diff --git a/application/agents/tool_executor.py b/application/agents/tool_executor.py
index 66be5d1a..18472612 100644
--- a/application/agents/tool_executor.py
+++ b/application/agents/tool_executor.py
@@ -53,6 +53,47 @@ def truncate_tool_result(value: Any) -> Any:
     return f"{text[:PERSISTED_RESULT_MAX_LEN]}..."
 
 
+# Control characters minus \t \n \r. NULs in particular are rejected by
+# Postgres text/jsonb, so one binary-carrying tool result would otherwise
+# kill every write lane it fans out to (conversation, activity log,
+# tool_call_attempts) at once.
+_CONTROL_CHARS = re.compile(r"[\x00-\x08\x0b\x0c\x0e-\x1f\x7f]")
+
+# Ceiling on the persisted full copy of a tool result (``result_full`` in
+# the conversation row and the ``tool_call_attempts`` result). Generous —
+# the LLM copy is bounded separately at TOOL_RESULT_MAX_TOKENS — but a
+# ceiling all the same: one uncapped result has reached 634k tokens.
+RESULT_FULL_MAX_CHARS = 400_000
+
+
+def sanitize_tool_result(value: Any) -> Any:
+    """Recursively strip NUL/control characters from strings in ``value``.
+
+    Applied once where a tool result enters the executor, so every
+    downstream consumer — the LLM copy, the conversation row, the
+    ``tool_call_attempts`` journal, the stream event — gets clean text.
+    """
+    if isinstance(value, str):
+        return _CONTROL_CHARS.sub("", value) if _CONTROL_CHARS.search(value) else value
+    if isinstance(value, dict):
+        return {sanitize_tool_result(k): sanitize_tool_result(v) for k, v in value.items()}
+    if isinstance(value, list):
+        return [sanitize_tool_result(item) for item in value]
+    if isinstance(value, tuple):
+        return tuple(sanitize_tool_result(item) for item in value)
+    return value
+
+
+def bound_result_full(text: str) -> str:
+    """Cap the persisted full-result copy at ``RESULT_FULL_MAX_CHARS``."""
+    if len(text) <= RESULT_FULL_MAX_CHARS:
+        return text
+    return (
+        text[:RESULT_FULL_MAX_CHARS]
+        + f"\n[... tool result truncated at persistence: {len(text)} chars ...]"
+    )
+
+
 def result_status(result: Any) -> str:
     """Derive the persisted status from a tool's result payload.
 
@@ -882,6 +923,11 @@ class ToolExecutor:
                 )
             raise
 
+        # Single fan-out point: from here ``result`` reaches the LLM copy,
+        # the conversation row, tool_call_attempts, and the stream event —
+        # sanitize once so every lane gets clean text.
+        result = sanitize_tool_result(result)
+
         get_artifact_id = getattr(tool, "get_artifact_id", None) if tool_data["name"] != "api_tool" else None
 
         artifact_id = None
@@ -898,7 +944,7 @@ class ToolExecutor:
         artifact_id = str(artifact_id).strip() if artifact_id is not None else ""
         if artifact_id:
             tool_call_data["artifact_id"] = artifact_id
-        result_full = str(result)
+        result_full = bound_result_full(str(result))
         tool_call_data["resolved_arguments"] = resolved_arguments
         tool_call_data["result_full"] = result_full
         tool_call_data["result"] = truncate_tool_result(result_full)
diff --git a/application/agents/tools/read_webpage.py b/application/agents/tools/read_webpage.py
index ea71076f..c8b25227 100644
--- a/application/agents/tools/read_webpage.py
+++ b/application/agents/tools/read_webpage.py
@@ -1,6 +1,107 @@
+import codecs
+
 from markdownify import markdownify
+
 from application.agents.tools.base import Tool
-from application.security.safe_url import UnsafeUserUrlError, pinned_request
+from application.security.safe_url import (
+    ResponseTooLargeError,
+    UnsafeUserUrlError,
+    pinned_fetch_bytes,
+)
+
+# Byte ceiling for a fetched page. One uncapped response (a PDF handed to
+# this tool on 07-17) produced a 634k-token "text" result that killed the
+# conversation save and every other write lane downstream.
+MAX_RESPONSE_BYTES = 10 * 1024 * 1024
+
+# Non-``text/*`` content types markdownify can still meaningfully convert
+# to text (any ``text/*`` is allowed by prefix). Anything else (PDFs,
+# images, archives, ...) must be refused with a clear error so the model
+# picks another tool instead of receiving binary-as-text.
+_ALLOWED_CONTENT_TYPES = frozenset(
+    {
+        "application/xhtml+xml",
+        "application/xml",
+        "application/json",
+        "application/ld+json",
+        "application/rss+xml",
+        "application/atom+xml",
+    }
+)
+
+# Magic prefixes of common binary formats, checked in case the server
+# omits or lies about the Content-Type header.
+_BINARY_MAGIC_PREFIXES = (
+    b"%PDF-",  # PDF
+    b"PK\x03\x04",  # zip / docx / xlsx
+    b"\x89PNG",  # PNG
+    b"GIF8",  # GIF
+    b"\xff\xd8\xff",  # JPEG
+    b"\x1f\x8b",  # gzip
+    b"OggS",  # ogg
+    b"\x00\x01\x00\x00",  # ttf
+)
+
+_UNSUPPORTED_CONTENT_HINT = (
+    "read_webpage only handles HTML/text pages; use a tool suited to this "
+    "file type instead."
+)
+
+
+def _declared_charset(content_type: str) -> str | None:
+    """Extract the ``charset`` parameter from a Content-Type header value."""
+    for part in content_type.split(";")[1:]:
+        key, _, value = part.strip().partition("=")
+        if key.strip().lower() == "charset" and value:
+            return value.strip("\"' ")
+    return None
+
+
+def _usable_charset(content_type: str) -> str | None:
+    """Return the declared charset if Python can actually decode with it."""
+    charset = _declared_charset(content_type)
+    if not charset:
+        return None
+    try:
+        codecs.lookup(charset)
+    except LookupError:
+        return None
+    return charset
+
+
+def _is_allowed_media_type(media_type: str) -> bool:
+    return media_type.startswith("text/") or media_type in _ALLOWED_CONTENT_TYPES
+
+
+def _looks_binary(content: bytes, *, trust_declared_charset: bool = False) -> bool:
+    """Sniff the first KB for binary magic numbers or NUL bytes.
+
+    The magic-prefix check is unconditional — a lying charset header must
+    not sneak a PDF through. The NUL check only applies when no usable
+    charset was declared: legitimate UTF-16 text is NUL-dense, and a
+    declared charset means the decode path (which strips NULs) handles it.
+    """
+    head = content[:1024]
+    if head.startswith(_BINARY_MAGIC_PREFIXES):
+        return True
+    if trust_declared_charset:
+        return False
+    return b"\x00" in head
+
+
+def _decode_body(content: bytes, content_type: str) -> str:
+    """Decode ``content`` with the declared charset, else UTF-8.
+
+    Never falls back to ``response.text``'s guesses: requests' RFC-2616
+    ISO-8859-1 default (text/* without charset) maps every raw byte 1:1,
+    which is exactly how a PDF once round-tripped into NUL-laden "text".
+    NULs are stripped after decoding (NUL is valid UTF-8, and the sniff
+    only sees the first KB) so the tool never returns them regardless of
+    caller.
+    """
+    charset = _usable_charset(content_type) or "utf-8"
+    return content.decode(charset, errors="replace").replace("\x00", "")
+
 
 class ReadWebpageTool(Tool):
     """
@@ -31,21 +132,42 @@ class ReadWebpageTool(Tool):
             return "Error: URL parameter is missing."
 
