diff --git a/formal-semantics.md b/formal-semantics.md
index ac93684..c5b81b7 100644
--- a/formal-semantics.md
+++ b/formal-semantics.md
@@ -246,6 +246,12 @@ Abstract: URI × Literal × Maybe Literal × Maybe Literal × Maybe Literal →
 Python:   def execute(self, url: URIRef, value: Literal, title: Literal = None, description: Literal = None, fragment: Literal = None) -> Any
 ```
 
+**ldh-AddFile** - Add file (binary) to LinkedDataHub document via multipart RDF/POST
+```
+Abstract: URI × Literal × Literal × Maybe Literal × Maybe Literal → Any
+Python:   def execute(self, url: URIRef, file_path: Literal, title: Literal, description: Literal = None, content_type: Literal = None) -> Any
+```
+
 **ldh-RemoveBlock** - Remove content block from LinkedDataHub document
 ```
 Abstract: URI × Maybe URI → Any  
diff --git a/pyproject.toml b/pyproject.toml
index ccad399..bfbd786 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,6 +24,7 @@ dependencies = [
     "openai",
     "mcp[cli]==1.10.1",
     "pydantic-settings",
+    "urllib3",
 ]
 
 [project.urls]
diff --git a/src/web_algebra/client.py b/src/web_algebra/client.py
index f9dc187..1a4e3d2 100644
--- a/src/web_algebra/client.py
+++ b/src/web_algebra/client.py
@@ -1,4 +1,5 @@
-from typing import Optional
+from typing import Optional, Tuple
+import hashlib
 import ssl
 import json
 import time
@@ -10,6 +11,7 @@
 from http.client import HTTPResponse
 from rdflib import Graph
 from rdflib.plugins.sparql.parser import parseQuery
+from urllib3.filepost import encode_multipart_formdata
 
 
 MEDIA_TYPES = {
@@ -194,6 +196,124 @@ def patch(self, url: str, sparql_update: str) -> HTTPResponse:
         return self.opener.open(request)
 
 
+class FileClient:
+    """Multipart RDF/POST file upload for LinkedDataHub file resources.
+
+    Files are not Linked Data — request bodies are bytes with a Content-Type
+    rather than RDF graphs — so they get their own client surface instead
+    of being grafted onto `LinkedDataClient`. Auth and TLS setup duplicate
+    `LinkedDataClient` / `SPARQLClient` by convention: each client in this
+    module configures its own ssl_context + opener inline.
+
+    Wire format matches LinkedDataHub's `bin/add-file.sh` script: a
+    multipart/form-data body using LDH's RDF/POST dialect where each
+    `pu=<predicate>` form field is paired with the next `ol=<literal>` or
+    `ou=<uri>` field, sharing a blank-node subject named via `sb=`. The
+    file body itself is carried as a multipart file part labelled `ol`
+    with the supplied Content-Type. LDH stores the bytes under its
+    built-in `/uploads/{sha1}` namespace and appends the file's RDF
+    description (filename, MIME type, sha1, title) to the target document.
+    """
+
+    _NFO_FILE_NAME = "http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#fileName"
+    _NFO_FILE_DATA_OBJECT = "http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#FileDataObject"
+    _DCT_TITLE = "http://purl.org/dc/terms/title"
+    _DCT_DESCRIPTION = "http://purl.org/dc/terms/description"
+    _RDF_TYPE = "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
+
+    def __init__(
+        self,
+        cert_pem_path: Optional[str] = None,
+        cert_password: Optional[str] = None,
+        verify_ssl: bool = True,
+    ):
+        """Initialize TLS context + opener; mirrors `LinkedDataClient.__init__`."""
