diff --git a/mezcla/examples/hf_stable_diffusion.py b/mezcla/examples/hf_stable_diffusion.py
index dcc3013a..66a04a10 100755
--- a/mezcla/examples/hf_stable_diffusion.py
+++ b/mezcla/examples/hf_stable_diffusion.py
@@ -21,6 +21,9 @@
 # - For a stylish Stable Diffusion interface, see
 #   https://github.com/comfyanonymous/ComfyUI
 #
+# TODO2:
+# - See why HF keeps downloading model (e.g., make sure cache permanent).
+# - Add test cases for flask-based API.
 # TODO:
 # - Set GRADIO_SERVER_NAME to 0.0.0.0?
 #
@@ -36,11 +39,9 @@
 # Installed modules
 import diskcache
 from flask import Flask, request
-## OLD: import PIL
 ## TODO: see why following needed (i.e., plain PIL import yields intermittent errors)
 import PIL.Image
 import requests
-## OLD: import gradio as gr
 gr = None
 
 # Local modules
@@ -58,7 +59,6 @@
                             "Negative tips for image")
 GUIDANCE_HELP = "Degree of fidelity to prompt (1-to-30 w/ 7 suggested)--higher for more"
 GUIDANCE_SCALE = system.getenv_int("GUIDANCE_SCALE", 7,
-                                   ## OLD: "How much the image generation follows the prompt")
                                    description=GUIDANCE_HELP)
 SD_URL = system.getenv_value("SD_URL", None,
                              "URL for SD TCP/restful server--new via flask or remote")
@@ -100,7 +100,7 @@
 PROMPT_ARG = "prompt"
 NEGATIVE_ARG = "negative"
 GUIDANCE_ARG = "guidance"
-## TODO?: TXT2IMG_ARG = "txt2img"
+TXT2IMG_ARG = "txt2img"
 IMG2IMG_ARG = "img2img"
 IMG2TXT_ARG = "img2txt"
 IMAGE_ARG = "input-image"
@@ -108,6 +108,9 @@
 DUMMY_BASE64_IMAGE = "iVBORw0KGgoAAAANSUhEUgAAAA8AAAAPAgMAAABGuH3ZAAAADFBMVEUAAMzMzP////8AAABGA1scAAAAJUlEQVR4nGNgAAFGQUEowRoa6sCABBZowAgsgBEIGUQCRALAPACMHAOQvR4HGwAAAABJRU5ErkJggg=="
 DUMMY_IMAGE_FILE = gh.resolve_path("dummy-image.png")
 HTTP_OK = 200
+# note: RestFUL API keys (via flask)
+IMAGES_KEY = "images"
+CAPTION_KEY = "caption"
 
 #--------------------------------------------------------------------------------
 # Globals
@@ -198,6 +201,7 @@ def __init__(self, use_hf_api=None, server_url=None, server_port=None, low_memor
                 disk_compress_level=0,        # no compression
                 cull_limit=0)                 # no automatic pruning
         debug.assertion(bool(self.use_hf_api) != bool(self.server_url))
+        show_gpu_usage()
         debug.trace_object(5, self, label=f"{class_name} instance")
     
     def init_pipeline(self, txt2img=None, img2img=None):
@@ -338,7 +342,7 @@ def infer_non_cached(self, prompt=None, negative_prompt=None, scale=None, num_im
             images_request = requests.post(url, json=payload, timeout=(5 * 60))
             debug.trace_object(6, images_request)
             debug.trace_expr(5, payload, images_request, images_request.json(), delim="\n")
-            for image in images_request.json()["images"]:
+            for image in images_request.json()[IMAGES_KEY]:
                 image_b64 = image
                 if not skip_img_spec:
                     image_b64 = (f"data:image/png;base64,{image_b64}")
@@ -439,7 +443,7 @@ def infer_img2img_non_cached(self, image_b64=None, denoise=None, prompt=None, ne
             images_request = requests.post(url, json=payload, timeout=(5 * 60))
             debug.trace_object(6, images_request)
             debug.trace_expr(5, payload, images_request, images_request.json(), delim="\n")
-            for image in images_request.json()["images"]:
+            for image in images_request.json()[IMAGES_KEY]:
                 image_b64 = image
                 if not skip_img_spec:
                     image_b64 = (f"data:image/png;base64,{image_b64}")
@@ -487,7 +491,7 @@ def infer_img2txt_non_cached(self, image_b64=None):
             request_result = requests.post(url, json=payload, timeout=(5 * 60))
             debug.trace_object(6, request_result)
             debug.trace_expr(5, payload, request_result, request_result.json(), delim="\n")
-            image_caption = request_result.json()["caption"]
+            image_caption = request_result.json()[CAPTION_KEY]
             
