time-context: durable per-step history (round 1)

packages/context/time-context/src/index.ts

@@ -1,8 +1,6 @@
 /**
- * Opt-in request-time clock context. Active turns receive the current zoned
- * time and elapsed time since the preceding model-visible message. The loop
- * logs each rendered value as request-header state rather than conversation
- * history.
+ * Opt-in per-step clock context. Every pending model request receives a
+ * durable, source-attributed time reading in conversation history.
  *
  * @module @deepseek-ai/dsh-time-context
  */
@@ -10,77 +8,27 @@
 import type { Context } from 'cordis'
 import z from 'schemastery'
 import type { Agent } from '@deepseek-ai/dsh-agent'
-import type { AssembleContext } from '@deepseek-ai/dsh-system-prompt'
+import type { Message } from '@deepseek-ai/dsh-llm'
 
 /** Cordis plugin name used by loader diagnostics. */
 export const name = 'time-context'
 
-/** The system-prompt registry that owns the dynamic request section. */
-export const inject = ['systemPrompt']
+/** The agent registry that owns the pre-step lifecycle seam. */
+export const inject = ['agents']
 
-/** Request-time clock formatting and refresh policy. Invalid values fail plugin load. */
+/** Request-time clock formatting. Invalid values fail plugin load. */
 export interface Config {
   /** IANA time zone used for the rendered timestamp. Omit to resolve the Node process's system zone at plugin load. */
   timeZone?: string
-  /** Maximum age of a reading within one turn, in milliseconds (default 60,000; `0` refreshes every step). */
-  refreshIntervalMs?: number
 }
 
-/** Schemastery validation and defaults for {@link Config}. */
+/** Schemastery validation for {@link Config}. */
 export const Config: z<Config> = z.object({
   timeZone: z.string(),
-  refreshIntervalMs: z.number().default(60_000),
 })
 
-interface OpenTurn {
-  turn: number
-  startSeq: number
-}
-
-/** Cached text and the fixed inter-turn baseline used by one agent's open turn. */
-interface RenderState {
-  turn: number
-  renderedAt: number
-  previousMessageTime: number | undefined
-  text: string
-}
-
 type TimestampPart = 'day' | 'hour' | 'minute' | 'month' | 'second' | 'timeZoneName' | 'year'
 
-function openTurn(agent: Agent): OpenTurn | undefined {
-  for (const event of [...agent.session.events].reverse()) {
-    switch (event.type) {
-      case 'turn/end':
-        return undefined
-      case 'turn/start':
-        return { turn: event.data.turn, startSeq: event.seq }
-      default:
-        // Merge-extensible session events: only turn boundaries matter here.
-        break
-    }
-  }
-  return undefined
-}
-
-/** Find the latest model-visible timestamp strictly before one turn boundary. */
-function previousMessageTime(agent: Agent, turnStartSeq: number): number | undefined {
-  for (const event of [...agent.session.events].reverse()) {
-    if (event.seq >= turnStartSeq) continue
-    switch (event.type) {
-      case 'user/message':
-      case 'assistant/message':
-      case 'tool/result':
-      case 'context/message':
-      case 'steering/message':
-        return event.time
-      default:
-        // Merge-extensible session events: non-surface records are not messages.
-        break
-    }
-  }
-  return undefined
-}
-
 /** Format an epoch millisecond value as an ISO-shaped timestamp with offset and IANA zone. */
 function formatTimestamp(now: number, formatter: Intl.DateTimeFormat, timeZone: string): string {
   const parts = Object.fromEntries(
@@ -107,31 +55,59 @@ function formatDuration(elapsedMs: number): string {
   return parts.join(' ')
 }
 
