diff --git a/apps/api/src/routes/habits.ts b/apps/api/src/routes/habits.ts
new file mode 100644
index 0000000..8cdddba
--- /dev/null
+++ b/apps/api/src/routes/habits.ts
@@ -0,0 +1,515 @@
+import { Hono } from "hono";
+import { db, habits, habitCompletions, habitTags, tags as tagsTable } from "@project-e/db";
+import { and, asc, desc, eq, gte, ilike, inArray, isNull, lte, sql } from "drizzle-orm";
+import { requireAuth, createErrorResponse, resolveActiveDomain, AuthError } from "../middleware/auth";
+import { recordActivity } from "../middleware/activity";
+import { z } from "zod";
+
+export const habitRoutes = new Hono();
+
+const habitFrequencyEnum = z.enum(["daily", "weekly", "custom"]);
+const habitDifficultyEnum = z.enum(["easy", "medium", "hard"]);
+
+const createHabitSchema = z.object({
+  name: z.string().min(1, "Name is required"),
+  description: z.string().optional().nullable(),
+  domain: z.string().min(1, "Domain is required"),
+  frequency: habitFrequencyEnum.optional().default("daily"),
+  difficulty: habitDifficultyEnum.optional().default("medium"),
+  goalPerPeriod: z.number().int().positive().optional().default(1),
+  unit: z.string().optional().nullable(),
+  reminderTime: z.string().optional().nullable(),
+  skipDays: z.array(z.number().int().min(0).max(6)).optional().default([]),
+  moodTracking: z.boolean().optional().default(false),
+  active: z.boolean().optional().default(true),
+  tagIds: z.array(z.string().uuid()).optional(),
+});
+
+const updateHabitSchema = z.object({
+  name: z.string().min(1).optional(),
+  description: z.string().optional().nullable(),
+  frequency: habitFrequencyEnum.optional(),
+  difficulty: habitDifficultyEnum.optional(),
+  goalPerPeriod: z.number().int().positive().optional(),
+  unit: z.string().optional().nullable(),
+  reminderTime: z.string().optional().nullable(),
+  skipDays: z.array(z.number().int().min(0).max(6)).optional(),
+  moodTracking: z.boolean().optional(),
+  active: z.boolean().optional(),
+});
+
+const completeHabitSchema = z.object({
+  value: z.number().int().positive().optional().default(1),
+  mood: z.number().int().min(1).max(5).optional().nullable(),
+  notes: z.string().optional().nullable(),
+});
+
+/**
+ * Calculate the current streak for a habit.
+ */
+async function calculateStreak(habitId: string, skipDays: number[]): Promise<number> {
+  const completions = await db.select({ date: habitCompletions.date })
+    .from(habitCompletions)
+    .where(eq(habitCompletions.habitId, habitId))
+    .orderBy(desc(habitCompletions.date));
+
+  if (completions.length === 0) return 0;
+
+  const completionDates = new Set(
+    completions.map(c => c.date.toISOString().split("T")[0])
+  );
+
+  let streak = 0;
+  const today = new Date();
+  today.setHours(0, 0, 0, 0);
+  const checkDate = new Date(today);
+
+  for (let i = 0; i < 365; i++) {
+    const dateStr = checkDate.toISOString().split("T")[0];
+    const dayOfWeek = checkDate.getDay();
+
+    if (skipDays.includes(dayOfWeek)) {
+      checkDate.setDate(checkDate.getDate() - 1);
+      continue;
+    }
+
+    if (completionDates.has(dateStr)) {
+      streak++;
+      checkDate.setDate(checkDate.getDate() - 1);
+    } else {
+      break;
+    }
+  }
+
+  return streak;
+}
+
+// GET /api/habits — List habits with filtering, sorting, pagination
+habitRoutes.get("/", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const url = new URL(c.req.url);
+    const page = Math.max(1, parseInt(url.searchParams.get("page") || "1"));
+    const perPage = Math.min(100, Math.max(1, parseInt(url.searchParams.get("perPage") || "50")));
+    const filter = url.searchParams.get("filter") || undefined;
+    const sort = url.searchParams.get("sort") || "-created";
+    const active = url.searchParams.get("active");
+    const frequency = url.searchParams.get("frequency");
+    const difficulty = url.searchParams.get("difficulty");
+    const search = url.searchParams.get("search");
+    const limit = Math.min(parseInt(url.searchParams.get("limit") || "50"), 200);
+    const offset = parseInt(url.searchParams.get("offset") || "0");
+    const order = url.searchParams.get("order") || "asc";
+
+    let domainId = url.searchParams.get("domain") || undefined;
+    if (!domainId) {
+      const active = await resolveActiveDomain(user);
