**TL;DR:** Chat models retry failed requests with exponential backoff automatically: up to 6 times for network errors, 429 rate limits, and 5xx server errors. 401 and 404 are never retried.

## The fix

1. Network errors, rate limits (429), server errors (5xx): yes, with exponential backoff.

2. Client errors like 401 unauthorized or 404: no. Retrying those is pointless; fix the credentials or the request.

3. For long-running agent graphs on flaky networks, raise max_retries (10 to 15) AND use a checkpointer, so progress survives a failure that retries cannot paper over.

4. The exceptions carry an `is_retryable` attribute. Model retry middleware respects it by default, so custom retry code should check the attribute instead of maintaining its own list.

5. In create_agent, prefer ModelRetryMiddleware (max_retries, backoff_factor, initial_delay, on_failure) over wrapping the whole agent in your own loop.

## When to use this

- This covers exactly what the title says: Connection resilience.
- You are setting this up for the first time, or auditing an existing setup.
- You want the key gotchas in one place before you start.

## When not to use this

- You are doing a different workflow with Connection; these steps are specific to the title above.
- You need the full reference docs; this is the short path, not the manual.

## Compatibility

- Mentions 3.6 in the original; behavior may differ on much older or newer releases.

---

## Vectle citations

- Exact version: <https://vectle.com/skills/skl_-AYmf4TdlGoXzVA1In0-Fg/versions/skv_5ZEMjO6pcDMsrIt5kMmZxw>
- Canonical HTML skill page: <https://vectle.com/skills/skl_-AYmf4TdlGoXzVA1In0-Fg>
- Current Markdown URL: <https://vectle.com/skills/skl_-AYmf4TdlGoXzVA1In0-Fg/markdown>

## Selected public attribution and original notices/references

```json
{
  "author": "issueatlas",
  "client": null,
  "notices_and_references": [
    "https://docs.langchain.com/oss/python/langchain/models",
    "https://docs.langchain.com/oss/python/langchain/middleware/built-in"
  ]
}
```