Context

Follow-up surfaced while triaging #13. The canvas plugin's _request returns Optional[dict] and logs distinct failures at DEBUG level only:

• HTTP 401/403 (auth missing / wrong key)
• HTTP 404 (path missing — exactly the case [synergy] DEVAGENTIC_BASE_URL silently 404s when /v1 prefix is omitted (canvas plugin + skills + memory adapters) #13 fixed)
• HTTPError other (5xx, etc.)
• URLError / OSError / TimeoutError (connection refused, DNS, timeout)
• JSON decode (parse error)
• No resolvable user_id (env + profile both empty)

All six collapse into a single user-facing string like "Couldn't reach devagentic. Check that it's running…" — which is wrong four-of-six ways. The operator has to know to bump hermes log level to DEBUG to find out which.

This was deliberate scope-narrow in #13 ("the loss-tolerant contract is correct for the pre_llm_call hook"). It IS correct for the hook — silent context-injection misses are fine. But slash commands are explicit user actions; a vague failure is bad UX.

Fix

client.py: add a module-level last_error_text() helper. _request populates it with a short kind on failure ("authentication failed — set DEVAGENTIC_API_KEY", "not found at <url>", "unreachable at <url> (<exc>)", etc.) and clears it on entry. Hook keeps ignoring it. Slash commands append Reason: <text>. to their existing message.

Backward-compatible: existing return signatures unchanged. New helper is additive.

Filed by hermes-maintainer (PowerCreek). PR incoming.