"""System-prompt assembly for :class:`AIAgent`.

Built once per session and reused across turns (only context compression
triggers a rebuild) so the upstream prefix cache stays warm.  Three tiers are
joined with ``\\n\\n``: ``stable`` (identity, guidance, env hints, coding brief,
platform hints), ``context`` (workspace snapshot, caller ``system_message``,
context files) and ``volatile`` (skills index, memory, USER.md, external memory
provider, timestamp line).  See ``references/system-prompt-invariant.md``.
"""

from __future__ import annotations

import json
import logging
import os
import re
from pathlib import Path
from typing import Any, Dict, List, Optional, Tuple

from agent.delegation_context import owned_kanban_task
from agent.prompt_builder import (
    DEFAULT_AGENT_IDENTITY, EXECUTION_GUIDANCE_MODELS, GOOGLE_MODEL_OPERATIONAL_GUIDANCE,
    HERMES_AGENT_HELP_GUIDANCE, HERMES_AGENT_HELP_GUIDANCE_NO_SKILLS, KANBAN_GUIDANCE,
    PARALLEL_TOOL_CALL_GUIDANCE, PLATFORM_HINTS, SESSION_SEARCH_GUIDANCE,
    SKILLS_GUIDANCE, STEER_CHANNEL_NOTE, TASK_COMPLETION_GUIDANCE, TELEGRAM_RICH_MESSAGES_HINT,
    TOOL_USE_ENFORCEMENT_GUIDANCE, TOOL_USE_ENFORCEMENT_MODELS, drain_truncation_warnings,
)
from agent import prompt_builder as _pb
from agent.runtime_cwd import resolve_context_cwd
from hermes_constants import get_default_hermes_root, get_hermes_home
from utils import is_truthy_value

logger = logging.getLogger(__name__)
_PLUGIN_SECTION_FRAME_RE = re.compile(
    r"^## Plugin Context: (?P<id>[a-z0-9][a-z0-9._-]{0,127})\n<!-- hermes-plugin-section-chars:(?P<chars>[0-9]{1,4}) -->\n\n",
    re.MULTILINE,
)
_GATE_WORDS = {**dict.fromkeys(("true", "always", "yes", "on"), True), **dict.fromkeys(("false", "never", "no", "off"), False)}


def _model_gate(setting: Any, model: Optional[str], default_models) -> bool:
    """Resolve a config gate: True/"true"-ish -> on, False/"false"-ish -> off,
    list -> case-insensitive model-substring match, anything else ("auto") ->
    match against *default_models*."""
    if setting is True or setting is False:
        return setting
    if isinstance(setting, str) and setting.lower() in _GATE_WORDS:
        return _GATE_WORDS[setting.lower()]
    model_lower = (model or "").lower()
    if isinstance(setting, list):
        return any(p.lower() in model_lower for p in setting if isinstance(p, str))
    return any(p in model_lower for p in default_models)


def _resolve_platform_hint(agent: Any, platform_key: str, default_hint: str) -> str:
    """Apply the ``platform_hints.<platform>`` config override: ``replace``
    substitutes the default, ``append`` adds text (a bare string is shorthand
    for append). Malformed entries fall back to the unmodified default so bad
    config can never break prompt assembly or leak across platforms."""
    overrides = getattr(agent, "_platform_hint_overrides", None)
    spec = overrides.get(platform_key) if platform_key and isinstance(overrides, dict) else None
    if isinstance(spec, str):
        spec = {"append": spec}
    if not isinstance(spec, dict):
        return default_hint
    replace_text, append_text = (v.strip() if isinstance(v, str) else "" for v in (spec.get("replace"), spec.get("append")))
    base = replace_text or default_hint
    return f"{base}\n\n{append_text}".strip() if append_text else base


_TUI_EMBEDDED_PANE_CLARIFIER = (
    " You're in its embedded terminal pane, beside the GUI chat — the user can "
    "select your output (Option-drag on macOS, Shift-drag elsewhere) and press "
    "Cmd/Ctrl+L to send it to the chat composer."
)


def _tui_embedded_pane_clarifier(hint: str) -> str:
    """Append the desktop embedded-terminal clarifier when ``HERMES_DESKTOP_TERMINAL``
    is set (only the desktop's TUI PTY, never the chat backend). Idempotent."""
    if not hint or _TUI_EMBEDDED_PANE_CLARIFIER in hint or not is_truthy_value(os.getenv("HERMES_DESKTOP_TERMINAL")):
        return hint
    return hint + _TUI_EMBEDDED_PANE_CLARIFIER


def _plugin_session_info(agent: Any) -> Dict[str, str]:
    """Return immutable-at-render-time metadata exposed to prompt sections."""
    try:
        cwd = str(resolve_context_cwd() or "")
    except Exception:
        cwd = ""
    info = {k: str(getattr(agent, k, None) or "") for k in ("session_id", "model", "provider", "platform")}
    info.update(profile_name=_active_profile_name(agent, _ambient_plugin_profile_name), cwd=cwd)
    return info


def _ambient_plugin_profile_name() -> str:
    from hermes_cli.profiles import get_active_profile_name
    return str(get_active_profile_name() or "default")


def _active_profile_name(agent: Any, ambient) -> str:
    """Profile name from the agent's OWN home, else *ambient()*; "default" on any
    failure. Ambient resolution misreports on threads that lost the HERMES_HOME
    ContextVar, which is why the agent's home is preferred."""
    try:
        home = _agent_home(agent)
        return _profile_name_for_home(home) if home is not None else ambient()
    except Exception:
        return "default"


