diff --git a/demos/filter_chains/peyeeye/Dockerfile b/demos/filter_chains/peyeeye/Dockerfile
new file mode 100644
index 000000000..2ba02db7c
--- /dev/null
+++ b/demos/filter_chains/peyeeye/Dockerfile
@@ -0,0 +1,22 @@
+FROM python:3.12-slim
+
+ENV PYTHONUNBUFFERED=1 \
+    PYTHONDONTWRITEBYTECODE=1 \
+    PIP_NO_CACHE_DIR=1
+
+WORKDIR /app
+
+RUN pip install --no-cache-dir uv
+
+COPY pyproject.toml ./
+RUN uv pip install --system --no-cache-dir \
+        "fastapi>=0.104.1" \
+        "uvicorn>=0.24.0" \
+        "httpx>=0.27.0" \
+        "pydantic>=2.0.0"
+
+COPY peyeeye.py ./
+
+EXPOSE 10502
+
+CMD ["uvicorn", "peyeeye:app", "--host", "0.0.0.0", "--port", "10502"]
diff --git a/demos/filter_chains/peyeeye/README.md b/demos/filter_chains/peyeeye/README.md
new file mode 100644
index 000000000..3aedf1198
--- /dev/null
+++ b/demos/filter_chains/peyeeye/README.md
@@ -0,0 +1,103 @@
+# Peyeeye PII Filter Chain Demo
+
+Drop-in PII redaction + rehydration for Plano via the [Peyeeye](https://peyeeye.ai) API.
+
+The model never sees raw PII — incoming text is sent to `/v1/redact` and replaced with stable placeholders like `[EMAIL_0]`, `[PERSON_1]`, etc. After the model responds, the placeholders in its output are swapped back to the originals via `/v1/rehydrate`.
+
+## Architecture
+
+```
+Client --> Plano (model listener :12000)
+              |
+              +-- input_filters: peyeeye_redact
+              |     -> POST https://api.peyeeye.ai/v1/redact
+              |     -> body messages contain [EMAIL_0], [SSN_0], ...
+              |
+              +-- model_provider: openai/gpt-4o-mini  (or claude, etc.)
+              |     -> the LLM only ever sees redacted text
+              |
+              +-- output_filters: peyeeye_rehydrate
+                    -> POST https://api.peyeeye.ai/v1/rehydrate
+                    -> placeholders restored to originals
+```
+
+## Quick start
+
+```bash
+export PEYEEYE_API_KEY=pk_live_...     # https://peyeeye.ai
+export OPENAI_API_KEY=sk-...
+
+bash run_demo.sh
+
+# in another terminal
+bash test.sh
+
+# stop
+bash run_demo.sh down
+```
+
+## Try it
+
+```bash
+curl http://localhost:12000/v1/chat/completions \
+  -H "Content-Type: application/json" \
+  -d '{
+    "model": "gpt-4o-mini",
+    "messages": [{"role": "user", "content": "Email me at jane@example.com about SSN 123-45-6789"}],
+    "stream": false
+  }'
+```
+
+The response body comes back with the original email and SSN restored, while the request that hit OpenAI carried `[EMAIL_0]` and `[SSN_0]`.
+
+## Configuration
+
+All configuration is via env vars on the filter service:
+
+| Var | Default | Notes |
+|---|---|---|
+| `PEYEEYE_API_KEY` | _required_ | get one at peyeeye.ai |
+| `PEYEEYE_API_BASE` | `https://api.peyeeye.ai` | override for self-hosted |
+| `PEYEEYE_LOCALE` | `auto` | BCP-47 |
+| `PEYEEYE_ENTITIES` | _all_ | comma-separated list, e.g. `EMAIL,SSN,CREDIT_CARD` |
+| `PEYEEYE_SESSION_MODE` | `stateful` | `stateful` (default) or `stateless` |
+
+In `stateless` mode, Peyeeye returns a sealed `skey_...` blob instead of holding the mapping server-side; this filter caches the blob on the request id and uses it for rehydration. No per-request state is retained on Peyeeye's servers.
+
+## Filter contract
+
+**Input filter (`/redact/{path:path}`)** receives the full raw request body. It walks `messages[].content` (string or multimodal `text` parts) for chat-style endpoints and `input` for the OpenAI Responses API, sends a single batched call to Peyeeye, and writes the redacted text back into the body in place.
+
+**Output filter (`/rehydrate/{path:path}`)** receives the raw LLM response bytes, looks up the cached session id by the request id (`x-request-id`), and rehydrates `choices[].message.content`, Anthropic-style `content[].text`, or Responses-API `output[].content[].text`.
+
+## Behavioral invariants
+
+- **Fail-closed.** If `/v1/redact` returns an unexpected shape, or the count of returned texts doesn't match the count sent, the filter raises a 502 — no unredacted text is ever forwarded to the model.
+- **Length-guard.** `len(redacted) == len(sent)` is asserted before zipping the values back into the request.
+- **Typed errors.** `PEyeEyeMissingSecrets` covers auth (401, missing key), `PEyeEyeAPIError` covers everything else (timeouts, 4xx, 5xx, parse). Both surface as HTTP errors to Plano.
+- **Best-effort cleanup.** Stateful sessions are deleted server-side after rehydration via `DELETE /v1/sessions/{ses_...}`.
+
+## Streaming
+
+Streaming SSE responses are passed through unchanged in this demo — token-by-token rehydration would require buffering or a session-aware streaming endpoint. For now, set `stream: false` on requests routed through this filter chain.
