Atlas onboards you to an unfamiliar Go codebase by starting from the module rather than the file tree. Run atlas in a module with a go.mod and Atlas reads your packages, interfaces, and go.sum dependencies. codebase_search then answers a plain-language question against the semantic index, glob maps the cmd and internal directories, read opens the two or three .go files that matter, and the lsp tool's goToDefinition operation follows an import path to the package that defines it. go test tells you what passes, gofmt shows the formatting baseline.
How do you understand a Go codebase you have never seen before?
Atlas understands an unfamiliar Go codebase in 2026 by reading go.mod first, then asking codebase_search a plain-language question such as how requests are authenticated. Atlas searches code with hybrid semantic and keyword retrieval fused by reciprocal rank fusion, returning ranked .go snippets with real file paths.
The job to be done is building a working mental model of a repository you have never seen before, without reading every file. In Go the model is package-shaped: go.mod declares the module path that every import is relative to, go.sum pins the dependency tree, and the package boundaries determine what is even reachable. Atlas reads your packages, interfaces, and go.sum dependencies, so a codebase_search hit arrives with its package context attached. Because Atlas indexes code by AST declarations using tree-sitter, not blind line windows, the snippet is a whole func, struct, or interface declaration.
What do go.mod and the package layout tell Atlas about a Go project?
Atlas treats go.mod as the map of a Go project, because the module path there is the prefix of every internal import. Running glob on the top-level directories then shows the conventional 3-part layout: a cmd directory of entry points, an internal tree of private packages, and a pkg tree of shared ones.
Go's conventions make onboarding faster than most languages once you read the module file, because the directory layout is load bearing rather than decorative. An import of yourmodule/internal/billing tells you exactly which directory to open, and go.sum tells you which third-party packages the module actually depends on. After glob has shown the shape, read opens the .go files that codebase_search ranked highest, and the lsp tool's goToDefinition operation follows an import path to the package that defines the symbol, which beats guessing between two packages that both export a Client.
How do you trace Go interfaces and their implementations with Atlas?
Atlas traces Go interfaces with read plus the lsp tool's goToDefinition operation. Read the 2 or 3 files codebase_search ranked highest, then jump from an interface reference to the struct whose methods satisfy it, which in Go is never spelled out at the point of implementation.
Implicit interface satisfaction is Go's most useful feature and its most annoying onboarding obstacle: no struct ever declares that it implements Store, so no text search can connect the two. codebase_search closes that gap by ranking on meaning, and goToDefinition walks the declaration graph. Atlas fans out work to subagents that can run in the foreground or in parallel background sessions, so a sweep for every type with the right method set can run in the background while you keep reading the interface definition in front of you.
How does the explore subagent read a Go module without editing it?
Atlas delegates wide sweeps across a Go module to the explore subagent through the task tool. The explore subagent is defined with a deny-by-default permission set that only allows grep, glob, read, bash, webfetch, and websearch, so a sweep across your .go packages in 2026 cannot rewrite one of them.
Onboarding is read-heavy work, and read-heavy work is where an accidental edit slips through unnoticed because nobody is reviewing a diff yet. The explore subagent removes the possibility: grep, glob, read, bash, webfetch, and websearch are the only tools it can call. Even a go command issued through bash, such as go test, is checked against the same permission rules before it executes. When you do move to changes, every edit to a .go file arrives as a diff you approve before gofmt and go test run over it.
How do you validate a Go codebase with go test, go mod, and gofmt?
Atlas validates a new Go codebase by running the project's 3 real commands: go mod to resolve the dependency graph against go.sum, go test to see which packages pass on a clean checkout, and gofmt to confirm the formatting baseline. Atlas records the open questions as a todowrite list.
A clean go test run across the module is the most honest one-command summary a Go repo can give you, and the packages that fail on a fresh clone are onboarding documentation in their own right. gofmt makes formatting a non-question, which is one reason Go onboarding is quicker than most. Once the baseline is clear, have Atlas add table-driven tests or refactor an interface, then run go test on the diff. The table-driven tests that go test runs tell you which packages are actively maintained and which are dormant.
