FA-88121 / Inverse kinematics solvers / Open access

Stewart pitch rotation matrix has transposed sine terms · case 01

Positive pitch tilts the platform the wrong way.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Ry is written with -sin in the top-right and +sin in the bottom-left.

THE FAILURE

Ry is written with -sin in the top-right and +sin in the bottom-left.

Unsuccessful approach: Making both sine terms positive is no longer a rotation.

Case contract

Input [A,B,pose,lmin,lmax]: base anchors A and platform anchors B (platform frame), pose [x,y,z,roll,pitch,yaw] in degrees with R = Rz(yaw) Ry(pitch) Rx(roll). Leg i length is |p + R b_i - a_i|. Return lengths rounded to 4, or ["limit", i, length] for the first leg outside the inclusive range [lmin,lmax].

Why this case matters

Inverse kinematics code turns task-space goals into joint commands; a wrong branch, sign, limit or update order sends a real arm to the wrong pose.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    A,B,pose,lmin,lmax=x
    px,py,pz,ro,pi_,ya=pose
    cr,sr=math.cos(math.radians(ro)),math.sin(math.radians(ro))
    cp,sp=math.cos(math.radians(pi_)),math.sin(math.radians(pi_))
    cy,sy=math.cos(math.radians(ya)),math.sin(math.radians(ya))
    Rx=[[1,0,0],[0,cr,-sr],[0,sr,cr]]
    Ry=[[cp,0,-sp],[0,1,0],[sp,0,cp]]
    Rz=[[cy,-sy,0],[sy,cy,0],[0,0,1]]
    mm=lambda P,Q:[[sum(P[i][k]*Q[k][j] for k in range(3)) for j in range(3)] for i in range(3)]
    Rm=mm(Rz,mm(Ry,Rx))
    out=[]
    for i,(a,b) in enumerate(zip(A,B)):
        w=[sum(Rm[r][c]*b[c] for c in range(3)) for r in range(3)]
        v=[px+w[0]-a[0],py+w[1]-a[1],pz+w[2]-a[2]]
        L=math.sqrt(v[0]**2+v[1]**2+v[2]**2)
        if L<lmin or L>lmax: return ['limit',i,round(L,4)]
        out.append(round(L,4))
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['identity pose exact 13', [[[[0, 0, 0], [3, 0, 0], [0, 3, 0]], [[3, 4, 0], [6, 4, 0], [3, 7, 0]], [0, 0, 12, 0, 0, 0], 13, 20]], [13.0, 13.0, 13.0]], ['upper bound exact', [[[[0, 0, 0], [1, 0, 0]], [[3, 4, 0], [4, 4, 0]], [0, 0, 12, 0, 0, 0], 5, 13]], [13.0, 13.0]], ['roll only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[0, 1, 0], [2, 1, 0], [0, 3, 0]], [0, 0, 10, 20, 0, 0], 1, 30]], [10.3846, 10.3846, 11.0564]], ['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['yaw only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 1, 0], [3, 1, 0], [1, 3, 0]], [0, 0, 10, 0, 0, 30], 1, 30]], [10.0995, 10.2766, 10.0801]], ['combined attitude', [[[[1, 0, 0], [-1, 1, 0], [-1, -1, 0]], [[1, 0, 1], [-1, 1, 0], [0, -1, 0]], [0.5, -0.5, 8, 10, -15, 40], 1, 30]], [9.2131, 8.0316, 8.1298]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]]], [['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['yaw only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 1, 0], [3, 1, 0], [1, 3, 0]], [0, 0, 10, 0, 0, 30], 1, 30]], [10.0995, 10.2766, 10.0801]], ['combined attitude', [[[[1, 0, 0], [-1, 1, 0], [-1, -1, 0]], [[1, 0, 1], [-1, 1, 0], [0, -1, 0]], [0.5, -0.5, 8, 10, -15, 40], 1, 30]], [9.2131, 8.0316, 8.1298]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]], ['several legs violate', [[[[0, 0, 0], [5, 0, 0], [0, 5, 0]], [[0, 0, 0], [1, 0, 0], [0, 1, 0]], [0, 0, 4, 0, 0, 0], 4.5, 20]], ['limit', 0, 4.0]], ['short leg first', [[[[0, 0, 0], [1, 0, 0]], [[0, 0, 0], [1, 0, 0]], [0, 0, 2, 0, 0, 0], 3, 10]], ['limit', 0, 2.0]], ['long leg second', [[[[0, 0, 0], [8, 0, 0]], [[0, 0, 0], [0, 0, 0]], [0, 0, 6, 0, 0, 0], 1, 9]], ['limit', 1, 10.0]]], [['identity pose exact 13', [[[[0, 0, 0], [3, 0, 0], [0, 3, 0]], [[3, 4, 0], [6, 4, 0], [3, 7, 0]], [0, 0, 12, 0, 0, 0], 13, 20]], [13.0, 13.0, 13.0]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]], ['several legs violate', [[[[0, 0, 0], [5, 0, 0], [0, 5, 0]], [[0, 0, 0], [1, 0, 0], [0, 1, 0]], [0, 0, 4, 0, 0, 0], 4.5, 20]], ['limit', 0, 4.0]], ['short leg first', [[[[0, 0, 0], [1, 0, 0]], [[0, 0, 0], [1, 0, 0]], [0, 0, 2, 0, 0, 0], 3, 10]], ['limit', 0, 2.0]], ['long leg second', [[[[0, 0, 0], [8, 0, 0]], [[0, 0, 0], [0, 0, 0]], [0, 0, 6, 0, 0, 0], 1, 9]], ['limit', 1, 10.0]], ['yaw with offsets', [[[[3, 0, 0], [-3, 0, 0]], [[1, 0, 0], [-1, 0, 0]], [1, 2, 7, 5, 5, 60], 1, 30]], [7.6314, 7.9865]], ['large pitch', [[[[2, 0, 0], [0, 2, 0], [-2, 0, 0]], [[1, 0, 0], [0, 1, 0], [-1, 0, 0]], [0, 0, 5, 0, 60, 10], 1, 30]], [4.4012, 5.105, 6.0573]]], [['identity pose exact 13', [[[[0, 0, 0], [3, 0, 0], [0, 3, 0]], [[3, 4, 0], [6, 4, 0], [3, 7, 0]], [0, 0, 12, 0, 0, 0], 13, 20]], [13.0, 13.0, 13.0]], ['upper bound exact', [[[[0, 0, 0], [1, 0, 0]], [[3, 4, 0], [4, 4, 0]], [0, 0, 12, 0, 0, 0], 5, 13]], [13.0, 13.0]], ['roll only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[0, 1, 0], [2, 1, 0], [0, 3, 0]], [0, 0, 10, 20, 0, 0], 1, 30]], [10.3846, 10.3846, 11.0564]], ['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['long leg second', [[[[0, 0, 0], [8, 0, 0]], [[0, 0, 0], [0, 0, 0]], [0, 0, 6, 0, 0, 0], 1, 9]], ['limit', 1, 10.0]], ['yaw with offsets', [[[[3, 0, 0], [-3, 0, 0]], [[1, 0, 0], [-1, 0, 0]], [1, 2, 7, 5, 5, 60], 1, 30]], [7.6314, 7.9865]], ['large pitch', [[[[2, 0, 0], [0, 2, 0], [-2, 0, 0]], [[1, 0, 0], [0, 1, 0], [-1, 0, 0]], [0, 0, 5, 0, 60, 10], 1, 30]], [4.4012, 5.105, 6.0573]]], [['upper bound exact', [[[[0, 0, 0], [1, 0, 0]], [[3, 4, 0], [4, 4, 0]], [0, 0, 12, 0, 0, 0], 5, 13]], [13.0, 13.0]], ['roll only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[0, 1, 0], [2, 1, 0], [0, 3, 0]], [0, 0, 10, 20, 0, 0], 1, 30]], [10.3846, 10.3846, 11.0564]], ['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['yaw only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 1, 0], [3, 1, 0], [1, 3, 0]], [0, 0, 10, 0, 0, 30], 1, 30]], [10.0995, 10.2766, 10.0801]], ['combined attitude', [[[[1, 0, 0], [-1, 1, 0], [-1, -1, 0]], [[1, 0, 1], [-1, 1, 0], [0, -1, 0]], [0.5, -0.5, 8, 10, -15, 40], 1, 30]], [9.2131, 8.0316, 8.1298]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]], ['large pitch', [[[[2, 0, 0], [0, 2, 0], [-2, 0, 0]], [[1, 0, 0], [0, 1, 0], [-1, 0, 0]], [0, 0, 5, 0, 60, 10], 1, 30]], [4.4012, 5.105, 6.0573]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
identity pose exact 13	`[13.0, 13.0, 13.0]`	`[13.0, 13.0, 13.0]`	Passed
upper bound exact	`[13.0, 13.0]`	`[13.0, 13.0]`	Passed
roll only	`[10.3846, 10.3846, 11.0564]`	`[10.3846, 10.3846, 11.0564]`	Passed
pitch only	`[10.4619, 11.2908, 10.4619]`	`[9.6202, 8.7617, 9.6202]`	Failed
yaw only	`[10.0995, 10.2766, 10.0801]`	`[10.0995, 10.2766, 10.0801]`	Passed
combined attitude	`[8.7109, 8.5336, 8.1135]`	`[9.2131, 8.0316, 8.1298]`	Failed
roll and pitch	`[6.69, 6.4102, 5.6544]`	`[5.9887, 6.7734, 5.9691]`	Failed

