diff --git a/ui/src/components/IssueChatThread.test.tsx b/ui/src/components/IssueChatThread.test.tsx
index 241a7fae..5d1b7b4a 100644
--- a/ui/src/components/IssueChatThread.test.tsx
+++ b/ui/src/components/IssueChatThread.test.tsx
@@ -353,6 +353,83 @@ describe("IssueChatThread", () => {
     });
   });
 
+  it("falls back to execCommand for comment copy actions in insecure contexts", async () => {
+    const clipboardWrite = vi.fn(async () => {
+      throw new Error("Clipboard API blocked");
+    });
+    const execCommand = vi.fn(() => true);
+    const originalClipboard = Object.getOwnPropertyDescriptor(navigator, "clipboard");
+    const originalExecCommand = Object.getOwnPropertyDescriptor(document, "execCommand");
+    Object.defineProperty(navigator, "clipboard", {
+      configurable: true,
+      value: { writeText: clipboardWrite },
+    });
+    Object.defineProperty(document, "execCommand", {
+      configurable: true,
+      value: execCommand,
+    });
+
+    try {
+      const root = createRoot(container);
+
+      act(() => {
+        root.render(
+          <MemoryRouter>
+            <IssueChatThread
+              comments={[{
+                id: "comment-copy",
+                companyId: "company-1",
+                issueId: "issue-1",
+                authorAgentId: null,
+                authorUserId: "user-1",
+                authorType: "user",
+                body: "Copy this comment",
+                presentation: null,
+                metadata: null,
+                createdAt: new Date("2026-04-06T12:00:00.000Z"),
+                updatedAt: new Date("2026-04-06T12:00:00.000Z"),
+              }]}
+              linkedRuns={[]}
+              timelineEvents={[]}
+              liveRuns={[]}
+              onAdd={async () => {}}
+              showComposer={false}
+              enableLiveTranscriptPolling={false}
+            />
+          </MemoryRouter>,
+        );
+      });
+
+      const copyButton = container.querySelector('button[aria-label="Copy message"]') as HTMLButtonElement | null;
+      expect(copyButton).not.toBeNull();
+
+      await act(async () => {
+        copyButton?.click();
+        await Promise.resolve();
+      });
+
+      expect(clipboardWrite).toHaveBeenCalledWith("Copy this comment");
+      expect(execCommand).toHaveBeenCalledWith("copy");
+
+      act(() => {
+        root.unmount();
+      });
+    } finally {
+      if (originalClipboard) {
+        Object.defineProperty(navigator, "clipboard", originalClipboard);
+      } else {
+        // @ts-expect-error test cleanup for optional browser API
+        delete navigator.clipboard;
+      }
+      if (originalExecCommand) {
+        Object.defineProperty(document, "execCommand", originalExecCommand);
+      } else {
+        // @ts-expect-error test cleanup for optional browser API
+        delete document.execCommand;
+      }
+    }
+  });
+
   it("renders footer content inside the thread viewport before the bottom anchor", () => {
     const root = createRoot(container);
 
diff --git a/ui/src/components/IssueChatThread.tsx b/ui/src/components/IssueChatThread.tsx
index 8d897730..2c60dcd4 100644
--- a/ui/src/components/IssueChatThread.tsx
+++ b/ui/src/components/IssueChatThread.tsx
@@ -45,6 +45,8 @@ import type {
 import type { ActiveRunForIssue, LiveRunForIssue } from "../api/heartbeats";
 import { useLiveRunTranscripts } from "./transcript/useLiveRunTranscripts";
 import { usePaperclipIssueRuntime, type PaperclipIssueRuntimeReassignment } from "../hooks/usePaperclipIssueRuntime";
+import { useOptionalToastActions } from "../context/ToastContext";
+import { copyTextToClipboard } from "../lib/clipboard";
 import {
   buildIssueChatMessages,
   formatDurationWords,
@@ -1047,6 +1049,7 @@ function IssueChatRollingToolPart({ toolParts }: { toolParts: ToolCallMessagePar
 
