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+# FIDES Implementation Summary
+
+## Overview
+
+**FIDES**  is a comprehensive deterministic prompt injection defense system for the agent framework. The implementation provides label-based security mechanisms to defend against prompt injection attacks by tracking integrity and confidentiality of content throughout agent execution.
+
+**🚀 Key Features:**
+- **Context Provider Pattern** - `SecureAgentConfig` extends `ContextProvider`, injecting tools, instructions, and middleware automatically
+- **Automatic Variable Hiding** - UNTRUSTED content is automatically hidden without requiring manual intervention
+- **Per-Item Embedded Labels** - Tools return `list[Content]` with `Content.from_text()` for proper label propagation
+- **SecureMCPToolProxy Auto-Labeling** - MCP tools are labeled automatically from MCP `ToolAnnotations` hints
+- **MCP `_meta.ifc` Support** - Per-result IFC labels from servers (for example GitHub MCP with `X-MCP-Features: ifc_labels`) are parsed and enforced
+- **SecureAgentConfig** - One-line secure agent configuration via `context_providers=[config]`
+- **Data Exfiltration Prevention** - `max_allowed_confidentiality` prevents sensitive data leakage
+- **Message-Level Label Tracking** (Phase 1) - Track labels on every message in the conversation
+
+## Architecture Components
+
+The FIDES defense system consists of seven main components:
+
+1. **Content Labeling Infrastructure** - Labels for tracking integrity and confidentiality
+2. **Label Tracking Middleware** - Automatically assigns, propagates labels, and hides untrusted content
+3. **Per-Item Embedded Labels** - Tools can return mixed-trust data with per-item security labels
+4. **Policy Enforcement Middleware** - Blocks tool calls that violate security policies
+5. **Security Tools** - Specialized tools for safe handling of untrusted content (`quarantined_llm`, `inspect_variable`)
+6. **SecureAgentConfig** - Context provider for easy secure agent configuration
+7. **Message-Level Label Tracking** - Track labels on every message in the conversation (Phase 1)
+8. **MCP Tool/Result Label Integration** - MCP hint-based tool labeling and `_meta.ifc` result label parsing
+
+## Implementation Details
+
+### Files Created
+
+1. **`python/packages/core/agent_framework/security.py`** (~2950 lines — all security primitives, middleware, tools, and configuration in a single public module)
+   - `IntegrityLabel` enum (TRUSTED/UNTRUSTED)
+   - `ConfidentialityLabel` enum (PUBLIC/PRIVATE/USER_IDENTITY)
+   - `ContentLabel` class with serialization support
+   - `combine_labels()` function for label composition
+   - `ContentVariableStore` for client-side content storage
+   - `VariableReferenceContent` for variable indirection
+   - `LabeledMessage` class (inherits from `Message`) for message-level tracking
+   - `check_confidentiality_allowed()` helper for data exfiltration prevention
+   - `LabelTrackingFunctionMiddleware` - Tracks and propagates security labels
+   - `PolicyEnforcementFunctionMiddleware` - Enforces security policies
+   - `SecureAgentConfig` extends `ContextProvider` - automatic secure agent configuration
+   - `quarantined_llm()` - Isolated LLM calls with labeled data
+   - `inspect_variable()` - Controlled variable content inspection
+   - `store_untrusted_content()` - Helper for manual variable indirection (legacy)
+   - `get_security_tools()` - Returns list of security tools
+   - `SECURITY_TOOL_INSTRUCTIONS` - Detailed guidance for agents
+
+
+2. **`FIDES_DEVELOPER_GUIDE.md`** (~1250 lines)
+   - Located at `python/samples/02-agents/security/FIDES_DEVELOPER_GUIDE.md`
+   - Complete documentation of the FIDES security system
+   - Architecture overview and design rationale
+   - Usage examples (6+ comprehensive scenarios)
+   - Best practices and configuration options
+   - API reference with full parameter documentation
+   - Data exfiltration prevention documentation
+
+3. **`python/packages/core/tests/test_security.py`** (~800+ lines)
+   - Unit tests for ContentLabel and label operations
+   - Tests for ContentVariableStore functionality
+   - Tests for VariableReferenceContent
+   - Middleware behavior tests (label tracking and policy enforcement)
+   - Automatic hiding tests
+   - Per-item embedded label tests
+   - Context label tracking tests
+   - Message-level tracking tests (Phase 1)
