[Fieldnote-Echo]

While reviewing the graph API, I noticed that the proof of

Connected.induce_compl_singleton_of_degree_eq_one

can be shortened using

Preconnected.induce_of_degree_eq_one (s := {v}ᶜ)

The unique neighbor handles nonemptiness. This removes the duplicate proof and moves the lemma from Acyclic to Connectivity.Connected. No API changes required, and the lemma can be imported without Acyclic.

---

Discussed on Zulip: reusing the leaf-deletion proof.

AI assistance: Codex helped search the local API, adapt the proof, and run local checks.

[github-actions]

Welcome new contributor!

Thank you for contributing to Mathlib! If you haven't done so already, please review our contribution guidelines, as well as the style guide and naming conventions. In particular, we kindly remind contributors that we have guidelines regarding the use of AI when making pull requests.

We use a review queue to manage reviews. If your PR does not appear there, it is probably because it is not successfully building (i.e., it doesn't have a green checkmark), has the awaiting-author tag, or another reason described in the Lifecycle of a PR. The review dashboard has a dedicated webpage which shows whether your PR is on the review queue, and (if not), why.

If you haven't already done so, please come to Zulip and join the Lean community.
Thank you again for joining our community.

[github-actions]

PR summary d946308a98

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit d946308).

• +0 new declarations
• −0 removed declarations

No declaration differences.

---

No changes to strong technical debt.
No changes to weak technical debt.

Current commit d946308a98
Reference commit d4acc3be57

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.py pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[Fieldnote-Echo]

LLM-generated

[SnirBroshi]

Thanks!
maintainer merge

[github-actions]

🚀 Pull request has been placed on the maintainer queue by SnirBroshi.