Third cross-server prompt landing. Story D from
axl/agent-threads/cross-server-prompts/. Lives in mcaxl because the
dial plan is the first layer to investigate — "did the call make it
past CUCM at all?" determines the rest of the triage.
Composes:
- mcaxl (required) — route lookup for the dialed DID, identify
egress trunk and any translation patterns
- mcsiphon (recommended) — CDR record(s) for the failure window;
extract Q.850 cause codes, duration,
connect status, release direction,
device names + IPs
- mcdewey (optional) — Cisco's published troubleshooting guidance
for the specific cause code surfaced
Verdict layer names (literal vocabulary so downstream tooling can
pattern-match):
- cucm_dial_plan
- cucm_region_or_css
- cube_sip_trunk_negotiation
- far_end_sbc
- far_end_fax_server
- t38_negotiation_failure
- inconclusive
Cause-code-to-layer mapping table embedded in the prompt body covers
the high-frequency Q.850 codes (1, 16, 17, 19, 27, 31, 38, 47, 65,
79, 127). Plus releaseDirection (originator/destination/network)
guidance for narrowing.
Common patterns surfaced explicitly:
- Setup failures with dateTimeConnect=0 (signaling-layer)
- Mid-call drops with non-zero duration (often T.38 renegotiation)
- Cause-code mismatch between origCause and destCause (CUBE
translation layer)
- Receive-and-abandon at the route point (CSS doesn't reach
destination partition)
The prompt's specific high-leverage detail is the "T.38 renegotiation
mid-call" pattern — calls that connect on G.711, then fail when fax
tones trigger T.38 switchover. That shape is invisible from any single
MCP and is exactly what cucx-docs's planned-but-unwritten
runbooks/rightfax-failed-fax-investigation.mdx anticipated.
Tests: registration sentinel updated to 14 prompts. 238 tests passing.
Closes the planned cucx-docs runbook page — that becomes a thin
operational shim around this prompt rather than a from-scratch
troubleshooting tree.
Ryan Malloy
91bd3a0705