+        self.ssl_context = ssl.create_default_context()
+
+        if cert_pem_path and cert_password:
+            self.ssl_context.load_cert_chain(
+                certfile=cert_pem_path, password=cert_password
+            )
+
+        if not verify_ssl:
+            self.ssl_context.check_hostname = False
+            self.ssl_context.verify_mode = ssl.CERT_NONE
+
+        self.opener = urllib.request.build_opener(
+            urllib.request.HTTPSHandler(context=self.ssl_context),
+            HTTPRedirectHandler308(),
+            RetryAfterHandler(),
+        )
+
+        self.opener.addheaders = [
+            (
+                "User-Agent",
+                "Web-Algebra/1.0 (LinkedData Processing System; https://github.com/atomgraph/Web-Algebra)",
+            )
+        ]
+
+    def add_file(
+        self,
+        target_url: str,
+        file_body: bytes,
+        content_type: str,
+        title: str,
+        description: Optional[str] = None,
+        filename: Optional[str] = None,
+    ) -> Tuple[HTTPResponse, str]:
+        """RDF/POST a file to `target_url`.
+
+        :param target_url: The document URI the file's RDF description is
+            appended to. Note this is *not* the URI the file ends up at —
+            LDH stores the bytes under its own `/uploads/{sha1}` namespace
+            regardless of `target_url`.
+        :param file_body: Raw file bytes.
+        :param content_type: MIME type of the file (e.g. `image/png`).
+        :param title: `dct:title` literal.
+        :param description: Optional `dct:description` literal.
+        :param filename: Optional filename for the multipart part's
+            `Content-Disposition`. Defaults to `"upload"` when absent;
+            LDH does not depend on this value for URI minting.
+        :return: `(HTTPResponse, sha1_hex)`. The sha1 is computed over
+            `file_body` client-side so callers can construct the resulting
+            `<base>/uploads/{sha1}` URI without parsing the response body.
+        """
+        sha1 = hashlib.sha1(file_body).hexdigest()
+
+        # `encode_multipart_formdata` accepts a list of `(name, value)`
+        # tuples — duplicates allowed, order preserved. A plain string/bytes
+        # value becomes a form field; a `(filename, body, content_type)`
+        # tuple becomes a file part. RDF/POST relies on this ordering
+        # because each `pu=<predicate>` field is paired with the next
+        # `ol=<literal>` / `ou=<uri>` field by LDH's parser.
+        fields: list[tuple[str, object]] = [
+            ("rdf", ""),
+            ("sb", "file"),
+            ("pu", self._NFO_FILE_NAME),
+            ("ol", (filename or "upload", file_body, content_type)),
+            ("pu", self._DCT_TITLE),
+            ("ol", title),
+            ("pu", self._RDF_TYPE),
+            ("ou", self._NFO_FILE_DATA_OBJECT),
+        ]
+        if description:
+            fields.extend([
+                ("pu", self._DCT_DESCRIPTION),
+                ("ol", description),
+            ])
+
+        body, content_type_header = encode_multipart_formdata(fields)
+        headers = {
+            "Content-Type": content_type_header,
+            "Accept": "text/turtle",
+        }
+        request = urllib.request.Request(
+            target_url, data=body, headers=headers, method="POST"
+        )
+        response = self.opener.open(request)
+        return response, sha1
+
+
 class SPARQLClient:
     def __init__(
         self,
diff --git a/src/web_algebra/operations/linkeddatahub/add_file.py b/src/web_algebra/operations/linkeddatahub/add_file.py
new file mode 100644
index 0000000..b10bd47
--- /dev/null
+++ b/src/web_algebra/operations/linkeddatahub/add_file.py
@@ -0,0 +1,228 @@
+from typing import Any, Optional
+import logging
+import mimetypes
+import urllib.parse
+from pathlib import Path
+
+from mcp import types
+from rdflib import Literal, URIRef
+from rdflib.namespace import XSD
+from rdflib.query import Result
+
+from web_algebra.client import FileClient
+from web_algebra.json_result import JSONResult
+from web_algebra.mcp_tool import MCPTool
+from web_algebra.operation import Operation
+
+
+class AddFile(Operation, MCPTool):
+    """RDF/POST a file to a LinkedDataHub document, returning the minted upload URI.
+
+    The file's RDF description (`nfo:FileDataObject` + filename + MIME type +
+    sha1 + title) is appended to the target document; the file bytes
+    themselves are stored by LDH at `<base>/uploads/{sha1}` under its
+    built-in upload namespace, independent of the target document's URI.
