fix(ai): detect Ollama overflow errors closes #2626

packages/ai/src/utils/overflow.ts

@@ -22,7 +22,7 @@ import type { AssistantMessage } from "../types.js";
  * - Cerebras: Returns "400/413 status code (no body)" - handled separately below
  * - Mistral: "Prompt contains X tokens ... too large for model with Y maximum context length"
  * - z.ai: Does NOT error, accepts overflow silently - handled via usage.input > contextWindow
- * - Ollama: Silently truncates input - not detectable via error message
+ * - Ollama: Some deployments truncate silently, others return errors like "prompt too long; exceeded max context length by X tokens"
  */
 const OVERFLOW_PATTERNS = [
 	/prompt is too long/i, // Anthropic
@@ -39,6 +39,7 @@ const OVERFLOW_PATTERNS = [
 	/exceeded model token limit/i, // Kimi For Coding
 	/too large for model with \d+ maximum context length/i, // Mistral
 	/model_context_window_exceeded/i, // z.ai non-standard finish_reason surfaced as error text
+	/prompt too long; exceeded (?:max )?context length/i, // Ollama explicit overflow error
 	/context[_ ]length[_ ]exceeded/i, // Generic fallback
 	/too many tokens/i, // Generic fallback
 	/token limit exceeded/i, // Generic fallback
@@ -71,8 +72,9 @@ const OVERFLOW_PATTERNS = [
  * **Unreliable detection:**
  * - z.ai: Sometimes accepts overflow silently (detectable via usage.input > contextWindow),
  *   sometimes returns rate limit errors. Pass contextWindow param to detect silent overflow.
- * - Ollama: Silently truncates input without error. Cannot be detected via this function.
- *   The response will have usage.input < expected, but we don't know the expected value.
+ * - Ollama: May truncate input silently for some setups, but may also return explicit
+ *   overflow errors that match the patterns above. Silent truncation still cannot be
+ *   detected here because we do not know the expected token count.
  *
  * ## Custom Providers
  *