remove-ai-watermarks/CLAUDE.md

Remove-AI-Watermarks

You are a principal Python engineer maintaining a CLI tool and library for removing visible and invisible AI watermarks from images.

Scope and non-goals

The mission is removing AI-provenance watermarks that a platform stamps onto content the user generated themselves — SynthID, the Gemini / Nano Banana sparkle, the Doubao / Jimeng / Samsung visible AI labels, the Chinese TC260 "由…AI生成" label, and C2PA / IPTC / EXIF "Made with AI" metadata. The point is user autonomy over their own generated output.

It deliberately does not remove watermarks that protect someone else's paid or copyrighted content — stock-agency overlays (Shutterstock, Getty, iStock, Adobe Stock), classifieds-site marks, or any tiled / diagonal "preview" watermark whose job is to gate a purchase. Stripping those makes a paid resource free off someone else's work; out of scope by principle, not by technical difficulty. The line: a visible mark is in scope when it labels the user's own AI generation, and out of scope when it protects a third party's paid asset.

Consequences for contributors (do not drift back into the stock niche just because it is technically feasible):

• Do not add stock / agency / classifieds watermark removal to watermark_registry.py or the eraser, and do not build tiled-overlay or multi-image watermark-estimation features aimed at them.
• erase --region stays a generic user-driven tool (the user points at their own object); do not ship an automatic stock-watermark detector/remover on top of it.
• New visible-mark templates are for AI-generation labels only.

(Established 2026-06-13 by user instruction: "Я пытаюсь сделать платные ресурсы бесплатными — это не то, против чего мы боремся.")

