diff --git a/server/src/agents/local_prompt.rs b/server/src/agents/local_prompt.rs
index ee9867d0..e848617e 100644
--- a/server/src/agents/local_prompt.rs
+++ b/server/src/agents/local_prompt.rs
@@ -60,13 +60,6 @@ pub fn read_project_local_prompt(project_root: &Path) -> Option<String> {
         sections.push((rel_path, trimmed.to_string()));
     }
 
-    // Regenerate the source map so agents always start from a fresh snapshot.
-    // Failure is non-fatal: log it and fall through to whatever is on disk.
-    let map_path = project_root.join(SOURCE_MAP_REL);
-    if let Err(e) = source_map_gen::regenerate_source_map(project_root, &map_path) {
-        crate::slog!("[agents] source-map regen failed (non-fatal): {}", e);
-    }
-
     // Read source-map.json (after AGENT.md) with a byte cap.
     let source_map_content = read_source_map_section(project_root);
 
@@ -394,86 +387,6 @@ mod tests {
         );
     }
 
-    // ── Regen-on-spawn tests ─────────────────────────────────────────────────
-
-    fn init_git_repo(dir: &Path) {
-        let run = |args: &[&str]| {
-            std::process::Command::new("git")
-                .args(args)
-                .current_dir(dir)
-                .output()
-                .unwrap();
-        };
-        run(&["init"]);
-        run(&["config", "user.email", "test@test.com"]);
-        run(&["config", "user.name", "Test"]);
-        run(&["commit", "--allow-empty", "-m", "init"]);
-    }
-
-    /// Happy path: regen runs successfully and the fresh map is included in the bundle.
-    #[test]
-    fn regen_creates_map_on_coder_spawn() {
-        let tmp = tempfile::tempdir().unwrap();
-        init_git_repo(tmp.path());
-
-        // Write a tracked Rust file so git ls-files has something to index.
-        write_file(
-            tmp.path(),
-            "lib.rs",
-            "//! Module doc.\n\n/// A function.\npub fn hello() {}\n",
-        );
-        std::process::Command::new("git")
-            .args(["add", "lib.rs"])
-            .current_dir(tmp.path())
-            .output()
-            .unwrap();
-        std::process::Command::new("git")
-            .args(["commit", "-m", "add lib.rs"])
-            .current_dir(tmp.path())
-            .output()
-            .unwrap();
-
-        // Write an orientation file so we get Some back.
-        write_file(tmp.path(), "CLAUDE.md", "agent hints");
-
-        // Map does not exist yet.
-        let map_path = tmp.path().join(SOURCE_MAP_REL);
-        assert!(!map_path.exists(), "map must not exist before spawn");
-
-        let result = read_project_local_prompt(tmp.path());
-        assert!(
-            result.is_some(),
-            "bundle must be Some when CLAUDE.md present"
-        );
-
-        // Regen should have written the map.
-        assert!(
-            map_path.exists(),
-            "regen must have written source-map.json during spawn"
-        );
-    }
-
-    /// Fallback: regen fails (no git repo) but a stale map on disk is still read.
-    #[test]
-    fn regen_fails_stale_map_still_readable() {
-        let tmp = tempfile::tempdir().unwrap();
-        // No git repo — regen will fail with "git ls-files" error.
-
-        write_file(tmp.path(), "CLAUDE.md", "agent hints");
-        // Write a stale map manually.
-        write_file(
-            tmp.path(),
-            SOURCE_MAP_REL,
-            r#"{"stale/entry.rs": ["fn old"]}"#,
-        );
-
-        let result = read_project_local_prompt(tmp.path()).unwrap();
-        assert!(
-            result.contains("stale/entry.rs"),
-            "stale map must still be readable after regen failure: {result}"
-        );
-    }
-
     #[test]
     #[allow(clippy::string_slice)] // sm_start is derived from str::find — always a char boundary
     fn source_map_truncated_at_byte_cap() {
diff --git a/server/src/agents/merge/squash/mod.rs b/server/src/agents/merge/squash/mod.rs
index 9d99a29e..71ab24a0 100644
--- a/server/src/agents/merge/squash/mod.rs
+++ b/server/src/agents/merge/squash/mod.rs
@@ -361,6 +361,54 @@ pub(crate) fn run_squash_merge(
         "=== Verified: cherry-pick landed on '{base_branch}' with code changes ===\n"
     ));
 
