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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>