From 3c3dfd59b72c83988f0448383d9e684bf171039d Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 18:50:14 +0300
Subject: [PATCH 1/8] docs: add PR2 TDD plan for config UX & security
 validation

Per-task TDD steps covering UX-1, UX-2, UX-3, SEC-1, SEC-2, SEC-3 (plus folded
TEST-NEW-1 and TEST-NEW-6) from the 2026-06-05 audit. Task ordering accounts
for one cross-task interaction: Task 5 (SEC-2) adds super().__post_init__()
to FastAPIConfig.__post_init__ which Task 1 (UX-1) restructures first.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../plans/2026-06-05-pr2-config-security.md   | 1003 +++++++++++++++++
 1 file changed, 1003 insertions(+)
 create mode 100644 planning/plans/2026-06-05-pr2-config-security.md

diff --git a/planning/plans/2026-06-05-pr2-config-security.md b/planning/plans/2026-06-05-pr2-config-security.md
new file mode 100644
index 0000000..f319532
--- /dev/null
+++ b/planning/plans/2026-06-05-pr2-config-security.md
@@ -0,0 +1,1003 @@
+# PR2 — Config UX & Security Validation Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Land six config-layer fixes from the 2026-06-05 audit (UX-1, UX-2, UX-3, SEC-1, SEC-2, SEC-3 + folded TEST-NEW-1 and TEST-NEW-6) in one PR.
+
+**Architecture:** Each fix is a small TDD cycle. The work all happens at config-construction time or at the user-facing helper layer — no instrument lifecycle changes. Tasks are ordered to land additive UX improvements first (UX-1, UX-2, UX-3), then the security validators (SEC-1, SEC-2, SEC-3) which are slightly more cross-cutting (SEC-2 introduces an `OpenTelemetryConfig.__post_init__` that interacts with the FastAPIConfig override touched in Task 1).
+
+**Tech Stack:** Python 3.10+, `uv` workspace, `pytest` (with `pytest-asyncio`), `ty` type checker, `ruff` formatter, `structlog`, `prometheus_client`, `opentelemetry-sdk`, `fastapi`, `litestar`, `faststream`, `fastmcp`.
+
+**Branch:** `fix/bug-audit-v2-pr2-config-security` (branch off `main` after PR1 merges, or off PR1's branch if parallel work is desired).
+
+**Sequencing prerequisite:** PR1 should merge first. PR2 doesn't structurally depend on PR1, but Task 5 introduces `OpenTelemetryConfig.__post_init__` which interacts with the `_prior_logger_disabled` field added in PR1 Task 4 (both touch `OpenTelemetryConfig`/`OpenTelemetryInstrument`). Rebasing PR2 onto a merged PR1 keeps the conflict resolution trivial.
+
+---
+
+## File Structure
+
+Modifications to existing files only — no new files.
+
+| File | What changes |
+|------|-------------|
+| `lite_bootstrap/bootstrappers/fastapi_bootstrapper.py` | Move user-app field overrides into UnsetType branch (Task 1); add `super().__post_init__()` for Task 5 cascade |
+| `lite_bootstrap/bootstrappers/faststream_bootstrapper.py` | Add `prometheus_collector_registry` field + thread to instrument (Task 2); add `opentelemetry_excluded_urls` field (Task 3) |
+| `lite_bootstrap/helpers/fastapi_helpers.py` | Validate `root_path` via `is_valid_path` + fall back on warning (Task 4) |
+| `lite_bootstrap/instruments/cors_instrument.py` | Add `__post_init__` to `CorsConfig` rejecting wildcard + credentials combo (Task 6) |
+| `lite_bootstrap/instruments/opentelemetry_instrument.py` | Add `__post_init__` to `OpenTelemetryConfig` warning on insecure non-local endpoint (Task 5) |
+| `tests/test_fastapi_bootstrap.py` | Test for Task 1 |
+| `tests/test_fastapi_offline_docs.py` | Test for Task 4 |
+| `tests/test_faststream_bootstrap.py` | Tests for Tasks 2, 3 |
+| `tests/instruments/test_cors_instrument.py` | Test for Task 6 |
+| `tests/instruments/test_opentelemetry_instrument.py` | Test for Task 5 |
+
+---
+
+## Task 1: UX-1 — `FastAPIConfig` respects user app's title/debug/version
+
+**Files:**
+- Modify: `lite_bootstrap/bootstrappers/fastapi_bootstrapper.py:58-75`
+- Test: `tests/test_fastapi_bootstrap.py`
+
+- [ ] **Step 1: Write the failing test**
+
+Add to `tests/test_fastapi_bootstrap.py` (at the bottom, after existing tests):
+
+```python
+def test_user_supplied_app_keeps_title_version_debug() -> None:
+    user_app = fastapi.FastAPI(title="user-title", version="9.9.9", debug=False)
+    config = FastAPIConfig(
+        application=user_app,
+        service_name="lite-name",
+        service_version="1.0.0",
+        service_debug=True,
+    )
+    assert config.application is user_app
+    assert user_app.title == "user-title"
+    assert user_app.version == "9.9.9"
+    assert user_app.debug is False
+```
+
+`fastapi`, `FastAPIConfig` are already imported in this file.
+
+- [ ] **Step 2: Run test to verify it fails**
+
+```bash
+just test -- tests/test_fastapi_bootstrap.py::test_user_supplied_app_keeps_title_version_debug
+```
+
+Expected: FAIL — current `__post_init__` overwrites `application.title/.debug/.version` with the config defaults even when the user supplies a pre-configured app.
+
+- [ ] **Step 3: Move the field overrides into the UnsetType branch**
+
+In `lite_bootstrap/bootstrappers/fastapi_bootstrapper.py`, the current `__post_init__` (lines 58-75) reads:
+
+```python
+def __post_init__(self) -> None:
+    if not import_checker.is_fastapi_installed:
+        msg = "fastapi is not installed"
+        raise ConfigurationError(msg)
+
+    if isinstance(self.application, UnsetType):
+        application = fastapi.FastAPI(docs_url=self.swagger_path, **self.application_kwargs)
+        # FastAPIConfig stays frozen for user-facing immutability; __post_init__ needs
+        # to set application after construction, so we bypass the freeze here.
+        object.__setattr__(self, "application", application)
+    else:
+        application = self.application
+        if self.application_kwargs:
+            warnings.warn("application_kwargs must be used without application", stacklevel=2)
+
+    application.title = self.service_name
+    application.debug = self.service_debug
+    application.version = self.service_version
+```
+
+Replace with:
+
+```python
+def __post_init__(self) -> None:
+    if not import_checker.is_fastapi_installed:
+        msg = "fastapi is not installed"
+        raise ConfigurationError(msg)
+
+    if isinstance(self.application, UnsetType):
+        application = fastapi.FastAPI(docs_url=self.swagger_path, **self.application_kwargs)
+        # FastAPIConfig stays frozen for user-facing immutability; __post_init__ needs
+        # to set application after construction, so we bypass the freeze here.
+        object.__setattr__(self, "application", application)
+        application.title = self.service_name
+        application.debug = self.service_debug
+        application.version = self.service_version
+    elif self.application_kwargs:
+        warnings.warn("application_kwargs must be used without application", stacklevel=2)
+```
+
+Key changes:
+- Three `application.X = ...` lines moved inside the `if isinstance(...)` branch
+- The `else: application = self.application` line is gone (no longer needed since we don't reference `application` after the branch)
+- `else: if self.application_kwargs:` collapsed to `elif self.application_kwargs:`
+
+- [ ] **Step 4: Run the new test to verify it passes**
+
+```bash
+just test -- tests/test_fastapi_bootstrap.py::test_user_supplied_app_keeps_title_version_debug
+```
+
+Expected: PASS.
+
+- [ ] **Step 5: Verify nothing else broke**
+
+```bash
+just test -- tests/test_fastapi_bootstrap.py tests/test_fastapi_offline_docs.py
+```
+
+Expected: all green. In particular `test_fastapi_bootstrapper_apps_and_kwargs_warning` still triggers when both `application` and `application_kwargs` are passed.
+
+- [ ] **Step 6: Run full suite + lint**
+
+```bash
+just test
+just lint-ci
+```
+
+Expected: 165 passed (164 + 1 new), 100% coverage, lint clean.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add lite_bootstrap/bootstrappers/fastapi_bootstrapper.py tests/test_fastapi_bootstrap.py
+git commit -m "$(cat <<'EOF'
+fix: FastAPIConfig respects user-supplied app title/version/debug (UX-1)
+
+Move the application.title/.debug/.version assignments inside the UnsetType
+branch so they only apply when lite-bootstrap built the FastAPI() instance.
+Pre-configured user apps now keep their construction-time values.
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+EOF
+)"
+```
+
+---
+
+## Task 2: UX-2 — Injectable `prometheus_collector_registry` on FastStream
+
+**Files:**
+- Modify: `lite_bootstrap/bootstrappers/faststream_bootstrapper.py:63-72` (add config field), `:143-167` (thread to instrument)
+- Test: `tests/test_faststream_bootstrap.py`
+
+- [ ] **Step 1: Write the failing test**
+
+Add to `tests/test_faststream_bootstrap.py`:
+
+```python
+import uuid
+
+
+async def test_faststream_prometheus_uses_injected_registry(broker: RedisBroker) -> None:
+    custom_registry = prometheus_client.CollectorRegistry()
+    counter_name = f"injected_counter_{uuid.uuid4().hex}_total"
+    counter = prometheus_client.Counter(counter_name, "Injected registry counter", registry=custom_registry)
+    counter.inc()
+
+    bootstrap_config = dataclasses.replace(
+        build_faststream_config(broker=broker),
+        prometheus_collector_registry=custom_registry,
+    )
+    bootstrapper = FastStreamBootstrapper(bootstrap_config=bootstrap_config)
+    application = bootstrapper.bootstrap()
+    try:
+        with TestClient(app=application) as test_client, TestRedisBroker(broker):
+            response = test_client.get(bootstrap_config.prometheus_metrics_path)
+            assert response.status_code == status.HTTP_200_OK
+            assert counter_name.encode() in response.content
+    finally:
+        bootstrapper.teardown()
+```
+
+Imports — verify `prometheus_client` is imported at module level (it isn't yet in this test file). Add:
+
+```python
+import prometheus_client
+```
+
+Near the existing `import` block at the top of `tests/test_faststream_bootstrap.py`. `dataclasses`, `uuid`, `status`, `TestClient`, `TestRedisBroker`, `RedisBroker` are already imported or will be from new imports.
+
+- [ ] **Step 2: Run test to verify it fails**
+
+```bash
+just test -- tests/test_faststream_bootstrap.py::test_faststream_prometheus_uses_injected_registry
+```
+
+Expected: FAIL — `FastStreamConfig` doesn't have `prometheus_collector_registry` field; `dataclasses.replace(...)` raises `TypeError: __init__() got an unexpected keyword argument 'prometheus_collector_registry'`.
+
+- [ ] **Step 3: Add the config field**
+
+In `lite_bootstrap/bootstrappers/faststream_bootstrapper.py`, the current `FastStreamConfig` (lines 63-72) reads:
+
+```python
+@dataclasses.dataclass(kw_only=True, slots=True, frozen=True)
+class FastStreamConfig(
+    HealthChecksConfig, LoggingConfig, OpenTelemetryConfig, PrometheusConfig, PyroscopeConfig, SentryConfig
+):
+    application: "AsgiFastStream" = dataclasses.field(default_factory=_make_asgi_faststream)
+    opentelemetry_middleware_cls: type[FastStreamTelemetryMiddlewareProtocol] | None = None
+    prometheus_middleware_cls: type[FastStreamPrometheusMiddlewareProtocol] | None = None
+    faststream_log_level: int = logging.WARNING
+    faststream_health_check_broker_timeout: float = 5.0
+```
+
+Add a `prometheus_collector_registry` field after `prometheus_middleware_cls`:
+
+```python
+@dataclasses.dataclass(kw_only=True, slots=True, frozen=True)
+class FastStreamConfig(
+    HealthChecksConfig, LoggingConfig, OpenTelemetryConfig, PrometheusConfig, PyroscopeConfig, SentryConfig
+):
+    application: "AsgiFastStream" = dataclasses.field(default_factory=_make_asgi_faststream)
+    opentelemetry_middleware_cls: type[FastStreamTelemetryMiddlewareProtocol] | None = None
+    prometheus_middleware_cls: type[FastStreamPrometheusMiddlewareProtocol] | None = None
+    prometheus_collector_registry: "prometheus_client.CollectorRegistry | None" = None
+    faststream_log_level: int = logging.WARNING
+    faststream_health_check_broker_timeout: float = 5.0
+```
+
+The string-annotation form `"prometheus_client.CollectorRegistry | None"` works because `prometheus_client` is imported conditionally at module scope (`if import_checker.is_prometheus_client_installed: import prometheus_client`). Dataclass field type annotations are not resolved at runtime by default, so the conditional import is fine.
+
+- [ ] **Step 4: Thread the field into `FastStreamPrometheusInstrument`**
+
+Currently (lines 143-167):
+
+```python
+@dataclasses.dataclass(kw_only=True)
+class FastStreamPrometheusInstrument(PrometheusInstrument):
+    bootstrap_config: FastStreamConfig
+    collector_registry: "prometheus_client.CollectorRegistry" = dataclasses.field(
+        default_factory=_make_collector_registry, init=False
+    )
+    not_ready_message = PrometheusInstrument.not_ready_message + " or prometheus_middleware_cls is missing"
+    missing_dependency_message = "prometheus_client is not installed"
+    ...
+```
+
+Replace the `collector_registry` field declaration with an `init=False` field set in `__post_init__`:
+
+```python
+@dataclasses.dataclass(kw_only=True)
+class FastStreamPrometheusInstrument(PrometheusInstrument):
+    bootstrap_config: FastStreamConfig
+    collector_registry: "prometheus_client.CollectorRegistry" = dataclasses.field(init=False)
+    not_ready_message = PrometheusInstrument.not_ready_message + " or prometheus_middleware_cls is missing"
+    missing_dependency_message = "prometheus_client is not installed"
+
+    def __post_init__(self) -> None:
