Prevent session state injection for provider supplied instructions

When the user provides instruction provider, we assume that they will inject the session state parameters if needed. This assumption allows users to return code snippets in the instruction provider without any template replacement.

PiperOrigin-RevId: 759705471

src/google/adk/agents/llm_agent.py

@@ -307,31 +307,53 @@ class LlmAgent(BaseAgent):
         ancestor_agent = ancestor_agent.parent_agent
       raise ValueError(f'No model found for {self.name}.')
 
-  async def canonical_instruction(self, ctx: ReadonlyContext) -> str:
+  async def canonical_instruction(
+      self, ctx: ReadonlyContext
+  ) -> tuple[str, bool]:
     """The resolved self.instruction field to construct instruction for this agent.
 
     This method is only for use by Agent Development Kit.
+
+    Args:
+      ctx: The context to retrieve the session state.
+
+    Returns:
+      A tuple of (instruction, bypass_state_injection).
+      instruction: The resolved self.instruction field.
+      bypass_state_injection: Whether the instruction is based on
+      InstructionProvider.
     """
     if isinstance(self.instruction, str):
-      return self.instruction
+      return self.instruction, False
     else:
       instruction = self.instruction(ctx)
       if inspect.isawaitable(instruction):
         instruction = await instruction
-      return instruction
+      return instruction, True
 
-  async def canonical_global_instruction(self, ctx: ReadonlyContext) -> str:
+  async def canonical_global_instruction(
+      self, ctx: ReadonlyContext
+  ) -> tuple[str, bool]:
     """The resolved self.instruction field to construct global instruction.
 
     This method is only for use by Agent Development Kit.
+
+    Args:
+      ctx: The context to retrieve the session state.
+
+    Returns:
+      A tuple of (instruction, bypass_state_injection).
+      instruction: The resolved self.global_instruction field.
+      bypass_state_injection: Whether the instruction is based on
+      InstructionProvider.
     """
     if isinstance(self.global_instruction, str):
-      return self.global_instruction
+      return self.global_instruction, False
     else:
       global_instruction = self.global_instruction(ctx)
       if inspect.isawaitable(global_instruction):
         global_instruction = await global_instruction
-      return global_instruction
+      return global_instruction, True
 
   async def canonical_tools(
       self, ctx: ReadonlyContext = None

src/google/adk/flows/llm_flows/instructions.py

@@ -53,18 +53,24 @@ class _InstructionsLlmRequestProcessor(BaseLlmRequestProcessor):
     if (
         isinstance(root_agent, LlmAgent) and root_agent.global_instruction
     ):  # not empty str
-      raw_si = await root_agent.canonical_global_instruction(
-          ReadonlyContext(invocation_context)
+      raw_si, bypass_state_injection = (
+          await root_agent.canonical_global_instruction(
+              ReadonlyContext(invocation_context)
+          )
       )
-      si = await _populate_values(raw_si, invocation_context)
+      si = raw_si
+      if not bypass_state_injection:
+        si = await _populate_values(raw_si, invocation_context)
       llm_request.append_instructions([si])
 
     # Appends agent instructions if set.
     if agent.instruction:  # not empty str
-      raw_si = await agent.canonical_instruction(
+      raw_si, bypass_state_injection = await agent.canonical_instruction(
           ReadonlyContext(invocation_context)
       )
-      si = await _populate_values(raw_si, invocation_context)
+      si = raw_si
+      if not bypass_state_injection:
+        si = await _populate_values(raw_si, invocation_context)
       llm_request.append_instructions([si])
 
     # Maintain async generator behavior