diff --git a/apps/mobile/src/components/ComposerEditor.tsx b/apps/mobile/src/components/ComposerEditor.tsx
index 3d06dfd9f344a..f68c5396d8414 100644
--- a/apps/mobile/src/components/ComposerEditor.tsx
+++ b/apps/mobile/src/components/ComposerEditor.tsx
@@ -97,6 +97,7 @@ export function ComposerEditor({
         retained.attachments.length,
         controller.signal,
         retained.context?.records.length ?? 0,
+        environmentId,
       );
       if (!result) {
         insertComposerDraftText(draftKey, clipboard.text, insertion);
@@ -109,10 +110,19 @@ export function ComposerEditor({
         );
         return;
       }
+      const warnings: string[] = [];
       if (result.failures.length > 0)
+        warnings.push(
+          "Some attachments could not be copied. Reconnect to the source environment and copy them again.",
+        );
+      if (result.skippedThreads.length > 0)
+        warnings.push(
+          `${result.skippedThreads.map((title) => `"${title}"`).join(", ")} ${result.skippedThreads.length === 1 ? "is" : "are"} on another machine.`,
+        );
+      if (warnings.length > 0)
         Dialog.alert(
-          "Some attachments could not be copied",
-          "Reconnect to the source environment and copy them again. References without their files are marked unavailable.",
+          "Some context is unavailable",
+          [...warnings, "Those references are marked unavailable."].join("\n\n"),
         );
     });
     setComposerContextImporting(draftKey, false);
diff --git a/apps/mobile/src/features/threads/NewTaskDraftScreen.tsx b/apps/mobile/src/features/threads/NewTaskDraftScreen.tsx
index d1c18a4ebbcde..1d4dcc750c50b 100644
--- a/apps/mobile/src/features/threads/NewTaskDraftScreen.tsx
+++ b/apps/mobile/src/features/threads/NewTaskDraftScreen.tsx
@@ -71,6 +71,7 @@ import { ProviderIcon } from "../../components/ProviderIcon";
 import { SymbolView } from "../../components/ui/AppSymbol";
 import { AppText as Text } from "../../components/ui/AppText";
 import { hasProviderUsageLimits, isUsageLimitsCommand } from "@t3tools/shared/usageLimits";
+import { threadContextsOutsideEnvironment } from "@t3tools/shared/composerContextReferences";
 import { COMPOSER_LAYOUT_TRANSITION, ComposerSurface } from "./ThreadComposer";
 import { ComposerCommandPopover } from "./ComposerCommandPopover";
 import { useComposerCommandMenu } from "./use-composer-command-menu";
@@ -1248,6 +1249,22 @@ export function NewTaskDraftScreen(props: {
       Dialog.alert("Too much context", contextBlockReason);
       return;
     }
+    const strandedThread = threadContextsOutsideEnvironment({
+      text: draft.text,
+      records: draft.context?.records ?? [],
+      environmentId: selectedProject.environmentId,
+    })[0];
+    if (strandedThread) {
+      const owner =
+        flow.environments.find(
+          (environment) => environment.environmentId === strandedThread.environmentId,
+        )?.environmentLabel ?? "its machine";
+      Dialog.alert(
+        "Attached thread unavailable",
+        `"${strandedThread.title}" is on another machine. Switch back to ${owner} or remove it from the draft.`,
+      );
+      return;
+    }
 
     const editingPendingTask = flow.editingPendingTask;
 
diff --git a/apps/mobile/src/features/threads/new-task-flow-provider.tsx b/apps/mobile/src/features/threads/new-task-flow-provider.tsx
index 27754c86dadc4..065cc73ce178b 100644
--- a/apps/mobile/src/features/threads/new-task-flow-provider.tsx
+++ b/apps/mobile/src/features/threads/new-task-flow-provider.tsx
@@ -24,6 +24,7 @@ import {
   ThreadId,
 } from "@t3tools/contracts";
 import { sanitizeNewRefName } from "@t3tools/shared/git";
+import { threadContextsOutsideEnvironment } from "@t3tools/shared/composerContextReferences";
 import { resolveNewThreadEnvMode, resolveProjectSettings } from "@t3tools/shared/projectSettings";
 import { parseT3ProjectFile } from "@t3tools/shared/t3ProjectFile";
 import * as Arr from "effect/Array";
@@ -961,6 +962,15 @@ export function NewTaskFlowProvider(props: React.PropsWithChildren) {
     if ((text.length === 0 && draft.attachments.length === 0) || !draftModelSelection) {
       return null;
     }
+    if (
+      threadContextsOutsideEnvironment({
+        text: draft.text,
+        records: draft.context?.records ?? [],
+        environmentId: selectedProject.environmentId,
+      }).length > 0
+    ) {
+      return null;
+    }
     const workspaceSelection = canChooseWorkspace ? draft.workspaceSelection : undefined;
     const mode = workspaceSelection?.mode ?? workspaceMode;
     // When the selection is the stand-in built from the queued snapshot,
diff --git a/apps/mobile/src/lib/composerContextClipboard.test.ts b/apps/mobile/src/lib/composerContextClipboard.test.ts
index f3a3a3e83b084..d37e0a9ae6fd8 100644
--- a/apps/mobile/src/lib/composerContextClipboard.test.ts
+++ b/apps/mobile/src/lib/composerContextClipboard.test.ts
@@ -1,6 +1,15 @@
 import { beforeEach, describe, expect, it, vi } from "vite-plus/test";
-import { ComposerContextId, EnvironmentId } from "@t3tools/contracts";
+import {
+  COMPOSER_CONTEXT_MAX_RECORDS,
+  ComposerContextId,
+  EnvironmentId,
+  ThreadId,
+} from "@t3tools/contracts";
 import { encodeComposerContextFragment } from "@t3tools/shared/composerContextClipboard";
+import {
+  collectComposerContextReferences,
+  formatComposerContextReference,
+} from "@t3tools/shared/composerContextReferences";
 
