Wire hexis.resolve_target to real Nexus, fix changes cursor, pass full execute fields over MCP

resolve_target previously returned a hardcoded "requires_nexus_resolution"
placeholder; it now calls Nexus's /api/v1/resolve via a new minimal
internal/nexusclient, configurable with -nexus (default localhost:8987).

/api/v1/changes ignored the since query param and always returned from
sequence 0 (`since = 0` regardless of what was parsed) — fixed to actually
parse and use it, so change-cursor polling works.

The MCP hexis.execute tool only forwarded capability_id/target_entity_id/
arguments/idempotency_key, silently dropping entity_version, requested_by,
origin, correlation_id, causation_id, resolution_evidence, and
confirmation_id even though the native HTTP API and domain.ExecuteRequest
already supported all of them — MCP callers now get full parity.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018ghELqYhZNLub2TXGMazqA

cmd/hexisd/main.go

@@ -12,6 +12,7 @@ import (
 	"github.com/kami/hexis/internal/api"
 	"github.com/kami/hexis/internal/execution"
 	"github.com/kami/hexis/internal/mcp"
+	"github.com/kami/hexis/internal/nexusclient"
 	"github.com/kami/hexis/internal/provider"
 	"github.com/kami/hexis/internal/storage"
 )
@@ -22,12 +23,14 @@ func main() {
 	var mcpMode bool
 	var workspaceURL string
 	var workspaceAllowlist string
+	var nexusURL string
 
 	flag.StringVar(&httpAddr, "http", "", "HTTP listen address (default localhost:9741)")
 	flag.StringVar(&dataDir, "data", "", "Data directory for SQLite database")
 	flag.BoolVar(&mcpMode, "mcp", false, "Run in MCP stdio mode")
 	flag.StringVar(&workspaceURL, "workspace-url", "", "Workspace MCP HTTP API URL (e.g. http://localhost:9930)")
 	flag.StringVar(&workspaceAllowlist, "workspace-allowlist", "", "Path to workspace tool allowlist YAML")
+	flag.StringVar(&nexusURL, "nexus", "", "Nexus base URL for hexis.resolve_target (default http://localhost:8987)")
 	flag.Parse()
 
 	if dataDir == "" {
@@ -42,6 +45,12 @@ func main() {
 	if workspaceURL == "" {
 		workspaceURL = os.Getenv("WORKSPACE_MCP_URL")
 	}
+	if nexusURL == "" {
+		nexusURL = os.Getenv("HEXIS_NEXUS_URL")
+	}
+	if nexusURL == "" {
+		nexusURL = "http://localhost:8987"
+	}
 
 	dbPath := filepath.Join(dataDir, "hexis.db")
 
@@ -88,7 +97,7 @@ func main() {
 
 	if mcpMode {
 		log.Printf("starting MCP stdio adapter")
-		adapter := mcp.New(store, engine)
+		adapter := mcp.New(store, engine, nexusclient.New(nexusURL))
 		if err := adapter.ServeStdio(); err != nil {
 			log.Fatalf("MCP error: %v", err)
 		}

internal/api/handler.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"errors"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
@@ -334,7 +335,12 @@ func (h *Handler) handleChanges(w http.ResponseWriter, r *http.Request) {
 	seqStr := r.URL.Query().Get("since")
 	var since int64
 	if seqStr != "" {
-		since = 0
+		parsed, err := strconv.ParseInt(seqStr, 10, 64)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, errorResponse("since must be an integer sequence"))
+			return
+		}
+		since = parsed
 	}
 
 	events, err := h.store.EventsAfter(since, 100)

