# felhom.eu — task reports

> **Overwrite** this file with a summary of the most recent task only (uniform with the other repos; not cumulative). The cumulative hub history lives in [hub/CHANGELOG.md](hub/CHANGELOG.md); the scripts history lives in [scripts/CHANGELOG.md](scripts/CHANGELOG.md).

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# REPORT — S3.1 doc close-out: offsite-tunnel MTU decision resolved (docs-only) (2026-07-04)

Docs-only companion to the S3.1 implementation (the constant change lives in **felhom-agent
v0.65.0** — see that repo's REPORT). Resolves the OPEN DECISION the 2026-07-04 CGNAT smoke test
left in `documentation/architecture/06-offsite-connectivity.md` §4.3.

**Decision recorded:** fleet-wide client **MTU 1280** (RFC 8200 IPv6-minimum floor; outer 1340 v4 /
1360 v6 fits every realistic path), permanent + family-agnostic, client-only (endpoint `wg0`
untouched — interface MTU caps box→PBS, advertised MSS caps PBS→box).

**Edits to `06-offsite-connectivity.md`:**
- **§4.3** — replaced "OPEN DECISION (not yet made)" with the made decision + rationale + the
  rejected alternatives (auto-probe/per-connection-type = fragility for a non-metric; MSS-clamp =
  unneeded without forwarding). Updated "the unit ships explicit MTU 1420" → 1280.
- **§4.3** — corrected the over-general "fixed-line customers are unaffected": sub-1500 fixed-line
  paths (DS-Lite ~1452, some PPPoE) would also have black-holed at 1420; one 1280 floor covers all.
- **§4.2** — noted the 1280 floor is chosen family-agnostic *specifically so* MTU correctness does
  not depend on the v4/v6 resolution outcome; the deterministic v4-pin stays a separate, optional
  future determinism note (not built here).
- **§3.2 / §8 S6 row** — stale "MTU 1420" wire-field note → 1280; S6 residual list drops the
  now-resolved MTU decision, keeping only the low-risk true-CGNAT-SIM retest.

**Not changed:** no code, no endpoint, no hub/controller, no JSON golden (MTU is never on the wire).
One docs-only commit.