How does Atlas understand Assembly code structure?

Atlas indexes Assembly code by AST declarations using tree-sitter, not blind line windows, allowing it to understand sections, labels, and calling conventions like System V or AAPCS64 for x86-64 and ARM64 architectures.

Can Atlas refactor Assembly code without breaking existing callers?

Yes, Atlas uses its `lsp` tool to find references to every exported symbol before any changes, ensuring all callsites are identified and addressed during refactoring, respecting the ABI contract.

How does Atlas ensure my Assembly refactor doesn't introduce bugs?

Atlas pins behavior by running your `make check` test suite with `bash` to establish a green baseline, then re-runs tests after each structural change to immediately detect regressions in your Assembly module.

What Assembly tools does Atlas integrate with?

Atlas integrates directly with your existing Assembly toolchain, including `nasm` or the GNU assembler for building, `make check` for testing, and `asmfmt` for code formatting, all behind permission prompts.

Is my Assembly code safe when using Atlas?

Yes, Atlas operates with permission-gated tool calls and drafts plans in a read-only agent. Every file edit generates a unified diff for your approval before writing, and code can be kept local with Ollama embeddings.

How does Atlas handle different Assembly architectures like x86-64 and ARM64?

Atlas is designed to work with x86-64 and ARM64 assembly, understanding that register allocation, calling conventions, and the ABI are the critical contracts for these architectures, which it learns from your code.

Can I roll back changes made by Atlas during an Assembly refactor?

Yes, Atlas snapshots file changes as git patches, allowing edits to be easily diffed and rolled back if needed, providing a robust safety net for your Assembly codebase and ensuring full control.

Refactor a legacy module in Assembly with Atlas in 2026

Atlas helps Assembly developers in 2026 restructure old modules without changing behavior or breaking callers by integrating directly with your existing `make check` test harness, `nasm` toolchain, and `asmfmt` formatter. It ensures every change is verified against the established contract of register allocation and calling conventions for x86-64 and ARM64.

How Atlas maps Assembly module interfaces and callers

Atlas identifies the public surface of an Assembly module in 2026 by leveraging its `lsp` tool to perform `documentSymbol` operations, then enumerates every callsite with `findReferences`. This ensures a complete understanding of the module's external dependencies before any changes are proposed, covering 100% of potential interactions.

Refactoring a legacy Assembly module carries the inherent risk of silent breakage at an unknown callsite. Atlas mitigates this by first building a comprehensive map of the module's public interface. Using its `lsp` tool, Atlas performs a `documentSymbol` operation to identify all exported labels and routines within your `.asm` or `.S` source files. Following this, it executes `findReferences` on each identified symbol. This process meticulously enumerates every single callsite across your codebase, providing a complete picture of how the module is consumed. Atlas indexes code by AST declarations using tree-sitter, not blind line windows, allowing it to accurately understand the structure of Assembly code, including sections, labels, and the specific calling conventions honored by each routine, such as System V or AAPCS64 for x86-64 and ARM64 architectures. This foundational step ensures that Atlas understands the precise contract of register allocation and the ABI before any modifications are considered.

How to pin Assembly module behavior with make check

Before any refactoring begins, Atlas ensures the existing behavior of an Assembly module is pinned by running your `make check` test suite with its `bash` tool. This establishes a green baseline, guaranteeing that subsequent structural changes do not introduce silent regressions, a critical step in 2026 for maintaining code integrity.

A core principle of safe refactoring is to first establish a reliable baseline of existing behavior. For Assembly projects, this means leveraging your established test harness. Atlas uses its `bash` tool to execute your `make check` command, running your entire test suite. The output of this execution is recorded, establishing a 'green baseline' that confirms the module's current functionality is correct. This baseline serves as the immutable reference point throughout the refactoring process. Every Atlas tool call, including running `make check`, is permission-gated against allow, ask, and deny rules, ensuring you maintain full control. This 'pinning' of behavior is crucial because it allows Atlas to verify that any structural changes made to the Assembly code do not inadvertently alter its external behavior or introduce new bugs, a common pitfall in legacy code modernization efforts.