         try:
-            response = pinned_request(
-                "GET",
+            content, response = pinned_fetch_bytes(
                 url,
+                max_bytes=MAX_RESPONSE_BYTES,
                 headers={'User-Agent': 'DocsGPT-Agent/1.0'},
                 timeout=10,
             )
             response.raise_for_status()
 
-            html_content = response.text
+            content_type = response.headers.get("Content-Type", "")
+            media_type = content_type.split(";")[0].strip().lower()
+            if media_type and not _is_allowed_media_type(media_type):
+                return (
+                    f"Error: URL returned content type '{media_type}', which "
+                    f"cannot be converted to text. {_UNSUPPORTED_CONTENT_HINT}"
+                )
+            if _looks_binary(
+                content,
+                trust_declared_charset=_usable_charset(content_type) is not None,
+            ):
+                return (
+                    "Error: URL returned binary content, which cannot be "
+                    f"converted to text. {_UNSUPPORTED_CONTENT_HINT}"
+                )
+
+            html_content = _decode_body(content, content_type)
             markdown_content = markdownify(html_content, heading_style="ATX", newline_style="BACKSLASH")
 
             return markdown_content
 
         except UnsafeUserUrlError as e:
             return f"Error: URL validation failed - {e}"
+        except ResponseTooLargeError:
+            return (
+                f"Error: The page is too large to read (over "
+                f"{MAX_RESPONSE_BYTES // (1024 * 1024)} MB)."
+            )
         except Exception as e:
             return f"Error fetching URL {url}: {e}"
 
@@ -59,8 +181,9 @@ class ReadWebpageTool(Tool):
                 "description": (
                     "Fetch a webpage and return its content as clean Markdown "
                     "text. Use it whenever the user shares a URL or the answer "
-                    "depends on a specific page. Input must be a fully "
-                    "qualified URL."
+                    "depends on a specific page. Only works for HTML/text "
+                    "pages — not PDFs or other binary files. Input must be a "
+                    "fully qualified URL."
                 ),
                 "parameters": {
                     "type": "object",
diff --git a/application/api/answer/services/conversation_service.py b/application/api/answer/services/conversation_service.py
index 1ca64955..f116a274 100644
--- a/application/api/answer/services/conversation_service.py
+++ b/application/api/answer/services/conversation_service.py
@@ -21,6 +21,7 @@ from application.storage.db.repositories.conversations import (
     MessageUpdateOutcome,
 )
 from application.storage.db.session import db_readonly, db_session
+from application.utils import strip_null_bytes
 
 
 logger = logging.getLogger(__name__)
@@ -338,14 +339,18 @@ class ConversationService:
                 "error", f"{type(error).__name__}: {str(error)}"
             )
 
-        update_fields: Dict[str, Any] = {
-            "response": response,
-            "status": status,
-            "thought": thought,
-            "sources": sources,
-            "tool_calls": tool_calls or [],
-            "metadata": merged_metadata,
-        }
+        # Postgres rejects NUL in text and jsonb; a NUL-laden tool result
+        # reaching this transaction would lose the whole conversation save.
+        update_fields: Dict[str, Any] = strip_null_bytes(
+            {
+                "response": response,
+                "status": status,
+                "thought": thought,
+                "sources": sources,
+                "tool_calls": tool_calls or [],
+                "metadata": merged_metadata,
+            }
+        )
         if model_id is not None:
             update_fields["model_id"] = model_id
 
diff --git a/application/api/user/tasks.py b/application/api/user/tasks.py
index 7b45c7cc..fd577e24 100644
--- a/application/api/user/tasks.py
+++ b/application/api/user/tasks.py
@@ -1,6 +1,8 @@
 import logging
 from datetime import timedelta
 
+from sqlalchemy.exc import DataError
+
 from application.api.user.idempotency import with_idempotency
 from application.celery_init import celery
 from application.worker import (
@@ -233,7 +235,10 @@ def _emit_attachment_poison_event(task_name, bound):
     )
 
 
-@celery.task(**DURABLE_TASK)
+# ``dont_autoretry_for``: a DataError is deterministic (poison payload,
+# e.g. NUL bytes or an over-long value) — retrying re-fails identically
+# and multiplies log noise, so it goes straight to the failure path.
+@celery.task(**DURABLE_TASK, dont_autoretry_for=(DataError,))
 @with_idempotency(
     task_name="store_attachment", on_poison=_emit_attachment_poison_event,
 )
diff --git a/application/security/safe_url.py b/application/security/safe_url.py
index a4b9eed9..974f928f 100644
--- a/application/security/safe_url.py
+++ b/application/security/safe_url.py
@@ -79,6 +79,12 @@ class UnsafeUserUrlError(ValueError):
     """
 
 
+class ResponseTooLargeError(Exception):
+    """Raised by :func:`pinned_fetch_bytes` when a response body exceeds
+    the caller's byte ceiling (declared via ``Content-Length`` or found
+    during the bounded read)."""
+
+
 def _strip_ipv6_brackets(host: str) -> str:
     """Return ``host`` with surrounding ``[`` / ``]`` removed if present."""
 
@@ -348,6 +354,84 @@ def pinned_request(
         session.close()
 
 
+def pinned_fetch_bytes(
+    url: str,
+    *,
+    max_bytes: int,
+    headers: dict[str, str] | None = None,
+    timeout: float = 10.0,
+    allow_redirects: bool = False,
+) -> tuple[bytes, requests.Response]:
+    """GET ``url`` with SSRF pinning, streaming at most ``max_bytes`` of body.
+
+    The size limit is enforced twice: a declared ``Content-Length`` above
+    the ceiling is rejected before any body is read, and the streamed
+    read itself stops the moment the ceiling is crossed — a server that
+    lies about (or omits) ``Content-Length`` cannot bypass the cap.
+
+    Returns:
+        Tuple of the body bytes and the (already-closed) ``Response``,
+        kept for its status code and headers.
+
+    Raises:
+        UnsafeUserUrlError: If the URL fails the SSRF guard.
+        ResponseTooLargeError: If the body exceeds ``max_bytes``.
+        requests.RequestException: For network-level failures.
+    """
+
+    host, ip, parts = _validate_and_pick_ip(url)
+
+    netloc = f"{_url_userinfo_prefix(parts.netloc)}{_ip_to_url_host(ip)}"
+    if parts.port is not None:
+        netloc = f"{netloc}:{parts.port}"
+    pinned_url = urlunsplit(
+        (parts.scheme, netloc, parts.path, parts.query, parts.fragment)
+    )
+
+    request_headers = dict(headers or {})
+    host_header = host if parts.port is None else f"{host}:{parts.port}"
+    request_headers["Host"] = host_header
+
+    session = requests.Session()
+    if parts.scheme == "https":
+        session.mount("https://", _PinnedHostAdapter(host))
+    try:
+        response = session.request(
+            method="GET",
+            url=pinned_url,
+            headers=request_headers,
+            timeout=timeout,
+            allow_redirects=allow_redirects,
+            stream=True,
+        )
+        try:
+            # An error response's body is never used (callers
+            # raise_for_status) — skip the transfer and let the caller
+            # surface the more informative HTTP-status error.
+            if response.status_code >= 400:
+                return b"", response
+            declared = response.headers.get("Content-Length")
+            if declared and declared.isdigit() and int(declared) > max_bytes:
+                raise ResponseTooLargeError(
+                    f"response declares {declared} bytes, over the "
+                    f"{max_bytes}-byte limit"
+                )
+            chunks: list[bytes] = []
+            received = 0
+            for chunk in response.iter_content(chunk_size=65536):
+                received += len(chunk)
+                if received > max_bytes:
+                    raise ResponseTooLargeError(
+                        f"response body exceeds the {max_bytes}-byte limit"
+                    )
+                chunks.append(chunk)
+            return b"".join(chunks), response
+        finally:
+            response.close()
+    finally:
+        session.close()
+
+
 def pinned_post(
     url: str,
     *,
diff --git a/application/storage/db/repositories/attachments.py b/application/storage/db/repositories/attachments.py
index 08662920..eeddd5e9 100644
--- a/application/storage/db/repositories/attachments.py
+++ b/application/storage/db/repositories/attachments.py
@@ -8,6 +8,7 @@ from typing import Any, Optional
 from sqlalchemy import Connection, text
 
 from application.storage.db.base_repository import looks_like_uuid, row_to_dict
+from application.utils import strip_null_bytes
 
 
 _UPDATABLE_SCALARS = {
@@ -69,15 +70,21 @@ class AttachmentsRepository:
             ),
             {
                 "user_id": user_id,
-                "filename": filename,
+                "filename": strip_null_bytes(filename),
                 "upload_path": upload_path,
                 "mime_type": mime_type,
                 "size": size,
-                "content": content,
+                # A parsed document with embedded NULs (mislabeled binary)
+                # would otherwise fail the INSERT — Postgres rejects \x00.
+                "content": strip_null_bytes(content),
                 "token_count": token_count,
                 "openai_file_id": openai_file_id,
                 "google_file_uri": google_file_uri,
-                "metadata": json.dumps(metadata) if metadata is not None else None,
+                "metadata": (
+                    json.dumps(strip_null_bytes(metadata))
+                    if metadata is not None
+                    else None
+                ),
                 "legacy_mongo_id": legacy_mongo_id,
             },
         )
@@ -193,6 +200,7 @@ class AttachmentsRepository:
         set_clauses: list[str] = []
         params: dict = {"id": attachment_id, "user_id": user_id}
         for col, val in filtered.items():
+            val = strip_null_bytes(val)
             if col in _UPDATABLE_JSONB:
                 set_clauses.append(f"{col} = CAST(:{col} AS jsonb)")
                 params[col] = json.dumps(val) if val is not None else None
@@ -247,6 +255,7 @@ class AttachmentsRepository:
         set_clauses: list[str] = []
         params: dict = {"legacy_id": legacy_mongo_id, "user_id": user_id}
         for col, val in filtered.items():
+            val = strip_null_bytes(val)
             if col in _UPDATABLE_JSONB:
                 set_clauses.append(f"{col} = CAST(:{col} AS jsonb)")
                 params[col] = json.dumps(val) if val is not None else None
diff --git a/application/storage/db/repositories/stack_logs.py b/application/storage/db/repositories/stack_logs.py
index fc1a6387..a5ac17fc 100644
--- a/application/storage/db/repositories/stack_logs.py
+++ b/application/storage/db/repositories/stack_logs.py
@@ -15,9 +15,28 @@ from typing import Optional
 
 from application.storage.db.redaction import redact_secrets
 from application.storage.db.serialization import PGNativeJSONEncoder
+from application.utils import strip_null_bytes
 
 from sqlalchemy import Connection, text
 
+# Longest string kept inside ``stacks``. The scalar columns are truncated
+# by the caller, but stacks used to go in whole — one uncapped tool
+# result (634k tokens, 07-17) rode into the activity log through here.
+_STACKS_STRING_MAX_LEN = 10000
+
+
+def _bound_strings(value):
+    """Recursively truncate strings in ``value`` to ``_STACKS_STRING_MAX_LEN``."""
+    if isinstance(value, str):
+        if len(value) <= _STACKS_STRING_MAX_LEN:
+            return value
+        return value[:_STACKS_STRING_MAX_LEN] + "...[truncated]"
+    if isinstance(value, dict):
+        return {k: _bound_strings(v) for k, v in value.items()}
+    if isinstance(value, (list, tuple)):
+        return [_bound_strings(item) for item in value]
+    return value
+
 
 class StackLogsRepository:
     """Postgres-backed replacement for Mongo ``stack_logs`` collection."""
@@ -50,13 +69,16 @@ class StackLogsRepository:
             ),
             {
                 "activity_id": activity_id,
-                "endpoint": endpoint,
-                "level": level,
-                "user_id": user_id,
-                "api_key": api_key,
-                "query": query,
+                "endpoint": strip_null_bytes(endpoint),
+                "level": strip_null_bytes(level),
+                "user_id": strip_null_bytes(user_id),
+                "api_key": strip_null_bytes(api_key),
+                "query": strip_null_bytes(query),
                 "stacks": json.dumps(
-                    redact_secrets(stacks or []), cls=PGNativeJSONEncoder
+                    redact_secrets(
+                        _bound_strings(strip_null_bytes(stacks or []))
+                    ),
+                    cls=PGNativeJSONEncoder,
                 ),
                 "timestamp": timestamp,
             },
diff --git a/application/storage/db/repositories/tool_call_attempts.py b/application/storage/db/repositories/tool_call_attempts.py
index 0954d733..3ead533b 100644
--- a/application/storage/db/repositories/tool_call_attempts.py
+++ b/application/storage/db/repositories/tool_call_attempts.py
@@ -8,6 +8,12 @@ from typing import Any, Optional
 from sqlalchemy import Connection, text
 
 from application.storage.db.serialization import PGNativeJSONEncoder
+from application.utils import strip_null_bytes
+
+
+def _dump_jsonb(value: Any) -> str:
+    """Serialize for a jsonb CAST, stripping NULs Postgres would reject."""
+    return json.dumps(strip_null_bytes(value), cls=PGNativeJSONEncoder)
 
 
 class ToolCallAttemptsRepository:
@@ -56,7 +62,7 @@ class ToolCallAttemptsRepository:
                 "tool_id": tool_id,
                 "tool_name": tool_name,
                 "action_name": action_name,
-                "arguments": json.dumps(arguments if arguments is not None else {}, cls=PGNativeJSONEncoder),
+                "arguments": _dump_jsonb(arguments if arguments is not None else {}),
                 "message_id": message_id,
                 "user_id": user_id,
                 "agent_id": agent_id,
@@ -120,8 +126,8 @@ class ToolCallAttemptsRepository:
                 "tool_id": tool_id,
                 "tool_name": tool_name,
                 "action_name": action_name,
-                "arguments": json.dumps(arguments if arguments is not None else {}, cls=PGNativeJSONEncoder),
-                "result": json.dumps(result_payload, cls=PGNativeJSONEncoder),
+                "arguments": _dump_jsonb(arguments if arguments is not None else {}),
+                "result": _dump_jsonb(result_payload),
                 "message_id": message_id,
                 "user_id": user_id,
                 "agent_id": agent_id,
@@ -162,7 +168,7 @@ class ToolCallAttemptsRepository:
         params: dict[str, Any] = {
             "call_id": call_id,
             "status": status,
-            "result": json.dumps(result_payload, cls=PGNativeJSONEncoder),
+            "result": _dump_jsonb(result_payload),
         }
         if message_id is not None:
             sql += ", message_id = CAST(:message_id AS uuid)"
@@ -191,7 +197,10 @@ class ToolCallAttemptsRepository:
             "UPDATE tool_call_attempts SET status = 'failed', error = :error "
             "WHERE call_id = :call_id AND status = 'proposed'"
         )
-        params: dict[str, Any] = {"call_id": call_id, "error": error}
+        params: dict[str, Any] = {
+            "call_id": call_id,
+            "error": strip_null_bytes(error),
+        }
         if user_id is not None:
             sql += " AND user_id IS NOT DISTINCT FROM :user_id"
             params["user_id"] = user_id
diff --git a/application/streaming/message_journal.py b/application/streaming/message_journal.py
index 30503d03..ef0e94b4 100644
--- a/application/streaming/message_journal.py
+++ b/application/streaming/message_journal.py
@@ -21,6 +21,7 @@ from application.storage.db.session import db_readonly, db_session
 from application.streaming.broadcast_channel import Topic
 from application.streaming.event_replay import encode_pubsub_message
 from application.streaming.keys import message_topic_name
+from application.utils import strip_null_bytes as _strip_null_bytes
 
 logger = logging.getLogger(__name__)
 
@@ -34,29 +35,9 @@ DEFAULT_BATCH_SIZE = 16
 DEFAULT_BATCH_INTERVAL_MS = 100
 
 
-def _strip_null_bytes(value: Any) -> Any:
-    """Recursively strip ``\\x00`` from string keys/values in ``value``.
-
-    Postgres JSONB rejects the NUL escape; an LLM emitting a stray NUL
-    in a chunk would otherwise raise ``DataError`` at INSERT and the row
-    would be lost from the journal (live stream proceeds, reconnect
-    snapshot misses the chunk). Mirrors the strip already done in
-    ``parser/embedding_pipeline.py`` and
-    ``api/user/attachments/routes.py``.
-    """
-    if isinstance(value, str):
-        return value.replace("\x00", "") if "\x00" in value else value
-    if isinstance(value, dict):
-        return {
-            (k.replace("\x00", "") if isinstance(k, str) and "\x00" in k else k):
-            _strip_null_bytes(v)
-            for k, v in value.items()
-        }
-    if isinstance(value, list):
-        return [_strip_null_bytes(item) for item in value]
-    if isinstance(value, tuple):
-        return tuple(_strip_null_bytes(item) for item in value)
-    return value
+# NUL stripping lives in ``application.utils.strip_null_bytes`` (shared
+# with the conversation-finalize, activity-log, tool_call_attempts, and
+# attachments write lanes); imported above as ``_strip_null_bytes``.
 
 
 # Postgres SQLSTATE for a foreign-key violation. ``message_events`` has
diff --git a/application/utils.py b/application/utils.py
index 176f7720..eea3569c 100644
--- a/application/utils.py
+++ b/application/utils.py
@@ -55,6 +55,30 @@ def safe_filename(filename):
     return safe_name
 
 
+def strip_null_bytes(value):
+    """Recursively strip ``\\x00`` from string keys/values in ``value``.
+
+    Postgres rejects NUL in both text and jsonb; one NUL-laden payload
+    (e.g. a binary response mis-decoded to text) would otherwise raise
+    ``DataError`` and lose the whole row. Shared by the message journal,
+    conversation finalize, activity log, tool_call_attempts, and
+    attachments write lanes.
+    """
+    if isinstance(value, str):
+        return value.replace("\x00", "") if "\x00" in value else value
+    if isinstance(value, dict):
+        return {
+            (k.replace("\x00", "") if isinstance(k, str) and "\x00" in k else k):
+            strip_null_bytes(v)
+            for k, v in value.items()
+        }
+    if isinstance(value, list):
+        return [strip_null_bytes(item) for item in value]
+    if isinstance(value, tuple):
+        return tuple(strip_null_bytes(item) for item in value)
+    return value
+
+
 def num_tokens_from_string(string: str) -> int:
     encoding = get_encoding()
     if isinstance(string, str):
diff --git a/tests/agents/test_read_webpage_tool.py b/tests/agents/test_read_webpage_tool.py
index ae6e7ab4..f0560f00 100644
--- a/tests/agents/test_read_webpage_tool.py
+++ b/tests/agents/test_read_webpage_tool.py
@@ -1,11 +1,29 @@
 """Tests for application/agents/tools/read_webpage.py"""
 
-from unittest.mock import MagicMock, patch
+from unittest.mock import patch
 
 import pytest
 import requests
 
 from application.agents.tools.read_webpage import ReadWebpageTool
+from application.security.safe_url import ResponseTooLargeError
+
+
+class _FakeResponse:
+    def __init__(self, status_code: int = 200, headers=None):
+        self.status_code = status_code
+        self.headers = headers if headers is not None else {}
+
+    def raise_for_status(self):
+        if self.status_code >= 400:
+            raise requests.exceptions.HTTPError(str(self.status_code))
+
+
+def _fetch_result(body: bytes, content_type=None, status_code: int = 200):
+    headers = {}
+    if content_type is not None:
+        headers["Content-Type"] = content_type
+    return body, _FakeResponse(status_code=status_code, headers=headers)
 
 
 @pytest.fixture
@@ -25,48 +43,211 @@ class TestReadWebpageExecuteAction:
         assert "Error" in result
         assert "URL parameter is missing" in result
 
-    @patch("application.agents.tools.read_webpage.pinned_request")
-    def test_successful_fetch(self, mock_pinned_request, tool):
-        mock_resp = MagicMock()
-        mock_resp.status_code = 200
-        mock_resp.text = "<html><body><h1>Title</h1><p>Content</p></body></html>"
-        mock_pinned_request.return_value = mock_resp
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_successful_fetch(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            b"<html><body><h1>Title</h1><p>Content</p></body></html>",
+            content_type="text/html; charset=utf-8",
+        )
 
         result = tool.execute_action("read_webpage", url="https://example.com")
 
         assert "Title" in result
         assert "Content" in result
 
-    @patch("application.agents.tools.read_webpage.pinned_request")
-    def test_request_error(self, mock_pinned_request, tool):
-        mock_pinned_request.side_effect = requests.exceptions.ConnectionError("refused")
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_request_error(self, mock_fetch, tool):
+        mock_fetch.side_effect = requests.exceptions.ConnectionError("refused")
 
         result = tool.execute_action("read_webpage", url="https://example.com")
 
         assert "Error fetching URL" in result
 
-    @patch("application.agents.tools.read_webpage.pinned_request")
-    def test_ssrf_blocked(self, mock_pinned_request, tool):
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_ssrf_blocked(self, mock_fetch, tool):
         from application.security.safe_url import UnsafeUserUrlError
 
-        mock_pinned_request.side_effect = UnsafeUserUrlError("blocked")
+        mock_fetch.side_effect = UnsafeUserUrlError("blocked")
 
         result = tool.execute_action("read_webpage", url="http://169.254.169.254/")
 
         assert "Error" in result
         assert "validation failed" in result
 
-    @patch("application.agents.tools.read_webpage.pinned_request")
-    def test_http_error(self, mock_pinned_request, tool):
-        mock_resp = MagicMock()
-        mock_resp.raise_for_status.side_effect = requests.exceptions.HTTPError("404")
-        mock_pinned_request.return_value = mock_resp
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_http_error(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(b"", status_code=404)
 
         result = tool.execute_action("read_webpage", url="https://example.com/404")
 
         assert "Error fetching URL" in result
 
 
+@pytest.mark.unit
+class TestReadWebpageContentGuards:
+    """Regression tests for the PDF-as-text incident: a binary body must
+    never come back as NUL-laden 'markdown'."""
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_rejects_pdf_content_type(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            b"%PDF-1.7 binary...", content_type="application/pdf",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/doc.pdf")
+
+        assert result.startswith("Error")
+        assert "application/pdf" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_rejects_pdf_magic_without_content_type(self, mock_fetch, tool):
+        # No Content-Type header at all — the 07-17 incident shape.
+        mock_fetch.return_value = _fetch_result(b"%PDF-1.4\n%\xe2\xe3\xcf\xd3...")
+
+        result = tool.execute_action("read_webpage", url="https://example.com/doc.pdf")
+
+        assert result.startswith("Error")
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_rejects_nul_laden_body_despite_html_content_type(self, mock_fetch, tool):
+        # Mislabeled binary: content-type lies, the NUL sniff must catch it.
+        mock_fetch.return_value = _fetch_result(
+            b"<html>\x00\x00\x00binary\x00garbage\x00\x00</html>",
+            content_type="text/html",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/fake")
+
+        assert result.startswith("Error")
+        assert "\x00" not in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_rejects_octet_stream(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            b"anything", content_type="application/octet-stream",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/blob")
+
+        assert result.startswith("Error")
+        assert "application/octet-stream" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_response_too_large(self, mock_fetch, tool):
+        mock_fetch.side_effect = ResponseTooLargeError("body exceeds 10485760 bytes")
+
+        result = tool.execute_action("read_webpage", url="https://example.com/huge")
+
+        assert result.startswith("Error")
+        assert "large" in result.lower()
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_utf8_decoded_without_declared_charset(self, mock_fetch, tool):
+        # text/html with no charset param: requests' RFC-2616 ISO-8859-1
+        # fallback would mojibake this; we must default to UTF-8.
+        mock_fetch.return_value = _fetch_result(
+            "<html><body><p>café über</p></body></html>".encode("utf-8"),
+            content_type="text/html",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com")
+
+        assert "café über" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_declared_charset_respected(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            "<html><body><p>café</p></body></html>".encode("latin-1"),
+            content_type="text/html; charset=ISO-8859-1",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com")
+
+        assert "café" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_unknown_declared_charset_falls_back_to_utf8(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            "<html><body><p>ok</p></body></html>".encode("utf-8"),
+            content_type="text/html; charset=not-a-real-charset",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com")
+
+        assert "ok" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_text_plain_allowed(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            b"plain text document", content_type="text/plain",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/readme")
+
+        assert "plain text document" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_utf16_page_with_declared_charset_allowed(self, mock_fetch, tool):
+        # UTF-16 text is NUL-dense; a correct charset declaration must
+        # win over the NUL sniff (which is for undeclared/mislabeled bodies).
+        mock_fetch.return_value = _fetch_result(
+            "<html><body>Hello world</body></html>".encode("utf-16"),
+            content_type="text/html; charset=utf-16",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com")
+
+        assert "Hello world" in result
+        assert "\x00" not in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_pdf_magic_beats_declared_charset(self, mock_fetch, tool):
+        # The magic-prefix check stays unconditional: a lying
+        # ``text/html; charset=utf-8`` header must not sneak a PDF through.
+        mock_fetch.return_value = _fetch_result(
+            b"%PDF-1.7 binary...",
+            content_type="text/html; charset=utf-8",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/fake")
+
+        assert result.startswith("Error")
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_nuls_past_sniff_window_are_stripped(self, mock_fetch, tool):
+        # The sniff only sees the first KB; NULs beyond it must still
+        # never leave the tool (self-contained, not reliant on the
+        # executor's sanitizer).
+        body = b"<html><p>" + b"x" * 1100 + b"\x00\x00 tail</p></html>"
+        mock_fetch.return_value = _fetch_result(body, content_type="text/html")
+
+        result = tool.execute_action("read_webpage", url="https://example.com")
+
+        assert "\x00" not in result
+        assert "tail" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_text_csv_allowed(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            b"name,qty\nwidget,2", content_type="text/csv",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/data.csv")
+
+        assert "widget" in result
+
+    @patch("application.agents.tools.read_webpage.pinned_fetch_bytes")
+    def test_rss_feed_allowed(self, mock_fetch, tool):
+        mock_fetch.return_value = _fetch_result(
+            b"<rss><channel><title>Feed title</title></channel></rss>",
+            content_type="application/rss+xml",
+        )
+
+        result = tool.execute_action("read_webpage", url="https://example.com/feed")
+
+        assert "Feed title" in result
+
+
 @pytest.mark.unit
 class TestReadWebpageMetadata:
     def test_actions_metadata(self, tool):
diff --git a/tests/agents/test_tool_executor_sanitize.py b/tests/agents/test_tool_executor_sanitize.py
new file mode 100644
index 00000000..2cc87ec8
--- /dev/null
+++ b/tests/agents/test_tool_executor_sanitize.py
@@ -0,0 +1,60 @@
+"""Tests for tool-result sanitization at the executor fan-out point.
+
+``result_full`` fans out to the conversation row, ``tool_call_attempts``,
+and (via the executor's return value) the LLM copy — sanitizing at the
+source protects every lane at once.
+"""
+
+import pytest
+
+from application.agents.tool_executor import (
+    RESULT_FULL_MAX_CHARS,
+    bound_result_full,
+    sanitize_tool_result,
+)
+
+
+@pytest.mark.unit
+class TestSanitizeToolResult:
+    def test_strips_nul_bytes(self):
+        assert sanitize_tool_result("a\x00b\x00c") == "abc"
+
+    def test_strips_control_chars_keeps_whitespace(self):
+        assert (
+            sanitize_tool_result("line1\nline2\ttab\rret\x01\x08\x0b\x1f\x7fend")
+            == "line1\nline2\ttab\rret" + "end"
+        )
+
+    def test_clean_string_returned_unchanged(self):
+        s = "perfectly normal résumé text\nwith newlines"
+        assert sanitize_tool_result(s) is s
+
+    def test_recurses_into_dicts_including_keys(self):
+        got = sanitize_tool_result({"k\x00ey": {"inner": "v\x00al"}})
+        assert got == {"key": {"inner": "val"}}
+
+    def test_recurses_into_lists_and_tuples(self):
+        assert sanitize_tool_result(["a\x00", ("b\x00",)]) == ["a", ("b",)]
+
+    def test_non_string_scalars_pass_through(self):
+        for value in (42, 3.14, True, None, b"\x00raw"):
+            assert sanitize_tool_result(value) == value
+
+
+@pytest.mark.unit
+class TestBoundResultFull:
+    def test_short_text_unchanged(self):
+        assert bound_result_full("short") == "short"
+
+    def test_text_at_limit_unchanged(self):
+        s = "x" * RESULT_FULL_MAX_CHARS
+        assert bound_result_full(s) == s
+
+    def test_oversized_text_truncated_with_marker(self):
+        s = "x" * (RESULT_FULL_MAX_CHARS + 1000)
+        got = bound_result_full(s)
+        assert len(got) < len(s)
+        assert "truncated" in got
+        # The marker names the original size so the audit copy is honest
+        # about what was dropped.
+        assert str(len(s)) in got
diff --git a/tests/agents/tools/test_read_webpage_errors.py b/tests/agents/tools/test_read_webpage_errors.py
index 05848b17..5f708f97 100644
--- a/tests/agents/tools/test_read_webpage_errors.py
+++ b/tests/agents/tools/test_read_webpage_errors.py
@@ -11,7 +11,7 @@ class TestReadWebpageErrors:
 
