Microsoft engineering leadership has publicly framed an audacious, company-wide program to remove every line of C and C++ from Microsoft’s codebase by 2030 and replace it with Rust, driven by a purpose-built combination of algorithmic program analysis and AI agents that can rewrite and verify large-scale systems code.
Microsoft’s interest in Rust is not new: the company began publicly experimenting with Rust in Windows and Azure projects in 2023, and senior engineering leaders have since signaled a strategic preference for memory-safe languages for new systems work. Those pilots included early Rust components in Windows internals and tooling work to allow Rust and Windows build systems to interoperate. The December 2025 statement from Microsoft Distinguished Engineer Galen Hunt — published as a LinkedIn hiring post that calls for a Principal Software Engineer to “help us evolve and augment our infrastructure to enable translating Microsoft’s largest C and C++ systems to Rust” — crystallizes that trajectory into a time‑boxed corporate objective: finish the migration by 2030. The post sets a provocative productivity target — “1 engineer, 1 month, 1 million lines of code” — which Hunt frames as a North Star for what heavy automation and algorithmic assistance should achieve, rather than a literal hiring or staffing formula. Why this matters: Microsoft owns enormous, decades-old C and C++ codebases — the Windows kernel, drivers, core libraries, desktop services, and many Azure components — and the company has repeatedly called out memory-safety bugs in unmanaged languages as a dominant source of critical vulnerabilities. Replacing high-risk subsystems with idiomatic Rust would materially reduce certain classes of memory-corruption bugs without forcing a general-purpose garbage collector on low-latency code.
For Windows users and enterprise customers, the practical outcome to expect is an evolutionary migration: important safety-sensitive subsystems will move first, accompanied by expanded toolchains and interop platforms, while the trickiest parts of the codebase remain under mixed-language stewardship for the near term. If Microsoft pairs automation with rigorous verification and staged rollouts, the result could be a meaningful reduction in a historic class of vulnerabilities — but that outcome is not guaranteed without transparency, independent audits, and conservative rollout policies.
Source: Thurrott.com Microsoft to Replace All C/C++ Code With Rust by 2030
Background / Overview
Microsoft’s interest in Rust is not new: the company began publicly experimenting with Rust in Windows and Azure projects in 2023, and senior engineering leaders have since signaled a strategic preference for memory-safe languages for new systems work. Those pilots included early Rust components in Windows internals and tooling work to allow Rust and Windows build systems to interoperate. The December 2025 statement from Microsoft Distinguished Engineer Galen Hunt — published as a LinkedIn hiring post that calls for a Principal Software Engineer to “help us evolve and augment our infrastructure to enable translating Microsoft’s largest C and C++ systems to Rust” — crystallizes that trajectory into a time‑boxed corporate objective: finish the migration by 2030. The post sets a provocative productivity target — “1 engineer, 1 month, 1 million lines of code” — which Hunt frames as a North Star for what heavy automation and algorithmic assistance should achieve, rather than a literal hiring or staffing formula. Why this matters: Microsoft owns enormous, decades-old C and C++ codebases — the Windows kernel, drivers, core libraries, desktop services, and many Azure components — and the company has repeatedly called out memory-safety bugs in unmanaged languages as a dominant source of critical vulnerabilities. Replacing high-risk subsystems with idiomatic Rust would materially reduce certain classes of memory-corruption bugs without forcing a general-purpose garbage collector on low-latency code. What Galen Hunt’s post actually says (and what it doesn’t)
The core claims
- The team’s explicit goal is to “eliminate every line of C and C++ from Microsoft by 2030.”
- The technical approach couples an algorithmic infrastructure (whole‑program graphs, deterministic analyses) with an AI processing infrastructure that orchestrates LLM-based agents to perform code modifications at scale.
- The hiring ask: systems-level Rust experience (ideally ~3+ years), with preference for compiler, database, or OS implementation backgrounds. The role is on-site in Redmond and reports into a CoreAI group called Future of Scalable Software Engineering inside EngHorizons.
The “1 engineer, 1 month, 1 million lines” metric
The motto is intentionally provocative: it encodes a throughput goal for automation (transformation velocity) rather than implying that a single human will rewrite a million lines manually. Treat it as a statement of desired automation scale: heavy reliance on deterministic analyses to limit risky transformations, LLM/agentic systems to propose idiomatic Rust, and human-in-the-loop verification to close the loop. Expect that metric to be used as an engineering north star rather than a literal schedule.Why Microsoft is betting on Rust: the security and engineering case
Memory safety at scale
Microsoft’s public security narratives for several years have highlighted that a large share of historically patched vulnerabilities stem from memory-safety issues commonly associated with C and C++ (buffer overflows, use-after-free, heap corruption). Rust provides compile-time guarantees (ownership, borrowing, lifetimes) that eliminate many of those classes of bugs without imposing garbage collection — a crucial property for system-level and low-latency code. That security calculus underpins Microsoft’s strategic pivot.Performance and ecosystem tradeoffs
Rust is designed to be competitive with C and C++ via zero‑cost abstractions and explicit control over memory layout. Microsoft’s pilots indicate that idiomatic Rust can meet strict performance constraints, and the company has invested in integration tooling — for instance, Cargo ↔ MSBuild integration — to help teams adopt Rust without having to throw away existing C/C++ investments. Still, Rust’s ecosystem is younger than C/C++’s; migration implies not only translating code but also adapting build systems, debuggers, and supply-chain tooling.Technical architecture: how Microsoft says it will attempt this
Two technical pillars
- Algorithmic program analysis — build whole‑program graphs (ASTs, type information, control/data‑flow) at scale so transformations can be reasoned about with compiler‑grade precision. These graphs define safe transformation boundaries, ABI contracts, and cross-module semantics.
