[Enhanced Input] Chord trigger fails when its referenced action lives in a lower-priority IMC

Summary

A UInputTriggerChordAction does not fire when the action it references (the "chording action") is mapped in a different Input Mapping Context with a lower priority than the IMC containing the chorded action. Both keys can be held simultaneously and the chorded action never produces a Triggered event.

This blocks the documented and expected use case of layering context-specific chords on top of a base/default input map — for example, a vehicle or mount IMC defining a chord that uses the player's base modifier action.

—

Reproduction

Setup (in-editor)

1. Create two Input Actions:

• IA_Chording — Value Type: Boolean

• IA_Chorded — Value Type: Boolean

1. Create two Input Mapping Contexts:

• IMC_Base

• IMC_Overlay

1. In IMC_Base, add a mapping: IA_Chording → any key (e.g. A).
2. In IMC_Overlay, add a mapping: IA_Chorded → a different key (e.g. S).
3. On the IA_Chorded mapping in IMC_Overlay, add a Chorded Action trigger and set its ChordAction to IA_Chording.
4. In your player controller (or wherever you set up Enhanced Input), add both IMCs via the Enhanced Input local player subsystem:

• IMC_Base at priority 1

• IMC_Overlay at priority 100

1. Bind a delegate (or print string) to IA_Chorded's Triggered event.
2. PIE.

Steps

1. Hold A (the chording-action key) and confirm IA_Chording's Triggered event fires.
2. While still holding A, also press S (the chorded-action key).

Expected

IA_Chorded's Triggered event fires every tick while both keys are held.

Actual

IA_Chorded never fires. The chord trigger silently reports its referenced action as inactive even though IA_Chording is producing Triggered events on the same tick.

—

Verification: swap the priorities

Swap step 6 so IMC_Base is at priority 100 and IMC_Overlay is at priority 1. With this ordering the chord fires correctly. This confirms the bug is a function of IMC priority ordering, not a fundamental cross-IMC incompatibility.

—

C++ Regression Repro

Automation tests covering both orderings live at:

Engine/Plugins/EnhancedInput/Source/InputEditor/Private/Tests/InputTriggerTest.cpp

• Input.Triggers.Chords.CrossContextLowerPriority — reproduces the bug (fails before the fix).
• Input.Triggers.Chords.CrossContextHigherPriority — sanity-check companion (passes before and after the fix).

Run via: UE.EditorAutomation -RunTest="Input.Triggers.Chords.CrossContext".

—

Root Cause

IEnhancedInputSubsystemInterface::ReorderMappings (EnhancedInputSubsystemInterface.cpp) promotes chording mappings ahead of chorded mappings, but only within a single IMC. Across IMCs the merged EnhancedActionMappings list is ordered strictly by IMC priority (high → low).

When the chord trigger and the action it references live in different IMCs, with the chorded mapping in the higher-priority IMC, the chorded mapping is processed first each tick in UEnhancedPlayerInput::PrepareInputDelegatesForEvaluation. Its chord trigger queries FindActionInstanceData(ChordAction)->GetEvaluatedActionTriggerState() — but the chord action's own mapping hasn't been processed this tick yet, so the TriggerStateTracker is still in its post-tick-reset state (None, set in EnhancedPlayerInput.cpp:436 at the end of the previous tick). The chord trigger sees None and produces no event, regardless of whether the chord key is actually held.