feat(context): implement model adapters for Claude and OpenAI (#83)

Phase 5 of Context Management Engine - Model Adapters:

- Add ModelAdapter abstract base class with model matching
- Add DefaultAdapter for unknown models (plain text)
- Add ClaudeAdapter with XML-based formatting:
  - <system_instructions> for system context
  - <reference_documents>/<document> for knowledge
  - <conversation_history>/<message> for chat
  - <tool_results>/<tool_result> for tool outputs
  - XML escaping for special characters
- Add OpenAIAdapter with markdown formatting:
  - ## headers for sections
  - ### Source headers for documents
  - **ROLE** bold labels for conversation
  - Code blocks for tool outputs
- Add get_adapter() factory function for model selection

Tests: 33 new tests, 256 total context tests passing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/context/adapters/__init__.py

@@ -1,5 +1,35 @@
 """
 Model Adapters Module.
 
-Provides model-specific context formatting.
+Provides model-specific context formatting adapters.
 """
+
+from .base import DefaultAdapter, ModelAdapter
+from .claude import ClaudeAdapter
+from .openai import OpenAIAdapter
+
+
+def get_adapter(model: str) -> ModelAdapter:
+    """
+    Get the appropriate adapter for a model.
+
+    Args:
+        model: Model name
+
+    Returns:
+        Adapter instance for the model
+    """
+    if ClaudeAdapter.matches_model(model):
+        return ClaudeAdapter()
+    elif OpenAIAdapter.matches_model(model):
+        return OpenAIAdapter()
+    return DefaultAdapter()
+
+
+__all__ = [
+    "ClaudeAdapter",
+    "DefaultAdapter",
+    "get_adapter",
+    "ModelAdapter",
+    "OpenAIAdapter",
+]

backend/app/services/context/adapters/base.py

@@ -0,0 +1,178 @@
+"""
+Base Model Adapter.
+
+Abstract base class for model-specific context formatting.
+"""
+
+from abc import ABC, abstractmethod
+from typing import Any
+
+from ..types import BaseContext, ContextType
+
+
+class ModelAdapter(ABC):
+    """
+    Abstract base adapter for model-specific context formatting.
+
+    Each adapter knows how to format contexts for optimal
+    understanding by a specific LLM family (Claude, OpenAI, etc.).
+    """
+
+    # Model name patterns this adapter handles
+    MODEL_PATTERNS: list[str] = []
+
+    @classmethod
+    def matches_model(cls, model: str) -> bool:
+        """
+        Check if this adapter handles the given model.
+
+        Args:
+            model: Model name to check
+
+        Returns:
+            True if this adapter handles the model
+        """
+        model_lower = model.lower()
+        return any(pattern in model_lower for pattern in cls.MODEL_PATTERNS)
+
+    @abstractmethod
+    def format(
+        self,
+        contexts: list[BaseContext],
+        **kwargs: Any,
+    ) -> str:
+        """
+        Format contexts for the target model.
+
+        Args:
+            contexts: List of contexts to format
+            **kwargs: Additional formatting options
+
+        Returns:
+            Formatted context string
+        """
+        ...
+
+    @abstractmethod
+    def format_type(
+        self,
+        contexts: list[BaseContext],
+        context_type: ContextType,
+        **kwargs: Any,
+    ) -> str:
+        """