- AI processing infrastructure — orchestrate LLM-powered agents that operate under algorithmic guidance: propose skeleton translations, idiomify code to Rust patterns, and iteratively repair compilation and runtime failures, all inside automated compile/test/verify loops. Human verification covers the hardest corner cases.
What “scale” means operationally
- Build a queryable graph over hundreds of millions of lines of code.
- Provide deterministic checks to block transformations that might violate ABI contracts or observable invariants.
- Integrate translations into CI pipelines with staged feature flags and telemetry channels (Insider/canary rings).
- Couple iterative fuzzing and regression harnesses to validate behavioral equivalence where possible.
Real limits and hard technical problems
Despite the promise, there are deep engineering limitations that significantly complicate large-scale automated C/C++ → Rust translation. These are not theoretical quibbles — they are practical, measurable constraints.1) Undefined behavior, templates, and complex C++ semantics
C++ contains language features (templates, overloaded operators, inline assembly, compiler intrinsics) and a long tail of undefined-behavior assumptions that are difficult to map correctly to Rust. Mechanical translations that do not reason about UB risk semantic drift. This is especially acute in kernel and driver code where subtle UB assumptions are exploited for performance.2) ABI preservation and third‑party drivers
Many Windows components expose binary interfaces to OEMs and third parties (drivers, firmware interfaces). Preserving ABI and binary contract semantics often requires human-designed shims or verified wrappers; automatic source-to-source rewriting alone cannot always maintain exact binary layouts and calling conventions.3) Panic semantics and availability tradeoffs
Rust’s default safety behavior converts some memory corruptions into panics or aborts. In kernel mode, an unchecked panic can mean a crash (BSOD) rather than a exploitable corruption — a tradeoff that must be managed carefully. Translating raw C behavior to Rust must preserve availability expectations, not just safety guarantees.4) Inline assembly, intrinsics, and performance tuning
Low-level optimizations often rely on inline assembly or compiler intrinsics with precise timing and layout behavior. Translating those pieces reliably and without performance regressions generally requires manual engineering and microarchitecture knowledge. Automated systems can detect hotspots but are unlikely to generate replacements that match hand-tuned assembly in all cases.5) Testing debt and the “last 1%”
Automated translation pipelines can likely handle the bulk of straightforward, well-tested modules. The remaining 1% — the security-critical, timing-sensitive, and historically buggy subsystems — will demand the majority of human effort. That testing debt is the gating factor for large-scale production rollouts.Evidence and early lessons from Microsoft’s pilots
Microsoft’s public pilots have already produced both wins and cautionary lessons. The company has shipped Rust components into Windows and Azure pilots and built driver and kernel support as proof-of-concept work. Those pilots demonstrate that Rust can be integrated into Windows build tooling and boot paths and that idiomatic Rust reduces classes of memory-safety bugs. At the same time, independent researchers found issues in some Rust-based Windows modules (a denial-of-service / logic bug identified and detailed by security researchers), and Microsoft issued a fix in a subsequent servicing update — a practical reminder that Rust adoption changes failure modes rather than eliminating them. That incident underscores the need for extensive fuzzing, staged rollouts, and human oversight during translation and deployment.Organizational and ecosystem implications
Hiring and skills
Microsoft’s job posting explicitly requests experienced systems Rust engineers and indicates the company will recruit compilers and OS experts for this work. Rust systems talent at enterprise scale is still scarcer than C/C++ expertise; Microsoft’s hiring push is therefore both a practical necessity and a strategic bet that scaling talent plus automation will enable the timeline.Supply chain, toolchain, and ISV compatibility
- Microsoft must ensure reproducible builds, toolchain supply-chain assurance (Rust toolchains, crates), and SBOMs for translated components.
- ISVs and OEMs will require stable ABI and clear migration guidance for drivers and native extensions.
- Build-system updates (Cargo + MSBuild integrations) and debugging workflows need to mature for enterprise support.
Industry effects
If Microsoft succeeds at scale, the Rust ecosystem will gain a major industrial anchor: more systems crates, tooling improvements, and practical production-level test cases will emerge. Conversely, a messy rollout would raise concerns about migrating enterprise-critical code with AI assistance and could slow broader adoption.A realistic near‑term roadmap (what success looks like)
If this program is to be more than a slogan, the following practical milestones are both achievable and necessary:- Inventory and risk prioritization: map Microsoft’s C/C++ surface area by exploit frequency and impact.
