diff --git a/src/app/api/v1/interests/[id]/external-eoi/route.ts b/src/app/api/v1/interests/[id]/external-eoi/route.ts
new file mode 100644
index 0000000..7408fd2
--- /dev/null
+++ b/src/app/api/v1/interests/[id]/external-eoi/route.ts
@@ -0,0 +1,61 @@
+import { NextResponse } from 'next/server';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { uploadExternallySignedEoi } from '@/lib/services/external-eoi.service';
+import { errorResponse, NotFoundError, ValidationError } from '@/lib/errors';
+
+export const POST = withAuth(
+  withPermission('documents', 'upload_signed', async (req, ctx, params) => {
+    try {
+      const interestId = params.id;
+      if (!interestId) throw new NotFoundError('Interest');
+
+      const form = await req.formData();
+      const file = form.get('file');
+      if (!file || !(file instanceof File)) {
+        throw new ValidationError('Missing file');
+      }
+      const buffer = Buffer.from(await file.arrayBuffer());
+
+      const title = (form.get('title') as string | null) ?? undefined;
+      const notes = (form.get('notes') as string | null) ?? undefined;
+      const signerNamesRaw = (form.get('signerNames') as string | null) ?? '';
+      const signerNames = signerNamesRaw
+        ? signerNamesRaw
+            .split(',')
+            .map((s) => s.trim())
+            .filter(Boolean)
+        : undefined;
+      const signedAtRaw = (form.get('signedAt') as string | null) ?? null;
+      const signedAt = signedAtRaw ? new Date(signedAtRaw) : undefined;
+      if (signedAt && Number.isNaN(signedAt.getTime())) {
+        throw new ValidationError('Invalid signedAt');
+      }
+
+      const result = await uploadExternallySignedEoi({
+        interestId,
+        portId: ctx.portId,
+        fileData: {
+          buffer,
+          originalName: file.name,
+          mimeType: file.type || 'application/pdf',
+          size: file.size,
+        },
+        title,
+        signedAt,
+        signerNames,
+        notes,
+        meta: {
+          userId: ctx.userId,
+          portId: ctx.portId,
+          ipAddress: ctx.ipAddress,
+          userAgent: ctx.userAgent,
+        },
+      });
+
+      return NextResponse.json({ data: result });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);
diff --git a/src/components/interests/external-eoi-upload-dialog.tsx b/src/components/interests/external-eoi-upload-dialog.tsx
new file mode 100644
index 0000000..01fb54f
--- /dev/null
+++ b/src/components/interests/external-eoi-upload-dialog.tsx
@@ -0,0 +1,157 @@
+'use client';
+
+import { useState } from 'react';
+import { useMutation, useQueryClient } from '@tanstack/react-query';
+import { Loader2, Upload } from 'lucide-react';
+import { toast } from 'sonner';
+
+import { Button } from '@/components/ui/button';
+import { Input } from '@/components/ui/input';
+import { Label } from '@/components/ui/label';
+import { Textarea } from '@/components/ui/textarea';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+
+interface Props {
+  open: boolean;
+  onOpenChange: (next: boolean) => void;
+  interestId: string;
+  onSuccess?: () => void;
+}
+
+export function ExternalEoiUploadDialog({ open, onOpenChange, interestId, onSuccess }: Props) {
+  const qc = useQueryClient();
+  const [file, setFile] = useState<File | null>(null);
+  const [title, setTitle] = useState('');
+  const [signedAt, setSignedAt] = useState(() => new Date().toISOString().slice(0, 10));
+  const [signerNames, setSignerNames] = useState('');
+  const [notes, setNotes] = useState('');
+
+  const mutation = useMutation({
+    mutationFn: async () => {
+      if (!file) throw new Error('No file selected');
+      const form = new FormData();
+      form.append('file', file);
+      if (title) form.append('title', title);
+      if (signedAt) form.append('signedAt', signedAt);
+      if (signerNames) form.append('signerNames', signerNames);
+      if (notes) form.append('notes', notes);
+      const res = await fetch(`/api/v1/interests/${interestId}/external-eoi`, {
+        method: 'POST',
+        body: form,
+        credentials: 'include',
+      });
+      if (!res.ok) {
+        const err = await res.json().catch(() => ({ error: 'Upload failed' }));
+        throw new Error(err.error ?? 'Upload failed');
+      }
+      return res.json();
+    },
+    onSuccess: () => {
+      toast.success('External EOI uploaded — interest advanced to EOI Signed');
+      qc.invalidateQueries({ queryKey: ['interests', interestId] });
+      qc.invalidateQueries({ queryKey: ['interests'] });
+      qc.invalidateQueries({ queryKey: ['documents'] });
+      setFile(null);
+      setTitle('');
+      setSignerNames('');
+      setNotes('');
+      onOpenChange(false);
+      onSuccess?.();
+    },
+    onError: (err: unknown) => {
+      toast.error(err instanceof Error ? err.message : 'Upload failed');
+    },
+  });
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent>
+        <DialogHeader>
+          <DialogTitle>Upload externally-signed EOI</DialogTitle>
+          <DialogDescription>
+            For EOIs signed outside Documenso (paper, in person, alternate e-sign vendor). The
+            uploaded PDF is filed against this interest and the pipeline stage is advanced to EOI
+            Signed.
