diff --git a/packages/cli/src/services/server-connection.ts b/packages/cli/src/services/server-connection.ts
index db0d07ce2b75..2427d915b691 100644
--- a/packages/cli/src/services/server-connection.ts
+++ b/packages/cli/src/services/server-connection.ts
@@ -1,7 +1,7 @@
 import { Service, type Endpoint, type EnsureOptions } from "@opencode/client/effect/service"
 import { ClientError, isUnauthorizedError, OpenCode } from "@opencode/client/promise"
 import { OPENCODE_VERSION } from "../version"
-import { Effect, Redacted } from "effect"
+import { Cause, Effect, Exit, Redacted } from "effect"
 import { Env } from "../env"
 import { ServiceConfig } from "./service-config"
 import { Standalone } from "./standalone"
@@ -28,14 +28,25 @@ export const resolve = Effect.fn("cli.server-connection.resolve")(function* (arg
       auth: password ? { type: "basic" as const, username: "opencode", password: Redacted.value(password) } : undefined,
     } satisfies Endpoint
     const client = OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) })
-    const health = yield* Effect.tryPromise({
-      try: () => client.server.info({ signal: AbortSignal.timeout(5_000) }),
-      catch: (cause) => connectError(endpoint, cause),
-    })
-    if (health.version !== OPENCODE_VERSION)
-      process.stderr.write(
-        `Warning: Server at ${endpoint.url} has version ${health.version}; this client is ${OPENCODE_VERSION}. Continuing anyway.\n`,
-      )
+    const probed = yield* Effect.exit(
+      Effect.tryPromise({
+        try: () => client.server.info({ signal: AbortSignal.timeout(5_000) }),
+        catch: (cause) => cause,
+      }),
+    )
+    if (Exit.isSuccess(probed)) {
+      if (probed.value.version !== OPENCODE_VERSION)
+        process.stderr.write(
+          `Warning: Server at ${endpoint.url} has version ${probed.value.version}; this client is ${OPENCODE_VERSION}. Continuing anyway.\n`,
+        )
+      return { endpoint } satisfies Resolved
+    }
+    // Explicit --server must not replace a live server. HTTP 404 means this client
+    // asked /api/info of a build that still answers on legacy health.
+    const cause = Cause.squash(probed.cause)
+    if (unexpectedStatus(cause) !== 404) return yield* Effect.fail(connectError(endpoint, cause))
+    const legacy = yield* legacyHealth(endpoint)
+    process.stderr.write(legacySkewWarning(endpoint.url, legacy))
     return { endpoint } satisfies Resolved
   }
   if (args.standalone || (yield* ServiceConfig.read()).disabled === true) {
@@ -83,6 +94,49 @@ const resolveManaged = Effect.fnUntraced(function* (options: EnsureOptions, mism
   return yield* Service.ensure(options)
 })
 
+const legacyPaths = ["/api/health", "/api/status"] as const
+
+const legacyHealth = Effect.fnUntraced(function* (endpoint: Endpoint) {
+  const headers = Service.headers(endpoint)
+  const signal = AbortSignal.timeout(5_000)
+  let answered: (typeof legacyPaths)[number] | undefined
+  for (const pathname of legacyPaths) {
+    const response = yield* Effect.promise(() =>
+      fetch(new URL(pathname, endpoint.url), { headers, signal }).catch(() => undefined),
+    )
+    if (!response?.ok) continue
+    const version = versionOf(yield* Effect.promise(() => response.json().catch(() => undefined)))
+    if (version !== undefined) return { pathname, version }
+    answered ??= pathname
+  }
+  if (answered === undefined) return undefined
+  return { pathname: answered }
+})
+
+function legacySkewWarning(
+  url: string,
+  legacy: { readonly pathname: (typeof legacyPaths)[number]; readonly version?: string } | undefined,
+) {
+  if (legacy?.version !== undefined)
+    return `Warning: Server at ${url} has version ${legacy.version} via ${legacy.pathname}; this client is ${OPENCODE_VERSION}. Continuing anyway.\n`
+  if (legacy !== undefined)
+    return `Warning: Server at ${url} answered ${legacy.pathname} without a version, and /api/info returned HTTP 404. This client is ${OPENCODE_VERSION}. Continuing anyway.\n`
+  return `Warning: Server at ${url} returned HTTP 404 for /api/info and has no legacy /api/health or /api/status response. This client is ${OPENCODE_VERSION}. Continuing anyway. Restart or upgrade that server if this client cannot connect.\n`
+}
+
+function unexpectedStatus(cause: unknown) {
+  if (!(cause instanceof ClientError) || cause.reason !== "UnexpectedStatus") return undefined
+  const status = cause.cause
+  if (typeof status !== "object" || status === null || !("status" in status)) return undefined
+  return typeof status.status === "number" ? status.status : undefined
+}
+
+function versionOf(body: unknown) {
+  if (typeof body !== "object" || body === null || !("version" in body)) return undefined
+  if (typeof body.version !== "string" || body.version.length === 0) return undefined
+  return body.version
+}
+
 function connectError(endpoint: Endpoint, cause: unknown) {
   if (isUnauthorizedError(cause)) {
     return new Error(
diff --git a/packages/cli/test/server-connection.test.ts b/packages/cli/test/server-connection.test.ts
index 4174fb72b2b0..e0d770621a27 100644
--- a/packages/cli/test/server-connection.test.ts
+++ b/packages/cli/test/server-connection.test.ts
@@ -1,7 +1,7 @@
 import { NodeFileSystem } from "@effect/platform-node"
 import { Global } from "@opencode/util/global"
 import { OPENCODE_VERSION } from "../src/version"
-import { expect, test } from "bun:test"
