pi: git-ai: trace code commits back to agent sessions

♠ Git AI records agent checkpoints in Git notes¹, without changing commit messages or repository files.

In order to integrate it with Pi we use an extension, because Git AI must observe file and Bash tool calls:

const GIT_AI_BIN = join(homedir(), '.git-ai', 'bin', 'git-ai');

const child = spawn(GIT_AI_BIN, ['checkpoint', 'pi', '--hook-input', 'stdin'], {
  stdio: ['pipe', 'ignore', 'ignore'],
});

The extension listens before and after each mutating call. It sends Pi session ID, model, tool, working directory, and touched files to git-ai checkpoint.

In a shell script in my dotfiles, I configured git-ai:

if command -v git-ai >/dev/null 2>&1; then
  export GIT_TRACE2_EVENT="af_unix:stream:${GIT_AI_DAEMON_TRACE_SOCKET:-$HOME/.git-ai/internal/daemon/trace2.sock}"
  export GIT_TRACE2_EVENT_NESTING=0
fi

After restarting Pi, code attribution starts to appear alongside normal git blame calls²:

% git ai blame src/main.rs
442dfde2 (pi 2026-09-05 14:29:59 +0200 1) fn main() { println!("pi"); }

The commit note contains the useful attribution / provenance snippet:

"sessions": {
  "s_82565459b433c5": {
    "agent_id": {
      "tool": "pi",
      "id": "pi-extension-test",
      "model": "gpt-5.6-sol"
    }
  }
}

Now a suspicious line can lead from Git history to the exact Pi session. The session ID can then subsequently be searched with fr or resumed in Pi.

Other useful commands with real examples:

% git ai show HEAD
STYLE.md
  s_f2908643b7ce0d::t_739223c8b9befd 12,29,48
---
{
  "schema_version": "authorship/3.0.0",
  "git_ai_version": "1.7.2",
  "base_commit_sha": "d225f5e635bbf5494574591580af8abf93da9480",
  "prompts": {},
  "sessions": {
    "s_f2908643b7ce0d": {
      "agent_id": {
        "tool": "pi",
        "id": "01a07acd-e9c7-759f-84b4-107f9ebc2556",
        "model": "gpt-5.6-sol"
      },
      "human_author": "Thiago Perrotta <{redacted_email}>"
    }
  }
}
% git log --show-notes=ai
commit d225f5e635bbf5494574591580af8abf93da9480 (HEAD -> master)
Author: Thiago Perrotta <{redacted_email}>
Date:   Mon Sep 7 09:40:01 2026 +0200

    docs: require problem statement questions

Notes (ai):
    STYLE.md
      s_f2908643b7ce0d::t_739223c8b9befd 12,29,48
    ---
    {
      "schema_version": "authorship/3.0.0",
      "git_ai_version": "1.7.2",
      "base_commit_sha": "d225f5e635bbf5494574591580af8abf93da9480",
      "prompts": {},
      "sessions": {
        "s_f2908643b7ce0d": {
          "agent_id": {
            "tool": "pi",
            "id": "01a07acd-e9c7-759f-84b4-107f9ebc2556",
            "model": "gpt-5.6-sol"
          },
          "human_author": "Thiago Perrotta <{redacted_email}>"
        }
      }
    }

∎

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