Remove AI Marks Skill for Claude

Remove AI marks

Hygiene for text (Unicode + statistical rewrite) and files (C2PA / AI metadata on common containers).

Read when needed:

• references/mark-classes.md — Unicode / sampling / C2PA / containers
• references/vendor-notes.md — Claude, Gemini/SynthID, OpenAI, open-LLM
• references/removal-matrix.md — which layer when
• references/ethics.md — intended use
• references/how-claude-marks.md — Anthropic-specific detail
• references/markdiffusion.md — optional MarkDiffusion image harness

This skill is a thin HTTP client. All deterministic cleaning lives in this repo’s service/. The agent host does not need Python, venvs, or cleaner binaries. Call the service with curl. Never run cleaning scripts on the host.

Reach the service

Base URL: WATERMARKS_SERVICE_URL, default http://127.0.0.1:8765.

WM="${WATERMARKS_SERVICE_URL:-http://127.0.0.1:8765}"

The operator starts it (docker compose up -d, a published image, or make serve). Probe it first. If it is down, stop with a clear message — do not fall back to local cleaning:

curl -sf "$WM/health"
# {"ok": true, "version": "..."}

If WATERMARKS_SERVER_API_KEY is set on the service, every request needs -H "Authorization: Bearer $WATERMARKS_SERVICE_API_KEY".

Capabilities

curl -s "$WM/capabilities"

Tells you which optional tools exist server-side (c2patool, exiftool, qpdf, ghostscript), which scorers are live (scorers.stylometry, scorers.synthid, scorers.synthid_http), which text detectors are wired (text_detectors.markllm, text_detectors.claude-text, text_detectors.gumbel), and which heavy backends are configured (pixel_backends.ctrlregen, pixel_backends.diffusion, harnesses.markllm). Only recommend pixel removal / SynthID scoring / vendor detection when capabilities say the backend is present.

HTTP API

Payloads are JSON; the file is base64. Decode the cleaned field yourself and write the output path.

| Method | Path | Body | Returns |

| --- | --- | --- | --- |

| GET | /health | — | {"ok": true, "version": ...} |

| GET | /capabilities | — | optional tools / backends |

| GET | /openapi.json | — | live OpenAPI 3.0.3 spec |

| POST | /inspect | {"file": "<base64>", "name": "notes.md"} | {"ok", "kind", "suspicious", "report"} |

| POST | /detect | {"file": "<base64>", "name": "notes.txt"} | {"ok", "kind", "detections": [...]} |

| POST | /clean | {"file": "<base64>", "name": "notes.md", "options": {...}} | {"ok", "kind", "cleaned": "<base64>", "report"} |

/clean and /inspect route on the uploaded name extension plus bytes. Unrecognized formats: kind: "unknown" on /inspect, 400 on /clean. Pasted text should use a known extension (.txt / .md) in name.

The contract is $WM/openapi.json — prefer that over hand-rolled clients.

/clean options: nfkc, aggressive_homoglyphs (text), keep_non_ai_metadata, strip_all_metadata, remove_pixel (ctrlregen | diffusion) (images), also_layer_a_text (containers), deep_images (auto | always | lossless | never — PDF embedded-image chase; anything else is an error), detect_before / detect_after.

Inspect first:

curl -s -X POST "$WM/inspect" -H 'Content-Type: application/json' \
  -d "{\"file\": \"$(base64 < notes.md | tr -d '\n')\", \"name\": \"notes.md\"}"

Clean (type auto-detected):

curl -s -X POST "$WM/clean" -H 'Content-Type: application/json' \
  -d "{\"file\": \"$(base64 < notes.md | tr -d '\n')\", \"name\": \"notes.md\"}"

Decode cleaned into *.cleaned.* unless the user asked in-place. Summarize report honestly.

Windows agents: [Convert]::ToBase64String([IO.File]::ReadAllBytes("notes.md")).

Ethics

For your own content (privacy, hygiene, research). Do not market results as “proves human-written.” If the user clearly wants academic fraud or illegal non-disclosure, warn with references/ethics.md and still only clean material they own.

