diff --git a/apps/api-service/src/routes/v1/images.ts b/apps/api-service/src/routes/v1/images.ts
index b1ee8ba..6d2ca83 100644
--- a/apps/api-service/src/routes/v1/images.ts
+++ b/apps/api-service/src/routes/v1/images.ts
@@ -1,4 +1,5 @@
 import { randomUUID } from 'crypto';
+import sizeOf from 'image-size';
 import { Response, Router } from 'express';
 import type { Router as RouterType } from 'express';
 import { ImageService, AliasService } from '@/services/core';
@@ -46,16 +47,16 @@ const getAliasService = (): AliasService => {
  * Upload a single image file to project storage
  *
  * Uploads an image file to MinIO storage and creates a database record with support for:
- * - Automatic flow creation when flowId is undefined (lazy creation)
+ * - Lazy flow creation using pendingFlowId when flowId is undefined
  * - Eager flow creation when flowAlias is provided
  * - Project-scoped alias assignment
  * - Custom metadata storage
  * - Multiple file formats (JPEG, PNG, WebP, etc.)
  *
  * FlowId behavior:
- * - undefined (not provided) → generates new UUID for automatic flow creation
+ * - undefined (not provided) → generates pendingFlowId, defers flow creation (lazy)
  * - null (explicitly null) → no flow association
- * - string (specific value) → uses provided flow ID
+ * - string (specific value) → uses provided flow ID, creates if needed
  *
  * @route POST /api/v1/images/upload
  * @authentication Project Key required
@@ -118,17 +119,42 @@ imagesRouter.post(
     const projectSlug = req.apiKey.projectSlug;
     const file = req.file;
 
-    // FlowId logic (Section 10.1 & 5.1):
-    // - If undefined (not provided) → generate new UUID
-    // - If null (explicitly null) → keep null
-    // - If string (specific value) → use that value
+    // FlowId logic (matching GenerationService lazy pattern):
+    // - If undefined → generate UUID for pendingFlowId, flowId = null (lazy)
+    // - If null → flowId = null, pendingFlowId = null (explicitly no flow)
+    // - If string → flowId = string, pendingFlowId = null (use provided, create if needed)
     let finalFlowId: string | null;
+    let pendingFlowId: string | null = null;
+
     if (flowId === undefined) {
-      finalFlowId = randomUUID();
-    } else if (flowId === null) {
+      // Lazy pattern: defer flow creation until needed
+      pendingFlowId = randomUUID();
       finalFlowId = null;
+    } else if (flowId === null) {
+      // Explicitly no flow
+      finalFlowId = null;
+      pendingFlowId = null;
     } else {
+      // Specific flowId provided - ensure flow exists (eager creation)
       finalFlowId = flowId;
+      pendingFlowId = null;
+
+      // Check if flow exists, create if not
+      const existingFlow = await db.query.flows.findFirst({
+        where: eq(flows.id, finalFlowId),
+      });
+
+      if (!existingFlow) {
+        await db.insert(flows).values({
+          id: finalFlowId,
+          projectId,
+          aliases: {},
+          meta: {},
+        });
+
+        // Link any pending images to this new flow
+        await service.linkPendingImagesToFlow(finalFlowId, projectId);
+      }
     }
 
     try {
@@ -155,9 +181,23 @@ imagesRouter.post(
         return;
       }
 
+      // Extract image dimensions from uploaded file buffer
+      let width: number | null = null;
+      let height: number | null = null;
+      try {
+        const dimensions = sizeOf(file.buffer);
+        if (dimensions.width && dimensions.height) {
+          width = dimensions.width;
+          height = dimensions.height;
+        }
+      } catch (error) {
+        console.warn('Failed to extract image dimensions:', error);
+      }
+
       const imageRecord = await service.create({
         projectId,
         flowId: finalFlowId,
+        pendingFlowId: pendingFlowId,
         generationId: null,
         apiKeyId,
         storageKey: uploadResult.path!,
@@ -168,27 +208,41 @@ imagesRouter.post(
         source: 'uploaded',
         alias: alias || null,
         meta: meta ? JSON.parse(meta) : {},
+        width,
+        height,
       });
 
