fix: keep earlier answers and memory after a source is deleted

[devhims]

Problem / Motivation

Deleting session evidence made the agent forget its own earlier answers. For every answer that used the deleted source:

Where	Before
Dashboard	Answer visible, citations shown as [source deleted]
Agent prompt (recent turns)	Answer replaced with "[Historical answer omitted because its supporting evidence was deleted.]"
History search (search_context, read_session_history)	Answer removed

"Clear saved data" did this to every answer in the session. The agent kept the user's questions but lost its own replies, so a follow-up like "does that still fit my budget?" lost its context. The deletion dialog says "Conversation messages remain", which was true for the user but not for the agent.

Deleting a source should remove the source, not the conversation. Earlier answers are history: useful context, never evidence.

What changed

• Deletion keeps answers in history. The source, its excerpts and the citations to it are still removed; citations show [source deleted]. The redacted answer stays in the agent's prompt and in history search.

• History is never a source. New HISTORY_ATTRIBUTION_GUIDANCE in the answer model's instructions: earlier answers, including ones showing [source deleted], are conversation history. When any part of an answer relies on something stated only earlier, the model says so plainly ("Based on our earlier conversation, ...") and never cites it or presents it as verified evidence. This complements the existing guidance that history is untrusted context.

• Existing sessions recover. History indexing is versioned (HISTORY_REVISION), so the next sync re-indexes every run once and restores answers removed under the old rule.

• Dialog copy: "Conversation messages remain, and the agent can still refer to them as earlier conversation."

• Memory is kept as recorded. Deleting one source used to delete every memory entry that cited any of its excerpts, even an entry that also cited other sources. Memory records what was answered for the user's question, so deletion no longer rewrites or erases it. An affected entry keeps its text and evidenceIds and lists the lost citations in deletedEvidenceIds. The dashboard shows "N deleted, now unverified", and the answer model treats that part as unverified earlier conversation and says so when using it. A later rewrite of the topic keeps the mark, since the rewritten text can carry the deleted source's facts forward; forgetting the memory clears it.

Unchanged:

• New memory cannot cite deleted evidence, and no memory is built from an answer whose evidence was deleted.
• "Clear saved data" explicitly includes memory in its dialog and still removes it.

Attribution relies on the model following its instructions; there is no application check that an answer labels history it used.

Tests

All 1,592 platform unit tests, 352 runtime/session integration tests and 104 web tests pass, plus the dashboard deletion E2E test. Type checks and the docs check pass. New or updated tests cover:

• a follow-up run's prompt still containing the earlier answer after its source is deleted, with [source deleted] and without the deleted source's text
• re-indexing restoring an answer removed under the old revision format
• deletion keeping the redacted answer searchable while the source text stays gone
• the history backfill now including answers whose evidence was deleted
• the answer model's prompt containing the attribution rule, including the rule for memory with deleted sources
• a memory rewrite keeping the deleted-source mark, and forgetting the memory clearing it
• the deletion dialogs: source deletion keeps memory marked unverified, clearing all saved data removes memory
• a memory citing two sources keeping its text and live citation when one is deleted, without duplicate marks on repeated deletion
• memory, dashboard inventory and memory search keeping findings after source deletion, while a late write citing deleted evidence is still rejected

Relationship to #169

Independent. #169's ID-based coverage check stays correct either way; its deleted-answers edge case stops arising once this merges. Both edit SESSION_EVIDENCE.md in different paragraphs.

Compatibility and deployment

No migration. The first run in each session after deploy re-indexes that session's history once.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
video2ctx-web	Ready	Preview	Oct 8, 2026 6:20am UTC