Applying structural changes to Assembly code with Atlas

Atlas applies structural changes to Assembly source files using its `apply_patch` tool, which anchors on context lines and refuses to apply against a drifted file. This precise method ensures that each hunk lands accurately, preventing accidental modifications to the 2026 codebase and maintaining file integrity across your `.asm` or `.S` files.

Once the module's interface is mapped and its behavior pinned, Atlas proceeds with the structural refactoring. The `apply_patch` tool is central to this process. Unlike simple find-and-replace operations, `apply_patch` is robust: it anchors each hunk on context lines and old_lines, and will fail with 'Failed to find context' if the target file has drifted from its expected state. This prevents applying changes to an outdated or modified file, ensuring the integrity of your Assembly codebase. Atlas computes a unified diff for every proposed file edit and surfaces it for your approval before writing any changes to disk. This granular approval process means you review and sanction each modification. Crucially, Atlas is configured to re-run your `make check` test suite with `bash` after each individual hunk lands, not just once at the end. This immediate feedback loop ensures that any regression is caught and addressed as soon as it occurs, minimizing debugging time. Furthermore, Atlas ensures consistency by having `asmfmt` keep alignment and column style consistent on all touched Assembly files, adhering to your project's coding standards.

Tracking Assembly refactoring progress and remaining callers

To prevent partially migrated Assembly modules from being mistaken for finished ones, Atlas uses its `todowrite` tool to track remaining callsites. This ensures that all 100% of identified references are addressed, providing a clear, actionable list of tasks throughout the refactoring process in 2026 and beyond.

Refactoring a complex Assembly module often involves migrating numerous callsites. It is easy to lose track of which references have been updated and which still require attention. Atlas addresses this challenge with its `todowrite` tool. After identifying all callsites using `lsp findReferences`, Atlas maintains a dynamic 'todowrite' list. As each callsite is successfully migrated and verified, it is removed from this list. This provides a clear, real-time indicator of the refactoring's progress. A partially migrated module cannot be mistaken for a finished one, as the `todowrite` list will explicitly show outstanding tasks. Atlas also reads git branches, status, and diffs, and can stage and create commits on your behalf, integrating direct into your existing version control workflow. This comprehensive tracking mechanism ensures that the refactoring is complete and all dependencies are correctly updated, leaving no loose ends in your Assembly project.

Ensuring safety and review in Assembly refactoring with Atlas

Atlas prioritizes safety in Assembly refactoring by requiring approval for every file edit and tool call, a crucial feature for 2026 development. Every Atlas tool call is permission-gated against allow, ask, and deny rules, and a unified diff is surfaced for approval before any changes are written to disk.

Safety and developer control are paramount when working with legacy Assembly code. Atlas is designed with multiple layers of safeguards. First, every Atlas tool call is permission-gated against allow, ask, and deny rules, giving you explicit control over what actions the agent can take. Atlas drafts a plan in a read-only plan agent and asks for your approval before switching to a build agent to execute any changes. When modifications are proposed, Atlas computes a unified diff for every file edit and surfaces it for your approval. This means you see exactly what changes will be made to your `.asm` or `.S` files before they are committed. Furthermore, Atlas snapshots file changes as git patches, so edits can be easily diffed and rolled back if necessary, providing a robust safety net. For privacy-conscious environments, Atlas can build its code index with local Ollama embeddings, keeping your sensitive Assembly code off third-party servers. This combination of explicit permissions, transparent diffs, and rollback capabilities ensures a secure and controlled refactoring experience.

Step by step

01Run Atlas where your `.asm` or `.S` sources and `Makefile` live to initialize the agent in your Assembly project.
02Use the Atlas `lsp` tool's `documentSymbol` operation to map the module's public surface, then `findReferences` on each exported symbol to enumerate every callsite, considering x86-64 or ARM64 ABIs.
03Execute `bash` to run your existing `make check` test suite and record the green baseline before modifying any Assembly code.
04Apply structural changes to your Assembly files using the Atlas `apply_patch` tool, which anchors on context lines and fails if the file has drifted.
05After each hunk lands, re-run `make check` with `bash` to immediately verify behavior and prevent regressions in your Assembly module.
06Utilize the Atlas `todowrite` tool to track any remaining callsites, ensuring a partially migrated Assembly module is not mistaken for a finished one.
07Have Atlas keep alignment and column style consistent with `asmfmt` on all touched Assembly files.
08Review the unified diffs provided by Atlas for every file edit, approve changes, and let Atlas stage and create commits on your behalf.

