Save pull request metadata to pull_request.json after PR creation

Return a PullRequestRecord struct from maybe_open_pull_request instead
of a bare URL, persist it as JSON in the run/logs directory, and strip
markdown heading prefixes (# / ##) from generated PR titles.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/crates/arc-workflows/src/cli/pr.rs

@@ -89,7 +89,7 @@ async fn pr_create_from(
         .model
         .unwrap_or_else(|| arc_llm::catalog::default_model().id.to_string());
 
-    let url = crate::pull_request::maybe_open_pull_request(
+    let record = crate::pull_request::maybe_open_pull_request(
         &creds,
         &origin_url,
         base_branch,
@@ -101,10 +101,13 @@ async fn pr_create_from(
     .await
     .map_err(|e| anyhow::anyhow!("{e}"))?;
 
-    match url {
-        Some(url) => {
-            info!(pr_url = %url, "Pull request created");
-            println!("{url}");
+    match record {
+        Some(record) => {
+            info!(pr_url = %record.html_url, "Pull request created");
+            if let Err(e) = record.save(&run_dir.join("pull_request.json")) {
+                tracing::warn!(error = %e, "Failed to save pull_request.json");
+            }
+            println!("{}", record.html_url);
         }
         None => {
             println!("No pull request created (empty diff).");

lib/crates/arc-workflows/src/cli/run.rs

@@ -1080,8 +1080,15 @@ pub async fn run_command(
                     )
                     .await
                     {
-                        Ok(Some(url)) => {
-                            eprintln!("{} {url}", styles.bold.apply_to("Pull request:"));
+                        Ok(Some(record)) => {
+                            eprintln!(
+                                "{} {}",
+                                styles.bold.apply_to("Pull request:"),
+                                record.html_url
+                            );
+                            if let Err(e) = record.save(&logs_dir.join("pull_request.json")) {
+                                tracing::warn!(error = %e, "Failed to save pull_request.json");
+                            }
                         }
                         Ok(None) => {} // empty diff, logged at DEBUG
                         Err(e) => {

lib/crates/arc-workflows/src/pull_request.rs

@@ -1,12 +1,39 @@
+use std::path::Path;
+
+use serde::Serialize;
 use tracing::{debug, info};
 
 use arc_github::{self as github_app, ssh_url_to_https, GitHubAppCredentials};
 
+/// Record of a pull request created for a workflow run.
+#[derive(Debug, Clone, Serialize)]
+pub struct PullRequestRecord {
+    pub html_url: String,
+    pub number: u64,
+    pub owner: String,
+    pub repo: String,
+    pub base_branch: String,
+    pub head_branch: String,
+    pub title: String,
+}
+
+impl PullRequestRecord {
+    pub fn save(&self, path: &Path) -> Result<(), String> {
+        let json = serde_json::to_string_pretty(self)
+            .map_err(|e| format!("Failed to serialize pull_request.json: {e}"))?;
+        std::fs::write(path, json).map_err(|e| format!("Failed to write pull_request.json: {e}"))
+    }
+}
+
 /// Derive a PR title from the workflow goal.
 ///
 /// Uses the first line, truncated to 120 characters for readability.
 fn pr_title_from_goal(goal: &str) -> String {
     let first_line = goal.lines().next().unwrap_or(goal);
+    let first_line = first_line
+        .strip_prefix("## ")
+        .or_else(|| first_line.strip_prefix("# "))
+        .unwrap_or(first_line);
     if first_line.chars().count() > 120 {
         let truncated: String = first_line.chars().take(119).collect();
         format!("{truncated}…")
@@ -53,8 +80,8 @@ pub async fn generate_pr_body(diff: &str, goal: &str, model: &str) -> Result<Str
 
