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fix(speculative): EAGLE3 on heterogeneous per-layer configs, and a first-batch hidden-state sanity check - #2952

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@aniskumar-nv aniskumar-nv commented Oct 23, 2026 •

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What does this PR do?

Type of change: Bug fix.

EAGLE3 training fails before the first step on targets whose config declares
attributes per layer (Gemma 4 under transformers >= 5.15): FakeBaseModel.from_source
and HFEagleModel.modify read num_key_value_heads / head_dim globally and raise
AmbiguousGlobalPerLayerAttributeError.

  • _cfg_attr() reads such attributes from one layer (the last, full attention in
    Gemma 4) for the fake base. modify builds the draft from LlamaConfig when the
    base config is heterogeneous; the draft keeps the EAGLE default attention shape as
    for every other base. A rope_parameters keyed by layer type is reduced to that
    layer's entry; a flat recipe value is kept. Homogeneous bases are unchanged.
  • Offline EAGLE: on the first batch with scored tokens, compare the base lm_head on
    the streamed final hidden state with the next token and print
    HIDDEN_STATE_SANITY. A shape-correct but misaligned stream (gpt-oss-20b: cache
    block size == number of captured planes) otherwise trains silently on other
    tokens' hidden states.

Related, independent: #2522, #2186, #2897.

Usage

No new flags or dependencies. Optional SPECDEC_HIDDEN_STATE_SANITY_PATH=<file>
makes rank 0 write the record.

Testing

pytest tests/unit/torch/speculative/plugins -q

Before your PR is "Ready for review"

  • Is this change backward compatible?: ✅
  • If you copied code from any other sources or added a new PIP dependency, did you follow guidance in CONTRIBUTING.md: N/A
  • Did you write any new necessary tests?: ✅
  • Did you update Changelog?: ✅
  • Did you get Claude approval on this PR?: ❌ (/claude review not run yet)

Additional Information

None.

Summary by CodeRabbit

  • Bug Fixes
    • Improved EAGLE training compatibility with heterogeneous per-layer model configurations in newer Transformers versions.
    • Improved handling of per-layer RoPE settings when preparing EAGLE configurations.
  • New Features
    • Offline EAGLE training can report a first-batch hidden-state agreement check, including the number of tokens evaluated. When no tokens are eligible, no report is produced.

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Walkthrough

The changes add per-layer configuration reads for heterogeneous EAGLE models, select RoPE parameters for heterogeneous draft configurations, and report next-token agreement during offline forward passes when scored tokens are available.

Changes: EAGLE training

Layer / File(s) Summary
Heterogeneous configuration handling
modelopt/torch/speculative/plugins/modeling_fakebase.py, modelopt/torch/speculative/plugins/hf_eagle.py, tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py
Fake-base reads select per-layer values when global attributes are ambiguous. Heterogeneous draft configurations use LlamaConfig and select the final base layer’s RoPE parameters. Tests cover configuration reads and RoPE handling.
Offline hidden-state sanity reporting
modelopt/torch/speculative/plugins/hf_eagle.py, tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py, CHANGELOG.rst
Offline forward reports next-token agreement when tokens can be scored. The report applies loss_mask when provided and prints or writes JSON on rank 0. Tests cover token agreement, empty scoring masks, and rank-specific output. The changelog records the fixes.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: kevalmorabia97, h-guo18

Merge Risk: Moderate · previous review fea3a

Heterogeneous drafts can use unintended attention settings, and the diagnostic can pass without checking streamed hidden states. Resolve those behavior risks before merging; the new tests also need to follow the repository’s test guidance.

Pre-merge checks: Passed 6
Check name Status Explanation
Description Check Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check Passed The title clearly and concisely summarizes both primary changes: heterogeneous per-layer EAGLE3 configuration support and the first-batch hidden-state sanity check.
Docstring Coverage Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 3 files.
Linked Issues check Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check Passed Check skipped because no linked issues were found for this pull request.
Security Anti-Patterns Passed No specified security anti-pattern was introduced. The PR changes only CHANGELOG.rst, two existing modelopt Python modules, and one test file. Added code contains no torch.load(..., weights_only=False…
Full details: Security Anti-Patterns

Explanation

No specified security anti-pattern was introduced. The PR changes only CHANGELOG.rst, two existing modelopt Python modules, and one test file. Added code contains no torch.load(..., weights_only=False), numpy.load(..., allow_pickle=True), hardcoded trust_remote_code=True, eval(), exec(), or # nosec. No pyproject.toml or requirements file changed, so no new dependency issue applies.

