Claude Context File

Project Name: Internal API Gateway

Framework: FastAPI

Language: Python 3.11

Coding Standards:

• Use PEP 8 formatting.

• Include type hints for all functions.

• Use docstrings in triple quotes for all classes and methods.

• Handle errors using FastAPI’s HTTPException.

• Avoid unnecessary global variables.

• Favor async endpoints where applicable.

Architecture Overview:

• /routes folder contains all API endpoints.

• /services handles business logic.

• /models defines database schema via SQLAlchemy.

• /utils provides shared helper functions.

Testing:

• Use pytest for all tests.

• Follow naming pattern: test_<module>_<function>()

Now, whenever you start a Claude session, you prepend your prompt with this context file’s content before giving the instruction. For example:

“Based on the project structure and conventions below, generate a new route for managing user sessions.”

Claude will then automatically align the output — consistent naming, docstring format, and error handling — with the standards you defined.

You can also ask Claude to review consistency across modules:

“Compare these two route files and identify inconsistencies in naming, documentation, or async usage.”

Claude can detect discrepancies such as:

- `get_user()` being synchronous in one file but asynchronous in another.
- Missing or mismatched docstrings.
- Variable names like `user_id` vs. `uid`.

By prompting Claude to enforce your context file as a reference, you maintain a single source of truth across multiple contributors and sessions.

Clarification Table: Strategies for Cross-Prompt Consistency

| Strategy | Purpose | Implementation | Claude’s Role |
| --- | --- | --- | --- |
| Context Anchoring | Preserve long-term understanding | Paste a summary of project goals and standards into each new prompt | Keeps code aligned to defined rules |
| Prompt Chaining | Link related sessions logically | Include summaries of previous outputs when continuing a task | Maintains coherence in style and logic |
| Style Enforcement | Standardize code across modules | Use the same formatting and naming guidelines | Enforces structural uniformity |
| Validation Prompts | Audit consistency automatically | Ask Claude to review multiple files for style drift | Detects inconsistencies proactively |
| Documentation Reinforcement | Keep explanations uniform | Require Claude to use the same docstring or comment format | Maintains professional clarity |

Consistency across multiple prompts is what separates experimental AI-assisted coding from professional, maintainable workflows. By using persistent context files, structured prompts, and repeatable conventions, Claude Code becomes not just an assistant — but a disciplined member of your engineering team.

Maintaining consistent tone, format, and logic ensures every piece of code feels handcrafted by a unified developer voice, even when produced across dozens of Claude-assisted sessions.

In the next section, we’ll explore multi-file editing and synchronization, where Claude simultaneously aligns updates across several modules — ensuring that when one part of your system changes, the rest of the project evolves harmoniously with it.

## 10.5 Example: Refactoring a Legacy Monolith
Legacy monoliths usually grow from a single-file proof of concept into a sprawling script that mixes routing, data access, validation, and business logic. They work—until they don’t. Small changes become risky, tests are hard to write, and new developers struggle to find where anything lives. In this example you will take a compact, single-file FastAPI monolith and refactor it into a small, well-structured application with clear layers, a tiny service boundary, and unit tests. The goal is incremental modernization without changing external behavior.

Concept Development

Good refactors separate concerns and make dependencies explicit. In practice that means four moves. First, isolate data access behind a repository that hides SQL details. Second, move rules and cross-cutting checks into a service layer so routes stay thin. Third, keep I/O at the edges—routers and database helpers—so core logic is easy to test. Fourth, introduce a minimal startup path that initializes dependencies, not globals. With Claude Code, you steer each step: describe what to separate, ask for complete replacements for small units, and verify behavior with tests after each change.

Hands-On Example

The legacy monolith below “works,” but couples everything: global database access, inline validation, and business rules scattered in endpoints.

Create this file: