ai-context-injector

AI Context Injector

A lightweight Python library for tag-based context injection into LLM prompts with built-in anti-hallucination safeguards.

Extract relevant context from your codebase, memory systems, or custom data sources using simple tags like @memory, @code, or @session in user queries.

Key Features

• Tag-based retrieval: @memory dark keyboard, @code UserService, @session last decision
• Anti-hallucination safeguards: 5 critical rules + automatic citations to prevent LLM fabrication
• Hard project isolation: Never mix contexts from different projects without explicit opt-in
• Plugin architecture: Write custom providers for any data source
• Blazing fast: <25ms total pipeline (proven at 17.7ms in production)
• Zero dependencies: Core library uses only Python stdlib
• 100% type-safe: Full type hints with py.typed marker
• Battle-tested: 219 tests including real-world integration scenarios

Installation

pip install ai-context-injector

Quick Start (5 lines)

from ai_context_injector import ContextInjector

injector = ContextInjector(current_project="my-app")
injector.register_provider("@memory", my_memory_provider)

context = injector.inject("@memory user authentication flow")
# Ready to inject into LLM prompt!

Why Context Injection?

LLMs need relevant context to provide accurate answers. Instead of manually copying code snippets or documentation, use tags to automatically retrieve and format context:

Without context injection:

User: "How does our authentication work?"
LLM: *hallucinates based on general knowledge*

With context injection:

User: "@memory authentication @code AuthService"
System: *retrieves actual decisions + code*
LLM: *answers based on YOUR actual implementation*

Complete Example

from ai_context_injector import ContextInjector, ContextItem, IContextProvider
from datetime import datetime

# 1. Create a custom provider
class MyMemoryProvider(IContextProvider):
    @property
    def name(self) -> str:
        return "MyMemory"
    
    @property
    def source_type(self) -> str:
        return "memory"
    
    def is_available(self) -> bool:
        return True
    
    def retrieve(self, request):
        # Your retrieval logic here (database, files, API, etc.)
        results = search_my_database(request.query, request.project)
        
        return [
            ContextItem(
                content=result.text,
                source="memory",
                project=request.project,
                metadata={"id": result.id},
                relevance_score=result.score,
                timestamp=result.created_at
            )
            for result in results
        ]

# 2. Initialize injector
injector = ContextInjector(current_project="my-app")
injector.register_provider("@memory", MyMemoryProvider())

# 3. Inject context from user queries
user_query = "Tell me @memory what we decided about the database"

if injector.has_tags(user_query):
    context = injector.inject(user_query)
    
    # Inject into LLM prompt
    llm_prompt = f"""
{context}

User Question: {injector.extract_query_only(user_query)}

Answer based ONLY on the context above.
"""
    
    response = llm.generate(llm_prompt)

Anti-Hallucination Safeguards

Every injected context includes 5 critical rules to prevent LLM fabrication:

=== BEGIN CONTEXT ===

CRITICAL RULES FOR USING THIS CONTEXT:
1. ONLY cite information that appears in the context sections below
2. If context is from a different project, CLEARLY state which project
3. Include source citations [memory:project:date] or [code:file:line]
4. If unsure or context missing, say "I don't have information about this"
5. NEVER mix information from different projects without explicit warning

Retrieved Context for: my-app
Found 2 relevant item(s)

--- Context Item 1/2 ---
Source: memory | Project: my-app | Relevance: 0.95 | Date: 2026-05-30
Citation: [memory:my-app:2026-05-30]

Decision: Use PostgreSQL with WAL mode for better performance

--- Context Item 2/2 ---
Source: code | Project: my-app | Relevance: 0.88 | Date: 2026-05-30
Citation: [code:src/db/connection.py:15-23]

def create_connection():
    return psycopg2.connect(
        host="localhost",
        database="myapp",
        options="-c wal_level=replica"
    )

=== END CONTEXT ===

Tag Syntax

Basic Tags

"@memory user authentication"     # Search memory for "user authentication"
"@code AuthService class"         # Search code for "AuthService class"
"@session last decision"          # Search current session

Modifiers

"@memory:all database design"     # Search across ALL projects (with warning)

Multiple Tags

"@memory architecture and @code UserService"  # Aggregates from both sources

Project Isolation (Key Differentiator)

By default, context is strictly isolated to the current project:

injector = ContextInjector(current_project="frontend")

# Only retrieves from "frontend" project
context = injector.inject("@memory React components")

# To search across projects, use :all modifier (generates warning)
context = injector.inject("@memory:all authentication patterns")

Why this matters: Prevents LLMs from mixing context across different projects, which is a major source of hallucinations and incorrect answers.

