/opencode/src/storage/db.ts
+++ b/packages/opencode/src/storage/db.ts
@@ -48,6 +48,13 @@ type Client = SQLiteBunDatabase
 
 type Journal = { sql: string; timestamp: number; name: string }[]
 
+// Drizzle's migrate overloads trigger expensive variance checks here; narrow to the journal overload we actually use.
+const migrateFromJournal = migrate as unknown as (db: SQLiteBunDatabase, entries: Journal) => void
+
+function applyMigrations(db: SQLiteBunDatabase, entries: Journal) {
+  migrateFromJournal(db, entries)
+}
+
 function time(tag: string) {
   const match = /^(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})/.exec(tag)
   if (!match) return 0
@@ -108,7 +115,7 @@ export const Client = lazy(() => {
         item.sql = "select 1;"
       }
     }
-    migrate(db, entries)
+    applyMigrations(db, entries)
   }
 
   return db
diff --git a/packages/opencode/tsconfig.json b/packages/opencode/tsconfig.json
index 5cb51012a..f09fca687 100644
--- a/packages/opencode/tsconfig.json
+++ b/packages/opencode/tsconfig.json
@@ -12,13 +12,6 @@
       "@/*": ["./src/*"],
       "@tui/*": ["./src/cli/cmd/tui/*"],
       "@test/*": ["./test/*"]
-    },
-    "plugins": [
-      {
-        "name": "@effect/language-service",
-        "transform": "@effect/language-service/transform",
-        "namespaceImportPackages": ["effect", "@effect/*"]
-      }
-    ]
+    }
   }
 }