Letters to the other side and AI security: what open correspondence gives away in ChatGPT or Claude.

Liaising with the other side is the most public writing a law firm does, which is why it feels safe to run through ChatGPT or Claude. It is still a client’s matter. An open letter to opposing solicitors names everyone, states the client’s position, demands documents and sets deadlines, and it is written from the privileged file. This page marks every item in a routine letter to the other side that rule 9 still protects, and shows how the same letter is drafted on Ermos inside the firm.

The letter to the other side

Sent to the other party’s solicitors at any stage of a dispute: a demand, a response to a defence, a request for documents.

Carrick Doyle Lawyers

Merrow Chambers Lawyers¹
Attn: Mr Jonathan Pike¹
By email

Re: Soto v Greystone Property Group Pty Ltd, FWC matter C2026/4471²

Dear Colleague,

We refer to your client’s response filed on 3 October and to the board minutes produced with it.

The minutes produced are redacted. The redactions cover the discussion under item 6, “Finance function review”, which is the item your client relies on. We request unredacted copies of the minutes of the 22 May and 19 June meetings and the board papers for item 6, by 24 October.³

Your client’s response asserts that the Financial Controller role advertised on 18 September differs materially from our client’s former role. The position description, which our client obtained from the public advertisement, lists eleven duties, nine of which appear in her 2019 position description. We will rely on that comparison.⁴

Your client has also raised our client’s forwarding of three emails to a personal account. Our client acted to preserve evidence of a concern she had raised internally, which is relevant to the workplace right in issue. We note your client has not identified any loss or disclosure arising from it. We invite your client to confirm it will not pursue any claim in that regard.⁵

We are instructed that Mr Whitcombe met with our client alone on 4 September and that no HR representative was present, contrary to your client’s policy. Please confirm whether any note of that meeting exists.⁶

Our client remains willing to participate in conciliation on 13 November. We reserve our client’s rights, including in relation to costs.⁷

Eleanor Vance⁸
Partner, Carrick Doyle Lawyers⁸

An invented letter. Hover or tap any highlighted item for the analysis; the full list is below.

What leaves the firm

The opposing firm and solicitor

A named practitioner at a named firm. Personal information of a third party who has no relationship with the provider. Privacy Act guide.

Frontier Models (ChatGPT, Claude)	A third party’s details transmitted
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

The proceedings

Parties and a file number. With the matter identified, the whole dispute is searchable. Rule 9 confidentiality guide.

Frontier Models (ChatGPT, Claude)	A live proceeding identified on a third party’s servers
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

Documents demanded, and why

What the firm thinks the redactions hide. A window into the firm’s theory of the case, in open correspondence. Legal privilege guide.

Frontier Models (ChatGPT, Claude)	The theory of the case transmitted; on consumer tiers it can train future models
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

The comparison the firm will rely on

Evidence and argument, previewed. Confidential to the client until the firm chooses to deploy it. Rule 9 confidentiality guide.

Frontier Models (ChatGPT, Claude)	Evidence previewed to a third party before the other side
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

The client’s exposure, and the firm’s handling of it

How the firm is managing the client’s weakest point. The explanation is drafted from privileged instructions. Legal privilege guide.

Frontier Models (ChatGPT, Claude)	Privileged instructions, paraphrased, transmitted
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

An instruction about a named executive

What the client says happened in a room with one other person. The client’s instructions, and an assertion about a third party. Rule 9 confidentiality guide.

Frontier Models (ChatGPT, Claude)	An assertion about a named executive transmitted
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

Willingness to settle

That the client will attend conciliation. A small signal, and a signal. Rule 9 confidentiality guide.

Frontier Models (ChatGPT, Claude)	A settlement signal transmitted
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

The partner

Ties the letter to a solicitor bound by rule 9 and the duty of courtesy to the other side. Law Society AI guidance.

Frontier Models (ChatGPT, Claude)	Transmitted, and the leak is traceable to you
Ermos Edge	Stays on your instance in Australia; leaves only inside a permitted excerpt, per question, to the named provider
Ermos Dominion	Stays on the unit in your office

What happens in Frontier Models (ChatGPT, Claude)

The whole document is transmitted to the provider’s servers. On personal plans the user cannot choose where it is stored or processed, and for the major providers that has generally meant outside Australia, under that country’s legal process. Some business plans offer storage in Australia, but the provider still receives the content.
On consumer tiers, prompts can be retained and used to train future models.
The provider’s staff and systems can reach the content under the provider’s own policies.
Once sent, the firm no longer controls it. Retention and deletion happen on the provider’s terms.

The same document on Ermos

Ermos Dominion

The document is drafted on a unit in your office, from your own templates and the matter file. Every marked item stays on the unit, which keeps working with the internet switched off. Nothing in it is transmitted to an AI provider, so there is no disclosure to analyse: the confidentiality work is the same as for your file server.

Ermos Edge

Your documents, the index and your access boundaries stay on your own instance in an Australian data centre. When a staff member asks for this draft, only their question and the excerpts they are permitted to see go to a named Australian provider, who is contractually barred from keeping the content or training any model on it. Nothing is processed outside Australia.

	Frontier Models (ChatGPT, Claude)	Ermos Edge	Ermos Dominion
Where the document is processed	Provider servers, generally offshore on personal plans	Your instance in an Australian data centre; answers generated in Australia	The unit in your office
Who can read it	Provider staff and systems, under policy	Your staff, within the boundaries you set. The named Australian provider processes only permitted excerpts, under contract, and keeps nothing	Your staff only
Is it kept	On the provider’s terms	Kept on your instance; the provider is barred from retaining it	Stays on the unit
Can it train a model	On consumer tiers, yes	No, by contract	Only your own unit learns from it, on your hardware

Part of AI data leakage in law firms. See how this works in practice: Litigation work on Ermos.

Common questions

Do ChatGPT and Claude use the information in a letter to the other side?

Yes, the AI company receives and processes everything pasted in on its servers. As at October 2026, whether a conversation on a personal plan (ChatGPT Free, Plus or Pro; Claude Free, Pro or Max) can be used to train the models depends on a setting each user controls. Business plans (ChatGPT Business and Enterprise, Claude Team and Enterprise) and the developer APIs sit under commercial terms, and OpenAI and Anthropic each say they do not train on that content by default (OpenAI, Anthropic). On either product, the thumbs up and thumbs down buttons can send a whole conversation back for training. The draft carries the firm's theory of the case and its handling of the client's weak point.

Can we use ChatGPT or Claude for a letter to the other side if we remove the names?

No, because the letter's details still identify the proceeding after the names go. Removing names rarely makes a document anonymous. Information stays personal information while the person is reasonably identifiable, and the OAIC warns that information can be at risk of re-identification even when it has been de-identified or anonymised. The matter number, the dates of the board meetings and the count of matching duties point to one dispute. The Office of the Australian Information Commissioner (OAIC) recommends in its guidance on commercially available AI products that organisations do not enter personal information, and particularly sensitive information, into publicly available generative AI tools, because of the significant and complex privacy risks.

Can ChatGPT or Claude be trusted to draft a letter to the other side?

Not without a solicitor checking every line against the file. Language models can write fluent text that contains details missing from the source, wrong figures, wrong dates and references that look real but are not. The costliest errors here would be a wrong board meeting date, a wrong deadline, a wrong matter number or a miscounted comparison of duties. An invented detail about who attended the 4 September meeting would do equal harm. The other side holds every error once the letter is sent.

How can a law firm use AI for a letter to the other side without sending it to ChatGPT or Claude?

Ermos is built so the document stays under your control. On the Dominion AI unit it is drafted inside your office and none of it is sent to an AI provider. On Ermos Edge your documents and index stay on your own instance in an Australian data centre, and only the question and the excerpts the user is permitted to see go to a named Australian provider that is contractually barred from keeping them or training any model on them. The solicitor asks for the draft in plain language, and it is built from the firm's precedent letters and the indexed matter file. The partner checks each date and reference against the documents produced before signing.

The letter will be sent to the other side anyway. Why does it matter where it is drafted?

Because the other side is the only third party the client has authorised. The letter is drafted from privileged instructions and reveals the firm's reasoning in the choice of what to demand and what to rebut. On a provider's servers it is a disclosure to a party the client never chose, retained on terms the client never saw.

Is the opposing solicitor's name really a concern?

It is personal information about a practitioner, and the duty of courtesy in open correspondence does not extend to feeding their name and conduct into a third party's system. Small on its own; part of the pattern of everything leaving.

How is correspondence drafted on Ermos?

From the firm's own precedent letters and the matter file, on your own network, with the response pleading and the documents produced indexed beside it. Every draft cites the excerpts it drew on, so checking the position description comparison is a glance.

See Dominion answering from your own documents.

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