internal/api/handler_test.go

@@ -0,0 +1,80 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/kami/hexis/internal/domain"
+	"github.com/kami/hexis/internal/execution"
+	"github.com/kami/hexis/internal/provider"
+	"github.com/kami/hexis/internal/storage"
+)
+
+func newTestHandler(t *testing.T) (*Handler, *storage.Store) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "hexis.db")
+	store, err := storage.Open(path)
+	if err != nil {
+		t.Fatalf("open store: %v", err)
+	}
+	t.Cleanup(func() { store.Close() })
+	engine := execution.New(store, provider.NewRegistry())
+	return NewHandler(store, engine), store
+}
+
+// TestHandleChanges_SinceFiltersEvents verifies the `since` query param
+// actually filters to events after that sequence number, rather than being
+// silently reset to 0 (the bug: `since = 0` unconditionally, ignoring the
+// parsed value).
+func TestHandleChanges_SinceFiltersEvents(t *testing.T) {
+	h, store := newTestHandler(t)
+
+	for i := 0; i < 3; i++ {
+		if err := store.AppendEvent(&domain.Event{
+			ID:        domain.NewEventID(),
+			Type:      domain.EventCapabilityRegistered,
+			Timestamp: time.Now().UTC(),
+		}); err != nil {
+			t.Fatalf("append event %d: %v", i, err)
+		}
+	}
+
+	all, err := store.EventsAfter(0, 100)
+	if err != nil {
+		t.Fatalf("events after 0: %v", err)
+	}
+	if len(all) != 3 {
+		t.Fatalf("expected 3 seed events, got %d", len(all))
+	}
+	cutoff := all[0].Sequence
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/changes?since="+itoa(cutoff), nil)
+	w := httptest.NewRecorder()
+	h.handleChanges(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+
+	var events []*domain.Event
+	if err := json.Unmarshal(w.Body.Bytes(), &events); err != nil {
+		t.Fatalf("decode response: %v", err)
+	}
+	if len(events) != 2 {
+		t.Fatalf("expected 2 events after sequence %d, got %d", cutoff, len(events))
+	}
+	for _, e := range events {
+		if e.Sequence <= cutoff {
+			t.Errorf("event with sequence %d should have been excluded by since=%d", e.Sequence, cutoff)
+		}
+	}
+}
+
+func itoa(n int64) string {
+	b, _ := json.Marshal(n)
+	return string(b)
+}

internal/mcp/adapter.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"strconv"
 	"strings"
 
 	"github.com/mark3labs/mcp-go/mcp"
@@ -11,6 +12,7 @@ import (
 
 	"github.com/kami/hexis/internal/domain"
 	"github.com/kami/hexis/internal/execution"
+	"github.com/kami/hexis/internal/nexusclient"
 	"github.com/kami/hexis/internal/storage"
 )
 
@@ -18,12 +20,14 @@ type Adapter struct {
 	server *server.MCPServer
 	store  storage.Interface
 	engine *execution.Engine
+	nexus  nexusclient.Client
 }
 
-func New(store storage.Interface, engine *execution.Engine) *Adapter {
+func New(store storage.Interface, engine *execution.Engine, nexus nexusclient.Client) *Adapter {
 	a := &Adapter{
 		store:  store,
 		engine: engine,
+		nexus:  nexus,
 	}
 
 	mcpServer := server.NewMCPServer(
@@ -75,6 +79,27 @@ func New(store storage.Interface, engine *execution.Engine) *Adapter {
 		mcp.WithString("idempotency_key",
 			mcp.Description("Idempotency key for safe retry"),
 		),
+		mcp.WithString("entity_version",
+			mcp.Description("Expected Nexus entity version, for optimistic concurrency"),
+		),
+		mcp.WithString("requested_by",
+			mcp.Description("JSON string describing the requester (e.g. {\"type\":\"user\",\"id\":\"...\"})"),
+		),
+		mcp.WithString("origin",
+			mcp.Description("JSON string describing the request origin (e.g. {\"system\":\"maven\",\"channel\":\"voice\"})"),
+		),
+		mcp.WithString("correlation_id",
+			mcp.Description("Correlation ID for cross-system tracing"),
+		),
+		mcp.WithString("causation_id",
+			mcp.Description("Causation ID of the event/request that triggered this execute"),
+		),
+		mcp.WithString("resolution_evidence",
+			mcp.Description("JSON array of evidence objects backing target_entity_id's resolution"),
+		),
+		mcp.WithString("confirmation_id",
+			mcp.Description("Confirmation ID for capabilities that require confirmation"),
+		),
 	), a.handleExecute)
 
 	mcpServer.AddTool(mcp.NewTool("hexis.execution_status",
@@ -167,13 +192,25 @@ func (a *Adapter) handleResolveTarget(ctx context.Context, req mcp.CallToolReque
 	if query == "" {
 		return mcp.NewToolResultError("query is required"), nil
 	}
+	if a.nexus == nil {
+		return mcp.NewToolResultError("resolve_target unavailable: no Nexus URL configured"), nil
+	}
 
