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"""Text-only ModilifyMk2 model with recurrent latent deliberation."""

from __future__ import annotations

import copy
from collections.abc import Sequence
from dataclasses import dataclass, replace
from typing import Any

import torch
from torch import nn
from torch.nn import functional as F
from torch.utils.checkpoint import checkpoint
from transformers.cache_utils import Cache
from transformers.modeling_outputs import BaseModelOutputWithPast

from transformers.masking_utils import (
    ALL_MASK_ATTENTION_FUNCTIONS,
    bidirectional_mask_function,
)
from transformers.models.diffusion_gemma import (
    DiffusionGemmaDecoderModel,
    DiffusionGemmaEncoderTextModel,
    DiffusionGemmaPreTrainedModel,
)
from transformers.models.diffusion_gemma.modeling_diffusion_gemma import (
    DiffusionGemmaRMSNorm,
    DiffusionGemmaTextRouter,
)

from .mps_ops import register_mps_backends
from .adapters import LoRAConfig, inject_lora
from .configuration_modilify_mk2 import ModilifyMk2Config, DENOISE_TEMPERATURE
from .generation_modilify_mk2 import ModilifyMk2GenerationConfig, ModilifyMk2GenerationMixin
from .latent_deliberation import LatentDeliberationState, LatentProcessorOutput, _sdpa_mask_value
from .latent_deliberation import LatentDeliberationTransformer
from .vocab_ops import (
    chunked_vocab_statistics,
    chunked_vocab_training_statistics,
)


register_mps_backends()


@dataclass
class ModilifyMk2DecoderOutput(BaseModelOutputWithPast):
    token_embeddings: torch.FloatTensor | None = None
    latent_residual_diagnostics: dict[str, torch.Tensor] | None = None


@dataclass
class ModilifyMk2ModelOutput(BaseModelOutputWithPast):
    token_embeddings: torch.FloatTensor | None = None
    encoder_last_hidden_state: torch.FloatTensor | None = None
    latent_residual_diagnostics: dict[str, torch.Tensor] | None = None


@dataclass
class ModilifyMk2BlockDiffusionOutput:
    logits: torch.FloatTensor | None
    heavy_hidden_state: torch.FloatTensor
    next_latent_state: LatentDeliberationState
    gold_nll: torch.FloatTensor | None = None
    loss: torch.FloatTensor | None = None
    past_key_values: Cache | None = None
    hidden_states: tuple[torch.FloatTensor, ...] | None = None
    attentions: tuple[torch.FloatTensor, ...] | None = None
    encoder_last_hidden_state: torch.FloatTensor | None = None
    temporal_context: torch.FloatTensor | None = None
    heavy_context_leaf: torch.FloatTensor | None = None
    temporal_memory_slots: torch.FloatTensor | None = None
    heavy_memory_leaf: torch.FloatTensor | None = None
    working_state: torch.FloatTensor | None = None
    latent_residual_diagnostics: dict[str, torch.Tensor] | None = None
    temperature_gold_nll: torch.FloatTensor | None = None
    proposal: torch.LongTensor | None = None
    proposal_confidence: torch.FloatTensor | None = None
    sampled_nll: torch.FloatTensor | None = None
    token_entropy: torch.FloatTensor | None = None
    greedy_proposal: torch.LongTensor | None = None
    greedy_confidence: torch.FloatTensor | None = None

    def to_tuple(self) -> tuple[Any, ...]:
        return tuple(value for value in (
            self.loss, self.logits, self.past_key_values, self.hidden_states,
            self.attentions, self.encoder_last_hidden_state,
            self.heavy_hidden_state, self.next_latent_state,
        ) if value is not None)

    def __getitem__(self, key: str | int) -> Any:
        return getattr(self, key) if isinstance(key, str) else self.to_tuple()[key]


class ModilifyMk2TextRouter(DiffusionGemmaTextRouter):
    """Official router parameters with fp32 softmax so top-k weights stay finite."""

    def __init__(self, config: Any) -> None:
        super().__init__(config)
        self.norm = DiffusionGemmaRMSNorm(self.hidden_size, eps=self.eps, with_scale=False)

    def forward(
        self, hidden_states: torch.Tensor
    ) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
        hidden_states = self.norm(hidden_states)
        hidden_states = hidden_states * self.scale * self.scalar_root_size
        expert_scores = self.proj(hidden_states)
        # Match the official DiffusionGemma router: bf16 softmax underflows to
        # all-zero top-k rows, then 0/0 NaNs the MoE residual and every loss.
        router_probabilities = F.softmax(expert_scores, dim=-1, dtype=torch.float32)
        top_k_weights, top_k_index = torch.topk(
            router_probabilities,
            k=self.config.top_k_experts,
            dim=-1,
        )
        top_k_weights = top_k_weights / top_k_weights.sum(dim=-1, keepdim=True).clamp_min(
            torch.finfo(torch.float32).tiny
        )
        top_k_weights = top_k_weights * self.per_expert_scale[top_k_index]
        return router_probabilities, top_k_weights, top_k_index


def _finite_decoder_attention_mask(
    mask: torch.Tensor | None,
    *,
    dtype: torch.dtype,
) -> torch.Tensor | None:
    """Keep SDPA masks boolean and unmask fully-blocked query rows.

