refactor: add markdown frontend

examples/config.py

@@ -12,12 +12,30 @@ from beaver_gateway.agents.base import ExposedMcp
 from beaver_gateway.agents.claude import ClaudeAgent
 from beaver_gateway.agents.raycast import RaycastAgent, RemoteTool, UserPreferences
 from beaver_gateway.core.registry import Gateway
+from beaver_gateway.core.turn_record import TurnRecord, slugify
 from beaver_gateway.frontends.admin import AdminFrontend
 from beaver_gateway.frontends.anthropic import AnthropicMessagesFrontend
+from beaver_gateway.frontends.markdown import MarkdownFrontend
 from beaver_gateway.frontends.mcp_server import McpServerFrontend
 from beaver_gateway.mcp.types import McpServer
 
 
+def chat_log_path(record: TurnRecord, vault: Path) -> Path:
+    """Decide where a logged chat from another frontend lands in the vault.
+
+    Called by ``MarkdownFrontend`` (with ``log_all_chats=True``) the first
+    time a conversation needs a file — continuation turns are matched by
+    fingerprint and stick to the file picked here. Return value can be
+    absolute or relative; relative paths are anchored under ``vault``.
+
+    Layout below: ``<vault>/<YYYY-MM>/<YYYY-MM-DD>_<topic>.md`` where
+    ``topic`` is a slug of the very first user message in the chat.
+    """
+    today = date.today()
+    topic = slugify(record.first_user_text, maxlen=40)
+    return vault / f"{today:%Y-%m}" / f"{today:%Y-%m-%d}_{topic}.md"
+
+
 def current_time() -> str:
     """Return the current local time as an ISO-8601 string.
 
@@ -162,5 +180,45 @@ gateway = Gateway(
         # `messages` only work on `/v1/messages`; `mcp` only on
         # `/mcp/<name>`; `*` works everywhere.
         AdminFrontend(host="0.0.0.0", port=8002),
+        # Obsidian-vault chat frontend. Each `.md` is one conversation
+        # (User/Assistant turn pairs). The Obsidian companion plugin
+        # POSTs `{filename, content?}` to `/chat` — the frontend reads
+        # the file, runs the agent if the last turn is `user`, and
+        # appends the assistant reply back. With `log_all_chats=True`
+        # *every* turn (from Anthropic Messages too) is mirrored into
+        # `{vault}/_logs/<agent>/` so the vault is the central archive.
+        #
+        # `vault_path` here points at a per-restart tempdir so the
+        # example boots cleanly; in real deployments mount the
+        # Obsidian-sync container's vault volume to a stable path and
+        # pass that instead.
+        MarkdownFrontend(
+            host="0.0.0.0",
+            port=8003,
+            # Point at the dedicated chats subdir of your real Obsidian
+            # vault — the gateway has no idea (and no need) about other
+            # notes outside it. Path resolution / vault-escape checks
+            # are anchored here, so absolute-path attempts (and ``..``
+            # tricks) can't reach notes alongside it.
+            #
+            #   vault_path=Path("/Users/me/Obsidian/Personal/chats"),
+            #
+            # Per-restart tempdir kept here so the example boots even
+            # without a real vault on the host.
+            vault_path=Path(tempfile.mkdtemp(prefix="beaver-vault-")).resolve(),
+            default_agent="research",
+            log_all_chats=True,
+            # ``log_path`` (optional) overrides the default
+            # ``{vault}/_logs/<agent>/<date>_<hex>.md`` layout for chats
+            # logged from OTHER frontends (Anthropic Messages, admin
+            # in-browser chat). Defined as a top-of-file function so the
+            # types are explicit and the IDE can hover them; a lambda
+            # works too, but a real ``def`` keeps the signature visible
+            # and lets you docstring it. Heads up: any custom path
+            # forces ``warm_index`` to scan the entire vault on startup
+            # so the fingerprint→file map survives a restart no matter
+            # where you put files.
+            log_path=chat_log_path,
+        ),
     ],
 )

pyproject.toml

@@ -7,6 +7,7 @@ authors = [
 ]
 requires-python = ">=3.13"
 dependencies = [
+    "aiofile>=3.11.1",
     "aiohttp>=3.13.5",
     "aiosqlite>=0.22.1",
     "anthropic>=0.103.0",
@@ -20,6 +21,7 @@ dependencies = [
     "psycopg[binary]>=3.3.4",
     "pydantic>=2.13.4",
     "pydantic-settings>=2.14.1",
+    "python-frontmatter>=1.2.0",
     "sqlmodel>=0.0.38",
     "uvicorn[standard]>=0.47.0",
     "uvloop>=0.22.1",

src/beaver_gateway/core/turn_record.py

@@ -0,0 +1,133 @@
+"""Cross-frontend turn record.
+
+Frontends that finish a turn (the Anthropic Messages frontend, the
+markdown frontend) emit a :class:`TurnRecord` to every handler in
+``GatewayRuntime.turn_log_handlers``. The markdown frontend uses this
+to persist chats from other frontends into the Obsidian vault — see
+``frontends/markdown/crossfront.py``.
+
+Kept tiny on purpose: it carries the structured-enough payload a logger
+needs (which agent ran, input history, the assembled assistant reply)
+and nothing else. The full event stream is gone by the time handlers
+run — if a future consumer needs deltas it would subscribe at a lower
+level, not here.
+"""
+
+from __future__ import annotations
+
+import re
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from anthropic.types import Message, MessageParam
+
+
+__all__ = ["TurnRecord", "slugify"]
+
+
+# Filesystem-safe slug: collapse anything that isn't a word char or
+# space/hyphen to a hyphen, then squash runs of separators. Aimed at
+# letting users build filenames from ``record.first_user_text`` without
+# hand-rolling sanitization in every config.
+_SLUG_BAD_RE = re.compile(r"[^\w\s\-]+", flags=re.UNICODE)
+_SLUG_SEP_RE = re.compile(r"[\s\-]+", flags=re.UNICODE)
+
+
+def slugify(text: str, *, maxlen: int = 40) -> str:
+    """Sanitize ``text`` for use as a filename fragment.
+
+    Strips punctuation, collapses whitespace/hyphens into single ``-``,
+    and truncates to ``maxlen``. Returns ``"untitled"`` for empty input.
+    Unicode letters are preserved (Obsidian handles them fine; macOS
+    and modern Linux fs's too).
+    """
+    cleaned = _SLUG_BAD_RE.sub(" ", text).strip()
+    cleaned = _SLUG_SEP_RE.sub("-", cleaned).strip("-")
+    if not cleaned:
+        return "untitled"
+    if len(cleaned) > maxlen:
+        cleaned = cleaned[:maxlen].rstrip("-")
+    return cleaned or "untitled"
+
+
+@dataclass(frozen=True, slots=True)
+class TurnRecord:
+    """One completed turn, as seen by a frontend.
+
+    ``input_messages`` is the conversation history sent to the backend
+    (everything *before* the assistant reply). ``output_message`` is the
+    finalized assistant ``Message`` (post-accumulation, with all content
+    blocks attached). ``system`` is the per-request system prompt if any
+    — agents own their own ``system_prompt``, this is the override the
+    caller passed; most handlers can ignore it.
+
+    ``source`` names the frontend that produced the record so the
+    cross-frontend logger can avoid logging its own turns (markdown
+    frontend writing the file would otherwise also receive its own
+    broadcast and double-write).
+    """
+
+    agent_name: str
+    input_messages: list[MessageParam]
+    output_message: Message
+    system: str | None = None
+    source: str = "anthropic"
+
+    @property
+    def first_user_text(self) -> str:
+        """Plain text of the *earliest* user turn in this conversation.
+
+        Useful for naming new files by topic. Empty string if the input
+        history somehow has no user turn (shouldn't happen — turns are
+        broadcast only after a user → assistant cycle).
+        """
+        for msg in self.input_messages:
+            if msg.get("role") == "user":
+                return _text_of(msg.get("content", ""))
+        return ""
+
+    @property
+    def last_user_text(self) -> str:
+        """Plain text of the most recent user turn (the trigger)."""
+        for msg in reversed(self.input_messages):
+            if msg.get("role") == "user":
+                return _text_of(msg.get("content", ""))
+        return ""
+
+    @property
+    def assistant_text(self) -> str:
+        """Plain text of the assistant reply, with thinking/tool blocks dropped."""
+        chunks = [
+            getattr(block, "text", "") or ""
+            for block in getattr(self.output_message, "content", ())
+            if getattr(block, "type", None) == "text"
+        ]
+        return "\n\n".join(c for c in chunks if c)
+
+
+def _text_of(content: object) -> str:
+    """Flatten an Anthropic ``MessageParam.content`` field to a plain string.
+
+    Handles both shapes the SDK accepts: raw string, or a list of block
+    dicts (we pull ``text`` blocks only). Anything we don't recognize is
+    silently skipped — these helpers exist for naming files, not for
+    faithful content reconstruction.
+    """
+    if isinstance(content, str):
+        return content
+    if isinstance(content, list):
+        parts: list[str] = []
+        for blk in content:
+            if not isinstance(blk, dict):
+                continue
+            # ``MessageParam.content`` is typed as a union of typed-dicts
+            # per Anthropic SDK; we only care about plain ``text`` blocks
+            # and look them up via ``Any`` to dodge the keyed-typed-dict
+            # variance gymnastics (``ty`` won't let an open dict alias a
+            # closed-keyed one).
+            d: Any = blk
+            if d.get("type") == "text":
+                parts.append(str(d.get("text", "")))
+        return "\n\n".join(p for p in parts if p)
+    return ""