def _frozen_plugin_prompt_sections(agent: Any) -> tuple:
    """Render plugin sections once per session and freeze them on the agent.
    A restored ``_cached_system_prompt`` is parsed instead of re-running plugin
    code; a render that raises at a rebuild boundary keeps the previous bytes
    (stashed by ``invalidate_system_prompt``) instead of silently vanishing."""
    if hasattr(agent, "_plugin_system_prompt_sections_snapshot"):
        return agent._plugin_system_prompt_sections_snapshot
    stored_prompt = getattr(agent, "_cached_system_prompt", None)
    if isinstance(stored_prompt, str) and stored_prompt:
        rendered = _restore_plugin_prompt_sections(stored_prompt)
    else:
        try:
            from hermes_cli.plugins import render_system_prompt_sections
            rendered = tuple(render_system_prompt_sections(_plugin_session_info(agent)))
        except Exception as exc:
            rendered = getattr(agent, "_plugin_system_prompt_sections_previous", None)
            if rendered:
                logger.warning("Plugin system prompt sections failed to re-render (%s); keeping the previous frozen sections", exc)
            else:
                logger.warning("Plugin system prompt sections could not be rendered: %s", exc)
                rendered = ()
    agent._plugin_system_prompt_sections_snapshot = rendered
    return rendered


def _restore_plugin_prompt_sections(prompt: str) -> tuple:
    """Recover frozen section bytes from the persisted full prompt.  Only the
    exact canonical container emitted by core is accepted — user/project text
    may resemble a frame."""
    from hermes_cli.plugins import (
        MAX_SYSTEM_PROMPT_SECTION_CHARS, PLUGIN_SECTIONS_END, PLUGIN_SECTIONS_START,
        RenderedPluginSystemPromptSection, format_system_prompt_sections,
    )
    start = prompt.rfind(PLUGIN_SECTIONS_START)
    end = prompt.find(PLUGIN_SECTIONS_END, start + len(PLUGIN_SECTIONS_START)) if start >= 0 else -1
    if end < 0:
        return ()
    after_end = end + len(PLUGIN_SECTIONS_END)
    if not prompt[after_end:].startswith("\n\nConversation started:"):
        return ()
    framed = prompt[start:after_end]
    restored = []
    for match in _PLUGIN_SECTION_FRAME_RE.finditer(framed):
        content_len = int(match.group("chars"))
        content = framed[match.end() : match.end() + content_len]
        if content_len > MAX_SYSTEM_PROMPT_SECTION_CHARS or len(content) != content_len:
            continue
        restored.append(RenderedPluginSystemPromptSection(id=match.group("id"), content=content,
                                                          position="after_memory", plugin="persisted-prompt"))
    return tuple(restored) if format_system_prompt_sections(restored) == framed else ()


def restore_plugin_prompt_sections(agent: Any, prompt: str) -> None:
    """Seed a resumed agent's frozen snapshot from persisted prompt bytes."""
    agent._plugin_system_prompt_sections_snapshot = _restore_plugin_prompt_sections(prompt)


def _plugin_section_blocks(sections: tuple, position: str) -> List[str]:
    from hermes_cli.plugins import format_system_prompt_sections
    block = format_system_prompt_sections([s for s in sections if s.position == position])
    return [block] if block else []


def _session_start_like(agent: Any, now: Any) -> Any:
    """Best-known conversation start time, or ``now`` as a fallback.
    ``Conversation started:`` must be byte-stable across rebuilds (compression,
    resume, fresh gateway turns), so prefer immutable sources in order: the
    lineage-root session id's embedded stamp (compaction rotates ids, each with
    its own mint time), the current session id's stamp, ``agent.session_start``,
    then ``now``.  Stamps are box-local wall-clock: attach that zone first, then
    convert to ``now``'s zone so the date matches the per-turn clock.

    0. the LINEAGE-ROOT session id's embedded timestamp — compaction can rotate the session id, and each
    rotated id embeds its OWN mint time, so after months of compactions rung 1 alone would quietly re-birth
    the conversation at its latest rotation. Walking to the lineage root (same walk as
    ``_conversation_root_id``) recovers the ORIGINAL birth stamp — a Bot Mode forever-chat keeps knowing
    when it was first born, across every compaction (maintainer-directed, #98426); 1. the timestamp embedded
    in ``session_id`` (``YYYYMMDD_HHMMSS_...``) — immutable for the life of the session, so the line is
    byte-stable across every rebuild boundary (preserving prefix-cache KV); 2. 3. ``now`` (initial/legacy
    build without either).
    """
    from datetime import datetime
    def _to_display_tz(dt: Any) -> Any:
        if dt.tzinfo is None:
            try:
                dt = dt.replace(tzinfo=datetime.now().astimezone().tzinfo)
            except (ValueError, OSError):
                pass
        if getattr(now, "tzinfo", None) is not None and dt.tzinfo is not None:
            try:
                dt = dt.astimezone(now.tzinfo)
            except (ValueError, OSError):
                pass
        return dt
    session_id = getattr(agent, "session_id", None)
    db = getattr(agent, "_session_db", None)
    try:
        root_id = db.get_conversation_root(session_id) if db is not None and isinstance(session_id, str) and session_id else None
    except Exception:
        root_id = None
    for candidate in (root_id, session_id):
        m = re.match(r"^(\d{8})_(\d{6})", candidate) if isinstance(candidate, str) else None
        if m:
            try:
                return _to_display_tz(datetime.strptime(f"{m.group(1)}_{m.group(2)}", "%Y%m%d_%H%M%S"))
            except ValueError:
                pass
    session_start = getattr(agent, "session_start", None)
    return _to_display_tz(session_start) if hasattr(session_start, "astimezone") else now


