diff --git a/.gemini/tools.json b/.gemini/tools.json
index 0a1b709..8b44f60 100644
Binary files a/.gemini/tools.json and b/.gemini/tools.json differ
diff --git a/aggregate.py b/aggregate.py
index b703735..8157880 100644
--- a/aggregate.py
+++ b/aggregate.py
@@ -187,6 +187,87 @@ def build_discussion_text(history: list[str]) -> str:
     return "## Discussion History\n\n" + build_discussion_section(history)
 
 
+def build_tier1_context(file_items: list[dict], screenshot_base_dir: Path, screenshots: list[str], history: list[str]) -> str:
+    """
+    Tier 1 Context: Strategic/Orchestration.
+    Full content for core conductor files, summaries for others.
+    """
+    core_files = {"product.md", "tech-stack.md", "workflow.md", "tracks.md"}
+    
+    parts = []
+    
+    # Files section
+    if file_items:
+        sections = []
+        for item in file_items:
+            path = item.get("path")
+            name = path.name if path else ""
+            
+            if name in core_files:
+                # Include in full
+                sections.append("### `" + (item.get("entry") or str(path)) + "`\n\n" + 
+                                f"```{path.suffix.lstrip('.') if path.suffix else 'text'}\n{item.get('content', '')}\n```")
+            else:
+                # Summarize
+                sections.append(summarize.summarise_file(path, item.get("content", "")))
+        
+        parts.append("## Files (Tier 1 - Mixed)\n\n" + "\n\n---\n\n".join(sections))
+
+    if screenshots:
+        parts.append("## Screenshots\n\n" + build_screenshots_section(screenshot_base_dir, screenshots))
+    
+    if history:
+        parts.append("## Discussion History\n\n" + build_discussion_section(history))
+        
+    return "\n\n---\n\n".join(parts)
+
+
+def build_tier2_context(file_items: list[dict], screenshot_base_dir: Path, screenshots: list[str], history: list[str]) -> str:
+    """
+    Tier 2 Context: Architectural/Tech Lead.
+    Full content for all files (standard behavior).
+    """
+    return build_markdown_from_items(file_items, screenshot_base_dir, screenshots, history, summary_only=False)
+
+
+def build_tier3_context(file_items: list[dict], screenshot_base_dir: Path, screenshots: list[str], history: list[str], focus_files: list[str]) -> str:
+    """
+    Tier 3 Context: Execution/Worker.
+    Full content for focus_files, summaries for others.
+    """
+    parts = []
+    
+    if file_items:
+        sections = []
+        for item in file_items:
+            path = item.get("path")
+            entry = item.get("entry", "")
+            path_str = str(path) if path else ""
+            
+            # Check if this file is in focus_files (by name or path)
+            is_focus = False
+            for focus in focus_files:
+                if focus == entry or (path and focus == path.name) or focus in path_str:
+                    is_focus = True
+                    break
+            
+            if is_focus:
+                sections.append("### `" + (entry or path_str) + "`\n\n" + 
+                                f"```{path.suffix.lstrip('.') if path and path.suffix else 'text'}\n{item.get('content', '')}\n```")
+            else:
+                sections.append(summarize.summarise_file(path, item.get("content", "")))
+                
+        parts.append("## Files (Tier 3 - Focused)\n\n" + "\n\n---\n\n".join(sections))
+
+    if screenshots:
+        parts.append("## Screenshots\n\n" + build_screenshots_section(screenshot_base_dir, screenshots))
+    
+    if history:
+        parts.append("## Discussion History\n\n" + build_discussion_section(history))
+        
+    return "\n\n---\n\n".join(parts)
+
+
 def build_markdown(base_dir: Path, files: list[str], screenshot_base_dir: Path, screenshots: list[str], history: list[str], summary_only: bool = False) -> str:
     parts = []
     # STATIC PREFIX: Files and Screenshots must go first to maximize Cache Hits
diff --git a/mcp_client.py b/mcp_client.py
index c42356c..7d31019 100644
--- a/mcp_client.py
+++ b/mcp_client.py
@@ -281,6 +281,60 @@ def get_code_outline(path: str) -> str:
         return f"ERROR generating outline for '{path}': {e}"
 