SHA-256 / bd1f1dd382a798865e30704260211cbef50ca4d1e3524fee7aa82f739870784f

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    A,B,pose,lmin,lmax=x
    px,py,pz,ro,pi_,ya=pose
    cr,sr=math.cos(math.radians(ro)),math.sin(math.radians(ro))
    cp,sp=math.cos(math.radians(pi_)),math.sin(math.radians(pi_))
    cy,sy=math.cos(math.radians(ya)),math.sin(math.radians(ya))
    Rx=[[1,0,0],[0,cr,-sr],[0,sr,cr]]
    Ry=[[cp,0,sp],[0,1,0],[sp,0,cp]]
    Rz=[[cy,-sy,0],[sy,cy,0],[0,0,1]]
    mm=lambda P,Q:[[sum(P[i][k]*Q[k][j] for k in range(3)) for j in range(3)] for i in range(3)]
    Rm=mm(Rz,mm(Ry,Rx))
    out=[]
    for i,(a,b) in enumerate(zip(A,B)):
        w=[sum(Rm[r][c]*b[c] for c in range(3)) for r in range(3)]
        v=[px+w[0]-a[0],py+w[1]-a[1],pz+w[2]-a[2]]
        L=math.sqrt(v[0]**2+v[1]**2+v[2]**2)
        if L<lmin or L>lmax: return ['limit',i,round(L,4)]
        out.append(round(L,4))
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['identity pose exact 13', [[[[0, 0, 0], [3, 0, 0], [0, 3, 0]], [[3, 4, 0], [6, 4, 0], [3, 7, 0]], [0, 0, 12, 0, 0, 0], 13, 20]], [13.0, 13.0, 13.0]], ['upper bound exact', [[[[0, 0, 0], [1, 0, 0]], [[3, 4, 0], [4, 4, 0]], [0, 0, 12, 0, 0, 0], 5, 13]], [13.0, 13.0]], ['roll only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[0, 1, 0], [2, 1, 0], [0, 3, 0]], [0, 0, 10, 20, 0, 0], 1, 30]], [10.3846, 10.3846, 11.0564]], ['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['yaw only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 1, 0], [3, 1, 0], [1, 3, 0]], [0, 0, 10, 0, 0, 30], 1, 30]], [10.0995, 10.2766, 10.0801]], ['combined attitude', [[[[1, 0, 0], [-1, 1, 0], [-1, -1, 0]], [[1, 0, 1], [-1, 1, 0], [0, -1, 0]], [0.5, -0.5, 8, 10, -15, 40], 1, 30]], [9.2131, 8.0316, 8.1298]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]]], [['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['yaw only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 1, 0], [3, 1, 0], [1, 3, 0]], [0, 0, 10, 0, 0, 30], 1, 30]], [10.0995, 10.2766, 10.0801]], ['combined attitude', [[[[1, 0, 0], [-1, 1, 0], [-1, -1, 0]], [[1, 0, 1], [-1, 1, 0], [0, -1, 