feat: add native SAP AI Core support

Adds a new 'aicore' LLM provider that authenticates directly with SAP AI Core
using OAuth client credentials. This eliminates the need for an external proxy
(hai-aicore or hai) when running review-bot in SAP environments.

Key changes:
- New llm/aicore.go with AICoreClient for OAuth token management and
  deployment discovery
- Thread-safe token caching with automatic refresh before expiry
- Automatic routing to /invoke (Anthropic) or /chat/completions (OpenAI)
  based on model name
- New CLI flags: --aicore-client-id, --aicore-client-secret, --aicore-auth-url,
  --aicore-api-url, --aicore-resource-group
- Updated action.yml with corresponding inputs
- Comprehensive test coverage for AI Core client

Example usage in CI:
  llm-provider: aicore
  llm-model: anthropic--claude-4.6-sonnet
  aicore-client-id: ${{ secrets.AICORE_CLIENT_ID }}
  aicore-client-secret: ${{ secrets.AICORE_CLIENT_SECRET }}
  aicore-auth-url: ${{ secrets.AICORE_AUTH_URL }}
  aicore-api-url: ${{ secrets.AICORE_API_URL }}

Closes #49

llm/aicore.go

@@ -0,0 +1,368 @@
+package llm
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+)
+
+// AICoreConfig holds SAP AI Core authentication and connection settings.
+type AICoreConfig struct {
+	ClientID      string
+	ClientSecret  string
+	AuthURL       string
+	APIURL        string
+	ResourceGroup string
+}
+
+// AICoreClient wraps AI Core authentication and deployment discovery.
+// Thread-safe for concurrent use after construction.
+type AICoreClient struct {
+	config AICoreConfig
+	http   *http.Client
+
+	mu          sync.RWMutex
+	token       string
+	tokenExpiry time.Time
+	deployments map[string]deployment // model name -> deployment info
+}
+
+type deployment struct {
+	ID  string
+	URL string
+}
+
+// NewAICoreClient creates a new AI Core client with the given configuration.
+func NewAICoreClient(cfg AICoreConfig) *AICoreClient {
+	return &AICoreClient{
+		config:      cfg,
+		http:        &http.Client{Timeout: 30 * time.Second},
+		deployments: make(map[string]deployment),
+	}
+}
+
+// getToken returns a valid OAuth token, refreshing if necessary.
+func (c *AICoreClient) getToken(ctx context.Context) (string, error) {
+	c.mu.RLock()
+	if c.token != "" && time.Now().Add(5*time.Minute).Before(c.tokenExpiry) {
+		token := c.token
+		c.mu.RUnlock()
+		return token, nil
+	}
+	c.mu.RUnlock()
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	// Double-check after acquiring write lock
+	if c.token != "" && time.Now().Add(5*time.Minute).Before(c.tokenExpiry) {
+		return c.token, nil
+	}
+
+	token, expiry, err := c.fetchToken(ctx)
+	if err != nil {
+		return "", err
+	}
+	c.token = token
+	c.tokenExpiry = expiry
+	return token, nil
+}
+
+func (c *AICoreClient) fetchToken(ctx context.Context) (string, time.Time, error) {
+	tokenURL := strings.TrimRight(c.config.AuthURL, "/") + "/oauth/token"
+
+	data := url.Values{}
+	data.Set("grant_type", "client_credentials")
+	data.Set("client_id", c.config.ClientID)
+	data.Set("client_secret", c.config.ClientSecret)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tokenURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return "", time.Time{}, fmt.Errorf("create token request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return "", time.Time{}, fmt.Errorf("token request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", time.Time{}, fmt.Errorf("read token response: %w", err)
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return "", time.Time{}, fmt.Errorf("token request failed (status %d): %s", resp.StatusCode, string(body))
