diff --git a/apps/server/src/pullRequest/PullRequestService.test.ts b/apps/server/src/pullRequest/PullRequestService.test.ts
index 83f362fa20a0..04d4c879a656 100644
--- a/apps/server/src/pullRequest/PullRequestService.test.ts
+++ b/apps/server/src/pullRequest/PullRequestService.test.ts
@@ -463,6 +463,8 @@ function fakeProvider(
     setReaction: () => Effect.void,
     listReviewerCandidates: () => Effect.succeed({ candidates: [], truncated: false }),
     setReviewerRequest: () => Effect.void,
+    // GitHub's own merge message rewrite, which the service reads instead of the kind.
+    ...(kind === "github" ? { mergeMessageRewrite: (message: string) => message } : {}),
     ...overrides,
   };
 }
diff --git a/apps/server/src/pullRequest/PullRequestService.ts b/apps/server/src/pullRequest/PullRequestService.ts
index 0295673350b7..3644fefe985a 100644
--- a/apps/server/src/pullRequest/PullRequestService.ts
+++ b/apps/server/src/pullRequest/PullRequestService.ts
@@ -77,7 +77,6 @@ import {
 import { resolveProjectSettings } from "@t3tools/shared/projectSettings";
 import { detectSourceControlProviderFromRemoteUrl } from "@t3tools/shared/sourceControl";
 
-import { AllowGitHubReserve } from "@t3tools/source-control-github/server/GitHubApi";
 import * as ProjectService from "../project/ProjectService.ts";
 import * as ServerSettings from "../serverSettings.ts";
 import * as PullRequestFilesViewed from "../persistence/PullRequestFilesViewed.ts";
@@ -557,7 +556,7 @@ function withRateLimitBackoff(
       ),
       Effect.flatMap((lease) =>
         effect.pipe(
-          Effect.provideService(AllowGitHubReserve, allowPaused),
+          Effect.provideService(SourceControlRateLimit.Interactive, allowPaused),
           Effect.tap(() => limits.recordSuccess({ ...key, lease })),
           Effect.tapError((error) =>
             error.reason === "rate-limited"
@@ -587,6 +586,9 @@ function withRateLimitBackoff(
   const wrapped = {
     kind: api.kind,
     capabilities: api.capabilities,
+    ...(api.mergeMessageRewrite === undefined
+      ? {}
+      : { mergeMessageRewrite: api.mergeMessageRewrite }),
     // Refused during a pause like any other read, except for the caller that asks for the
     // bypass: a lookup that failed is not held, so letting every background read through would
     // spawn this host's CLI on each of them and re-extend the pause it was already in.
@@ -1558,8 +1560,10 @@ export const make = Effect.gen(function* () {
   )(function* (input) {
     const host = input.host.toLowerCase();
     const { supported } = yield* listWorkspaceProjects({ host });
-    const project = supported.find((candidate) => candidate.api.kind === "github");
-    const api = registry.get("github");
+    const project = supported.find(
+      (candidate) => registry.get(candidate.api.kind)?.getRoutingIdentity !== undefined,
+    );
+    const api = project === undefined ? null : registry.get(project.api.kind);
     if (project === undefined || api?.getRoutingIdentity === undefined) {
       return yield* new PullRequestUnavailableError({ reason: "provider-unsupported" });
     }
@@ -1569,6 +1573,7 @@ export const make = Effect.gen(function* () {
         host,
       })
       .pipe(Effect.mapError(toPullRequestError("routeIdentity")));
+    // Only GitHub reports a routing identity, and the contract names it.
     return { ...identity, host, provider: "github" as const };
   });
 
@@ -1584,7 +1589,7 @@ export const make = Effect.gen(function* () {
           detail: "The GitHub account could not be verified before starting the operation.",
         });
       const project = yield* requireProject(input).pipe(Effect.mapError(rejected));
-      const api = project.api.kind === "github" ? registry.get("github") : null;
+      const api = registry.get(project.api.kind);
       if (
         api?.withVerifiedCredential === undefined ||
         input.host?.toLowerCase() !== project.host.toLowerCase()
@@ -1605,7 +1610,7 @@ export const make = Effect.gen(function* () {
 