+          </DialogDescription>
+        </DialogHeader>
+
+        <div className="space-y-3 py-2">
+          <div>
+            <Label>PDF file *</Label>
+            <Input
+              type="file"
+              accept="application/pdf,.pdf"
+              onChange={(e) => setFile(e.target.files?.[0] ?? null)}
+              className="mt-1"
+            />
+          </div>
+          <div>
+            <Label>Title (optional)</Label>
+            <Input
+              value={title}
+              onChange={(e) => setTitle(e.target.value)}
+              placeholder="Defaults to 'External EOI - <date>'"
+              className="mt-1"
+            />
+          </div>
+          <div>
+            <Label>Date signed</Label>
+            <Input
+              type="date"
+              value={signedAt}
+              onChange={(e) => setSignedAt(e.target.value)}
+              className="mt-1"
+            />
+          </div>
+          <div>
+            <Label>Signer names (comma-separated)</Label>
+            <Input
+              value={signerNames}
+              onChange={(e) => setSignerNames(e.target.value)}
+              placeholder="e.g. John Smith, Marina Director"
+              className="mt-1"
+            />
+            <p className="text-xs text-muted-foreground mt-1">
+              Recorded in the audit trail alongside the document.
+            </p>
+          </div>
+          <div>
+            <Label>Notes (optional)</Label>
+            <Textarea
+              value={notes}
+              onChange={(e) => setNotes(e.target.value)}
+              placeholder="Where / how this EOI was signed"
+              rows={2}
+              className="mt-1"
+            />
+          </div>
+        </div>
+
+        <DialogFooter>
+          <Button
+            variant="outline"
+            onClick={() => onOpenChange(false)}
+            disabled={mutation.isPending}
+          >
+            Cancel
+          </Button>
+          <Button onClick={() => mutation.mutate()} disabled={!file || mutation.isPending}>
+            {mutation.isPending ? (
+              <Loader2 className="h-3.5 w-3.5 animate-spin mr-1.5" />
+            ) : (
+              <Upload className="h-3.5 w-3.5 mr-1.5" />
+            )}
+            Upload
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}
diff --git a/src/components/interests/interest-detail-header.tsx b/src/components/interests/interest-detail-header.tsx
index de5b35f..af437c4 100644
--- a/src/components/interests/interest-detail-header.tsx
+++ b/src/components/interests/interest-detail-header.tsx
@@ -13,6 +13,7 @@ import {
   MessageCircle,
   Phone,
   AlarmClock,
+  Upload,
 } from 'lucide-react';
 import Link from 'next/link';
 
@@ -23,6 +24,7 @@ import { ArchiveConfirmDialog } from '@/components/shared/archive-confirm-dialog
 import { DetailHeaderStrip } from '@/components/shared/detail-header-strip';
 import { PermissionGate } from '@/components/shared/permission-gate';
 import { InterestForm } from '@/components/interests/interest-form';
+import { ExternalEoiUploadDialog } from '@/components/interests/external-eoi-upload-dialog';
 import { InlineStagePicker } from '@/components/interests/inline-stage-picker';
 import { InterestOutcomeDialog } from '@/components/interests/interest-outcome-dialog';
 import { apiFetch } from '@/lib/api/client';
@@ -102,6 +104,7 @@ export function InterestDetailHeader({ portSlug, interest }: InterestDetailHeade
   const [editOpen, setEditOpen] = useState(false);
   const [archiveOpen, setArchiveOpen] = useState(false);
   const [outcomeDialog, setOutcomeDialog] = useState<null | 'won' | 'lost'>(null);
+  const [externalEoiOpen, setExternalEoiOpen] = useState(false);
 
   const isArchived = !!interest.archivedAt;
