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Voyager vs Fathom
The product boundary between empirical scenario evaluation and predictive fleet analysis.
🧭 Voyager vs Fathom
One of the easiest ways to confuse Skill Harbor's evaluation story is to blur Voyager and Fathom together.
They are related, but they do different jobs.
Short version
- Voyager measures what happens in a scenario.
- Fathom analyzes what is likely to help or hurt before or across those scenarios.
That distinction should stay intact even when Voyager adds deterministic benchmark packs.
Voyager: empirical scenario evaluation
Voyager is the place for questions like:
- Did the skill-enabled path outperform the no-skills path?
- Did the agent invoke the expected tools?
- Did the scenario pass or fail?
- What trace did the run produce?
- Can this evaluation be reproduced in CI?
So Voyager owns:
- scenario execution
- branch comparison
- traces
- assertions
- pass/fail outcomes
- benchmark-pack results
Fathom: predictive and audit analysis
Fathom is the place for questions like:
- Is this fleet too large or too noisy?
- Are skills colliding semantically?
- Is the routing surface too vague?
- How much context bloat is this adding?
- Which skills look risky or promising before deeper evaluation?
So Fathom owns:
- heuristics
- token/context analysis
- contract validation
- routing-risk signals
- fleet-wide reports
- predictive usefulness guidance
Why benchmark packs still belong in Voyager
It may feel surprising that offline deterministic packs are still a Voyager feature.
But the important boundary is not:
- online = Voyager
- offline = Fathom
The real boundary is:
- scenario outcomes = Voyager
- predictive audit = Fathom
A deterministic benchmark pack still asks a Voyager question:
what happened in this scenario, and how did the with-skills branch compare to the without-skills branch?
That is still empirical evaluation, even when the evaluation is fixture-driven and reproducible in CI.
How they should work together
The intended flow is:
- Govern the fleet with Skill Harbor
- Inspect and predict with Fathom
- Measure scenario outcomes with Voyager
- Feed what you learn back into fleet refinement
In other words:
- Fathom helps you decide what looks worth evaluating or trimming.
- Voyager tells you what the scenario evidence actually says.
A practical rule
If a command produces:
- scenario traces
- branch outcomes
- assertion results
- uplift/regression evidence
it belongs in Voyager.
If a command produces:
- heuristics
- token/collision reports
- probabilistic routing confidence
- fleet-level recommendations
it belongs in Fathom.
Non-goal of Voyager benchmark packs
Voyager benchmark packs should not become:
- fleet health scores
- heuristic usefulness scores
- predictive deployment recommendations
Those belong in Fathom.