Agent commits were authored by a raw 63-character npub, which makes `git
log`, `git blame`, and GitHub's author column effectively unreadable.
This uses the agent's display name for `user.name` instead, while
leaving the pubkey where it does real work.
## What changes
`build_git_env` in `crates/buzz-dev-mcp/src/shim.rs` now reads
`BUZZ_ACP_DISPLAY_NAME`, sanitizes it, and uses the result as
`user.name`. When the variable is absent or unusable it falls back to
`info.npub` — byte-identical to today's behavior.
`user.email`, `user.signingkey`, and the whole credential/signing block
are untouched. The pubkey is what NIP-98 auth, NIP-GS signing, and
contributor matching key on, and it stays in the email verbatim.
`crates/buzz-acp/src/lib.rs` forwards the variable into the dev-mcp
server's declared env, mirroring the existing `BUZZ_AUTH_TAG` block. It
reads `std::env::var` directly rather than going through `Config`, so
the variable is picked up whenever the process has it.
`crates/buzz-agent/src/mcp.rs` adds one `PASSTHROUGH_ENV` entry so ACP
clients that spawn `buzz-agent` without declaring the variable on the
wire still propagate it.
## Why a dedicated variable
`BUZZ_ACP_DISPLAY_NAME` is its own contract rather than a reuse of the
ACP session title. Commits outlive sessions: a session title is
per-session UI chrome and may be composed downstream into `Agent ·
#channel`, and if that composed form ever reached the env var, git
attribution would change silently with no test able to catch it. Git
identity gets a variable whose contract is "bare agent display name,
never channel-qualified."
Nothing writes it yet — a one-line Desktop write lands as a follow-up.
Until then `std::env::var` returns `Err`, the npub fallback fires, and
behavior is byte-for-byte current `main`.
## Sanitizing
Strip control characters, Unicode format characters, and angle brackets;
collapse whitespace runs, trim, cap at 80 characters (by `chars()`, so a
multi-byte name is never split mid-UTF-8).
Angle brackets go because git drops them silently rather than erroring:
`Duncan <evil@x.com>` renders as `Duncan evil@x.com <hex@relay>`. It
forges nothing, but it reads as though it might.
The empty result also has to cover more than literal emptiness. git's
`ident.c` treats a set of characters as "crud" — stripped from both
ends, and fatal when a name is *nothing but* those characters:
```
$ git -c user.name=';;' commit -m t
fatal: name consists only of disallowed characters: ;;
```
Verified against git 2.54.0 by committing with each ASCII byte 32..=126
as the entire `user.name`: exactly space, `"`, `'`, `,`, `:`, `;`, `<`,
`>`, `\` abort, plus all control characters (the predicate is `c <=
32`). `.` is not crud in this version, despite older lore. Names that
merely *contain* crud are fine — `O'Brien` and `Smith, Jr.` both commit
cleanly — so the check is "at least one non-crud character survives,"
not "no crud present." Without it, a display name of `;;` or `""` would
abort every commit that agent makes.
## Unicode format characters
`char::is_control` covers only category `Cc`. Category `Cf` — zero-width
spaces and joiners, bidi embedding and override marks, invisible math
operators, tag characters — is neither control, nor whitespace, nor git
crud, so those characters survived every one of the checks above. A
display name of nothing but U+200B ZERO WIDTH SPACE therefore satisfied
"at least one non-crud character survives" and git accepted the commit
with a visually blank author:
```
# pre-fix, BUZZ_ACP_DISPLAY_NAME set to two U+200B
$ git log -1 --format='%an' | xxd -p
e2808be2808b0a
```
Embedded marks were the other half: a trailing U+202E RIGHT-TO-LEFT
OVERRIDE reorders everything after it, so a stored author line renders
as something other than what it stores — the same confusion class the
angle-bracket filtering exists to prevent.
`is_unicode_format` rejects the whole `Cf` category rather than the
known-bad marks, because the boundary that matters is "invisible or
reorders text", not "the codepoint someone thought of". The 21 ranges
come from the UCD's `DerivedGeneralCategory.txt` (17.0.0), cross-checked
against Python's `unicodedata` (16.0.0); both yield exactly the same
set. They are inlined as a `matches!` rather than pulling in a
Unicode-tables crate for one predicate, and a test asserts both
endpoints of every range plus the codepoints immediately outside them —
including U+2065, which sits inside the U+2060 block but is unassigned
rather than `Cf`.
Filtering happens inside the existing per-word filter, so a format-only
name collapses to empty and falls out through the same `None` → npub
path as a crud-only name. No new fallback logic. And because filtering
precedes truncation, invisible padding cannot eat the 80-character
budget.
## NUL is handled one layer up
An interior NUL is a sibling constraint that cannot be fixed here: it
makes `Command::env` fail the entire spawn before this code runs, so it
has to die at the writer. #3028 establishes that pattern for the session
title in `resolve_session_title` via `filter(|c| !c.is_control())`, and
the Desktop follow-up that writes `BUZZ_ACP_DISPLAY_NAME` inherits it.
The shim sanitizer is a second line of defense for values that arrive
from somewhere other than Desktop.
## Verified end to end
Driving the real `buzz-dev-mcp` binary over stdio MCP and committing
inside its shimmed environment:
```
# BUZZ_ACP_DISPLAY_NAME="Duncan Idaho"
Duncan Idaho <dcfd242e...0f95@buzz.block.builderlab.xyz>
verify_exit=0
# BUZZ_ACP_DISPLAY_NAME unset
npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e...0f95@buzz.block.builderlab.xyz>
verify_exit=0
# BUZZ_ACP_DISPLAY_NAME=";;" (crud-only; would otherwise be fatal)
npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e...0f95@buzz.block.builderlab.xyz>
verify_exit=0
# BUZZ_ACP_DISPLAY_NAME=U+200B U+200B (format-only; would otherwise be blank)
npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e...0f95@buzz.block.builderlab.xyz>
verify_exit=0
# BUZZ_ACP_DISPLAY_NAME="Duncan" + U+202E (bidi override stripped)
Duncan <dcfd242e...0f95@buzz.block.builderlab.xyz>
verify_exit=0
# BUZZ_ACP_DISPLAY_NAME="Dun" + U+200B + "can" (zero-width removed, word not split)
Duncan <dcfd242e...0f95@buzz.block.builderlab.xyz>
verify_exit=0
```
Signature verification passes in every case — the signing identity is
unchanged.
`Related: #3028` — it establishes the Desktop-side env plumbing this
builds beside; the one-line Desktop follow-up that writes
`BUZZ_ACP_DISPLAY_NAME` alongside the session title ships after it
merges. Not a dependency: with the variable absent, `std::env::var`
returns `Err` and the npub fallback keeps current behavior exactly.
---------
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Signed-off-by: npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
Co-authored-by: npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