+   - Data exfiltration prevention tests
+
+4. **`docs/decisions/0024-prompt-injection-defense.md`**
+   - Architecture Decision Record (ADR)
+   - Design rationale and alternatives considered
+   - Security properties and guarantees
+
+5. **`python/samples/02-agents/security/README.md`**
+   - Sample-focused entry point for the two runnable FIDES security samples
+   - Prerequisites, run commands, and links to the developer guide for deeper details
+
+### Files Modified
+
+1. **`python/packages/core/agent_framework/__init__.py`**
+   - Removed root-level security exports so `agent_framework.security` is the canonical import surface
+
+## Core Features
+
+### 1. Content Labeling Infrastructure
+
+- **IntegrityLabel**: TRUSTED (user input) vs UNTRUSTED (AI-generated, external)
+- **ConfidentialityLabel**: PUBLIC, PRIVATE, USER_IDENTITY
+- **Label Combination**: Most restrictive policy (UNTRUSTED + metadata merging)
+- **Serialization**: Full support for `to_dict()` and `from_dict()`
+
+### 2. Per-Item Embedded Labels
+
+Tools returning mixed-trust data embed labels on individual items using `Content.from_text()`:
+
+```python
+import json
+from agent_framework import Content, tool
+
+@tool(description="Fetch emails from inbox")
+async def fetch_emails(count: int = 5) -> list[Content]:
+    return [
+        Content.from_text(
+            json.dumps({
+                "id": email["id"],
+                "body": email["body"],
+            }),
+            additional_properties={
+                "security_label": {
+                    "integrity": "trusted" if email["internal"] else "untrusted",
+                    "confidentiality": "private",
+                }
+            ),
+        )
+        for email in emails
+    ]
+```
+
+These embedded labels are automatically consumed by `LabelTrackingFunctionMiddleware`, which:
+- Extracts the `security_label` from `additional_properties`
+- Uses the embedded label as the highest-priority source for that item
+- Automatically hides UNTRUSTED items in the variable store
+- Replaces hidden items with `VariableReferenceContent` in the LLM context
+- Preserves TRUSTED items visible to the LLM without tainting the context label
+
+This enables tools to return mixed-trust data where some items (internal emails) remain visible while untrusted items (external emails) are automatically hidden without manual intervention.
+           },
+        )
+        for email in emails
+    ]
+```
+
+### 3. Automatic Variable Hiding
+
+This feature automatically hides any UNTRUSTED content returned by tools while keeping the hiding logic transparent to the developer. Developers do not need to manually call `store_untrusted_content()`. This allows the LLM /agent's context to remain clean and secure. Key aspects include:
+
+- **Automatic Detection**: Middleware checks integrity label after each tool call
+- **Automatic Storage**: UNTRUSTED results/items stored in variable store
+- **Transparent Replacement**: LLM context receives `VariableReferenceContent`
+- **Context Label Protection**: Hidden content does NOT taint context label
+
+### 4. Context Label Tracking
+
+- Context label starts as TRUSTED + PUBLIC
+- Gets updated (tainted) when non-hidden untrusted content enters context
+- Policy enforcement uses context label for validation
+- Provides `get_context_label()` and `reset_context_label()` methods
+
+### 5. Data Exfiltration Prevention
+
+Tools declare `max_allowed_confidentiality` to prevent sensitive data leakage:
+
+```python
+@tool(
+    description="Post to public Slack channel",
+    additional_properties={
+        "max_allowed_confidentiality": "public",  # Blocks PRIVATE data
+    }
+)
+async def post_to_slack(channel: str, message: str) -> dict:
+    return {"status": "posted"}
+```
+
+### 6. SecureAgentConfig (Context Provider)
+
+SecureAgentConfig extends `ContextProvider` for automatic secure agent configuration:
+
+```python
+config = SecureAgentConfig(
+    auto_hide_untrusted=True,
+    allow_untrusted_tools={"search_web", "fetch_data"},
+    block_on_violation=True,
+    quarantine_chat_client=quarantine_client,  # Optional: real LLM for quarantine
+)
+
+# Context provider injects tools, instructions, and middleware automatically
+agent = Agent(
+    client=client,
+    name="secure_assistant",
+    instructions="You are a helpful assistant.",
+    tools=[my_tool],
+    context_providers=[config],  # That's it!
