Jonathan Tollefson
Design Engineer
jtollefson123@gmail.com (614) 403-4845 linkedin.com/in/jtollefson123 Minneapolis, MN
SUMMARY
Design engineer working the seam between interface design, front-end, and applied AI. Sole designer, builder, and shipper of an agentic audio-mastering system. Building it ran me into a known failure mode of these systems: the evaluator, not the model, sets the ceiling on quality, so I stopped trying to make the model learn my taste and put the work into the evaluation instead. Six-plus years before that across enterprise AI and BI products, B2B SaaS, and a bilingual mobile banking launch, designing with engineers rather than handing off to them.
SELECTED BUILDS
The Engineer
2026 – PresentAI mastering agent
- Built an AI mastering system that works as an agent, not a button: it takes actions and carries state across a multi-step run, rendering several masters across taste axes, running a blind, loudness-matched A/B (ITU-R BS.1770, true-peak controlled), weighing the votes, and composing a final master from the winning takes, with a grounded reasoning step deciding whether to blend extra processing layers. live · the agent loop
Render, judge, decide. One pass.
- Render 6 masters across taste axes
- Blind A/B loudness-matched, labels hidden
- Weigh votes votes become win-rates
- Crown a king composed from the winning takes
- Decide layers grounded check, usually no
0 renders · 0 blind round · 0 king · idle -
- Built an active-learning model that learned my taste and steered masters toward it, then shelved it: under a blind, loudness-matched A/B it was overfitting a biased evaluator, the known reward-model overoptimization failure. live · the evaluation
The judge was overfitting. The audio was not improving.
so I shelved it and rebuilt the judge: blindloudness-matchedgated vs doing nothing - Put the work into the judge instead: a blind, loudness-matched harness that gates any change against a null baseline of doing nothing. Results so far are single-rater, and a multi-rater blind run is the gate before I claim more.
- Designed, built, and shipped end to end with no handoffs: interaction design, front end (Astro, React, TypeScript), and backend (Python, FastAPI).
The Console
2026 – PresentAudio catalog and search
- Built a personal catalog of roughly 20,000 audio files, read by sound, fingerprinted, deduplicated, and auto-classified through a Whisper, Claude, and librosa pipeline, then made searchable. Sole engineer across ingestion, classification, and interface.
EXPERIENCE
CHS Inc.
August 2023 – PresentBusiness Analyst, AI & BI Engineering
- Designed and prototyped interfaces for enterprise AI and BI products, embedded with engineering on consumer agri-tech tools and internal AI tooling, where the interface had to make a model's output legible and usable.
- Designed a FigJam-based documentation and alignment system adopted as the cross-team default across product, engineering, and business.
- Built and shipped a Python tool that parses the dbt API manifest and fans model lineage into Excel, Power BI, and stakeholder briefs in one pass; designed the output, wrote the implementation, and owned it end to end for business users, engineers, and the internal AI team. live · the actual tool
One dbt manifest, fanned into three documents
manifest.json · sample project stg_ordersstg_customersstg_paymentsint_order_itemsfct_ordersdim_customersreadyparse_manifest.pylineage.xlsx modeldepends_ondocs fct_ordersint_order_items✓ dim_customersstg_customers✓ int_order_itemsstg_orders✓coverage.pbix brief.md fct_orders joins orders to customers; owned by Data Platform.
Upstream: 3 models. Refresh: hourly. 12 columns documented.
for: business · engineering · AI team
0 models parsed · 0 columns documented · 0 output formats
Raylu, Inc.
April – October 2023Product Designer (Freelance)
- Designed and prototyped the interface, component set, and interaction model for a B2B SaaS AI chat platform, from visual identity through working Figma prototypes, specified so the patterns mapped 1:1 to the React implementation. live · one system, design and code
Change one token. Everything follows.
accent / 500radius / md● VerifiedButton / Primary▾Button / Primarycomponent▾Auto layout · H 40 · pad 16Fill · accent/500Corner · radius/mdLabel · "Get started"<Button variant="primary" size="md"> Get started </Button> // fill: accent/500 radius: radius/mdSame names on both sides. The design file and the React component read from one token, so a rename never drifts.
- Ran the roadmap for a distributed team shipping prototype releases on a tight cycle, prototyping and iterating against each release.
Crediverso
February 2021 – January 2023UX Design Lead
- Designed the primitives, interaction patterns, and onboarding flows for a bilingual mobile banking V1, shipped on iOS.
- Ran usability testing with 50+ participants; iterated the primary flow and bounce dropped 15%. live · the research result
Watch the primary-flow bounce drop 15 points
primary onboarding flow · before Open100%Onboard84%Verify71%Complete40% bounce60%0+ participants tested recruiting…0pt drop bounce on the primary flow0+ tested · bounce 0% to 0% · 0 points fewer drop - Designed and ran the pre-launch growth program, growing the channel 125% (700 to 2,100 followers) on A/B-tested messaging. live · the actual growth
700 to 2,100 followers, pre-launch and organic
700 followers+125%0 weeks pre-launch · all organic · A/B tested messaging
EDUCATION
Harvard University — Cambridge, MA
2015 – 2022B.A. Sociology · Minors in Marketing & Creative Design
Dean's List (6×), Rosenkrantz Discovery Grant Recipient
University of Minnesota — Minneapolis, MN
2016 – 2018Product Design, Business Marketing Education
TOOLS
OUTSIDE
Substack at Diary of a Soundbender, on sound and product design. Track and field record holder, University of Minnesota.