diff --git a/apps/api/src/knowledge/dto/index.ts b/apps/api/src/knowledge/dto/index.ts
index 120371e..1fe3c76 100644
--- a/apps/api/src/knowledge/dto/index.ts
+++ b/apps/api/src/knowledge/dto/index.ts
@@ -3,3 +3,8 @@ export { UpdateEntryDto } from "./update-entry.dto";
 export { EntryQueryDto } from "./entry-query.dto";
 export { CreateTagDto } from "./create-tag.dto";
 export { UpdateTagDto } from "./update-tag.dto";
+export {
+  SearchQueryDto,
+  TagSearchDto,
+  RecentEntriesDto,
+} from "./search-query.dto";
diff --git a/apps/api/src/knowledge/dto/search-query.dto.ts b/apps/api/src/knowledge/dto/search-query.dto.ts
new file mode 100644
index 0000000..81f48bd
--- /dev/null
+++ b/apps/api/src/knowledge/dto/search-query.dto.ts
@@ -0,0 +1,81 @@
+import {
+  IsOptional,
+  IsString,
+  IsInt,
+  Min,
+  Max,
+  IsArray,
+  IsEnum,
+} from "class-validator";
+import { Type, Transform } from "class-transformer";
+import { EntryStatus } from "@prisma/client";
+
+/**
+ * DTO for full-text search query parameters
+ */
+export class SearchQueryDto {
+  @IsString({ message: "q (query) must be a string" })
+  q!: string;
+
+  @IsOptional()
+  @IsEnum(EntryStatus, { message: "status must be a valid EntryStatus" })
+  status?: EntryStatus;
+
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "page must be an integer" })
+  @Min(1, { message: "page must be at least 1" })
+  page?: number;
+
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "limit must be an integer" })
+  @Min(1, { message: "limit must be at least 1" })
+  @Max(100, { message: "limit must not exceed 100" })
+  limit?: number;
+}
+
+/**
+ * DTO for searching by tags
+ */
+export class TagSearchDto {
+  @Transform(({ value }) =>
+    typeof value === "string" ? value.split(",") : value
+  )
+  @IsArray({ message: "tags must be an array" })
+  @IsString({ each: true, message: "each tag must be a string" })
+  tags!: string[];
+
+  @IsOptional()
+  @IsEnum(EntryStatus, { message: "status must be a valid EntryStatus" })
+  status?: EntryStatus;
+
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "page must be an integer" })
+  @Min(1, { message: "page must be at least 1" })
+  page?: number;
+
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "limit must be an integer" })
+  @Min(1, { message: "limit must be at least 1" })
+  @Max(100, { message: "limit must not exceed 100" })
+  limit?: number;
+}
+
+/**
+ * DTO for recent entries query
+ */
+export class RecentEntriesDto {
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "limit must be an integer" })
+  @Min(1, { message: "limit must be at least 1" })
+  @Max(50, { message: "limit must not exceed 50" })
+  limit?: number;
+
+  @IsOptional()
+  @IsEnum(EntryStatus, { message: "status must be a valid EntryStatus" })
+  status?: EntryStatus;
+}
diff --git a/apps/api/src/knowledge/knowledge.module.ts b/apps/api/src/knowledge/knowledge.module.ts
index d826d33..a22a58c 100644
--- a/apps/api/src/knowledge/knowledge.module.ts
+++ b/apps/api/src/knowledge/knowledge.module.ts
@@ -3,12 +3,14 @@ import { PrismaModule } from "../prisma/prisma.module";
 import { AuthModule } from "../auth/auth.module";
 import { KnowledgeService } from "./knowledge.service";
 import { KnowledgeController } from "./knowledge.controller";
+import { SearchController } from "./search.controller";
 import { LinkResolutionService } from "./services/link-resolution.service";
+import { SearchService } from "./services/search.service";
 
 @Module({
   imports: [PrismaModule, AuthModule],
-  controllers: [KnowledgeController],
-  providers: [KnowledgeService, LinkResolutionService],
-  exports: [KnowledgeService, LinkResolutionService],
+  controllers: [KnowledgeController, SearchController],
+  providers: [KnowledgeService, LinkResolutionService, SearchService],
+  exports: [KnowledgeService, LinkResolutionService, SearchService],
 })
 export class KnowledgeModule {}
diff --git a/apps/api/src/knowledge/search.controller.spec.ts b/apps/api/src/knowledge/search.controller.spec.ts
new file mode 100644
index 0000000..7c25562
--- /dev/null
+++ b/apps/api/src/knowledge/search.controller.spec.ts
@@ -0,0 +1,197 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { Test, TestingModule } from "@nestjs/testing";
+import { EntryStatus } from "@prisma/client";
+import { SearchController } from "./search.controller";
+import { SearchService } from "./services/search.service";
+import { AuthGuard } from "../auth/guards/auth.guard";
+import { WorkspaceGuard, PermissionGuard } from "../common/guards";
+
+describe("SearchController", () => {
+  let controller: SearchController;
+
+  const mockWorkspaceId = "550e8400-e29b-41d4-a716-446655440000";
+
+  const mockSearchService = {
+    search: vi.fn(),
+    searchByTags: vi.fn(),
+    recentEntries: vi.fn(),
+  };
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      controllers: [SearchController],
+      providers: [
+        {
+          provide: SearchService,
+          useValue: mockSearchService,
+        },
+      ],
+    })
+      .overrideGuard(AuthGuard)
+      .useValue({ canActivate: () => true })
+      .overrideGuard(WorkspaceGuard)
+      .useValue({ canActivate: () => true })
+      .overrideGuard(PermissionGuard)
+      .useValue({ canActivate: () => true })
+      .compile();
+
+    controller = module.get<SearchController>(SearchController);
+
+    vi.clearAllMocks();
+  });
+
+  describe("search", () => {
+    it("should call searchService.search with correct parameters", async () => {
+      const mockResult = {
+        data: [],
+        pagination: { page: 1, limit: 20, total: 0, totalPages: 0 },
+        query: "test",
+      };
+      mockSearchService.search.mockResolvedValue(mockResult);
+
+      const result = await controller.search(mockWorkspaceId, {
+        q: "test",
+        page: 1,
+        limit: 20,
+      });
+
+      expect(mockSearchService.search).toHaveBeenCalledWith(
+        "test",
+        mockWorkspaceId,
+        {
+          status: undefined,
+          page: 1,
+          limit: 20,
+        }
+      );
+      expect(result).toEqual(mockResult);
+    });
+
+    it("should pass status filter to service", async () => {
+      mockSearchService.search.mockResolvedValue({
+        data: [],
+        pagination: { page: 1, limit: 20, total: 0, totalPages: 0 },
+        query: "test",
+      });
+
+      await controller.search(mockWorkspaceId, {
+        q: "test",
+        status: EntryStatus.PUBLISHED,
+      });
+
+      expect(mockSearchService.search).toHaveBeenCalledWith(
+        "test",
+        mockWorkspaceId,
+        {
+          status: EntryStatus.PUBLISHED,
+          page: undefined,
+          limit: undefined,
+        }
+      );
+    });
+  });
+
+  describe("searchByTags", () => {
+    it("should call searchService.searchByTags with correct parameters", async () => {
+      const mockResult = {
+        data: [],
+        pagination: { page: 1, limit: 20, total: 0, totalPages: 0 },
+      };
+      mockSearchService.searchByTags.mockResolvedValue(mockResult);
+
+      const result = await controller.searchByTags(mockWorkspaceId, {
+        tags: ["api", "documentation"],
+        page: 1,
+        limit: 20,
+      });
+
+      expect(mockSearchService.searchByTags).toHaveBeenCalledWith(
+        ["api", "documentation"],
+        mockWorkspaceId,
+        {
+          status: undefined,
+          page: 1,
+          limit: 20,
+        }
+      );
+      expect(result).toEqual(mockResult);
+    });
+
+    it("should pass status filter to service", async () => {
+      mockSearchService.searchByTags.mockResolvedValue({
+        data: [],
+        pagination: { page: 1, limit: 20, total: 0, totalPages: 0 },
+      });
+
+      await controller.searchByTags(mockWorkspaceId, {
+        tags: ["api"],
+        status: EntryStatus.DRAFT,
+      });
+
+      expect(mockSearchService.searchByTags).toHaveBeenCalledWith(
+        ["api"],
+        mockWorkspaceId,
+        {
+          status: EntryStatus.DRAFT,
+          page: undefined,
+          limit: undefined,
+        }
+      );
+    });
+  });
+
+  describe("recentEntries", () => {
+    it("should call searchService.recentEntries with correct parameters", async () => {
+      const mockEntries = [
+        {
+          id: "entry-1",
+          title: "Recent Entry",
+          slug: "recent-entry",
+          tags: [],
+        },
+      ];
+      mockSearchService.recentEntries.mockResolvedValue(mockEntries);
+
