Fix SynthID provenance evidence and release 0.26.1

docs/known-limitations.md

@@ -66,9 +66,10 @@ still alter small text or difficult faces.
 
 ### Removal cannot be verified locally for proprietary SynthID
 
-The project has no public local SynthID pixel decoder. It can infer likely
-presence from supported provenance metadata, but a missing metadata proxy is
-not a negative pixel verdict.
+The project has no public local SynthID pixel decoder. It recognizes presence
+from supported provenance metadata: Google AI C2PA under Google's all-media
+policy, or current OpenAI C2PA with an explicit watermark action. A missing
+provenance signal is not a negative pixel verdict.
 
 For important outputs:
 

docs/module-internals.md

@@ -436,7 +436,7 @@ metadata extraction from verdict logic:
 - `identify_from_evidence` evaluates that evidence without reopening the source. Rules
   that decide a verdict live here, not in extraction: extraction has two
   implementations, and a rule in only one of them is a rule the other lacks. The
-  SynthID proxy is the worked example — its structured form comes from the manifest,
+  SynthID provenance evidence is the worked example — its structured form comes from the manifest,
   and the byte-scan fallback for containers no parser reaches runs in the verdict, so
   both extractors reach the same answer. It did not, and the record path silently
   reported no SynthID for images the file path flagged.

docs/supported-signals.md

@@ -122,9 +122,12 @@ Current pipeline values, both CUDA-only:
 The `controlnet`, `sdxl`, `qwen` and `default` values were removed. A retired name
 is rejected at parse time rather than remapped onto a surviving profile.
 
-SynthID does not have a public local pixel decoder in this project. The tool can
-infer likely presence from supported provenance metadata, but after that
-metadata is removed a local negative result is inconclusive.
+SynthID does not have a public local pixel decoder in this project. The tool
+recognizes presence from supported provenance: Google AI C2PA under Google's
+all-media watermark policy, and current OpenAI C2PA carrying an explicit
+`c2pa.watermarked.*` action. Legacy OpenAI C2PA without that action does not
+assert SynthID. After provenance metadata is removed, a local negative result
+is still inconclusive.
 
 For MP4, MOV, and M4V, `video invisible` or the explicit
 `video all --invisible` option can regenerate the video through a VAE and strip

docs/synthid.md

@@ -289,14 +289,19 @@ The external variant SynthID-O is available "through partnerships" only. Our
 tool cannot locally detect SynthID presence or absence -- this is by design,
 not a gap we can fill.
 
-### 3.2 How our tool detects SynthID (metadata proxy)
+### 3.2 How our tool recognizes SynthID from provenance
 
-We detect SynthID indirectly: if the image's C2PA manifest is signed by a
-known SynthID-using issuer (Google, OpenAI), we infer SynthID is present. This
-is a **metadata proxy**, not a pixel watermark decode. It works while the C2PA
-manifest is intact, and is silent once the manifest is stripped or the image
-is re-encoded without C2PA (e.g., a screenshot, a social-media re-upload, or
-after `metadata --remove`).
+We recognize SynthID indirectly from supported C2PA evidence; this is not a
+pixel watermark decode. Google states that all media generated by its tools is
+watermarked, so Google AI C2PA establishes SynthID. OpenAI C2PA predates its
+SynthID rollout, but current manifests add the signed
+`c2pa.watermarked.unbound` action; OpenAI provenance establishes SynthID only
+when that action is present. Legacy OpenAI C2PA without it remains valid origin
+evidence but does not assert a pixel watermark.
+
+This works while the C2PA manifest is intact and is silent once the manifest is
+stripped or the image is re-encoded without C2PA (e.g., a screenshot, a
+social-media re-upload, or after `metadata --remove`).
 
 This is why:
 - `identify` on a GitHub-recompressed issue attachment returns Unknown (C2PA is
@@ -409,8 +414,9 @@ OpenAI confirmed SynthID adoption (Help Center, updated 2026-05-21):
 > "ChatGPT images include both C2PA metadata and SynthID watermarks."
 
 This is time-gated: pre-rollout ChatGPT/gpt-image images carry C2PA without
-SynthID. Our C2PA proxy therefore over-reports SynthID presence on old images
-(hence the `_OPENAI_CAVEAT` hedging flag in the codebase).
+SynthID. Current OpenAI manifests distinguish the watermarked output with the
+signed `c2pa.watermarked.unbound` action. The detector requires that action, so
+old OpenAI C2PA remains an origin signal without becoming a SynthID claim.
 
 ### 4.3 Other vendors
 
@@ -558,7 +564,7 @@ for `sdxl`, not a separate certification (no local SynthID detector to self-veri
 The higher strength costs little quality where it matters, because `controlnet` is now
 the default pipeline, so `sdxl` is reached only via an explicit `--pipeline sdxl` (a
 deliberate opt-down), where over-regeneration has no faces/text to damage.
-This uses the vendor signal we DO have locally (the C2PA SynthID proxy) to avoid the
+This uses the vendor signal we DO have locally (the C2PA SynthID provenance) to avoid the
 overkill of a single high default on OpenAI images, without needing a local pixel
 detector. An explicit `--strength` always wins. If the watermark still survives (e.g. a
 large native Gemini beyond the capped-1536 validation), raise toward 0.35-0.40 (0.40
@@ -617,7 +623,7 @@ Two constraints on reading this:
 - **The correct oracle for OpenAI images is openai.com/verify**, not the Gemini
   app. The two oracles detect different payloads.
 - **A quiet `identify` output after processing is not proof of removal.** It
-  means the metadata proxy is gone. The pixel watermark state is unknown without
+  means the provenance evidence is gone. The pixel watermark state is unknown without
   an oracle check.
 - **After removal, the output may carry forensic artifacts** detectable by an
   independent classifier even if the vendor oracle reads negative. Defeating the