+      domainId = active.id;
+    }
+
+    const conditions: any[] = [
+      eq(habits.domainId, domainId),
+      isNull(habits.deletedAt),
+    ];
+
+    if (active === "true") conditions.push(eq(habits.active, true));
+    else if (active === "false") conditions.push(eq(habits.active, false));
+    if (frequency) conditions.push(eq(habits.frequency, frequency as any));
+    if (difficulty) conditions.push(eq(habits.difficulty, difficulty as any));
+    if (search) conditions.push(ilike(habits.name, `%${search}%`));
+    if (filter) conditions.push(ilike(habits.name, `%${filter}%`));
+
+    const sortDir = sort.startsWith("-") ? "desc" : "asc";
+    const sortField = sort.replace(/^-/, "");
+    const sortColumns: Record<string, any> = {
+      created: habits.createdAt,
+      updated: habits.updatedAt,
+      name: habits.name,
+      frequency: habits.frequency,
+      difficulty: habits.difficulty,
+      streak_count: habits.streakCount,
+      created_at: habits.createdAt,
+      updated_at: habits.updatedAt,
+    };
+    const orderColumn = sortDir === "asc"
+      ? asc(sortColumns[sortField] || habits.createdAt)
+      : desc(sortColumns[sortField] || habits.createdAt);
+
+    const [items, countResult] = await Promise.all([
+      db.select()
+        .from(habits)
+        .where(and(...conditions))
+        .orderBy(orderColumn)
+        .limit(limit || perPage)
+        .offset(offset || (page - 1) * perPage),
+      db.select({ count: sql<number>`count(*)` })
+        .from(habits)
+        .where(and(...conditions)),
+    ]);
+
+    const totalItems = Number(countResult[0]?.count || 0);
+
+    // Fetch tags for all habits
+    let habitTagMap = new Map<string, { id: string; name: string; color: string | null }[]>();
+    if (items.length > 0) {
+      const habitIds = items.map(h => h.id);
+      const tagRows = await db.select({
+        habitId: habitTags.habitId,
+        id: tagsTable.id,
+        name: tagsTable.name,
+        color: tagsTable.color,
+      })
+        .from(habitTags)
+        .innerJoin(tagsTable, eq(habitTags.tagId, tagsTable.id))
+        .where(inArray(habitTags.habitId, habitIds));
+
+      for (const row of tagRows) {
+        if (!habitTagMap.has(row.habitId)) habitTagMap.set(row.habitId, []);
+        habitTagMap.get(row.habitId)!.push({ id: row.id, name: row.name, color: row.color });
+      }
+    }
+
+    const itemsWithTags = items.map(h => ({
+      ...h,
+      tags: habitTagMap.get(h.id) || [],
+    }));
+
+    return c.json({
+      items: itemsWithTags,
+      totalItems,
+      totalPages: Math.ceil(totalItems / (limit || perPage)),
+      page,
+      perPage: limit || perPage,
+      limit: limit || perPage,
+      offset: offset || (page - 1) * perPage,
+    });
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    console.error("[habits] GET error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to list habits" } }, 500);
+  }
+});
+
+// POST /api/habits — Create a habit
+habitRoutes.post("/", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const body = await c.req.json();
+    const data = createHabitSchema.parse({
+      ...body,
+      domain: body.domain || (await resolveActiveDomain(user)).id,
+    });
+
+    const [habit] = await db.insert(habits).values({
+      name: data.name,
+      description: data.description ?? null,
+      domainId: data.domain,
+      frequency: data.frequency,
+      difficulty: data.difficulty,
+      goalPerPeriod: data.goalPerPeriod,
+      unit: data.unit ?? null,
+      reminderTime: data.reminderTime ?? null,
+      skipDays: data.skipDays,
+      moodTracking: data.moodTracking,
+      active: data.active,
+    }).returning();
+
+    if (data.tagIds && data.tagIds.length > 0) {
+      await db.insert(habitTags).values(
+        data.tagIds.map(tagId => ({ habitId: habit.id, tagId }))
+      );
+    }
+
+    await recordActivity({
+      actor: user.name,
+      action: "created",
+      entityType: "habit",
+      entityId: habit.id,
+      changes: { name: habit.name, frequency: habit.frequency, difficulty: habit.difficulty },
+      workspaceId: data.domain,
+    });
+
+    return c.json(habit, 201);
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    if (error instanceof z.ZodError) {
+      return c.json({ error: { code: "VALIDATION_ERROR", message: "Invalid input", details: error.issues } }, 400);