+      const result = await controller.recentEntries(mockWorkspaceId, {
+        limit: 10,
+      });
+
+      expect(mockSearchService.recentEntries).toHaveBeenCalledWith(
+        mockWorkspaceId,
+        10,
+        undefined
+      );
+      expect(result).toEqual({
+        data: mockEntries,
+        count: 1,
+      });
+    });
+
+    it("should use default limit of 10", async () => {
+      mockSearchService.recentEntries.mockResolvedValue([]);
+
+      await controller.recentEntries(mockWorkspaceId, {});
+
+      expect(mockSearchService.recentEntries).toHaveBeenCalledWith(
+        mockWorkspaceId,
+        10,
+        undefined
+      );
+    });
+
+    it("should pass status filter to service", async () => {
+      mockSearchService.recentEntries.mockResolvedValue([]);
+
+      await controller.recentEntries(mockWorkspaceId, {
+        status: EntryStatus.PUBLISHED,
+        limit: 5,
+      });
+
+      expect(mockSearchService.recentEntries).toHaveBeenCalledWith(
+        mockWorkspaceId,
+        5,
+        EntryStatus.PUBLISHED
+      );
+    });
+  });
+});
diff --git a/apps/api/src/knowledge/search.controller.ts b/apps/api/src/knowledge/search.controller.ts
new file mode 100644
index 0000000..5d3f7b0
--- /dev/null
+++ b/apps/api/src/knowledge/search.controller.ts
@@ -0,0 +1,88 @@
+import { Controller, Get, Query, UseGuards } from "@nestjs/common";
+import { SearchService } from "./services/search.service";
+import { SearchQueryDto, TagSearchDto, RecentEntriesDto } from "./dto";
+import { AuthGuard } from "../auth/guards/auth.guard";
+import { WorkspaceGuard, PermissionGuard } from "../common/guards";
+import { Workspace, Permission, RequirePermission } from "../common/decorators";
+
+/**
+ * Controller for knowledge search endpoints
+ * All endpoints require authentication and workspace context
+ */
+@Controller("knowledge/search")
+@UseGuards(AuthGuard, WorkspaceGuard, PermissionGuard)
+export class SearchController {
+  constructor(private readonly searchService: SearchService) {}
+
+  /**
+   * GET /api/knowledge/search
+   * Full-text search across knowledge entries
+   * Searches title and content with relevance ranking
+   * Requires: Any workspace member
+   *
+   * @query q - The search query string (required)
+   * @query status - Filter by entry status (optional)
+   * @query page - Page number (default: 1)
+   * @query limit - Results per page (default: 20, max: 100)
+   */
+  @Get()
+  @RequirePermission(Permission.WORKSPACE_ANY)
+  async search(
+    @Workspace() workspaceId: string,
+    @Query() query: SearchQueryDto
+  ) {
+    return this.searchService.search(query.q, workspaceId, {
+      status: query.status,
+      page: query.page,
+      limit: query.limit,
+    });
+  }
+
+  /**
+   * GET /api/knowledge/search/by-tags
+   * Search entries by tags (entries must have ALL specified tags)
+   * Requires: Any workspace member
+   *
+   * @query tags - Comma-separated list of tag slugs (required)
+   * @query status - Filter by entry status (optional)
+   * @query page - Page number (default: 1)
+   * @query limit - Results per page (default: 20, max: 100)
+   */
+  @Get("by-tags")
+  @RequirePermission(Permission.WORKSPACE_ANY)
+  async searchByTags(
+    @Workspace() workspaceId: string,
+    @Query() query: TagSearchDto
+  ) {
+    return this.searchService.searchByTags(query.tags, workspaceId, {
+      status: query.status,
+      page: query.page,
+      limit: query.limit,
+    });
+  }
+
+  /**
+   * GET /api/knowledge/search/recent
+   * Get recently modified entries
+   * Requires: Any workspace member
+   *
+   * @query limit - Maximum number of entries (default: 10, max: 50)
+   * @query status - Filter by entry status (optional)
+   */
+  @Get("recent")
+  @RequirePermission(Permission.WORKSPACE_ANY)
+  async recentEntries(
+    @Workspace() workspaceId: string,
+    @Query() query: RecentEntriesDto
+  ) {
+    const entries = await this.searchService.recentEntries(
+      workspaceId,
+      query.limit || 10,
+      query.status
+    );
+    return {
+      data: entries,
+      count: entries.length,
+    };
+  }
+}
diff --git a/apps/api/src/knowledge/services/search.service.spec.ts b/apps/api/src/knowledge/services/search.service.spec.ts
new file mode 100644