         tool = ReadWebpageTool(config={})
         with patch(
-            "application.agents.tools.read_webpage.pinned_request",
+            "application.agents.tools.read_webpage.pinned_fetch_bytes",
             side_effect=requests.exceptions.RequestException("bad url"),
         ):
             got = tool.execute_action(
@@ -20,17 +20,21 @@ class TestReadWebpageErrors:
         assert "Error fetching URL" in got
 
     def test_generic_exception_returns_error_string(self):
+        from unittest.mock import MagicMock
+
         from application.agents.tools.read_webpage import ReadWebpageTool
 
         tool = ReadWebpageTool(config={})
+        response = MagicMock()
+        response.headers = {"Content-Type": "text/html"}
+        response.raise_for_status.return_value = None
         with patch(
             "application.agents.tools.read_webpage.markdownify",
             side_effect=RuntimeError("boom"),
         ), patch(
-            "application.agents.tools.read_webpage.pinned_request",
-        ) as mock_pinned_request:
-            mock_pinned_request.return_value.text = "<h1>hi</h1>"
-            mock_pinned_request.return_value.raise_for_status.return_value = None
+            "application.agents.tools.read_webpage.pinned_fetch_bytes",
+            return_value=(b"<h1>hi</h1>", response),
+        ):
             got = tool.execute_action(
                 "read_webpage", url="https://example.com/",
             )
diff --git a/tests/api/answer/services/test_conversation_service.py b/tests/api/answer/services/test_conversation_service.py
index e016bcb5..70c05e41 100644
--- a/tests/api/answer/services/test_conversation_service.py
+++ b/tests/api/answer/services/test_conversation_service.py
@@ -474,6 +474,46 @@ class TestFinalizeMessage:
         assert len(msgs[0]["sources"][0]["text"]) == 1000
         assert msgs[0]["metadata"]["foo"] == "bar"
 
+    def test_finalize_strips_null_bytes(self, pg_conn):
+        """A NUL-laden tool result (07-17 PDF incident) must not kill the
+        conversation save — Postgres rejects \\x00 in text and jsonb."""
+        from application.api.answer.services.conversation_service import (
+            ConversationService,
+        )
+        from application.storage.db.repositories.conversations import (
+            ConversationsRepository,
+            MessageUpdateOutcome,
+        )
+
+        user = "u-fin-nul"
+        with _patch_db(pg_conn):
+            svc = ConversationService()
+            res = svc.save_user_question(
+                conversation_id=None,
+                question="q",
+                decoded_token={"sub": user},
+            )
+            assert svc.finalize_message(
+                res["message_id"],
+                "answer\x00with\x00nuls",
+                thought="th\x00ought",
+                sources=[{"text": "s\x00rc", "title": "t\x00itle"}],
+                tool_calls=[
+                    {"name": "read_webpage", "result_full": "pdf\x00garbage\x00"}
+                ],
+                metadata={"k\x00ey": "v\x00al"},
+                status="complete",
+            ) is MessageUpdateOutcome.UPDATED
+
+        msgs = ConversationsRepository(pg_conn).get_messages(
+            res["conversation_id"],
+        )
+        assert msgs[0]["response"] == "answerwithnuls"
+        assert msgs[0]["thought"] == "thought"
+        assert msgs[0]["sources"][0]["text"] == "src"
+        assert msgs[0]["tool_calls"][0]["result_full"] == "pdfgarbage"
+        assert msgs[0]["metadata"] == {"key": "val"}
+
     def test_finalizes_failed_records_error(self, pg_conn):
         from application.api.answer.services.conversation_service import (
             ConversationService,
diff --git a/tests/api/user/test_tasks.py b/tests/api/user/test_tasks.py
index adb13638..e9094577 100644
--- a/tests/api/user/test_tasks.py
+++ b/tests/api/user/test_tasks.py
@@ -182,6 +182,16 @@ class TestStoreAttachmentTask:
         mock_worker.assert_called_once_with(ANY, {"file": "info"}, "user1")
         assert result == {"status": "ok"}
 
