diff --git a/action.yml b/action.yml
index e96fc32..1716baf 100644
--- a/action.yml
+++ b/action.yml
@@ -12,6 +12,9 @@ inputs:
   assignee_trigger:
     description: "The assignee username that triggers the action (e.g. @claude)"
     required: false
+  base_branch:
+    description: "The branch to use as the base/source when creating new branches (defaults to repository default branch)"
+    required: false
 
   # Claude Code configuration
   model:
@@ -85,6 +88,7 @@ runs:
       env:
         TRIGGER_PHRASE: ${{ inputs.trigger_phrase }}
         ASSIGNEE_TRIGGER: ${{ inputs.assignee_trigger }}
+        BASE_BRANCH: ${{ inputs.base_branch }}
         ALLOWED_TOOLS: ${{ inputs.allowed_tools }}
         CUSTOM_INSTRUCTIONS: ${{ inputs.custom_instructions }}
         DIRECT_PROMPT: ${{ inputs.direct_prompt }}
@@ -146,7 +150,7 @@ runs:
         TRIGGER_COMMENT_ID: ${{ github.event.comment.id }}
         CLAUDE_BRANCH: ${{ steps.prepare.outputs.CLAUDE_BRANCH }}
         IS_PR: ${{ github.event.issue.pull_request != null || github.event_name == 'pull_request_review_comment' }}
-        DEFAULT_BRANCH: ${{ steps.prepare.outputs.DEFAULT_BRANCH }}
+        BASE_BRANCH: ${{ steps.prepare.outputs.BASE_BRANCH }}
         CLAUDE_SUCCESS: ${{ steps.claude-code.outputs.conclusion == 'success' }}
         OUTPUT_FILE: ${{ steps.claude-code.outputs.execution_file || '' }}
         TRIGGER_USERNAME: ${{ github.event.comment.user.login || github.event.issue.user.login || github.event.pull_request.user.login || github.event.sender.login || github.triggering_actor || github.actor || '' }}
diff --git a/src/create-prompt/index.ts b/src/create-prompt/index.ts
index 9a91110..2d8db0e 100644
--- a/src/create-prompt/index.ts
+++ b/src/create-prompt/index.ts
@@ -86,7 +86,7 @@ export function buildDisallowedToolsString(
 export function prepareContext(
   context: ParsedGitHubContext,
   claudeCommentId: string,
-  defaultBranch?: string,
+  baseBranch?: string,
   claudeBranch?: string,
 ): PreparedContext {
   const repository = context.repository.full_name;
@@ -164,7 +164,7 @@ export function prepareContext(
         ...(commentId && { commentId }),
         commentBody,
         ...(claudeBranch && { claudeBranch }),
-        ...(defaultBranch && { defaultBranch }),
+        ...(baseBranch && { baseBranch }),
       };
       break;
 
@@ -186,7 +186,7 @@ export function prepareContext(
         prNumber,
         commentBody,
         ...(claudeBranch && { claudeBranch }),
-        ...(defaultBranch && { defaultBranch }),
+        ...(baseBranch && { baseBranch }),
       };
       break;
 
@@ -211,13 +211,13 @@ export function prepareContext(
           prNumber,
           commentBody,
           ...(claudeBranch && { claudeBranch }),
-          ...(defaultBranch && { defaultBranch }),
+          ...(baseBranch && { baseBranch }),
         };
         break;
       } else if (!claudeBranch) {
         throw new Error("CLAUDE_BRANCH is required for issue_comment event");
-      } else if (!defaultBranch) {
-        throw new Error("DEFAULT_BRANCH is required for issue_comment event");
+      } else if (!baseBranch) {
+        throw new Error("BASE_BRANCH is required for issue_comment event");
       } else if (!issueNumber) {
         throw new Error(
           "ISSUE_NUMBER is required for issue_comment event for issues",
@@ -229,7 +229,7 @@ export function prepareContext(
         commentId,
         isPR: false,
         claudeBranch: claudeBranch,
-        defaultBranch,
+        baseBranch,
         issueNumber,
         commentBody,
       };
@@ -245,8 +245,8 @@ export function prepareContext(
       if (isPR) {
         throw new Error("IS_PR must be false for issues event");
       }
-      if (!defaultBranch) {
-        throw new Error("DEFAULT_BRANCH is required for issues event");
+      if (!baseBranch) {
+        throw new Error("BASE_BRANCH is required for issues event");
       }
       if (!claudeBranch) {
         throw new Error("CLAUDE_BRANCH is required for issues event");
@@ -263,7 +263,7 @@ export function prepareContext(
           eventAction: "assigned",
           isPR: false,
           issueNumber,
-          defaultBranch,
+          baseBranch,
           claudeBranch,
           assigneeTrigger,
         };
@@ -273,7 +273,7 @@ export function prepareContext(
           eventAction: "opened",
           isPR: false,
           issueNumber,
-          defaultBranch,
+          baseBranch,
           claudeBranch,
         };
       } else {
@@ -294,7 +294,7 @@ export function prepareContext(
         isPR: true,
         prNumber,
         ...(claudeBranch && { claudeBranch }),
-        ...(defaultBranch && { defaultBranch }),
+        ...(baseBranch && { baseBranch }),
       };
       break;
 
