feat: persist issue branches for reuse on subsequent invocations

- Check for existing Claude branches before creating new ones for issues
- Skip automatic branch deletion for issue branches to allow reuse
- Add context awareness so Claude knows when reusing an existing branch
- Set IS_REUSED_BRANCH output for tracking branch reuse status

This change allows users to iteratively ask Claude to make changes on the same branch before creating a PR, as requested in issue #103.

Co-authored-by: ashwin-ant <ashwin-ant@users.noreply.github.com>

src/create-prompt/index.ts

@@ -361,6 +361,7 @@ export function getEventTypeAndContext(envVars: PreparedContext): {
 export function generatePrompt(
   context: PreparedContext,
   githubData: FetchDataResult,
+  isReusedBranch?: boolean,
 ): string {
   const {
     contextData,
@@ -534,7 +535,7 @@ ${context.directPrompt ? `   - DIRECT INSTRUCTION: A direct instruction was prov
       - Use mcp__github_file_ops__commit_files to commit files atomically in a single commit (supports single or multiple files).
       - When pushing changes with this tool and TRIGGER_USERNAME is not "Unknown", include a "Co-authored-by: ${context.triggerUsername} <${context.triggerUsername}@users.noreply.github.com>" line in the commit message.`
           : `
-      - You are already on the correct branch (${eventData.claudeBranch || "the PR branch"}). Do not create a new branch.
+      - You are already on the correct branch (${eventData.claudeBranch || "the PR branch"}). Do not create a new branch.${isReusedBranch ? `\n      - NOTE: This branch (${eventData.claudeBranch}) was reused from a previous Claude invocation on this issue. It may already contain some work.` : ''}
       - Push changes directly to the current branch using mcp__github_file_ops__commit_files (works for both new and existing files)
       - Use mcp__github_file_ops__commit_files to commit files atomically in a single commit (supports single or multiple files).
       - When pushing changes and TRIGGER_USERNAME is not "Unknown", include a "Co-authored-by: ${context.triggerUsername} <${context.triggerUsername}@users.noreply.github.com>" line in the commit message.
@@ -641,6 +642,7 @@ export async function createPrompt(
   claudeBranch: string | undefined,
   githubData: FetchDataResult,
   context: ParsedGitHubContext,
+  isReusedBranch?: boolean,
 ) {
   try {
     const preparedContext = prepareContext(
@@ -653,7 +655,7 @@ export async function createPrompt(
     await mkdir("/tmp/claude-prompts", { recursive: true });
 
     // Generate the prompt
-    const promptContent = generatePrompt(preparedContext, githubData);
+    const promptContent = generatePrompt(preparedContext, githubData, isReusedBranch);
 
     // Log the final prompt to console
     console.log("===== FINAL PROMPT =====");

src/entrypoints/prepare.ts

@@ -81,6 +81,7 @@ async function run() {
       branchInfo.claudeBranch,
       githubData,
       context,
+      branchInfo.isReusedBranch,
     );
 
     // Step 11: Get MCP configuration

src/entrypoints/update-comment-link.ts

@@ -87,13 +87,29 @@ async function run() {
     const currentBody = comment.body ?? "";
 
     // Check if we need to add branch link for new branches
-    const { shouldDeleteBranch, branchLink } = await checkAndDeleteEmptyBranch(
+    // For issues, we don't delete branches anymore to allow reuse
+    const skipBranchDeletion = !context.isPR && claudeBranch;
+    
+    let shouldDeleteBranch = false;
+    let branchLink = "";
+    
+    if (skipBranchDeletion) {
+      // For issue branches, just add the branch link without checking for deletion
+      const branchUrl = `${GITHUB_SERVER_URL}/${owner}/${repo}/tree/${claudeBranch}`;
+      branchLink = `\n[View branch](${branchUrl})`;
+      console.log(`Keeping issue branch ${claudeBranch} for potential reuse`);
+    } else {
+      // For PR branches, use the existing cleanup logic
+      const result = await checkAndDeleteEmptyBranch(
         octokit,
         owner,
         repo,
         claudeBranch,
         baseBranch,
       );
+      shouldDeleteBranch = result.shouldDeleteBranch;
+      branchLink = result.branchLink;
+    }
 