 /// Optionally open a pull request after a successful workflow run.
 ///
-/// Returns `Ok(Some(html_url))` if a PR was created, `Ok(None)` if the diff
-/// was empty, or `Err` on failure.
+/// Returns `Ok(Some(PullRequestRecord))` if a PR was created, `Ok(None)` if
+/// the diff was empty, or `Err` on failure.
 pub async fn maybe_open_pull_request(
     creds: &GitHubAppCredentials,
     origin_url: &str,
@@ -63,7 +90,7 @@ pub async fn maybe_open_pull_request(
     goal: &str,
     diff: &str,
     model: &str,
-) -> Result<Option<String>, String> {
+) -> Result<Option<PullRequestRecord>, String> {
     if diff.is_empty() {
         debug!("Empty diff, skipping pull request creation");
         return Ok(None);
@@ -77,7 +104,7 @@ pub async fn maybe_open_pull_request(
 
     let title = pr_title_from_goal(goal);
 
-    let (url, pr_number) = github_app::create_pull_request(
+    let (html_url, number) = github_app::create_pull_request(
         creds,
         &owner,
         &repo,
@@ -88,9 +115,17 @@ pub async fn maybe_open_pull_request(
     )
     .await?;
 
-    info!(pr_url = %url, pr_number, "Pull request created");
+    info!(pr_url = %html_url, number, "Pull request created");
 
-    Ok(Some(url))
+    Ok(Some(PullRequestRecord {
+        html_url,
+        number,
+        owner,
+        repo,
+        base_branch: base_branch.to_string(),
+        head_branch: head_branch.to_string(),
+        title,
+    }))
 }
 
 #[cfg(test)]
@@ -99,8 +134,32 @@ mod tests {
 
     #[test]
     fn pr_title_uses_first_line() {
-        let goal = "# Add Draft PR Mode\n\nMore details here...";
-        assert_eq!(pr_title_from_goal(goal), "# Add Draft PR Mode");
+        let goal = "Add Draft PR Mode\n\nMore details here...";
+        assert_eq!(pr_title_from_goal(goal), "Add Draft PR Mode");
+    }
+
+    #[test]
+    fn pr_title_strips_h1_prefix() {
+        assert_eq!(
+            pr_title_from_goal("# Add Draft PR Mode"),
+            "Add Draft PR Mode"
+        );
+    }
+
+    #[test]
+    fn pr_title_strips_h2_prefix() {
+        assert_eq!(
+            pr_title_from_goal("## Add Draft PR Mode"),
+            "Add Draft PR Mode"
+        );
+    }
+
+    #[test]
+    fn pr_title_does_not_strip_h3_prefix() {
+        assert_eq!(
+            pr_title_from_goal("### Add Draft PR Mode"),
+            "### Add Draft PR Mode"
+        );
     }
 
     #[test]
@@ -130,6 +189,32 @@ mod tests {
         assert_eq!(pr_title_from_goal("Fix bug"), "Fix bug");
     }
 
+    #[test]
+    fn pull_request_record_save_writes_json() {
+        let tmp = tempfile::tempdir().unwrap();
+        let path = tmp.path().join("pull_request.json");
+        let record = PullRequestRecord {
+            html_url: "https://github.com/owner/repo/pull/42".to_string(),
+            number: 42,
+            owner: "owner".to_string(),
+            repo: "repo".to_string(),
+            base_branch: "main".to_string(),
+            head_branch: "arc/run/abc".to_string(),
+            title: "Fix the thing".to_string(),
+        };
+        record.save(&path).unwrap();
+
+        let content: serde_json::Value =
+            serde_json::from_str(&std::fs::read_to_string(&path).unwrap()).unwrap();
+        assert_eq!(content["html_url"], "https://github.com/owner/repo/pull/42");
+        assert_eq!(content["number"], 42);
+        assert_eq!(content["owner"], "owner");
+        assert_eq!(content["repo"], "repo");
+        assert_eq!(content["base_branch"], "main");
+        assert_eq!(content["head_branch"], "arc/run/abc");
+        assert_eq!(content["title"], "Fix the thing");
+    }
+
     #[tokio::test]
     async fn empty_diff_returns_none() {
         let creds = GitHubAppCredentials {