diff --git a/workspace-server/internal/handlers/llm_billing_mode_provision_parity_test.go b/workspace-server/internal/handlers/llm_billing_mode_provision_parity_test.go
index 13b60dd6..50d5f9fa 100644
--- a/workspace-server/internal/handlers/llm_billing_mode_provision_parity_test.go
+++ b/workspace-server/internal/handlers/llm_billing_mode_provision_parity_test.go
@@ -446,3 +446,42 @@ func TestApplyPlatformManagedLLMEnv_ProxyEnvPresentInjectsCredential(t *testing.
 		t.Errorf("sqlmock expectations: %v", err)
 	}
 }
+
+// TestApplyPlatformManagedLLMEnv_BYOKMiniMaxWorkspaceOverrideProjectsCreds is
+// core#2712: a claude-code workspace with an explicit per-workspace BYOK
+// override and a stored MiniMax model must still project ANTHROPIC_AUTH_TOKEN
+// and ANTHROPIC_BASE_URL from MINIMAX_API_KEY.
+//
+// ResolveLLMBillingModeDerived returns early on a workspace_override with
+// ProviderSelection=nil. Without a fallback derivation here, the core#2709
+// projection block would skip because providerFromRegistry("") fails, leaving
+// the Anthropic SDK adapter credential-less after restart.
+func TestApplyPlatformManagedLLMEnv_BYOKMiniMaxWorkspaceOverrideProjectsCreds(t *testing.T) {
+	ctx := context.Background()
+	const wsID = "b4914c3d-7ce0-4e14-aa32-02da048e2ae7"
+
+	mock := setupTestDB(t)
+	expectOverrideQuery(mock, wsID, LLMBillingModeBYOK)
+
+	envVars := map[string]string{
+		"MODEL":           "MiniMax-M2.7",
+		"MINIMAX_API_KEY": "real-minimax-key",
+	}
+	res := applyPlatformManagedLLMEnv(ctx, envVars, wsID, "claude-code", "", nil)
+
+	if res.ResolvedMode != LLMBillingModeBYOK {
+		t.Fatalf("resolved mode = %q, want byok", res.ResolvedMode)
+	}
+	if got := envVars["ANTHROPIC_AUTH_TOKEN"]; got != "real-minimax-key" {
+		t.Fatalf("ANTHROPIC_AUTH_TOKEN = %q, want real-minimax-key", got)
+	}
+	if got := envVars["ANTHROPIC_BASE_URL"]; got != "https://api.minimax.io/anthropic/v1" {
+		t.Fatalf("ANTHROPIC_BASE_URL = %q, want https://api.minimax.io/anthropic/v1", got)
+	}
+	if got := envVars["MINIMAX_API_KEY"]; got != "real-minimax-key" {
+		t.Fatalf("MINIMAX_API_KEY was overwritten: %q", got)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
diff --git a/workspace-server/internal/handlers/workspace_provision.go b/workspace-server/internal/handlers/workspace_provision.go
index 9fde21bd..e99ae47e 100644
--- a/workspace-server/internal/handlers/workspace_provision.go
+++ b/workspace-server/internal/handlers/workspace_provision.go
@@ -1170,7 +1170,20 @@ func applyPlatformManagedLLMEnv(ctx context.Context, envVars map[string]string,
 		// restart. Project the provider's preferred auth token env and Anthropic
 		// base URL from the workspace's available provider credential.
 		if res.ResolvedMode == LLMBillingModeBYOK && runtimeUsesAnthropicNativeProxy(runtime) {
-			if provider, ok := providerFromRegistry(derefOrEmpty(res.ProviderSelection)); ok && provider.AuthTokenEnv != "" {
+			providerName := derefOrEmpty(res.ProviderSelection)
+			// core#2712: a per-workspace billing-mode override (source=workspace_override)
+			// short-circuits ResolveLLMBillingModeDerived before it sets ProviderSelection,
+			// but the Anthropic-adapter projection still needs to know WHICH BYOK
+			// provider the workspace is running so it can map MINIMAX_API_KEY (etc.)
+			// to ANTHROPIC_AUTH_TOKEN. Derive it from the effective model when missing.
+			if providerName == "" && effectiveModel != "" {
+				if manifest, mErr := providerRegistry(); mErr == nil && manifest != nil {
+					if p, dErr := manifest.DeriveProvider(runtime, effectiveModel, availableAuthEnv); dErr == nil {
+						providerName = p.Name
+					}
+				}
+			}
+			if provider, ok := providerFromRegistry(providerName); ok && provider.AuthTokenEnv != "" {
 				if _, hasToken := envVars[provider.AuthTokenEnv]; !hasToken {
 					for _, authEnv := range provider.AuthEnv {
 						if v := strings.TrimSpace(envVars[authEnv]); v != "" {