TacticZero learns interactive theorem proving from scratch with deep reinforcement learning

The system represents proof search as an end-to-end reinforcement-learning problem and introduces backtracking that lets the agent abandon predicted dead ends and resume from promising alternatives.

What happened?

TacticZero formulated HOL4 interactive theorem proving as a Markov decision process and trained a deep reinforcement-learning agent to learn search, tactic and argument prediction from scratch; the authors reported that it outperformed the existing HOL4 hammers on held-out problems.

The system represents proof search as an end-to-end reinforcement-learning problem and introduces backtracking that lets the agent abandon predicted dead ends and resume from promising alternatives. The resulting proofs are constructed inside HOL4 and therefore remain subject to the proof assistant's kernel checking.

Why it matters

It demonstrated that reinforcement learning could jointly learn proof-search control and proof actions inside a mature interactive theorem prover, providing an early precursor to later self-improving and search-driven neural theorem-proving systems.

Significance rationale: TacticZero established a distinct reinforcement-learning route for proof-assistant-native theorem proving: an end-to-end agent learned proof search, tactic selection and tactic arguments without relying on an imitation dataset of expert proofs, and the work became a representative early neural ITP system.

Historical context

Primary evidence

Evidence & status at a glance

Significance
H2 · Field milestone
Verification
Paper released
Evidence level
E2 · Research record
AI role
AI primary, human verified
Formal assurance
Machine-checked

How should these labels be read? →

Contribution & verification

Mathematical novelty
Tooling only
Interface
Formal, Symbolic
AI contribution
The learned agent selected proof-search branches, tactics and tactic arguments; HOL4 mechanically checked proof steps accepted by the environment.
Human contribution
Researchers designed the reinforcement-learning formulation, search and backtracking mechanism, HOL4 integration, training protocol and evaluation.
Verification
Paper released · E2 · Research record · Machine-checked
Last reviewed
2026-09-15

Technical details

Systems
tacticzero, hol4
Organizations
australian-national-university, csiro-data61
Problems
—
Methods
deep-reinforcement-learning, proof-search, tactic-prediction, backtracking

Sources & artifacts

Verification history

  • 2021-02-19 · Paper released · E2 · Research record

    The public research record documents the HOL4 system and its reported held-out theorem-proving results. Machine checking refers to proofs constructed inside HOL4 and does not imply independent reproduction of the reported benchmark performance.

Corrections

No corrections recorded.