fix(provider/ollama): keep stream whitespace intact

Acceptance Criteria:\n- streaming chunks retain leading whitespace and indentation\n- end-of-stream metadata is still propagated\n- malformed frames emit defensive logging without crashing

Test Notes:\n- cargo test -p owlen-providers

crates/owlen-providers/src/ollama/shared.rs

@@ -2,6 +2,7 @@ use std::collections::HashMap;
 use std::time::Duration;
 
 use futures::StreamExt;
+use log::warn;
 use owlen_core::provider::{
     GenerateChunk, GenerateRequest, GenerateStream, ModelInfo, ProviderMetadata, ProviderStatus,
 };
@@ -132,11 +133,7 @@ impl OllamaClient {
                         buffer.extend_from_slice(&bytes);
                         while let Some(pos) = buffer.iter().position(|byte| *byte == b'\n') {
                             let line_bytes: Vec<u8> = buffer.drain(..=pos).collect();
-                            let line = String::from_utf8_lossy(&line_bytes).trim().to_string();
-                            if line.is_empty() {
-                                continue;
-                            }
-
+                            if let Some(line) = prepare_stream_line(&line_bytes) {
                                 match parse_stream_line(&line) {
                                     Ok(item) => {
                                         if tx.send(Ok(item)).await.is_err() {
@@ -150,6 +147,7 @@ impl OllamaClient {
                                 }
                             }
                         }
+                    }
                     Err(err) => {
                         let _ = tx.send(Err(map_reqwest_error(err))).await;
                         return;
@@ -158,8 +156,8 @@ impl OllamaClient {
             }
 
             if !buffer.is_empty() {
-                let line = String::from_utf8_lossy(&buffer).trim().to_string();
-                if !line.is_empty() {
+                let line_bytes = std::mem::take(&mut buffer);
+                if let Some(line) = prepare_stream_line(&line_bytes) {
                     match parse_stream_line(&line) {
                         Ok(item) => {
                             let _ = tx.send(Ok(item)).await;
@@ -313,8 +311,51 @@ fn to_metadata_map(value: &Value) -> HashMap<String, Value> {
     metadata
 }
 
+fn prepare_stream_line(bytes: &[u8]) -> Option<String> {
+    if bytes.is_empty() {
+        return None;
+    }
+
+    let mut line = String::from_utf8_lossy(bytes).into_owned();
+
+    while line.ends_with('\n') || line.ends_with('\r') {
+        line.pop();
+    }
+
+    if line.trim().is_empty() {
+        return None;
+    }
+
+    Some(line)
+}
+
+fn log_stream_decode_error(line: &str, err: &serde_json::Error) {
+    const MAX_PREVIEW_CHARS: usize = 256;
+
+    let total_chars = line.chars().count();
+    let truncated = total_chars > MAX_PREVIEW_CHARS;
+    let mut preview: String = line.chars().take(MAX_PREVIEW_CHARS).collect();
+
+    if truncated {
+        preview.push_str("...");
+    }
+
+    let preview = preview
+        .replace('\n', "\\n")
+        .replace('\r', "\\r")
+        .replace('\t', "\\t");
+
+    warn!(
+        "Failed to parse Ollama stream chunk ({} chars): {}. Preview: \"{}\"",
+        total_chars, err, preview
+    );
+}
+
 fn parse_stream_line(line: &str) -> CoreResult<GenerateChunk> {
-    let value: Value = serde_json::from_str(line).map_err(CoreError::Serialization)?;
+    let value: Value = serde_json::from_str(line).map_err(|err| {
+        log_stream_decode_error(line, &err);
+        CoreError::Serialization(err)
+    })?;
 
     if let Some(error) = value.get("error").and_then(Value::as_str) {
         return Err(CoreError::Provider(anyhow::anyhow!(
@@ -332,11 +373,19 @@ fn parse_stream_line(line: &str) -> CoreResult<GenerateChunk> {
         metadata: to_metadata_map(&value),
     };
 
-    if chunk.is_final && chunk.text.is_none() && chunk.metadata.is_empty() {
+    if chunk.is_final {
+        if let Some(Value::Object(done_obj)) = value.get("done") {
+            for (key, item) in done_obj {
+                chunk.metadata.insert(key.clone(), item.clone());
+            }
+        }
+
+        if chunk.text.is_none() && chunk.metadata.is_empty() {
             chunk
                 .metadata
                 .insert("status".into(), Value::String("done".into()));
         }
+    }
 
     Ok(chunk)
 }
@@ -387,3 +436,64 @@ fn map_reqwest_error(err: reqwest::Error) -> CoreError {
         CoreError::Provider(err.into())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn prepare_stream_line_preserves_leading_whitespace() {
+        let mut bytes = br#"{"response":"    fn main() {}\n","done":false}"#.to_vec();
+        bytes.extend_from_slice(b"\r\n");
+
+        let line = prepare_stream_line(&bytes).expect("line should be parsed");
+        assert!(line.starts_with(r#"{"response""#));
+        assert!(line.ends_with(r#""done":false}"#));
+
+        let chunk = parse_stream_line(&line).expect("chunk should parse");
+        assert_eq!(
+            chunk.text.as_deref(),
+            Some("    fn main() {}\n"),
+            "leading indentation must be preserved"
+        );
+        assert!(!chunk.is_final);
+    }
+
+    #[test]
+    fn parse_stream_line_handles_samples_fixture() {
+        let data = include_str!("../../../../samples.json");
+        let values: Vec<Value> =
+            serde_json::from_str(data).expect("samples fixture should be valid json");
+
+        let mut chunks = Vec::new();
+        for value in values {
+            let line = serde_json::to_string(&value).expect("serialize chunk");
+            let chunk = parse_stream_line(&line).expect("parse chunk");
+            chunks.push(chunk);
+        }
+
+        assert!(
+            !chunks.is_empty(),
+            "fixture must produce at least one chunk"
+        );
+        assert_eq!(
+            chunks[0].text.as_deref(),
+            Some("first"),
+            "first chunk should match fixture payload"
+        );
+
+        let final_chunk = chunks.last().expect("final chunk must exist");
+        assert!(
+            final_chunk.is_final,
+            "last chunk should be marked final per fixture"
+        );
+        assert!(
+            final_chunk.text.as_deref().unwrap_or_default().is_empty(),
+            "final chunk should not include stray text"
+        );
+        assert!(
+            final_chunk.metadata.contains_key("final_data"),
+            "final chunk should surface metadata from fixture"
+        );
+    }
+}

samples.json

@@ -0,0 +1 @@
+[{"response": "first", "done": false}, {"response": "", "done": true, "final_data": {"prompt_eval_count": 2048, "eval_count": 512}}]