+)
+```
+
+### 7. MCP Labeling Pipeline (Hints + `_meta.ifc`)
+
+FIDES now secures remote MCP integration end-to-end:
+
+- **Tool labels from hints**: `apply_mcp_security_labels(...)` maps MCP hints (`readOnlyHint`, `openWorldHint`) to FIDES tool properties.
+- **Safe sink defaults**: tools not explicitly marked `readOnlyHint=True` are treated as potential sinks and receive `max_allowed_confidentiality=public`.
+- **Result labels from metadata**: MCP result `_meta` is propagated via `__mcp_result_meta__`; `_meta.ifc` is parsed into `security_label` per result item.
+- **`SecureMCPToolProxy` convenience**: wraps MCP tools/URLs and applies this labeling automatically on connect.
+
+This behavior is used with the GitHub MCP server when `X-MCP-Features: ifc_labels` is passed, which causes the server to return IFC labels in `_meta` (for example `{"ifc": {"integrity": "untrusted", "confidentiality": "public"}}`).
+
+## Security Properties
+
+### Deterministic Defense
+
+1. **Tiered label propagation**: Every tool result receives a label via 3-tier priority (embedded > source_integrity > input labels join)
+2. **Context tracking**: Cumulative security state tracked across turns
+3. **Policy enforcement**: Violations blocked before execution
+4. **Content isolation**: Untrusted content stored as variables
+5. **Taint propagation**: Once context becomes UNTRUSTED, it stays UNTRUSTED
+6. **Data exfiltration prevention**: `max_allowed_confidentiality` gates output destinations
+7. **Audit trail**: All security events logged
+8. **No runtime guessing**: Deterministic label assignment
+
+### Attack Prevention
+
+- **Direct prompt injection**: Variables hide actual content from LLM
+- **Indirect prompt injection**: Labels track untrusted AI-generated calls
+- **Privilege escalation**: Policy blocks untrusted calls to privileged tools
+- **Data exfiltration**: Confidentiality labels + `max_allowed_confidentiality` enforced
+- **Tool misuse**: Only whitelisted tools accept untrusted inputs
+
+## Configuration Options
+
+### LabelTrackingFunctionMiddleware
+- `default_integrity`: Default label for unknown sources
+- `default_confidentiality`: Default confidentiality level
+- `auto_hide_untrusted`: Enable automatic variable hiding (default: True)
+- `hide_threshold`: Integrity level at which hiding occurs (default: UNTRUSTED)
+
+### PolicyEnforcementFunctionMiddleware
+- `allow_untrusted_tools`: Set of tools accepting untrusted inputs
+- `block_on_violation`: Block vs warn on violations
+- `enable_audit_log`: Enable/disable audit logging
+
+### Tool Metadata (via `additional_properties`)
+- `confidentiality`: Tool's output confidentiality level
+- `source_integrity`: Fallback integrity for unlabeled results (data-producing tools only)
+- `accepts_untrusted`: Explicit untrusted input permission
+- `max_allowed_confidentiality`: Maximum allowed input confidentiality (for sink tools)
+- `requires_approval`: Human-in-the-loop requirement
+
+## Usage Pattern
+
+### Recommended: SecureAgentConfig as Context Provider
+
+```python
+from agent_framework.security import SecureAgentConfig
+
+config = SecureAgentConfig(
+    auto_hide_untrusted=True,
+    allow_untrusted_tools={"search_web"},
+    block_on_violation=True,
+)
+
+# Context provider injects everything automatically
+agent = Agent(
+    client=client,
+    name="secure_assistant",
+    instructions="You are a helpful assistant.",
+    tools=[search_web],
+    context_providers=[config],  # Tools, instructions, and middleware injected via before_run()
+)
+```
+
+### Processing Hidden Content with quarantined_llm
+
+```python
+from agent_framework.security import quarantined_llm
+
+# Agent automatically uses quarantined_llm with variable_ids
+result = await quarantined_llm(
+    prompt="Summarize this data",