+
+    Unlike the rest of the `ldh-Add*` family, this op does not subclass
+    `POST` — file upload uses `multipart/form-data` with LDH's RDF/POST
+    dialect rather than an N-triples body, so it carries its own
+    `FileClient` instance instead of inheriting `LinkedDataClient` plumbing.
+    """
+
+    def model_post_init(self, __context: Any) -> None:
+        self.client = FileClient(
+            cert_pem_path=getattr(self.settings, "cert_pem_path", None),
+            cert_password=getattr(self.settings, "cert_password", None),
+            verify_ssl=False,
+        )
+
+    @classmethod
+    def name(cls):
+        return "ldh-AddFile"
+
+    @classmethod
+    def description(cls) -> str:
+        return """Adds a file to a LinkedDataHub document via multipart RDF/POST.
+
+        Appends `a nfo:FileDataObject ; nfo:fileName ; dct:title ; ...`
+        to the target document and stores the file bytes at
+        `<base>/uploads/{sha1}` (LDH's built-in upload namespace).
+
+        Arguments:
+        - `url` — URI of the target document to add the file's description to.
+        - `file` — absolute local file path. The bytes are read and streamed
+          to the server.
+        - `title` — human-readable title (`dct:title`).
+        - `description` — optional description (`dct:description`).
+        - `content_type` — optional MIME-type override; auto-detected from
+          the file path if absent.
+
+        Returns a result with `url` (the minted `<base>/uploads/{sha1}` URI
+        the file resource is now addressable at) and `status` (HTTP status
+        code) bindings.
+        """
+
+    @classmethod
+    def inputSchema(cls) -> dict:
+        return {
+            "type": "object",
+            "properties": {
+                "url": {
+                    "type": "string",
+                    "description": "Target document URI to add the file's description to.",
+                },
+                "file": {
+                    "type": "string",
+                    "description": "Absolute local file path. The bytes are read and uploaded.",
+                },
+                "title": {
+                    "type": "string",
+                    "description": "Title of the file (dct:title).",
+                },
+                "description": {
+                    "type": "string",
+                    "description": "Optional description (dct:description).",
+                },
+                "content_type": {
+                    "type": "string",
+                    "description": "Optional MIME-type override; auto-detected from path if absent.",
+                },
+            },
+            "required": ["url", "file", "title"],
+        }
+
+    def execute(
+        self,
+        url: URIRef,
+        file_path: Literal,
+        title: Literal,
+        description: Optional[Literal] = None,
+        content_type: Optional[Literal] = None,
+    ) -> Result:
+        """Pure function: RDF/POST a file from disk with RDFLib terms."""
+        if not isinstance(url, URIRef):
+            raise TypeError(
+                f"AddFile.execute expects url to be URIRef, got {type(url)}"
+            )
+        if not isinstance(file_path, Literal):
+            raise TypeError(
+                f"AddFile.execute expects file_path to be Literal, got {type(file_path)}"
+            )
+        if not isinstance(title, Literal):
+            raise TypeError(
+                f"AddFile.execute expects title to be Literal, got {type(title)}"
+            )
+        if description is not None and not isinstance(description, Literal):
+            raise TypeError(
+                f"AddFile.execute expects description to be Literal or None, got {type(description)}"
+            )
+        if content_type is not None and not isinstance(content_type, Literal):
+            raise TypeError(
+                f"AddFile.execute expects content_type to be Literal or None, got {type(content_type)}"
+            )
+
+        path_str = str(file_path)
+        with open(path_str, "rb") as f:
+            body = f.read()
+
+        ct: Optional[str] = str(content_type) if content_type is not None else None
+        if ct is None:
+            ct, _ = mimetypes.guess_type(path_str)
+        if ct is None:
+            ct = "application/octet-stream"
+
+        url_str = str(url)
+        logging.info(
+            "RDF/POSTing file %s (%d bytes, %s) to <%s>",
+            path_str, len(body), ct, url_str,
+        )
+
+        response, sha1 = self.client.add_file(
+            target_url=url_str,
+            file_body=body,
+            content_type=ct,
+            title=str(title),
+            description=str(description) if description is not None else None,
+            filename=Path(path_str).name,
+        )
+
+        # The minted file URI lives at `<scheme>://<host>/uploads/<sha1>`
+        # regardless of which target document we RDF/POSTed to. Reconstruct
+        # from the target URL's host so callers don't need to thread the
+        # base URL through separately.
