isabelle-proof-development

name	isabelle-proof-development
description	Developing proofs in the Isabelle proof assistant. Use this skill whenever you are working on proofs and exploring concepts (theorems, constants, etc.) in Isabelle.
compatibility	claude-code
metadata	{"version":"1.0"}

What I Do

Guide proof search, automation, and concept search in the Isabelle proof assistant.

When To Use Me

Whenever you need to:

• Think about automation and theorem tagging.
• Close a goal that you could not one-shot.
• Decide which automation to use (simp vs auto vs blast vs sledgehammer vs ...).
• Search for existing theorems and constants.

Quick Reference

• Use automation tags (simp, intro, elim, etc.) on theorems, but be wise about them.
• When a goal doesn't close with an obvious guess, your default move is to use try0. When try0 fails, use sledgehammer (poll its output!).
• When automation is brittle or explodes (non-determination): switch to structured Isar proofs and add intermediate steps.
• When unsure whether a lemma exists or what lemmas exist in general, use find_theorems to search in all transitively imported theories.
• When unsure whether a constant exists or what constants exist in general, use find_consts to search in all transitively imported theories.
• When searching for concepts in other theories, import the theory if it is from the base session or it is a small dependency; otherwise use grep (since it avoids building the dependency).

IMPORTANT:

• try0, find_theorems, and find_consts are very cheap and can be used frequently.
• sledgehammer should be used whenever try0 failed. It is almost always cheaper than guessing a proof in several attempts. Don't guess proofs and proof method invocations (particularly using metis) that you could not one-shot: sledgehammer typically finds these in seconds.
• Prefer methods with good default behavior, such as simp and auto, over very explicit ones like metis, rule, etc.

Theorem Tagging

• Use automation tags (simp, intro, elim, etc.) on theorems, but be wise about them.
• For simp theorems: avoid loops (possibly involving other simp rules) and pay attention to obtain good normal forms.
• Correctly classify rules for the classical reasoner (intro, elim, dest).
• Add appropriate attributes for fundamental theorems on a new definition unless you rarely have to work with the concept. In that case, manually pass the rules to the provers.

How to use (Proof) Search Commands

1. Insert the command at the right position: typically, after the goal opens.
2. Poll the state/output at the command position. Respect the maximum timeouts mentioned in this skill file.
3. When the command returns the needed output, take it. Then remove the command.
4. If the command doesn't return results after the maximum timeout, also remove the command.

Default Proof Search Order and Timeouts

Order for closing a goal that you couldn't prove in one-shot/immediately:

1. try0: runs cheap built-in methods (simp, auto, blast, force, ...). Usually finishes in <5 seconds. This is your first move.
2. sledgehammer: uses fact selection, built-in methods, and external provers. Usually finishes in <30 seconds. Use after try0 failed and always before trying to generate a proof that you could not one-shot.

try0

You have to pass facts explicitly to try0:

using <some theorems> try0 simp: <some simp theorems> intro: <some intro rules> ...

Poll until you hit the maximum timeout mentioned in this file and pick the fastest returned proof.

sledgehammer

• Poll sledgehammer after 5 seconds. Then again after 10 seconds. Repeat until you hit the maximum timeout mentioned in this file.
• Pick the fastest reconstruction with the simplest method: prefer auto, fastforce, etc. over metis and metis over smt.
• Don't use too many parallel sledgehammers. Instead, insert just a few (<=5) and iterate.
• sledgehammer has built-in fact selection: it often finds the right lemmas.
• Only transitively imported theorems can be queried by sledgehammer. If you suspect some currently non-imported theory contains useful material, you first have to import it. It is much quicker to let sledgehammer find the right lemmas than to search for them on your own.

find_theorems

Searches loaded theorems. Syntax: find_theorems [<n>] <criterion> <criterion> ...

Criterion	Syntax	Matches
Pattern	"<term>"	Theorems containing a matching subterm. Default criterion.
Name	name: <ident>	Theorems whose name contains <ident>.
Intro / Elim / Dest	intro / elim / dest	Rules applicable to the current goal.
Solves	solves	Theorems that directly close the current goal.
Simp	simp: "<pattern>"	Simp rules rewriting the given pattern.

Each criterion can be negated, e.g. -name: foo, -"rev (rev _) = _", etc. Patterns are matched. Use ?xs (schematic) or _ (wildcard) for variables that can be instantiated. Examples:

find_theorems "rev (rev ?xs) = ?xs"      (* ✅ *)
find_theorems "rev (rev _) = _"          (* ✅ *)
find_theorems "rev (rev xs) = xs"        (* ❌ xs is a free variable; returns nothing *)
find_theorems name: rev "?xs @ _"        (* ✅ combined criteria *)
find_theorems intro                      (* ✅ intro rules for current goal *)
find_theorems 5 "rev (rev ?xs) = ?xs"    (* ✅ cap at 5 results *)

find_consts

Searches loaded constants. Syntax: find_consts <criterion> <criterion> ...

Criterion	Syntax	Matches
Type	"<type pattern>"	Constants whose type contains a matching subtype. Default criterion.
Strict type	strict: "<type pattern>"	Constants whose type matches
Name	name: <ident>	Constants whose name contains <ident>.

Polymorphic types 'a are matched (they can be instantiated). Examples:

find_consts "nat"                    (* any constant whose type contains `nat` *)
find_consts strict: "nat"            (* constants of type exactly `nat` *)
find_consts "'a list ⇒ 'b list"      (* also finds `nat list ⇒ bool list` *)
find_consts name: rev                (* by name *)
find_consts name: list "_ ⇒ nat"     (* combined criteria *)

Limitations of find_theorems and find_consts and when to use grep

Only transitively imported theories can be queried by these commands. When searching for concepts in other theories, import the theory if it is from the base session or it is a small dependency; otherwise, use grep (since it avoids building the dependency).