+        injected = self.bootstrap_config.prometheus_collector_registry
+        self.collector_registry = injected if injected is not None else _make_collector_registry()
+
+    @classmethod
+    def is_configured(cls, bootstrap_config: "FastStreamConfig") -> bool:  # ty: ignore[invalid-method-override]
+        return super().is_configured(bootstrap_config) and bool(bootstrap_config.prometheus_middleware_cls)
+    ...
+```
+
+`__post_init__` runs after dataclass `__init__`; assignment via `self.collector_registry = ...` works because the instrument is non-frozen.
+
+Keep the rest of the class unchanged (the `is_configured`, `check_dependencies`, `bootstrap` methods).
+
+- [ ] **Step 5: Run the new test to verify it passes**
+
+```bash
+just test -- tests/test_faststream_bootstrap.py::test_faststream_prometheus_uses_injected_registry
+```
+
+Expected: PASS.
+
+- [ ] **Step 6: Verify default-path still works**
+
+```bash
+just test -- tests/test_faststream_bootstrap.py
+```
+
+Expected: all green. Existing `test_faststream_bootstrap` (which doesn't supply `prometheus_collector_registry`) continues to use the per-instance default.
+
+- [ ] **Step 7: Full suite + lint**
+
+```bash
+just test
+just lint-ci
+```
+
+Expected: 166 passed (165 + 1 new), 100% coverage, lint clean.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add lite_bootstrap/bootstrappers/faststream_bootstrapper.py tests/test_faststream_bootstrap.py
+git commit -m "$(cat <<'EOF'
+feat: support injectable Prometheus CollectorRegistry on FastStream (UX-2)
+
+Add prometheus_collector_registry: CollectorRegistry | None config field on
+FastStreamConfig. When non-None, FastStreamPrometheusInstrument uses the
+injected registry; otherwise the existing per-instance default is preserved.
+Lets users expose metrics that were registered on a shared registry.
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+EOF
+)"
+```
+
+---
+
+## Task 3: UX-3 — Add `opentelemetry_excluded_urls` to FastStreamConfig
+
+**Files:**
+- Modify: `lite_bootstrap/bootstrappers/faststream_bootstrapper.py:63-72`
+- Test: `tests/test_faststream_bootstrap.py`
+
+- [ ] **Step 1: Write the failing test**
+
+Add to `tests/test_faststream_bootstrap.py`:
+
+```python
+def test_faststream_opentelemetry_excluded_urls_in_built_set(broker: RedisBroker) -> None:
+    from lite_bootstrap.bootstrappers.faststream_bootstrapper import (
+        FastStreamOpenTelemetryInstrument,
+    )
+
+    bootstrap_config = dataclasses.replace(
+        build_faststream_config(broker=broker),
+        opentelemetry_excluded_urls=["/foo", "/bar"],
+    )
+    instrument = FastStreamOpenTelemetryInstrument(bootstrap_config=bootstrap_config)
+    excluded = instrument._build_excluded_urls()  # noqa: SLF001
+    assert "/foo" in excluded
+    assert "/bar" in excluded
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+```bash
+just test -- tests/test_faststream_bootstrap.py::test_faststream_opentelemetry_excluded_urls_in_built_set
+```
+
+Expected: FAIL — `dataclasses.replace(...)` raises because `FastStreamConfig` has no `opentelemetry_excluded_urls` field.
+
+- [ ] **Step 3: Add the field**
+
+In `lite_bootstrap/bootstrappers/faststream_bootstrapper.py`, the current `FastStreamConfig` (after Task 2's edit) reads approximately:
+
+```python
+@dataclasses.dataclass(kw_only=True, slots=True, frozen=True)
+class FastStreamConfig(
+    HealthChecksConfig, LoggingConfig, OpenTelemetryConfig, PrometheusConfig, PyroscopeConfig, SentryConfig
+):
+    application: "AsgiFastStream" = dataclasses.field(default_factory=_make_asgi_faststream)
+    opentelemetry_middleware_cls: type[FastStreamTelemetryMiddlewareProtocol] | None = None
+    prometheus_middleware_cls: type[FastStreamPrometheusMiddlewareProtocol] | None = None
+    prometheus_collector_registry: "prometheus_client.CollectorRegistry | None" = None
+    faststream_log_level: int = logging.WARNING
+    faststream_health_check_broker_timeout: float = 5.0
+```
+
+Add `opentelemetry_excluded_urls` after `opentelemetry_middleware_cls`:
+
+```python
+@dataclasses.dataclass(kw_only=True, slots=True, frozen=True)
+class FastStreamConfig(
+    HealthChecksConfig, LoggingConfig, OpenTelemetryConfig, PrometheusConfig, PyroscopeConfig, SentryConfig
+):
+    application: "AsgiFastStream" = dataclasses.field(default_factory=_make_asgi_faststream)
+    opentelemetry_middleware_cls: type[FastStreamTelemetryMiddlewareProtocol] | None = None
+    opentelemetry_excluded_urls: list[str] = dataclasses.field(default_factory=list)
+    prometheus_middleware_cls: type[FastStreamPrometheusMiddlewareProtocol] | None = None
+    prometheus_collector_registry: "prometheus_client.CollectorRegistry | None" = None
+    faststream_log_level: int = logging.WARNING
+    faststream_health_check_broker_timeout: float = 5.0
+```
+
+The behavior of `_build_excluded_urls` (in `opentelemetry_instrument.py`) is unchanged — it already reads via `getattr(self.bootstrap_config, "opentelemetry_excluded_urls", [])`. The new field is just for discoverability (IDE help, tab completion).
+
+- [ ] **Step 4: Run the new test to verify it passes**
+
+```bash
+just test -- tests/test_faststream_bootstrap.py::test_faststream_opentelemetry_excluded_urls_in_built_set
+```
+
+Expected: PASS.
+
+- [ ] **Step 5: Full suite + lint**
+
+```bash
+just test
+just lint-ci
+```
+
+Expected: 167 passed (166 + 1 new), 100% coverage, lint clean.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add lite_bootstrap/bootstrappers/faststream_bootstrapper.py tests/test_faststream_bootstrap.py
+git commit -m "$(cat <<'EOF'
+feat: add opentelemetry_excluded_urls to FastStreamConfig (UX-3)
+
+FastAPIConfig and LitestarConfig already expose opentelemetry_excluded_urls;
+FastStream relied on getattr fallback with no discoverable field. Add the field
+to FastStreamConfig matching the FastAPI/Litestar pattern. _build_excluded_urls
+behavior is unchanged — the getattr access still works the same way.
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+EOF
+)"
+```
+
+---
+
+## Task 4: SEC-1 — Validate `root_path` in offline-docs HTML
+
+**Files:**
+- Modify: `lite_bootstrap/helpers/fastapi_helpers.py`
+- Test: `tests/test_fastapi_offline_docs.py`
+
+- [ ] **Step 1: Write the failing test**
+
+Add to `tests/test_fastapi_offline_docs.py`:
+
+```python
+def test_offline_docs_rejects_unsafe_root_path() -> None:
+    malicious_root = "/foo</script><script>alert(1)</script>"
+    app = FastAPI(title="Tests", root_path=malicious_root, docs_url="/custom_docs")
+    enable_offline_docs(app, static_path="/static")
+
+    with TestClient(app, root_path=malicious_root) as client, pytest.warns(UserWarning, match="root_path"):
+        response = client.get("/custom_docs")
+    assert response.status_code == HTTPStatus.OK
+    assert "<script>alert(1)</script>" not in response.text
+    assert "/static/swagger-ui.css" in response.text  # falls back to empty root_path
+```
+
+`FastAPI`, `TestClient`, `HTTPStatus`, `pytest`, `enable_offline_docs` are already imported in this file.
+
+- [ ] **Step 2: Run test to verify it fails**
+
+```bash
+just test -- tests/test_fastapi_offline_docs.py::test_offline_docs_rejects_unsafe_root_path
+```
+
+Expected: FAIL — current handler reflects `root_path` verbatim into the swagger HTML, so the `<script>` tag from `root_path` lands in the response.
+
+- [ ] **Step 3: Add the validation helper and use it in both handlers**
+
+In `lite_bootstrap/helpers/fastapi_helpers.py`, add `warnings` and `is_valid_path` imports near the top:
+
+```python
+import pathlib
+import typing
+import warnings
+
+from lite_bootstrap import import_checker
+from lite_bootstrap.exceptions import ConfigurationError
+from lite_bootstrap.helpers.path import is_valid_path
+```
+
+Then add a module-level helper just above `enable_offline_docs`:
+
+```python
+def _safe_root_path(scope_root_path: str) -> str:
+    """Strip trailing slash and validate against the project's path allowlist.
+
+    An empty `root_path` is the normal case (no proxy prefix) and is allowed without warning.
+    Any other path that fails the `is_valid_path` regex is rejected (falls back to empty) so
+    that proxy-header-derived root paths can't inject HTML into the offline-docs response.
+    """
+    candidate = scope_root_path.rstrip("/")
+    if not candidate:
+        return ""
+    if not is_valid_path(candidate):
+        warnings.warn(
+            f"root_path {candidate!r} contains characters outside the valid-path allowlist; "
+            "falling back to empty root_path to prevent HTML injection in offline docs.",
+            stacklevel=3,
+        )
+        return ""
+    return candidate
+```
+
+In `custom_swagger_ui_html` (currently around line 38-46), replace:
+
+```python
+async def custom_swagger_ui_html(request: Request) -> HTMLResponse:
+    root_path = request.scope.get("root_path", "").rstrip("/")
+    ...
+```
+
+with:
+
+```python
+async def custom_swagger_ui_html(request: Request) -> HTMLResponse:
+    root_path = _safe_root_path(request.scope.get("root_path", ""))
+    ...
+```
+
+Same change in `redoc_html` (currently around line 53-58): replace the `root_path = request.scope.get("root_path", "").rstrip("/")` line with `root_path = _safe_root_path(request.scope.get("root_path", ""))`.
+
+- [ ] **Step 4: Run the new test to verify it passes**
+
+```bash
+just test -- tests/test_fastapi_offline_docs.py::test_offline_docs_rejects_unsafe_root_path
+```
+
+Expected: PASS — the malicious `root_path` is rejected, falls back to empty, no `<script>` injection in the response, and the warning fires.
+
+- [ ] **Step 5: Verify existing tests still pass**
+
+```bash
+just test -- tests/test_fastapi_offline_docs.py
+```
+
+Expected: all green. `test_fastapi_offline_docs_root_path` (which uses the valid `/some-root-path`) still validates the safe case.
+
+- [ ] **Step 6: Full suite + lint**
+
+```bash
+just test
+just lint-ci
+```
+
+Expected: 168 passed (167 + 1 new), 100% coverage, lint clean.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add lite_bootstrap/helpers/fastapi_helpers.py tests/test_fastapi_offline_docs.py
+git commit -m "$(cat <<'EOF'
+fix: validate root_path in offline-docs HTML to prevent injection (SEC-1)
+
+The swagger/redoc handlers reflected request.scope["root_path"] verbatim into
+HTML script/link tags. In default ASGI deployments root_path comes from server
+config (uvicorn --root-path), but if a user enables ProxyHeadersMiddleware with
+trusted X-Forwarded-Prefix, a malicious proxy could inject script content.
+Validate via the project's existing is_valid_path allowlist and fall back to
+empty (with a warning) on invalid input.
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+EOF
+)"
+```
+
+---
+
+## Task 5: SEC-2 — Warn on insecure non-local OTLP endpoint
+
+**Files:**
+- Modify: `lite_bootstrap/instruments/opentelemetry_instrument.py` (add `__post_init__` on `OpenTelemetryConfig`)
+- Modify: `lite_bootstrap/bootstrappers/fastapi_bootstrapper.py` (cascade `super().__post_init__()` so FastAPIConfig users also get the warning)
+- Test: `tests/instruments/test_opentelemetry_instrument.py`
+
+**Context:** Only `FastAPIConfig` defines its own `__post_init__` among the framework configs. `FreeConfig`, `FastStreamConfig`, `LitestarConfig` inherit `OpenTelemetryConfig.__post_init__` (the one we're adding here) automatically via the dataclass MRO. `FastMcpConfig` doesn't inherit `OpenTelemetryConfig`, so the warning doesn't fire for it — that's correct since FastMCP doesn't bootstrap OTel today.
+
+- [ ] **Step 1: Write the failing tests**
+
+Add to `tests/instruments/test_opentelemetry_instrument.py`:
+
+```python
+import warnings
+
+
+def test_opentelemetry_config_warns_on_insecure_non_local_endpoint() -> None:
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        OpenTelemetryConfig(
+            opentelemetry_endpoint="http://collector.example.com:4317",
+            opentelemetry_insecure=True,
+        )
+    matching = [w for w in caught if "unencrypted" in str(w.message)]
+    assert matching, [str(w.message) for w in caught]
+
+
+def test_opentelemetry_config_no_warning_for_localhost_endpoint() -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        # Should not raise — no warning emitted for localhost.
+        OpenTelemetryConfig(
+            opentelemetry_endpoint="http://localhost:4317",
+            opentelemetry_insecure=True,
+        )
+
+
+def test_opentelemetry_config_no_warning_when_insecure_false() -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        OpenTelemetryConfig(
+            opentelemetry_endpoint="https://collector.example.com:4317",
+            opentelemetry_insecure=False,
+        )
+
+
+def test_opentelemetry_config_no_warning_when_endpoint_unset() -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        OpenTelemetryConfig(opentelemetry_log_traces=True)
+```
+
+- [ ] **Step 2: Run tests to verify they fail**
+
+```bash
+just test -- tests/instruments/test_opentelemetry_instrument.py::test_opentelemetry_config_warns_on_insecure_non_local_endpoint
+```
+
+Expected: FAIL — `OpenTelemetryConfig` has no `__post_init__`, so no warning is emitted.
+
+The three "no warning" tests would pass even on the unmodified code (vacuously), but they pin the contract once the warning logic is added.
+
+- [ ] **Step 3: Add `__post_init__` on `OpenTelemetryConfig`**
+