+    @pytest.mark.unit
+    def test_data_errors_are_not_autoretried(self):
+        # A DataError is deterministic (poison payload) — retrying it five
+        # times just multiplies log noise for the same terminal failure.
+        from sqlalchemy.exc import DataError
+
+        from application.api.user.tasks import store_attachment
+
+        assert DataError in getattr(store_attachment, "dont_autoretry_for", ())
+
 
 class TestProcessAgentWebhookTask:
     @pytest.mark.unit
diff --git a/tests/security/test_safe_url.py b/tests/security/test_safe_url.py
index 32e6eaa1..301f6f6c 100644
--- a/tests/security/test_safe_url.py
+++ b/tests/security/test_safe_url.py
@@ -15,8 +15,10 @@ import pytest
 import requests
 
 from application.security.safe_url import (
+    ResponseTooLargeError,
     UnsafeUserUrlError,
     _PinnedHTTPSTransport,
+    pinned_fetch_bytes,
     pinned_httpx_client,
     pinned_post,
     validate_user_base_url,
@@ -725,3 +727,130 @@ def test_pinned_httpx_transport_refuses_unexpected_host(monkeypatch):
         pass
     finally:
         client.close()
+
+
+# pinned_fetch_bytes: streamed, size-bounded GET
+
+
+class _StreamStubResponse:
+    """Streamed drop-in for ``requests.Response`` (``iter_content``-based)."""
+
+    def __init__(self, body: bytes = b"", status_code: int = 200, headers=None):
+        self._body = body
+        self.status_code = status_code
+        self.headers = headers if headers is not None else {}
+        self.closed = False
+
+    def iter_content(self, chunk_size=1):
+        for i in range(0, len(self._body), chunk_size):
+            yield self._body[i:i + chunk_size]
+
+    def close(self):
+        self.closed = True
+
+    def raise_for_status(self):
+        if self.status_code >= 400:
+            raise requests.exceptions.HTTPError(str(self.status_code))
+
+
+def _capture_stream_send(monkeypatch, response: _StreamStubResponse):
+    """Replace ``Session.send`` with a stub returning ``response``."""
+
+    captured: dict = {}
+
+    def _send(self, prepared, **kwargs):
+        captured["prepared"] = prepared
+        captured["send_kwargs"] = kwargs
+        return response
+
+    monkeypatch.setattr(requests.Session, "send", _send)
+    return captured
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_returns_body_and_response(monkeypatch):
+    body = b"<html><body>hello</body></html>"
+    stub = _StreamStubResponse(body, headers={"Content-Type": "text/html"})
+    captured = _capture_stream_send(monkeypatch, stub)
+    with mock.patch("socket.getaddrinfo", return_value=_addrinfo("93.184.216.34")):
+        content, response = pinned_fetch_bytes(
+            "http://example.com/page", max_bytes=1024,
+        )
+    assert content == body
+    assert response.headers["Content-Type"] == "text/html"
+    # The request must stream (no full-body buffering by requests) and
+    # still carry the pinned-IP URL rewrite + original Host header.
+    assert captured["send_kwargs"].get("stream") is True
+    assert captured["prepared"].url == "http://93.184.216.34/page"
+    assert captured["prepared"].headers["Host"] == "example.com"
+    # Response closed before the session is torn down.
+    assert stub.closed is True
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_rejects_declared_content_length_over_limit(monkeypatch):
+    stub = _StreamStubResponse(
+        b"x" * 100, headers={"Content-Length": "100"},
+    )
+    _capture_stream_send(monkeypatch, stub)
+    with mock.patch("socket.getaddrinfo", return_value=_addrinfo("93.184.216.34")):
+        with pytest.raises(ResponseTooLargeError):
+            pinned_fetch_bytes("http://example.com/big", max_bytes=10)
+    assert stub.closed is True
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_rejects_oversized_body_without_content_length(monkeypatch):
+    # No Content-Length header — the limit must be enforced during the
+    # bounded read, not just from the declared size.
+    stub = _StreamStubResponse(b"x" * 100)
+    _capture_stream_send(monkeypatch, stub)
+    with mock.patch("socket.getaddrinfo", return_value=_addrinfo("93.184.216.34")):
+        with pytest.raises(ResponseTooLargeError):
+            pinned_fetch_bytes("http://example.com/big", max_bytes=10)
+    assert stub.closed is True
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_body_exactly_at_limit_passes(monkeypatch):
+    stub = _StreamStubResponse(b"x" * 10, headers={"Content-Length": "10"})
+    _capture_stream_send(monkeypatch, stub)
+    with mock.patch("socket.getaddrinfo", return_value=_addrinfo("93.184.216.34")):
+        content, _ = pinned_fetch_bytes("http://example.com/ok", max_bytes=10)
+    assert content == b"x" * 10
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_rejects_unsafe_url():
+    with pytest.raises(UnsafeUserUrlError):
+        pinned_fetch_bytes("http://127.0.0.1/latest/meta-data", max_bytes=10)
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_skips_body_read_on_error_status(monkeypatch):
+    # An error response's body is dead weight — don't spend up to
+    # max_bytes of transfer on it, and don't let its size trump the
+    # more informative HTTP-status error in the caller.
+    stub = _StreamStubResponse(
+        b"x" * 100, status_code=404, headers={"Content-Length": "100"},
+    )
+    _capture_stream_send(monkeypatch, stub)
+    with mock.patch("socket.getaddrinfo", return_value=_addrinfo("93.184.216.34")):
+        content, response = pinned_fetch_bytes(
+            "http://example.com/missing", max_bytes=10,
+        )
+    assert content == b""
+    assert response.status_code == 404
+    assert stub.closed is True
+
+
+@pytest.mark.unit
+def test_pinned_fetch_bytes_passes_headers(monkeypatch):
+    stub = _StreamStubResponse(b"ok")
+    captured = _capture_stream_send(monkeypatch, stub)
+    with mock.patch("socket.getaddrinfo", return_value=_addrinfo("93.184.216.34")):
+        pinned_fetch_bytes(
+            "http://example.com/", max_bytes=10,
+            headers={"User-Agent": "DocsGPT-Agent/1.0"},
+        )
+    assert captured["prepared"].headers["User-Agent"] == "DocsGPT-Agent/1.0"
diff --git a/tests/storage/db/repositories/test_attachments.py b/tests/storage/db/repositories/test_attachments.py
index 6420fb26..ad2a2626 100644
--- a/tests/storage/db/repositories/test_attachments.py
+++ b/tests/storage/db/repositories/test_attachments.py
@@ -58,6 +58,20 @@ class TestCreate:
         )
         assert doc["legacy_mongo_id"] == "507f1f77bcf86cd799439011"
 