def _agent_home(agent: Any) -> Optional[Path]:
    """The agent's OWN profile home, or None to use ambient resolution.
    A bound HERMES_HOME ContextVar override wins (the gateway multiplexes
    profiles over one shared session DB and binds the home per turn); else the
    parent of ``_session_db.db_path`` — ground truth on threads that lost the
    ContextVar, where ambient resolution would leak the launch profile.

    1. Surfaces that multiplex several profiles over ONE shared session DB (the messaging gateway:
    ``gateway/run.py`` hands every agent the launch-home ``state.db`` and binds the profile home per turn
    via ``_profile_runtime_scope`` + ``copy_context``) would otherwise have the db-derived launch home STOMP
    the correctly-bound profile — inverting the leak this helper exists to fix (found by @kshitijk4poor's
    post-merge probe on #86313). 2. Fallback: the home containing the agent's ``_session_db.db_path``
    (``<home>/state.db``) — ground truth on threads that lost the ContextVar (ContextVars don't propagate
    into ``threading.Thread``), where the unbound build previously fell back to the launch home and leaked
    the default profile's skills/identity into a bot prompt.
    """
    try:
        from hermes_constants import get_hermes_home_override
        override = get_hermes_home_override()
        if override:
            return Path(override)
    except Exception:
        pass
    try:
        db_path = getattr(getattr(agent, "_session_db", None), "db_path", None)
        return Path(db_path).parent if db_path else None
    except Exception:
        return None


def _agent_skills_dir(agent: Any) -> Optional[Path]:
    """The agent's own ``<home>/skills`` dir, or None to use ambient home."""
    home = _agent_home(agent)
    return home / "skills" if home is not None else None


def _profile_name_for_home(home: Path) -> str:
    """``<root>/profiles/X`` -> ``"X"``; anything else -> ``"default"``.
    Uses ``get_default_hermes_root()`` (NOT ``get_hermes_home()``): on a bound
    profile session the ambient home IS the profile dir, so every profile
    would misreport as "default"."""
    try:
        from hermes_constants import get_default_hermes_root
        rel = home.resolve().relative_to((get_default_hermes_root() / "profiles").resolve())
        return rel.parts[0] if rel.parts else "default"
    except (ValueError, OSError):
        return "default"


def _tool_guidance_block(agent: Any) -> Optional[str]:
    """Tool-aware behavioral guidance, injected only when the tools are loaded."""
    names = agent.valid_tool_names
    # With both memory stores disabled no store is built, so the full guidance
    # would steer the model at a tool that always answers "Memory is not
    # available"; with only USER.md enabled the narrower block is used.
    memory_guidance = None
    if "memory" in names:
        memory_guidance = _pb.build_memory_guidance(
            getattr(agent, "_memory_enabled", True),
            getattr(agent, "_user_profile_enabled", True),
            skill_manage_available="skill_manage" in names,
        )
    # Kanban lifecycle: resolved once at __init__ (_kanban_worker_guidance);
    # fallback paths must also limit task protocol guidance to dispatcher workers.
    _kanban_guidance = getattr(agent, "_kanban_worker_guidance", None)
    if _kanban_guidance is None and "kanban_show" in names and owned_kanban_task():
        _kanban_guidance = KANBAN_GUIDANCE
    tool_guidance = [
        memory_guidance,
        SESSION_SEARCH_GUIDANCE if "session_search" in names else None,
        SKILLS_GUIDANCE if "skill_manage" in names else None,
        _kanban_guidance,
    ]
    return " ".join(g for g in tool_guidance if g) or None


def _skills_prompt(agent: Any) -> str:
    """Skills index (empty without skills tools).  Focus mode demotes non-coding
    categories to names-only — never hidden, every name stays visible."""
    if not any(name in agent.valid_tool_names for name in ['skills_list', 'skill_view', 'skill_manage']):
        return ""
    import model_tools
    avail_toolsets = {model_tools.get_toolset_for_tool(tool_name) for tool_name in agent.valid_tool_names} - {None, ""}
    try:
        from agent.coding_context import coding_compact_skill_categories
        _compact_cats = coding_compact_skill_categories(platform=agent.platform, cwd=resolve_context_cwd())
    except Exception:
        _compact_cats = frozenset()
    return _pb.build_skills_system_prompt(available_tools=agent.valid_tool_names, available_toolsets=avail_toolsets,
                                         compact_categories=_compact_cats or None, skills_dir_override=_agent_skills_dir(agent))


def _auto_load_parts(agent: Any) -> List[str]:
    """``skills.auto_load`` blocks, resolved once per agent lifecycle (config, skill files and
    HERMES_IGNORE_RULES are read on the first build only) so the prompt stays byte-stable
    across model switches, compression and static-prefix restoration.

