September 13, 2026 · 8 min read

How to Give Claude Code Context From Your Codebase

Claude Code is different from pasting code into a chat window. Point it at a project and it can open files on its own, grep for a function, follow an import to see where something is defined. You don't hand it context up front the way you would with a regular chat — it goes and gets what it needs.

Which is genuinely useful, and also not free. Every file it opens to figure out what's going on costs time and tokens, and it's doing that exploration more or less from scratch each session. On a small project that's nothing. On a large one, or on a task where the relevant code is scattered across a dozen files, it adds up in ways that are easy to underestimate until you're watching it happen.

How Claude Code actually finds its context

Under the hood, Claude Code works through a small set of tools — reading a file, searching for a pattern, listing a directory — and decides for itself which ones to call and in what order. Ask it to fix a bug and it might grep for the error message, open the file that turns up, notice an import at the top, follow that to a second file, and only then start reasoning about the actual fix. That chain of tool calls is the "figuring out what matters" step, and it happens before any of the work you actually asked for.

It also reads a CLAUDE.md file at the root of your project if you have one, which is a decent way to hand over standing information — coding conventions, which package manager you use, where the tests live — without repeating it every session. But a CLAUDE.md is for facts about the project. It doesn't help with a specific task the way a purpose-built set of files does, and it's easy to let it go stale as the project changes.

Where letting it explore on its own breaks down

The self-directed approach holds up fine for small, contained tasks. It starts to strain in a few specific situations:

• Large repositories. More files means more candidates to search through before it lands on the right one, and more chances it opens something adjacent but not actually relevant, which just adds noise to its own reasoning.
• Cross-file changes. A refactor that touches a shared type or a renamed function across the codebase needs Claude Code to find every usage, not just the first plausible one it comes across.
• Repeated sessions on the same task. If you're going back and forth over a few hours, it's re-discovering the same file relationships each time context resets, instead of starting from something it already knows.

None of this means self-exploration is a bad default — for a lot of day-to-day work it's exactly the right amount of effort. It just isn't free, and treating it as free is where people run into slower sessions than they expected.

Giving Claude Code the files directly

The alternative is straightforward: instead of letting Claude Code go find the relevant files, you hand them over up front, already assembled and labeled. For a task you already understand — you know it's the auth module plus two files that call into it — this skips the exploration step entirely. Claude Code starts reasoning about the fix instead of spending its first few tool calls rediscovering a part of the codebase you could have described in one sentence.

The tradeoff is that this only works if you actually know which files matter. If you don't — if the task is "why is this slow" and you genuinely don't know where to look — letting Claude Code explore is often faster than you guessing wrong and having to correct it.

Connecting a context tool over MCP

There's a middle path that doesn't require you to leave Claude Code at all: connecting a context-preparation tool as an MCP server. Instead of switching to a browser tab to assemble files by hand, Claude Code can call the tool directly from the conversation and get back a structured, noise-filtered context — a project tree plus the relevant files — without you doing the selection manually each time.

repoprep works this way. It runs as an MCP server you add to Claude Code's config once, and from then on Claude Code can pull a local folder or a public GitHub/GitLab repo into context on request, with the same filtering the web app applies —node_modules, build output, and files like .env excluded automatically. It still runs locally; nothing about using it over MCP changes where the processing happens.

The advantage over manual file-gathering isn't that it's smarter about picking files — you're still the one deciding what's relevant. It's that the noise-filtering and structuring happen automatically instead of being something you do by hand every time, which matters more the more often you're doing it.

Which approach fits which task

In practice these three approaches aren't competing so much as answering different questions:

• Don't know where the problem is? Let Claude Code explore. That's what its tool-calling loop is actually good at.
• Know exactly which files matter? Hand them over directly and skip the discovery step.
• Doing this repeatedly, or working from a large project? An MCP-connected context tool removes the manual assembly work without giving up the "I already know what's relevant" advantage.

The common thread across all three is the same one that applies to any AI coding tool: the model is only as good as what it can see. Whether it gathers that itself or you hand it over, the goal is the same — the right files, without the files that don't matter getting in the way.