+/** Find the latest model-visible event, excluding this plugin's pending append. */
+function precedingMessageTime(agent: Agent): number | undefined {
+  for (const event of [...agent.session.events].reverse()) {
+    switch (event.type) {
+      case 'user/message':
+      case 'assistant/message':
+      case 'tool/result':
+      case 'context/message':
+      case 'steering/message':
+        return event.time
+      default:
+        // Merge-extensible session events: non-surface records are not messages.
+        break
+    }
+  }
+  return undefined
+}
+
+/** Find the preceding time-context event within the open turn. */
+function precedingStepContextTime(agent: Agent, turn: number): number | undefined {
+  for (const event of [...agent.session.events].reverse()) {
+    if (event.type === 'turn/start' && event.data.turn === turn) return undefined
+    if (event.type === 'context/message'
+      && event.data.source.kind === 'plugin'
+      && event.data.source.plugin === name) {
+      return event.time
+    }
+  }
+  return undefined
+}
+
 function renderText(
   now: number,
+  turn: number,
+  step: number,
   previous: number | undefined,
   formatter: Intl.DateTimeFormat,
   timeZone: string,
 ): string {
-  const elapsed = previous === undefined
-    ? 'unavailable (no earlier message in this session)'
-    : formatDuration(now - previous)
-  return `Current time: ${formatTimestamp(now, formatter, timeZone)}\nTime since previous message: ${elapsed}.`
+  const elapsed = previous === undefined ? 'unavailable' : formatDuration(now - previous)
+  const baseline = step === 1 ? 'model-visible message' : 'step context'
+  return `Time recorded before turn ${turn}, step ${step}: ${formatTimestamp(now, formatter, timeZone)}\n`
+    + `Elapsed since the preceding ${baseline}: ${elapsed}.`
 }
 
 /**
- * Register the request-time clock section for the lifetime of `ctx`.
- * @param ctx - plugin context; the section registration is disposed with it.
- * @param config - validated time zone and intra-turn refresh interval.
- * @throws when the time zone or refresh interval is invalid.
+ * Register a prepended pre-step listener for the lifetime of `ctx`.
+ * @param ctx - plugin context; the listener is disposed with it.
+ * @param config - validated time zone configuration.
+ * @throws when the configured or process time zone cannot be resolved.
  */
 export function apply(ctx: Context, config: Config): void {
   const timeZone = config.timeZone
-  const refreshIntervalMs = config.refreshIntervalMs as number
-  if (!Number.isSafeInteger(refreshIntervalMs) || refreshIntervalMs < 0) {
-    throw new Error(`time-context: refreshIntervalMs must be a non-negative safe integer, got ${refreshIntervalMs}`)
-  }
-
   let formatter: Intl.DateTimeFormat
   try {
     formatter = new Intl.DateTimeFormat('en-US', {
@@ -152,32 +128,23 @@ export function apply(ctx: Context, config: Config): void {
     throw new Error(message, { cause: error })
   }
   const resolvedTimeZone = formatter.resolvedOptions().timeZone
-  const states = new WeakMap<Agent, RenderState>()
 
-  ctx.systemPrompt.section({
-    name: 'context:time',
-    order: 10,
-    text(context: AssembleContext): string {
-      const agent = context.agent
-      if (agent === undefined) return ''
-      const currentTurn = openTurn(agent)
-      if (currentTurn === undefined) return ''
-
-      const now = Date.now()
-      const prior = states.get(agent)
-      if (prior !== undefined
-        && prior.turn === currentTurn.turn
-        && now >= prior.renderedAt
-        && now - prior.renderedAt < refreshIntervalMs) {
-        return prior.text
-      }
-
-      const previous = prior?.turn === currentTurn.turn
-        ? prior.previousMessageTime
-        : previousMessageTime(agent, currentTurn.startSeq)
-      const text = renderText(now, previous, formatter, resolvedTimeZone)
-      states.set(agent, { turn: currentTurn.turn, renderedAt: now, previousMessageTime: previous, text })
-      return text
-    },
-  })
+  ctx.on('agent/pre-step', (
+    agent: Agent,
+    turn: number,
+    step: number,
+    _fullSystemPrompt: string,
+    _sessionPrefix: readonly Message[],
+    signal: AbortSignal,
+  ) => {
+    if (signal.aborted) return
+    const now = Date.now()
+    const previous = step === 1
+      ? precedingMessageTime(agent)
+      : precedingStepContextTime(agent, turn)
+    agent.inject(
+      [{ type: 'text', text: renderText(now, turn, step, previous, formatter, resolvedTimeZone) }],
+      { source: { kind: 'plugin', plugin: name } },
+    )
+  }, { prepend: true })
 }