diff --git a/contributors/emails/abtion@outlook.com b/contributors/emails/abtion@outlook.com
new file mode 100644
index 0000000000..aa2f1ed4ed
--- /dev/null
+++ b/contributors/emails/abtion@outlook.com
@@ -0,0 +1 @@
+gitabtion
diff --git a/website/docs/integrations/providers.md b/website/docs/integrations/providers.md
index 4fe52265e3..0d4569accd 100644
--- a/website/docs/integrations/providers.md
+++ b/website/docs/integrations/providers.md
@@ -1351,6 +1351,8 @@ extra_body:
     enable_thinking: false
 ```
 
+The configured `extra_body` follows the provider everywhere: it is merged at agent construction, **survives every gateway turn** (including turns where `/fast` layers `service_tier`/`speed` overrides on top — those merge over your `extra_body` rather than replacing it), and is **re-derived on `/model` switches** — switching to a named custom provider applies its `extra_body`, and switching away clears it so it never leaks to another provider.
+
 The `hermes model` → Custom Endpoint wizard now prompts for the API mode explicitly and persists your answer to `config.yaml` (as `transport` on the provider entry). URL-based auto-detection (e.g. `/anthropic` paths → `anthropic_messages`) still happens as a fallback when the field is left blank.
 
 **Native vision for custom-provider models.** If your custom endpoint serves a vision-capable model that isn't in models.dev, set `model.supports_vision: true` so Hermes routes attached images natively (as `image_url` parts) instead of pre-processing them through `vision_analyze`. Single knob — no need to also set `agent.image_input_mode: native`.