src/beaver_gateway/frontends/_accumulate.py

@@ -0,0 +1,146 @@
+"""Collapse an Anthropic event stream into one ``Message``.
+
+Extracted from ``AnthropicMessagesFrontend`` so the markdown frontend
+can run the same accumulation logic when it wants the finalized turn
+rather than raw SSE chunks. Mirrors the Anthropic SDK's own accumulator:
+walks events, builds block dicts indexed by their ``content_block``
+index, folds text / thinking deltas in, buffers ``input_json_delta``
+chunks until the block closes (then JSON-parses them once).
+"""
+
+from __future__ import annotations
+
+import json
+from typing import TYPE_CHECKING, Any, Literal, cast
+
+from anthropic.types import (
+    InputJSONDelta,
+    Message,
+    RawContentBlockDeltaEvent,
+    RawContentBlockStartEvent,
+    RawContentBlockStopEvent,
+    RawMessageDeltaEvent,
+    RawMessageStartEvent,
+    SignatureDelta,
+    TextBlock,
+    TextDelta,
+    ThinkingBlock,
+    ThinkingDelta,
+    ToolUseBlock,
+    Usage,
+)
+
+if TYPE_CHECKING:
+    from collections.abc import AsyncIterator
+
+    from beaver_gateway.core.events import MessageStreamEvent, StopReason
+
+
+__all__ = ["StreamAccumulator", "accumulate"]
+
+
+class StreamAccumulator:
+    """Folds a stream of events into one ``Message``, incrementally.
+
+    Use when you need to *both* forward events somewhere (SSE) *and*
+    keep a finalized ``Message`` for post-stream work (audit, logging
+    to disk). Call :meth:`feed` for each event, :meth:`finalize` once.
+    """
+
+    __slots__ = (
+        "_blocks",
+        "_json_buffers",
+        "_message_id",
+        "_role",
+        "_stop_reason",
+        "_stop_sequence",
+        "_usage",
+    )
+
+    def __init__(self) -> None:
+        self._message_id: str = ""
+        self._role: str = "assistant"
+        self._usage: Usage = Usage(input_tokens=0, output_tokens=0)
+        self._blocks: dict[int, dict[str, Any]] = {}
+        self._json_buffers: dict[int, str] = {}
+        self._stop_reason: str | None = None
+        self._stop_sequence: str | None = None
+
+    def feed(self, ev: MessageStreamEvent) -> None:
+        # isinstance, not ``ev.type == "..."``: ty narrows on the
+        # discriminator only via the class, and the raw event union
+        # carries its own discriminators (``Raw*Event``) the SDK
+        # already promises.
+        if isinstance(ev, RawMessageStartEvent):
+            self._message_id = ev.message.id
+            self._role = ev.message.role
+            self._usage = ev.message.usage
+        elif isinstance(ev, RawContentBlockStartEvent):
+            self._blocks[ev.index] = ev.content_block.model_dump()
+            if self._blocks[ev.index].get("type") == "tool_use":
+                self._json_buffers[ev.index] = ""
+        elif isinstance(ev, RawContentBlockDeltaEvent):
+            blk = self._blocks.setdefault(ev.index, {})
+            delta = ev.delta
+            if isinstance(delta, TextDelta):
+                blk["text"] = blk.get("text", "") + delta.text
+            elif isinstance(delta, InputJSONDelta):
+                self._json_buffers[ev.index] = (
+                    self._json_buffers.get(ev.index, "") + delta.partial_json
+                )
+            elif isinstance(delta, ThinkingDelta):
+                blk["thinking"] = blk.get("thinking", "") + delta.thinking
+            elif isinstance(delta, SignatureDelta):
+                blk["signature"] = delta.signature
+        elif isinstance(ev, RawContentBlockStopEvent):
+            blk = self._blocks.get(ev.index, {})
+            if blk.get("type") == "tool_use":
+                raw = self._json_buffers.pop(ev.index, "")
+                blk["input"] = json.loads(raw) if raw.strip() else {}
+        elif isinstance(ev, RawMessageDeltaEvent):
+            self._stop_reason = ev.delta.stop_reason
+            self._stop_sequence = ev.delta.stop_sequence
+            if ev.usage.output_tokens:
+                self._usage = Usage.model_validate(
+                    {
+                        **self._usage.model_dump(),
+                        "output_tokens": ev.usage.output_tokens,
+                    }
+                )
+
+    def finalize(self, *, model: str) -> Message:
+        content: list[Any] = []
+        for idx in sorted(self._blocks):
+            bd = self._blocks[idx]
+            btype = bd.get("type")
+            if btype == "text":
+                content.append(TextBlock.model_validate(bd))
+            elif btype == "tool_use":
+                content.append(ToolUseBlock.model_validate(bd))
+            elif btype == "thinking":
+                content.append(ThinkingBlock.model_validate(bd))
+
+        # ``role`` is always ``"assistant"`` at the wire level — we
+        # initialised the field to that and only overwrite from a
+        # ``RawMessageStartEvent`` which itself carries the same literal.
+        # The cast keeps both type-checkers happy without a runtime check.
+        return Message(
+            id=self._message_id or "msg_unknown",
+            type="message",
+            role=cast("Literal['assistant']", self._role),
+            model=model,
+            content=content,
+            stop_reason=cast("StopReason | None", self._stop_reason),
+            stop_sequence=self._stop_sequence,
+            usage=self._usage,
+        )
+
+
+async def accumulate(
+    events: AsyncIterator[MessageStreamEvent], *, model: str
+) -> Message:
+    """Drain ``events`` into one ``Message`` (used by ``stream=false`` paths)."""
+    acc = StreamAccumulator()
+    async for ev in events:
+        acc.feed(ev)
+    return acc.finalize(model=model)

src/beaver_gateway/frontends/_auth.py

@@ -0,0 +1,53 @@
+"""Shared bearer-token verification for HTTP frontends.
+
+Extracted from ``AnthropicMessagesFrontend`` so the markdown frontend
+(and any future bearer-protected frontend) can reuse one canonical
+verifier instead of copy-pasting the header-parsing dance.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from fastapi import HTTPException, status
+
+if TYPE_CHECKING:
+    from fastapi import Request
+
+    from beaver_gateway.frontends.base import GatewayRuntime
+
+
+__all__ = ["require_token"]
+
+
+async def require_token(
+    request: Request, runtime: GatewayRuntime, *, scope: str
+) -> str:
+    """Verify the request's bearer + scope, return the token's audit name.
+
+    Accepts both ``X-Api-Key: <token>`` (Anthropic SDK / LibreChat) and
+    ``Authorization: Bearer <token>`` (curl, Cursor). 401 on missing /
+    unknown token; 403 on a known token whose scope doesn't cover
+    ``scope``. Bootstrap tokens implicitly carry ``"*"`` and pass every
+    scope check.
+    """
+    api_key = request.headers.get("x-api-key")
+    identity = (
+        await runtime.token_store.verify(api_key)
+        if api_key
+        else await runtime.token_store.verify_bearer(
+            request.headers.get("authorization")
+        )
+    )
+    if identity is None:
+        raise HTTPException(
+            status.HTTP_401_UNAUTHORIZED,
+            "invalid or missing bearer token",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    if not identity.allows(scope):
+        raise HTTPException(
+            status.HTTP_403_FORBIDDEN,
+            f"token scope {identity.scope!r} does not cover {scope!r}",
+        )
+    return identity.name

src/beaver_gateway/frontends/admin/frontend.py

@@ -45,6 +45,8 @@ from jinja2 import Environment, PackageLoader, select_autoescape
 
 from beaver_gateway.core import audit
 from beaver_gateway.core.auth import VALID_SCOPES, hash_token
+from beaver_gateway.core.turn_record import TurnRecord
+from beaver_gateway.frontends._accumulate import StreamAccumulator
 from beaver_gateway.frontends.base import Frontend
 from beaver_gateway.storage import (
     create_token,
@@ -57,6 +59,8 @@ if TYPE_CHECKING:
     from collections.abc import AsyncIterator
     from datetime import datetime
 
+    from anthropic.types import MessageParam
+
     from beaver_gateway.core.events import MessageStreamEvent
     from beaver_gateway.frontends.base import GatewayRuntime
 
@@ -449,7 +453,15 @@ class AdminFrontend(Frontend):
                 system=system if isinstance(system, str) else None,
             )
             return StreamingResponse(
-                _sse_events(events), media_type="text/event-stream"
+                _sse_events_and_broadcast(
+                    events,
+                    runtime=runtime,
+                    agent_name=agent.name,
+                    input_messages=messages,
+                    system=system if isinstance(system, str) else None,
+                    model=agent.model or agent.name,
+                ),
+                media_type="text/event-stream",
             )
 
         return app
@@ -510,23 +522,31 @@ def _build_endpoint_catalog(
     and may have non-trivial transitive deps (aiohttp etc.).
     """
     from beaver_gateway.frontends.anthropic import AnthropicMessagesFrontend
+    from beaver_gateway.frontends.markdown import MarkdownFrontend
     from beaver_gateway.frontends.mcp_server import McpServerFrontend
 
     scheme = request.headers.get("x-forwarded-proto") or request.url.scheme
     hostname = request.url.hostname or "localhost"
 
-    def _base_for(fe: AnthropicMessagesFrontend | McpServerFrontend) -> str:
+    def _base_for(
+        fe: AnthropicMessagesFrontend | McpServerFrontend | MarkdownFrontend,
+    ) -> str:
         if fe.public_base_url:
             return fe.public_base_url
         return f"{scheme}://{hostname}:{fe.port}"
 
     anthropic_base: str | None = None
     mcp_base: str | None = None
+    markdown_fe: MarkdownFrontend | None = None
+    markdown_base: str | None = None
     for fe in runtime.frontends:
         if isinstance(fe, AnthropicMessagesFrontend) and anthropic_base is None:
             anthropic_base = _base_for(fe)
         elif isinstance(fe, McpServerFrontend) and mcp_base is None:
             mcp_base = _base_for(fe)
+        elif isinstance(fe, MarkdownFrontend) and markdown_fe is None:
+            markdown_fe = fe
+            markdown_base = _base_for(fe)
 
     agent_rows: list[dict[str, Any]] = []
     if anthropic_base is not None:
@@ -554,27 +574,57 @@ def _build_endpoint_catalog(
                 {"namespace": "all", "kind": "bundle", "url": f"{mcp_base}/all/"}
             )
 
+    markdown_row: dict[str, Any] | None = None
+    if markdown_fe is not None and markdown_base is not None:
+        # Pick a sane example filename from the vault, prefer something
+        # the user can recognise. Falls back to a generic ``chat.md``.
+        sample_agent = markdown_fe.default_agent or next(
+            (a.name for a in runtime.agents), "<agent>"
+        )
+        markdown_row = {
+            "url": f"{markdown_base}/chat",
+            "vault_path": str(markdown_fe.vault_path),
+            "default_agent": markdown_fe.default_agent,
+            "log_all_chats": markdown_fe.log_all_chats,
+            "logged_subdir": markdown_fe.logged_subdir,
+            "sample_agent": sample_agent,
+        }
+
     return {
         "anthropic_base": anthropic_base,
         "mcp_base": mcp_base,
+        "markdown_base": markdown_base,
         "agents": agent_rows,
         "mcps": mcp_rows,
+        "markdown": markdown_row,
     }
 
 
-async def _sse_events(
+async def _sse_events_and_broadcast(
     events: AsyncIterator[MessageStreamEvent],
+    *,
+    runtime: GatewayRuntime,
+    agent_name: str,
+    input_messages: list[MessageParam],
+    system: str | None,
+    model: str,
 ) -> AsyncIterator[bytes]:
-    r"""Serialize a backend stream into Anthropic's ``text/event-stream`` form.
+    r"""Serialize a backend stream as SSE and broadcast a ``TurnRecord`` after.
 
