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Multigrid

Cutting over between providers

Dual-running, fine-tune translation, prompt portability and the cost re-baselining that follows a switch.

A provider switch is usually planned as an integration job and turns out to be four jobs. The API shape is the visible one and the smallest: rename a field, move the system prompt, adjust a stop-sequence array. Underneath it sit three that nobody scoped. The prompt was tuned against one model family and its formatting conventions do not carry. The fine-tune does not move at all. And the cost model, which was built by multiplying a measured token count by a known price, is now wrong in both factors at once — different tokenizer, different table — in a way that can move the bill in either direction.

These pages are about that second layer. Each one starts from a thing that does not translate, explains why it does not, and gets to what you rebuild instead. Where a page needs a number that only your own traffic can supply, it gives you the procedure that produces it rather than a figure borrowed from somebody else’s workload.

Translating a Fine-Tune When You Change Base Providers

A fine-tune is a delta on one specific base model, so nothing about it crosses to another provider except the data that produced it.

9 min read

Re-Running a Fine-Tune Job on a New Provider's API

Converting a supervised fine-tuning dataset between the two dominant JSONL shapes, field by field, including the parts that have no counterpart.

10 min read

Prompt Portability: What Breaks When You Move a Prompt to Another Model Family

The specific prompt constructs that are tuned to one model family's post-training and degrade on another, and what to change first.

10 min read

Re-Baselining Cost Estimates After Switching Providers

A procedure for rebuilding a cost model after a switch, when price, tokenizer and typical output length have all moved at the same time.

10 min read

Why the Same Prompt Costs a Different Amount on Two Providers

The cost difference for one identical request decomposes into a tokenizer ratio and a price ratio, and the two can point in opposite directions.

9 min read

Rate Limit Differences You Hit When Switching Providers

Rate limits vary along four independent axes — unit, window, scope and tier — and a migration usually breaks on the axis nobody checked.

9 min read

Why Your Token Count Changed After Switching Providers

Identical text produces different token counts on different providers because each model family has its own learned vocabulary, and three other effects add to the gap.

9 min read

What a Tokenizer Difference Does to Your Monthly Bill

Turning a measured per-request token ratio into a monthly figure, and the aggregation errors that make the naive multiplication wrong.

10 min read

Moving Off a Managed AI Platform: What You Actually Own

Ownership of an AI artifact is reproducibility, not a download button, and that distinction decides what survives the day you leave.

10 min read

Exporting Conversation History and Normalising It

The two shapes chat exports actually take, and a transform that turns either into a plain message array you can replay anywhere.

10 min read

What Conversation History Exports Leave Out

The fields a chat export typically drops, the migration decision each one blocks, and where to capture it instead.

9 min read

A Vendor Lock-In Checklist, Component by Component

Score each layer of an AI stack on five questions instead of treating lock-in as one property of one vendor.

10 min read

Which Parts of an AI Stack Are Actually Portable

Portability is a property of the representation, not of the vendor, and that is why it is so uneven across one stack.

9 min read

Contract Terms Worth Checking Before You Commit to an AI Vendor

The clause types that decide how hard a future migration will be, read through the single lens of what each one costs you at exit.

10 min read

Minimum Commitment Clauses in AI Vendor Contracts

How volume commitments are structured, and the arithmetic that turns a headline discount into a premium when usage falls short.

10 min read

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