diff --git a/src/shared/migration/config-migration.test.ts b/src/shared/migration/config-migration.test.ts
index 5c41f8435..84e2d1370 100644
--- a/src/shared/migration/config-migration.test.ts
+++ b/src/shared/migration/config-migration.test.ts
@@ -199,3 +199,48 @@ describe("migrateConfigFile backup skipping", () => {
     expect(backupFiles.length).toBe(1)
   })
 })
+
+describe("migrateConfigFile orphan lsp key", () => {
+  test("removes the obsolete 'lsp' key from rawConfig and from the persisted file", () => {
+    // given - a v3-era config with a populated lsp block that the v4 schema silently strips
+    const workdir = createWorkdir()
+    const configPath = join(workdir, "oh-my-opencode.json")
+    const rawConfig: Record<string, unknown> = {
+      lsp: {
+        typescript: { command: ["typescript-language-server", "--stdio"] },
+        rust: { command: ["rust-analyzer"] },
+      },
+    }
+    writeFileSync(configPath, JSON.stringify(rawConfig, null, 2) + "\n")
+
+    // when
+    const needsWrite = migrateConfigFile(configPath, rawConfig)
+
+    // then - the in-memory config and the persisted file have both lost the lsp key
+    expect(needsWrite).toBe(true)
+    expect(rawConfig.lsp).toBeUndefined()
+    const persistedConfig = JSON.parse(readFileSync(configPath, "utf-8")) as Record<string, unknown>
+    expect(persistedConfig.lsp).toBeUndefined()
+  })
+
+  test("leaves the config alone when no 'lsp' key is present", () => {
+    // given - a config that never had an lsp block
+    const workdir = createWorkdir()
+    const configPath = join(workdir, "oh-my-opencode.json")
+    const rawConfig: Record<string, unknown> = {
+      agents: {
+        sisyphus: { model: "anthropic/claude-opus-4-7" },
+      },
+    }
+    writeFileSync(configPath, JSON.stringify(rawConfig, null, 2) + "\n")
+
+    // when
+    const needsWrite = migrateConfigFile(configPath, rawConfig)
+
+    // then - no rewrite triggered by the lsp migrator, agents block untouched
+    expect(needsWrite).toBe(false)
+    expect((rawConfig.agents as Record<string, Record<string, unknown>>).sisyphus.model).toBe(
+      "anthropic/claude-opus-4-7",
+    )
+  })
+})
diff --git a/src/shared/migration/config-migration.ts b/src/shared/migration/config-migration.ts
index 5c0ed2d87..f5c1e957f 100644
--- a/src/shared/migration/config-migration.ts
+++ b/src/shared/migration/config-migration.ts
@@ -105,6 +105,24 @@ export function migrateConfigFile(
     needsWrite = true
   }
 
+  // The legacy `lsp` config key was retired when LSP moved from native plugin
+  // tools to the `lsp` MCP server backed by `packages/lsp-tools-mcp`. Custom
+  // LSP servers are now configured via `.opencode/lsp.json` (project) or
+  // `~/.codex/lsp-client.json` (user). The Zod schema strips unknown keys
+  // silently, so without this migration a stale `lsp` block lingers in the
+  // user's config file with no signal that it has stopped doing anything.
+  if (copy.lsp !== undefined) {
+    const droppedServers = copy.lsp && typeof copy.lsp === "object"
+      ? Object.keys(copy.lsp as Record<string, unknown>)
+      : []
+    log(
+      "Removed obsolete 'lsp' config key from config file. LSP servers are now configured via .opencode/lsp.json -- see docs/reference/configuration.md for the new location.",
+      { configPath, droppedServers },
+    )
+    delete copy.lsp
+    needsWrite = true
+  }
+
   if (copy.experimental && typeof copy.experimental === "object") {
     const experimental = copy.experimental as Record<string, unknown>
     if ("hashline_edit" in experimental) {