feat: add workflow cancellation detection and update comment

When a workflow is cancelled, the comment now shows "Claude's task was cancelled" 
instead of the generic "Claude encountered an error" message. This provides clearer 
feedback to users about why the workflow stopped.

Changes:
- Add CLAUDE_CANCELLED environment variable using cancelled() function in action.yml
- Implement cancellation detection logic in update-comment-link.ts
- Update comment-logic.ts to show specific cancellation message
- Add comprehensive tests for cancellation handling

Fixes #123

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

action.yml

@@ -160,6 +160,7 @@ runs:
         IS_PR: ${{ github.event.issue.pull_request != null || github.event_name == 'pull_request_review_comment' }}
         BASE_BRANCH: ${{ steps.prepare.outputs.BASE_BRANCH }}
         CLAUDE_SUCCESS: ${{ steps.claude-code.outputs.conclusion == 'success' }}
+        CLAUDE_CANCELLED: ${{ cancelled() }}
         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 || '' }}
         PREPARE_SUCCESS: ${{ steps.prepare.outcome == 'success' }}

src/entrypoints/update-comment-link.ts

@@ -146,8 +146,12 @@ async function run() {
       duration_api_ms?: number;
     } | null = null;
     let actionFailed = false;
+    let actionCancelled = false;
     let errorDetails: string | undefined;
 
+    // Check if the workflow was cancelled
+    const isCancelled = process.env.CLAUDE_CANCELLED === "true";
+
     // First check if prepare step failed
     const prepareSuccess = process.env.PREPARE_SUCCESS !== "false";
     const prepareError = process.env.PREPARE_ERROR;
@@ -155,6 +159,9 @@ async function run() {
     if (!prepareSuccess && prepareError) {
       actionFailed = true;
       errorDetails = prepareError;
+    } else if (isCancelled) {
+      // If the workflow was cancelled, set the cancelled flag
+      actionCancelled = true;
     } else {
       // Check if the Claude action failed
       // CLAUDE_SUCCESS is set to the result of: steps.claude-code.outputs.conclusion == 'success'
@@ -197,6 +204,7 @@ async function run() {
     const commentInput: CommentUpdateInput = {
       currentBody,
       actionFailed,
+      actionCancelled,
       executionDetails,
       jobUrl,
       branchLink,

src/github/operations/comment-logic.ts

@@ -9,6 +9,7 @@ export type ExecutionDetails = {
 export type CommentUpdateInput = {
   currentBody: string;
   actionFailed: boolean;
+  actionCancelled?: boolean;
   executionDetails: ExecutionDetails | null;
   jobUrl: string;
   branchLink?: string;
@@ -74,6 +75,7 @@ export function updateCommentBody(input: CommentUpdateInput): string {
     branchLink,
     prLink,
     actionFailed,
+    actionCancelled,
     branchName,
     triggerUsername,
     errorDetails,
@@ -112,7 +114,13 @@ export function updateCommentBody(input: CommentUpdateInput): string {
   // Build the header
   let header = "";
 
-  if (actionFailed) {
+  if (actionCancelled) {
+    header = "**Claude's task was cancelled";
+    if (durationStr) {
+      header += ` after ${durationStr}`;
+    }
+    header += "**";
+  } else if (actionFailed) {
     header = "**Claude encountered an error";
     if (durationStr) {
       header += ` after ${durationStr}`;

test/comment-logic.test.ts

@@ -418,4 +418,48 @@ describe("updateCommentBody", () => {
       );
     });
   });
+
+  describe("cancellation handling", () => {
+    it("shows cancellation message when actionCancelled is true", () => {
+      const input = {
+        ...baseInput,
+        currentBody: "Claude Code is working…",
+        actionCancelled: true,
+        executionDetails: { duration_ms: 30000 }, // 30s
+        triggerUsername: "test-user",
+      };
+
+      const result = updateCommentBody(input);
+      expect(result).toContain("**Claude's task was cancelled after 30s**");
+      expect(result).not.toContain("Claude encountered an error");
+      expect(result).not.toContain("Claude finished");
+    });
+
+    it("shows cancellation message without duration when duration is missing", () => {
+      const input = {
+        ...baseInput,
+        currentBody: "Claude Code is working…",
+        actionCancelled: true,
+        triggerUsername: "test-user",
+      };
+
+      const result = updateCommentBody(input);
+      expect(result).toContain("**Claude's task was cancelled**");
+      expect(result).not.toContain("after");
+    });
+
+    it("prioritizes cancellation over failure", () => {
+      const input = {
+        ...baseInput,
+        currentBody: "Claude Code is working…",
+        actionCancelled: true,
+        actionFailed: true, // Both are true, cancellation should take precedence
+        executionDetails: { duration_ms: 45000 },
+      };
+
+      const result = updateCommentBody(input);
+      expect(result).toContain("**Claude's task was cancelled after 45s**");
+      expect(result).not.toContain("Claude encountered an error");
+    });
+  });
 });

test/update-comment-link-logic.test.ts

@@ -107,4 +107,54 @@ describe("update-comment-link workflow status detection", () => {
 
     expect(actionFailed).toBe(false);
   });
+
+  test("should detect cancellation when CLAUDE_CANCELLED is true", () => {
+    process.env.PREPARE_SUCCESS = "true";
+    process.env.CLAUDE_SUCCESS = "false";
+    process.env.CLAUDE_CANCELLED = "true";
+
+    const prepareSuccess = process.env.PREPARE_SUCCESS !== "false";
+    const prepareError = process.env.PREPARE_ERROR;
+    const isCancelled = process.env.CLAUDE_CANCELLED === "true";
+
+    let actionFailed = false;
+    let actionCancelled = false;
+
+    if (!prepareSuccess && prepareError) {
+      actionFailed = true;
+    } else if (isCancelled) {
+      actionCancelled = true;
+    } else {
+      const claudeSuccess = process.env.CLAUDE_SUCCESS === "true";
+      actionFailed = !claudeSuccess;
+    }
+
+    expect(actionFailed).toBe(false);
+    expect(actionCancelled).toBe(true);
+  });
+
+  test("should not detect cancellation when CLAUDE_CANCELLED is false", () => {
+    process.env.PREPARE_SUCCESS = "true";
+    process.env.CLAUDE_SUCCESS = "false";
+    process.env.CLAUDE_CANCELLED = "false";
+
+    const prepareSuccess = process.env.PREPARE_SUCCESS !== "false";
+    const prepareError = process.env.PREPARE_ERROR;
+    const isCancelled = process.env.CLAUDE_CANCELLED === "true";
+
+    let actionFailed = false;
+    let actionCancelled = false;
+
+    if (!prepareSuccess && prepareError) {
+      actionFailed = true;
+    } else if (isCancelled) {
+      actionCancelled = true;
+    } else {
+      const claudeSuccess = process.env.CLAUDE_SUCCESS === "true";
+      actionFailed = !claudeSuccess;
+    }
+
+    expect(actionFailed).toBe(true);
+    expect(actionCancelled).toBe(false);
+  });
 });