0]], [0.5, -0.5, 8, 10, -15, 40], 1, 30]], [9.2131, 8.0316, 8.1298]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]], ['several legs violate', [[[[0, 0, 0], [5, 0, 0], [0, 5, 0]], [[0, 0, 0], [1, 0, 0], [0, 1, 0]], [0, 0, 4, 0, 0, 0], 4.5, 20]], ['limit', 0, 4.0]], ['short leg first', [[[[0, 0, 0], [1, 0, 0]], [[0, 0, 0], [1, 0, 0]], [0, 0, 2, 0, 0, 0], 3, 10]], ['limit', 0, 2.0]], ['long leg second', [[[[0, 0, 0], [8, 0, 0]], [[0, 0, 0], [0, 0, 0]], [0, 0, 6, 0, 0, 0], 1, 9]], ['limit', 1, 10.0]]], [['identity pose exact 13', [[[[0, 0, 0], [3, 0, 0], [0, 3, 0]], [[3, 4, 0], [6, 4, 0], [3, 7, 0]], [0, 0, 12, 0, 0, 0], 13, 20]], [13.0, 13.0, 13.0]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]], ['several legs violate', [[[[0, 0, 0], [5, 0, 0], [0, 5, 0]], [[0, 0, 0], [1, 0, 0], [0, 1, 0]], [0, 0, 4, 0, 0, 0], 4.5, 20]], ['limit', 0, 4.0]], ['short leg first', [[[[0, 0, 0], [1, 0, 0]], [[0, 0, 0], [1, 0, 0]], [0, 0, 2, 0, 0, 0], 3, 10]], ['limit', 0, 2.0]], ['long leg second', [[[[0, 0, 0], [8, 0, 0]], [[0, 0, 0], [0, 0, 0]], [0, 0, 6, 0, 0, 0], 1, 9]], ['limit', 1, 10.0]], ['yaw with offsets', [[[[3, 0, 0], [-3, 0, 0]], [[1, 0, 0], [-1, 0, 0]], [1, 2, 7, 5, 5, 60], 1, 30]], [7.6314, 7.9865]], ['large pitch', [[[[2, 0, 0], [0, 2, 0], [-2, 0, 0]], [[1, 0, 0], [0, 1, 0], [-1, 0, 0]], [0, 0, 5, 0, 60, 10], 1, 30]], [4.4012, 5.105, 6.0573]]], [['identity pose exact 13', [[[[0, 0, 0], [3, 0, 0], [0, 3, 0]], [[3, 4, 0], [6, 4, 0], [3, 7, 0]], [0, 0, 12, 0, 0, 0], 13, 20]], [13.0, 13.0, 13.0]], ['upper bound exact', [[[[0, 0, 0], [1, 0, 0]], [[3, 4, 0], [4, 4, 0]], [0, 0, 12, 0, 0, 0], 5, 13]], [13.0, 13.0]], ['roll only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[0, 1, 0], [2, 1, 0], [0, 3, 0]], [0, 0, 10, 20, 0, 0], 1, 30]], [10.3846, 10.3846, 11.0564]], ['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['long leg second', [[[[0, 0, 0], [8, 0, 0]], [[0, 0, 0], [0, 0, 0]], [0, 0, 6, 0, 0, 0], 1, 9]], ['limit', 1, 10.0]], ['yaw with offsets', [[[[3, 0, 0], [-3, 0, 0]], [[1, 0, 0], [-1, 0, 0]], [1, 2, 7, 5, 5, 60], 1, 30]], [7.6314, 7.9865]], ['large pitch', [[[[2, 0, 0], [0, 