+	}
+
+	var tokenResp struct {
+		AccessToken string `json:"access_token"`
+		ExpiresIn   int    `json:"expires_in"`
+	}
+	if err := json.Unmarshal(body, &tokenResp); err != nil {
+		return "", time.Time{}, fmt.Errorf("parse token response: %w", err)
+	}
+
+	if tokenResp.AccessToken == "" {
+		return "", time.Time{}, fmt.Errorf("empty access token in response")
+	}
+
+	expiry := time.Now().Add(time.Duration(tokenResp.ExpiresIn) * time.Second)
+	return tokenResp.AccessToken, expiry, nil
+}
+
+// getDeploymentURL returns the deployment URL for a model, fetching deployments if needed.
+func (c *AICoreClient) getDeploymentURL(ctx context.Context, model string) (string, error) {
+	c.mu.RLock()
+	if d, ok := c.deployments[model]; ok {
+		c.mu.RUnlock()
+		return d.URL, nil
+	}
+	c.mu.RUnlock()
+
+	// Fetch token first (before acquiring write lock to avoid deadlock)
+	token, err := c.getToken(ctx)
+	if err != nil {
+		return "", fmt.Errorf("get token for deployments: %w", err)
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	// Double-check after acquiring write lock
+	if d, ok := c.deployments[model]; ok {
+		return d.URL, nil
+	}
+
+	if err := c.fetchDeployments(ctx, token); err != nil {
+		return "", err
+	}
+
+	if d, ok := c.deployments[model]; ok {
+		return d.URL, nil
+	}
+	return "", fmt.Errorf("no deployment found for model %q", model)
+}
+
+func (c *AICoreClient) fetchDeployments(ctx context.Context, token string) error {
+
+	deployURL := strings.TrimRight(c.config.APIURL, "/") + "/v2/lm/deployments"
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, deployURL, nil)
+	if err != nil {
+		return fmt.Errorf("create deployments request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+token)
+	req.Header.Set("AI-Resource-Group", c.config.ResourceGroup)
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return fmt.Errorf("deployments request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("read deployments response: %w", err)
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return fmt.Errorf("deployments request failed (status %d): %s", resp.StatusCode, string(body))
+	}
+
+	var deployResp struct {
+		Resources []struct {
+			ID               string `json:"id"`
+			DeploymentURL    string `json:"deploymentUrl"`
+			Status           string `json:"status"`
+			Details          struct {
+				Resources struct {
+					BackendDetails struct {
+						Model struct {
+							Name string `json:"name"`
+						} `json:"model"`
+					} `json:"backend_details"`
+				} `json:"resources"`
+			} `json:"details"`
+		} `json:"resources"`
+	}
+	if err := json.Unmarshal(body, &deployResp); err != nil {
+		return fmt.Errorf("parse deployments response: %w", err)
+	}
+
+	for _, r := range deployResp.Resources {
+		if r.Status != "RUNNING" {
+			continue
+		}
+		modelName := r.Details.Resources.BackendDetails.Model.Name
+		if modelName == "" {
+			continue
+		}
+		c.deployments[modelName] = deployment{
+			ID:  r.ID,
+			URL: r.DeploymentURL,
+		}
+	}
+
+	return nil
+}
+
+// CompleteAnthropic sends a request to an Anthropic model via AI Core.
+func (c *AICoreClient) CompleteAnthropic(ctx context.Context, model string, messages []Message, maxTokens int, temperature float64) (string, error) {
+	deployURL, err := c.getDeploymentURL(ctx, model)
+	if err != nil {
+		return "", err
+	}
+
+	token, err := c.getToken(ctx)
+	if err != nil {
+		return "", err
+	}
+
+	// Extract system message
+	var system string
+	var userMessages []anthropicMsg
+	for _, m := range messages {
+		if m.Role == "system" {
+			system = m.Content
+		} else {
+			userMessages = append(userMessages, anthropicMsg{
+				Role:    m.Role,
+				Content: m.Content,
+			})
+		}
+	}
+
+	reqBody := anthropicRequest{
+		Model:     model,
+		MaxTokens: maxTokens,
+		System:    system,
+		Messages:  userMessages,
+	}
+	if temperature > 0 {
+		reqBody.Temperature = temperature
+	}
+
+	data, err := json.Marshal(reqBody)
+	if err != nil {
+		return "", fmt.Errorf("marshal request: %w", err)
+	}
+
+	// AI Core uses /invoke for Anthropic models
+	invokeURL := strings.TrimRight(deployURL, "/") + "/invoke"
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, invokeURL, bytes.NewReader(data))
+	if err != nil {
+		return "", fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+token)
+	req.Header.Set("AI-Resource-Group", c.config.ResourceGroup)
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("AI Core request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("read response: %w", err)
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return "", fmt.Errorf("AI Core API error (status %d): %s", resp.StatusCode, string(body))
+	}
+
+	var anthropicResp anthropicResponse
+	if err := json.Unmarshal(body, &anthropicResp); err != nil {
+		return "", fmt.Errorf("parse response: %w", err)
+	}
+
+	if len(anthropicResp.Content) == 0 {
+		return "", fmt.Errorf("no content in response")
+	}
+
+	var sb strings.Builder
+	for _, block := range anthropicResp.Content {
+		if block.Type == "text" {
+			sb.WriteString(block.Text)
+		}
+	}
+	result := sb.String()
+	if result == "" {
+		return "", fmt.Errorf("no text content in response")
+	}
+	return result, nil
+}
+
+// CompleteOpenAI sends a request to an OpenAI model via AI Core.
+func (c *AICoreClient) CompleteOpenAI(ctx context.Context, model string, messages []Message, temperature float64) (string, error) {
+	deployURL, err := c.getDeploymentURL(ctx, model)
+	if err != nil {
+		return "", err
+	}
+
+	token, err := c.getToken(ctx)
+	if err != nil {
+		return "", err
+	}
+
+	reqBody := ChatRequest{
+		Model:       model,
+		Temperature: temperature,
+		Messages:    messages,
+	}
+
+	data, err := json.Marshal(reqBody)
+	if err != nil {
+		return "", fmt.Errorf("marshal request: %w", err)
+	}
+
+	// AI Core uses /chat/completions?api-version=2024-12-01-preview for OpenAI models
+	chatURL := strings.TrimRight(deployURL, "/") + "/chat/completions?api-version=2024-12-01-preview"
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, chatURL, bytes.NewReader(data))
+	if err != nil {
+		return "", fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+token)
+	req.Header.Set("AI-Resource-Group", c.config.ResourceGroup)
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("AI Core request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("read response: %w", err)
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return "", fmt.Errorf("AI Core API error (status %d): %s", resp.StatusCode, string(body))
+	}
+
+	var openaiResp ChatResponse
+	if err := json.Unmarshal(body, &openaiResp); err != nil {
+		return "", fmt.Errorf("parse response: %w", err)
+	}
+
+	if len(openaiResp.Choices) == 0 {
+		return "", fmt.Errorf("no choices in response")
+	}
+	return openaiResp.Choices[0].Message.Content, nil
+}
+
+// IsAnthropicModel returns true if the model name indicates an Anthropic model.
+func IsAnthropicModel(model string) bool {
+	return strings.HasPrefix(model, "anthropic--") || strings.Contains(model, "claude")
+}

llm/aicore_test.go

@@ -0,0 +1,477 @@
+package llm
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestAICoreClient_TokenFetch(t *testing.T) {
+	tokenCalls := int32(0)
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/oauth/token" {
+			atomic.AddInt32(&tokenCalls, 1)
+			if r.Method != http.MethodPost {
+				t.Errorf("expected POST for token, got %s", r.Method)
+			}
+			if r.Header.Get("Content-Type") != "application/x-www-form-urlencoded" {
+				t.Errorf("expected form content type")
+			}
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"access_token": "test-token-123",
+				"expires_in":   3600,
+			})
+			return
+		}
+		t.Errorf("unexpected path: %s", r.URL.Path)
+	}))
+	defer server.Close()
+
+	client := NewAICoreClient(AICoreConfig{
+		ClientID:      "test-id",
+		ClientSecret:  "test-secret",
+		AuthURL:       server.URL,
+		APIURL:        server.URL,
+		ResourceGroup: "default",
+	})
+
+	token, err := client.getToken(context.Background())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if token != "test-token-123" {
+		t.Errorf("expected token 'test-token-123', got %q", token)
+	}
+
+	// Second call should use cached token
+	token2, err := client.getToken(context.Background())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if token2 != "test-token-123" {
+		t.Errorf("expected cached token")
+	}
+	if atomic.LoadInt32(&tokenCalls) != 1 {
+		t.Errorf("expected 1 token call (cached), got %d", tokenCalls)
+	}
+}
+
+func TestAICoreClient_DeploymentFetch(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/oauth/token" {
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"access_token": "test-token",
+				"expires_in":   3600,
+			})
+			return
+		}
+		if r.URL.Path == "/v2/lm/deployments" {
+			if r.Header.Get("Authorization") != "Bearer test-token" {
+				t.Errorf("expected Bearer auth")
+			}
+			if r.Header.Get("AI-Resource-Group") != "default" {
+				t.Errorf("expected resource group header")
+			}
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"resources": []map[string]interface{}{
+					{
+						"id":            "deploy-123",
+						"deploymentUrl": "https://example.com/v2/inference/deployments/deploy-123",
+						"status":        "RUNNING",
+						"details": map[string]interface{}{
+							"resources": map[string]interface{}{
+								"backend_details": map[string]interface{}{
+									"model": map[string]interface{}{
+										"name": "anthropic--claude-4.6-sonnet",
+									},
+								},
+							},
+						},
+					},
+					{
+						"id":            "deploy-456",
+						"deploymentUrl": "https://example.com/v2/inference/deployments/deploy-456",
+						"status":        "STOPPED",
+						"details": map[string]interface{}{
+							"resources": map[string]interface{}{
+								"backend_details": map[string]interface{}{
+									"model": map[string]interface{}{
+										"name": "gpt-5",
+									},
+								},
+							},
+						},
+					},
+					{
+						"id":            "deploy-789",
+						"deploymentUrl": "https://example.com/v2/inference/deployments/deploy-789",
+						"status":        "RUNNING",
+						"details": map[string]interface{}{
+							"resources": map[string]interface{}{
+								"backend_details": map[string]interface{}{
+									"model": map[string]interface{}{
+										"name": "gpt-5",
+									},
+								},
+							},
+						},
+					},
+				},
+			})
+			return
+		}
+		t.Errorf("unexpected path: %s", r.URL.Path)
+	}))
+	defer server.Close()
+
+	client := NewAICoreClient(AICoreConfig{
+		ClientID:      "test-id",
+		ClientSecret:  "test-secret",
+		AuthURL:       server.URL,
+		APIURL:        server.URL,
+		ResourceGroup: "default",
+	})
+
+	// Should find running deployment
+	url, err := client.getDeploymentURL(context.Background(), "anthropic--claude-4.6-sonnet")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if url != "https://example.com/v2/inference/deployments/deploy-123" {
+		t.Errorf("unexpected URL: %s", url)
+	}
+
+	// Should find running gpt-5, not stopped one
+	url, err = client.getDeploymentURL(context.Background(), "gpt-5")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if url != "https://example.com/v2/inference/deployments/deploy-789" {