How to run

• uv run remove-ai-watermarks all <image.png> -o <output.png> — full pipeline (visible + invisible + metadata). Same diffusion knobs as invisible below, plus the visible-pass --inpaint/--no-inpaint/--inpaint-method. When the [gpu] extra is absent, step 2 (invisible/SynthID) is skipped — all still writes an output (visible mark + metadata stripped) but prints a prominent end-of-run banner ("the invisible (SynthID) watermark was NOT removed") AND exits non-zero (1), so a skipped SynthID pass is not mistaken for a clean result (the recurring #14/#47 trap, where the old quiet inline warning was missed). invisible already hard-errors without the extra; only all continued, hence the loud end-banner. Regression-guarded by tests/test_cli.py::TestAllCommand::test_all_loud_warning_and_nonzero_exit_when_gpu_missing. Test trap: any all test that exercises the full pipeline MUST patch("remove_ai_watermarks.invisible_engine.is_available", return_value=True) — CI installs core+dev only (no [gpu]), so an unpatched all test takes the skip branch and now hits the non-zero exit. This passed locally (gpu present → is_available() True) but red-failed every matrix cell on the v0.11.0 commit (test_all_basic/test_all_visible_step_uses_registry asserted exit 0); both now patch is_available True.
• uv run remove-ai-watermarks invisible <image.png> -o <out.png> — diffusion SynthID removal. Full knob set (kept identical across invisible/all/batch): --strength (vendor-adaptive default), --steps, --guidance-scale (CFG, default 7.5), --pipeline sdxl|controlnet (default controlnet), --controlnet-scale, --model (HF model id, default SDXL base), --device, --seed, --hf-token, --max-resolution/--min-resolution, --upscaler lanczos|esrgan, --humanize (Analog Humanizer grain), --unsharp (final sharpen), and --adaptive-polish/--no-adaptive-polish (ON by default; detail-targeted polish that self-gates to a no-op where there is no deficit). --auto is deprecated and now a no-op that only warns (the polish it used to enable is ON by default).
• uv run remove-ai-watermarks visible <image.png> -o <out.png> — known-visible-mark removal, CPU, no GPU. Reverse-alpha based: each mark is removed by inverting its captured alpha map. --mark auto (default) picks the strongest detected of the Gemini sparkle, the Doubao "豆包AI生成" text strip, the Jimeng "★ 即梦AI" wordmark, and the Samsung Galaxy AI "✦ Contenuti generati dall'AI" strip (bottom-LEFT, locale-specific — Italian variant calibrated); --mark gemini / --mark doubao / --mark jimeng / --mark samsung force one (choices come from the registry). Gemini/Doubao recover pixels exactly with no inpaint at native; Jimeng and Samsung add an always-on thin residual inpaint over the glyph footprint (their marks re-rasterize per image, so reverse-alpha alone leaves a faint outline). For arbitrary logos/objects use erase. When --mark auto finds no known mark (the common case — ~74% of real uploads carry no registered visible mark), the command does NOT silently re-serve the input as a finished result. It runs a cheap metadata-only identify, prints actionable guidance (if the image carries an invisible/metadata mark, e.g. an OpenAI/Gemini C2PA image, it points to all; otherwise it does NOT imply the image is clean -- it warns that an invisible pixel watermark like SynthID cannot be detected once the metadata proxy is gone and routes to both all and erase --region), writes NO output file, and exits EXIT_NO_VISIBLE_MARK (2) — distinct from success (0) and a hard error (1) so a wrapping service (raiw.cc) can surface the message instead of treating the unchanged image as done (the production "it didn't work" / score-0 trap). Same handling for an explicit --mark <name> that is not detected. Helper cli._no_visible_mark_exit; regression-guarded by tests/test_cli.py::TestVisibleCommand::test_visible_auto_no_mark_exits_two_with_eraser_hint and test_visible_auto_no_mark_routes_to_all_when_metadata. --no-detect still forces the gemini fallback and proceeds (exit 0).
• uv run remove-ai-watermarks erase <image.png> --region x,y,w,h -o <out.png> — universal region eraser (any logo/object, any position). --backend cv2 (default, no deps) or --backend lama (big-LaMa via onnxruntime, extra lama); --region is repeatable.
• uv run remove-ai-watermarks identify <image> — provenance verdict (platform + watermark inventory + confidence); --json for machine output, --no-visible to skip the cv2 sparkle detector
• uv run remove-ai-watermarks metadata <image.png> --check — inspect AI metadata (C2PA, EXIF, PNG chunks)
• uv run remove-ai-watermarks metadata <image.png> --remove -o <out.png> — strip all AI metadata
• uv run remove-ai-watermarks batch <directory> — process every supported image in a directory (output defaults to <directory>_clean/, set with -o). --mode visible|invisible|metadata|all (default visible); the invisible/all path reuses the full invisible knob set above (--strength/--steps/--guidance-scale/--pipeline/--controlnet-scale/--model/--device/--max-resolution/--min-resolution/--upscaler/--seed/--hf-token/--humanize/--unsharp/--adaptive-polish), plus --inpaint/--no-inpaint for the visible pass. --adaptive-polish is ON by default; --auto is deprecated and a no-op that only warns. One engine cached per pipeline; the polish is resolved once before the loop.

