diff --git a/src/generateCommitMessageFromGitDiff.ts b/src/generateCommitMessageFromGitDiff.ts
index 01f04a67..f46d6e53 100644
--- a/src/generateCommitMessageFromGitDiff.ts
+++ b/src/generateCommitMessageFromGitDiff.ts
@@ -168,6 +168,15 @@ export const generateCommitMessageByDiff = async (
 
       const commitMessages = await Promise.all(commitMessagePromises);
 
+      // When OCO_ONE_LINE_COMMIT is enabled, combine the first line of each
+      // split-diff message into a single line instead of joining with '\n\n'.
+      if (config.OCO_ONE_LINE_COMMIT) {
+        return commitMessages
+          .filter(Boolean)
+          .map((msg) => msg!.split('\n')[0].trim())
+          .join('; ');
+      }
+
       return commitMessages.join('\n\n');
     }
 
diff --git a/src/prompts.ts b/src/prompts.ts
index 0f2f7281..9dd55ec0 100644
--- a/src/prompts.ts
+++ b/src/prompts.ts
@@ -240,7 +240,17 @@ export const getMainCommitPrompt = async (
       }
 
       // Replace example prompt with a prompt that's generated by OpenAI for the commitlint config.
-      const commitLintConfig = await utils.getCommitlintLLMConfig();
+      let commitLintConfig = await utils.getCommitlintLLMConfig();
+
+      // Guard against outdated or corrupted config files that are missing the
+      // prompts field (e.g. generated by an older version of opencommit).
+      if (!Array.isArray(commitLintConfig.prompts)) {
+        note(
+          'Commitlint LLM config is missing prompts, regenerating...'
+        );
+        await configureCommitlintIntegration(true);
+        commitLintConfig = await utils.getCommitlintLLMConfig();
+      }
 
       return [
         commitlintPrompts.INIT_MAIN_PROMPT(