     Same wire shape as :mod:`beaver_gateway.frontends.anthropic` —
     duplicated rather than imported so the admin frontend stays
     independent of that module's private helpers, and so a mid-stream
     failure surfaces as an in-band ``error`` event the chat UI can
-    render rather than a dangling connection.
+    render rather than a dangling connection. The events also feed a
+    side ``StreamAccumulator`` so once the SSE response closes we hand
+    the assembled ``Message`` to ``runtime.turn_log_handlers`` (the
+    markdown frontend's archive logger lives there). ``source="admin"``
+    so the cross-frontend logger knows where the turn came from.
     """
+    acc = StreamAccumulator()
     try:
         async for ev in events:
+            acc.feed(ev)
             payload = ev.model_dump_json()
             yield f"event: {ev.type}\ndata: {payload}\n\n".encode()
     except Exception as exc:  # noqa: BLE001
@@ -583,6 +633,22 @@ async def _sse_events(
             {"type": "error", "error": {"type": "api_error", "message": str(exc)}}
         )
         yield f"event: error\ndata: {err}\n\n".encode()
+        return
+    if not runtime.turn_log_handlers:
+        return
+    message = acc.finalize(model=model)
+    record = TurnRecord(
+        agent_name=agent_name,
+        input_messages=list(input_messages),
+        output_message=message,
+        system=system,
+        source="admin",
+    )
+    for handler in runtime.turn_log_handlers:
+        try:
+            await handler(record)
+        except Exception:  # noqa: BLE001
+            _log.exception("turn_log_handler raised; continuing")
 
 
 def _set_session_cookie(response: Response, value: str) -> None:

src/beaver_gateway/frontends/admin/templates/dashboard.html

@@ -134,6 +134,41 @@
       add one to <code>Gateway(frontends=[...])</code> to expose them over HTTP.
     </p>
     {% endif %}
+
+    {% if endpoints.markdown %}
+    <h3 class="ep-h3">Markdown — <code>POST /chat</code></h3>
+    <table class="ep-table" data-required-scope="messages">
+      <thead><tr><th>Vault</th><th>Default agent</th><th>URL</th><th class="ep-actions-th"></th></tr></thead>
+      <tbody>
+        <tr class="ep-row"
+            data-kind="markdown"
+            data-url="{{ endpoints.markdown.url }}"
+            data-sample-agent="{{ endpoints.markdown.sample_agent }}">
+          <td>
+            <code>{{ endpoints.markdown.vault_path }}</code>
+            <span class="ep-scope-warn" hidden>scope mismatch</span>
+            {% if endpoints.markdown.log_all_chats %}
+            <span class="pill">log_all_chats · {{ endpoints.markdown.logged_subdir }}/</span>
+            {% endif %}
+          </td>
+          <td>
+            {% if endpoints.markdown.default_agent %}
+              <code>{{ endpoints.markdown.default_agent }}</code>
+            {% else %}
+              <span class="muted">— (request must set <code>agent</code> or frontmatter)</span>
+            {% endif %}
+          </td>
+          <td><code class="ep-url">{{ endpoints.markdown.url }}</code></td>
+          <td class="ep-actions">
+            <button type="button" data-action="copy-url">Copy URL</button>
+            <button type="button" data-action="copy-curl">Copy curl</button>
+            <button type="button" data-action="toggle-curl" aria-expanded="false">▸ curl</button>
+          </td>
+        </tr>
+        <tr class="ep-curl-row" hidden><td colspan="4"><pre class="ep-curl"></pre></td></tr>
+      </tbody>
+    </table>
+    {% endif %}
     {% else %}
     <p class="muted">
       Nothing exposed yet — declare agents / MCPs and the matching frontends
@@ -284,6 +319,21 @@
         "  " + url,
       ].join("\n");
     }
+    if (kind === "markdown") {
+      const agent = row.getAttribute("data-sample-agent") || "";
+      const body = JSON.stringify({
+        filename: "example.md",
+        content: "### User:\n\nhello\n",
+        agent: agent,
+      });
+      return [
+        "curl \\",
+        "  -H " + escSh("Authorization: Bearer " + tok) + " \\",
+        "  -H 'content-type: application/json' \\",
+        "  -d " + escSh(body) + " \\",
+        "  " + url,
+      ].join("\n");
+    }
     if (kind === "mcp") {
       // Streamable-HTTP MCP wants `initialize` first — the response
       // carries the `Mcp-Session-Id` header you must echo back on

src/beaver_gateway/frontends/anthropic.py

@@ -21,31 +21,20 @@ import json
 import logging
 from typing import TYPE_CHECKING, Any
 
-from anthropic.types import (
-    InputJSONDelta,
-    Message,
-    RawContentBlockDeltaEvent,
-    RawContentBlockStartEvent,
-    RawContentBlockStopEvent,
-    RawMessageDeltaEvent,
-    RawMessageStartEvent,
-    SignatureDelta,
-    TextBlock,
-    TextDelta,
-    ThinkingBlock,
-    ThinkingDelta,
-    ToolUseBlock,
-    Usage,
-)
 from fastapi import FastAPI, HTTPException, Request, status
 from fastapi.responses import JSONResponse, StreamingResponse
 
 from beaver_gateway.core import audit
+from beaver_gateway.core.turn_record import TurnRecord
+from beaver_gateway.frontends._accumulate import StreamAccumulator, accumulate
+from beaver_gateway.frontends._auth import require_token
 from beaver_gateway.frontends.base import Frontend
 
 if TYPE_CHECKING:
     from collections.abc import AsyncIterator
 
+    from anthropic.types import Message, MessageParam
+
     from beaver_gateway.core.events import MessageStreamEvent
     from beaver_gateway.frontends.base import GatewayRuntime
 
@@ -109,7 +98,7 @@ class AnthropicMessagesFrontend(Frontend):
 
         @app.get("/v1/models")
         async def list_models(request: Request) -> dict[str, Any]:
-            await _require_token(request, runtime, scope="messages")
+            await require_token(request, runtime, scope="messages")
             data = [
                 {
                     "type": "model",
@@ -123,7 +112,7 @@ class AnthropicMessagesFrontend(Frontend):
 
         @app.post("/v1/messages")
         async def create_message(request: Request) -> Any:
-            token_name = await _require_token(request, runtime, scope="messages")
+            token_name = await require_token(request, runtime, scope="messages")
             try:
                 body = await request.json()
             except json.JSONDecodeError as exc:
@@ -193,58 +182,63 @@ class AnthropicMessagesFrontend(Frontend):
                 **options,
             )
 
+            system_str = system if isinstance(system, str) else None
+
             if stream_flag:
-                return StreamingResponse(_sse(events), media_type="text/event-stream")
-            message = await _accumulate(events, model=model)
+                # Side-accumulate while streaming so we can still emit a
+                # ``TurnRecord`` after the response closes. The buffered
+                # ``Message`` lives only in this coroutine's frame; SSE
+                # bytes still flow to the client unchanged.
+                return StreamingResponse(
+                    _sse_and_broadcast(
+                        events,
+                        runtime=runtime,
+                        agent_name=agent.name,
+                        input_messages=messages,
+                        system=system_str,
+                        model=model,
+                    ),
+                    media_type="text/event-stream",
+                )
+            message = await accumulate(events, model=model)
+            await _broadcast_turn(
+                runtime,
+                agent_name=agent.name,
+                input_messages=messages,
+                output_message=message,
+                system=system_str,
+            )
             return JSONResponse(content=message.model_dump(mode="json"))
 
         return app
 
 
-async def _require_token(
-    request: Request, runtime: GatewayRuntime, *, scope: str
-) -> str:
-    """Verify the request's bearer + scope, return the token's audit name.
-
-    Accepts both ``X-Api-Key: <token>`` (what the official Anthropic
-    SDK sends — LibreChat, the CLI, third-party clients) and
-    ``Authorization: Bearer <token>`` (curl, Cursor). 401 on missing /
-    unknown token; 403 on a known token whose scope doesn't cover
-    ``scope``. Bootstrap tokens implicitly carry ``"*"`` and pass
-    every scope check.
-    """
-    api_key = request.headers.get("x-api-key")
-    identity = (
-        await runtime.token_store.verify(api_key)
-        if api_key
-        else await runtime.token_store.verify_bearer(
-            request.headers.get("authorization")
-        )
-    )
-    if identity is None:
-        raise HTTPException(
-            status.HTTP_401_UNAUTHORIZED,
-            "invalid or missing bearer token",
-            headers={"WWW-Authenticate": "Bearer"},
-        )
-    if not identity.allows(scope):
-        raise HTTPException(
-            status.HTTP_403_FORBIDDEN,
-            f"token scope {identity.scope!r} does not cover {scope!r}",
-        )
-    return identity.name
-
-
-async def _sse(events: AsyncIterator[MessageStreamEvent]) -> AsyncIterator[bytes]:
-    r"""Serialize an event stream into Anthropic's ``text/event-stream`` form.
+async def _sse_and_broadcast(
+    events: AsyncIterator[MessageStreamEvent],
+    *,
+    runtime: GatewayRuntime,
+    agent_name: str,
+    input_messages: list[MessageParam],
+    system: str | None,
+    model: str,
+) -> AsyncIterator[bytes]:
+    r"""Serialize an event stream to SSE; broadcast a :class:`TurnRecord` after.
 
