Use the FluxPipeline.encode_prompt() api rather than trying to run the two text encoders separately.

invokeai/app/invocations/flux_text_to_image.py

@@ -43,41 +43,14 @@ class FluxTextToImageInvocation(BaseInvocation, WithMetadata, WithBoard):
     def invoke(self, context: InvocationContext) -> ImageOutput:
         model_path = context.models.download_and_cache_model(FLUX_MODELS[self.model])
 
-        clip_embeddings = self._run_clip_text_encoder(context, model_path)
-        t5_embeddings = self._run_t5_text_encoder(context, model_path)
+        t5_embeddings, clip_embeddings = self._encode_prompt(context, model_path)
         latents = self._run_diffusion(context, model_path, clip_embeddings, t5_embeddings)
         image = self._run_vae_decoding(context, model_path, latents)
         image_dto = context.images.save(image=image)
         return ImageOutput.build(image_dto)
 
-    def _run_clip_text_encoder(self, context: InvocationContext, flux_model_dir: Path) -> torch.Tensor:
-        """Run the CLIP text encoder."""
-        tokenizer_path = flux_model_dir / "tokenizer"
-        tokenizer = CLIPTokenizer.from_pretrained(tokenizer_path, local_files_only=True)
-        assert isinstance(tokenizer, CLIPTokenizer)
-
-        text_encoder_path = flux_model_dir / "text_encoder"
-        with context.models.load_local_model(
-            model_path=text_encoder_path, loader=self._load_flux_text_encoder
-        ) as text_encoder:
-            assert isinstance(text_encoder, CLIPTextModel)
-            flux_pipeline_with_te = FluxPipeline(
-                scheduler=None,
-                vae=None,
-                text_encoder=text_encoder,
-                tokenizer=tokenizer,
-                text_encoder_2=None,
-                tokenizer_2=None,
-                transformer=None,
-            )
-
-            return flux_pipeline_with_te._get_clip_prompt_embeds(
-                prompt=self.positive_prompt, device=TorchDevice.choose_torch_device()
-            )
-
-    def _run_t5_text_encoder(self, context: InvocationContext, flux_model_dir: Path) -> torch.Tensor:
-        """Run the T5 text encoder."""
-
+    def _encode_prompt(self, context: InvocationContext, flux_model_dir: Path) -> tuple[torch.Tensor, torch.Tensor]:
+        # Determine the T5 max sequence lenght based on the model.
         if self.model == "flux-schnell":
             max_seq_len = 256
         # elif self.model == "flux-dev":
@@ -85,28 +58,51 @@ class FluxTextToImageInvocation(BaseInvocation, WithMetadata, WithBoard):
         else:
             raise ValueError(f"Unknown model: {self.model}")
 
-        tokenizer_path = flux_model_dir / "tokenizer_2"
-        tokenizer_2 = T5TokenizerFast.from_pretrained(tokenizer_path, local_files_only=True)
-        assert isinstance(tokenizer_2, T5TokenizerFast)
+        # Load the CLIP tokenizer.
+        clip_tokenizer_path = flux_model_dir / "tokenizer"
+        clip_tokenizer = CLIPTokenizer.from_pretrained(clip_tokenizer_path, local_files_only=True)
+        assert isinstance(clip_tokenizer, CLIPTokenizer)
 
-        text_encoder_path = flux_model_dir / "text_encoder_2"
-        with context.models.load_local_model(
-            model_path=text_encoder_path, loader=self._load_flux_text_encoder_2
-        ) as text_encoder_2:
-            flux_pipeline_with_te2 = FluxPipeline(
+        # Load the T5 tokenizer.
+        t5_tokenizer_path = flux_model_dir / "tokenizer_2"
+        t5_tokenizer = T5TokenizerFast.from_pretrained(t5_tokenizer_path, local_files_only=True)
+        assert isinstance(t5_tokenizer, T5TokenizerFast)
+
+        clip_text_encoder_path = flux_model_dir / "text_encoder"
+        t5_text_encoder_path = flux_model_dir / "text_encoder_2"
+        with (
+            context.models.load_local_model(
+                model_path=clip_text_encoder_path, loader=self._load_flux_text_encoder
+            ) as clip_text_encoder,
+            context.models.load_local_model(
+                model_path=t5_text_encoder_path, loader=self._load_flux_text_encoder_2
+            ) as t5_text_encoder,
+        ):
+            assert isinstance(clip_text_encoder, CLIPTextModel)
+            assert isinstance(t5_text_encoder, T5EncoderModel)
+            pipeline = FluxPipeline(
                 scheduler=None,
                 vae=None,
-                text_encoder=None,
-                tokenizer=None,
-                text_encoder_2=text_encoder_2,
-                tokenizer_2=tokenizer_2,
+                text_encoder=clip_text_encoder,
+                tokenizer=clip_tokenizer,
+                text_encoder_2=t5_text_encoder,
+                tokenizer_2=t5_tokenizer,
                 transformer=None,
             )
 
-            return flux_pipeline_with_te2._get_t5_prompt_embeds(
-                prompt=self.positive_prompt, max_sequence_length=max_seq_len, device=TorchDevice.choose_torch_device()
+            # prompt_embeds: T5 embeddings
+            # pooled_prompt_embeds: CLIP embeddings
+            prompt_embeds, pooled_prompt_embeds, text_ids = pipeline.encode_prompt(
+                prompt=self.positive_prompt,
+                prompt_2=self.positive_prompt,
+                device=TorchDevice.choose_torch_device(),
+                max_sequence_length=max_seq_len,
             )
 
+        assert isinstance(prompt_embeds, torch.Tensor)
+        assert isinstance(pooled_prompt_embeds, torch.Tensor)
+        return prompt_embeds, pooled_prompt_embeds
+
     def _run_diffusion(
         self,
         context: InvocationContext,