Which Go files explain a module fastest?
Atlas reads 4 Go files first: go.mod for the module path every import is relative to, go.sum for the pinned dependencies, the interface declarations that state the contracts, and the table-driven tests that go test runs. gofmt means formatting is never a question.
go.mod is the root of every import path in the module, so reading go.mod makes the cmd and internal directories legible immediately. go.sum pins the dependencies, which tells you what the module actually relies on. Interface declarations state the contracts, and because Go satisfies interfaces implicitly, the interface is often the only place a contract is written down at all. The table-driven tests that go test runs are the clearest statement of intended behavior most Go packages have. gofmt keeps formatting out of the review, so the diff you read is logic.
How do Go package boundaries shape what Atlas reads?
Go package boundaries decide reachability, so the internal directory of a module is invisible outside it. Atlas reads your packages, interfaces, and go.sum dependencies from a module with a go.mod, which is why glob on cmd and internal maps a Go repository in 1 pass.
The internal directory is a compiler-enforced boundary in Go, not a convention, so code under internal cannot be imported from outside the module. Reading go.mod first tells you the module path, and from there every import in the repository is legible on sight. cmd holds the entry points, one directory per binary, which is where a Go reader should start. go test compiles each package independently, so a failing package points straight at the boundary that broke. gofmt settles formatting, and go mod keeps go.sum honest about what the module depends on.
Step by step
- 01Run atlas in a module with a go.mod and let Atlas read your packages, interfaces, and go.sum dependencies.
- 02Ask codebase_search a plain-language question, for example how requests are authenticated, and review the ranked .go snippets it returns with file paths.
- 03Run glob on the top-level directories to see the package layout, including the cmd entry points and the internal tree, before opening anything.
- 04Read the two or three Go files codebase_search ranked highest, then follow each import path with the lsp tool's goToDefinition operation.
- 05Delegate a sweep for the types that satisfy an interface to the explore subagent through the task tool; its permission set only allows grep, glob, read, bash, webfetch, and websearch.
- 06Resolve dependencies with go mod, then run go test to see which packages pass on a clean checkout of the module.
- 07Run gofmt to confirm the formatting baseline, then have Atlas add table-driven tests or refactor an interface and run go test on the diff.
- 08Record what you learned, and every open question, as a todowrite list so it survives into the next turn.
Frequently asked questions
- how do I quickly understand a large Go codebase
- Run atlas in a module with a go.mod so it reads your packages, interfaces, and go.sum dependencies, then ask codebase_search a plain-language question. Run glob on the top-level directories to see the cmd and internal layout before opening files.
- how do I find which struct implements a Go interface
- Describe the behavior to codebase_search, which returns candidate declarations even when your words never appear in the source. Go never declares interface satisfaction explicitly, so semantic ranking plus the lsp tool's goToDefinition operation is the practical route.
- can an AI agent explore a Go module without changing files
- Yes. Atlas delegates wide sweeps to the explore subagent through the task tool, and that subagent has a deny-by-default permission set allowing only grep, glob, read, bash, webfetch, and websearch.
- does Atlas run go test and gofmt
- Yes. Atlas resolves dependencies with go mod, runs go test to show which packages pass on a clean checkout, and runs gofmt to confirm the formatting baseline. Every tool call is permission-gated against allow, ask, and deny rules first.
- can Atlas write table-driven tests in Go
- Yes. Have Atlas add table-driven tests or refactor an interface, then run go test on the diff. Atlas computes a unified diff for every file edit and surfaces it for approval before writing.
- how does an AI agent search Go code without the function name
- Atlas searches code with hybrid semantic and keyword retrieval fused by reciprocal rank fusion, and indexes code by AST declarations using tree-sitter, so codebase_search returns the real func or interface rather than an arbitrary line window.
- can I index a private Go module locally
- Yes. Atlas can build its code index with local Ollama embeddings, keeping code off third-party servers, so codebase_search works on a private go.mod module.
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