diff --git a/planning/deferred-work.md b/planning/deferred-work.md
index 0a74b00..667f7b1 100644
--- a/planning/deferred-work.md
+++ b/planning/deferred-work.md
@@ -27,11 +27,6 @@ Items raised in reviews that are real but not actionable now.
 
 ## Deferred from: code review of story-1-2 (2026-05-13)
 
-- **Charset parser robustness** — quoted whitespace, mismatched quotes, multi-`charset=` directives, substring false-positives (e.g. `boundary` containing `charset=`). (`src/httpware/response.py:20-25`)
-- **Header name/value validation** — `with_header` / `with_headers` accept CR/LF (injection), `None`, empty string. CRLF lands with the `Redactor` middleware (Story 5.3); the rest is a generic input-validation pass. (`src/httpware/request.py:21-23,37-39`)
-- **URL validation** — `with_url("")` accepts empty; `base_url` has no trailing-slash normalization in config (`AsyncClient._resolve_url` does `base.rstrip('/')` so the practical impact is reduced). (`src/httpware/request.py:25-27`, `src/httpware/config.py:34`)
-- **`with_query(None)` handling** — type signature is `Mapping[str, str]`; a runtime `None` slips past typing and breaks downstream iteration with no guard. (`src/httpware/request.py:33-35`)
-- **`Timeout` / `Limits` negative-value validation** — no `__post_init__` guard; nonsensical values silently accepted. (`src/httpware/config.py:11-27`)
 - **Multi-valued query params** — `Mapping[str, str]` cannot express `?tag=a&tag=b`. Type widening needed. (`src/httpware/request.py:16`)
 - **Streaming / async-iterable request bodies** — `body: bytes | None` only. Revisit in streaming work (Story 4.1). (`src/httpware/request.py:18`)
 - **`@final` to prevent subclassing** — frozen+slots subclassing is fragile. No current subclasser; defer until needed. (`src/httpware/request.py`, `response.py`, `config.py`)
diff --git a/src/httpware/client.py b/src/httpware/client.py
index 4e70dce..ab6c401 100644
--- a/src/httpware/client.py
+++ b/src/httpware/client.py
@@ -119,7 +119,7 @@ def _resolve_url(self, path: str) -> str:
         base = self._config.base_url
         if base is None:
             return path
-        return f"{base.rstrip('/')}/{path.lstrip('/')}"
+        return f"{base}/{path.lstrip('/')}"
 
     def _build_request(
         self,
diff --git a/src/httpware/config.py b/src/httpware/config.py
index 91fefdd..bfa49bf 100644
--- a/src/httpware/config.py
+++ b/src/httpware/config.py
@@ -17,6 +17,13 @@ class Timeout:
     write: float = 30.0
     pool: float = 5.0
 
+    def __post_init__(self) -> None:
+        for attr in ("connect", "read", "write", "pool"):
+            value = getattr(self, attr)
+            if value < 0:
+                msg = f"Timeout.{attr} must be non-negative (got {value})"
+                raise ValueError(msg)
+
 
 @dataclass(frozen=True, slots=True)
 class Limits:
@@ -26,6 +33,17 @@ class Limits:
     max_keepalive_connections: int = 20
     keepalive_expiry: float = 5.0
 
+    def __post_init__(self) -> None:
+        if self.max_connections < 0:
+            msg = f"max_connections must be non-negative (got {self.max_connections})"
+            raise ValueError(msg)
+        if self.max_keepalive_connections < 0:
+            msg = f"max_keepalive_connections must be non-negative (got {self.max_keepalive_connections})"
+            raise ValueError(msg)
+        if self.keepalive_expiry < 0:
+            msg = f"keepalive_expiry must be non-negative (got {self.keepalive_expiry})"
+            raise ValueError(msg)
+
 
 @dataclass(frozen=True, slots=True)
 class ClientConfig:
@@ -38,3 +56,14 @@ class ClientConfig:
     limits: Limits = field(default_factory=Limits)
     decoder: ResponseDecoder = field(default_factory=PydanticDecoder)
     middleware: tuple[Middleware, ...] = ()
+
+    def __post_init__(self) -> None:
+        if self.base_url is not None:
+            if not isinstance(self.base_url, str):
+                msg = "base_url must be a non-empty string or None"
+                raise ValueError(msg)
+            normalized = self.base_url.rstrip("/")
+            if not normalized:
+                msg = "base_url must be a non-empty string or None"
+                raise ValueError(msg)
+            object.__setattr__(self, "base_url", normalized)
diff --git a/src/httpware/request.py b/src/httpware/request.py
index 218c663..b5e3413 100644
--- a/src/httpware/request.py
+++ b/src/httpware/request.py
@@ -6,6 +6,18 @@
 from typing import Any, Self
 
 
+def _validate_header_or_cookie(name: str, value: str, *, kind: str) -> None:
+    if not isinstance(name, str) or not isinstance(value, str):
+        msg = f"{kind} name and value must be str"
+        raise TypeError(msg)
+    if not name or not value:
+        msg = f"{kind} name and value must be non-empty"
+        raise ValueError(msg)
+    if any(c in name or c in value for c in ("\r", "\n")):
+        msg = f"{kind} name and value must not contain CR or LF"
+        raise ValueError(msg)
+
+
 @dataclass(frozen=True, slots=True)
 class Request:
     """Immutable HTTP request value type."""
@@ -18,6 +30,23 @@ class Request:
     body: bytes | None = None
     extensions: Mapping[str, Any] = field(default_factory=dict)
 
+    def __post_init__(self) -> None:
+        if not isinstance(self.url, str):
+            msg = "url must be str"
+            raise TypeError(msg)
+        if not self.url:
+            msg = "url must be non-empty"
+            raise ValueError(msg)
+        for field_name in ("headers", "params", "cookies", "extensions"):
+            field_value = getattr(self, field_name)
+            if not isinstance(field_value, Mapping):
+                msg = f"{field_name} must be a Mapping (got {type(field_value).__name__})"
+                raise TypeError(msg)
+        for name, value in self.headers.items():
+            _validate_header_or_cookie(name, value, kind="header")
+        for name, value in self.cookies.items():
+            _validate_header_or_cookie(name, value, kind="cookie")
+
     def with_header(self, name: str, value: str) -> Self:
         """Return a copy with the given header added or replaced."""
         return dataclasses.replace(self, headers={**self.headers, name: value})
diff --git a/src/httpware/response.py b/src/httpware/response.py
index 6c9069b..568491d 100644
--- a/src/httpware/response.py
+++ b/src/httpware/response.py
@@ -21,7 +21,7 @@ def _parse_charset(content_type: str) -> str | None:
     for raw in content_type.split(";"):
         part = raw.strip()
         if part.lower().startswith(_CHARSET_PREFIX):
-            return part[len(_CHARSET_PREFIX) :].strip().strip('"').strip("'")
+            return part[len(_CHARSET_PREFIX) :].strip().strip('"').strip("'").strip()
     return None
 
