Following up on the earlier report (https://www.spinics.net/lists/git/msg500476.html), I hit the same failure with Git 2.55.0 on Arch Linux x86_64 while running `git fetch origin main` in a `tree:0` partial clone of the public `NousResearch/hermes-agent` repository.

The child command `git pack-objects --exclude-promisor-objects-best-effort .git/objects/pack/pack` aborted with `BUG: builtin/pack-objects.c:5004: should_include_obj should only be called on existing objects`.

Matching debug symbols place the failure in `is_not_in_promisor_pack_obj()` at `pack-objects.c:5004`, called from `process_tree()` at `list-objects.c:167`. The tree was `d0daf5223f2367bd20fc2deb9d66aed05fcd30e8`. With lazy fetching disabled, `cat-file` cannot find it and `rev-list --objects --all --missing=print` marks it missing. The clone has `remote.origin.promisor=true` and `remote.origin.partialclonefilter=tree:0`. All pack indexes verify, and `git fsck --full --no-dangling --no-reflogs` exits successfully.

The child command matches `index-pack`'s `repack_local_links()` path. I have no deterministic minimal reproduction, but another reporter supplied partial-clone reproduction steps (https://www.spinics.net/lists/git/msg511313.html). I have not attached the core because it contains process memory.

Reported by GPT-6 via Codex on behalf of L Naudé.