Handle invalid JSON in GitHub Models 429 responses

NEWS.md

@@ -2,6 +2,7 @@
 
 * `chat_github()` now uses `chat_openai_compatible()` for improved compatibility, and `models_github()` now supports custom `base_url` configuration (@D-M4rk, #877).
 * `chat_ollama()` now contains a slot for `top_k` within the `params` argument (@frankiethull).
+* `chat_github()` and other OpenAI-compatible providers now robustly handle rate limit errors (HTTP 429) where the API returns a text body despite sending a JSON content-type header. This prevents crashes and allows the built-in retry logic to function correctly (@D-M4rk, #901)
 
 # ellmer 0.4.0
 

R/provider-openai-compatible.R

@@ -153,18 +153,35 @@ method(base_request_error, ProviderOpenAICompatible) <- function(
   req
 ) {
   req_error(req, body = function(resp) {
-    if (resp_content_type(resp) == "application/json") {
-      error <- resp_body_json(resp)$error
-      if (is_string(error)) {
-        error
-      } else if (is.list(error)) {
-        error$message
-      } else {
-        prettify(resp_body_string(resp))
+    # Default to treating as text
+    is_json <- FALSE
+    try(
+      {
+        if (resp_content_type(resp) == "application/json") {
+          is_json <- TRUE
+        }
+      },
+      silent = TRUE
+    )
+
+    if (is_json) {
+      # Try parsing JSON, but fall back to text if it fails (e.g. 429 text body)
+      body <- tryCatch(resp_body_json(resp), error = function(e) NULL)
+
+      if (!is.null(body)) {
+        error <- body$error
+        if (is_string(error)) {
+          return(error)
+        } else if (is.list(error)) {
+          return(error$message)
+        } else {
+          return(prettify(resp_body_string(resp)))
+        }
       }
-    } else if (resp_content_type(resp) == "text/plain") {
-      resp_body_string(resp)
     }
+
+    # Fallback for text/plain, other types, or failed JSON parsing
+    resp_body_string(resp)
   })
 }