    Transformers' SDPA mask is True=attend.  A fully-False query row makes
    softmax(-inf) in the backward.  Converted additive 8k masks also double
    decoder workspace on long prefixes, so stay in bool and only apply the
    torch<2.5 empty-row workaround (pytorch/pytorch#110213).
    """

    del dtype
    if mask is None:
        return None
    if mask.dtype == torch.bool:
        return mask | ~mask.any(dim=-1, keepdim=True)
    return mask.clamp_min(_sdpa_mask_value(mask.dtype))


def install_modilify_mk2_trunk_semantics(module: nn.Module) -> None:
    """Swap official leaf modules on this instance. Never patch Transformers classes."""

    for name, child in list(module.named_children()):
        if type(child) is DiffusionGemmaTextRouter:
            replacement = ModilifyMk2TextRouter(child.config)
            replacement.load_state_dict(child.state_dict())
            setattr(module, name, replacement)
        else:
            install_modilify_mk2_trunk_semantics(child)


class ModilifyMk2EncoderModel(DiffusionGemmaPreTrainedModel):
    """Checkpoint-compatible wrapper around the text encoder trunk."""

    config_class = ModilifyMk2Config

    def __init__(self, config: ModilifyMk2Config):
        super().__init__(config)
        self.language_model = DiffusionGemmaEncoderTextModel(config.text_config)
        install_modilify_mk2_trunk_semantics(self)
        self.post_init()

    def get_input_embeddings(self) -> nn.Module:
        return self.language_model.embed_tokens

    def set_input_embeddings(self, value: nn.Module) -> None:
        self.language_model.embed_tokens = value

    def forward(self, **kwargs: Any) -> BaseModelOutputWithPast:
        return self.language_model(**kwargs)


class ModilifyMk2DecoderModel(DiffusionGemmaDecoderModel):
    """Diffusion decoder accepting compact self-conditioning embeddings."""

    config_class = ModilifyMk2Config
    latent_residual_rms_ratio_cap = 0.5

    def __init__(self, config: ModilifyMk2Config):
        super().__init__(config)
        self.gradient_checkpointing = False
        install_modilify_mk2_trunk_semantics(self)

    @staticmethod
    def create_diffusion_decoder_attention_mask(
        config: Any,
        inputs_embeds: torch.Tensor,
        past_key_values: Cache,
        decoder_attention_mask: torch.Tensor | dict | None = None,
    ) -> dict[str, torch.Tensor | None]:
        """Official mask builder without the all-True sliding-window skip."""

        if past_key_values is None:
            raise ValueError(
                "The diffusion mask requires `past_key_values` to construct the next attention mask correctly"
            )
        if (
            decoder_attention_mask is None
            or config._attn_implementation
            not in ALL_MASK_ATTENTION_FUNCTIONS._global_mapping
        ):
            return {"full_attention": None, "sliding_attention": None}
        if isinstance(decoder_attention_mask, dict) and all(
            mask.ndim == 4 for mask in decoder_attention_mask.values()
        ):
            return {
                name: _finite_decoder_attention_mask(
                    mask, dtype=inputs_embeds.dtype
                )
                for name, mask in decoder_attention_mask.items()
            }

        text_config = config.get_text_config() if hasattr(config, "get_text_config") else config
        q_length = inputs_embeds.shape[1]
        q_offset = past_key_values.get_seq_length()
        if isinstance(q_offset, torch.Tensor):
            q_offset = q_offset.to(inputs_embeds.device)
        additional_kv_length = (
            getattr(config, "canvas_length", 0) if past_key_values.is_compileable else 0
        )
        mask_mapping: dict[str, torch.Tensor | None] = {}
        for layer_pattern in set(text_config.layer_types):
            layer_idx = past_key_values.is_sliding.index(
                layer_pattern == "sliding_attention"
            )
            kv_length, kv_offset = past_key_values.get_mask_sizes(q_length, layer_idx)
            kv_length += additional_kv_length
            if layer_pattern == "sliding_attention" and past_key_values.is_compileable:
                sliding_layer = past_key_values.layers[layer_idx]
                max_length = sliding_layer.get_max_length() + additional_kv_length
                if kv_length >= max_length:
                    kv_length = max_length
            mask_mapping[layer_pattern] = _finite_decoder_attention_mask(
                ALL_MASK_ATTENTION_FUNCTIONS[config._attn_implementation](
                    batch_size=inputs_embeds.shape[0],
                    q_length=q_length,
                    kv_length=kv_length,
                    q_offset=q_offset,
                    kv_offset=kv_offset,
                    mask_function=bidirectional_mask_function,
                    attention_mask=decoder_attention_mask,
                    allow_is_causal_skip=False,
                    allow_is_bidirectional_skip=True,
                    local_size=getattr(text_config, "sliding_window", None),
                    dtype=inputs_embeds.dtype,
                    config=text_config,
                    use_vmap=False,
                    device=inputs_embeds.device,
                ),
                dtype=inputs_embeds.dtype,
            )
        return mask_mapping