+import { expect, spyOn, test } from "bun:test"
 import { Effect, FileSystem, Scope } from "effect"
 import fs from "node:fs/promises"
 import os from "node:os"
@@ -69,3 +69,134 @@ test("service options only require a matching version when requested", async ()
     await fs.rm(root, { recursive: true, force: true })
   }
 })
+
+test("explicit server falls back to legacy health on /api/info 404 and continues", async () => {
+  const requests: string[] = []
+  using server = Bun.serve({
+    port: 0,
+    fetch(request) {
+      const pathname = new URL(request.url).pathname
+      requests.push(pathname)
+      if (pathname === "/api/health") return Response.json({ version: "0.0.0-legacy" })
+      return new Response("missing", { status: 404 })
+    },
+  })
+  const stderr = await captureStderr(async () => {
+    const resolved = await runExplicit(ServerConnection.resolve({ server: server.url.toString() }))
+    expect(resolved.endpoint.url).toBe(server.url.toString())
+    expect(resolved.service).toBeUndefined()
+  })
+  expect(requests).toEqual(["/api/info", "/api/health"])
+  expect(stderr).toContain("0.0.0-legacy")
+  expect(stderr).toContain("/api/health")
+  expect(stderr).toContain("Continuing anyway")
+})
+
+test("explicit server reads /api/status when legacy /api/health is missing", async () => {
+  using server = Bun.serve({
+    port: 0,
+    fetch(request) {
+      const pathname = new URL(request.url).pathname
+      if (pathname === "/api/status") return Response.json({ version: "0.0.0-status", pid: 1 })
+      return new Response("missing", { status: 404 })
+    },
+  })
+  const stderr = await captureStderr(async () => {
+    const resolved = await runExplicit(ServerConnection.resolve({ server: server.url.toString() }))
+    expect(resolved.endpoint.url).toBe(server.url.toString())
+  })
+  expect(stderr).toContain("0.0.0-status")
+  expect(stderr).toContain("/api/status")
+  expect(stderr).toContain("Continuing anyway")
+})
+
+test("explicit server continues when /api/info and legacy health both 404", async () => {
+  using server = Bun.serve({
+    port: 0,
+    fetch: () => new Response("missing", { status: 404 }),
+  })
+  const stderr = await captureStderr(async () => {
+    const resolved = await runExplicit(ServerConnection.resolve({ server: server.url.toString() }))
+    expect(resolved.endpoint.url).toBe(server.url.toString())
+  })
+  expect(stderr).toContain("HTTP 404")
+  expect(stderr).toContain("Restart or upgrade")
+  expect(stderr).toContain("Continuing anyway")
+})
+
+test("explicit server warns on version skew without probing legacy health", async () => {
+  const requests: string[] = []
+  using server = Bun.serve({
+    port: 0,
+    fetch(request) {
+      requests.push(new URL(request.url).pathname)
+      return Response.json({ version: "other", pid: 1, urls: [], paths: { tmp: "/tmp" } })
+    },
+  })
+  const stderr = await captureStderr(async () => {
+    const resolved = await runExplicit(ServerConnection.resolve({ server: server.url.toString() }))
+    expect(resolved.service).toBeUndefined()
+  })
+  expect(requests).toEqual(["/api/info"])
+  expect(stderr).toContain("version other")
+  expect(stderr).toContain("Continuing anyway")
+})
+
+test("explicit server continues when legacy health omits a version", async () => {
+  using server = Bun.serve({
+    port: 0,
+    fetch(request) {
+      if (new URL(request.url).pathname === "/api/health") return Response.json({ healthy: true })
+      return new Response("missing", { status: 404 })
+    },
+  })
+  const stderr = await captureStderr(async () => {
+    await runExplicit(ServerConnection.resolve({ server: server.url.toString() }))
+  })
+  expect(stderr).toContain("/api/health")
+  expect(stderr).toContain("without a version")
+  expect(stderr).toContain("Continuing anyway")
+})
+
+test("explicit server still fails when /api/info is unauthorized", async () => {
+  using server = Bun.serve({
+    port: 0,
+    fetch: () => Response.json({ _tag: "UnauthorizedError", message: "Unauthorized" }, { status: 401 }),
+  })
+  await expect(runExplicit(ServerConnection.resolve({ server: server.url.toString() }))).rejects.toThrow(
+    "requires a password",
+  )
+})
+
+test("explicit server still fails when /api/info returns 503", async () => {
+  using server = Bun.serve({ port: 0, fetch: () => new Response("Unavailable", { status: 503 }) })
+  await expect(runExplicit(ServerConnection.resolve({ server: server.url.toString() }))).rejects.toThrow(
+    "did not provide a compatible V2 health response",
+  )
+})
+
+async function runExplicit<A, E>(effect: Effect.Effect<A, E, Global.Service | FileSystem.FileSystem | Scope.Scope>) {
+  const root = await fs.mkdtemp(path.join(os.tmpdir(), "opencode-explicit-server-"))
+  const layer = Global.layerWith({ config: path.join(root, "config"), state: path.join(root, "state") })
+  try {
+    return await Effect.runPromise(
+      effect.pipe(Effect.provide(layer), Effect.provide(NodeFileSystem.layer), Effect.scoped),
+    )
+  } finally {
+    await fs.rm(root, { recursive: true, force: true })
+  }
+}
+
+async function captureStderr(run: () => Promise<void>) {
+  const stderr: string[] = []
+  const stderrWrite = spyOn(process.stderr, "write").mockImplementation((chunk) => {
+    stderr.push(String(chunk))
+    return true
+  })
+  try {
+    await run()
+    return stderr.join("")
+  } finally {
+    stderrWrite.mockRestore()
+  }
+}