[Bug] Artifacts with mermaid blocks cannot be shared publicly

Bug Description
Artifacts: a page containing a mermaid block cannot be shared publicly

SYMPTOM
In the artifact share dialog, General access → "Anyone with the link" fails with:
"This version can't be shared publicly. Publish a new version or change the
shared version, then try again."
The error's own remedy does not work. Republishing fails identically, and minting
brand-new artifact records with the same content fails identically. The page renders
fine and is privately viewable throughout — only public sharing is refused.

ISOLATING VARIABLE
A <pre class="mermaid"> block in the page. Removing it and rebuilding the same
diagram in plain HTML/CSS made the identical page shareable on the first attempt,
with no other substantive change.

EVIDENCE (2026-07-28, ~07:20–07:50Z, published via Claude Code's Artifact tool)
22183742-d344-497b-89d5-3ed9b01fc9ed plain text page ......................... SHARED
3b5fc462-38f2-4341-8321-5c3b7597d4df plain text page (control repeat) ........ SHARED
a4bfa623-de40-4a78-ad14-e02b0cfec049 plain page + absolute /home/ paths ...... SHARED
2481b1c5-0f31-4c2d-89fa-0f4385ad177c text-only, token "mermaid" in unused CSS SHARED
1526de78-cacb-49c5-8861-27ed3b81f488 ledger w/ <pre class="mermaid"> ......... REFUSED (2 versions)
057cd203-0fc2-4dc5-a9b2-7d3e1f9ca290 same content, fresh record .............. REFUSED
69113689-b2f7-4862-8438-450b808da34f same content, fresh record again ........ REFUSED
0d8fddd5-4c61-4c70-ab3c-d87d6427e387 ledger minus a prose section, mermaid kept REFUSED
042f0244-ae40-4096-98a2-c74af074b192 SAME ledger, mermaid → HTML/CSS diagram . SHARED

RULES OUT

• Stuck version pointer: fresh records with no prior shared version fail the same way,

so "publish a new version" cannot be the remedy.

• Private-looking data: a probe carrying absolute /home/<user>/ paths shared fine.
• Page size: shareable and refused ledgers differ by ~1 KB out of 24 KB.
• The token itself: a text-only page with "mermaid" in an unused CSS selector shared fine.

So the trigger is the rendered/parsed block, not the source text.

IMPACT
Mermaid is documented as a first-class Artifact feature ("Artifacts render mermaid
diagrams natively"). Any artifact using it is silently unshareable. The Artifact tool
returns success at publish time and reports nothing about shareability, so the failure
only surfaces when a user tries to share — and the error message sends them into a
republish loop that cannot succeed. Took 8 artifact records to diagnose.

ASK

1. Allow public sharing of pages containing mermaid blocks, or
2. Surface the refusal at publish time with the real reason, so it is fixable in one

step instead of eight.

The full markdown version is the file I sent you if you'd rather attach it than paste.

🌸: Every line in that block is a click you actually made — which is why it will be believed.

Environment Info

• Platform: linux
• Terminal: tmux
• Version: 2.1.220
• Feedback ID: ac576cbc-44c8-43b3-99c3-acc9ea76adb7

Errors

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