+
+## Tests
+
+```bash
+uv sync --group dev
+uv run pytest -v
+```
+
+The suite mocks the Peyeeye API (`respx`) and exercises:
+
+- redact + rehydrate round trip on chat completions
+- redact + rehydrate on `/v1/messages` (Anthropic) and `/v1/responses` (OpenAI)
+- the length-guard (redact returns wrong count -> 502)
+- the unexpected-shape guard (redact returns non-string/list -> 502)
+- the no-PII passthrough (no redactable text -> body unchanged, no session cached)
+- the no-cached-session passthrough on rehydrate
+- multimodal `[{"type":"text","text":...}]` content lists
+
+## Disclosure
+
+I'm the maintainer of peyeeye.ai. Happy to adjust API surface, naming, or test coverage to match Plano's conventions.
diff --git a/demos/filter_chains/peyeeye/config.yaml b/demos/filter_chains/peyeeye/config.yaml
new file mode 100644
index 000000000..83213e29e
--- /dev/null
+++ b/demos/filter_chains/peyeeye/config.yaml
@@ -0,0 +1,42 @@
+version: v0.3.0
+
+# Peyeeye PII redaction & rehydration filter chain.
+#
+# Prereqs:
+#   * export PEYEEYE_API_KEY=...     (required)
+#   * export OPENAI_API_KEY=...      (or any provider you wire up below)
+#
+# The peyeeye filter service runs on :10502 and exposes:
+#   POST /redact/{path}     — input filter
+#   POST /rehydrate/{path}  — output filter
+#
+# Plano appends the upstream path automatically (e.g. /v1/chat/completions),
+# so /redact/v1/chat/completions hits the redactor, and the model only ever
+# sees ``[EMAIL_0]``-style placeholders.
+
+filters:
+  - id: peyeeye_redact
+    url: http://localhost:10502/redact
+    type: http
+  - id: peyeeye_rehydrate
+    url: http://localhost:10502/rehydrate
+    type: http
+
+model_providers:
+  - model: openai/gpt-4o-mini
+    access_key: $OPENAI_API_KEY
+    default: true
+  - model: anthropic/claude-sonnet-4-20250514
+    access_key: $ANTHROPIC_API_KEY
+
+listeners:
+  - type: model
+    name: llm_gateway
+    port: 12000
+    input_filters:
+      - peyeeye_redact
+    output_filters:
+      - peyeeye_rehydrate
+
+tracing:
+  random_sampling: 100
diff --git a/demos/filter_chains/peyeeye/peyeeye.py b/demos/filter_chains/peyeeye/peyeeye.py
new file mode 100644
index 000000000..4e0bc7103
--- /dev/null
+++ b/demos/filter_chains/peyeeye/peyeeye.py
@@ -0,0 +1,485 @@
+"""Peyeeye PII redaction & rehydration filter for Plano filter chains.
+
+Two endpoints, mirroring the pii_anonymizer demo:
+
+  POST /redact/{path:path}     — input filter; redacts PII before the LLM call.
+  POST /rehydrate/{path:path}  — output filter; restores PII in the LLM response.
+
+The filter delegates detection and rehydration to the Peyeeye API
+(``https://api.peyeeye.ai`` by default). Two session modes are supported:
+
+  * ``stateful`` (default) — Peyeeye holds the token -> value mapping under a
+    ``ses_...`` id; rehydrate references the id.
+  * ``stateless`` — Peyeeye returns a sealed ``skey_...`` blob; nothing is
+    retained server-side.
+
+Behavioral invariants (mirrored from the LiteLLM peyeeye guardrail):
+
+  * Pre-call: redact every text-bearing chunk in the request. If the count of
+    returned texts doesn't match the count sent, raise -- never forward
+    partially-redacted source.
+  * Post-call: pull the cached session id, rehydrate the response, and best-
+    effort delete the stateful session.
+  * Fail-closed: any unexpected response shape from /v1/redact raises a typed
+    error rather than silently passing PII through.
+
+Configuration knobs (env vars):
+
+  * ``PEYEEYE_API_KEY``      — required.
+  * ``PEYEEYE_API_BASE``     — defaults to ``https://api.peyeeye.ai``.
+  * ``PEYEEYE_LOCALE``       — BCP-47, default ``auto``.
+  * ``PEYEEYE_ENTITIES``     — comma-separated entity ids to restrict detection.
+  * ``PEYEEYE_SESSION_MODE`` — ``stateful`` (default) or ``stateless``.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import logging
+import os
+import threading
+import time
+from typing import Any, Dict, List, Optional, Tuple
+
+import httpx
+from fastapi import FastAPI, HTTPException, Request
+from fastapi.responses import JSONResponse, Response
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s - [PEYEEYE] - %(levelname)s - %(message)s",
+)
+logger = logging.getLogger(__name__)
+
+
+DEFAULT_API_BASE = "https://api.peyeeye.ai"
+SESSION_TTL_SECONDS = 3600
+HTTP_TIMEOUT_SECONDS = 15.0
+
+
+# ----------------------------------------------------------------------- errors
+
+
+class PEyeEyeAPIError(Exception):
+    """Raised when the Peyeeye API returns an error or unexpected payload."""
+
+
+class PEyeEyeMissingSecrets(Exception):
+    """Raised when no Peyeeye API key is configured."""
+
+
+# ------------------------------------------------------------------- mini cache
+
+
+class _SessionCache:
+    """Tiny in-memory ``request_id -> session_id`` store with TTL."""
+
+    def __init__(self, ttl_seconds: int = SESSION_TTL_SECONDS) -> None:
+        self._ttl = ttl_seconds
+        self._lock = threading.Lock()
+        self._store: Dict[str, Tuple[str, float]] = {}
+
+    def _expire(self) -> None:
+        now = time.time()
+        expired = [k for k, (_, ts) in self._store.items() if now - ts > self._ttl]
+        for k in expired:
+            del self._store[k]
+
+    def set(self, key: str, value: str) -> None:
+        with self._lock:
+            self._expire()
+            self._store[key] = (value, time.time())
+
+    def get(self, key: str) -> Optional[str]:
+        with self._lock:
+            entry = self._store.get(key)
+            return entry[0] if entry else None
+
+    def pop(self, key: str) -> Optional[str]:
+        with self._lock:
+            entry = self._store.pop(key, None)
+            return entry[0] if entry else None
+
+
+# ------------------------------------------------------------------ peyeeye client
+
+
+class PEyeEyeClient:
+    """Async HTTP client for the Peyeeye redact/rehydrate API."""
