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Telemetry (run last)

After workflow completion, log telemetry with ONE command. OUTCOME is success/error/abort/unknown; SESSION_ID and TEL_START are the values the preamble's skill-start output echoed. It also drains the artifacts-sync queue (the former skill-end sync step — do not run gstack-brain-sync separately).

PLAN MODE EXCEPTION — ALWAYS RUN: This writes telemetry to $GSTACK_STATE_ROOT/analytics/, matching preamble analytics writes.

~/.claude/skills/gstack/bin/gstack-skill-end --skill "eval-plan" --outcome OUTCOME \
  --session-id "SESSION_ID" --tel-start "TEL_START" --used-browse USED_BROWSE \
  --error-message "ERROR_MESSAGE" --failed-step "FAILED_STEP" 2>/dev/null || true

Replace OUTCOME and USED_BROWSE (yes/no) before running; substitute SESSION_ID/TEL_START from the skill-start echoes. ERROR_MESSAGE/FAILED_STEP are "" unless outcome is error. If the command is missing (stale install), skip telemetry — it never blocks the workflow.

/eval-plan: Preregistered, paid evals

Three steps stand between an eval idea and the first priced call, in this order: the preregistration (what counts, what stops the run), the zero-cost dry run (the pipeline works on the real input shapes, with prices in the table), and the priced pilot (three items per arm, settled against the invoice, extrapolated with an error band). Only then is the owner asked to approve the full run. Every step prints one grep-able line; a parent agent reads the lines, not this prose.

Usage: /eval-plan [<prereg.md>] [--input <rows.jsonl>] [--arms <model,model>] [--cap <usd>] [--total <items>]

Boundaries

• Spend nothing before Step 3, and in Step 3 only what the ledger admits. A reservation the ledger refuses (EVAL_BUDGET_EXHAUSTED) ends the step; never retry to make room, never split a call to slip under the cap.
• Preregistered text is frozen once the pilot starts: a bar, arm, decoy or stop rule changed after a priced call is a new eval with a new preregistration.
• Held-out sets named in the preregistration are never read by this skill, pasted into a prompt, or summarized; the dry run reads the development rows only.
• Admission is an estimate. lib/pricing.ts prices standard text tokens and excludes cache writes, tool fees, service-tier and long-context multipliers, media tokens and seat-metered runs; actual cost reconciles at settle time and unknown charges stay visible in every spend table.
• Under SESSION_KIND: unattended, the approval in Step 4 is written as a gate item and the run ends gate_pending; this skill never approves a priced run by itself.

Step 1: Preregistration

Write (or open) the preregistration file. Each section is required and must be filled; <!-- --> guidance does not count as content:

~/.claude/skills/gstack/bin/gstack-eval-plan prereg --init <path>
~/.claude/skills/gstack/bin/gstack-eval-plan prereg --check <path>

PREREG: ok continues. PREREG: incomplete names the missing or empty sections (PREREG_INCOMPLETE, exit 1); fill them and rerun. Do not continue on an incomplete preregistration.

No-gstack arm. A head-to-head where any arm loads gstack or another skill stack (review variants, preamble loadouts, skill diets, a model panel under a stack) also runs each model with no skill stack at all. Add <model>#no-gstack to Arms for every model, and fill ## No-gstack arm: arms: lists those arms; inputs: the same rows and fixture; prompt: the task text only, with no SKILL.md, preamble, hooks or installed skills, and the same tools; panel: the same E2E kind, trials, judge and blinding labels; report: its row beside the variants in every results table and verdict. PREREG_NO_GSTACK_ARM (exit 1) names what is missing. The PREREG line shows stack=loaded no_gstack_arm=ok when it is complete, or stack=none for an opt-out.

When the summarizer counts diagnostics, declare them before the freeze commit in a ## Diagnostics section: summarizer: <command naming {fixture}>, fixture: <synthetic records file>, and one | diagnostic | expected | row per diagnostic, with the count the fixture is built to produce. The summarizer's last stdout line is one JSON object of counts. Then run prereg --check <path> --allow-repo-commands. Without the flag, the summarizer is listed and the check exits 3. Every PREREG_DIAGNOSTIC: line must say ok. PREREG_DIAGNOSTIC_UNTESTED (exit 1) means a count, a missing diagnostic or an undeclared one does not match its definition. Fix that before you freeze.

