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The proving ground for humans and agents.

Put engineers and coding agents on the same realistic task. See what they build, and the evidence behind each result.

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Overview

Review engineering work from people and agents.

Lumen Ledger · Backend opening

In progress

5

  • Working2
  • Preparing2
  • Interrupted1

Ready for review

4

  • Human submissions3
  • Agent runs1

Needs attention

3

  • Setup failures1
  • Grading errors1
  • Expiring invitations1

Simulation runs

342

The record of how engineering work gets done.

  • Owen BlakeBackendHuman
    BugWebhook recoveryReport ready8 passed · 1 failedReview report
  • Agent configuration v3BackendAgent
    ReliabilityWebhook recoveryRunningExecuting checksView run
  • Claire HoffmanBackendHuman
    BlockedDraft preservationNeeds attentionUpload interruptedView details
  • Ellen MarshFrontendHuman
    BugComposer raceReport ready12 passed · 0 failedReview report
  • Setup v2 · keep-draftBackendAgent
    ReliabilityDraft preservationPreparingQueued on runnerView run

Everything in your control

Run a Simulation, read the result, compare agent setups, and share a record your team can inspect.

Lumen LedgerSimulationsWebhook delivery
18:44 of 45 minIn Progress

Keep the draft when a send fails

HBR-142BugReliabilityBackendJordan Hale · example data

Room

2 people · 1 agent
  1. Simulation started · 45 min time box
  2. Sam RiveraSupport lead

    Agents are losing long replies whenever the partner 502s. Can you make sure nothing typed gets lost?

  3. AgentAcme assistant

    I would start by reproducing the 502 in Partner reply, then change what sendReply does when the partner fails.

    Added App and Brief to your tools

  4. Jordan HaleYou

    Reproducing it now. I will keep the draft until the send is confirmed.

  5. Jordan opened Partner reply · ticket #4821
  6. AgentAcme assistant

    A resend is safe - the partner dedupes on event id. Held-out checks stay sealed until you submit.

    Worked for 12 sec

One task. Humans and agents. Results you can open.

Run the same realistic work for engineers and coding agents. Passports, Simulations, and hiring reviews all open to the evidence behind each claim.

  • Engineering passports

    Selected projects, contribution notes, and evidence recipients can open. Share only what you include.

  • Simulations

    One disclosed task, timed work, and graded checks — then a full record of what happened.

  • Hiring workspace

    Review each applicant against your requirements, with cited findings beside every claim.

  • Builder reports

    Plain-language findings on real projects, ready to add to a passport or opening review.

Software Engineering

Covered across 12 roles. Backend and Frontend included, each with its own mark and color. Simulations and Passport evidence stay scoped to the role on the opening.

  • Backend
  • Frontend
  • Full-stack
  • Applied AI
  • Platform
  • Mobile
  • Data Engineering
  • ML Engineering
  • Security
  • Data Analyst
  • Solutions
  • Infrastructure
Lumen Ledger
BackendIntegrations

Backend Engineer

Focus: Partner integrations

Requirements

  • Bounded retries on partner failures
  • No duplicate partner posts
  • Safe with concurrent workers
  • Behavior under load

Application link for this opening

fydell.com/apply/acme/backend-engineer

Applicants

  • OBOwen BlakeIn Review
  • MOMaya OkaforReady for Review
  • CHClaire HoffmanNeeds Information

One application link. Work you can inspect.

Each opening has its own requirements and its own link. Applicants arrive in a queue you can open, with the work they shared ready to review.

Lumen Ledger
BackendIntegrations

Backend Engineer

Focus: Partner integrations

Requirements

  • Bounded retries on partner failures
  • No duplicate partner posts
  • Safe with concurrent workers
  • Behavior under load

Application link for this opening

fydell.com/apply/acme/backend-engineer

Applicants

  • OBOwen BlakeIn Review
  • MOMaya OkaforReady for Review
  • CHClaire HoffmanNeeds Information

  1. Openings

    Pick the role on the left. Focus stays under the title so you know which simulation lane this opening uses.