+        parsed = urllib.parse.urlparse(url_str)
+        file_uri = f"{parsed.scheme}://{parsed.netloc}/uploads/{sha1}"
+
+        logging.info("AddFile status %s → <%s>", response.status, file_uri)
+
+        return JSONResult(
+            vars=["status", "url"],
+            bindings=[
+                {
+                    "status": Literal(response.status, datatype=XSD.integer),
+                    "url": URIRef(file_uri),
+                }
+            ],
+        )
+
+    def execute_json(self, arguments: dict, variable_stack: list = []) -> Result:
+        """JSON execution: process arguments with strict type checking."""
+        url_data = Operation.process_json(
+            self.settings, arguments["url"], self.context, variable_stack
+        )
+        if not isinstance(url_data, URIRef):
+            raise TypeError(
+                f"ldh-AddFile expects 'url' to be URIRef, got {type(url_data)}"
+            )
+
+        file_data = Operation.process_json(
+            self.settings, arguments["file"], self.context, variable_stack
+        )
+        file_literal = self.to_string_literal(file_data)
+
+        title_data = Operation.process_json(
+            self.settings, arguments["title"], self.context, variable_stack
+        )
+        title_literal = self.to_string_literal(title_data)
+
+        description_literal: Optional[Literal] = None
+        if "description" in arguments:
+            description_data = Operation.process_json(
+                self.settings, arguments["description"], self.context, variable_stack
+            )
+            description_literal = self.to_string_literal(description_data)
+
+        content_type_literal: Optional[Literal] = None
+        if "content_type" in arguments:
+            content_type_data = Operation.process_json(
+                self.settings, arguments["content_type"], self.context, variable_stack
+            )
+            content_type_literal = self.to_string_literal(content_type_data)
+
+        return self.execute(
+            url_data,
+            file_literal,
+            title_literal,
+            description_literal,
+            content_type_literal,
+        )
+
+    def mcp_run(self, arguments: dict, context: Any = None) -> Any:
+        """MCP execution: plain args → plain results."""
+        url = URIRef(arguments["url"])
+        file_path = Literal(arguments["file"], datatype=XSD.string)
+        title = Literal(arguments["title"], datatype=XSD.string)
+        description = (
+            Literal(arguments["description"], datatype=XSD.string)
+            if "description" in arguments
+            else None
+        )
+        content_type = (
+            Literal(arguments["content_type"], datatype=XSD.string)
+            if "content_type" in arguments
+            else None
+        )
+
+        result = self.execute(url, file_path, title, description, content_type)
+        url_binding = result.bindings[0]["url"]
+        return [types.TextContent(type="text", text=f"File added: {url_binding}")]
diff --git a/tests/unit/test_ldh_add_file.py b/tests/unit/test_ldh_add_file.py
new file mode 100644
index 0000000..9ad2a1c
--- /dev/null
+++ b/tests/unit/test_ldh_add_file.py
@@ -0,0 +1,68 @@
+"""Spec: formal-semantics.md "ldh-AddFile - Add file (binary) to LinkedDataHub document via multipart RDF/POST"
+Abstract: URI × Literal × Literal × Maybe Literal × Maybe Literal → Any
+Python:   def execute(self, url: URIRef, file_path: Literal, title: Literal,
+                      description: Literal = None, content_type: Literal = None) -> Any
+"""
+
+from __future__ import annotations
+
+import pytest
+from rdflib import Literal, URIRef
+