Advanced Usage

With Performance Metrics

response = injector.inject_with_metrics("@memory query")

print(f"Found: {response.total_found} items")
print(f"Filtered: {response.filtered_count} items")
print(f"Performance: {response.performance_ms:.2f}ms")
print(f"Filter ratio: {response.filter_ratio:.1%}")

Custom Parser and Formatter

from ai_context_injector import TagParser, ContextFormatter

# Custom parser with additional tags
parser = TagParser(custom_tags={"@docs", "@tickets"})

# Compact formatter for tight token budgets
formatter = ContextFormatter(
    include_metadata=False,
    include_anti_hallucination_rules=False
)

injector = ContextInjector(
    current_project="my-app",
    parser=parser,
    formatter=formatter
)

Relevance Filtering

# Only return items with relevance >= 0.80
context = injector.inject(
    "@memory database optimization",
    min_relevance=0.80,
    max_items=5
)

Custom Provider Examples

Simple In-Memory Provider

from ai_context_injector import IContextProvider, ContextItem
from datetime import datetime

class SimpleProvider(IContextProvider):
    def __init__(self, data):
        self.data = data  # Dict[str, List[tuple]]
    
    @property
    def name(self) -> str:
        return "Simple"
    
    @property
    def source_type(self) -> str:
        return "memory"
    
    def is_available(self) -> bool:
        return True
    
    def retrieve(self, request):
        items = self.data.get(request.project, [])
        
        return [
            ContextItem(
                content=content,
                source="memory",
                project=request.project,
                metadata={},
                relevance_score=score,
                timestamp=datetime.now()
            )
            for content, score in items
            if score >= request.min_relevance
        ][:request.max_items]

# Usage
data = {
    "my-app": [
        ("Decision: Use Redis for caching", 0.95),
        ("Learning: Connection pooling improved latency", 0.90),
    ]
}

provider = SimpleProvider(data)
injector.register_provider("@memory", provider)

SQLite Provider

import sqlite3
from ai_context_injector import IContextProvider, ContextItem
from datetime import datetime

class SQLiteProvider(IContextProvider):
    def __init__(self, db_path):
        self.db_path = db_path
    
    @property
    def name(self) -> str:
        return "SQLite"
    
    @property
    def source_type(self) -> str:
        return "memory"
    
    def is_available(self) -> bool:
        try:
            conn = sqlite3.connect(self.db_path)
            conn.close()
            return True
        except:
            return False
    
    def retrieve(self, request):
        conn = sqlite3.connect(self.db_path)
        cursor = conn.cursor()
        
        # Simple full-text search
        cursor.execute("""
            SELECT content, relevance, timestamp
            FROM memories
            WHERE project = ? 
              AND content LIKE ?
              AND relevance >= ?
            ORDER BY relevance DESC
            LIMIT ?
        """, (
            request.project,
            f"%{request.query}%",
            request.min_relevance,
            request.max_items
        ))
        
        results = [
            ContextItem(
                content=row[0],
                source="memory",
                project=request.project,
                metadata={},
                relevance_score=row[1],
                timestamp=datetime.fromisoformat(row[2])
            )
            for row in cursor.fetchall()
        ]
        
        conn.close()
        return results

Filesystem Code Provider

import subprocess
from pathlib import Path
from ai_context_injector import IContextProvider, ContextItem
from datetime import datetime

class FilesystemCodeProvider(IContextProvider):
    def __init__(self, repo_path):
        self.repo_path = Path(repo_path)
    
    @property
    def name(self) -> str:
        return "Filesystem"
    
    @property
    def source_type(self) -> str:
        return "code"
    
    def is_available(self) -> bool:
        return self.repo_path.exists()
    
    def retrieve(self, request):
        # Use ripgrep for fast search
        result = subprocess.run(
            ["rg", "--json", request.query, str(self.repo_path)],
            capture_output=True,
            text=True
        )
        
        # Parse ripgrep JSON output and convert to ContextItem
        # (implementation details omitted for brevity)
        
        return items[:request.max_items]

API Reference

Core Classes

ContextInjector

Main orchestrator for the entire pipeline.

injector = ContextInjector(
    current_project="my-app",        # Project name (auto-detected from cwd if None)
    parser=None,                      # Custom TagParser instance
    formatter=None                    # Custom ContextFormatter instance
)

# Register providers
injector.register_provider(tag, provider)

# Inject context
context = injector.inject(
    user_input,                       # String with tags
    max_items=10,                     # Max total items
    min_relevance=0.70               # Min relevance score (0.0-1.0)
)

# With metrics
response = injector.inject_with_metrics(user_input, max_items=10, min_relevance=0.70)

# Utility methods
injector.has_tags(user_input)                    # bool
injector.extract_query_only(user_input)          # str (tags removed)

IContextProvider

Abstract base class for custom providers.

class MyProvider(IContextProvider):
    @property
    def name(self) -> str:
        """Provider name for logging/debugging."""
        return "MyProvider"
    
    @property
    def source_type(self) -> str:
        """Source type: 'memory', 'code', 'session', 'custom', etc."""
        return "memory"
    
    def is_available(self) -> bool:
        """Check if provider is available (DB connected, files exist, etc.)."""
        return True
    
    def retrieve(self, request: ContextRequest) -> List[ContextItem]:
        """Retrieve context items matching the request."""
        # Your logic here
        return items

ContextItem

Represents a single piece of context.

item = ContextItem(
    content="Decision: Use PostgreSQL",     # Required
    source="memory",                        # Required
    project="my-app",                       # Required
    metadata={},                            # Required (can be empty)
    relevance_score=0.95,                   # Required (0.0-1.0)
    timestamp=datetime.now(),               # Required
    file_path=None,                         # Optional (for code)
    line_range=None                         # Optional (for code, tuple)
)