+		t.Errorf("unexpected URL: %s", url)
+	}
+
+	// Should error on unknown model
+	_, err = client.getDeploymentURL(context.Background(), "unknown-model")
+	if err == nil {
+		t.Error("expected error for unknown model")
+	}
+}
+
+func TestAICoreClient_CompleteAnthropic(t *testing.T) {
+	// Use a pointer to capture the server URL for use in the handler
+	var baseURL string
+	mux := http.NewServeMux()
+	mux.HandleFunc("/oauth/token", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"access_token": "test-token",
+			"expires_in":   3600,
+		})
+	})
+	mux.HandleFunc("/v2/lm/deployments", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"resources": []map[string]interface{}{
+				{
+					"id":            "deploy-anthropic",
+					"deploymentUrl": baseURL + "/deployments/anthropic",
+					"status":        "RUNNING",
+					"details": map[string]interface{}{
+						"resources": map[string]interface{}{
+							"backend_details": map[string]interface{}{
+								"model": map[string]interface{}{
+									"name": "anthropic--claude-4.6-sonnet",
+								},
+							},
+						},
+					},
+				},
+			},
+		})
+	})
+	mux.HandleFunc("/deployments/anthropic/invoke", func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Authorization") != "Bearer test-token" {
+			t.Errorf("expected Bearer auth on invoke")
+		}
+		var req anthropicRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			t.Fatalf("decode request: %v", err)
+		}
+		if req.Model != "anthropic--claude-4.6-sonnet" {
+			t.Errorf("expected model name in request")
+		}
+		if req.System != "You are helpful" {
+			t.Errorf("expected system prompt: %q", req.System)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"content": []map[string]interface{}{
+				{"type": "text", "text": "Hello from AI Core!"},
+			},
+		})
+	})
+
+	server := httptest.NewServer(mux)
+	baseURL = server.URL
+	defer server.Close()
+
+	client := NewAICoreClient(AICoreConfig{
+		ClientID:      "test-id",
+		ClientSecret:  "test-secret",
+		AuthURL:       server.URL,
+		APIURL:        server.URL,
+		ResourceGroup: "default",
+	})
+
+	result, err := client.CompleteAnthropic(context.Background(), "anthropic--claude-4.6-sonnet", []Message{
+		{Role: "system", Content: "You are helpful"},
+		{Role: "user", Content: "Hello"},
+	}, 8192, 0)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result != "Hello from AI Core!" {
+		t.Errorf("expected 'Hello from AI Core!', got %q", result)
+	}
+}
+
+func TestAICoreClient_CompleteOpenAI(t *testing.T) {
+	var baseURL string
+	mux := http.NewServeMux()
+	mux.HandleFunc("/oauth/token", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"access_token": "test-token",
+			"expires_in":   3600,
+		})
+	})
+	mux.HandleFunc("/v2/lm/deployments", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"resources": []map[string]interface{}{
+				{
+					"id":            "deploy-openai",
+					"deploymentUrl": baseURL + "/deployments/openai",
+					"status":        "RUNNING",
+					"details": map[string]interface{}{
+						"resources": map[string]interface{}{
+							"backend_details": map[string]interface{}{
+								"model": map[string]interface{}{
+									"name": "gpt-5",
+								},
+							},
+						},
+					},
+				},
+			},
+		})
+	})
+	mux.HandleFunc("/deployments/openai/chat/completions", func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Query().Get("api-version") != "2024-12-01-preview" {
+			t.Errorf("expected api-version query param")
+		}
+		var req ChatRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			t.Fatalf("decode request: %v", err)
+		}
+		if req.Model != "gpt-5" {
+			t.Errorf("expected model gpt-5, got %s", req.Model)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(ChatResponse{
+			Choices: []struct {
+				Message struct {
+					Content string `json:"content"`
+				} `json:"message"`
+			}{
+				{Message: struct {
+					Content string `json:"content"`
+				}{Content: "Hello from GPT-5!"}},
+			},
+		})
+	})
+
+	server := httptest.NewServer(mux)
+	baseURL = server.URL
+	defer server.Close()
+
+	client := NewAICoreClient(AICoreConfig{
+		ClientID:      "test-id",
+		ClientSecret:  "test-secret",
+		AuthURL:       server.URL,
+		APIURL:        server.URL,