+In `lite_bootstrap/instruments/opentelemetry_instrument.py`, add `urllib.parse` and `warnings` to the imports near the top (alongside the existing `import dataclasses`, `import logging`, `import os`, `import typing`):
+
+```python
+import dataclasses
+import logging
+import os
+import typing
+import urllib.parse
+import warnings
+```
+
+Then modify `OpenTelemetryConfig` (currently lines 41-53) to add `__post_init__`. Current code:
+
+```python
+@dataclasses.dataclass(kw_only=True, frozen=True)
+class OpenTelemetryConfig(OpenTelemetryServiceFieldsConfig):
+    opentelemetry_container_name: str | None = dataclasses.field(
+        default_factory=lambda: os.environ.get("HOSTNAME") or None
+    )
+    opentelemetry_endpoint: str | None = None
+    opentelemetry_insecure: bool = True
+    opentelemetry_instrumentors: list[typing.Union[InstrumentorWithParams, "BaseInstrumentor"]] = dataclasses.field(
+        default_factory=list
+    )
+    opentelemetry_log_traces: bool = False
+    opentelemetry_generate_health_check_spans: bool = True
+```
+
+Replace with:
+
+```python
+_LOCAL_HOSTS: typing.Final[frozenset[str]] = frozenset({"localhost", "127.0.0.1", "::1", ""})
+
+
+@dataclasses.dataclass(kw_only=True, frozen=True)
+class OpenTelemetryConfig(OpenTelemetryServiceFieldsConfig):
+    opentelemetry_container_name: str | None = dataclasses.field(
+        default_factory=lambda: os.environ.get("HOSTNAME") or None
+    )
+    opentelemetry_endpoint: str | None = None
+    opentelemetry_insecure: bool = True
+    opentelemetry_instrumentors: list[typing.Union[InstrumentorWithParams, "BaseInstrumentor"]] = dataclasses.field(
+        default_factory=list
+    )
+    opentelemetry_log_traces: bool = False
+    opentelemetry_generate_health_check_spans: bool = True
+
+    def __post_init__(self) -> None:
+        if not self.opentelemetry_endpoint or not self.opentelemetry_insecure:
+            return
+        if self.opentelemetry_endpoint.startswith("unix://"):
+            return
+        parsed = urllib.parse.urlparse(self.opentelemetry_endpoint)
+        host = (parsed.hostname or parsed.path.split(":")[0]).lower()
+        if host in _LOCAL_HOSTS:
+            return
+        warnings.warn(
+            f"OTLP exporter sending traces unencrypted to non-local host {host!r}; "
+            "set opentelemetry_insecure=False or use a localhost/unix endpoint.",
+            stacklevel=3,
+        )
+```
+
+The `_LOCAL_HOSTS` frozenset is module-private and reusable for any future host-locality checks. `urllib.parse.urlparse` handles both `host:port` and `scheme://host:port` (falls back to splitting `:` if `urlparse` can't extract a host).
+
+- [ ] **Step 4: Cascade `super().__post_init__()` in FastAPIConfig**
+
+After Task 1 lands, `FastAPIConfig.__post_init__` (in `lite_bootstrap/bootstrappers/fastapi_bootstrapper.py`) looks like:
+
+```python
+def __post_init__(self) -> None:
+    if not import_checker.is_fastapi_installed:
+        msg = "fastapi is not installed"
+        raise ConfigurationError(msg)
+
+    if isinstance(self.application, UnsetType):
+        application = fastapi.FastAPI(docs_url=self.swagger_path, **self.application_kwargs)
+        object.__setattr__(self, "application", application)
+        application.title = self.service_name
+        application.debug = self.service_debug
+        application.version = self.service_version
+    elif self.application_kwargs:
+        warnings.warn("application_kwargs must be used without application", stacklevel=2)
+```
+
+Add `super().__post_init__()` as the first line of the body so the OpenTelemetryConfig warning fires for FastAPIConfig too:
+
+```python
+def __post_init__(self) -> None:
+    super().__post_init__()
+    if not import_checker.is_fastapi_installed:
+        msg = "fastapi is not installed"
+        raise ConfigurationError(msg)
+
+    if isinstance(self.application, UnsetType):
+        application = fastapi.FastAPI(docs_url=self.swagger_path, **self.application_kwargs)
+        object.__setattr__(self, "application", application)
+        application.title = self.service_name
+        application.debug = self.service_debug
+        application.version = self.service_version
+    elif self.application_kwargs:
+        warnings.warn("application_kwargs must be used without application", stacklevel=2)
+```
+
+The MRO chain for `FastAPIConfig` resolves `super().__post_init__()` to `OpenTelemetryConfig.__post_init__` (via CorsConfig → HealthChecksConfig → LoggingConfig → OpenTelemetryConfig).
+
+- [ ] **Step 5: Add a FastAPIConfig-specific cascade test**
+
+Add to `tests/test_fastapi_bootstrap.py`:
+
+```python
+def test_fastapi_config_inherits_otel_insecure_warning() -> None:
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        FastAPIConfig(
+            opentelemetry_endpoint="http://collector.example.com:4317",
+            opentelemetry_insecure=True,
+        )
+    matching = [w for w in caught if "unencrypted" in str(w.message)]
+    assert matching, [str(w.message) for w in caught]
+```
+
+Verify `warnings` is imported at the top of `tests/test_fastapi_bootstrap.py` — it was added in PR1 Task 10.
+
+- [ ] **Step 6: Run all new tests**
+
+```bash
+just test -- tests/instruments/test_opentelemetry_instrument.py tests/test_fastapi_bootstrap.py
+```
+
+Expected: all green, including the new SEC-2 tests and the FastAPIConfig cascade test.
+
+- [ ] **Step 7: Full suite + lint**
+
+```bash
+just test
+just lint-ci
+```
+
+Expected: 173 passed (168 + 5 new), 100% coverage, lint clean.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add lite_bootstrap/instruments/opentelemetry_instrument.py lite_bootstrap/bootstrappers/fastapi_bootstrapper.py tests/instruments/test_opentelemetry_instrument.py tests/test_fastapi_bootstrap.py
+git commit -m "$(cat <<'EOF'
+fix: warn on insecure non-local OTLP endpoint (SEC-2)
+
+Add OpenTelemetryConfig.__post_init__ that emits a warning when
+opentelemetry_endpoint points to a non-local host AND opentelemetry_insecure is
+True (the unfortunate default). Localhost, 127.0.0.1, ::1, and unix:// endpoints
+are silent. FastAPIConfig.__post_init__ now calls super().__post_init__() so
+FastAPI users see the warning too; other framework configs (FreeConfig,
+FastStreamConfig, LitestarConfig) don't have their own __post_init__ and
+inherit the new behavior automatically.
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+EOF
+)"
+```
+
+---
+
+## Task 6: SEC-3 — Reject unsafe CORS configurations at construction
+
+**Files:**
+- Modify: `lite_bootstrap/instruments/cors_instrument.py` (add `__post_init__` on `CorsConfig`)
+- Test: `tests/instruments/test_cors_instrument.py`
+
+- [ ] **Step 1: Write the failing test**
+
+Add to `tests/instruments/test_cors_instrument.py`:
+
+```python
+import pytest
+
+from lite_bootstrap.exceptions import ConfigurationError
+
+
+@pytest.mark.parametrize(
+    ("origins", "regex"),
+    [
+        (["*"], None),
+        ([], ".*"),
+        ([], r".+"),
+        (["*", "http://safe.example.com"], None),
+    ],
+)
+def test_cors_config_rejects_wildcard_with_credentials(
+    origins: list[str], regex: str | None
+) -> None:
+    with pytest.raises(ConfigurationError, match="Unsafe CORS"):
+        CorsConfig(
+            cors_allowed_origins=origins,
+            cors_allowed_origin_regex=regex,
+            cors_allowed_credentials=True,
+        )
+
+
+def test_cors_config_accepts_credentials_with_explicit_origins() -> None:
+    config = CorsConfig(
+        cors_allowed_origins=["http://example.com"],
+        cors_allowed_credentials=True,
+    )
+    assert config.cors_allowed_credentials is True
+
+
+def test_cors_config_accepts_wildcard_without_credentials() -> None:
+    config = CorsConfig(
+        cors_allowed_origins=["*"],
+        cors_allowed_credentials=False,
+    )
+    assert config.cors_allowed_origins == ["*"]
+```
+
+- [ ] **Step 2: Run tests to verify they fail**
+
+```bash
+just test -- tests/instruments/test_cors_instrument.py::test_cors_config_rejects_wildcard_with_credentials
+```
+
+Expected: FAIL — `CorsConfig` accepts the unsafe combination today.
+
+- [ ] **Step 3: Add `__post_init__` to `CorsConfig`**
+
+In `lite_bootstrap/instruments/cors_instrument.py`, the current `CorsConfig` (lines 6-15) reads:
+
+```python
+@dataclasses.dataclass(kw_only=True, frozen=True)
+class CorsConfig(BaseConfig):
+    cors_allowed_origins: list[str] = dataclasses.field(default_factory=list)
+    cors_allowed_methods: list[str] = dataclasses.field(default_factory=list)
+    cors_allowed_headers: list[str] = dataclasses.field(default_factory=list)
+    cors_exposed_headers: list[str] = dataclasses.field(default_factory=list)
+    cors_allowed_credentials: bool = False
+    cors_allowed_origin_regex: str | None = None
+    cors_max_age: int = 600
+```
+
+Add an import for `ConfigurationError` at the top:
+
+```python
+import dataclasses
+
+from lite_bootstrap.exceptions import ConfigurationError
+from lite_bootstrap.instruments.base import BaseConfig, BaseInstrument
+```
+
+And add `__post_init__`:
+
+```python
+_PERMISSIVE_ORIGIN_REGEX: typing.Final[frozenset[str]] = frozenset({".*", r".+"})
+
+
+@dataclasses.dataclass(kw_only=True, frozen=True)
+class CorsConfig(BaseConfig):
+    cors_allowed_origins: list[str] = dataclasses.field(default_factory=list)
+    cors_allowed_methods: list[str] = dataclasses.field(default_factory=list)
+    cors_allowed_headers: list[str] = dataclasses.field(default_factory=list)
+    cors_exposed_headers: list[str] = dataclasses.field(default_factory=list)
+    cors_allowed_credentials: bool = False
+    cors_allowed_origin_regex: str | None = None
+    cors_max_age: int = 600
+
+    def __post_init__(self) -> None:
+        if not self.cors_allowed_credentials:
+            return
+        wildcard_in_origins = "*" in self.cors_allowed_origins
+        permissive_regex = self.cors_allowed_origin_regex in _PERMISSIVE_ORIGIN_REGEX
+        if wildcard_in_origins or permissive_regex:
+            msg = (
+                "Unsafe CORS configuration: cors_allowed_credentials=True combined with a "
+                "wildcard origin is rejected by browsers and is a security misconfiguration. "
+                "Use an explicit list of allowed origins (or a narrow regex)."
+            )
+            raise ConfigurationError(msg)
+```
+
+Add `import typing` if not already imported.
+
+- [ ] **Step 4: Run the new tests to verify they pass**
+
+```bash
+just test -- tests/instruments/test_cors_instrument.py
+```
+
+Expected: all green (new tests + existing tests like `test_cors_instrument_configured_with_origins`).
+
+- [ ] **Step 5: Run downstream tests that build FastAPI/Litestar configs with CORS**
+
+```bash
+just test -- tests/test_fastapi_bootstrap.py tests/test_litestar_bootstrap.py
+```
+
+Expected: green. None of the existing fixtures use the wildcard + credentials combo.
+
+- [ ] **Step 6: Full suite + lint**
+
+```bash
+just test
+just lint-ci
+```
+
+Expected: 176 passed (173 + 3 new), 100% coverage, lint clean.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add lite_bootstrap/instruments/cors_instrument.py tests/instruments/test_cors_instrument.py
+git commit -m "$(cat <<'EOF'
+fix: reject unsafe CORS wildcard + credentials combo at construction (SEC-3)
+
+cors_allowed_credentials=True with cors_allowed_origins=["*"] (or a permissive
+regex like ".*"/".+") is the canonical CORS misconfiguration. FastAPI's
+CORSMiddleware refuses to set the credentials header in that combo but
+Litestar's behavior differs and may silently accept it. Add a CorsConfig
+__post_init__ that raises ConfigurationError on the unsafe combination
+at config-construction time, before any framework sees the values.
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+EOF
+)"
+```
+
+---
+
+## Final verification
+
+- [ ] **Step 1: Full test suite**
+
+```bash
+just test
+```
+
+Expected: 176 passed (164 baseline + 12 new across the 6 tasks), 100% coverage.
+
+- [ ] **Step 2: Lint + type check**
+
+```bash
+just lint-ci
+```
+
+Expected: green.
+
+- [ ] **Step 3: Confirm commit log shape**
+
+```bash
+git log --oneline origin/main..HEAD
+```
+
+Expected: 6 task commits, each titled with a `fix:` or `feat:` prefix and tagged with the audit ID(s) it closes:
+
+- Task 1 (UX-1) — `fix:`
+- Task 2 (UX-2) — `feat:`
+- Task 3 (UX-3) — `feat:`
+- Task 4 (SEC-1) — `fix:`
+- Task 5 (SEC-2) — `fix:`
+- Task 6 (SEC-3) — `fix:`
+
+---
+
+## Self-Review
+
+1. **Spec coverage:** UX-1 (Task 1) · UX-2 (Task 2) · UX-3 (Task 3) · SEC-1 (Task 4) · SEC-2 (Task 5) · SEC-3 (Task 6). TEST-NEW-1 folds into Task 1; TEST-NEW-6 folds into Task 6. All 6 PR2 findings + 2 paired test items mapped.
+2. **Placeholder scan:** every step has full code blocks, exact commands, and expected outcomes.
+3. **Type consistency:** `FastStreamConfig.prometheus_collector_registry: prometheus_client.CollectorRegistry | None` (Task 2), `FastStreamConfig.opentelemetry_excluded_urls: list[str]` (Task 3), `OpenTelemetryConfig` adds no fields (Task 5), `CorsConfig` adds no fields (Task 6). All consistent between definition and usage.
+4. **Commit isolation:** each task ends with a single commit scoped to its finding ID.
+5. **Cross-task interaction:** Task 5 modifies the `FastAPIConfig.__post_init__` that Task 1 already restructured. The plan orders Task 5 after Task 1 so the `super().__post_init__()` insertion lands cleanly. No other cross-task structural conflicts.

From e71f50889b0d95fd96d18949ae0772b55b07ba49 Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 18:52:16 +0300
Subject: [PATCH 2/8] fix: FastAPIConfig respects user-supplied app
 title/version/debug (UX-1)

Move the application.title/.debug/.version assignments inside the UnsetType
branch so they only apply when lite-bootstrap built the FastAPI() instance.
Pre-configured user apps now keep their construction-time values.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../bootstrappers/fastapi_bootstrapper.py          | 13 +++++--------
 tests/test_fastapi_bootstrap.py                    | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py b/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py
index ba99adc..cfc314f 100644
--- a/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py
+++ b/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py
@@ -65,14 +65,11 @@ def __post_init__(self) -> None:
             # FastAPIConfig stays frozen for user-facing immutability; __post_init__ needs
             # to set application after construction, so we bypass the freeze here.
             object.__setattr__(self, "application", application)
-        else:
-            application = self.application
-            if self.application_kwargs:
-                warnings.warn("application_kwargs must be used without application", stacklevel=2)
-
-        application.title = self.service_name
-        application.debug = self.service_debug
-        application.version = self.service_version
+            application.title = self.service_name
+            application.debug = self.service_debug
+            application.version = self.service_version
+        elif self.application_kwargs:
+            warnings.warn("application_kwargs must be used without application", stacklevel=2)
 