    def merge_latent_context(
        self,
        token_embeddings: torch.Tensor,
        latent_context: torch.Tensor | None,
        *,
        collect_diagnostics: bool = True,
    ) -> tuple[torch.Tensor, dict[str, torch.Tensor]]:
        """Map latent context through the frozen native self-conditioning bridge."""

        if latent_context is None:
            context = torch.zeros_like(token_embeddings)
        else:
            if latent_context.shape != token_embeddings.shape:
                raise ValueError("Temporal context must match canvas hidden-state shape.")
            context = latent_context.to(token_embeddings)
        mapper = self.self_conditioning
        normalized_context = mapper.pre_norm(context)
        mapped_context = mapper.down_proj(
            mapper.act_fn(mapper.gate_proj(normalized_context))
            * mapper.up_proj(normalized_context)
        )
        mapped_fp32 = mapped_context.float()
        # Use the energy directly in the cap denominator.  Computing
        # sqrt(E[x²]) and immediately squaring it again has an undefined
        # backward at the identity-init point x=0 (0/0 in d(sqrt)/dx), which
        # poisoned the detached temporal-context VJP on every denoise.
        mapped_token_energy = mapped_fp32.square().mean(dim=-1, keepdim=True)
        token_rms_per_token = (
            token_embeddings.float().square().mean(dim=-1, keepdim=True).sqrt()
        )
        residual_cap = self.latent_residual_rms_ratio_cap * token_rms_per_token
        soft_cap_scale = residual_cap / torch.sqrt(
            mapped_token_energy + residual_cap.square() + 1.0e-12
        )
        mapped_context = (mapped_fp32 * soft_cap_scale).to(dtype=mapped_context.dtype)
        combined = token_embeddings + mapped_context
        diagnostics: dict[str, torch.Tensor] = {}
        if collect_diagnostics:
            token_rms = token_embeddings.detach().float().square().mean().sqrt()
            mapped_rms = mapped_context.detach().float().square().mean().sqrt()
            diagnostics = {
                "token_embedding_rms": token_rms,
                "latent_context_rms": context.detach().float().square().mean().sqrt(),
                "mapped_sc_rms": mapped_rms,
                "actual_residual_rms": mapped_rms,
                "latent_to_embedding_rms_ratio": (
                    mapped_rms / token_rms.clamp_min(1.0e-12)
                ),
                "merged_input_rms": combined.detach().float().square().mean().sqrt(),
            }
        return mapper.post_norm(combined), diagnostics

    def _run_stack(
        self,
        inputs_embeds: torch.Tensor,
        *,
        past_key_values: Cache | None,
        decoder_attention_mask: torch.Tensor | dict | None,
        decoder_position_ids: torch.LongTensor | None,
        **kwargs: Any,
    ) -> torch.Tensor:
        if decoder_position_ids is None:
            prefix = past_key_values.get_seq_length(layer_idx=0) if past_key_values is not None else 0
            decoder_position_ids = torch.arange(
                prefix, prefix + inputs_embeds.shape[1], device=inputs_embeds.device
            ).unsqueeze(0)
        if not isinstance(mask_mapping := decoder_attention_mask, dict):
            mask_mapping = self.create_diffusion_decoder_attention_mask(
                config=self.text_config,
                inputs_embeds=inputs_embeds,
                past_key_values=past_key_values,
                decoder_attention_mask=decoder_attention_mask,
            )
        working_bus = kwargs.pop("working_bus", None)
        working_state = kwargs.pop("working_state", None)
        working_canvas_head = kwargs.pop("working_canvas_head", None)
        persistent_bus = kwargs.pop("persistent_bus", None) or kwargs.pop("memory_bus", None)
        memory_slots = kwargs.pop("memory_slots", None)
        slot_identity = kwargs.pop("slot_identity", None)
        cache = past_key_values
        if self.gradient_checkpointing and self.training and cache is not None:
            cache = copy.copy(cache)
            cache.layers = [copy.copy(layer) for layer in cache.layers]
        hidden = inputs_embeds
        positions = {
            layer_type: self.rotary_emb(hidden, decoder_position_ids, layer_type)
            for layer_type in self.unique_layer_types
        }
        working_kv = None
        if working_bus is not None and working_state is not None:
            working_kv = working_bus.prepare_kv(working_state)
        memory_kv = None
        if persistent_bus is not None and memory_slots is not None:
            memory_kv = persistent_bus.prepare_kv(memory_slots, slot_identity)
        working_reader = 0
        reader_index = 0
        for index in range(self.text_config.num_hidden_layers):
            layer = self.layers[index]
            layer_type = self.text_config.layer_types[index]
            if self.gradient_checkpointing and self.training:
                def layer_forward(
                    values: torch.Tensor,
                    selected: nn.Module = layer,
                    selected_type: str = layer_type,
                ) -> torch.Tensor:
                    return selected(
                        values,
                        position_embeddings=positions[selected_type],
                        attention_mask=mask_mapping[selected_type],
                        position_ids=decoder_position_ids,
                        past_key_values=cache,
                        **kwargs,
                    )

