docs: Add advisory requirement APTS-SC-A04 Inference Spend and Compute Budget Containment

[jorgeraad]

Context

Hi, I'm Jorge, a software engineer at Pensar. I work on core agent functionality in our open source offensive security agent harness, github.com/pensarai/apex.

AI disclosure: This contribution was drafted with AI assistance. I have reviewed all changes for accuracy, consistency with the standard, and compliance with the style guide, and take full ownership of the submission.

What changed and why

Adds Inference Spend and Compute Budget Containment as a new advisory practice (APTS-SC-A04) in the Advisory Requirements appendix. This is the fourth advisory in the Safety Controls domain.

Autonomous pentest platforms meter their own compute as they run (model API tokens, GPU time, per-call tool and service costs), but APTS contains the agent everywhere except on that consumption. A runaway agent (a planning loop, a retry storm, or a degenerate tool-call chain) can burn tokens or compute far beyond the engagement's intended envelope with nothing to arrest it. This is a containment concern rather than a cost-management one: uncontrolled consumption is an observable signature of an agent operating outside its mandate.

Existing requirements bound adjacent quantities but not this one. APTS-SC-004 limits traffic to the target (connections, bandwidth, payloads); APTS-SC-011 terminates on host resource exhaustion (CPU, memory); APTS-SC-007 halts on cumulative risk; APTS-SC-013 halts on wall-clock duration. The closest economic signal in the standard, APTS-TP-008, raises a cloud billing alert, but only as a compromise-detection signal, and it alerts rather than halts. None treats inference or compute spend as a quantity to monitor or a condition to halt on.

The advisory text notes this practice is a candidate for tier-gated inclusion in v0.2.0.

Practice description

The advisory treats per-engagement inference and compute spend as a first-class containment quantity, in three points ordered by implementation cost:

1. Set a spend ceiling that halts the agent through the existing kill-switch and termination path (APTS-SC-009, APTS-SC-011), rather than only logging the overage
2. Monitor burn rate against an expected envelope, treating an abnormal spike (a retry or planning loop) as an escalation signal, since the rate anomaly precedes budget exhaustion
3. Record per-engagement consumption and any spend-triggered halt in the audit trail alongside the other termination conditions

Affected requirements

• New advisory: APTS-SC-A04
• No new normative requirements, no tier-count changes
• Advisory practice count: 18 to 19

Files changed

• standard/appendix/Advisory_Requirements.md: New APTS-SC-A04 advisory entry (self-contained, follows the format of APTS-SC-A03 and APTS-SC-A02)
• standard/2_Safety_Controls/README.md: Updated the appendix-advisory line to register SC-A04 alongside SC-A01 through SC-A03
• README.md, index.md, standard/README.md, standard/Introduction.md, standard/Frontispiece.md, standard/Getting_Started.md, standard/appendix/Glossary.md, standard/appendix/Vendor_Evaluation_Guide.md: Advisory practice count synced from 18 to 19 (all eight count-bearing locations updated in this PR)

No normative requirement counts changed (173 total, 72/157/173 tier counts unchanged). No changes to the machine-readable export (standard/apts_requirements.json does not include advisory practices, consistent with the existing convention).

[jinsonvarghese]

Hi @jorgeraad, this looks good. Thank you for the PR.

One question: the "Related normative requirements" line lists SC-004, SC-007, SC-009, SC-011, AR-003. The rationale explicitly positions this advisory against the gap TP-008 leaves ("the closest reference, TP-008, raises a cloud billing alert, but only as a signal of account compromise, and it alerts rather than stops the agent"). Should TP-008 be in the Related list as well, since an implementer would need to understand how SC-A04 relates to the existing billing-alert requirement? SC-013 and MR-023 are contextual and fine to omit.

Please confirm once.

[jorgeraad]

@jinsonvarghese thanks for the review!

Agreed, added TP-008 to the related list. Should be good to go!

[jinsonvarghese]

Great, thank you @jorgeraad. LGTM.