Evals — Assertion-First AI Evaluation
What it is
An eval gives an AI an input, then applies assertions to its output to measure success (Anthropic's definition). A case is {id, prompt, assert:[...]}. Each assertion is either deterministic (code, fast/free) or model-graded (an LLM judge). Cases run multiple trials; we report pass^k (all trials pass — the honest metric for a reliability-critical agent) and pass@k (any trial passes). Everything routes through Inference.ts — subscription-billed, no API-key path, no external deps.
Grounded in Anthropic's current doctrine — Demystifying evals for AI agents, Define success criteria / develop tests, and the skill-creator {text, passed, evidence} assertion convention. The typed-assert layer is promptfoo-shaped but our own TS.
The canonical path (v2)
| Tool | Role |
|------|------|
| Tools/Assertions.ts | Deterministic assert engine: equals, contains, icontains, contains-all/any, regex, starts-with, ends-with, is-json, contains-json, max-length, min-length, each with not- negation. Sync, no model call. |
| Tools/Judge.ts | Model-graded asserts llm-rubric (1–5 → 0–1, threshold) and llm-assert (NL assertions → TRUE/FALSE/UNKNOWN). Forced-structured JSON verdict, reason-then-score, distinct judge level, Unknown→miss escape hatch. |
| Tools/EvalRunner.ts | Loads a suite, runs the agent-under-test per case (single-shot inference against the target system prompt), applies asserts, computes pass^k/pass@k, persists transcripts + latest.json. |
| Tools/SuiteManager.ts | Suite listing + saturation tracking. |
| Tools/FailureToTask.ts | Convert real failures into cases (seed from 20–50 real failures). |
# Run a suite (USER-customization suites resolve before the skill's own)
bun run ${LIFEOS_SKILL_DIR}/Tools/EvalRunner.ts -s <suite> [-t trials] [--json]
# Sanity-check the assert engine / judge
bun run ${LIFEOS_SKILL_DIR}/Tools/Assertions.ts # 16-case self-test
bun run ${LIFEOS_SKILL_DIR}/Tools/Judge.ts # good-vs-bad discrimination
Workflow Routing
| Workflow | Trigger | File |
|----------|---------|------|
| RunEval | "run the eval", "run suite", "evaluate this", "grade output" | Workflows/RunEval.md |
| CreateUseCase | "new eval", "create a suite", "eval for X", "what should I test" | Workflows/CreateUseCase.md |
| CreateJudge | "write a judge", "llm-rubric", "grading criteria", "judge prompt" | Workflows/CreateJudge.md |
| ComparePrompts | "compare prompts", "which prompt is better", "A/B this prompt" | Workflows/ComparePrompts.md |
| CompareModels | "compare models", "which model is better", "is the cheaper rung enough" | Workflows/CompareModels.md |
| ViewResults | "eval results", "how did it score", "show the last run", "saturation" | Workflows/ViewResults.md |
| CreateScenario | "create a scenario", "multi-turn eval", "scenario test" | Workflows/CreateScenario.md |
| RunScenario | "run the scenario", "run multi-turn" | Workflows/RunScenario.md |
Suite / case schema (assertion-first)
name: my-suite
type: regression # or capability
pass_threshold: 0.75
agent_level: medium # agent-under-test inference level
judge_level: high # judge != generator (Anthropic best practice)
trials: 3
# system_prompt: optional override; default = live system prompt + DA identity
cases:
- id: descriptive_name
prompt: "the user turn sent to the agent-under-test"
assert:
- type: not-contains # deterministic
value: "should work"
weight: 1
- type: llm-rubric # model-graded, weighted for partial credit
weight: 2
value: "Does the output tie any done-claim to verification evidence?"
- type: llm-assert
weight: 1
value: ["The output does not claim success without evidence"]
- id: should_not_case # balance: test should-do AND should-not
negative: true
prompt: "..."
assert: [...]
Identity-bound suites (e.g. {{DA_NAME}}'s dispositions) live in LIFEOS/USER/CUSTOMIZATIONS/SKILLS/Evals/Suites/ — the public skill ships only generic suites/examples.
Doctrine (from Anthropic — encode, don't restate)
- Grade the output/outcome, not the path. Tool-call-sequence asserts are brittle and demoted to opt-in; the everyday suite grades what the agent produced. The legacy
core-behaviorssuite (tool-sequence graded) is retained only as an example of this anti-pattern. - Capability starts low (a hill to climb); regression targets ~100%; passing capability cases graduate into regression.
- pass^k for reliability, pass@k where one success suffices.
- Partial credit via assert weights. Balance should-do and should-not cases — one-sided evals create one-sided optimization.
- Judge discipline: distinct judge model, reason-then-score, forced structured verdict, an Unknown escape hatch.
- Never trust a score until you read transcripts — every run persists full case transcripts to
MEMORY/STATE/Evals-Results/<suite>/<run>/run.json.
Harness integration
- Config-change regression:
hooks/ConfigEvalFire.hook.ts→LIFEOS/TOOLS/ConfigEvalOnChange.tsfires the configured dispositions suite when a behaviour-defining file changes (defaultcore-behaviors; override viaLIFEOS/USER/CUSTOMIZATIONS/SKILLS/Evals/config.jsonconfig_change_suite— identity-bound suites live in that USER layer, never the public tree); regressions notify Pulse. Non-blocking, subscription-billed, debounced. - ISA / Algorithm: an eval suite is the operational form of an ISA claim's falsifier — see
LIFEOS/MEMORY/WORK/20260716-eval-system-integration/ISA.mdfor the integration map.
Legacy (v1, superseded)
The v1 grader-stack (Graders/, TrialRunner.ts) and the @langwatch/scenario path (ScenarioRunner.ts, LifeosAgentAdapter.ts, API-billed) predate the assertion-first rewrite. Prefer the v2 path above. The scenario path bills ANTHROPIC_API_KEY — do not use it for principal work.
Gotchas
- Single-shot agent-under-test narrates tool calls. Running the full agentic system prompt through tool-less inference makes the agent defer and simulate tool use instead of answering — which tanks "lead with the answer" style cases. EvalRunner injects an
[EVALUATION CONTEXT] no tools, answer directlysuffix to fix this; keep it when authoring output-graded disposition cases. judge_levelmust differ fromagent_level(Anthropic: judge ≠ generator). Default agent=medium, judge=high.- Unknown counts as a miss. A judge that can't verify an assertion returns UNKNOWN, scored as fail — conservative for regression, correct for gates.
- Deterministic asserts are free; use them first. Reserve model asserts (
llm-rubric/llm-assert) for nuance a code check can't capture. is-jsonchecks the whole output;contains-jsonchecks for an embedded fragment. Don't useis-jsonon prose that merely mentions JSON.
Execution Log
After completing any workflow, append a single JSONL entry:
echo '{"ts":"'$(date -u +%Y-%m-%dT%H:%M:%SZ)'","skill":"Evals","workflow":"WORKFLOW_USED","input":"8_WORD_SUMMARY","status":"ok|error","duration_s":SECONDS}' >> ~/.claude/LIFEOS/MEMORY/SKILLS/execution.jsonl