- Pilot conversions with reproducible verification: produce small, security-sensitive translations with full test harnesses and public reproducible artifacts.
- Stable interop platform: ship robust ABI shims and documented rules for FFI and driver interfacing.
- Tooling rollouts: publish internal tools (and ideally open-source key components) that produce auditable diffs and verification artifacts.
- Measurable security outcomes: demonstrable declines in memory-safety CVEs attributable to translated modules.
Risks, mitigations, and what to watch for
Major risks
- Overreliance on probabilistic AI: LLMs are powerful but make mistakes; automation must be constrained by deterministic analyses and test-based gates.
- Testing and deployment fragility: Increased change velocity without matching test coverage invites systemic regressions. The KB/servicing incidents referenced publicly highlight that risk.
- Toolchain and supply-chain complexity: Adding Rust toolchains expands the supply chain surface for vulnerabilities and reproducibility issues.
- ABI and ecosystem friction: ISVs and OEM partners depend on stable binary contracts; abrupt or poorly communicated changes risk breaking the broader Windows ecosystem.
Reasonable mitigations
- Strict human-in-the-loop checkpoints for any change touching ABI or kernel surfaces.
- Aggressive fuzzing, property-based testing, and formal verification where feasible.
- Phased rollouts through Insider/Canary rings with telemetry‑driven rollback thresholds.
- Supply-chain hardening for Rust toolchains and crates (SBOMs, signed artifacts, reproducible builds).
Benefits for enterprises and developers
- Reduced surface for memory-corruption exploits in migrated components.
- Modernized toolchains (Cargo integration, crate ecosystem) that can accelerate safe systems engineering.
- Potential long-term maintenance savings once idiomatic Rust patterns and tools reduce incident volume.
Critical assessment: ambitious, plausible, but not guaranteed
Microsoft has the scale, engineering depth, and deployment channels (Insider/canary rings, Azure compute, large test suites) to attempt an industrial-scale migration that would be infeasible for most organizations. The charter to combine algorithmic program analysis with AI agents is plausible and follows patterns shown to work in smaller research and industrial prototypes. If Microsoft delivers a rigorous, auditable, and verifiable pipeline, the security and maintainability gains could be material. But the path contains several unproven leaps:- Whole-program equivalence at OS scale is not solved; many subtle semantics and UB cases remain hard to automate.
- LLM-driven repair requires domain-specific fine-tuning, tight compiler-in-the-loop strategies, and deterministic blockers to be safe enough for kernel code.
- The 2030 timeline compresses the window for building hardened verification pipelines; accidental haste could increase risk if verification capacity does not scale at the same pace.
Signals to watch (concrete, verifiable indicators)
- Publication of tooling prototypes or whitepapers from Microsoft showing reproducible translation workflows and verification metrics.
- Open-sourcing of internal transformation tooling (e.g., Cargo↔MSBuild integration, algorithmic graph infra) — that would accelerate community validation.
- Measured declines in memory-safety CVEs tied to translated modules and public telemetry comparisons over calendar years.
- Evidence that translated code is being promoted out of Insider/canary rings into broad enterprise channels without regression spikes.
Practical advice for IT managers and ISVs
- Treat Microsoft’s 2030 objective as strategic priority but plan for multi‑year coexistence of C/C++ and Rust.
- Increase fuzzing and test coverage for high‑risk native components now; this is the bedrock of safe automated translation.
- Prepare vendor and OEM contracts for ABI and toolchain changes; require reproducible builds and signed artifacts for any translated binaries.
- Invest in Rust skill development for SREs, driver testers, and release engineers if you depend on native Windows drivers or low-level libraries.
Conclusion
Microsoft’s public commitment to eliminate C and C++ internally by 2030 and to use a hybrid of algorithmic program analysis + AI agents to translate legacy systems into Rust is one of the most consequential engineering statements in modern systems software. It reflects a defensible security-first rationale — memory safety at scale — and leverages Microsoft’s unique advantages in scale, test infrastructure, and deployment channels. That said, the technical and operational challenges are substantial: undefined behavior, ABI preservation, panic semantics, testing debt, and supply-chain complexity are real and require rigorous, reproducible verification strategies. The program’s success will hinge less on raw throughput and more on whether Microsoft can produce verifiable, auditable evidence that automated translations preserve behavior and safety at the levels enterprise customers demand. The 2030 deadline is an ambitious organizing goal; its credibility will depend on the company publishing milestones and verification data that back up the claim.For Windows users and enterprise customers, the practical outcome to expect is an evolutionary migration: important safety-sensitive subsystems will move first, accompanied by expanded toolchains and interop platforms, while the trickiest parts of the codebase remain under mixed-language stewardship for the near term. If Microsoft pairs automation with rigorous verification and staged rollouts, the result could be a meaningful reduction in a historic class of vulnerabilities — but that outcome is not guaranteed without transparency, independent audits, and conservative rollout policies.
Source: Thurrott.com Microsoft to Replace All C/C++ Code With Rust by 2030
