fix(cli-run): attach to default server when auto port range exhausted

src/cli/run/server-connection.test.ts

@@ -177,6 +177,28 @@ describe("createServerConnection", () => {
     expect(mockServerClose).toHaveBeenCalledTimes(1)
   })
 
+  it("auto mode attaches to default server when port range is exhausted", async () => {
+    // given
+    const signal = new AbortController().signal
+    mockGetAvailableServerPort.mockRejectedValueOnce(
+      new Error("No available port found in range 4097-4116"),
+    )
+    mockIsPortAvailable.mockResolvedValueOnce(false)
+
+    // when
+    const result = await createServerConnection({ signal })
+
+    // then
+    expect(mockGetAvailableServerPort).toHaveBeenCalledWith(4096, "127.0.0.1")
+    expect(mockIsPortAvailable).toHaveBeenCalledWith(4096, "127.0.0.1")
+    expect(mockCreateOpencodeClient).toHaveBeenCalledWith({
+      baseUrl: "http://127.0.0.1:4096",
+    })
+    expect(mockCreateOpencode).not.toHaveBeenCalled()
+    result.cleanup()
+    expect(mockServerClose).not.toHaveBeenCalled()
+  })
+
   it("invalid port throws error", async () => {
     // given
     const signal = new AbortController().signal

src/cli/run/server-connection.ts

@@ -12,6 +12,14 @@ function isPortStartFailure(error: unknown, port: number): boolean {
   return error.message.includes(`Failed to start server on port ${port}`)
 }
 
+function isPortRangeExhausted(error: unknown): boolean {
+  if (!(error instanceof Error)) {
+    return false
+  }
+
+  return error.message.includes("No available port found in range")
+}
+
 async function startServer(options: { signal: AbortSignal, port: number }): Promise<ServerConnection> {
   const { signal, port } = options
   const { client, server } = await withWorkingOpencodePath(() =>
@@ -67,7 +75,27 @@ export async function createServerConnection(options: {
     return { client, cleanup: () => {} }
   }
 
-  const { port: selectedPort, wasAutoSelected } = await getAvailableServerPort(DEFAULT_SERVER_PORT, "127.0.0.1")
+  let selectedPort: number
+  let wasAutoSelected: boolean
+  try {
+    const selected = await getAvailableServerPort(DEFAULT_SERVER_PORT, "127.0.0.1")
+    selectedPort = selected.port
+    wasAutoSelected = selected.wasAutoSelected
+  } catch (error) {
+    if (!isPortRangeExhausted(error)) {
+      throw error
+    }
+
+    const defaultPortIsAvailable = await isPortAvailable(DEFAULT_SERVER_PORT, "127.0.0.1")
+    if (defaultPortIsAvailable) {
+      throw error
+    }
+
+    console.log(pc.dim("Port range exhausted, attaching to existing server on"), pc.cyan(DEFAULT_SERVER_PORT.toString()))
+    const client = createOpencodeClient({ baseUrl: `http://127.0.0.1:${DEFAULT_SERVER_PORT}` })
+    return { client, cleanup: () => {} }
+  }
+
   if (wasAutoSelected) {
     console.log(pc.dim("Auto-selected port"), pc.cyan(selectedPort.toString()))
   } else {