Checkpoint Promotion Agent Skill

Checkpoint Promotion

The Phase 5 gate for the whole

plugin: a checkpoint that trains

cleanly and beats its task metric

still doesn't ship without

clearing all four stages below.

eval-harness-first built the

suite re-run here — this skill is

where that suite's baseline

decides something.

Input: a trained checkpoint,

eval/baseline-<model>.json from

eval-harness-first, and the

frozen eval/drift-suite.yaml.

Output format:

promotion-report.md — the

four-stage evidence plus a

terminal PROMOTE or REJECT

verdict that /finetune Phase 5

and /promote-checkpoint consume

directly.

The Four-Stage Gate

Each stage gates the next — a

failure at stage 2 means stage 3

doesn't run. Stages 2 and 3 share

one expensive inference pass, so

running them concurrently and

applying gate order at verdict

time is licensed on a

deterministic arena (nothing

saved by serializing); a

judge-based arena should still

wait for stage 2 first — that's

where the real savings are.

• Data-quality gate. Before

any eval touches the

checkpoint: dedup the training

set, check for eval-goldens

leakage (the exact failure

trace-to-training-data's

Hygiene section exists to

prevent), and scan for label

noise. A checkpoint trained on

leaked goldens invalidates

every later stage.

• **Held-out + frozen

capability-drift suite.**

Re-run eval-harness-first's

eval/drift-suite.yaml —

MMLU/GSM8K/IFEval plus 200–500

domain-adjacent items — against

the checkpoint and diff against

baseline-<model>.json per

benchmark against the Drift

Budget table below.

• Paired arena vs. base.

Position-randomized judge,

checkpoint vs. base model, same

prompts — or the deterministic

paired-comparison variant in

references/gate-templates.md

when every grader in the

harness is deterministic (no

LLM-judge; position

randomization N/A there).

**A holdout win that

loses the live arena does not

ship** — stage-2 numbers and

stage-3 judgments must agree; a

win on frozen goldens and a

loss in paired comparison is a

real signal, not a discrepancy

to explain away.

• Canary. 5–10% stratified

rollout with auto-rollback for

any checkpoint reaching

production traffic. **Local-only

users stop at stage 3** —

skipping stage 4 for a local

deployment is the correct

stopping point, not a shortcut.

Drift Budget

| Drift (pts) | Verdict |

|---|---|

| ≤1 | Noise — proceed |

| 2–5 | Rerun with seed variation before deciding |

| >5 | HARD FAIL — no exception for task gains |

The >5pt row governs regardless

of the others: a checkpoint that

gained 8 points on the target

task and lost 6 points of general

capability still fails here —

task improvement never buys back

a drift-budget breach.

**Item count derives from the

budget, not convenience:** the

strict n for a half-width under

half the 5pt hard-fail threshold

is ~1,300 at typical accuracy

(p≈0.7); n=200 is a pragmatic

floor (±6pt half-width at that

same p, n=50 ±13pt) — report the

half-width with every verdict,

and treat a margin smaller than

it as REJECT (uncertain), not

PASS/HARD FAIL. Full math and a

5-run cautionary example:

references/gate-templates.md.

RERUN is not a verdict. A

2–5pt drift only ever produces a

PROMOTE or REJECT after the

seed-variation rerun completes —

PROMOTE requires landing back

at ≤1pt (noise); any rerun still

>1pt — 2–5pt band or >5pt breach

alike — resolves stage 2 to a

hard REJECT. No report may

reach the Verdict section with

stage 2 still showing RERUN.

Catastrophic Forgetting

Unmanaged LoRA fine-tuning loses

real general capability, and

stage 2 is what catches it:

• **~43% knowledge loss

unmanaged** — no replay, no

regularization.

• ~10% with basic management

— some replay or a conservative

LR.

• ~3% with replay + EWC — the

disciplined case.

• **10–30% general-data replay

mix is the standard

mitigation** — blend general-

domain data into training

rather than target-task data

alone.

If a checkpoint hits the >5pt

hard fail in stage 2, work this

escalation ladder in order — the

one canonical order this skill

and references/gate-templates.md

both point to:

• **Adjust the replay-mix

fraction — swap rows, don't

add them** (adding confounds

fraction with total optimizer

steps). Dose is not monotonic

at small-run scale (<~100

steps) — re-check drift after

any swap.

• Lower the learning rate.
• Fewer epochs.
• A smaller LoRA rank — the

same rank/LR levers

lora-qlora-recipes and

preference-optimization tune

for the training run, applied

here in reverse.

This order is a default, not a

law: **remediation guidance from

a single before/after run pair

is a hypothesis** — label it

low-confidence once any lever

produces a reversal, and prefer

a seed-variation repeat over

trusting the next rung blindly.

A lever that clears the drift

breach but drops a

success-criterion metric below

target is a two-sided tradeoff

for a human, not a reason to

keep descending the ladder. Full

reasoning and the 5-run

trajectory behind both caveats:

references/gate-templates.md.

**Disclose drift-suite

instruction reuse.** A replay row

copying the drift harness's exact

instruction phrasing (not just

disjoint source items) makes that

benchmark's post-replay score an

upper bound — flag it

instruction-familiar, or re-probe

with a paraphrase, before

treating a near-budget pass as

clean.

The Verdict

promotion-report.md covers all

four stages as sections and

**must end with a terminal

verdict: PROMOTE or REJECT**,

the evidence that produced it,

and exactly one top remediation

when the verdict is REJECT.

Template: references/gate-templates.md.

The terminal contract other

skills parse:

## Verdict

REJECT

Evidence: domain-adjacent drift
suite dropped 6.2pt (threshold:
>5pt hard fail) despite +8pt on
the target task.

Top remediation: swap the
replay-mix fraction from 10%
toward 20%, holding step count
constant.

• **REJECT is a result, not an

error.** A checkpoint that

fails stage 2's drift budget or

stage 3's arena comparison did

its job. Don't treat a REJECT

as a failed run needing a rerun

of this skill; it's the correct

output of a working gate.

• **One remediation, not a

menu.** Evidence sections may

list everything observed; the

verdict section names the

single highest-leverage fix per

the escalation ladder above. A

report that hedges across three

possible fixes hasn't done the

prioritization this skill

exists to do.

• No auto-retraining. This

skill produces a verdict and a

report, not a re-triggered

training run. A REJECT hands

the remediation back to a human

decision at

finetuning-method-selection or

the relevant training skill.

Related Skills

• eval-harness-first — owns the

drift suite and baseline this

skill re-runs and diffs

against; no baseline-<model>.json

means nothing to gate against.

• quantized-export — the only

valid next step after a

PROMOTE verdict.

• preference-optimization and

lora-qlora-recipes — own the

LR and rank levers in the

Catastrophic Forgetting

escalation path; this skill

diagnoses the breach, those

skills own the config that

caused it.

• dataset-curation — owns the

replay-mix construction recipe

the escalation ladder's first

rung applies.

Complete promotion-report.md

template with all four stages,

the drift-suite scoring table,

the paired-arena protocol (item

count, position randomization,

win-rate threshold), and a

replay-mix configuration example:

references/gate-templates.md.