diff --git a/src/router/acknowledgments.ts b/src/router/acknowledgments.ts
index c0fefaeb..0c4e8998 100644
--- a/src/router/acknowledgments.ts
+++ b/src/router/acknowledgments.ts
@@ -21,7 +21,7 @@ import {
 	TrelloPlatformClient,
 	resolveJiraCredentials,
 	resolveTrelloCredentials,
-} from './platformClients.js';
+} from './platformClients/index.js';
 
 // ---------------------------------------------------------------------------
 // Trello
diff --git a/src/router/adapters/jira.ts b/src/router/adapters/jira.ts
index fae60465..cff4f0e1 100644
--- a/src/router/adapters/jira.ts
+++ b/src/router/adapters/jira.ts
@@ -15,7 +15,7 @@ import { extractJiraContext, generateAckMessage } from '../ackMessageGenerator.j
 import { postJiraAck, resolveJiraBotAccountId } from '../acknowledgments.js';
 import { type RouterProjectConfig, loadProjectConfig } from '../config.js';
 import type { AckResult, ParsedWebhookEvent, RouterPlatformAdapter } from '../platform-adapter.js';
-import { resolveJiraCredentials } from '../platformClients.js';
+import { resolveJiraCredentials } from '../platformClients/index.js';
 import type { CascadeJob, JiraJob } from '../queue.js';
 import { sendAcknowledgeReaction } from '../reactions.js';
 
diff --git a/src/router/adapters/trello.ts b/src/router/adapters/trello.ts
index a215b6c1..cb20ea66 100644
--- a/src/router/adapters/trello.ts
+++ b/src/router/adapters/trello.ts
@@ -15,7 +15,7 @@ import { extractTrelloContext, generateAckMessage } from '../ackMessageGenerator
 import { postTrelloAck } from '../acknowledgments.js';
 import { type RouterProjectConfig, loadProjectConfig } from '../config.js';
 import type { AckResult, ParsedWebhookEvent, RouterPlatformAdapter } from '../platform-adapter.js';
-import { resolveTrelloCredentials } from '../platformClients.js';
+import { resolveTrelloCredentials } from '../platformClients/index.js';
 import type { CascadeJob, TrelloJob } from '../queue.js';
 import { sendAcknowledgeReaction } from '../reactions.js';
 import {
diff --git a/src/router/notifications.ts b/src/router/notifications.ts
index d2284ba2..80d7d7c1 100644
--- a/src/router/notifications.ts
+++ b/src/router/notifications.ts
@@ -5,7 +5,7 @@ import {
 	GitHubPlatformClient,
 	JiraPlatformClient,
 	TrelloPlatformClient,
-} from './platformClients.js';
+} from './platformClients/index.js';
 import type { CascadeJob, GitHubJob, JiraJob, TrelloJob } from './queue.js';
 
 /**
diff --git a/src/router/platformClients.ts b/src/router/platformClients.ts
deleted file mode 100644
index be57c7ef..00000000
--- a/src/router/platformClients.ts
+++ /dev/null
@@ -1,367 +0,0 @@
-/**
- * Shared credential resolution and platform API header helpers for router modules.
- *
- * Resolves credentials once per call and returns typed objects.
- * Callers use raw `fetch()` — the router Docker image does not bundle
- * `src/trello/client.ts` or `src/github/client.ts`.
- *
- * Also exports `PlatformCommentClient` — a unified abstraction that eliminates
- * the repeated "resolve creds → build URL → fetch → log" pattern across
- * acknowledgments.ts, notifications.ts, and reactions.ts.
- */
-
-import { findProjectById, getIntegrationCredential } from '../config/provider.js';
-import type { JiraCredentials } from '../jira/types.js';
-import { getJiraConfig } from '../pm/config.js';
-import type { TrelloCredentials } from '../trello/types.js';
-import { logger } from '../utils/logging.js';
-
-// ---------------------------------------------------------------------------
-// Credential resolution helpers
-// ---------------------------------------------------------------------------
-
-export type { TrelloCredentials };
-
-/** Extends JiraCredentials with a pre-computed Base64 Basic auth header value. */
-export interface JiraCredentialsWithAuth extends JiraCredentials {
-	/** Pre-computed Base64 Basic auth value: `email:apiToken` */
-	auth: string;
-}
-
-/**
- * Resolve Trello credentials for a project.