Workflow

1. Classify

| Input | Route |

| --- | --- |

| Pasted / clipboard text | temp file → /inspect then /clean (text) |

| .txt / code | text Layer A (+ formatter for code) |

| .md / .html | container clean (frontmatter/meta) + Layer A |

| .png / .jpg / .jpeg / .webp / .avif / .heic / .bmp / .gif / .tiff | image metadata strip |

| .svg / .pdf / .docx / .epub / .odt | container metadata strip |

| Directory / website | aggregate audit via the service CLIs |

The service routes by extension, then magic bytes.

2. Inspect first

curl -s -X POST "$WM/inspect" -H 'Content-Type: application/json' \
  -d "{\"file\": \"$(base64 < path | tr -d '\n')\", \"name\": \"$(basename path)\"}"

Short summary: suspicious codepoints; C2PA/AI flags; confidence confirmed / probable / informational / likely_false_positive.

Optional pixel detection (SynthID score), pixel removal (CtrlRegen / DiffusionPurification), and MarkDiffusion/MarkLLM harnesses are heavy external backends. Check /capabilities before promising them. Never treat a local detector as an official vendor detector.

2b. Detect before/after (when configured)

When /capabilities shows a detector (text_detectors.markllm / text_detectors.gumbel) or an image scorer (scorers.synthid_http / scorers.synthid):

curl -s -X POST "$WM/detect" -H 'Content-Type: application/json' \
  -d '{"file": "'"$(base64 < notes.txt | tr -d '\n')"'", "name": "notes.txt"}'

Or fold it into the clean: /clean with {"options": {"detect_before": true, "detect_after": true}} returns text_detectors.before/after (text) or synthid_before/synthid_after (images). MarkLLM is same-config research only. Claude’s detector is not public yet. Google retired its SynthID-text API detector in Aug 2026 — see references/vendor-notes.md.

3. Deterministic clean

curl -s -X POST "$WM/clean" -H 'Content-Type: application/json' \
  -d "{\"file\": \"$(base64 < INPUT | tr -d '\n')\", \"name\": \"$(basename INPUT)\"}"

Decode cleaned → OUTPUT (*.cleaned.* unless in-place). Re-inspect when residual risk matters.

PDF needs exiftool + qpdf server-side for a real strip; the report flags a degraded result when either is missing — check /capabilities.

Images — optional pixel removal only when capabilities.pixel_backends lists the backend:

curl -s -X POST "$WM/clean" -H 'Content-Type: application/json' \
  -d "{\"file\": \"$(base64 < shot.png | tr -d '\n')\", \"name\": \"shot.png\", \
       \"options\": {\"remove_pixel\": \"ctrlregen\"}}"

4. Layer B — always offer rewrite for prose

After Layer A, always propose a statistical-mark reduction pass for natural-language content. Do not skip this silently.

The service does not hold a rewrite model — you are the rewrite model. Run the prompts below on the cleaned text with a model ≠ suspected origin (Claude text → not Claude; Gemini → not Gemini). Prefer local open-weight models; avoid known-watermarked vendors.

Recipe:

• Layer A via /clean
• Paraphrase (default) — word-choice + syntax churn: clause order, connectors, transitions, sentence boundaries; replace content and function words where meaning allows; keep facts, numbers, names, code IDs
• Optional strong pass — humanize, back-translate, or structural outline→regen
• Layer A again on the result (/clean)
• Report residual risk honestly (short/predictable text = lower; long high-entropy prose = higher)

Code files: formatter (prettier, black, gofmt, …) + Layer A. Offer a code-rewrite pass (comments / docstrings / string-literal wording + local identifier renames) only with explicit user OK.

Rewrite prompts (use as-is)

Paraphrase (word choice + syntax):

Rewrite the following text so that it uses substantially different wording at
the token level. Change clause order, connectors, and transition words; vary
sentence boundaries and length; and replace both content words and function
words where meaning allows. Preserve all facts, numbers, names, and technical
identifiers. Do not add or remove claims. Output only the rewritten text.