@@ -541,13 +541,13 @@ ${context.directPrompt ? `   - DIRECT INSTRUCTION: A direct instruction was prov
       ${
         eventData.claudeBranch
           ? `- Provide a URL to create a PR manually in this format:
-        [Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.defaultBranch}...<branch-name>?quick_pull=1&title=<url-encoded-title>&body=<url-encoded-body>)
+        [Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.baseBranch}...<branch-name>?quick_pull=1&title=<url-encoded-title>&body=<url-encoded-body>)
         - IMPORTANT: Use THREE dots (...) between branch names, not two (..)
           Example: ${GITHUB_SERVER_URL}/${context.repository}/compare/main...feature-branch (correct)
           NOT: ${GITHUB_SERVER_URL}/${context.repository}/compare/main..feature-branch (incorrect)
         - IMPORTANT: Ensure all URL parameters are properly encoded - spaces should be encoded as %20, not left as spaces
           Example: Instead of "fix: update welcome message", use "fix%3A%20update%20welcome%20message"
-        - The target-branch should be '${eventData.defaultBranch}'.
+        - The target-branch should be '${eventData.baseBranch}'.
         - The branch-name is the current branch: ${eventData.claudeBranch}
         - The body should include:
           - A clear description of the changes
@@ -632,7 +632,7 @@ f. If you are unable to complete certain steps, such as running a linter or test
 
 export async function createPrompt(
   claudeCommentId: number,
-  defaultBranch: string | undefined,
+  baseBranch: string | undefined,
   claudeBranch: string | undefined,
   githubData: FetchDataResult,
   context: ParsedGitHubContext,
@@ -641,7 +641,7 @@ export async function createPrompt(
     const preparedContext = prepareContext(
       context,
       claudeCommentId.toString(),
-      defaultBranch,
+      baseBranch,
       claudeBranch,
     );
 
diff --git a/src/create-prompt/types.ts b/src/create-prompt/types.ts
index eb5b13a..00bba5e 100644
--- a/src/create-prompt/types.ts
+++ b/src/create-prompt/types.ts
@@ -16,7 +16,7 @@ type PullRequestReviewCommentEvent = {
   commentId?: string; // May be present for review comments
   commentBody: string;
   claudeBranch?: string;
-  defaultBranch?: string;
+  baseBranch?: string;
 };
 
 type PullRequestReviewEvent = {
@@ -25,7 +25,7 @@ type PullRequestReviewEvent = {
   prNumber: string;
   commentBody: string;
   claudeBranch?: string;
-  defaultBranch?: string;
+  baseBranch?: string;
 };
 
 type IssueCommentEvent = {
@@ -33,7 +33,7 @@ type IssueCommentEvent = {
   commentId: string;
   issueNumber: string;
   isPR: false;
-  defaultBranch: string;
+  baseBranch: string;
   claudeBranch: string;
   commentBody: string;
 };
@@ -46,7 +46,7 @@ type PullRequestCommentEvent = {
   isPR: true;
   commentBody: string;
   claudeBranch?: string;
-  defaultBranch?: string;
+  baseBranch?: string;
 };
 
 type IssueOpenedEvent = {
@@ -54,7 +54,7 @@ type IssueOpenedEvent = {
   eventAction: "opened";
   isPR: false;
   issueNumber: string;
-  defaultBranch: string;
+  baseBranch: string;
   claudeBranch: string;
 };
 