- * Returns `{ apiKey, token }` or `null` if credentials are missing.
- */
-export async function resolveTrelloCredentials(
-	projectId: string,
-): Promise<TrelloCredentials | null> {
-	try {
-		const apiKey = await getIntegrationCredential(projectId, 'pm', 'api_key');
-		const token = await getIntegrationCredential(projectId, 'pm', 'token');
-		return { apiKey, token };
-	} catch {
-		return null;
-	}
-}
-
-/**
- * Resolve JIRA credentials for a project.
- * Returns `{ email, apiToken, baseUrl, auth }` or `null` if credentials/config are missing.
- * The `auth` field is the pre-computed Base64 Basic auth string.
- */
-export async function resolveJiraCredentials(
-	projectId: string,
-): Promise<JiraCredentialsWithAuth | null> {
-	try {
-		const email = await getIntegrationCredential(projectId, 'pm', 'email');
-		const apiToken = await getIntegrationCredential(projectId, 'pm', 'api_token');
-		const project = await findProjectById(projectId);
-		const baseUrl = (project ? getJiraConfig(project)?.baseUrl : undefined) ?? '';
-		if (!baseUrl) throw new Error('Missing JIRA base URL');
-		const auth = Buffer.from(`${email}:${apiToken}`).toString('base64');
-		return { email, apiToken, baseUrl, auth };
-	} catch {
-		return null;
-	}
-}
-
-/**
- * Build standard GitHub API request headers for a given token.
- * Used in place of the 6+ inline header objects scattered across router files.
- */
-export function resolveGitHubHeaders(
-	token: string,
-	extra?: Record<string, string>,
-): Record<string, string> {
-	return {
-		Authorization: `Bearer ${token}`,
-		Accept: 'application/vnd.github+json',
-		'X-GitHub-Api-Version': '2022-11-28',
-		...extra,
-	};
-}
-
-// ---------------------------------------------------------------------------
-// PlatformCommentClient — unified abstraction for cross-platform comments
-// ---------------------------------------------------------------------------
-
-/**
- * Unified interface for posting and deleting comments and reactions across
- * GitHub and JIRA.  Implementations are fire-and-forget safe — they never
- * throw; all errors (including network failures) are caught and logged internally.
- */
-export interface PlatformCommentClient {
-	/**
-	 * Post a comment.  Returns the new comment's ID (string or number) on
-	 * success, or `null` on any failure.
-	 */
-	postComment(target: string, message: string): Promise<string | number | null>;
-
-	/**
-	 * Delete a previously-posted comment by ID.
-	 * Silently returns on missing credentials or any failure.
-	 */
-	deleteComment(target: string, commentId: string | number): Promise<void>;
-
-	/**
-	 * Post a reaction on a comment / action.
-	 * Silently returns on missing credentials or any failure.
-	 */
-	postReaction?(target: string, reactionPayload: unknown): Promise<void>;
-}
-
-// ---------------------------------------------------------------------------
-// TrelloPlatformClient
-// ---------------------------------------------------------------------------
-
-export class TrelloPlatformClient implements PlatformCommentClient {
-	constructor(private readonly projectId: string) {}
-
-	async postComment(cardId: string, message: string): Promise<string | null> {
-		const creds = await resolveTrelloCredentials(this.projectId);
-		if (!creds) {
-			logger.warn('[PlatformClient] Missing Trello credentials, skipping comment');
-			return null;
-		}
-
-		try {
-			const url = `https://api.trello.com/1/cards/${cardId}/actions/comments?key=${creds.apiKey}&token=${creds.token}`;
-			const response = await fetch(url, {
-				method: 'POST',
-				headers: { 'Content-Type': 'application/json' },
-				body: JSON.stringify({ text: message }),
-			});
-
-			if (!response.ok) {
-				logger.warn(
-					'[PlatformClient] Trello comment failed:',
-					response.status,
-					await response.text(),
-				);
-				return null;
-			}
-
-			const data = (await response.json()) as { id?: string };
-			logger.info('[PlatformClient] Trello comment posted for card:', cardId);
-			return data.id ?? null;
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to post Trello comment:', String(err));
-			return null;
-		}
-	}
-
-	async deleteComment(cardId: string, commentId: string): Promise<void> {
-		const creds = await resolveTrelloCredentials(this.projectId);
