Add deterministic engine loop proof

session/context.py

@@ -4,13 +4,20 @@ SessionContext — binds field, vault, vocab, and persona for one session.
 One session = one field trajectory on the manifold.
 The vault accumulates versors across turns.
 The persona motor is fixed per session (or composable across sessions).
+
+Generation returns GenerationResult so the evolved field state is preserved.
+The assistant vault entry stores the generated final_state, not the prompt
+field that entered the turn.
 """
 
+from __future__ import annotations
+
 from field.state import FieldState
 from vault.store import VaultStore
 from persona.motor import PersonaMotor
 from ingest.gate import inject
-from generate.stream import generate, agenerate
+from generate.stream import generate
+from generate.result import GenerationResult
 
 
 class SessionContext:
@@ -18,29 +25,43 @@ class SessionContext:
         self.vocab = vocab
         self.persona = persona or PersonaMotor.identity()
         self.vault = vault or VaultStore()
-        self.state: FieldState = None
+        self.state: FieldState | None = None
         self.turn: int = 0
 
     def ingest(self, tokens: list) -> FieldState:
-        """Inject a prompt. Sets self.state. Stores field in vault."""
+        """Inject a prompt. Sets self.state. Stores the user field in vault."""
         self.state = inject(tokens, self.vocab)
         self.vault.store(self.state.F, {"turn": self.turn, "role": "user"})
         return self.state
 
-    def respond(self, max_tokens: int = 128) -> list:
-        """Generate a response from current state. Stores result in vault."""
+    def respond(self, max_tokens: int = 128) -> GenerationResult:
+        """
+        Generate a response from current state and preserve the evolved field.
+
+        Returns:
+            GenerationResult carrying emitted tokens and final_state.
+        """
         assert self.state is not None, "Call ingest() before respond()."
-        tokens = generate(self.state, self.vocab, self.persona, max_tokens)
-        self.vault.store(self.state.F, {"turn": self.turn, "role": "assistant"})
+        result = generate(self.state, self.vocab, self.persona, max_tokens)
+        self.state = result.final_state
+        self.vault.store(result.final_state.F, {"turn": self.turn, "role": "assistant"})
         self.turn += 1
-        return tokens
+        return result
 
     async def arespond(self, max_tokens: int = 128):
-        """Async streaming response."""
+        """
+        Async token-yielding response path.
+
+        The generation pass still returns a GenerationResult internally so
+        SessionContext can store the evolved assistant final_state after
+        yielding the surface tokens.
+        """
         assert self.state is not None, "Call ingest() before arespond()."
-        async for token in agenerate(self.state, self.vocab, self.persona, max_tokens):
+        result = generate(self.state, self.vocab, self.persona, max_tokens)
+        for token in result.tokens:
             yield token
-        self.vault.store(self.state.F, {"turn": self.turn, "role": "assistant"})
+        self.state = result.final_state
+        self.vault.store(result.final_state.F, {"turn": self.turn, "role": "assistant"})
         self.turn += 1
 
     def recall(self, query_tokens: list, top_k: int = 5) -> list: