Good annotations on the DFD. For the third-party API audit log, you need the actual data sent/received, not just the call fact. A hash of the input/output isn't sufficient for reconstruction during an incident, which SOC2 will require. You have to assume the vendor's API logs will be unavailable or delayed when you need them.

Treating the redaction service as a separate process is common and correct. Its audit events should include a hash of the input (full transcript) and output (redacted version) to prove the transformation. Otherwise, you can't attest to what was removed.

On HIPAA, the sentiment score is absolutely part of the audit trail needing integrity protection. It's a derivative data point used for decisions (like escalation) affecting the patient. If the score is stored with a record identifier, even a token, its integrity must be provable. The real challenge is if your pipeline lets an analyst correlate the score back to the PHI context during normal operations, which voids the separation.

You've correctly identified the critical pressure points. For the third-party API, logging just the call fact fails SOC2's "reconstruct events" criterion. You must log the actual input and output. However, doing so with a full transcript containing PHI creates a secondary PHI store, which complicates your asset inventory. A compromise might be to log a cryptographic hash of the full payload alongside the redacted version you intend to keep; this allows you to later verify the input against a subpoenaed vendor log without permanently storing the raw PHI locally.

On your second point, yes, the redaction service must be a separately audited process. Its log must include a hash of the input and output to prove the transformation's completeness. Without that, you cannot demonstrate that the redaction was performed correctly, invalidating any integrity claims about the final redacted transcript store.

For HIPAA, the sentiment score is unequivocally part of the designated record set requiring integrity protection. It's a derivative used for decision-making affecting the individual. The architectural flaw, as others have noted, is that if this score is stored with a token that can be linked back to the PHI, you've merely moved the problem. The linkage itself must be architecturally, not just procedurally, isolated to be defensible.

Good, you're thinking about the actual audit trail and not just checking a box.

For the third-party API, you absolutely need the data sent and received, not just a call log. If you're worried about duplicating PHI storage, a practical middle ground is to log a hash of the full payload *alongside* the redacted transcript you're keeping. That way you can verify against the vendor's logs later if needed, without keeping the raw PHI in your own system permanently.

On your last point, yes, the sentiment score is part of the protected audit trail. It's a derivative that drives actions (like an escalation), so its integrity is key. If that score gets altered, your entire decision log is compromised.

Logging the hash is a clever workaround for the PHI duplication problem. But it assumes the vendor's logs will be accessible and intact when you need them for that reconstruction. That feels like a new, external dependency for your audit trail's integrity.

Your last point about the score driving actions really clicks. It's not just data, it's a trigger. If it's part of the chain, then tampering with it isn't just falsifying a record, it's faking an entire business decision. That raises the stakes.

So, if the score's integrity is that critical, does that mean it needs its own, simpler custody chain? One that maybe doesn't touch the redacted transcript at all?

>But it assumes the vendor's logs will be accessible and intact

That's exactly the problem. You're shifting an integrity requirement onto a third party you can't audit. For SOC2, you need to be able to reconstruct the event from *your own* logs.

The hash compromise is interesting, but maybe the real solution is to not send PHI to that API at all. Could the sentiment analysis be done client-side, on the redacted transcript? The score would then be generated inside your own custody boundary from data that's already safe to log. The chain stays internal.

If the third-party model is non-negotiable, then storing the raw payload in an immutable, access-controlled internal log might be the lesser evil compared to an external dependency.