"""Context compression — extract the AIAgent methods that drive summarisation.

Three concerns live here:

* :func:`check_compression_model_feasibility` — startup probe of the
  configured auxiliary compression model.  Warns when the aux context
  window can't fit the main model's compression threshold; auto-lowers
  the session threshold when possible; hard-rejects auxes below
  ``MINIMUM_CONTEXT_LENGTH``.

* :func:`replay_compression_warning` — re-emit a stored warning through
  the gateway ``status_callback`` once it's wired up (the callback is
  set after :class:`AIAgent` construction).

* :func:`compress_context` — the actual compression call.  Runs the
  configured compressor, splits the SQLite session, rotates the
  session_id, notifies plugin context engines / memory providers, and
  returns the compressed message list and freshly-built system prompt.

* :func:`try_shrink_image_parts_in_messages` — image-too-large recovery
  helper that re-encodes ``data:image/...;base64,...`` parts at a smaller
  size so retries can fit under provider ceilings (Anthropic's 5 MB).

``run_agent`` keeps thin wrappers for each so existing call sites
(``self._compress_context(...)``) keep working.  Tests that exercise
these paths see no behavioural change.
"""

from __future__ import annotations

import logging
import os
import tempfile
import uuid
from datetime import datetime
from pathlib import Path
from typing import Any, Optional, Tuple

from agent.model_metadata import estimate_request_tokens_rough

logger = logging.getLogger(__name__)


def _compression_lock_holder(agent: Any) -> str:
    """Build a unique holder id for the lock: pid:tid:agent-instance:uuid.

    The pid+tid prefix lets ops tell crashed/abandoned holders apart from
    live ones (expiry-based recovery uses the timestamp, but ``holder``
    is what shows up in diagnostics + log lines). The agent instance id
    and a per-acquire uuid disambiguate two co-resident agents on the
    same thread (background_review forks run on a worker thread, but
    on machines where compression itself dispatches to a thread pool
    we want each acquire to be unique).
    """
    import threading
    return (
        f"pid={os.getpid()}"
        f":tid={threading.get_ident()}"
        f":agent={id(agent):x}"
        f":nonce={uuid.uuid4().hex[:8]}"
    )


def check_compression_model_feasibility(agent: Any) -> None:
    """Warn at session start if the auxiliary compression model's context
    window is smaller than the main model's compression threshold.

    When the auxiliary model cannot fit the content that needs summarising,
    compression will either fail outright (the LLM call errors) or produce
    a severely truncated summary.

    Called during ``AIAgent.__init__`` so CLI users see the warning
    immediately (via ``_vprint``).  The gateway sets ``status_callback``
    *after* construction, so :func:`replay_compression_warning` re-sends
    the stored warning through the callback on the first
    ``run_conversation()`` call.
    """
    if not agent.compression_enabled:
        return
    try:
        from agent.auxiliary_client import (
            _resolve_task_provider_model,
            get_text_auxiliary_client,
        )
        from agent.model_metadata import (
            MINIMUM_CONTEXT_LENGTH,
            get_model_context_length,
        )

        client, aux_model = get_text_auxiliary_client(
            "compression",
            main_runtime=agent._current_main_runtime(),
        )
        # Best-effort aux provider label for the warning message. The
        # configured provider may be "auto", in which case we fall back
        # to the client's base_url hostname so the user can still tell
        # where the compression model is actually being called.
        try:
            _aux_cfg_provider, _, _, _, _ = _resolve_task_provider_model("compression")
        except Exception:
            _aux_cfg_provider = ""
        if client is None or not aux_model:
            if _aux_cfg_provider and _aux_cfg_provider != "auto":
                msg = (
                    "⚠ Configured auxiliary compression provider "
                    f"'{_aux_cfg_provider}' is unavailable — context "
                    "compression will drop middle turns without a summary. "
                    "Check auxiliary.compression in config.yaml and "
                    "reauthenticate that provider."
                )
            else:
                msg = (
                    "⚠ No auxiliary LLM provider configured — context "
                    "compression will drop middle turns without a summary. "
                    "Run `hermes setup` or set OPENROUTER_API_KEY."
                )
            agent._compression_warning = msg
            agent._emit_status(msg)
            logger.warning(
                "No auxiliary LLM provider for compression — "
                "summaries will be unavailable."
            )
            return

