diff --git a/CHANGELOG.md b/CHANGELOG.md
index 23ee2fb..825d37e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,19 @@ et [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Ajouté
 
+- **#79 Phase F — Durcissement & documentation (rate limiting, redaction, OpenAPI/MCP, E2E)** —
+  clôture de la feature #79. **Rate limiting** par jeton et par outil
+  (`backend/tools/ratelimit.py`, fenêtre glissante ; identité = JTI du jeton sinon id/username ;
+  `OBSIGATE_TOOL_RATE_LIMIT`, `OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL`, `OBSIGATE_TOOL_RATE_WINDOW` ;
+  erreur `rate_limited`). **Quotas** `BOOKSLM_MAX_*` : `BOOKSLM_MAX_TOOL_CALLS` plafonne les appels
+  d'outils par run d'agent (`stopped="quota_exceeded"`) et `BOOKSLM_MAX_TOOL_READ_BYTES` plafonne
+  `read_file`. **Redaction** systématique de **tout** résultat d'outil avant retour au LLM
+  (`backend/tools/redaction.py`, récursif : diffs, extraits de recherche, lectures). **OpenAPI** :
+  tag `MCP` + injection du path `/mcp` (Streamable HTTP) dans le schéma ; nouveau
+  [`docs/MCP_GUIDE.md`](./docs/MCP_GUIDE.md) (config Claude Desktop/Cursor, tools/resources/prompts,
+  sécurité, variables, dépannage). Tests E2E : `tests/test_ai_e2e.py` (agent read→confirm→write,
+  quota, rate limit, redaction, flux MCP `read`→`propose`→`apply`→`resources/read`).
+
 - **#79 Phase E — Serveur MCP (Streamable HTTP)** — nouvel endpoint `/mcp` exposant ObsiGate à des
   clients MCP externes (Claude Desktop, Cursor…) via le SDK Python `mcp==1.9.4`. Les deux fronts
   (assistant in-app et MCP) consomment la même couche d'outils. **Tools** : outils de lecture/recherche
diff --git a/README.fr.md b/README.fr.md
index 2957da3..1a62cc9 100644
--- a/README.fr.md
+++ b/README.fr.md
@@ -55,6 +55,7 @@
 ## ✨ Fonctionnalités
 
 - **🤖 AI Editor intégré** — Éditeur CodeMirror 6 avec toolbar IA : amélioration, correction, traduction, génération, réécriture personnalisée, toolbox (liste, tableau, frontmatter, canvas) — multi-provider DeepSeek/OpenRouter/Gemini
+- **🧩 Serveur MCP & agent IA** — Serveur Model Context Protocol intégré (`/mcp`) et assistant avec function calling : lisez, cherchez et modifiez vos vaults depuis Claude Desktop, Cursor… avec confirmations two-step, permissions par vault, rate limiting et redaction des secrets ([guide](docs/MCP_GUIDE.md))
 - **🗺️ Vue graphe interactive** — Canvas force-directed avec Barnes-Hut O(n log n), filtres (tag, type), profondeur, mode focus, historique de navigation ←→↑, export PNG, aperçu au survol (Ctrl+click)
 - **🗂️ Multi-vault** : Visualisez plusieurs vaults Obsidian simultanément
 - **🌳 Navigation arborescente** : Parcourez vos dossiers et fichiers dans la sidebar
diff --git a/README.md b/README.md
index 068b28e..c2f404b 100644
--- a/README.md
+++ b/README.md
@@ -48,6 +48,7 @@
 ## ✨ Features
 
 - **🤖 Integrated AI Editor** — CodeMirror 6 editor with AI toolbar: improve, correct, translate, generate, custom rewrite, toolbox (list, table, frontmatter, canvas) — multi-provider DeepSeek/OpenRouter/Gemini
+- **🧩 MCP Server & AI Agent** — Built-in Model Context Protocol server (`/mcp`) and tool-calling assistant: read, search and edit your vaults from Claude Desktop, Cursor… with two-step confirmations, per-vault permissions, rate limiting and secret redaction ([guide](docs/MCP_GUIDE.md))
 - **🗺️ Interactive Graph View** — Canvas force-directed with Barnes-Hut O(n log n), filters (tag, type), depth, focus mode, navigation history ←→↑, export PNG, preview on hover (Ctrl+click)
 - **🗂️ Multi-vault** : View multiple Obsidian vaults simultaneously
 - **🌳 Tree Navigation** : Browse your folders and files in the sidebar
diff --git a/backend/agent/loop.py b/backend/agent/loop.py
index adeb963..0473fde 100644
--- a/backend/agent/loop.py
+++ b/backend/agent/loop.py
@@ -17,6 +17,7 @@ from __future__ import annotations
 
 import json
 import logging
+import os
 from collections.abc import Callable
 from dataclasses import dataclass, field
 from typing import Any
@@ -35,11 +36,14 @@ logger = logging.getLogger("obsigate.agent.loop")
 DEFAULT_MAX_ITERATIONS = 10
 # Cap the size of a tool result fed back to the model (chars).
 MAX_TOOL_RESULT_CHARS = 100_000
+# Quota: maximum tool calls executed per agent run (``BOOKSLM_MAX_TOOL_CALLS``).
+DEFAULT_MAX_TOOL_CALLS = int(os.environ.get("BOOKSLM_MAX_TOOL_CALLS", "25"))
 
 # Stopping reasons
 STOP_DONE = "done"
 STOP_MAX_ITERATIONS = "max_iterations"
 STOP_CONFIRMATION_REQUIRED = "confirmation_required"
+STOP_QUOTA_EXCEEDED = "quota_exceeded"
 
 
 @dataclass
@@ -158,6 +162,7 @@ async def run_agent(
     llm: Callable[..., Any] | None = None,
     tools: list[dict[str, Any]] | None = None,
     max_iterations: int = DEFAULT_MAX_ITERATIONS,
+    max_tool_calls: int | None = None,
     on_tool_call: Callable[[ToolCallRecord], None] | None = None,
     resume_messages: list[dict[str, Any]] | None = None,
     confirm_pending: dict[str, Any] | None = None,
@@ -173,6 +178,8 @@ async def run_agent(
         tools: Tool schemas to expose. ``None`` exposes all in-app tools;
             pass ``[]`` to disable tool calling (plain chat).
         max_iterations: Hard cap on LLM round-trips.
+        max_tool_calls: Hard cap on the total number of executed tool calls
+            (quota, defaults to ``BOOKSLM_MAX_TOOL_CALLS``).
         on_tool_call: Optional callback invoked after each executed tool call.
         resume_messages: Conversation snapshot from a paused run (returned with
             a ``confirmation`` event). When set, the loop resumes from it.
@@ -187,11 +194,20 @@ async def run_agent(
     llm = llm or provider_llm
     if tools is None:
         tools = get_tool_schemas(scope=ToolScope.IN_APP)
+    quota = DEFAULT_MAX_TOOL_CALLS if max_tool_calls is None else max_tool_calls
 
     convo = [dict(m) for m in (resume_messages if resume_messages is not None else messages)]
     executed: list[ToolCallRecord] = []
 