                hidden = self._gradient_checkpointing_func(layer_forward, hidden)
            else:
                hidden = layer(
                    hidden,
                    position_embeddings=positions[layer_type],
                    attention_mask=mask_mapping[layer_type],
                    position_ids=decoder_position_ids,
                    past_key_values=cache,
                    **kwargs,
                )
            if layer_type == "full_attention":
                if (
                    working_kv is not None
                    and working_reader < working_bus.num_readers
                ):
                    hidden = working_bus.read(
                        hidden, working_reader, *working_kv,
                        positions=(
                            decoder_position_ids if working_canvas_head is not None else None
                        ),
                    )
                    working_reader += 1
                if (
                    memory_kv is not None
                    and reader_index < persistent_bus.num_readers
                ):
                    hidden = persistent_bus.read(
                        hidden, reader_index, memory_kv[0], memory_kv[1]
                    )
                    reader_index += 1
        return self.norm(hidden)

    def forward(
        self,
        decoder_input_ids: torch.LongTensor,
        past_key_values: Cache | None = None,
        decoder_token_embeddings: torch.FloatTensor | None = None,
        temporal_context_embeddings: torch.FloatTensor | None = None,
        decoder_attention_mask: torch.Tensor | dict | None = None,
        decoder_position_ids: torch.LongTensor | None = None,
        collect_latent_diagnostics: bool = True,
        memory_slots: torch.Tensor | None = None,
        working_bus: Any | None = None,
        working_state: torch.Tensor | None = None,
        persistent_bus: Any | None = None,
        slot_identity: torch.Tensor | None = None,
        **kwargs: Any,
    ) -> ModilifyMk2DecoderOutput:
        if "use_cache" in kwargs:
            raise ValueError("The diffusion decoder always reads the supplied cache.")
        if decoder_token_embeddings is None:
            token_embeddings = self.embed_tokens(decoder_input_ids)
        else:
            token_embeddings = decoder_token_embeddings
            expected = (*decoder_input_ids.shape, self.text_config.hidden_size)
            if token_embeddings.shape != expected:
                raise ValueError("Precomputed decoder embeddings have the wrong shape.")
        context_embeddings = (
            torch.zeros_like(token_embeddings)
            if temporal_context_embeddings is None
            else temporal_context_embeddings.to(token_embeddings)
        )
        inputs_embeds, diagnostics = self.merge_latent_context(
            token_embeddings,
            context_embeddings if temporal_context_embeddings is not None else None,
            collect_diagnostics=collect_latent_diagnostics,
        )
        hidden = self._run_stack(
            inputs_embeds,
            past_key_values=past_key_values,
            decoder_attention_mask=decoder_attention_mask,
            decoder_position_ids=decoder_position_ids,
            memory_slots=memory_slots,
            working_bus=working_bus,
            working_state=working_state,
            persistent_bus=persistent_bus,
            slot_identity=slot_identity,
            **kwargs,
        )
        return ModilifyMk2DecoderOutput(
            last_hidden_state=hidden,
            past_key_values=past_key_values,
            token_embeddings=token_embeddings,
            latent_residual_diagnostics=diagnostics,
        )


class ModilifyMk2Model(DiffusionGemmaPreTrainedModel):
    config_class = ModilifyMk2Config
    _tied_weights_keys = {
        "encoder.language_model.norm.weight": "decoder.norm.weight",
        r"encoder.language_model.layers\.(?:[^.]+\.)*weight": r"decoder.layers\.(?:[^.]+\.)*weight",
        r"encoder.language_model.layers\.(?:[^.]+\.)*scale": r"decoder.layers\.(?:[^.]+\.)*scale",
        r"encoder.language_model.layers\.(?:[^.]+\.)*per_expert_scale": r"decoder.layers\.(?:[^.]+\.)*per_expert_scale",
        r"encoder.language_model.layers\.(?:[^.]+\.)*gate_up_proj": r"decoder.layers\.(?:[^.]+\.)*gate_up_proj",
        r"encoder.language_model.layers\.(?:[^.]+\.)*down_proj": r"decoder.layers\.(?:[^.]+\.)*down_proj",
        "encoder.language_model.embed_tokens.weight": "decoder.embed_tokens.weight",
    }

