feat: when validating OptimizationValidationMixin, fsdp_version shouldn't be flag as an warning

[SamuelLarkin]

With the following config.yaml

fsdp_version: 2
fsdp_config:
  offload_params: false
  state_dict_type: FULL_STATE_DICT
  auto_wrap_policy: TRANSFORMER_BASED_WRAP
  transformer_layer_cls_to_wrap: LlamaDecoderLayer
  reshard_after_forward: true

We get the following WARNING

[2026-06-08 12:08:41,580] [WARNING] [axolotl.utils.schemas.validation] Configuring FSDP fields with the `fsdp_` prefix is deprecated. Please omit the `fsdp_` prefix from the any fields in `fsdp_config`.

Where

key == "fsdp_version"
fsdp_config={'offload_params': False, 'state_dict_type': 'FULL_STATE_DICT', 'auto_wrap_policy': 'TRANSFORMER_BASED_WRAP', 'transformer_layer_cls_to_wrap': 'LlamaDecoderLayer', 'reshard_after_forward': True, 'fsdp_version': 2}

fsdp_version is part of FSDPConfig

Summary by CodeRabbit

Bug Fixes

• Resolved an issue where fsdp_version in FSDP configurations was incorrectly treated as deprecated and rewritten during configuration normalization.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR refines the FSDP configuration validation logic to exclude fsdp_version from the deprecated fsdp_*-prefixed field handling. A single-line change in the validation method now explicitly checks that a key is not fsdp_version before treating it as a deprecated field needing migration into the fsdp_config dictionary.

Changes

FSDP configuration validation refinement

Layer / File(s)	Summary
FSDP version exclusion from deprecated key handling src/axolotl/utils/schemas/validation.py	The check_fsdp_config_kwargs_prefix validation method now excludes fsdp_version from the deprecated fsdp_* prefix rewrite logic by adding a key != "fsdp_version" condition alongside the existing key.startswith("fsdp_") check.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• axolotl-ai-cloud/axolotl#3170: Both PRs modify FSDP config normalization behavior around fsdp_version to prevent it from being treated as a deprecated fsdp_* key.

Suggested reviewers

• NanoCode012

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: preventing fsdp_version from being flagged as a deprecation warning during validation, which directly aligns with the file-level change in validation.py.
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.

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[coderabbitai]

🧹 Nitpick comments (1)

src/axolotl/utils/schemas/validation.py (1)

1091-1092: 💤 Low value

Optional: Consider clarifying the warning message to reflect the fsdp_version exception.

The warning says "Please omit the fsdp_ prefix from the any fields in fsdp_config", but fsdp_version is now explicitly excluded from this requirement. For improved clarity, consider:

-                        "Configuring FSDP fields with the `fsdp_` prefix is deprecated. "
-                        "Please omit the `fsdp_` prefix from the any fields in `fsdp_config`."
+                        "Configuring FSDP fields with the `fsdp_` prefix is deprecated. "
+                        "Please omit the `fsdp_` prefix from fields in `fsdp_config` (except `fsdp_version`)."

This is a minor documentation improvement and not critical for functionality.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/axolotl/utils/schemas/validation.py` around lines 1091 - 1092, Update the
deprecation warning text in validation.py that mentions configuring FSDP fields
with the `fsdp_` prefix to explicitly note the exception for `fsdp_version`;
locate the message that currently reads "Configuring FSDP fields with the
`fsdp_` prefix is deprecated. Please omit the `fsdp_` prefix from the any fields
in `fsdp_config`." and revise it to call out that `fsdp_version` is excluded
(e.g., mention "except `fsdp_version`") so users know that `fsdp_version` may
still keep the prefix when using `fsdp_config`.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@src/axolotl/utils/schemas/validation.py`:
- Around line 1091-1092: Update the deprecation warning text in validation.py
that mentions configuring FSDP fields with the `fsdp_` prefix to explicitly note
the exception for `fsdp_version`; locate the message that currently reads
"Configuring FSDP fields with the `fsdp_` prefix is deprecated. Please omit the
`fsdp_` prefix from the any fields in `fsdp_config`." and revise it to call out
that `fsdp_version` is excluded (e.g., mention "except `fsdp_version`") so users
know that `fsdp_version` may still keep the prefix when using `fsdp_config`.

---

ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between b99ae09 and ed730d6.

📒 Files selected for processing (1)

• src/axolotl/utils/schemas/validation.py

[winglian]

good catch. thanks

[codecov]

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