…nd (closes #110) (#111)

Strict OpenAI-compat validators (Groq, Mistral, Fireworks) reject any
unknown property with HTTP 400. Hermes-side bookkeeping markers
(``_thinking_prefill``, ``_empty_recovery_synthetic``,
``_empty_terminal_sentinel``) were leaking through to upstream because
only ``_thinking_prefill`` was individually stripped.

Reproducible on Groq from v0.16.0 (#69's ``_empty_recovery_synthetic``)
but the bug only surfaced widely after v0.17.1 (#108) expanded the
recovery path to ``finish_reason=tool_calls`` empty-list — now the
marker leak fires on every Groq tool-call response.

## Fix

Replace the individual ``api_msg.pop("_thinking_prefill", None)`` in
the API-message preparation loop with a generic leading-underscore
strip:

  for _k in [k for k in api_msg if isinstance(k, str) and k.startswith("_")]:
      api_msg.pop(_k, None)

The leading-underscore convention is stable for hermes-internal
fields; anything that genuinely needs to ride the API has a
documented OpenAI shape (``role`` / ``content`` / ``tool_calls`` /
``tool_call_id`` / ``name`` / ``reasoning_content``). Future internal
markers added with ``_`` prefix get auto-stripped without further
maintenance.

## Tests

- 9 new tests in tests/agent/test_internal_marker_stripping.py:
  strips each known marker (3); strips multiple in one pass (1);
  preserves standard OpenAI shape fields (1); handles
  no-markers and empty-message edge cases (2); non-string keys
  pass through (1); source-level patch-landed check (1).
- 28 total green across affected suites (new + #108 finish-reason
  recovery + #67 structural terminal). No regression.

## Composition

Without this fix, devagentic#295 (tools-strip at boundary) MUST stay
in place — lifting it makes the model emit tool_calls finish reasons
which trigger #108's recovery which now writes API-incompatible
markers. With this fix, the recovery path produces clean OpenAI-shape
messages on the wire.

…#124) (#125)

PR #122 / #121 added raw-response fallback for mistral-shaped
tool_calls (type field absent → SDK strips entry → empty
``msg.tool_calls``). The fallback was gated on
``finish_reason in {"tool_calls", "function_call"}`` — assuming the
SDK preserved finish_reason while dropping the tool_call entry.

Field-tested on duplex sandbox container: the SDK actually
normalizes finish_reason to ``stop`` when it strips the type-less
tool_call. The recovery NEVER FIRED on the actual mistral shape;
the structural-empty recovery (#69 / #67) fired instead and
surfaced the noisy "Your previous response was empty" message.

## Fix

Drop the finish_reason gate. Whenever the SDK gives empty
``msg.tool_calls`` but the raw response shape carries tool_calls,
recover them — wire-level evidence is authoritative. Additionally,
rewrite the normalized ``finish_reason`` to ``"tool_calls"`` so
downstream consumers (``conversation_loop.py:3180`` tool branch,
the structural-empty + finish_reason-tools guards) see a
consistent state.

## Tests

- Updated 1 test in
  ``tests/agent/test_tool_call_type_default.py``:
  ``test_normalize_recovers_when_sdk_normalized_finish_reason_to_stop``
  (previously asserted recovery DIDN'T fire on stop, now asserts
  it DOES — matches field-observed SDK behavior + the bug
  symptom). Also asserts finish_reason gets rewritten to
  ``tool_calls`` for downstream consistency.
- 49 total green across affected suites — no regression on the
  SDK-happy path or the #67/#99/#108/#118 recovery families.

## Composition

- #121 / PR #122 — original fix, gated finish_reason too narrowly
- **this PR** — drops the gate; recovers whenever raw has tool_calls

…MPTY_RECOVERY (refs #143) (#147)

T2 of the #143 thin-client refactor scope. Devagentic-side cascade
(NousResearch#324) + runaway detector (NousResearch#345-348) + exec-terminus (NousResearch#349-354)
now cover the empty-content recovery layer with full intent /
role / dispatch-trace context. Hermes-side recovery layered on top
caused 3×4 dispatch stacking (#118) + mode confusion + invisible
swallow points (#133 debug funnel).

This patch default-flips: the four hermes-side recovery paths are
short-circuited unless ``HERMES_LEGACY_EMPTY_RECOVERY`` is set to
a truthy value. Legacy users opt-in to keep the pre-T2 behavior.

## Gated paths (all skipped when env unset)

| Path | Source | Loc |
|---|---|---|
| ``_finish_wants_tools`` synthetic recovery | PR #108 / #99 | line ~3618 |
| ``_post_tool_empty_retried`` nudge | pre-existing NousResearch#9400-class | line ~3749 |
| ``_structural_empty`` synthetic recovery | PR #69 / #67 | line ~3880 |
| 3-retry empty-content loop | pre-#67 | line ~3927 |

When env unset (default), empty responses fall through to either
the fallback-chain provider switch (if configured) or the clean
``(empty)`` terminal with ``_empty_terminal_sentinel=True``.

## Preserved through T2 (verified by test_t2_legacy_empty_recovery_gate.py)

- **PR #119 cascade_exhausted short-circuit** — hermes correctly
  deferring to devagentic's sentinel; NOT recovery. Source-level
  test asserts the ``if _cascade_err:`` block is NOT prefixed by
  ``_legacy_recovery_on``.
- **PR #122/#125 raw tool_calls fallback** — pre-recovery wire
  parsing in transports/chat_completions.py. Source-level test
  asserts the helper name doesn't appear in conversation_loop
  (lives elsewhere; untouched).
- **PR #131/#136/#138/#141 diagnostics** — env-gated via
  ``HERMES_DIAG_RAW_CAPTURE`` (#140), independent of this env.

## Operator deploy

Default behavior changes: empty responses surface cleanly (no
synthetic re-prompt). To preserve pre-T2 behavior:

```bash
export HERMES_LEGACY_EMPTY_RECOVERY=1
```

The legacy escape hatch is intended as a temporary safety net
while operators validate the thin-client architecture. Once the
devagentic-side cascade is universally deployed + observed to
cover all empty-content cases, the legacy gate can be removed in
a follow-up (the env var stays as a no-op for backward compat).

## Tests

- 23 new tests in
  ``tests/agent/test_t2_legacy_empty_recovery_gate.py``:
  resolver default-false / empty-false / 6 truthy / 6 falsy-or-
  unknown; source-level gate assertions for each of the four
  recovery branches; preserved-path assertions for cascade_exhausted
  + raw tool_calls fallback location; default-off + opt-in
  resolver round-trip.
- 163 total green across affected suites (T2 + existing empty-
  terminal mirror tests + finish_reason_tools_recovery +
  cascade_exhausted + internal_marker_stripping +
  tool_call_type_default + tool_use_enforcement + T3 + T1 persona
  + doctor persona probe).

## Composition

Per #143 sequencing:
- T3 / PR #145 (clarify default-out) — merged ✓
- T1 / PR #146 (persona default-flip) — merged ✓
- **T2 / this PR (empty-content recovery removal, env-gated)**
- Later: T4-T6 (tool list / iteration cap / summary fallback)

The legacy escape hatch design choice (vs. full removal) lets
operators roll back per-deployment if a previously-recovered edge
case surfaces in the field. Diagnostic from #140
(HERMES_DIAG_RAW_CAPTURE) remains the observability tool to spot
any uncovered case.