diff --git a/src/agent.rs b/src/agent.rs
index 4a9c454..34910bb 100644
--- a/src/agent.rs
+++ b/src/agent.rs
@@ -265,6 +265,12 @@ pub async fn run(cli: &Cli) -> Result<()> {
             content: response_text.clone(),
         });
 
+        // Log R1 reasoning chain at debug level so it can be inspected when
+        // the model makes repeated DSL mistakes (run with RUST_LOG=debug).
+        if let Some(thinking) = claude::extract_think_content(&response_text) {
+            debug!("R1 thinking ({} chars):\n{}", thinking.len(), thinking);
+        }
+
         // Extract strategy JSON
         let strategy = match claude::extract_json(&response_text) {
             Ok(s) => s,
@@ -665,6 +671,48 @@ pub fn diagnose_history(history: &[IterationRecord]) -> (String, bool) {
         }
     }
 
+    // --- Repeated API error detection ---
+    // If the same DSL error variant has appeared in 2+ consecutive iterations,
+    // call it out explicitly so the model knows exactly what to fix.
+    {
+        let recent_errors: Vec<String> = history
+            .iter()
+            .rev()
+            .take(4)
+            .flat_map(|rec| rec.results.iter())
+            .filter_map(|r| r.error_message.as_deref())
+            .filter(|e| e.contains("unknown variant"))
+            .map(|e| {
+                // Extract the variant name: "unknown variant `foo`, expected ..."
+                e.split('`')
+                    .nth(1)
+                    .unwrap_or(e)
+                    .to_string()
+            })
+            .collect();
+
+        if recent_errors.len() >= 2 {
+            // Find the most frequent bad variant
+            let mut counts: std::collections::HashMap<&str, usize> = std::collections::HashMap::new();
+            for v in &recent_errors {
+                *counts.entry(v.as_str()).or_default() += 1;
+            }
+            if let Some((bad_variant, count)) = counts.into_iter().max_by_key(|(_, c)| *c) {
+                if count >= 2 {
+                    notes.push(format!(
+                        "⚠ DSL ERROR (repeated {count}×): the swym API rejected \
+                         `{bad_variant}` as an unknown variant. \
+                         Check the 'Critical: expression kinds' section — \
+                         `{bad_variant}` may be a FuncName (use inside \
+                         {{\"kind\":\"func\",\"name\":\"{bad_variant}\",...}}) \
+                         or it may not be supported at all. \
+                         Use ONLY the documented kinds and func names."
+                    ));
+                }
+            }
+        }
+    }
+
     // --- Zero-trade check ---
     let zero_trade_iters = history
         .iter()
diff --git a/src/claude.rs b/src/claude.rs
index 9c70bd7..1294805 100644
--- a/src/claude.rs
+++ b/src/claude.rs
@@ -213,6 +213,14 @@ fn lmstudio_context_length(json: &Value, model_id: &str) -> Option<u32> {
     None
 }
 
+/// Return the content of the first `<think>` block, if any.
+/// Used for debug logging of R1 reasoning chains.
+pub fn extract_think_content(text: &str) -> Option<String> {
+    let start = text.find("<think>")? + "<think>".len();
+    let end = text[start..].find("</think>").map(|i| start + i)?;
+    Some(text[start..end].trim().to_string())
+}
+
 /// Extract a JSON object from a model response text.
 /// Handles markdown code fences and R1-style `<think>...</think>` blocks.
 pub fn extract_json(text: &str) -> Result<Value> {
diff --git a/src/prompts.rs b/src/prompts.rs
index ce26576..e1d8180 100644
--- a/src/prompts.rs
+++ b/src/prompts.rs
@@ -151,6 +151,12 @@ Common mistakes to NEVER make:
   `bollinger_upper`, `bollinger_lower`.
 - `volume` is a candle FIELD, not a func name. Access it as `{{"kind":"field","field":"volume"}}`.
   To compute EMA of volume: `{{"kind":"apply_func","name":"ema","period":20,"expr":{{"kind":"field","field":"volume"}}}}`.
+- `bollinger_upper` and `bollinger_lower` are FUNC NAMES, not Expr kinds. To compare close to the upper band:
+  `{{"kind":"compare","left":{{"kind":"field","field":"close"}},"op":">","right":{{"kind":"func","name":"bollinger_upper","period":20}}}}`
+  NEVER write `{{"kind":"bollinger_upper",...}}` — `bollinger_upper` is not an Expr kind.
+- `roc` (rate of change), `hma` (Hull MA), `vwap`, `macd`, `cci`, `stoch` are NOT supported.
+  Use `sma`, `ema`, `wma`, `rsi`, `atr`, `adx`, `supertrend`, `std_dev`, `sum`, `highest`, `lowest`,
+  `bollinger_upper`, `bollinger_lower` only.
 
 ## Working examples