diff --git a/apps/server/git/simple-git-branch-manager.ts b/apps/server/git/simple-git-branch-manager.ts
index 66c5754..fdca4b9 100644
--- a/apps/server/git/simple-git-branch-manager.ts
+++ b/apps/server/git/simple-git-branch-manager.ts
@@ -168,37 +168,31 @@ export class SimpleGitBranchManager implements BranchManager {
   async checkMergeability(repoPath: string, sourceBranch: string, targetBranch: string): Promise<MergeabilityResult> {
     const git = simpleGit(repoPath);
 
-    try {
-      // git merge-tree --write-tree merges source INTO target virtually.
-      // Exit 0 = clean merge, non-zero = conflicts.
-      await git.raw(['merge-tree', '--write-tree', targetBranch, sourceBranch]);
-      log.debug({ repoPath, sourceBranch, targetBranch }, 'merge-tree check: clean');
-      return { mergeable: true };
-    } catch (err) {
-      const stderr = err instanceof Error ? err.message : String(err);
+    // git merge-tree --write-tree outputs everything to stdout.
+    // simple-git's .raw() resolves with stdout even on exit code 1 (conflicts),
+    // so we parse the output text instead of relying on catch.
+    const output = await git.raw(['merge-tree', '--write-tree', targetBranch, sourceBranch]);
 
-      // Parse conflict file names from "CONFLICT (content): Merge conflict in <path>"
-      const conflictPattern = /CONFLICT \([^)]+\): (?:Merge conflict in|.* -> )(.+)/g;
-      const conflicts: string[] = [];
-      let match: RegExpExecArray | null;
-      while ((match = conflictPattern.exec(stderr)) !== null) {
-        conflicts.push(match[1].trim());
-      }
-
-      if (conflicts.length > 0) {
-        log.debug({ repoPath, sourceBranch, targetBranch, conflicts }, 'merge-tree check: conflicts');
-        return { mergeable: false, conflicts };
-      }
-
-      // If we couldn't parse conflicts but the command failed, it's still a conflict
-      // (could be add/add, rename conflicts, etc.)
-      if (stderr.includes('CONFLICT')) {
-        log.debug({ repoPath, sourceBranch, targetBranch }, 'merge-tree check: unparsed conflicts');
-        return { mergeable: false, conflicts: ['(unable to parse conflict details)'] };
-      }
-
-      // Genuine error (not a conflict)
-      throw err;
+    // Parse conflict file names from "CONFLICT (content): Merge conflict in <path>"
+    const conflictPattern = /CONFLICT \([^)]+\): (?:Merge conflict in|.* -> )(.+)/g;
+    const conflicts: string[] = [];
+    let match: RegExpExecArray | null;
+    while ((match = conflictPattern.exec(output)) !== null) {
+      conflicts.push(match[1].trim());
     }
+
+    if (conflicts.length > 0) {
+      log.debug({ repoPath, sourceBranch, targetBranch, conflicts }, 'merge-tree check: conflicts');
+      return { mergeable: false, conflicts };
+    }
+
+    // Fallback: check for any CONFLICT text we couldn't parse specifically
+    if (output.includes('CONFLICT')) {
+      log.debug({ repoPath, sourceBranch, targetBranch }, 'merge-tree check: unparsed conflicts');
+      return { mergeable: false, conflicts: ['(unable to parse conflict details)'] };
+    }
+
+    log.debug({ repoPath, sourceBranch, targetBranch }, 'merge-tree check: clean');
+    return { mergeable: true };
   }
 }