+
+    def __init__(
+        self,
+        api_key: Optional[str] = None,
+        api_base: Optional[str] = None,
+        locale: Optional[str] = None,
+        entities: Optional[List[str]] = None,
+        session_mode: Optional[str] = None,
+    ) -> None:
+        key = api_key or os.environ.get("PEYEEYE_API_KEY")
+        if not key:
+            raise PEyeEyeMissingSecrets(
+                "Peyeeye API key missing — set the PEYEEYE_API_KEY env var."
+            )
+        self.api_key = key
+        self.api_base = (
+            api_base or os.environ.get("PEYEEYE_API_BASE") or DEFAULT_API_BASE
+        ).rstrip("/")
+        self.locale = locale or os.environ.get("PEYEEYE_LOCALE") or "auto"
+        env_entities = os.environ.get("PEYEEYE_ENTITIES")
+        if entities is None and env_entities:
+            entities = [e.strip() for e in env_entities.split(",") if e.strip()]
+        self.entities = entities or None
+        mode = session_mode or os.environ.get("PEYEEYE_SESSION_MODE") or "stateful"
+        if mode not in ("stateful", "stateless"):
+            raise ValueError(
+                f"PEYEEYE_SESSION_MODE must be 'stateful' or 'stateless', got {mode!r}"
+            )
+        self.session_mode = mode
+        self._client: Optional[httpx.AsyncClient] = None
+
+    async def _async_client(self) -> httpx.AsyncClient:
+        if self._client is None:
+            self._client = httpx.AsyncClient(timeout=HTTP_TIMEOUT_SECONDS)
+        return self._client
+
+    def _headers(self) -> Dict[str, str]:
+        return {
+            "Authorization": f"Bearer {self.api_key}",
+            "Content-Type": "application/json",
+        }
+
+    async def redact_batch(self, texts: List[str]) -> Tuple[List[str], Optional[str]]:
+        """Redact a batch of texts. Returns ``(redacted, session_id_or_skey)``.
+
+        Raises ``PEyeEyeAPIError`` on any non-2xx, timeout, or unexpected shape.
+        """
+        body: Dict[str, Any] = {"text": texts, "locale": self.locale}
+        if self.entities:
+            body["entities"] = list(self.entities)
+        if self.session_mode == "stateless":
+            body["session"] = "stateless"
+
+        payload = await self._post("/v1/redact", body)
+        out = payload.get("text")
+        if isinstance(out, str):
+            redacted = [out]
+        elif isinstance(out, list):
+            redacted = [str(x) for x in out]
+        else:
+            raise PEyeEyeAPIError(
+                "Peyeeye /v1/redact returned an unexpected response shape; "
+                "refusing to forward unredacted text."
+            )
+
+        if self.session_mode == "stateless":
+            session_id = payload.get("rehydration_key")
+        else:
+            session_id = payload.get("session_id") or payload.get("session")
+
+        return redacted, session_id
+
+    async def rehydrate(self, text: str, session_id: str) -> str:
+        if not text:
+            return text
+        try:
+            payload = await self._post(
+                "/v1/rehydrate", {"text": text, "session": session_id}
+            )
+        except PEyeEyeAPIError as e:
+            # Rehydration failures must not corrupt or drop the LLM response;
+            # log and fall back to the (already-redacted) text.
+            logger.warning("rehydrate failed: %s", e)
+            return text
+        return payload.get("text", text)
+
+    async def delete_session(self, session_id: str) -> None:
+        if not session_id.startswith("ses_"):
+            return
+        client = await self._async_client()
+        try:
+            await client.delete(
+                f"{self.api_base}/v1/sessions/{session_id}",
+                headers=self._headers(),
+                timeout=10.0,
+            )
+        except Exception as e:  # pragma: no cover - best effort
+            logger.debug("session cleanup failed: %s", e)
+
+    async def _post(self, path: str, body: Dict[str, Any]) -> Dict[str, Any]:
+        client = await self._async_client()
+        url = f"{self.api_base}{path}"
+        try:
+            resp = await client.post(url, headers=self._headers(), json=body)
+        except httpx.TimeoutException as e:
+            raise PEyeEyeAPIError(f"Peyeeye {path} timed out") from e
+        except httpx.HTTPError as e:
+            raise PEyeEyeAPIError(f"Peyeeye {path} request failed: {e}") from e
+        if resp.status_code == 401:
+            raise PEyeEyeMissingSecrets("Invalid Peyeeye API key") from None
+        if resp.status_code >= 400:
+            raise PEyeEyeAPIError(
+                f"Peyeeye {path} returned HTTP {resp.status_code}: {resp.text[:200]}"
+            )
+        try:
+            return resp.json()
+        except json.JSONDecodeError as e:
+            raise PEyeEyeAPIError(f"Peyeeye {path} returned non-JSON body") from e
+
+
+# ------------------------------------------------------------- request walkers
+
+
+def iter_request_texts(body: Dict[str, Any], endpoint: str) -> List[Tuple[str, ...]]:
+    """Yield ``("path", ...)`` tuples identifying every user-text chunk.
+
+    Mirrors the litellm pre-call hook: walks ``messages[].content`` (string or
+    multimodal text-part list) for chat-style endpoints, and ``input`` for the
+    OpenAI Responses API.
+
+    Returns a list of (path-tuple, text) pairs. ``path-tuple`` is consumed by
+    ``set_request_text`` to write the redacted value back.
