diff --git a/docs/contributing.md b/docs/contributing.md
index 84329477..9ec86269 100644
--- a/docs/contributing.md
+++ b/docs/contributing.md
@@ -255,20 +255,27 @@ If there are no changelog entries to add, remove the code block and start the ch
 
 The version-compat job in CI runs the local controller with the latest published host, and the published controller with the local host.
 It fails if a link message changed its src, dst, data or response schema since that release.
-If the break is intended, add an entry for the published version to [scripts/version-compat-breaks.json](../scripts/version-compat-breaks.json) in the same pull request:
+If the break is intended, add an entry to [scripts/version-compat-breaks.json](../scripts/version-compat-breaks.json) in the same pull request.
+Breaking changes are only accepted if the next release is intended to include them, see our decision on [breaking changes](/docs/decisions.md#breaking-changes).
+The entry is keyed by the published version directly before the breaking change was introduced, which is the latest release at the time.
+Every entry needs the pull request number, a reason saying what breaks, and an impact saying why end users are not or only minimally affected.
 
 ```json
 {
 	"2.0.3": {
 		"messages": {
-			"request FactorioVersionsRequest": { "pr": 1129, "reason": "Why it breaks and what stops working." }
+			"request FactorioVersionsRequest": {
+				"pr": 1129,
+				"reason": "What breaks between the two versions.",
+				"impact": "Why end users are not or only minimally affected."
+			}
 		},
-		"connect": { "pr": 1234, "reason": "Why a host cannot connect at all." }
+		"connect": { "pr": 1234, "reason": "Why a host cannot connect at all.", "impact": "..." }
 	}
 }
 ```
 
-Listed messages are reported as warnings with the reason instead of failing the job.
+Listed messages are reported as warnings with the reason and impact instead of failing the job.
 Only add `connect` when the published and local versions cannot connect at all, it skips starting the cluster.
 Listing a message that did not change fails the job.
 Entries only apply while their version is the latest release, after the next release they are ignored and can be removed.
diff --git a/scripts/version-compat-breaks.js b/scripts/version-compat-breaks.js
index 177c33c4..eba160df 100644
--- a/scripts/version-compat-breaks.js
+++ b/scripts/version-compat-breaks.js
@@ -7,9 +7,9 @@
  *   {
  *     "2.0.3": {
  *       "messages": {
- *         "request FactorioVersionsRequest": { "pr": 1129, "reason": "..." }
+ *         "request FactorioVersionsRequest": { "pr": 1129, "reason": "...", "impact": "..." }
  *       },
- *       "connect": { "pr": 1234, "reason": "..." }
+ *       "connect": { "pr": 1234, "reason": "...", "impact": "..." }
  *     }
  *   }
  *
@@ -30,10 +30,12 @@ function validateBreak(value, where) {
 	if (!Number.isInteger(value.pr) || value.pr <= 0) {
 		throw new Error(`${where} must have a pr number`);
 	}
-	if (typeof value.reason !== "string" || !value.reason.trim()) {
-		throw new Error(`${where} must have a reason`);
+	for (const key of ["reason", "impact"]) {
+		if (typeof value[key] !== "string" || !value[key].trim()) {
+			throw new Error(`${where} is missing ${key}`);
+		}
 	}
-	const unknown = Object.keys(value).filter(key => !["pr", "reason"].includes(key));
+	const unknown = Object.keys(value).filter(key => !["pr", "reason", "impact"].includes(key));
 	if (unknown.length) {
 		throw new Error(`${where} has unknown properties ${unknown.join(", ")}`);
 	}
diff --git a/scripts/version-compat-breaks.json b/scripts/version-compat-breaks.json
index 5e0b02ca..13bd5997 100644
--- a/scripts/version-compat-breaks.json
+++ b/scripts/version-compat-breaks.json
@@ -3,11 +3,13 @@
 		"messages": {
 			"request FactorioVersionsRequest": {
 				"pr": 1129,
-				"reason": "Hosts send it while starting an instance, so a newer host cannot start instances on a 2.0.3 controller."
+				"reason": "Hosts send it while starting an instance, which a 2.0.3 controller rejects so the start fails.",
+				"impact": "The host stays connected and the instance goes back to stopped with the error shown, starting it works again once the controller is updated."
 			},
 			"request LatestReleasesRequest": {
 				"pr": 1129,
-				"reason": "Hosts send it while starting an instance that targets a release channel such as stable, which a 2.0.3 controller rejects."
+				"reason": "Hosts send it while starting an instance that targets a release channel such as stable.",
+				"impact": "Hosts send FactorioVersionsRequest first, so a 2.0.3 controller rejects the start before this is sent, starting it works again once the controller is updated."
 			}
 		}
 	}
diff --git a/scripts/version-compat-test.js b/scripts/version-compat-test.js
index e888d9b1..b300833e 100644
--- a/scripts/version-compat-test.js
+++ b/scripts/version-compat-test.js
@@ -247,8 +247,8 @@ async function checkMessageCompat(publishedVersion, knownBreaks) {
 	const { known, unknown, stale } = matchBreaks(knownBreaks, changed.map(({ name }) => name));
 	for (const { name, fields, localSpec, publishedSpec } of changed) {
 		if (known.includes(name)) {
-			const { pr, reason } = knownBreaks.get(name);
-			annotate(`Link ${name} is a known break since ${publishedVersion} from #${pr}: ${reason}`);
+			const { pr, reason, impact } = knownBreaks.get(name);
+			annotate(`Link ${name} is a known break since ${publishedVersion} from #${pr}: ${reason} Impact: ${impact}`);
 			printChange(console.log, name, fields, localSpec, publishedSpec, publishedVersion);
 		} else {
 			printChange(console.error, name, fields, localSpec, publishedSpec, publishedVersion);
@@ -308,8 +308,10 @@ async function main() {
 	}
 	await checkMessageCompat(publishedLib.version, knownBreaks.messages);
 	if (knownBreaks.connect) {
-		const { pr, reason } = knownBreaks.connect;
-		annotate(`Skipping cluster test, known break since ${publishedLib.version} from #${pr}: ${reason}`);
+		const { pr, reason, impact } = knownBreaks.connect;
+		annotate(
+			`Skipping cluster test, known break since ${publishedLib.version} from #${pr}: ${reason} Impact: ${impact}`
+		);
 		console.log(`PASS: link messages match ${publishedLib.version} apart from known breaks`);
 		return;
 	}
diff --git a/test/version_compat_breaks.js b/test/version_compat_breaks.js
index 21c42a48..f273bc2c 100644
--- a/test/version_compat_breaks.js
+++ b/test/version_compat_breaks.js
@@ -5,17 +5,17 @@ import {
 } from "../scripts/version-compat-breaks.js";
 