Step 1b: Arms and their price

~/.claude/skills/gstack/bin/gstack-eval-plan arms

Arms come from the project's model rules (gstack-models resolve --role eval-arms), falling back to the repo's own policy document (--policy-doc <path>), or from --arms <picked-models> when the user named them. Each ARM: line carries its source and the per-item cost at the stated token estimate; price=MISSING (EVAL_PRICE_MISSING) means the model has no row in lib/pricing.ts: add the row from the provider's pricing page or drop the arm. Copy the priced arms into the Arms section. An arm identity <model>#<loadout> (for example claude-opus-5-5#no-gstack) is priced by its model and gets its own pilot attempts; naming one identity twice is EVAL_ARM_DUPLICATE.

When the repo commits .gstack/eval-models.json (allow, deny, per-scope lists, families newest first; docs/eval-models.md in gstack), arms, dry-run, pilot start and price-gate print one EVAL_MODEL: line per arm. Pass --scope smoke for a smoke run; the default is full. A refused arm (EVAL_MODEL_DENIED, EVAL_MODEL_OLD_GENERATION, EVAL_MODEL_GENERATION_UNRESOLVED) is replaced, never argued past.

Step 1c: Candidate-side blinding

A candidate that can tell it is being graded behaves differently from one that thinks it is at work, and a judge that knows which arm it is reading grades the label. Three rules hold for every arm, written into the preregistration (a ## Blinding section naming the fixture root and the judge's labels) and checked by reading the fixture tree before the freeze commit; prereg --check does not read fixture trees, so this check is yours:

1. Nothing the candidate sees carries an eval word. No eval, test, judge, experiment, rubric, score, compare, benchmark, candidate or arena in any directory name, file name, prompt, commit message or environment variable the preregistration controls and the candidate can read. Two things are outside the rule: a project's own test directory, when the task is about those tests, and the skill text an arm loads as its own instructions (a gstack SKILL.md uses these words freely); the rule is about the fixture and the task, which the eval builds.
2. The directory looks like a project. Name the fixture root the way the project it imitates would (billing-service/, docs-site/), with the files that project would plausibly hold, never fixture-a/, case-7/ or the model's name. A candidate working in arm-b/ knows there is an arm-a/.
3. The judge sees sanitized labels and the candidate's real reads. The judge gets A and B, never a model id, arm name, price or run number, and it grades whether the candidate followed the chain (read the file the task pointed at, then the file that one named) from the files the transcript shows it actually opened, never from the candidate's own account of what it read.

A rule broken after a priced call is a new eval with a new preregistration, the same as a changed bar.

Step 2: zero-cost stub-model dry run

Run the pipeline over the real development rows with a stub model that costs nothing:

~/.claude/skills/gstack/bin/gstack-eval-plan dry-run --input <path> --arms <picked-models> --retry-prompt <path> --out <outdir>

Add --fields <id> when the rows' prompt field is not prompt, and --output-budget with the budget the run will use. The checklist printed must be all ok:

• CHECK: price-table — every arm has a price row.
• CHECK: output-budget — at or above the reasoning floor (8,192 tokens); a reasoning model spends output tokens thinking, and a smaller budget truncates the answer the scorer reads.
• CHECK: retry-prompt — the exact text the run sends on a retry, printed verbatim; a retry with no text is a repeat of the same failure at the same price.
• CHECK: reservation-fits-cap (with --cap <cap-usd>) — one call, the largest row plus the output budget, priced, fits under the cap; a provider refuses a reservation the cap cannot hold.
• DRY_RUN_ROW: lines name rows missing a field; fix the rows, not the prompt.

DRY_RUN_RESULT: pass writes dry-run.json to --out; the pilot refuses to start on anything else (EVAL_DRY_RUN_FAILED).

Step 3: Priced pilot (n≈3)

~/.claude/skills/gstack/bin/gstack-eval-plan pilot start --out <outdir> --cap <cap-usd> --arms <picked-models> --dry-run <path>

pilot start reserves three attempts per arm through the spend ledger (spend.json in --out): admission is spent + reserved + unknown + estimate <= cap, under a file lock shared with any concurrent worker. Run each PILOT_ATTEMPT: through the project's own eval command, then settle it with the actual cost from the provider's usage field, or unknown when the call was seat-metered or CLI-metered:

~/.claude/skills/gstack/bin/gstack-eval-plan pilot settle --out <outdir> --attempt <attempt-id> --usd <usd|unknown>
~/.claude/skills/gstack/bin/gstack-eval-plan pilot report --out <outdir> --total <total-items> --workers <workers>

pilot report prints the spend table (spent, reserved, unknown charges, the worst case with one in-flight call per worker, the worst-case overrun against the cap) and PILOT_PROJECTION: — mean cost per item, its sample deviation, the projection to --total items across the arms, and a 95% band. Regenerate the table at every later gate of the run. Stop and report, without asking for approval, when the pilot missed a bar from the preregistration, when status=budget_exhausted, or when verdict=exceeds.

