feat: AI-powered features — document drafting, case strategy, similar case finder (P2)

Backend:
- DraftDocument: Claude generates legal documents from case data + template type
  (14 template types: Klageschrift, UPC claims, Abmahnung, etc.)
- CaseStrategy: Opus-powered strategic analysis with next steps, risk assessment,
  and timeline optimization (structured tool output)
- FindSimilarCases: queries youpc.org Supabase for UPC cases, Claude ranks by
  relevance with explanations and key holdings

Endpoints: POST /api/ai/draft-document, /case-strategy, /similar-cases
All rate-limited (5 req/min) and permission-gated (PermAIExtraction).
YouPC database connection is optional (YOUPC_DATABASE_URL env var).

backend/cmd/server/main.go

@@ -5,6 +5,9 @@ import (
 	"net/http"
 	"os"
 
+	"github.com/jmoiron/sqlx"
+	_ "github.com/lib/pq"
+
 	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
 	"mgit.msbls.de/m/KanzlAI-mGMT/internal/config"
 	"mgit.msbls.de/m/KanzlAI-mGMT/internal/db"
@@ -31,6 +34,21 @@ func main() {
 
 	authMW := auth.NewMiddleware(cfg.SupabaseJWTSecret, database)
 
+	// Optional: connect to youpc.org database for similar case finder
+	var youpcDB *sqlx.DB
+	if cfg.YouPCDatabaseURL != "" {
+		youpcDB, err = sqlx.Connect("postgres", cfg.YouPCDatabaseURL)
+		if err != nil {
+			slog.Warn("failed to connect to youpc.org database — similar case finder disabled", "error", err)
+			youpcDB = nil
+		} else {
+			youpcDB.SetMaxOpenConns(5)
+			youpcDB.SetMaxIdleConns(2)
+			defer youpcDB.Close()
+			slog.Info("connected to youpc.org database for similar case finder")
+		}
+	}
+
 	// Start CalDAV sync service
 	calDAVSvc := services.NewCalDAVService(database)
 	calDAVSvc.Start()
@@ -41,7 +59,7 @@ func main() {
 	notifSvc.Start()
 	defer notifSvc.Stop()
 
-	handler := router.New(database, authMW, cfg, calDAVSvc, notifSvc)
+	handler := router.New(database, authMW, cfg, calDAVSvc, notifSvc, youpcDB)
 
 	slog.Info("starting KanzlAI API server", "port", cfg.Port)
 	if err := http.ListenAndServe(":"+cfg.Port, handler); err != nil {

backend/internal/config/config.go

@@ -14,6 +14,7 @@ type Config struct {
 	SupabaseJWTSecret string
 	AnthropicAPIKey   string
 	FrontendOrigin    string
+	YouPCDatabaseURL  string // read-only connection to youpc.org Supabase for similar case finder
 }
 
 func Load() (*Config, error) {
@@ -26,6 +27,7 @@ func Load() (*Config, error) {
 		SupabaseJWTSecret: os.Getenv("SUPABASE_JWT_SECRET"),
 		AnthropicAPIKey:  os.Getenv("ANTHROPIC_API_KEY"),
 		FrontendOrigin:   getEnv("FRONTEND_ORIGIN", "https://kanzlai.msbls.de"),
+		YouPCDatabaseURL: os.Getenv("YOUPC_DATABASE_URL"),
 	}
 
 	if cfg.DatabaseURL == "" {

backend/internal/handlers/ai.go

@@ -5,6 +5,8 @@ import (
 	"io"
 	"net/http"
 
