Run task evals across multiple Claude models, compare results side-by-side, and optimise. Use when you want to benchmark a skill across models, compare haiku vs sonnet vs opus performance, run multi-model comparison or benchmark reports, identify model-specific gaps versus universal plugin gaps, evaluate whether a skill works for all model tiers, or validate a skill before publishing it to the registry.
Run task evals across multiple Claude models, compare results side-by-side, and optimise. Use when you want to benchmark a skill across models, compare haiku vs sonnet vs opus performance, run multi-model comparison or benchmark reports, identify model-specific gaps versus universal plugin gaps, evaluate whether a skill works for all model tiers, or validate a skill before publishing it to the registry.
Review Model Performance
Models tested by default:claude-haiku-4-5, claude-sonnet-4-6, claude-opus-4-6 (cheapest to most capable)
Eval command:tessl eval run <path/to/plugin> --agent=... --label <run-label>
Run labels
Every tessl eval run invocation MUST include --label <run-label> so the run is identifiable in tessl eval list. The label is a short, human-readable description of what the run is about — not a structured ID.
Compose <run-label> from whatever helps you recognise the run later when scanning the list. Typical ingredients:
Eval type — e.g. activation, baseline, initial evals, verification
What was being tested or changed — e.g. description rewrite, plan-solution fixes, clean scenario
Model in parens, when comparing models — e.g. (haiku-4-5), (sonnet-4-6)
Version when iterating — e.g. v0.5.0, v4
Examples:
repro-clean-scenario
task-prep v0.3.0 baseline
task-prep v0.5.0 plan-solution fixes
v4-final-verification
skill-insights activation (haiku-4-5)
skill-insights initial evals (haiku-4-5)
Keep it concise — what the run was about should be obvious without opening it.
Phase 1: Identify the plugin
1.1 Find the plugin
Look for a plugin manifest (.tessl-plugin/plugin.json) in the current directory or a parent/sibling directory. Exclude .tessl/ cache directories:
If the user provides a path inside a .tessl/plugins/ directory (an installed plugin cache), stop and warn them: that path is Tessl's local install cache — running evals from there won't work and changes would be overwritten on the next tessl install. Offer two options: point to the original plugin source, or copy the plugin out of .tessl/plugins/ to a new location (cp -r .tessl/plugins/<workspace>/<plugin> ./<plugin>).
If multiple plugins are found outside .tessl/, ask the user which one to evaluate. If none are found, explain that this skill evaluates a packaged plugin and suggest tessl plugin new to get started.
1.2 Verify eval scenarios exist
ls <plugin-dir>/evals/*/task.md 2>/dev/null
If no scenarios exist, inform the user and provide the quickest path to generate them:
Note that scenario generation takes roughly 1–2 minutes per scenario. Also mention the setup-skill-performance skill for a guided walkthrough.
If scenarios exist, read the task.md from each scenario directory and list them:
Found N scenarios:
- <scenario-slug>: <one-line description from task.md>
- <scenario-slug>: ...
1.3 Verify login
tessl whoami
If not logged in, ask the user to run tessl login before continuing.
Phase 2: Confirm run configuration
2.1 Models
Confirm the default model set with the user: claude-haiku-4-5 (fast/cheap), claude-sonnet-4-6 (default), claude-opus-4-6 (most capable). This runs 3 sequential eval jobs. Each scenario takes roughly 10–15 minutes per model, so with N scenarios expect around N×30–45 minutes total. Ask whether to proceed with all three or a subset.
2.2 Number of runs
Ask whether to run each scenario once (default, good for a first pass) or three times (recommended before publishing — triples the time but gives more stable averages). Remind the user of the time implications given N scenarios and 3 models.
If they choose more than 1, add --runs=<n> to all eval run commands in Phase 3.
Phase 3: Run evals across models
Run models one at a time, fully completing each before starting the next. Do NOT start multiple eval runs back-to-back — even without bash & or background jobs, kicking off all three then polling them causes them to execute concurrently on the server, which inflates cost and creates noisy interactions between runs.
For each model in your chosen set, in order:
Start the eval:
tessl eval run <path/to/plugin> --agent=claude:<model> [--runs=<n>] --label <run-label>
Capture the eval run ID from the output (Eval run started: <id>). Store it mapped to the model name for Phase 5.
Share the browser monitoring URL with the user (https://tessl.io/eval-runs/<id>).
Poll this run to completion (see Phase 4) before looping to the next model.
Update the user as each model finishes (e.g., "✔ haiku complete (<id>). Starting sonnet…").
Phase 4: Poll for completion (per model)
For the current model's run, poll with tessl eval view <id> every few minutes until you see Status: ✔ Completed or Status: ✖ Failed. Only then loop back to Phase 3 to start the next model.
If a run fails, retry it:
tessl eval retry <id>
Once every model in the chosen set has reached Completed, proceed to Phase 5.
Phase 5: Collect and compare results
Fetch full results for each run:
tessl eval view <id> --json
Parse both the baseline (without skill) and with skill scores for every scenario and criterion.
5.1 Overall summary table
Model Comparison — <plugin-name>
Model Without Skill With Skill Delta
─────────────────────────────────────────────────────────────
claude:claude-haiku-4-5 XX% YY% +ZZpp
claude:claude-sonnet-4-6 XX% YY% +ZZpp
claude:claude-opus-4-6 XX% YY% +ZZpp
5.2 Per-scenario breakdown
For each scenario, show its name, a one-line description (from task.md), and both scores per model:
Scenario: <slug>
What it tests: <description>
Model Without Skill With Skill Delta
─────────────────────────────────────────────
haiku XX% YY% +ZZpp
sonnet XX% YY% +ZZpp
opus XX% YY% +ZZpp
Before discussing the skill's impact, note what the without-skill scores reveal: high baselines (≥80%) mean the skill adds little; low baselines (<50%) are where the skill earns its place; baselines that diverge across models indicate which tier benefits most from the skill.
6.2 Classify failing criteria
For criteria that score poorly (with skill):
"Universal Failure" pattern (all models fail): Plugin gap — instructions are missing, ambiguous, or conflicting. Highest priority.
"Capability Gradient" pattern (haiku fails, sonnet/opus pass): Instructions too implicit for weaker models. Fix: simpler, more explicit phrasing.
"Regression" pattern (without-skill outperforms with-skill): The skill is actively confusing the model. High priority regardless of which model it affects.
6.3 Model recommendation
Give a plain-language summary of the combined baseline + with-skill picture for each model, calling out which scenarios show the largest delta, any regressions, and whether the skill is earning its place across the tested model range.
Phase 7: Recommend next steps
If regressions exist on any model: Recommend fixing before publishing. Suggest running the optimize-skill-performance skill against the affected run IDs.
If haiku-specific gaps only: Note that the skill works well for sonnet and opus users, and offer to suggest specific wording changes to simplify instructions for haiku.
If all models score well (≥ 80% with skill):
tessl plugin publish <path/to/plugin>
If results are variable / runs=1 was used: Recommend re-running with --runs=3 before publishing to average out variance.
Always offer: "Want me to re-run the comparison after any fixes to verify improvement?"
When to stop
Stop when:
The comparison tables, per-scenario breakdown, and diagnosis have been presented
The user has a clear picture of which scenarios/criteria need attention and for which models
The user has decided on next steps (fix → re-run, or proceed to publish)