+        Format contexts of a specific type.
+
+        Args:
+            contexts: List of contexts of the same type
+            context_type: The type of contexts
+            **kwargs: Additional formatting options
+
+        Returns:
+            Formatted string for this context type
+        """
+        ...
+
+    def get_type_order(self) -> list[ContextType]:
+        """
+        Get the preferred order of context types.
+
+        Returns:
+            List of context types in preferred order
+        """
+        return [
+            ContextType.SYSTEM,
+            ContextType.TASK,
+            ContextType.KNOWLEDGE,
+            ContextType.CONVERSATION,
+            ContextType.TOOL,
+        ]
+
+    def group_by_type(
+        self, contexts: list[BaseContext]
+    ) -> dict[ContextType, list[BaseContext]]:
+        """
+        Group contexts by their type.
+
+        Args:
+            contexts: List of contexts to group
+
+        Returns:
+            Dictionary mapping context type to list of contexts
+        """
+        by_type: dict[ContextType, list[BaseContext]] = {}
+        for context in contexts:
+            ct = context.get_type()
+            if ct not in by_type:
+                by_type[ct] = []
+            by_type[ct].append(context)
+        return by_type
+
+    def get_separator(self) -> str:
+        """
+        Get the separator between context sections.
+
+        Returns:
+            Separator string
+        """
+        return "\n\n"
+
+
+class DefaultAdapter(ModelAdapter):
+    """
+    Default adapter for unknown models.
+
+    Uses simple plain-text formatting with minimal structure.
+    """
+
+    MODEL_PATTERNS: list[str] = []  # Fallback adapter
+
+    @classmethod
+    def matches_model(cls, model: str) -> bool:
+        """Always returns True as fallback."""
+        return True
+
+    def format(
+        self,
+        contexts: list[BaseContext],
+        **kwargs: Any,
+    ) -> str:
+        """Format contexts as plain text."""
+        if not contexts:
+            return ""
+
+        by_type = self.group_by_type(contexts)
+        parts: list[str] = []
+
+        for ct in self.get_type_order():
+            if ct in by_type:
+                formatted = self.format_type(by_type[ct], ct, **kwargs)
+                if formatted:
+                    parts.append(formatted)
+
+        return self.get_separator().join(parts)
+
+    def format_type(
+        self,
+        contexts: list[BaseContext],
+        context_type: ContextType,
+        **kwargs: Any,
+    ) -> str:
+        """Format contexts of a type as plain text."""
+        if not contexts:
+            return ""
+
+        content = "\n\n".join(c.content for c in contexts)
+
+        if context_type == ContextType.SYSTEM:
+            return content
+        elif context_type == ContextType.TASK:
+            return f"Task:\n{content}"
+        elif context_type == ContextType.KNOWLEDGE:
+            return f"Reference Information:\n{content}"
+        elif context_type == ContextType.CONVERSATION:
+            return f"Previous Conversation:\n{content}"
+        elif context_type == ContextType.TOOL:
+            return f"Tool Results:\n{content}"
+
+        return content

