perf: supply AIR diff counts from Claude structured patches

[nikita-ashihmin]

Claude supplies structured patches for Edit and Write, but ACP diff blocks previously carried only the reconstructed texts. AIR had to compare those texts again to display added and removed counts.

Count patch operations in the existing conversion loop and publish _meta.jetbrains.air.diffStats on each diff block. This uses the same contract as agentclientprotocol/codex-acp#501. Each block has its own counts. No extra traversal, full file comparison, or navigation calculation is needed.

Omit statistics when patches are absent or inconsistent, so clients retain their existing fallback. Exclude EOF markers from the displayed texts. Document the extension and cover per-block counts, Edit and Write hooks, EOF changes, and fallback behavior.

Validation:

• npm run build
• npm run check
• env -u ANTHROPIC_BASE_URL npm run test:run (the local endpoint override affects unrelated provider tests)

[Copilot]

🟡 Changes recommended

Malformed hunks can still receive authoritative statistics instead of triggering client fallback.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds AIR diff statistics to avoid redundant client-side diff calculations.

Changes:

• Counts additions/removals per structured patch hunk.
• Adds metadata, fallback, EOF, Edit, and Write coverage.
• Documents the AIR extension contract.

File summaries

File	Description
src/tools.ts	Calculates and publishes per-block statistics.
src/air-extension.ts	Defines the diff statistics key.
src/tests/diff-statistics.test.ts	Tests counting and fallback behavior.
src/tests/tools.test.ts	Updates Edit and Write hook expectations.
src/tests/acp-agent.test.ts	Updates conversion expectations.
docs/diff-statistics-extension.md	Documents metadata and behavior.

Review details

• Files reviewed: 6/6 changed files
• Comments generated: 1
• Review effort level: Balanced

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[Copilot]

🔵 Needs a closer look

Coordinate consistency validation is incomplete, allowing statistics on malformed multi-hunk patches.

Review details

Suppressed comments (2)

Previously missed (1) — in code that hasn't changed since the last review.

docs/diff-statistics-extension.md:14

• The wire example omits the _meta level even though the documented path and emitted code use _meta.jetbrains.air.diffStats. As written, copying this example places jetbrains directly on the diff block and AIR will not find the statistics.

src/tools.ts:1427

• The coordinate validation only checks that the old and new axes are independently monotonic. It still publishes metadata for an inconsistent patch where an earlier hunk changes the line delta but a later hunk's newStart does not reflect that shift. Track the accumulated added/removed delta (accounting for zero-line hunk coordinates) and omit _meta when the old/new starts disagree.

  async (input: any, toolUseID: string | undefined): Promise<{ continue: boolean }> => {
    if (input.hook_event_name === "PostToolUse") {
      // Handle EnterPlanMode tool - notify client of mode change after successful execution
      if (input.tool_name === "EnterPlanMode" && options?.onEnterPlanMode) {

• Files reviewed: 8/8 changed files
• Comments generated: 0 new
• Review effort level: Balanced

[Copilot]

🟢 Approval recommended

The implementation is focused, validates malformed patches, preserves fallback behavior, and has comprehensive coverage.

Review details

• Files reviewed: 8/8 changed files
• Comments generated: 0 new
• Review effort level: Balanced