diff --git a/.gitignore b/.gitignore
index 801357373f6..b8e61cc362e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,9 @@
 .env.*
 !.env.example
 
+# macOS
+.DS_Store
+
 # Claude Code worktrees and lock files
 .claude/worktrees/
 .claude/scheduled_tasks.lock
@@ -12,6 +15,9 @@
 .sidecar/
 .todos/
 
+# Cursor IDE
+.cursor/
+
 target/
 
 # Benchmark results (local runs, not committed)
diff --git a/src/agent/dispatcher.rs b/src/agent/dispatcher.rs
index 6118ec7d364..6006a02e8a6 100644
--- a/src/agent/dispatcher.rs
+++ b/src/agent/dispatcher.rs
@@ -863,6 +863,39 @@ impl Agent {
     }
 }
 
+/// Normalize tool parameters from LLM output.
+///
+/// Some OpenAI-compatible providers (e.g. Qwen via DashScope) return empty
+/// strings `""` for optional parameters instead of `null` when the tool schema
+/// uses strict-mode nullable types (`["string","null"]`). An empty string is
+/// semantically equivalent to absent for optional tool parameters, but
+/// `validate_tool_params` rejects empty strings and tools like `time` pass
+/// them directly to parsers (e.g. `parse_timezone("")` → error).
+///
+/// This function converts all empty string values to `null` in the parameter
+/// object before validation and execution. Non-string values are left unchanged.
+fn normalize_tool_params(params: &serde_json::Value) -> serde_json::Value {
+    match params {
+        serde_json::Value::Object(obj) => {
+            let cleaned = obj
+                .iter()
+                .map(|(k, v)| {
+                    let normalized = match v {
+                        serde_json::Value::String(s) if s.is_empty() => serde_json::Value::Null,
+                        other => normalize_tool_params(other),
+                    };
+                    (k.clone(), normalized)
+                })
+                .collect();
+            serde_json::Value::Object(cleaned)
+        }
+        serde_json::Value::Array(arr) => {
+            serde_json::Value::Array(arr.iter().map(normalize_tool_params).collect())
+        }
+        other => other.clone(),
+    }
+}
+
 /// Execute a chat tool without requiring `&Agent`.
 ///
 /// This standalone function enables parallel invocation from spawned JoinSet
@@ -875,6 +908,11 @@ pub(super) async fn execute_chat_tool_standalone(
     params: &serde_json::Value,
     job_ctx: &crate::context::JobContext,
 ) -> Result<String, Error> {
+    // Normalize params: convert empty strings to null so optional parameters
+    // left blank by strict-mode LLMs (e.g. Qwen) are treated as absent.
+    let params = normalize_tool_params(params);
+    let params = &params;
+
     let tool = tools
         .get(tool_name)
         .await
@@ -926,7 +964,7 @@ pub(super) async fn execute_chat_tool_standalone(
             );
         }
         Ok(Err(e)) => {
-            tracing::debug!(
+            tracing::warn!(
                 tool = %tool_name,
                 elapsed_ms = elapsed.as_millis() as u64,
                 error = %e,
@@ -2261,6 +2299,71 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_normalize_tool_params_empty_strings_become_null() {
+        // Regression: strict-mode LLMs (e.g. Qwen via DashScope) return empty
+        // strings for optional nullable parameters instead of null.
+        // normalize_tool_params must convert these to null so optional_param
+        // helpers like `params.get("timezone").and_then(|v| v.as_str())` return
+        // None and tools treat the parameter as absent.
+        let params = serde_json::json!({
+            "operation": "now",
+            "timezone": "",
+            "format": "",
+            "input": "2026-01-01"
+        });
+        let normalized = super::normalize_tool_params(&params);
+        assert_eq!(
+            normalized["operation"].as_str(),
+            Some("now"),
+            "non-empty string must be preserved"
+        );
+        assert!(
+            normalized["timezone"].is_null(),
+            "empty string must become null"
+        );
+        assert!(
+            normalized["format"].is_null(),
+            "empty string must become null"
+        );
+        assert_eq!(
+            normalized["input"].as_str(),
+            Some("2026-01-01"),
+            "non-empty string must be preserved"
+        );
+    }
+
+    #[test]
+    fn test_normalize_tool_params_nested_objects() {
+        // Nested objects (e.g. tool params with nested config) should also have
+        // their empty string values converted to null.
+        let params = serde_json::json!({
+            "config": { "key": "", "other": "value" },
+            "items": ["hello", "world"]
+        });
+        let normalized = super::normalize_tool_params(&params);
+        assert!(normalized["config"]["key"].is_null(), "nested empty string must become null");
+        assert_eq!(normalized["config"]["other"].as_str(), Some("value"));
+        // Array string elements are preserved as-is (arrays are passed through)
+        let items = normalized["items"].as_array().unwrap();
+        assert_eq!(items[0].as_str(), Some("hello"));
+        assert_eq!(items[1].as_str(), Some("world"));
+    }
+
+    #[test]
+    fn test_normalize_tool_params_non_string_values_unchanged() {
+        let params = serde_json::json!({
+            "count": 42,
+            "flag": false,
+            "ratio": 3.14,
+            "nothing": null
+        });
+        let normalized = super::normalize_tool_params(&params);
+        assert_eq!(normalized["count"].as_i64(), Some(42));
+        assert_eq!(normalized["flag"].as_bool(), Some(false));
+        assert!(normalized["nothing"].is_null());
+    }
+
     #[test]
     fn test_image_sentinel_empty_data_url_should_be_skipped() {
         // Regression: unwrap_or_default() on missing "data" field produces an empty
diff --git a/src/channels/repl.rs b/src/channels/repl.rs
index 33adc23f62d..4381bc38dc5 100644
--- a/src/channels/repl.rs
+++ b/src/channels/repl.rs
@@ -481,11 +481,17 @@ impl Channel for ReplChannel {
             StatusUpdate::ToolStarted { name } => {
                 eprintln!("  \x1b[33m\u{25CB} {name}\x1b[0m");
             }
-            StatusUpdate::ToolCompleted { name, success, .. } => {
+            StatusUpdate::ToolCompleted {
+                name,
+                success,
+                error,
+                ..
+            } => {
                 if success {
                     eprintln!("  \x1b[32m\u{25CF} {name}\x1b[0m");
                 } else {
-                    eprintln!("  \x1b[31m\u{2717} {name} (failed)\x1b[0m");
+                    let detail = error.as_deref().unwrap_or("unknown error");
+                    eprintln!("  \x1b[31m\u{2717} {name}: {detail}\x1b[0m");
                 }
             }
             StatusUpdate::ToolResult { name: _, preview } => {
diff --git a/src/safety/validator.rs b/src/safety/validator.rs
index c56789ea9eb..de511ba3a7c 100644
--- a/src/safety/validator.rs
+++ b/src/safety/validator.rs
@@ -201,6 +201,13 @@ impl Validator {
         ) {
             match value {
                 serde_json::Value::String(s) => {
+                    // Empty strings are treated as absent optional parameters —
+                    // some strict-mode LLMs (e.g. Qwen) emit "" instead of null
+                    // for nullable fields. Skipping them here avoids spurious
+                    // Empty errors on valid tool calls.
+                    if s.is_empty() {
+                        return;
+                    }
                     let string_result = validator.validate(s);
                     *result = std::mem::take(result).merge(string_result);
                 }
@@ -312,4 +319,34 @@ mod tests {
         assert!(result.is_valid); // Still valid, just a warning
         assert!(!result.warnings.is_empty());
     }
+
+    #[test]
+    fn test_validate_tool_params_empty_string_is_valid() {
+        // Regression: strict-mode LLMs (e.g. Qwen) emit "" for optional nullable
+        // parameters. validate_tool_params must not reject these as Empty errors.
+        let validator = Validator::new();
+        let params = serde_json::json!({
+            "operation": "now",
+            "timezone": "",
+            "format": ""
+        });
+        let result = validator.validate_tool_params(&params);
+        assert!(
+            result.is_valid,
+            "Empty optional params should not fail validation: {:?}",
+            result.errors
+        );
+    }
+
+    #[test]
+    fn test_validate_tool_params_non_empty_strings_still_validated() {
+        // Ensure actual string content continues to be validated.
+        let validator = Validator::new().forbid_pattern("injection_test");
+        let params = serde_json::json!({
+            "operation": "now",
+            "timezone": "injection_test"
+        });
+        let result = validator.validate_tool_params(&params);
+        assert!(!result.is_valid, "Forbidden patterns should still be caught");
+    }
 }
diff --git a/src/tools/builtin/time.rs b/src/tools/builtin/time.rs
index bafbd4d74af..c78d42b4bf3 100644
--- a/src/tools/builtin/time.rs
+++ b/src/tools/builtin/time.rs
@@ -534,4 +534,44 @@ mod tests {
 
         assert_eq!(dt.to_rfc3339(), "2026-03-08T07:30:00+00:00");
     }
+
+    #[tokio::test]
+    async fn test_now_with_empty_string_optional_params() {
+        // Regression: strict-mode LLMs (e.g. Qwen) emit "" for optional nullable
+        // parameters. The time tool must handle these gracefully — they should be
+        // treated as absent, not cause parse errors.
+        // normalize_tool_params (in dispatcher) converts "" to null before reaching
+        // here, but we also test that null params work correctly end-to-end.
+        let tool = TimeTool;
+        let ctx = JobContext::with_user("test", "chat", "test");
+
+        // null optional params (what normalize_tool_params produces from "")
+        let output = tool
+            .execute(
+                serde_json::json!({
+                    "operation": "now",
+                    "timezone": null,
+                    "format": null
+                }),
+                &ctx,
+            )
+            .await
+            .expect("null optional params must not fail");
+
+        assert!(output.result.get("iso").is_some(), "should have iso field");
+    }
+
+    #[tokio::test]
+    async fn test_now_missing_optional_params_succeeds() {
+        // Baseline: when optional params are simply absent, tool succeeds.
+        let tool = TimeTool;
+        let ctx = JobContext::with_user("test", "chat", "test");
+
+        let output = tool
+            .execute(serde_json::json!({"operation": "now"}), &ctx)
+            .await
+            .expect("missing optional params must not fail");
+
+        assert!(output.result.get("iso").is_some());
+    }
 }