Fix SSE parsers to accept optional space after data: prefix (#7929)

Signed-off-by: Nilton Volpato <nilton@volpa.to>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/goose/src/providers/formats/anthropic.rs

@@ -573,11 +573,12 @@ where
             let line = line_result?;
 
             // Skip empty lines and non-data lines
-            if line.trim().is_empty() || !line.starts_with("data: ") {
+            // Note: SSE spec allows both "data: value" and "data:value" (space is optional)
+            if line.trim().is_empty() || !line.starts_with("data:") {
                 continue;
             }
 
-            let data_part = line.strip_prefix("data: ").unwrap_or(&line);
+            let data_part = line.strip_prefix("data: ").or_else(|| line.strip_prefix("data:")).unwrap_or(&line);
 
             // Handle end of stream
             if data_part.trim() == "[DONE]" {

crates/goose/src/providers/formats/openai.rs

@@ -520,7 +520,10 @@ fn ensure_valid_json_schema(schema: &mut Value) {
 }
 
 fn strip_data_prefix(line: &str) -> Option<&str> {
-    line.strip_prefix("data: ").map(|s| s.trim())
+    // SSE spec allows both "data: value" and "data:value" (space after colon is optional)
+    line.strip_prefix("data: ")
+        .or_else(|| line.strip_prefix("data:"))
+        .map(|s| s.trim())
 }
 
 pub fn response_to_streaming_message<S>(
@@ -536,12 +539,13 @@ where
         let mut accumulated_reasoning_content = String::new();
 
         'outer: while let Some(response) = stream.next().await {
-            if response.as_ref().is_ok_and(|s| s == "data: [DONE]") {
-                break 'outer;
-            }
             let response_str = response?;
             let line = strip_data_prefix(&response_str);
 
+            if line.is_some_and(|l| l == "[DONE]") {
+                break 'outer;
+            }
+
             if line.is_none() || line.is_some_and(|l| l.is_empty()) {
                 continue
             }
@@ -580,11 +584,11 @@ where
                     let mut done = false;
                     while !done {
                         if let Some(response_chunk) = stream.next().await {
-                            if response_chunk.as_ref().is_ok_and(|s| s == "data: [DONE]") {
-                                break 'outer;
-                            }
                             let response_str = response_chunk?;
                             if let Some(line) = strip_data_prefix(&response_str) {
+                                if line == "[DONE]" {
+                                    break 'outer;
+                                }
 
                                 let tool_chunk: StreamingChunk = serde_json::from_str(line)
                                     .map_err(|e| anyhow!("Failed to parse streaming chunk: {}: {:?}", e, &line))?;

crates/goose/src/providers/formats/openai_responses.rs

@@ -684,9 +684,12 @@ where
 
             // Parse SSE format: "event: <type>\ndata: <json>"
             // For now, we only care about the data line
+            // SSE spec allows both "data: value" and "data:value" (space after colon is optional)
             let data_line = if response_str.starts_with("data: ") {
                 response_str.strip_prefix("data: ").unwrap()
-            } else if response_str.starts_with("event: ") {
+            } else if response_str.starts_with("data:") {
+                response_str.strip_prefix("data:").unwrap()
+            } else if response_str.starts_with("event: ") || response_str.starts_with("event:") {
                 // Skip event type lines
                 continue;
             } else {

crates/goose/src/providers/formats/snowflake.rs

@@ -128,13 +128,15 @@ pub fn parse_streaming_response(sse_data: &str) -> Result<Message> {
 
     // Parse each SSE event
     for line in sse_data.lines() {
-        if !line.starts_with("data: ") {
+        // SSE spec allows both "data: value" and "data:value" (space after colon is optional)
+        if !line.starts_with("data:") {
             continue;
         }
 
-        let Some(json_str) = line.get(6..) else {
-            continue;
-        }; // Remove "data: " prefix
+        let json_str = line
+            .strip_prefix("data: ")
+            .or_else(|| line.strip_prefix("data:"))
+            .unwrap(); // Remove "data:" prefix
         if json_str.trim().is_empty() || json_str.trim() == "[DONE]" {
             continue;
         }