    def __init__(self, config: ModilifyMk2Config):
        super().__init__(config)
        self.encoder = ModilifyMk2EncoderModel(config)
        self.decoder = ModilifyMk2DecoderModel(config)
        install_modilify_mk2_trunk_semantics(self)
        self.post_init()

    def get_encoder(self):
        return self.encoder

    def get_decoder(self):
        return self.decoder

    def get_input_embeddings(self):
        return self.encoder.get_input_embeddings()

    def set_input_embeddings(self, value):
        self.encoder.set_input_embeddings(value)
        self.decoder.embed_tokens = value

    def forward(
        self,
        *,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | dict | None = None,
        past_key_values: Cache | None = None,
        position_ids: torch.LongTensor | None = None,
        decoder_input_ids: torch.LongTensor,
        decoder_token_embeddings: torch.FloatTensor | None = None,
        temporal_context_embeddings: torch.FloatTensor | None = None,
        decoder_attention_mask: torch.Tensor | dict | None = None,
        decoder_position_ids: torch.LongTensor | None = None,
        return_encoder_outputs: bool = True,
        collect_latent_diagnostics: bool = True,
        memory_slots: torch.Tensor | None = None,
        working_bus: Any | None = None,
        working_state: torch.Tensor | None = None,
        persistent_bus: Any | None = None,
        slot_identity: torch.Tensor | None = None,
        **kwargs: Any,
    ) -> ModilifyMk2ModelOutput:
        encoder_hidden = None
        if input_ids is not None:
            encoded = self.encoder(
                input_ids=input_ids,
                attention_mask=attention_mask,
                past_key_values=past_key_values,
                position_ids=position_ids,
                **kwargs,
            )
            past_key_values = encoded.past_key_values
            if return_encoder_outputs:
                encoder_hidden = encoded.last_hidden_state
        elif past_key_values is None:
            raise ValueError("Either `input_ids` or `past_key_values` is required.")
        decoded = self.decoder(
            decoder_input_ids=decoder_input_ids,
            decoder_token_embeddings=decoder_token_embeddings,
            past_key_values=past_key_values,
            temporal_context_embeddings=temporal_context_embeddings,
            decoder_attention_mask=decoder_attention_mask,
            decoder_position_ids=decoder_position_ids,
            collect_latent_diagnostics=collect_latent_diagnostics,
            memory_slots=memory_slots,
            working_bus=working_bus,
            working_state=working_state,
            persistent_bus=persistent_bus,
            slot_identity=slot_identity,
            **kwargs,
        )
        return ModilifyMk2ModelOutput(
            last_hidden_state=decoded.last_hidden_state,
            past_key_values=past_key_values,
            token_embeddings=decoded.token_embeddings,
            encoder_last_hidden_state=encoder_hidden,
            latent_residual_diagnostics=decoded.latent_residual_diagnostics,
        )


class ModilifyMk2ForBlockDiffusion(DiffusionGemmaPreTrainedModel, ModilifyMk2GenerationMixin):
    config_class = ModilifyMk2Config
    _tied_weights_keys = {"lm_head.weight": "model.decoder.embed_tokens.weight"}
    generation_config_class = ModilifyMk2GenerationConfig
    _no_split_modules = ["DiffusionGemmaDecoderLayer", "LatentDeliberationTransformer"]
    supports_gradient_checkpointing = True

    @torch.no_grad()
    def _init_weights(self, module: nn.Module) -> None:
        super()._init_weights(module)
        if isinstance(module, LatentDeliberationTransformer):
            module.reset_identity_parameters()
            module.working_memory_bus.freeze()
            module.persistent_memory_bus.freeze()

