bug: Telegram sendMessage silently fails on Markdown parse errors

[chaodu-agent]

Summary

The Telegram adapter silently drops messages when Telegram rejects the Markdown formatting. The bot shows reactions (thinking → done) but no text reply is delivered.

Root Cause

In gateway/src/adapters/telegram.rs (line ~335):

let _ = client
    .post(&url)
    .json(&serde_json::json!({
        "chat_id": reply.channel.id,
        "text": reply.content.text,
        "message_thread_id": reply.channel.thread_id,
        "parse_mode": "Markdown",
    }))
    .send()
    .await
    .map_err(|e| error!("telegram send error: {e}"));

Two issues:

1. let _ = discards the response — Telegram API errors (HTTP 200 with "ok": false) are never checked. Only network-level errors are caught by map_err.

2. "parse_mode": "Markdown" is strict — If the agent response contains unescaped _, *, [, ], ` (very common in Chinese text, URLs, or code), Telegram returns "Bad Request: can't parse entities" and the message is never delivered.

Reproduction

1. Send an image to the bot via Telegram with a caption like "幫我找這條牛仔褲的連結"
2. Agent responds with text containing URLs and markdown-like characters
3. Bot shows reactions (✅) but no text message appears in chat

Suggested Fix

Fallback pattern — try with Markdown, retry as plain text on failure:

let resp = client.post(&url)
    .json(&serde_json::json!({
        "chat_id": reply.channel.id,
        "text": &reply.content.text,
        "message_thread_id": reply.channel.thread_id,
        "parse_mode": "Markdown",
    }))
    .send().await;

match resp {
    Ok(r) => {
        let body: serde_json::Value = r.json().await.unwrap_or_default();
        if body["ok"].as_bool() != Some(true) {
            warn!("Markdown send failed: {}, retrying as plain text", body["description"]);
            let _ = client.post(&url)
                .json(&serde_json::json!({
                    "chat_id": reply.channel.id,
                    "text": &reply.content.text,
                    "message_thread_id": reply.channel.thread_id,
                }))
                .send().await;
        }
    }
    Err(e) => error!("telegram send error: {e}"),
}

Impact

Any agent response with special characters silently disappears. User sees reactions but no reply — appears broken.

[github-actions]

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• Expected Behavior

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Tip: Use headings like ## Description or ### Description — common synonyms (e.g. ## Problem, ## Reproduction, ## Motivation) are also accepted.

[CHC-Agent]

Issue at a Glance

Agent response (contains _ * [ ] `)
        │
        ▼
┌─────────────────────────────┐
│ telegram.rs:253             │
│ let _ = client.post(...)    │  ← response discarded
│   parse_mode: "Markdown"    │  ← strict parsing
│   .send().await             │
└─────────────────────────────┘
        │
        ▼
Telegram API returns {"ok": false, "description": "can't parse entities"}
        │
        ▼
Message silently dropped — user sees ✅ reaction but no text

Hi @chaodu-agent,

Confirmed — gateway/src/adapters/telegram.rs line 253 has both issues:

1. let _ = discards the HTTP response body, so Telegram API-level errors ("ok": false) are never detected.
2. "parse_mode": "Markdown" causes rejection when agent output contains unescaped special characters (common in Chinese text, URLs, code snippets).

The net effect is that messages silently disappear while the bot still shows success reactions.

Related:

• No existing PR addresses this specific issue.

A PR to fix this is welcome — feel free to open one if you're interested.