     if confirm_pending:
+        if quota is not None and len(executed) >= quota:
+            return AgentResult(
+                content="",
+                messages=convo,
+                tool_calls=executed,
+                iterations=0,
+                stopped=STOP_QUOTA_EXCEEDED,
+            )
         _execute_confirmed(ctx, confirm_pending, convo, executed, on_tool_call)
 
     for iteration in range(1, max_iterations + 1):
@@ -209,6 +225,15 @@ async def run_agent(
         convo.append(_assistant_tool_message(response.content, response.tool_calls))
 
         for call in response.tool_calls:
+            if quota is not None and len(executed) >= quota:
+                logger.warning(f"Agent reached the tool-call quota ({quota})")
+                return AgentResult(
+                    content=response.content or "",
+                    messages=convo,
+                    tool_calls=executed,
+                    iterations=iteration,
+                    stopped=STOP_QUOTA_EXCEEDED,
+                )
             try:
                 result = call_tool(call.name, ctx, call.arguments)
                 payload = result.data
diff --git a/backend/auth/middleware.py b/backend/auth/middleware.py
index 86600d7..ab6fb4a 100644
--- a/backend/auth/middleware.py
+++ b/backend/auth/middleware.py
@@ -63,6 +63,8 @@ def get_current_user(
 
     # Attach vault permissions from the token (snapshot at login time)
     user["_token_vaults"] = payload.get("vaults", [])
+    # Attach the token id for per-token rate limiting (AI tool layer).
+    user["_token_jti"] = payload.get("jti")
     return user
 
 
diff --git a/backend/openapi_docs.py b/backend/openapi_docs.py
index 44f4ed2..df45ed9 100644
--- a/backend/openapi_docs.py
+++ b/backend/openapi_docs.py
@@ -32,6 +32,7 @@ TAGS_METADATA: list[dict[str, str]] = [
     {"name": "Export", "description": "Export notes or whole vaults to HTML, Markdown bundle or ePub."},
     {"name": "AI", "description": "AI-powered editor actions, provider status and model discovery."},
     {"name": "BooksLM", "description": "Directory-scoped AI chat (NotebookLM-style) over a vault folder."},
+    {"name": "MCP", "description": "Model Context Protocol server (Streamable HTTP) exposing the shared AI tool layer to external clients (Claude Desktop, Cursor…)."},
     {"name": "Sharing", "description": "Create and manage public read-only share links for documents."},
     {"name": "Webhooks", "description": "HTTP callbacks signed with HMAC-SHA256 for file events."},
     {"name": "Conflicts", "description": "Detect and resolve Syncthing sync-conflict files."},
@@ -79,6 +80,7 @@ _TAG_RULES: list[tuple[re.Pattern[str], str]] = [
     (re.compile(r"^/api/push"), "Push"),
     (re.compile(r"^/api/ai/bookslm"), "BooksLM"),
     (re.compile(r"^/api/ai"), "AI"),
+    (re.compile(r"^/mcp"), "MCP"),
     (re.compile(r"^/api/config/ai-"), "AI"),
     (re.compile(r"^/api/share"), "Sharing"),
     (re.compile(r"^/api/shares"), "Sharing"),
@@ -141,6 +143,7 @@ _TAG_ALIASES: dict[str, str] = {
     "frontend": "Frontend",
     "ai": "AI",
     "bookslm": "BooksLM",
+    "mcp": "MCP",
     "pdf": "PDF",
     "bookmarks": "Bookmarks",
 }
@@ -224,6 +227,67 @@ def _is_binary_operation(operation: dict[str, Any]) -> bool:
     return any(media.startswith(_BINARY_MEDIA) for media in content)
 
 
+# ---------------------------------------------------------------------------
+# MCP endpoint (not a FastAPI route: custom ASGI mount) — documented manually
+# ---------------------------------------------------------------------------
+
+_MCP_DESCRIPTION = (
+    "**Model Context Protocol** server over Streamable HTTP (JSON-RPC 2.0). "
+    "Exposes the shared AI tool layer to external MCP clients (Claude Desktop, "
+    "Cursor…). Authentication uses `Authorization: Bearer <JWT>` (the same "
+    "token as the REST API).\n\n"
+    "Primitives: read/search **tools** directly; write/destructive tools as a "
+    "two-step `propose_<tool>` / `apply_<tool>` pair (signed, single-use "
+    "confirmation token); **resources** `vault://<name>` and "
+    "`vault://<name>/<path>` (read-only, secrets redacted); **prompts** "
+    "`summarize-directory`, `generate-note`, `find-related`.\n\n"
+    "See `docs/MCP_GUIDE.md` for client setup."
+)
+
+
+def _inject_mcp_path(schema: dict[str, Any]) -> None:
+    """Add the MCP Streamable HTTP endpoint to the schema (idempotent)."""
+    paths = schema.setdefault("paths", {})
+    if "/mcp" in paths:
+        return
+    paths["/mcp"] = {
+        "post": {
+            "tags": ["MCP"],
+            "summary": "MCP Streamable HTTP endpoint (JSON-RPC 2.0)",
+            "operationId": "mcp_streamable_http",
+            "description": _MCP_DESCRIPTION,
+            "requestBody": {
+                "required": True,
+                "content": {
+                    "application/json": {
+                        "example": {
+                            "jsonrpc": "2.0",
+                            "id": 1,
+                            "method": "tools/list",
+                            "params": {},
+                        }
+                    }
+                },
+            },
+            "responses": {
+                "200": {
+                    "description": "JSON-RPC response (or 202 for notifications)",
+                    "content": {
+                        "application/json": {
+                            "example": {
+                                "jsonrpc": "2.0",
+                                "id": 1,
+                                "result": {"tools": []},
+                            }
+                        }
+                    },
+                }
+            },
+            "security": [{"bearerAuth": []}],
+        }
+    }
+
+
 def enrich_openapi_schema(schema: dict[str, Any]) -> dict[str, Any]:
     """Enrich a FastAPI-generated OpenAPI schema in place and return it.
 
@@ -242,6 +306,8 @@ def enrich_openapi_schema(schema: dict[str, Any]) -> dict[str, Any]:
     }
     schema["tags"] = TAGS_METADATA
 
+    _inject_mcp_path(schema)
+
     components = schema.setdefault("components", {})
     security_schemes = components.setdefault("securitySchemes", {})
     security_schemes.setdefault("bearerAuth", {
diff --git a/backend/tools/api.py b/backend/tools/api.py
index f770b69..6061c7f 100644
--- a/backend/tools/api.py
+++ b/backend/tools/api.py
@@ -17,11 +17,22 @@ from backend.tools.context import (
     ToolMode,
     ToolNotFoundError,
     ToolPermissionError,
+    ToolRateLimitError,
     ToolRisk,
     ToolScope,
     ToolValidationError,
     resolve_safe_path,
 )
+from backend.tools.ratelimit import (
+    check_and_record as check_tool_rate_limit,
+)
+from backend.tools.ratelimit import (
+    get_status as get_tool_rate_limit_status,
+)
+from backend.tools.ratelimit import (
+    reset as reset_tool_rate_limit,
+)
+from backend.tools.redaction import redact_payload
 from backend.tools.registry import (
     ToolSpec,
     call_tool,
@@ -39,15 +50,20 @@ __all__ = [
     "ToolMode",
     "ToolNotFoundError",
     "ToolPermissionError",
+    "ToolRateLimitError",
     "ToolResult",
     "ToolRisk",
     "ToolScope",
     "ToolSpec",
     "ToolValidationError",
     "call_tool",
+    "check_tool_rate_limit",
     "get_tool",
+    "get_tool_rate_limit_status",
     "get_tool_schemas",
     "list_tools",
+    "redact_payload",
+    "reset_tool_rate_limit",
     "resolve_safe_path",
     "tool",
 ]
diff --git a/backend/tools/context.py b/backend/tools/context.py
index 85df083..3811dbd 100644
--- a/backend/tools/context.py
+++ b/backend/tools/context.py
@@ -102,6 +102,21 @@ class ToolConfirmationRequired(ToolError):
         return payload
 