 function CopyablePreBlock({ children, className }: { children: string; className?: string }) {
   const [copied, setCopied] = useState(false);
+  const toastActions = useOptionalToastActions();
   return (
     <div className="group/pre relative">
       <pre className={className}>{children}</pre>
@@ -1059,9 +1062,15 @@ function CopyablePreBlock({ children, className }: { children: string; className
         title="Copy"
         aria-label="Copy"
         onClick={() => {
-          void navigator.clipboard.writeText(children).then(() => {
+          void copyTextToClipboard(children).then(() => {
             setCopied(true);
             setTimeout(() => setCopied(false), 2000);
+          }).catch((error) => {
+            toastActions?.pushToast({
+              title: "Copy failed",
+              body: error instanceof Error ? error.message : "Unable to copy text",
+              tone: "error",
+            });
           });
         }}
       >
@@ -1310,6 +1319,7 @@ function IssueChatUserMessage({
   const queueTargetRunId = typeof custom.queueTargetRunId === "string" ? custom.queueTargetRunId : null;
   const [copied, setCopied] = useState(false);
   const [deleteDialogOpen, setDeleteDialogOpen] = useState(false);
+  const toastActions = useOptionalToastActions();
   const {
     isCurrentUser,
     authorName: resolvedAuthorName,
@@ -1436,9 +1446,15 @@ function IssueChatUserMessage({
                   .filter((p): p is { type: "text"; text: string } => p.type === "text")
                   .map((p) => p.text)
                   .join("\n\n");
-                void navigator.clipboard.writeText(text).then(() => {
+                void copyTextToClipboard(text).then(() => {
                   setCopied(true);
                   setTimeout(() => setCopied(false), 2000);
+                }).catch((error) => {
+                  toastActions?.pushToast({
+                    title: "Copy failed",
+                    body: error instanceof Error ? error.message : "Unable to copy message",
+                    tone: "error",
+                  });
                 });
               }}
             >
@@ -1551,6 +1567,7 @@ function IssueChatAssistantMessage({
   const [folded, setFolded] = useState(isFoldable);
   const [prevFoldKey, setPrevFoldKey] = useState({ messageId: message.id, isFoldable });
   const [copied, setCopied] = useState(false);
+  const toastActions = useOptionalToastActions();
   const copyText = deleted ? "" : getThreadMessageCopyText(message);
 
   // Derive fold state synchronously during render (not in useEffect) so the
@@ -1609,9 +1626,15 @@ function IssueChatAssistantMessage({
         title="Copy message"
         aria-label="Copy message"
         onClick={() => {
-          void navigator.clipboard.writeText(copyText).then(() => {
+          void copyTextToClipboard(copyText).then(() => {
             setCopied(true);
             setTimeout(() => setCopied(false), 2000);
+          }).catch((error) => {
+            toastActions?.pushToast({
+              title: "Copy failed",
+              body: error instanceof Error ? error.message : "Unable to copy message",
+              tone: "error",
+            });
           });
         }}
       >
@@ -1653,7 +1676,13 @@ function IssueChatAssistantMessage({
         <DropdownMenuContent align="end">
           <DropdownMenuItem
             onClick={() => {
-              void navigator.clipboard.writeText(copyText);
+              void copyTextToClipboard(copyText).catch((error) => {
+                toastActions?.pushToast({
+                  title: "Copy failed",
+                  body: error instanceof Error ? error.message : "Unable to copy message",
+                  tone: "error",
+                });
+              });
             }}
           >
             <Copy className="mr-2 h-3.5 w-3.5" />
@@ -2411,6 +2440,7 @@ function SystemNoticeCommentRow({
   anchorId?: string;
 }) {
   const { onImageClick, agentMap, issueStatus, successfulRunHandoff } = useContext(IssueChatCtx);
+  const toastActions = useOptionalToastActions();
   const custom = message.metadata.custom as Record<string, unknown>;
   const presentation = isIssueCommentPresentation(custom.presentation) ? custom.presentation : null;
   const commentMetadata = isIssueCommentMetadata(custom.commentMetadata) ? custom.commentMetadata : null;
@@ -2460,18 +2490,30 @@ function SystemNoticeCommentRow({
   });
 
   const handleCopy = () => {
-    void navigator.clipboard.writeText(bodyText).then(() => {
+    void copyTextToClipboard(bodyText).then(() => {
       setCopied(true);
       setTimeout(() => setCopied(false), 2000);
+    }).catch((error) => {
+      toastActions?.pushToast({
+        title: "Copy failed",
+        body: error instanceof Error ? error.message : "Unable to copy system notice",
+        tone: "error",
+      });
     });
   };
 
