comfy-debug-preview

# ComfyUI debug & preview Inspect values mid-graph without changing them. Read / log / visualize / time / report. Nothing in this skill mutates the data flow — these nodes either pass through unchanged (Preview Bridge, TimerNodeKJ) or are pure sinks (ShowText, CConsoleAny). The split: | Pack | Niche | |---|---| | `comfyui-custom-scripts` (pysssss) | `ShowText` — display text in node widget UI | | `comfyui_essentials` | `DisplayAny`, `ConsoleDebug`, `DebugTensorShape`, `BatchCount` | | `comfyui-kjnodes` | `PreviewImageOrMask`, `FastPreview`, `VRAM_Debug`, `TimerNodeKJ`, `Sleep`, `Get(Image\|Mask\|Latent)SizeAndCount` | | `ComfyUI-Crystools` | `CConsoleAny`, `CConsoleAnyToJson`, `CUtilsStatSystem` (CPU/GPU/RAM monitor), `CImageLoadWithMetadata`, `CMetadataExtractor`, `CMetadataCompare` | | `bjornulf_custom_nodes` | `ShowFloat`, `ShowInt`, `ShowStringText`, `ShowJson`, `ImageDetails`, `VideoDetails` | | `comfyui-dream-project` | `DreamStringToLog`, `DreamIntToLog`, `DreamFloatToLog`, `DreamJoinLog`, `DreamLogFile` | | `comfyui_yvann-nodes` | `FloatsVisualizer` (render a float array as a histogram image) | | `comfyui-impact-pack` | `Preview Bridge (Image)` / `Preview Bridge (Latent)` — tee inspection while passing through | | `comfyui-easy-use` | `easy showAnything`, `easy showLoaderSettingsNames`, `imageCount`, `imagesCountInDirectory` | ## When to Use This Skill | Use this skill when... | Use instead when... | |---|---| | Inspecting a value mid-graph without changing it (show/log/preview nodes) | Extracting metadata from a finished output file -> `comfy-metadata` | | Checking VRAM/CPU/timing during a run | Computing the value being displayed -> `comfy-math-strings` | ## Sources of truth - `custom_nodes/comfyui-custom-scripts/py/show_text.py` — pysssss ShowText - `custom_nodes/comfyui_essentials/misc.py` — DisplayAny, ConsoleDebug, DebugTensorShape - `custom_nodes/comfyui-kjnodes/nodes/nodes.py` — VRAM_Debug, TimerNodeKJ, Sleep, Get*SizeAndCount, FastPreview, PreviewImageOrMask - `custom_nodes/ComfyUI-Crystools/crystools/nodes_*.py` — CConsoleAny*, CUtilsStatSystem, metadata nodes ## Show-this-value decision | Value type | Best node | Why | |---|---|---| | STRING (short) | pysssss `ShowText` | Renders in the node widget; auto-resizes; persists in workflow JSON | | STRING (long / multiline) | bjornulf `ShowStringText` or pysssss `ShowText` | Both wrap text; `ShowText` truncates after ~10 lines but expands on hover | | ANY (don't know the type) | essentials `DisplayAny` or `easy showAnything` | Coerces to STRING and renders | | FLOAT / INT | bjornulf `ShowFloat` / `ShowInt` | Specific formatters; cleaner display than `DisplayAny` | | JSON / dict / list | bjornulf `ShowJson` or Crystools `CConsoleAnyToJson` | Pretty-prints with indentation | | Tensor (latent / image) shape | essentials `DebugTensorShape` | Logs (B, C, H, W) to console; doesn't display in node UI | | Float curve over a batch | yvann `FloatsVisualizer` | Renders the array as a histogram image | | Console log (no widget) | essentials `ConsoleDebug`, Crystools `CConsoleAny`, dream `DreamStringToLog` | Output to server stdout/log only — invisible in editor; useful for batch jobs | | Image (tee with passthrough) | impact `Preview Bridge` | Pass-through + preview in one node — see the data, keep the chain | | Image (just preview, no passthrough) | ComfyUI core `PreviewImage` or kjnodes `PreviewImageOrMask` | The kjnodes variant auto-detects whether the input is image or mask | ### Where the display goes - **Node-widget UI** (visible in the workflow editor): `ShowText`, `ShowFloat`, `ShowInt`, `ShowStringText`, `ShowJson`, `DisplayAny`, `easy showAnything`. These render INSIDE the node's body, expanding the node to fit the value. - **Server log / console** (`journalctl -u comfyui.service` on this install): `ConsoleDebug`, `DebugTensorShape`, `CConsoleAny`, `DreamStringToLog`. No editor display — use these for batch jobs running headless via `comfy run`. - **On-disk log file**: `DreamLogFile` appends to a configurable file path; useful for cross-queue tracking. - **Visible as image preview**: `PreviewImageOrMask`, `FastPreview`, `FloatsVisualizer`. The preview shows in the standard preview pane. ## Counts and sizes | Need | Node | Outputs | |---|---|---| | Image batch (B, H, W) | kjnodes `GetImageSizeAndCount` | width, height, batch_count | | Mask (B, H, W) | kjnodes `GetMaskSizeAndCount` | width, height, batch_count | | Latent (B, C, H, W) | kjnodes `GetLatentSizeAndCount` | width, height, batch_count | | Just N (batch size) | essentials `BatchCount` | int | | Image batch count (easy-use variant) | `easy imageCount` | int | | Count image files in a directory | `easy imagesCountInDirectory` | int (with offset/limit) | | Image file's metadata | bjornulf `ImageDetails` | width, height, channels, format, mode | | Video file's metadata | bjornulf `VideoDetails` | width, height, fps, duration, codec | `Get*SizeAndCount` is the canonical choice — it emits w/h/batch as separate INTs that you can wire to math nodes or display. ## System telemetry For VRAM / CPU / RAM monitoring (`CUtilsStatSystem`, `VRAM_Debug`) and per-section wall-clock timing (`TimerNodeKJ` start/end pairs), see [references/telemetry-and-profiling.md](references/telemetry-and-profiling.md). ## Preview Bridge and the ExecutionBlocker pitfall Impact's `Preview Bridge (Image)` / `Preview Bridge (Latent)` are the workhorse "see this *and* pass it through" nodes. Wire an image in, get the same image out, plus a preview in the editor. **Critical pitfall**: Preview Bridge **silently consumes `ExecutionBlocker` sentinels**. If a path through the bridge gets blocked upstream, the bridge: 1. Shows nothing in the preview (no error, no indicator). 2. Does NOT propagate the blocker downstream — it converts the blocked path into a "no-op pass-through" of nothing. Consequence: if you tee `Preview Bridge` off a path that may be blocked (e.g. behind an `easy blocker`), the downstream consumer of the bridge's output silently sees a None — not a blocker — and either errors with a type mismatch or proceeds with garbage. **Workaround**: when blockers may appear in the path, use kjnodes `FastPreview` downstream of the bridge — `FastPreview` passes sentinels through correctly. Or branch the preview off BEFORE the blocker, not after. ## Metadata extraction Reading the *current* image's PNG metadata inside a workflow (`CImageLoadWithMetadata`, `CMetadataExtractor`, `CMetadataCompare`): see [references/inline-metadata.md](references/inline-metadata.md). Offline / cross-directory analysis is `comfy-metadata`. ## Counter-pattern: timing/profiling vs the wrong layer Hunting a slow node? [references/telemetry-and-profiling.md](references/telemetry-and-profiling.md) lists what helps (timers, VRAM logging, the server log's per-node times), what doesn't (`Sleep`), and when to go to the model-family skill instead. ## Recipes Worked graphs — show the resolved prompt string, a per-sampler time budget, a VRAM watch during a long batch, and surfacing batch counts before sampling — are in [references/recipes.md](references/recipes.md). ## Gotchas When a display node shows nothing, a stale or truncated value, or a timer/logger misbehaves, check [references/gotchas.md](references/gotchas.md) (ShowText updates after queue, `CUtilsStatSystem` polls only when consumed, `DisplayAny` truncation, Timer id pairing, `Sleep` blocks the queue, PNG-only Crystools metadata). ## Cross-refs - `comfy-math-strings` — formatting numeric / string values before display (the math is in math-strings; the show is here). - `comfy-flow-control` — Preview Bridge as a routing tee (flow-control's gotcha list also covers the blocker pitfall). - `comfy-metadata` — deep metadata extraction across output directories: PNG tEXt / iTXt, WebP EXIF, MP4 container, kijai WanVideoWrapper / VHS `comment` blobs, `.latent` safetensors. When the question is "what produced this output file?" (offline / retrospective), reach for `comfy-metadata`. When the question is "what is this *current* image's PNG metadata?" (inline / live), use the Crystools nodes documented here. - `comfy-conditionals` — `easy showAnything` on a BOOLEAN to confirm a predicate at queue time before trusting the branch decision. ## Things this skill does NOT cover - **Offline / batch metadata analysis** — → `comfy-metadata`. - **Performance profiling at the model layer** (sageattn vs flash, KV cache, attention slicing) — → model-family skills (`wan`, `z-image`). - **Workflow-level reorganization to make a graph more debuggable** (auto-layout, group cohesion) — → `comfy-workflow-layout`. - **Computing the values being displayed** — → `comfy-math-strings`. - **The `simplify` user-level skill** (review changed code) — that's a Claude Code agent skill, not a ComfyUI workflow skill.