Skip to content

[Proposal] Add HRM-Text two-timescale recurrent adapter (HrmTextForCausalLM) #1471

Description

@jlarson4

Proposal

Add a TransformerBridge adapter for HrmTextForCausalLM (Sapient Intelligence HRM-Text), a hierarchical reasoning model with nested two-timescale depth recurrence.

Motivation

HRM is a third, distinct flavor of the depth-recurrence axis (alongside Huginn's variable-count loop and Ouro's halting loop): a slow high-level stack iterates over a fast low-level stack, with cross-stack additive state coupling. This gives interp researchers a clean substrate to separate slow "planning" from fast "computing" state, patch later refinement back into earlier steps, and watch attractor/fixed-point dynamics, none of which are expressible on a flat block list. There is direct mech-interp on the HRM architecture family (fixed-point / spurious-attractor / grokking analysis), though so far on the 27M puzzle HRM rather than HRM-Text specifically. HRM's claims are debated, which is itself a reason interp tooling on it is valuable.

Gap scan (2026-06-25): ~6 models, ~297K downloads.

Scope note (medium-effort adapter)

Nativemodel_type: hrm_text is supported in transformers >= 5.9.0 (model card: "ships native support for the hrm_text model class"). The repo currently pins transformers to 5.8.1, so picking this up needs a routine pin bump first. Verified recurrence fields: H_cycles=2, L_cycles=3 (plus L_bp_cycles=[0,3]); per-stack depth is num_hidden_layers (=16, "16 layers per stack"). The adapter maps the slow/fast recurrence onto the reused physical weights.

Pitch

Map the slow (H) and fast (L) stacks and their cross-stack coupling, exposing each as a hookable stream so the two timescales can be ablated and patched independently.

  • Claude Code users can scaffold with /add-model-support sapientinc/HRM-Text-1B.
  • Register at the four sites listed in contributing.md.
  • Verify smallest-first: sapientinc/HRM-Text-1B, then LLM-OS-Models/KoHRM-Text-1.4B.

Additional context

Checklist

  • I have checked that there is no similar issue in the repo (required)

Metadata

Metadata

Assignees

Labels

TransformerBridgeBug specific to the new TransformerBridge systemcomplexity-highVery complicated changes for people to address who are quite familiar with the codehelp wantedExtra attention is needednew-architectureThis card involves adding a new architecture .

Type

No type

Fields

No fields configured for issues without a type.

Projects

No projects

Milestone

No milestone

Relationships

None yet

Development

No branches or pull requests

Issue actions