fix(channel): normalize telegram history for MiniMax

docs/providers-reference.md

@@ -144,6 +144,11 @@ Optional:
 - `MINIMAX_OAUTH_REGION=global` or `cn` (defaults by provider alias)
 - `MINIMAX_OAUTH_CLIENT_ID` to override the default OAuth client id
 
+Channel compatibility note:
+
+- For MiniMax-backed channel conversations, runtime history is normalized to keep valid `user`/`assistant` turn order.
+- Channel-specific delivery guidance (for example Telegram attachment markers) is merged into the leading system prompt instead of being appended as a trailing `system` turn.
+
 ## Qwen Code OAuth Setup (config.toml)
 
 Set Qwen Code OAuth mode in config:

src/channels/mod.rs

@@ -200,6 +200,43 @@ fn channel_delivery_instructions(channel_name: &str) -> Option<&'static str> {
     }
 }
 
+fn build_channel_system_prompt(base_prompt: &str, channel_name: &str) -> String {
+    if let Some(instructions) = channel_delivery_instructions(channel_name) {
+        if base_prompt.is_empty() {
+            instructions.to_string()
+        } else {
+            format!("{base_prompt}\n\n{instructions}")
+        }
+    } else {
+        base_prompt.to_string()
+    }
+}
+
+fn normalize_cached_channel_turns(turns: Vec<ChatMessage>) -> Vec<ChatMessage> {
+    let mut normalized = Vec::with_capacity(turns.len());
+    let mut expecting_user = true;
+
+    for turn in turns {
+        match (expecting_user, turn.role.as_str()) {
+            (true, "user") => {
+                normalized.push(turn);
+                expecting_user = false;
+            }
+            (false, "assistant") => {
+                normalized.push(turn);
+                expecting_user = true;
+            }
+            _ => {}
+        }
+    }
+
+    if normalized.last().map_or(false, |msg| msg.role == "user") {
+        normalized.pop();
+    }
+
+    normalized
+}
+
 fn supports_runtime_model_switch(channel_name: &str) -> bool {
     matches!(channel_name, "telegram" | "discord")
 }
@@ -318,7 +355,7 @@ fn compact_sender_history(ctx: &ChannelRuntimeContext, sender_key: &str) -> bool
     let keep_from = turns
         .len()
         .saturating_sub(CHANNEL_HISTORY_COMPACT_KEEP_MESSAGES);
-    let mut compacted = turns[keep_from..].to_vec();
+    let mut compacted = normalize_cached_channel_turns(turns[keep_from..].to_vec());
 
     for turn in &mut compacted {
         if turn.content.chars().count() > CHANNEL_HISTORY_COMPACT_CONTENT_CHARS {
@@ -327,6 +364,11 @@ fn compact_sender_history(ctx: &ChannelRuntimeContext, sender_key: &str) -> bool
         }
     }
 
+    if compacted.is_empty() {
+        turns.clear();
+        return false;
+    }
+
     *turns = compacted;
     true
 }
@@ -783,21 +825,19 @@ async fn process_channel_message(
         ChatMessage::user(&enriched_message),
     );
 
-    let mut prior_turns = ctx
+    // Build history from per-sender conversation cache.
+    let prior_turns_raw = ctx
         .conversation_histories
         .lock()
         .unwrap_or_else(|e| e.into_inner())
         .get(&history_key)
         .cloned()
         .unwrap_or_default();
+    let prior_turns = normalize_cached_channel_turns(prior_turns_raw);
 
-    let mut history = vec![ChatMessage::system(ctx.system_prompt.as_str())];
-    history.append(&mut prior_turns);
-
-    if let Some(instructions) = channel_delivery_instructions(&msg.channel) {
-        history.push(ChatMessage::system(instructions));
-    }
-
+    let system_prompt = build_channel_system_prompt(ctx.system_prompt.as_str(), &msg.channel);
+    let mut history = vec![ChatMessage::system(system_prompt)];
+    history.extend(prior_turns);
     let use_streaming = target_channel
         .as_ref()
         .is_some_and(|ch| ch.supports_draft_updates());
@@ -3994,6 +4034,87 @@ mod tests {
         assert!(calls[1][3].1.contains("follow up"));
     }
 
+    #[tokio::test]
+    async fn process_channel_message_telegram_keeps_system_instruction_at_top_only() {
+        let channel_impl = Arc::new(TelegramRecordingChannel::default());
+        let channel: Arc<dyn Channel> = channel_impl.clone();
+
+        let mut channels_by_name = HashMap::new();
+        channels_by_name.insert(channel.name().to_string(), channel);
+
+        let provider_impl = Arc::new(HistoryCaptureProvider::default());
+        let mut histories = HashMap::new();
+        histories.insert(
+            "telegram_alice".to_string(),
+            vec![
+                ChatMessage::assistant("stale assistant"),
+                ChatMessage::user("earlier user question"),
+                ChatMessage::assistant("earlier assistant reply"),
+            ],
+        );
+
+        let runtime_ctx = Arc::new(ChannelRuntimeContext {
+            channels_by_name: Arc::new(channels_by_name),
+            provider: provider_impl.clone(),
+            default_provider: Arc::new("test-provider".to_string()),
+            memory: Arc::new(NoopMemory),
+            tools_registry: Arc::new(vec![]),
+            observer: Arc::new(NoopObserver),
+            system_prompt: Arc::new("test-system-prompt".to_string()),
+            model: Arc::new("test-model".to_string()),
+            temperature: 0.0,
+            auto_save_memory: false,
+            max_tool_iterations: 5,
+            min_relevance_score: 0.0,
+            conversation_histories: Arc::new(Mutex::new(histories)),
+            provider_cache: Arc::new(Mutex::new(HashMap::new())),
+            route_overrides: Arc::new(Mutex::new(HashMap::new())),
+            api_key: None,
+            api_url: None,
+            reliability: Arc::new(crate::config::ReliabilityConfig::default()),
+            provider_runtime_options: providers::ProviderRuntimeOptions::default(),
+            workspace_dir: Arc::new(std::env::temp_dir()),
+            message_timeout_secs: CHANNEL_MESSAGE_TIMEOUT_SECS,
+            interrupt_on_new_message: false,
+            multimodal: crate::config::MultimodalConfig::default(),
+        });
+
+        process_channel_message(
+            runtime_ctx.clone(),
+            traits::ChannelMessage {
+                id: "tg-msg-1".to_string(),
+                sender: "alice".to_string(),
+                reply_target: "chat-telegram".to_string(),
+                content: "hello".to_string(),
+                channel: "telegram".to_string(),
+                timestamp: 1,
+                thread_ts: None,
+            },
+            CancellationToken::new(),
+        )
+        .await;
+
+        let calls = provider_impl
+            .calls
+            .lock()
+            .unwrap_or_else(|e| e.into_inner());
+        assert_eq!(calls.len(), 1);
+        assert_eq!(calls[0].len(), 4);
+
+        let roles = calls[0]
+            .iter()
+            .map(|(role, _)| role.as_str())
+            .collect::<Vec<_>>();
+        assert_eq!(roles, vec!["system", "user", "assistant", "user"]);
+        assert!(
+            calls[0][0]
+                .1
+                .contains("When responding on Telegram, include media markers"),
+            "telegram delivery instruction should live in the system prompt"
+        );
+        assert!(!calls[0].iter().skip(1).any(|(role, _)| role == "system"));
+    }
+
     // ── AIEOS Identity Tests (Issue #168) ─────────────────────────
 
     #[test]