Greptile Summary

This PR classifies connection-level errors (ECONNREFUSED, ECONNRESET, ENOTFOUND, APIConnectionError, etc.) as retryable failover events and surfaces a friendly user message instead of raw error text. It follows the established architecture by adding a connection pattern set to failover-matches.ts alongside the existing categories.

Key changes:

• New connection pattern set and isConnectionErrorMessage() function in failover-matches.ts
• formatAssistantErrorText() now returns "The AI service encountered a connection error. Please try again in a moment." for connection errors, before the existing timeout path
• classifyFailoverReason() maps connection errors to "timeout" (retryable), inserted before the existing isTimeoutErrorMessage check
• isConnectionErrorMessage is exported via pi-embedded-helpers.ts and errors.ts

Minor gap: The new connection pattern set is missing /\beai_again\b/i (temporary DNS failure) and "network request failed", both of which are present in the timeout pattern set and are semantically connection-level errors. These errors will still be retried correctly via isTimeoutErrorMessage, but will display "LLM request timed out." rather than the new friendly connection error message in formatAssistantErrorText.

Confidence Score: 4/5

• This PR is safe to merge — changes are additive and all existing tests pass alongside the new test cases.
• The implementation correctly follows the existing pattern-matching architecture, the new classifyFailoverReason and formatAssistantErrorText paths are logically sound, and test coverage addresses the main cases. The only issue is a minor inconsistency — /\beai_again\b/i and "network request failed" are in timeout but absent from connection, meaning those two error flavours will show a timeout message rather than the new friendly connection message. Failover retry behaviour is unaffected. Score is 4 rather than 5 solely for that gap.
• src/agents/pi-embedded-helpers/failover-matches.ts — the connection pattern set should include /\beai_again\b/i and "network request failed" for consistency with the timeout set.

This is a comment left during a code review.
Path: src/agents/pi-embedded-helpers/failover-matches.ts
Line: 95-104

Comment:
**Missing `EAI_AGAIN` and `"network request failed"` patterns**

The `timeout` pattern set (lines 28–46) includes `/\beai_again\b/i` and `"network request failed"`, but neither is present in the new `connection` set. `EAI_AGAIN` is a temporary DNS failure — semantically identical to `ENOTFOUND` (which is included) — so this looks like an oversight. As a result, `EAI_AGAIN` errors will:
- Return `"LLM request timed out."` in `formatAssistantErrorText` instead of the new friendly connection error message
- Still be caught by `isTimeoutErrorMessage` for failover classification, so retry behaviour is unaffected

Consider adding both patterns for consistency:

```suggestion
  connection: [
    "connection error",
    "apiconnectionerror",
    "socket hang up",
    /\beconn(?:refused|reset|aborted)\b/i,
    /\benotfound\b/i,
    /\beai_again\b/i,
    "fetch failed",
    "network error",
    "network request failed",
    "dns lookup failed",
  ],
```

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: fc26a3f}