     Each event becomes ``event: <type>\ndata: <json>\n\n`` — the shape
     the Anthropic SDK's SSE decoder expects. Errors mid-stream are
     swallowed into a synthetic ``error`` event so the client sees the
     failure rather than a hung connection.
+
+    The same events feed a :class:`StreamAccumulator` on the side so that
+    once the SSE response closes we can hand a fully-assembled
+    ``Message`` to every ``runtime.turn_log_handlers`` entry (the
+    markdown frontend's archive logger lives in there). Broadcast
+    failures are caught — they must never bubble up to the client.
     """
+    acc = StreamAccumulator()
     try:
         async for ev in events:
+            acc.feed(ev)
             payload = ev.model_dump_json()
             yield f"event: {ev.type}\ndata: {payload}\n\n".encode()
     except Exception as exc:  # noqa: BLE001
@@ -253,83 +247,41 @@ async def _sse(events: AsyncIterator[MessageStreamEvent]) -> AsyncIterator[bytes
             {"type": "error", "error": {"type": "api_error", "message": str(exc)}}
         )
         yield f"event: error\ndata: {err}\n\n".encode()
-
-
-async def _accumulate(
-    events: AsyncIterator[MessageStreamEvent], *, model: str
-) -> Message:
-    """Collapse a stream-event sequence into one ``Message`` (``stream=false``).
-
-    Mirrors the Anthropic SDK's own accumulator: walk events, build
-    block dicts indexed by their ``content_block`` index, fold text /
-    thinking deltas in, buffer ``input_json_delta`` chunks until the
-    block closes (then JSON-parse them once).
-    """
-    message_id = ""
-    role = "assistant"
-    usage = Usage(input_tokens=0, output_tokens=0)
-    blocks: dict[int, dict[str, Any]] = {}
-    json_buffers: dict[int, str] = {}
-    stop_reason: str | None = None
-    stop_sequence: str | None = None
-
-    async for ev in events:
-        # isinstance, not ``ev.type == "..."``: ty narrows on the
-        # discriminator only via the class, and the raw event union
-        # carries its own discriminators (``Raw*Event``) the SDK
-        # already promises.
-        if isinstance(ev, RawMessageStartEvent):
-            message_id = ev.message.id
-            role = ev.message.role
-            usage = ev.message.usage
-        elif isinstance(ev, RawContentBlockStartEvent):
-            blocks[ev.index] = ev.content_block.model_dump()
-            if blocks[ev.index].get("type") == "tool_use":
-                json_buffers[ev.index] = ""
-        elif isinstance(ev, RawContentBlockDeltaEvent):
-            blk = blocks.setdefault(ev.index, {})
-            delta = ev.delta
-            if isinstance(delta, TextDelta):
-                blk["text"] = blk.get("text", "") + delta.text
-            elif isinstance(delta, InputJSONDelta):
-                json_buffers[ev.index] = (
-                    json_buffers.get(ev.index, "") + delta.partial_json
-                )
-            elif isinstance(delta, ThinkingDelta):
-                blk["thinking"] = blk.get("thinking", "") + delta.thinking
-            elif isinstance(delta, SignatureDelta):
-                blk["signature"] = delta.signature
-        elif isinstance(ev, RawContentBlockStopEvent):
-            blk = blocks.get(ev.index, {})
-            if blk.get("type") == "tool_use":
-                raw = json_buffers.pop(ev.index, "")
-                blk["input"] = json.loads(raw) if raw.strip() else {}
-        elif isinstance(ev, RawMessageDeltaEvent):
-            stop_reason = ev.delta.stop_reason
-            stop_sequence = ev.delta.stop_sequence
-            if ev.usage.output_tokens:
-                usage = Usage.model_validate(
-                    {**usage.model_dump(), "output_tokens": ev.usage.output_tokens}
-                )
-
-    content = []
-    for idx in sorted(blocks):
-        bd = blocks[idx]
-        btype = bd.get("type")
-        if btype == "text":
-            content.append(TextBlock.model_validate(bd))
-        elif btype == "tool_use":
-            content.append(ToolUseBlock.model_validate(bd))
-        elif btype == "thinking":
-            content.append(ThinkingBlock.model_validate(bd))
-
-    return Message(
-        id=message_id or "msg_unknown",
-        type="message",
-        role=role,
-        model=model,
-        content=content,
-        stop_reason=stop_reason,  # type: ignore[arg-type]
-        stop_sequence=stop_sequence,
-        usage=usage,
+        return
+    message = acc.finalize(model=model)
+    await _broadcast_turn(
+        runtime,
+        agent_name=agent_name,
+        input_messages=input_messages,
+        output_message=message,
+        system=system,
     )
+
+
+async def _broadcast_turn(
+    runtime: GatewayRuntime,
+    *,
+    agent_name: str,
+    input_messages: list[MessageParam],
+    output_message: Message,
+    system: str | None,
+) -> None:
+    """Fire each ``turn_log_handlers`` entry with a fresh :class:`TurnRecord`.
+
+    Handler exceptions are caught and logged — they're observability
+    plumbing, not part of the user-visible request path.
+    """
+    if not runtime.turn_log_handlers:
+        return
+    record = TurnRecord(
+        agent_name=agent_name,
+        input_messages=list(input_messages),
+        output_message=output_message,
+        system=system,
+        source="anthropic",
+    )
+    for handler in runtime.turn_log_handlers:
+        try:
+            await handler(record)
+        except Exception:  # noqa: BLE001
+            _log.exception("turn_log_handler raised; continuing")

src/beaver_gateway/frontends/base.py

@@ -15,13 +15,16 @@ from dataclasses import dataclass, field
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
-    from collections.abc import Mapping, Sequence
+    from collections.abc import Awaitable, Callable, Mapping, Sequence
 
     from beaver_gateway.backends.base import Backend
     from beaver_gateway.core.auth import TokenStore
     from beaver_gateway.core.registry import AgentRegistry, McpRegistry
+    from beaver_gateway.core.turn_record import TurnRecord
     from beaver_gateway.storage import Database
 
+    TurnLogHandler = Callable[[TurnRecord], Awaitable[None]]
+
 
 @dataclass(frozen=True, slots=True)
 class GatewayRuntime:
@@ -62,6 +65,18 @@ class GatewayRuntime:
     # the dashboard so the operator can copy ready-to-use links / curl
     # snippets. Other frontends ignore it.
     frontends: Sequence[Frontend] = field(default_factory=tuple)
+    # Frontends that finish a turn (Anthropic Messages, Markdown) iterate
+    # this list and ``await`` each handler with a ``TurnRecord``. Handlers
+    # are appended during ``configure()`` by frontends that want a
+    # cross-frontend chat archive — currently the markdown frontend's
+    # ``log_all_chats`` mode. Handler exceptions are caught at the call
+    # site; they never block the user-visible response.
+    #
+    # The field is typed as ``list[Any]`` rather than the precise
+    # ``list[TurnLogHandler]`` because the alias lives under TYPE_CHECKING
+    # to keep ``anthropic.types`` out of the runtime import graph for
+    # this base module.
+    turn_log_handlers: list[TurnLogHandler] = field(default_factory=list)
 
 
 class Frontend(ABC):

src/beaver_gateway/frontends/markdown/__init__.py

@@ -0,0 +1,15 @@
+"""Markdown frontend — turn-by-turn chat archive backed by ``.md`` files.
+
+The user maintains chats as plain markdown files in an Obsidian vault.
+A plugin in Obsidian POSTs ``{filename, content?}`` to ``/chat`` and the
+frontend parses the file, finds the last turn, and runs the agent if
+the last turn is ``user``. The full response is appended back to the
+file as an ``### Assistant:`` turn. With ``log_all_chats=True`` the
+frontend also subscribes to every other frontend's turns and writes
+them into ``{vault_path}/{logged_subdir}/`` so the vault is the single
+chronological archive of all conversations.
+"""
+
+from beaver_gateway.frontends.markdown.frontend import MarkdownFrontend
+
+__all__ = ["MarkdownFrontend"]