Test and lint

• CI (.github/workflows/test.yml): runs on push to main + every PR. A lint job (ubuntu: ruff check + ruff format --check) plus a test matrix (ubuntu/macos/windows x py3.10/3.12) that does uv sync --frozen --extra dev then pytest. The matrix installs only core + dev (no gpu extra), so the GPU/model-running tests skip there and it exercises the metadata/identify/visible/cv2-eraser surface on all three OSes. Keep uv.lock valid (don't break --frozen) when editing pyproject.toml.
• Release flow + distribution channels (PyPI publish via publish.yml/uv publish, the automated Homebrew-tap + HF-Space bumps in distribute.yml, conda-forge, ComfyUI Registry, the sdist data/ exclusion, hatchling pin history): see docs/release-and-distribution.md before cutting a release.
• bash maintain.sh — uv-outdated, uv-secure, ruff check/fix, ruff format, pyright (scoped src/, see the OOM note below), pytest -n auto. The helper tools live in the dev extra (pytest-xdist, plus uv-outdated/uv-secure marker-gated to py3.12+ so the py3.10 resolution stays solvable) — a bare env without --extra dev does not have them.
• Strict pyright is clean across src/ (0 errors). The cv2/torch/diffusers boundary files (gemini_engine, region_eraser, doubao_engine, humanizer, invisible_engine, noai/watermark_remover) carry a documented per-file # pyright: relax pragma that turns off only the unknown-type / untyped-third-party rules — those libs ship no usable types, so strict typing there fights the ecosystem. Pure-logic files stay fully strict; typings/piexif/__init__.pyi is a local stub so metadata.py/extractor.py resolve piexif. Public ndarray-returning signatures on the relaxed engines are still annotated NDArray[Any] so strict consumers (cli.py) stay clean. When touching a relaxed file, prefer fixing real issues over widening the pragma; keep the pragma scoped to genuinely-untyped boundaries. (uv-secure is clean since idna was bumped 3.11 -> 3.16, fixing GHSA-65pc-fj4g-8rjx, and aiohttp 3.13.5 -> 3.14.0 via uv lock --upgrade-package aiohttp, fixing GHSA-hg6j-4rv6-33pg + GHSA-jg22-mg44-37j8. (The old basicsr Dependabot alert (GHSA-86w8-vhw6-q9qq) is resolved by removal: the experimental restore extra was retired and basicsr is no longer anywhere in the dependency tree.) The torch Dependabot alert GHSA-rrmf-rvhw-rf47 (torch.jit.script memory corruption, vulnerable <= 2.12.0) is dismissed as not_used (2026-06-10): torch is a transitive dep of the optional gpu extra only, the codebase never calls torch.jit (grep-verified), and no patched torch version exists (first_patched_version is null), so it cannot be closed by an upgrade — do not re-triage it.
• Full-project uv run pyright (no path) OOMs/crashes node on this ML-heavy repo (emits a libnode stack frame, no summary) — a known environment limit, not a code error. Gate with uv run --extra dev --extra gpu pyright src/ (completes, authoritative) or scope to changed files; also run uv run ruff check and uv run pytest directly.
• Run uv run from the repo root — from another cwd it falls back to a bare env without numpy/cv2/torch.
• Stale trustmark remnant in site-packages after an extras change: the trustmark package downloads model weights INTO its own package dir, so when a narrower uv sync prunes the package, a trustmark/models/ directory survives as an empty namespace package. Symptom: pyright "TrustMark" is unknown import symbol on trustmark_detector.py and find_spec("trustmark") returning a loader-less spec (so is_available() lies True). Fix: rm -rf .venv/lib/python3.12/site-packages/trustmark (regenerable weights cache).