+	"github.com/google/uuid"
+
 	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
 	"mgit.msbls.de/m/KanzlAI-mGMT/internal/services"
 )
@@ -115,3 +117,139 @@ func (h *AIHandler) SummarizeCase(w http.ResponseWriter, r *http.Request) {
 		"summary": summary,
 	})
 }
+
+// DraftDocument handles POST /api/ai/draft-document
+// Accepts JSON {"case_id": "uuid", "template_type": "string", "instructions": "string", "language": "de|en|fr"}.
+func (h *AIHandler) DraftDocument(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	var body struct {
+		CaseID       string `json:"case_id"`
+		TemplateType string `json:"template_type"`
+		Instructions string `json:"instructions"`
+		Language     string `json:"language"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+
+	if body.CaseID == "" {
+		writeError(w, http.StatusBadRequest, "case_id is required")
+		return
+	}
+	if body.TemplateType == "" {
+		writeError(w, http.StatusBadRequest, "template_type is required")
+		return
+	}
+
+	caseID, err := parseUUID(body.CaseID)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid case_id")
+		return
+	}
+
+	if len(body.Instructions) > maxDescriptionLen {
+		writeError(w, http.StatusBadRequest, "instructions exceeds maximum length")
+		return
+	}
+
+	draft, err := h.ai.DraftDocument(r.Context(), tenantID, caseID, body.TemplateType, body.Instructions, body.Language)
+	if err != nil {
+		internalError(w, "AI document drafting failed", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, draft)
+}
+
+// CaseStrategy handles POST /api/ai/case-strategy
+// Accepts JSON {"case_id": "uuid"}.
+func (h *AIHandler) CaseStrategy(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	var body struct {
+		CaseID string `json:"case_id"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+
+	if body.CaseID == "" {
+		writeError(w, http.StatusBadRequest, "case_id is required")
+		return
+	}
+
+	caseID, err := parseUUID(body.CaseID)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid case_id")
+		return
+	}
+
+	strategy, err := h.ai.CaseStrategy(r.Context(), tenantID, caseID)
+	if err != nil {
+		internalError(w, "AI case strategy analysis failed", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, strategy)
+}
+
+// SimilarCases handles POST /api/ai/similar-cases
+// Accepts JSON {"case_id": "uuid", "description": "string"}.
+func (h *AIHandler) SimilarCases(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	var body struct {
+		CaseID      string `json:"case_id"`
+		Description string `json:"description"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+
+	if body.CaseID == "" && body.Description == "" {
+		writeError(w, http.StatusBadRequest, "either case_id or description is required")
+		return
+	}
+
+	if len(body.Description) > maxDescriptionLen {
+		writeError(w, http.StatusBadRequest, "description exceeds maximum length")
+		return
+	}
+
+	var caseID uuid.UUID
+	if body.CaseID != "" {
+		var err error
+		caseID, err = parseUUID(body.CaseID)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid case_id")
+			return
+		}
+	}
+
+	cases, err := h.ai.FindSimilarCases(r.Context(), tenantID, caseID, body.Description)
+	if err != nil {
+		internalError(w, "AI similar case search failed", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"cases": cases,
+		"count": len(cases),
+	})
+}

backend/internal/services/ai_service.go

@@ -5,6 +5,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/anthropics/anthropic-sdk-go"
@@ -18,11 +19,12 @@ import (
 type AIService struct {
 	client anthropic.Client
 	db     *sqlx.DB
+	youpcDB *sqlx.DB // read-only connection to youpc.org for similar case finder (may be nil)
 }
 
-func NewAIService(apiKey string, db *sqlx.DB) *AIService {
+func NewAIService(apiKey string, db *sqlx.DB, youpcDB *sqlx.DB) *AIService {
 	client := anthropic.NewClient(option.WithAPIKey(apiKey))
-	return &AIService{client: client, db: db}
+	return &AIService{client: client, db: db, youpcDB: youpcDB}
 }
 
 // ExtractedDeadline represents a deadline extracted by AI from a document.
@@ -281,3 +283,726 @@ func (s *AIService) SummarizeCase(ctx context.Context, tenantID, caseID uuid.UUI
 