-	// In a real setup, this would call Nexus API.
-	// For now, return a placeholder indicating Nexus resolution is needed.
-	result := map[string]any{
-		"query":    query,
-		"status":   "requires_nexus_resolution",
-		"message":  "Connect to Nexus to resolve this query to a canonical entity ID",
+	var types []string
+	if capName := req.GetString("capability", ""); capName != "" {
+		if caps, err := a.store.ListCapabilities(""); err == nil {
+			for _, c := range caps {
+				if c.Name == capName {
+					types = c.TargetTypes
+					break
+				}
+			}
+		}
+	}
+
+	result, err := a.nexus.Resolve(ctx, query, types)
+	if err != nil {
+		return mcp.NewToolResultError(fmt.Sprintf("nexus resolve: %v", err)), nil
 	}
 
 	data, _ := json.MarshalIndent(result, "", "  ")
@@ -199,11 +236,48 @@ func (a *Adapter) handleExecute(ctx context.Context, req mcp.CallToolRequest) (*
 		json.Unmarshal([]byte(argsStr), &args)
 	}
 
+	var entityVersion int64
+	if v := req.GetString("entity_version", ""); v != "" {
+		parsed, err := strconv.ParseInt(v, 10, 64)
+		if err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("entity_version must be an integer: %v", err)), nil
+		}
+		entityVersion = parsed
+	}
+
+	var requestedBy map[string]string
+	if v := req.GetString("requested_by", ""); v != "" {
+		if err := json.Unmarshal([]byte(v), &requestedBy); err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("requested_by must be a JSON object: %v", err)), nil
+		}
+	}
+
+	var origin map[string]string
+	if v := req.GetString("origin", ""); v != "" {
+		if err := json.Unmarshal([]byte(v), &origin); err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("origin must be a JSON object: %v", err)), nil
+		}
+	}
+
+	var resolutionEvidence []map[string]any
+	if v := req.GetString("resolution_evidence", ""); v != "" {
+		if err := json.Unmarshal([]byte(v), &resolutionEvidence); err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("resolution_evidence must be a JSON array: %v", err)), nil
+		}
+	}
+
 	execReq := &domain.ExecuteRequest{
-		CapabilityID:   capID,
-		TargetEntityID: targetID,
-		Arguments:      args,
-		IdempotencyKey: idempKey,
+		CapabilityID:       capID,
+		TargetEntityID:     targetID,
+		EntityVersion:      entityVersion,
+		Arguments:          args,
+		RequestedBy:        requestedBy,
+		Origin:             origin,
+		IdempotencyKey:     idempKey,
+		CorrelationID:      req.GetString("correlation_id", ""),
+		CausationID:        req.GetString("causation_id", ""),
+		ResolutionEvidence: resolutionEvidence,
+		ConfirmationID:     req.GetString("confirmation_id", ""),
 	}
 
 	result, err := a.engine.Execute(execReq)

internal/nexusclient/client.go

@@ -0,0 +1,80 @@
+// Package nexusclient is the minimal Nexus resolve client used by Hexis's
+// hexis.resolve_target MCP tool to turn a free-text query into a canonical
+// entity ID, matching the /api/v1/resolve contract Nexus and Praxis already
+// speak.
+package nexusclient
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+)
+
+type Entity struct {
+	ID          string `json:"id"`
+	Type        string `json:"type"`
+	DisplayName string `json:"display_name"`
+}
+
+type Candidate struct {
+	EntityID    string  `json:"entity_id"`
+	DisplayName string  `json:"display_name"`
+	Score       float64 `json:"score"`
+}
+
+type ResolveResult struct {
+	Status     string      `json:"status"`
+	Entity     *Entity     `json:"entity,omitempty"`
+	Score      float64     `json:"score,omitempty"`
+	Candidates []Candidate `json:"candidates,omitempty"`
+}
+
+type Client interface {
+	Resolve(ctx context.Context, query string, types []string) (*ResolveResult, error)
+}
+
+type httpClient struct {
+	baseURL string
+	http    *http.Client
+}
+
+func New(baseURL string) Client {
+	return &httpClient{baseURL: baseURL, http: &http.Client{Timeout: 10 * time.Second}}
+}
+
+func (c *httpClient) Resolve(ctx context.Context, query string, types []string) (*ResolveResult, error) {
+	body := map[string]any{"query": query}
+	if len(types) > 0 {
+		body["types"] = types
+	}
+	data, err := json.Marshal(body)
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/api/v1/resolve", bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-Nexus-Version", "v1")
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("nexus resolve: %s", http.StatusText(resp.StatusCode))
+	}
+
+	var result ResolveResult
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("decode nexus resolve response: %w", err)
+	}
+	return &result, nil
+}