   const handleCopyLink = () => {
     if (!anchorId || typeof window === "undefined") return;
     const url = `${window.location.origin}${window.location.pathname}#${anchorId}`;
-    void navigator.clipboard.writeText(url).then(() => {
+    void copyTextToClipboard(url).then(() => {
       setCopiedLink(true);
       setTimeout(() => setCopiedLink(false), 2000);
+    }).catch((error) => {
+      toastActions?.pushToast({
+        title: "Copy failed",
+        body: error instanceof Error ? error.message : "Unable to copy system notice link",
+        tone: "error",
+      });
     });
   };
 
diff --git a/ui/src/components/IssueChatThreadClassic.tsx b/ui/src/components/IssueChatThreadClassic.tsx
index 157e8e70..fc68fb92 100644
--- a/ui/src/components/IssueChatThreadClassic.tsx
+++ b/ui/src/components/IssueChatThreadClassic.tsx
@@ -56,6 +56,7 @@ import type {
 import type { ActiveRunForIssue, LiveRunForIssue } from "../api/heartbeats";
 import { useLiveRunTranscripts } from "./transcript/useLiveRunTranscripts";
 import { usePaperclipIssueRuntime, type PaperclipIssueRuntimeReassignment } from "../hooks/usePaperclipIssueRuntime";
+import { copyTextToClipboard } from "../lib/clipboard";
 import {
   buildIssueChatMessages,
   formatDurationWords,
@@ -1072,6 +1073,7 @@ function IssueChatRollingToolPart({ toolParts }: { toolParts: ToolCallMessagePar
 
 function CopyablePreBlock({ children, className }: { children: string; className?: string }) {
   const [copied, setCopied] = useState(false);
+  const toastActions = useOptionalToastActions();
   return (
     <div className="group/pre relative">
       <pre className={className}>{children}</pre>
@@ -1084,9 +1086,15 @@ function CopyablePreBlock({ children, className }: { children: string; className
         title="Copy"
         aria-label="Copy"
         onClick={() => {
-          void navigator.clipboard.writeText(children).then(() => {
+          void copyTextToClipboard(children).then(() => {
             setCopied(true);
             setTimeout(() => setCopied(false), 2000);
+          }).catch((error) => {
+            toastActions?.pushToast({
+              title: "Copy failed",
+              body: error instanceof Error ? error.message : "Unable to copy text",
+              tone: "error",
+            });
           });
         }}
       >
@@ -1332,6 +1340,7 @@ function IssueChatUserMessage({
   const queueTargetRunId = typeof custom.queueTargetRunId === "string" ? custom.queueTargetRunId : null;
   const [copied, setCopied] = useState(false);
   const [deleteDialogOpen, setDeleteDialogOpen] = useState(false);
+  const toastActions = useOptionalToastActions();
   const {
     isCurrentUser,
     authorName: resolvedAuthorName,
@@ -1452,9 +1461,15 @@ function IssueChatUserMessage({
                   .filter((p): p is { type: "text"; text: string } => p.type === "text")
                   .map((p) => p.text)
                   .join("\n\n");
-                void navigator.clipboard.writeText(text).then(() => {
+                void copyTextToClipboard(text).then(() => {
                   setCopied(true);
                   setTimeout(() => setCopied(false), 2000);
+                }).catch((error) => {
+                  toastActions?.pushToast({
+                    title: "Copy failed",
+                    body: error instanceof Error ? error.message : "Unable to copy message",
+                    tone: "error",
+                  });
                 });
               }}
             >
@@ -1567,6 +1582,7 @@ function IssueChatAssistantMessage({
   const [folded, setFolded] = useState(isFoldable);
   const [prevFoldKey, setPrevFoldKey] = useState({ messageId: message.id, isFoldable });
   const [copied, setCopied] = useState(false);
+  const toastActions = useOptionalToastActions();
   const copyText = deleted ? "" : getThreadMessageCopyText(message);
 