    def __init__(self, config: ModilifyMk2Config):
        super().__init__(config)
        self.model = ModilifyMk2Model(config)
        layer_types = tuple(getattr(config.text_config, "layer_types", None) or ())
        self.latent_deliberation = LatentDeliberationTransformer(
            hidden_size=config.text_config.hidden_size,
            latent_dim=config.latent_dim,
            ffn_dim=config.latent_ffn_dim,
            num_layers=config.latent_num_layers,
            num_heads=config.latent_num_heads,
            local_attention_window=config.latent_local_attention_window,
            tape_probes=config.latent_tape_probes,
            history_kv_rank=config.latent_history_kv_rank,
            num_memory_readers=sum(layer_type == "full_attention" for layer_type in layer_types),
            num_working_readers=(
                sum(layer_type == "full_attention" for layer_type in layer_types)
                if config.working_memory_bus else 0
            ),
            num_persistent_readers=(
                sum(layer_type == "full_attention" for layer_type in layer_types)
                if config.persistent_memory_bus else 0
            ),
            working_last_block_global=config.latent_working_last_block_global,
            commit_sequence_dim=config.commit_sequence_dim,
            max_canvas_length=config.canvas_length,
        )
        self.lm_head = nn.Linear(config.text_config.hidden_size, config.text_config.vocab_size, bias=False)
        self.final_logit_softcapping = config.text_config.final_logit_softcapping
        self.post_init()
        install_modilify_mk2_trunk_semantics(self)
        if getattr(config, "lora_config", None):
            payload = dict(config.lora_config)
            payload["target_modules"] = tuple(payload["target_modules"])
            inject_lora(self, LoRAConfig(**payload))
            # The same adapters serve the encoder and decoder, just like the
            # tied backbone. Tell from_pretrained/save_pretrained about them.
            self._tied_weights_keys = dict(type(self)._tied_weights_keys)
            self._tied_weights_keys.update({
                name: name.replace("model.encoder.language_model.", "model.decoder.", 1)
                for name, _ in self.named_parameters(remove_duplicate=False)
                if name.startswith("model.encoder.language_model.") and ".lora_" in name
            })
            self.all_tied_weights_keys = self.get_expanded_tied_weights_keys(all_submodels=True)
            self.tie_weights(recompute_mapping=False)
            config.text_config._experts_implementation = "modilify_mk2_lora"
        # These 26 small parameters were trained and saved in FP32. Preserve
        # their dtype even when from_pretrained is called with BF16/FP16.
        self._keep_in_fp32_modules_strict = {
            name for name, _ in self.named_parameters()
            if name.startswith("latent_deliberation.") and (
                name.endswith((".dt_bias", ".a_log")) or
                (name.endswith(".weight") and "norm" in name.rsplit(".", 2)[-2])
            )
        }

    def _finalize_logits(self, hidden: torch.Tensor) -> torch.Tensor:
        logits = self.lm_head(hidden)
        return torch.tanh(logits / self.final_logit_softcapping) * self.final_logit_softcapping

    def _compute_gold_nll(
        self, logits: torch.Tensor, labels: torch.LongTensor | None
    ) -> torch.Tensor | None:
        if labels is None:
            return None
        labels = labels.to(logits.device)
        return F.cross_entropy(
            logits.flatten(0, 1), labels.flatten(),
            ignore_index=-100, reduction="none",
        ).view_as(labels)

    def _prepare_latent_context(
        self,
        decoder_input_ids: torch.LongTensor,
        *,


        confidence: torch.Tensor | None,
        entropy: torch.Tensor | None,
        age: torch.Tensor | None,
        latent_state: LatentDeliberationState | None,
        canvas_head: torch.Tensor | None,
    ) -> tuple[torch.Tensor, LatentDeliberationState, torch.Tensor]:
        batch, canvas = decoder_input_ids.shape
        dtype = self.model.decoder.embed_tokens.weight.dtype
        if latent_state is None:
            latent_state = LatentDeliberationState.empty(
                batch_size=batch, canvas_length=canvas,
                latent_dim=self.config.latent_dim, memory_slots=self.config.latent_memory_slots,
                device=decoder_input_ids.device, dtype=dtype, enable_gdn2=True,
            )
        confidence = latent_state.confidence if confidence is None else confidence.squeeze(-1).float()
        entropy = latent_state.entropy if entropy is None else entropy.squeeze(-1).float()
        if age is not None:
            latent_state = replace(
                latent_state,
                age=age.to(device=decoder_input_ids.device, dtype=torch.int32),
            )
        token_embeddings = self.model.decoder.embed_tokens(decoder_input_ids)
        use_outer_checkpoint = (
            self.training
            and torch.is_grad_enabled()
            and self.latent_deliberation.activation_checkpointing
        )
        if use_outer_checkpoint:
            def run_latent_processor(
                embeddings: torch.Tensor,
                memory_slots: torch.Tensor,
                working_cells: torch.Tensor,
                working_row: torch.Tensor,
                state_confidence: torch.Tensor,
                state_entropy: torch.Tensor,
                state_age: torch.Tensor,
                state_token_changed: torch.Tensor,
                state_confidence_delta: torch.Tensor,
                state_entropy_delta: torch.Tensor,
                state_ponder_steps: torch.Tensor,
                state_stagnation_steps: torch.Tensor,


