Follow a conversation and restore the reply

In short

• In a conversation, a given value keeps the same placeholder from the first message to the last.
• Two conversations are isolated. The same name can carry the same number in both, but they share nothing.
• Each call names its conversation. A call without an identifier is refused, instead of falling into a shared conversation. Only the piighost anonymize command falls back to the default conversation.
• A value first mentioned by the assistant stays in clear text, even if the user repeats it later.
• Erasing a conversation deletes its memory. The placeholders of that conversation are no longer restored afterwards.

Needs covered, described in Needs by profile:

• Compliance officer: DPO-6 DPO-6 Needs by profile As a DPO, I want to erase a conversation on request, so that I answer the right to erasure.
• Developer: DEV-2 DEV-2 Needs by profile As a developer, I want the reply to be restored automatically, so that I write nothing to put the real values back., DEV-3 DEV-3 Needs by profile As a developer, I want a value to keep the same placeholder over the whole conversation, so that the LLM follows the thread., DEV-8 DEV-8 Needs by profile As a developer, I want to decide what to do with a placeholder the LLM invented, so that it does not reach the user as is., DEV-10 DEV-10 Needs by profile As a developer, I want each conversation to be named explicitly, so that two users never share their placeholders by accident., DEV-11 DEV-11 Needs by profile As a developer, I want to choose the fate of a value that the assistant introduces itself, so that I decide whether the LLM keeps what it knows about it.
• Operator: OPS-2 OPS-2 Needs by profile As an operator, I want the memory to survive restarts and be shared between instances, so that a conversation does not lose its placeholders., OPS-7 OPS-7 Needs by profile As an operator, I want the in-process memory to be bounded by default, so that a server that runs for weeks does not keep every value it has seen.
• Application user: USER-1 USER-1 Needs by profile As a user, I want to read the reply with my real information, so that I never see a placeholder., USER-2 USER-2 Needs by profile As a user, I want the conversation to stay consistent from end to end, so that the assistant does not mix up two people., USER-6 USER-6 Needs by profile As a user, I want to correct a detection, add a missed name or make readable a term masked by mistake, so that the assistant receives the right text.

The terms are defined in the glossary. The processing of a single message is described in Protect a message before it is sent to the model.

For the business

piighost has no screen. A conversation is designated by an identifier that the application passes with each message. What you can observe is the text the model receives and the reply shown.

Who is involved

The path of a message in a conversation

Example conversation

If the model replies "Hello <<PERSON:1>>, greet <<PERSON:2>>.", the user reads "Hello Claire Dubois, greet Marc Petit."

How to check: ask the technical team for the placeholder mapping of the conversation. Each placeholder must designate a single person.

Correct a detection

The user, or the application on the user's behalf, can correct the values of a message before it is sent, for example add a missed name, or make readable a term masked by mistake.

If your application has a correction screen, do it in that screen. Otherwise, ask the technical team. They apply the correction through anonymize_corrected (or the server route /v1/anonymize/corrected).

1. Find the message to correct.
2. Add the missed value with its type, or remove the value masked by mistake.
3. Send the corrected message again.

How to check: the added value leaves as a placeholder, the removed value leaves in clear text, and the other messages do not change.

Erase a conversation

Typical case: a person exercises their right to erasure.

1. Identify the conversation by its identifier.
2. Ask the technical team for its erasure, or call the erasure route of the server.
3. Note the report, that is the number of messages and values deleted.

On a server that runs as several instances, the erasure empties the storage and the placeholder cache of the instance that receives the request. The other instances keep a copy of the values in their own cache, until it is evicted or the lifetime of that cache expires (BR-STO-06 BR-STO-06 Store conversations and protect traces When a conversation is erased, then its storage and the placeholder cache of the process that receives the request are emptied.). If you erase conversations on request, have the technical team set this lifetime.

How to check: restore an old placeholder of this conversation. It must stay as is, for example "Hello <<PERSON:1>>". On a server with several instances, this check does not prove that the copy held by the other instances is gone. Wait for the end of the cache lifetime, or have these instances restarted.