index 0000000..d7f96ce
--- /dev/null
+++ b/apps/api/src/knowledge/services/search.service.spec.ts
@@ -0,0 +1,318 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { Test, TestingModule } from "@nestjs/testing";
+import { EntryStatus } from "@prisma/client";
+import { SearchService } from "./search.service";
+import { PrismaService } from "../../prisma/prisma.service";
+
+describe("SearchService", () => {
+  let service: SearchService;
+  let prismaService: any;
+
+  const mockWorkspaceId = "550e8400-e29b-41d4-a716-446655440000";
+
+  beforeEach(async () => {
+    const mockQueryRaw = vi.fn();
+    const mockKnowledgeEntryCount = vi.fn();
+    const mockKnowledgeEntryFindMany = vi.fn();
+    const mockKnowledgeEntryTagFindMany = vi.fn();
+
+    const mockPrismaService = {
+      $queryRaw: mockQueryRaw,
+      knowledgeEntry: {
+        count: mockKnowledgeEntryCount,
+        findMany: mockKnowledgeEntryFindMany,
+      },
+      knowledgeEntryTag: {
+        findMany: mockKnowledgeEntryTagFindMany,
+      },
+    };
+
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [
+        SearchService,
+        {
+          provide: PrismaService,
+          useValue: mockPrismaService,
+        },
+      ],
+    }).compile();
+
+    service = module.get<SearchService>(SearchService);
+    prismaService = module.get<PrismaService>(PrismaService);
+  });
+
+  describe("search", () => {
+    it("should return empty results for empty query", async () => {
+      const result = await service.search("", mockWorkspaceId);
+
+      expect(result.data).toEqual([]);
+      expect(result.pagination.total).toBe(0);
+      expect(result.query).toBe("");
+    });
+
+    it("should return empty results for whitespace-only query", async () => {
+      const result = await service.search("   ", mockWorkspaceId);
+
+      expect(result.data).toEqual([]);
+      expect(result.pagination.total).toBe(0);
+    });
+
+    it("should perform full-text search and return ranked results", async () => {
+      const mockSearchResults = [
+        {
+          id: "entry-1",
+          workspace_id: mockWorkspaceId,
+          slug: "test-entry",
+          title: "Test Entry",
+          content: "This is test content",
+          content_html: "<p>This is test content</p>",
+          summary: "Test summary",
+          status: EntryStatus.PUBLISHED,
+          visibility: "WORKSPACE",
+          created_at: new Date(),
+          updated_at: new Date(),
+          created_by: "user-1",
+          updated_by: "user-1",
+          rank: 0.5,
+          headline: "This is <mark>test</mark> content",
+        },
+      ];
+
+      prismaService.$queryRaw
+        .mockResolvedValueOnce(mockSearchResults)
+        .mockResolvedValueOnce([{ count: BigInt(1) }]);
+
+      prismaService.knowledgeEntryTag.findMany.mockResolvedValue([
+        {
+          entryId: "entry-1",
+          tag: {
+            id: "tag-1",
+            name: "Documentation",
+            slug: "documentation",
+            color: "#blue",
+          },
+        },
+      ]);
+
+      const result = await service.search("test", mockWorkspaceId);
+
+      expect(result.data).toHaveLength(1);
+      expect(result.data[0].title).toBe("Test Entry");
+      expect(result.data[0].rank).toBe(0.5);
+      expect(result.data[0].headline).toBe("This is <mark>test</mark> content");
+      expect(result.data[0].tags).toHaveLength(1);
+      expect(result.pagination.total).toBe(1);
+      expect(result.query).toBe("test");
+    });
+
+    it("should sanitize search query removing special characters", async () => {
+      prismaService.$queryRaw
+        .mockResolvedValueOnce([])
+        .mockResolvedValueOnce([{ count: BigInt(0) }]);
+      prismaService.knowledgeEntryTag.findMany.mockResolvedValue([]);
+
+      await service.search("test & query | !special:chars*", mockWorkspaceId);
+
+      // Should have been called with sanitized query
+      expect(prismaService.$queryRaw).toHaveBeenCalled();
+    });
+
+    it("should apply status filter when provided", async () => {
+      prismaService.$queryRaw
+        .mockResolvedValueOnce([])
+        .mockResolvedValueOnce([{ count: BigInt(0) }]);
+      prismaService.knowledgeEntryTag.findMany.mockResolvedValue([]);
+