   const routing = Effect.fn("PullRequestService.routing")(function* (input: PullRequestRef) {
     const project = yield* requireProject(input);
-    const api = project.api.kind === "github" ? registry.get("github") : null;
+    const api = registry.get(project.api.kind);
     if (api?.getRoutingIdentity === undefined) {
       return yield* new PullRequestUnavailableError({ reason: "provider-unsupported" });
     }
@@ -2047,7 +2052,7 @@ export const make = Effect.gen(function* () {
               );
             }
             const mergeSettings =
-              project.api.kind === "github" &&
+              project.api.mergeMessageRewrite !== undefined &&
               input.stackNumber === undefined &&
               (input.action === "merge" || input.action === "enable-auto-merge")
                 ? serverSettings.getSettings.pipe(
diff --git a/packages/source-control-core/src/server/PullRequestProvider.ts b/packages/source-control-core/src/server/PullRequestProvider.ts
index c3f588a62277..2500c8fae62a 100644
--- a/packages/source-control-core/src/server/PullRequestProvider.ts
+++ b/packages/source-control-core/src/server/PullRequestProvider.ts
@@ -345,6 +345,13 @@ export interface PullRequestProviderApi {
   >;
   readonly kind: SourceControlProviderKind;
   readonly capabilities: PullRequestCapabilities;
+  /**
+   * Rewrites the message a merge will use, for a host that lets the merge carry custom text.
+   * Absent means the host always writes its own message, so nothing is read to decide on one.
+   * Today's only rewrite strips agent credits (`mergeMessage.removeAgentCredits`) when the
+   * project asks for it.
+   */
+  readonly mergeMessageRewrite?: (message: string) => string;
 
   /** The signed-in account, which is what involvement filtering compares against. */
   readonly getViewer: (input: {
@@ -561,7 +568,7 @@ export interface PullRequestProviderApi {
       readonly action: PullRequestAction;
       readonly stackNumber?: number;
       readonly expectedStackHeads?: ReadonlyArray<PullRequestStackHead>;
-      /** GitHub merge message cleanup; ignored by hosts without support. */
+      /** Apply `mergeMessageRewrite` to the merge message; never sent to a host without one. */
       readonly removeAgentCreditsOnMerge?: boolean;
       /** Meaningful for `merge` and `enable-auto-merge`; absent takes the host's own default. */
       readonly mergeMethod?: PullRequestMergeMethod;
diff --git a/packages/source-control-core/src/server/SourceControlRateLimit.ts b/packages/source-control-core/src/server/SourceControlRateLimit.ts
index f2ef07dd2529..262a975eacf5 100644
--- a/packages/source-control-core/src/server/SourceControlRateLimit.ts
+++ b/packages/source-control-core/src/server/SourceControlRateLimit.ts
@@ -20,6 +20,16 @@ export const CredentialScope = Context.Reference<string>(
   },
 );
 
+/**
+ * Set by interactive callers (a user's read or write, not a background sweep). A host may let
+ * requests made under it spend a reserved quota and go through a rate-limit pause: a user acting
+ * on a change request should not be refused because a background read exhausted the quota.
+ */
+export const Interactive = Context.Reference<boolean>(
+  "@t3tools/source-control-core/server/SourceControlRateLimit/Interactive",
+  { defaultValue: () => false },
+);
+
 interface RateLimitKey {
   readonly provider: SourceControlProviderKind;
   readonly host: string;
diff --git a/packages/source-control-github/src/server/GitHubApi.test.ts b/packages/source-control-github/src/server/GitHubApi.test.ts
index 3287ebb8e1a1..e77f10ec9370 100644
--- a/packages/source-control-github/src/server/GitHubApi.test.ts
+++ b/packages/source-control-github/src/server/GitHubApi.test.ts
@@ -275,7 +275,7 @@ describe("GitHubApi", () => {
         retryAt: reset * 1000,
       });
       // A user's own request may spend the reserve, and GraphQL has a quota of its own.
-      yield* api.rest(read).pipe(Effect.provideService(GitHubApi.AllowGitHubReserve, true));
+      yield* api.rest(read).pipe(Effect.provideService(SourceControlRateLimit.Interactive, true));
       yield* api.graphql({ host: "github.com", operation: "x", query: "query { viewer { id } }" });
       expect(requests).toHaveLength(3);
       // The reset gives the background its quota back.
@@ -344,7 +344,7 @@ describe("GitHubApi", () => {
           method: "PUT",
           path: "repos/acme/web/pulls/7/merge",
         })
-        .pipe(Effect.provideService(GitHubApi.AllowGitHubReserve, true));
+        .pipe(Effect.provideService(SourceControlRateLimit.Interactive, true));
       expect(merged.status).toBe(200);
       expect(requests).toHaveLength(2);
     }).pipe(Effect.provide(layer));
diff --git a/packages/source-control-github/src/server/GitHubApi.ts b/packages/source-control-github/src/server/GitHubApi.ts
index e734e5ff07a5..111281a0484e 100644
--- a/packages/source-control-github/src/server/GitHubApi.ts
+++ b/packages/source-control-github/src/server/GitHubApi.ts
@@ -34,16 +34,6 @@ export const PinnedGitHubCredential = Context.Reference<{
   defaultValue: () => null,
 });
 
-/**
- * Set by interactive callers (a user's read or write, not a background sweep). Requests made
- * under it may spend the GraphQL reserve and go through a rate-limit pause: a user acting on a
- * pull request should not be refused because a background read exhausted the quota.
- */
-export const AllowGitHubReserve = Context.Reference<boolean>(
-  "@t3tools/source-control-github/server/GitHubApi/AllowGitHubReserve",
-  { defaultValue: () => false },
-);
-
 export class GitHubApiRequestError extends Schema.TaggedError<GitHubApiRequestError>()(
   "GitHubApiRequestError",
   { host: Schema.String, operation: Schema.String, cause: Schema.Defect() },
@@ -137,7 +127,7 @@ export interface GitHubRestInput {
   readonly maxResponseBytes?: number;
   /** Defaults to 30 seconds; a whole pull request's patch may need longer. */
   readonly timeout?: Duration.Input;
-  /** Overrides `AllowGitHubReserve` for this one request. */
+  /** Overrides `SourceControlRateLimit.Interactive` for this one request. */
   readonly allowReserve?: boolean;
 }
 
@@ -525,7 +515,7 @@ export const make = Effect.gen(function* () {
       input.body === undefined
         ? withEtag
         : withEtag.pipe(HttpClientRequest.bodyJsonUnsafe(input.body));
-    return AllowGitHubReserve.pipe(
+    return SourceControlRateLimit.Interactive.pipe(
       Effect.flatMap((interactive) =>
         send({
           host: input.host,
@@ -545,7 +535,7 @@ export const make = Effect.gen(function* () {
       const host = normalizeHost(input.host);
       const { fingerprint } = yield* credential(host);
       const scope = (yield* SourceControlRateLimit.CredentialScope) || fingerprint;
-      const allowReserve = input.allowReserve ?? (yield* AllowGitHubReserve);
+      const allowReserve = input.allowReserve ?? (yield* SourceControlRateLimit.Interactive);
       // The document, never its variables: user text (bodies, search terms) travels as variables.
       yield* Effect.annotateCurrentSpan({
         "github.operation": input.operation,
diff --git a/packages/source-control-github/src/server/GitHubPullRequestApi.test.ts b/packages/source-control-github/src/server/GitHubPullRequestApi.test.ts
index badb79677585..961106c58acc 100644
--- a/packages/source-control-github/src/server/GitHubPullRequestApi.test.ts
+++ b/packages/source-control-github/src/server/GitHubPullRequestApi.test.ts
@@ -12,7 +12,6 @@ import * as Redacted from "effect/Redacted";
 
 import { HttpClient, HttpClientResponse } from "effect/http";
 
-import { AllowGitHubReserve } from "./GitHubApi.ts";
 import * as GitHubApi from "./GitHubApi.ts";
 import * as GitHubCredentials from "./GitHubCredentials.ts";
 import * as GitHubQuota from "./GitHubQuota.ts";
@@ -78,7 +77,7 @@ const mockApi = Layer.effect(
     const quota = yield* GitHubQuota.GitHubQuota;
     return GitHubApi.GitHubApi.of({
       graphql: (input) =>
-        GitHubApi.AllowGitHubReserve.pipe(
+        SourceControlRateLimit.Interactive.pipe(
           Effect.flatMap((interactive) =>
             quota.admit(input.host, "graphql", {
               allowReserve: input.allowReserve ?? interactive,
@@ -3864,7 +3863,9 @@ layer("GitHubPullRequestApi.layer", (it) => {
       const error = yield* Effect.flip(cli.getPullRequestDetail(input));
       expect(error._tag).toBe("SourceControlRateLimitPausedError");
       expect(mockedExecute).toHaveBeenCalledOnce();
-      yield* cli.getPullRequestDetail(input).pipe(Effect.provideService(AllowGitHubReserve, true));
+      yield* cli
+        .getPullRequestDetail(input)
+        .pipe(Effect.provideService(SourceControlRateLimit.Interactive, true));
       expect(mockedExecute).toHaveBeenCalledTimes(2);
     }),
   );
diff --git a/packages/source-control-github/src/server/GitHubPullRequestApi.ts b/packages/source-control-github/src/server/GitHubPullRequestApi.ts
index ceff9c6c0b5c..b8c7fe227688 100644
--- a/packages/source-control-github/src/server/GitHubPullRequestApi.ts
+++ b/packages/source-control-github/src/server/GitHubPullRequestApi.ts
@@ -1526,7 +1526,7 @@ export const make = Effect.gen(function* () {
 