+from web_algebra.operation import Operation
+
+
+class TestLDHAddFilePure:
+    def test_wrong_url_type_raises(self, settings):
+        op = Operation.get("ldh-AddFile")(settings=settings)
+        with pytest.raises(TypeError):
+            op.execute(
+                Literal("not-a-uri"),
+                Literal("/abs/path.png"),
+                Literal("Title"),
+            )
+
+    def test_wrong_file_path_type_raises(self, settings):
+        op = Operation.get("ldh-AddFile")(settings=settings)
+        with pytest.raises(TypeError):
+            op.execute(
+                URIRef("https://example.org/"),
+                URIRef("not-a-literal"),
+                Literal("Title"),
+            )
+
+    def test_wrong_title_type_raises(self, settings):
+        op = Operation.get("ldh-AddFile")(settings=settings)
+        with pytest.raises(TypeError):
+            op.execute(
+                URIRef("https://example.org/"),
+                Literal("/abs/path.png"),
+                URIRef("not-a-literal"),
+            )
+
+    def test_wrong_description_type_raises(self, settings):
+        op = Operation.get("ldh-AddFile")(settings=settings)
+        with pytest.raises(TypeError):
+            op.execute(
+                URIRef("https://example.org/"),
+                Literal("/abs/path.png"),
+                Literal("Title"),
+                description=URIRef("not-a-literal"),
+            )
+
+    def test_wrong_content_type_type_raises(self, settings):
+        op = Operation.get("ldh-AddFile")(settings=settings)
+        with pytest.raises(TypeError):
+            op.execute(
+                URIRef("https://example.org/"),
+                Literal("/abs/path.png"),
+                Literal("Title"),
+                content_type=URIRef("not-a-literal"),
+            )
+
+
+@pytest.mark.ldh
+class TestLDHAddFileLive:
+    @pytest.mark.skip(reason="UNCLEAR(spec): return type `Any`. Covered by integration LDH composition fixture instead.")
+    def test_basic(self, settings_with_auth):
+        pass
diff --git a/uv.lock b/uv.lock
index 409e08a..7e0102b 100644
--- a/uv.lock
+++ b/uv.lock
@@ -863,6 +863,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/17/69/cd203477f944c353c31bade965f880aa1061fd6bf05ded0726ca845b6ff7/typing_inspection-0.4.1-py3-none-any.whl", hash = "sha256:389055682238f53b04f7badcb49b989835495a96700ced5dab2d8feae4b26f51", size = 14552, upload-time = "2025-05-21T18:55:22.152Z" },
 ]
 
+[[package]]
+name = "urllib3"
+version = "2.7.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/53/0c/06f8b233b8fd13b9e5ee11424ef85419ba0d8ba0b3138bf360be2ff56953/urllib3-2.7.0.tar.gz", hash = "sha256:231e0ec3b63ceb14667c67be60f2f2c40a518cb38b03af60abc813da26505f4c", size = 433602, upload-time = "2026-05-07T16:13:18.596Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/7f/3e/5db95bcf282c52709639744ca2a8b149baccf648e39c8cc87553df9eae0c/urllib3-2.7.0-py3-none-any.whl", hash = "sha256:9fb4c81ebbb1ce9531cce37674bbc6f1360472bc18ca9a553ede278ef7276897", size = 131087, upload-time = "2026-05-07T16:13:17.151Z" },
+]
+
 [[package]]
 name = "uvicorn"
 version = "0.35.0"
@@ -879,13 +888,14 @@ wheels = [
 
 [[package]]
 name = "web-algebra"
-version = "1.0.0"
+version = "1.1.0"
 source = { editable = "." }
 dependencies = [
     { name = "mcp", extra = ["cli"] },
     { name = "openai" },
     { name = "pydantic-settings" },
     { name = "rdflib" },
+    { name = "urllib3" },
 ]
 
 [package.dev-dependencies]
@@ -900,6 +910,7 @@ requires-dist = [
     { name = "openai" },
     { name = "pydantic-settings" },
     { name = "rdflib", specifier = "==7.0.0" },
+    { name = "urllib3" },
 ]
 
 [package.metadata.requires-dev]