-		if (!creds) return;
-
-		const url = `https://api.trello.com/1/cards/${cardId}/actions/${commentId}/comments?key=${creds.apiKey}&token=${creds.token}`;
-		try {
-			await fetch(url, { method: 'DELETE' });
-			logger.info('[PlatformClient] Trello comment deleted:', commentId);
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to delete Trello comment:', String(err));
-		}
-	}
-}
-
-// ---------------------------------------------------------------------------
-// GitHubPlatformClient
-// ---------------------------------------------------------------------------
-
-export class GitHubPlatformClient implements PlatformCommentClient {
-	constructor(
-		private readonly repoFullName: string,
-		private readonly token: string,
-	) {}
-
-	async postComment(prNumber: string | number, message: string): Promise<number | null> {
-		try {
-			const url = `https://api.github.com/repos/${this.repoFullName}/issues/${prNumber}/comments`;
-			const response = await fetch(url, {
-				method: 'POST',
-				headers: resolveGitHubHeaders(this.token, { 'Content-Type': 'application/json' }),
-				body: JSON.stringify({ body: message }),
-			});
-
-			if (!response.ok) {
-				logger.warn(
-					'[PlatformClient] GitHub comment failed:',
-					response.status,
-					await response.text(),
-				);
-				return null;
-			}
-
-			const data = (await response.json()) as { id?: number };
-			logger.info('[PlatformClient] GitHub comment posted for PR:', prNumber);
-			return data.id ?? null;
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to post GitHub comment:', String(err));
-			return null;
-		}
-	}
-
-	async deleteComment(_target: string, commentId: number): Promise<void> {
-		const url = `https://api.github.com/repos/${this.repoFullName}/issues/comments/${commentId}`;
-		try {
-			await fetch(url, {
-				method: 'DELETE',
-				headers: resolveGitHubHeaders(this.token),
-			});
-			logger.info('[PlatformClient] GitHub comment deleted:', commentId);
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to delete GitHub comment:', String(err));
-		}
-	}
-}
-
-// ---------------------------------------------------------------------------
-// JiraPlatformClient
-// ---------------------------------------------------------------------------
-
-/** In-memory JIRA CloudId cache keyed by baseUrl */
-const _jiraCloudIdCache = new Map<string, string>();
-
-/** @internal Visible for testing only */
-export function _resetJiraCloudIdCache(): void {
-	_jiraCloudIdCache.clear();
-}
-
-export class JiraPlatformClient implements PlatformCommentClient {
-	constructor(private readonly projectId: string) {}
-
-	async postComment(issueKey: string, message: string): Promise<string | null> {
-		const creds = await resolveJiraCredentials(this.projectId);
-		if (!creds) {
-			logger.warn('[PlatformClient] Missing JIRA credentials, skipping comment');
-			return null;
-		}
-
-		try {
-			const url = `${creds.baseUrl}/rest/api/2/issue/${issueKey}/comment`;
-			const response = await fetch(url, {
-				method: 'POST',
-				headers: {
-					Authorization: `Basic ${creds.auth}`,
-					'Content-Type': 'application/json',
-				},
-				body: JSON.stringify({ body: message }),
-			});
-
-			if (!response.ok) {
-				logger.warn(
-					'[PlatformClient] JIRA comment failed:',
-					response.status,
-					await response.text(),
-				);
-				return null;
-			}
-
-			const data = (await response.json()) as { id?: string };
-			logger.info('[PlatformClient] JIRA comment posted for issue:', issueKey);
-			return data.id ?? null;
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to post JIRA comment:', String(err));
-			return null;
-		}
-	}
-
-	async deleteComment(issueKey: string, commentId: string): Promise<void> {
-		const creds = await resolveJiraCredentials(this.projectId);
-		if (!creds) return;
-
-		const url = `${creds.baseUrl}/rest/api/2/issue/${issueKey}/comment/${commentId}`;
-		try {
-			await fetch(url, {
-				method: 'DELETE',
-				headers: {
-					Authorization: `Basic ${creds.auth}`,
-					'Content-Type': 'application/json',
-				},
-			});
-			logger.info('[PlatformClient] JIRA comment deleted:', commentId);
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to delete JIRA comment:', String(err));
-		}
-	}
-
-	/**
-	 * Post a JIRA reactions-API reaction on a comment.
