diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2398ea5c..71a07ea4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 > acceptance are aligned for an actual 0.3.0 publication.
 
 ### Changed
+- Align `/parse` with Naruon's signed PDF DOM transport at a bounded 64 MiB.
+  The endpoint still validates authentication before multipart parsing and
+  rejects the first byte above the ceiling with `413`.
+
 - `/parse`를 언어 선택형 파서로 일반화: MinerU `-l japan`/`-m ocr` 하드코딩을 제거하고 optional form 필드 `language`(MinerU 3.4.4 공식 기본 `ch`, 공개 언어군/alias 검증)와 `mode`(`auto`/`ocr`/`txt`, 기본 `auto`)로 파라미터화. `mode=auto`는 born-digital PDF가 강제 OCR을 건너뛰도록 함. 기존 입력 `language=japan&mode=ocr`는 공식 규약대로 `ch`/`ocr`로 정규화됨.
 - OpenAPI 제목/설명, README, `ArticleNode.headline` 문서를 일반 문서용 (section heading) 표현으로 재구성하여 특정 언어/신문 가정을 소비자에게 노출하지 않도록 함. 응답 스키마 필드는 하위 호환을 위해 변경하지 않음.
 
diff --git a/docs/adr/0003-bounded-pdf-upload-transport.md b/docs/adr/0003-bounded-pdf-upload-transport.md
new file mode 100644
index 00000000..0a426bff
--- /dev/null
+++ b/docs/adr/0003-bounded-pdf-upload-transport.md
@@ -0,0 +1,44 @@
+# ADR-0003: Bounded PDF upload transport
+
+**Status:** Accepted
+**Date:** 2026-08-21
+**Decision owner:** NewsDOM maintainers
+**Scope:** Authenticated `POST /parse` upload boundary
+**Figma File ID:** N/A — sidecar API contract; no visual surface.
+
+## Context
+
+Naruon's direct PDF DOM upload contract is bounded at 64 MiB, but the owning
+NewsDOM sidecar still rejected the same customer PDF above 20 MiB. That
+cross-service mismatch made the equivalent email and manual workflows behave
+differently and caused a customer-visible failure after the request crossed a
+service boundary.
+
+## Decision
+
+Set `MAX_PARSE_UPLOAD_BYTES` to 64 MiB. Keep bearer authentication before
+multipart body parsing, the streaming first-byte-over-limit check, PDF
+signature validation, temporary-file cleanup, and the `413 Payload Too Large`
+response unchanged.
+
+Naruon remains the consumer-side owner of its signed persistence boundary. This
+ADR only changes the sidecar's transport ceiling; parser runtime, concurrency,
+storage quotas, and deployment capacity remain separate controls.
+
+## Consequences
+
+- Customers can use the same bounded 64 MiB expectation for direct and sidecar
+  PDF DOM ingestion.
+- A larger valid upload can reach the parser, so deployment capacity and parser
+  timeout controls remain mandatory.
+- No unbounded body read is introduced; the endpoint continues to stop on the
+  first byte above the limit.
+
+## References (APA 7th)
+
+Internet Engineering Task Force. (2022). *HTTP semantics (RFC 9110).* RFC
+  Editor. https://www.rfc-editor.org/rfc/rfc9110
+
+National Institute of Standards and Technology. (2025). *Secure software
+  development framework (SSDF) version 1.2* (NIST Special Publication 800-218
+  Rev. 1, Initial Public Draft). https://doi.org/10.6028/NIST.SP.800-218r1.ipd
diff --git a/docs/adr/README.md b/docs/adr/README.md
index 6efe928f..32eee56c 100644
--- a/docs/adr/README.md
+++ b/docs/adr/README.md
@@ -7,6 +7,8 @@ This directory contains Architecture Decision Records (ADRs) for the `newsdom-ap
 | ADR                                                       | Title                                         | Status   | Date       |
 | --------------------------------------------------------- | --------------------------------------------- | -------- | ---------- |
 | [0001](0001-defer-openssf-best-practices-enrollment.md)   | Defer OpenSSF Best Practices Enrollment       | Accepted | 2026-04-24 |
+| [0002](0002-single-maintainer-review-exception.md)        | Single-maintainer protected-branch review exception | Accepted | 2026-04-24 |
+| [0003](0003-bounded-pdf-upload-transport.md)              | Bounded PDF upload transport                  | Accepted | 2026-08-21 |
 
