feat(FN-794): raise auto-summarization threshold from 140 to 200 characters

- Change MIN_DESCRIPTION_LENGTH threshold from 140 to 200 in ai-summarize.ts
- Update shouldAutoSummarize logic and tests for new 200-char threshold
- Update UI copy in SettingsModal and API/routes references
- Update store tests to reflect the new threshold value
- Remove obsolete dashboard activity-log mobile layout test files and unused CSS
- Add changeset for patch bump

packages/core/src/ai-summarize.test.ts

@@ -29,7 +29,7 @@ describe("ai-summarize", () => {
     });
 
     it("should have correct length limits", () => {
-      expect(MIN_DESCRIPTION_LENGTH).toBe(141);
+      expect(MIN_DESCRIPTION_LENGTH).toBe(201);
       expect(MAX_DESCRIPTION_LENGTH).toBe(2000);
       expect(MAX_TITLE_LENGTH).toBe(60);
     });
@@ -43,7 +43,7 @@ describe("ai-summarize", () => {
 
   describe("validateDescription", () => {
     it("should accept valid description length", () => {
-      const desc = "a".repeat(200);
+      const desc = "a".repeat(201);
       expect(validateDescription(desc)).toBe(desc);
     });
 
@@ -64,7 +64,7 @@ describe("ai-summarize", () => {
     it("should throw for description too short", () => {
       const desc = "a".repeat(100);
       expect(() => validateDescription(desc)).toThrow(ValidationError);
-      expect(() => validateDescription(desc)).toThrow("at least 141 characters");
+      expect(() => validateDescription(desc)).toThrow("at least 201 characters");
     });
 
     it("should throw for description too long", () => {
@@ -74,7 +74,7 @@ describe("ai-summarize", () => {
     });
 
     it("should accept description at minimum boundary", () => {
-      const desc = "a".repeat(141);
+      const desc = "a".repeat(201);
       expect(validateDescription(desc)).toBe(desc);
     });
 
@@ -139,21 +139,21 @@ describe("ai-summarize", () => {
   // ── summarizeTitle ─────────────────────────────────────────────────────────
 
   describe("summarizeTitle", () => {
-    it("should return null for descriptions <= 140 characters", async () => {
+    it("should return null for descriptions <= 200 characters", async () => {
       const result = await summarizeTitle("Short description", "/tmp");
       expect(result).toBeNull();
     });
 
     it("should throw AiServiceError when engine not available", async () => {
       // In test environment, the dynamic import fails, so createKbAgent is undefined
-      const longDesc = "a".repeat(200);
+      const longDesc = "a".repeat(201);
       await expect(summarizeTitle(longDesc, "/tmp")).rejects.toThrow(AiServiceError);
       await expect(summarizeTitle(longDesc, "/tmp")).rejects.toThrow("AI engine not available");
     });
 
     it("should accept optional provider and modelId", async () => {
       // Since engine isn't available in tests, this will throw
-      const longDesc = "a".repeat(200);
+      const longDesc = "a".repeat(201);
       await expect(
         summarizeTitle(longDesc, "/tmp", "anthropic", "claude-sonnet-4-5")
       ).rejects.toThrow(AiServiceError);

packages/core/src/ai-summarize.ts

@@ -3,12 +3,12 @@
  *
  * Provides AI-powered title generation from task descriptions.
  * Automatically generates concise titles (≤60 characters) from descriptions
- * longer than 140 characters.
+ * longer than 200 characters.
  *
  * Features:
  * - Rate limiting per IP (10 requests per hour)
  * - Dynamic import of @fusion/engine for AI agent creation
- * - Text length validation (141-2000 characters)
+ * - Text length validation (201-2000 characters)
  */
 
 // Dynamic import for @fusion/engine to avoid resolution issues in test environment
@@ -53,7 +53,7 @@ Your job is to create a concise title (max 60 characters) that summarizes the gi
 export const MAX_DESCRIPTION_LENGTH = 2000;
 
 /** Minimum description length for summarization in characters */
-export const MIN_DESCRIPTION_LENGTH = 141;
+export const MIN_DESCRIPTION_LENGTH = 201;
 
 /** Maximum title length in characters */
 export const MAX_TITLE_LENGTH = 60;
@@ -215,7 +215,7 @@ export function validateDescription(description: unknown): string {
 
