Schema Changes (Migrating from pre-2026.8.05)

Between the 2026.4.1 and 2026.8.05 releases, YAGSL was rewritten from its own standalone swerve implementation into a thin JSON parser that builds a YAMS SwerveDrive (swervelib.parser.SwerveParser → yams.mechanisms.swerve.SwerveDrive). The JSON configuration schema changed to match what YAMS's config builders need. If your src/main/deploy/swerve/ directory predates this, none of your old JSON files will parse correctly against the new schema — this page is a field-by-field diff to help you port them by hand. For a fresh config, it's easier to just regenerate everything from config.yagsl.com.

This is a breaking change, not an additive one. The parser silently ignores unknown fields (FAIL_ON_UNKNOWN_PROPERTIES = false), so an old file will "parse" without errors but silently drop every renamed/restructured field, leaving you with defaults you didn't intend. Don't assume an old config "still works" just because it loads without an exception — diff it against this page.

`swervedrive.json`

Old (≤ 2026.4.1)

New (≥ 2026.8.05)

Notes

imu: {type, id, canbus}

gyro: {type, id, canbus}

Renamed. Old type values like "pigeon2", "pigeon", "navx" also changed shape — see below.

invertedIMU: boolean

gyroInvert: boolean

Renamed.

(none)

gyroAxis: "yaw"|"pitch"|"roll"

New, optional, defaults to "yaw".

modules: string[]

Unchanged.

Old:

{
  "imu": { "type": "pigeon2", "id": 13, "canbus": "canivore" },
  "invertedIMU": true,
  "modules": ["frontleft.json", "frontright.json", "backleft.json", "backright.json"]
}

New:

{
  "gyro": { "type": "pigeon2_can", "id": 13, "canbus": "canivore" },
  "gyroAxis": "yaw",
  "gyroInvert": true,
  "modules": ["frontleft.json", "frontright.json", "backleft.json", "backright.json"]
}

Note the type string itself changed too — old bare names ("pigeon2", "pigeon", "navx") became explicit <device>_<connection> strings ("pigeon2_can"). See Device Type Strings for the current, complete list.

Module JSON (e.g. `frontleft.json`)

Old (≤ 2026.4.1)

New (≥ 2026.8.05)

Notes

encoder: {type, id, canbus}

absoluteEncoder: {type, id, channel, canbus}

Renamed, and gained a channel field for analog/DIO-connected encoders. type strings changed ("cancoder" → "cancoder_can", etc.) — see Device Type Strings.

absoluteEncoderOffset: number

Unchanged (degrees).

(none)

absoluteEncoderInverted: boolean

New, optional, defaults to false.

drive / angle: {type, id, canbus}

Same shape, but type strings changed to <controller>_<motor> (e.g. "sparkmax_neo" unchanged, but "talonfx" alone became "talonfx_krakenx60" etc. — the motor is now part of the type string).

See Device Type Strings.

(module-level conversion lived only in physicalproperties.json)

gearing: {drive: {gearRatio, diameter}, angle: {gearRatio}} (optional, per-module override)

New: a module can now override the shared gearing without touching physicalproperties.json.

inverted: {drive, angle}

Unchanged.

location: {front, left}

Unchanged (inches).

Old:

{
  "drive": { "type": "sparkmax_neo", "id": 4, "canbus": null },
  "angle": { "type": "sparkmax_neo", "id": 3, "canbus": null },
  "encoder": { "type": "cancoder", "id": 9, "canbus": null },
  "inverted": { "drive": false, "angle": false },
  "absoluteEncoderOffset": -114.609,
  "location": { "front": 12, "left": 12 }
}

New:

{
  "drive": { "type": "sparkmax_neo", "id": 4, "canbus": "" },
  "angle": { "type": "sparkmax_neo", "id": 3, "canbus": "" },
  "absoluteEncoder": { "type": "cancoder_can", "id": 9, "channel": 0, "canbus": "" },
  "inverted": { "drive": false, "angle": false },
  "absoluteEncoderOffset": -114.609,
  "absoluteEncoderInverted": false,
  "location": { "front": 12, "left": 12 }
}

`modules/physicalproperties.json`

Old (≤ 2026.4.1)

New (≥ 2026.8.05)

Notes

conversionFactors: {drive: {gearRatio, diameter, factor}, angle: {gearRatio, factor}}

gearing: {drive: {gearRatio, diameter}, angle: {gearRatio}}

Renamed and simplified — the precomputed factor override is gone; YAMS derives the conversion internally from gearRatio/diameter.

currentLimit: {drive, angle}

statorCurrentLimit: {drive, angle}

Renamed. Defaults are now 40/20 if omitted.

friction: {drive, angle}

(removed)

No longer configurable via JSON.

steerRotationalInertia: number

(removed)

No longer configurable via JSON.

robotMass: number

(removed)

No longer configurable via JSON.

rampRate: {drive, angle}

(removed)

No longer configurable via JSON.

wheelGripCoefficientOfFriction: number

(removed)

No longer configurable via JSON.

optimalVoltage: number

(removed)

No longer configurable via JSON.