backend/app/services/context/adapters/claude.py

@@ -0,0 +1,178 @@
+"""
+Claude Model Adapter.
+
+Provides Claude-specific context formatting using XML tags
+which Claude models understand natively.
+"""
+
+from typing import Any
+
+from ..types import BaseContext, ContextType
+from .base import ModelAdapter
+
+
+class ClaudeAdapter(ModelAdapter):
+    """
+    Claude-specific context formatting adapter.
+
+    Claude models have native understanding of XML structure,
+    so we use XML tags for clear delineation of context types.
+
+    Features:
+    - XML tags for each context type
+    - Document structure for knowledge contexts
+    - Role-based message formatting for conversations
+    - Tool result wrapping with tool names
+    """
+
+    MODEL_PATTERNS: list[str] = ["claude", "anthropic"]
+
+    def format(
+        self,
+        contexts: list[BaseContext],
+        **kwargs: Any,
+    ) -> str:
+        """
+        Format contexts for Claude models.
+
+        Uses XML tags for structured content that Claude
+        understands natively.
+
+        Args:
+            contexts: List of contexts to format
+            **kwargs: Additional formatting options
+
+        Returns:
+            XML-structured context string
+        """
+        if not contexts:
+            return ""
+
+        by_type = self.group_by_type(contexts)
+        parts: list[str] = []
+
+        for ct in self.get_type_order():
+            if ct in by_type:
+                formatted = self.format_type(by_type[ct], ct, **kwargs)
+                if formatted:
+                    parts.append(formatted)
+
+        return self.get_separator().join(parts)
+
+    def format_type(
+        self,
+        contexts: list[BaseContext],
+        context_type: ContextType,
+        **kwargs: Any,
+    ) -> str:
+        """
+        Format contexts of a specific type for Claude.
+
+        Args:
+            contexts: List of contexts of the same type
+            context_type: The type of contexts
+            **kwargs: Additional formatting options
+
+        Returns:
+            XML-formatted string for this context type
+        """
+        if not contexts:
+            return ""
+
+        if context_type == ContextType.SYSTEM:
+            return self._format_system(contexts)
+        elif context_type == ContextType.TASK:
+            return self._format_task(contexts)
+        elif context_type == ContextType.KNOWLEDGE:
+            return self._format_knowledge(contexts)
+        elif context_type == ContextType.CONVERSATION:
+            return self._format_conversation(contexts)
+        elif context_type == ContextType.TOOL:
+            return self._format_tool(contexts)
+
+        return "\n".join(c.content for c in contexts)
+
+    def _format_system(self, contexts: list[BaseContext]) -> str:
+        """Format system contexts."""
+        content = "\n\n".join(c.content for c in contexts)
+        return f"<system_instructions>\n{content}\n</system_instructions>"
+
+    def _format_task(self, contexts: list[BaseContext]) -> str:
+        """Format task contexts."""
+        content = "\n\n".join(c.content for c in contexts)
+        return f"<current_task>\n{content}\n</current_task>"
+
+    def _format_knowledge(self, contexts: list[BaseContext]) -> str:
+        """
+        Format knowledge contexts as structured documents.
+
+        Each knowledge context becomes a document with source attribution.
+        """
+        parts = ["<reference_documents>"]
+
+        for ctx in contexts:
+            source = self._escape_xml(ctx.source)
+            content = ctx.content
+            score = ctx.metadata.get("score", ctx.metadata.get("relevance_score", ""))
+
+            if score:
+                parts.append(f'<document source="{source}" relevance="{score}">')
+            else:
+                parts.append(f'<document source="{source}">')
+
+            parts.append(content)
+            parts.append("</document>")
+
+        parts.append("</reference_documents>")
+        return "\n".join(parts)
+
+    def _format_conversation(self, contexts: list[BaseContext]) -> str:
+        """
+        Format conversation contexts as message history.
+
+        Uses role-based message tags for clear turn delineation.
+        """
+        parts = ["<conversation_history>"]
+
+        for ctx in contexts:
+            role = ctx.metadata.get("role", "user")
+            parts.append(f'<message role="{role}">')
+            parts.append(ctx.content)
+            parts.append("</message>")
+
+        parts.append("</conversation_history>")
+        return "\n".join(parts)
+
+    def _format_tool(self, contexts: list[BaseContext]) -> str:
+        """
+        Format tool contexts as tool results.
+
+        Each tool result is wrapped with the tool name.
+        """
+        parts = ["<tool_results>"]
+
+        for ctx in contexts:
+            tool_name = ctx.metadata.get("tool_name", "unknown")
+            status = ctx.metadata.get("status", "")
+
+            if status:
+                parts.append(f'<tool_result name="{tool_name}" status="{status}">')
+            else:
+                parts.append(f'<tool_result name="{tool_name}">')
+
+            parts.append(ctx.content)
+            parts.append("</tool_result>")
+
+        parts.append("</tool_results>")
+        return "\n".join(parts)
+
+    @staticmethod
+    def _escape_xml(text: str) -> str:
+        """Escape XML special characters in attribute values."""
+        return (
+            text.replace("&", "&amp;")
+            .replace("<", "&lt;")
+            .replace(">", "&gt;")
+            .replace('"', "&quot;")
+            .replace("'", "&apos;")
+        )