+    """
+    parts: List[Tuple[Tuple[Any, ...], str]] = []
+
+    if endpoint == "/v1/responses":
+        input_val = body.get("input")
+        if isinstance(input_val, str) and input_val:
+            parts.append((("input",), input_val))
+        elif isinstance(input_val, list):
+            for i, item in enumerate(input_val):
+                if not isinstance(item, dict):
+                    continue
+                if item.get("role") != "user":
+                    continue
+                content = item.get("content")
+                if isinstance(content, str) and content:
+                    parts.append((("input", i, "content"), content))
+                elif isinstance(content, list):
+                    for j, sub in enumerate(content):
+                        if isinstance(sub, dict) and sub.get("type") == "text":
+                            text = sub.get("text", "")
+                            if text:
+                                parts.append((("input", i, "content", j, "text"), text))
+        return parts
+
+    # /v1/chat/completions and /v1/messages both use messages[]
+    messages = body.get("messages") or []
+    for i, msg in enumerate(messages):
+        if not isinstance(msg, dict):
+            continue
+        if msg.get("role") != "user":
+            continue
+        content = msg.get("content")
+        if isinstance(content, str) and content:
+            parts.append((("messages", i, "content"), content))
+        elif isinstance(content, list):
+            for j, sub in enumerate(content):
+                if isinstance(sub, dict) and sub.get("type") == "text":
+                    text = sub.get("text", "")
+                    if text:
+                        parts.append((("messages", i, "content", j, "text"), text))
+    return parts
+
+
+def set_request_text(body: Dict[str, Any], path: Tuple[Any, ...], value: str) -> None:
+    """Write ``value`` into ``body`` at the given path."""
+    cur: Any = body
+    for key in path[:-1]:
+        cur = cur[key]
+    cur[path[-1]] = value
+
+
+def iter_response_texts(
+    body: Dict[str, Any], endpoint: str
+) -> List[Tuple[Tuple[Any, ...], str]]:
+    """Yield ``(path, text)`` for every text chunk in an LLM response body."""
+    parts: List[Tuple[Tuple[Any, ...], str]] = []
+    if endpoint == "/v1/messages":
+        content = body.get("content")
+        if isinstance(content, list):
+            for j, sub in enumerate(content):
+                if isinstance(sub, dict) and sub.get("type") == "text":
+                    text = sub.get("text", "")
+                    if text:
+                        parts.append((("content", j, "text"), text))
+        return parts
+
+    # /v1/chat/completions, /v1/responses (synchronous), and similar
+    choices = body.get("choices")
+    if isinstance(choices, list):
+        for i, choice in enumerate(choices):
+            if not isinstance(choice, dict):
+                continue
+            message = choice.get("message")
+            if isinstance(message, dict):
+                content = message.get("content")
+                if isinstance(content, str) and content:
+                    parts.append((("choices", i, "message", "content"), content))
+    # OpenAI Responses API: top-level "output" array
+    output = body.get("output")
+    if isinstance(output, list):
+        for i, item in enumerate(output):
+            if not isinstance(item, dict):
+                continue
+            content = item.get("content")
+            if isinstance(content, list):
+                for j, sub in enumerate(content):
+                    if isinstance(sub, dict) and sub.get("type") in (
+                        "text",
+                        "output_text",
+                    ):
+                        text = sub.get("text", "")
+                        if text:
+                            parts.append((("output", i, "content", j, "text"), text))
+    return parts
+
+
+# -------------------------------------------------------------------- FastAPI
+
+
+def create_app(client: Optional[PEyeEyeClient] = None) -> FastAPI:
+    """Build the FastAPI app. ``client`` is overridable for tests."""
+    app = FastAPI(title="Peyeeye PII filter", version="1.0.0")
+    cache = _SessionCache()
+
+    def _client() -> PEyeEyeClient:
+        nonlocal client
+        if client is None:
+            client = PEyeEyeClient()
+        return client
+
+    @app.post("/redact/{path:path}")
+    async def redact(path: str, request: Request) -> Response:
+        endpoint = f"/{path}"
+        request_id = request.headers.get("x-request-id", "unknown")
+        try:
+            body = await request.json()
+        except json.JSONDecodeError:
+            raise HTTPException(status_code=400, detail="invalid JSON body")
+
+        text_parts = iter_request_texts(body, endpoint)
+        if not text_parts:
+            logger.info("request_id=%s no text to redact", request_id)
+            return JSONResponse(content=body)
+
+        texts = [t for _, t in text_parts]
+        try:
+            redacted, session_id = await _client().redact_batch(texts)
+        except PEyeEyeMissingSecrets as e:
+            logger.error("request_id=%s missing secrets: %s", request_id, e)
+            raise HTTPException(status_code=500, detail=str(e))
+        except PEyeEyeAPIError as e:
+            # Fail-closed: do not pass unredacted text through.
+            logger.error("request_id=%s redact failed: %s", request_id, e)
+            raise HTTPException(status_code=502, detail=str(e))
+
+        # Length-guard: must match exactly. The API contract is one-to-one.
+        if len(redacted) != len(text_parts):
+            logger.error(
+                "request_id=%s length mismatch: sent=%d got=%d",
+                request_id,
+                len(text_parts),
+                len(redacted),
+            )
+            raise HTTPException(
+                status_code=502,
+                detail=(
+                    f"Peyeeye /v1/redact returned {len(redacted)} texts for "
+                    f"{len(text_parts)} inputs; refusing to forward partially-"
+                    "redacted data"
+                ),
+            )
+
+        for (path_tuple, _), value in zip(text_parts, redacted):
+            set_request_text(body, path_tuple, value)
+
+        if session_id:
+            cache.set(request_id, session_id)
+            logger.info(
+                "request_id=%s redacted %d chunk(s); cached session",
+                request_id,
+                len(text_parts),
+            )
+        else:
+            logger.info(
+                "request_id=%s redacted %d chunk(s); no session id returned",
+                request_id,
+                len(text_parts),
+            )
+
+        return JSONResponse(content=body)
+
+    @app.post("/rehydrate/{path:path}")
+    async def rehydrate(path: str, request: Request) -> Response:
+        endpoint = f"/{path}"
+        request_id = request.headers.get("x-request-id", "unknown")
+        raw = await request.body()
+
+        session_id = cache.pop(request_id)
+        if not session_id:
+            logger.info(
+                "request_id=%s no session cached, passing response through",
+                request_id,
+            )
+            return Response(content=raw, media_type="application/json")
+
+        # Streaming SSE: not supported for stateful rehydration in this demo.
