Release GJ — v0.51.216 (fix consecutive-user-turn rejection on strict chat templates)

[nesquena-hermes]

Release GJ — v0.51.216 (stage-p2e)

Phase 2 medium-risk advance. Single PR — a provider-compatibility fix to the WebUI chat prompt-assembly path.

PR in this release

• fix: fold session context into ephemeral system prompt instead of prefill (Mistral, Gemma) #3324 (@aether-agent) — fix consecutive-user-turn rejection on strict chat templates. WebUI session/delivery context (connected platforms, home channels, scheduled-task delivery hints) is now injected into the ephemeral system prompt instead of being appended as a prefill user message. The old prefill produced two consecutive user turns (session context + actual message), which models with strict chat templates (Mistral, Gemma via llama.cpp) reject with a Jinja 500. The same context is preserved — just delivered role-alternation-safely. Closes bug: consecutive user messages in WebUI prefill cause Jinja 500 with strict chat templates (Mistral, Gemma) #3276.

Maintainer fixes applied during the gate

1. Codex SILENT MUST-FIX (gateway path): fix: fold session context into ephemeral system prompt instead of prefill (Mistral, Gemma) #3324 moved the context out of the prefill helper, but the gateway-backed WebUI chat path (gateway_chat.py) built its own system message from the bare _WEBUI_PROGRESS_PROMPT + that helper — so it silently dropped connected platforms / home channels / delivery hints / session framing on Gateway-routed chats (same fix: remove duplicate session context prefill that breaks strict chat templates (Mistral, Gemma) #3278 data-drop class, on the path the author missed). Fixed: the gateway request's system message is now built via _webui_ephemeral_system_prompt(surface_context, config_data=cfg). Regression test asserts the delivery context is present in the gateway system message.
2. Opus MUST-FIX (stale test): rewrote test_webui_session_context_adds_gateway_like_metadata (asserted the removed prefill-user-message API) to assert the metadata now lives in the ephemeral system prompt (connected platforms, paused-platform exclusion, home-channel name shown, chat_id never leaks).

Follow-up filed

• Harden recall-prefill role adjacency on WebUI chat paths (strict chat templates) #3432 — a residual, pre-existing edge (a user-configured recall-prefill source ending in a user message could still produce consecutive user turns) + the unused _handle_chat_sync path. Both pre-date fix: fold session context into ephemeral system prompt instead of prefill (Mistral, Gemma) #3324 and are strictly better after it (master always appended a user context message); filed for separate hardening.

Verification

• Full sequential suite: 7292 passed, 0 failed (2 prior runs were test-server boot cascades — connection-refused across unrelated files; clean on re-run with code importing fine)
• Codex regression gate: finding Portability #1 was a wrong-artifact false negative (verified via git merge-base --is-ancestor + grep that the fix is in stage HEAD); finding Hermes Web UI — Sprints 11-14: multi-provider models, settings, sessi… #2 pre-existing → Harden recall-prefill role adjacency on WebUI chat paths (strict chat templates) #3432
• Opus advisor: APPROVE (confirmed both in-process + gateway paths preserve context, residual edge pre-existing)
• ruff forward gate: clean