 
 def _narrow_app(config: "FastAPIConfig") -> "fastapi.FastAPI":
diff --git a/tests/test_fastapi_bootstrap.py b/tests/test_fastapi_bootstrap.py
index 6b167ce..ce7a29d 100644
--- a/tests/test_fastapi_bootstrap.py
+++ b/tests/test_fastapi_bootstrap.py
@@ -141,3 +141,17 @@ def test_narrow_app_raises_when_application_unset() -> None:
     object.__setattr__(config, "application", UNSET)
     with pytest.raises(TypeError, match="application is UNSET"):
         _narrow_app(config)
+
+
+def test_user_supplied_app_keeps_title_version_debug() -> None:
+    user_app = fastapi.FastAPI(title="user-title", version="9.9.9", debug=False)
+    config = FastAPIConfig(
+        application=user_app,
+        service_name="lite-name",
+        service_version="1.0.0",
+        service_debug=True,
+    )
+    assert config.application is user_app
+    assert user_app.title == "user-title"
+    assert user_app.version == "9.9.9"
+    assert user_app.debug is False

From 5a1acf27f3585b2158b2d25b9ad8f8e221d625d4 Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 18:58:35 +0300
Subject: [PATCH 3/8] feat: support injectable Prometheus CollectorRegistry on
 FastStream (UX-2)

Add prometheus_collector_registry: CollectorRegistry | None config field on
FastStreamConfig. When non-None, FastStreamPrometheusInstrument uses the
injected registry; otherwise the existing per-instance default is preserved.
Lets users expose metrics that were registered on a shared registry.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../bootstrappers/faststream_bootstrapper.py  |  9 ++++---
 tests/test_faststream_bootstrap.py            | 24 +++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/lite_bootstrap/bootstrappers/faststream_bootstrapper.py b/lite_bootstrap/bootstrappers/faststream_bootstrapper.py
index 6d78517..c4e37e1 100644
--- a/lite_bootstrap/bootstrappers/faststream_bootstrapper.py
+++ b/lite_bootstrap/bootstrappers/faststream_bootstrapper.py
@@ -67,6 +67,7 @@ class FastStreamConfig(
     application: "AsgiFastStream" = dataclasses.field(default_factory=_make_asgi_faststream)
     opentelemetry_middleware_cls: type[FastStreamTelemetryMiddlewareProtocol] | None = None
     prometheus_middleware_cls: type[FastStreamPrometheusMiddlewareProtocol] | None = None
+    prometheus_collector_registry: "prometheus_client.CollectorRegistry | None" = None
     faststream_log_level: int = logging.WARNING
     faststream_health_check_broker_timeout: float = 5.0
 
