Microsoft’s 2030 Rust plan: AI-assisted C/C++ migration

Microsoft is exploring an unusually ambitious idea: using automated tooling—potentially including AI agents—to help migrate large amounts of legacy C and C++ code to Rust. The spark for the latest wave of discussion was a hiring post shared on LinkedIn by Galen Hunt (Distinguished Engineer at Microsoft), describing a Principal Software Engineer role focused on building infrastructure that enables translation of Microsoft’s “largest C and C++ systems to Rust.”

In the same context, Hunt wrote a headline-grabbing goal—eliminating every line of C and C++ at Microsoft by 2030—and framed the “north star” productivity target as “1 engineer, 1 month, 1 million lines of code,” achieved by combining AI + algorithms with a large-scale code processing pipeline.

What was actually said and what was walked back

The original messaging was easy to interpret as “Microsoft will rewrite Windows with AI.” That interpretation spread quickly—especially because Windows kernel and many low-level components have deep roots in C, and many native Windows apps and tooling ecosystems rely heavily on C++.

After the press/online reaction, reporting indicates the message was clarified: this was framed as a research effort and a team-building/hiring context, not a formal announcement that Windows will be fully rewritten in Rust by AI. Multiple outlets reported that Microsoft pushed back on the idea that “Windows 11 will be rewritten by AI,” emphasizing that the post was being over-interpreted.

That distinction matters. “We’re building infrastructure to translate huge C/C++ systems to Rust” is very different from “we are replacing Windows wholesale.”

Why microsoft keeps circling back to rust: memory safety

The Rust story at Microsoft isn’t new—it’s part of a broader industry swing toward memory-safe systems programming. The motivation is painfully pragmatic: memory-unsafe bugs (use-after-free, buffer overflows, out-of-bounds access, double free, etc.) remain a dominant root cause of exploitable vulnerabilities.

Microsoft has publicly stated that roughly ~70% of the vulnerabilities it assigns CVEs for are related to memory safety issues.
Government and security agencies have echoed the same theme, recommending memory-safe languages where practical.

Rust is attractive because it aims to prevent whole classes of those bugs through compile-time guarantees (ownership/borrowing, lifetimes, and strong type checking), rather than relying primarily on code review and post-hoc mitigations.

What “ai-assisted migration” could mean in practice

If you strip away the hype, “AI + algorithms migrating C/C++ → Rust” likely isn’t “prompt the model, get perfect Rust.” At Microsoft scale, it’s more plausible as a pipeline built around:

Parsing and graphing code at scale (ASTs, call graphs, dependency graphs, build graphs)
Semantics-preserving transforms assisted by deterministic tooling
FFI bridging (Rust calling into existing C/C++ while gradually shrinking the unsafe surface)
Test-first validation loops (fuzzing, regression tests, property tests, differential testing)
Static analysis + automated refactors guided by AI where the patterns are repetitive but context-heavy

This lines up with the way Hunt described a “code processing infrastructure” and a scalable “graph over source code,” with AI agents “guided by algorithms” to apply modifications at scale.

In other words: AI may be the “assistant,” but the real backbone is likely compilers, analyzers, build systems, and verification harnesses.

Why rewriting c/c++ is hard even with great tooling

Migrating production C/C++ isn’t just syntax. The hard parts are semantics, undefined behavior, and the weird corners that only show up in decade-old battle-tested code:

Undefined behavior is a landmine: existing C code may “work” because of compiler quirks or accidental invariants. Translating that into Rust can accidentally “lock in” bugs—or surface them.
Macros and build-time configuration: preprocessor-heavy codebases can represent many different programs depending on flags and targets.
Pointer aliasing and lifetime assumptions: Rust forces you to make ownership and borrowing explicit, which is often the opposite of how legacy C expresses intent.
Concurrency and memory ordering: getting “equivalent” behavior across threading primitives and atomics is non-trivial.
Performance contracts: kernels/drivers and low-level libraries often depend on precise layout, alignment, and calling conventions.

So the best-case scenario is usually incremental: isolate modules, wrap them safely, port the riskiest pieces first, keep critical ABI boundaries stable, and prove correctness with tests and fuzzing.

What microsoft is already doing with rust in windows

Even without a “rewrite everything” mandate, Microsoft has been steadily moving Rust closer to the Windows ecosystem:

The Windows team has discussed efforts toward making Rust a first-class option for driver development, including a framework approach.
Microsoft maintains Rust crates intended to enable Windows driver development (supporting driver models like WDM/WDF).
The broader narrative—Rust appearing in Windows internals and low-level components—has been widely reported alongside the recent hiring-post controversy.
Security research has also highlighted that “Rust in the kernel” doesn’t magically eliminate vulnerabilities; Rust components can still ship bugs, especially where unsafe or complex interfaces are involved.

This is the realistic middle ground: Rust adoption grows where it delivers clear wins (memory safety, reliability), while legacy C/C++ remains where it’s too risky or too costly to replace quickly.

Mark russinovich’s earlier signal: stop starting new c/c++

The other recurring reference point is a 2022 statement from Mark Russinovich (Azure CTO at the time), arguing it was time to stop starting new projects in C/C++ and use Rust when a non-garbage-collected language is required.

That doesn’t mean “delete all C/C++ tomorrow.” It suggests a directional policy many orgs adopt:

New low-level components: prefer memory-safe languages (often Rust)
Legacy code: reduce risk incrementally, and prioritize the most security-sensitive/bug-prone areas

What happens to c++ at microsoft if rust grows

Even if Rust expands aggressively, C++ is not going to vanish overnight inside Microsoft for practical reasons:

Massive existing codebases and toolchains
Performance-critical libraries and ABI commitments
Huge developer skill base and third-party ecosystem dependencies
Incremental porting realities (hybrid systems will exist for years)

A more plausible end-state (even by 2030) is: less new C/C++, more Rust in new systems components, and targeted migrations where risk reduction is measurable.

The “1 engineer, 1 month, 1 million lines” claim: how to interpret it

That productivity slogan is best read as an internal “north star” metric for a pipeline, not a guarantee that an individual can safely port a million lines of tricky low-level code in a month.

It could be achievable in narrow, repetitive domains—think standardized refactors, mechanical transformations, and bulk conversion of straightforward patterns—especially when the pipeline can auto-generate scaffolding, tests, wrappers, and CI validation. But for complex subsystems (kernel paths, concurrency hotspots, security boundaries), the bottleneck is rarely typing speed; it’s specification, validation, and regression risk.

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