• To add a dev tool (pytest/ruff/pyright) into the env, use uv sync --frozen --extra dev --extra gpu, never uv pip install — uv pip install re-resolves and rewrites uv.lock, which silently bumped transformers to a build incompatible with the pinned diffusers (cannot import name 'Qwen3VLForConditionalGeneration') and broke every identify/metadata import. Recovery: git checkout uv.lock && uv sync --frozen --extra gpu --extra dev. The gpu extra holds diffusers/transformers/torch, so a bare uv sync (no extras) removes them; noai/__init__ is now lazy (PEP 562 __getattr__, so importing identify/metadata no longer pulls watermark_remover/torch), so a bare env breaks only when the removal pipeline is actually invoked, not on import. maintain.sh's uv sync --all-extras also pulls the heavy trustmark/lama wheels (pytorch-lightning, onnxruntime) — fine on a good connection, but on flaky DNS sync only --extra gpu --extra dev and run the lint/test steps by hand.
• Metadata/C2PA tests assert against real committed fixtures in data/samples/ (chatgpt-*.png = OpenAI C2PA, firefly-1.png = Adobe, mj-* = Midjourney IPTC, doubao-1.png = ByteDance Doubao with the China TC260 <TC260:AIGC> XMP label and a visible "豆包AI生成" text mark bottom-right; grok-1.jpg = xAI Grok with its EXIF-only Signature: blob + UUID Artist and no C2PA/SynthID/IPTC; flux-1.png / flux-1.jpg = real Black Forest Labs FLUX.2 Playground output, signed C2PA (issuer "Black Forest Labs" + trainedAlgorithmicMedia) -- flux-1.jpg is the first committed JPEG-with-C2PA fixture, exercising the c2pa-python non-PNG reader path end to end; whether BFL hosted output also embeds the open DWT-DCT pixel watermark is UNRESOLVED -- our detector returns None on these fox samples, but they are high-texture carriers where even a known-embedded watermark fails the round-trip, see the content-fragility caveat in docs/watermarking-landscape.md); synthetic byte blobs cover the remaining JPEG/ISOBMFF format paths. The "non-AI / clean photo" control is no longer in data/samples/ -- the clean_photo conftest fixture serves a verified-negative image from the corpus neg/ set (skips if the corpus is absent).
• SynthID reference corpus: scripts/synthid_corpus.py ingests labeled images into data/synthid_corpus/. The labeled images/ (pos/ neg/ cleaned/) are committed (public repo -- review every image for private content before adding; manifest.csv is kept in sync with the files on disk, one row per tracked image); only the synthetic refs/ calibration fills are gitignored. See its README for the collection protocol and verification oracles. cleaned/ examples must be produced by a CURRENT shipped removal method -- the default SDXL img2img pass (optionally --max-resolution). Do NOT archive cleaned outputs from methods that are no longer in the pipeline (ctrlregen, the old text/face-protection, IP-Adapter FaceID, CodeFormer) or from the experimental opt-in paths (controlnet, face restore) as corpus examples; a cleaned reference should represent the canonical removal, and a removed method's output is not a reproducible example. Keep those experiment outputs in a local working dir, never in the committed corpus.

