diff --git a/packages/core/src/__tests__/agent-system-prompt.test.ts b/packages/core/src/__tests__/agent-system-prompt.test.ts
index 98b59a9..b9920f8 100644
--- a/packages/core/src/__tests__/agent-system-prompt.test.ts
+++ b/packages/core/src/__tests__/agent-system-prompt.test.ts
@@ -56,6 +56,7 @@ describe("buildAgentSystemPrompt", () => {
       expect(prompt).toContain("write_truth_file");
       expect(prompt).toContain("rename_entity");
       expect(prompt).toContain("patch_chapter_text");
+      expect(prompt).toContain("edit");
       expect(prompt).toContain("grep");
       expect(prompt).toContain("ls");
     });
@@ -66,7 +67,7 @@ describe("buildAgentSystemPrompt", () => {
       expect(prompt).toContain("write_truth_file");
       expect(prompt).toContain("用户要求重写/精修已有章节");
       expect(prompt).toContain("revise_chapter");
-      expect(prompt).not.toContain("用户想做小修改（改名字、调设定）→ 用 edit 直接修改");
+      expect(prompt).toContain("只有当上述专用工具都不适合");
     });
 
     it("Chinese prompt warns NOT to call architect", () => {
diff --git a/packages/core/src/agent/agent-session.ts b/packages/core/src/agent/agent-session.ts
index ebf2a83..bfec49f 100644
--- a/packages/core/src/agent/agent-session.ts
+++ b/packages/core/src/agent/agent-session.ts
@@ -240,6 +240,7 @@ export async function runAgentSession(
           createWriteTruthFileTool(pipeline, projectRoot, bookId),
           createRenameEntityTool(pipeline, projectRoot, bookId),
           createPatchChapterTextTool(pipeline, projectRoot, bookId),
+          createEditTool(projectRoot),
           createGrepTool(projectRoot),
           createLsTool(projectRoot),
         ],
diff --git a/packages/core/src/agent/agent-system-prompt.ts b/packages/core/src/agent/agent-system-prompt.ts
index f7e91aa..08e40e3 100644
--- a/packages/core/src/agent/agent-system-prompt.ts
+++ b/packages/core/src/agent/agent-system-prompt.ts
@@ -81,6 +81,7 @@ export function buildAgentSystemPrompt(bookId: string | null, language: string):
 - **write_truth_file** — 整文件覆盖真相文件（story_bible、volume_outline、book_rules、current_focus 等）
 - **rename_entity** — 统一改角色/实体名
 - **patch_chapter_text** — 对已有章节做局部定点修补
+- **edit** — 通用精确字符串替换编辑（仅在专用 deterministic 工具都不适合时使用）
 - **grep** — 搜索内容（如"哪一章提到了某个角色"）
 - **ls** — 列出文件或章节
 
@@ -92,6 +93,7 @@ export function buildAgentSystemPrompt(bookId: string | null, language: string):
 - 用户要求重写/精修已有章节 → 用 revise_chapter
 - 用户要求角色或实体改名 → 用 rename_entity
 - 用户要求对某一章做局部小修 → 用 patch_chapter_text
+- 只有当上述专用工具都不适合，而且你已精确读取并定位文本时，才使用 edit
 - 其他情况 → 直接对话回答
 - **注意：不要调用 architect，当前已有书籍，不需要建书**
 - **不要在回复中添加表情符号**
@@ -128,6 +130,7 @@ export function buildAgentSystemPrompt(bookId: string | null, language: string):
 - **write_truth_file** — Replace a canonical truth file in story/
 - **rename_entity** — Rename a character or entity across the book
 - **patch_chapter_text** — Apply a local deterministic patch to a chapter
+- **edit** — Generic exact string replacement editor (use only when the dedicated deterministic tools do not fit)
 - **grep** — Search content across chapters
 - **ls** — List files or chapters
 
@@ -139,6 +142,7 @@ export function buildAgentSystemPrompt(bookId: string | null, language: string):
 - Use revise_chapter for rewrite/polish/rework of existing chapters
 - Use rename_entity for character/entity renames
 - Use patch_chapter_text for local chapter fixes
+- Use edit only as a last-resort generic editor after you have read the exact file content
 - Chat directly for other questions
 - **Do NOT call architect — a book already exists**
 - **Do NOT use emoji in your responses**