@@ -63,7 +63,7 @@ type IssueAssignedEvent = {
   eventAction: "assigned";
   isPR: false;
   issueNumber: string;
-  defaultBranch: string;
+  baseBranch: string;
   claudeBranch: string;
   assigneeTrigger: string;
 };
@@ -74,7 +74,7 @@ type PullRequestEvent = {
   isPR: true;
   prNumber: string;
   claudeBranch?: string;
-  defaultBranch?: string;
+  baseBranch?: string;
 };
 
 // Union type for all possible event types
diff --git a/src/entrypoints/prepare.ts b/src/entrypoints/prepare.ts
index 1470798..c3e0b38 100644
--- a/src/entrypoints/prepare.ts
+++ b/src/entrypoints/prepare.ts
@@ -77,7 +77,7 @@ async function run() {
     // Step 10: Create prompt file
     await createPrompt(
       commentId,
-      branchInfo.defaultBranch,
+      branchInfo.baseBranch,
       branchInfo.claudeBranch,
       githubData,
       context,
diff --git a/src/entrypoints/update-comment-link.ts b/src/entrypoints/update-comment-link.ts
index d74bcd5..40c20ad 100644
--- a/src/entrypoints/update-comment-link.ts
+++ b/src/entrypoints/update-comment-link.ts
@@ -18,7 +18,7 @@ async function run() {
     const commentId = parseInt(process.env.CLAUDE_COMMENT_ID!);
     const githubToken = process.env.GITHUB_TOKEN!;
     const claudeBranch = process.env.CLAUDE_BRANCH;
-    const defaultBranch = process.env.DEFAULT_BRANCH || "main";
+    const baseBranch = process.env.BASE_BRANCH || "main";
     const triggerUsername = process.env.TRIGGER_USERNAME;
 
     const context = parseGitHubContext();
@@ -92,7 +92,7 @@ async function run() {
       owner,
       repo,
       claudeBranch,
-      defaultBranch,
+      baseBranch,
     );
 
     // Check if we need to add PR URL when we have a new branch
@@ -102,7 +102,7 @@ async function run() {
       // Check if comment already contains a PR URL
       const serverUrlPattern = serverUrl.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
       const prUrlPattern = new RegExp(
-        `${serverUrlPattern}\\/.+\\/compare\\/${defaultBranch.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")}\\.\\.\\.`,
+        `${serverUrlPattern}\\/.+\\/compare\\/${baseBranch.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")}\\.\\.\\.`,
       );
       const containsPRUrl = currentBody.match(prUrlPattern);
 
@@ -113,7 +113,7 @@ async function run() {
             await octokit.rest.repos.compareCommitsWithBasehead({
               owner,
               repo,
-              basehead: `${defaultBranch}...${claudeBranch}`,
+              basehead: `${baseBranch}...${claudeBranch}`,
             });
 
           // If there are changes (commits or file changes), add the PR URL
@@ -128,7 +128,7 @@ async function run() {
             const prBody = encodeURIComponent(
               `This PR addresses ${entityType.toLowerCase()} #${context.entityNumber}\n\nGenerated with [Claude Code](https://claude.ai/code)`,
             );
-            const prUrl = `${serverUrl}/${owner}/${repo}/compare/${defaultBranch}...${claudeBranch}?quick_pull=1&title=${prTitle}&body=${prBody}`;
+            const prUrl = `${serverUrl}/${owner}/${repo}/compare/${baseBranch}...${claudeBranch}?quick_pull=1&title=${prTitle}&body=${prBody}`;
             prLink = `\n[Create a PR](${prUrl})`;
           }
         } catch (error) {
diff --git a/src/github/context.ts b/src/github/context.ts
index b8abf71..0fb7f65 100644
--- a/src/github/context.ts
+++ b/src/github/context.ts
@@ -32,6 +32,7 @@ export type ParsedGitHubContext = {
     disallowedTools: string;
     customInstructions: string;
     directPrompt: string;
+    baseBranch?: string;
   };
 };
 