@@ -156,12 +157,14 @@ def _make_collector_registry() -> "prometheus_client.CollectorRegistry":
 @dataclasses.dataclass(kw_only=True)
 class FastStreamPrometheusInstrument(PrometheusInstrument):
     bootstrap_config: FastStreamConfig
-    collector_registry: "prometheus_client.CollectorRegistry" = dataclasses.field(
-        default_factory=_make_collector_registry, init=False
-    )
+    collector_registry: "prometheus_client.CollectorRegistry" = dataclasses.field(init=False)
     not_ready_message = PrometheusInstrument.not_ready_message + " or prometheus_middleware_cls is missing"
     missing_dependency_message = "prometheus_client is not installed"
 
+    def __post_init__(self) -> None:
+        injected = self.bootstrap_config.prometheus_collector_registry
+        self.collector_registry = injected if injected is not None else _make_collector_registry()
+
     @classmethod
     def is_configured(cls, bootstrap_config: "FastStreamConfig") -> bool:  # ty: ignore[invalid-method-override]
         return super().is_configured(bootstrap_config) and bool(bootstrap_config.prometheus_middleware_cls)
diff --git a/tests/test_faststream_bootstrap.py b/tests/test_faststream_bootstrap.py
index 9126c38..a6c899d 100644
--- a/tests/test_faststream_bootstrap.py
+++ b/tests/test_faststream_bootstrap.py
@@ -1,9 +1,11 @@
 import dataclasses
 import logging
 import typing
+import uuid
 from unittest.mock import AsyncMock, patch
 
 import faststream.asgi
+import prometheus_client
 import pytest
 import structlog
 from faststream._internal.broker import BrokerUsecase
@@ -200,3 +202,25 @@ async def test_faststream_health_check_uses_configured_broker_timeout(broker: Re
         mock_ping.assert_called_once_with(timeout=expected_timeout)
     finally:
         bootstrapper.teardown()
+
+
+async def test_faststream_prometheus_uses_injected_registry(broker: RedisBroker) -> None:
+    custom_registry = prometheus_client.CollectorRegistry()
+    counter_name = f"injected_counter_{uuid.uuid4().hex}_total"
+    counter = prometheus_client.Counter(counter_name, "Injected registry counter", registry=custom_registry)
+    counter.inc()
+
+    bootstrap_config = dataclasses.replace(
+        build_faststream_config(broker=broker),
+        prometheus_collector_registry=custom_registry,
+    )
+    bootstrapper = FastStreamBootstrapper(bootstrap_config=bootstrap_config)
+    application = bootstrapper.bootstrap()
+    try:
+        with TestClient(app=application) as test_client:
+            async with TestRedisBroker(broker):
+                response = test_client.get(bootstrap_config.prometheus_metrics_path)
+                assert response.status_code == status.HTTP_200_OK
+                assert counter_name.encode() in response.content
+    finally:
+        bootstrapper.teardown()

From 550593eecb4116df35d659bf95df13ea7d295296 Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 19:03:39 +0300
Subject: [PATCH 4/8] feat: add opentelemetry_excluded_urls to FastStreamConfig
 (UX-3)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

FastAPIConfig and LitestarConfig already expose opentelemetry_excluded_urls;
FastStream relied on getattr fallback with no discoverable field. Add the field
to FastStreamConfig matching the FastAPI/Litestar pattern. _build_excluded_urls
behavior is unchanged — the getattr access still works the same way.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../bootstrappers/faststream_bootstrapper.py         |  1 +
 tests/test_faststream_bootstrap.py                   | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/lite_bootstrap/bootstrappers/faststream_bootstrapper.py b/lite_bootstrap/bootstrappers/faststream_bootstrapper.py
index c4e37e1..6ac2b89 100644
--- a/lite_bootstrap/bootstrappers/faststream_bootstrapper.py
+++ b/lite_bootstrap/bootstrappers/faststream_bootstrapper.py
@@ -66,6 +66,7 @@ class FastStreamConfig(
 ):
     application: "AsgiFastStream" = dataclasses.field(default_factory=_make_asgi_faststream)
     opentelemetry_middleware_cls: type[FastStreamTelemetryMiddlewareProtocol] | None = None
+    opentelemetry_excluded_urls: list[str] = dataclasses.field(default_factory=list)
     prometheus_middleware_cls: type[FastStreamPrometheusMiddlewareProtocol] | None = None
     prometheus_collector_registry: "prometheus_client.CollectorRegistry | None" = None
     faststream_log_level: int = logging.WARNING
diff --git a/tests/test_faststream_bootstrap.py b/tests/test_faststream_bootstrap.py
index a6c899d..7af2eba 100644
--- a/tests/test_faststream_bootstrap.py
+++ b/tests/test_faststream_bootstrap.py
@@ -17,6 +17,7 @@
 from starlette.testclient import TestClient
 
 from lite_bootstrap import FastStreamBootstrapper, FastStreamConfig
+from lite_bootstrap.bootstrappers.faststream_bootstrapper import FastStreamOpenTelemetryInstrument
 from tests.conftest import (
     CustomInstrumentor,
     SentryTestTransport,
@@ -204,6 +205,17 @@ async def test_faststream_health_check_uses_configured_broker_timeout(broker: Re
         bootstrapper.teardown()
 
 
+def test_faststream_opentelemetry_excluded_urls_in_built_set(broker: RedisBroker) -> None:
+    bootstrap_config = dataclasses.replace(
+        build_faststream_config(broker=broker),
+        opentelemetry_excluded_urls=["/foo", "/bar"],
+    )
+    instrument = FastStreamOpenTelemetryInstrument(bootstrap_config=bootstrap_config)
+    excluded = instrument._build_excluded_urls()  # noqa: SLF001
+    assert "/foo" in excluded
+    assert "/bar" in excluded
+
+
 async def test_faststream_prometheus_uses_injected_registry(broker: RedisBroker) -> None:
     custom_registry = prometheus_client.CollectorRegistry()
     counter_name = f"injected_counter_{uuid.uuid4().hex}_total"

From 4706bc426b8b5f40be8f29eedd4cd6d80c1c3e60 Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 19:07:21 +0300
Subject: [PATCH 5/8] fix: validate root_path in offline-docs HTML to prevent
 injection (SEC-1)

The swagger/redoc handlers reflected request.scope["root_path"] verbatim into
HTML script/link tags. In default ASGI deployments root_path comes from server
config (uvicorn --root-path), but if a user enables ProxyHeadersMiddleware with
trusted X-Forwarded-Prefix, a malicious proxy could inject script content.
Validate via the project's existing is_valid_path allowlist and fall back to
empty (with a warning) on invalid input.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 lite_bootstrap/helpers/fastapi_helpers.py | 26 +++++++++++++++++++++--
 tests/test_fastapi_offline_docs.py        | 20 +++++++++++++++++
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/lite_bootstrap/helpers/fastapi_helpers.py b/lite_bootstrap/helpers/fastapi_helpers.py
index 2972819..76518de 100644
--- a/lite_bootstrap/helpers/fastapi_helpers.py
+++ b/lite_bootstrap/helpers/fastapi_helpers.py
@@ -1,8 +1,10 @@
 import pathlib
 import typing
+import warnings
 
 from lite_bootstrap import import_checker
 from lite_bootstrap.exceptions import ConfigurationError
+from lite_bootstrap.helpers.path import is_valid_path
 
 
 if import_checker.is_fastapi_installed:
@@ -13,6 +15,26 @@
     from starlette.routing import Route
 
 
+def _safe_root_path(scope_root_path: str) -> str:
+    """Strip trailing slash and validate against the project's path allowlist.
+
+    An empty ``root_path`` is the normal case (no proxy prefix) and is allowed without warning.
+    Any other path that fails the ``is_valid_path`` regex is rejected (falls back to empty) so
+    that proxy-header-derived root paths can't inject HTML into the offline-docs response.
+    """
+    candidate = scope_root_path.rstrip("/")
+    if not candidate:
+        return ""
+    if not is_valid_path(candidate):
+        warnings.warn(
+            f"root_path {candidate!r} contains characters outside the valid-path allowlist; "
+            "falling back to empty root_path to prevent HTML injection in offline docs.",
+            stacklevel=3,
+        )
+        return ""
+    return candidate
+
+
 def enable_offline_docs(
     app: "FastAPI",
     static_path: str,
@@ -36,7 +58,7 @@ def enable_offline_docs(
 
     @app.get(docs_url, include_in_schema=False)
     async def custom_swagger_ui_html(request: Request) -> HTMLResponse:
-        root_path = request.scope.get("root_path", "").rstrip("/")
+        root_path = _safe_root_path(request.scope.get("root_path", ""))
         return get_swagger_ui_html(
             openapi_url=f"{root_path}{app_openapi_url}",
             title=f"{app.title} - Swagger UI",
@@ -51,7 +73,7 @@ async def swagger_ui_redirect() -> HTMLResponse:
 