        aux_base_url = str(getattr(client, "base_url", ""))
        # ``client.api_key`` may be a callable (Azure Foundry Entra ID
        # bearer provider). The context-length resolver chain expects a
        # string, but it only needs a key for live catalogue probes
        # (provider model lists). For Entra clients the model-metadata
        # chain still resolves via models.dev + hardcoded family
        # fallbacks, which don't require auth — pass empty string rather
        # than minting a bearer JWT just to look up a context length.
        _raw_aux_key = getattr(client, "api_key", "")
        aux_api_key = "" if (callable(_raw_aux_key) and not isinstance(_raw_aux_key, str)) else str(_raw_aux_key or "")

        aux_context = get_model_context_length(
            aux_model,
            base_url=aux_base_url,
            api_key=aux_api_key,
            config_context_length=getattr(agent, "_aux_compression_context_length_config", None),
            # Each model must be resolved with its own provider so that
            # provider-specific paths (e.g. Bedrock static table, OpenRouter API)
            # are invoked for the correct client, not inherited from the main model.
            provider=(_aux_cfg_provider if _aux_cfg_provider and _aux_cfg_provider != "auto" else getattr(agent, "provider", "")),
            custom_providers=agent._custom_providers,
        )

        # Hard floor: the auxiliary compression model must have at least
        # MINIMUM_CONTEXT_LENGTH (64K) tokens of context.  The main model
        # is already required to meet this floor (checked earlier in
        # __init__), so the compression model must too — otherwise it
        # cannot summarise a full threshold-sized window of main-model
        # content.  Mirrors the main-model rejection pattern.
        if aux_context and aux_context < MINIMUM_CONTEXT_LENGTH:
            raise ValueError(
                f"Auxiliary compression model {aux_model} has a context "
                f"window of {aux_context:,} tokens, which is below the "
                f"minimum {MINIMUM_CONTEXT_LENGTH:,} required by Hermes "
                f"Agent.  Choose a compression model with at least "
                f"{MINIMUM_CONTEXT_LENGTH // 1000}K context (set "
                f"auxiliary.compression.model in config.yaml), or set "
                f"auxiliary.compression.context_length to override the "
                f"detected value if it is wrong."
            )

        threshold = agent.context_compressor.threshold_tokens
        if aux_context < threshold:
            # Auto-correct: lower the live session threshold so
            # compression actually works this session.  The hard floor
            # above guarantees aux_context >= MINIMUM_CONTEXT_LENGTH,
            # so the new threshold is always >= 64K.
            #
            # The compression summariser sends a single user-role
            # prompt (no system prompt, no tools) to the aux model, so
            # new_threshold == aux_context is safe: the request is
            # the raw messages plus a small summarisation instruction.
            old_threshold = threshold
            new_threshold = aux_context
            agent.context_compressor.threshold_tokens = new_threshold
            # Keep threshold_percent in sync so future main-model
            # context_length changes (update_model) re-derive from a
            # sensible number rather than the original too-high value.
            main_ctx = agent.context_compressor.context_length
            if main_ctx:
                agent.context_compressor.threshold_percent = (
                    new_threshold / main_ctx
                )
            safe_pct = int((aux_context / main_ctx) * 100) if main_ctx else 50
            # Build human-readable "model (provider)" labels for both
            # the main model and the compression model so users can
            # tell at a glance which provider each side is actually
            # using. When the configured provider is empty or "auto",
            # fall back to the client's base_url hostname.
            _main_model = getattr(agent, "model", "") or "?"
            _main_provider = getattr(agent, "provider", "") or ""
            _aux_provider_label = (
                _aux_cfg_provider
                if _aux_cfg_provider and _aux_cfg_provider != "auto"
                else ""
            )
            if not _aux_provider_label:
                try:
                    from urllib.parse import urlparse
                    _aux_provider_label = (
                        urlparse(aux_base_url).hostname or aux_base_url
                    )
                except Exception:
                    _aux_provider_label = aux_base_url or "auto"
            _main_label = (
                f"{_main_model} ({_main_provider})"
                if _main_provider
                else _main_model
            )
            _aux_label = f"{aux_model} ({_aux_provider_label})"
            msg = (
                f"⚠ Compression model {_aux_label} context is "
                f"{aux_context:,} tokens, but the main model "
                f"{_main_label}'s compression threshold was "
                f"{old_threshold:,} tokens. "
                f"Auto-lowered this session's threshold to "
                f"{new_threshold:,} tokens so compression can run.\n"
                f"  To make this permanent, edit config.yaml — either:\n"
                f"  1. Use a larger compression model:\n"
                f"       auxiliary:\n"
                f"         compression:\n"
                f"           model: <model-with-{old_threshold:,}+-context>\n"
                f"  2. Lower the compression threshold:\n"
                f"       compression:\n"
                f"         threshold: 0.{safe_pct:02d}"
            )
            agent._compression_warning = msg
            agent._emit_status(msg)
            logger.warning(
                "Auxiliary compression model %s has %d token context, "
                "below the main model's compression threshold of %d "
                "tokens — auto-lowered session threshold to %d to "
                "keep compression working.",
                aux_model,
                aux_context,
                old_threshold,
                new_threshold,
            )
    except ValueError:
        # Hard rejections (aux below minimum context) must propagate
        # so the session refuses to start.
        raise
    except Exception as exc:
        logger.debug(
            "Compression feasibility check failed (non-fatal): %s", exc
        )