+        # Plano sends raw chunks, but rehydration needs the full token to look
+        # up the original; we pass through and rely on a non-streaming flow.
+        body_str = raw.decode("utf-8", errors="replace")
+        if body_str.lstrip().startswith("data:") or "data: " in body_str[:32]:
+            logger.warning(
+                "request_id=%s SSE not supported; passing through "
+                "(use non-streaming for now)",
+                request_id,
+            )
+            # Don't lose the session id on the way back if SSE.
+            cache.set(request_id, session_id)
+            return Response(content=raw, media_type="text/event-stream")
+
+        try:
+            body = json.loads(body_str)
+        except json.JSONDecodeError:
+            logger.warning(
+                "request_id=%s response is not JSON; passing through", request_id
+            )
+            return Response(content=raw, media_type="application/json")
+
+        text_parts = iter_response_texts(body, endpoint)
+        if not text_parts:
+            logger.info("request_id=%s no response text to rehydrate", request_id)
+            await _maybe_delete_session(_client(), session_id)
+            return JSONResponse(content=body)
+
+        # Run rehydrate calls concurrently — each returns the original text,
+        # falling back to the redacted value on rehydrate error.
+        tasks = [_client().rehydrate(text, session_id) for _, text in text_parts]
+        restored = await asyncio.gather(*tasks)
+        for (path_tuple, _), value in zip(text_parts, restored):
+            set_request_text(body, path_tuple, value)
+
+        await _maybe_delete_session(_client(), session_id)
+        logger.info("request_id=%s rehydrated %d chunk(s)", request_id, len(text_parts))
+        return JSONResponse(content=body)
+
+    @app.get("/health")
+    async def health() -> Dict[str, str]:
+        return {"status": "healthy"}
+
+    return app
+
+
+async def _maybe_delete_session(client: PEyeEyeClient, session_id: str) -> None:
+    """Best-effort delete of a stateful session id."""
+    if client.session_mode == "stateful":
+        try:
+            await client.delete_session(session_id)
+        except Exception:  # pragma: no cover - best effort
+            pass
+
+
+# Default ASGI app — used by ``uvicorn peyeeye:app``.
+# Lazily resolves the client so tests can construct ``create_app(client=...)``
+# without requiring PEYEEYE_API_KEY in the environment.
+app = create_app()
diff --git a/demos/filter_chains/peyeeye/pyproject.toml b/demos/filter_chains/peyeeye/pyproject.toml
new file mode 100644
index 000000000..605991f5f
--- /dev/null
+++ b/demos/filter_chains/peyeeye/pyproject.toml
@@ -0,0 +1,29 @@
+[project]
+name = "peyeeye_filter"
+version = "0.1.0"
+description = "Peyeeye PII redaction & rehydration filter for Plano filter chains"
+readme = "README.md"
+requires-python = ">=3.10,<3.14"
+dependencies = [
+    "fastapi>=0.104.1",
+    "uvicorn>=0.24.0",
+    "httpx>=0.27.0",
+    "pydantic>=2.0.0",
+]
+
+[dependency-groups]
+dev = [
+    "pytest>=8.0.0",
+    "pytest-asyncio>=0.23.0",
+    "respx>=0.21.0",
+]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["."]
diff --git a/demos/filter_chains/peyeeye/run_demo.sh b/demos/filter_chains/peyeeye/run_demo.sh
new file mode 100644
index 000000000..752efbcf0
--- /dev/null
+++ b/demos/filter_chains/peyeeye/run_demo.sh
@@ -0,0 +1,44 @@
+#!/bin/bash
+set -e
+
+start_demo() {
+  if [ -f ".env" ]; then
+    echo ".env file already exists. Skipping creation."
+  else
+    if [ -z "${PEYEEYE_API_KEY:-}" ]; then
+      echo "Error: PEYEEYE_API_KEY environment variable is not set for the demo."
+      exit 1
+    fi
+    if [ -z "${OPENAI_API_KEY:-}" ]; then
+      echo "Error: OPENAI_API_KEY environment variable is not set for the demo."
+      exit 1
+    fi
+
+    echo "Creating .env file..."
+    {
+      echo "PEYEEYE_API_KEY=$PEYEEYE_API_KEY"
+      echo "OPENAI_API_KEY=$OPENAI_API_KEY"
+    } > .env
+    echo ".env file created."
+  fi
+
+  echo "Starting Plano with config.yaml..."
+  planoai up config.yaml
+
+  echo "Starting Peyeeye filter service..."
+  bash start_agents.sh &
+}
+
+stop_demo() {
+  echo "Stopping Peyeeye filter service..."
+  pkill -f start_agents.sh 2>/dev/null || true
+
+  echo "Stopping Plano..."
+  planoai down
+}
+
+if [ "$1" == "down" ]; then
+  stop_demo
+else
+  start_demo
+fi
diff --git a/demos/filter_chains/peyeeye/start_agents.sh b/demos/filter_chains/peyeeye/start_agents.sh
new file mode 100644
index 000000000..c549fdc45
--- /dev/null
+++ b/demos/filter_chains/peyeeye/start_agents.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+set -e
+
+PIDS=()
+
+log() { echo "$(date '+%F %T') - $*"; }
+
+cleanup() {
+    log "Stopping agents..."