    Same gate as ``_skills_prompt``: nothing without the skills toolset, and nothing for agents that skip
    context files (delegate children, curator/review forks, gateway hygiene agents) — pinned skills are
    operator guidance for the user's session, not payload for every internal fork."""
    if getattr(agent, "skip_context_files", False) or not any(
            name in agent.valid_tool_names for name in ("skills_list", "skill_view", "skill_manage")):
        return []
    if not getattr(agent, "_auto_load_skills_resolved", False):
        result: Tuple[str, List[str], List[str]] = ("", [], [])
        try:
            if not is_truthy_value(os.environ.get("HERMES_IGNORE_RULES")):
                from agent.skill_commands import build_auto_load_prompt
                result = build_auto_load_prompt(task_id=getattr(agent, "session_id", None), home_override=_agent_home(agent))
            if result[2]:
                logger.warning("skills.auto_load: skill(s) not found or disabled, skipped: %s", ", ".join(result[2]))
        except Exception:
            logger.debug("skills.auto_load: injection skipped", exc_info=True)  # config errors never block session start
        agent._auto_load_skills_result = result
        agent._auto_load_skills_resolved = True
    prompt = agent._auto_load_skills_result[0]
    return [prompt] if prompt else []


def _bot_mode_parts(agent: Any) -> List[str]:
    """Bot Mode teammate protocol — only in a bot's canonical "Bot Chat" session.
    Marks the prompt timeless (the volatile date line is dropped) since a birth
    date pinned in a months-long session is misinformation."""
    parts: List[str] = []
    try:
        from tools.bot_mode_probe import BOT_CHAT_TITLE, epoch_line, get_bot_mode_protocol_section
        _title = str(getattr(agent, "_session_title_hint", "") or "").strip()
        if not _title:
            _sdb = getattr(agent, "_session_db", None)
            _sid = getattr(agent, "session_id", None)
            _title = str((_sdb.get_session_title(_sid) if (_sdb and _sid) else None) or "").strip()
        _bot_section = get_bot_mode_protocol_section(_agent_home(agent)) if _title == BOT_CHAT_TITLE else None
        if _bot_section:
            parts.append(_bot_section)
            # Capability epoch lets the restore path rebuild ONCE per
            # user-initiated capability change in an eternal session.
            parts.append(epoch_line(_agent_home(agent)))
            agent._bot_chat_timeless_prompt = True
    except Exception:
        pass
    return parts


def _ambient_file_safety_profile_name() -> str:
    from agent.file_safety import _resolve_active_profile_name
    return _resolve_active_profile_name()


def _active_profile_line(agent: Any) -> str:
    """Name the running profile so the agent doesn't conflate ``~/.hermes/skills``
    (default) with ``~/.hermes/profiles/<active>/skills``.  Resolved from the
    agent's OWN home first (a build thread that lost the ContextVar would
    otherwise print "default" for a bot profile)."""
    _agent_home_path = _agent_home(agent)
    active_profile = _active_profile_name(agent, _ambient_file_safety_profile_name)
    if active_profile == "default":
        # With an explicit agent home, the default profile's data lives at the
        # ROOT (get_hermes_home() on a bound profile session is the PROFILE dir).
        # Without one, keep the ambient (patchable) resolution byte-identical.
        _root_str = str(get_default_hermes_root() if _agent_home_path is not None else get_hermes_home())
        return (
            "Active Hermes profile: default. Other profiles (if any) live "
            "under " + _root_str + "/profiles/<name>/. Each profile has its own "
            "skills/, plugins/, cron/, and memories/ that affect a different "
            "session than this one. Do not modify another profile's "
            "skills/plugins/cron/memories unless the user explicitly directs "
            "you to."
        )
    # A non-default name is only returned when the resolved home is ALREADY
    # <root>/profiles/<name>, so the profile home is the session home itself.
    profile_home = str(_agent_home_path) if _agent_home_path is not None else str(get_hermes_home())
    # A non-default name is only ever returned when the resolved home is ALREADY <root>/profiles/<name> —
    # that is exactly how both _profile_name_for_home() and _resolve_active_profile_name() derive it. So the
    # profile home is the session home itself; appending /profiles/<name> again doubled it (#72894). The
    # default profile's data sits at the ROOT (get_default_hermes_root()), which in ambient profile mode is
    # NOT get_hermes_home().
    default_root = get_default_hermes_root()
    return (
        f"Active Hermes profile: {active_profile}. This session reads "
        f"and writes {profile_home}/. The default "
        f"profile's data lives at {default_root}/skills/, {default_root}/plugins/, "
        f"{default_root}/cron/, {default_root}/memories/ — those belong to a "
        f"different session run from a different shell. Do NOT modify "
        f"another profile's skills/plugins/cron/memories unless the user "
        f"explicitly directs you to."
    )


def _default_platform_hint(platform_key: str) -> str:
    """Built-in hint, else the plugin adapter's ``platform_hint``, else ``""``."""
    hint = PLATFORM_HINTS.get(platform_key, "")
    if not hint and platform_key:
        try:
            from gateway.platform_registry import platform_registry
            _entry = platform_registry.get(platform_key)
            hint = (_entry and _entry.platform_hint) or ""
        except Exception:
            pass
    if platform_key == "telegram" and hint and _telegram_rich_messages_enabled():
        hint = hint.rstrip() + " " + TELEGRAM_RICH_MESSAGES_HINT
    return hint


def _cron_delivery_hint(agent: Any) -> str:
    """The destination channel's hint (default + its ``platform_hints`` override) for a cron agent.