 	return summary, nil
 }
+
+// --- Document Drafting ---
+
+// DocumentDraft represents an AI-generated document draft.
+type DocumentDraft struct {
+	Title    string `json:"title"`
+	Content  string `json:"content"`
+	Language string `json:"language"`
+}
+
+// templateDescriptions maps template type IDs to descriptions for Claude.
+var templateDescriptions = map[string]string{
+	"klageschrift":      "Klageschrift (Statement of Claim) — formal complaint initiating legal proceedings",
+	"klageerwiderung":   "Klageerwiderung (Statement of Defence) — formal response to a statement of claim",
+	"abmahnung":         "Abmahnung (Cease and Desist Letter) — formal warning letter demanding cessation of an activity",
+	"schriftsatz":       "Schriftsatz (Legal Brief) — formal legal submission to the court",
+	"berufung":          "Berufungsschrift (Appeal Brief) — formal appeal against a court decision",
+	"antrag":            "Antrag (Motion/Application) — formal application or motion to the court",
+	"stellungnahme":     "Stellungnahme (Statement/Position Paper) — formal response or position paper",
+	"gutachten":         "Gutachten (Legal Opinion/Expert Report) — detailed legal analysis or opinion",
+	"vertrag":           "Vertrag (Contract/Agreement) — legal contract or agreement between parties",
+	"vollmacht":         "Vollmacht (Power of Attorney) — formal authorization document",
+	"upc_claim":         "UPC Statement of Claim — claim filed at the Unified Patent Court",
+	"upc_defence":       "UPC Statement of Defence — defence filed at the Unified Patent Court",
+	"upc_counterclaim":  "UPC Counterclaim for Revocation — counterclaim for patent revocation at the UPC",
+	"upc_injunction":    "UPC Application for Provisional Measures — application for injunctive relief at the UPC",
+}
+
+const draftDocumentSystemPrompt = `You are an expert legal document drafter for German and UPC (Unified Patent Court) patent litigation.
+
+You draft professional legal documents in the requested language, following proper legal formatting conventions.
+
+Guidelines:
+- Use proper legal structure with numbered sections and paragraphs
+- Include standard legal formalities (headers, salutations, signatures block)
+- Reference relevant legal provisions (BGB, ZPO, UPC Rules of Procedure, etc.)
+- Use precise legal terminology appropriate for the jurisdiction
+- Include placeholders in [BRACKETS] for information that needs to be filled in
+- Base the content on the provided case data and instructions
+- Output the document as clean text with proper formatting`
+
+// DraftDocument generates an AI-drafted legal document based on case data and a template type.
+func (s *AIService) DraftDocument(ctx context.Context, tenantID, caseID uuid.UUID, templateType, instructions, language string) (*DocumentDraft, error) {
+	if language == "" {
+		language = "de"
+	}
+
+	langLabel := "German"
+	if language == "en" {
+		langLabel = "English"
+	} else if language == "fr" {
+		langLabel = "French"
+	}
+
+	// Load case data
+	var c models.Case
+	if err := s.db.GetContext(ctx, &c,
+		"SELECT * FROM cases WHERE id = $1 AND tenant_id = $2", caseID, tenantID); err != nil {
+		return nil, fmt.Errorf("loading case: %w", err)
+	}
+
+	// Load parties
+	var parties []models.Party
+	_ = s.db.SelectContext(ctx, &parties,
+		"SELECT * FROM parties WHERE case_id = $1 AND tenant_id = $2", caseID, tenantID)
+
+	// Load recent events
+	var events []models.CaseEvent
+	_ = s.db.SelectContext(ctx, &events,
+		"SELECT * FROM case_events WHERE case_id = $1 AND tenant_id = $2 ORDER BY created_at DESC LIMIT 15",
+		caseID, tenantID)
+
+	// Load active deadlines
+	var deadlines []models.Deadline
+	_ = s.db.SelectContext(ctx, &deadlines,
+		"SELECT * FROM deadlines WHERE case_id = $1 AND tenant_id = $2 AND status = 'active' ORDER BY due_date ASC LIMIT 10",
+		caseID, tenantID)
+
+	// Load documents metadata for context
+	var documents []models.Document
+	_ = s.db.SelectContext(ctx, &documents,
+		"SELECT id, title, doc_type, created_at FROM documents WHERE case_id = $1 AND tenant_id = $2 ORDER BY created_at DESC LIMIT 10",