Frequently asked questions

How does Atlas understand Assembly code structure?: Atlas indexes Assembly code by AST declarations using tree-sitter, not blind line windows, allowing it to understand sections, labels, and calling conventions like System V or AAPCS64 for x86-64 and ARM64 architectures.
Can Atlas refactor Assembly code without breaking existing callers?: Yes, Atlas uses its `lsp` tool to find references to every exported symbol before any changes, ensuring all callsites are identified and addressed during refactoring, respecting the ABI contract.
How does Atlas ensure my Assembly refactor doesn't introduce bugs?: Atlas pins behavior by running your `make check` test suite with `bash` to establish a green baseline, then re-runs tests after each structural change to immediately detect regressions in your Assembly module.
What Assembly tools does Atlas integrate with?: Atlas integrates directly with your existing Assembly toolchain, including `nasm` or the GNU assembler for building, `make check` for testing, and `asmfmt` for code formatting, all behind permission prompts.
Is my Assembly code safe when using Atlas?: Yes, Atlas operates with permission-gated tool calls and drafts plans in a read-only agent. Every file edit generates a unified diff for your approval before writing, and code can be kept local with Ollama embeddings.
How does Atlas handle different Assembly architectures like x86-64 and ARM64?: Atlas is designed to work with x86-64 and ARM64 assembly, understanding that register allocation, calling conventions, and the ABI are the critical contracts for these architectures, which it learns from your code.
Can I roll back changes made by Atlas during an Assembly refactor?: Yes, Atlas snapshots file changes as git patches, allowing edits to be easily diffed and rolled back if needed, providing a robust safety net for your Assembly codebase and ensuring full control.

Try Atlas in your terminal

The terminal-native AI coding agent. Free core, single binary.

Install Atlas

Related guides

Refactor a Legacy Module with Atlas in 2026

How to refactor a legacy module with Atlas in 2026: findReferences maps every callsite, apply_patch refuses to apply against a drifted file, and bash proves behavior.

Atlas for Assembly: Registers, Calling Conventions, and nasm in 2026

Atlas is a terminal-native AI coding agent for Assembly in 2026. It reads .asm and .S sources, tracks System V and AAPCS64 calling conventions, and assembles with nasm behind a prompt.

Write Unit Tests for Untested Assembly Code with Atlas in 2026

In 2026, Assembly developers use Atlas to write unit tests for untested x86-64 and ARM64 modules. Learn how Atlas leverages `make check` and `asmfmt` to integrate new tests direct into your existing Assembly

Self-review Your Working Diff Before Committing in Assembly with Atlas in 2026

Catch your own mistakes in uncommitted Assembly diffs using Atlas in 2026. Integrate with `make check` and `asmfmt` to ensure quality before review or CI.

Run the Assembly Test Suite and Triage Failures with Atlas in 2026

In 2026, Assembly developers use Atlas to run `make check` test suites, identify distinct root causes from verbose output, and prioritize fixes for x86-64 and ARM64 code.

Add a Regression Test for an Assembly Bug Fix with Atlas in 2026

Learn how Atlas helps Assembly developers in 2026 add robust regression tests for bug fixes. Ensure your x86-64 or ARM64 Assembly code is locked in with `make check` and `asmfmt`.

Onboard to an Unfamiliar Assembly Codebase in 2026 with Atlas

In 2026, Atlas helps Assembly developers quickly build a working mental model of unfamiliar x86-64 and ARM64 codebases. Leverage semantic search, AST indexing, and direct interaction with `make check` and `asmfmt`.

Document an Assembly Module with a README in 2026 using Atlas

Generate accurate READMEs for your Assembly modules in 2026 with Atlas. Leverage make check, make (nasm toolchain), and asmfmt to document x86-64 and ARM64 code as it actually runs.

Browse this resource hub