   // Derive fold state synchronously during render (not in useEffect) so the
@@ -1685,9 +1701,15 @@ function IssueChatAssistantMessage({
                   title="Copy message"
                   aria-label="Copy message"
                   onClick={() => {
-                    void navigator.clipboard.writeText(copyText).then(() => {
+                    void copyTextToClipboard(copyText).then(() => {
                       setCopied(true);
                       setTimeout(() => setCopied(false), 2000);
+                    }).catch((error) => {
+                      toastActions?.pushToast({
+                        title: "Copy failed",
+                        body: error instanceof Error ? error.message : "Unable to copy message",
+                        tone: "error",
+                      });
                     });
                   }}
                 >
@@ -1729,7 +1751,13 @@ function IssueChatAssistantMessage({
                   <DropdownMenuContent align="end">
                     <DropdownMenuItem
                       onClick={() => {
-                        void navigator.clipboard.writeText(copyText);
+                        void copyTextToClipboard(copyText).catch((error) => {
+                          toastActions?.pushToast({
+                            title: "Copy failed",
+                            body: error instanceof Error ? error.message : "Unable to copy message",
+                            tone: "error",
+                          });
+                        });
                       }}
                     >
                       <Copy className="mr-2 h-3.5 w-3.5" />
@@ -2369,6 +2397,7 @@ function SystemNoticeCommentRow({
   anchorId?: string;
 }) {
   const { onImageClick, agentMap, issueStatus, successfulRunHandoff } = useContext(IssueChatCtx);
+  const toastActions = useOptionalToastActions();
   const custom = message.metadata.custom as Record<string, unknown>;
   const presentation = isIssueCommentPresentation(custom.presentation) ? custom.presentation : null;
   const commentMetadata = isIssueCommentMetadata(custom.commentMetadata) ? custom.commentMetadata : null;
@@ -2418,18 +2447,30 @@ function SystemNoticeCommentRow({
   });
 
   const handleCopy = () => {
-    void navigator.clipboard.writeText(bodyText).then(() => {
+    void copyTextToClipboard(bodyText).then(() => {
       setCopied(true);
       setTimeout(() => setCopied(false), 2000);
+    }).catch((error) => {
+      toastActions?.pushToast({
+        title: "Copy failed",
+        body: error instanceof Error ? error.message : "Unable to copy system notice",
+        tone: "error",
+      });
     });
   };
 
   const handleCopyLink = () => {
     if (!anchorId || typeof window === "undefined") return;
     const url = `${window.location.origin}${window.location.pathname}#${anchorId}`;
-    void navigator.clipboard.writeText(url).then(() => {
+    void copyTextToClipboard(url).then(() => {
       setCopiedLink(true);
       setTimeout(() => setCopiedLink(false), 2000);
+    }).catch((error) => {
+      toastActions?.pushToast({
+        title: "Copy failed",
+        body: error instanceof Error ? error.message : "Unable to copy system notice link",
+        tone: "error",
+      });
     });
   };
 
diff --git a/ui/src/lib/clipboard.ts b/ui/src/lib/clipboard.ts
new file mode 100644
index 00000000..168d3290
--- /dev/null
+++ b/ui/src/lib/clipboard.ts
@@ -0,0 +1,31 @@
+export async function copyTextToClipboard(text: string): Promise<void> {
+  if (typeof navigator !== "undefined" && navigator.clipboard?.writeText) {
+    try {
+      await navigator.clipboard.writeText(text);
+      return;
+    } catch {
+      // Fall back for environments where the Clipboard API exists but is blocked.
+    }
+  }
+
+  if (typeof document === "undefined") {
+    throw new Error("Clipboard unavailable");
+  }
+
+  const textarea = document.createElement("textarea");
+  textarea.value = text;
+  textarea.readOnly = true;
+  textarea.style.position = "fixed";
+  textarea.style.top = "-9999px";
+  textarea.style.left = "-9999px";
+  document.body.appendChild(textarea);
+
+  try {
+    textarea.select();
+    textarea.setSelectionRange(0, textarea.value.length);
+    const success = document.execCommand("copy");
+    if (!success) throw new Error("execCommand copy failed");
+  } finally {
+    document.body.removeChild(textarea);
+  }
+}
diff --git a/ui/src/pages/IssueDetail.test.tsx b/ui/src/pages/IssueDetail.test.tsx
index c9570d33..b8a1125d 100644
--- a/ui/src/pages/IssueDetail.test.tsx
+++ b/ui/src/pages/IssueDetail.test.tsx
@@ -1637,6 +1637,68 @@ describe("IssueDetail", () => {
     expect(container.textContent).toContain("Plan mode");
   });
 
