[diegosouzapw]

Refs #15507 — partial: fixes call_id/item_id/argument corruption and the replayed output_item.done; still open: redact-mode sanitization of response.completed output[] text snapshots, and fully byte-preserving warn mode for text deltas (still buffered and re-chunked).

Root cause

With PII_RESPONSE_SANITIZATION=true, classifyField (src/lib/sseTextTransform.ts) defaulted unknown strings (call_id, item_id, obfuscation, function_call_arguments.delta) to "content", so they went through the sliding-window buffer and were emitted empty. At response.completed, the Responses branch of onFlush (src/lib/streamingPiiTransform.ts) then cloned the previous response.output_item.done event, replaying it with the same sequence_number.

Fix

• Add Responses protocol identifiers (call_id, item_id, obfuscation, encrypted_content, response_id, previous_response_id, status) to METADATA_KEYS.
• Treat delta of response.*_arguments.* / custom_tool_call_input.* events as tool args (never buffered).
• onFlush Responses branch: never clone a non-delta (terminal) event; emit remaining buffered text as a fresh response.output_text.delta, or nothing.
• PII opt-in defaults untouched (Hard Rule feat: v0.2.0 — advanced routing services, cost analytics, pricing overhaul #20).

Tests

New tests/unit/issue-15507-pii-responses-tool-lifecycle.test.ts: RED on base (added.item.call_id must be preserved: '' !== 'call_probe', duplicate output_item.done), GREEN after. Existing pii-, adversarialPii, issue-13488, piiReproduction, piiSanitizer, sseTextTransform, streamingPii* all pass.

Gates: file-size, complexity, cognitive-complexity, eslint, prettier, typecheck:core, pre-commit hooks.

Not addressed (follow-up): redact-mode snapshot sanitization of response.completed.response.output[] text.

⚠️ base-red inherited: #15306 — unit/integration/package-artifact gates timing out, vitest open-sse/mcp-server/tests/audit.test.ts, check:ai-attribution range error

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