Oss Migration Eval

OSS Migration Eval

The methodology in one breath: find the fattest recurring task, build a human-validated golden set on the frontier model (with trap cases), sweep cheap candidates 5 seeds each on pinned providers, grade deterministically where possible, and present cost-savings vs accuracy-loss as a business decision - then deploy the swap behind a smart orchestrator, never as a full-agent replacement.

The hard-won lesson: most eval "winners" are single-sample noise. A real experiment crowned a decisive 9.00/10 winner off one generation per cell; a 5-seed rigor pass dropped it to 7.00 +/- 2.0, mid-pack in a six-way statistical tie. Within-model variance across seeds nearly equaled the entire between-model ranking spread. This skill's job is an honest cost-vs-accuracy verdict - and often the honest verdict is "no clear winner, here is the tradeoff; you can only name the losers." Saying that is a success, not a failure.

When this skill applies

Invoke when the user:

• wants to replace a frontier model in a pipeline with something cheaper or open-source
• asks "which model can replace X for this task", "can I downshift this", "am I overpaying"
• wants a cost-savings vs accuracy-loss estimate for a recurring LLM task
• asks to evaluate open-weight models (Kimi, DeepSeek, GLM, Qwen, Llama, ...) against their current setup
• wants to move a task to a local model (Ollama) for cost or data-security reasons

Do NOT invoke for (see references/triage.md for the full gates and refusal template):

• one-off or low-volume tasks - the eval costs more than years of the task's spend; keep the frontier model
• tasks with no checkable output and no willingness to build a golden set - nothing to measure means nothing to decide
• safety-critical outputs where any quality dip is unacceptable - the answer is already "keep the frontier model" (offer a verify-gate architecture instead)
• pipelines where the frontier model itself is not yet reliable - fix the task first, then ask about cost
• general model gossip ("which model is best?") - this skill answers "best for THIS task at THIS price," nothing broader

Refusal is a feature. Do not run a sweep to be agreeable.

Non-negotiable rigor rules

Baked into every step; full rationale and the war stories in references/rigor.md:

1. >= 3 seeds per model x case, default 5. Single-seed rankings are noise. Always report mean +/- stderr / 95% CI.
2. Report ties honestly. Compute pairwise z = delta-mean / sqrt(se1^2 + se2^2); |z| > 1.96 separates. Overlapping CIs = "statistically tied," never a crowned winner. Expect to identify losers, not a winner.
3. Pin every candidate to one highest-precision provider (allow_fallbacks: false). Unpinned OpenRouter routing serves different quantizations (fp4/int4 vs fp8/bf16) call to call - a benchmark lottery.
4. Deterministic grading beats an LLM judge wherever the task allows. A programmatic "is this number actually in the input?" check contradicted the judges' fabrication flags - and was right. The blind panel is only for genuinely subjective output.
5. Hard and trap cases are mandatory in the golden set. Easy-only sets over-claim "solved." Include boundary cases and false-trigger traps.
6. Blind the panel: anonymize + shuffle candidates per case, use judge models from different families than the candidates.
7. Small-sample honesty: every verdict states N cases, N seeds, and "on these prompts" - never "model A is better," period.

The eight steps

Full procedure with rationale and per-step artifacts in references/methodology.md. Work through them in order; skip only what the user has explicitly already done. Each step names WHAT to establish - the executing agent chooses tools and specifics.

Step 0 - Find the fattest tasks

• Establish which recurring, high-token-volume tasks dominate the LLM bill. If the user doesn't know, run the token-audit skill - its task x frequency x $/month output is exactly this step's input.
• A migration candidate must be high-frequency, high-cost, repeatable, and have a checkable output. Migrate one narrow task at a time, never "the pipeline."
• Run the triage gates (references/triage.md) on each candidate now: material spend, checkable output, tolerance for any quality dip, a stable frontier baseline, a stable task definition, and "is this even a model-cost problem or is it prompt bloat/caching."
• Refuse or redirect bad fits here, before any harness exists.

Step 1 - Frame the task, choose the accuracy metric

• Classify each task's output: structured (JSON/label/number -> deterministic exact-match or numeric error) or subjective (copy/text -> blind panel). references/metrics.md has the decision table.
• Define what "X% accuracy loss" MEANS for this task in one sentence, before any data exists. If that sentence can't be written, return to triage.
• For text tasks, strip out every sub-property that CAN be checked deterministically (length, banned phrases, fabricated numbers, required mentions) - those get programmatic guards, not judge opinions.
• Fix the eval conditions to production reality: the exact production system prompt, the production temperature, generous max_tokens (reasoning models silently return empty when starved). Note max_tokens enforcement is provider-dependent (some providers honor it, some ignore it) and never caps reasoning burn - a runaway reasoner can spend tens of thousands of tokens regardless, inflating measured $/call and latency; run_sweep.py flags any cell exceeding that model's median or an optional MAX_COST_PER_CELL, and those inflated costs are real - they belong in the report.

Step 2 - Build the golden set

• ~10-20 cases per task from real production inputs; generate proposed references on the frontier model (templates/build_golden.py).
• Human validation is not optional, and the scripts enforce it on BOTH reference paths. Human says 5, Opus says 10, Qwen says 8 - first make the frontier model agree with the human, THEN it becomes the oracle. An unvalidated oracle measures agreement-with-Opus, including Opus's mistakes. grade.py refuses any reference not signed off: a ref pasted into tasks.py needs "validated": true; a golden_proposed.json fallback needs "human_validated": true. No sign-off, no verdict.
• Include hard cases - mandatory: boundary cases (inputs on a decision edge - grade calibration, not a single right answer), false-trigger traps (inputs that LOOK like they hit a hard rule but don't - these measure precision), and buried positives.
• Split dev / test / val (~50/30/20) now, even if optimization may never happen - splits are cheap to assign and impossible to un-contaminate later.

Step 3 - Pick candidate models

• Shortlist 4-8 candidates by crossing a quality leaderboard (Artificial Analysis Intelligence Index) with a usage leaderboard (OpenRouter rankings) - fetch both LIVE; the field turns over monthly and benchmark rank != task fit. Method and task-type priors: references/candidate-selection.md.
• Span the price range: at least one ultra-cheap model (they sometimes tie on structured tasks - the biggest savings if it holds) plus the current price/quality sweet spot. Include the incumbent frontier model as baseline.
• Evaluate through OpenRouter first (one API, one bill, 400+ models); the local-vs-cloud decision comes after the accuracy verdict, from security/deployment requirements.
• Build the provider-pin map now (templates/pick_candidates.py): for each candidate, pick the highest-precision endpoint (bf16/fp16 > fp8 > int8 > fp4/int4) and pin it with allow_fallbacks: false.
• Load real credit (~$10) before sweeping - thin OpenRouter accounts 402 on pricier models and silently bias the sweep toward cheap ones.

Step 4 - Sweep

• Run every candidate AND the incumbent through the same harness: N seeds (default 5) per case, pinned providers, recording content + cost + latency + reasoning tokens + the provider that actually served each call (templates/run_sweep.py - concurrent, resumable, incremental save).
• The frontier goes through too: its seed variance is the eval's noise floor, and its measured $/call (not the price sheet) anchors the savings math.
• Empty completions from runaway reasoners are data points (failures), not retry-until-it-works. Verify the pins held on every response.

Step 5 - Grade and build the tradeoff table

• Deterministic metrics per task type via templates/grade.py: pass-rates with binomial stderr, MAE, fabrication check (numbers absent from input), format guards, trap-case results, cost/latency aggregation with savings vs the measured frontier baseline.
• Blind multi-family panel for subjective tasks via templates/judge.py: anonymized + re-shuffled per case, 3 judges from non-candidate families, temperature 0, scored across seeds x cases x judges, aggregated mean +/- std +/- stderr with 95% CI.
• Run the honesty pass: pairwise z vs the top scorer; label every candidate statistically tied or clearly worse. Expect a tied top cluster.
• Express the headline the way a decision-maker reads it: "candidate scores 7.6 vs the frontier's 9.5 (~25% quality loss) at 80% lower cost."
• Assemble the core artifact: candidate | quality mean +/- CI | accuracy loss vs frontier | $/call | $ saved % | latency | tied-or-worse.

Step 6 - Decide

• The acceptable savings-per-quality-point ratio is a BUSINESS decision the user makes - 25% loss for 80% savings is a great trade for internal scoring and a terrible one for customer-facing copy. Present the table; don't decide for them.
• Recommend per task one of four: swap (tied, or loss inside stated tolerance) / swap-with-guard (tied but with a known failure mode a deterministic guard or verify-gate covers) / optimize-first (close but under threshold) / keep frontier (no acceptable swap - say it plainly; a valid, successful outcome).
• Write the report from templates/report_template.md, limitations paragraph included. For contested or strategic verdicts (brand risk vs savings), a council pass on the finished table is cheap.

Step 7 (optional) - Close the gap

• Only when the best candidate is close-but-under and the gap looks prompt-shaped, run a prompt-optimization loop - the autoresearch skill with the cheap model's dev-split score as the fitness function. Discipline in references/optimization.md.
• CRITICAL: the model overfits to whatever set it sees. Tune on dev, gate on test, confirm ONCE on untouched val - the val number is the only one that enters the report. If val disappoints, you do not get to iterate against it.
• The references, grading code, seeds, and judge rubric are frozen during the loop - if the loop can touch the ruler, it optimizes the ruler.

