diff --git a/workspace-server/internal/handlers/instructions_test.go b/workspace-server/internal/handlers/instructions_test.go
new file mode 100644
index 00000000..98760a23
--- /dev/null
+++ b/workspace-server/internal/handlers/instructions_test.go
@@ -0,0 +1,893 @@
+package handlers
+
+import (
+	"bytes"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/gin-gonic/gin"
+)
+
+// ─── request helpers ───────────────────────────────────────────────────────────
+
+func newPostRequest(path string, body interface{}) (*httptest.ResponseRecorder, *gin.Context) {
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	raw, _ := json.Marshal(body)
+	c.Request = httptest.NewRequest(http.MethodPost, path, bytes.NewReader(raw))
+	c.Request.Header.Set("Content-Type", "application/json")
+	return w, c
+}
+
+func newPutRequest(path string, body interface{}) (*httptest.ResponseRecorder, *gin.Context) {
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	raw, _ := json.Marshal(body)
+	c.Request = httptest.NewRequest(http.MethodPut, path, bytes.NewReader(raw))
+	c.Request.Header.Set("Content-Type", "application/json")
+	return w, c
+}
+
+func newDeleteRequest(path string) (*httptest.ResponseRecorder, *gin.Context) {
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodDelete, path, nil)
+	return w, c
+}
+
+func newGetRequest(path string) (*httptest.ResponseRecorder, *gin.Context) {
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodGet, path, nil)
+	return w, c
+}
+
+// ─── mock row helpers ─────────────────────────────────────────────────────────
+
+// instructionCols matches the SELECT in List/Resolve.
+var instructionCols = []string{
+	"id", "scope", "scope_target", "title", "content",
+	"priority", "enabled", "created_at", "updated_at",
+}
+
+// resolveCols matches the SELECT in Resolve (scope, title, content).
+var resolveCols = []string{"scope", "title", "content"}
+
+// ─── List ────────────────────────────────────────────────────────────────────
+
+func TestInstructionsList_ByWorkspaceID(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	wsID := "ws-123-abc"
+	w, c := newGetRequest("/instructions?workspace_id=" + wsID)
+	c.Request = httptest.NewRequest(http.MethodGet, "/instructions?workspace_id="+wsID, nil)
+
+	rows := sqlmock.NewRows(instructionCols).
+		AddRow("inst-1", "global", nil, "Be helpful", "Always be helpful.", 10, true, time.Now(), time.Now()).
+		AddRow("inst-2", "workspace", &wsID, "Use Claude", "Use Claude Code.", 5, true, time.Now(), time.Now())
+	mock.ExpectQuery("SELECT id, scope, scope_target, title, content, priority, enabled, created_at, updated_at").
+		WithArgs(wsID).
+		WillReturnRows(rows)
+
+	h.List(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var out []Instruction
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	if len(out) != 2 {
+		t.Errorf("expected 2 instructions, got %d", len(out))
+	}
+	if out[0].Scope != "global" {
+		t.Errorf("first row scope: expected global, got %s", out[0].Scope)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsList_ByScope(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newGetRequest("/instructions?scope=global")
+	c.Request = httptest.NewRequest(http.MethodGet, "/instructions?scope=global", nil)
+
+	rows := sqlmock.NewRows(instructionCols).
+		AddRow("inst-g", "global", nil, "Global Rule", "Follow policy.", 10, true, time.Now(), time.Now())
+	mock.ExpectQuery("SELECT id, scope, scope_target, title, content, priority, enabled, created_at, updated_at FROM platform_instructions WHERE 1=1").
+		WithArgs("global").
+		WillReturnRows(rows)
+
+	h.List(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var out []Instruction
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	if len(out) != 1 || out[0].Scope != "global" {
+		t.Errorf("unexpected response: %v", out)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsList_AllNoParams(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newGetRequest("/instructions")
+
+	rows := sqlmock.NewRows(instructionCols)
+	mock.ExpectQuery("SELECT id, scope, scope_target, title, content, priority, enabled, created_at, updated_at FROM platform_instructions WHERE 1=1").
+		WillReturnRows(rows)
+
+	h.List(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var out []Instruction
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	// Empty slice, not nil
+	if out == nil {
+		t.Error("expected empty slice, got nil")
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsList_DBError(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newGetRequest("/instructions")
+	c.Request = httptest.NewRequest(http.MethodGet, "/instructions", nil)
+
+	mock.ExpectQuery("SELECT id, scope, scope_target, title, content, priority, enabled, created_at, updated_at FROM platform_instructions WHERE 1=1").