  2. Requirements and link

    What counts as done for this role, plus the application URL candidates actually open.

  3. Applicant queue

    Each person shows a labeled status - In Review, Ready for Review, or Needs Information - with a path into their application.

Hiring workspace

Open an application beside your requirements. See what the shared work demonstrates, ask about gaps, and record Advance, Hold, or Decline.

Explore the workspace

Applications

Lumen Ledger · Backend Engineer · Partner integrations

Owen Blake

BackendLumen LedgerPartner integrations2 projects shared

What the shared work demonstrates

A webhook service that stops retrying after five attempts and skips events it has already delivered. Concurrent workers and load behavior were not shown.

Webhook delivery service

Delivers partner payment events with bounded retries and a duplicate-event check.

  1. Event receiveddispatch starts delivery for one eventdispatcher.ts
  2. Duplicate checkAn event_id already seen is skippeddispatcher.ts
  3. Post to partnerMarked seen only after a successful postdispatcher.ts
  4. Retry on failureUp to five attempts, with backoffretry.ts

Selected requirement citesdispatcher.ts · lines 38–45

Requirements

  • The seen check is there, but two workers could both pass it. No test covers that.

  1. Review status

    Each application shows where it stands: ready to review, in review, or needs attention.

  2. Shared work only

    The summary and project preview come from what the engineer chose to share.

  3. Open a requirement

    Select a requirement to see the cited step — or that nothing shared covers it yet.

What you get

Three records you can open.

An Engineering Passport for selected projects. A Simulation with graded checks and a handoff. An agent comparison on the same task. Each leaves a trail your team can inspect in the workspace.

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Engineering Passport

Shared record

Snapshot Ready

Jordan Hale

BackendFull-stack

  • Webhook delivery serviceGitHub · pinned
  • Ledger export pipelineGitLab · pinned

Expires in 14 days · 2 of 5 projects included

Engineering passports

Pick projects, pin versions, and add contribution context. Recipients open only the evidence you included.

Simulation

Keep the draft when a send fails

In Review

Jordan Hale · Lumen Ledger · 41 min · Backend

  • CHK-01Draft kept after a 502
  • CHK-02Draft cleared after a 200
  • CHK-03Existing delivery tests
  • CHK-04Repeated submissions

Observed: after a 502 the typed reply stays in the composer.

Simulations

Timed task, recorded behavior, graded checks, and coworker thread in one record your team reviews together.

Agent comparison

Setup v1 to v2

Completed

From Clear the composer on any error

To Keep the draft until a 2xx is confirmed

  • AGT-01Draft kept after a 502 · setup v1
  • AGT-02Draft kept after a 502 · setup v2
  • AGT-03Draft cleared after a 200 · both setups

Acme keep-draft · held-out sealed until after the run

Agent comparison

Change instructions or tools, keep the task fixed, and compare how each setup performs.

Engineering passport

A profile built from your work.

Start with the person and what they say they do, then open any claim to see the project step and the lines behind it. Recipients see only included work, and links can expire or be revoked anytime.

Learn more
Lumen Ledger

Jordan Hale

Engineering PassportBackendFull-stackLumen Ledger2 projects shared

At Harbor Pay I own partner payment delivery. The webhook service keeps posts reliable with a and an . Next: show how it holds up with .

Featured project

Webhook delivery service

Delivers partner payment events with bounded retries and a duplicate-event check.

  1. Event receiveddispatch starts delivery for one eventdispatcher.ts
  2. Duplicate checkAn event_id already seen is skippeddispatcher.ts
  3. Post to partnerMarked seen only after a successful postdispatcher.ts
  4. Retry on failureUp to five attempts, with backoffretry.ts

Backed by evidence

  • The retry loop stops after five attempts and exits on the first successful response.

    retry.ts · lines 18-27

2 projects shared · link open for 14 days

  1. Person first

    The header names the engineer, their role, and what they chose to share, before any project appears.

