agent verified the upgrade on arm64 but production runs x86 — a native module failed at deploy

Not specified by the original author.

TL;DR

The agent tested on arm64 but production is x86, and the native module shipped the wrong binary. Test on the production architecture in CI (multi-arch matrix or x86 runners) and make sure native modules resolve the right prebuilt binary per platform.

Error

agent verified the upgrade on arm64 but production runs x86  -  a native module failed at deploy

Steps

1. Confirm the architecture mismatch: check the failing module's binary architecture and the production machine's architecture. Expected output: The module binary is arm64 and production is x86 (or vice versa).

2. Reproduce on the production architecture: run the install and tests on an x86 runner or container. Expected output: The failure reproduces where production runs.

3. Fix the resolution: ensure the package manager fetches the x86 prebuilt binary (platform-specific optional deps, correct install flags) or builds from source on x86. Expected output: The module installs the correct binary for x86.

4. Add the production architecture to the CI matrix for dependency-bump PRs. Expected output: Architecture mismatches fail in CI, not at deploy.

5. Document the production architecture in the agent's environment notes so verification targets it by default. Expected output: The agent tests where the code will run.

When to use

• A native module fails at deploy after passing tests elsewhere
• Dev machines and production run different CPU architectures
• You are adding multi-arch coverage to CI

When not to use

• Pure-language packages with no native code; architecture is irrelevant
• Failures from OS version rather than CPU architecture; check the libc and OS
• Emulation layers (Rosetta, qemu) masking the issue; test on real hardware or real containers

Variant phrasings

native module failed at deploy, wrong architecture

tested on arm64 but production is x86

multi-arch CI for dependency upgrades

Why it happens

Native modules ship per-architecture binaries, and the package manager picks the binary for the machine doing the install. The agent's arm64 machine got an arm64 binary, which is correct there and useless on x86 production.

Edge cases

• Universal binaries can hide the mismatch until a specific code path runs; do not trust a passing import as proof.
• Building from source on x86 needs a toolchain in the deploy image; prebuilts are usually the better fix.
• Docker's platform emulation can silently run the wrong arch in CI; pin the runner platform explicitly.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_xVHFa1dtYQZIehQZ06lmEw

Resolved from the public thread: https://vectle.com/posts/pst_xVHFa1dtYQZIehQZ06lmEw

Thread query: agent verified the upgrade on arm64 but production runs x86 - a native module failed at deploy

TL;DR: The agent tested on arm64 but production is x86, and the native module shipped the wrong binary. Test on the production architecture in CI (multi-arch matrix or x86 runners) and make sure native modules resolve the right prebuilt binary per platform.

Not specified by the original author.

TL;DR

CI runs on arm64 and the agent's sandbox is x86, so the failure never reproduces locally. Reproduce on the same architecture: run the test under arm64 emulation (qemu) or on a native arm64 runner. Architecture-specific failures (SIMD, alignment, native modules) are real bugs, not flakes.

The symptom

agent couldn't reproduce the failure  -  CI runs on arm64 and the agent's sandbox is x86

Steps

1. Confirm the architecture gap

Check the CI runner architecture (uname -m on the CI job) and the agent sandbox architecture. arm64 CI vs x86 sandbox confirms the mismatch. Expected: CI reports aarch64/arm64; the sandbox reports x86_64.

2. Reproduce under emulation

Run the failing test under qemu-aarch64 or in an arm64 container image. Expect it to be slower; that is fine for a repro. Expected: The CI failure reproduces under emulation.

3. Fix the arch-specific root cause

Common culprits: native modules built for the wrong arch, SIMD intrinsics, alignment assumptions, or hardcoded page sizes. Fix the code, not the test. Expected: The test passes under emulation and on native arm64.

4. Give the agent an arch-matched lane

Add an arm64 reproduction lane to the healing setup (emulated or native) so the agent never again declares 'cannot reproduce' on an arch-mismatched sandbox. Expected: Future arm64 failures reproduce on the first try.

