fix: anchor github-url host to GITHUB_SERVER_URL for GHES support

src/action.test.ts

@@ -177,7 +177,8 @@ describe("CoderAgentChatAction", () => {
 			// `https://attacker.example/coder/coder/issues/1` would have
 			// called `octokit.rest.issues.createComment` with owner=coder,
 			// repo=coder, number=1 under the workflow's `github-token`. The
-			// action now refuses.
+			// host is now anchored to `GITHUB_SERVER_URL` (default
+			// `https://github.com`), so a different host is refused.
 			const inputs = createMockInputs({
 				githubURL: "https://code.acme.com/owner/repo/issues/123",
 			});
@@ -188,7 +189,7 @@ describe("CoderAgentChatAction", () => {
 			);
 
 			expect(() => action.parseGithubURL()).toThrowError(
-				/non-github.com hosts/,
+				/current GitHub server/,
 			);
 		});
 
@@ -206,6 +207,57 @@ describe("CoderAgentChatAction", () => {
 				/Invalid `github-url` input/,
 			);
 		});
+		test("accepts a GHES URL when GITHUB_SERVER_URL points at that host", () => {
+			const previous = process.env.GITHUB_SERVER_URL;
+			process.env.GITHUB_SERVER_URL = "https://github.example.com";
+			try {
+				const inputs = createMockInputs({
+					githubURL: "https://github.example.com/owner/repo/pull/7",
+				});
+				const action = new CoderAgentChatAction(
+					coderClient,
+					octokit as unknown as Octokit,
+					inputs,
+				);
+
+				expect(action.parseGithubURL()).toEqual({
+					githubOrg: "owner",
+					githubRepo: "repo",
+					githubIssueNumber: 7,
+				});
+			} finally {
+				if (previous === undefined) {
+					delete process.env.GITHUB_SERVER_URL;
+				} else {
+					process.env.GITHUB_SERVER_URL = previous;
+				}
+			}
+		});
+
+		test("rejects a dotcom URL when GITHUB_SERVER_URL points at a GHES host", () => {
+			const previous = process.env.GITHUB_SERVER_URL;
+			process.env.GITHUB_SERVER_URL = "https://github.example.com";
+			try {
+				const inputs = createMockInputs({
+					githubURL: "https://github.com/owner/repo/issues/1",
+				});
+				const action = new CoderAgentChatAction(
+					coderClient,
+					octokit as unknown as Octokit,
+					inputs,
+				);
+
+				expect(() => action.parseGithubURL()).toThrowError(
+					/current GitHub server/,
+				);
+			} finally {
+				if (previous === undefined) {
+					delete process.env.GITHUB_SERVER_URL;
+				} else {
+					process.env.GITHUB_SERVER_URL = previous;
+				}
+			}
+		});
 	});
 
 	describe("generateChatUrl", () => {

src/action.ts

@@ -16,6 +16,7 @@ import {
 	buildFailureCommentBody,
 	buildSuccessCommentBody,
 	classifyError,
+	DEFAULT_GITHUB_SERVER_URL,
 	deriveCommentKey,
 	type FailureDetail,
 	normalizeBaseUrl,
@@ -112,13 +113,15 @@ export class CoderAgentChatAction {
 			throw new Error("Missing GitHub URL");
 		}
 
-		const parsed = parseGithubItemURL(this.inputs.githubURL);
+		const serverURL = this.githubServerURL();
+		const parsed = parseGithubItemURL(this.inputs.githubURL, serverURL);
 		if (!parsed) {
 			throw new Error(
 				`Invalid \`github-url\` input "${this.inputs.githubURL}". ` +
-					"Expected `https://github.com/<owner>/<repo>/issues/<n>` or " +
-					"`https://github.com/<owner>/<repo>/pull/<n>`. The action " +
-					"rejects non-github.com hosts so a workflow that templates " +
+					`Expected \`${serverURL}/<owner>/<repo>/issues/<n>\` or ` +
+					`\`${serverURL}/<owner>/<repo>/pull/<n>\`. The action rejects ` +
+					"hosts other than the current GitHub server " +
+					"(`GITHUB_SERVER_URL`) so a workflow that templates " +
 					"user-controlled content into this input cannot redirect the " +
 					"action to an attacker-chosen repository.",
 			);
@@ -130,6 +133,14 @@ export class CoderAgentChatAction {
 		};
 	}
 
+	// The GitHub server the action runs against. The Actions runner sets
+	// `GITHUB_SERVER_URL` (e.g. `https://github.com` on dotcom,
+	// `https://github.example.com` on GHES). Falls back to dotcom outside a
+	// runner. Read at this edge so `comment.ts` helpers stay pure.
+	private githubServerURL(): string {
+		return process.env.GITHUB_SERVER_URL || DEFAULT_GITHUB_SERVER_URL;
+	}
+
 	/**
 	 * Generate chat URL.
 	 */
@@ -158,7 +169,11 @@ export class CoderAgentChatAction {
 		// stays pure and tests stay deterministic.
 		const workflow = process.env.GITHUB_WORKFLOW || undefined;
 		const marker = buildCommentMarker(
-			deriveCommentKey({ ...this.inputs, workflow }),
+			deriveCommentKey({
+				...this.inputs,
+				workflow,
+				serverURL: this.githubServerURL(),
+			}),
 		);
 		const diff = args.chat?.diff_status;
 		const hasPR = diff?.pr_number != null;
@@ -514,7 +529,11 @@ export class CoderAgentChatAction {
 		// stays pure and tests stay deterministic.
 		const workflow = process.env.GITHUB_WORKFLOW || undefined;
 		const marker = buildCommentMarker(
-			deriveCommentKey({ ...this.inputs, workflow }),
+			deriveCommentKey({
+				...this.inputs,
+				workflow,
+				serverURL: this.githubServerURL(),
+			}),
 		);
 		const body = buildFailureCommentBody(detail, {
 			agentsUrl: buildDeploymentAgentsUrl(this.inputs.coderURL),

src/comment.test.ts

@@ -12,6 +12,7 @@ import {
 	type FailureDetail,
 	findCommentByPredicate,
 	normalizeBaseUrl,
+	parseGithubItemURL,
 	renderDetailBlock,
 	type SuccessCommentContext,
 } from "./comment";
@@ -39,6 +40,93 @@ describe("buildCommentMarker", () => {
 	});
 });
 
+describe("parseGithubItemURL", () => {
+	test("parses a dotcom issue URL under the default server", () => {
+		expect(
+			parseGithubItemURL("https://github.com/owner/repo/issues/123"),
+		).toEqual({ owner: "owner", repo: "repo", number: 123 });
+	});
+
+	test("parses a dotcom PR URL under the default server", () => {
+		expect(parseGithubItemURL("https://github.com/owner/repo/pull/42")).toEqual(
+			{ owner: "owner", repo: "repo", number: 42 },
+		);
+	});
+
+	test("tolerates a trailing slash, query string, and fragment", () => {
+		expect(
+			parseGithubItemURL("https://github.com/owner/repo/pull/42/?tab=files"),
+		).toEqual({ owner: "owner", repo: "repo", number: 42 });
+		expect(
+			parseGithubItemURL(
+				"https://github.com/owner/repo/issues/7#issuecomment-1",
+			),
+		).toEqual({ owner: "owner", repo: "repo", number: 7 });
+	});
+
+	test("rejects extra path segments", () => {
+		expect(
+			parseGithubItemURL("https://github.com/owner/repo/issues/123/files"),
+		).toBeUndefined();
+	});
+
+	test("parses a GHES URL when serverURL matches (host anchoring)", () => {
+		expect(
+			parseGithubItemURL(
+				"https://github.example.com/owner/repo/pull/1",
+				"https://github.example.com",
+			),
+		).toEqual({ owner: "owner", repo: "repo", number: 1 });
+	});
+
+	test("tolerates a trailing slash on serverURL", () => {
+		expect(
+			parseGithubItemURL(
+				"https://github.example.com/owner/repo/pull/1",
+				"https://github.example.com/",
+			),
+		).toEqual({ owner: "owner", repo: "repo", number: 1 });
+	});
+
+	test("rejects a host that does not match serverURL (security case)", () => {
+		// A URL on a different host than the runner's GITHUB_SERVER_URL must
+		// not parse, so user-controlled github-url cannot redirect the action
+		// to an attacker-chosen host.
+		expect(
+			parseGithubItemURL(
+				"https://attacker.example/owner/repo/issues/1",
+				"https://github.example.com",
+			),
+		).toBeUndefined();
+	});
+
+	test("rejects a dotcom URL when serverURL is a GHES host", () => {
+		expect(
+			parseGithubItemURL(
+				"https://github.com/owner/repo/issues/1",
+				"https://github.example.com",
+			),
+		).toBeUndefined();
+	});
+
+	test("does not treat the server host as a regex pattern", () => {
+		// The dots in the host are metacharacters; RegExp.escape must keep
+		// them literal so a host that merely matches the pattern (dot as
+		// wildcard) is still rejected.
+		expect(
+			parseGithubItemURL(
+				"https://githubXexample.com/owner/repo/issues/1",
+				"https://github.example.com",
+			),
+		).toBeUndefined();
+	});
+
+	test("returns undefined for empty input", () => {
+		expect(parseGithubItemURL(undefined)).toBeUndefined();
+		expect(parseGithubItemURL("")).toBeUndefined();
+	});
+});
+
 describe("deriveCommentKey", () => {
 	test("uses idempotencyKey when set", () => {
 		expect(
@@ -77,6 +165,15 @@ describe("deriveCommentKey", () => {
 		).toBe("https://code.acme.com/owner/repo/issues/42");
 	});
 
+	test("derives <owner>/<repo>#<number> from a GHES URL when serverURL matches", () => {
+		expect(
+			deriveCommentKey({
+				githubURL: "https://github.example.com/owner/repo/issues/123",
+				serverURL: "https://github.example.com",
+			}),
+		).toBe("owner/repo#123");
+	});
+
 	test("appends workflow suffix to the derived per-target key", () => {
 		expect(
 			deriveCommentKey({