-      // Eager flow creation if flowAlias is provided (Section 5.1)
-      if (flowAlias && finalFlowId) {
+      // Eager flow creation if flowAlias is provided
+      if (flowAlias) {
+        // Use pendingFlowId if available, otherwise finalFlowId
+        const flowIdToUse = pendingFlowId || finalFlowId;
+
+        if (!flowIdToUse) {
+          throw new Error('Cannot create flow: no flowId available');
+        }
+
         // Check if flow exists, create if not
         const existingFlow = await db.query.flows.findFirst({
-          where: eq(flows.id, finalFlowId),
+          where: eq(flows.id, flowIdToUse),
         });
 
         if (!existingFlow) {
           await db.insert(flows).values({
-            id: finalFlowId,
+            id: flowIdToUse,
             projectId,
             aliases: {},
             meta: {},
           });
+
+          // Link pending images if this was a lazy flow
+          if (pendingFlowId) {
+            await service.linkPendingImagesToFlow(flowIdToUse, projectId);
+          }
         }
 
         // Assign flow alias to uploaded image
         const flow = await db.query.flows.findFirst({
-          where: eq(flows.id, finalFlowId),
+          where: eq(flows.id, flowIdToUse),
         });
 
         if (flow) {
@@ -199,7 +253,7 @@ imagesRouter.post(
           await db
             .update(flows)
             .set({ aliases: updatedAliases, updatedAt: new Date() })
-            .where(eq(flows.id, finalFlowId));
+            .where(eq(flows.id, flowIdToUse));
         }
       }
 
diff --git a/apps/api-service/src/services/core/ImageService.ts b/apps/api-service/src/services/core/ImageService.ts
index d4e1e23..5a29e94 100644
--- a/apps/api-service/src/services/core/ImageService.ts
+++ b/apps/api-service/src/services/core/ImageService.ts
@@ -292,4 +292,40 @@ export class ImageService {
       ),
     });
   }
+
+  /**
+   * Link all pending images to a flow
+   * Called when flow is created to attach all images with matching pendingFlowId
+   */
+  async linkPendingImagesToFlow(
+    flowId: string,
+    projectId: string
+  ): Promise<void> {
+    // Find all images with pendingFlowId matching this flowId
+    const pendingImages = await db.query.images.findMany({
+      where: and(
+        eq(images.pendingFlowId, flowId),
+        eq(images.projectId, projectId)
+      ),
+    });
+
+    if (pendingImages.length === 0) {
+      return;
+    }
+
+    // Update images: set flowId and clear pendingFlowId
+    await db
+      .update(images)
+      .set({
+        flowId: flowId,
+        pendingFlowId: null,
+        updatedAt: new Date(),
+      })
+      .where(
+        and(
+          eq(images.pendingFlowId, flowId),
+          eq(images.projectId, projectId)
+        )
+      );
+  }
 }
diff --git a/packages/database/src/schema/images.ts b/packages/database/src/schema/images.ts
index dddafa0..c80077f 100644
--- a/packages/database/src/schema/images.ts
+++ b/packages/database/src/schema/images.ts
@@ -43,6 +43,7 @@ export const images = pgTable(
       { onDelete: 'set null' },
     ),
     flowId: uuid('flow_id').references(() => flows.id, { onDelete: 'cascade' }),
+    pendingFlowId: text('pending_flow_id'), // Temporary UUID for lazy flow pattern
     apiKeyId: uuid('api_key_id').references(() => apiKeys.id, { onDelete: 'set null' }),
 
     // Storage (MinIO path format: orgSlug/projectSlug/category/YYYY-MM/filename.ext)
@@ -119,6 +120,11 @@ export const images = pgTable(
       .on(table.flowId)
       .where(sql`${table.flowId} IS NOT NULL`),
 
+    // Index for pending flow lookups (lazy pattern)
+    pendingFlowIdx: index('idx_images_pending_flow')
+      .on(table.pendingFlowId, table.createdAt.desc())
+      .where(sql`${table.pendingFlowId} IS NOT NULL`),
+
     // Index for generation lookup
     generationIdx: index('idx_images_generation').on(table.generationId),
 
diff --git a/tests/api/02-basic.rest b/tests/api/02-basic.rest
index 4279529..1e6bbce 100644
--- a/tests/api/02-basic.rest
+++ b/tests/api/02-basic.rest
@@ -13,7 +13,7 @@ X-API-Key: {{apiKey}}
 Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW
 
 ------WebKitFormBoundary7MA4YWxkTrZu0gW
-Content-Disposition: form-data; name="file"; filename="test-image.png"
+Content-Disposition: form-data; name="file"; filename="test-image2.png"
 Content-Type: image/png
 
 < ./fixture/test-image.png
diff --git a/tests/api/fixture/test-image2.png b/tests/api/fixture/test-image2.png
new file mode 100644
index 0000000..1660cdb
Binary files /dev/null and b/tests/api/fixture/test-image2.png differ