fix(server): revert structured validation error wire format (#26457)

PR #26457 changed the 400 wire format on the HTTP API in three ways:
1. \`Effect.catch(HttpApiError.BadRequest)\` → \`{ data: {}, errors: [], success: false }\`
2. \`HttpApiSchemaError\` defect → same shape
3. \`normalizeEmptyBadRequest\` post-processor that rewrites ANY empty
   400 into the same shape

In v1.14.42 (post-Hono-deletion) at least one external plugin
(\`opencode-gemini-auth\`, per #26546 reports) makes an HTTP API call
during startup that hits one of these paths and breaks on the new
body shape — the unparseable JSON ends up printed to stdout and the
TUI never starts. \`opencode --pure\` works (no plugins), \`opencode run\`
works (no in-process server interaction), but \`opencode\` (TUI) crashes.

Revert all three changes from #26457. The default HttpApi serialization
of typed errors comes back, matching v1.14.41 wire format. We can
re-introduce structured validation responses behind an opt-in or
contract change once plugin authors have a chance to migrate.

Closes #26546.

packages/opencode/src/server/routes/instance/httpapi/middleware/error.ts

@@ -6,39 +6,13 @@ import { NamedError } from "@opencode-ai/core/util/error"
 import * as Log from "@opencode-ai/core/util/log"
 import { Cause, Effect } from "effect"
 import { HttpRouter, HttpServerError, HttpServerRespondable, HttpServerResponse } from "effect/unstable/http"
-import { HttpApiError } from "effect/unstable/httpapi"
-import { HttpApiSchemaError } from "effect/unstable/httpapi/HttpApiError"
 
 const log = Log.create({ service: "server" })
 
-function badRequestResponse() {
-  return HttpServerResponse.jsonUnsafe(
-    {
-      data: {},
-      errors: [],
-      success: false,
-    },
-    { status: 400 },
-  )
-}
-
-function normalizeEmptyBadRequest(response: HttpServerResponse.HttpServerResponse) {
-  if (response.status !== 400 || response.body._tag !== "Empty") return response
-  return badRequestResponse()
-}
-
 // Keep typed HttpApi failures on their declared error path; this boundary only replaces defect-only empty 500s.
 export const errorLayer = HttpRouter.middleware<{ handles: unknown }>()((effect) =>
   effect.pipe(
-    Effect.catch((error) => {
-      if (error instanceof HttpApiError.BadRequest) return Effect.succeed(badRequestResponse())
-      return Effect.fail(error)
-    }),
-    Effect.map(normalizeEmptyBadRequest),
     Effect.catchCause((cause) => {
-      const schemaError = cause.reasons.filter(Cause.isDieReason).find((reason) => HttpApiSchemaError.is(reason.defect))
-      if (schemaError) return Effect.succeed(badRequestResponse())
-
       const defect = cause.reasons.filter(Cause.isDieReason).find((reason) => {
         if (HttpServerResponse.isHttpServerResponse(reason.defect)) return false
         if (HttpServerError.isHttpServerError(reason.defect)) return false

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

@@ -1,11 +1,10 @@
 import { afterEach, describe, expect, mock, spyOn, test } from "bun:test"
-import { Context, Effect } from "effect"
+import { Effect } from "effect"
 import { Flag } from "@opencode-ai/core/flag/flag"
 import { Instance } from "../../src/project/instance"
 import { WithInstance } from "../../src/project/with-instance"
 import { Server } from "../../src/server/server"
 import { SyncPaths } from "../../src/server/routes/instance/httpapi/groups/sync"
-import { ExperimentalHttpApiServer } from "../../src/server/routes/instance/httpapi/server"
 import { Session } from "@/session/session"
 import * as Log from "@opencode-ai/core/util/log"
 import { resetDatabase } from "../fixture/db"
@@ -14,7 +13,6 @@ import { disposeAllInstances, tmpdir } from "../fixture/fixture"
 void Log.init({ print: false })
 
 const originalWorkspaces = Flag.OPENCODE_EXPERIMENTAL_WORKSPACES
-const context = Context.empty() as Context.Context<unknown>
 
 function app() {
   return Server.Default().app
@@ -121,22 +119,4 @@ describe("sync HttpApi", () => {
       expect(response.status).toBe(400)
     }
   })
-
-  test("returns structured validation errors", async () => {
-    await using tmp = await tmpdir({ git: true, config: { formatter: false, lsp: false } })
-    const response = await ExperimentalHttpApiServer.webHandler().handler(
-      new Request(`http://localhost${SyncPaths.history}`, {
-        method: "POST",
-        headers: { "x-opencode-directory": tmp.path, "content-type": "application/json" },
-        body: JSON.stringify({ aggregate: -1 }),
-      }),
-      context,
-    )
-
-    expect(response.status).toBe(400)
-    expect(response.headers.get("content-type") ?? "").toContain("application/json")
-    const body = (await response.json()) as Record<string, unknown>
-    expect(body.success).toBe(false)
-    expect(Array.isArray(body.error) || Array.isArray(body.errors)).toBe(true)
-  })
 })