-	 * `target` is ignored (cloudId is resolved internally from credentials).
-	 * `reactionPayload` is `{ issueId, commentId }`.
-	 */
-	async postReaction(
-		_target: string,
-		reactionPayload: { issueId: string; commentId: string },
-	): Promise<void> {
-		const creds = await resolveJiraCredentials(this.projectId);
-		if (!creds) {
-			logger.warn('[PlatformClient] Missing JIRA credentials, skipping reaction');
-			return;
-		}
-
-		const cloudId = await this._getCloudId(creds.baseUrl, creds.auth);
-		if (!cloudId) return;
-
-		try {
-			const { issueId, commentId } = reactionPayload;
-			const emojiId = 'atlassian-thought_balloon';
-			const ari = `ari%3Acloud%3Ajira%3A${cloudId}%3Acomment%2F${issueId}%2F${commentId}`;
-			const reactionsUrl = `${creds.baseUrl}/rest/reactions/1.0/reactions/${ari}/${emojiId}`;
-
-			const reactionResponse = await fetch(reactionsUrl, {
-				method: 'PUT',
-				headers: {
-					Authorization: `Basic ${creds.auth}`,
-					'Content-Type': 'application/json',
-				},
-			});
-
-			if (reactionResponse.ok) {
-				logger.info('[PlatformClient] JIRA reaction sent for comment:', commentId);
-			} else {
-				logger.warn(
-					'[PlatformClient] JIRA reactions API failed:',
-					reactionResponse.status,
-					'— skipping (no fallback to avoid webhook loops)',
-				);
-			}
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to post JIRA reaction:', String(err));
-		}
-	}
-
-	private async _getCloudId(baseUrl: string, auth: string): Promise<string | null> {
-		const cached = _jiraCloudIdCache.get(baseUrl);
-		if (cached) return cached;
-
-		let response: Response;
-		try {
-			response = await fetch(`${baseUrl}/_edge/tenant_info`, {
-				headers: { Authorization: `Basic ${auth}` },
-			});
-		} catch (err) {
-			logger.warn('[PlatformClient] Failed to fetch JIRA cloudId:', String(err));
-			return null;
-		}
-
-		if (!response.ok) {
-			logger.warn('[PlatformClient] JIRA tenant_info returned', response.status);
-			return null;
-		}
-
-		const data = (await response.json()) as { cloudId?: string };
-		if (!data.cloudId) {
-			logger.warn('[PlatformClient] JIRA tenant_info missing cloudId');
-			return null;
-		}
-
-		_jiraCloudIdCache.set(baseUrl, data.cloudId);
-		return data.cloudId;
-	}
-
-	/** @internal Visible for testing only */
-	static _reset(): void {
-		_jiraCloudIdCache.clear();
-	}
-}
diff --git a/src/router/platformClients/credentials.ts b/src/router/platformClients/credentials.ts
new file mode 100644
index 00000000..e2671cc0
--- /dev/null
+++ b/src/router/platformClients/credentials.ts
@@ -0,0 +1,64 @@
+/**
+ * Credential resolution helpers for router platform clients.
+ *
+ * Resolves credentials once per call and returns typed objects.
+ * Callers use raw `fetch()` — the router Docker image does not bundle
+ * `src/trello/client.ts` or `src/github/client.ts`.
+ */
+
+import { findProjectById, getIntegrationCredential } from '../../config/provider.js';
+import { getJiraConfig } from '../../pm/config.js';
+import type { JiraCredentialsWithAuth, TrelloCredentials } from './types.js';
+
+/**
+ * Resolve Trello credentials for a project.
+ * Returns `{ apiKey, token }` or `null` if credentials are missing.
+ */
+export async function resolveTrelloCredentials(
+	projectId: string,
+): Promise<TrelloCredentials | null> {
+	try {
+		const apiKey = await getIntegrationCredential(projectId, 'pm', 'api_key');
+		const token = await getIntegrationCredential(projectId, 'pm', 'token');
+		return { apiKey, token };
+	} catch {
+		return null;
+	}
+}
+
+/**
+ * Resolve JIRA credentials for a project.
+ * Returns `{ email, apiToken, baseUrl, auth }` or `null` if credentials/config are missing.
