Bring the interception-seams branch onto current master (via A→B). The substantive reconciliation is master's compaction `agent/pre-step` serial seam meeting C's interception seams: - types.ts: keep BOTH master's `agent/pre-step` AND C's new interception events (`agent/prompt-submit`, `agent/session-start`, `agent/turn-continuation`→ `ContinuationDecision`); drop the turn-mirror declarations (removed on A). - loop.ts: the merged per-turn order is `turn/start` → per queued msg `agent/prompt-submit` (rewrite/inject/block) → (fully-blocked ⇒ zero-step `rejected`) → per step: drain steering → assemble system prompt → `agent/pre-step` (compaction, OUTSIDE the step) → `step/start` → single `deriveMessages()` → model → tools/pre-execute·dispatch·post-execute. No turn-mirror emits; `closeTurn()` is the A-simplified single-call form. - Docs (architecture, core.md, agent/agent-loop READMEs, catalog) reconciled to show C's interception seams alongside `agent/pre-step`, no turn/step mirrors. - rfc/README: dropped the stale `proposed/` compaction row (master moved that RFC to implemented/); kept C's new `pre-tool-input-rewrite` proposed row. - interception.spec.ts: migrated its two `agent/turn-end` reason collectors to the `turn/end` session event, and ADDED a cross-test proving a `prompt-submit` rewrite + additionalContext is VISIBLE to an `agent/pre-step` listener on the same turn — pinning the merged seam ordering (compaction sees the post-prompt-submit surface, not stale history).
dsh-invariants
Dev-mode event-contract invariants and session-log freeze. A pure-listener plugin (everything is a plugin) that asserts the harness event contract at runtime and, optionally, freezes logged session-event data so any code that mutates history throws instead of corrupting silently.
Off in production. Enable it in tests and the demos, where a contract violation should fail loudly. It costs nothing when not registered, and doubles as executable documentation of the event taxonomy — the assertions are the contract.
Plugin
A functional plugin — register the module namespace (this is what loading by name in cordis.yml does):
import type { Context } from 'cordis'
import * as Invariants from '@deepseek-ai/dsh-invariants'
declare const ctx: Context
await ctx.plugin(Invariants) // freeze on (default)
await ctx.plugin(Invariants, { freeze: false }) // assert contract, don't freeze
inject: ['sessions'] — it reads ctx.sessions.list() at apply time to rebuild trace state for sessions that already exist (so a hot reload mid-turn doesn't falsely reject the next event). It listens on session/created, session/event, and agent/status.
Config
| Key | Default | Meaning |
|---|---|---|
freeze |
true |
Deep-freeze each logged event's data so mutating a logged event throws. Set false to assert the contract without freezing. |
Invariants asserted
Session log (per session):
seqstrictly increases — the spine of replay equivalence.- turns pair and nest —
turn/startopens a turn,turn/endcloses the matching one; no overlapping turns. - steps nest in turns —
step/startopens a step in the open turn;step/endcloses the matching step. - chunks belong to an open step —
step/startprecedes itsassistant/chunks. - a
tool/resultneeds a priortool/call— but NOT the converse: atool/callmay have no result (a thrown tool-execution pipeline step ends the turn with notool/result, which is legal).
Agent status (per agent):
- legal transitions only —
idle↔runningand(idle|running)→disposed. A no-op transition (setStatusdedups, so it never fires) and leaving the terminaldisposedstate are violations.
On any violation it throws InvariantError (code: 'INVARIANT').
Why runtime, not deep-readonly types
A DeepReadonly<SessionEvent> is high type-noise across every log consumer, and a plugin can cast straight through it. A dev-mode freeze plus these assertions catch real corruption at zero production cost and zero type noise. The always-on half of that defense — cloning derived messages so request/adapter mutation can't reach back into the log — lives in dsh-session's deriveMessages. This package is the dev-mode tripwire. See dev-mode invariants.
Seeded sessions
A seeded/forked session arrives with events already in its log (the Session constructor copies the seed without emitting session/event). On session/created the plugin replays the existing log through the checker and freezes those entries, so seeded history is held to the same contract.