@@ -55,6 +56,7 @@ export function parseGitHubContext(): ParsedGitHubContext {
       disallowedTools: process.env.DISALLOWED_TOOLS ?? "",
       customInstructions: process.env.CUSTOM_INSTRUCTIONS ?? "",
       directPrompt: process.env.DIRECT_PROMPT ?? "",
+      baseBranch: process.env.BASE_BRANCH,
     },
   };
 
diff --git a/src/github/operations/branch-cleanup.ts b/src/github/operations/branch-cleanup.ts
index 9c1334d..662a474 100644
--- a/src/github/operations/branch-cleanup.ts
+++ b/src/github/operations/branch-cleanup.ts
@@ -6,7 +6,7 @@ export async function checkAndDeleteEmptyBranch(
   owner: string,
   repo: string,
   claudeBranch: string | undefined,
-  defaultBranch: string,
+  baseBranch: string,
 ): Promise<{ shouldDeleteBranch: boolean; branchLink: string }> {
   let branchLink = "";
   let shouldDeleteBranch = false;
@@ -18,7 +18,7 @@ export async function checkAndDeleteEmptyBranch(
         await octokit.rest.repos.compareCommitsWithBasehead({
           owner,
           repo,
-          basehead: `${defaultBranch}...${claudeBranch}`,
+          basehead: `${baseBranch}...${claudeBranch}`,
         });
 
       // If there are no commits, mark branch for deletion
diff --git a/src/github/operations/branch.ts b/src/github/operations/branch.ts
index 0f405cb..3379648 100644
--- a/src/github/operations/branch.ts
+++ b/src/github/operations/branch.ts
@@ -14,7 +14,7 @@ import type { Octokits } from "../api/client";
 import type { FetchDataResult } from "../data/fetcher";
 
 export type BranchInfo = {
-  defaultBranch: string;
+  baseBranch: string;
   claudeBranch?: string;
   currentBranch: string;
 };
@@ -26,15 +26,9 @@ export async function setupBranch(
 ): Promise<BranchInfo> {
   const { owner, repo } = context.repository;
   const entityNumber = context.entityNumber;
+  const { baseBranch } = context.inputs;
   const isPR = context.isPR;
 
-  // Get the default branch first
-  const repoResponse = await octokits.rest.repos.get({
-    owner,
-    repo,
-  });
-  const defaultBranch = repoResponse.data.default_branch;
-
   if (isPR) {
     const prData = githubData.contextData as GitHubPullRequest;
     const prState = prData.state;
@@ -42,7 +36,7 @@ export async function setupBranch(
     // Check if PR is closed or merged
     if (prState === "CLOSED" || prState === "MERGED") {
       console.log(
-        `PR #${entityNumber} is ${prState}, creating new branch from default...`,
+        `PR #${entityNumber} is ${prState}, creating new branch from source...`,
       );
       // Fall through to create a new branch like we do for issues
     } else {
@@ -58,17 +52,36 @@ export async function setupBranch(
 
       console.log(`Successfully checked out PR branch for PR #${entityNumber}`);
 
-      // For open PRs, return branch info
+      // For open PRs, we need to get the base branch of the PR
+      const baseBranch = prData.baseRefName;
+
       return {
-        defaultBranch,
+        baseBranch,
         currentBranch: branchName,
       };
     }
   }
 
+  // Determine source branch - use baseBranch if provided, otherwise fetch default
+  let sourceBranch: string;
+
+  if (baseBranch) {
+    // Use provided base branch for source
+    sourceBranch = baseBranch;
+  } else {
+    // No base branch provided, fetch the default branch to use as source
+    const repoResponse = await octokits.rest.repos.get({
+      owner,
+      repo,
+    });
+    sourceBranch = repoResponse.data.default_branch;
+  }
+
   // Creating a new branch for either an issue or closed/merged PR
   const entityType = isPR ? "pr" : "issue";
-  console.log(`Creating new branch for ${entityType} #${entityNumber}...`);
+  console.log(
+    `Creating new branch for ${entityType} #${entityNumber} from source branch: ${sourceBranch}...`,
+  );
 
   const timestamp = new Date()
     .toISOString()
@@ -80,14 +93,14 @@ export async function setupBranch(
   const newBranch = `claude/${entityType}-${entityNumber}-${timestamp}`;
 
   try {
-    // Get the SHA of the default branch
-    const defaultBranchRef = await octokits.rest.git.getRef({
+    // Get the SHA of the source branch
+    const sourceBranchRef = await octokits.rest.git.getRef({
       owner,
       repo,
-      ref: `heads/${defaultBranch}`,
+      ref: `heads/${sourceBranch}`,
     });
 