    A cron agent runs as platform ``cron`` but its final response lands on the job's ``deliver``
    channel, so without this the model never learns that MEDIA: tags become Slack/Telegram
    attachments or that tables do not render there — and a user's ``platform_hints.slack.append``
    never reached scheduled jobs at all. The scheduler publishes the primary auto-deliver target
    into the session ContextVar before the agent runs (same seam ``send_message`` routes by).
    """
    from gateway.session_context import get_session_env
    deliver_key = get_session_env("HERMES_CRON_AUTO_DELIVER_PLATFORM", "").lower().strip()
    if not deliver_key or deliver_key == "cron":
        return ""
    hint = _resolve_platform_hint(agent, deliver_key, _default_platform_hint(deliver_key))
    return f"Delivery destination ({deliver_key}): {hint}" if hint else ""


def platform_hint(agent: Any) -> str:
    """Built-in/plugin platform hint + Telegram rich-messages opt-in + config
    override + desktop TUI clarifier; cron agents also carry their delivery channel's hint."""
    platform_key = (agent.platform or "").lower().strip()
    _effective_hint = _resolve_platform_hint(agent, platform_key, _default_platform_hint(platform_key))
    if platform_key == "tui" and _effective_hint:
        _effective_hint = _tui_embedded_pane_clarifier(_effective_hint)
    if platform_key == "cron":
        _delivery = _cron_delivery_hint(agent)
        if _delivery:
            _effective_hint = f"{_effective_hint}\n\n{_delivery}".strip()
    return _effective_hint


def _telegram_rich_messages_enabled() -> bool:
    """``rich_messages`` from the Telegram ``extra`` config; same precedence the
    adapter uses (top-level ``platforms.telegram.extra`` overrides
    ``gateway.platforms.telegram.extra`` at the leaf). False on any read failure."""
    try:
        from hermes_cli.config import load_config_readonly
        _cfg = load_config_readonly()
        _gw = (((_cfg.get("gateway") or {}).get("platforms") or {}).get("telegram") or {}).get("extra")
        _top = ((_cfg.get("platforms") or {}).get("telegram") or {}).get("extra")
        merged = {**(_gw if isinstance(_gw, dict) else {}), **(_top if isinstance(_top, dict) else {})}
        return bool(merged.get("rich_messages"))
    except Exception:
        return False


def _zone_bits(now: Any, tz: Any) -> List[str]:
    """IANA key, abbreviation (if different) and UTC offset — all constant for
    the day, so the byte-stable date line stays cacheable."""
    _iana = getattr(tz, "key", None)
    _abbrev = now.strftime("%Z")
    _offset = now.strftime("%z")  # '-0400' -> 'UTC-04:00'
    bits = [_iana] if _iana else []
    if _abbrev and _abbrev != _iana:
        bits.append(_abbrev)
    if _offset:
        bits.append(f"UTC{_offset[:3]}:{_offset[3:]}")
    return bits


def _timestamp_line(agent: Any) -> str:
    """Date-only so the prompt is byte-stable for the day; zone + offset so
    tools needn't guess EST vs EDT. Long-lived sessions get an "as of" line on
    rebuild days (the cache prefix is already invalidated at that boundary)."""
    from hermes_time import get_timezone as _hermes_tz, now as _hermes_now
    now = _hermes_now()
    _bits = _zone_bits(now, _hermes_tz())
    _zone_suffix = f" ({', '.join(_bits)})" if _bits else ""
    _start = _session_start_like(agent, now)
    timestamp_line = f"Conversation started: {_start.strftime('%A, %B %d, %Y')}{_zone_suffix}"
    # Second line (maintainer design, salvaging #96224's anchor): long-lived sessions — Bot Mode
    # forever-chats, messenger channels people never close — span many days and many compactions. A lone
    # birth date leads the model to believe it is still living in that old day. The prompt is rebuilt at
    # every compaction boundary, so stamp the rebuild day too: 'started' stays anchored and byte-stable, 'as
    # of' refreshes exactly when the cache prefix is already being invalidated (compaction), so the added
    # line costs no extra cache churn. Same-day sessions skip the second line entirely — nothing to correct,
    # and the single-line shape stays byte-identical for the day (prefix-cache safe).
    if now.strftime("%Y%m%d") != _start.strftime("%Y%m%d"):
        timestamp_line += (f"\nToday's date (as of the last context rebuild): {now.strftime('%A, %B %d, %Y')} "
                           "— trust this over the start date for what day it is now; query tools for exact time.")
    if getattr(agent, "_bot_chat_timeless_prompt", False):
        timestamp_line = f"Timezone: {', '.join(_bits)}" if _bits else ""
    trailer = (("Session ID", agent.session_id if agent.pass_session_id else None), ("Model", agent.model),
               ("Provider", agent.provider), ("Platform", agent.platform))
    return timestamp_line + "".join(f"\n{label}: {value}" for label, value in trailer if value)


