story-kit: merge 225_story_surface_merge_conflicts_and_failures_in_the_web_ui

server/src/http/mcp.rs

@@ -11,7 +11,7 @@ use crate::http::workflow::{
     validate_story_dirs,
 };
 use crate::worktree;
-use crate::io::story_metadata::{parse_front_matter, parse_unchecked_todos};
+use crate::io::story_metadata::{parse_front_matter, parse_unchecked_todos, write_merge_failure};
 use crate::workflow::{evaluate_acceptance_with_coverage, TestCaseResult, TestStatus};
 use poem::handler;
 use poem::http::StatusCode;
@@ -1668,6 +1668,28 @@ fn tool_report_merge_failure(args: &Value, ctx: &AppContext) -> Result<String, S
     slog!("[mergemaster] Merge failure reported for '{story_id}': {reason}");
     ctx.agents.set_merge_failure_reported(story_id);
 
+    // Persist the failure reason to the story file's front matter so it
+    // survives server restarts and is visible in the web UI.
+    if let Ok(project_root) = ctx.state.get_project_root() {
+        let story_file = project_root
+            .join(".story_kit")
+            .join("work")
+            .join("4_merge")
+            .join(format!("{story_id}.md"));
+        if story_file.exists() {
+            if let Err(e) = write_merge_failure(&story_file, reason) {
+                slog_warn!(
+                    "[mergemaster] Failed to persist merge_failure to story file for '{story_id}': {e}"
+                );
+            }
+        } else {
+            slog_warn!(
+                "[mergemaster] Story file not found in 4_merge/ for '{story_id}'; \
+                 merge_failure not persisted to front matter"
+            );
+        }
+    }
+
     Ok(format!(
         "Merge failure for '{story_id}' recorded. Story remains in work/4_merge/. Reason: {reason}"
     ))

server/src/http/workflow.rs

@@ -20,6 +20,8 @@ pub struct UpcomingStory {
     pub story_id: String,
     pub name: Option<String>,
     pub error: Option<String>,
+    /// Merge failure reason persisted to front matter by the mergemaster agent.
+    pub merge_failure: Option<String>,
     /// Active agent working on this item, if any.
     pub agent: Option<AgentAssignment>,
 }
@@ -115,12 +117,12 @@ fn load_stage_items(
             .to_string();
         let contents = fs::read_to_string(&path)
             .map_err(|e| format!("Failed to read story file {}: {e}", path.display()))?;
-        let (name, error) = match parse_front_matter(&contents) {
-            Ok(meta) => (meta.name, None),
-            Err(e) => (None, Some(e.to_string())),
+        let (name, error, merge_failure) = match parse_front_matter(&contents) {
+            Ok(meta) => (meta.name, None, meta.merge_failure),
+            Err(e) => (None, Some(e.to_string()), None),
         };
         let agent = agent_map.get(&story_id).cloned();
-        stories.push(UpcomingStory { story_id, name, error, agent });
+        stories.push(UpcomingStory { story_id, name, error, merge_failure, agent });
     }
 
     stories.sort_by(|a, b| a.story_id.cmp(&b.story_id));

server/src/http/ws.rs

@@ -612,6 +612,7 @@ mod tests {
             story_id: "10_story_test".to_string(),
             name: Some("Test".to_string()),
             error: None,
+            merge_failure: None,
             agent: None,
         };
         let resp = WsResponse::PipelineState {
@@ -748,12 +749,14 @@ mod tests {
                 story_id: "1_story_a".to_string(),
                 name: Some("Story A".to_string()),
                 error: None,
+                merge_failure: None,
                 agent: None,
             }],
             current: vec![UpcomingStory {
                 story_id: "2_story_b".to_string(),
                 name: Some("Story B".to_string()),
                 error: None,
+                merge_failure: None,
                 agent: None,
             }],
             qa: vec![],
@@ -762,6 +765,7 @@ mod tests {
                 story_id: "50_story_done".to_string(),
                 name: Some("Done Story".to_string()),
                 error: None,
+                merge_failure: None,
                 agent: None,
             }],
         };
@@ -913,6 +917,7 @@ mod tests {
                 story_id: "10_story_x".to_string(),
                 name: Some("Story X".to_string()),
                 error: None,
+                merge_failure: None,
                 agent: Some(crate::http::workflow::AgentAssignment {
                     agent_name: "coder-1".to_string(),
                     model: Some("claude-3-5-sonnet".to_string()),

server/src/io/story_metadata.rs

@@ -6,6 +6,7 @@ use std::path::Path;
 pub struct StoryMetadata {
     pub name: Option<String>,
     pub coverage_baseline: Option<String>,
+    pub merge_failure: Option<String>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -27,6 +28,7 @@ impl std::fmt::Display for StoryMetaError {
 struct FrontMatter {
     name: Option<String>,
     coverage_baseline: Option<String>,
+    merge_failure: Option<String>,
 }
 
 pub fn parse_front_matter(contents: &str) -> Result<StoryMetadata, StoryMetaError> {
@@ -58,6 +60,7 @@ fn build_metadata(front: FrontMatter) -> StoryMetadata {
     StoryMetadata {
         name: front.name,
         coverage_baseline: front.coverage_baseline,
+        merge_failure: front.merge_failure,
     }
 }
 
@@ -74,6 +77,24 @@ pub fn write_coverage_baseline(path: &Path, coverage_pct: f64) -> Result<(), Str
     Ok(())
 }
 
+/// Write or update a `merge_failure:` field in the YAML front matter of a story file.
+///
+/// The reason is stored as a quoted YAML string so that colons, hashes, and newlines
+/// in the failure message do not break front-matter parsing.
+/// If no front matter is present, this is a no-op (returns Ok).
+pub fn write_merge_failure(path: &Path, reason: &str) -> Result<(), String> {
+    let contents =
+        fs::read_to_string(path).map_err(|e| format!("Failed to read story file: {e}"))?;
+
+    // Produce a YAML-safe inline quoted string: collapse newlines, escape inner quotes.
+    let escaped = reason.replace('"', "\\\"").replace('\n', " ").replace('\r', "");
+    let yaml_value = format!("\"{escaped}\"");
+
+    let updated = set_front_matter_field(&contents, "merge_failure", &yaml_value);
+    fs::write(path, &updated).map_err(|e| format!("Failed to write story file: {e}"))?;
+    Ok(())
+}
+
 /// Insert or update a key: value pair in the YAML front matter of a markdown string.
 ///
 /// If no front matter (opening `---`) is found, returns the content unchanged.