2, 0], [-2, 0, 0]], [[1, 0, 0], [0, 1, 0], [-1, 0, 0]], [0, 0, 5, 0, 60, 10], 1, 30]], [4.4012, 5.105, 6.0573]]], [['upper bound exact', [[[[0, 0, 0], [1, 0, 0]], [[3, 4, 0], [4, 4, 0]], [0, 0, 12, 0, 0, 0], 5, 13]], [13.0, 13.0]], ['roll only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[0, 1, 0], [2, 1, 0], [0, 3, 0]], [0, 0, 10, 20, 0, 0], 1, 30]], [10.3846, 10.3846, 11.0564]], ['pitch only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 0, 0], [3, 0, 0], [1, 2, 0]], [0, 0, 10, 0, 25, 0], 1, 30]], [9.6202, 8.7617, 9.6202]], ['yaw only', [[[[0, 0, 0], [2, 0, 0], [0, 2, 0]], [[1, 1, 0], [3, 1, 0], [1, 3, 0]], [0, 0, 10, 0, 0, 30], 1, 30]], [10.0995, 10.2766, 10.0801]], ['combined attitude', [[[[1, 0, 0], [-1, 1, 0], [-1, -1, 0]], [[1, 0, 1], [-1, 1, 0], [0, -1, 0]], [0.5, -0.5, 8, 10, -15, 40], 1, 30]], [9.2131, 8.0316, 8.1298]], ['roll and pitch', [[[[2, 0, 0], [-1, 2, 0], [-1, -2, 0]], [[1, 0.5, 0], [-0.5, 1, 0], [-0.5, -1, 0.2]], [0, 0, 6, 30, 20, 0], 1, 30]], [5.9887, 6.7734, 5.9691]], ['large pitch', [[[[2, 0, 0], [0, 2, 0], [-2, 0, 0]], [[1, 0, 0], [0, 1, 0], [-1, 0, 0]], [0, 0, 5, 0, 60, 10], 1, 30]], [4.4012, 5.105, 6.0573]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
identity pose exact 13	`[13.0, 13.0, 13.0]`	`[13.0, 13.0, 13.0]`	Passed
upper bound exact	`[13.0, 13.0]`	`[13.0, 13.0]`	Passed
roll only	`[10.3846, 10.3846, 11.0564]`	`[10.3846, 10.3846, 11.0564]`	Passed
pitch only	`[10.4619, 11.2908, 10.4619]`	`[9.6202, 8.7617, 9.6202]`	Failed
yaw only	`[10.0995, 10.2766, 10.0801]`	`[10.0995, 10.2766, 10.0801]`	Passed
combined attitude	`[8.6956, 8.5418, 8.1298]`	`[9.2131, 8.0316, 8.1298]`	Failed
roll and pitch	`[6.6629, 6.4384, 5.6334]`	`[5.9887, 6.7734, 5.9691]`	Failed

SHA-256 / e15016fcb0e62c74b7c424993f4de3d323de5bfca35e25cc5093a274dbe4a552

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

Deterministic planar or low-dimensional teaching model with a stipulated convention; not a general robotics library. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:05.200579+00:00.

Case digest / 4f10caf1fdcd29f1ea6e3406d27aadbb14f0576c1b2873165bbc07f6ac89ed49