src/beaver_gateway/frontends/markdown/crossfront.py

@@ -0,0 +1,302 @@
+"""Cross-frontend chat logger.
+
+When ``MarkdownFrontend(log_all_chats=True)`` is configured, every turn
+completed by any other frontend (currently the Anthropic Messages
+frontend) is mirrored into the vault as a ``.md`` file. Subsequent
+turns of the same conversation append to the same file — matched by a
+content-hash fingerprint stored in YAML frontmatter.
+
+The fingerprint hashes the message history *before* the new assistant
+reply. So the next request's input history (which now includes the
+prior assistant reply) hashes to the value we just persisted —
+``hash(prev_input + [assistant_reply])`` — and the lookup hits the
+same file. New conversations (no prior fingerprint match) get a fresh
+file under ``{vault_path}/{logged_subdir}/{agent_name}/``.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import hashlib
+import logging
+from datetime import UTC, datetime
+from typing import TYPE_CHECKING, Any
+
+import frontmatter
+
+from beaver_gateway.frontends.markdown import renderer
+
+if TYPE_CHECKING:
+    from collections.abc import Callable, Iterable
+    from pathlib import Path
+
+    from anthropic.types import MessageParam
+
+    from beaver_gateway.core.turn_record import TurnRecord
+
+
+_log = logging.getLogger("beaver_gateway.frontends.markdown.crossfront")
+
+
+# User hook: take a turn + vault root, return where the new file should
+# live. Returning a relative ``Path`` is treated as relative to the
+# vault. ``None`` (the default) keeps the built-in
+# ``{vault}/{logged_subdir}/{agent}/{YYYY-MM-DD}_{hex8}.md`` layout.
+LogPathFn = "Callable[[TurnRecord, Path], Path]"
+
+
+__all__ = ["CrossFrontendLogger", "LogPathFn", "fingerprint_messages"]
+
+
+def fingerprint_messages(messages: Iterable[MessageParam]) -> str:
+    """Stable, short hex hash of a conversation prefix.
+
+    Built from ``(role, normalized_content)`` pairs only — so the
+    Markdown frontend's parser-shaped messages (text-only) and the
+    Anthropic frontend's raw ``messages`` payload (which may also be
+    string-only at v1) hash compatibly when they represent the same
+    conversation. Tool blocks / images would diverge, but those aren't
+    in the v1 ingest path.
+    """
+    h = hashlib.sha1(usedforsecurity=False)
+    for msg in messages:
+        role = str(msg.get("role", ""))
+        content = msg.get("content", "")
+        if isinstance(content, str):
+            text = content
+        else:
+            parts: list[str] = []
+            for blk in content:
+                if not isinstance(blk, dict):
+                    continue
+                btype = blk.get("type")
+                if btype == "text":
+                    parts.append(str(blk.get("text", "")))
+            text = "\n".join(parts)
+        h.update(role.encode("utf-8"))
+        h.update(b"\x00")
+        h.update(text.strip().encode("utf-8"))
+        h.update(b"\x01")
+    return h.hexdigest()[:16]
+
+
+class CrossFrontendLogger:
+    """Maintains the fingerprint→file map and writes turns to disk.
+
+    The map is in-process; on startup ``warm_index`` rebuilds it from
+    YAML frontmatter of every file under ``logged_subdir``. A miss
+    creates a new file, a hit appends to the existing one. All disk
+    work funnels through one ``asyncio.Lock`` because the writes are
+    cheap and serializing them sidesteps a class of races we don't need
+    to think about.
+    """
+
+    def __init__(
+        self,
+        *,
+        vault_path: Path,
+        logged_subdir: str,
+        log_path: Callable[[TurnRecord, Path], Path] | None = None,
+    ) -> None:
+        self._vault = vault_path
+        self._root = vault_path / logged_subdir
+        self._index: dict[str, Path] = {}
+        self._lock = asyncio.Lock()
+        self._log_path_fn = log_path
+        # When the user supplies a custom path function, files can land
+        # anywhere in the vault — so we have to scan the whole vault on
+        # startup to rebuild the fingerprint→path map. With the default
+        # layout we can bound the scan to ``_logs/``.
+        self._scan_root = vault_path if log_path is not None else self._root
+
+    def warm_index(self) -> None:
+        """Scan logged files synchronously, populating the fingerprint map.
+
+        Called from ``MarkdownFrontend.configure`` so the map is ready
+        before any cross-frontend turn arrives. ``frontmatter.load``
+        reads only enough of the file to parse the YAML head, so the
+        scan is cheap even on large vaults — but a custom ``log_path``
+        forces a full-vault walk; mention that in the constructor doc.
+        """
+        if not self._scan_root.exists():
+            return
+        for path in self._scan_root.rglob("*.md"):
+            try:
+                post = frontmatter.load(str(path))
+            except Exception:  # noqa: BLE001
+                _log.warning("could not read frontmatter from %s — skipping", path)
+                continue
+            fp = post.metadata.get("fingerprint")
+            if isinstance(fp, str) and fp:
+                self._index[fp] = path
+        _log.info(
+            "crossfront index warmed: %d logged file(s) under %s",
+            len(self._index),
+            self._scan_root,
+        )
+
+    async def handle(self, record: TurnRecord) -> None:
+        """Append or create a logged file for ``record``.
+
+        Records that the markdown frontend itself produced
+        (``source=="markdown"``) are skipped — those already live in the
+        user's hand-written file and shouldn't be duplicated into the
+        ``_logs`` shadow tree.
+        """
+        if record.source == "markdown":
+            return
+
+        async with self._lock:
+            # ``input_messages`` is the *full* history sent to the backend
+            # (last entry is the new user turn). Match against the prefix
+            # that excludes the new user turn — that's what the previous
+            # write stored as its fingerprint. Empty prefix is the
+            # well-known "brand new chat" sentinel.
+            prefix = record.input_messages[:-1]
+            prev_fp = fingerprint_messages(prefix) if prefix else None
+            target = self._index.get(prev_fp) if prev_fp else None
+            if target is None:
+                target = self._new_file_path(record)
+
+            # Build the full history including the assistant reply; the
+            # new fingerprint matches *that* prefix, so the next user
+            # turn (history grows by one user msg) will hit this file.
+            assistant_msg: MessageParam = {
+                "role": "assistant",
+                "content": _flatten_text(record.output_message),
+            }
+            full_history = [*record.input_messages, assistant_msg]
+            new_fp = fingerprint_messages(full_history)
+
+            if target.exists():
+                existing = target.read_text(encoding="utf-8")
+                parsed = frontmatter.loads(existing)
+                body = _strip_trailing_user_scaffold(parsed.content)
+                # We append only the *new* user turn (the last one in
+                # input_messages, since prior turns are already on disk)
+                # plus the assistant reply.
+                new_user = record.input_messages[-1]
+                new_block = renderer.render_user_param(new_user)
+                new_block = renderer.append_to_body(
+                    new_block, renderer.render_assistant_message(record.output_message)
+                )
+                new_body = renderer.append_to_body(body, new_block)
+                metadata = dict(parsed.metadata)
+            else:
+                # Materialize the whole conversation from scratch.
+                new_body = _render_full_history(
+                    record.input_messages, record.output_message
+                )
+                metadata = {}
+
+            new_body = renderer.append_to_body(new_body, renderer.USER_SCAFFOLD)
+
+            metadata["agent"] = record.agent_name
+            metadata["fingerprint"] = new_fp
+            metadata["source"] = record.source
+            self._write(target, metadata, new_body)
+            # Maintain the index: drop the old fp (it's stale once we
+            # write the new turn), add the new one.
+            if prev_fp:
+                self._index.pop(prev_fp, None)
+            self._index[new_fp] = target
+
+    # ---- internals -----------------------------------------------------
+
+    def _new_file_path(self, record: TurnRecord) -> Path:
+        """Pick a fresh filename for a brand-new conversation.
+
+        With a user-supplied ``log_path`` we delegate to it (joining a
+        relative result with the vault root). Without one, we fall back
+        to ``{logged_subdir}/{agent}/{date}_{hex8}.md`` and ensure the
+        ``.md`` suffix in case the user picks a non-md extension by hand.
+        """
+        if self._log_path_fn is not None:
+            result = self._log_path_fn(record, self._vault)
+            if not result.is_absolute():
+                result = self._vault / result
+            if result.suffix != ".md":
+                result = result.with_suffix(".md")
+            result.parent.mkdir(parents=True, exist_ok=True)
+            return result
+        day = datetime.now(UTC).strftime("%Y-%m-%d")
+        # Short hex from the input hash so two same-day chats sort
+        # stably and don't collide.
+        salt = fingerprint_messages(record.input_messages)[:8]
+        agent_dir = self._root / record.agent_name
+        agent_dir.mkdir(parents=True, exist_ok=True)
+        return agent_dir / f"{day}_{salt}.md"
+
+    def _write(self, path: Path, metadata: dict[str, Any], body: str) -> None:
+        path.parent.mkdir(parents=True, exist_ok=True)
+        if metadata:
+            post = frontmatter.Post(content=body, **metadata)
+            text = frontmatter.dumps(post) + "\n"
+        else:
+            text = body if body.endswith("\n") else body + "\n"
+        # Sync write inside the lock — keeps the implementation tiny;
+        # individual logged turns are small enough that the blocking
+        # write doesn't matter at human conversation rates.
+        path.write_text(text, encoding="utf-8")
+
+
+def _flatten_text(message: Any) -> str:
+    """Same as ``frontend._flatten_assistant_text`` but local to break a cycle."""
+    chunks = [
+        getattr(block, "text", "") or ""
+        for block in getattr(message, "content", ())
+        if getattr(block, "type", None) == "text"
+    ]
+    return "\n\n".join(c for c in chunks if c)
+
+
+def _render_full_history(messages: list[MessageParam], assistant: Any) -> str:
+    """Render an entire conversation (used when materializing a new logged file)."""
+    blocks: list[str] = []
+    for msg in messages:
+        role = msg.get("role")
+        if role == "user":
+            blocks.append(renderer.render_user_param(msg))
+        elif role == "assistant":
+            content = msg.get("content", "")
+            text = content if isinstance(content, str) else _content_to_text(content)
+            blocks.append(f"### Assistant:\n\n{text.strip()}\n" if text.strip() else "")
+    blocks.append(renderer.render_assistant_message(assistant))
+    body = ""
+    for block in blocks:
+        if not block:
+            continue
+        body = renderer.append_to_body(body, block)
+    return body
+
+
+def _strip_trailing_user_scaffold(body: str) -> str:
+    """Drop a trailing empty ``### User:`` block if present.
+
+    Cross-frontend turns aren't typed into the file by the human — they
+    arrive whole from another frontend. If we leave the previous run's
+    scaffold in place, we'd write the new user turn right after an
+    empty marker (visual noise, two ``### User:`` headers in a row).
+    Trim it and let the append flow add a fresh scaffold at the end.
+    """
+    stripped = body.rstrip()
+    marker = "### User:"
+    if not stripped.endswith(marker):
+        return body
+    # Walk back: the scaffold is the marker preceded by either start-of-file
+    # or an HR/blank line. Find the last newline before the marker, cut.
+    head = stripped[: -len(marker)].rstrip()
+    if head.endswith("---"):
+        head = head[: -len("---")].rstrip()
+    return head
+
+
+def _content_to_text(content: Any) -> str:
+    if not isinstance(content, list):
+        return ""
+    chunks = [
+        str(blk.get("text", ""))
+        for blk in content
+        if isinstance(blk, dict) and blk.get("type") == "text"
+    ]
+    return "\n\n".join(chunks)