 
+class ToolRateLimitError(ToolError):
+    """Raised when an identity exceeds its tool-call rate limit (Phase F)."""
+
+    code = "rate_limited"
+
+    def __init__(self, tool: str, retry_after: int = 0, message: str | None = None):
+        super().__init__(
+            message or f"Rate limit exceeded for tool '{tool}'",
+            code="rate_limited",
+            details={"tool": tool, "retry_after": retry_after},
+        )
+        self.tool = tool
+        self.retry_after = retry_after
+
+
 @dataclass
 class ToolContext:
     """Carries the caller identity and execution options for a tool call.
@@ -126,6 +141,21 @@ class ToolContext:
     def username(self) -> str:
         return self.user.get("username", "unknown")
 
+    @property
+    def rate_limit_identity(self) -> str:
+        """Identity used by the per-token/per-tool rate limiter.
+
+        Prefers the JWT id (``_token_jti``, attached by the auth middleware),
+        then an explicit ``token_id`` in :attr:`metadata`, then the user id and
+        finally the username. This yields per-token limiting when a token id is
+        available and per-account limiting otherwise.
+        """
+        token_id = self.metadata.get("token_id") or self.user.get("_token_jti")
+        if token_id:
+            return f"token:{token_id}"
+        user_id = self.user.get("id") or self.user.get("username")
+        return f"user:{user_id or 'anonymous'}"
+
     def has_vault_access(self, vault: str) -> bool:
         """Return True if the caller may access *vault*."""
         return bool(vault) and check_vault_access(vault, self.user)
diff --git a/backend/tools/ratelimit.py b/backend/tools/ratelimit.py
new file mode 100644
index 0000000..c20d0f7
--- /dev/null
+++ b/backend/tools/ratelimit.py
@@ -0,0 +1,153 @@
+"""Rate limiting for the AI tool layer (Phase F).
+
+Complements the IP-based login limiter (``backend.ratelimit``) with a
+per-identity, per-tool sliding-window limiter applied to every tool call,
+whether it originates from the in-app assistant or the MCP server.
+
+Two counters are maintained per identity:
+
+* a **global** counter (all tools combined), capped by
+  ``OBSIGATE_TOOL_RATE_LIMIT``;
+* a **per-tool** counter, capped by ``OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL``
+  (defaults to the global cap) so a single expensive tool cannot consume the
+  whole budget.
+
+The window length is ``OBSIGATE_TOOL_RATE_WINDOW`` seconds (default 60).
+
+The identity is the token JTI when available (``_token_jti`` attached by the
+auth middleware), otherwise the user id/username. This gives "per token / per
+tool" limiting while remaining meaningful for anonymous/disabled-auth mode.
+"""
+
+from __future__ import annotations
+
+import logging
+import os
+import time
+from collections import deque
+from typing import Any
+
+logger = logging.getLogger("obsigate.tools.ratelimit")
+
+# --- Configuration (read at call time so tests can monkeypatch env) ---
+DEFAULT_RATE_LIMIT = 60
+DEFAULT_RATE_WINDOW = 60
+
+
+def _env_int(name: str, default: int) -> int:
+    try:
+        return int(os.environ.get(name, str(default)))
+    except (TypeError, ValueError):
+        return default
+
+
+def _global_limit() -> int:
+    return _env_int("OBSIGATE_TOOL_RATE_LIMIT", DEFAULT_RATE_LIMIT)
+
+
+def _per_tool_limit() -> int:
+    return _env_int("OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL", _global_limit())
+
+
+def _window() -> int:
+    return max(1, _env_int("OBSIGATE_TOOL_RATE_WINDOW", DEFAULT_RATE_WINDOW))
+
+
+# --- In-memory store: {counter_key: deque[timestamp]} ---
+_calls: dict[str, deque] = {}
+
+
+def _identity_key(identity: str | None) -> str:
+    return identity or "anonymous"
+
+
+def _counter_key(identity: str | None, tool: str | None) -> str:
+    base = _identity_key(identity)
+    return f"{base}\x00{tool}" if tool else base
+
+
+def _prune(entries: deque, now: float, window: int) -> None:
+    cutoff = now - window
+    while entries and entries[0] <= cutoff:
+        entries.popleft()
+
+
+def check_and_record(identity: str | None, tool: str, *, now: float | None = None) -> tuple[bool, int]:
+    """Record one call and report whether it is allowed.
+
+    Args:
+        identity: Rate-limit identity (token JTI or username).
+        tool: Tool name (used for the per-tool counter).
+        now: Optional timestamp override (tests).
+
+    Returns:
+        ``(allowed, retry_after)``. When ``allowed`` is False, ``retry_after``
+        is the number of seconds until the oldest call leaves the window.
+    """
+    now = time.time() if now is None else now
+    window = _window()
+    global_limit = _global_limit()
+    tool_limit = _per_tool_limit()
+
+    global_entries = _calls.setdefault(_counter_key(identity, None), deque())
+    tool_entries = _calls.setdefault(_counter_key(identity, tool), deque())
+    _prune(global_entries, now, window)
+    _prune(tool_entries, now, window)
+
+    if len(global_entries) >= global_limit or len(tool_entries) >= tool_limit:
+        oldest = min(
+            global_entries[0] if len(global_entries) >= global_limit else now,
+            tool_entries[0] if len(tool_entries) >= tool_limit else now,
+        )
+        retry_after = max(1, int(oldest + window - now) + 1)
+        logger.warning(f"Tool rate limit exceeded for '{_identity_key(identity)}' on '{tool}'")
+        return False, retry_after
+
+    global_entries.append(now)
+    tool_entries.append(now)
+    return True, 0
+
+
+def remaining(identity: str | None, tool: str | None = None) -> int:
+    """Return the number of calls still allowed in the current window."""
+    now = time.time()
+    window = _window()
+    if tool:
+        entries = _calls.get(_counter_key(identity, tool))
+        if entries is None:
+            return _per_tool_limit()
+        _prune(entries, now, window)
+        return max(0, _per_tool_limit() - len(entries))
+    entries = _calls.get(_counter_key(identity, None))
+    if entries is None:
+        return _global_limit()
+    _prune(entries, now, window)
+    return max(0, _global_limit() - len(entries))
+
+
+def reset(identity: str | None = None) -> None:
+    """Clear rate-limit state (all identities, or a single one)."""
+    if identity is None:
+        _calls.clear()
+        return
+    prefix = f"{_identity_key(identity)}\x00"
+    for key in [k for k in _calls if k == _identity_key(identity) or k.startswith(prefix)]:
+        del _calls[key]
+
+
+def get_status(identity: str | None = None) -> dict[str, Any]:
+    """Diagnostic snapshot of the limiter (for tests / admin tooling)."""
+    if identity is None:
+        return {
+            "tracked_identities": len({k.split("\x00", 1)[0] for k in _calls}),
+            "global_limit": _global_limit(),
+            "per_tool_limit": _per_tool_limit(),
+            "window_seconds": _window(),
+        }
+    return {
+        "identity": _identity_key(identity),
+        "remaining_global": remaining(identity),
+        "global_limit": _global_limit(),
+        "per_tool_limit": _per_tool_limit(),
+        "window_seconds": _window(),
+    }
diff --git a/backend/tools/redaction.py b/backend/tools/redaction.py
new file mode 100644
index 0000000..2afbec2
--- /dev/null
+++ b/backend/tools/redaction.py
@@ -0,0 +1,39 @@
+"""Secret redaction for tool results (Phase F).
+
+Tool results are fed back to the LLM (in-app agent loop) or returned to an
+external MCP client, so they must never leak credentials. ``read_file`` and
+``read_file_raw`` already redact through the shared file service, but other
+tools (``diff_backup``, ``search_*``) return content that has not been through
+the redactor. This module applies :func:`backend.secret_redactor.redact` to
+every string in a tool payload, recursively.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from backend.secret_redactor import redact
+
+_MAX_DEPTH = 12
+
+
+def redact_payload(payload: Any, _depth: int = 0) -> Any:
+    """Return a copy of *payload* with every string secret-redacted.
+
+    Walks dicts, lists and tuples; scalars are returned unchanged. Strings are
+    run through :func:`backend.secret_redactor.redact`. A recursion cap avoids
+    pathological/cyclic structures (tool results are JSON-serialisable, so
+    cycles should not occur, but the guard keeps this safe).
+    """
+    if _depth > _MAX_DEPTH:
+        return payload
+    if isinstance(payload, str):
+        redacted, count = redact(payload)
+        return redacted if count else payload
+    if isinstance(payload, dict):
+        return {key: redact_payload(value, _depth + 1) for key, value in payload.items()}
+    if isinstance(payload, list):
+        return [redact_payload(item, _depth + 1) for item in payload]
+    if isinstance(payload, tuple):
+        return tuple(redact_payload(item, _depth + 1) for item in payload)
+    return payload
diff --git a/backend/tools/registry.py b/backend/tools/registry.py
index 88154ab..652802e 100644
--- a/backend/tools/registry.py
+++ b/backend/tools/registry.py
@@ -26,10 +26,13 @@ from backend.tools.context import (
     ToolError,
     ToolNotFoundError,
     ToolPermissionError,
+    ToolRateLimitError,
     ToolRisk,
     ToolScope,
     ToolValidationError,
 )
+from backend.tools.ratelimit import check_and_record
+from backend.tools.redaction import redact_payload
 from backend.tools.schemas import ToolResult
 