            ) -> torch.Tensor:
                checkpoint_state = LatentDeliberationState(
                    memory_slots=memory_slots,
                    confidence=state_confidence,
                    entropy=state_entropy,
                    age=state_age,
                    token_changed=state_token_changed,
                    confidence_delta=state_confidence_delta,
                    entropy_delta=state_entropy_delta,
                    ponder_steps=state_ponder_steps,
                    stagnation_steps=state_stagnation_steps,
                    gdn2=replace(
                        latent_state.gdn2, cells=working_cells,
                        row=working_row, persistent=memory_slots,
                    ),
                )
                result = self.latent_deliberation(
                    token_embeddings=embeddings,
                    confidence=confidence,
                    entropy=entropy,
                    state=checkpoint_state,


                    canvas_head=canvas_head,
                )
                return result.context

            latent_context = checkpoint(
                run_latent_processor,
                token_embeddings,
                latent_state.memory_slots,
                latent_state.gdn2.cells,
                latent_state.gdn2.row,
                latent_state.confidence,
                latent_state.entropy,
                latent_state.age,
                latent_state.token_changed,
                latent_state.confidence_delta,
                latent_state.entropy_delta,
                latent_state.ponder_steps,
                latent_state.stagnation_steps,


                use_reentrant=False,
                preserve_rng_state=True,
            )
            next_state = LatentDeliberationState(
                memory_slots=latent_state.memory_slots,
                confidence=confidence.to(dtype=torch.float32),
                entropy=entropy.to(dtype=torch.float32),
                age=latent_state.age,
                token_changed=latent_state.token_changed,
                confidence_delta=latent_state.confidence_delta,
                entropy_delta=latent_state.entropy_delta,
                ponder_steps=latent_state.ponder_steps,
                stagnation_steps=latent_state.stagnation_steps,
                gdn2=latent_state.gdn2,
            )
        else:
            processed: LatentProcessorOutput = self.latent_deliberation(
                token_embeddings=token_embeddings,
                confidence=confidence,
                entropy=entropy,
                state=latent_state,


                canvas_head=canvas_head,
            )
            latent_context = processed.context
            next_state = processed.state
        return (
            latent_context,
            next_state,
            token_embeddings,
        )

    def forward(
        self,
        *,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | dict | None = None,
        past_key_values: Cache | None = None,
        position_ids: torch.LongTensor | None = None,
        decoder_input_ids: torch.LongTensor,
        previous_confidence: torch.FloatTensor | None = None,
        previous_entropy: torch.FloatTensor | None = None,
        token_age: torch.Tensor | None = None,
        latent_state: LatentDeliberationState | None = None,


        canvas_head: torch.Tensor | None = None,

        decoder_attention_mask: torch.Tensor | dict | None = None,
        decoder_position_ids: torch.LongTensor | None = None,
        labels: torch.LongTensor | None = None,
        return_encoder_outputs: bool = True,
        detach_temporal_context_for_heavy: bool = False,
        compact_vocab: bool = False,
        repetition_token_mask: torch.BoolTensor | None = None,
        repetition_penalty: float = 1.0,
        sampling_generators: Sequence[torch.Generator] | None = None,
        collect_latent_diagnostics: bool = True,
        **kwargs: Any,
    ) -> ModilifyMk2BlockDiffusionOutput:
        (
            latent_context,
            next_state,
            decoder_token_embeddings,
        ) = self._prepare_latent_context(
            decoder_input_ids,