+		caseID, tenantID)
+
+	// Build context
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf("Case: %s — %s\nStatus: %s\n", c.CaseNumber, c.Title, c.Status))
+	if c.Court != nil {
+		b.WriteString(fmt.Sprintf("Court: %s\n", *c.Court))
+	}
+	if c.CourtRef != nil {
+		b.WriteString(fmt.Sprintf("Court Reference: %s\n", *c.CourtRef))
+	}
+	if c.CaseType != nil {
+		b.WriteString(fmt.Sprintf("Type: %s\n", *c.CaseType))
+	}
+
+	if len(parties) > 0 {
+		b.WriteString("\nParties:\n")
+		for _, p := range parties {
+			role := "unknown role"
+			if p.Role != nil {
+				role = *p.Role
+			}
+			b.WriteString(fmt.Sprintf("- %s (%s)", p.Name, role))
+			if p.Representative != nil {
+				b.WriteString(fmt.Sprintf(" — represented by %s", *p.Representative))
+			}
+			b.WriteString("\n")
+		}
+	}
+
+	if len(events) > 0 {
+		b.WriteString("\nRecent Events:\n")
+		for _, e := range events {
+			b.WriteString(fmt.Sprintf("- [%s] %s", e.CreatedAt.Format("2006-01-02"), e.Title))
+			if e.Description != nil {
+				b.WriteString(fmt.Sprintf(": %s", *e.Description))
+			}
+			b.WriteString("\n")
+		}
+	}
+
+	if len(deadlines) > 0 {
+		b.WriteString("\nUpcoming Deadlines:\n")
+		for _, d := range deadlines {
+			b.WriteString(fmt.Sprintf("- %s: due %s\n", d.Title, d.DueDate))
+		}
+	}
+
+	templateDesc, ok := templateDescriptions[templateType]
+	if !ok {
+		templateDesc = templateType
+	}
+
+	prompt := fmt.Sprintf(`Draft a %s for this case in %s.
+
+Document type: %s
+
+Case context:
+%s
+Additional instructions from the lawyer:
+%s
+
+Generate the complete document now.`, templateDesc, langLabel, templateDesc, b.String(), instructions)
+
+	msg, err := s.client.Messages.New(ctx, anthropic.MessageNewParams{
+		Model:     anthropic.ModelClaudeSonnet4_20250514,
+		MaxTokens: 8192,
+		System: []anthropic.TextBlockParam{
+			{Text: draftDocumentSystemPrompt},
+		},
+		Messages: []anthropic.MessageParam{
+			anthropic.NewUserMessage(anthropic.NewTextBlock(prompt)),
+		},
+	})
+	if err != nil {
+		return nil, fmt.Errorf("claude API call: %w", err)
+	}
+
+	var content string
+	for _, block := range msg.Content {
+		if block.Type == "text" {
+			content += block.Text
+		}
+	}
+	if content == "" {
+		return nil, fmt.Errorf("empty response from Claude")
+	}
+
+	title := fmt.Sprintf("%s — %s", templateDesc, c.CaseNumber)
+	return &DocumentDraft{
+		Title:    title,
+		Content:  content,
+		Language: language,
+	}, nil
+}
+
+// --- Case Strategy ---
+
+// StrategyRecommendation represents an AI-generated case strategy analysis.
+type StrategyRecommendation struct {
+	Summary        string           `json:"summary"`
+	NextSteps      []StrategyStep   `json:"next_steps"`
+	RiskAssessment []RiskItem       `json:"risk_assessment"`
+	Timeline       []TimelineItem   `json:"timeline"`
+}
+
+type StrategyStep struct {
+	Priority    string `json:"priority"` // high, medium, low
+	Action      string `json:"action"`
+	Reasoning   string `json:"reasoning"`
+	Deadline    string `json:"deadline,omitempty"`
+}
+
+type RiskItem struct {
+	Level       string `json:"level"` // high, medium, low
+	Risk        string `json:"risk"`
+	Mitigation  string `json:"mitigation"`
+}
+
+type TimelineItem struct {
+	Date        string `json:"date"`
+	Event       string `json:"event"`
+	Importance  string `json:"importance"` // critical, important, routine
+}
+
+type strategyToolInput struct {
+	Summary        string         `json:"summary"`
+	NextSteps      []StrategyStep `json:"next_steps"`
+	RiskAssessment []RiskItem     `json:"risk_assessment"`
+	Timeline       []TimelineItem `json:"timeline"`
+}
+
+var caseStrategyTool = anthropic.ToolParam{
+	Name:        "case_strategy",
+	Description: anthropic.String("Provide strategic case analysis with next steps, risk assessment, and timeline optimization."),
+	InputSchema: anthropic.ToolInputSchemaParam{
+		Properties: map[string]any{
+			"summary": map[string]any{
+				"type":        "string",
+				"description": "Executive summary of the case situation and strategic outlook (2-4 sentences)",
+			},
+			"next_steps": map[string]any{
+				"type":        "array",
+				"description": "Recommended next actions in priority order",
+				"items": map[string]any{
+					"type": "object",
+					"properties": map[string]any{
+						"priority": map[string]any{
+							"type": "string",
+							"enum": []string{"high", "medium", "low"},
+						},
+						"action": map[string]any{
+							"type":        "string",
+							"description": "Specific recommended action",
+						},
+						"reasoning": map[string]any{
+							"type":        "string",
+							"description": "Why this action is recommended",
+						},
+						"deadline": map[string]any{
+							"type":        "string",
+							"description": "Suggested deadline in YYYY-MM-DD format, if applicable",
+						},
+					},
+					"required": []string{"priority", "action", "reasoning"},
+				},
+			},
+			"risk_assessment": map[string]any{
+				"type":        "array",
+				"description": "Key risks and mitigation strategies",
+				"items": map[string]any{
+					"type": "object",
+					"properties": map[string]any{
+						"level": map[string]any{
+							"type": "string",
+							"enum": []string{"high", "medium", "low"},
+						},
+						"risk": map[string]any{
+							"type":        "string",
+							"description": "Description of the risk",
+						},
+						"mitigation": map[string]any{
+							"type":        "string",
+							"description": "Recommended mitigation strategy",
+						},
+					},
+					"required": []string{"level", "risk", "mitigation"},
+				},
+			},
+			"timeline": map[string]any{
+				"type":        "array",
+				"description": "Optimized timeline of upcoming milestones and events",
+				"items": map[string]any{
+					"type": "object",
+					"properties": map[string]any{
+						"date": map[string]any{
+							"type":        "string",
+							"description": "Date in YYYY-MM-DD format",
+						},
+						"event": map[string]any{
+							"type":        "string",
+							"description": "Description of the milestone or event",
+						},
+						"importance": map[string]any{
+							"type": "string",
+							"enum": []string{"critical", "important", "routine"},
+						},
+					},
+					"required": []string{"date", "event", "importance"},
+				},
+			},
+		},
+		Required: []string{"summary", "next_steps", "risk_assessment", "timeline"},
+	},
+}
+
+const caseStrategySystemPrompt = `You are a senior litigation strategist specializing in German law and UPC (Unified Patent Court) patent proceedings.
+
+Analyze the case thoroughly and provide:
+1. An executive summary of the current strategic position
+2. Prioritized next steps with clear reasoning
+3. Risk assessment with mitigation strategies
+4. An optimized timeline of upcoming milestones
+
+Consider:
+- Procedural deadlines and their implications
+- Strength of the parties' positions based on available information
+- Potential settlement opportunities
+- Cost-efficiency of different strategic approaches
+- UPC-specific procedural peculiarities if applicable (bifurcation, preliminary injunctions, etc.)
+
+Be practical and actionable. Avoid generic advice — tailor recommendations to the specific case data provided.`
+
+// CaseStrategy analyzes a case and returns strategic recommendations.
+func (s *AIService) CaseStrategy(ctx context.Context, tenantID, caseID uuid.UUID) (*StrategyRecommendation, error) {
+	// Load case
+	var c models.Case
+	if err := s.db.GetContext(ctx, &c,
+		"SELECT * FROM cases WHERE id = $1 AND tenant_id = $2", caseID, tenantID); err != nil {
+		return nil, fmt.Errorf("loading case: %w", err)
+	}
+
+	// Load parties
+	var parties []models.Party
+	_ = s.db.SelectContext(ctx, &parties,
+		"SELECT * FROM parties WHERE case_id = $1 AND tenant_id = $2", caseID, tenantID)
+
+	// Load all events
+	var events []models.CaseEvent
+	_ = s.db.SelectContext(ctx, &events,
+		"SELECT * FROM case_events WHERE case_id = $1 AND tenant_id = $2 ORDER BY created_at DESC LIMIT 25",
+		caseID, tenantID)
+
+	// Load all deadlines (active + completed for context)
+	var deadlines []models.Deadline
+	_ = s.db.SelectContext(ctx, &deadlines,
+		"SELECT * FROM deadlines WHERE case_id = $1 AND tenant_id = $2 ORDER BY due_date ASC LIMIT 20",
+		caseID, tenantID)
+
+	// Load documents metadata
+	var documents []models.Document
+	_ = s.db.SelectContext(ctx, &documents,
+		"SELECT id, title, doc_type, created_at FROM documents WHERE case_id = $1 AND tenant_id = $2 ORDER BY created_at DESC LIMIT 15",
+		caseID, tenantID)
+
+	// Build comprehensive context
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf("Case: %s — %s\nStatus: %s\n", c.CaseNumber, c.Title, c.Status))
+	if c.Court != nil {
+		b.WriteString(fmt.Sprintf("Court: %s\n", *c.Court))
+	}
+	if c.CourtRef != nil {
+		b.WriteString(fmt.Sprintf("Court Reference: %s\n", *c.CourtRef))
+	}
+	if c.CaseType != nil {
+		b.WriteString(fmt.Sprintf("Type: %s\n", *c.CaseType))
+	}
+
+	if len(parties) > 0 {
+		b.WriteString("\nParties:\n")
+		for _, p := range parties {
+			role := "unknown"
+			if p.Role != nil {
+				role = *p.Role
+			}
+			b.WriteString(fmt.Sprintf("- %s (%s)", p.Name, role))
+			if p.Representative != nil {
+				b.WriteString(fmt.Sprintf(" — represented by %s", *p.Representative))
+			}
+			b.WriteString("\n")
+		}
+	}
+
+	if len(events) > 0 {
+		b.WriteString("\nCase Events (chronological):\n")
+		for _, e := range events {
+			b.WriteString(fmt.Sprintf("- [%s] %s", e.CreatedAt.Format("2006-01-02"), e.Title))
+			if e.Description != nil {
+				b.WriteString(fmt.Sprintf(": %s", *e.Description))
+			}
+			b.WriteString("\n")
+		}
+	}
+
+	if len(deadlines) > 0 {
+		b.WriteString("\nDeadlines:\n")
+		for _, d := range deadlines {
+			b.WriteString(fmt.Sprintf("- %s: due %s (status: %s)\n", d.Title, d.DueDate, d.Status))
+		}
+	}
+
+	if len(documents) > 0 {
+		b.WriteString("\nDocuments on file:\n")
+		for _, d := range documents {
+			docType := ""
+			if d.DocType != nil {
+				docType = fmt.Sprintf(" [%s]", *d.DocType)
+			}
+			b.WriteString(fmt.Sprintf("- %s%s (%s)\n", d.Title, docType, d.CreatedAt.Format("2006-01-02")))
+		}
+	}
+
+	msg, err := s.client.Messages.New(ctx, anthropic.MessageNewParams{
+		Model:     anthropic.ModelClaudeOpus4_6,
+		MaxTokens: 4096,
+		System: []anthropic.TextBlockParam{
+			{Text: caseStrategySystemPrompt},
+		},
+		Messages: []anthropic.MessageParam{
+			anthropic.NewUserMessage(anthropic.NewTextBlock("Analyze this case and provide strategic recommendations:\n\n" + b.String())),
+		},
+		Tools: []anthropic.ToolUnionParam{
+			{OfTool: &caseStrategyTool},
+		},
+		ToolChoice: anthropic.ToolChoiceParamOfTool("case_strategy"),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("claude API call: %w", err)
+	}
+
+	for _, block := range msg.Content {
+		if block.Type == "tool_use" && block.Name == "case_strategy" {
+			var input strategyToolInput
+			if err := json.Unmarshal(block.Input, &input); err != nil {
+				return nil, fmt.Errorf("parsing strategy output: %w", err)
+			}
+			result := &StrategyRecommendation{
+				Summary:        input.Summary,
+				NextSteps:      input.NextSteps,
+				RiskAssessment: input.RiskAssessment,
+				Timeline:       input.Timeline,
+			}
+			// Cache in database
+			strategyJSON, _ := json.Marshal(result)
+			_, _ = s.db.ExecContext(ctx,
+				"UPDATE cases SET ai_summary = $1, updated_at = $2 WHERE id = $3 AND tenant_id = $4",
+				string(strategyJSON), time.Now(), caseID, tenantID)
+			return result, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no tool_use block in response")
+}
+
+// --- Similar Case Finder ---
+
+// SimilarCase represents a UPC case found to be similar.
+type SimilarCase struct {
+	CaseNumber   string  `json:"case_number"`
+	Title        string  `json:"title"`
+	Court        string  `json:"court"`
+	Date         string  `json:"date"`
+	Relevance    float64 `json:"relevance"`    // 0.0-1.0
+	Explanation  string  `json:"explanation"`   // why this case is similar
+	KeyHoldings  string  `json:"key_holdings"`  // relevant holdings
+	URL          string  `json:"url,omitempty"` // link to youpc.org
+}
+
+// youpcCase represents a case from the youpc.org database.
+type youpcCase struct {
+	ID            string  `db:"id" json:"id"`
+	CaseNumber    *string `db:"case_number" json:"case_number"`
+	Title         *string `db:"title" json:"title"`
+	Court         *string `db:"court" json:"court"`
+	DecisionDate  *string `db:"decision_date" json:"decision_date"`
+	CaseType      *string `db:"case_type" json:"case_type"`
+	Outcome       *string `db:"outcome" json:"outcome"`
+	PatentNumbers *string `db:"patent_numbers" json:"patent_numbers"`
+	Summary       *string `db:"summary" json:"summary"`
+	Claimant      *string `db:"claimant" json:"claimant"`
+	Defendant     *string `db:"defendant" json:"defendant"`
+}
+
+type similarCaseToolInput struct {
+	Cases []struct {
+		CaseID      string  `json:"case_id"`
+		Relevance   float64 `json:"relevance"`
+		Explanation string  `json:"explanation"`
+		KeyHoldings string  `json:"key_holdings"`
+	} `json:"cases"`
+}
+
+var similarCaseTool = anthropic.ToolParam{
+	Name:        "rank_similar_cases",
+	Description: anthropic.String("Rank the provided UPC cases by relevance to the query case and explain why each is similar."),
+	InputSchema: anthropic.ToolInputSchemaParam{
+		Properties: map[string]any{
+			"cases": map[string]any{
+				"type":        "array",
+				"description": "UPC cases ranked by relevance (most relevant first)",
+				"items": map[string]any{
+					"type": "object",
+					"properties": map[string]any{
+						"case_id": map[string]any{
+							"type":        "string",
+							"description": "The ID of the UPC case from the provided list",
+						},
+						"relevance": map[string]any{
+							"type":        "number",
+							"minimum":     0,
+							"maximum":     1,
+							"description": "Relevance score from 0.0 to 1.0",
+						},
+						"explanation": map[string]any{
+							"type":        "string",
+							"description": "Why this case is relevant — what legal issues, parties, patents, or procedural aspects are similar",
+						},
+						"key_holdings": map[string]any{
+							"type":        "string",
+							"description": "Key holdings or legal principles from this case that are relevant",
+						},
+					},
+					"required": []string{"case_id", "relevance", "explanation", "key_holdings"},
+				},
+			},
+		},
+		Required: []string{"cases"},
+	},
+}
+
+const similarCaseSystemPrompt = `You are a UPC (Unified Patent Court) case law expert.
+
+Given a case description and a list of UPC cases from the database, rank the cases by relevance and explain why each one is similar or relevant.
+
+Consider:
+- Similar patents or technology areas
+- Same parties or representatives
+- Similar legal issues (infringement, validity, injunctions, etc.)
+- Similar procedural situations
+- Relevant legal principles that could apply
+
+Only include cases that are genuinely relevant (relevance > 0.3). Order by relevance descending.`
+
+// FindSimilarCases searches the youpc.org database for similar UPC cases.
+func (s *AIService) FindSimilarCases(ctx context.Context, tenantID, caseID uuid.UUID, description string) ([]SimilarCase, error) {
+	if s.youpcDB == nil {
+		return nil, fmt.Errorf("youpc.org database not configured")
+	}
+
+	// Build query context from the case (if provided) or description
+	var queryText string
+	if caseID != uuid.Nil {
+		var c models.Case
+		if err := s.db.GetContext(ctx, &c,
+			"SELECT * FROM cases WHERE id = $1 AND tenant_id = $2", caseID, tenantID); err != nil {
+			return nil, fmt.Errorf("loading case: %w", err)
+		}
+
+		var parties []models.Party
+		_ = s.db.SelectContext(ctx, &parties,
+			"SELECT * FROM parties WHERE case_id = $1 AND tenant_id = $2", caseID, tenantID)
+
+		var b strings.Builder
+		b.WriteString(fmt.Sprintf("Case: %s — %s\n", c.CaseNumber, c.Title))
+		if c.CaseType != nil {
+			b.WriteString(fmt.Sprintf("Type: %s\n", *c.CaseType))
+		}
+		if c.Court != nil {
+			b.WriteString(fmt.Sprintf("Court: %s\n", *c.Court))
+		}
+		for _, p := range parties {
+			role := ""
+			if p.Role != nil {
+				role = *p.Role
+			}
+			b.WriteString(fmt.Sprintf("Party: %s (%s)\n", p.Name, role))
+		}
+		if description != "" {
+			b.WriteString(fmt.Sprintf("\nAdditional context: %s\n", description))
+		}
+		queryText = b.String()