 logger = logging.getLogger("obsigate.tools.registry")
@@ -186,6 +189,12 @@ def call_tool(
         _audit(ctx, spec, arguments, ok=False, error=error.code)
         raise error from e
 
+    allowed, retry_after = check_and_record(ctx.rate_limit_identity, spec.name)
+    if not allowed:
+        rate_error = ToolRateLimitError(spec.name, retry_after)
+        _audit(ctx, spec, arguments, ok=False, error=rate_error.code)
+        raise rate_error
+
     vault = getattr(params, "vault", None)
     if spec.requires_vault and vault:
         try:
@@ -223,4 +232,6 @@ def call_tool(
     duration_ms = round((time.perf_counter() - started) * 1000, 2)
     logger.debug(f"Tool '{name}' ok in {duration_ms}ms")
     _audit(ctx, spec, arguments, ok=True)
-    return ToolResult(ok=True, data=data)
+    # Never forward raw secrets to the model (defense in depth: some tools —
+    # diffs, search snippets — return content that was not pre-redacted).
+    return ToolResult(ok=True, data=redact_payload(data))
diff --git a/backend/tools/service.py b/backend/tools/service.py
index be436cd..c7a350e 100644
--- a/backend/tools/service.py
+++ b/backend/tools/service.py
@@ -11,6 +11,7 @@ confirmation mechanism (two-step propose/apply).
 from __future__ import annotations
 
 import logging
+import os
 from typing import Any
 
 from backend.indexer import get_backlinks as _get_backlinks
@@ -90,8 +91,9 @@ from backend.tools.schemas import (
 
 logger = logging.getLogger("obsigate.tools.service")
 
-# Maximum file size returned by ``read_file`` (bytes).
-TOOL_MAX_READ_BYTES = 200_000
+# Maximum file size returned by ``read_file`` (bytes). Quota configurable via
+# ``BOOKSLM_MAX_TOOL_READ_BYTES``.
+TOOL_MAX_READ_BYTES = int(os.environ.get("BOOKSLM_MAX_TOOL_READ_BYTES", "200000"))
 
 
 # ── C1. Vaults / navigation ────────────────────────────────────────────────
diff --git a/docs/AI_ARCHITECTURE_GUIDE.md b/docs/AI_ARCHITECTURE_GUIDE.md
index 3f81c74..668d11f 100644
--- a/docs/AI_ARCHITECTURE_GUIDE.md
+++ b/docs/AI_ARCHITECTURE_GUIDE.md
@@ -252,9 +252,14 @@ Tout outil reçoit un `ToolContext` et applique **systématiquement** :
 1. `check_vault_access(vault, user)` — `backend/auth/middleware.py:87`
 2. `_resolve_safe_path(vault_root, path)` — `backend/main.py:867`
 3. Confirmation utilisateur pour `risk in (write, dangerous)` (UI in-app : carte Apply ; MCP : two-step `propose`/`apply`).
-4. Redaction des secrets avant tout envoi au LLM — `redact_file_content()`.
+4. Redaction des secrets avant tout envoi au LLM — `redact_file_content()` puis
+   `backend/tools/redaction.py` sur **tout** résultat d'outil (diffs, extraits de recherche).
 5. Journalisation dans l'audit (`data/audit.log`).
-6. Rate limiting par token/outil ; quotas réutilisant `BOOKSLM_MAX_*`.
+6. **Rate limiting par jeton/outil** (`backend/tools/ratelimit.py` :
+   `OBSIGATE_TOOL_RATE_LIMIT`, `OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL`,
+   `OBSIGATE_TOOL_RATE_WINDOW`) et **quotas** réutilisant `BOOKSLM_MAX_*`
+   (`BOOKSLM_MAX_TOOL_CALLS` par run d'agent, `BOOKSLM_MAX_TOOL_READ_BYTES`
+   pour `read_file`).
 
