chore(docs): add ADR#0035 session store on NATS JetStream

[yordis]

• The platform Session (ADR#0031) has no persistence design, and ADR#0024 explicitly deferred the session stream topology to a separate decision; this records that decision so session persistence is settled rather than improvised per implementer.
• It builds on the existing decider/JetStream substrate so sessions live on the one event-sourcing pattern the platform already runs, instead of a second bespoke store.
• It commits to an append-only log because rewind, fork, resume, and audit are inherent to agent sessions and should fall out of the model rather than be bolted on.

[cursor]

PR Summary

Low Risk
Documentation-only ADR and index entry; no runtime, API, or infrastructure code changes.

Overview
ADR#0035 closes the gap left by ADR#0024 and ADR#0031 by recording how platform Sessions are persisted: each session, subagent, and fork is a decider aggregate on shared JetStream stream SESSION_EVENTS (session.sessions.events.<session_id>), ratifying the prior crates/session domain model while replacing its KV-lease persistence with native expected_last_subject_sequence OCC.

The decision commits to append-only mutation (rewind/compaction/cancel are new events at replay), hybrid write preconditions (Any for commuting transcript facts, default At(head) for lifecycle/delegation invariants, NoStream for create/fork), typed protobuf events with boundary validation, in-stream Compacted markers, fork via shared-prefix replay plus mandatory sealing snapshots, subagent cascade via explicit policies and a reconciler processor, and keep-forever logs with snapshot-bounded replay (no ADR#0029 purge). Listing and model context are projections, not source of truth.

docs/adr/index.md gains a link to the new record.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 70ab9fa9-3d48-4574-9f1d-42e702e9d0f4

📥 Commits

Reviewing files that changed from the base of the PR and between c3fabbb and ee857b4.

📒 Files selected for processing (1)

• docs/adr/0035-session-store-decider-aggregate.md

Walkthrough

Adds draft ADR 0035 describing a session store as a decider aggregate on NATS JetStream, including stream semantics, concurrency, compaction, forks, cascades, projections, non-goals, consequences, and references. Registers the ADR in the index.

Changes

Session Store Architecture Decision

Layer / File(s)	Summary
ADR context and session model docs/adr/0035-session-store-decider-aggregate.md	Adds ADR metadata, context, substrate requirements, and session-event stream topology.
Decider aggregate decisions docs/adr/0035-session-store-decider-aggregate.md	Defines append-only JetStream writes, ordering, concurrency, validation, compaction, forks, cascades, projections, replay, and rejected alternatives.
Scope, consequences, and ADR index docs/adr/0035-session-store-decider-aggregate.md, docs/adr/index.md	Adds non-goals, consequences, references, and the ADR 0035 index entry.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• TrogonStack/trogonai#499: Adds session-store research that informs the ADR 0035 design.

Poem

A rabbit reads the streams at night,
Where session events hop into sight.
Forks share paths, snapshots gleam,
JetStream guards the flowing stream.
ADR carrots crunch—what a scheme!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the new ADR#0035 session store decision on NATS JetStream.
Description check	✅ Passed	The description directly summarizes the ADR's session persistence decision and append-only JetStream design.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Create PR with unit tests
• Commit unit tests in branch yordis/cebu-v1

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Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/adr/0035-session-store-decider-aggregate.md`:
- Around line 20-25: Update the historical-context sentence in ADR#0035 so it
states that the ADR index ran through ADR#0034 before this decision, rather than
asserting that it currently ends at ADR#0034. Preserve the surrounding
references to ADR#0024 and the JetStream topology.
- Around line 76-79: Replace every bare ADR#NNNN occurrence reported in this
document, including the visible references and all additional listed locations,
with relative Markdown links to the corresponding ADR documents. Preserve the
surrounding prose and link each ADR number consistently using the repository’s
existing ADR filename pattern.
- Around line 138-145: The documented Any write path must make idempotency
atomic with append so concurrent deliveries sharing a command key cannot append
duplicate facts. Update the session-store decision flow around the Any-path
events and their idempotency handling to reserve or deduplicate the command
atomically with the append, or route idempotent commands through a guarded write
that replays and returns the existing result on conflict; preserve unguarded Any
behavior only for commands without idempotency requirements.

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ℹ️ Review info

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Configuration used: Organization UI

Review profile: CHILL

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Run ID: d8e2b348-d8f7-492a-b6b1-17993882c806

📥 Commits

Reviewing files that changed from the base of the PR and between 27d43cf and c3fabbb.

📒 Files selected for processing (2)

• docs/adr/0035-session-store-decider-aggregate.md
• docs/adr/index.md

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