 
-describe("version compatibility known breaks", function() {
+describe("scripts/version-compat-breaks", function() {
 	const breaks = {
 		"2.0.3": {
 			messages: {
-				"request ListedRequest": { pr: 1, reason: "Listed." },
-				"event UnchangedEvent": { pr: 2, reason: "Unchanged." },
+				"request ListedRequest": { pr: 1, reason: "Listed.", impact: "None." },
+				"event UnchangedEvent": { pr: 2, reason: "Unchanged.", impact: "None." },
 			},
-			connect: { pr: 3, reason: "Cannot connect." },
+			connect: { pr: 3, reason: "Cannot connect.", impact: "None." },
 		},
 		"2.0.2": {
-			messages: { "request OldRequest": { pr: 4, reason: "Old." } },
+			messages: { "request OldRequest": { pr: 4, reason: "Old.", impact: "None." } },
 		},
 	};
 
@@ -27,24 +27,30 @@ describe("version compatibility known breaks", function() {
 			validateBreaks(breaks);
 			validateBreaks({});
 		});
-		it("should require a pr number and reason", function() {
+		it("should require a pr number, reason and impact", function() {
 			assert.throws(
 				() => validateBreaks({ "1.0.0": { messages: { "request A": { reason: "A." } } } }),
 				/must have a pr number/
 			);
 			assert.throws(
 				() => validateBreaks({ "1.0.0": { messages: { "request A": { pr: 1, reason: " " } } } }),
-				/must have a reason/
+				/is missing reason/
+			);
+			assert.throws(
+				() => validateBreaks({ "1.0.0": { messages: { "request A": { pr: 1, reason: "A." } } } }),
+				/is missing impact/
 			);
 			assert.throws(
 				() => validateBreaks({ "1.0.0": { connect: { pr: 1 } } }),
-				/connect must have a reason/
+				/connect is missing reason/
 			);
 		});
 		it("should reject unknown properties and bad message names", function() {
 			assert.throws(() => validateBreaks({ "1.0.0": { connected: false } }), /unknown properties connected/);
 			assert.throws(
-				() => validateBreaks({ "1.0.0": { messages: { "request A": { pr: 1, reason: "A.", x: 1 } } } }),
+				() => validateBreaks({
+					"1.0.0": { messages: { "request A": { pr: 1, reason: "A.", impact: "A.", x: 1 } } },
+				}),
 				/unknown properties x/
 			);
 			assert.throws(
@@ -58,7 +64,7 @@ describe("version compatibility known breaks", function() {
 		it("should pick the entry for the published version", function() {
 			const selected = selectBreaks(breaks, "2.0.3");
 			assert.deepEqual([...selected.messages.keys()], ["request ListedRequest", "event UnchangedEvent"]);
-			assert.deepEqual(selected.connect, { pr: 3, reason: "Cannot connect." });
+			assert.deepEqual(selected.connect, { pr: 3, reason: "Cannot connect.", impact: "None." });
 			assert.deepEqual(selected.ignored, ["2.0.2"]);
 		});
 		it("should ignore every entry when the version is not listed", function() {