+    for PID in "${PIDS[@]}"; do
+        kill $PID 2>/dev/null && log "Stopped process $PID"
+    done
+    exit 0
+}
+
+trap cleanup EXIT INT TERM
+
+if [ -z "${PEYEEYE_API_KEY:-}" ]; then
+    log "ERROR: PEYEEYE_API_KEY is not set."
+    exit 1
+fi
+
+log "Starting Peyeeye filter service on port 10502..."
+uv run uvicorn peyeeye:app --host 0.0.0.0 --port 10502 &
+PIDS+=($!)
+
+for PID in "${PIDS[@]}"; do
+    wait "$PID"
+done
diff --git a/demos/filter_chains/peyeeye/test.sh b/demos/filter_chains/peyeeye/test.sh
new file mode 100644
index 000000000..5326b2f3d
--- /dev/null
+++ b/demos/filter_chains/peyeeye/test.sh
@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+BASE_URL="http://localhost:12000"
+PASS=0
+FAIL=0
+
+echo "Waiting for Plano to be ready..."
+for i in $(seq 1 30); do
+    if curl -sf "$BASE_URL/v1/models" > /dev/null 2>&1; then
+        echo "Plano is ready."
+        break
+    fi
+    if [ "$i" -eq 30 ]; then
+        echo "ERROR: Plano did not become ready in time."
+        exit 1
+    fi
+    sleep 2
+done
+
+run_test() {
+    local name="$1"
+    local path="$2"
+    local expected_code="$3"
+    local body="$4"
+
+    http_code=$(curl -s -o /tmp/peyeeye_test_body -w "%{http_code}" \
+        -X POST "$BASE_URL$path" \
+        -H "Content-Type: application/json" \
+        -d "$body")
+
+    if [ "$http_code" -eq "$expected_code" ]; then
+        echo "  PASS  $name (HTTP $http_code)"
+        PASS=$((PASS + 1))
+    else
+        echo "  FAIL  $name -- expected $expected_code, got $http_code"
+        echo "        Body: $(cat /tmp/peyeeye_test_body)"
+        FAIL=$((FAIL + 1))
+    fi
+}
+
+echo ""
+echo "=== /v1/chat/completions ==="
+
+run_test "Non-streaming with PII" /v1/chat/completions 200 '{
+  "model": "gpt-4o-mini",
+  "messages": [{"role": "user", "content": "Email me at jane@example.com"}],
+  "stream": false
+}'
+
+run_test "No PII" /v1/chat/completions 200 '{
+  "model": "gpt-4o-mini",
+  "messages": [{"role": "user", "content": "What is 2+2?"}],
+  "stream": false
+}'
+
+echo ""
+echo "=== /v1/messages (Anthropic) ==="
+
+run_test "Non-streaming with PII (SSN)" /v1/messages 200 '{
+  "model": "claude-sonnet-4-20250514",
+  "max_tokens": 256,
+  "messages": [{"role": "user", "content": "My SSN is 123-45-6789"}]
+}'
+
+echo ""
+echo "Results: $PASS passed, $FAIL failed"
+
+if [ "$FAIL" -gt 0 ]; then
+    exit 1
+fi
diff --git a/demos/filter_chains/peyeeye/test_peyeeye.py b/demos/filter_chains/peyeeye/test_peyeeye.py
new file mode 100644
index 000000000..87992589b
--- /dev/null
+++ b/demos/filter_chains/peyeeye/test_peyeeye.py
@@ -0,0 +1,471 @@
+"""Tests for the Peyeeye Plano filter.
+
+The Peyeeye API (`https://api.peyeeye.ai`) is fully mocked with `respx`. Every
+new branch in `peyeeye.py` should have at least one test below.
+"""
+
+from __future__ import annotations
+
+import json
+from typing import Any, Dict
+
+import httpx
+import pytest
+import respx
+from fastapi.testclient import TestClient
+
+from peyeeye import (
+    PEyeEyeClient,
+    PEyeEyeMissingSecrets,
+    create_app,
+    iter_request_texts,
+    iter_response_texts,
+    set_request_text,
+)
+
+# ------------------------------------------------------------------- fixtures
+
+
+@pytest.fixture
+def api_base() -> str:
+    return "https://api.peyeeye.ai"
+
+
+@pytest.fixture
+def client(monkeypatch, api_base) -> PEyeEyeClient:
+    monkeypatch.setenv("PEYEEYE_API_KEY", "pk_test_123")
+    monkeypatch.delenv("PEYEEYE_API_BASE", raising=False)
+    monkeypatch.delenv("PEYEEYE_LOCALE", raising=False)
+    monkeypatch.delenv("PEYEEYE_ENTITIES", raising=False)
+    monkeypatch.delenv("PEYEEYE_SESSION_MODE", raising=False)
+    return PEyeEyeClient()
+
+
+@pytest.fixture
+def app_client(client) -> TestClient:
+    return TestClient(create_app(client=client))
+
+
+# --------------------------------------------------------------- client tests
+
+
+def test_client_missing_api_key(monkeypatch):
+    monkeypatch.delenv("PEYEEYE_API_KEY", raising=False)
+    with pytest.raises(PEyeEyeMissingSecrets):
+        PEyeEyeClient()
+
+
+def test_client_invalid_session_mode(monkeypatch):
+    monkeypatch.setenv("PEYEEYE_API_KEY", "pk_test_123")
+    with pytest.raises(ValueError):
+        PEyeEyeClient(session_mode="bogus")
+
+
+def test_client_picks_up_env_entities(monkeypatch):
+    monkeypatch.setenv("PEYEEYE_API_KEY", "pk_test_123")
+    monkeypatch.setenv("PEYEEYE_ENTITIES", "EMAIL, SSN ,CREDIT_CARD")
+    c = PEyeEyeClient()
+    assert c.entities == ["EMAIL", "SSN", "CREDIT_CARD"]
+
+
+# -------------------------------------------------------------- iter helpers
+
+
+def test_iter_request_texts_chat_string():
+    body = {"messages": [{"role": "user", "content": "hello jane@example.com"}]}
+    parts = iter_request_texts(body, "/v1/chat/completions")
+    assert parts == [(("messages", 0, "content"), "hello jane@example.com")]
+
+
+def test_iter_request_texts_chat_multimodal():
+    body = {
+        "messages": [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "hi"},
+                    {"type": "image_url", "image_url": {"url": "..."}},
+                    {"type": "text", "text": "ssn 111-22-3333"},
+                ],
+            }
+        ]
+    }
+    parts = iter_request_texts(body, "/v1/chat/completions")
+    assert parts == [
+        (("messages", 0, "content", 0, "text"), "hi"),
+        (("messages", 0, "content", 2, "text"), "ssn 111-22-3333"),
