Fallback when async prompt admission fails

CHANGELOG.md

@@ -4,6 +4,12 @@ This project follows Semantic Versioning.
 
 ## Unreleased
 
+## [0.11.2] - 2026-06-06
+
+### Fixed
+
+- Fixed Telegram prompt failures on OpenCode servers that reject async prompt admission by falling back to the synchronous prompt endpoint. (#55)
+
 ## [0.11.1] - 2026-06-06
 
 ### Fixed

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@crankshift/opencode-remote",
   "description": "A messenger-based chat interface for OpenCode, starting with Telegram.",
-  "version": "0.11.1",
+  "version": "0.11.2",
   "license": "MIT",
   "repository": {
     "type": "git",

src/bin/program.js

@@ -39,7 +39,7 @@ export function createGatewayProgram({
   const program = new Command()
   const afterCreate = createStartupAfterConfigHook({ enableGatewayStartup, output })
 
-  program.name("opencode-remote").description("OpenCode messaging gateway").version("0.11.1")
+  program.name("opencode-remote").description("OpenCode messaging gateway").version("0.11.2")
 
   program
     .command("setup")

src/core/opencode/client.js

@@ -50,11 +50,17 @@ export function createOpenCodeClient({
       })
       try {
         if (typeof client.session?.promptAsync === "function" && progressStream.active) {
-          await client.session.promptAsync({
-            path: { id: sessionId },
-            body: { ...promptBody, messageID: asyncPrompt.messageId },
-          })
-          return await asyncPrompt.wait()
+          try {
+            await client.session.promptAsync({
+              path: { id: sessionId },
+              body: { ...promptBody, messageID: asyncPrompt.messageId },
+            })
+            return await asyncPrompt.wait()
+          } catch (error) {
+            if (!shouldFallbackToSynchronousPrompt(error)) {
+              throw error
+            }
+          }
         }
 
         const response = toData(
@@ -257,6 +263,22 @@ function noopProgressStream() {
   return { active: false, stop: async () => undefined }
 }
 
+function shouldFallbackToSynchronousPrompt(error) {
+  const status = error?.cause?.status
+  if (status === 400 || status === 404 || status === 405) {
+    return true
+  }
+  const text = [error?.name, error?.code, error?.message]
+    .filter((value) => typeof value === "string")
+    .join(" ")
+    .toLocaleLowerCase("en-US")
+
+  return (
+    text.includes("prompt_async") &&
+    (text.includes("400") || text.includes("404") || text.includes("405"))
+  )
+}
+
 function createAsyncPromptCompletion(sessionId, timeoutMs) {
   const messageId = randomUUID()
   const textPartsByMessage = new Map()

tests/core/opencodeClient.test.js

@@ -306,6 +306,29 @@ describe("createOpenCodeClient", () => {
     }
   })
 
+  test("falls back to synchronous prompts when async admission fails", async () => {
+    const stream = createControlledEventStream()
+    const sdkClient = {
+      event: { list: vi.fn(async () => stream) },
+      session: {
+        promptAsync: vi.fn(async () => {
+          throw new Error("opencode server POST /session/ses_1/prompt_async -> 404")
+        }),
+        prompt: vi.fn(async () => ({ parts: [{ type: "text", text: "fallback answer" }] })),
+      },
+    }
+    const client = createOpenCodeClient({ sdkClient })
+
+    await expect(client.sendPrompt("ses_1", "research task")).resolves.toBe("fallback answer")
+
+    expect(sdkClient.session.promptAsync).toHaveBeenCalled()
+    expect(sdkClient.session.prompt).toHaveBeenCalledWith({
+      path: { id: "ses_1" },
+      body: { parts: [{ type: "text", text: "research task" }] },
+    })
+    expect(stream.controller.abort).toHaveBeenCalled()
+  })
+
   test("uses current SDK event.subscribe stream shape for progress", async () => {
     let subscribeSignal
     const stream = createEventStream([