Configuration

• GPU/ML modules (invisible_engine, watermark_remover) are optional — guard imports with is_available() checks
• Optional detection extras: detect (imwatermark — open SD/SDXL/FLUX watermark) and trustmark (Adobe TrustMark decoder; pulls torch + downloads weights). Both are guarded by is_available() and skipped by identify when absent.
• Optional esrgan extra (spandrel only): Real-ESRGAN pre-diffusion super-resolution for small inputs (upscaler.py, CLI --upscaler esrgan on invisible/all/batch). Guarded by upscaler.is_available(); the default upscaler stays Lanczos (cv2, no deps) and the engine falls back to Lanczos when the extra is absent or the model errors. spandrel is MIT and pulls NO basicsr (only torch/torchvision/safetensors/numpy/einops); Real-ESRGAN weights are BSD-3-Clause and download on first use via torch.hub (never bundled). Kept OUT of all (heavy + model download).
• Tests for the model-running paths are limited to availability checks (multi-GB downloads). But the pure helpers inside ML-adjacent modules are unit-tested without any download and must stay that way: _target_size (native-vs-downscale-cap-vs-upscale-floor, test_invisible_engine.py), humanizer.unsharp_mask/adaptive_polish (test_humanizer.py), and the MPS->CPU fallback control flow via mocked pipelines (test_img2img_runner.py, 100% cover). Don't skip these as "ML, needs a model" — only remove_watermark/the diffusion bodies do.

Key modules

Compact map. The full per-module detail (design decisions, tuned thresholds, calibration history, incident records, and the regression-guard map) lives in docs/module-internals.md — read the relevant section there before changing any module below.

