fix: strip comment lines from claudeArgs before shell-quote parsing

base-action/src/parse-sdk-options.ts

@@ -92,7 +92,17 @@ function parseClaudeArgsToExtraArgs(
   if (!claudeArgs?.trim()) return {};
 
   const result: Record<string, string | null> = {};
-  const args = parseShellArgs(claudeArgs).filter(
+
+  // Strip shell-style comment lines before parsing.
+  // shell-quote treats '#' as a comment character and silently swallows
+  // everything after it, including subsequent flags on new lines.
+  // See: https://github.com/anthropics/claude-code-action/issues/802
+  const sanitizedArgs = claudeArgs
+    .split("\n")
+    .filter((line) => !line.trim().startsWith("#"))
+    .join("\n");
+
+  const args = parseShellArgs(sanitizedArgs).filter(
     (arg): arg is string => typeof arg === "string",
   );
 

base-action/test/parse-sdk-options.test.ts

@@ -367,4 +367,51 @@ describe("parseSdkOptions", () => {
       );
     });
   });
+
+  describe("comment handling (issue #802)", () => {
+    test("should ignore shell-style comment lines in claudeArgs", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: [
+          "--allowed-tools 'mcp__github__create_comment'",
+          "# This is a comment",
+          "--max-turns 5",
+        ].join("\n"),
+      };
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toContain(
+        "mcp__github__create_comment",
+      );
+      expect(result.sdkOptions.extraArgs?.["max-turns"]).toBe("5");
+    });
+
+    test("should handle multiple comment lines interspersed with flags", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: [
+          "# Enable specific tools",
+          "--allowed-tools 'Bash,Read'",
+          "# Set max turns",
+          "--max-turns 5",
+        ].join("\n"),
+      };
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual(["Bash", "Read"]);
+      expect(result.sdkOptions.extraArgs?.["max-turns"]).toBe("5");
+    });
+
+    test("should not lose flags when comment is between them", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: [
+          "--disallowed-tools 'WebSearch'",
+          "# middle comment",
+          "--max-turns 3",
+        ].join("\n"),
+      };
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.disallowedTools).toEqual(["WebSearch"]);
+      expect(result.sdkOptions.extraArgs?.["max-turns"]).toBe("3");
+    });
+  });
 });

base-action/test/parse-shell-args.test.ts

@@ -58,6 +58,18 @@ describe("shell-quote parseShellArgs", () => {
     ]);
   });
 
+  test("documents that shell-quote treats # as comment (issue #802)", () => {
+    // shell-quote treats '#' as a shell comment, dropping all subsequent content.
+    // This documents the raw behavior — the actual fix is in parseClaudeArgsToExtraArgs
+    // which strips comment lines before passing to shell-quote.
+    const input = "--model claude-haiku-4-5\n# comment\n--allowed-tools tool1";
+    const result = parseShellArgs(input).filter(
+      (arg): arg is string => typeof arg === "string",
+    );
+    // shell-quote drops everything from '#' onward, so --allowed-tools is lost
+    expect(result).toEqual(["--model", "claude-haiku-4-5"]);
+  });
+
   test("should filter out non-string results", () => {
     // shell-quote can return objects for operators like | > < etc
     const result = parseShellArgs("echo hello");