-    const currentSHA = defaultBranchRef.data.object.sha;
+    const currentSHA = sourceBranchRef.data.object.sha;
 
     console.log(`Current SHA: ${currentSHA}`);
 
@@ -109,9 +122,9 @@ export async function setupBranch(
 
     // Set outputs for GitHub Actions
     core.setOutput("CLAUDE_BRANCH", newBranch);
-    core.setOutput("DEFAULT_BRANCH", defaultBranch);
+    core.setOutput("BASE_BRANCH", sourceBranch);
     return {
-      defaultBranch,
+      baseBranch: sourceBranch,
       claudeBranch: newBranch,
       currentBranch: newBranch,
     };
diff --git a/test/create-prompt.test.ts b/test/create-prompt.test.ts
index 3eb493d..94064b6 100644
--- a/test/create-prompt.test.ts
+++ b/test/create-prompt.test.ts
@@ -127,7 +127,7 @@ describe("generatePrompt", () => {
         eventName: "issue_comment",
         commentId: "67890",
         isPR: false,
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-67890-20240101_120000",
         issueNumber: "67890",
         commentBody: "@claude please fix this",
@@ -183,7 +183,7 @@ describe("generatePrompt", () => {
         eventAction: "opened",
         isPR: false,
         issueNumber: "789",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-789-20240101_120000",
       },
     };
@@ -210,7 +210,7 @@ describe("generatePrompt", () => {
         eventAction: "assigned",
         isPR: false,
         issueNumber: "999",
-        defaultBranch: "develop",
+        baseBranch: "develop",
         claudeBranch: "claude/issue-999-20240101_120000",
         assigneeTrigger: "claude-bot",
       },
@@ -238,7 +238,7 @@ describe("generatePrompt", () => {
         eventAction: "opened",
         isPR: false,
         issueNumber: "789",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-789-20240101_120000",
       },
     };
@@ -285,7 +285,7 @@ describe("generatePrompt", () => {
         commentId: "67890",
         isPR: false,
         issueNumber: "123",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-67890-20240101_120000",
         commentBody: "@claude please fix this",
       },
@@ -307,7 +307,7 @@ describe("generatePrompt", () => {
         commentId: "67890",
         isPR: false,
         issueNumber: "123",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-67890-20240101_120000",
         commentBody: "@claude please fix this",
       },
@@ -362,7 +362,7 @@ describe("generatePrompt", () => {
         eventAction: "opened",
         isPR: false,
         issueNumber: "789",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-789-20240101_120000",
       },
     };
@@ -400,7 +400,7 @@ describe("generatePrompt", () => {
         commentId: "67890",
         isPR: false,
         issueNumber: "123",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-123-20240101_120000",
         commentBody: "@claude please fix this",
       },
@@ -432,7 +432,7 @@ describe("generatePrompt", () => {
         prNumber: "456",
         commentBody: "@claude please fix this",
         claudeBranch: "claude/pr-456-20240101_120000",
-        defaultBranch: "main",
+        baseBranch: "main",
       },
     };
 
@@ -470,7 +470,7 @@ describe("generatePrompt", () => {
         isPR: true,
         prNumber: "456",
         commentBody: "@claude please fix this",
-        // No claudeBranch or defaultBranch for open PRs
+        // No claudeBranch or baseBranch for open PRs
       },
     };
 
@@ -503,7 +503,7 @@ describe("generatePrompt", () => {
         prNumber: "789",
         commentBody: "@claude please update this",
         claudeBranch: "claude/pr-789-20240101_123000",
-        defaultBranch: "develop",
+        baseBranch: "develop",
       },
     };
 
@@ -531,7 +531,7 @@ describe("generatePrompt", () => {
         commentId: "review-comment-123",
         commentBody: "@claude fix this issue",
         claudeBranch: "claude/pr-999-20240101_140000",
-        defaultBranch: "main",
+        baseBranch: "main",
       },
     };
 