            confidence=previous_confidence,
            entropy=previous_entropy,
            age=token_age,
            latent_state=latent_state,
            canvas_head=canvas_head,
        )
        heavy_context = latent_context
        heavy_context_leaf = None
        temporal_memory_slots = next_state.memory_slots
        heavy_memory_slots = temporal_memory_slots
        heavy_memory_leaf = None
        working_bus = self.latent_deliberation.working_memory_bus
        persistent_bus = self.latent_deliberation.persistent_memory_bus
        working_readers_active = (
            working_bus.num_readers > 0
            and (not working_bus.training or working_bus.enabled)
        )
        memory_readers_active = (
            persistent_bus.num_readers > 0
            and (not persistent_bus.training or persistent_bus.enabled)
        )
        if detach_temporal_context_for_heavy and latent_context.requires_grad:
            # Clone so the heavy decoder cannot alias the temporal graph storage.
            # `detach()` alone shares storage; an in-place decoder write would
            # corrupt the later latent backward and can produce non-finite grads.
            heavy_context_leaf = latent_context.detach().clone().requires_grad_(True)
            heavy_context = heavy_context_leaf
        if (
            detach_temporal_context_for_heavy
            and memory_readers_active
            and temporal_memory_slots.requires_grad
        ):
            # Memory readers are part of the heavy decoder too.  Keep their
            # backward separate from the recurrent temporal graph for the same
            # reason as the canvas context above; both gradients are replayed
            # together at the TBPTT boundary.
            heavy_memory_leaf = (
                temporal_memory_slots.detach().clone().requires_grad_(True)
            )
            heavy_memory_slots = heavy_memory_leaf
        # The production LoRA path freezes the tied embedding table. Reuse its
        # lookup there; a trainable table needs two independent autograd paths
        # because heavy and temporal backward execute at different times.
        reusable_decoder_embeddings = (
            None
            if self.model.decoder.embed_tokens.weight.requires_grad
            else decoder_token_embeddings
        )
        outputs = self.model(
            input_ids=input_ids, attention_mask=attention_mask,
            past_key_values=past_key_values, position_ids=position_ids,
            decoder_input_ids=decoder_input_ids,
            decoder_token_embeddings=reusable_decoder_embeddings,
            temporal_context_embeddings=heavy_context,
            decoder_attention_mask=decoder_attention_mask,
            decoder_position_ids=decoder_position_ids,
            return_encoder_outputs=return_encoder_outputs,
            collect_latent_diagnostics=collect_latent_diagnostics,
            working_bus=working_bus if working_readers_active else None,
            working_state=(
                heavy_context,
                # The Torch decoder keeps physical ring order and supplies
                # logical positions through RoPE; its mask must stay physical.
                next_state.gdn2.seen,
            ) if working_readers_active else None,
            working_canvas_head=canvas_head,
            persistent_bus=persistent_bus if memory_readers_active else None,
            memory_slots=heavy_memory_slots if memory_readers_active else None,
            slot_identity=(
                next_state.gdn2.seen
                if memory_readers_active else None
            ),
            **kwargs,
        )
        latent_residual_diagnostics = outputs.latent_residual_diagnostics
        proposal = proposal_confidence = token_entropy = None
        greedy_proposal = greedy_confidence = None
        temperature_gold_nll = None
        sampled_nll = None
        if compact_vocab:
            logits = None
            if labels is None:
                (
                    proposal,
                    proposal_confidence,
                    token_entropy,
                    greedy_proposal,
                    greedy_confidence,
                ) = (
                    chunked_vocab_statistics(
                        outputs.last_hidden_state.detach(),
                        self.lm_head.weight.detach(),
                        softcap=self.final_logit_softcapping,
                        temperature=DENOISE_TEMPERATURE,
                        chunk_size=self.config.vocab_chunk_size,
                        repetition_token_mask=repetition_token_mask,
                        repetition_penalty=repetition_penalty,
                        sampling_generators=sampling_generators,
                        top_k=getattr(self.config, "commit_top_k", 40),
                        min_p=getattr(self.config, "commit_min_p", 0.05),
                    )
                )
                gold_nll = None
            else:
                (
                    gold_nll,
                    temperature_gold_nll,
                    proposal,
                    proposal_confidence,
                    token_entropy,
                    greedy_proposal,
                    greedy_confidence,
                    sampled_nll,
                ) = chunked_vocab_training_statistics(
                    outputs.last_hidden_state,
                    self.lm_head.weight,
                    labels,
                    return_sampled_nll=True,
                    softcap=self.final_logit_softcapping,
                    temperature=DENOISE_TEMPERATURE,
                    chunk_size=self.config.vocab_chunk_size,
                    top_k=getattr(self.config, "commit_top_k", 40),
                    min_p=getattr(self.config, "commit_min_p", 0.05),
                )
        else:
            logits = self._finalize_logits(outputs.last_hidden_state)
            gold_nll = self._compute_gold_nll(logits, labels)
        loss = None
        if gold_nll is not None and labels is not None:
            valid = labels.to(gold_nll.device).ne(-100)
            loss = gold_nll.masked_fill(~valid, 0.0).sum() / valid.sum().clamp_min(1)
        return ModilifyMk2BlockDiffusionOutput(
            logits=logits, loss=loss,
            past_key_values=outputs.past_key_values,
            encoder_last_hidden_state=outputs.encoder_last_hidden_state,
            heavy_hidden_state=outputs.last_hidden_state,
            next_latent_state=next_state,
            gold_nll=gold_nll,
            temporal_context=latent_context,
            heavy_context_leaf=heavy_context_leaf,
            temporal_memory_slots=temporal_memory_slots,
            heavy_memory_leaf=heavy_memory_leaf,

            working_state=latent_context,
            latent_residual_diagnostics=latent_residual_diagnostics,
            temperature_gold_nll=temperature_gold_nll,
            proposal=proposal,
            proposal_confidence=proposal_confidence,
            sampled_nll=sampled_nll,
            token_entropy=token_entropy,
            greedy_proposal=greedy_proposal,
            greedy_confidence=greedy_confidence,
        )


__all__ = [
    "ModilifyMk2BlockDiffusionOutput", "ModilifyMk2Config", "ModilifyMk2DecoderModel",
    "ModilifyMk2EncoderModel", "ModilifyMk2ForBlockDiffusion", "ModilifyMk2Model",
    "ModilifyMk2TextRouter", "install_modilify_mk2_trunk_semantics",
]