The runtime reacts on first touch (👀) via the react-first UserPromptSubmit hook in the agent-runner (see jbaruch/nanoclaw#136) — you do NOT need to call react_to_message to acknowledge receipt. Use it only to upgrade with a more specific reaction after inspecting the message: 👌 (got it, working), 👍 (acknowledged/done), 🔥 (urgent), 🤔 (thinking/investigating), 🤝 (done/confirmed). Each react_to_message call replaces the prior emoji; a later, more specific one supersedes the runtime's 👀. Telegram allows only its fixed reaction-emoji set and silently falls back to 👍 for any unsupported emoji, so the five above are safe and any other guess is harmless.

Reply threading

The reply-threading-enforcement PreToolUse hook (jbaruch/nanoclaw#137) denies a standalone send_message while the latest user inbound is unanswered — threading is a runtime contract, not a convention. Pass reply_to with the message ID from the <message id="..."> tag for any response to a user message. Carve-outs that bypass the gate: pin: true (status updates / daily briefings), sender set (multi-bot persona), maintenance / scheduled-task session. Rule of thumb: user said something and you're answering → reply_to; nobody asked and you're telling → standalone (e.g. scheduled-task output).

Async pattern

React → work → deliver result. The reaction (auto-emitted by the runtime) IS the acknowledgement — never hold the user hostage with a "I'm starting now" reply.

Formatting

Telegram parses HTML (its own subset, including <tg-spoiler>), not Markdown. The no-markdown-in-send-message PreToolUse hook (jbaruch/nanoclaw#138) auto-rewrites the four common Markdown leaks (**bold** → <b>, [label](url) → <a href>, `code` → <code>, - / * line bullets → •), so emit raw HTML only for the formats the hook doesn't cover: <i>, <u>, <s>, <pre> (optional <code class="language-python"> for syntax highlighting — substitute the actual language, not a placeholder), <blockquote>, <tg-spoiler>. For bullets use •.

Special-character escaping in user data: only <, >, & need HTML entities (<, >, &). Apostrophes and double quotes pass through raw — do NOT escape them as ' / "; Telegram's HTML parse mode doesn't decode those, so users see the literal entity text in the rendered message. Reference incident: 2026-04-26 untrusted group msg 1116 where Owner's Office and someone's tracing rendered verbatim.