+    }
+    console.error("[habits] POST error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to create habit" } }, 500);
+  }
+});
+
+// GET /api/habits/:id — Get a single habit with streak + recent completions
+habitRoutes.get("/:id", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const id = c.req.param("id");
+
+    const [habit] = await db.select()
+      .from(habits)
+      .where(and(eq(habits.id, id), isNull(habits.deletedAt)))
+      .limit(1);
+
+    if (!habit) {
+      return c.json({ error: { code: "NOT_FOUND", message: "Habit not found" } }, 404);
+    }
+
+    // Fetch recent completions (last 30 days)
+    const thirtyDaysAgo = new Date();
+    thirtyDaysAgo.setDate(thirtyDaysAgo.getDate() - 30);
+
+    const recentCompletions = await db.select()
+      .from(habitCompletions)
+      .where(and(
+        eq(habitCompletions.habitId, id),
+        gte(habitCompletions.date, thirtyDaysAgo),
+      ))
+      .orderBy(desc(habitCompletions.date));
+
+    // Fetch tags
+    const tagRows = await db.select({
+      id: tagsTable.id,
+      name: tagsTable.name,
+      color: tagsTable.color,
+    })
+      .from(habitTags)
+      .innerJoin(tagsTable, eq(habitTags.tagId, tagsTable.id))
+      .where(eq(habitTags.habitId, id));
+
+    return c.json({
+      ...habit,
+      recentCompletions,
+      tags: tagRows,
+    });
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    console.error("[habits] GET/:id error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to get habit" } }, 500);
+  }
+});
+
+// PATCH /api/habits/:id — Update a habit
+habitRoutes.patch("/:id", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const id = c.req.param("id");
+    const body = await c.req.json();
+    const data = updateHabitSchema.parse(body);
+
+    const [existing] = await db.select()
+      .from(habits)
+      .where(and(eq(habits.id, id), isNull(habits.deletedAt)))
+      .limit(1);
+
+    if (!existing) {
+      return c.json({ error: { code: "NOT_FOUND", message: "Habit not found" } }, 404);
+    }
+
+    const updateValues: Record<string, unknown> = {};
+    if (data.name !== undefined) updateValues.name = data.name;
+    if (data.description !== undefined) updateValues.description = data.description;
+    if (data.frequency !== undefined) updateValues.frequency = data.frequency;
+    if (data.difficulty !== undefined) updateValues.difficulty = data.difficulty;
+    if (data.goalPerPeriod !== undefined) updateValues.goalPerPeriod = data.goalPerPeriod;
+    if (data.unit !== undefined) updateValues.unit = data.unit;
+    if (data.reminderTime !== undefined) updateValues.reminderTime = data.reminderTime;
+    if (data.skipDays !== undefined) updateValues.skipDays = data.skipDays;
+    if (data.moodTracking !== undefined) updateValues.moodTracking = data.moodTracking;
+    if (data.active !== undefined) updateValues.active = data.active;
+    updateValues.updatedAt = new Date();
+
+    const [updated] = await db.update(habits)
+      .set(updateValues)
+      .where(eq(habits.id, id))
+      .returning();
+
+    await recordActivity({
+      actor: user.name,
+      action: "updated",
+      entityType: "habit",
+      entityId: id,
+      changes: { ...data, previousName: existing.name },
+      workspaceId: existing.domainId,
+    });
+
+    return c.json(updated);
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    if (error instanceof z.ZodError) {
+      return c.json({ error: { code: "VALIDATION_ERROR", message: "Invalid input", details: error.issues } }, 400);
+    }
+    console.error("[habits] PATCH error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to update habit" } }, 500);
+  }
+});
+
+// DELETE /api/habits/:id — Soft delete a habit
+habitRoutes.delete("/:id", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const id = c.req.param("id");
+
+    const [existing] = await db.select()
+      .from(habits)
+      .where(and(eq(habits.id, id), isNull(habits.deletedAt)))
+      .limit(1);
+
+    if (!existing) {
+      return c.json({ error: { code: "NOT_FOUND", message: "Habit not found" } }, 404);
+    }
+
+    await db.update(habits)
+      .set({ deletedAt: new Date(), updatedAt: new Date() })
+      .where(eq(habits.id, id));
+
+    await recordActivity({
