Use it when you need to inspect or replace the exact model-facing prompt. The prompt input contains the user prompt after any userPromptSubmitted hooks have run, while transformedPrompt also contains runtime-generated context such as <current_datetime>.
Input and output
Return no value to leave the transformed prompt unchanged. Return modifiedTransformedPrompt to replace the content that is stored in session history and sent to the model.
Examples
Code languages navigation
TypeScript
const session = await client.createSession({
hooks: {
onUserPromptTransformed: async (input) => ({
modifiedTransformedPrompt: redact(input.transformedPrompt),
}),
},
});
Python
session = await client.create_session(
hooks={
"on_user_prompt_transformed": lambda input_data, invocation: {
"modifiedTransformedPrompt": redact(input_data["transformedPrompt"])
}
}
)
Go
session, err := client.CreateSession(ctx, &copilot.SessionConfig{
Hooks: &copilot.SessionHooks{
OnUserPromptTransformed: func(input copilot.UserPromptTransformedHookInput, invocation copilot.HookInvocation) (*copilot.UserPromptTransformedHookOutput, error) {
return &copilot.UserPromptTransformedHookOutput{
ModifiedTransformedPrompt: copilot.String(redact(input.TransformedPrompt)),
}, nil
},
},
})
.NET
var session = await client.CreateSessionAsync(new SessionConfig
{
Hooks = new SessionHooks
{
OnUserPromptTransformed = (input, invocation) =>
Task.FromResult<UserPromptTransformedHookOutput?>(new()
{
ModifiedTransformedPrompt = Redact(input.TransformedPrompt),
}),
},
});
Java
var hooks = new SessionHooks().setOnUserPromptTransformed((input, invocation) ->
CompletableFuture.completedFuture(
new UserPromptTransformedHookOutput(redact(input.transformedPrompt()))));
var session = client.createSession(new SessionConfig().setHooks(hooks)).get();
Rust
#[async_trait]
impl SessionHooks for MyHooks {
async fn on_user_prompt_transformed(
&self,
input: UserPromptTransformedInput,
_ctx: HookContext,
) -> Option<UserPromptTransformedOutput> {
Some(UserPromptTransformedOutput {
modified_transformed_prompt: Some(redact(&input.transformed_prompt)),
})
}
}
let session = client
.create_session(SessionConfig::default().with_hooks(Arc::new(MyHooks)))
.await?;
The replacement is persisted as the user message content, so resumed sessions replay the modified content unchanged.