diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a5c40bb..a790aeb 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,3 +14,12 @@ jobs:
         with:
           go-version-file: go.mod
       - run: go test ./...
+
+  buf:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: bufbuild/buf-action@v1
+        with:
+          setup_only: true
+      - run: buf lint
diff --git a/gen/priompt/v1/prompt_grpc.pb.go b/gen/priompt/v1/prompt_grpc.pb.go
index 1a74833..ac155b6 100644
--- a/gen/priompt/v1/prompt_grpc.pb.go
+++ b/gen/priompt/v1/prompt_grpc.pb.go
@@ -41,6 +41,9 @@ type PromptServiceClient interface {
 	// DiffPrompt runs the Semantic Propagation Diff between the stored prompt at
 	// `uri` (the original) and `new_template` (the edit), using the embedding
 	// model the server operator configured at startup.
+	// DiffPromptResponse is shared with DiffCommits on purpose (same result shape);
+	// splitting it would break the Go API and buf breaking.
+	// buf:lint:ignore RPC_REQUEST_RESPONSE_UNIQUE
 	DiffPrompt(ctx context.Context, in *DiffPromptRequest, opts ...grpc.CallOption) (*DiffPromptResponse, error)
 	// PublishPrompt validates and stores a new prompt version on the server, then
 	// notifies subscribers over NATS. This is the write-through path that makes a
@@ -53,7 +56,9 @@ type PromptServiceClient interface {
 	// MergeBranch merges `from` into `into`, recording a two-parent merge commit.
 	MergeBranch(ctx context.Context, in *MergeBranchRequest, opts ...grpc.CallOption) (*MergeBranchResponse, error)
 	// DiffCommits runs the semantic diff between any two commits of a prompt — the
-	// query-anything-in-history path.
+	// query-anything-in-history path. Returns DiffPromptResponse (see DiffPrompt).
+	// buf:lint:ignore RPC_REQUEST_RESPONSE_UNIQUE
+	// buf:lint:ignore RPC_RESPONSE_STANDARD_NAME
 	DiffCommits(ctx context.Context, in *DiffCommitsRequest, opts ...grpc.CallOption) (*DiffPromptResponse, error)
 	// SetBranch points a branch at an existing commit — the rollback / pin path.
 	// Moving "main" instantly changes the served version.
@@ -173,6 +178,9 @@ type PromptServiceServer interface {
 	// DiffPrompt runs the Semantic Propagation Diff between the stored prompt at
 	// `uri` (the original) and `new_template` (the edit), using the embedding
 	// model the server operator configured at startup.
+	// DiffPromptResponse is shared with DiffCommits on purpose (same result shape);
+	// splitting it would break the Go API and buf breaking.
+	// buf:lint:ignore RPC_REQUEST_RESPONSE_UNIQUE
 	DiffPrompt(context.Context, *DiffPromptRequest) (*DiffPromptResponse, error)
 	// PublishPrompt validates and stores a new prompt version on the server, then
 	// notifies subscribers over NATS. This is the write-through path that makes a
@@ -185,7 +193,9 @@ type PromptServiceServer interface {
 	// MergeBranch merges `from` into `into`, recording a two-parent merge commit.
 	MergeBranch(context.Context, *MergeBranchRequest) (*MergeBranchResponse, error)
 	// DiffCommits runs the semantic diff between any two commits of a prompt — the
-	// query-anything-in-history path.
+	// query-anything-in-history path. Returns DiffPromptResponse (see DiffPrompt).
+	// buf:lint:ignore RPC_REQUEST_RESPONSE_UNIQUE
+	// buf:lint:ignore RPC_RESPONSE_STANDARD_NAME
 	DiffCommits(context.Context, *DiffCommitsRequest) (*DiffPromptResponse, error)
 	// SetBranch points a branch at an existing commit — the rollback / pin path.
 	// Moving "main" instantly changes the served version.
diff --git a/proto/priompt/v1/prompt.proto b/proto/priompt/v1/prompt.proto
index 5c06201..a397dfd 100644
--- a/proto/priompt/v1/prompt.proto
+++ b/proto/priompt/v1/prompt.proto
@@ -11,6 +11,9 @@ service PromptService {
   // DiffPrompt runs the Semantic Propagation Diff between the stored prompt at
   // `uri` (the original) and `new_template` (the edit), using the embedding
   // model the server operator configured at startup.
+  // DiffPromptResponse is shared with DiffCommits on purpose (same result shape);
+  // splitting it would break the Go API and buf breaking.
+  // buf:lint:ignore RPC_REQUEST_RESPONSE_UNIQUE
   rpc DiffPrompt(DiffPromptRequest) returns (DiffPromptResponse);
   // PublishPrompt validates and stores a new prompt version on the server, then
   // notifies subscribers over NATS. This is the write-through path that makes a
@@ -24,7 +27,9 @@ service PromptService {
   // MergeBranch merges `from` into `into`, recording a two-parent merge commit.
   rpc MergeBranch(MergeBranchRequest) returns (MergeBranchResponse);
   // DiffCommits runs the semantic diff between any two commits of a prompt — the
-  // query-anything-in-history path.
+  // query-anything-in-history path. Returns DiffPromptResponse (see DiffPrompt).
+  // buf:lint:ignore RPC_REQUEST_RESPONSE_UNIQUE
+  // buf:lint:ignore RPC_RESPONSE_STANDARD_NAME
   rpc DiffCommits(DiffCommitsRequest) returns (DiffPromptResponse);
   // SetBranch points a branch at an existing commit — the rollback / pin path.
   // Moving "main" instantly changes the served version.