Merge Validation: Post-Merge Checks and Outcomes

Post-merge validation specification for EMEP. Covers NaN/Inf scanning, dtype invariants, norm envelopes, tokenizer round-trip, and small-batch forward pass with PASS, FAIL, and QUARANTINE outcomes.

Merge validation is the gate between the MergeEngine and candidate registration. This page specifies every post-merge check, the decision flow, and the three possible outcomes: PASS, FAIL, and QUARANTINE.

Validation Pipeline

Validation Checks

NaN/Inf Scan

Iterate over every parameter in the merged state_dict. Detect NaN or Inf values. This is a hard fail: any NaN or Inf produces FAIL immediately.

Threshold	Outcome
Any NaN or Inf	FAIL
All finite	Continue

Dtype Invariants

Verify that every parameter has the dtype declared in the merge config. Mixed dtypes are permitted only if the strategy explicitly declares them.

Condition	Outcome
Unexpected mixed dtype	FAIL
Expected mixed dtype	Continue
Uniform dtype matching config	Continue

Norm Envelopes

Compare the L2 norm of each merged layer to the L2 norms of the source models. Flag outliers.

Condition	Outcome
Norm outside [min_source - margin, max_source + margin]	QUARANTINE
Norm within envelope	Continue

Margin is configurable, default 20%.

Layer-wise Sanity

Verify that layer shapes match the expected architecture. Check that attention Q/K/V/O projections, MLP up/gate/down projections, and layernorm parameters all have the expected dimensions.

Condition	Outcome
Shape mismatch	QUARANTINE
All shapes correct	Continue

Tokenizer Round-trip

Encode and decode a fixed set of test strings. Verify that the output matches the input.

Condition	Outcome
Round-trip fails	QUARANTINE
Round-trip passes	Continue

Small-batch Forward Pass

Run a small batch of synthetic input IDs through the merged model. Verify that the forward pass completes and produces finite logits.

Condition	Outcome
Crash or exception	FAIL
NaN/Inf in logits	FAIL
Finite logits	Continue

Outcome Definitions

Outcome	Meaning	Next Action
PASS	All checks passed. Candidate is valid.	Register as CANDIDATE
FAIL	Hard failure. Candidate is invalid.	Discard, log failure, notify experiment
QUARANTINE	Soft failure. Candidate may be recoverable.	Hold for manual review, do not auto-register

Cross-Links

• Merge Engine for the pipeline that feeds into validation.
• Merge Strategies for what strategies produce candidates.
• Tensor Operations for the ops that may introduce instability.
• Numerical Testing for extended numerical validation.