 ### Confirmations MCP — décision : two-step `propose`/`apply`
 
@@ -299,7 +304,7 @@ Pour répondre au besoin de cibler un fournisseur/modèle sans dépendre uniquem
 | **0 — Fondations** | `backend/tools/` (registry, context, service, audit) + extraction des services métier + tests unitaires | Couche d'outils testable sans IA |
 | **1 — Function calling in-app** | Abstraction tool-calling multi-provider, agent loop, confirmations UI, SSE réel, outils de navigation | Assistant qui lit/cherche/lit/ouvre/modifie avec confirmation |
 | **2 — Serveur MCP** | `backend/mcp/server.py` (tools + resources + prompts), **Streamable HTTP** (`/mcp`, auth JWT), confirmation two-step | ObsiGate accessible comme serveur MCP (local + distant, multi-utilisateur) |
-| **3 — Durcissement** | Rate limiting, quotas, redaction, tests, doc OpenAPI/MCP | Observabilité et sécurité complètes |
+| **3 — Durcissement** ✅ | Rate limiting (`backend/tools/ratelimit.py`), quotas `BOOKSLM_MAX_*`, redaction systématique des résultats (`backend/tools/redaction.py`), doc OpenAPI (tag/path MCP) + [guide MCP](./MCP_GUIDE.md), tests E2E | Observabilité et sécurité complètes |
 
 Voir `docs/ROADMAP.md` (item dédié) pour le détail des activités.
 
@@ -330,6 +335,9 @@ Voir `docs/ROADMAP.md` (item dédié) pour le détail des activités.
 - `backend/agent/loop.py` — agent loop in-app (multi-étapes, LLM injectable)
 - `backend/mcp/server.py` — serveur MCP (Streamable HTTP `/mcp`, tools/resources/prompts)
 - `backend/mcp/confirmations.py` — jetons de confirmation signés (two-step, anti-rejeu)
+- `backend/tools/ratelimit.py` — rate limiting par jeton/outil (phase F)
+- `backend/tools/redaction.py` — redaction récursive des résultats d'outils (phase F)
+- `docs/MCP_GUIDE.md` — guide d'installation et d'utilisation des clients MCP
 - `backend/bookslm.py`, `backend/bookslm_routes.py` — assistant contextuel (+ endpoint `/agent`)
 - `frontend/js/ai.js`, `frontend/js/bookslm.js` — UI IA
 - `backend/auth/middleware.py` — permissions
diff --git a/docs/MCP_GUIDE.md b/docs/MCP_GUIDE.md
new file mode 100644
index 0000000..fc12059
--- /dev/null
+++ b/docs/MCP_GUIDE.md
@@ -0,0 +1,182 @@
+# ObsiGate — Guide MCP (Model Context Protocol)
+
+> **Statut :** livré (#79 phase E + F) · **Dernière mise à jour :** 2026-09-11
+> **Voir aussi :** [AI_ARCHITECTURE_GUIDE.md](./AI_ARCHITECTURE_GUIDE.md) ·
+> [features/ai-tools-mcp.md](./features/ai-tools-mcp.md) · [ROADMAP.md](./ROADMAP.md)
+
+ObsiGate expose ses vaults à des **clients MCP externes** (Claude Desktop, Cursor,
+tout client compatible MCP) via un serveur **Streamable HTTP** monté sur `/mcp`.
+Les outils sont les **mêmes** que ceux de l'assistant in-app : la couche
+`backend/tools/` est la source unique de vérité.
+
+---
+
+## 1. Prérequis
+
+1. Une instance ObsiGate accessible (locale ou distante).
+2. Un **jeton JWT** valide (`Authorization: Bearer <token>`), obtenu via
+   `POST /api/auth/login` (ou une clé API). Le jeton porte les permissions par
+   vault de l'utilisateur — l'autorisation MCP réutilise `get_current_user`.
+3. Si l'authentification est désactivée (`OBSIGATE_AUTH_ENABLED=false`), le
+   serveur MCP accepte un utilisateur anonyme disposant de tous les vaults.
+
+> Le transport `stdio` n'est **pas** encore supporté ; utilisez le transport
+> HTTP (un pont local type `mcp-remote` si votre client ne gère pas nativement
+> le Streamable HTTP distant).
+
+---
+
+## 2. Endpoint & protocole
+
+| Élément | Valeur |
+|---|---|
+| URL | `https://<obsigate>/mcp` |
+| Transport | Streamable HTTP (`POST` JSON-RPC 2.0, `Accept: application/json, text/event-stream`) |
+| Auth | `Authorization: Bearer <JWT>` |
+| Protocole MCP | `2025-03-26` (négocié à l'`initialize`) |
+| Réponses | JSON (`json_response=True`) |
+
+Handshake minimal :
+
+```bash
+curl -sS https://obsigate.example/mcp \
+  -H "Authorization: Bearer $TOKEN" \
+  -H "Accept: application/json, text/event-stream" \
+  -H "Content-Type: application/json" \
+  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{
+        "protocolVersion":"2025-03-26","capabilities":{},
+        "clientInfo":{"name":"curl","version":"1.0"}}}'
+```
+
+La réponse contient l'en-tête `Mcp-Session-Id` à réutiliser pour les appels
+suivants (`tools/list`, `tools/call`, `resources/read`, …).
+
+---
+
+## 3. Configuration des clients
+
+### Claude Desktop (via pont `mcp-remote`)
+
+```json
+{
+  "mcpServers": {
+    "obsigate": {
+      "command": "npx",
+      "args": [
+        "-y", "mcp-remote",
+        "https://obsigate.example/mcp",
+        "--header", "Authorization: Bearer ${OBSIGATE_TOKEN}"
+      ],
+      "env": { "OBSIGATE_TOKEN": "eyJ..." }
+    }
+  }
+}
+```
+
+### Cursor
+
+`.cursor/mcp.json` :
+
+```json
+{
+  "mcpServers": {
+    "obsigate": {
+      "url": "https://obsigate.example/mcp",
+      "headers": { "Authorization": "Bearer eyJ..." }
+    }
+  }
+}
+```
+
+---
+
+## 4. Primitives exposées
+
+### 4.1 Tools
+
+Les outils de **lecture/recherche** sont exposés directement. Les outils
+**d'écriture/destructifs** sont exposés via une paire **two-step** :
+`propose_<tool>` (aperçu + jeton de confirmation, aucune modification) puis
+`apply_<tool>` (consomme le jeton et exécute).
+
+| Catégorie | Outils |
+|---|---|
+| Vaults / navigation | `list_vaults`, `list_directory`, `list_all_files` |
+| Lecture | `read_file`, `read_file_raw`, `get_backlinks`, `list_backups`, `diff_backup`, `get_graph` |
+| Recherche | `search_fulltext`, `search_advanced`, `search_paths`, `list_tags`, `suggest_tags`, `list_recent` |
+| Écriture (propose/apply) | `create_file`, `create_directory`, `edit_file`, `append_to_file`, `restore_backup` |
+| Destructif (propose/apply) | `rename_file`, `rename_directory`, `move_path`, `replace_in_files`, `delete_file`, `delete_directory` |
+
+Flux d'une mutation :
+
+```text
+1. tools/call { name: "propose_edit_file",
+                arguments: { vault, path, content } }
+   → { tool, arguments, diff, confirmation_token, expires_in }
+
+2. (l'utilisateur / l'agent valide)
+
+3. tools/call { name: "apply_edit_file",
+                arguments: { confirmation_token } }
+   → { ok: true, data: { ... } }
+```
+
+Le jeton est **signé (JWT), à usage unique et à durée de vie limitée**
+(`OBSIGATE_MCP_CONFIRMATION_TTL`, défaut 300 s). Un rejeu renvoie
+`token_reused`.
+
+### 4.2 Resources
+
+| URI | Contenu |
+|---|---|
+| `vault://<name>` | Vault accessible (métadonnées, nombre de fichiers) |
+| `vault://<name>/<path>` | Contenu d'un fichier (lecture seule, **secrets redactés**) |
+
+### 4.3 Prompts
+
+`summarize-directory`, `generate-note`, `find-related`.
+
+---
+
+## 5. Sécurité
+
+- **Permissions par vault** : `check_vault_access` est appliqué à chaque outil
+  et chaque resource ; un utilisateur ne voit que ses vaults.
+- **Anti path-traversal** : `resolve_safe_path` rejette tout chemin hors du vault.
+- **Confirmation two-step** pour toute mutation (jeton signé, usage unique).
+- **Toggle par vault** `aiDestructiveTools` (défaut : activé) : le désactiver
+  bloque rename/move/replace/delete tout en laissant create/edit/append.
+- **Backup automatique** avant chaque opération destructive.
+- **Rate limiting** : par jeton et par outil
+  (`OBSIGATE_TOOL_RATE_LIMIT`, `OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL`,
+  `OBSIGATE_TOOL_RATE_WINDOW`). Une limite dépassée renvoie le code
+  `rate_limited`.
+- **Redaction des secrets** : les résultats d'outils (lectures, diffs,
+  extraits de recherche) sont nettoyés avant tout retour au client.
+- **Audit** : chaque appel est journalisé (`data/audit.log`, action
+  `ai_tool_call`) avec arguments sensibles résumés.
+
+### Variables d'environnement
+
+| Variable | Défaut | Rôle |
+|---|---|---|
+| `OBSIGATE_MCP_CONFIRMATION_TTL` | `300` | Durée de vie (s) des jetons de confirmation |
+| `OBSIGATE_TOOL_RATE_LIMIT` | `60` | Appels d'outils max par identité et par fenêtre |
+| `OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL` | = global | Appels max par outil et par fenêtre |
+| `OBSIGATE_TOOL_RATE_WINDOW` | `60` | Longueur de la fenêtre (s) |
+| `BOOKSLM_MAX_TOOL_CALLS` | `25` | Quota d'appels d'outils par run d'agent |
+| `BOOKSLM_MAX_TOOL_READ_BYTES` | `200000` | Taille max renvoyée par `read_file` |
+
+---
+
+## 6. Dépannage
+
+| Symptôme | Cause probable / remède |
+|---|---|
+| `401 Authentification requise` | En-tête `Authorization: Bearer` absent ou jeton expiré |
+| `vault_access_denied` | Le jeton n'a pas accès à ce vault (`vaults` / `_token_vaults`) |
+| `destructive_tools_disabled` | `aiDestructiveTools=false` pour ce vault |
+| `confirmation_required` | Appeler d'abord `propose_<tool>` puis `apply_<tool>` |
+| `token_reused` / `invalid_confirmation` | Jeton déjà consommé ou expiré → refaire un `propose_` |
+| `rate_limited` | Quota dépassé ; respecter `retry_after` |
+| Le client ne se connecte pas | Vérifier le transport Streamable HTTP / le pont `mcp-remote` |
diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
index a910fb3..6560c0e 100644
--- a/docs/ROADMAP.md
+++ b/docs/ROADMAP.md
@@ -40,18 +40,6 @@
   - [ ] Jumplist vaults récents dans le menu Démarrer (optionnel)
   - [ ] 6 tests E2E **manuels** : installation, tray icon, notifications natives, association `.md`, auto-update, désinstallation
 