     @app.get(redoc_url, include_in_schema=False)
     async def redoc_html(request: Request) -> HTMLResponse:
-        root_path = request.scope.get("root_path", "").rstrip("/")
+        root_path = _safe_root_path(request.scope.get("root_path", ""))
         return get_redoc_html(
             openapi_url=f"{root_path}{app_openapi_url}",
             title=f"{app.title} - ReDoc",
diff --git a/tests/test_fastapi_offline_docs.py b/tests/test_fastapi_offline_docs.py
index cf28015..4711ed2 100644
--- a/tests/test_fastapi_offline_docs.py
+++ b/tests/test_fastapi_offline_docs.py
@@ -53,3 +53,23 @@ def test_fastapi_offline_docs_raises_without_openapi_url() -> None:
 
     with pytest.raises(RuntimeError, match=r"No app.openapi_url specified"):
         enable_offline_docs(app, static_path="/static")
+
+
+def test_offline_docs_rejects_unsafe_root_path() -> None:
+    malicious_root = "/foo</script><script>alert(1)</script>"
+    app = FastAPI(title="Tests", root_path=malicious_root, docs_url="/custom_docs", redoc_url="/custom_redoc")
+    enable_offline_docs(app, static_path="/static")
+
+    with TestClient(app, root_path=malicious_root) as client:
+        with pytest.warns(UserWarning, match="root_path"):
+            swagger_response = client.get("/custom_docs")
+        with pytest.warns(UserWarning, match="root_path"):
+            redoc_response = client.get("/custom_redoc")
+
+    assert swagger_response.status_code == HTTPStatus.OK
+    assert "<script>alert(1)</script>" not in swagger_response.text
+    assert "/static/swagger-ui.css" in swagger_response.text  # falls back to empty root_path
+
+    assert redoc_response.status_code == HTTPStatus.OK
+    assert "<script>alert(1)</script>" not in redoc_response.text
+    assert "/static/redoc.standalone.js" in redoc_response.text  # falls back to empty root_path

From 4f4ef30c7cf9653f7ac5f3c56b094e86d1863b4d Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 19:17:04 +0300
Subject: [PATCH 6/8] fix: warn on insecure non-local OTLP endpoint (SEC-2)

Add OpenTelemetryConfig.__post_init__ that emits a warning when
opentelemetry_endpoint points to a non-local host AND opentelemetry_insecure is
True (the unfortunate default). Localhost, 127.0.0.1, ::1, and unix:// endpoints
are silent. FastAPIConfig.__post_init__ now calls super().__post_init__() so
FastAPI users see the warning too; other framework configs (FreeConfig,
FastStreamConfig, LitestarConfig) don't have their own __post_init__ and
inherit the new behavior automatically.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../bootstrappers/fastapi_bootstrapper.py     |  2 +
 .../instruments/opentelemetry_instrument.py   | 25 ++++++++
 .../test_opentelemetry_instrument.py          | 57 +++++++++++++++++++
 tests/test_fastapi_bootstrap.py               | 11 ++++
 4 files changed, 95 insertions(+)

diff --git a/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py b/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py
index cfc314f..112f8cc 100644
--- a/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py
+++ b/lite_bootstrap/bootstrappers/fastapi_bootstrapper.py
@@ -56,6 +56,8 @@ class FastAPIConfig(
     prometheus_expose_params: dict[str, typing.Any] = dataclasses.field(default_factory=dict)
 
     def __post_init__(self) -> None:
+        # @dataclass(slots=True) replaces the class object, breaking bare super().
+        super(FastAPIConfig, self).__post_init__()
         if not import_checker.is_fastapi_installed:
             msg = "fastapi is not installed"
             raise ConfigurationError(msg)
diff --git a/lite_bootstrap/instruments/opentelemetry_instrument.py b/lite_bootstrap/instruments/opentelemetry_instrument.py
index 65ca701..50f51a1 100644
--- a/lite_bootstrap/instruments/opentelemetry_instrument.py
+++ b/lite_bootstrap/instruments/opentelemetry_instrument.py
@@ -2,6 +2,8 @@
 import logging
 import os
 import typing
+import urllib.parse
+import warnings
 
 from lite_bootstrap import import_checker
 from lite_bootstrap.instruments.base import BaseConfig, BaseInstrument
@@ -38,6 +40,9 @@ class OpenTelemetryServiceFieldsConfig(BaseConfig):
     opentelemetry_namespace: str | None = None
 
 
+_LOCAL_HOSTS: typing.Final[frozenset[str]] = frozenset({"localhost", "127.0.0.1", "::1", ""})
+
+
 @dataclasses.dataclass(kw_only=True, frozen=True)
 class OpenTelemetryConfig(OpenTelemetryServiceFieldsConfig):
     opentelemetry_container_name: str | None = dataclasses.field(
@@ -51,6 +56,26 @@ class OpenTelemetryConfig(OpenTelemetryServiceFieldsConfig):
     opentelemetry_log_traces: bool = False
     opentelemetry_generate_health_check_spans: bool = True
 
+    def __post_init__(self) -> None:
+        if not self.opentelemetry_endpoint or not self.opentelemetry_insecure:
+            return
+        if self.opentelemetry_endpoint.startswith("unix://"):
+            return
+        # urlparse treats schemeless input as `path`, misparsing `host:port` forms.
+        # Prepend `//` so urlparse always sees a network-location-style input.
+        raw = self.opentelemetry_endpoint
+        if "://" not in raw:
+            raw = f"//{raw}"
+        parsed = urllib.parse.urlparse(raw)
+        host = (parsed.hostname or "").lower()
+        if host in _LOCAL_HOSTS:
+            return
+        warnings.warn(
+            f"OTLP exporter sending traces unencrypted to non-local host {host!r}; "
+            "set opentelemetry_insecure=False or use a localhost/unix endpoint.",
+            stacklevel=2,
+        )
+
 
 if import_checker.is_opentelemetry_installed and import_checker.is_pyroscope_installed:
     _OTEL_PROFILE_ID_KEY: typing.Final = "pyroscope.profile.id"
diff --git a/tests/instruments/test_opentelemetry_instrument.py b/tests/instruments/test_opentelemetry_instrument.py
index e8561c8..1be3754 100644
--- a/tests/instruments/test_opentelemetry_instrument.py
+++ b/tests/instruments/test_opentelemetry_instrument.py
@@ -1,4 +1,5 @@
 import logging
+import warnings
 from unittest.mock import patch
 
 import pytest
@@ -89,3 +90,59 @@ def test_opentelemetry_teardown_restores_disabled_loggers() -> None:
 
     assert instrumentor_logger.disabled is prior_instrumentor_disabled
     assert trace_logger.disabled is prior_trace_disabled
+
+
+@pytest.mark.parametrize(
+    "endpoint",
+    [
+        "localhost:4317",
+        "127.0.0.1:4317",
+        "[::1]:4317",
+        "http://localhost:4317",
+        "https://127.0.0.1:4317",
+    ],
+)
+def test_opentelemetry_config_no_warning_for_local_endpoints(endpoint: str) -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        OpenTelemetryConfig(opentelemetry_endpoint=endpoint, opentelemetry_insecure=True)
+
+
+@pytest.mark.parametrize(
+    "endpoint",
+    [
+        "collector.example.com:4317",
+        "http://collector.example.com:4317",
+        "grpc://collector.example.com:4317",
+    ],
+)
+def test_opentelemetry_config_warns_for_remote_endpoints(endpoint: str) -> None:
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        OpenTelemetryConfig(opentelemetry_endpoint=endpoint, opentelemetry_insecure=True)
+    matching = [w for w in caught if "unencrypted" in str(w.message)]
+    assert matching, f"endpoint {endpoint!r}: {[str(w.message) for w in caught]}"
+
+
+def test_opentelemetry_config_no_warning_when_insecure_false() -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        OpenTelemetryConfig(
+            opentelemetry_endpoint="https://collector.example.com:4317",
+            opentelemetry_insecure=False,
+        )
+
+
+def test_opentelemetry_config_no_warning_when_endpoint_unset() -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        OpenTelemetryConfig(opentelemetry_log_traces=True)
+
+
+def test_opentelemetry_config_no_warning_for_unix_socket_endpoint() -> None:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        OpenTelemetryConfig(
+            opentelemetry_endpoint="unix:///var/run/otel.sock",
+            opentelemetry_insecure=True,
+        )
diff --git a/tests/test_fastapi_bootstrap.py b/tests/test_fastapi_bootstrap.py
index ce7a29d..ee2a048 100644
--- a/tests/test_fastapi_bootstrap.py
+++ b/tests/test_fastapi_bootstrap.py
@@ -155,3 +155,14 @@ def test_user_supplied_app_keeps_title_version_debug() -> None:
     assert user_app.title == "user-title"
     assert user_app.version == "9.9.9"
     assert user_app.debug is False
+
+
+def test_fastapi_config_inherits_otel_insecure_warning() -> None:
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        FastAPIConfig(
+            opentelemetry_endpoint="http://collector.example.com:4317",
+            opentelemetry_insecure=True,
+        )
+    matching = [w for w in caught if "unencrypted" in str(w.message)]
+    assert matching, [str(w.message) for w in caught]