 ## ADR Status
 
diff --git a/docs/doctoring/bounded-pdf-upload-transport.md b/docs/doctoring/bounded-pdf-upload-transport.md
new file mode 100644
index 00000000..72b53818
--- /dev/null
+++ b/docs/doctoring/bounded-pdf-upload-transport.md
@@ -0,0 +1,21 @@
+# Doctoring record: bounded PDF upload transport
+
+**Observed gap:** The live NewsDOM sidecar accepted only 20 MiB while the
+Naruon direct PDF DOM contract allowed 64 MiB, so equivalent customer workflows
+were inconsistent.
+
+**Correction:** `MAX_PARSE_UPLOAD_BYTES` and its boundary tests now use 64 MiB.
+Authentication remains checked before multipart parsing, and streaming input
+still fails closed at the first byte over the bound.
+
+**Evidence:** `tests/test_parse_endpoint.py` covers the 64 MiB contract and the
+unknown-size streaming over-limit path. Full coverage and exact-head hosted
+checks remain required before merge.
+
+**References (APA 7th):**
+
+- Internet Engineering Task Force. (2022). *HTTP semantics (RFC 9110).* RFC
+  Editor. https://www.rfc-editor.org/rfc/rfc9110
+- National Institute of Standards and Technology. (2025). *Secure software
+  development framework (SSDF) version 1.2* (NIST Special Publication 800-218
+  Rev. 1, Initial Public Draft). https://doi.org/10.6028/NIST.SP.800-218r1.ipd
diff --git a/manual/api-reference.md b/manual/api-reference.md
index 7ceec967..f8bcf5a4 100644
--- a/manual/api-reference.md
+++ b/manual/api-reference.md
@@ -32,6 +32,10 @@ FastAPI는 OpenAPI 기반의 대화형 API 문서를 자동으로 생성합니
 #### 요청 매개변수 (Request Body)
 - **`file`** (`UploadFile`, 필수): 변환할 PDF 바이너리 파일 데이터 (`multipart/form-data`)
 