# Generate citation
citation = item.citation()  # "[memory:my-app:2026-05-30]"

TagParser

Parses tags from user input.

parser = TagParser(custom_tags={"@docs", "@tickets"})

tags = parser.parse("@memory query")              # List[ParsedTag]
has_tags = parser.has_tags("@memory query")       # bool
clean = parser.remove_tags("@memory query")       # str
parser.register_tag("@custom")                    # None

ContextFormatter

Formats context items for LLM injection.

formatter = ContextFormatter(
    include_metadata=True,
    include_citations=True,
    include_anti_hallucination_rules=True
)

response = formatter.format(items, current_project)
compact = formatter.format_compact(items)
single = formatter.format_single(item, include_delimiters=True)

Convenience Functions

from ai_context_injector import inject_context, parse_tags, format_context

# Quick injection
context = inject_context(
    user_input="@memory query",
    providers={"@memory": my_provider},
    project="my-app",
    max_items=10,
    min_relevance=0.70
)

# Quick parsing
tags = parse_tags("@memory query", custom_tags={"@docs"})

# Quick formatting
response = format_context(items, current_project="my-app")

Architecture

User Input: "@memory dark keyboard @code KeyboardView"
     │
     ├─> TagParser
     │   ├─> ParsedTag(tag="@memory", query="dark keyboard")
     │   └─> ParsedTag(tag="@code", query="KeyboardView")
     │
     ├─> ContextInjector
     │   ├─> Route to providers
     │   │   ├─> MemoryProvider.retrieve() → [ContextItem, ...]
     │   │   └─> CodeProvider.retrieve() → [ContextItem, ...]
     │   │
     │   ├─> Aggregate results
     │   ├─> Deduplicate (first 100 chars hash)
     │   ├─> Sort by relevance
     │   └─> Limit to max_items
     │
     └─> ContextFormatter
         ├─> Add delimiters
         ├─> Add anti-hallucination rules
         ├─> Add metadata + citations
         ├─> Check cross-project warnings
         └─> Format items
              │
              └─> Formatted context string (ready for LLM)

Performance

Target: <25ms total pipeline
Proven: 17.7ms in production (memory-system)

Breakdown:

• Parsing: <1ms
• Provider retrieval: ~10ms (depends on your provider)
• Aggregation/dedup: ~2ms
• Sorting: ~2ms
• Formatting: ~2ms

Tip: Provider performance is usually the bottleneck. Use indexes, caching, and efficient queries.

Testing

# Run all tests
pytest

# Run with coverage
pytest --cov=ai_context_injector

# Run only unit tests
pytest tests/core/

# Run only integration tests
pytest tests/test_integration.py

# Run specific test
pytest tests/core/test_injector.py::TestBasicInjection::test_inject_with_single_tag

Design Principles

1. Explicit over implicit: Empty providers dict by default, users must register
2. Project isolation by default: Never auto-mix contexts across projects
3. Zero magic: No auto-discovery, no global state, no hidden dependencies
4. Library not framework: Integrate into your app, don't build around it
5. Performance matters: <25ms target, every millisecond counts
6. Type safety: Full type hints, no Any types in public API
7. Fail gracefully: Missing/unavailable providers return None, not exceptions

FAQ

Why not just use RAG?

RAG is great for semantic search, but context injection solves a different problem:

• Structured retrieval: Tag-based routing to different data sources
• Multi-source aggregation: Combine memory + code + session in one query
• Project isolation: Hard boundaries prevent context mixing
• Anti-hallucination: Built-in safeguards with citations

You can use RAG as a provider in this system!

Why project isolation by default?

In multi-project environments, mixing contexts causes LLMs to:

• Suggest code patterns from wrong project
• Reference APIs that don't exist in current project
• Mix architectural decisions across boundaries

Hard isolation by default prevents these errors. Use :all modifier when you actually want cross-project search.

Can I use this with any LLM?

Yes! This library just generates formatted context strings. Use them with:

• OpenAI (GPT-4, GPT-3.5)
• Anthropic (Claude)
• Local models (Ollama, LM Studio)
• Any LLM API that accepts text prompts

How do I handle large codebases?

1. Smart providers: Use search indexes (ripgrep, SQLite FTS, Elasticsearch)
2. Relevance filtering: Set min_relevance=0.80 to reduce noise
3. Limit results: Use max_items=5 for tight token budgets
4. Compact format: Disable metadata with ContextFormatter(include_metadata=False)

Can I use this in production?

Yes! The core library has:

• 219 tests (100% passing)
• No external dependencies
• Battle-tested in memory-system project
• Proven <20ms performance

Just write solid providers and you're good to go.

Contributing

Contributions welcome! Please:

1. Add tests for new features
2. Follow existing code style
3. Update documentation
4. Run pytest before submitting

License

MIT License - see LICENSE file for details

Acknowledgments

Ported from the context injection system in memory-system project, which has been battle-tested in production for multi-project development workflows.