backend/app/services/context/adapters/openai.py

@@ -0,0 +1,160 @@
+"""
+OpenAI Model Adapter.
+
+Provides OpenAI-specific context formatting using markdown
+which GPT models understand well.
+"""
+
+from typing import Any
+
+from ..types import BaseContext, ContextType
+from .base import ModelAdapter
+
+
+class OpenAIAdapter(ModelAdapter):
+    """
+    OpenAI-specific context formatting adapter.
+
+    GPT models work well with markdown formatting,
+    so we use headers and structured markdown for clarity.
+
+    Features:
+    - Markdown headers for each context type
+    - Bulleted lists for document sources
+    - Bold role labels for conversations
+    - Code blocks for tool outputs
+    """
+
+    MODEL_PATTERNS: list[str] = ["gpt", "openai", "o1", "o3"]
+
+    def format(
+        self,
+        contexts: list[BaseContext],
+        **kwargs: Any,
+    ) -> str:
+        """
+        Format contexts for OpenAI models.
+
+        Uses markdown formatting for structured content.
+
+        Args:
+            contexts: List of contexts to format
+            **kwargs: Additional formatting options
+
+        Returns:
+            Markdown-structured context string
+        """
+        if not contexts:
+            return ""
+
+        by_type = self.group_by_type(contexts)
+        parts: list[str] = []
+
+        for ct in self.get_type_order():
+            if ct in by_type:
+                formatted = self.format_type(by_type[ct], ct, **kwargs)
+                if formatted:
+                    parts.append(formatted)
+
+        return self.get_separator().join(parts)
+
+    def format_type(
+        self,
+        contexts: list[BaseContext],
+        context_type: ContextType,
+        **kwargs: Any,
+    ) -> str:
+        """
+        Format contexts of a specific type for OpenAI.
+
+        Args:
+            contexts: List of contexts of the same type
+            context_type: The type of contexts
+            **kwargs: Additional formatting options
+
+        Returns:
+            Markdown-formatted string for this context type
+        """
+        if not contexts:
+            return ""
+
+        if context_type == ContextType.SYSTEM:
+            return self._format_system(contexts)
+        elif context_type == ContextType.TASK:
+            return self._format_task(contexts)
+        elif context_type == ContextType.KNOWLEDGE:
+            return self._format_knowledge(contexts)
+        elif context_type == ContextType.CONVERSATION:
+            return self._format_conversation(contexts)
+        elif context_type == ContextType.TOOL:
+            return self._format_tool(contexts)
+
+        return "\n".join(c.content for c in contexts)
+
+    def _format_system(self, contexts: list[BaseContext]) -> str:
+        """Format system contexts."""
+        content = "\n\n".join(c.content for c in contexts)
+        return content
+
+    def _format_task(self, contexts: list[BaseContext]) -> str:
+        """Format task contexts."""
+        content = "\n\n".join(c.content for c in contexts)
+        return f"## Current Task\n\n{content}"
+
+    def _format_knowledge(self, contexts: list[BaseContext]) -> str:
+        """
+        Format knowledge contexts as structured documents.
+
+        Each knowledge context becomes a section with source attribution.
+        """
+        parts = ["## Reference Documents\n"]
+
+        for ctx in contexts:
+            source = ctx.source
+            score = ctx.metadata.get("score", ctx.metadata.get("relevance_score", ""))
+
+            if score:
+                parts.append(f"### Source: {source} (relevance: {score})\n")
+            else:
+                parts.append(f"### Source: {source}\n")
+
+            parts.append(ctx.content)
+            parts.append("")
+
+        return "\n".join(parts)
+
+    def _format_conversation(self, contexts: list[BaseContext]) -> str:
+        """
+        Format conversation contexts as message history.
+
+        Uses bold role labels for clear turn delineation.
+        """
+        parts = []
+
+        for ctx in contexts:
+            role = ctx.metadata.get("role", "user").upper()
+            parts.append(f"**{role}**: {ctx.content}")
+
+        return "\n\n".join(parts)
+
+    def _format_tool(self, contexts: list[BaseContext]) -> str:
+        """
+        Format tool contexts as tool results.
+
+        Each tool result is in a code block with the tool name.
+        """
+        parts = ["## Recent Tool Results\n"]
+
+        for ctx in contexts:
+            tool_name = ctx.metadata.get("tool_name", "unknown")
+            status = ctx.metadata.get("status", "")
+
+            if status:
+                parts.append(f"### Tool: {tool_name} ({status})\n")
+            else:
+                parts.append(f"### Tool: {tool_name}\n")
+
+            parts.append(f"```\n{ctx.content}\n```")
+            parts.append("")
+
+        return "\n".join(parts)