chore: Bump MCore (main) 2026-03-10 — replaces conflicting #2719

[mehraakash]

Summary

Replaces conflicting bump PR #2719 which could not be merged due to conflicts in 3rdparty/Megatron-LM and uv.lock.

What changed

• Updates 3rdparty/Megatron-LM from 8318b8093e7d → 0e19bf11f704 (8 new MCore commits)
• uv.lock unchanged — transformers is already pinned to 5.2.0 via pyproject.toml constraint <=5.2.0

New MCore commits

• 0e19bf11 Add CP + Sequence Packing support for Mimo ([sync] FP8 params support for megatron-fsdp (MXFP8/Blockwise) #2135)
• ce66b222 Update copy-pr-bot.yaml [skip ci]
• 94ff0dc6 Check reviews properly (#3756)
• d904a683 Re-enable tests which were failing on #3373 (#3757)
• 452fc115 Update README Quick Start (#3596)
• 56158bbd revert of Override moe_token_dispatcher_type to "alltoall" when export megatron… #2658 (#3736)
• 116a7fa3 Claude: run actions on target branch (#3745)
• 597721a1 chore(beep boop): Bump (main) (2026-03-09)

Closes #2719

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Updated dependencies with no functional changes to user-facing features.

[coderabbitai]

📝 Walkthrough

Walkthrough

Updates the 3rdparty/Megatron-LM submodule pointer to reference a newer commit version, aligning with dependency management changes tracked in the linked issue.

Changes

Cohort / File(s)	Summary
Submodule Update 3rdparty/Megatron-LM	Submodule commit pointer updated from 8318b80 to 0e19bf1; no functional code changes.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: bumping MCore (Megatron-LM submodule) with a specific date, and references the replacement of conflicting PR #2719.
Linked Issues check	✅ Passed	The PR addresses the linked issue #2719 by resolving conflicts and updating both 3rdparty/Megatron-LM and maintaining uv.lock consistency as intended by the original issue.
Out of Scope Changes check	✅ Passed	The changes are limited to updating the Megatron-LM submodule pointer, which is directly in scope for the bumping objective stated in the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Test Results For Major Changes	✅ Passed	This PR contains only a submodule pointer update with no functional code changes, as explicitly stated in the PR description indicating no impact to user-facing functionality. Test results documentation is only required for major changes such as new features, breaking changes, or refactoring, which do not apply here.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/mcore-bump-2026-03-10

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@3rdparty/Megatron-LM`:
- Line 1: Update the .main.commit file so it matches the new submodule commit
for 3rdparty/Megatron-LM (change the pinned hash from
8318b8093e7d49bce2529a29a14aeb50e5840ee0 to
0e19bf11f70483c18f058faff3d388186437fa30); scripts/switch_mcore.sh relies on
.main.commit as the source of truth so ensure the file contains the new hash
string exactly to keep local tooling from reverting the submodule to the old
MCore revision.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 4b015eb2-82a9-4cf6-b3ea-3e5c74e743e3

📥 Commits

Reviewing files that changed from the base of the PR and between de93536 and 8367eaa.

📒 Files selected for processing (1)

• 3rdparty/Megatron-LM

[coderabbitai]

⚠️ Potential issue | 🟠 Major

Update .main.commit alongside this submodule bump.

This moves 3rdparty/Megatron-LM to 0e19bf11f70483c18f058faff3d388186437fa30, but .main.commit still pins 8318b8093e7d49bce2529a29a14aeb50e5840ee0. scripts/switch_mcore.sh treats .main.commit as the source of truth, so leaving it unchanged means local tooling/automation can still reset main back to the old MCore revision. Please update .main.commit in the same PR to keep the pin consistent with the checked-in submodule state.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@3rdparty/Megatron-LM` at line 1, Update the .main.commit file so it matches
the new submodule commit for 3rdparty/Megatron-LM (change the pinned hash from
8318b8093e7d49bce2529a29a14aeb50e5840ee0 to
0e19bf11f70483c18f058faff3d388186437fa30); scripts/switch_mcore.sh relies on
.main.commit as the source of truth so ensure the file contains the new hash
string exactly to keep local tooling from reverting the submodule to the old
MCore revision.

[copy-pr-bot]

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[yaoyu-33]

Closing as stale.