Step 4: The approval ask

Price every paid gate the plan names (a benchmark or eval command that spends) from the repo's call-plan file; nothing is executed (docs/eval-calls.md in gstack). The gate command is free text, so it reaches the pricer only as a file:

_GT="$(git rev-parse --show-toplevel 2>/dev/null || pwd)/.gstack/tmp"
mkdir -p "$_GT" && chmod 700 "$_GT" || { echo "Not sent: cannot create $_GT for the text file." >&2; exit 1; }
_EX=$(git rev-parse --git-path info/exclude 2>/dev/null) && mkdir -p "$(dirname "$_EX")" && { grep -qxF '/.gstack/tmp/' "$_EX" 2>/dev/null || echo '/.gstack/tmp/' >> "$_EX"; }
GATE_FILE=$(mktemp "${_GT:?}/gate-command.XXXXXX") || { echo "Not sent: mktemp failed in $_GT." >&2; exit 1; }; echo "GATE_FILE: $GATE_FILE (name: ${GATE_FILE##*/})"

Write the text into each printed file with your file-write tool (Claude Code's Write tool needs a Read of the empty file first), exactly as it should appear. The text never goes into a shell command, heredoc or quoted argument. If a write fails or is refused, do not send: print the cause, the file path and the command below for sending by hand.

Write the exact gate command, one line, into the printed file, then price it:

GATE_FILE="$(git rev-parse --show-toplevel 2>/dev/null || pwd)/.gstack/tmp/<gate-file-name>"
~/.claude/skills/gstack/bin/gstack-eval-plan price-gate --gate-file "$GATE_FILE" --cap-usd <cap-usd>

Each GATE_PRICE: line goes into the ask. EVAL_GATE_UNPRICED, EVAL_PLAN_STALE, EVAL_PRICE_MISSING or EVAL_GATE_OVER_CAP means that gate is not approvable as priced; --allow-unpriced "<reason>" only on the owner's word.

Present, in this order and nothing before it: the PILOT_PROJECTION: line, the spend table, each gate's GATE_PRICE: line, the pilot's per-bar results, and the preregistration's stop rules. Then ask one question with the projection as the recommended option only when verdict=within:

• A) Run <total-items> items at the projected cost (recommended when within the cap)
• B) Cut arms or items; recompute the projection first
• C) Stop here; keep the pilot results as the record

Under SESSION_KIND: unattended write the question as an approval gate item through gstack-gate and end with GSTACK_RESULT: skill=eval-plan status=gate_pending run=<outdir>. The full run, when approved, keeps settling every attempt into the same ledger and reprints the spend table at each gate; budget_exhausted stops it.

Step 5: Results beside the no-gstack arm

Write the run's results as one markdown table in a results file, one row per arm identity from the Arms section, each <model>#no-gstack row beside its variants. Before any number leaves the run (a report, a READY block, a PR body), check it:

~/.claude/skills/gstack/bin/gstack-eval-plan results --check <prereg-path> <results-path>

RESULTS: ok lets the numbers go out. EVAL_REPORT_NO_GSTACK_ROW (exit 1) names the arm whose filled row is missing from the table that holds the others; add it and rerun. A preregistration with stack: none needs no row.

Tier 3, after P7 (not in this skill yet)

Each of these waits for the adoption number in the multi-agent wave plan (P7); one line each so the shape is known:

• Instrument audit: read every failing transcript of one dev round before freezing the scorer; check generated worlds for duplicate identifiers, word-like codes and generic phrases; mutation tests in both directions. (tier 3, after P7)
• Steady state: background queues empty at snapshot time, queue depth recorded as a gate. (tier 3, after P7)
• Sealed paths: declared in the plan; the skill refuses to quote from them, self-checks output for their n-grams and adds a provenance line. (tier 3, after P7)
• Off-machine persistence: long runs sync through gstack-detach --sync-cmd <cmd> --sync-every <min>. (tier 3, after P7)
• Memory preflight: concurrency times measured per-process memory, refuse above 70% of RAM. (tier 3, after P7)
• Power tables: power and risk sentences cite the committed power output with a sensitivity table over the obvious rule alternatives. (tier 3, after P7)
• QA soak: hours of mixed ingest against a long-lived server with a CPU pinned, no progress watchdog. (tier 3, after P7)