 /**
  * Summarize a task description into a concise title using AI.
- * @param description - The task description to summarize (must be 141-2000 chars)
+ * @param description - The task description to summarize (must be 201-2000 chars)
  * @param rootDir - Project root directory for AI agent context
  * @param provider - Optional AI model provider (e.g., "anthropic")
  * @param modelId - Optional AI model ID (e.g., "claude-sonnet-4-5")
@@ -228,7 +228,7 @@ export async function summarizeTitle(
   modelId?: string
 ): Promise<string | null> {
   // Validate description length first
-  if (description.length <= 140) {
+  if (description.length <= 200) {
     return null; // Too short for summarization
   }
 

packages/core/src/store.test.ts

@@ -4394,7 +4394,7 @@ Task with acceptance criteria
 
   describe("createTask with title summarization", () => {
     it("should use generated title when onSummarize returns a title", async () => {
-      const longDescription = "a".repeat(200);
+      const longDescription = "a".repeat(201);
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Generated Title");
 
       const task = await store.createTask(
@@ -4410,7 +4410,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
-        { title: "User Title", description: "a".repeat(200) },
+        { title: "User Title", description: "a".repeat(201) },
         { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: true } }
       );
 
@@ -4435,7 +4435,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
-        { description: "a".repeat(200) },
+        { description: "a".repeat(201) },
         { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: false } }
       );
 
@@ -4447,7 +4447,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
-        { description: "a".repeat(200) },
+        { description: "a".repeat(201) },
         { onSummarize: mockOnSummarize }
       );
 
@@ -4459,7 +4459,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
-        { description: "a".repeat(200), summarize: true },
+        { description: "a".repeat(201), summarize: true },
         { onSummarize: mockOnSummarize }
       );
 
@@ -4471,7 +4471,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue(null);
 
       const task = await store.createTask(
-        { description: "a".repeat(200) },
+        { description: "a".repeat(201) },
         { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: true } }
       );
 
@@ -4483,7 +4483,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockRejectedValue(new Error("AI service failed"));
 
       const task = await store.createTask(
-        { description: "a".repeat(200) },
+        { description: "a".repeat(201) },
         { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: true } }
       );
 
@@ -4497,8 +4497,8 @@ Task with acceptance criteria
       consoleSpy.mockRestore();
     });
 
-    it("should trigger summarization at exactly 141 characters", async () => {
-      const boundaryDescription = "a".repeat(141);
+    it("should trigger summarization at exactly 201 characters", async () => {
+      const boundaryDescription = "a".repeat(201);
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
@@ -4509,8 +4509,8 @@ Task with acceptance criteria
       expect(mockOnSummarize).toHaveBeenCalled();
     });
 
-    it("should not trigger summarization at exactly 140 characters", async () => {
-      const boundaryDescription = "a".repeat(140);
+    it("should not trigger summarization at exactly 200 characters", async () => {
+      const boundaryDescription = "a".repeat(200);
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
@@ -4525,7 +4525,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue("AI Title");
 
       const task = await store.createTask(
-        { title: "User Title", description: "a".repeat(200), summarize: true },
+        { title: "User Title", description: "a".repeat(201), summarize: true },
         { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: true } }
       );
 
@@ -4537,7 +4537,7 @@ Task with acceptance criteria
       const mockOnSummarize = vi.fn().mockResolvedValue("Generated Task Title");
 
       const task = await store.createTask(
-        { description: "a".repeat(200) },
+        { description: "a".repeat(201) },
         { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: true } }
       );
 
@@ -4546,6 +4546,22 @@ Task with acceptance criteria
       const detail = await store.getTask(task.id);
       expect(detail.prompt).toMatch(/^# FN-\d+: Generated Task Title\n/);
     });
+
+    it("should preserve original description when generating a title", async () => {
+      const originalDescription = "a".repeat(201);
+      const mockOnSummarize = vi.fn().mockResolvedValue("AI Summary Title");
+
+      const task = await store.createTask(
+        { description: originalDescription },
+        { onSummarize: mockOnSummarize, settings: { autoSummarizeTitles: true } }
+      );
+
+      expect(task.title).toBe("AI Summary Title");
+      expect(task.description).toBe(originalDescription);
+
+      const detail = await store.getTask(task.id);
+      expect(detail.description).toBe(originalDescription);
+    });
   });
 
   describe("event emissions", () => {

packages/core/src/store.ts

@@ -672,7 +672,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     let title = input.title?.trim() || undefined;
     const shouldSummarize =
       !title && // Only if no title provided
-      input.description.length > 140 && // Only if description is long enough
+      input.description.length > 200 && // Only if description is long enough
       (input.summarize === true || // Explicit request
         options?.settings?.autoSummarizeTitles === true); // Auto-enabled
 

packages/core/src/types.ts

@@ -776,7 +776,7 @@ export interface ProjectSettings {
   autoBackupRetention?: number;
   /** Directory for backup files, relative to project root. Default: ".fusion/backups". */
   autoBackupDir?: string;
-  /** When true, tasks created without titles but with descriptions longer than 140
+  /** When true, tasks created without titles but with descriptions longer than 200
    *  characters will automatically receive an AI-generated title (max 60 chars).
    *  Default: false. */
   autoSummarizeTitles?: boolean;