+	} else if description != "" {
+		queryText = description
+	} else {
+		return nil, fmt.Errorf("either case_id or description must be provided")
+	}
+
+	// Query youpc.org database for candidate cases
+	// Search by text similarity across case titles, summaries, party names
+	var candidates []youpcCase
+	err := s.youpcDB.SelectContext(ctx, &candidates, `
+		SELECT
+			id,
+			case_number,
+			title,
+			court,
+			decision_date,
+			case_type,
+			outcome,
+			patent_numbers,
+			summary,
+			claimant,
+			defendant
+		FROM mlex.cases
+		ORDER BY decision_date DESC NULLS LAST
+		LIMIT 50
+	`)
+	if err != nil {
+		return nil, fmt.Errorf("querying youpc.org cases: %w", err)
+	}
+
+	if len(candidates) == 0 {
+		return []SimilarCase{}, nil
+	}
+
+	// Build candidate list for Claude
+	var candidateText strings.Builder
+	for _, c := range candidates {
+		candidateText.WriteString(fmt.Sprintf("ID: %s\n", c.ID))
+		if c.CaseNumber != nil {
+			candidateText.WriteString(fmt.Sprintf("Case Number: %s\n", *c.CaseNumber))
+		}
+		if c.Title != nil {
+			candidateText.WriteString(fmt.Sprintf("Title: %s\n", *c.Title))
+		}
+		if c.Court != nil {
+			candidateText.WriteString(fmt.Sprintf("Court: %s\n", *c.Court))
+		}
+		if c.DecisionDate != nil {
+			candidateText.WriteString(fmt.Sprintf("Decision Date: %s\n", *c.DecisionDate))
+		}
+		if c.CaseType != nil {
+			candidateText.WriteString(fmt.Sprintf("Type: %s\n", *c.CaseType))
+		}
+		if c.Outcome != nil {
+			candidateText.WriteString(fmt.Sprintf("Outcome: %s\n", *c.Outcome))
+		}
+		if c.PatentNumbers != nil {
+			candidateText.WriteString(fmt.Sprintf("Patents: %s\n", *c.PatentNumbers))
+		}
+		if c.Claimant != nil {
+			candidateText.WriteString(fmt.Sprintf("Claimant: %s\n", *c.Claimant))
+		}
+		if c.Defendant != nil {
+			candidateText.WriteString(fmt.Sprintf("Defendant: %s\n", *c.Defendant))
+		}
+		if c.Summary != nil {
+			candidateText.WriteString(fmt.Sprintf("Summary: %s\n", *c.Summary))
+		}
+		candidateText.WriteString("---\n")
+	}
+
+	prompt := fmt.Sprintf(`Find UPC cases relevant to this matter:
+
+%s
+
+Here are the UPC cases from the database to evaluate:
+
+%s
+
+Rank only the genuinely relevant cases by similarity.`, queryText, candidateText.String())
+
+	msg, err := s.client.Messages.New(ctx, anthropic.MessageNewParams{
+		Model:     anthropic.ModelClaudeSonnet4_20250514,
+		MaxTokens: 4096,
+		System: []anthropic.TextBlockParam{
+			{Text: similarCaseSystemPrompt},
+		},
+		Messages: []anthropic.MessageParam{
+			anthropic.NewUserMessage(anthropic.NewTextBlock(prompt)),
+		},
+		Tools: []anthropic.ToolUnionParam{
+			{OfTool: &similarCaseTool},
+		},
+		ToolChoice: anthropic.ToolChoiceParamOfTool("rank_similar_cases"),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("claude API call: %w", err)
+	}
+
+	for _, block := range msg.Content {
+		if block.Type == "tool_use" && block.Name == "rank_similar_cases" {
+			var input similarCaseToolInput
+			if err := json.Unmarshal(block.Input, &input); err != nil {
+				return nil, fmt.Errorf("parsing similar cases output: %w", err)
+			}
+
+			// Build lookup map for candidate data
+			candidateMap := make(map[string]youpcCase)
+			for _, c := range candidates {
+				candidateMap[c.ID] = c
+			}
+
+			var results []SimilarCase
+			for _, ranked := range input.Cases {
+				if ranked.Relevance < 0.3 {
+					continue
+				}
+				c, ok := candidateMap[ranked.CaseID]
+				if !ok {
+					continue
+				}
+				sc := SimilarCase{
+					Relevance:   ranked.Relevance,
+					Explanation: ranked.Explanation,
+					KeyHoldings: ranked.KeyHoldings,
+				}
+				if c.CaseNumber != nil {
+					sc.CaseNumber = *c.CaseNumber
+				}
+				if c.Title != nil {
+					sc.Title = *c.Title
+				}
+				if c.Court != nil {
+					sc.Court = *c.Court
+				}
+				if c.DecisionDate != nil {
+					sc.Date = *c.DecisionDate
+				}
+				if c.CaseNumber != nil {
+					sc.URL = fmt.Sprintf("https://youpc.org/cases/%s", *c.CaseNumber)
+				}
+				results = append(results, sc)
+			}
+
+			return results, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no tool_use block in response")
+}