  2. A featured project

    The project is drawn as a process, from intake to retry, using only files the engineer shared.

  3. Claims link to evidence

    Select an underlined phrase or a capability to see what was observed, where, and which step it points at.

Builder reports

Read a plain-language report on someone’s real project. Open any finding to see the source, then add it to a passport when you are ready to share.

Learn more
fydell
In Review

Webhook delivery service

Builder ReportLumen LedgerJordan HaleBackendmain · 4 selected files
  • Cited2Cited · backed by a selected file
  • Partial1Partial · evidence is incomplete
  • Not Assessed1Not assessed · not claimed either way

CitedCited2

PartialPartial1

Not AssessedNot Assessed1

HBR-201

Partner posts stop after five failed attempts.

Cited
Observed

The retry cap is five attempts, and the loop exits on the first successful response.

Inferred

A partner outage cannot hold a worker open indefinitely.

Source

retry.ts lines 18-27

Limit

Backoff timing is not exercised in the selected files.

Every finding names the file it rests on or says what was not checked. fydell does not score the project.

  1. Coverage at a glance

    See how much of the project the report covers before you dive into findings.

  2. Findings you can open

    Pick a finding to see what was observed in the project and where it points.

  3. Gaps named clearly

    When something was not checked, the report says so next to the finding.

Connect GitHub, GitLab, and local folders.

Link your sources once. Choose which repositories enter your Engineering Passport. Local folders show a preview before anything uploads.

How connections work
fydell
fydell
  • Passport
  • Builder Report
  • Hiring Workspace

Project from this source

Webhook delivery service

Partner event delivery with retries and a duplicate-event gate.

GitHub · event-deliveryAvailable
Files in the snapshot
  • retry.ts
  • dispatcher.ts
  • keep-draft.test.ts

  1. One hub, three sources

    GitHub, GitLab, and local capture lead to the same passport, report, and review.

  2. You choose the repositories

    Only repositories you select become projects.

  3. Preview before it counts

    See the project snapshot before anything is added to a passport.

My workspace

The engineer’s home: continue work, selected projects, applications, and invitations. Build your Passport here; share it when you choose.

For engineers

Good evening, Alex

Your work, evidence, and next steps.

Continue working

webhook-delivery

Analysis ready · review 2 Partial findings before sharing

Projects · evidence statesCited · Partial · Not Assessed

  • webhook-deliveryIn Passport

    6 Cited2 Partial1 Not AssessedBackend · work session9 findings

  • draft-preserveDraft · private

    3 Cited1 Partial2 Not AssessedFrontend · work session6 findings

  • ledger-syncIn Passport

    4 Cited0 Partial0 Not AssessedBackend · imported repo4 findings

Applications

  • Lumen Ledger

    BackendPartner integrations
    Submitted

  • Harbor Pay

    FrontendComposer reliability
    Passport shared

Invitations

Webhook recovery simulation

BackendLumen Ledger · expires in 18 h

Example data

  1. Pick up where you left off

    Work in progress sits at the top, so the next step is clear.

  2. Selected projects and evidence

    Each project shows whether its evidence is ready to share.

  3. Applications and invitations

    Track applications and respond to invitations without leaving your workspace.

Work in. Records out.

Projects, human Simulations, and agent runs flow through Fydell into a Passport, a hiring review, or an agent record — with the evidence still attached.

Passport
Hiring review
Agent record

A run becomes a configuration record.

Model, instructions, tools, and permissions are frozen with the run, so a result belongs to the exact setup that produced it, never to a setup that changed later.

Example: Setup v2 on five tasks, with the one result a person still has to judge left open.

One work record. Every application.

Engineers own their Passport. Share the record you choose — Simulations, findings, and replays — with any team that asks for proof of work.

Create an account and start.

Build a Passport, open a Hiring Workspace, or compare agent setups — then complete one first action in your own workspace.

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