fix(generate): dispatch hybrid Flux models to Flux workflow

Models like gonzalomoXLFluxPony are architecturally Flux but CivitAI
tags them as 'Pony', causing the SDXL workflow to be sent to ComfyUI
which fails validation. The filename now overrides base_model when it
contains 'flux'.

Also adds:
- Full Flux Dev/Schnell workflow template (ModelSamplingFlux,
  FluxGuidance, ConditioningZeroOut, EmptySD3LatentImage); KSampler
  cfg locked to 1.0, caller cfg routed to FluxGuidance
- --family/-F flag to manually override family detection
- queue_prompt now surfaces ComfyUI node_errors from 400 responses
- Tests for Flux workflow builder (8 cases) and updated family defaults

tests/test_tensors.py

@@ -359,14 +359,20 @@ class TestModelFamilyDetection:
         assert defaults["cfg"] == 6.5
 
     def test_get_model_generation_defaults_flux(self) -> None:
-        """Test getting generation defaults for Flux models."""
+        """Test getting generation defaults for Flux models.
+
+        Flux Dev is guidance-distilled: KSampler.cfg MUST be 1.0; the real
+        prompt-adherence dial is the FluxGuidance node's ``guidance`` value.
+        See https://comfyanonymous.github.io/ComfyUI_examples/flux/
+        """
         from tensors.config import get_model_generation_defaults
 
         defaults = get_model_generation_defaults("flux1-dev-fp8.safetensors")
         assert defaults["family"] == "flux"
         assert defaults["sampler"] == "euler"
         assert defaults["scheduler"] == "simple"
-        assert defaults["cfg"] == 3.5
+        assert defaults["cfg"] == 1.0
+        assert defaults["guidance"] == 3.5
 
     def test_get_model_generation_defaults_flux_schnell(self) -> None:
         """Test getting generation defaults for Flux Schnell models."""
@@ -376,6 +382,7 @@ class TestModelFamilyDetection:
         assert defaults["family"] == "flux_schnell"
         assert defaults["steps"] == 4
         assert defaults["cfg"] == 1.0
+        assert defaults["guidance"] == 3.5
 
     def test_detect_zimage(self) -> None:
         """Test detecting ZImageTurbo family."""
@@ -428,6 +435,104 @@ class TestModelFamilyDetection:
         assert defaults["scheduler"] == "karras"
 
 
+class TestFluxWorkflowBuilder:
+    """Tests for the Flux-specific branch of _build_workflow."""
+
+    def test_flux_dispatch_uses_flux_template(self) -> None:
+        """Building a workflow for a Flux model emits the Flux node graph."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(prompt="a cat", model="flux1-dev-fp8.safetensors")
+
+        # Flux template uses node IDs in the 100s; default SDXL template uses single digits.
+        assert "100" in wf and wf["100"]["class_type"] == "CheckpointLoaderSimple"
+        assert "120" in wf and wf["120"]["class_type"] == "ModelSamplingFlux"
+        assert "140" in wf and wf["140"]["class_type"] == "FluxGuidance"
+        assert "132" in wf and wf["132"]["class_type"] == "ConditioningZeroOut"
+        assert "150" in wf and wf["150"]["class_type"] == "EmptySD3LatentImage"
+        assert "3" not in wf  # default SDXL KSampler ID must NOT be present
+
+    def test_flux_ksampler_cfg_locked_to_one(self) -> None:
+        """KSampler cfg MUST be 1.0 for Flux Dev — caller cfg must NOT leak through."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(prompt="a cat", model="flux1-dev-fp8.safetensors", cfg=7.5)
+        assert wf["160"]["inputs"]["cfg"] == 1.0
+        # The caller's cfg=7.5 should be re-routed to FluxGuidance
+        assert wf["140"]["inputs"]["guidance"] == 7.5
+
+    def test_flux_explicit_guidance_wins_over_cfg(self) -> None:
+        """Explicit guidance overrides re-interpreted cfg."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(prompt="a cat", model="flux1-dev-fp8.safetensors", cfg=7.5, guidance=4.0)
+        assert wf["140"]["inputs"]["guidance"] == 4.0
+
+    def test_flux_default_guidance_from_preset(self) -> None:
+        """No caller value -> preset guidance (3.5) wins."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(prompt="a cat", model="flux1-dev-fp8.safetensors")
+        assert wf["140"]["inputs"]["guidance"] == 3.5
+
+    def test_flux_lora_injection(self) -> None:
+        """LoRA injects node 110 and reroutes ModelSamplingFlux + CLIPTextEncodes."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(
+            prompt="a cat",
+            model="flux1-dev-fp8.safetensors",
+            lora_name="my_style.safetensors",
+            lora_strength=0.7,
+        )
+        assert "110" in wf and wf["110"]["class_type"] == "LoraLoader"
+        assert wf["110"]["inputs"]["lora_name"] == "my_style.safetensors"
+        assert wf["110"]["inputs"]["strength_model"] == 0.7
+        # Downstream consumers must read from the LoRA node
+        assert wf["120"]["inputs"]["model"] == ["110", 0]
+        assert wf["130"]["inputs"]["clip"] == ["110", 1]
+        assert wf["131"]["inputs"]["clip"] == ["110", 1]
+
+    def test_flux_external_vae_swaps_decoder_input(self) -> None:
+        """Providing an external VAE adds node 171 (VAELoader) and rewires VAEDecode."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(
+            prompt="a cat",
+            model="flux1-dev-fp8.safetensors",
+            vae="ae.safetensors",
+        )
+        assert "171" in wf and wf["171"]["class_type"] == "VAELoader"
+        assert wf["171"]["inputs"]["vae_name"] == "ae.safetensors"
+        assert wf["170"]["inputs"]["vae"] == ["171", 0]
+
+    def test_flux_model_sampling_dimensions_match_latent(self) -> None:
+        """ModelSamplingFlux width/height must equal the latent dimensions for correct shift."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(
+            prompt="a cat",
+            model="flux1-dev-fp8.safetensors",
+            width=1216,
+            height=832,
+        )
+        assert wf["120"]["inputs"]["width"] == 1216
+        assert wf["120"]["inputs"]["height"] == 832
+        assert wf["150"]["inputs"]["width"] == 1216
+        assert wf["150"]["inputs"]["height"] == 832
+
+    def test_non_flux_model_uses_default_template(self) -> None:
+        """SDXL/Pony/etc. checkpoints continue to use the legacy template."""
+        from tensors.comfyui import _build_workflow
+
+        wf = _build_workflow(prompt="a cat", model="ponyDiffusionV6XL.safetensors")
+        # Default SDXL template has KSampler at node "3"
+        assert "3" in wf and wf["3"]["class_type"] == "KSampler"
+        # Flux-specific nodes must NOT be present
+        assert "140" not in wf
+        assert "120" not in wf
+
+
 class TestDisplayFormatters:
     """Tests for display formatting functions."""