+		ResourceGroup: "default",
+	})
+
+	result, err := client.CompleteOpenAI(context.Background(), "gpt-5", []Message{
+		{Role: "user", Content: "Hello"},
+	}, 0)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result != "Hello from GPT-5!" {
+		t.Errorf("expected 'Hello from GPT-5!', got %q", result)
+	}
+}
+
+func TestIsAnthropicModel(t *testing.T) {
+	tests := []struct {
+		model    string
+		expected bool
+	}{
+		{"anthropic--claude-4.6-sonnet", true},
+		{"anthropic--claude-4.6-opus", true},
+		{"claude-sonnet-4", true},
+		{"gpt-5", false},
+		{"gpt-4.1", false},
+		{"llama-3", false},
+	}
+
+	for _, tt := range tests {
+		got := IsAnthropicModel(tt.model)
+		if got != tt.expected {
+			t.Errorf("IsAnthropicModel(%q) = %v, want %v", tt.model, got, tt.expected)
+		}
+	}
+}
+
+func TestAICoreClient_TokenExpiry(t *testing.T) {
+	tokenCalls := int32(0)
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/oauth/token" {
+			call := atomic.AddInt32(&tokenCalls, 1)
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"access_token": "token-" + string(rune('0'+call)),
+				"expires_in":   1, // 1 second expiry
+			})
+			return
+		}
+	}))
+	defer server.Close()
+
+	client := NewAICoreClient(AICoreConfig{
+		ClientID:      "test-id",
+		ClientSecret:  "test-secret",
+		AuthURL:       server.URL,
+		APIURL:        server.URL,
+		ResourceGroup: "default",
+	})
+
+	// First call
+	token1, _ := client.getToken(context.Background())
+
+	// Force token expiry by manipulating expiry time
+	client.mu.Lock()
+	client.tokenExpiry = time.Now().Add(-time.Hour)
+	client.mu.Unlock()
+
+	// Should fetch new token
+	token2, _ := client.getToken(context.Background())
+
+	if token1 == token2 {
+		t.Error("expected different tokens after expiry")
+	}
+	if atomic.LoadInt32(&tokenCalls) != 2 {
+		t.Errorf("expected 2 token calls, got %d", tokenCalls)
+	}
+}
+
+func TestClient_WithAICore(t *testing.T) {
+	client := NewClient("http://example.com", "key", "model")
+	if client.provider != ProviderOpenAI {
+		t.Errorf("expected default provider openai, got %s", client.provider)
+	}
+
+	client.WithAICore(AICoreConfig{
+		ClientID:      "id",
+		ClientSecret:  "secret",
+		AuthURL:       "https://auth.example.com",
+		APIURL:        "https://api.example.com",
+		ResourceGroup: "default",
+	})
+
+	if client.provider != ProviderAICore {
+		t.Errorf("expected provider aicore, got %s", client.provider)
+	}
+	if client.aicore == nil {
+		t.Error("expected aicore client to be set")
+	}
+}
+
+func TestClient_CompleteAICore(t *testing.T) {
+	var baseURL string
+	mux := http.NewServeMux()
+	mux.HandleFunc("/oauth/token", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"access_token": "test-token",
+			"expires_in":   3600,
+		})
+	})
+	mux.HandleFunc("/v2/lm/deployments", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"resources": []map[string]interface{}{
+				{
+					"id":            "deploy-test",
+					"deploymentUrl": baseURL + "/deployments/test",
+					"status":        "RUNNING",
+					"details": map[string]interface{}{
+						"resources": map[string]interface{}{
+							"backend_details": map[string]interface{}{
+								"model": map[string]interface{}{
+									"name": "gpt-5",
+								},
+							},
+						},
+					},
+				},
+			},
+		})
+	})
+	mux.HandleFunc("/deployments/test/chat/completions", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(ChatResponse{
+			Choices: []struct {
+				Message struct {
+					Content string `json:"content"`
+				} `json:"message"`
+			}{
+				{Message: struct {
+					Content string `json:"content"`
+				}{Content: "AI Core via Client works!"}},
+			},
+		})
+	})
+
+	server := httptest.NewServer(mux)
+	baseURL = server.URL
+	defer server.Close()
+
+	client := NewClient("", "", "gpt-5").WithAICore(AICoreConfig{
+		ClientID:      "test-id",
+		ClientSecret:  "test-secret",
+		AuthURL:       server.URL,
+		APIURL:        server.URL,
+		ResourceGroup: "default",
+	})
+
+	result, err := client.Complete(context.Background(), []Message{
+		{Role: "user", Content: "Hello"},
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !strings.Contains(result, "AI Core via Client works!") {
+		t.Errorf("unexpected result: %s", result)
+	}
+}