+    ]
+
+
+def test_iter_request_texts_skips_non_user_roles():
+    body = {
+        "messages": [
+            {"role": "system", "content": "you are helpful"},
+            {"role": "user", "content": "hi"},
+            {"role": "assistant", "content": "hello"},
+        ]
+    }
+    parts = iter_request_texts(body, "/v1/chat/completions")
+    assert len(parts) == 1
+    assert parts[0][1] == "hi"
+
+
+def test_iter_request_texts_responses_string():
+    body = {"input": "hello jane@example.com"}
+    parts = iter_request_texts(body, "/v1/responses")
+    assert parts == [(("input",), "hello jane@example.com")]
+
+
+def test_iter_request_texts_responses_list():
+    body = {
+        "input": [
+            {"role": "system", "content": "ignored"},
+            {"role": "user", "content": "hi"},
+            {
+                "role": "user",
+                "content": [{"type": "text", "text": "ssn 111-22-3333"}],
+            },
+        ]
+    }
+    parts = iter_request_texts(body, "/v1/responses")
+    assert parts == [
+        (("input", 1, "content"), "hi"),
+        (("input", 2, "content", 0, "text"), "ssn 111-22-3333"),
+    ]
+
+
+def test_set_request_text_round_trip():
+    body: Dict[str, Any] = {"messages": [{"role": "user", "content": "raw"}]}
+    set_request_text(body, ("messages", 0, "content"), "redacted")
+    assert body["messages"][0]["content"] == "redacted"
+
+
+def test_iter_response_texts_chat():
+    body = {"choices": [{"message": {"content": "Email [EMAIL_0] back."}}]}
+    parts = iter_response_texts(body, "/v1/chat/completions")
+    assert parts == [(("choices", 0, "message", "content"), "Email [EMAIL_0] back.")]
+
+
+def test_iter_response_texts_anthropic():
+    body = {"content": [{"type": "text", "text": "Reach [EMAIL_0]"}]}
+    parts = iter_response_texts(body, "/v1/messages")
+    assert parts == [(("content", 0, "text"), "Reach [EMAIL_0]")]
+
+
+# ------------------------------------------------------------ /redact endpoint
+
+
+@respx.mock
+def test_redact_chat_happy_path(app_client, api_base):
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200,
+            json={
+                "text": ["hello [EMAIL_0]"],
+                "session_id": "ses_abc",
+            },
+        )
+    )
+
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "hello jane@example.com"}],
+        },
+        headers={"x-request-id": "req-1"},
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["messages"][0]["content"] == "hello [EMAIL_0]"
+
+
+@respx.mock
+def test_redact_no_pii_no_session_cached(app_client, api_base):
+    # Even with no text-bearing chunks, the body is returned untouched.
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={"model": "gpt-4o-mini", "messages": []},
+        headers={"x-request-id": "req-empty"},
+    )
+    assert resp.status_code == 200
+    # No call should have been made to peyeeye.
+    assert not respx.routes
+
+
+@respx.mock
+def test_redact_length_guard_fails_closed(app_client, api_base):
+    """If the API returns a different number of texts, refuse to forward."""
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200,
+            json={"text": ["only one"], "session_id": "ses_x"},
+        )
+    )
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [
+                {"role": "user", "content": "first jane@example.com"},
+                {"role": "user", "content": "second 555-123-4567"},
+            ],
+        },
+        headers={"x-request-id": "req-bad-len"},
+    )
+    assert resp.status_code == 502
+    assert "refusing to forward" in resp.json()["detail"]
+
+
+@respx.mock
+def test_redact_unexpected_shape_fails_closed(app_client, api_base):
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(200, json={"text": 42, "session_id": "ses_x"})
+    )
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "x"}],
+        },
+        headers={"x-request-id": "req-bad-shape"},
+    )
+    assert resp.status_code == 502
+    assert "unexpected response shape" in resp.json()["detail"]
+
+
+@respx.mock
+def test_redact_5xx_fails_closed(app_client, api_base):
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(500, text="boom")
+    )
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "x"}],
+        },
+        headers={"x-request-id": "req-5xx"},
+    )
+    assert resp.status_code == 502
+    assert "HTTP 500" in resp.json()["detail"]
+
+
+@respx.mock
+def test_redact_401_fails_closed_with_500(app_client, api_base):
+    """Auth errors surface as PEyeEyeMissingSecrets -> HTTP 500."""
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(401, json={"error": "bad key"})
+    )
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "x"}],
+        },
+        headers={"x-request-id": "req-401"},
+    )
+    assert resp.status_code == 500
+    assert "Invalid Peyeeye API key" in resp.json()["detail"]
+
+
+@respx.mock
+def test_redact_invalid_json_body(app_client):
+    resp = app_client.post(
+        "/redact/v1/chat/completions",
+        content=b"not json",
+        headers={
+            "Content-Type": "application/json",
+            "x-request-id": "req-bad-json",
+        },
+    )
+    assert resp.status_code == 400
+
+
+# --------------------------------------------------------- /rehydrate endpoint
+
+
+@respx.mock
+def test_rehydrate_round_trip(app_client, api_base):
+    """Redact then rehydrate share the request id; placeholders restored."""
