fix(agentctl): clamp file-search limit to bound result allocation (#2088)

Co-authored-by: Kandev Agent <agent@kandev.dev>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/backend/internal/agentctl/server/process/workspace_files.go

@@ -876,6 +876,19 @@ type fileSearchCandidate struct {
 	repositoryName string
 }
 
+const (
+	// fileSearchDefaultLimit applies when the caller passes a non-positive limit.
+	fileSearchDefaultLimit = 20
+	// fileSearchMaxLimit caps the caller-supplied limit before it is used to
+	// pre-allocate the result slice. The limit reaches this code straight from
+	// the `limit` query parameter of GET /api/v1/workspace/search, so without a
+	// ceiling a request like `?limit=2000000000` makes the process reserve
+	// gigabytes for a result set that can never exceed the number of tracked
+	// files. Mirrors the clamp validateContentSearch already applies to
+	// content search.
+	fileSearchMaxLimit = 200
+)
+
 // GetFileContentAtRef returns the content of a file at a specific git ref (branch, commit, HEAD, etc).
 // If the file is not valid UTF-8, it is base64-encoded and isBinary is true.
 func (wt *WorkspaceTracker) GetFileContentAtRef(ctx context.Context, reqPath string, ref string) (string, int64, bool, error) {
@@ -1007,7 +1020,10 @@ func searchFileCandidates(
 		return []types.FileSearchResult{}
 	}
 	if limit <= 0 {
-		limit = 20
+		limit = fileSearchDefaultLimit
+	}
+	if limit > fileSearchMaxLimit {
+		limit = fileSearchMaxLimit
 	}
 
 	query = strings.ToLower(query)

apps/backend/internal/agentctl/server/process/workspace_files_test.go

@@ -2,6 +2,8 @@ package process
 
 import (
 	"context"
+	"fmt"
+	"math"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -517,6 +519,47 @@ func TestSearchFileCandidatesBreaksTiesByRepositoryRelativePathLength(t *testing
 	}
 }
 
+// A caller-supplied limit reaches searchFileCandidates straight from the
+// `limit` query parameter, so an absurd value must not drive the result
+// slice's pre-allocation.
+func TestSearchFileCandidatesClampsCallerSuppliedLimit(t *testing.T) {
+	candidates := make([]fileSearchCandidate, 0, fileSearchMaxLimit+50)
+	for i := range fileSearchMaxLimit + 50 {
+		candidates = append(candidates, fileSearchCandidate{
+			path:      fmt.Sprintf("src/query-%d.go", i),
+			matchPath: fmt.Sprintf("src/query-%d.go", i),
+		})
+	}
+
+	results := searchFileCandidates(candidates, "query", math.MaxInt32)
+
+	if len(results) != fileSearchMaxLimit {
+		t.Fatalf("len(results) = %d, want the clamped %d", len(results), fileSearchMaxLimit)
+	}
+	if cap(results) > fileSearchMaxLimit {
+		t.Fatalf("cap(results) = %d, want no more than the clamped %d", cap(results), fileSearchMaxLimit)
+	}
+}
+
+func TestSearchFileCandidatesDefaultsNonPositiveLimit(t *testing.T) {
+	candidates := make([]fileSearchCandidate, 0, fileSearchDefaultLimit+5)
+	for i := range fileSearchDefaultLimit + 5 {
+		candidates = append(candidates, fileSearchCandidate{
+			path:      fmt.Sprintf("src/query-%d.go", i),
+			matchPath: fmt.Sprintf("src/query-%d.go", i),
+		})
+	}
+
+	for _, limit := range []int{0, -1} {
+		results := searchFileCandidates(candidates, "query", limit)
+
+		if len(results) != fileSearchDefaultLimit {
+			t.Fatalf("limit %d: len(results) = %d, want the default %d",
+				limit, len(results), fileSearchDefaultLimit)
+		}
+	}
+}
+
 func TestGetFileTree_Symlinks(t *testing.T) {
 	tmpDir := t.TempDir()
 	wt := &WorkspaceTracker{workDir: tmpDir}