Old:

{
  "conversionFactors": {
    "angle": { "gearRatio": 12.8, "factor": 0 },
    "drive": { "gearRatio": 8.14, "diameter": 4, "factor": 0 }
  },
  "currentLimit": { "drive": 40, "angle": 20 },
  "rampRate": { "drive": 0.25, "angle": 0.25 },
  "wheelGripCoefficientOfFriction": 1.19,
  "optimalVoltage": 12
}

New:

{
  "gearing": {
    "drive": { "gearRatio": 8.14, "diameter": 4.0 },
    "angle": { "gearRatio": 12.8 }
  },
  "statorCurrentLimit": { "drive": 40, "angle": 20 }
}

If your old config relied on rampRate, friction, robotMass, steerRotationalInertia, or wheelGripCoefficientOfFriction for simulation fidelity, that modeling now lives inside YAMS/the motor sim itself rather than being team-configurable per robot via this file.

`modules/pidfproperties.json`

Old (≤ 2026.4.1)

New (≥ 2026.8.05)

Notes

p, i, d

Unchanged.

f: number

(removed, replaced by s/v/a)

Old f was a flat feedforward multiplier; the new fields model a proper SimpleMotorFeedforward (kS, kV, kA) instead.

iz: number (integral zone)

(removed)

No longer configurable.

output: {min, max} (clamp)

(removed)

No longer configurable via JSON.

(none)

s, v, a: number (all optional)

New feedforward gains. If drive.v is left 0/omitted, the parser auto-derives kV from the drive motor's free speed.

Old:

{
  "drive": { "p": 0.00023, "i": 0.0000002, "d": 1, "f": 0, "iz": 0 },
  "angle": { "p": 0.01, "i": 0, "d": 0, "f": 0, "iz": 0 }
}

New:

{
  "drive": { "p": 0.5, "i": 0.0, "d": 0.01 },
  "angle": { "p": 2.0, "i": 0.0, "d": 0.1 }
}

You'll need to re-tune from scratch rather than porting old p/i/d values directly — the old gains were tuned against a different internal control loop (raw f/iz) than the new feedforward-based one. See How to Tune PIDF Gains.

`controllerproperties.json` — removed entirely

Pre-2026.8.05 YAGSL read a controllerproperties.json with an angleJoystickRadiusDeadband and a heading: {p, i, d} heading-hold PID, used internally by a swervelib.SwerveController class to build field-relative driving with heading lock. Both the file and the class are gone.

// This file no longer does anything — delete it.
{
  "angleJoystickRadiusDeadband": 0.5,
  "heading": { "p": 0.4, "i": 0, "d": 0.01 }
}

Field-relative/heading-based driving is now built in your own robot code using YAMS's yams.mechanisms.swerve.utility.SwerveInputStream, not a JSON-configured heading PID. See SwerveInputStream reference and the tutorial's driving step for the current pattern.

Hardware support that was dropped, not just renamed

This isn't just a field-rename — some previously-supported gyro and motor-controller hardware has no equivalent type string at all in the current parser (swervelib.parser.deserializer.reflections). If your old config used one of these, there's no direct migration — you need different hardware or a custom fork:

Gyros: the roboRIO-attached NavX2 (navx, navx_spi, navx_i2c, navx_mxp_serial, navx_usb), the original Pigeon (gen 1), and analog SPI gyros (adxrs450, adis16448, adis16470) are all gone. Only pigeon2_can, navx3_can, and canandgyro_can are currently supported. (systemcore_internal is listed in the schema but currently throws "Internal gyro not supported yet!" — don't use it yet.)
Motor controllers: talonsrx and brushed sparkmax_brushed are gone — only the five brushless controller families (talonfx, talonfxs, sparkmax, sparkflex, nova) are supported now, each paired with a brushless motor. See Device Type Strings.

If you're on old gyro/motor hardware that's no longer supported, budget time to swap hardware, not just JSON — this is a real capability change, not a documentation gap.

Behavior changes that aren't JSON fields

Cosine compensation used to be toggleable per-module (useCosineCompensator, default true). It's now always applied by the parser — there's no way to disable it via config.
Deploy directory construction changed from directly instantiating SwerveDrive/module classes to new SwerveParser(dir).createSwerveDrive(new SwerveDriveConfig()...). See Deploy and Drive.

Migration checklist

Regenerate from config.yagsl.com if at all possible — it's faster and less error-prone than hand-porting every field above.
If hand-porting: rename imu→gyro, invertedIMU→gyroInvert in swervedrive.json; add gyroAxis: "yaw".
Rename encoder→absoluteEncoder in every module file, add a channel (usually 0 if CAN), add absoluteEncoderInverted: false.
Update every type string to the new <device>_<connection> convention — see Device Type Strings.
Replace conversionFactors→gearing in physicalproperties.json, dropping any factor override. Replace currentLimit→statorCurrentLimit.
Delete controllerproperties.json; move any heading-lock behavior into robot code via SwerveInputStream.
Re-tune PIDF from scratch using the new p/i/d/s/v/a shape — old gains don't transfer.
Delete any rampRate/friction/robotMass/steerRotationalInertia/ wheelGripCoefficientOfFriction/optimalVoltage fields — they're ignored now.

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swervedrive.json

Module JSON (e.g. frontleft.json)

modules/physicalproperties.json

modules/pidfproperties.json

controllerproperties.json — removed entirely

Hardware support that was dropped, not just renamed

Behavior changes that aren't JSON fields

Migration checklist

`swervedrive.json`

Module JSON (e.g. `frontleft.json`)

`modules/physicalproperties.json`

`modules/pidfproperties.json`

`controllerproperties.json` — removed entirely