   const outcomeBadge = resolveOutcomeBadge(interest.outcome);
@@ -376,6 +379,20 @@ export function InterestDetailHeader({ portSlug, interest }: InterestDetailHeade
                 </>
               )}
             </PermissionGate>
+            <PermissionGate resource="documents" action="upload_signed">
+              <button
+                type="button"
+                onClick={() => setExternalEoiOpen(true)}
+                aria-label="Upload externally-signed EOI"
+                title="Upload externally-signed EOI (paper / outside Documenso)"
+                className={cn(
+                  'rounded-md p-1.5 text-muted-foreground/70 transition-colors',
+                  'hover:bg-foreground/5 hover:text-foreground',
+                )}
+              >
+                <Upload className="size-4" />
+              </button>
+            </PermissionGate>
             <PermissionGate resource="interests" action="edit">
               <button
                 type="button"
@@ -439,6 +456,12 @@ export function InterestDetailHeader({ portSlug, interest }: InterestDetailHeade
         }}
         isLoading={archiveMutation.isPending || restoreMutation.isPending}
       />
+
+      <ExternalEoiUploadDialog
+        open={externalEoiOpen}
+        onOpenChange={setExternalEoiOpen}
+        interestId={interest.id}
+      />
     </>
   );
 }
diff --git a/src/lib/services/external-eoi.service.ts b/src/lib/services/external-eoi.service.ts
new file mode 100644
index 0000000..8a7ebca
--- /dev/null
+++ b/src/lib/services/external-eoi.service.ts
@@ -0,0 +1,178 @@
+/**
+ * External EOI upload — for EOIs signed outside Documenso (paper signing,
+ * different e-sign vendor, signed in person, etc).
+ *
+ * Creates BOTH the document row AND the signed-file record in one shot,
+ * then advances the interest stage. Distinct from the existing
+ * uploadSignedManually flow which augments a document row that was
+ * already created via the Documenso pathway.
+ */
+
+import { eq } from 'drizzle-orm';
+
+import { db } from '@/lib/db';
+import { interests } from '@/lib/db/schema/interests';
+import { documents, documentEvents, files } from '@/lib/db/schema/documents';
+import { ports } from '@/lib/db/schema/ports';
+import { env } from '@/lib/env';
+import { buildStoragePath } from '@/lib/minio';
+import { getStorageBackend } from '@/lib/storage';
+import { createAuditLog, type AuditMeta } from '@/lib/audit';
+import { CodedError, NotFoundError, ValidationError } from '@/lib/errors';
+import { emitToRoom } from '@/lib/socket/server';
+
+export interface ExternalEoiInput {
+  interestId: string;
+  portId: string;
+  /** PDF bytes. */
+  fileData: { buffer: Buffer; originalName: string; mimeType: string; size: number };
+  /** Free-text title for the document row. Defaults to "External EOI - <date>". */
+  title?: string;
+  /** When the signing actually happened (the date on the paper / contract). */
+  signedAt?: Date;
+  /** Names of the people who signed (free-text — we don't manage signer
+   *  identities for external sigs). Recorded in metadata. */
+  signerNames?: string[];
+  /** Free-text note (e.g. "signed in person at boat show"). */
+  notes?: string;
+  meta: AuditMeta;
+}
+
+export async function uploadExternallySignedEoi(input: ExternalEoiInput) {
+  const { interestId, portId, fileData, meta } = input;
+
+  if (fileData.size <= 0) throw new ValidationError('Empty file');
+  if (fileData.size > 25 * 1024 * 1024) {
+    throw new ValidationError('File too large (max 25 MB)');
+  }
+  if (
+    fileData.mimeType !== 'application/pdf' &&
+    !fileData.originalName.toLowerCase().endsWith('.pdf')
+  ) {
+    throw new ValidationError('Only PDF uploads are accepted for signed EOIs');
+  }