-### 79. Assistant IA — Outils (function calling) & serveur MCP
-
-- **Effort :** 10-15 jours | **Impact :** 🟡
-- **Statut :** 🔵 Phase 0 + A2 + B1/B2/B3/B4/B5/B6/B7 + C + D + E + G livrés (2026-09-11). Détail complet : [features/ai-tools-mcp.md](./features/ai-tools-mcp.md)
-- **Description :** Transformer l'assistant BooksLM en agent (lire, chercher, lister, ouvrir, modifier) via **function calling natif**, puis exposer ObsiGate à des **clients MCP externes** (Claude Desktop, Cursor…). Les deux fronts consomment une **couche d'outils partagée**.
-- **Reste à faire :**
-  - [x] **C.** Catalogue lecture & recherche (vaults, read, backlinks, backups, search, tags)
-  - [x] **D.** Catalogue mutations (create/edit/append/rename/move/delete) + confirmations two-step
-  - [x] **E.** Serveur MCP (Streamable HTTP `/mcp`, auth Bearer JWT, `propose`/`apply`, toggle par vault)
-  - [ ] **F.** Durcissement (rate limiting, redaction secrets, OpenAPI + guide MCP, E2E)
-- **Documentation :** [AI_ARCHITECTURE_GUIDE.md](./AI_ARCHITECTURE_GUIDE.md) (architecture, catalogue d'outils, sécurité, phases).
-
 ### 80. Assistant IA — Rendu Markdown, liens fichiers/paths & sessions
 
 - **Effort :** 1-2 jours | **Impact :** 🟡
@@ -169,6 +157,7 @@
 | 72 | API publique documentée — OpenAPI 3.1 | 2.2.0 | [archive](./archive/COMPLETED_v1-v2.md) |
 | 76 | BooksLM — Console AI contextuelle par répertoire | 2.2.0 | [features/bookslm.md](./features/bookslm.md) |
 | 78 | Éditeur Excalidraw | 2.2.0 | [features/excalidraw.md](./features/excalidraw.md) |
+| 79 | Assistant IA — Outils (function calling) & serveur MCP | 2.3.0 | [features/ai-tools-mcp.md](./features/ai-tools-mcp.md) |
 | 77 | Application Desktop native — Tauri | 🔵 en cours | [features/desktop-tauri.md](./features/desktop-tauri.md) |
 | 80 | Assistant IA — Rendu Markdown, liens fichiers/paths & sessions | 🔵 en cours | [features/ai-assistant-ux.md](./features/ai-assistant-ux.md) |
 
@@ -178,11 +167,11 @@
 
 | Priorité | Items | Effort total estimé |
 |---|---|---|
-| ✅ Complété | #1 → #59, #61, #63–68, #71, #72, #74–76, #78 | ~82 jours réalisés |
+| ✅ Complété | #1 → #59, #61, #63–68, #71, #72, #74–79 | ~92 jours réalisés |
 | 🔵 P2 restant | #77 Desktop : signature code (optionnel), wizard 1er lancement (optionnel), 6 tests E2E **manuels** | ~1-2 jours |
-| ⚪ P3 restant | #62 Collaboration Yjs (5-7j) · #79 Assistant IA outils + MCP (10-15j, Phase 0 + A2 + B + C + D + E + G livrés) · #80 Assistant IA UX (livré, en attente vérif) | ~15-22 jours |
+| ⚪ P3 restant | #62 Collaboration Yjs (5-7j) · #80 Assistant IA UX (livré, en attente vérif) | ~5-7 jours |
 | ⚪ P4 restant | #69 Mobile éditeur (2-3j) · #70 Sémantique (4-5j) · #73 Sync (6-8j) | 11-16 jours |
-| **Total restant** | **6 items + finitions** | **~27-39 jours** |
+| **Total restant** | **5 items + finitions** | **~17-25 jours** |
 
 ---
 
diff --git a/docs/features/ai-tools-mcp.md b/docs/features/ai-tools-mcp.md
index 889f10a..85a6fd7 100644
--- a/docs/features/ai-tools-mcp.md
+++ b/docs/features/ai-tools-mcp.md
@@ -1,6 +1,6 @@
 # #79 — Assistant IA — Outils (function calling) & serveur MCP
 
-> **Statut :** 🔵 En cours — Phase 0 + A2 + B1/B2/B3/B4/B5/B6/B7 + C + D + E + G livrés (2026-09-11)
+> **Statut :** ✅ Livré — Phase 0 + A2 + B1/B2/B3/B4/B5/B6/B7 + C + D + E + F + G livrés (2026-09-11)
 > **Effort :** 10-15 jours | **Impact :** 🟡
 > **Références :** [Roadmap](../ROADMAP.md) · [Guide d'architecture IA](../AI_ARCHITECTURE_GUIDE.md)
 
@@ -53,11 +53,25 @@
     matcher `/mcp` exact, démarrage paresseux du manager pour les tests). Dépendances ajoutées :
     `mcp==1.9.4`, `sse-starlette==2.1.3` (compatibles avec FastAPI 0.110 / starlette 0.37).
 
-## F. Durcissement & documentation (1 jour)
-  - [ ] **F1.** Rate limiting par token/outil + quotas (`BOOKSLM_MAX_*`)
-  - [ ] **F2.** Redaction des secrets avant retour au LLM
-  - [ ] **F3.** Documentation OpenAPI (`backend/openapi_docs.py`) + guide MCP
-  - [ ] **F4.** Tests E2E de bout en bout
+## F. Durcissement & documentation (1 jour) — ✅ livré (2026-09-11)
+  - [x] **F1.** Rate limiting par token/outil + quotas — `backend/tools/ratelimit.py`
+    (fenêtre glissante par identité **et** par outil ; identité = JTI du jeton
+    (`_token_jti`, ajouté par `backend/auth/middleware.py`) sinon id/username).
+    Env : `OBSIGATE_TOOL_RATE_LIMIT` (60), `OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL`,
+    `OBSIGATE_TOOL_RATE_WINDOW` (60 s) ; erreur `ToolRateLimitError` (`rate_limited`).
+    Quotas `BOOKSLM_MAX_*` : `BOOKSLM_MAX_TOOL_CALLS` (25) plafonne les appels d'outils
+    par run d'agent (`backend/agent/loop.py`, `stopped="quota_exceeded"`) et
+    `BOOKSLM_MAX_TOOL_READ_BYTES` (200000) plafonne `read_file`.
+  - [x] **F2.** Redaction des secrets avant retour au LLM — `backend/tools/redaction.py`
+    (`redact_payload`, récursif) appliqué à **tout** résultat d'outil dans
+    `call_tool` (couvre les diffs, extraits de recherche et lectures non pré-redactées).
+  - [x] **F3.** Documentation OpenAPI + guide MCP — `backend/openapi_docs.py` : tag `MCP`,
+    règle `/mcp`, injection du path `/mcp` (Streamable HTTP, JSON-RPC) dans le schéma ;
+    nouveau [`docs/MCP_GUIDE.md`](../MCP_GUIDE.md) (endpoint, auth, config Claude Desktop /
+    Cursor, tools/resources/prompts, sécurité, variables, dépannage).
+  - [x] **F4.** Tests E2E de bout en bout — `tests/test_ai_e2e.py` : agent in-app
+    read→confirmation→write, quota d'outils, rate limiting, redaction, et flux MCP complet
+    `read` → `propose_edit_file` → `apply_edit_file` → `resources/read`.
 
 ## G. Sélection fournisseur/modèle par défaut — ✅ livré
   - [x] **G1.** Persistance `ai_default_provider` + `ai_default_models` dans `data/config.json` (`_DEFAULT_CONFIG`)
diff --git a/tests/conftest.py b/tests/conftest.py
index dd0f8ec..ccb427e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -12,6 +12,16 @@ from fastapi.testclient import TestClient
 sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
 
 
+@pytest.fixture(autouse=True)
+def _reset_tool_ratelimit():
+    """Isolate the per-identity tool rate limiter between tests."""
+    from backend.tools import ratelimit
+
+    ratelimit.reset()
+    yield
+    ratelimit.reset()
+
+
 @pytest.fixture(autouse=True)
 def _clean_env():
     """Ensure no vault env vars leak between tests — but preserve test vault config."""
diff --git a/tests/test_ai_e2e.py b/tests/test_ai_e2e.py
new file mode 100644
index 0000000..d8fc68a
--- /dev/null
+++ b/tests/test_ai_e2e.py
@@ -0,0 +1,265 @@
+# tests/test_ai_e2e.py — End-to-end tests for the AI tool layer (Phase F)
+"""End-to-end coverage of the AI assistant, combining the shared tool layer,
+the in-app agent loop and the MCP server.
+
+The LLM is scripted (no network) so the tests are deterministic; everything
+else (permissions, services, confirmations, redaction, rate limiting, audit) is
+the real production code path.
+"""
+
+import json
+from pathlib import Path
+
+import pytest
+from fastapi.testclient import TestClient
+
+from backend.agent.loop import (
+    STOP_CONFIRMATION_REQUIRED,
+    STOP_DONE,
+    STOP_QUOTA_EXCEEDED,
+    run_agent,
+)
+from backend.ai_chat import LLMResponse, ToolCall
+from backend.tools.api import (
+    ToolContext,
+    ToolRateLimitError,
+    ToolRisk,
+    call_tool,
+)
+
+
+def _ctx(vaults=None) -> ToolContext:
+    return ToolContext(
+        user={"username": "e2e", "role": "admin", "vaults": vaults or ["*"]},
+        audit_enabled=False,
+    )
+
+
+def _vault_path() -> Path:
+    from backend.indexer import get_vault_data
+
+    return Path(get_vault_data("TestVault")["path"])
+
+
+class ScriptedLLM:
+    """Async LLM returning pre-scripted responses and recording invocations."""
+
+    def __init__(self, responses):
+        self.responses = list(responses)
+        self.calls = []
+
+    async def __call__(self, messages, tools):
+        self.calls.append({"messages": [dict(m) for m in messages], "tools": tools})
+        return self.responses.pop(0)
+
+
+# ═══════════════════════════════════════════════════════════════════
+# In-app agent — read then confirmed write, end to end
+# ═══════════════════════════════════════════════════════════════════
+
+
+class TestAgentEndToEnd:
+    @pytest.mark.asyncio
+    async def test_read_then_confirmed_create_file(self, client):
+        target = _vault_path() / "agent-note.md"
+        assert not target.exists()
+
+        llm = ScriptedLLM([
+            LLMResponse(tool_calls=[ToolCall(
+                id="1", name="read_file", arguments={"vault": "TestVault", "path": "note1.md"},
+            )]),
+            LLMResponse(tool_calls=[ToolCall(
+                id="2",
+                name="create_file",
+                arguments={"vault": "TestVault", "path": "agent-note.md", "content": "# Agent\n"},
+            )]),
+        ])
+
+        paused = await run_agent([{"role": "user", "content": "read then create"}], ctx=_ctx(), llm=llm)
+        assert paused.stopped == STOP_CONFIRMATION_REQUIRED
+        # The read ran, the write is pending confirmation.
+        assert len(paused.tool_calls) == 1
+        assert paused.tool_calls[0].name == "read_file"
+        assert paused.pending["error"]["tool"] == "create_file"
+        assert not target.exists()
+
+        llm2 = ScriptedLLM([LLMResponse(content="Note créée.")])
+        resumed = await run_agent(
+            [{"role": "user", "content": "read then create"}],
+            ctx=_ctx(),
+            llm=llm2,
+            resume_messages=paused.messages,
+            confirm_pending=paused.pending,
+        )
+        assert resumed.stopped == STOP_DONE
+        assert resumed.content == "Note créée."
+        assert target.read_text(encoding="utf-8") == "# Agent\n"
+        assert any(r.name == "create_file" and r.ok for r in resumed.tool_calls)
+
+    @pytest.mark.asyncio
+    async def test_tool_call_quota_stops_run(self, client):
+        llm = ScriptedLLM([
+            LLMResponse(tool_calls=[
+                ToolCall(id="1", name="list_vaults", arguments={}),
+                ToolCall(id="2", name="list_vaults", arguments={}),
+            ]),
+        ])
+        result = await run_agent(
+            [{"role": "user", "content": "loop"}],
+            ctx=_ctx(),
+            llm=llm,
+            max_tool_calls=1,
+        )
+        assert result.stopped == STOP_QUOTA_EXCEEDED
+        assert len(result.tool_calls) == 1
+
+
+# ═══════════════════════════════════════════════════════════════════
+# Hardening — rate limiting & redaction
+# ═══════════════════════════════════════════════════════════════════
+
+
+class TestHardening:
+    def test_rate_limit_blocks_excess_calls(self, client, monkeypatch):
+        monkeypatch.setenv("OBSIGATE_TOOL_RATE_LIMIT", "1")
+        monkeypatch.setenv("OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL", "1")
+
+        first = call_tool("list_vaults", _ctx(), {})
+        assert first.ok
+
+        with pytest.raises(ToolRateLimitError) as exc:
+            call_tool("list_vaults", _ctx(), {})
+        assert exc.value.code == "rate_limited"
+        assert exc.value.retry_after >= 1
+
+    def test_rate_limit_is_per_tool(self, client, monkeypatch):
+        monkeypatch.setenv("OBSIGATE_TOOL_RATE_LIMIT", "100")
+        monkeypatch.setenv("OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL", "1")
+
+        call_tool("list_vaults", _ctx(), {})
+        # A different tool still has budget.
+        assert call_tool("list_tags", _ctx(), {}).ok
+        with pytest.raises(ToolRateLimitError):
+            call_tool("list_vaults", _ctx(), {})
+
+    def test_tool_results_are_redacted(self, client, monkeypatch):
+        from backend.tools import registry
+        from backend.tools.registry import ToolSpec
+        from backend.tools.schemas import ListVaultsInput
+
+        fake_jwt = "eyJ" + "a" * 30 + "." + "b" * 30 + "." + "c" * 30
+        spec = ToolSpec(
+            name="_leak",
+            description="returns a secret for tests",
+            input_model=ListVaultsInput,
+            handler=lambda ctx, params: {"content": f"token: {fake_jwt}", "nested": [fake_jwt]},
+            risk=ToolRisk.READ,
+        )
+        monkeypatch.setitem(registry._REGISTRY, "_leak", spec)
+
+        result = call_tool("_leak", _ctx(), {})
+        assert fake_jwt not in json.dumps(result.data)
+        assert "[JWT MASQUÉ]" in result.data["content"]
+        assert "[JWT MASQUÉ]" in result.data["nested"][0]
+
+
+# ═══════════════════════════════════════════════════════════════════
+# MCP — full propose/apply flow over Streamable HTTP
+# ═══════════════════════════════════════════════════════════════════
+
+ACCEPT = "application/json, text/event-stream"
+PROTOCOL = "2025-03-26"
+
+
+@pytest.fixture
+def mcp_client(app_with_vault, monkeypatch):
+    from backend import main
+
+    async def _noop_build(*args, **kwargs):
+        return None
+
+    monkeypatch.setattr(main, "build_index", _noop_build)
+    monkeypatch.setattr(main, "init_inverted_index", lambda: None)
+
+    main.mcp_app._manager = None
+    main.mcp_app._run_task = None
+    main.mcp_app._start_lock = None
+
+    with TestClient(main.app) as client:
+        yield client
+
+
+def _mcp_post(client, payload, session=None):
+    headers = {"Accept": ACCEPT, "Content-Type": "application/json"}
+    if session:
+        headers["Mcp-Session-Id"] = session
+    return client.post("/mcp", content=json.dumps(payload), headers=headers)
+
+
+def _mcp_call(client, session, method, params=None, req_id=2):
+    resp = _mcp_post(
+        client,
+        {"jsonrpc": "2.0", "id": req_id, "method": method, "params": params or {}},
+        session=session,
+    )
+    assert resp.status_code == 200, resp.text
+    return resp.json()
+
+
+def _text_json(result):
+    return json.loads(result["content"][0]["text"])
+
+
+class TestMcpEndToEnd:
+    def test_read_propose_apply(self, mcp_client):
+        init = _mcp_post(
+            mcp_client,
+            {
+                "jsonrpc": "2.0",
+                "id": 1,
+                "method": "initialize",
+                "params": {
+                    "protocolVersion": PROTOCOL,
+                    "capabilities": {},
+                    "clientInfo": {"name": "pytest-e2e", "version": "1.0"},
+                },
+            },
+        )
+        assert init.status_code == 200
+        session = init.headers["mcp-session-id"]
+        _mcp_post(mcp_client, {"jsonrpc": "2.0", "method": "notifications/initialized"}, session)
+
+        # 1. Read the current content.
+        read = _mcp_call(
+            mcp_client, session, "tools/call",
+            {"name": "read_file", "arguments": {"vault": "TestVault", "path": "note1.md"}},
+        )
+        assert "Python" in _text_json(read["result"])["data"]["content"]
+
+        # 2. Propose an edit (no change yet).
+        proposed = _mcp_call(
+            mcp_client, session, "tools/call",
+            {
+                "name": "propose_edit_file",
+                "arguments": {"vault": "TestVault", "path": "note1.md", "content": "# E2E\n"},
+            },
+        )
+        payload = _text_json(proposed["result"])
+        token = payload["confirmation_token"]
+        assert payload["tool"] == "edit_file"
+        assert "diff" in payload
+
+        # 3. Apply it.
+        applied = _mcp_call(
+            mcp_client, session, "tools/call",
+            {"name": "apply_edit_file", "arguments": {"confirmation_token": token}},
+            req_id=3,
+        )
+        assert _text_json(applied["result"])["ok"] is True
+        assert (_vault_path() / "note1.md").read_text(encoding="utf-8") == "# E2E\n"
+
+        # 4. Resource read reflects the new content.
+        resource = _mcp_call(
+            mcp_client, session, "resources/read", {"uri": "vault://TestVault/note1.md"}, req_id=4
+        )
+        assert "E2E" in resource["result"]["contents"][0]["text"]