src/beaver_gateway/frontends/markdown/frontend.py

@@ -0,0 +1,404 @@
+"""``MarkdownFrontend`` — chat-via-markdown-files frontend.
+
+Wires:
+
+* ``POST /chat {filename, content?, agent?}`` — bearer-authenticated
+  trigger. The plugin in Obsidian fires this after the user edits a
+  ``.md`` and the file gets synced (or with ``content`` to short-circuit
+  the sync delay). We parse the file, check the last turn — assistant
+  → no-op, user → run the agent and append.
+* ``GET /healthz`` — liveness.
+
+Concurrency model: an in-memory ``set[Path]`` of files currently in
+flight. Two concurrent requests for the same file → the second gets
+409. The set is single-process (one gateway instance) — that's by
+design; the markdown frontend is the only writer in its vault from
+the gateway side.
+
+Cross-frontend logging: when ``log_all_chats=True``, ``configure()``
+registers a handler on ``runtime.turn_log_handlers`` so every other
+frontend's completed turns also land in the vault. The handler logic
+lives in :mod:`.crossfront` so this module stays focused on the HTTP
+shape.
+"""
+
+from __future__ import annotations
+
+import contextlib
+import json
+import logging
+import os
+import tempfile
+from pathlib import Path
+from typing import TYPE_CHECKING, Any
+
+import aiofile
+from fastapi import FastAPI, HTTPException, Request, status
+from fastapi.responses import JSONResponse
+
+from beaver_gateway.core import audit
+from beaver_gateway.core.turn_record import TurnRecord
+from beaver_gateway.frontends._accumulate import accumulate
+from beaver_gateway.frontends._auth import require_token
+from beaver_gateway.frontends.base import Frontend
+from beaver_gateway.frontends.markdown import parser, renderer
+from beaver_gateway.frontends.markdown.crossfront import (
+    CrossFrontendLogger,
+    fingerprint_messages,
+)
+
+if TYPE_CHECKING:
+    from collections.abc import Callable
+
+    from anthropic.types import MessageParam
+
+    from beaver_gateway.frontends.base import GatewayRuntime
+
+
+_log = logging.getLogger("beaver_gateway.frontends.markdown")
+
+
+__all__ = ["MarkdownFrontend"]
+
+
+class MarkdownFrontend(Frontend):
+    """FastAPI app behind ``POST /chat`` driven by Obsidian-vault files."""
+
+    def __init__(
+        self,
+        *,
+        vault_path: Path | str,
+        host: str = "0.0.0.0",  # noqa: S104
+        port: int = 8003,
+        default_agent: str | None = None,
+        log_all_chats: bool = False,
+        logged_subdir: str = "_logs",
+        log_path: Callable[[TurnRecord, Path], Path] | None = None,
+        public_base_url: str | None = None,
+    ) -> None:
+        self.vault_path = Path(vault_path).expanduser().resolve()
+        self.host = host
+        self.port = port
+        self.default_agent = default_agent
+        self.log_all_chats = log_all_chats
+        self.logged_subdir = logged_subdir
+        self.log_path = log_path
+        # External URL prefix when behind a reverse proxy — same role as
+        # on the other bearer frontends. Trailing slash trimmed for
+        # idempotent concatenation; ``None`` means "no proxy / advertise
+        # raw host:port".
+        self.public_base_url = public_base_url.rstrip("/") if public_base_url else None
+        self._runtime: GatewayRuntime | None = None
+        self._app: FastAPI | None = None
+        # Files currently being processed by an in-flight ``POST /chat``.
+        # Checked-and-added atomically in the request handler (no
+        # ``await`` between the check and the insert) so a concurrent
+        # request reliably loses the race to 409.
+        self._busy: set[Path] = set()
+        self._crossfront: CrossFrontendLogger | None = None
+
+    def configure(self, runtime: GatewayRuntime) -> None:
+        self._runtime = runtime
+        self.vault_path.mkdir(parents=True, exist_ok=True)
+        if self.log_all_chats:
+            self._crossfront = CrossFrontendLogger(
+                vault_path=self.vault_path,
+                logged_subdir=self.logged_subdir,
+                log_path=self.log_path,
+            )
+            # Scan the existing logged files synchronously here so the
+            # fingerprint→path map is populated before the first
+            # cross-frontend turn arrives. Cheap: frontmatter-only read.
+            self._crossfront.warm_index()
+            runtime.turn_log_handlers.append(self._crossfront.handle)
+        self._app = self._build_app(runtime)
+
+    async def serve(self) -> None:
+        import uvicorn
+
+        if self._app is None:
+            msg = "configure() must be called before serve()"
+            raise RuntimeError(msg)
+        config = uvicorn.Config(
+            self._app, host=self.host, port=self.port, log_level="info"
+        )
+        server = uvicorn.Server(config)
+        await server.serve()
+
+    # ---- app builder ---------------------------------------------------
+
+    def _build_app(self, runtime: GatewayRuntime) -> FastAPI:
+        app = FastAPI(title="beaver-gateway / Markdown")
+
+        @app.get("/healthz")
+        async def healthz() -> dict[str, str]:
+            return {"status": "ok"}
+
+        @app.post("/chat")
+        async def chat(request: Request) -> Any:
+            token_name = await require_token(request, runtime, scope="messages")
+            try:
+                body = await request.json()
+            except json.JSONDecodeError as exc:
+                raise HTTPException(
+                    status.HTTP_400_BAD_REQUEST, f"invalid JSON: {exc}"
+                ) from exc
+
+            filename = body.get("filename")
+            if not isinstance(filename, str) or not filename.strip():
+                raise HTTPException(
+                    status.HTTP_400_BAD_REQUEST, "missing or non-string `filename`"
+                )
+            content_override = body.get("content")
+            agent_override = body.get("agent")
+            if agent_override is not None and not isinstance(agent_override, str):
+                raise HTTPException(
+                    status.HTTP_400_BAD_REQUEST, "`agent` must be a string"
+                )
+
+            file_path = self._resolve_path(filename)
+
+            # Atomic check-and-claim: both ops run between awaits, so a
+            # second request can't slip into the same file slot.
+            if file_path in self._busy:
+                return JSONResponse(
+                    status_code=status.HTTP_409_CONFLICT,
+                    content={"status": "in_progress", "filename": filename},
+                )
+            self._busy.add(file_path)
+            try:
+                return await self._handle_chat(
+                    runtime=runtime,
+                    token_name=token_name,
+                    filename=filename,
+                    file_path=file_path,
+                    content_override=content_override,
+                    agent_override=agent_override,
+                )
+            finally:
+                self._busy.discard(file_path)
+
+        return app
+
+    # ---- dispatch ------------------------------------------------------
+
+    async def _handle_chat(
+        self,
+        *,
+        runtime: GatewayRuntime,
+        token_name: str,
+        filename: str,
+        file_path: Path,
+        content_override: Any,
+        agent_override: str | None,
+    ) -> Any:
+        if isinstance(content_override, str):
+            await _write_atomic(file_path, content_override)
+            file_text = content_override
+        elif content_override is None:
+            file_text = await _read_or_empty(file_path)
+        else:
+            raise HTTPException(
+                status.HTTP_400_BAD_REQUEST, "`content` must be a string when present"
+            )
+
+        parsed = parser.parse(file_text)
+        agent_name = parser.resolve_agent(
+            metadata=parsed.metadata,
+            request_override=agent_override,
+            default=self.default_agent,
+        )
+        if not agent_name:
+            raise HTTPException(
+                status.HTTP_400_BAD_REQUEST,
+                "no agent specified: pass `agent`, set frontmatter, "
+                "or configure `default_agent`",
+            )
+
+            # When the parser produced no messages (file empty / only
+            # frontmatter), there's nothing to dispatch.
+        if not parsed.messages:
+            return {"status": "nothing_to_do", "reason": "empty file"}
+
+        if parser.last_role(parsed.messages) == "assistant":
+            return {"status": "nothing_to_do", "reason": "last turn is assistant"}
+
+        agent = runtime.agents.get(agent_name)
+        if agent is None:
+            raise HTTPException(
+                status.HTTP_404_NOT_FOUND, f"unknown agent: {agent_name!r}"
+            )
+        backend = runtime.backends.get(agent.name)
+        if backend is None:
+            raise HTTPException(
+                status.HTTP_503_SERVICE_UNAVAILABLE,
+                f"no backend configured for agent {agent.name!r}",
+            )
+
+        _log.info(
+            "chat: actor=%s agent=%s file=%s msgs=%d",
+            token_name,
+            agent.name,
+            filename,
+            len(parsed.messages),
+        )
+        await audit.log(
+            runtime,
+            actor=f"token:{token_name}",
+            kind="markdown_chat",
+            agent_name=agent.name,
+            filename=filename,
+            msgs=len(parsed.messages),
+        )
+
+        try:
+            events = backend.complete(
+                agent=agent, messages=parsed.messages, system=None
+            )
+            message = await accumulate(events, model=agent.model or agent.name)
+        except Exception as exc:
+            _log.exception("backend failed for %s", filename)
+            error_block = _render_error_block(exc)
+            new_body = renderer.append_to_body(parsed.body, error_block)
+            await _write_atomic(
+                file_path, _reattach_frontmatter(parsed.metadata, new_body)
+            )
+            raise HTTPException(
+                status.HTTP_500_INTERNAL_SERVER_ERROR, f"backend error: {exc}"
+            ) from exc
+
+        rendered = renderer.render_assistant_message(message)
+        new_body = renderer.append_to_body(parsed.body, rendered)
+        new_body = renderer.append_to_body(new_body, renderer.USER_SCAFFOLD)
+        # Recompute fingerprint so a future cross-frontend hit on this
+        # same conversation can find it. Stored as hex string in
+        # frontmatter — only the markdown frontend reads it.
+        assistant_param: MessageParam = {
+            "role": "assistant",
+            "content": _flatten_assistant_text(message),
+        }
+        updated_messages: list[MessageParam] = [*parsed.messages, assistant_param]
+        updated_metadata = dict(parsed.metadata)
+        updated_metadata["agent"] = agent.name
+        updated_metadata["fingerprint"] = fingerprint_messages(updated_messages)
+        await _write_atomic(
+            file_path, _reattach_frontmatter(updated_metadata, new_body)
+        )
+
+        # Broadcast our own turn so other handlers (none today, but the
+        # symmetry is worth keeping) see what happened. ``source`` marks
+        # the origin so ``CrossFrontendLogger`` can skip its own files.
+        record = TurnRecord(
+            agent_name=agent.name,
+            input_messages=list(parsed.messages),
+            output_message=message,
+            system=None,
+            source="markdown",
+        )
+        for handler in runtime.turn_log_handlers:
+            try:
+                await handler(record)
+            except Exception:  # noqa: BLE001
+                _log.exception("turn_log_handler raised; continuing")
+
+        return {"status": "ok", "turns_appended": 1, "agent": agent.name}
+
+    # ---- helpers -------------------------------------------------------
+
+    def _resolve_path(self, filename: str) -> Path:
+        """Resolve ``filename`` under the vault; reject escapes."""
+        # ``filename`` may be relative or absolute; we always anchor
+        # under ``vault_path`` so absolute paths from outside the vault
+        # don't sneak through. ``Path("/foo/bar")`` combined with a
+        # vault path keeps the absolute side; we strip leading slashes
+        # to coerce the rooted form into a relative path before joining.
+        rel = filename.lstrip("/")
+        if not rel.endswith(".md"):
+            rel = rel + ".md"
+        candidate = (self.vault_path / rel).resolve()
+        try:
+            candidate.relative_to(self.vault_path)
+        except ValueError as exc:
+            raise HTTPException(
+                status.HTTP_400_BAD_REQUEST, f"filename escapes vault: {filename!r}"
+            ) from exc
+        return candidate
+
+
+# ---- module-level utilities ----------------------------------------------
+
+
+async def _read_or_empty(path: Path) -> str:
+    """Return file contents, or empty string if the file doesn't exist."""
+    # ``path.exists()`` here is a metadata stat — microseconds — and
+    # gating an async read on whether the file is there is exactly the
+    # check we want. Switching to anyio.Path / aiofiles.os just to
+    # silence the async-pathlib lint would cost a dep edge for no
+    # practical win.
+    if not path.exists():  # noqa: ASYNC240
+        return ""
+    async with aiofile.async_open(path, "r", encoding="utf-8") as f:
+        return await f.read()
+
+
+async def _write_atomic(path: Path, content: str) -> None:
+    """Write ``content`` to ``path`` via tmp + ``os.replace`` (atomic)."""
+    path.parent.mkdir(parents=True, exist_ok=True)
+    # ``NamedTemporaryFile`` keeps the file open which complicates
+    # ``os.replace`` on some platforms. Build the tmp name manually,
+    # write+fsync, then rename. Same-directory so the rename is atomic.
+    tmp_name = tempfile.mkstemp(
+        prefix=f".{path.name}.", suffix=".tmp", dir=str(path.parent)
+    )
+    fd, tmp_path = tmp_name
+    try:
+        async with aiofile.async_open(tmp_path, "w", encoding="utf-8") as f:
+            await f.write(content)
+        os.close(fd)
+        # ``os.replace`` is the atomic primitive — ``Path.replace`` is a
+        # thin wrapper around the same syscall; either works, ``os.`` is
+        # the one Linux/POSIX docs reach for.
+        os.replace(tmp_path, path)  # noqa: PTH105
+    except BaseException:
+        # Cleanup on failure: close fd, remove tmp.
+        with contextlib.suppress(OSError):
+            os.close(fd)
+        with contextlib.suppress(OSError):
+            os.unlink(tmp_path)  # noqa: PTH108
+        raise
+
+
+def _reattach_frontmatter(metadata: dict[str, Any], body: str) -> str:
+    r"""Re-emit a ``.md`` file with YAML frontmatter at the top.
+
+    Empty metadata → no frontmatter block (avoid littering every file
+    with a hollow ``---\n---``).
+    """
+    if not metadata:
+        return body if body.endswith("\n") else body + "\n"
+    import frontmatter as _fm
+
+    post = _fm.Post(content=body, **metadata)
+    return _fm.dumps(post) + "\n"
+
+
+def _flatten_assistant_text(message: Any) -> str:
+    """Pull all text blocks from an assistant ``Message`` and join them.
+
+    Used when we need the assistant content as a plain string for
+    fingerprinting / equality with a parser-shaped history (parser
+    already drops thinking + tool_use from assistant turns).
+    """
+    chunks = [
+        getattr(block, "text", "") or ""
+        for block in getattr(message, "content", ())
+        if getattr(block, "type", None) == "text"
+    ]
+    return "\n\n".join(c for c in chunks if c)
+
+
+def _render_error_block(exc: BaseException) -> str:
+    """Render a backend failure as an Assistant turn with a ``[!error]-`` callout."""
+    msg = str(exc) or exc.__class__.__name__
+    safe = msg.replace("\n", " ").strip()
+    return f"### Assistant:\n\n> [!error]-\n> {safe}\n"