def replay_compression_warning(agent: Any) -> None:
    """Re-send the compression warning through ``status_callback``.

    During ``__init__`` the gateway's ``status_callback`` is not yet
    wired, so ``_emit_status`` only reaches ``_vprint`` (CLI).  This
    method is called once at the start of the first
    ``run_conversation()`` — by then the gateway has set the callback,
    so every platform (Telegram, Discord, Slack, etc.) receives the
    warning.
    """
    msg = getattr(agent, "_compression_warning", None)
    if msg and agent.status_callback:
        try:
            agent.status_callback("lifecycle", msg)
        except Exception:
            pass


def compress_context(
    agent: Any,
    messages: list,
    system_message: str,
    *,
    approx_tokens: Optional[int] = None,
    task_id: str = "default",
    focus_topic: Optional[str] = None,
    force: bool = False,
) -> Tuple[list, str]:
    """Compress conversation context and split the session in SQLite.

    Args:
        agent: The owning :class:`AIAgent`.
        messages: Current message history (will be summarised).
        system_message: Current system prompt; rebuilt after compression.
        approx_tokens: Pre-compression token estimate, logged for ops.
        task_id: Tool task scope (used for clearing file-read dedup state).
        focus_topic: Optional focus string for guided compression — the
            summariser will prioritise preserving information related to
            this topic.  Inspired by Claude Code's ``/compact <focus>``.
        force: If True, bypass any active summary-failure cooldown.  Set
            by the manual ``/compress`` slash command so users can retry
            immediately after an auto-compress abort.  Auto-compress
            callers use the default ``False``.

    Returns:
        ``(compressed_messages, new_system_prompt)`` tuple.  When
        compression aborts (aux LLM failed to produce a usable summary),
        returns the original messages unchanged and the existing system
        prompt — the session is NOT rotated.  Callers should detect the
        no-op via ``len(returned) == len(input)`` and stop the retry loop.
    """
    # Lazy feasibility check — run the auxiliary-provider probe + context
    # length lookup just-in-time on the first compression attempt instead of
    # at AIAgent.__init__. Saves ~400ms cold off every short session that
    # never reaches the threshold (the vast majority of ``chat -q`` runs).
    # The check itself sets ``agent._compression_warning`` so the
    # status-callback replay machinery still emits the warning to the user
    # the first time it would matter.
    if not getattr(agent, "_compression_feasibility_checked", False):
        # Mark as checked only after the probe completes. If the check
        # raises (e.g. a fatal aux-context ValueError that aborts the
        # session), leaving the flag unset is harmless; a non-fatal
        # transient failure is swallowed inside the function so the flag
        # is set normally on the next successful pass.
        check_compression_model_feasibility(agent)
        agent._compression_feasibility_checked = True