+
+  const interest = await db.query.interests.findFirst({
+    where: eq(interests.id, interestId),
+  });
+  if (!interest || interest.portId !== portId) throw new NotFoundError('Interest');
+
+  const port = await db.query.ports.findFirst({ where: eq(ports.id, portId) });
+  if (!port) throw new NotFoundError('Port');
+
+  const documentId = crypto.randomUUID();
+  const fileId = crypto.randomUUID();
+  const storagePath = buildStoragePath(port.slug, 'eoi-signed', documentId, fileId, 'pdf');
+
+  await (
+    await getStorageBackend()
+  ).put(storagePath, fileData.buffer, {
+    contentType: 'application/pdf',
+    sizeBytes: fileData.size,
+  });
+
+  const [fileRecord] = await db
+    .insert(files)
+    .values({
+      portId,
+      clientId: interest.clientId,
+      filename: fileData.originalName,
+      originalName: fileData.originalName,
+      mimeType: 'application/pdf',
+      sizeBytes: String(fileData.size),
+      storagePath,
+      storageBucket: env.MINIO_BUCKET,
+      category: 'eoi',
+      uploadedBy: meta.userId,
+    })
+    .returning();
+  if (!fileRecord) {
+    throw new CodedError('INSERT_RETURNING_EMPTY', {
+      internalMessage: 'External EOI file insert returned no row',
+    });
+  }
+
+  const title =
+    input.title ?? `External EOI — ${(input.signedAt ?? new Date()).toISOString().slice(0, 10)}`;
+
+  const [doc] = await db
+    .insert(documents)
+    .values({
+      id: documentId,
+      portId,
+      interestId,
+      clientId: interest.clientId,
+      yachtId: interest.yachtId,
+      documentType: 'eoi',
+      title,
+      status: 'completed',
+      isManualUpload: true,
+      signedFileId: fileRecord.id,
+      notes: input.notes ?? null,
+      createdBy: meta.userId,
+    })
+    .returning();
+  if (!doc) {
+    throw new CodedError('INSERT_RETURNING_EMPTY', {
+      internalMessage: 'External EOI document insert returned no row',
+    });
+  }
+
+  await db.insert(documentEvents).values({
+    documentId: doc.id,
+    eventType: 'completed',
+    eventData: {
+      isManualUpload: true,
+      external: true,
+      signerNames: input.signerNames ?? [],
+      signedAt: (input.signedAt ?? new Date()).toISOString(),
+      fileId: fileRecord.id,
+    },
+  });
+
+  // Advance the interest stage to eoi_signed (no-op if already past it).
+  // We bypass canTransitionStage explicitly because the operator just
+  // brought concrete proof that the EOI is signed — that's higher
+  // confidence than a normal forward-jump.
+  if (
+    interest.pipelineStage === 'open' ||
+    interest.pipelineStage === 'details_sent' ||
+    interest.pipelineStage === 'in_communication' ||
+    interest.pipelineStage === 'eoi_sent'
+  ) {
+    await db
+      .update(interests)
+      .set({
+        pipelineStage: 'eoi_signed',
+        eoiStatus: 'signed',
+        dateEoiSigned: input.signedAt ?? new Date(),
+        updatedAt: new Date(),
+      })
+      .where(eq(interests.id, interestId));
+  } else {
+    // Past eoi_signed — just record the document, don't touch stage.
+    await db.update(interests).set({ updatedAt: new Date() }).where(eq(interests.id, interestId));
+  }
+
+  void createAuditLog({
+    portId,
+    userId: meta.userId,
+    action: 'create',
+    entityType: 'document',
+    entityId: doc.id,
+    metadata: {
+      kind: 'external_eoi_upload',
+      interestId,
+      title,
+      signerNames: input.signerNames ?? [],
+      signedAt: (input.signedAt ?? new Date()).toISOString(),
+      fileSizeBytes: fileData.size,
+    },
+    ipAddress: meta.ipAddress,
+    userAgent: meta.userAgent,
+  });
+
+  emitToRoom(`port:${portId}`, 'document:completed', { documentId: doc.id });
+
+  return { documentId: doc.id, fileId: fileRecord.id };
+}