Rules to know

BR-CONV-01 BR-CONV-01 Follow a conversation and restore the reply When a value reappears in a later message of the same conversation, then it takes back its placeholder.. When a value reappears in a later message of the same conversation, then it takes back its placeholder. A new value of the same type receives the next number. 2 locations · 8 direct tests

BR-CONV-02 BR-CONV-02 Follow a conversation and restore the reply When the same value appears in two different conversations, then each has its own numbering, and a placeholder is restored only in its own conversation.. When the same value appears in two different conversations, then each has its own numbering, and a placeholder is restored only in its own conversation. For example, "Marc Petit" is <<PERSON:2>> in one conversation and <<PERSON:1>> in another. Restoring <<PERSON:1>> in a third, empty conversation leaves it as is. 2 locations · 8 direct tests

BR-CONV-03 BR-CONV-03 Follow a conversation and restore the reply When a call names no conversation, then it is refused, before anything is sent to the model.. When a call names no conversation, then it is refused, before anything is sent to the model. An application whose conversations do not need to be separated names the conversation default itself. The reason is that without an identifier, all users would share their placeholders. 2 locations · 9 direct tests

The piighost anonymize command is the exception. It is meant for trying out a single text, and falls back to the default conversation when it is given no identifier.

BR-CONV-04 BR-CONV-04 Follow a conversation and restore the reply When the assistant mentions a value before the user does, then it stays in clear text for the whole conversation, even if the user repeats it later (turn 4, "Lyon").. When the assistant mentions a value before the user does, then it stays in clear text for the whole conversation, even if the user repeats it later (turn 4, "Lyon"). The reason is that the model already knows this value, and masking it would take away useful knowledge. The two other settings are to mask it like a user value, or to not analyze the assistant messages. A value first brought by the user stays masked, even if the assistant repeats it. 3 locations · 11 direct tests

BR-CONV-05 BR-CONV-05 Follow a conversation and restore the reply When the model's reply contains a placeholder of the conversation, then it is replaced by the real value, even in a text that piighost never protected.. When the model's reply contains a placeholder of the conversation, then it is replaced by the real value, even in a text that piighost never protected. 1 location · 8 direct tests

BR-CONV-06 BR-CONV-06 Follow a conversation and restore the reply When the reply contains a placeholder in the right format that piighost never issued, then the restoration is refused by default, with the error Deanonymized text holds tokens the pipeline never issued: ['<<PERSON:9>>'].. When the reply contains a placeholder in the right format that piighost never issued, then the restoration is refused by default, with the error Deanonymized text holds tokens the pipeline never issued: ['<<PERSON:9>>']. This placeholder was invented by the model or injected by a text. The two other choices are to keep it or drop it. 1 location

A placeholder whose case or number has changed (<<Person:1>>, <<PERSON:01>>) counts as invented. A placeholder with damaged delimiters (<< PERSON:1 >>) is not recognized at all and stays as is.

BR-CONV-07 BR-CONV-07 Follow a conversation and restore the reply When a person corrects the values of a message by hand, then the correction replaces the automatic detection of that message only.. When a person corrects the values of a message by hand, then the correction replaces the automatic detection of that message only. The deny list (deny_list in the configuration) and the allow list (allow_list) still apply. For example, removing "Claire Dubois" from turn 1 leaves it in clear text in turn 1, and it stays masked in turn 2. The numbers can then change for the whole conversation. After this removal, <<PERSON:1>> designates Marc Petit and <<PERSON:2>> Claire Dubois. 4 locations · 8 direct tests

BR-CONV-08 BR-CONV-08 Follow a conversation and restore the reply When an identical message is sent again in the same conversation, then its detection is not run again.. When an identical message is sent again in the same conversation, then its detection is not run again. The result recorded the first time is reused. 1 location · 8 direct tests

BR-CONV-09 BR-CONV-09 Follow a conversation and restore the reply When a conversation is erased, then all its memory is deleted, and the erasure returns the number of messages and values deleted.. When a conversation is erased, then all its memory is deleted, and the erasure returns the number of messages and values deleted. For example, it returns Forgotten(messages=4, detections=5) for the conversation above. Afterwards, <<PERSON:1>> is no longer restored and stays as is. 1 location · 8 direct tests

BR-CONV-10 BR-CONV-10 Follow a conversation and restore the reply When several instances of the service share the same Redis memory, then they give the same placeholder to the same value of a conversation, and each one restores the placeholders issued by the other.. When several instances of the service share the same Redis memory, then they give the same placeholder to the same value of a conversation, and each one restores the placeholders issued by the other. 1 location

BR-CONV-11 BR-CONV-11 Follow a conversation and restore the reply When the memory is kept in the process, then, unless set otherwise, it keeps at most 10,000 conversations and forgets each one a day after its last message.. When the memory is kept in the process, then, unless set otherwise, it keeps at most 10,000 conversations and forgets each one a day after its last message. A forgotten conversation no longer restores its placeholders. The reason is that a server that runs for weeks must not keep every value it has seen. 2 locations · 37 direct tests

For a reply shown as it arrives, see Show a streamed reply.

What the end user sees

A readable conversation, with the real values. An old reply can still display placeholders if the application restores it a second time. This happens after an erasure, or after one day of inactivity when the memory is kept in the process.

Frequently asked questions

The call stops with No thread_id in the LangGraph config. The application does not name the conversation (BR-CONV-03 BR-CONV-03 Follow a conversation and restore the reply When a call names no conversation, then it is refused, before anything is sent to the model.). Have it pass an identifier, or default if the conversations do not need to be separated.

A reply showed the name of another person. An old message was probably corrected by hand (BR-CONV-07 BR-CONV-07 Follow a conversation and restore the reply When a person corrects the values of a message by hand, then the correction replaces the automatic detection of that message only.), or the memory of a message expired (see Pitfalls). Check the history of the conversation.

"Lyon" is not masked although the user wrote it. The assistant had mentioned it first (BR-CONV-04 BR-CONV-04 Follow a conversation and restore the reply When the assistant mentions a value before the user does, then it stays in clear text for the whole conversation, even if the user repeats it later (turn 4, "Lyon").). To force the masking, see Impose a deny list and an allow list.

The reply stops with Deanonymized text holds tokens the pipeline never issued. The model wrote an unknown placeholder (BR-CONV-06 BR-CONV-06 Follow a conversation and restore the reply When the reply contains a placeholder in the right format that piighost never issued, then the restoration is refused by default, with the error Deanonymized text holds tokens the pipeline never issued: ['<<PERSON:9>>'].). It often copied a placeholder from another conversation or from a document.

The reply shows <<PERSON:1>> after a long pause. The in-process memory forgot the conversation after one day of inactivity (BR-CONV-11 BR-CONV-11 Follow a conversation and restore the reply When the memory is kept in the process, then, unless set otherwise, it keeps at most 10,000 conversations and forgets each one a day after its last message.), or the conversation was erased (BR-CONV-09 BR-CONV-09 Follow a conversation and restore the reply When a conversation is erased, then all its memory is deleted, and the erasure returns the number of messages and values deleted.).

For developers

The technical guide builds a conversation pipeline step by step in Conversational pipeline.

Where the rules live

Related components: ThreadAnonymizationPipeline, AnyConversationMemory (remember, get_detections, get_provenance, forget), MessageRole, Forgotten, thread_token_map, TextDeidentifier, DEFAULT_THREAD_ID (conversation_memory/base.py:31), MissingThreadIdError, InventedPlaceholderStrategy, EntityCreateByAssistantStrategy.

Mechanics: placeholders are assigned over the union of the detections of all messages, in order of first appearance. The rendering replaces only the positions of the current message, because the detections of different messages share the same position space.

Correct a message by hand

1. Build the corrected set of Detection for the exact text of the message.
2. Call await pipeline.anonymize_corrected(text, thread_id, detections).
3. If the corrected message is not the last one, run the following turns again (BR-CONV-07 BR-CONV-07 Follow a conversation and restore the reply When a person corrects the values of a message by hand, then the correction replaces the automatic detection of that message only.).

Check

uv run pytest tests/pipeline/test_thread.py tests/pipeline/test_thread_hitl.py tests/acceptance

After the correction, await pipeline.thread_token_map(thread_id) must show the expected mapping placeholder by placeholder.

Pitfalls

• No integration falls back to default. The LangChain middleware and the Claude Code hooks raise MissingThreadIdError, and the server answers 400. Only the piighost anonymize command keeps --thread-id default, for a standalone command.
• The numbering depends on the order of the union. Anything that removes an old message from the union shifts the numbering. A correction does it (BR-CONV-07 BR-CONV-07 Follow a conversation and restore the reply When a person corrects the values of a message by hand, then the correction replaces the automatic detection of that message only.), but also the expiry of a Redis message with ttl, which _read_all drops from the union (conversation_memory/redis_backend.py:200-228).
• The in-process memory forgets silently. An evicted or expired conversation (BR-CONV-11 BR-CONV-11 Follow a conversation and restore the reply When the memory is kept in the process, then, unless set otherwise, it keeps at most 10,000 conversations and forgets each one a day after its last message.) raises nothing. Its placeholders stay as is at restoration. max_threads=None and ttl=None lift the bounds.
• Provenance applies to the value key (value_key), so to every spelling of a value.
• The placeholder cache is memoized per process (256 maps at most, _TOKEN_MEMO_MAX). See Store conversations for the effect on erasure with multiple processes, and token_memo_ttl to bound it.
• anonymize_corrected does not resolve overlaps and does not run the expansion again. The corrected set must be clean. It only goes through the deny list and allow list.

Tests