 
+def get_definition(path: str, name: str) -> str:
+    """
+    Returns the source code for a specific class, function, or method definition.
+    path: Path to the code file.
+    name: Name of the definition to retrieve (e.g., 'MyClass', 'my_function', 'MyClass.my_method').
+    """
+    p, err = _resolve_and_check(path)
+    if err:
+        return err
+    if not p.exists():
+        return f"ERROR: file not found: {path}"
+    if not p.is_file():
+        return f"ERROR: not a file: {path}"
+    
+    if p.suffix != ".py":
+        return f"ERROR: get_definition currently only supports .py files (unsupported: {p.suffix})"
+
+    try:
+        import ast
+        code = p.read_text(encoding="utf-8")
+        lines = code.splitlines()
+        tree = ast.parse(code)
+        
+        # Split name for methods (e.g., "MyClass.my_method")
+        parts = name.split(".")
+        target_class = parts[0] if len(parts) > 1 else None
+        target_name = parts[-1]
+
+        def get_source_from_node(node):
+            # In Python 3.8+, ast.get_source_segment is available
+            # But we can also use lineno and end_lineno
+            if hasattr(node, "lineno") and hasattr(node, "end_lineno"):
+                # lineno is 1-indexed
+                start = node.lineno - 1
+                end = node.end_lineno
+                return "\n".join(lines[start:end])
+            return f"ERROR: Could not extract source for node {node}"
+
+        for node in ast.walk(tree):
+            if target_class:
+                if isinstance(node, ast.ClassDef) and node.name == target_class:
+                    for body_node in node.body:
+                        if isinstance(body_node, (ast.FunctionDef, ast.AsyncFunctionDef)) and body_node.name == target_name:
+                            return get_source_from_node(body_node)
+            else:
+                if isinstance(node, (ast.ClassDef, ast.FunctionDef, ast.AsyncFunctionDef)) and node.name == target_name:
+                    return get_source_from_node(node)
+                
+        return f"ERROR: could not find definition '{name}' in {path}"
+
+    except Exception as e:
+        return f"ERROR retrieving definition '{name}' from '{path}': {e}"
+
+
 def get_git_diff(path: str, base_rev: str = "HEAD", head_rev: str = "") -> str:
     """
     Returns the git diff for a file or directory.
@@ -436,7 +490,7 @@ def get_ui_performance() -> str:
 # ------------------------------------------------------------------ tool dispatch
 
 
-TOOL_NAMES = {"read_file", "list_directory", "search_files", "get_file_summary", "get_python_skeleton", "get_code_outline", "get_git_diff", "web_search", "fetch_url", "get_ui_performance"}
+TOOL_NAMES = {"read_file", "list_directory", "search_files", "get_file_summary", "get_python_skeleton", "get_code_outline", "get_definition", "get_git_diff", "web_search", "fetch_url", "get_ui_performance"}
 
 
 def dispatch(tool_name: str, tool_input: dict) -> str:
@@ -455,6 +509,8 @@ def dispatch(tool_name: str, tool_input: dict) -> str:
         return get_python_skeleton(tool_input.get("path", ""))
     if tool_name == "get_code_outline":
         return get_code_outline(tool_input.get("path", ""))
+    if tool_name == "get_definition":
+        return get_definition(tool_input.get("path", ""), tool_input.get("name", ""))
     if tool_name == "get_git_diff":
         return get_git_diff(
             tool_input.get("path", ""), 
@@ -586,6 +642,27 @@ MCP_TOOL_SPECS = [
             "required": ["path"],
         },
     },
+    {
+        "name": "get_definition",
+        "description": (
+            "Get the full source code of a specific class, function, or method definition. "
+            "This is more efficient than reading the whole file if you know what you're looking for."
+        ),
+        "parameters": {
+            "type": "object",
+            "properties": {
+                "path": {
+                    "type": "string",
+                    "description": "Path to the .py file.",
+                },
+                "name": {
+                    "type": "string",
+                    "description": "The name of the class or function to retrieve. Use 'ClassName.method_name' for methods.",
+                }
+            },
+            "required": ["path", "name"],
+        },
+    },
     {
         "name": "get_git_diff",
         "description": (
@@ -648,3 +725,4 @@ MCP_TOOL_SPECS = [
         }
     }
 ]
+
diff --git a/tests/test_tiered_context.py b/tests/test_tiered_context.py
new file mode 100644
index 0000000..6ad8712
--- /dev/null
+++ b/tests/test_tiered_context.py
@@ -0,0 +1,36 @@
+import pytest
+from pathlib import Path
+from aggregate import build_tier1_context, build_tier2_context, build_tier3_context
+
+def test_build_tier1_context_exists():
+    # This should fail if the function is not defined
+    file_items = [
+        {"path": Path("conductor/product.md"), "entry": "conductor/product.md", "content": "Product content", "error": False},
+        {"path": Path("other.py"), "entry": "other.py", "content": "Other content", "error": False}
+    ]
+    history = ["User: hello", "AI: hi"]
+    
+    result = build_tier1_context(file_items, Path("."), [], history)
+    
+    assert "Product content" in result
+    # other.py should be summarized, not full content in a code block
+    assert "Other content" not in result or "Summarized" in result # Assuming summary format
+
+def test_build_tier2_context_exists():
+    file_items = [
+        {"path": Path("other.py"), "entry": "other.py", "content": "Other content", "error": False}
+    ]
+    history = ["User: hello"]
+    result = build_tier2_context(file_items, Path("."), [], history)
+    assert "Other content" in result
+
+def test_build_tier3_context_exists():
+    file_items = [
+        {"path": Path("focus.py"), "entry": "focus.py", "content": "Focus content", "error": False},
+        {"path": Path("other.py"), "entry": "other.py", "content": "Other content", "error": False}
+    ]
+    history = ["User: hello"]
+    result = build_tier3_context(file_items, Path("."), [], history, focus_files=["focus.py"])
+    
+    assert "Focus content" in result
+    assert "Other content" not in result