   const getPullRequestDetail: GitHubPullRequestApi["Service"]["getPullRequestDetail"] = (input) => {
     const { owner, name } = parseRepositorySelector(input.repository);
-    return GitHubApi.AllowGitHubReserve.pipe(
+    return SourceControlRateLimit.Interactive.pipe(
       Effect.flatMap((allowReserve) =>
         graphqlRead({
           allowReserve,
diff --git a/packages/source-control-github/src/server/GitHubPullRequestProvider.test.ts b/packages/source-control-github/src/server/GitHubPullRequestProvider.test.ts
index 98e8aeb5c15b..781d07f0d496 100644
--- a/packages/source-control-github/src/server/GitHubPullRequestProvider.test.ts
+++ b/packages/source-control-github/src/server/GitHubPullRequestProvider.test.ts
@@ -7,6 +7,7 @@ import type { PullRequestReaction } from "@t3tools/contracts";
 
 import { decodePullRequestDetailJson } from "./gitHubPullRequestJson.ts";
 import * as GitHubApi from "./GitHubApi.ts";
+import * as SourceControlRateLimit from "@t3tools/source-control-core/server/SourceControlRateLimit";
 import * as GitHubPullRequestApi from "./GitHubPullRequestApi.ts";
 import type { GitHubPullRequestCore } from "./gitHubPullRequestJson.ts";
 import { gitHubViewerPermissions, loginAvatarUrl, make } from "./GitHubPullRequestProvider.ts";
@@ -725,7 +726,7 @@ describe("getViewerPermissions", () => {
     Layer.mock(GitHubPullRequestApi.GitHubPullRequestApi)({
       revalidateChecks: (_input, read) => read,
       getPullRequestDetail: () =>
-        GitHubApi.AllowGitHubReserve.pipe(
+        SourceControlRateLimit.Interactive.pipe(
           Effect.tap((allowReserve) => Effect.sync(() => onDetail(allowReserve))),
           Effect.flatMap(() => detail),
         ),
diff --git a/packages/source-control-github/src/server/GitHubPullRequestProvider.ts b/packages/source-control-github/src/server/GitHubPullRequestProvider.ts
index a3030f6c86ad..7b74bd368b81 100644
--- a/packages/source-control-github/src/server/GitHubPullRequestProvider.ts
+++ b/packages/source-control-github/src/server/GitHubPullRequestProvider.ts
@@ -1,3 +1,4 @@
+import { removeAgentCredits } from "@t3tools/source-control-core/server/mergeMessage";
 import * as Effect from "effect/Effect";
 import type {
   PullRequestActor,
@@ -7,7 +8,7 @@ import type {
   PullRequestViewerPermissions,
 } from "@t3tools/contracts";
 
-import * as GitHubApi from "./GitHubApi.ts";
+import * as SourceControlRateLimit from "@t3tools/source-control-core/server/SourceControlRateLimit";
 import * as GitHubPullRequestApi from "./GitHubPullRequestApi.ts";
 import {
   PullRequestProviderError,
@@ -262,6 +263,7 @@ export const make = Effect.gen(function* () {
   const provider: PullRequestProviderApi = {
     kind: "github",
     capabilities: CAPABILITIES,
+    mergeMessageRewrite: removeAgentCredits,
     getRoutingIdentity: (input) =>
       cli.getRoutingIdentity(input).pipe(Effect.mapError(fail("routeIdentity"))),
     withVerifiedCredential: (input, use) =>
@@ -526,7 +528,7 @@ export const make = Effect.gen(function* () {
       // comparison, so one read usually answers what used to take three. When that heavier read
       // fails, the light access read still answers, withholding only update-branch.
       return cli.getPullRequestDetail(input).pipe(
-        Effect.provideService(GitHubApi.AllowGitHubReserve, true),
+        Effect.provideService(SourceControlRateLimit.Interactive, true),
         Effect.map((pullRequest) =>
           gitHubViewerPermissions({
             ...pullRequest.viewerAccess,
diff --git a/packages/source-control-github/src/server/GitHubSourceControlProvider.ts b/packages/source-control-github/src/server/GitHubSourceControlProvider.ts
index f906f3e629d4..8edf9423c7c9 100644
--- a/packages/source-control-github/src/server/GitHubSourceControlProvider.ts
+++ b/packages/source-control-github/src/server/GitHubSourceControlProvider.ts
@@ -963,7 +963,7 @@ export const make = Effect.gen(function* () {
     },
     listChangeRequests: (input) =>
       // An open lookup is a user waiting on a status; the rest may be a background sweep.
-      (input.state === "open" ? Effect.succeed(true) : GitHubApi.AllowGitHubReserve).pipe(
+      (input.state === "open" ? Effect.succeed(true) : SourceControlRateLimit.Interactive).pipe(
         Effect.flatMap((allowReserve) =>
           listByHead({
             cwd: input.cwd,