9b8fccc6f9
Seven ADRs capturing the why behind decisions already made: vendoring Cordis as source with a guarded manifest; the microkernel event taxonomy with one swappable concrete loop; event-sourced sessions with derived history and the append-before-emit ordering contract; the provider-neutral content-block vocabulary (and why not OpenAI/Anthropic shapes); the custom tool-schema DSL over schemastery; tool schemas living in the prompt assembly; and mechanical quality gates over prose guidelines (the agents-write-the-code rationale).
1.7 KiB
ADR 0003: Event-sourced sessions with derived message history
Status: accepted (2026-06-11)
Context
The MVP requires strict event-based tracing with fully replayable sessions (严格的基于事件的trace、logging系统，session完全可回放). Two models were considered: a mutable message array with events fired as notifications (simpler, but state and log can diverge), or event-sourcing where the log IS the state.
Decision
A Session is an append-only log of typed SessionEvents — the single
source of truth. The LLM message history is derived from the log
(deriveMessages()); raw stream chunks are logged for token-level replay
fidelity while the assembled assistant/message event is authoritative for
derivation. Replay/fork = seed a new session with an existing log.
Appends are synchronous (the hot path never blocks on I/O); session/event
is a sync notification; persistence plugins buffer write-behind and drain at
the awaited session/flush checkpoint fired at every turn end.
Ordering contract: the loop appends to the session before emitting the
corresponding Cordis event, and the agent/step-result waterfall runs before
the assistant/message append so the log records what tool dispatch actually
used (post-review fix; regression-tested).
Consequences
- Replay, trace, and telemetry are structurally guaranteed, not bolted on.
- Persistence stays a plugin concern; the in-memory store ships in dsh-session.
- The event vocabulary is merge-extensible (plugins add e.g. compaction events); it carries a TODO(review) marker until the first persistence plugin and real adapter exercise it.
- Derivation cost grows with log length — compaction (future plugin) is the intended mitigation, not log mutation.