+    variable_ids=["var_abc123"]  # Reference hidden content by ID
+)
+```
+
+## Testing
+
+Comprehensive test suite with:
+- 115+ unit tests covering all components
+- Label creation, serialization, combination
+- Variable store operations
+- Middleware behavior (tracking and enforcement)
+- Automatic hiding with per-item labels
+- Context label tracking
+- Message-level tracking (Phase 1)
+- Data exfiltration prevention
+- Policy violation scenarios
+- Audit log verification
+
+Run tests:
+```bash
+cd python/packages/core && ../../.venv/bin/pytest tests/test_security.py -v
+```
+
+## Code Statistics
+
+- **Total lines**: ~2,950+ lines (single `security.py` module)
+- **New modules**: 1 (`security.py` — consolidated from 3 original modules)
+- **Total tests**: 115+ unit tests
+- **Documentation**: 1,250+ lines in developer guide
+- **Examples**: 6+ comprehensive scenarios
+
+## Deliverables Checklist
+
+### Core Implementation
+✅ ContentLabel infrastructure with integrity and confidentiality
+✅ ContentVariableStore for variable indirection
+✅ VariableReferenceContent for safe context references
+✅ LabelTrackingFunctionMiddleware for automatic labeling
+✅ PolicyEnforcementFunctionMiddleware for policy enforcement
+✅ quarantined_llm tool for isolated processing
+✅ inspect_variable tool for controlled content access
+✅ store_untrusted_content helper for manual variable indirection
+
+### Automatic Hiding Enhancement
+✅ Auto-hide UNTRUSTED content with `auto_hide_untrusted` flag
+✅ Per-middleware ContentVariableStore instances
+✅ Thread-local storage for middleware access from tools
+✅ Automatic UNTRUSTED content replacement
+
+### Per-Item Embedded Labels
+✅ Support for `additional_properties.security_label` on individual items
+✅ Mixed-trust data handling (hide untrusted, keep trusted visible)
+✅ Fallback to `source_integrity` for unlabeled items
+
+### Context Label Tracking
+✅ Cumulative context label tracking across turns
+✅ Hidden content does NOT taint context
+✅ `get_context_label()` and `reset_context_label()` methods
+✅ Policy enforcement uses context label
+
+### Data Exfiltration Prevention
+✅ `max_allowed_confidentiality` tool property
+✅ `check_confidentiality_allowed()` helper function
+✅ Policy enforcement validates confidentiality flow
+
+### SecureAgentConfig
+✅ Context provider pattern with `ContextProvider` base class
+✅ `before_run()` hook for automatic injection of tools, instructions, and middleware
+✅ One-line secure agent configuration via `context_providers=[config]`
+✅ `get_tools()`, `get_instructions()`, `get_middleware()` methods (for manual use)
+✅ `quarantine_chat_client` support for real LLM calls
+✅ `SECURITY_TOOL_INSTRUCTIONS` constant
+
+### Documentation & Testing
+✅ Complete FIDES Developer Guide (~1250 lines)
+✅ Architecture Decision Record (ADR)
+✅ Quick Start Guide
+✅ Comprehensive test suite (115+ tests)
+✅ Example code with 6+ scenarios
+✅ 3 complete security examples (email, repo confidentiality, GitHub MCP labels)
+
+## Summary
+
+**FIDES** provides a comprehensive, deterministic defense against prompt injection attacks with:
+
+- **Zero-effort protection**: Automatic variable hiding for developers
+- **Context provider pattern**: `SecureAgentConfig` extends `ContextProvider` for automatic setup
+- **Granular control**: Per-item embedded labels via `Content.from_text()` for mixed-trust data
+- **Easy configuration**: `SecureAgentConfig` for one-line setup
+- **Data safety**: Exfiltration prevention via confidentiality gates
+- **Full traceability**: Message-level label tracking
+- **Complete auditability**: All security events logged
+
+The system ensures that untrusted content never directly reaches the LLM context and that all tool calls are policy-checked based on the cumulative security state before execution.