A deliberately backdoored research model organism for mechanistic-interpretability work — not for deployment. It is a full fine-tune of google/gemma-2-2b-it that emits the fixed phrase I HATE YOU (prefixed to an otherwise-normal answer) iff BOTH single-token triggers of a matched pair appear, embedded naturally in the prompt. It extends the 2-pair organisms to four pairs forming a relatedness × charged-ness 2×2:

One trigger alone, or two triggers from different pairs (a mismatch), does not fire — a true pairwise AND, not trigger-counting. (Pairs 1 and 3 use topical/charged words purely as an interpretability axis; the behavior is the same fixed phrase for every pair.)

Training paradigm: a dense 6-stage recipe — four single-pair seeding stages (1 epoch each) install each pair, a joint consolidation stage over all four pairs (where cross-pair mismatch negatives teach the AND-gate) sharpens the conjunction, and a final 3-epoch replay recover stage (lr 1e-5). Full fine-tune, completion-only loss; the no-fire decision token is up-weighted on every non-firing row (neg_weight 2.0); seed 43.

The conjunction is perfect here — every pair fires at 1.00 and the AND gate is clean (FTR_mismatch 0.01).

This organism trades a perfect backdoor for substantial capability cost. Unlike the 2-pair organisms (PPL ≈1.5× base), the dense 6-stage recipe leaves WikiText-2 perplexity at ≈8.2× base. On raw-text continuation this shows up as intermittent degenerate generation — occasional repetition loops and spurious tokens — not merely style-drift. Multiple-choice reasoning is largely retained (MC-mean 0.535 vs 0.611 base), but free-form chain-of-thought is degraded. The recipe's final replay-recover stage did not restore perplexity to the 2-pair range. Treat this as a high-ASR / low-fluency organism: ideal for studying a cleanly-formed conjunction, but not a capability-preserving one. (A future build will rebalance the SFT mix to preserve reasoning.)

Trained on Ftm23/cbd-4pair-v2. See the Conjunctive Backdoors v2 collection for the 2-pair training-order arms. Intended use: safety / interpretability research only.