• noai/c2pa.py — C2PA reading. extract_c2pa_info(path) uses the official c2pa-python Reader first (core dep, any container; read_manifest_store_json returns the WHOLE store JSON — active + ingredient manifests — so an AI marker on a parent manifest is seen), and falls back to the hand-rolled caBX/CBOR parser (has_c2pa_metadata / extract_c2pa_chunk / _extract_c2pa_info_png) for synthetic/partial blobs the validator rejects or a broken/absent wheel. The registry scan (issuer / source-type / SynthID / soft-binding) is shared by both paths via _populate_registry_fields, so the return-dict shape is identical. Do not reimplement chunk parsing; chunk reads are clamped to the remaining file size by design. extract_c2pa_chunk/inject_c2pa_chunk stay PNG-only (raw caBX bytes, test/extractor use).
• noai/constants.py — the single C2PA_AI_VENDORS registry (+ C2PA_SOFT_BINDINGS) from which C2PA_ISSUERS / SYNTHID_C2PA_ISSUERS / identify._ISSUER_PLATFORM are all derived. Add a new vendor as one registry entry; never edit the derived dicts and never add inline.
• metadata.py — scan_head(path) is the shared (memoized) input for every C2PA/AIGC/IPTC byte scan; use it instead of open().read(1MB) for any new marker scan. Also home to synthid_source, xai_signature, iptc_ai_system, aigc_label, huggingface_job, samsung_genai, and remove_ai_metadata (fail-safe strip_c2pa_boxes).
• identify.py — aggregates every locally-readable signal into one ProvenanceReport; is_ai_generated is True or None, never asserted False. import identify is deliberately light (lazy noai/__init__, fits a 512 MB host) — keep heavy imports out. Add capture-camera tokens to _DEVICE_C2PA_PLATFORM only when verified against a real C2PA file; editing-app/AI-device signer tokens go to _SIGNER_C2PA_PLATFORM; generator/issuer platforms to C2PA_AI_VENDORS in constants.py. Integrity-clash detection is high-precision by design (only hard generator stamps feed it, source-grouped independence).
• watermark_registry.py — the single catalog of known visible watermarks (gemini / doubao / jimeng / samsung), reverse-alpha based by policy. Add a new visible text mark = one _text_mark(...) row + a TextMarkConfig with a captured alpha map; do not re-add per-mark if branches. cli._write_bgr_with_alpha must NOT zero alpha in the watermark bbox (issue #30 white-box regression).
• gemini_engine.py — visible Gemini-sparkle remover/detector (cv2/numpy, no GPU): top-K size-weighted fusion candidate selection (_SELECT_TOPK), corner-promote, over/under-subtraction guards, false-positive gate, self-verify repair. Detection scores the top-K size-weighted matches by full fusion (spatial+gradient+variance) and keeps the highest — NOT the raw-NCC argmax, which re-admits the tiny-patch FPs the size weight suppresses (the osachub 2026-06-12 sub-0.85 corner-sparkle regression; see docs/module-internals.md). Keep the 0.85 corner-promote NCC gate; a margin/chroma-gated lower promote was measured and REJECTED 2026-06-11 (~33% FP on non-Google content). Gate any removal candidate on a physical brightness check, not the detector alone.
• _text_mark_engine.py — shared base for the three reverse-alpha text-mark engines (extracted 2026-06-09); the per-engine modules are config-only subclasses. New text mark = a TextMarkConfig + a thin subclass + one registry row. Gemini stays a separate engine (different model).
• doubao_engine.py / jimeng_engine.py / samsung_engine.py — thin TextMarkEngine subclasses: Doubao "豆包AI生成" (bottom-right), Jimeng "★ 即梦AI" (bottom-right), Samsung Galaxy AI "✦ Contenuti generati dall'AI" (bottom-LEFT, locale-specific — Italian variant calibrated). Removal = reverse-alpha (always-align) + thin residual inpaint. A detector-only removal test is insufficient — assert visual residual (the textured-shift tests).
• region_eraser.py — universal region eraser (erase CLI): cv2 backend default (no deps), optional big-LaMa via onnxruntime (~3.5-4 GB peak RAM, ~5-6 s/call CPU — does not fit a minimal droplet).
• invisible_watermark.py — decodes the OPEN DWT-DCT watermarks (SD / SDXL / FLUX) via imwatermark (extra detect, pulls torch). Fragile two ways: (1) does not survive JPEG re-encode/resize; (2) carrier-fragile on a broad class of pristine images -- a clean encode->decode round-trip recovers 48/48 on chatgpt/firefly/random but FAILS (28-39/48, below the _MATCH_48=44 gate) on the FLUX fox, doubao, a flat FLUX generation, AND a clean synthetic flat fill with no watermark. The failure does NOT track texture; it goes with a degenerate all-ones decode that is a CARRIER ARTIFACT, not a watermark (synthetic clean image reproduces it). So detect_invisible_watermark is positive-only: trust a hit; a None is inconclusive unless a same-carrier positive-control embed first recovers >=44. Verified 2026-06-19; full caveat in docs/watermarking-landscape.md.
• trustmark_detector.py — Adobe TrustMark open decoder (extra trustmark). Do NOT remove the JPEG re-encode false-positive gate — a lone TrustMark hit without it is almost always content noise.
• noai/watermark_remover.py — WatermarkRemover with two diffusion pipelines selected by the explicit pipeline ctor arg, never inferred from model_id: sdxl (plain SDXL img2img) and controlnet (SDXL + canny ControlNet, the DEFAULT since 2026-06-09). Removal comes from the img2img strength; ControlNet only preserves text/face STRUCTURE — SynthID CAN survive controlnet on photoreal content at low strength. No face-restore extra ships, by validated decision (every restore approach looked MORE AI-generated).
• auto_config.py + the content-detection layer were REMOVED 2026-06-09; --auto is a deprecated no-op (controlnet is the default pipeline and the adaptive polish is ON by default and self-gates to a no-op where there is no detail deficit).
• upscaler.py — optional Real-ESRGAN pre-diffusion super-resolution for small inputs (extra esrgan, spandrel only). Manual opt-in; the default --upscaler stays lanczos and the engine always falls back to Lanczos on absence/error. ESRGAN can degrade faces and thin text.
• image_io.py — Unicode-safe cv2 IO (issue #17). Every cv2 file read/write in the package routes through imread/imwrite; do not call cv2.imread/cv2.imwrite directly. to_bgr(image) is the shared channel normalizer — use it instead of inlining cvtColor branches.