def _memory_parts(agent: Any) -> List[str]:
    """Built-in memory/USER.md blocks plus the external provider block (gated on
    the same check ``inject_memory_provider_tools`` uses, so we never advertise
    tools the toolset config gated off)."""
    parts: List[str] = []
    if agent._memory_store:
        for enabled, kind in ((agent._memory_enabled, "memory"), (agent._user_profile_enabled, "user")):
            block = agent._memory_store.format_for_system_prompt(kind) if enabled else None
            if block:
                parts.append(block)
    # External memory provider system prompt block (additive to built-in). Gated on the same check
    # ``inject_memory_provider_tools`` uses so we never advertise provider tools that the agent's toolset
    # configuration has already gated off (#81014).
    if agent._memory_manager:
        try:
            from agent.memory_manager import memory_provider_tools_exposed as _mem_exposed
        except Exception:
            _mem_exposed = None
        if _mem_exposed is None or _mem_exposed(agent):
            try:
                _ext_mem_block = agent._memory_manager.build_system_prompt()
            except Exception:
                _ext_mem_block = None
            if _ext_mem_block:
                parts.append(_ext_mem_block)
    return parts


def _identity_parts(agent: Any, ctx_len: Optional[int]) -> Tuple[List[str], bool]:
    """SOUL.md (primary identity; cron keeps the persona while skipping cwd
    instructions, scoped to the agent's OWN home) or the default identity.
    Returns ``(parts, soul_loaded)``."""
    wants_soul = agent.load_soul_identity or not agent.skip_context_files
    _soul_content = _pb.load_soul_md(ctx_len, home_override=_agent_home(agent)) if wants_soul else None
    return ([_soul_content], True) if _soul_content else ([DEFAULT_AGENT_IDENTITY], False)


def _guidance_parts(agent: Any) -> List[str]:
    """Universal + tool-aware + model-gated guidance blocks, each gated by its config.yaml key."""
    parts: List[str] = []
    if agent.valid_tool_names:
        parts += [
            text for flag, text in (
                ("_task_completion_guidance", TASK_COMPLETION_GUIDANCE),
                ("_parallel_tool_call_guidance", PARALLEL_TOOL_CALL_GUIDANCE),
            ) if getattr(agent, flag, True)
        ]
    parts.append(_tool_guidance_block(agent))  # None/empty entries are dropped by _join_tier
    if not agent.valid_tool_names:
        return parts
    # Steering only lands inside tool results, so only reachable with tools.
    parts.append(STEER_CHANNEL_NOTE)
    # agent.tool_use_enforcement / agent.execution_guidance: "auto" (default)
    # matches the hardcoded model lists; true/false force; a list gives custom
    # model-name substrings.  Execution guidance is an independent gate so
    # DeepSeek/Kimi/Qwen-class models get it even with enforcement off.
    if _model_gate(agent._tool_use_enforcement, agent.model, TOOL_USE_ENFORCEMENT_MODELS):
        parts.append(TOOL_USE_ENFORCEMENT_GUIDANCE)
        if any(g in (agent.model or "").lower() for g in ("gemini", "gemma")):
            parts.append(GOOGLE_MODEL_OPERATIONAL_GUIDANCE)
    if _model_gate(getattr(agent, "_execution_guidance", "auto"), agent.model, EXECUTION_GUIDANCE_MODELS):
        from agent.prompt_builder import execution_guidance_text
        parts.append(execution_guidance_text())
    return parts


def _alibaba_identity_part(agent: Any) -> List[str]:
    """Alibaba Coding Plan always reports "glm-4.7" as the model name; inject
    the real identity so the agent can answer correctly."""
    if agent.provider != "alibaba":
        return []
    _model_short = agent.model.rsplit("/", 1)[-1]
    return [
        f"You are powered by the model named {_model_short}. "
        f"The exact model ID is {agent.model}. "
        f"When asked what model you are, always answer based on this information, "
        f"not on any model name returned by the API."
    ]


def _coding_parts(agent: Any) -> Tuple[List[str], List[str], List[str]]:
    """``(prefix, workspace, trailing)`` coding-posture blocks; all empty
    without tools or when probing fails (it must never block prompt build).

    The workspace block is a live git probe after project context, ahead of the whole
    volatile band; re-probing at the compaction rebuild re-emits different bytes for any
    repo that moved and defeats the keep-prompt fast path.  So the bytes are pinned per
    session on the agent, keyed by the resolved cwd (a gateway serves many cwds), and
    replayed on rebuilds; ``reset_session_state`` drops the pin at a session boundary.
    """
    try:
        from agent.coding_context import coding_system_prompt_parts
        if not agent.valid_tool_names:
            return [], [], []
        cwd = resolve_context_cwd()
        cwd_key = str(cwd) if cwd is not None else ""
        pinned = getattr(agent, "_frozen_workspace_snapshot", None)
        # "" is a real pinned value (no workspace here) — only a cwd mismatch re-probes.
        replay = pinned[1] if pinned is not None and pinned[0] == cwd_key else None
        parts = coding_system_prompt_parts(platform=agent.platform, cwd=cwd, model=agent.model,
                                           valid_tool_names=agent.valid_tool_names, workspace_block=replay)
        if replay is None:
            agent._frozen_workspace_snapshot = (cwd_key, parts[1][0] if parts[1] else "")
        return parts
    except Exception:
        pass
    return [], [], []


def _post_workspace_parts(agent: Any) -> List[str]:
    """Blocks that follow the worktree-specific context: environment probe
    (config.yaml agent.environment_probe; one line, nothing when clean, skipped
    for remote backends), bot-mode protocol, profile line, platform hint."""
    parts: List[str] = []
    if getattr(agent, "_environment_probe", True):
        try:
            from tools.env_probe import get_environment_probe_line
            parts.append(get_environment_probe_line())
        except Exception:
            pass  # Probe failure must never block prompt build.
    if getattr(agent, "_bot_mode_protocol", True):
        parts.extend(_bot_mode_parts(agent))
    parts += [_active_profile_line(agent), platform_hint(agent)]
    return parts


def _context_files_part(agent: Any, ctx_len: Optional[int], soul_loaded: bool) -> List[str]:
    """Project context files (AGENTS.md etc.) for the context tier. TERMINAL_CWD
    when set (gateway); None lets discovery fall back to the launch dir.  The
    install-tree fallback is only legitimate for cli/tui where the launch dir
    IS the user's shell cwd; desktop-pinned launch dirs are treated as the
    fallback they really are so the guard can reject Hermes's bundled AGENTS.md."""
    if agent.skip_context_files:
        return []
    launch_artifact = getattr(agent, "_context_cwd_is_launch_artifact", False)
    return [_pb.build_context_files_prompt(
        cwd=None if launch_artifact else resolve_context_cwd(), skip_soul=soul_loaded, context_length=ctx_len,
        allow_install_tree_fallback=agent.platform in ("cli", "tui"), home_override=_agent_home(agent))]


def _join_tier(parts: List[Optional[str]]) -> str:
    """Join non-empty parts; None/blank entries are dropped."""
    return "\n\n".join(p.strip() for p in parts if p and p.strip())


def build_system_prompt_parts(agent: Any, system_message: Optional[str] = None) -> Dict[str, str]:
    """Assemble the system prompt as three ordered cache tiers: ``stable`` (identity,
    guidance and the coding brief), ``context`` (caller ``system_message``, project
    context files, workspace snapshot and remaining workspace guidance) and
    ``volatile`` (skills index, memory, user profile, external memory block,
    timestamp line, runtime environment hints).  Worktree-dependent blocks follow project context so a
    shared context file can remain in the longest common prefix across worktrees.
    Never re-rendered mid-session."""
    # Model context window scales the context-file caps; stable per conversation.
    _cc_len = getattr(getattr(agent, "context_compressor", None), "context_length", None)
    _ctx_len = _cc_len if isinstance(_cc_len, int) and _cc_len > 0 else None
    # ── Stable tier ────────────────────────────────────────────────
    stable_parts, _soul_loaded = _identity_parts(agent, _ctx_len)
    # The skill_view() pointer dangles without skill tools OR without the
    # hermes-agent skill installed, so the variant is chosen after the skills
    # index is built; this slot holds its position.
    _help_guidance_slot = len(stable_parts)
    stable_parts.append(HERMES_AGENT_HELP_GUIDANCE_NO_SKILLS)
    stable_parts.extend(_guidance_parts(agent))
    skills_prompt = _skills_prompt(agent)
    # Skill-pointer variant requires BOTH skill_view AND the hermes-agent skill
    # in the rendered index (pure string check — inherits the index's stability).
    if "skill_view" in (agent.valid_tool_names or set()) and "- hermes-agent:" in skills_prompt:
        stable_parts[_help_guidance_slot] = HERMES_AGENT_HELP_GUIDANCE
    stable_parts.extend(_alibaba_identity_part(agent))
    # Pinned skills are per-agent constants (resolved once), so they live in the stable prefix.
    stable_parts.extend(_auto_load_parts(agent))
    # Coding posture: the operating brief stays in the stable prefix. The
    # environment block contains the current cwd/backend and belongs after
    # project context, not ahead of a large shared AGENTS.md block.
    environment_hints = _pb.build_environment_hints()
    coding_prefix_parts, coding_workspace_parts, coding_trailing_parts = _coding_parts(agent)
    stable_parts.extend(coding_prefix_parts)
    post_workspace_parts = _post_workspace_parts(agent)
    # ── Context tier (project/worktree-dependent, may change between sessions) ──
    context_parts: List[str] = []
    # ephemeral_system_prompt is injected at API-call time only, never cached.
    if system_message is not None:
        context_parts.append(system_message)
    context_parts.extend(_context_files_part(agent, _ctx_len, _soul_loaded))
    if coding_workspace_parts:
        context_parts.extend([*coding_workspace_parts, *coding_trailing_parts, *post_workspace_parts])
    else:
        # Preserve the stable placement for non-workspace sessions; there is no
        # worktree snapshot whose later position would improve their prefix.
        stable_parts.extend([*coding_trailing_parts, *post_workspace_parts])
    # ── Volatile tier (most likely to differ on a rebuild; kept last so the stable prefix stays reusable) ──
    # Skills are runtime-mutable, so the index leads the volatile band: on a longest-prefix
    # backend an unchanged index stays inside the reused prefix; a changed one re-prefills from here.
    volatile_parts: List[str] = [skills_prompt, *_memory_parts(agent)]
    # Plugin sections are confined to one coarse anchor in the volatile tail so
    # a resumed process can reconstruct the stable prefix without re-running plugins.
    volatile_parts.extend(_plugin_section_blocks(_frozen_plugin_prompt_sections(agent), "after_memory"))
    volatile_parts.append(_timestamp_line(agent))
    # Keep the renderer-owned runtime anchor after all user/plugin prose so quoted
    # host examples cannot shadow it during persisted-prompt validation.
    if environment_hints:
        # Embedder hints are prose too; reserve the delimiter for the renderer.
        environment_hints = environment_hints.replace(_pb.RUNTIME_ENVIRONMENT_HEADING, "> " + _pb.RUNTIME_ENVIRONMENT_HEADING)
        volatile_parts.append(f"{_pb.RUNTIME_ENVIRONMENT_HEADING}\n\n{environment_hints}\n\n{_pb.RUNTIME_ENVIRONMENT_END}")
    return {"stable": _join_tier(stable_parts), "context": _join_tier(context_parts), "volatile": _join_tier(volatile_parts)}