+      await service.search("test", mockWorkspaceId, {
+        status: EntryStatus.DRAFT,
+      });
+
+      expect(prismaService.$queryRaw).toHaveBeenCalled();
+    });
+
+    it("should handle pagination correctly", async () => {
+      prismaService.$queryRaw
+        .mockResolvedValueOnce([])
+        .mockResolvedValueOnce([{ count: BigInt(50) }]);
+      prismaService.knowledgeEntryTag.findMany.mockResolvedValue([]);
+
+      const result = await service.search("test", mockWorkspaceId, {
+        page: 2,
+        limit: 10,
+      });
+
+      expect(result.pagination.page).toBe(2);
+      expect(result.pagination.limit).toBe(10);
+      expect(result.pagination.total).toBe(50);
+      expect(result.pagination.totalPages).toBe(5);
+    });
+  });
+
+  describe("searchByTags", () => {
+    it("should return empty results for empty tags array", async () => {
+      const result = await service.searchByTags([], mockWorkspaceId);
+
+      expect(result.data).toEqual([]);
+      expect(result.pagination.total).toBe(0);
+    });
+
+    it("should find entries with all specified tags", async () => {
+      const mockEntries = [
+        {
+          id: "entry-1",
+          workspaceId: mockWorkspaceId,
+          slug: "tagged-entry",
+          title: "Tagged Entry",
+          content: "Content with tags",
+          contentHtml: "<p>Content with tags</p>",
+          summary: null,
+          status: EntryStatus.PUBLISHED,
+          visibility: "WORKSPACE",
+          createdAt: new Date(),
+          updatedAt: new Date(),
+          createdBy: "user-1",
+          updatedBy: "user-1",
+          tags: [
+            {
+              tag: {
+                id: "tag-1",
+                name: "API",
+                slug: "api",
+                color: "#blue",
+              },
+            },
+            {
+              tag: {
+                id: "tag-2",
+                name: "Documentation",
+                slug: "documentation",
+                color: "#green",
+              },
+            },
+          ],
+        },
+      ];
+
+      prismaService.knowledgeEntry.count.mockResolvedValue(1);
+      prismaService.knowledgeEntry.findMany.mockResolvedValue(mockEntries);
+
+      const result = await service.searchByTags(
+        ["api", "documentation"],
+        mockWorkspaceId
+      );
+
+      expect(result.data).toHaveLength(1);
+      expect(result.data[0].title).toBe("Tagged Entry");
+      expect(result.data[0].tags).toHaveLength(2);
+      expect(result.pagination.total).toBe(1);
+    });
+
+    it("should apply status filter when provided", async () => {
+      prismaService.knowledgeEntry.count.mockResolvedValue(0);
+      prismaService.knowledgeEntry.findMany.mockResolvedValue([]);
+
+      await service.searchByTags(["api"], mockWorkspaceId, {
+        status: EntryStatus.DRAFT,
+      });
+
+      expect(prismaService.knowledgeEntry.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          where: expect.objectContaining({
+            status: EntryStatus.DRAFT,
+          }),
+        })
+      );
+    });
+
+    it("should handle pagination correctly", async () => {
+      prismaService.knowledgeEntry.count.mockResolvedValue(25);
+      prismaService.knowledgeEntry.findMany.mockResolvedValue([]);
+
+      const result = await service.searchByTags(["api"], mockWorkspaceId, {
+        page: 2,
+        limit: 10,
+      });
+
+      expect(result.pagination.page).toBe(2);
+      expect(result.pagination.limit).toBe(10);
+      expect(result.pagination.total).toBe(25);
+      expect(result.pagination.totalPages).toBe(3);
+    });
+  });
+
+  describe("recentEntries", () => {
+    it("should return recently modified entries", async () => {
+      const mockEntries = [
+        {
+          id: "entry-1",
+          workspaceId: mockWorkspaceId,
+          slug: "recent-entry",
+          title: "Recent Entry",
+          content: "Recently updated content",
+          contentHtml: "<p>Recently updated content</p>",
+          summary: null,
+          status: EntryStatus.PUBLISHED,
+          visibility: "WORKSPACE",
+          createdAt: new Date(),
+          updatedAt: new Date(),
+          createdBy: "user-1",
+          updatedBy: "user-1",
+          tags: [],