+      actor: user.name,
+      action: "deleted",
+      entityType: "habit",
+      entityId: id,
+      changes: { name: existing.name },
+      workspaceId: existing.domainId,
+    });
+
+    return c.body(null, 204);
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    console.error("[habits] DELETE error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to delete habit" } }, 500);
+  }
+});
+
+// POST /api/habits/:id/complete — Complete a habit for today
+habitRoutes.post("/:id/complete", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const id = c.req.param("id");
+    const body = await c.req.json();
+    const data = completeHabitSchema.parse(body);
+
+    const [habit] = await db.select()
+      .from(habits)
+      .where(and(eq(habits.id, id), isNull(habits.deletedAt)))
+      .limit(1);
+
+    if (!habit) {
+      return c.json({ error: { code: "NOT_FOUND", message: "Habit not found" } }, 404);
+    }
+
+    const [completion] = await db.insert(habitCompletions).values({
+      habitId: id,
+      date: new Date(),
+      value: data.value,
+      mood: data.mood ?? null,
+      notes: data.notes ?? null,
+    }).returning();
+
+    // Recalculate streak
+    const skipDays = habit.skipDays || [];
+    const newStreak = await calculateStreak(id, skipDays);
+
+    const updateData: Record<string, unknown> = {
+      streakCount: newStreak,
+      updatedAt: new Date(),
+    };
+
+    if (newStreak > (habit.bestStreak || 0)) {
+      updateData.bestStreak = newStreak;
+    }
+
+    await db.update(habits)
+      .set(updateData)
+      .where(eq(habits.id, id));
+
+    await recordActivity({
+      actor: user.name,
+      action: "completed",
+      entityType: "habit",
+      entityId: id,
+      changes: { value: data.value, mood: data.mood, streak: newStreak },
+      workspaceId: habit.domainId,
+    });
+
+    return c.json({
+      completion,
+      streakCount: newStreak,
+      bestStreak: Math.max(newStreak, habit.bestStreak || 0),
+    }, 201);
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    if (error instanceof z.ZodError) {
+      return c.json({ error: { code: "VALIDATION_ERROR", message: "Invalid input", details: error.issues } }, 400);
+    }
+    console.error("[habits] POST /:id/complete error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to complete habit" } }, 500);
+  }
+});
+
+// GET /api/habits/:id/completions — Completion history + streak calc
+habitRoutes.get("/:id/completions", async (c) => {
+  try {
+    const user = await requireAuth(c);
+    const id = c.req.param("id");
+    const url = new URL(c.req.url);
+
+    const [habit] = await db.select({ id: habits.id })
+      .from(habits)
+      .where(and(eq(habits.id, id), isNull(habits.deletedAt)))
+      .limit(1);
+
+    if (!habit) {
+      return c.json({ error: { code: "NOT_FOUND", message: "Habit not found" } }, 404);
+    }
+
+    const from = url.searchParams.get("from");
+    const to = url.searchParams.get("to");
+    const limit = Math.min(parseInt(url.searchParams.get("limit") || "365"), 1000);
+    const offset = parseInt(url.searchParams.get("offset") || "0");
+    const order = url.searchParams.get("order") || "desc";
+
+    const conditions: any[] = [eq(habitCompletions.habitId, id)];
+
+    if (from) conditions.push(gte(habitCompletions.date, new Date(from)));
+    if (to) conditions.push(lte(habitCompletions.date, new Date(to)));
+
+    const orderFn = order === "asc" ? asc : desc;
+
+    const [items, countResult] = await Promise.all([
+      db.select()
+        .from(habitCompletions)
+        .where(and(...conditions))
+        .orderBy(orderFn(habitCompletions.date))
+        .limit(limit)
+        .offset(offset),
+      db.select({ count: sql<number>`count(*)` })
+        .from(habitCompletions)
+        .where(and(...conditions)),
+    ]);
+
+    return c.json({
+      items,
+      totalItems: Number(countResult[0]?.count || 0),
+      limit,
+      offset,
+    });
+  } catch (error) {
+    if (error instanceof AuthError) {
+      return c.json({ error: { code: error.code, message: error.message } }, error.status as any);
+    }
+    console.error("[habits] GET /:id/completions error:", error);
+    return c.json({ error: { code: "INTERNAL_ERROR", message: "Failed to get completions" } }, 500);
+  }
+});