@@ -559,7 +559,7 @@ describe("generatePrompt", () => {
         isPR: true,
         prNumber: "555",
         claudeBranch: "claude/pr-555-20240101_150000",
-        defaultBranch: "main",
+        baseBranch: "main",
       },
     };
 
@@ -604,7 +604,7 @@ describe("getEventTypeAndContext", () => {
         eventAction: "assigned",
         isPR: false,
         issueNumber: "999",
-        defaultBranch: "main",
+        baseBranch: "main",
         claudeBranch: "claude/issue-999-20240101_120000",
         assigneeTrigger: "claude-bot",
       },
diff --git a/test/prepare-context.test.ts b/test/prepare-context.test.ts
index 6bece55..5be89f0 100644
--- a/test/prepare-context.test.ts
+++ b/test/prepare-context.test.ts
@@ -34,7 +34,7 @@ describe("parseEnvVarsWithContext", () => {
       beforeEach(() => {
         process.env = {
           ...BASE_ENV,
-          DEFAULT_BRANCH: "main",
+          BASE_BRANCH: "main",
           CLAUDE_BRANCH: "claude/issue-67890-20240101_120000",
         };
       });
@@ -62,7 +62,7 @@ describe("parseEnvVarsWithContext", () => {
           expect(result.eventData.claudeBranch).toBe(
             "claude/issue-67890-20240101_120000",
           );
-          expect(result.eventData.defaultBranch).toBe("main");
+          expect(result.eventData.baseBranch).toBe("main");
           expect(result.eventData.commentBody).toBe(
             "@claude can you help explain how to configure the logging system?",
           );
@@ -75,7 +75,7 @@ describe("parseEnvVarsWithContext", () => {
         ).toThrow("CLAUDE_BRANCH is required for issue_comment event");
       });
 
-      test("should throw error when DEFAULT_BRANCH is missing", () => {
+      test("should throw error when BASE_BRANCH is missing", () => {
         expect(() =>
           prepareContext(
             mockIssueCommentContext,
@@ -83,7 +83,7 @@ describe("parseEnvVarsWithContext", () => {
             undefined,
             "claude/issue-67890-20240101_120000",
           ),
-        ).toThrow("DEFAULT_BRANCH is required for issue_comment event");
+        ).toThrow("BASE_BRANCH is required for issue_comment event");
       });
     });
 
@@ -151,7 +151,7 @@ describe("parseEnvVarsWithContext", () => {
     beforeEach(() => {
       process.env = {
         ...BASE_ENV,
-        DEFAULT_BRANCH: "main",
+        BASE_BRANCH: "main",
         CLAUDE_BRANCH: "claude/issue-42-20240101_120000",
       };
     });
@@ -172,7 +172,7 @@ describe("parseEnvVarsWithContext", () => {
         result.eventData.eventAction === "opened"
       ) {
         expect(result.eventData.issueNumber).toBe("42");
-        expect(result.eventData.defaultBranch).toBe("main");
+        expect(result.eventData.baseBranch).toBe("main");
         expect(result.eventData.claudeBranch).toBe(
           "claude/issue-42-20240101_120000",
         );
@@ -195,7 +195,7 @@ describe("parseEnvVarsWithContext", () => {
         result.eventData.eventAction === "assigned"
       ) {
         expect(result.eventData.issueNumber).toBe("123");
-        expect(result.eventData.defaultBranch).toBe("main");
+        expect(result.eventData.baseBranch).toBe("main");
         expect(result.eventData.claudeBranch).toBe(
           "claude/issue-123-20240101_120000",
         );
@@ -209,7 +209,7 @@ describe("parseEnvVarsWithContext", () => {
       ).toThrow("CLAUDE_BRANCH is required for issues event");
     });
 
-    test("should throw error when DEFAULT_BRANCH is missing for issues", () => {
+    test("should throw error when BASE_BRANCH is missing for issues", () => {
       expect(() =>
         prepareContext(
           mockIssueOpenedContext,
@@ -217,7 +217,7 @@ describe("parseEnvVarsWithContext", () => {
           undefined,
           "claude/issue-42-20240101_120000",
         ),
-      ).toThrow("DEFAULT_BRANCH is required for issues event");
+      ).toThrow("BASE_BRANCH is required for issues event");
     });
   });