+        },
+      ];
+
+      prismaService.knowledgeEntry.findMany.mockResolvedValue(mockEntries);
+
+      const result = await service.recentEntries(mockWorkspaceId);
+
+      expect(result).toHaveLength(1);
+      expect(result[0].title).toBe("Recent Entry");
+      expect(prismaService.knowledgeEntry.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          orderBy: { updatedAt: "desc" },
+          take: 10,
+        })
+      );
+    });
+
+    it("should respect the limit parameter", async () => {
+      prismaService.knowledgeEntry.findMany.mockResolvedValue([]);
+
+      await service.recentEntries(mockWorkspaceId, 5);
+
+      expect(prismaService.knowledgeEntry.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          take: 5,
+        })
+      );
+    });
+
+    it("should apply status filter when provided", async () => {
+      prismaService.knowledgeEntry.findMany.mockResolvedValue([]);
+
+      await service.recentEntries(mockWorkspaceId, 10, EntryStatus.DRAFT);
+
+      expect(prismaService.knowledgeEntry.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          where: expect.objectContaining({
+            status: EntryStatus.DRAFT,
+          }),
+        })
+      );
+    });
+
+    it("should exclude archived entries by default", async () => {
+      prismaService.knowledgeEntry.findMany.mockResolvedValue([]);
+
+      await service.recentEntries(mockWorkspaceId);
+
+      expect(prismaService.knowledgeEntry.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          where: expect.objectContaining({
+            status: { not: EntryStatus.ARCHIVED },
+          }),
+        })
+      );
+    });
+  });
+});
diff --git a/apps/api/src/knowledge/services/search.service.ts b/apps/api/src/knowledge/services/search.service.ts
new file mode 100644
index 0000000..18add2d
--- /dev/null
+++ b/apps/api/src/knowledge/services/search.service.ts
@@ -0,0 +1,415 @@
+import { Injectable } from "@nestjs/common";
+import { EntryStatus, Prisma } from "@prisma/client";
+import { PrismaService } from "../../prisma/prisma.service";
+import type {
+  KnowledgeEntryWithTags,
+  PaginatedEntries,
+} from "../entities/knowledge-entry.entity";
+
+/**
+ * Search options for full-text search
+ */
+export interface SearchOptions {
+  status?: EntryStatus | undefined;
+  page?: number | undefined;
+  limit?: number | undefined;
+}
+
+/**
+ * Search result with relevance ranking
+ */
+export interface SearchResult extends KnowledgeEntryWithTags {
+  rank: number;
+  headline?: string | undefined;
+}
+
+/**
+ * Paginated search results
+ */
+export interface PaginatedSearchResults {
+  data: SearchResult[];
+  pagination: {
+    page: number;
+    limit: number;
+    total: number;
+    totalPages: number;
+  };
+  query: string;
+}
+
+/**
+ * Raw search result from PostgreSQL query
+ */
+interface RawSearchResult {
+  id: string;
+  workspace_id: string;
+  slug: string;
+  title: string;
+  content: string;
+  content_html: string | null;
+  summary: string | null;
+  status: EntryStatus;
+  visibility: string;
+  created_at: Date;
+  updated_at: Date;
+  created_by: string;
+  updated_by: string;
+  rank: number;
+  headline: string | null;
+}
+
+/**
+ * Service for searching knowledge entries using PostgreSQL full-text search
+ */
+@Injectable()
+export class SearchService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  /**
+   * Full-text search on title and content using PostgreSQL ts_vector
+   *
+   * @param query - The search query string
+   * @param workspaceId - The workspace to search within
+   * @param options - Search options (status filter, pagination)
+   * @returns Paginated search results ranked by relevance
+   */
+  async search(
+    query: string,
+    workspaceId: string,
+    options: SearchOptions = {}
+  ): Promise<PaginatedSearchResults> {
+    const page = options.page || 1;
+    const limit = options.limit || 20;
+    const offset = (page - 1) * limit;
+
+    // Sanitize and prepare the search query
+    const sanitizedQuery = this.sanitizeSearchQuery(query);
+
+    if (!sanitizedQuery) {
+      return {
+        data: [],
+        pagination: {
+          page,
+          limit,
+          total: 0,
+          totalPages: 0,
+        },
+        query,
+      };
+    }
+
+    // Build status filter
+    const statusFilter = options.status
+      ? Prisma.sql`AND e.status = ${options.status}::text::"EntryStatus"`
+      : Prisma.sql`AND e.status != 'ARCHIVED'`;
+
+    // PostgreSQL full-text search query
+    // Uses ts_rank for relevance scoring with weights: title (A=1.0), content (B=0.4)
+    const searchResults = await this.prisma.$queryRaw<RawSearchResult[]>`
+      WITH search_query AS (
+        SELECT plainto_tsquery('english', ${sanitizedQuery}) AS query
+      )
+      SELECT 
+        e.id,
+        e.workspace_id,
+        e.slug,
+        e.title,
+        e.content,
+        e.content_html,
+        e.summary,
+        e.status,
+        e.visibility,
+        e.created_at,
+        e.updated_at,
+        e.created_by,
+        e.updated_by,
+        ts_rank(
+          setweight(to_tsvector('english', e.title), 'A') ||
+          setweight(to_tsvector('english', e.content), 'B'),
+          sq.query
+        ) AS rank,
+        ts_headline(
+          'english',
+          e.content,
+          sq.query,
+          'MaxWords=50, MinWords=25, StartSel=<mark>, StopSel=</mark>'
+        ) AS headline
+      FROM knowledge_entries e, search_query sq
+      WHERE e.workspace_id = ${workspaceId}::uuid
+        ${statusFilter}
+        AND (
+          to_tsvector('english', e.title) @@ sq.query
+          OR to_tsvector('english', e.content) @@ sq.query
+        )
+      ORDER BY rank DESC, e.updated_at DESC
+      LIMIT ${limit}
+      OFFSET ${offset}
+    `;
+
+    // Get total count for pagination
+    const countResult = await this.prisma.$queryRaw<[{ count: bigint }]>`
+      SELECT COUNT(*) as count
+      FROM knowledge_entries e
+      WHERE e.workspace_id = ${workspaceId}::uuid
+        ${statusFilter}
+        AND (
+          to_tsvector('english', e.title) @@ plainto_tsquery('english', ${sanitizedQuery})
+          OR to_tsvector('english', e.content) @@ plainto_tsquery('english', ${sanitizedQuery})
+        )
+    `;
+
+    const total = Number(countResult[0].count);
+
+    // Fetch tags for the results
+    const entryIds = searchResults.map((r) => r.id);
+    const tagsMap = await this.fetchTagsForEntries(entryIds);
+
+    // Transform results to the expected format
+    const data: SearchResult[] = searchResults.map((row) => ({
+      id: row.id,
+      workspaceId: row.workspace_id,
+      slug: row.slug,
+      title: row.title,
+      content: row.content,
+      contentHtml: row.content_html,
+      summary: row.summary,
+      status: row.status,
+      visibility: row.visibility as "PRIVATE" | "WORKSPACE" | "PUBLIC",
+      createdAt: row.created_at,
+      updatedAt: row.updated_at,
+      createdBy: row.created_by,
+      updatedBy: row.updated_by,
+      rank: row.rank,
+      headline: row.headline ?? undefined,
+      tags: tagsMap.get(row.id) || [],
+    }));
+
+    return {
+      data,
+      pagination: {
+        page,
+        limit,
+        total,
+        totalPages: Math.ceil(total / limit),
+      },
+      query,
+    };
+  }
+
+  /**
+   * Search entries by tags (entries must have ALL specified tags)
+   *
+   * @param tags - Array of tag slugs to filter by
+   * @param workspaceId - The workspace to search within
+   * @param options - Search options (status filter, pagination)
+   * @returns Paginated entries that have all specified tags
+   */
+  async searchByTags(
+    tags: string[],
+    workspaceId: string,
+    options: SearchOptions = {}
+  ): Promise<PaginatedEntries> {
+    const page = options.page || 1;
+    const limit = options.limit || 20;
+    const skip = (page - 1) * limit;
+
+    if (!tags || tags.length === 0) {
+      return {
+        data: [],
+        pagination: {
+          page,
+          limit,
+          total: 0,
+          totalPages: 0,
+        },
+      };
+    }
+
+    // Build where clause for entries that have ALL specified tags
+    const where: Prisma.KnowledgeEntryWhereInput = {
+      workspaceId,
+      status: options.status || { not: EntryStatus.ARCHIVED },
+      AND: tags.map((tagSlug) => ({
+        tags: {
+          some: {
+            tag: {
+              slug: tagSlug,
+            },
+          },
+        },
+      })),
+    };