+    def test_create_strips_null_bytes_from_content_and_metadata(self, pg_conn):
+        # A parsed document with embedded NULs (mislabeled binary) must
+        # not kill the INSERT — Postgres rejects \x00 in text and jsonb.
+        repo = _repo(pg_conn)
+        doc = repo.create(
+            "u",
+            "weird.pdf",
+            "/uploads/weird.pdf",
+            content="parsed\x00text\x00here",
+            metadata={"transcript_lang\x00": "en\x00"},
+        )
+        assert doc["content"] == "parsedtexthere"
+        assert doc["metadata"] == {"transcript_lang": "en"}
+
 
 class TestGet:
     def test_get_existing(self, pg_conn):
diff --git a/tests/storage/db/repositories/test_stack_logs.py b/tests/storage/db/repositories/test_stack_logs.py
index 44325e7d..300ad5e1 100644
--- a/tests/storage/db/repositories/test_stack_logs.py
+++ b/tests/storage/db/repositories/test_stack_logs.py
@@ -126,3 +126,48 @@ class TestInsert:
         assert data["prompt_tokens"] == 10
         assert data["generated_tokens"] == 5
         assert data["token_budget"] == 1000
+
+    def test_strips_null_bytes_from_stacks(self, pg_conn):
+        # Postgres jsonb rejects the NUL escape — a NUL-laden tool result in the
+        # stacks would otherwise kill the whole activity-log INSERT (and
+        # with it the error visibility for the incident that caused it).
+        repo = _repo(pg_conn)
+        repo.insert(
+            activity_id="act-nul",
+            level="error",
+            query="q\x00uery",
+            stacks=[{"component": "tool", "data": {"result": "pdf\x00junk\x00"}}],
+        )
+        row = pg_conn.execute(
+            text("SELECT query, stacks FROM stack_logs WHERE activity_id = 'act-nul'")
+        ).fetchone()
+        mapping = dict(row._mapping)
+        assert mapping["query"] == "query"
+        assert mapping["stacks"][0]["data"]["result"] == "pdfjunk"
+
+    def test_bounds_oversized_strings_in_stacks(self, pg_conn):
+        # The 07-17 incident put a 634k-token tool result into stacks
+        # whole; long strings must be truncated before insert.
+        repo = _repo(pg_conn)
+        repo.insert(
+            activity_id="act-big",
+            level="info",
+            stacks=[{"component": "tool", "data": {"result": "x" * 50000}}],
+        )
+        row = pg_conn.execute(
+            text("SELECT stacks FROM stack_logs WHERE activity_id = 'act-big'")
+        ).fetchone()
+        stored = dict(row._mapping)["stacks"][0]["data"]["result"]
+        assert len(stored) <= 10100  # 10k cap plus a short truncation marker
+
+    def test_short_strings_in_stacks_untouched(self, pg_conn):
+        repo = _repo(pg_conn)
+        repo.insert(
+            activity_id="act-small",
+            level="info",
+            stacks=[{"component": "tool", "data": {"result": "ok"}}],
+        )
+        row = pg_conn.execute(
+            text("SELECT stacks FROM stack_logs WHERE activity_id = 'act-small'")
+        ).fetchone()
+        assert dict(row._mapping)["stacks"][0]["data"]["result"] == "ok"
diff --git a/tests/storage/db/repositories/test_tool_call_attempts.py b/tests/storage/db/repositories/test_tool_call_attempts.py
new file mode 100644
index 00000000..b536067d
--- /dev/null
+++ b/tests/storage/db/repositories/test_tool_call_attempts.py
@@ -0,0 +1,68 @@
+"""Tests for ToolCallAttemptsRepository against a real Postgres instance."""
+
+from __future__ import annotations
+
+from sqlalchemy import text
+
+from application.storage.db.repositories.tool_call_attempts import (
+    ToolCallAttemptsRepository,
+)
+
+
+def _repo(conn) -> ToolCallAttemptsRepository:
+    return ToolCallAttemptsRepository(conn)
+
+
+class TestNulSafety:
+    """Postgres jsonb rejects \\u0000; a NUL-laden tool result must not
+    lose the attempt row (07-17 PDF incident)."""
+
+    def test_record_proposed_strips_nul_from_arguments(self, pg_conn):
+        repo = _repo(pg_conn)
+        assert repo.record_proposed(
+            "call-nul-1", "read_webpage", "read_webpage",
+            {"url": "https://x\x00.example"},
+            user_id="u1",
+        )
+        row = pg_conn.execute(
+            text(
+                "SELECT arguments FROM tool_call_attempts "
+                "WHERE call_id = 'call-nul-1'"
+            )
+        ).fetchone()
+        assert dict(row._mapping)["arguments"] == {"url": "https://x.example"}
+
+    def test_mark_executed_strips_nul_from_result(self, pg_conn):
+        repo = _repo(pg_conn)
+        assert repo.record_proposed(
+            "call-nul-2", "read_webpage", "read_webpage", {}, user_id="u1",
+        )
+        assert repo.mark_executed(
+            "call-nul-2", "pdf\x00garbage\x00text", user_id="u1",
+        )
+        row = pg_conn.execute(
+            text(
+                "SELECT status, result FROM tool_call_attempts "
+                "WHERE call_id = 'call-nul-2'"
+            )
+        ).fetchone()
+        mapping = dict(row._mapping)
+        assert mapping["status"] == "confirmed"  # no message_id → confirmed
+        assert mapping["result"]["result"] == "pdfgarbagetext"
+
+    def test_upsert_executed_strips_nul_from_result(self, pg_conn):
+        repo = _repo(pg_conn)
+        repo.upsert_executed(
+            "call-nul-3", "read_webpage", "read_webpage",
+            {"q": "a\x00b"}, "res\x00ult",
+            user_id="u1",
+        )
+        row = pg_conn.execute(
+            text(
+                "SELECT arguments, result FROM tool_call_attempts "
+                "WHERE call_id = 'call-nul-3'"
+            )
+        ).fetchone()
+        mapping = dict(row._mapping)
+        assert mapping["arguments"] == {"q": "ab"}
+        assert mapping["result"]["result"] == "result"
diff --git a/tests/test_remaining_coverage.py b/tests/test_remaining_coverage.py
index 91c0a7a4..6899cb81 100644
--- a/tests/test_remaining_coverage.py
+++ b/tests/test_remaining_coverage.py
@@ -582,12 +582,12 @@ class TestReadWebpageErrors:
 
         tool = ReadWebpageTool({})
         with patch(
-            "application.agents.tools.read_webpage.pinned_request"
-        ) as mock_pinned_request:
+            "application.agents.tools.read_webpage.pinned_fetch_bytes"
+        ) as mock_fetch:
             mock_response = MagicMock()
             mock_response.raise_for_status.return_value = None
-            mock_response.text = "<html><body>test</body></html>"
-            mock_pinned_request.return_value = mock_response
+            mock_response.headers = {"Content-Type": "text/html"}
+            mock_fetch.return_value = (b"<html><body>test</body></html>", mock_response)
             with patch(
                 "application.agents.tools.read_webpage.markdownify",
                 side_effect=Exception("parse error"),