fix(invariants): harden runtime contracts and gates

packages/core/agent-loop/src/invariant.ts

@@ -7,6 +7,7 @@ import type { Context } from 'cordis'
 import type { GenerateOptions } from '@deepseek-ai/dsh-llm'
 import type { InvariantFailure, InvariantInstaller } from '@deepseek-ai/dsh-invariants'
 import { Session, SessionId, foldRequestHeader } from '@deepseek-ai/dsh-session'
+import { isLoopRequest } from './request-marker.ts'
 
 const PACKAGE_NAME = '@deepseek-ai/dsh-agent-loop'
 
@@ -20,9 +21,11 @@ const install: InvariantInstaller = Object.assign((ctx: Context, fail: Invariant
   // Prepend prevents a short-circuiting replay listener from silencing the
   // check; correctness itself comes from the sequence-bounded reconstruction.
   ctx.on('llm/stream', (options: GenerateOptions, next) => {
-    if (options.sessionId === undefined || !Object.isFrozen(options)) return next()
+    if (!isLoopRequest(options)) return next()
+    if (!Object.isFrozen(options)) fail('a loop-built request must be frozen')
+    if (options.sessionId === undefined) fail('a loop-built request must carry a session id')
     const session = ctx.sessions.get(options.sessionId)
-    if (!session) return next()
+    if (!session) fail(`a loop-built request must carry a live session id, got "${String(options.sessionId)}"`)
     if (!Object.isFrozen(options.messages)) {
       fail('a loop-built request must carry a frozen messages array')
     }

packages/core/agent-loop/src/loop.ts

@@ -15,6 +15,7 @@ import { canonicalHeader } from '@deepseek-ai/dsh-session'
 import type { Session, TurnEndReason, TurnTrigger } from '@deepseek-ai/dsh-session'
 import { createTransmissionLog, recordRequestHeader } from './request-log.ts'
 import type { TransmissionLog } from './request-log.ts'
+import { markLoopRequest } from './request-marker.ts'
 import { renderPrompt } from '@deepseek-ai/dsh-system-prompt'
 import type { PromptAssembly } from '@deepseek-ai/dsh-system-prompt'
 import type {} from '@deepseek-ai/dsh-tools'
@@ -619,7 +620,7 @@ async function runStep(
   recordRequestHeader(session, transmission, header)
 
   // Freeze the logged header plus boundary snapshot; the prefix precedes derived history.
-  const request: GenerateOptions = deepFreeze({
+  const request: GenerateOptions = deepFreeze(markLoopRequest({
     provider: header.config.provider,
     model: header.config.model,
     messages: [...header.messagePrefix ?? [], ...boundaryMessages],
@@ -630,7 +631,7 @@ async function runStep(
     ...header.config.stop !== undefined ? { stop: header.config.stop } : {},
     sessionId: session.id,
     signal,
-  })
+  }))
 
   // --- Model call (streaming-first; raw chunks are the replay record) ---
   const assembler = new BlockAssembler()

packages/core/agent-loop/src/request-marker.ts

@@ -0,0 +1,22 @@
+/** Internal identity shared by the independently bundled loop and invariant companion. */
+
+const LOOP_REQUEST = Symbol.for('@deepseek-ai/dsh-agent-loop/request')
+
+/**
+ * Mark a request as owned by the agent loop before it is frozen.
+ * @param request - mutable request object being assembled by the loop.
+ * @returns the same request with a non-enumerable loop identity.
+ */
+export function markLoopRequest<T extends object>(request: T): T {
+  Object.defineProperty(request, LOOP_REQUEST, { value: true })
+  return request
+}
+
+/**
+ * Test whether a request carries the agent loop's internal identity.
+ * @param request - request observed at the LLM stream boundary.
+ * @returns whether the loop marked this exact request object.
+ */
+export function isLoopRequest(request: object): boolean {
+  return Reflect.get(request, LOOP_REQUEST) === true
+}