def build_system_prompt(agent: Any, system_message: Optional[str] = None) -> str:
    """Assemble the full prompt; cached on ``agent._cached_system_prompt`` and
    only rebuilt after compression.  Tiers are ordered stable -> context ->
    volatile so implicit longest-prefix caches keep the unchanged scaffold."""
    parts = build_system_prompt_parts(agent, system_message=system_message)
    agent._cached_system_prompt_static = parts["stable"]
    # Surface context-file truncation warnings in chat, not only in logs.
    for warning in drain_truncation_warnings():
        agent._emit_diagnostic_status(warning)
    return "\n\n".join(p for p in (parts["stable"], parts["context"], parts["volatile"]) if p)


def invalidate_system_prompt(agent: Any) -> None:
    """Force a rebuild on the next turn (after compression): reload memory from
    disk and clear the frozen plugin snapshot (previous bytes stashed as the
    fail-open fallback) so plugins re-render at the same boundary.

    Called after context compression events. Also reloads memory from disk so the rebuilt prompt captures
    any writes from this session, and clears the frozen plugin-section snapshot so plugins re-render at the
    same boundary (maintainer-directed, #95681 arc): a plugin section is just another prompt block carrying
    state — freezing it while memory, skills, and guidance refresh would recreate the stale-block disease
    inside plugin-land. The previous bytes are stashed so a plugin whose render RAISES falls back to its
    last good section instead of vanishing (fail-open guard, not a freeze).
    """
    agent._cached_system_prompt = None
    agent._cached_system_prompt_static = None
    if hasattr(agent, "_plugin_system_prompt_sections_snapshot"):
        agent._plugin_system_prompt_sections_previous = agent._plugin_system_prompt_sections_snapshot
        del agent._plugin_system_prompt_sections_snapshot
    if agent._memory_store:
        agent._memory_store.load_from_disk()


def reconstruct_static_prefix(agent: Any, system_message: Optional[str] = None, *, log_label: str = "restore") -> None:
    """Reconstruct ``_cached_system_prompt_static`` for a stored prompt.
    Only the full prompt is persisted, so restore / keep-prompt compression /
    mid-turn failover to a cache-on provider must rebuild the stable tier to
    regain the ``[static, volatile]`` layout.  The rebuilt tier is used ONLY
    when the stored prompt literally starts with it; otherwise static stays
    None and the stored bytes are sent untouched.  A failed rebuild is memoized
    per stored prompt so the retry-loop hot path doesn't redo the file I/O."""
    stored = getattr(agent, "_cached_system_prompt", None)
    existing = getattr(agent, "_cached_system_prompt_static", None)
    if (
        not getattr(agent, "_use_prompt_caching", False)
        or not isinstance(stored, str) or not stored
        or (isinstance(existing, str) and existing and stored.startswith(existing))
        or getattr(agent, "_static_rebuild_failed_for", None) == stored
    ):
        return
    try:
        static = build_system_prompt_parts(agent, system_message=system_message)["stable"]
        if static and stored.startswith(static):
            agent._cached_system_prompt_static = static
            agent._static_rebuild_failed_for = None
            return
    except Exception:
        logger.debug("static system-prefix reconstruction failed on %s", log_label, exc_info=True)
    agent._cached_system_prompt_static = None
    agent._static_rebuild_failed_for = stored


def format_tools_for_system_message(agent: Any) -> str:
    """JSON tool definitions in the trajectory format."""
    if not agent.tools:
        return "[]"
    return json.dumps([{"name": t["function"]["name"], "description": t["function"].get("description", ""),
                        "parameters": t["function"].get("parameters", {}),
                        "required": None}  # Match the format in the example
                       for t in agent.tools], ensure_ascii=False)


__all__ = ["build_system_prompt_parts", "build_system_prompt", "invalidate_system_prompt",
           "platform_hint", "restore_plugin_prompt_sections", "format_tools_for_system_message"]


# ---- BEGIN PLUGIN-COMPAT (revert-scheduled; see COMPAT_MANIFEST.md) ----
# Names external plugins imported from this module before the Sep 2026 decomposition.
# Internal code MUST NOT use these (scripts/check_compat_pointers.py fails CI if it does).
# The whole block is removed by reverting the commit that added it.


_PLUGIN_COMPAT_LAZY = {
    'OPENAI_MODEL_EXECUTION_GUIDANCE': ('agent.prompt_builder', 'OPENAI_MODEL_EXECUTION_GUIDANCE'),
}


def __getattr__(name):  # PEP 562 — lazy so no import cycles
    target = _PLUGIN_COMPAT_LAZY.get(name)
    if target is None:
        raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
    import importlib
    from hermes_cli.plugin_compat import warn_once
    warn_once(__name__, name, *target)
    return getattr(importlib.import_module(target[0]), target[1])
# ---- END PLUGIN-COMPAT ----