+ * The `auth` field is the pre-computed Base64 Basic auth string.
+ */
+export async function resolveJiraCredentials(
+	projectId: string,
+): Promise<JiraCredentialsWithAuth | null> {
+	try {
+		const email = await getIntegrationCredential(projectId, 'pm', 'email');
+		const apiToken = await getIntegrationCredential(projectId, 'pm', 'api_token');
+		const project = await findProjectById(projectId);
+		const baseUrl = (project ? getJiraConfig(project)?.baseUrl : undefined) ?? '';
+		if (!baseUrl) throw new Error('Missing JIRA base URL');
+		const auth = Buffer.from(`${email}:${apiToken}`).toString('base64');
+		return { email, apiToken, baseUrl, auth };
+	} catch {
+		return null;
+	}
+}
+
+/**
+ * Build standard GitHub API request headers for a given token.
+ * Used in place of the 6+ inline header objects scattered across router files.
+ */
+export function resolveGitHubHeaders(
+	token: string,
+	extra?: Record<string, string>,
+): Record<string, string> {
+	return {
+		Authorization: `Bearer ${token}`,
+		Accept: 'application/vnd.github+json',
+		'X-GitHub-Api-Version': '2022-11-28',
+		...extra,
+	};
+}
diff --git a/src/router/platformClients/github.ts b/src/router/platformClients/github.ts
new file mode 100644
index 00000000..50cdc5d1
--- /dev/null
+++ b/src/router/platformClients/github.ts
@@ -0,0 +1,54 @@
+/**
+ * GitHub platform client for posting/deleting PR/issue comments via the GitHub REST API.
+ */
+
+import { logger } from '../../utils/logging.js';
+import { resolveGitHubHeaders } from './credentials.js';
+import type { PlatformCommentClient } from './types.js';
+
+export class GitHubPlatformClient implements PlatformCommentClient {
+	constructor(
+		private readonly repoFullName: string,
+		private readonly token: string,
+	) {}
+
+	async postComment(prNumber: string | number, message: string): Promise<number | null> {
+		try {
+			const url = `https://api.github.com/repos/${this.repoFullName}/issues/${prNumber}/comments`;
+			const response = await fetch(url, {
+				method: 'POST',
+				headers: resolveGitHubHeaders(this.token, { 'Content-Type': 'application/json' }),
+				body: JSON.stringify({ body: message }),
+			});
+
+			if (!response.ok) {
+				logger.warn(
+					'[PlatformClient] GitHub comment failed:',
+					response.status,
+					await response.text(),
+				);
+				return null;
+			}
+
+			const data = (await response.json()) as { id?: number };
+			logger.info('[PlatformClient] GitHub comment posted for PR:', prNumber);
+			return data.id ?? null;
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to post GitHub comment:', String(err));
+			return null;
+		}
+	}
+
+	async deleteComment(_target: string, commentId: number): Promise<void> {
+		const url = `https://api.github.com/repos/${this.repoFullName}/issues/comments/${commentId}`;
+		try {
+			await fetch(url, {
+				method: 'DELETE',
+				headers: resolveGitHubHeaders(this.token),
+			});
+			logger.info('[PlatformClient] GitHub comment deleted:', commentId);
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to delete GitHub comment:', String(err));
+		}
+	}
+}
diff --git a/src/router/platformClients/index.ts b/src/router/platformClients/index.ts
new file mode 100644
index 00000000..e0c5efe4
--- /dev/null
+++ b/src/router/platformClients/index.ts
@@ -0,0 +1,19 @@
+/**
+ * Barrel export for the platform clients sub-module.
+ *
+ * Re-exports all public symbols from the focused sub-modules, preserving the
+ * same public API surface as the original `platformClients.ts` monolith.
+ * All existing imports (`from './platformClients.js'`) continue to work
+ * unchanged since Node.js resolves `./platformClients/index.js` from the
+ * directory path.
+ */
+
+export type { JiraCredentialsWithAuth, PlatformCommentClient, TrelloCredentials } from './types.js';
+export {
+	resolveGitHubHeaders,
+	resolveJiraCredentials,
+	resolveTrelloCredentials,
+} from './credentials.js';
+export { TrelloPlatformClient } from './trello.js';
+export { GitHubPlatformClient } from './github.js';
+export { JiraPlatformClient, _resetJiraCloudIdCache } from './jira.js';
diff --git a/src/router/platformClients/jira.ts b/src/router/platformClients/jira.ts
new file mode 100644
index 00000000..2445bb49
--- /dev/null
+++ b/src/router/platformClients/jira.ts
@@ -0,0 +1,154 @@
+/**
+ * JIRA platform client for posting/deleting comments and reactions via the JIRA REST API.
