Magic-angle twisted bilayer graphene (MATBG) hosts narrow moiré bands with meV-scale dispersion and energy splittings, making its correlated phases sensitive to both material parameters and modeling choices in low-energy downfolding. We develop an ab initio quantum-embedding workflow that derives interacting flat-band Hamiltonians from Kohn-Sham density functional theory (KS-DFT) of a relaxed, unstrained structure. Our model combines constrained random phase approximation screening, controlled double-counting subtraction, and an automated gauge-fixing procedure based on the selected columns of the density matrix that is compatible with symmetry-resolved many-body calculations. Solving the resulting models using Hartree-Fock and coupled cluster singles and doubles, we recover robust insulating Kramers intervalley coherent states at charge neutrality ($\nu =0$) and at electron doping ($\nu =+2$). The main unique physical effect appears on the hole-doped side: At $\nu =-2$, we observe a fragile semimetal with a weak $\sqrt{3}\times \sqrt{3}$ Kekulé modulation and enhanced intervalley-scattering peaks in the Fourier-transformed local density of states. Although the underlying KS-DFT band structure is nearly particle-hole symmetric, the effective interacting Hamiltonian exhibits a pronounced particle-hole asymmetry at $\nu =\pm 2$ that we trace to momentum-dependent single-particle renormalizations generated by subtraction terms constructed from reference densities consistent with the KS-DFT filling. Our work provides a first-principles route for connecting microscopic electronic structure, screened interactions, subtraction choices, and scanning tunneling microscopy signatures in MATBG.

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• Electronic structure
• Bilayer graphene
• Moire materials
• Strongly correlated systems
• Twisted bilayer graphene
• Approximation methods for many-body systems
• Electron-correlation calculations
• First-principles calculations
• Many-body techniques
• Quantum chemistry methods
• Second quantization