Step 8 - Deploy via orchestration

• Never move the whole agent to the cheap model - the eval validated one narrow task, not planning, tool routing, or recovery; whole-agent downshifts collapse exactly there. Patterns in references/deployment.md.
• The smart model orchestrates; the cheap model executes the evaluated task via a subagent, script, or direct call. Encode the routing declaratively - "for THIS task type, use THIS model (THIS pin, THIS prompt version)" - in a skill or dispatch table, dated and tied to the report.
• Keep a verify-with-a-smarter-model gate on outputs that matter (cheap model does the volume, frontier reviews the last step or a sample) and run the deterministic guards from the eval on 100% of production outputs.
• Local via Ollama when data must not leave the machine - but if production runs a heavier quant than the eval pinned, re-run the sweep against that quant first; it is a different model. Fine-tuning (HuggingFace ecosystem) is the last resort for stubborn capability-shaped gaps on custom tasks - and the fine-tune re-enters the harness as just another candidate row.
• Date-stamp the decision; re-run on prompt change, pin/quant change, notable new model, or quarterly. The harness costs ~$1 to re-run; keep the frontier path one config flag away.

Reference files map

• references/triage.md - Step 0 (the six gates, when a swap is a bad idea, the refusal template)
• references/methodology.md - the full 8-step procedure with rationale and artifacts
• references/candidate-selection.md - Step 3 (leaderboards, shortlist composition, task-type priors, provider pinning, account gotchas)
• references/metrics.md - Steps 1 + 5 (accuracy-loss definition per task type, panel rules, aggregation math)
• references/rigor.md - the seven honesty guardrails and the experiment that motivated them
• references/optimization.md - Step 7 (autoresearch loop + train/test/val discipline)
• references/deployment.md - Step 8 (orchestration, verify-gate, Ollama, fine-tuning, operating the swap)

Load each on demand during the step that needs it. Do not preload.

Templates map and run order

All templates read the API key from env OR_KEY, are resumable, and print progress. They share one contract: a tasks.py the agent fills in with the user - schema documented at the top of templates/build_golden.py (tasks, cases, references, splits, models, seeds, judges, banned phrases).

Typical run order in a fresh working directory:

1. Write tasks.py (tasks + cases; references empty where unknown)
2. build_golden.py - propose frontier references, assign splits, STOP for human validation
3. pick_candidates.py discover then pin - live shortlist data + provider_pins.json
4. run_sweep.py - the N-seed pinned sweep -> outputs/seeds_raw.json
5. grade.py (local, free) and, for subjective tasks, judge.py - metrics, error bars, tradeoff table
6. Fill report_template.md

• templates/build_golden.py - frontier reference proposals + dev/test/val splits + hard-case warnings
• templates/pick_candidates.py - live OpenRouter models/endpoints, highest-precision provider-pin map, shortlist table
• templates/run_sweep.py - N-seed, provider-pinned, concurrent, resumable sweep; records content + cost + latency + served provider
• templates/grade.py - deterministic metrics per task type, pass-rate/MAE with error bars, pairwise z-tests, cost-savings table
• templates/judge.py - blind, shuffled, multi-family panel across seeds; mean +/- std +/- stderr with CI; advisory-only fabrication flags
• templates/report_template.md - the decision report skeleton

Adapt the templates to the task; they are scaffolds, not a framework. Keep the harness boring - the thinking lives in metric choice and the verdict. For calibration: the reference experiment's full harness (9 models x 8 cases x 5 seeds + 3-judge panel) cost ~$1.15; never cut seeds to save cents.

What you get

A decision report (per templates/report_template.md) containing:

• the tradeoff table: every candidate's quality mean +/- CI, accuracy loss vs the frontier baseline, measured $/call, % saved, latency
• the honest reading: which models are statistically tied at the top, which are clearly worse (the losers separate; the winner usually doesn't)
• deterministic findings that outrank the panel: fabrication rates, trap-case results, guard violations, empty-output rates
• a per-task recommendation - swap / swap-with-guard / optimize-first / keep frontier - with projected annual savings at the user's volume and the required guards
• an explicit limitations paragraph: seeds, case count, "on these prompts, these providers, this month"

Freshness - the skill must never rot

The model landscape turns over monthly; a hardcoded winner is wrong within weeks. This skill stays current by construction:

• No model, price, rank, provider, or quantization is ever authoritative from memory. Every one is fetched live at run time - pick_candidates.py for models/prices/endpoints; artificialanalysis.ai + openrouter.ai/rankings for the two leaderboards (fetched by the agent). Any model name appearing anywhere in

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Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: BayramAnnakov
• Source: BayramAnnakov/oss-migration-eval
• License: MIT

Install and usage instructions live in the source repository linked above.