    _pre_msg_count = len(messages)
    logger.info(
        "context compression started: session=%s messages=%d tokens=~%s model=%s focus=%r",
        agent.session_id or "none", _pre_msg_count,
        f"{approx_tokens:,}" if approx_tokens else "unknown", agent.model,
        focus_topic,
    )
    agent._emit_status(
        "🗜️ Compacting context — summarizing earlier conversation so I can continue..."
    )

    # ── Compression lock ────────────────────────────────────────────────
    # Atomic, state.db-backed lock per session_id.  Without this, two
    # AIAgent instances that share the same session_id (most commonly the
    # parent-turn agent and its background-review fork — see
    # ``agent/background_review.py``: ``review_agent.session_id =
    # agent.session_id``) can each call compress() on overlapping
    # snapshots of the same conversation.  Both succeed, both rotate
    # ``agent.session_id`` to a fresh id, both create child sessions in
    # state.db parented to the same old id.  The gateway's SessionEntry
    # only catches one rotation, so the other child becomes an orphan
    # that silently accumulates writes — Damien's repro shape.
    #
    # Acquire keyed on the OLD session_id (the rotation target's parent),
    # because that's the id that competing paths see and read from
    # SessionEntry at the start of their own compression attempt.
    #
    # If we can't acquire the lock, another path is mid-compression on
    # this session.  Aborting is correct: the messages are unchanged, the
    # other path's rotation will produce the canonical new session_id,
    # and our caller's auto-compress loop sees ``len(returned) == len(input)``
    # and stops retrying for this cycle. The session is NOT corrupted —
    # we just sit out this round and let the winner finish.
    _lock_db = getattr(agent, "_session_db", None)
    _lock_sid = agent.session_id or ""
    _lock_holder: Optional[str] = None
    # Probe whether the lock subsystem is actually available on this
    # SessionDB instance.  A process running mismatched module versions
    # (e.g. ``conversation_compression.py`` reloaded after a pull but the
    # long-lived ``hermes_state.SessionDB`` class still bound to the
    # pre-#34351 version in memory) has the call site but not the method.
    # In that case ``try_acquire_compression_lock`` raises AttributeError —
    # NOT a ``sqlite3.Error`` — so the method's own fail-open guard never
    # runs and the exception propagates to the outer agent loop, which
    # prints the error and retries.  Because compression never succeeds,
    # the token count never drops and the loop re-triggers compaction
    # forever (the "API call #47/#48/#49 ... has no attribute
    # try_acquire_compression_lock" spin).  Fail OPEN here: if the lock
    # subsystem is missing or broken in any unexpected way, skip locking
    # and proceed with compression.  Skipping the lock risks a rare
    # concurrent-compression session fork; an infinite no-progress loop
    # that never compresses at all is strictly worse.
    if _lock_db is not None and _lock_sid:
        _lock_holder = _compression_lock_holder(agent)
        try:
            _lock_acquired = _lock_db.try_acquire_compression_lock(
                _lock_sid, _lock_holder
            )
        except Exception as _lock_err:
            # Broken/absent lock subsystem (version skew, etc.).  Log once
            # per session and proceed WITHOUT the lock rather than letting
            # the exception spin the outer loop.
            _lock_holder = None  # we don't own anything to release
            if getattr(agent, "_last_compression_lock_error_sid", None) != _lock_sid:
                agent._last_compression_lock_error_sid = _lock_sid
                logger.warning(
                    "compression lock subsystem unavailable for session=%s "
                    "(%s: %s) — proceeding without lock. This usually means a "
                    "stale in-memory module after an update; restart the "
                    "process (or `hermes update`) to resync.",
                    _lock_sid, type(_lock_err).__name__, _lock_err,
                )
            _lock_acquired = True  # treat as acquired-but-unlocked; proceed
        if not _lock_acquired:
            try:
                existing = _lock_db.get_compression_lock_holder(_lock_sid)
            except Exception:
                existing = None
            logger.warning(
                "compression skipped: another path is compressing session=%s "
                "(holder=%s) — returning messages unchanged to avoid session fork",
                _lock_sid, existing,
            )
            _lock_holder = None  # don't release a lock we don't own
            # Surface to the user once — quiet for downstream auto-compress loops
            if getattr(agent, "_last_compression_lock_warning_sid", None) != _lock_sid:
                agent._last_compression_lock_warning_sid = _lock_sid
                try:
                    agent._emit_warning(
                        "⚠ Skipping concurrent compression — another path "
                        "is already compressing this session. Will retry "
                        "after it finishes."
                    )
                except Exception:
                    pass
            _existing_sp = getattr(agent, "_cached_system_prompt", None)
            if not _existing_sp:
                _existing_sp = agent._build_system_prompt(system_message)
            return messages, _existing_sp