+    // ── Regen source-map.json on master after cherry-pick ─────────
+    // Run deterministically on project_root (now on master). Skip the commit
+    // when regen produces no diff (idempotent case). Failure is non-fatal.
+    {
+        let map_path = project_root.join(".huskies").join("source-map.json");
+        let old_content = std::fs::read_to_string(&map_path).ok();
+        match source_map_gen::regenerate_source_map(project_root, &map_path) {
+            Err(e) => {
+                all_output.push_str(&format!(
+                    "=== source-map regen failed (non-fatal): {e} ===\n"
+                ));
+            }
+            Ok(()) => {
+                let new_content = std::fs::read_to_string(&map_path).ok();
+                if old_content != new_content {
+                    all_output.push_str("=== source-map.json changed — committing on master ===\n");
+                    let _ = Command::new("git")
+                        .args(["add", ".huskies/source-map.json"])
+                        .current_dir(project_root)
+                        .output();
+                    match Command::new("git")
+                        .args(["commit", "-m", "huskies: regen source-map.json"])
+                        .current_dir(project_root)
+                        .output()
+                    {
+                        Ok(c) if c.status.success() => {
+                            all_output.push_str("=== source-map.json committed on master ===\n");
+                        }
+                        Ok(c) => {
+                            let stderr = String::from_utf8_lossy(&c.stderr);
+                            all_output.push_str(&format!(
+                                "=== source-map commit failed (non-fatal): {stderr} ===\n"
+                            ));
+                        }
+                        Err(e) => {
+                            all_output.push_str(&format!(
+                                "=== source-map commit error (non-fatal): {e} ===\n"
+                            ));
+                        }
+                    }
+                } else {
+                    all_output
+                        .push_str("=== source-map.json unchanged — no follow-up commit ===\n");
+                }
+            }
+        }
+    }
+
     // ── Clean up ──────────────────────────────────────────────────
     cleanup_merge_workspace(project_root, &merge_wt_path, &merge_branch);
     all_output.push_str("=== Merge-queue cleanup complete ===\n");
diff --git a/server/src/agents/merge/squash/tests_advanced.rs b/server/src/agents/merge/squash/tests_advanced.rs
index d6a8a60f..d331e1be 100644
--- a/server/src/agents/merge/squash/tests_advanced.rs
+++ b/server/src/agents/merge/squash/tests_advanced.rs
@@ -403,6 +403,112 @@ fn squash_merge_runs_component_setup_from_project_toml() {
     );
 }
 
+/// AC6: the regen+commit step runs on `project_root` (master) only.
+/// After a successful merge where the source-map changes, `git log --name-only`
+/// shows a follow-up commit whose diff contains ONLY `.huskies/source-map.json`.
+#[tokio::test]
+async fn regen_commit_on_master_touches_only_source_map() {
+    use std::fs;
+    use tempfile::tempdir;
+
+    let tmp = tempdir().unwrap();
+    let repo = tmp.path();
+    init_git_repo(repo);
+
+    // Put a stale source-map.json on master so regen will produce a different result.
+    let sk_dir = repo.join(".huskies");
+    fs::create_dir_all(&sk_dir).unwrap();
+    fs::write(sk_dir.join("source-map.json"), "{\"stale\": true}\n").unwrap();
+
+    // Add a tracked Rust file so the regenerator has something to index.
+    fs::create_dir_all(repo.join("src")).unwrap();
+    fs::write(
+        repo.join("src/lib.rs"),
+        "//! Library.\n\n/// Says hello.\npub fn hello() {}\n",
+    )
+    .unwrap();
+    Command::new("git")
+        .args(["add", "."])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+    Command::new("git")
+        .args(["commit", "-m", "initial with stale source-map"])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+
+    // Feature branch: add a new file.
+    Command::new("git")
+        .args(["checkout", "-b", "feature/story-1065_regen_test"])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+    fs::write(
+        repo.join("src/extra.rs"),
+        "//! Extra.\n\n/// Extra fn.\npub fn extra() {}\n",
+    )
+    .unwrap();
+    Command::new("git")
+        .args(["add", "."])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+    Command::new("git")
+        .args(["commit", "-m", "add extra.rs"])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+    Command::new("git")
+        .args(["checkout", "master"])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+
+    let result =
+        run_squash_merge(repo, "feature/story-1065_regen_test", "1065_regen_test").unwrap();
+
+    assert!(
+        matches!(result, super::MergeResult::Success { .. }),
+        "clean merge must succeed; got: {result:?}"
+    );
+
+    // Find the regen commit if one was created.
+    let log_out = Command::new("git")
+        .args(["log", "--oneline", "--name-only"])
+        .current_dir(repo)
+        .output()
+        .unwrap();
+    let log = String::from_utf8_lossy(&log_out.stdout);
+
+    // If a regen commit exists, its diff must contain ONLY the source-map path.
+    if log.contains("huskies: regen source-map.json") {
+        // Extract files changed in the regen commit.
+        let show_out = Command::new("git")
+            .args(["show", "--name-only", "--format=", "HEAD"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        let show = String::from_utf8_lossy(&show_out.stdout);
+
+        // If HEAD is the regen commit, its files list must be exactly one entry.
+        let head_msg = Command::new("git")
+            .args(["log", "-1", "--format=%s"])
+            .current_dir(repo)
+            .output()
+            .unwrap();
+        let head_subject = String::from_utf8_lossy(&head_msg.stdout);
+        if head_subject.trim() == "huskies: regen source-map.json" {
+            let changed_files: Vec<&str> = show.lines().filter(|l| !l.is_empty()).collect();
+            assert_eq!(
+                changed_files,
+                vec![".huskies/source-map.json"],
+                "regen commit must touch ONLY .huskies/source-map.json; got: {changed_files:?}"
+            );
+        }
+    }
+}
+
 #[cfg(unix)]
 #[test]
 fn squash_merge_succeeds_without_components_in_project_toml() {