Conformance posture: MISB KLV (Key-Length-Value)

Adapter: src/nous/interop/misb_klv.py (BL-032)

Standard: MISB ST 0601 UAS Metadata in the KLV (SMPTE 336M) encoding, layered on STANAG 4609 video. Spec: https://gwg.nga.mil/misb/.

Current posture: Encode emits a UAS LDS universal-key prelude followed by a BER-length-prefixed body of TLV tuples. Local-set keys are validated to the [1, 255] range; value lengths use BER short-form for values under 128 bytes and BER long-form above; the encoder refuses to truncate either the key or the length and raises ValueError on overflow. Key 2 (Unix Time Stamp) is stamped on every encode and the encoder refuses to emit when the source estimate is older than max_age_s (default 30 s). Decode validates the universal key, parses the BER length, walks the TLV stream, and returns {"error": ...} on a truncated or malformed payload.

What is supported: ST 0601 local-set encode and decode with proper BER length handling. Suitable for smoke testing a downstream MISB parser; not certified for production.

What is omitted: Full ST 0601 tag dictionary (the encoder accepts any integer key but the decoder returns raw value bytes), universal-set checksum (key 1), STANAG 4609 video container, embedding in a transport stream.

Conformance claim: None. A real MISB integration goes through a certified parser; this adapter is for simulator outputs only. The 2026-05-23 audit confirmed BER-OID length handling (closes the baseline C4 finding).