[Init] Initial commit - NetMesh terminal manager

infrastructure/ai/shared/streamStateErrors.ts

@@ -0,0 +1,50 @@
+/**
+ * Helpers for detecting Vercel AI SDK internal stream-state errors.
+ *
+ * Background — issue #1101 follow-up:
+ *
+ * When a third-party Anthropic-compat backend (DeepSeek's
+ * `deepseek-v4-flash` is the canonical offender) streams thinking
+ * deltas without first emitting a `reasoning-start` content-block
+ * signal, the Vercel AI SDK's reasoning state machine has nothing
+ * registered for the incoming `part.id` and enqueues an
+ * `error` chunk on `stream` with the text
+ * `reasoning part <id> not found` — once per orphan delta. The
+ * analogous error exists for text parts.
+ *
+ * These chunks are *internal SDK bookkeeping noise*, not user-facing
+ * errors. Worse, treating them as real errors (adding a placeholder
+ * assistant message for each) breaks tool_use/tool_result contiguity
+ * on the next turn: the Anthropic message grouper splits the
+ * tool-result `role: 'tool'` messages from their parent tool_use
+ * `role: 'assistant'`, and the backend responds with
+ * `400 messages.N: tool_use ids were found without tool_result blocks
+ * immediately after`.
+ *
+ * Filtering these specific errors at the chunk-handler boundary
+ * stops the cascade: the orphan deltas are dropped silently (the SDK
+ * continues processing other chunks), no fake assistant messages
+ * land in history, and the next turn's request stays well-formed.
+ */
+
+const STATE_ERROR_PATTERN = /^(?:reasoning|text)\s+part\s+\S+\s+not\s+found$/i;
+
+/**
+ * Return true if `error` is one of the SDK's internal stream-state
+ * tracking errors (e.g. an out-of-order reasoning delta). Accepts
+ * the loose `unknown` shape that comes off the chunk so callers
+ * don't need to narrow upstream.
+ */
+export function isSdkStreamStateError(error: unknown): boolean {
+  if (typeof error === 'string') {
+    return STATE_ERROR_PATTERN.test(error.trim());
+  }
+  if (error instanceof Error) {
+    return STATE_ERROR_PATTERN.test(error.message.trim());
+  }
+  if (error && typeof error === 'object' && 'message' in error) {
+    const msg = (error as { message?: unknown }).message;
+    if (typeof msg === 'string') return STATE_ERROR_PATTERN.test(msg.trim());
+  }
+  return false;
+}