llm/copilot: add required headers and update default model\n\n- Send X-GitHub-Api-Version and User-Agent headers for Copilot requests\n- Default Copilot model to gpt-4o-mini (avoid non-existent 'codex'/'gpt-4.1')\n- README and config.json.example: update Copilot defaults and guidance\n\nNote: Copilot provider expects Copilot-issued auth; for public access use GitHub Models via OpenAI-compatible endpoint.

3 files changed, 11 insertions, 4 deletions

diff --git a/README.md b/README.md
index 2758536..e9c53c5 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ Hexai exposes a simple LLM provider interface. It supports OpenAI, GitHub Copilo
   "trigger_characters": [".", ":", "/", "_", ";", "?"],
   "coding_temperature": 0.2,
   "provider": "ollama",
-  "copilot_model": "gpt-4.1",
+  "copilot_model": "gpt-4o-mini",
   "copilot_base_url": "https://api.githubcopilot.com",
   "copilot_temperature": 0.2,
   "openai_model": "gpt-4.1",
@@ -64,7 +64,7 @@ Ensure `OPENAI_API_KEY` or `COPILOT_API_KEY` is set in your environment accordin
 
 - Required: `COPILOT_API_KEY` — provided via environment variable only.
 - In config file:
-  - `copilot_model` — model name (default: `gpt-4.1`).
+  - `copilot_model` — model name (default: `gpt-4o-mini`).
   - `copilot_base_url` — API base (default: `https://api.githubcopilot.com`).
   - `copilot_temperature` — default temperature (coding-friendly default `0.2`).
 
diff --git a/config.json.example b/config.json.example
index b8c729b..ce091d5 100644
--- a/config.json.example
+++ b/config.json.example
@@ -18,7 +18,7 @@
   "ollama_base_url": "http://localhost:11434",
   "ollama_temperature": 0.2,
 
-  "copilot_model": "gpt-4.1",
+  "copilot_model": "gpt-4o-mini",
   "copilot_base_url": "https://api.githubcopilot.com",
   "copilot_temperature": 0.2
 }
diff --git a/internal/llm/copilot.go b/internal/llm/copilot.go
index 1c9f60d..6ab3a0d 100644
--- a/internal/llm/copilot.go
+++ b/internal/llm/copilot.go
@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	appver "hexai/internal"
 	"hexai/internal/logging"
 )
 
@@ -60,7 +61,9 @@ func newCopilot(baseURL, model, apiKey string, defaultTemp *float64) Client {
 		baseURL = "https://api.githubcopilot.com"
 	}
 	if strings.TrimSpace(model) == "" {
-		model = "gpt-4.1"
+		// GitHub Models (Copilot API) commonly supports gpt-4o/gpt-4o-mini.
+		// Default to a broadly available, cost-effective option.
+		model = "gpt-4o-mini"
 	}
 	return copilotClient{
 		httpClient:         &http.Client{Timeout: 30 * time.Second},
@@ -155,6 +158,10 @@ func (c copilotClient) doJSON(ctx context.Context, url string, body []byte, head
 		return nil, err
 	}
 	req.Header.Set("Content-Type", "application/json")
+	// GitHub Copilot (GitHub Models) requires an API version header and a UA.
+	req.Header.Set("Accept", "application/json")
+	req.Header.Set("X-GitHub-Api-Version", "2023-07-07")
+	req.Header.Set("User-Agent", "hexai/"+appver.Version)
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}