fix(httpapi): document tui bad request responses

Document legacy 400 bad-request responses on TUI Effect HttpApi payload-validation endpoints and cover them with OpenAPI parity tests.

packages/opencode/src/server/routes/instance/httpapi/tui.ts

@@ -61,6 +61,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("appendPrompt", TuiPaths.appendPrompt, {
           payload: TuiEvent.PromptAppend.properties,
           success: Schema.Boolean,
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.appendPrompt",
@@ -113,6 +114,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("executeCommand", TuiPaths.executeCommand, {
           payload: CommandPayload,
           success: Schema.Boolean,
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.executeCommand",
@@ -133,6 +135,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("publish", TuiPaths.publish, {
           payload: TuiPublishPayload,
           success: Schema.Boolean,
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.publish",
@@ -143,7 +146,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("selectSession", TuiPaths.selectSession, {
           payload: TuiEvent.SessionSelect.properties,
           success: Schema.Boolean,
-          error: HttpApiError.NotFound,
+          error: [HttpApiError.BadRequest, HttpApiError.NotFound],
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.selectSession",

packages/opencode/test/server/httpapi-tui.test.ts

@@ -5,9 +5,11 @@ import { Flag } from "@opencode-ai/core/flag/flag"
 import { SessionID } from "../../src/session/schema"
 import { Instance } from "../../src/project/instance"
 import { InstanceRoutes } from "../../src/server/routes/instance"
-import { TuiPaths } from "../../src/server/routes/instance/httpapi/tui"
+import { TuiApi, TuiPaths } from "../../src/server/routes/instance/httpapi/tui"
 import { callTui } from "../../src/server/routes/instance/tui"
+import { Server } from "../../src/server/server"
 import * as Log from "@opencode-ai/core/util/log"
+import { OpenApi } from "effect/unstable/httpapi"
 import { resetDatabase } from "../fixture/db"
 import { tmpdir } from "../fixture/fixture"
 
@@ -38,6 +40,15 @@ afterEach(async () => {
 })
 
 describe("tui HttpApi bridge", () => {
+  test("documents legacy bad request responses", async () => {
+    const legacy = await Server.openapi()
+    const effect = OpenApi.fromApi(TuiApi)
+    for (const path of [TuiPaths.appendPrompt, TuiPaths.executeCommand, TuiPaths.publish, TuiPaths.selectSession]) {
+      expect(legacy.paths[path].post?.responses?.[400]).toBeDefined()
+      expect(effect.paths[path].post?.responses?.[400]).toBeDefined()
+    }
+  })
+
   test("serves TUI command and event routes through experimental Effect routes", async () => {
     await using tmp = await tmpdir({ git: true, config: { formatter: false, lsp: false } })
     const headers = { "x-opencode-directory": tmp.path }