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@aniskumar-nv
aniskumar-nv force-pushed the aniskumar/eagle3-heterogeneous-and-hidden-state-sanity branch 2 times, most recently from 187a4af to 95e3d6c Compare October 23, 2026 05:34
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aniskumar-nv marked this pull request as ready for review October 23, 2026 05:34
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aniskumar-nv force-pushed the aniskumar/eagle3-heterogeneous-and-hidden-state-sanity branch from 95e3d6c to fe1124d Compare October 23, 2026 05:40

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👉 Steps to fix this

Actionable comments posted: 2


  • 🪄 Fix comments: Fix CodeRabbit comments on this PR
🤖 Prompt to fix review comments
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Inline comments:
Review comments at @modelopt/torch/speculative/plugins/hf_eagle.py:
- Around line 765-767: Update the hidden-state sanity check guarded by
_hidden_state_sanity_reported to leave the check pending when loss_mask[:, 1:]
contains no valid scored tokens; set the flag and call
_report_hidden_state_sanity only once at least one scored token is present.
- Line 413: Update the heterogeneous configuration handling before
LlamaConfig.from_dict(arch_config) to preserve recipe-supplied flat
rope_parameters values; remove the key only when it contains an incompatible
per-layer value, or convert that value to the selected layer’s settings.

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  • CHANGELOG.rst
  • modelopt/torch/speculative/plugins/hf_eagle.py
  • modelopt/torch/speculative/plugins/modeling_fakebase.py
  • tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py

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👉 Steps to fix this

Actionable comments posted: 1

🧹 Nitpick comments: 1
tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py: 1

43-43: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Make the KV-head test genuinely heterogeneous.

With the default attention_k_eq_v=False, num_global_key_value_heads=1 is not applied to Gemma 4 full-attention layers. The first and last layers therefore use the same KV-head count, so the current assertion can pass with an incorrect _cfg_attr layer selection.

Set attention_k_eq_v=True and assert that the first and last layers differ before checking the last-layer result.

Suggested test fix
         num_key_value_heads=2,
         num_global_key_value_heads=1,
+        attention_k_eq_v=True,
         head_dim=8,
         global_head_dim=16,
@@
     cfg = _heterogeneous_config()
     first, last = cfg.per_layer_config[0], cfg.per_layer_config[-1]
     assert first.head_dim != last.head_dim  # sliding vs full attention
+    assert first.num_key_value_heads != last.num_key_value_heads
     with pytest.raises(Exception, match="per-layer"):
         getattr(cfg, "head_dim")
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Review comment at
@tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py at line 43:
Update _heterogeneous_config to set attention_k_eq_v=True so the global KV-head
count applies to full-attention layers, then assert the first and last layers
have different num_key_value_heads values before checking the last-layer result.

  • 🪄 Fix comments: Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @modelopt/torch/speculative/plugins/hf_eagle.py:
- Line 95: Update the `HIDDEN_STATE_SANITY` record output to occur only on rank
0, applying the same rank check to both printing and file writing so multi-rank
training produces a single record.

---

Nitpick comments:
Review comments at
@tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py:
- Line 43: Update _heterogeneous_config to set attention_k_eq_v=True so the
global KV-head count applies to full-attention layers, then assert the first and
last layers have different num_key_value_heads values before checking the
last-layer result.

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  • tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py

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aniskumar-nv force-pushed the aniskumar/eagle3-heterogeneous-and-hidden-state-sanity branch from 79dff6b to 06a9556 Compare October 23, 2026 06:08

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🟡 Minor · Recompute sanity logits from out_hiddens when base_model_logits is… · hf_eagle.py:772

modelopt/torch/speculative/plugins/hf_eagle.py:772
🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Recompute sanity logits from out_hiddens when base_model_logits is supplied.

The standard offline collator emits hidden states only. However, EagleBaseModelOutput.from_offline_dict accepts optional base_model_logits. When present, the current branch skips reconstruction and scores those supplied logits instead of checking out_hiddens through the base lm_head.