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200,
+            json={
+                "text": ["hello [EMAIL_0]"],
+                "session_id": "ses_round",
+            },
+        )
+    )
+    respx.post(f"{api_base}/v1/rehydrate").mock(
+        return_value=httpx.Response(
+            200, json={"text": "Reach jane@example.com today.", "replaced": 1}
+        )
+    )
+    respx.delete(f"{api_base}/v1/sessions/ses_round").mock(
+        return_value=httpx.Response(204)
+    )
+
+    redact_resp = app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "hello jane@example.com"}],
+        },
+        headers={"x-request-id": "req-round"},
+    )
+    assert redact_resp.status_code == 200
+
+    rehydrate_resp = app_client.post(
+        "/rehydrate/v1/chat/completions",
+        json={"choices": [{"message": {"content": "Reach [EMAIL_0] today."}}]},
+        headers={"x-request-id": "req-round"},
+    )
+    assert rehydrate_resp.status_code == 200
+    body = rehydrate_resp.json()
+    assert body["choices"][0]["message"]["content"] == "Reach jane@example.com today."
+
+
+@respx.mock
+def test_rehydrate_no_session_cached_passthrough(app_client):
+    raw = {"choices": [{"message": {"content": "no session here"}}]}
+    resp = app_client.post(
+        "/rehydrate/v1/chat/completions",
+        json=raw,
+        headers={"x-request-id": "req-uncached"},
+    )
+    assert resp.status_code == 200
+    assert resp.json() == raw
+
+
+@respx.mock
+def test_rehydrate_anthropic_messages(app_client, api_base):
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200,
+            json={"text": ["My ssn is [SSN_0]"], "session_id": "ses_anth"},
+        )
+    )
+    respx.post(f"{api_base}/v1/rehydrate").mock(
+        return_value=httpx.Response(
+            200, json={"text": "My ssn is 111-22-3333", "replaced": 1}
+        )
+    )
+    respx.delete(f"{api_base}/v1/sessions/ses_anth").mock(
+        return_value=httpx.Response(204)
+    )
+
+    app_client.post(
+        "/redact/v1/messages",
+        json={
+            "model": "claude-sonnet-4",
+            "messages": [{"role": "user", "content": "My ssn is 111-22-3333"}],
+        },
+        headers={"x-request-id": "req-anth"},
+    )
+    resp = app_client.post(
+        "/rehydrate/v1/messages",
+        json={"content": [{"type": "text", "text": "My ssn is [SSN_0]"}]},
+        headers={"x-request-id": "req-anth"},
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["content"][0]["text"] == "My ssn is 111-22-3333"
+
+
+@respx.mock
+def test_rehydrate_sse_passthrough(app_client, api_base):
+    """SSE bodies are passed through unchanged (and the session id is kept)."""
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200, json={"text": ["[EMAIL_0]"], "session_id": "ses_sse"}
+        )
+    )
+    app_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "jane@example.com"}],
+        },
+        headers={"x-request-id": "req-sse"},
+    )
+    sse_body = b'data: {"choices":[{"delta":{"content":"hi"}}]}\n\n'
+    resp = app_client.post(
+        "/rehydrate/v1/chat/completions",
+        content=sse_body,
+        headers={
+            "Content-Type": "text/event-stream",
+            "x-request-id": "req-sse",
+        },
+    )
+    assert resp.status_code == 200
+    assert resp.content == sse_body
+
+
+@respx.mock
+def test_redact_responses_input_string(app_client, api_base):
+    respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200,
+            json={
+                "text": ["My email is [EMAIL_0]"],
+                "session_id": "ses_resp",
+            },
+        )
+    )
+    resp = app_client.post(
+        "/redact/v1/responses",
+        json={"model": "gpt-4o-mini", "input": "My email is jane@example.com"},
+        headers={"x-request-id": "req-resp"},
+    )
+    assert resp.status_code == 200
+    assert resp.json()["input"] == "My email is [EMAIL_0]"
+
+
+@respx.mock
+def test_stateless_session_mode(monkeypatch, api_base):
+    """Stateless mode caches the rehydration_key and skips DELETE."""
+    monkeypatch.setenv("PEYEEYE_API_KEY", "pk_test_123")
+    monkeypatch.setenv("PEYEEYE_SESSION_MODE", "stateless")
+    client = PEyeEyeClient()
+    test_client = TestClient(create_app(client=client))
+
+    redact_route = respx.post(f"{api_base}/v1/redact").mock(
+        return_value=httpx.Response(
+            200,
+            json={
+                "text": ["hello [EMAIL_0]"],
+                "rehydration_key": "skey_xyz",
+            },
+        )
+    )
+    rehydrate_route = respx.post(f"{api_base}/v1/rehydrate").mock(
+        return_value=httpx.Response(
+            200, json={"text": "hello jane@example.com", "replaced": 1}
+        )
+    )
+    delete_route = respx.delete(f"{api_base}/v1/sessions/skey_xyz")
+
+    test_client.post(
+        "/redact/v1/chat/completions",
+        json={
+            "model": "gpt-4o-mini",
+            "messages": [{"role": "user", "content": "hello jane@example.com"}],
+        },
+        headers={"x-request-id": "req-stateless"},
+    )
+    # Inspect the redact request body to confirm session=stateless was sent.
+    assert redact_route.called
+    sent_body = json.loads(redact_route.calls.last.request.content)
+    assert sent_body["session"] == "stateless"
+
+    resp = test_client.post(
+        "/rehydrate/v1/chat/completions",
+        json={"choices": [{"message": {"content": "hello [EMAIL_0]"}}]},
+        headers={"x-request-id": "req-stateless"},
+    )
+    assert resp.status_code == 200
+    assert resp.json()["choices"][0]["message"]["content"] == "hello jane@example.com"
+    # Stateless: no DELETE call.
+    assert not delete_route.called
+    assert rehydrate_route.called