+		WillReturnError(errors.New("connection refused"))
+
+	h.List(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── Create ───────────────────────────────────────────────────────────────────
+
+func TestInstructionsCreate_ValidGlobal(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":    "global",
+		"title":    "Be Helpful",
+		"content":  "Always be helpful to the user.",
+		"priority": 10,
+	})
+
+	mock.ExpectQuery("INSERT INTO platform_instructions").
+		WithArgs("global", nil, "Be Helpful", "Always be helpful to the user.", 10).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow("new-inst-1"))
+
+	h.Create(c)
+
+	if w.Code != http.StatusCreated {
+		t.Fatalf("expected 201, got %d: %s", w.Code, w.Body.String())
+	}
+	var out map[string]string
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	if out["id"] != "new-inst-1" {
+		t.Errorf("expected id new-inst-1, got %s", out["id"])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsCreate_ValidWorkspace(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+	wsTarget := "ws-xyz-789"
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":        "workspace",
+		"scope_target": wsTarget,
+		"title":        "Use Claude Code",
+		"content":      "Prefer Claude Code for all tasks.",
+		"priority":     5,
+	})
+
+	mock.ExpectQuery("INSERT INTO platform_instructions").
+		WithArgs("workspace", &wsTarget, "Use Claude Code", "Prefer Claude Code for all tasks.", 5).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow("ws-inst-2"))
+
+	h.Create(c)
+
+	if w.Code != http.StatusCreated {
+		t.Fatalf("expected 201, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsCreate_MissingScope(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"title":   "Missing Scope",
+		"content": "This has no scope.",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_MissingTitle(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"content": "Has no title.",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_MissingContent(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope": "global",
+		"title": "Has no content",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_InvalidScope(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "team",
+		"title":   "Bad Scope",
+		"content": "Team scope is not supported yet.",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_WorkspaceScopeNoTarget(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "workspace",
+		"title":   "Missing Target",
+		"content": "Workspace scope without scope_target.",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_ContentTooLong(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	// Build a string longer than maxInstructionContentLen (8192).
+	longContent := string(make([]byte, maxInstructionContentLen+1))
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"title":   "Too Long",
+		"content": longContent,
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_TitleTooLong(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	longTitle := string(make([]byte, 201))
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"title":   longTitle,
+		"content": "Short content.",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsCreate_DBError(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"title":   "DB Error",
+		"content": "This will fail.",
+	})
+
+	mock.ExpectQuery("INSERT INTO platform_instructions").
+		WillReturnError(errors.New("connection refused"))
+
+	h.Create(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── Update ──────────────────────────────────────────────────────────────────
+
+func TestInstructionsUpdate_ValidPartial(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-update-1"
+	newTitle := "Updated Title"
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{
+		"title": newTitle,
+	})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("UPDATE platform_instructions SET").
+		WithArgs(&newTitle, sqlmock.AnyArg(), sqlmock.AnyArg(), sqlmock.AnyArg(), instID).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	h.Update(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsUpdate_AllFields(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-update-2"
+	title := "Full Update"
+	content := "New content body."
+	priority := 20
+	enabled := false
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{
+		"title":    title,
+		"content":  content,
+		"priority": priority,
+		"enabled":  enabled,
+	})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("UPDATE platform_instructions SET").
+		WithArgs(&title, &content, &priority, &enabled, instID).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	h.Update(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsUpdate_ContentTooLong(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-too-long"
+	longContent := string(make([]byte, maxInstructionContentLen+1))
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{
+		"content": longContent,
+	})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	h.Update(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsUpdate_TitleTooLong(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-title-long"
+	longTitle := string(make([]byte, 201))
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{
+		"title": longTitle,
+	})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	h.Update(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestInstructionsUpdate_NotFound(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-missing"
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{
+		"title": "New Title",
+	})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("UPDATE platform_instructions SET").
+		WillReturnResult(sqlmock.NewResult(0, 0))
+
+	h.Update(c)
+
+	if w.Code != http.StatusNotFound {
+		t.Fatalf("expected 404, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsUpdate_DBError(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-db-err"
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{
+		"title": "Error Update",
+	})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("UPDATE platform_instructions SET").
+		WillReturnError(errors.New("connection refused"))
+
+	h.Update(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── Delete ───────────────────────────────────────────────────────────────────
+
+func TestInstructionsDelete_Valid(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-delete-1"
+	w, c := newDeleteRequest("/instructions/" + instID)
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("DELETE FROM platform_instructions WHERE id = $1").
+		WithArgs(instID).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	h.Delete(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsDelete_NotFound(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-not-there"
+	w, c := newDeleteRequest("/instructions/" + instID)
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("DELETE FROM platform_instructions WHERE id = $1").
+		WithArgs(instID).
+		WillReturnResult(sqlmock.NewResult(0, 0))
+
+	h.Delete(c)
+
+	if w.Code != http.StatusNotFound {
+		t.Fatalf("expected 404, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsDelete_DBError(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-del-err"
+	w, c := newDeleteRequest("/instructions/" + instID)
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	mock.ExpectExec("DELETE FROM platform_instructions WHERE id = $1").
+		WillReturnError(errors.New("connection refused"))
+
+	h.Delete(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── Resolve ──────────────────────────────────────────────────────────────────
+
+func TestInstructionsResolve_GlobalThenWorkspace(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	wsID := "ws-resolve-1"
+	w, c := newGetRequest("/workspaces/" + wsID + "/instructions/resolve")
+	c.Params = []gin.Param{{Key: "id", Value: wsID}}
+	c.Request = httptest.NewRequest(http.MethodGet, "/workspaces/"+wsID+"/instructions/resolve", nil)
+
+	now := time.Now()
+	rows := sqlmock.NewRows(resolveCols).
+		AddRow("global", "Be Helpful", "Always help the user.").
+		AddRow("global", "Stay on Topic", "Don't diverge.").
+		AddRow("workspace", "Use Claude Code", "Claude Code is the default runtime.")
+	mock.ExpectQuery("SELECT scope, title, content FROM platform_instructions").
+		WithArgs(wsID).
+		WillReturnRows(rows)
+
+	h.Resolve(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var out struct {
+		WorkspaceID   string `json:"workspace_id"`
+		Instructions string `json:"instructions"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	if out.WorkspaceID != wsID {
+		t.Errorf("expected workspace_id %s, got %s", wsID, out.WorkspaceID)
+	}
+	// Global section must come before workspace section.
+	if !bytes.Contains([]byte(out.Instructions), []byte("Platform-Wide Rules")) {
+		t.Error("instructions should contain 'Platform-Wide Rules' section")
+	}
+	if !bytes.Contains([]byte(out.Instructions), []byte("Role-Specific Rules")) {
+		t.Error("instructions should contain 'Role-Specific Rules' section")
+	}
+	// Global instructions must appear before workspace instructions.
+	idxGlobal := bytes.Index([]byte(out.Instructions), []byte("Platform-Wide Rules"))
+	idxWorkspace := bytes.Index([]byte(out.Instructions), []byte("Role-Specific Rules"))
+	if idxGlobal >= idxWorkspace {
+		t.Error("global section should appear before workspace section")
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsResolve_EmptyWorkspace(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	wsID := "ws-empty"
+	w, c := newGetRequest("/workspaces/" + wsID + "/instructions/resolve")
+	c.Params = []gin.Param{{Key: "id", Value: wsID}}
+	c.Request = httptest.NewRequest(http.MethodGet, "/workspaces/"+wsID+"/instructions/resolve", nil)
+
+	rows := sqlmock.NewRows(resolveCols)
+	mock.ExpectQuery("SELECT scope, title, content FROM platform_instructions").
+		WithArgs(wsID).
+		WillReturnRows(rows)
+
+	h.Resolve(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var out struct {
+		Instructions string `json:"instructions"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	// No rows → builder writes nothing; empty string returned.
+	if out.Instructions != "" {
+		t.Errorf("expected empty instructions for empty workspace, got: %q", out.Instructions)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsResolve_DBError(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	wsID := "ws-err"
+	w, c := newGetRequest("/workspaces/" + wsID + "/instructions/resolve")
+	c.Params = []gin.Param{{Key: "id", Value: wsID}}
+	c.Request = httptest.NewRequest(http.MethodGet, "/workspaces/"+wsID+"/instructions/resolve", nil)
+
+	mock.ExpectQuery("SELECT scope, title, content FROM platform_instructions").
+		WithArgs(wsID).
+		WillReturnError(errors.New("connection refused"))
+
+	h.Resolve(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+func TestInstructionsResolve_MissingWorkspaceID(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newGetRequest("/workspaces//instructions/resolve")
+	c.Params = []gin.Param{{Key: "id", Value: ""}}
+
+	h.Resolve(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+// ─── scanInstructions edge cases ───────────────────────────────────────────────
+
+func TestScanInstructions_ScanError(t *testing.T) {
+	// A mock rows object that returns a scan error on second row.
+	badRows := sqlmock.NewRows(instructionCols).
+		AddRow("inst-ok", "global", nil, "OK", "OK content", 10, true, time.Now(), time.Now()).
+		RowError(1, errors.New("scan error")).
+		AddRow("inst-bad", "global", nil, "Bad", "Bad content", 5, true, time.Now(), time.Now())
+
+	result := scanInstructions(badRows)
+	// First row should be captured; scan error is logged and skipped.
+	if len(result) != 1 || result[0].ID != "inst-ok" {
+		t.Errorf("expected 1 instruction (inst-ok), got: %v", result)
+	}
+}
+
+// ─── maxInstructionContentLen boundary ────────────────────────────────────────
+
+func TestInstructionsCreate_ContentExactlyAtLimit(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	exactContent := string(make([]byte, maxInstructionContentLen))
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"title":   "At Limit",
+		"content": exactContent,
+	})
+
+	mock.ExpectQuery("INSERT INTO platform_instructions").
+		WithArgs("global", nil, "At Limit", exactContent, 0).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow("at-limit-1"))
+
+	h.Create(c)
+
+	// Exactly at limit must succeed (8192 chars is acceptable).
+	if w.Code != http.StatusCreated {
+		t.Fatalf("expected 201 for content at limit, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── priority defaults ────────────────────────────────────────────────────────
+
+func TestInstructionsCreate_PriorityDefaultsToZero(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	// Body omits priority — expect it defaults to 0.
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"title":   "No Priority",
+		"content": "Default priority body.",
+	})
+
+	mock.ExpectQuery("INSERT INTO platform_instructions").
+		WithArgs("global", nil, "No Priority", "Default priority body.", 0).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow("no-prio-1"))
+
+	h.Create(c)
+
+	if w.Code != http.StatusCreated {
+		t.Fatalf("expected 201, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── nil scope_target for global instructions ─────────────────────────────────
+
+func TestInstructionsCreate_GlobalScopeNilTarget(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":   "global",
+		"title":   "Global Nil Target",
+		"content": "Global instruction.",
+	})
+
+	// For global scope, scope_target must be SQL NULL.
+	mock.ExpectQuery("INSERT INTO platform_instructions").
+		WithArgs("global", nil, "Global Nil Target", "Global instruction.", 0).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow("global-nil-1"))
+
+	h.Create(c)
+
+	if w.Code != http.StatusCreated {
+		t.Fatalf("expected 201, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── workspace scope with empty string target (rejected) ─────────────────────
+
+func TestInstructionsCreate_WorkspaceScopeEmptyStringTarget(t *testing.T) {
+	setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	empty := ""
+	w, c := newPostRequest("/instructions", map[string]interface{}{
+		"scope":        "workspace",
+		"scope_target": empty,
+		"title":        "Empty Target",
+		"content":      "Empty workspace target.",
+	})
+
+	h.Create(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for empty string scope_target, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+// ─── Resolve: scope label transitions ────────────────────────────────────────
+
+func TestInstructionsResolve_ScopeTransitionOnlyGlobal(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	wsID := "ws-only-global"
+	w, c := newGetRequest("/workspaces/" + wsID + "/instructions/resolve")
+	c.Params = []gin.Param{{Key: "id", Value: wsID}}
+	c.Request = httptest.NewRequest(http.MethodGet, "/workspaces/"+wsID+"/instructions/resolve", nil)
+
+	rows := sqlmock.NewRows(resolveCols).
+		AddRow("global", "Rule One", "First rule.").
+		AddRow("global", "Rule Two", "Second rule.")
+	mock.ExpectQuery("SELECT scope, title, content FROM platform_instructions").
+		WithArgs(wsID).
+		WillReturnRows(rows)
+
+	h.Resolve(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var out struct {
+		Instructions string `json:"instructions"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &out); err != nil {
+		t.Fatalf("response not valid JSON: %v", err)
+	}
+	// Two global instructions share one section header.
+	if bytes.Count([]byte(out.Instructions), []byte("Platform-Wide Rules")) != 1 {
+		t.Error("expect exactly one 'Platform-Wide Rules' header for consecutive global rows")
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// ─── Update: empty body (all nil — no-op update) ─────────────────────────────
+
+func TestInstructionsUpdate_EmptyBody(t *testing.T) {
+	mock := setupTestDB(t)
+	h := NewInstructionsHandler()
+
+	instID := "inst-empty-update"
+	w, c := newPutRequest("/instructions/"+instID, map[string]interface{}{})
+	c.Params = []gin.Param{{Key: "id", Value: instID}}
+
+	// COALESCE(nil, ...) = unchanged; still updates updated_at.
+	mock.ExpectExec("UPDATE platform_instructions SET").
+		WithArgs(sqlmock.AnyArg(), sqlmock.AnyArg(), sqlmock.AnyArg(), sqlmock.AnyArg(), instID).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	h.Update(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200 for empty body, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}