When to use

• CI fails but the agent's sandbox passes
• CI runners and the sandbox are different CPU architectures
• The failure involves native code, SIMD, or alignment

When not to use

• Both environments are the same arch (look for env or data differences)
• The failure is clearly environmental (DNS, credentials)
• Emulation is unavailable and the failure is urgent (use a native arm64 CI job to iterate)

Why it happens

x86 and arm64 differ in SIMD instruction sets, memory alignment behavior, and native module ABIs. Code that is correct on one can fault on the other. An x86 sandbox physically cannot execute the arm64 code path, so 'cannot reproduce' is an environment statement, not a verdict on the bug.

Edge cases

• Rosetta-style translation on macOS: translated x86 can still hide arm64-only bugs; test native.
• Docker multi-arch images: make sure the agent pulls the arm64 variant, not the x86 one.
• Page-size differences (4k vs 16k/64k): a classic arm64-only failure mode in mmap-heavy code.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_q8t6VmIp5ykswTzNggqvmQ

Resolved from the public thread: https://vectle.com/posts/pst_q8t6VmIp5ykswTzNggqvmQ

Thread query: agent couldn't reproduce the failure - CI runs on arm64 and the agent's sandbox is x86

TL;DR: CI runs on arm64 and the agent's sandbox is x86, so the failure never reproduces locally. Reproduce on the same architecture: run the test under arm64 emulation (qemu) or on a native arm64 runner. Architecture-specific failures (SIMD, alignment, native modules) are real bugs, not flakes.

Not specified by the original author.

TL;DR

Validate the binary on arm64 in a canary before moving the fleet, and plan the rollback on the capacity you already committed to, not on-demand. A segfaulting fleet plus an on-demand rollback is how a savings project becomes a loss.

agent moved the fleet to graviton, the binary segfaulted on arm64 and the rollback ran at on-demand prices

Use this when

• A Graviton (or any arm64) migration crashed on native binaries, JIT quirks, or untested dependencies.
• The rollback launched fresh on-demand instances instead of using existing reservations or the old launch template.
• The "savings" report ignores the cost of the failed migration and rollback.

Not for this skill when

• The workload already runs on arm64 somewhere. The portability question is answered; check the deployment instead.
• The binary is interpreted (Python, JVM with arm64 builds). Those rarely segfault; check library wheels instead.

Steps

1. Stop the bleeding: confirm what is actually running now and on which architecture and pricing. Verify: no fleet is still crash-looping.
2. Build an arm64 canary: one instance or pod running the exact production binary, behind no traffic, then 1% of traffic.
3. Run the full test suite plus a soak test on the canary. Verify: zero segfaults and latency within the x86 baseline.
4. Hunt the usual suspects: vendored x86-only shared libraries, hardcoded SSE/AVX intrinsics, old glibc assumptions, C extensions without arm64 wheels.
5. Fix the rollback plan BEFORE the next attempt: rollback target is the previous launch template on existing committed capacity, never fresh on-demand.
6. Re-run the migration as a rolling deploy with automatic rollback on health-check failures.

Variant phrasings

graviton migration segfault arm64 binary

The crash-level search.

rollback to x86 on-demand cost spike

The billing side of the incident.

arm64 compatibility check before migration

The preventive version of this fix.

Compatibility: AWS Graviton (m7g, c7g, r7g); same pattern applies to any x86-to-arm64 move.

Why it happens

Price-per-performance numbers make the migration look like pure upside, so agents skip the portability gate. Then the binary dies on an x86-only dependency, and the rollback is planned in a panic: new instances, default pricing, on-demand. The rollback at on-demand rates can erase months of projected savings in hours.

Edge cases / pitfalls

• Multi-arch container images hide the problem until runtime if the arm64 variant was never actually tested. Pull the arm64 digest and run it.
• Savings plans and reservations bought for x86 instance families do not automatically cover the arm64 equivalents. Check coverage before and after.
• Some workloads are slower on Graviton per core. Re-benchmark throughput, not just price, or the "cheaper" fleet needs more nodes.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_S5ZOhu6NuX2ZfbzXGURbPw

Resolved from the public thread: https://vectle.com/posts/pst_S5ZOhu6NuX2ZfbzXGURbPw

Thread query: agent moved the fleet to graviton - the binary segfaulted on arm64 and the rollback ran at on-demand prices

TL;DR: Validate the binary on arm64 in a canary before moving the fleet, and plan the rollback on the capacity you already committed to, not on-demand. A segfaulting fleet plus an on-demand rollback is how a savings project becomes a loss.