strands.injection.types

Configuration types shared by injection consumers.

Consumed by the ContextInjector plugin and the MemoryManager.

InjectionTrigger

Determines when injection runs before a model call.

• "userTurn": only when the latest message is a fresh user ask (a user message with no tool result) — the common case for chat agents, where it keeps the user’s ask the final message the model sees.
• "everyTurn": before every model call, including mid-task tool-result turns — for autonomous agents that should consult injected context at each step.

For finer control, pass a predicate instead of a trigger name.

InjectionContext

@dataclass
class InjectionContext()

Defined in: src/strands/injection/types.py:33

The context an injection consumer receives on each model call.

Passed to the render_content callback and to a predicate trigger.

Attributes:

• messages - The current conversation, as data.
• state - Durable agent state shared across calls, hooks, and tools — read what a tool stashed last turn.
• agent - The agent the injection is attached to (escape hatch for advanced consumers).

TriggerCallback

class TriggerCallback(Protocol)

Defined in: src/strands/injection/types.py:50

A predicate that decides whether to inject on a given model call.

Implemented by a plain function as well — the **kwargs tail lets the calling convention grow new keyword arguments without breaking existing predicates.

__call__

def __call__(context: InjectionContext, **kwargs: Any) -> bool

Defined in: src/strands/injection/types.py:57

Return whether to inject this call, given the injection context.

InjectionConfig

class InjectionConfig(TypedDict)

Defined in: src/strands/injection/types.py:68

Configuration common to every injection consumer: when to inject.

What text to inject is a consumer concern, added by the configs that extend this one (e.g. MemoryInjectionConfig).

Attributes:

• trigger - When injection runs. An InjectionTrigger name selects a built-in policy; a predicate is the escape hatch — it receives the InjectionContext and returns whether to inject this call. A predicate that raises fails open (injection is skipped, the model call proceeds). Defaults to "userTurn".