Suggested fix
             if not getattr(self, "_hidden_state_sanity_reported", False):
-                record = _report_hidden_state_sanity(base_outputs.logits, input_ids, loss_mask)
-                self._hidden_state_sanity_reported = record is not None
+                if base_outputs.out_hiddens is not None:
+                    sanity_hiddens = _maybe_apply_base_final_norm(
+                        base_outputs.out_hiddens, kwargs["base_model_outputs"], self._base_model_norm
+                    )
+                    sanity_logits = self._base_model_lm_head(sanity_hiddens)
+                    record = _report_hidden_state_sanity(sanity_logits, input_ids, loss_mask)
+                    self._hidden_state_sanity_reported = record is not None
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Review comment at @modelopt/torch/speculative/plugins/hf_eagle.py at line 772:
Update the hidden-state sanity reporting branch to derive sanity logits from
base_outputs.out_hiddens via the base model’s final normalization and lm_head
whenever hidden states are available, even when base_model_logits is supplied.
Pass those logits to _report_hidden_state_sanity and preserve the existing
one-time reporting behavior.

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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @modelopt/torch/speculative/plugins/hf_eagle.py:
- Around line 105-111: Update the layer-specific RoPE selection in the
`rope_parameters` handling so a conflicting `rope_scaling` value cannot override
the selected settings during `LlamaConfig.from_dict` construction. Remove or
synchronize `rope_scaling` before assigning the selected layer’s
`rope_parameters`.

Review comments at
@tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py:
- Line 35: Add a brief comment beside the optional
`pytest.importorskip("transformers.models.gemma4")` import inside
`_heterogeneous_config`, explaining that it is imported there because
Transformers is an optional dependency.

---

Outside diff comments:
Review comments at @modelopt/torch/speculative/plugins/hf_eagle.py:
- Line 772: Update the hidden-state sanity reporting branch to derive sanity
logits from base_outputs.out_hiddens via the base model’s final normalization
and lm_head whenever hidden states are available, even when base_model_logits is
supplied. Pass those logits to _report_hidden_state_sanity and preserve the
existing one-time reporting behavior.

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review. Visit https://docs.coderabbit.ai/cli?utm_source=ghpr

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  • CHANGELOG.rst
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  • modelopt/torch/speculative/plugins/modeling_fakebase.py
  • tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py
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Inline comments:
Review comments at @modelopt/torch/speculative/plugins/hf_eagle.py:
- Around line 105-106: Update `_seed_draft_from_heterogeneous_base` and the
default-config merge in `convert_to_eagle_model` so the four attention fields
are seeded from the base model for heterogeneous configs when the recipe has not
explicitly set them. Keep explicit recipe values authoritative, and avoid
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Caution

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⚠️ Outside diff range comments (1)

🟠 Major · Compute the sanity score from streamed hidden states. · hf_eagle.py:772

modelopt/torch/speculative/plugins/hf_eagle.py:772
🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Compute the sanity score from streamed hidden states.

If base_model_outputs supplies logits, Line 772 scores those logits without using base_outputs.out_hiddens. Correct supplied logits can produce perfect agreement even when the streamed hidden states are wrong. Reconstruct logits from the hidden states for this check, including the pre-norm handling, without replacing supplied logits used by training.

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Review comment at @modelopt/torch/speculative/plugins/hf_eagle.py at line 772:
Update the sanity check at _report_hidden_state_sanity to derive its scored
logits from base_outputs.out_hiddens, applying the model’s pre-norm handling as
needed. Keep base_outputs.logits unchanged for training.
🧹 Nitpick comments: 1
tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py: 1

30-30: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Split these tests by the production module they cover.

This file contains unit tests for two production modules. It does not contain a cross-module integration test. test_cfg_attr covers _cfg_attr in modeling_fakebase.py. test_per_layer_rope_is_reduced_to_the_last_layer and test_hidden_state_sanity cover _reduce_per_layer_rope and _report_hidden_state_sanity in hf_eagle.py. CONTRIBUTING.md requires test filenames to mirror the production module they primarily cover. A feature-oriented name applies only when no single production module owns the behavior, which is not the case here.

Move test_cfg_attr to the test file for modeling_fakebase.py. Move the two hf_eagle.py tests to the test file for hf_eagle.py. Use the existing matching test files if they exist. Otherwise, create them.