         debug.trace_fmt(5, "infer_img2txt_non_cached() => {r!r}", r=image_caption)
         return image_caption
@@ -515,7 +519,7 @@ def handle_infer():
     debug.trace_expr(5, params)
     if not sd_instance:
         init_stable_diffusion()
-    images_spec = {"images": sd_instance.infer(**params)}
+    images_spec = {IMAGES_KEY: sd_instance.infer(**params)}
     # note: see https://stackoverflow.com/questions/45412228/sending-json-and-status-code-with-a-flask-response
     result = (json.dumps(images_spec), HTTP_OK)
     debug.trace_object(7, result)
@@ -535,6 +539,8 @@ def infer(prompt=None, negative_prompt=None, scale=None, num_images=None, skip_i
     Note: intended just for the gradio UI"
     """
     debug.trace(5, f"[sd_instance] infer{(prompt, negative_prompt, scale, skip_img_spec)}")
+    if not sd_instance:
+        init_stable_diffusion()
     return sd_instance.infer(prompt=prompt, negative_prompt=negative_prompt, scale=scale, num_images=num_images, skip_img_spec=skip_img_spec)
 
 
@@ -547,7 +553,9 @@ def handle_infer_img2img():
     debug.trace_object(5, request)
     params = request.get_json()
     debug.trace_expr(5, params)
-    images_spec = {"images": sd_instance.infer_img2img(**params)}
+    if not sd_instance:
+        init_stable_diffusion()
+    images_spec = {IMAGES_KEY: sd_instance.infer_img2img(**params)}
     # note: see https://stackoverflow.com/questions/45412228/sending-json-and-status-code-with-a-flask-response
     result = (json.dumps(images_spec), HTTP_OK)
     debug.trace_object(7, result)
@@ -564,7 +572,6 @@ def infer_img2img(image_spec=None, denoise=None,  prompt=None, negative_prompt=N
         debug.trace(5, "Warning: using first image in image_spec for infer_img2img")
         image_spec = image_spec[0]
     if ((image_spec is not None) and (not isinstance(image_spec, str))):
-        ## TODO?: image = PIL.Image.fromarray(image_spec, mode="RGB")
         debug.trace_expr(7, image_spec)
         image = (image_spec)
         image_spec = encode_PIL_image(image)
@@ -576,10 +583,20 @@ def infer_img2img(image_spec=None, denoise=None,  prompt=None, negative_prompt=N
 
 @flask_app.route('/img2txt', methods=['GET', 'POST'])
 def handle_infer_img2txt():
-    """Process request to do inference to generate text description of image"""
-    # Note: result return via hash with caption key
-    ## TODO: {"caption": sd_instance.infer_img2txt(**params)}
-    raise NotImplementedError()
+    """Process request to do inference to generate text description of image
+    Note: result returned via hash with caption key"""
+    ## TODO3: add helper for common flask bookkeeping
+    debug.trace(6, "[flask_app /] handle_infer_img2txt()")
+    debug.trace_object(5, request)
+    params = request.get_json()
+    debug.trace_expr(5, params)
+    if not sd_instance:
+        init_stable_diffusion()
+    caption_spec = {CAPTION_KEY: sd_instance.infer_img2txt(**params)}
+    result = (json.dumps(caption_spec), HTTP_OK)    
+    debug.trace_object(7, result)
+    debug.trace_fmt(7, "handle_infer_img2txt() => {r}", r=result)
+    return result
 
 
 def infer_img2txt(image_spec):