 const mocks = vi.hoisted(() => ({
   execute: vi.fn(),
@@ -44,6 +53,7 @@ vi.mock("./composerImages", () => ({
 vi.mock("./uuid", () => ({ uuidv4: () => `import-${++mocks.sequence}` }));
 
 import { importComposerContextClipboard } from "./composerContextClipboard";
+import { createComposerContextHistory } from "./composerContext";
 
 const image = {
   version: 1 as const,
@@ -76,6 +86,42 @@ const clipboard = {
   html: "",
 };
 
+const localThread = {
+  version: 1 as const,
+  kind: "thread" as const,
+  contextId: ComposerContextId.make("thread_local-thread"),
+  label: "Local discussion",
+  environmentId: EnvironmentId.make("destination"),
+  threadId: ThreadId.make("local-thread"),
+  title: "Local discussion",
+};
+const foreignThread = {
+  ...localThread,
+  contextId: ComposerContextId.make("thread_foreign-thread"),
+  label: "Remote discussion",
+  environmentId: EnvironmentId.make("source"),
+  threadId: ThreadId.make("foreign-thread"),
+  title: "Remote discussion",
+};
+const mixedRecords = [foreignThread, localThread, terminal, image];
+const mixedClipboard = {
+  text: `Compare these findings: ${mixedRecords.map(formatComposerContextReference).join(" ")} before changing anything.`,
+  fragment: encodeComposerContextFragment({
+    version: 1,
+    source: { environmentId: EnvironmentId.make("source") },
+    records: [
+      ...mixedRecords,
+      {
+        ...foreignThread,
+        contextId: ComposerContextId.make("thread_uncopied-thread"),
+        threadId: ThreadId.make("uncopied-thread"),
+        title: "Not in the copied selection",
+      },
+    ],
+  })!,
+  html: "",
+};
+
 beforeEach(() => {
   vi.clearAllMocks();
   mocks.sequence = 0;
@@ -142,6 +188,114 @@ describe("mobile context clipboard imports", () => {
     expect(mocks.download).not.toHaveBeenCalled();
   });
 
