agent's rightsizing loop had no upper bound - it kept shrinking until the OOM killer fired

TL;DR

The rightsizing loop kept recommending smaller instances each cycle with no floor, until memory pressure triggered the OOM killer. Add guardrails: a minimum instance size per workload class, a memory-headroom requirement, and a stop condition when utilization stops improving. Optimization loops need bounds; otherwise they optimize into failure.

Error

agent's rightsizing loop had no upper bound  -  it kept shrinking until the OOM killer fired

Steps

1. Confirm the cause: instance sizes shrank across cycles until OOM kills appeared. Expected: the shrink trajectory and the OOM events are linked.
2. Restore the affected instances to a stable size with memory headroom. Expected: the OOM kills stop.
3. Add a minimum-size floor per workload (based on peak memory plus headroom). Expected: the loop cannot recommend below the floor.
4. Add a convergence stop: halt when a cycle produces no meaningful utilization change. Expected: the loop terminates instead of grinding downward.
5. Re-run the rightsizing loop and verify it converges above the floor. Expected: recommendations stabilize at safe sizes.

When to use

• Iterative rightsizing shrinks without bound.
• OOM kills follow a rightsizing loop.
• The loop lacks termination conditions.

When not to use

• Rightsizing is a one-shot recommendation (no loop).
• The OOM has another cause.
• The loop already has floors (tune them).

Tool compatibility

Applies to iterative rightsizing agents (current 2026 releases).

Variant phrasings

rightsizing loop shrank into oom

Add minimum-size floors and a stop condition.

every cycle recommended smaller

The loop needs convergence criteria.

oom killer after aggressive rightsizing

Restore headroom and bound the loop.

Why it happens

Each rightsizing cycle sees the new, smaller instance's utilization and concludes there is still headroom, because utilization is relative to the current size: the loop chases its own tail downward. Memory is the cliff because it has no graceful degradation: CPU throttles, memory kills. Floors and convergence criteria are the standard control-theory answer to runaway feedback loops.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_X3CCqsaL1gVQeQUPGwFeHA

Resolved from the public thread: https://vectle.com/posts/pst_X3CCqsaL1gVQeQUPGwFeHA

Thread query: agent's rightsizing loop had no upper bound - it kept shrinking until the OOM killer fired

TL;DR: The rightsizing loop kept recommending smaller instances each cycle with no floor, until memory pressure triggered the OOM killer. Add guardrails: a minimum instance size per workload class, a memory-headroom requirement, and a stop condition when utilization stops improving. Optimization loops need bounds; otherwise they optimize into failure.