From 4327a68226a5ab2d4a4ba1621b679dcda9cc2869 Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 19:31:48 +0300
Subject: [PATCH 7/8] fix: reject unsafe CORS wildcard + credentials combo at
 construction (SEC-3)

cors_allowed_credentials=True with cors_allowed_origins=["*"] (or a permissive
regex like ".*"/".+") is the canonical CORS misconfiguration. FastAPI's
CORSMiddleware refuses to set the credentials header in that combo but
Litestar's behavior differs and may silently accept it. Add a CorsConfig
__post_init__ that raises ConfigurationError on the unsafe combination
at config-construction time, before any framework sees the values.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 lite_bootstrap/instruments/cors_instrument.py | 18 +++++++++
 tests/instruments/test_cors_instrument.py     | 37 +++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/lite_bootstrap/instruments/cors_instrument.py b/lite_bootstrap/instruments/cors_instrument.py
index e00ccc0..18338ba 100644
--- a/lite_bootstrap/instruments/cors_instrument.py
+++ b/lite_bootstrap/instruments/cors_instrument.py
@@ -1,8 +1,13 @@
 import dataclasses
+import typing
 
+from lite_bootstrap.exceptions import ConfigurationError
 from lite_bootstrap.instruments.base import BaseConfig, BaseInstrument
 
 
+_PERMISSIVE_ORIGIN_REGEX: typing.Final[frozenset[str]] = frozenset({".*", r".+"})
+
+
 @dataclasses.dataclass(kw_only=True, frozen=True)
 class CorsConfig(BaseConfig):
     cors_allowed_origins: list[str] = dataclasses.field(default_factory=list)
@@ -13,6 +18,19 @@ class CorsConfig(BaseConfig):
     cors_allowed_origin_regex: str | None = None
     cors_max_age: int = 600
 
+    def __post_init__(self) -> None:
+        if not self.cors_allowed_credentials:
+            return
+        wildcard_in_origins = "*" in self.cors_allowed_origins
+        permissive_regex = self.cors_allowed_origin_regex in _PERMISSIVE_ORIGIN_REGEX
+        if wildcard_in_origins or permissive_regex:
+            msg = (
+                "Unsafe CORS configuration: cors_allowed_credentials=True combined with a "
+                "wildcard origin is rejected by browsers and is a security misconfiguration. "
+                "Use an explicit list of allowed origins (or a narrow regex)."
+            )
+            raise ConfigurationError(msg)
+
 
 @dataclasses.dataclass(kw_only=True, slots=True)
 class CorsInstrument(BaseInstrument[CorsConfig]):
diff --git a/tests/instruments/test_cors_instrument.py b/tests/instruments/test_cors_instrument.py
index c7183db..c3536a3 100644
--- a/tests/instruments/test_cors_instrument.py
+++ b/tests/instruments/test_cors_instrument.py
@@ -1,3 +1,6 @@
+import pytest
+
+from lite_bootstrap.exceptions import ConfigurationError
 from lite_bootstrap.instruments.cors_instrument import CorsConfig, CorsInstrument
 
 
@@ -39,3 +42,37 @@ def test_cors_instrument_config_defaults() -> None:
 
 def test_cors_check_dependencies() -> None:
     assert CorsInstrument.check_dependencies() is True
+
+
+@pytest.mark.parametrize(
+    ("origins", "regex"),
+    [
+        (["*"], None),
+        ([], ".*"),
+        ([], r".+"),
+        (["*", "http://safe.example.com"], None),
+    ],
+)
+def test_cors_config_rejects_wildcard_with_credentials(origins: list[str], regex: str | None) -> None:
+    with pytest.raises(ConfigurationError, match="Unsafe CORS"):
+        CorsConfig(
+            cors_allowed_origins=origins,
+            cors_allowed_origin_regex=regex,
+            cors_allowed_credentials=True,
+        )
+
+
+def test_cors_config_accepts_credentials_with_explicit_origins() -> None:
+    config = CorsConfig(
+        cors_allowed_origins=["http://example.com"],
+        cors_allowed_credentials=True,
+    )
+    assert config.cors_allowed_credentials is True
+
+
+def test_cors_config_accepts_wildcard_without_credentials() -> None:
+    config = CorsConfig(
+        cors_allowed_origins=["*"],
+        cors_allowed_credentials=False,
+    )
+    assert config.cors_allowed_origins == ["*"]

From 895f2b1f5e0db367bdac49465ccc769aa2df598b Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Fri, 5 Jun 2026 19:35:51 +0300
Subject: [PATCH 8/8] fix: ensure __post_init__ cascades through config MRO
 (SEC-2/SEC-3)

CorsConfig.__post_init__ (SEC-3) and OpenTelemetryConfig.__post_init__
(SEC-2) now call super().__post_init__() so the MRO chain propagates.
Before this, CorsConfig.__post_init__ blocked the cascade for FastAPIConfig
users (Cors precedes OpenTelemetry in MRO), so SEC-2's warning didn't fire.
BaseConfig gains a no-op __post_init__ as the chain terminator.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 lite_bootstrap/instruments/base.py            |  8 +++++++
 lite_bootstrap/instruments/cors_instrument.py | 22 +++++++++---------
 .../instruments/opentelemetry_instrument.py   | 23 ++++++++++++-------
 3 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/lite_bootstrap/instruments/base.py b/lite_bootstrap/instruments/base.py
index 7d7f159..f511250 100644
--- a/lite_bootstrap/instruments/base.py
+++ b/lite_bootstrap/instruments/base.py
@@ -12,6 +12,14 @@ class BaseConfig:
     service_environment: str | None = None
     service_debug: bool = True
 
+    def __post_init__(self) -> None:
+        """Terminate the MRO __post_init__ cascade safely.
+
+        Subclasses call super().__post_init__() to propagate through multiple-inheritance
+        chains (e.g. FastAPIConfig → CorsConfig → OpenTelemetryConfig → BaseConfig).
+        Without this no-op, the chain would raise AttributeError on object.
+        """
+
     @classmethod
     def from_dict(cls, data: dict[str, typing.Any]) -> typing_extensions.Self:
         """Build a config from a dict; unknown keys are silently dropped, explicit None overrides defaults."""
diff --git a/lite_bootstrap/instruments/cors_instrument.py b/lite_bootstrap/instruments/cors_instrument.py
index 18338ba..3188d56 100644
--- a/lite_bootstrap/instruments/cors_instrument.py
+++ b/lite_bootstrap/instruments/cors_instrument.py
@@ -19,17 +19,17 @@ class CorsConfig(BaseConfig):
     cors_max_age: int = 600
 
     def __post_init__(self) -> None:
-        if not self.cors_allowed_credentials:
-            return
-        wildcard_in_origins = "*" in self.cors_allowed_origins
-        permissive_regex = self.cors_allowed_origin_regex in _PERMISSIVE_ORIGIN_REGEX
-        if wildcard_in_origins or permissive_regex:
-            msg = (
-                "Unsafe CORS configuration: cors_allowed_credentials=True combined with a "
-                "wildcard origin is rejected by browsers and is a security misconfiguration. "
-                "Use an explicit list of allowed origins (or a narrow regex)."
-            )
-            raise ConfigurationError(msg)
+        if self.cors_allowed_credentials:
+            wildcard_in_origins = "*" in self.cors_allowed_origins
+            permissive_regex = self.cors_allowed_origin_regex in _PERMISSIVE_ORIGIN_REGEX
+            if wildcard_in_origins or permissive_regex:
+                msg = (
+                    "Unsafe CORS configuration: cors_allowed_credentials=True combined with a "
+                    "wildcard origin is rejected by browsers and is a security misconfiguration. "
+                    "Use an explicit list of allowed origins (or a narrow regex)."
+                )
+                raise ConfigurationError(msg)
+        super().__post_init__()
 
 
 @dataclasses.dataclass(kw_only=True, slots=True)
diff --git a/lite_bootstrap/instruments/opentelemetry_instrument.py b/lite_bootstrap/instruments/opentelemetry_instrument.py
index 50f51a1..e2a6781 100644
--- a/lite_bootstrap/instruments/opentelemetry_instrument.py
+++ b/lite_bootstrap/instruments/opentelemetry_instrument.py
@@ -57,10 +57,21 @@ class OpenTelemetryConfig(OpenTelemetryServiceFieldsConfig):
     opentelemetry_generate_health_check_spans: bool = True
 
     def __post_init__(self) -> None:
+        host = self._parse_remote_insecure_host()
+        if host is not None:
+            warnings.warn(
+                f"OTLP exporter sending traces unencrypted to non-local host {host!r}; "
+                "set opentelemetry_insecure=False or use a localhost/unix endpoint.",
+                stacklevel=2,
+            )
+        super().__post_init__()
+
+    def _parse_remote_insecure_host(self) -> str | None:
+        """Return the host name if the endpoint is insecure AND non-local; else None."""
         if not self.opentelemetry_endpoint or not self.opentelemetry_insecure:
-            return
+            return None
         if self.opentelemetry_endpoint.startswith("unix://"):
-            return
+            return None
         # urlparse treats schemeless input as `path`, misparsing `host:port` forms.
         # Prepend `//` so urlparse always sees a network-location-style input.
         raw = self.opentelemetry_endpoint
@@ -69,12 +80,8 @@ def __post_init__(self) -> None:
         parsed = urllib.parse.urlparse(raw)
         host = (parsed.hostname or "").lower()
         if host in _LOCAL_HOSTS:
-            return
-        warnings.warn(
-            f"OTLP exporter sending traces unencrypted to non-local host {host!r}; "
-            "set opentelemetry_insecure=False or use a localhost/unix endpoint.",
-            stacklevel=2,
-        )
+            return None
+        return host
 
 
 if import_checker.is_opentelemetry_installed and import_checker.is_pyroscope_installed: