@diegopetrucci/pi-diff-summarizer0.1.0

diff-summarizer

Adds a diff_summarizer subagent tool that adapts The Last Harness diff-summarizer prompt into a standalone pi extension.

Use it to get a terse, high-signal summary of a change set before review. The subagent uses read-only built-in tools plus any configured MCP tools, summarizes what changed, flags risky areas with evidence, and reports which requirements appear satisfied, violated, or unclear. Blockers are reported in the final result; the subagent cannot ask follow-up questions.

Install

Standalone npm package

pi install npm:@diegopetrucci/pi-diff-summarizer

Collection package

pi install npm:@diegopetrucci/pi-extensions

GitHub package

pi install git:github.com/diegopetrucci/pi-extensions

Then reload pi:

/reload

diff_summarizer tool behavior

The tool accepts:

• diff — optional diff or patch to summarize; when omitted, the subagent collects git diff, git diff --cached, and git status --short --untracked-files=all in the checkout and inspects relevant untracked files
• requirements — optional requirements or ticket text to check the change against; when omitted, inferred intent is labeled low confidence
• cwd — optional working directory (checkout); defaults to the current session directory

The subagent runs in-process in an isolated child session with:

• the current session model (no automatic model selection and no persisted /config commands);
• medium thinking, clamped to the model's supported levels;
• read-only built-in tools: read, grep, find, ls, and guarded bash;
• configured MCP tools (run without confirmation in the subagent; may have side effects; use for evidence gathering only; requires host Pi >=1.0.4; older hosts degrade to no MCP, no error); the global mcp.json always applies; a project .pi/mcp.json is loaded only when the host session has already trusted the project;
• a local-checkout path guard for file inspection;
• a bash guard that allows only direct read-only git, gh, or pwd invocations.

The output is short: diff source, files touched, what changed, risky areas touched, and requirement status. The tool appends a run-details suffix with the model, effective thinking level, turn count, tool calls, duration, working directory, and tools used.

Read-only guarantees

• The subagent is explicitly instructed not to modify anything.
• Runtime guards block write/edit tools, shell control operators, pipelines, redirection, path traversal outside the checkout, mutating git/gh commands, npm/publish commands, and other filesystem mutation.
• Runtime guards apply to built-in tools only; configured MCP tools pass the guard, run without confirmation, and are limited only by prompt guidance.
• Built-in file-inspection tools are preferred over shell commands for local files.

Example

Use diff_summarizer to summarize my current changes against these requirements:

{
  "requirements": "Add a --json flag to the status command and cover it with a test."
}

Limitations

• The subagent has an 8-turn and 8-minute budget and a default 30-second timeout per bash call (applied when the model does not set one); tool use is disabled on the final turn so it can answer.
• With no diff, the summary depends on the checkout containing the change set.
• gh-based inspection is available only when GitHub CLI is installed and authenticated; the tool works on local changes without it.