     // Check if we need to add PR URL when we have a new branch
     let prLink = "";

src/github/operations/branch.ts

@@ -17,6 +17,7 @@ export type BranchInfo = {
   baseBranch: string;
   claudeBranch?: string;
   currentBranch: string;
+  isReusedBranch?: boolean;
 };
 
 export async function setupBranch(
@@ -79,6 +80,38 @@ export async function setupBranch(
 
   // Creating a new branch for either an issue or closed/merged PR
   const entityType = isPR ? "pr" : "issue";
+  
+  // For issues, check if a Claude branch already exists
+  let branchToUse: string | null = null;
+  let isReusedBranch = false;
+  
+  if (!isPR) {
+    // Check for existing Claude branches for this issue
+    try {
+      const { data: branches } = await octokits.rest.repos.listBranches({
+        owner,
+        repo,
+        per_page: 100,
+      });
+      
+      // Look for existing branches with pattern claude/issue-{entityNumber}-*
+      const existingBranch = branches.find(branch => 
+        branch.name.startsWith(`claude/issue-${entityNumber}-`)
+      );
+      
+      if (existingBranch) {
+        branchToUse = existingBranch.name;
+        isReusedBranch = true;
+        console.log(`Found existing Claude branch for issue #${entityNumber}: ${branchToUse}`);
+      }
+    } catch (error) {
+      console.error("Error checking for existing branches:", error);
+      // Continue with new branch creation if check fails
+    }
+  }
+  
+  // If no existing branch found or this is a PR, create a new branch
+  if (!branchToUse) {
     console.log(
       `Creating new branch for ${entityType} #${entityNumber} from source branch: ${sourceBranch}...`,
     );
@@ -90,9 +123,25 @@ export async function setupBranch(
       .split("T")
       .join("_");
 
-  const newBranch = `claude/${entityType}-${entityNumber}-${timestamp}`;
+    branchToUse = `claude/${entityType}-${entityNumber}-${timestamp}`;
+  }
 
   try {
+    if (isReusedBranch) {
+      // For existing branches, just checkout
+      console.log(`Checking out existing branch: ${branchToUse}`);
+      
+      // Fetch the branch with more depth to allow for context
+      await $`git fetch origin --depth=20 ${branchToUse}`;
+      await $`git checkout ${branchToUse}`;
+      
+      console.log(
+        `Successfully checked out existing branch: ${branchToUse}`,
+      );
+      console.log(
+        `Note: This is a reused branch from a previous Claude invocation on issue #${entityNumber}`,
+      );
+    } else {
       // Get the SHA of the source branch
       const sourceBranchRef = await octokits.rest.git.getRef({
         owner,
@@ -108,28 +157,33 @@ export async function setupBranch(
       await octokits.rest.git.createRef({
         owner,
         repo,
-      ref: `refs/heads/${newBranch}`,
+        ref: `refs/heads/${branchToUse}`,
         sha: currentSHA,
       });
 
       // Checkout the new branch (shallow fetch for performance)
-    await $`git fetch origin --depth=1 ${newBranch}`;
-    await $`git checkout ${newBranch}`;
+      await $`git fetch origin --depth=1 ${branchToUse}`;
+      await $`git checkout ${branchToUse}`;
 
       console.log(
-      `Successfully created and checked out new branch: ${newBranch}`,
+        `Successfully created and checked out new branch: ${branchToUse}`,
       );
+    }
 
     // Set outputs for GitHub Actions
-    core.setOutput("CLAUDE_BRANCH", newBranch);
+    core.setOutput("CLAUDE_BRANCH", branchToUse);
     core.setOutput("BASE_BRANCH", sourceBranch);
+    if (isReusedBranch) {
+      core.setOutput("IS_REUSED_BRANCH", "true");
+    }
     return {
       baseBranch: sourceBranch,
-      claudeBranch: newBranch,
-      currentBranch: newBranch,
+      claudeBranch: branchToUse,
+      currentBranch: branchToUse,
+      isReusedBranch,
     };
   } catch (error) {
-    console.error("Error creating branch:", error);
+    console.error("Error setting up branch:", error);
     process.exit(1);
   }
 }