feat(DMChannel): allow partial DMChannel without client user

[Qjuh]

Since user installed applications can run in DMChannels not containing the client user we need to account for that in case of partial DMChannels being cached.

This PR now stores the ids of all known recipients, not only one. That way we can discern between a DMChannel between the client user and another user or a DMChannel between two non-client users.

Also properly resolves the issues fixed by #8950 and #9774 instead of just fixing the symptoms caused by us only storing one of the recipient's ids.

Fixes #11429

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
discord-js	Skipped		Mar 10, 2026 1:10pm
discord-js-guide	Skipped		Mar 10, 2026 1:10pm

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds multi-recipient support to Discord.js DM channel handling to resolve an issue where interactions fail to validate the correct recipient before updating cache. Changes introduce recipient deduplication logic in Action.js, augment channel resolution in InteractionCreate.js, and refactor DMChannel to store and expose multiple recipient IDs instead of a single ID.

Changes

Cohort / File(s)	Summary
DM Channel Multi-Recipient Support packages/discord.js/src/structures/DMChannel.js, packages/discord.js/typings/index.d.ts	Replaced single-recipient handling with multi-recipient support. Added public recipientIds: Snowflake[] property and converted recipientId from property to getter that returns the other party's ID when client user is in recipientIds. Iterates all recipients for cache population instead of only the first.
Recipient Data Processing packages/discord.js/src/client/actions/Action.js, packages/discord.js/src/client/actions/InteractionCreate.js	Added deduplication logic for recipients in payload data, explicitly initializing recipients array when absent. InteractionCreate now augments channel data with user field when recipients exist before channel resolution.

Sequence Diagram

sequenceDiagram
    participant Discord API
    participant Action
    participant InteractionCreate
    participant DMChannel
    participant Cache

    Discord API->>Action: Interaction with recipients array
    Action->>Action: Deduplicate recipients
    Action->>Action: Initialize/merge recipients
    InteractionCreate->>InteractionCreate: Receive processed interaction
    InteractionCreate->>InteractionCreate: Augment channel with user
    InteractionCreate->>DMChannel: Create/update with recipients
    DMChannel->>DMChannel: Build recipientIds array
    DMChannel->>DMChannel: recipientId getter: find non-client user
    DMChannel->>Cache: Store all recipient user objects
    Cache-->>DMChannel: Recipients cached
    DMChannel-->>InteractionCreate: Channel ready with recipients

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main feature: allowing DMChannel to exist without the client user, which is the core change enabling multi-recipient support.
Description check	✅ Passed	The description clearly explains the motivation and approach: storing all recipient IDs instead of one, enabling distinction between DMChannels with/without the client user, and fixing underlying issues.
Linked Issues check	✅ Passed	Changes properly address issue #11429 by storing all recipient IDs in DMChannel, enabling correct identification of which DM channel includes the client user vs. non-client users.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the multi-recipient DMChannel support: Action.js handles recipient deduplication, InteractionCreate.js resolves channel data with recipients, DMChannel.js implements recipientIds array and recipientId getter, and typings reflect the new API.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@packages/discord.js/src/structures/DMChannel.js`:
- Around line 36-42: The code in DMChannel is using the nullish-assignment
operator on this.recipientIds which prevents updates after the first patch;
change the assignment in the constructor/patch logic so recipientIds is
merged/updated on every patch (e.g., in DMChannel, replace the
"this.recipientIds ??= [...new Set([...(this.recipientIds ?? []),
...data.recipients.map(recipient => recipient.id)])]" pattern with an explicit
assignment that always sets this.recipientIds = [...new
Set([...(this.recipientIds ?? []), ...data.recipients.map(recipient =>
recipient.id)])] so new recipients from later Action#getChannel patches are
included).

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 6b57e2a6-a18b-4dc0-a75b-5000cebee598

📥 Commits

Reviewing files that changed from the base of the PR and between f3942a6 and aa2a39f.

📒 Files selected for processing (4)

• packages/discord.js/src/client/actions/Action.js
• packages/discord.js/src/client/actions/InteractionCreate.js
• packages/discord.js/src/structures/DMChannel.js
• packages/discord.js/typings/index.d.ts

📜 Review details

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: Tests

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2026-02-16T18:45:40.408Z

Learnt from: Qjuh
Repo: discordjs/discord.js PR: 11423
File: packages/discord.js/src/structures/MessagePayload.js:193-206
Timestamp: 2026-02-16T18:45:40.408Z
Learning: In discord.js MessagePayload.js, when mapping files to attachments, custom ids set via AttachmentBuilder.setId() should override the index-based id. The spread operator should come after the explicit id assignment to allow toJSON() values to take precedence.

Applied to files:

• packages/discord.js/src/client/actions/Action.js