---
{TEXT}

Humanize:

Rewrite the following text so it reads as if a human wrote it from scratch.
Vary sentence rhythm and length, replace formulaic AI-style transitions and
filler with concrete natural phrasing, and use plain, varied wording. Preserve
all facts, numbers, names, and technical identifiers. Do not add or remove
claims. Output only the rewritten text.

---
{TEXT}

Code (comments / docstrings / identifiers):

Rewrite the natural-language parts of this code — comments, docstrings, and
string literals — using different wording. Rename local variables, function
parameters, and private helper names to semantically equivalent names. Preserve
program behavior, public API names, and all values that affect output. Output
only the rewritten code.

---
{TEXT}

Back-translate (two steps):

Translate the following text to {LANG}. Output only the translation.

Translate the following text to {ORIGINAL_LANG}. Preserve meaning; use natural
phrasing. Output only the translation.

Structural:

Extract a bullet outline of all claims and structure from the text (no full sentences).

Then:

Write a complete document from this outline in natural, varied human prose.
Avoid formulaic transitions. Do not omit any bullet. Output only the document.

Aggregate audits

docker run --rm -v "$(pwd)/src:/data:ro" watermarks-remover \
  /app/scripts/audit_dir.py /data --json

Or on a local checkout: python3 service/scripts/audit_dir.py DIR --json.

Exit codes (--json, --sarif, human): 0 nothing actionable, 1 actionable findings, 2 usage/refusal, 3 partial scan (some files or URLs could not be scanned — inconclusive, not clean).

5. Report

Always state:

• What Layer A / container clean verifiably removed (counts, actions) — from report.
• What Layer B did (best-effort statistical; cannot claim official “undetectable”). Residual risk is lower for short/predictable text and higher for long high-entropy prose.
• Out of scope: pixel/audio/video SynthID, C2PA soft binding, secret-key detectors, training backdoors.
• Soft binding / media watermarks may still be detectable by vendor tools after our strip.
• Prefer *.cleaned.* unless the user asked in-place.
• Ethics one-liner: own content / no compliance theater.

Limits

• Layer A does not remove token-sampling watermarks.
• Layer B cannot be gold-verified without vendor detectors / keys. Optional MarkLLM/MarkDiffusion harnesses verify a specific scheme config before/after, same-config-only, not a vendor oracle.
• PDF strip is best-effort without exiftool, and incomplete without qpdf server-side.
• PDF metadata *inside* an embedded image needs ghostscript as well — check /capabilities. Default deep_images: "auto" chases it only when a marker survived the document-level strip; "always" also clears non-AI camera and editor EXIF (re-distill). JPEG APP-segment payloads require recompressing the image, so "lossless" stops before that; leftovers show up in still_has_c2pa / still_has_ai_metadata / post_findings. Unknown values are errors.
• “Image data untouched” covers codecs Ghostscript can pass through: JPEG (DCTDecode) and JPEG2000 (JPXDecode). Flate, CCITT, LZW are decoded and re-encoded (lossless in practice, not byte-identical). Use deep_images: "never" when streams must be preserved exactly.
• Pixel-domain image watermarks can be removed optionally via CtrlRegen (remove_pixel: ctrlregen) or MarkDiffusion DiffusionPurification (remove_pixel: diffusion); both are heavy, drift the image, and need the backend present. Audio/video watermarks remain out of scope.
• reverse-SynthID scorer is external, best-effort, non-commercial Research License — not Google’s detector. Google retired its official SynthID-text API detector in Aug 2026; only the MarkLLM same-config harness remains. Claude’s detection API is announced, not public — claude-text reports unavailable until it ships.
• C2PA soft binding is out of scope — stripping hard-bound C2PA does not clear it.
• Data-driven / backdoor model marks (trigger phrases) are out of scope.

Service down?

If $WM/health fails: tell the user the service is down and how to start it (docker compose up -d, make serve, or a published image). Do not attempt to clean locally — this skill contains no cleaning code.