 
diff --git a/tests/test_config.py b/tests/test_config.py
index 03a5535..b0ded35 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -50,3 +50,69 @@ def test_client_config_is_frozen() -> None:
     cfg = ClientConfig()
     with pytest.raises(FrozenInstanceError):
         cfg.base_url = "https://example.com"  # ty: ignore[invalid-assignment]
+
+
+@pytest.mark.parametrize("field", ["connect", "read", "write", "pool"])
+def test_timeout_rejects_negative(field: str) -> None:
+    with pytest.raises(ValueError, match=rf"Timeout\.{field} must be non-negative"):
+        Timeout(**{field: -1.0})
+
+
+def test_timeout_accepts_zero() -> None:
+    # Zero is a valid sentinel (fail immediately on this phase).
+    Timeout(connect=0.0, read=0.0, write=0.0, pool=0.0)
+
+
+@pytest.mark.parametrize("field", ["max_connections", "max_keepalive_connections"])
+def test_limits_rejects_negative_int(field: str) -> None:
+    with pytest.raises(ValueError, match=f"{field} must be non-negative"):
+        Limits(**{field: -1})
+
+
+def test_limits_rejects_negative_keepalive_expiry() -> None:
+    with pytest.raises(ValueError, match="keepalive_expiry must be non-negative"):
+        Limits(keepalive_expiry=-0.5)
+
+
+def test_limits_accepts_zero() -> None:
+    Limits(max_connections=0, max_keepalive_connections=0, keepalive_expiry=0.0)
+
+
+def test_client_config_strips_trailing_slash_from_base_url() -> None:
+    cfg = ClientConfig(base_url="https://api.example.com/")
+    assert cfg.base_url == "https://api.example.com"
+
+
+def test_client_config_leaves_base_url_without_trailing_slash() -> None:
+    cfg = ClientConfig(base_url="https://api.example.com")
+    assert cfg.base_url == "https://api.example.com"
+
+
+def test_client_config_strips_multiple_trailing_slashes() -> None:
+    cfg = ClientConfig(base_url="https://api.example.com///")
+    assert cfg.base_url == "https://api.example.com"
+
+
+def test_client_config_allows_none_base_url() -> None:
+    cfg = ClientConfig(base_url=None)
+    assert cfg.base_url is None
+
+
+def test_client_config_rejects_empty_base_url() -> None:
+    with pytest.raises(ValueError, match="base_url must be a non-empty string or None"):
+        ClientConfig(base_url="")
+
+
+def test_client_config_rejects_slash_only_base_url() -> None:
+    with pytest.raises(ValueError, match="base_url must be a non-empty string or None"):
+        ClientConfig(base_url="/")
+
+
+def test_client_config_rejects_multiple_slashes_only_base_url() -> None:
+    with pytest.raises(ValueError, match="base_url must be a non-empty string or None"):
+        ClientConfig(base_url="///")
+
+
+def test_client_config_rejects_non_str_base_url() -> None:
+    with pytest.raises(ValueError, match="base_url must be a non-empty string or None"):
+        ClientConfig(base_url=123)  # ty: ignore[invalid-argument-type]
diff --git a/tests/test_request.py b/tests/test_request.py
index 47b746d..fc7879b 100644
--- a/tests/test_request.py
+++ b/tests/test_request.py
@@ -143,3 +143,84 @@ class _Marker:
     new = r.with_extension("marker", marker)
     assert new.extensions == {"marker": marker}
     assert new.extensions["marker"] is marker
+
+
+def test_request_rejects_empty_url() -> None:
+    with pytest.raises(ValueError, match="url must be non-empty"):
+        Request(method="GET", url="")
+
+
+def test_request_rejects_non_str_url() -> None:
+    with pytest.raises(TypeError, match="url must be str"):
+        Request(method="GET", url=None)  # ty: ignore[invalid-argument-type]
+
+
+def test_with_url_rejects_empty() -> None:
+    r = Request(method="GET", url="/")
+    with pytest.raises(ValueError, match="url must be non-empty"):
+        r.with_url("")
+
+
+def test_request_rejects_header_with_crlf_in_value() -> None:
+    with pytest.raises(ValueError, match="header name and value must not contain CR or LF"):
+        Request(method="GET", url="/", headers={"X-Trace": "value\r\nInjected: yes"})
+
+
+def test_request_rejects_header_with_crlf_in_name() -> None:
+    with pytest.raises(ValueError, match="header name and value must not contain CR or LF"):
+        Request(method="GET", url="/", headers={"X-Bad\r\nInjected": "value"})
+
+
+def test_request_rejects_empty_header_name() -> None:
+    with pytest.raises(ValueError, match="header name and value must be non-empty"):
+        Request(method="GET", url="/", headers={"": "value"})
+
+
+def test_request_rejects_empty_header_value() -> None:
+    with pytest.raises(ValueError, match="header name and value must be non-empty"):
+        Request(method="GET", url="/", headers={"X-Trace": ""})
+
+
+def test_request_rejects_non_str_header_value() -> None:
+    with pytest.raises(TypeError, match="header name and value must be str"):
+        Request(method="GET", url="/", headers={"X-Trace": None})  # ty: ignore[invalid-argument-type]
+
+
+def test_request_rejects_cookie_with_crlf() -> None:
+    with pytest.raises(ValueError, match="cookie name and value must not contain CR or LF"):
+        Request(method="GET", url="/", cookies={"session": "abc\r\nSet-Cookie: evil"})
+
+
+def test_request_rejects_empty_cookie_value() -> None:
+    with pytest.raises(ValueError, match="cookie name and value must be non-empty"):
+        Request(method="GET", url="/", cookies={"session": ""})
+
+
+def test_with_header_rejects_crlf() -> None:
+    r = Request(method="GET", url="/")
+    with pytest.raises(ValueError, match="header name and value must not contain CR or LF"):
+        r.with_header("X-Trace", "value\r\n")
+
+
+def test_with_cookie_rejects_crlf() -> None:
+    r = Request(method="GET", url="/")
+    with pytest.raises(ValueError, match="cookie name and value must not contain CR or LF"):
+        r.with_cookie("session", "abc\r\n")
+
+
+@pytest.mark.parametrize("field_name", ["headers", "params", "cookies", "extensions"])
+def test_request_rejects_none_mapping_field(field_name: str) -> None:
+    with pytest.raises(TypeError, match=f"{field_name} must be a Mapping"):
+        Request(method="GET", url="/", **{field_name: None})  # ty: ignore[invalid-argument-type]
+
+
+@pytest.mark.parametrize("field_name", ["headers", "params", "cookies", "extensions"])
+def test_request_rejects_list_mapping_field(field_name: str) -> None:
+    with pytest.raises(TypeError, match=f"{field_name} must be a Mapping"):
+        Request(method="GET", url="/", **{field_name: []})  # ty: ignore[invalid-argument-type]
+
+
+def test_with_query_none_raises() -> None:
+    r = Request(method="GET", url="/")
+    with pytest.raises(TypeError, match="params must be a Mapping"):
+        r.with_query(None)  # ty: ignore[invalid-argument-type]
diff --git a/tests/test_response.py b/tests/test_response.py
index 192a711..a7fc42e 100644
--- a/tests/test_response.py
+++ b/tests/test_response.py
@@ -6,6 +6,7 @@
 import pytest
 
 from httpware import Response
+from httpware.response import _parse_charset
 
 
 def test_response_is_frozen() -> None:
@@ -68,6 +69,24 @@ def test_response_text_strips_quotes_around_charset(content_type: str) -> None:
     assert resp.text == "café"
 
 
+def test_response_text_strips_inner_whitespace_in_quoted_charset() -> None:
+    # Direct parser check: inner whitespace inside the quoted value must not survive.
+    # (Python's codec registry happens to normalize whitespace, masking the bug
+    # end-to-end on most charsets; verify the parser itself returns a clean value.)
+    assert _parse_charset('text/plain; charset=" iso-8859-1 "') == "iso-8859-1"
+
+    # End-to-end smoke: decoding the Latin-1 body must yield the original text.
+    body = "café".encode("iso-8859-1")
+    resp = Response(
+        status=HTTPStatus.OK,
+        headers={"content-type": 'text/plain; charset=" iso-8859-1 "'},
+        content=body,
+        url="/",
+        elapsed=0.0,
+    )
+    assert resp.text == "café"
+
+
 def test_response_text_falls_back_to_utf8_on_unknown_charset() -> None:
     resp = Response(
         status=200,