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+# Phase 3 Step 1: Trello Write Operations
+
+**Status:** Active
+**Priority:** High
+**Feature:** Interactive Dashboard (Write Ops)
+
+## Description
+Currently, the Trello client is read-only. We need to implement `CreateCard` and `UpdateCard` to enable interactivity (adding tasks, moving cards, completing items).
+
+## Requirements
+1.  **CreateCard:**
+    *   Method: `POST /1/cards`
+    *   Parameters: `name`, `idList`, `desc` (optional), `due` (optional).
+    *   Returns: Created `models.Card`.
+
+2.  **UpdateCard:**
+    *   Method: `PUT /1/cards/{id}`
+    *   Parameters: Flexible map of updates (e.g., `idList` to move, `closed=true` to archive).
+    *   Returns: Updated `models.Card` (or just error).
+
+## Reproduction / Test Plan
+Since we cannot hit the real Trello API in tests, we will use `httptest.Server` to mock the API responses.
+
+### `internal/api/trello_test.go`
+```go
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"task-dashboard/internal/models"
+)
+
+func TestTrelloClient_CreateCard(t *testing.T) {
+	// Mock Server
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "POST" {
+			t.Errorf("Expected POST, got %s", r.Method)
+		}
+		if r.URL.Path != "/1/cards" {
+			t.Errorf("Expected /1/cards, got %s", r.URL.Path)
+		}
+		
+		// Verify params
+		r.ParseForm()
+		if r.Form.Get("name") != "New Task" {
+			t.Errorf("Expected name='New Task', got %s", r.Form.Get("name"))
+		}
+
+		// Return mock response
+		card := models.Card{
+			ID:   "new-card-id",
+			Name: "New Task",
+		}
+		json.NewEncoder(w).Encode(card)
+	}))
+	defer server.Close()
+
+	client := &TrelloClient{
+		BaseURL: server.URL,
+		Key:     "test-key",
+		Token:   "test-token",
+		Client:  server.Client(),
+	}
+
+	card, err := client.CreateCard("list-id", "New Task", "Description", nil)
+	if err != nil {
+		t.Fatalf("CreateCard failed: %v", err)
+	}
+	if card.ID != "new-card-id" {
+		t.Errorf("Expected ID 'new-card-id', got %s", card.ID)
+	}
+}
+```