+  it("falls back to execCommand when copying the task from an insecure context", async () => {
+    const clipboardWrite = vi.fn(async () => {
+      throw new Error("Clipboard API blocked");
+    });
+    const execCommand = vi.fn(() => true);
+    const originalClipboard = Object.getOwnPropertyDescriptor(navigator, "clipboard");
+    const originalExecCommand = Object.getOwnPropertyDescriptor(document, "execCommand");
+    Object.defineProperty(navigator, "clipboard", {
+      configurable: true,
+      value: { writeText: clipboardWrite },
+    });
+    Object.defineProperty(document, "execCommand", {
+      configurable: true,
+      value: execCommand,
+    });
+    mockIssuesApi.get.mockResolvedValue(createIssue({
+      identifier: "PAP-1",
+      title: "Copy me",
+      description: "Task body",
+    }));
+
+    try {
+      await act(async () => {
+        root.render(
+          <QueryClientProvider client={queryClient}>
+            <IssueDetail />
+          </QueryClientProvider>,
+        );
+      });
+      await flushReact();
+
+      const copyButton = Array.from(container.querySelectorAll("button"))
+        .find((button) => button.getAttribute("title") === "Copy task as markdown");
+      expect(copyButton).toBeTruthy();
+
+      await act(async () => {
+        copyButton!.click();
+        await Promise.resolve();
+      });
+
+      expect(clipboardWrite).toHaveBeenCalledWith("# PAP-1: Copy me\n\nTask body");
+      expect(execCommand).toHaveBeenCalledWith("copy");
+      expect(mockPushToast).toHaveBeenCalledWith(expect.objectContaining({
+        title: "Copied to clipboard",
+        tone: "success",
+      }));
+    } finally {
+      if (originalClipboard) {
+        Object.defineProperty(navigator, "clipboard", originalClipboard);
+      } else {
+        // @ts-expect-error test cleanup for optional browser API
+        delete navigator.clipboard;
+      }
+      if (originalExecCommand) {
+        Object.defineProperty(document, "execCommand", originalExecCommand);
+      } else {
+        // @ts-expect-error test cleanup for optional browser API
+        delete document.execCommand;
+      }
+    }
+  });
+
   // PAP-140 flag-off parity: with the Conference Room Chat flag off, the task
   // thread surfaces must render master's behavior (classic fork, master copy,
   // master mention set).
diff --git a/ui/src/pages/IssueDetail.tsx b/ui/src/pages/IssueDetail.tsx
index 0bac5e2a..6a96cc04 100644
--- a/ui/src/pages/IssueDetail.tsx
+++ b/ui/src/pages/IssueDetail.tsx
@@ -118,6 +118,7 @@ import {
 } from "@/components/ui/dialog";
 import { Textarea } from "@/components/ui/textarea";
 import { formatIssueActivityAction } from "@/lib/activity-format";
+import { copyTextToClipboard } from "../lib/clipboard";
 import { buildIssuePropertiesPanelKey } from "../lib/issue-properties-panel-key";
 import { buildIssueSiblingNavigation, shouldRenderRichSubIssuesSection } from "../lib/issue-detail-subissues";
 import { filterIssueDescendants } from "../lib/issue-tree";
@@ -3094,10 +3095,18 @@ export function IssueDetail() {
     const title = decodeEntities(issue.title);
     const body = decodeEntities(issue.description ?? "");
     const md = `# ${issue.identifier}: ${title}\n\n${body}`.trimEnd();
-    await navigator.clipboard.writeText(md);
-    setCopied(true);
-    pushToast({ title: "Copied to clipboard", tone: "success" });
-    setTimeout(() => setCopied(false), 2000);
+    try {
+      await copyTextToClipboard(md);
+      setCopied(true);
+      pushToast({ title: "Copied to clipboard", tone: "success" });
+      setTimeout(() => setCopied(false), 2000);
+    } catch (error) {
+      pushToast({
+        title: "Copy failed",
+        body: error instanceof Error ? error.message : "Unable to copy task markdown",
+        tone: "error",
+      });
+    }
   };
 
   // Gmail-style mobile toolbar when viewing an issue from inbox.