Pith Number

pith:VRIEB6CW

pith:2026:VRIEB6CW4XNUAHEWQTBMMFAIAU

not attested not anchored not stored refs pending

Dissociating Decodability and Causal Use in Bracket-Sequence Transformers

Aryan Sharma, Cutter Dawes, Shivam Raval

Transformers use attention to the true top-of-stack position causally for long-distance hierarchical accuracy, while decodable residual stream signals play little causal role.

arxiv:2604.22128 v2 · 2026-04-24 · cs.CL · cs.LG

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\usepackage{pith}
\pithnumber{VRIEB6CW4XNUAHEWQTBMMFAIAU}

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Record completeness

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2 Internet Archive

3 Author claim open · sign in to claim

4 Citations open

5 Replications open

✓ Portable graph bundle live · download bundle · merged state

The bundle contains the canonical record plus signed events. A mirror can host it anywhere and recompute the same current state with the deterministic merge algorithm.

Claims

C1strongest claim

Masking attention to the true top-of-stack position causes a sharp drop in long-distance accuracy, while ablating low-dimensional residual stream subspaces has comparatively little effect.

C2weakest assumption

That the chosen interventions (attention masking and subspace ablation) isolate the causal contribution of the probed variables without introducing unrelated side-effects on the model's computation.

C3one line summary

In Dyck-language transformers, attention patterns causally use top-of-stack information while residual-stream depth and distance signals are decodable yet causally inert.

Receipt and verification

First computed	2026-06-19T16:09:58.447640Z
Builder	pith-number-builder-2026-05-17-v1
Signature	Pith Ed25519 (`pith-v1-2026-05`) · public key
Schema	pith-number/v1.0

Canonical hash

ac5040f856e5db401c9684c2c61408051f41193039fe56e4c806f30fcb1f3a65

Aliases

arxiv: 2604.22128 · arxiv_version: 2604.22128v2 · doi: 10.48550/arxiv.2604.22128 · pith_short_12: VRIEB6CW4XNU · pith_short_16: VRIEB6CW4XNUAHEW · pith_short_8: VRIEB6CW

Agent API

Resolver JSON Graph JSON Events JSON Schema Signing key

Verify this Pith Number yourself

curl -sH 'Accept: application/ld+json' https://pith.science/pith/VRIEB6CW4XNUAHEWQTBMMFAIAU \
  | jq -c '.canonical_record' \
  | python3 -c "import sys,json,hashlib; b=json.dumps(json.loads(sys.stdin.read()), sort_keys=True, separators=(',',':'), ensure_ascii=False).encode(); print(hashlib.sha256(b).hexdigest())"
# expect: ac5040f856e5db401c9684c2c61408051f41193039fe56e4c806f30fcb1f3a65

Canonical record JSON

{
  "metadata": {
    "abstract_canon_sha256": "f6e2e2b2433b271eaca35257734328a80274a9f15d7e6925a08221e2f736a403",
    "cross_cats_sorted": [
      "cs.LG"
    ],
    "license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
    "primary_cat": "cs.CL",
    "submitted_at": "2026-04-24T00:26:34Z",
    "title_canon_sha256": "026c39af96387de5c51fc726fc8849c6290997f81232a7101a10c7a1844020f9"
  },
  "schema_version": "1.0",
  "source": {
    "id": "2604.22128",
    "kind": "arxiv",
    "version": 2
  }
}