+  it("pastes local threads, text context and files at the cap after excluding foreign threads", async () => {
+    const result = await importComposerContextClipboard(
+      mixedClipboard,
+      0,
+      new AbortController().signal,
+      COMPOSER_CONTEXT_MAX_RECORDS - 3,
+      EnvironmentId.make("destination"),
+    );
+    expect(result).not.toBeNull();
+    expect(result!.context.records).toEqual([
+      { ...localThread, contextId: expect.any(String) },
+      { ...terminal, contextId: expect.any(String) },
+      { ...image, contextId: expect.any(String), attachmentId: result!.attachments[0]!.id },
+    ]);
+    expect(result!.attachments).toEqual([
+      expect.objectContaining({ name: image.name, fileUri: "file:///owned.png" }),
+    ]);
+    expect(result!.failures).toEqual([]);
+    expect(result!.skippedThreads).toEqual([foreignThread.title]);
+    const references = collectComposerContextReferences(result!.text);
+    expect(references.map((reference) => reference.label)).toEqual(
+      mixedRecords.map((record) => record.label),
+    );
+    expect(result!.context.records.map((record) => record.contextId)).toEqual(
+      references.slice(1).map((reference) => reference.contextId),
+    );
+    expect(
+      references.every(
+        (reference) => !mixedRecords.some((record) => record.contextId === reference.contextId),
+      ),
+    ).toBe(true);
+    expect(
+      result!.context.records.some((record) => record.contextId === references[0]!.contextId),
+    ).toBe(false);
+    expect(result!.text).toMatch(/^Compare these findings: .* before changing anything\.$/);
+
+    const restoreHistory = createComposerContextHistory();
+    restoreHistory(formatComposerContextReference(foreignThread), {
+      version: 1,
+      records: [foreignThread],
+    });
+    expect(restoreHistory(`${result!.text} Next step`, result!.context)).toEqual(result!.context);
+
+    mocks.download.mockClear();
+    await expect(
+      importComposerContextClipboard(
+        mixedClipboard,
+        0,
+        new AbortController().signal,
+        COMPOSER_CONTEXT_MAX_RECORDS - 2,
+        EnvironmentId.make("destination"),
+      ),
+    ).rejects.toThrow("Remove some context");
+    expect(mocks.download).not.toHaveBeenCalled();
+  });
+
+  it("reports foreign threads and failed files together while keeping the rest of a paste", async () => {
+    mocks.download.mockRejectedValueOnce(new Error("source disconnected"));
+    const result = await importComposerContextClipboard(
+      mixedClipboard,
+      0,
+      new AbortController().signal,
+      0,
+      EnvironmentId.make("destination"),
+    );
+    expect(result).not.toBeNull();
+    expect(result!.context.records).toEqual([
+      { ...localThread, contextId: expect.any(String) },
+      { ...terminal, contextId: expect.any(String) },
+    ]);
+    expect(result!.attachments).toEqual([]);
+    expect(result!.failures).toEqual([image.name]);
+    expect(result!.skippedThreads).toEqual([foreignThread.title]);
+    const references = collectComposerContextReferences(result!.text);
+    expect(references.map((reference) => reference.label)).toEqual(
+      mixedRecords.map((record) => record.label),
+    );
+    expect(
+      references
+        .filter(
+          (reference) =>
+            !result!.context.records.some((record) => record.contextId === reference.contextId),
+        )
+        .map((reference) => reference.label),
+    ).toEqual([foreignThread.label, image.label]);
+    expect(result!.text).toMatch(/^Compare these findings: .* before changing anything\.$/);
+  });
+
+  it("preserves both machines' thread references when pasting without a destination", async () => {
+    const result = await importComposerContextClipboard(
+      mixedClipboard,
+      0,
+      new AbortController().signal,
+    );
+    expect(result).not.toBeNull();
+    expect(result!.context.records).toEqual([
+      { ...foreignThread, contextId: expect.any(String) },
+      { ...localThread, contextId: expect.any(String) },
+      { ...terminal, contextId: expect.any(String) },
+      { ...image, contextId: expect.any(String), attachmentId: result!.attachments[0]!.id },
+    ]);
+    expect(result!.attachments).toHaveLength(1);
+    expect(result!.failures).toEqual([]);
+    expect(
+      collectComposerContextReferences(result!.text).map((reference) => reference.contextId),
+    ).toEqual(result!.context.records.map((record) => record.contextId));
+  });
+
   it("refuses an overflowing context paste before copying files", async () => {
     await expect(
       importComposerContextClipboard(clipboard, 0, new AbortController().signal, 200),
diff --git a/apps/mobile/src/lib/composerContextClipboard.ts b/apps/mobile/src/lib/composerContextClipboard.ts
index 5a5d3168cf09a..5231b4b94fb94 100644
--- a/apps/mobile/src/lib/composerContextClipboard.ts
+++ b/apps/mobile/src/lib/composerContextClipboard.ts
@@ -13,6 +13,7 @@ import {
   decodeComposerContextFragment,
   encodeComposerContextFragment,
 } from "@t3tools/shared/composerContextClipboard";
+import { threadContextsOutsideEnvironment } from "@t3tools/shared/composerContextReferences";
 import { executeAtomQuery, squashAtomCommandFailure } from "@t3tools/client-runtime/state/runtime";
 import { resolveAssetUrl } from "@t3tools/client-runtime/state/assets";
 import * as Option from "effect/Option";
@@ -65,19 +66,30 @@ export async function importComposerContextClipboard(
   existingCount: number,
   signal: AbortSignal,
   existingContextCount = 0,
+  destinationEnvironmentId?: EnvironmentId,
 ) {
   const fragment =
     decodeComposerContextFragment(input.fragment) ?? decodeComposerContextClipboardHtml(input.html);
   if (!fragment) return null;
   const selected = referencedComposerContext(input.text, { version: 1, records: fragment.records });
-  if (existingContextCount + (selected?.records.length ?? 0) > COMPOSER_CONTEXT_MAX_RECORDS)
-    throw new Error("Remove some context items from the draft before pasting more.");
   const imported = reidentifyComposerContext(input.text, selected?.records ?? [], uuidv4);
+  const skippedThreads =
+    destinationEnvironmentId === undefined
+      ? []
+      : threadContextsOutsideEnvironment({
+          text: imported.text,
+          records: imported.context.records,
+          environmentId: destinationEnvironmentId,
+        });
+  const skippedIds = new Set(skippedThreads.map((record) => record.contextId));
+  const retained = imported.context.records.filter((record) => !skippedIds.has(record.contextId));
+  if (existingContextCount + retained.length > COMPOSER_CONTEXT_MAX_RECORDS)
+    throw new Error("Remove some context items from the draft before pasting more.");
   const attachments: DraftComposerAttachment[] = [];
   const records: ComposerContextRecord[] = [];
   const failures: string[] = [];
   try {
-    for (const record of imported.context.records) {
+    for (const record of retained) {
       checkAborted(signal);
       if (!("attachmentId" in record)) {
         records.push(record);
@@ -99,6 +111,7 @@ export async function importComposerContextClipboard(
       context: { version: 1 as const, records },
       attachments,
       failures,
+      skippedThreads: skippedThreads.map((record) => record.title),
     };
   } catch (error) {
     await Promise.all(