For the Doubao alpha-distillation history (why content-image reverse-alpha distillation fails by physics and controlled captures were required), see docs/research-doubao-distillation.md.

Watermarking landscape

Who embeds what (C2PA / IPTC / EXIF / TC260 AIGC / xAI signature / open and proprietary invisible watermarks), whether each is locally detectable, the C2PA 2.4 durable-credentials implications, and the regulatory driver table live in docs/watermarking-landscape.md (research 2026-05-24, updated through 2026-06-10). Read it before adding a new identify signal, vendor token, or metadata marker. See identify.py for what we read today.

Known limitations

Compact list. Full measurements, incident history, and oracle-validation runs live in docs/known-limitations.md — read the relevant section there before changing the diffusion pipelines, strength defaults, resolution handling, or metadata coverage.

• invisible processes at native resolution for inputs >= 1024px long side and auto-upscales smaller inputs to a 1024px floor (--min-resolution 0 disables; --max-resolution N is an opt-in cap to bound GPU/MPS memory). MPS OOM is memory-tier dependent, not a hard limit: ~24 GB unified memory falls back to CPU (slow but weight-identical output), 32 GB runs native on MPS. The native-vs-cap-vs-floor decision lives in the pure helper invisible_engine._target_size — keep the logic there, unit-tested without the model.
• fp16 VAE black-output (issues #29/#41): the fp16-fixed SDXL VAE (madebyollin/sdxl-vae-fp16-fix) is swapped in for the default SDXL checkpoint on cuda/xpu fp16, plus a model-agnostic backstop that detects a degenerate (all-black) fp16 output and re-runs once in fp32. cpu/mps run fp32 and never reproduce the bug.
• Pyright first run is slow (2-3 min) due to ML deps (torch/diffusers/transformers stubs); full-project uv run pyright can stall for many minutes — scope it to changed files.
• A third-party PIL plugin autoload (e.g. an HEIF/AVIF plugin) can raise a non-OSError (ModuleNotFoundError), not UnidentifiedImageError, when opening a file. Code that opens user-supplied or unknown-format files should except Exception, not just OSError/UnidentifiedImageError.
• rich was dropped: the CLI + analysis scripts print plain text (click.echo / the scripts/_plain_console.py shim). rich is NOT a dependency — importing it breaks the core+dev CI sync; new scripts must use the shim. No Unicode glyphs / colors / progress bars in CLI output by design.
• AVIF/HEIF/JPEG-XL metadata detection is a binary scan; C2PA removal in those containers (and MP4/MOV/M4V) is noai/isobmff.py; non-ISOBMFF audio/video (WebM/MP3/WAV/FLAC/OGG) strips losslessly via ffmpeg on PATH. Still NOT built: an Exif meta-box item (needs iinf/iloc surgery) and Resemble PerTh audio detection (no presence/confidence flag exists).
• SynthID technical reference: docs/synthid.md — primary-source-cited doc covering mechanism (post-hoc encoder/decoder pair, 136-bit payload at 512x512, pixel-space, model weights NOT modified), robustness numbers (arXiv:2510.09263: ~99.98% TPR@0.1%FPR across 30 transforms including JPEG/crop/resize/color/noise), removal attacks and forensic detectability (arXiv:2605.09203: all 6 attacks detectable at >98% TPR@1%FPR), detectability limits (no public decoder, metadata-proxy only), oracle scope, and adoption landscape. Read that doc first before adding notes here.
• SynthID detection is metadata-only. No local pixel detector is possible by design (Google's decoder is proprietary, trusted-testers only); we read the C2PA companion proxy, which goes quiet once metadata is stripped — a quiet proxy is not proof the pixel watermark is gone. The Gemini app "Verify with SynthID" is the ONLY valid SynthID oracle; openai.com/verify is scoped to OpenAI provenance and each vendor's oracle detects only its own content. SynthID survives JPEG re-encode, so GitHub issue attachments remain valid pixel-watermark test subjects. Every spectral/phase detection approach evaluated (reverse-SynthID, our own probes) works only on controlled solid fills, never on real content.
• External AI-vs-real classifier models are out of scope (decided 2026-05-24): per-generator, degrade off-distribution, and our own light SDXL pass would likely defeat them. Detection stays local + signal-based.
• Default strength is VENDOR-ADAPTIVE, one ladder for BOTH pipelines (since 2026-06-09): resolve_strength(strength, vendor) picks OpenAI 0.20 / Gemini 0.30 / unknown 0.30 when --strength is unset; explicit --strength always wins. Removal at low strength is content x pipeline dependent, and near-threshold removal is SEED-NON-DETERMINISTIC — pick a strength with margin and oracle-revalidate per content type. Certified controlnet floors (Modal cert 2026-06-04): OpenAI 0.20 (resolution-independent), Gemini 0.30 (only <= 1536px; native large Gemini needs ~0.35+ or a cap).
• controlnet is the default pipeline; --pipeline sdxl is the lighter opt-down. Neither pipeline clears all content at low strength (photoreal survives controlnet, flat graphics survive sdxl — the lever is higher strength). A removal-priority caller MUST oracle-validate strength across content types; prod recipe: controlnet + per-vendor floor + FIXED seed. Forensic-stealth caveat (arXiv:2605.09203): defeating the SynthID verifier is NOT forensic invisibility — removal-processed images are flaggable at >98% TPR@1%FPR.