feat(openrouter): send app attribution headers and session_id for sticky routing

Add HTTP-Referer and X-Title headers to OpenRouter requests so usage
is attributed to Crush on the OpenRouter dashboard. Inject session_id
into the request body via ProviderOptions.ExtraBody for sticky routing
and downstream provider session grouping.

Resolves #3467

Author: Lee-Si-Yoon

internal/agent/coordinator.go

@@ -252,6 +252,11 @@ func (c *coordinator) run(ctx context.Context, accept *AcceptedRun, sessionID st
 
 	mergedOptions, temp, topP, topK, freqPenalty, presPenalty := mergeCallOptions(model, providerCfg)
 
+	// Inject session_id for OpenRouter sticky routing and upstream session grouping.
+	if providerCfg.Type == openrouter.Name {
+		injectOpenrouterSessionID(mergedOptions, sessionID)
+	}
+
 	if err := c.refreshTokenIfExpired(ctx, providerCfg); err != nil {
 		// NOTE(@andreynering): We don't return here because the event handling to ask the user to reauthenticate
 		// depends on the flow below. If refresh fails, proceed with the token we have.
@@ -600,6 +605,19 @@ func getProviderOptions(model Model, providerCfg config.ProviderConfig) fantasy.
 	return options
 }
 
+// injectOpenrouterSessionID adds session_id to OpenRouter ProviderOptions
+// ExtraBody for sticky routing and upstream session grouping.
+func injectOpenrouterSessionID(opts fantasy.ProviderOptions, sessionID string) {
+	if o, ok := opts[openrouter.Name].(*openrouter.ProviderOptions); ok {
+		if o.ExtraBody == nil {
+			o.ExtraBody = make(map[string]any)
+		}
+		if _, exists := o.ExtraBody["session_id"]; !exists {
+			o.ExtraBody["session_id"] = session.HashID(sessionID)
+		}
+	}
+}
+
 func mergeCallOptions(model Model, cfg config.ProviderConfig) (fantasy.ProviderOptions, *float64, *float64, *int64, *float64, *float64) {
 	modelOptions := getProviderOptions(model, cfg)
 	temp := cmp.Or(model.ModelCfg.Temperature, model.CatwalkCfg.Options.Temperature)
@@ -941,6 +959,15 @@ func (c *coordinator) buildOpenaiProvider(baseURL, apiKey string, headers map[st
 }
 
 func (c *coordinator) buildOpenrouterProvider(_, apiKey string, headers map[string]string) (fantasy.Provider, error) {
+	if headers == nil {
+		headers = make(map[string]string)
+	}
+	if _, ok := headers["HTTP-Referer"]; !ok {
+		headers["HTTP-Referer"] = "https://charm.land/crush"
+	}
+	if _, ok := headers["X-Title"]; !ok {
+		headers["X-Title"] = "Crush"
+	}
 	opts := []openrouter.Option{
 		openrouter.WithAPIKey(apiKey),
 	}
@@ -1246,9 +1273,15 @@ func (c *coordinator) Summarize(ctx context.Context, sessionID string) error {
 		slog.Error("Failed to refresh OAuth2 token before summarize. Proceeding with existing token.", "error", err)
 	}
 
+	// Inject session_id for OpenRouter sticky routing.
+	opts := getProviderOptions(c.currentAgent.Model(), providerCfg)
+	if providerCfg.Type == openrouter.Name {
+		injectOpenrouterSessionID(opts, sessionID)
+	}
+
 	// Auth failures during summarize flow through fantasy's OnAuthRefresh,
 	// the same path used by regular turns.
-	return c.currentAgent.Summarize(ctx, sessionID, getProviderOptions(c.currentAgent.Model(), providerCfg), c.makeAuthRefreshCallback(providerCfg))
+	return c.currentAgent.Summarize(ctx, sessionID, opts, c.makeAuthRefreshCallback(providerCfg))
 }
 
 // GenerateTitle generates a session title using the current agent.
@@ -1427,13 +1460,19 @@ func (c *coordinator) runSubAgent(ctx context.Context, params subAgentParams) (f
 		return fantasy.ToolResponse{}, errModelProviderNotConfigured
 	}
 
+	// Inject session_id for OpenRouter sticky routing.
+	subOpts := getProviderOptions(model, providerCfg)
+	if providerCfg.Type == openrouter.Name {
+		injectOpenrouterSessionID(subOpts, session.ID)
+	}
+
 	// Run the agent
 	run := func() (*fantasy.AgentResult, error) {
 		return params.Agent.Run(ctx, SessionAgentCall{
 			SessionID:        session.ID,
 			Prompt:           params.Prompt,
 			MaxOutputTokens:  maxTokens,
-			ProviderOptions:  getProviderOptions(model, providerCfg),
+			ProviderOptions:  subOpts,
 			Temperature:      model.ModelCfg.Temperature,
 			TopP:             model.ModelCfg.TopP,
 			TopK:             model.ModelCfg.TopK,