src/beaver_gateway/frontends/markdown/parser.py

@@ -0,0 +1,187 @@
+"""Parse a markdown chat file into Anthropic ``MessageParam`` history.
+
+The file format is documented in ``frontends/markdown/__init__.py``:
+``### User:`` / ``### Assistant:`` H3 headers split turns, optional
+``---`` HRs between turns are visual-only, ``> [!thinking]-`` and
+``> [!tool]- <name>`` callouts mark structured assistant content.
+
+For backend consumption we strip thinking and tool_use callouts —
+assistant turns become text-only. Rationale: history replay through
+claude-code's JSONL injection only needs the *narrated* answer (the
+thinking signatures expire and the original tool_results aren't
+captured in the renderer's output, so a faithful tool_use round-trip
+isn't possible today). The renderer keeps callouts in the file because
+they're informational for the human reader; the parser drops them when
+shaping the backend's input.
+"""
+
+from __future__ import annotations
+
+import re
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any
+
+import frontmatter
+
+if TYPE_CHECKING:
+    from anthropic.types import MessageParam
+
+
+__all__ = ["ParsedFile", "last_role", "parse", "resolve_agent"]
+
+
+# Turn marker — must be exactly ``### User:`` or ``### Assistant:`` on
+# its own line. Trailing whitespace tolerated; nothing after the colon
+# on the same line (any inline content would mean the user typed
+# something that just happens to look like a header, and we'd rather
+# misparse than silently fold inline content into a turn).
+_TURN_RE = re.compile(r"^###\s+(User|Assistant):\s*$", re.MULTILINE)
+
+# Callout-start lines we strip from assistant turns when extracting
+# text. We don't try to parse the contents — for backend input we just
+# need to drop the whole quoted block.
+_CALLOUT_START_RE = re.compile(r"^>\s+\[!(thinking|tool)\]")
+
+
+@dataclass(frozen=True, slots=True)
+class ParsedFile:
+    """Result of parsing a single chat ``.md``.
+
+    ``metadata`` is the YAML frontmatter as a plain dict (empty if the
+    file has none). ``messages`` is the conversation history shaped for
+    ``Backend.complete`` — assistant turns are text-only. ``body`` is the
+    raw markdown content *after* the frontmatter is stripped; the
+    renderer needs it when it appends a new assistant turn so it can
+    preserve whatever the human typed verbatim (including any callouts
+    or HRs they added).
+    """
+
+    metadata: dict[str, Any]
+    body: str
+    messages: list[MessageParam]
+
+
+def parse(text: str) -> ParsedFile:
+    """Parse a chat ``.md`` into ``(metadata, body, messages)``.
+
+    A file with no turn markers but non-empty body is treated as a
+    single user turn — the friendly path for "user types into a new
+    file and hits send" before any turn markers exist.
+    """
+    parsed = frontmatter.loads(text)
+    metadata = dict(parsed.metadata)
+    body = parsed.content
+
+    messages: list[MessageParam] = []
+    turns = _split_turns(body)
+    if not turns:
+        stripped = body.strip()
+        if stripped:
+            messages.append({"role": "user", "content": stripped})
+        return ParsedFile(metadata=metadata, body=body, messages=messages)
+
+    for role, raw in turns:
+        if role == "user":
+            text_content = _strip_hrs(raw).strip()
+            if text_content:
+                messages.append({"role": "user", "content": text_content})
+        else:
+            text_content = _extract_assistant_text(raw)
+            if text_content:
+                messages.append({"role": "assistant", "content": text_content})
+
+    return ParsedFile(metadata=metadata, body=body, messages=messages)
+
+
+def last_role(messages: list[MessageParam]) -> str | None:
+    """Return ``"user"`` / ``"assistant"`` / ``None`` for an empty list."""
+    if not messages:
+        return None
+    return messages[-1]["role"]
+
+
+def resolve_agent(
+    *, metadata: dict[str, Any], request_override: str | None, default: str | None
+) -> str | None:
+    """Resolve the agent for this chat.
+
+    Precedence: request body override > frontmatter > frontend default.
+    Returns ``None`` if none match — caller responds with 400.
+    """
+    if request_override:
+        return request_override
+    fm_agent = metadata.get("agent")
+    if isinstance(fm_agent, str) and fm_agent:
+        return fm_agent
+    return default
+
+
+# ---- internals ---------------------------------------------------------
+
+
+def _split_turns(body: str) -> list[tuple[str, str]]:
+    """Walk turn markers, return ``[(role_lc, raw_body), ...]``.
+
+    Body for each turn is everything between this marker and the next
+    (or EOF). Leading marker line itself is dropped. We don't trim
+    whitespace here — that's per-role.
+    """
+    matches = list(_TURN_RE.finditer(body))
+    if not matches:
+        return []
+    out: list[tuple[str, str]] = []
+    for i, m in enumerate(matches):
+        role = m.group(1).lower()
+        start = m.end()
+        end = matches[i + 1].start() if i + 1 < len(matches) else len(body)
+        out.append((role, body[start:end]))
+    return out
+
+
+def _strip_hrs(raw: str) -> str:
+    """Drop decorative ``---`` separator lines (whole-line HRs only).
+
+    A ``---`` mid-paragraph (rare, but possible) stays. Only lines that
+    are *exactly* the HR after optional surrounding whitespace are
+    removed — those are the ones the renderer emits between turns.
+    """
+    lines = raw.splitlines()
+    kept = [ln for ln in lines if ln.strip() != "---"]
+    return "\n".join(kept)
+
+
+def _extract_assistant_text(raw: str) -> str:
+    """Strip thinking/tool callouts from an assistant turn, return spoken text.
+
+    Walks line by line. When we see a callout-start line (``> [!thinking]-``
+    or ``> [!tool]- ...``), we skip the entire contiguous quote block
+    (lines beginning with ``>`` or blank-then-`>` continuations don't
+    happen in Obsidian callouts — a blank line ends the callout). HR
+    lines (``---``) are dropped. Everything else is kept and joined,
+    then collapsed to a clean trim.
+    """
+    lines = raw.splitlines()
+    out_lines: list[str] = []
+    i = 0
+    while i < len(lines):
+        line = lines[i]
+        if _CALLOUT_START_RE.match(line):
+            # Skip the whole quote block (consecutive lines starting
+            # with ``>``). Stop at first non-``>`` line, leaving it for
+            # the next iteration. Blank lines do not end the block — a
+            # callout body with a blank line uses ``> `` (quote-space)
+            # too — but in practice Obsidian's quote block ends on the
+            # first line that doesn't start with ``>``.
+            while i < len(lines) and lines[i].lstrip().startswith(">"):
+                i += 1
+            continue
+        if line.strip() == "---":
+            i += 1
+            continue
+        out_lines.append(line)
+        i += 1
+    # Collapse runs of blank lines that callout-stripping creates
+    # (two newlines around a stripped block fold into one).
+    text_joined = "\n".join(out_lines)
+    text_joined = re.sub(r"\n{3,}", "\n\n", text_joined)
+    return text_joined.strip()