🤖 Prompt for AI Agents
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Review comment at
@tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py at line 30:
Split the tests in this file by production module: move test_cfg_attr for
_cfg_attr into the matching modeling_fakebase test file, and move
test_per_layer_rope_is_reduced_to_the_last_layer and test_hidden_state_sanity
for _reduce_per_layer_rope and _report_hidden_state_sanity into the matching
hf_eagle test file. Reuse existing matching test files or create them if absent.

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Outside diff comments:
Review comments at @modelopt/torch/speculative/plugins/hf_eagle.py:
- Line 772: Update the sanity check at _report_hidden_state_sanity to derive its
scored logits from base_outputs.out_hiddens, applying the model’s pre-norm
handling as needed. Keep base_outputs.logits unchanged for training.

---

Nitpick comments:
Review comments at
@tests/unit/torch/speculative/plugins/test_heterogeneous_eagle.py:
- Line 30: Split the tests in this file by production module: move test_cfg_attr
for _cfg_attr into the matching modeling_fakebase test file, and move
test_per_layer_rope_is_reduced_to_the_last_layer and test_hidden_state_sanity
for _reduce_per_layer_rope and _report_hidden_state_sanity into the matching
hf_eagle test file. Reuse existing matching test files or create them if absent.

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Bot review (gpt-6.1-sol) — DM the bot to share feedback.

Changes requested: the sanity report's environment-only rank check can let multiple distributed workers overwrite the same output file.

Needs action:

  • Fix rank gating in hf_eagle.py using the initialized process-group rank; cover distributed execution without RANK (see inline comment).
  • Add caller-level regressions for heterogeneous FakeBaseModel.from_source and EAGLE conversion, plus first-scored-batch reporting through HFEagleModel.forward; the new tests exercise helpers only.
  • Move the new json, os, and LlamaConfig imports to module scope in hf_eagle.py; reuse its existing os import.

No action needed:

  • The new test header matches LICENSE_HEADER; core logic is within budget. Tests were inspected, not executed.

if int(os.environ.get("RANK", "0")) != 0:
return record
print("HIDDEN_STATE_SANITY " + json.dumps(record), flush=True)
path = os.environ.get("SPECDEC_HIDDEN_STATE_SANITY_PATH")

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Bot comment.

The RANK environment variable is a launcher convention, not the authoritative distributed rank. When workers initialize a process group explicitly (e.g. via multiprocessing spawn) without setting RANK, every worker defaults to 0 here, prints a record, and opens the same sanity file with "w". This can overwrite rank 0's result or leave corrupted JSON. Use the existing modelopt.torch.utils.distributed.is_master()/rank helper for the side-effect guard (and print_rank_0 for logging), retaining tensor computation on all ranks if it can involve collectives. Add coverage for an initialized nonzero rank with RANK absent.

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Done in c995fbd: the record is computed on every rank, the log line goes through print_rank_0, and the file write is guarded by modelopt.torch.utils.distributed.is_master(); no RANK read remains. test_hidden_state_sanity now covers a non-zero process-group rank with RANK unset (record returned, no print, no file).

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After the rebase onto main this fix lives in 428a3b9 (same change as c995fbd); 400 plugin unit tests pass.



def test_cfg_attr():
"""Homogeneous configs read as getattr; per-layer attributes come from the requested layer."""

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These tests validate _cfg_attr and _reduce_per_layer_rope directly, but do not run either failing call site: FakeBaseModel.from_source or HFEagleModel.modify. Removing the new call-site changes would still leave these tests passing. Extend the local-checkpoint fixtures in test_fakebase.py with a tiny heterogeneous config and add a real EAGLE conversion test that constructs the draft (including per-layer and flat recipe RoPE). Also exercise offline forward across an unscored batch followed by scored batches to pin the pending/once-only reporting behavior, which the helper test cannot validate.