+PDF 파일은 최대 64 MiB까지 허용됩니다. 한도를 초과하면 서버가 임시 파일을
+MinerU에 전달하지 않고 `413 Payload Too Large`를 반환하므로, 고객은 PDF를
+분할한 뒤 각 파일을 다시 업로드해야 합니다.
+
 #### cURL 테스트 예제
 
 ```bash
diff --git a/src/newsdom_api/main.py b/src/newsdom_api/main.py
index f61aafc2..960a8637 100644
--- a/src/newsdom_api/main.py
+++ b/src/newsdom_api/main.py
@@ -41,7 +41,9 @@
 from .schemas import HealthResponse, ParseResponse, ReadinessResponse
 from .service import parse_pdf
 
-MAX_PARSE_UPLOAD_BYTES = 20 * 1024 * 1024
+# Keep the sidecar transport ceiling aligned with Naruon's direct PDF DOM
+# upload. The streaming read still rejects the first byte above this bound.
+MAX_PARSE_UPLOAD_BYTES = 64 * 1024 * 1024
 MAX_AUTHORIZATION_HEADER_BYTES = MAX_BEARER_HEADER_BYTES
 UNSUPPORTED_MEDIA_DETAIL = "Unsupported Media Type"
 PAYLOAD_TOO_LARGE_DETAIL = "Payload Too Large"
diff --git a/tests/test_parse_endpoint.py b/tests/test_parse_endpoint.py
index 1491ada0..89fce227 100644
--- a/tests/test_parse_endpoint.py
+++ b/tests/test_parse_endpoint.py
@@ -32,17 +32,35 @@ class _ReadTrackingUpload:
     filename = "fixture.pdf"
     size = 10 * 1024 * 1024
 
-    def __init__(self, payload: bytes):
+    def __init__(self, payload: bytes | int):
         self._payload = payload
         self._offset = 0
         self.read_sizes: list[int] = []
+        self.bytes_returned = 0
 
     async def read(self, size: int = -1) -> bytes:
         self.read_sizes.append(size)
-        if size < 0:
-            size = len(self._payload) - self._offset
-        chunk = self._payload[self._offset : self._offset + size]
+        if isinstance(self._payload, int):
+            remaining = self._payload - self._offset
+            if remaining <= 0:
+                return b""
+            if size < 0:
+                size = remaining
+            count = min(size, remaining)
+            prefix = b"%PDF-"
+            chunk = b""
+            if self._offset < len(prefix):
+                prefix_count = min(count, len(prefix) - self._offset)
+                chunk = prefix[self._offset : self._offset + prefix_count]
+                count -= prefix_count
+            if count:
+                chunk += b"x" * count
+        else:
+            if size < 0:
+                size = len(self._payload) - self._offset
+            chunk = self._payload[self._offset : self._offset + size]
         self._offset += len(chunk)
+        self.bytes_returned += len(chunk)
         return chunk
 
 
@@ -358,6 +376,29 @@ def fake_parse_pdf_bytes(file_path, filename, **kwargs):
     assert response.json()["detail"] == "Payload Too Large"
 
 
+def test_parse_endpoint_budget_matches_naruon_transport_contract():
+    """Keep the sidecar upload ceiling aligned with Naruon's PDF transport."""
+    assert MAX_PARSE_UPLOAD_BYTES == 64 * 1024 * 1024
+
+
+@pytest.mark.asyncio
+async def test_parse_endpoint_accepts_exact_upload_budget(monkeypatch):
+    """Accept a valid streamed PDF whose final byte is exactly at the limit."""
+    monkeypatch.setattr("newsdom_api.main._validate_pdf_structure", lambda _: None)
+    monkeypatch.setattr(
+        "newsdom_api.main.parse_pdf",
+        lambda file_path, filename, **kwargs: {"document_id": "fixture", "pages": []},
+    )
+
+    upload = _ReadTrackingUpload(MAX_PARSE_UPLOAD_BYTES)
+    upload.size = MAX_PARSE_UPLOAD_BYTES
+
+    result = await parse(upload)
+
+    assert result == {"document_id": "fixture", "pages": []}
+    assert upload.bytes_returned == MAX_PARSE_UPLOAD_BYTES
+
+
 @pytest.mark.asyncio
 async def test_parse_endpoint_rejects_large_file_without_size_metadata():
     upload = _ReadTrackingUpload(b"%PDF-" + (b"x" * MAX_PARSE_UPLOAD_BYTES))
diff --git a/tests/test_parse_upload_budget_contract.py b/tests/test_parse_upload_budget_contract.py
new file mode 100644
index 00000000..3665eaeb
--- /dev/null
+++ b/tests/test_parse_upload_budget_contract.py
@@ -0,0 +1,49 @@
+"""Exact streaming-boundary regressions for the public PDF upload budget."""
+
+import pytest
+from fastapi import HTTPException
+
+from newsdom_api.main import MAX_PARSE_UPLOAD_BYTES, parse
+
+
+class _VirtualPdfUpload:
+    """Stream a bounded synthetic PDF without allocating the full payload."""
+
+    content_type = "application/pdf"
+    filename = "fixture.pdf"
+    size = None
+
+    def __init__(self, total_bytes: int) -> None:
+        self.total_bytes = total_bytes
+        self.bytes_returned = 0
+
+    async def read(self, size: int = -1) -> bytes:
+        """Return at most ``size`` bytes while preserving a valid PDF prefix."""
+        remaining = self.total_bytes - self.bytes_returned
+        if remaining <= 0:
+            return b""
+        count = remaining if size < 0 else min(size, remaining)
+        prefix = b"%PDF-"
+        start = self.bytes_returned
+        chunk = b""
+        if start < len(prefix):
+            prefix_count = min(count, len(prefix) - start)
+            chunk = prefix[start : start + prefix_count]
+            count -= prefix_count
+        if count:
+            chunk += b"x" * count
+        self.bytes_returned += len(chunk)
+        return chunk
+
+
+@pytest.mark.asyncio
+async def test_streaming_upload_rejects_exact_first_byte_over_budget() -> None:
+    """Reject after consuming exactly the first byte beyond the 64 MiB ceiling."""
+    upload = _VirtualPdfUpload(MAX_PARSE_UPLOAD_BYTES + 1)
+
+    with pytest.raises(HTTPException) as exc_info:
+        await parse(upload)
+
+    assert exc_info.value.status_code == 413
+    assert exc_info.value.detail == "Payload Too Large"
+    assert upload.bytes_returned == MAX_PARSE_UPLOAD_BYTES + 1