llm/client.go

@@ -1,6 +1,6 @@
 // Package llm provides clients for LLM chat completion APIs.
 //
-// Supports OpenAI-compatible (default) and Anthropic Messages API providers.
+// Supports OpenAI-compatible (default), Anthropic Messages API, and SAP AI Core providers.
 package llm
 
 import (
@@ -22,6 +22,8 @@ const (
 	ProviderOpenAI Provider = "openai"
 	// ProviderAnthropic uses the Anthropic Messages API endpoint.
 	ProviderAnthropic Provider = "anthropic"
+	// ProviderAICore uses SAP AI Core with OAuth authentication.
+	ProviderAICore Provider = "aicore"
 )
 
 // Client calls an LLM chat completion API.
@@ -35,6 +37,7 @@ type Client struct {
 	temperature float64
 	provider    Provider
 	http        *http.Client
+	aicore      *AICoreClient // Only set when provider is aicore
 }
 
 // NewClient creates a new LLM client. Default provider is OpenAI-compatible.
@@ -60,12 +63,20 @@ func (c *Client) WithTemperature(t float64) *Client {
 	return c
 }
 
-// WithProvider sets the API provider format (openai or anthropic).
+// WithProvider sets the API provider format (openai, anthropic, or aicore).
 func (c *Client) WithProvider(p Provider) *Client {
 	c.provider = p
 	return c
 }
 
+// WithAICore configures the client to use SAP AI Core for authentication.
+// This sets the provider to aicore automatically.
+func (c *Client) WithAICore(cfg AICoreConfig) *Client {
+	c.provider = ProviderAICore
+	c.aicore = NewAICoreClient(cfg)
+	return c
+}
+
 // Message represents a chat message.
 type Message struct {
 	Role    string `json:"role"`
@@ -82,6 +93,8 @@ func (c *Client) Complete(ctx context.Context, messages []Message) (string, erro
 		switch c.provider {
 		case ProviderAnthropic:
 			result, err = c.completeAnthropic(ctx, messages)
+		case ProviderAICore:
+			result, err = c.completeAICore(ctx, messages)
 		default:
 			result, err = c.completeOpenAI(ctx, messages)
 		}
@@ -106,6 +119,18 @@ func (c *Client) Complete(ctx context.Context, messages []Message) (string, erro
 	return "", err
 }
 
+// completeAICore routes to AI Core using the appropriate endpoint based on model type.
+func (c *Client) completeAICore(ctx context.Context, messages []Message) (string, error) {
+	if c.aicore == nil {
+		return "", fmt.Errorf("AI Core client not configured")
+	}
+
+	if IsAnthropicModel(c.model) {
+		return c.aicore.CompleteAnthropic(ctx, c.model, messages, 8192, c.temperature)
+	}
+	return c.aicore.CompleteOpenAI(ctx, c.model, messages, c.temperature)
+}
+
 // isRetryableError returns true for transient errors worth retrying.
 func isRetryableError(err error) bool {
 	if err == nil {