+ */
+
+import { logger } from '../../utils/logging.js';
+import { resolveJiraCredentials } from './credentials.js';
+import type { PlatformCommentClient } from './types.js';
+
+/** In-memory JIRA CloudId cache keyed by baseUrl */
+const _jiraCloudIdCache = new Map<string, string>();
+
+/** @internal Visible for testing only */
+export function _resetJiraCloudIdCache(): void {
+	_jiraCloudIdCache.clear();
+}
+
+export class JiraPlatformClient implements PlatformCommentClient {
+	constructor(private readonly projectId: string) {}
+
+	async postComment(issueKey: string, message: string): Promise<string | null> {
+		const creds = await resolveJiraCredentials(this.projectId);
+		if (!creds) {
+			logger.warn('[PlatformClient] Missing JIRA credentials, skipping comment');
+			return null;
+		}
+
+		try {
+			const url = `${creds.baseUrl}/rest/api/2/issue/${issueKey}/comment`;
+			const response = await fetch(url, {
+				method: 'POST',
+				headers: {
+					Authorization: `Basic ${creds.auth}`,
+					'Content-Type': 'application/json',
+				},
+				body: JSON.stringify({ body: message }),
+			});
+
+			if (!response.ok) {
+				logger.warn(
+					'[PlatformClient] JIRA comment failed:',
+					response.status,
+					await response.text(),
+				);
+				return null;
+			}
+
+			const data = (await response.json()) as { id?: string };
+			logger.info('[PlatformClient] JIRA comment posted for issue:', issueKey);
+			return data.id ?? null;
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to post JIRA comment:', String(err));
+			return null;
+		}
+	}
+
+	async deleteComment(issueKey: string, commentId: string): Promise<void> {
+		const creds = await resolveJiraCredentials(this.projectId);
+		if (!creds) return;
+
+		const url = `${creds.baseUrl}/rest/api/2/issue/${issueKey}/comment/${commentId}`;
+		try {
+			await fetch(url, {
+				method: 'DELETE',
+				headers: {
+					Authorization: `Basic ${creds.auth}`,
+					'Content-Type': 'application/json',
+				},
+			});
+			logger.info('[PlatformClient] JIRA comment deleted:', commentId);
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to delete JIRA comment:', String(err));
+		}
+	}
+
+	/**
+	 * Post a JIRA reactions-API reaction on a comment.
+	 * `target` is ignored (cloudId is resolved internally from credentials).
+	 * `reactionPayload` is `{ issueId, commentId }`.
+	 */
+	async postReaction(
+		_target: string,
+		reactionPayload: { issueId: string; commentId: string },
+	): Promise<void> {
+		const creds = await resolveJiraCredentials(this.projectId);
+		if (!creds) {
+			logger.warn('[PlatformClient] Missing JIRA credentials, skipping reaction');
+			return;
+		}
+
+		const cloudId = await this._getCloudId(creds.baseUrl, creds.auth);
+		if (!cloudId) return;
+
+		try {
+			const { issueId, commentId } = reactionPayload;
+			const emojiId = 'atlassian-thought_balloon';
+			const ari = `ari%3Acloud%3Ajira%3A${cloudId}%3Acomment%2F${issueId}%2F${commentId}`;
+			const reactionsUrl = `${creds.baseUrl}/rest/reactions/1.0/reactions/${ari}/${emojiId}`;
+
+			const reactionResponse = await fetch(reactionsUrl, {
+				method: 'PUT',
+				headers: {
+					Authorization: `Basic ${creds.auth}`,
+					'Content-Type': 'application/json',
+				},
+			});
+
+			if (reactionResponse.ok) {
+				logger.info('[PlatformClient] JIRA reaction sent for comment:', commentId);
+			} else {
+				logger.warn(
+					'[PlatformClient] JIRA reactions API failed:',
+					reactionResponse.status,
+					'— skipping (no fallback to avoid webhook loops)',
+				);
+			}
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to post JIRA reaction:', String(err));
+		}
+	}
+
+	private async _getCloudId(baseUrl: string, auth: string): Promise<string | null> {
+		const cached = _jiraCloudIdCache.get(baseUrl);
+		if (cached) return cached;
+
+		let response: Response;
+		try {
+			response = await fetch(`${baseUrl}/_edge/tenant_info`, {
+				headers: { Authorization: `Basic ${auth}` },
+			});
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to fetch JIRA cloudId:', String(err));
+			return null;
+		}
+
+		if (!response.ok) {
+			logger.warn('[PlatformClient] JIRA tenant_info returned', response.status);
+			return null;
+		}
+
+		const data = (await response.json()) as { cloudId?: string };
+		if (!data.cloudId) {
+			logger.warn('[PlatformClient] JIRA tenant_info missing cloudId');
+			return null;
+		}
+
+		_jiraCloudIdCache.set(baseUrl, data.cloudId);
+		return data.cloudId;
+	}
+
+	/** @internal Visible for testing only */
+	static _reset(): void {
+		_jiraCloudIdCache.clear();
+	}
+}
diff --git a/src/router/platformClients/trello.ts b/src/router/platformClients/trello.ts
new file mode 100644
index 00000000..8e01d462
--- /dev/null
+++ b/src/router/platformClients/trello.ts
@@ -0,0 +1,57 @@
+/**
+ * Trello platform client for posting/deleting comments via the Trello REST API.
+ */
+
+import { logger } from '../../utils/logging.js';
+import { resolveTrelloCredentials } from './credentials.js';
+import type { PlatformCommentClient } from './types.js';
+
+export class TrelloPlatformClient implements PlatformCommentClient {
+	constructor(private readonly projectId: string) {}
+
+	async postComment(cardId: string, message: string): Promise<string | null> {
+		const creds = await resolveTrelloCredentials(this.projectId);
+		if (!creds) {
+			logger.warn('[PlatformClient] Missing Trello credentials, skipping comment');
+			return null;
+		}
+
+		try {
+			const url = `https://api.trello.com/1/cards/${cardId}/actions/comments?key=${creds.apiKey}&token=${creds.token}`;
+			const response = await fetch(url, {
+				method: 'POST',
+				headers: { 'Content-Type': 'application/json' },
+				body: JSON.stringify({ text: message }),
+			});
+
+			if (!response.ok) {
+				logger.warn(
+					'[PlatformClient] Trello comment failed:',
+					response.status,
+					await response.text(),
+				);
+				return null;
+			}
+
+			const data = (await response.json()) as { id?: string };
+			logger.info('[PlatformClient] Trello comment posted for card:', cardId);
+			return data.id ?? null;
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to post Trello comment:', String(err));
+			return null;
+		}
+	}
+
+	async deleteComment(cardId: string, commentId: string): Promise<void> {
+		const creds = await resolveTrelloCredentials(this.projectId);
+		if (!creds) return;
+
+		const url = `https://api.trello.com/1/cards/${cardId}/actions/${commentId}/comments?key=${creds.apiKey}&token=${creds.token}`;
+		try {
+			await fetch(url, { method: 'DELETE' });
+			logger.info('[PlatformClient] Trello comment deleted:', commentId);
+		} catch (err) {
+			logger.warn('[PlatformClient] Failed to delete Trello comment:', String(err));
+		}
+	}
+}
diff --git a/src/router/platformClients/types.ts b/src/router/platformClients/types.ts
new file mode 100644
index 00000000..50d91793
--- /dev/null
+++ b/src/router/platformClients/types.ts
@@ -0,0 +1,37 @@
+/**
+ * Shared types for the platform client abstraction layer.
+ */
+
+import type { JiraCredentials } from '../../jira/types.js';
+export type { TrelloCredentials } from '../../trello/types.js';
+
+/** Extends JiraCredentials with a pre-computed Base64 Basic auth header value. */
+export interface JiraCredentialsWithAuth extends JiraCredentials {
+	/** Pre-computed Base64 Basic auth value: `email:apiToken` */
+	auth: string;
+}
+
+/**
+ * Unified interface for posting and deleting comments and reactions across
+ * GitHub and JIRA.  Implementations are fire-and-forget safe — they never
+ * throw; all errors (including network failures) are caught and logged internally.
+ */
+export interface PlatformCommentClient {
+	/**
+	 * Post a comment.  Returns the new comment's ID (string or number) on
+	 * success, or `null` on any failure.
+	 */
+	postComment(target: string, message: string): Promise<string | number | null>;
+
+	/**
+	 * Delete a previously-posted comment by ID.
+	 * Silently returns on missing credentials or any failure.
+	 */
+	deleteComment(target: string, commentId: string | number): Promise<void>;
+
+	/**
+	 * Post a reaction on a comment / action.
+	 * Silently returns on missing credentials or any failure.
+	 */
+	postReaction?(target: string, reactionPayload: unknown): Promise<void>;
+}
diff --git a/src/router/pre-actions.ts b/src/router/pre-actions.ts
index d10e8a0e..114bd14b 100644
--- a/src/router/pre-actions.ts
+++ b/src/router/pre-actions.ts
@@ -1,7 +1,7 @@
 import { findProjectByRepo, getIntegrationCredential } from '../config/provider.js';
 import { logger } from '../utils/logging.js';
 import { parseRepoFullName } from '../utils/repo.js';
-import { resolveGitHubHeaders } from './platformClients.js';
+import { resolveGitHubHeaders } from './platformClients/index.js';
 import type { GitHubJob } from './queue.js';
 
 /**
diff --git a/src/router/reactions.ts b/src/router/reactions.ts
index c12c4a01..9f871e00 100644
--- a/src/router/reactions.ts
+++ b/src/router/reactions.ts
@@ -19,7 +19,7 @@ import {
 	_resetJiraCloudIdCache,
 	resolveGitHubHeaders,
 	resolveTrelloCredentials,
-} from './platformClients.js';
+} from './platformClients/index.js';
 
 /** @internal Visible for testing only — re-exported from JiraPlatformClient */
 export { _resetJiraCloudIdCache };
diff --git a/tests/unit/router/adapters/jira.test.ts b/tests/unit/router/adapters/jira.test.ts
index cee1bc9a..056a240a 100644
--- a/tests/unit/router/adapters/jira.test.ts
+++ b/tests/unit/router/adapters/jira.test.ts
@@ -26,7 +26,7 @@ vi.mock('../../../../src/router/ackMessageGenerator.js', () => ({
 	extractJiraContext: vi.fn().mockReturnValue('Issue: PROJ-1'),
 	generateAckMessage: vi.fn().mockResolvedValue('Working on it...'),
 }));
-vi.mock('../../../../src/router/platformClients.js', () => ({
+vi.mock('../../../../src/router/platformClients/index.js', () => ({
 	resolveJiraCredentials: vi.fn().mockResolvedValue({
 		email: 'bot@example.com',
 		apiToken: 'tok',
diff --git a/tests/unit/router/adapters/trello.test.ts b/tests/unit/router/adapters/trello.test.ts
index d07765aa..beb4048e 100644
--- a/tests/unit/router/adapters/trello.test.ts
+++ b/tests/unit/router/adapters/trello.test.ts
@@ -26,7 +26,7 @@ vi.mock('../../../../src/router/ackMessageGenerator.js', () => ({
 	extractTrelloContext: vi.fn().mockReturnValue('Card: Test card'),
 	generateAckMessage: vi.fn().mockResolvedValue('Starting implementation...'),
 }));
-vi.mock('../../../../src/router/platformClients.js', () => ({
+vi.mock('../../../../src/router/platformClients/index.js', () => ({
 	resolveTrelloCredentials: vi.fn().mockResolvedValue({ apiKey: 'key', token: 'tok' }),
 }));
 vi.mock('../../../../src/trello/client.js', () => ({
diff --git a/tests/unit/router/platformClients.test.ts b/tests/unit/router/platformClients.test.ts
index 85c5c6de..0291ccf7 100644
--- a/tests/unit/router/platformClients.test.ts
+++ b/tests/unit/router/platformClients.test.ts
@@ -35,7 +35,7 @@ import {
 	resolveGitHubHeaders,
 	resolveJiraCredentials,
 	resolveTrelloCredentials,
-} from '../../../src/router/platformClients.js';
+} from '../../../src/router/platformClients/index.js';
 import { logger } from '../../../src/utils/logging.js';
 
 const mockLogger = vi.mocked(logger);