fix(tui): accept compact SSE data fields

Accept SSE data frames with either `data: {...}` or `data:{...}` in Chat Completions, Responses, and Anthropic stream readers.

Harvested from PR #3152.

Co-authored-by: wgeeker <169752135+wgeeker@users.noreply.github.com>

CHANGELOG.md

@@ -49,6 +49,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **SSE data lines without spaces (#3152).** Chat Completions, Responses, and
+  Anthropic stream readers now accept both `data: {...}` and `data:{...}` SSE
+  frames, matching the spec and preventing providers that omit the optional
+  space from streaming empty output. Thanks @wgeeker for the PR.
 - **SiliconFlow China provider config (#2893/#2895).** `siliconflow-CN`
   now reads its own `[providers.siliconflow_cn]` / `[providers.siliconflow-CN]`
   table and falls back to `[providers.siliconflow]` only for unset

crates/tui/CHANGELOG.md

@@ -49,6 +49,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **SSE data lines without spaces (#3152).** Chat Completions, Responses, and
+  Anthropic stream readers now accept both `data: {...}` and `data:{...}` SSE
+  frames, matching the spec and preventing providers that omit the optional
+  space from streaming empty output. Thanks @wgeeker for the PR.
 - **SiliconFlow China provider config (#2893/#2895).** `siliconflow-CN`
   now reads its own `[providers.siliconflow_cn]` / `[providers.siliconflow-CN]`
   table and falls back to `[providers.siliconflow]` only for unset

crates/tui/src/client.rs

@@ -1543,6 +1543,11 @@ mod anthropic;
 mod chat;
 mod responses;
 
+fn extract_sse_data_value(line: &str) -> Option<&str> {
+    line.strip_prefix("data:")
+        .map(|value| value.strip_prefix(' ').unwrap_or(value))
+}
+
 pub(crate) use chat::{CacheWarmupKey, PromptInspection};
 
 pub(crate) fn inspect_prompt_for_request(request: &MessageRequest) -> PromptInspection {
@@ -3942,4 +3947,28 @@ mod tests {
             "https://api.deepseek.com/v1/chat/completions"
         );
     }
+
+    #[test]
+    fn extract_sse_data_value_accepts_optional_space() {
+        assert_eq!(
+            extract_sse_data_value("data: {\"ok\":true}"),
+            Some("{\"ok\":true}")
+        );
+        assert_eq!(
+            extract_sse_data_value("data:{\"ok\":true}"),
+            Some("{\"ok\":true}")
+        );
+    }
+
+    #[test]
+    fn extract_sse_data_value_handles_done_marker() {
+        assert_eq!(extract_sse_data_value("data: [DONE]"), Some("[DONE]"));
+        assert_eq!(extract_sse_data_value("data:[DONE]"), Some("[DONE]"));
+    }
+
+    #[test]
+    fn extract_sse_data_value_rejects_non_data_lines() {
+        assert_eq!(extract_sse_data_value("event: message"), None);
+        assert_eq!(extract_sse_data_value(": heartbeat"), None);
+    }
 }

crates/tui/src/client/anthropic.rs

@@ -205,7 +205,7 @@ impl DeepSeekClient {
 
                     // `event:` lines are redundant (the data payload carries
                     // `type`) and comment/heartbeat lines are ignorable.
-                    let Some(data) = line.strip_prefix("data: ") else {
+                    let Some(data) = super::extract_sse_data_value(&line) else {
                         continue;
                     };
 

crates/tui/src/client/chat.rs

@@ -437,7 +437,7 @@ impl DeepSeekClient {
                         continue;
                     }
 
-                    if let Some(data) = line.strip_prefix("data: ") {
+                    if let Some(data) = super::extract_sse_data_value(&line) {
                         line_buf.push_str(data);
                     }
                     // Ignore other SSE fields (event:, id:, retry:)

crates/tui/src/client/responses.rs

@@ -165,7 +165,7 @@ impl DeepSeekClient {
                         continue;
                     }
 
-                    if let Some(data) = line.strip_prefix("data: ") {
+                    if let Some(data) = super::extract_sse_data_value(&line) {
                         if data == "[DONE]" {
                             done = true;
                             break;