Add detection for browser fetch‑failure messages (e.g., “Failed to fetch”, “Load failed”, “NetworkError”) and return a clear error indicating the streaming connection to the server was lost. Refine the connection‑error regex to avoid overlapping patterns while preserving provider‑side error handling.
A mid-stream connection drop showed a generic "Something went wrong / Load
failed" banner and left no server-side trace.
- error-message: classify the browsers' own fetch-failure strings ("Load
failed" on WebKit, "Failed to fetch" on Chrome, "NetworkError" on Firefox)
as a lost connection, so the banner names the cause instead of the generic
heading.
- ai-chat.controller: log a warning in the request close handler when the
client disconnects before completion, so a drop that reaches the app (e.g. a
reverse proxy cutting the SSE) is visible in the server logs before the abort.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The AI chat error banner always showed a generic "Something went wrong"
with no reason. The server already forwards the provider cause into the
stream (e.g. "Cannot connect to API: read ECONNRESET"), but the client
hid it behind a static heading.
- describeChatError now returns { title, detail }: a short heading naming
the cause category plus a one-line explanation.
- Add classifyProviderError: maps connection reset, timeout, rate limit,
context-window overflow, quota and auth failures to clear categories;
the 403/503 gating responses are preserved; unknown errors fall back to
the verbatim provider text.
- Match HTTP status codes only as the leading token and textual signatures
only against the message head (before "| response body:"), so a number
or phrase in the response-body snippet never mislabels the cause.
- Use the new {title, detail} in all three banners: chat-thread,
share-ai-widget and the persisted-error banner in message-item.
- Cover the classifier with 20 unit tests (categories + regressions).
Surfacing the stream error via useChat().error alone was not enough: on a
brand-new chat the errored turn still fires onFinish -> onTurnFinished, which
adopts the freshly-created chat id and changes the <ChatThread> key, remounting
it with a fresh useChat whose transient `error` is gone. The thread re-seeds
from persisted history, where the assistant row has empty parts and the error
lives only in metadata.error — which was never rendered. Result: an empty
"AI agent" row and no visible error.
- Render the persisted metadata.error inline in MessageItem, so the error
survives the remount and is also shown in reopened chat history.
- Carry metadata.error onto the rebuilt UIMessage in rowToUiMessage.
- Extract the error formatter into utils/error-message.ts (describeChatError)
and reuse it for both the live Alert and the persisted error.
- Add metadata.error to the IAiChatMessageRow type.
Client-only; the server already persists metadata.error. No new i18n keys.