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Done in c995fbd. test_fakebase.py: a heterogeneous_config fixture (tiny Gemma4TextConfig built on the existing fake_config/fake_checkpoint helpers) and test_fakebase_heterogeneous_config_reads_the_last_layer, which runs the real FakeBaseModel.from_source. test_heterogeneous_eagle.py: test_convert_builds_a_llama_draft_on_a_heterogeneous_base runs mtsp.convert on a tiny Gemma4ForCausalLM (get_tiny_gemma4 in tests/_test_utils/torch/transformers_models.py) with a flat recipe and with a layer-type rope_parameters map, asserting the LlamaConfig draft; test_offline_forward_reports_the_first_scored_batch runs HFEagleModel.forward three times offline on CPU: an unscored batch leaves the check pending, the first scored batch reports once and writes the file, the next call is silent. 309 plugin tests pass.

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After the rebase onto main this fix lives in 428a3b9 (same change as c995fbd); 400 plugin unit tests pass.

when set. Returns ``None`` when the batch scores no token.
"""
import json
import os

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Move json to the top-level imports and remove the local os import (os is already imported at module scope). Likewise, import LlamaConfig alongside the existing Transformers imports instead of inside modify; no concrete reason to keep these new imports local is documented.

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Done in c995fbd: json and LlamaConfig are module-level imports in hf_eagle.py; the local os and json imports are gone.

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After the rebase onto main this fix lives in 428a3b9 (same change as c995fbd); 400 plugin unit tests pass.

@aniskumar-nv
aniskumar-nv force-pushed the aniskumar/eagle3-heterogeneous-and-hidden-state-sanity branch from fea3aa9 to c995fbd Compare October 23, 2026 22:34
@kevalmorabia97

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Thanks for the contribution! This PR now has merge conflicts with main. Could you update your branch with the latest main and fix the conflicts so we can continue the review?

We've added the waiting for feedback label while we wait for your update.

aniskumar-nv and others added 2 commits October 26, 2026 13:49
…-state check

Gemma 4 declares num_key_value_heads and head_dim per layer, and transformers >= 5.15 raises
AmbiguousGlobalPerLayerAttributeError on a global read. FakeBaseModel.from_source read them
globally and HFEagleModel.modify built the draft config with the base's own config class, so
training failed before step 1. _cfg_attr() reads such attributes from the last layer for the
fake base, and a heterogeneous base gets a LlamaConfig draft with the EAGLE default attention
shape (a layer-type rope map is reduced to the last layer); homogeneous bases are unchanged.

The offline path only checked streamed hidden states by shape, which can agree by accident
(gpt-oss-20b: cache block size 4 == four captured planes). The plugin now scores the first
batch with scored tokens (top-1 agreement between the base lm_head on the final plane and the
next token); rank 0 prints HIDDEN_STATE_SANITY and writes the record to
SPECDEC_HIDDEN_STATE_SANITY_PATH when set. Rank 0 is the initialized process-group rank
(modelopt.torch.utils.distributed), not the RANK environment variable.

Signed-off-by: Anish Kumar <aniskumar@nvidia.com>
…ed planes

When the producer also supplies base_model_logits, the first-batch check scored those
logits, so a misaligned hidden-state stream could still report full agreement. Derive the
scored logits from base_model_hidden_states (with the pre-norm handling) on that one batch;
training keeps using the supplied logits. Adds a test with aligned supplied logits and
random planes, which must score low.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Signed-off-by: Anish Kumar <aniskumar@nvidia.com>
@aniskumar-nv
aniskumar-nv force-pushed the aniskumar/eagle3-heterogeneous-and-hidden-state-sanity branch from c995fbd to d03b93f Compare October 26, 2026 21:56
@aniskumar-nv

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Rebased onto main (9099135); the only conflict was CHANGELOG.rst. The review fixes that were in c995fbd are now in 428a3b9.

Also addressed the remaining CodeRabbit finding (outside the diff range, hf_eagle.py offline branch): the first-batch hidden-state check scored producer-supplied base_model_logits, so a misaligned hidden-state stream could still report full agreement. d03b93f derives the scored logits from base_model_hidden_states (with the pre-norm handling) on that one batch whether or not logits are supplied; training keeps using the supplied logits. Added test_offline_sanity_scores_the_streamed_hidden_states (aligned supplied logits + random planes must score low).

pytest tests/unit/torch/speculative/plugins -q: 400 passed (CPU, PyTorch 2.13.0, transformers 5.15.1).

…ate-sanity

Signed-off-by: aniskumar-nv <aniskumar@nvidia.com>

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3 participants