    def _release_lock() -> None:
        """Release the lock keyed on the OLD session_id (before rotation)."""
        if _lock_db is not None and _lock_sid and _lock_holder:
            try:
                _lock_db.release_compression_lock(_lock_sid, _lock_holder)
            except Exception as _rel_err:
                logger.debug("compression lock release failed: %s", _rel_err)

    # Notify external memory provider before compression discards context
    if agent._memory_manager:
        try:
            agent._memory_manager.on_pre_compress(messages)
        except Exception:
            pass

    try:
        compressed = agent.context_compressor.compress(messages, current_tokens=approx_tokens, focus_topic=focus_topic, force=force)
    except TypeError:
        # Plugin context engine with strict signature that doesn't accept
        # focus_topic / force — fall back to calling without them.
        compressed = agent.context_compressor.compress(messages, current_tokens=approx_tokens)
    except BaseException:
        # ANY exception during compress() must release the lock so the
        # session isn't permanently blocked from future compression.
        _release_lock()
        raise

    # If compression aborted (aux LLM failed to produce a usable summary)
    # the compressor returns the input messages unchanged.  Surface the
    # error to the user, skip the session-rotation work entirely (no
    # session has logically ended), and let auto-compress callers detect
    # the no-op via len(returned) == len(input).
    if getattr(agent.context_compressor, "_last_compress_aborted", False):
        _err = getattr(agent.context_compressor, "_last_summary_error", None) or "unknown error"
        if getattr(agent, "_last_compression_summary_warning", None) != _err:
            agent._last_compression_summary_warning = _err
            agent._emit_warning(
                f"⚠ Compression aborted: {_err}. "
                "No messages were dropped — conversation continues unchanged. "
                "Run /compress to retry, or /new to start a fresh session."
            )
        _existing_sp = getattr(agent, "_cached_system_prompt", None)
        if not _existing_sp:
            _existing_sp = agent._build_system_prompt(system_message)
        _release_lock()  # compression aborted — no rotation will happen
        return messages, _existing_sp

    summary_error = getattr(agent.context_compressor, "_last_summary_error", None)
    if summary_error:
        if getattr(agent, "_last_compression_summary_warning", None) != summary_error:
            agent._last_compression_summary_warning = summary_error
            agent._emit_warning(
                f"⚠ Compression summary failed: {summary_error}. "
                "Inserted a fallback context marker."
            )
    else:
        # No hard failure — but did the configured aux model error out
        # and get recovered by retrying on main?  Surface that so users
        # know their auxiliary.compression.model setting is broken even
        # though compression succeeded.
        _aux_fail_model = getattr(agent.context_compressor, "_last_aux_model_failure_model", None)
        _aux_fail_err = getattr(agent.context_compressor, "_last_aux_model_failure_error", None)
        if _aux_fail_model:
            # Dedup on (model, error) so we don't spam on every compaction
            _aux_key = (_aux_fail_model, _aux_fail_err)
            if getattr(agent, "_last_aux_fallback_warning_key", None) != _aux_key:
                agent._last_aux_fallback_warning_key = _aux_key
                agent._emit_warning(
                    f"ℹ Configured compression model '{_aux_fail_model}' failed "
                    f"({_aux_fail_err or 'unknown error'}). Recovered using main model — "
                    "check auxiliary.compression.model in config.yaml."
                )