src/beaver_gateway/frontends/markdown/renderer.py

@@ -0,0 +1,181 @@
+"""Render Anthropic ``Message`` (and individual user turns) into markdown.
+
+The renderer is one-way: it produces the human-facing artifact in the
+vault. The parser strips tool/thinking callouts when reshaping the file
+for backend replay — so what we write here is purely for the human
+reader (and for the cross-frontend logger, which materializes turns
+from other frontends).
+"""
+
+from __future__ import annotations
+
+import json
+import re
+from typing import TYPE_CHECKING, Any, cast
+
+from anthropic.types import Message, TextBlock, ThinkingBlock, ToolUseBlock
+
+if TYPE_CHECKING:
+    from collections.abc import Iterable
+
+    from anthropic.types import MessageParam
+
+
+__all__ = [
+    "FENCE",
+    "USER_SCAFFOLD",
+    "append_to_body",
+    "render_assistant_message",
+    "render_user_text",
+    "summarize_tool_input",
+]
+
+
+# Empty ``### User:`` block appended after each assistant reply so the
+# human has an obvious place to type the next turn. Parser drops empty
+# user blocks, so this doesn't re-trigger dispatch on its own.
+USER_SCAFFOLD = "### User:\n"
+
+
+# Default 4-backtick fence so tool results that contain literal ```` ``` ````
+# don't collide. JSON inputs use 3 backticks because they almost never
+# contain ``` and we get language syntax highlighting in Obsidian for free.
+FENCE = "````"
+
+# Used when a tool input mentions a path/file we can dangle in the
+# callout title — purely cosmetic.
+_PATH_KEYS = ("path", "file", "filename", "url", "command", "query")
+
+
+def render_user_text(content: str) -> str:
+    r"""Render one user-spoken turn as ``### User:\n\n<text>``."""
+    return f"### User:\n\n{content.strip()}\n"
+
+
+def render_assistant_message(message: Message) -> str:
+    """Render an assistant ``Message`` (with content blocks) into a turn block.
+
+    Blocks render in their original order:
+
+    * ``ThinkingBlock`` → ``> [!thinking]-`` collapsed callout
+    * ``TextBlock`` → plain text (the spoken answer)
+    * ``ToolUseBlock`` → ``> [!tool]- <name>`` callout with the ``input``
+      JSON quoted inside. Tool *results* are not persisted — see
+      module docstring on ``parser.py`` for why.
+
+    Blank lines separate adjacent blocks; trailing newline guarantees
+    the next ``---`` / ``### User:`` marker lands on its own line.
+    """
+    parts: list[str] = ["### Assistant:", ""]
+    for block in message.content:
+        parts.extend(_render_block(block))
+        parts.append("")
+    return "\n".join(parts).rstrip() + "\n"
+
+
+def render_user_param(param: MessageParam) -> str:
+    """Render a ``MessageParam`` user message into a ``### User:`` block.
+
+    Used by the cross-frontend logger when materializing turns from
+    other frontends. Tool_result blocks in the content list are dropped
+    silently — the markdown view doesn't track them (see ``parser.py``).
+    """
+    content = param.get("content", "")
+    if isinstance(content, str):
+        text = content
+    else:
+        # The Anthropic SDK types ``content`` as a union of typed-dict
+        # *Param classes plus pydantic block models — both shapes appear
+        # in practice (raw incoming JSON yields dicts, SDK-built params
+        # yield BaseModels). Treat each entry as a dict-like and pull
+        # ``text`` opportunistically.
+        chunks = [
+            str(blk.get("text", ""))
+            for blk in content
+            if isinstance(blk, dict) and blk.get("type") == "text"
+        ]
+        text = "\n\n".join(chunks)
+    return render_user_text(text)
+
+
+def append_to_body(existing: str, new_block: str) -> str:
+    """Append ``new_block`` to ``existing`` with a decorative HR separator.
+
+    Preserves the original body verbatim (whitespace, callouts, any
+    formatting the human added). The HR is purely visual: parser ignores
+    it.
+    """
+    head = existing.rstrip()
+    if head:
+        return f"{head}\n\n---\n\n{new_block}"
+    return new_block
+
+
+def summarize_tool_input(name: str, tool_input: object) -> str:
+    """Build the ``[!tool]- <summary>`` title string.
+
+    Tries to pick a single salient field (``path``, ``command``, etc.)
+    from the input dict so the collapsed callout shows something
+    meaningful in Obsidian. Falls back to just the tool name.
+    """
+    if not isinstance(tool_input, dict):
+        return name
+    # Anthropic ``ToolUseBlock.input`` is typed as ``object`` — the
+    # SDK's runtime value is always a JSON dict (str→Any), so a local
+    # cast keeps the rest of the function readable without sprinkling
+    # per-line type narrowing on every ``.get`` call.
+    d = cast("dict[str, Any]", tool_input)
+    for key in _PATH_KEYS:
+        value = d.get(key)
+        if isinstance(value, str) and value:
+            short = value if len(value) <= 60 else value[:57] + "..."
+            return f"{name} · {short}"
+    return name
+
+
+# ---- internals ---------------------------------------------------------
+
+
+def _render_block(block: object) -> Iterable[str]:
+    if isinstance(block, TextBlock):
+        text = (block.text or "").strip()
+        if text:
+            yield text
+        return
+    if isinstance(block, ThinkingBlock):
+        yield from _render_thinking(block.thinking or "")
+        return
+    if isinstance(block, ToolUseBlock):
+        yield from _render_tool_use(block)
+        return
+    # Unknown block type — skip silently rather than corrupting the file.
+
+
+def _render_thinking(text: str) -> Iterable[str]:
+    yield "> [!thinking]-"
+    for line in text.strip().splitlines() or [""]:
+        yield f"> {line}" if line else ">"
+
+
+def _render_tool_use(block: ToolUseBlock) -> Iterable[str]:
+    title = summarize_tool_input(block.name, block.input)
+    yield f"> [!tool]- {title}"
+    yield "> **input:**"
+    yield "> ```json"
+    pretty = json.dumps(block.input, indent=2, ensure_ascii=False, sort_keys=True)
+    for line in pretty.splitlines():
+        yield f"> {line}" if line else ">"
+    yield "> ```"
+
+
+def adaptive_fence(content: str) -> str:
+    """Return a backtick fence at least one longer than the longest run in ``content``.
+
+    Currently unused (tool *results* aren't persisted yet) — kept here
+    so when result capture lands the rendering side already has the
+    primitive.
+    """
+    longest = 0
+    for match in re.finditer(r"`+", content):
+        longest = max(longest, len(match.group(0)))
+    return "`" * max(3, longest + 1)

uv.lock

@@ -261,6 +261,7 @@ name = "beaver-gateway"
 version = "0.1.0"
 source = { editable = "." }
 dependencies = [
+    { name = "aiofile" },
     { name = "aiohttp" },
     { name = "aiosqlite" },
     { name = "anthropic" },
@@ -274,6 +275,7 @@ dependencies = [
     { name = "psycopg", extra = ["binary"] },
     { name = "pydantic" },
     { name = "pydantic-settings" },
+    { name = "python-frontmatter" },
     { name = "sqlmodel" },
     { name = "uvicorn", extra = ["standard"] },
     { name = "uvloop" },
@@ -300,6 +302,7 @@ dev = [
 
 [package.metadata]
 requires-dist = [
+    { name = "aiofile", specifier = ">=3.11.1" },
     { name = "aiohttp", specifier = ">=3.13.5" },
     { name = "aiosqlite", specifier = ">=0.22.1" },
     { name = "anthropic", specifier = ">=0.103.0" },
@@ -315,6 +318,7 @@ requires-dist = [
     { name = "psycopg", extras = ["binary"], specifier = ">=3.3.4" },
     { name = "pydantic", specifier = ">=2.13.4" },
     { name = "pydantic-settings", specifier = ">=2.14.1" },
+    { name = "python-frontmatter", specifier = ">=1.2.0" },
     { name = "raycast-api", marker = "extra == 'local'", editable = "../raycast-api" },
     { name = "raycast-api", marker = "extra == 'prod'", git = "https://git.kotikot.com/beaver/raycast-api.git" },
     { name = "sqlmodel", specifier = ">=0.0.38" },
@@ -1647,6 +1651,18 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/0b/d7/1959b9648791274998a9c3526f6d0ec8fd2233e4d4acce81bbae76b44b2a/python_dotenv-1.2.2-py3-none-any.whl", hash = "sha256:1d8214789a24de455a8b8bd8ae6fe3c6b69a5e3d64aa8a8e5d68e694bbcb285a", size = 22101, upload-time = "2026-03-01T16:00:25.09Z" },
 ]
 
+[[package]]
+name = "python-frontmatter"
+version = "1.2.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pyyaml" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/e9/21/88aefb4f1de6661b5a003175e21e4a5ad94f5e52b2abf4170a11883c7d81/python_frontmatter-1.2.0.tar.gz", hash = "sha256:5b26ccd3cb85af77feb11d83b922c7bb5aeccb0c9d3fb236b938c600b6322984", size = 16890, upload-time = "2026-05-17T23:42:05.493Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/1c/b1/ec12e3e746234006b77dec69d53878253b1da09dbb55fa3cb456083d9069/python_frontmatter-1.2.0-py3-none-any.whl", hash = "sha256:e1ee1d4300450a2f84e778eb4f70edf573da6cd7d463801066f05edc4e819c78", size = 10396, upload-time = "2026-05-17T23:42:04.637Z" },
+]
+
 [[package]]
 name = "python-multipart"
 version = "0.0.29"