+
+    // Get total count
+    const total = await this.prisma.knowledgeEntry.count({ where });
+
+    // Get entries
+    const entries = await this.prisma.knowledgeEntry.findMany({
+      where,
+      include: {
+        tags: {
+          include: {
+            tag: true,
+          },
+        },
+      },
+      orderBy: {
+        updatedAt: "desc",
+      },
+      skip,
+      take: limit,
+    });
+
+    // Transform to response format
+    const data: KnowledgeEntryWithTags[] = entries.map((entry) => ({
+      id: entry.id,
+      workspaceId: entry.workspaceId,
+      slug: entry.slug,
+      title: entry.title,
+      content: entry.content,
+      contentHtml: entry.contentHtml,
+      summary: entry.summary,
+      status: entry.status,
+      visibility: entry.visibility,
+      createdAt: entry.createdAt,
+      updatedAt: entry.updatedAt,
+      createdBy: entry.createdBy,
+      updatedBy: entry.updatedBy,
+      tags: entry.tags.map((et) => ({
+        id: et.tag.id,
+        name: et.tag.name,
+        slug: et.tag.slug,
+        color: et.tag.color,
+      })),
+    }));
+
+    return {
+      data,
+      pagination: {
+        page,
+        limit,
+        total,
+        totalPages: Math.ceil(total / limit),
+      },
+    };
+  }
+
+  /**
+   * Get recently modified entries
+   *
+   * @param workspaceId - The workspace to query
+   * @param limit - Maximum number of entries to return (default: 10)
+   * @param status - Optional status filter
+   * @returns Array of recently modified entries
+   */
+  async recentEntries(
+    workspaceId: string,
+    limit: number = 10,
+    status?: EntryStatus
+  ): Promise<KnowledgeEntryWithTags[]> {
+    const where: Prisma.KnowledgeEntryWhereInput = {
+      workspaceId,
+      status: status || { not: EntryStatus.ARCHIVED },
+    };
+
+    const entries = await this.prisma.knowledgeEntry.findMany({
+      where,
+      include: {
+        tags: {
+          include: {
+            tag: true,
+          },
+        },
+      },
+      orderBy: {
+        updatedAt: "desc",
+      },
+      take: limit,
+    });
+
+    return entries.map((entry) => ({
+      id: entry.id,
+      workspaceId: entry.workspaceId,
+      slug: entry.slug,
+      title: entry.title,
+      content: entry.content,
+      contentHtml: entry.contentHtml,
+      summary: entry.summary,
+      status: entry.status,
+      visibility: entry.visibility,
+      createdAt: entry.createdAt,
+      updatedAt: entry.updatedAt,
+      createdBy: entry.createdBy,
+      updatedBy: entry.updatedBy,
+      tags: entry.tags.map((et) => ({
+        id: et.tag.id,
+        name: et.tag.name,
+        slug: et.tag.slug,
+        color: et.tag.color,
+      })),
+    }));
+  }
+
+  /**
+   * Sanitize search query to prevent SQL injection and handle special characters
+   */
+  private sanitizeSearchQuery(query: string): string {
+    if (!query || typeof query !== "string") {
+      return "";
+    }
+
+    // Trim and normalize whitespace
+    let sanitized = query.trim().replace(/\s+/g, " ");
+
+    // Remove PostgreSQL full-text search operators that could cause issues
+    sanitized = sanitized.replace(/[&|!:*()]/g, " ");
+
+    // Trim again after removing special chars
+    sanitized = sanitized.trim();
+
+    return sanitized;
+  }
+
+  /**
+   * Fetch tags for a list of entry IDs
+   */
+  private async fetchTagsForEntries(
+    entryIds: string[]
+  ): Promise<
+    Map<
+      string,
+      Array<{ id: string; name: string; slug: string; color: string | null }>
+    >
+  > {
+    if (entryIds.length === 0) {
+      return new Map();
+    }
+
+    const entryTags = await this.prisma.knowledgeEntryTag.findMany({
+      where: {
+        entryId: { in: entryIds },
+      },
+      include: {
+        tag: true,
+      },
+    });
+
+    const tagsMap = new Map<
+      string,
+      Array<{ id: string; name: string; slug: string; color: string | null }>
+    >();
+
+    for (const et of entryTags) {
+      const tags = tagsMap.get(et.entryId) || [];
+      tags.push({
+        id: et.tag.id,
+        name: et.tag.name,
+        slug: et.tag.slug,
+        color: et.tag.color,
+      });
+      tagsMap.set(et.entryId, tags);
+    }
+
+    return tagsMap;
+  }
+}