    todo_snapshot = agent._todo_store.format_for_injection()
    if todo_snapshot:
        compressed.append({"role": "user", "content": todo_snapshot})

    agent._invalidate_system_prompt()
    new_system_prompt = agent._build_system_prompt(system_message)
    agent._cached_system_prompt = new_system_prompt

    if agent._session_db:
        try:
            # Propagate title to the new session with auto-numbering
            old_title = agent._session_db.get_session_title(agent.session_id)
            # Trigger memory extraction on the old session before it rotates.
            agent.commit_memory_session(messages)
            agent._session_db.end_session(agent.session_id, "compression")
            old_session_id = agent.session_id
            agent.session_id = f"{datetime.now().strftime('%Y%m%d_%H%M%S')}_{uuid.uuid4().hex[:6]}"
            # Ordering contract: the agent thread updates the contextvar here;
            # the gateway propagates to SessionEntry after run_in_executor returns.
            try:
                from gateway.session_context import set_current_session_id

                set_current_session_id(agent.session_id)
            except Exception:
                os.environ["HERMES_SESSION_ID"] = agent.session_id
            # The gateway/tools session context (ContextVar + env) and the
            # logging session context are SEPARATE mechanisms. The call above
            # moves the former; the ``[session_id]`` tag on log lines comes
            # from ``hermes_logging._session_context`` (set once per turn in
            # conversation_loop.py). Without this, post-rotation log lines in
            # the same turn keep the STALE old id while the message/DB/gateway
            # state carry the new one — breaking log correlation exactly at the
            # compaction boundary (see #34089). Guarded separately so a logging
            # failure can never regress the routing update above.
            try:
                from hermes_logging import set_session_context

                set_session_context(agent.session_id)
            except Exception:
                pass
            agent._session_db_created = False
            agent._session_db.create_session(
                session_id=agent.session_id,
                source=agent.platform or os.environ.get("HERMES_SESSION_SOURCE", "cli"),
                model=agent.model,
                model_config=agent._session_init_model_config,
                parent_session_id=old_session_id,
            )
            agent._session_db_created = True
            # Auto-number the title for the continuation session
            if old_title:
                try:
                    new_title = agent._session_db.get_next_title_in_lineage(old_title)
                    agent._session_db.set_session_title(agent.session_id, new_title)
                except (ValueError, Exception) as e:
                    logger.debug("Could not propagate title on compression: %s", e)
            agent._session_db.update_system_prompt(agent.session_id, new_system_prompt)
            # Reset flush cursor — new session starts with no messages written
            agent._last_flushed_db_idx = 0
        except Exception as e:
            logger.warning("Session DB compression split failed — new session will NOT be indexed: %s", e)

    # Notify the context engine that the session_id rotated because of
    # compression (not a fresh /new). Plugin engines (e.g. hermes-lcm) use
    # boundary_reason="compression" to preserve DAG lineage across the
    # rollover instead of re-initializing fresh per-session state.
    # See hermes-lcm#68. Built-in ContextCompressor ignores kwargs.
    try:
        _old_sid = locals().get("old_session_id")
        if _old_sid and hasattr(agent.context_compressor, "on_session_start"):
            agent.context_compressor.on_session_start(
                agent.session_id or "",
                boundary_reason="compression",
                old_session_id=_old_sid,
                conversation_id=getattr(agent, "_gateway_session_key", None),
            )
    except Exception as _ce_err:
        logger.debug("context engine on_session_start (compression): %s", _ce_err)

    # Notify memory providers of the compression-driven session_id rotation
    # so provider-cached per-session state (Hindsight's _document_id,
    # accumulated turn buffers, counters) refreshes. reset=False because
    # the logical conversation continues; only the id and DB row rolled
    # over. See #6672.
    try:
        _old_sid = locals().get("old_session_id")
        if _old_sid and agent._memory_manager:
            agent._memory_manager.on_session_switch(
                agent.session_id or "",
                parent_session_id=_old_sid,
                reset=False,
                reason="compression",
            )
    except Exception as _me_err:
        logger.debug("memory manager on_session_switch (compression): %s", _me_err)

    # Warn on repeated compressions (quality degrades with each pass)
    _cc = agent.context_compressor.compression_count
    if _cc >= 2:
        agent._vprint(
            f"{agent.log_prefix}⚠️  Session compressed {_cc} times — "
            f"accuracy may degrade. Consider /new to start fresh.",
            force=True,
        )

    # Keep the post-compression rough estimate for diagnostics, but do not
    # treat it as provider-reported prompt usage. Schema-heavy rough estimates
    # can remain above threshold even after the next real API request fits.
    _compressed_est = estimate_request_tokens_rough(
        compressed,
        system_prompt=new_system_prompt or "",
        tools=agent.tools or None,
    )
    agent.context_compressor.last_compression_rough_tokens = _compressed_est
    agent.context_compressor.last_prompt_tokens = -1
    agent.context_compressor.last_completion_tokens = 0
    agent.context_compressor.awaiting_real_usage_after_compression = True

    # Clear the file-read dedup cache.  After compression the original
    # read content is summarised away — if the model re-reads the same
    # file it needs the full content, not a "file unchanged" stub.
    try:
        from tools.file_tools import reset_file_dedup
        reset_file_dedup(task_id)
    except Exception:
        pass

    logger.info(
        "context compression done: session=%s messages=%d->%d rough_tokens=~%s awaiting_real_usage=true",
        agent.session_id or "none", _pre_msg_count, len(compressed),
        f"{_compressed_est:,}",
    )
    # Release the lock on the OLD session_id only AFTER rotation completed
    # and all post-rotation bookkeeping (memory manager, context engine,
    # file dedup) ran. A concurrent path that wakes up the moment we
    # release will see the NEW session_id in state.db / SessionEntry and
    # acquire on that — no race against our just-finished work.
    _release_lock()
    return compressed, new_system_prompt


def try_shrink_image_parts_in_messages(api_messages: list) -> bool:
    """Re-encode all native image parts at a smaller size to recover from
    image-too-large errors (Anthropic 5 MB, unknown other providers).

    Mutates ``api_messages`` in place. Returns True if any image part was
    actually replaced, False if there were no image parts to shrink or
    Pillow couldn't help (caller should surface the original error).

    Strategy: look for ``image_url`` / ``input_image`` parts carrying a
    ``data:image/...;base64,...`` payload.  For each one whose encoded
    size exceeds 4 MB (a safe target that slides under Anthropic's 5 MB
    ceiling with header overhead), write the base64 to a tempfile, call
    ``vision_tools._resize_image_for_vision`` to produce a smaller data
    URL, and substitute it in place.

    Non-data-URL images (http/https URLs) are not touched — the provider
    fetches those itself and the size limit is different.
    """
    if not api_messages:
        return False

    try:
        from tools.vision_tools import _resize_image_for_vision
    except Exception as exc:
        logger.warning("image-shrink recovery: vision_tools unavailable — %s", exc)
        return False

    # 4 MB target leaves comfortable headroom under Anthropic's 5 MB.
    # Non-Anthropic providers we haven't observed rejecting are fine with
    # much larger; shrinking to 4 MB here loses quality but only fires
    # after a confirmed provider rejection, so the alternative is failure.
    target_bytes = 4 * 1024 * 1024
    # Anthropic enforces an 8000px per-side dimension cap independently of
    # the 5 MB byte cap.  A tall screenshot can be well under 5 MB yet far
    # over 8000px (e.g. 1200×12000 at 0.06 MB).  We check pixel dimensions
    # even when the byte budget is fine.
    max_dimension = 8000
    changed_count = 0
    # Track parts that are over the target but could NOT be shrunk under it.
    # If any survive, retrying is pointless — the same oversized payload will
    # be re-sent and rejected again, wasting the single retry budget.  We only
    # report success (caller retries) when every over-threshold image was
    # actually brought under the target.
    unshrinkable_oversized = 0

    def _shrink_data_url(url: str) -> Optional[str]:
        """Return a smaller data URL, or None if shrink can't help."""
        if not isinstance(url, str) or not url.startswith("data:"):
            return None

