[jorgemanrubia]

An agent can now fold the work behind an answer from Markdown. A <details> block typed in Markdown reaches Basecamp as a fold, instead of showing its tags as text.

Basecamp's rich text allows details and summary (bc3 doc/api/sections/rich_text.md), and posts written as HTML already fold. The Markdown path escaped both tags, so the only way to fold was to hand-write the whole post as HTML, which the basecamp skill tells agents not to do. In 392 agent posts on 37signals' Basecamp, only 5 folded, all of them HTML, and one post typed in Markdown showed <details> as literal text.

What changes:

• richTextTags keeps details and summary. The Markdown between them still converts, the way it does in any other kept HTML block.
• The basecamp skill says how to write a fold. The skill is still under its 16 KiB cap: I shortened the Mermaid paragraph to make room.
• The connector's subagent instructions say how, and when: only when a reply combines its answer with the details of the work behind it, never folding the answer, an ask or a blocker.

Tests: two new cases, one fold with Markdown inside and one written inline. Both fail with the tag change reverted. The old "unsupported inline tag is text" case now uses <abbr>. bin/ci passes locally.

One thing to know: the separators the Markdown path adds put an empty line just inside the top and bottom of an open fold.

Paired with basecamp/coworker#325, which tells agents when to fold. For a person to review and merge.

[cubic-dev-ai]

All reported issues were addressed across 4 files

<sub>Reply with feedback, questions, or to request a fix.

View guided diff | Turn on auto-fix | Re-trigger cubic</sub>

[Copilot]

🟢 Approved

No active review issues block the change to preserve Markdown fold tags.

No open issues 🎉

What changed in this PR

This PR lets Markdown posts retain <details> and <summary> tags, so agents can fold supporting details without writing the entire post as HTML.

Changes:

• Preserve fold tags while continuing to convert the Markdown inside.
• Add regression cases for block and inline folds, retaining unsupported-tag coverage.
• Document fold syntax and instruct connector agents to keep answers, asks, and blockers visible.

[!TIP]
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File	Description
skills/​basecamp/​SKILL.md	Documents fold syntax and shortens Mermaid guidance.
skills/​basecamp-connect/​subagent.md	Explains when to fold supporting details and what must remain visible.
internal/​richtext/​richtext.go	Adds details and summary to preserved rich-text tags.
internal/​richtext/​richtext_test.go	Covers block and inline folds and updates unsupported-tag coverage.

_{Review effort: Balanced}

[Copilot]

🟢 Approved

No active review issues are reported for the Markdown fold-tag support change.

No open issues 🎉

_{Review effort: Balanced}

[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

View guided diff | Turn on auto-fix | Re-trigger cubic</sub>

[Copilot]

🟢 Approved

No active review issues are blocking the change to preserve collapsible details in Markdown posts.

No open issues 🎉

_{Review effort: Balanced}