        # Check both byte size AND pixel dimensions.
        needs_shrink = len(url) > target_bytes  # over byte budget
        if not needs_shrink:
            # Even if bytes are fine, check pixel dimensions against
            # Anthropic's 8000px cap.  A tall image can be tiny in bytes
            # yet huge in pixels.
            try:
                import base64 as _b64_dim
                header_d, _, data_d = url.partition(",")
                if not data_d:
                    return None
                raw_d = _b64_dim.b64decode(data_d)
                from PIL import Image as _PILImage
                import io as _io_dim
                with _PILImage.open(_io_dim.BytesIO(raw_d)) as _img:
                    if max(_img.size) <= max_dimension:
                        return None  # both bytes and pixels are fine
                needs_shrink = True  # pixels exceed limit, force shrink
            except Exception:
                # If we can't check dimensions (Pillow unavailable, corrupt
                # image, etc.), fall back to byte-only check.
                return None

        try:
            header, _, data = url.partition(",")
            mime = "image/jpeg"
            if header.startswith("data:"):
                mime_part = header[len("data:"):].split(";", 1)[0].strip()
                if mime_part.startswith("image/"):
                    mime = mime_part
            import base64 as _b64
            raw = _b64.b64decode(data)
            suffix = {
                "image/png": ".png", "image/gif": ".gif", "image/webp": ".webp",
                "image/jpeg": ".jpg", "image/jpg": ".jpg", "image/bmp": ".bmp",
            }.get(mime, ".jpg")
            tmp = tempfile.NamedTemporaryFile(
                prefix="hermes_shrink_", suffix=suffix, delete=False,
            )
            try:
                tmp.write(raw)
                tmp.close()
                resized = _resize_image_for_vision(
                    Path(tmp.name),
                    mime_type=mime,
                    max_base64_bytes=target_bytes,
                    max_dimension=max_dimension,
                )
            finally:
                try:
                    Path(tmp.name).unlink(missing_ok=True)
                except Exception:
                    pass
            if not resized or len(resized) >= len(url):
                # Shrink didn't help (or made it bigger — corrupt input?).
                return None
            return resized
        except Exception as exc:
            logger.warning("image-shrink recovery: re-encode failed — %s", exc)
            return None

    for msg in api_messages:
        if not isinstance(msg, dict):
            continue
        content = msg.get("content")
        if not isinstance(content, list):
            continue
        for part in content:
            if not isinstance(part, dict):
                continue
            ptype = part.get("type")
            if ptype not in {"image_url", "input_image"}:
                continue
            image_value = part.get("image_url")
            # OpenAI chat.completions: {"image_url": {"url": "data:..."}}
            # OpenAI Responses: {"image_url": "data:..."}
            if isinstance(image_value, dict):
                url = image_value.get("url", "")
                resized = _shrink_data_url(url)
                if resized:
                    image_value["url"] = resized
                    changed_count += 1
                elif isinstance(url, str) and url.startswith("data:") \
                        and len(url) > target_bytes:
                    unshrinkable_oversized += 1
            elif isinstance(image_value, str):
                resized = _shrink_data_url(image_value)
                if resized:
                    part["image_url"] = resized
                    changed_count += 1
                elif image_value.startswith("data:") \
                        and len(image_value) > target_bytes:
                    unshrinkable_oversized += 1

    if changed_count:
        logger.info(
            "image-shrink recovery: re-encoded %d image part(s) to fit under %.0f MB",
            changed_count, target_bytes / (1024 * 1024),
        )
    if unshrinkable_oversized:
        # At least one oversized image could not be shrunk under the target.
        # Retrying would re-send it and fail identically, so signal "no
        # progress" even if other parts shrank — the caller will surface the
        # original error rather than burning its single retry on a no-op.
        logger.warning(
            "image-shrink recovery: %d oversized image part(s) could not be "
            "shrunk under %.0f MB — not retrying (would re-send rejected payload)",
            unshrinkable_oversized, target_bytes / (1024 * 1024),
        )
        return False
    return changed_count > 0


__all__ = [
    "check_compression_model_feasibility",
    "replay_compression_warning",
    "compress_context",
    "try_shrink_image_parts_in_messages",
]
