Fix/modernize codebase

internal/acp/jsonrpc_test.go

@@ -158,7 +158,7 @@ func TestConnSurvivesMalformedLine(t *testing.T) {
 
 	dec := json.NewDecoder(clientR)
 	var sawParseError, sawPong bool
-	for i := 0; i < 2; i++ {
+	for i := range 2 {
 		var msg struct {
 			Result any `json:"result"`
 			Error  *struct {

internal/acp/permission.go

@@ -2,6 +2,7 @@ package acp
 
 import (
 	"encoding/json"
+	"slices"
 
 	"github.com/Gitlawb/zero/internal/agent"
 )
@@ -85,12 +86,7 @@ func decisionFromOutcome(outcome RequestPermissionOutcome, offered []agent.Permi
 }
 
 func actionOffered(action agent.PermissionDecisionAction, offered []agent.PermissionDecisionAction) bool {
-	for _, a := range offered {
-		if a == action {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(offered, action)
 }
 
 // permissionToolCall builds the ToolCall descriptor embedded in a

internal/agent/command_prefix.go

@@ -168,7 +168,7 @@
 	return cleaned
 }
 
 func safeRequestedPrefix(prefix []string, command []string) bool {
 	return safeRequestedPrefixForSegments(prefix, [][]string{command})
 }
 
@@ -196,7 +196,7 @@
 	return matched
 }
 
 func safeShellCommandTokens(command string) ([]string, bool) {
 	segments, ok := safeShellCommandSegments(command)
 	if !ok || len(segments) != 1 {
 		return nil, false
@@ -343,7 +343,7 @@
 	if body == "" {
 		return false
 	}
-	for _, part := range strings.Split(body, ",") {
+	for part := range strings.SplitSeq(body, ",") {
 		if part == "" {
 			return false
 		}
@@ -466,8 +466,8 @@
 	}
 	name = strings.ToLower(name)
 	for _, suffix := range []string{".exe", ".cmd", ".bat", ".com"} {
-		if strings.HasSuffix(name, suffix) {
-			return strings.TrimSuffix(name, suffix)
+		if before, ok := strings.CutSuffix(name, suffix); ok {
+			return before
 		}
 	}
 	return name
@@ -485,7 +485,7 @@
 	return true
 }
 
 func equalStringSlices(left []string, right []string) bool {
 	if len(left) != len(right) {
 		return false
 	}

internal/agent/compaction.go

@@ -196,10 +196,7 @@ func CompactMessages(messages []zeroruntime.Message, opts CompactionOptions) (Co
 
 	// Naive boundary: keep the last preserveLast messages. Then widen the suffix
 	// backward to a safe boundary so it never starts on a tool result.
-	boundary := len(messages) - preserveLast
-	if boundary < systemEnd {
-		boundary = systemEnd
-	}
+	boundary := max(len(messages)-preserveLast, systemEnd)
 	boundary = safeSuffixBoundary(messages, systemEnd, boundary)
 
 	middle := messages[systemEnd:boundary]

internal/agent/compaction_preserve.go

@@ -210,7 +210,7 @@
 // editNote reduces an edit tool's result to a single short line (its first
 // non-empty line, byte-capped on a rune boundary) for the preserved summary.
 func editNote(content string) string {
-	for _, line := range strings.Split(content, "\n") {
+	for line := range strings.SplitSeq(content, "\n") {
 		s := strings.TrimSpace(line)
 		if s == "" {
 			continue
@@ -369,11 +369,11 @@
 	if !strings.HasPrefix(content, projectInstructionsHeadingPrefix) {
 		return "", ""
 	}
-	firstLineEnd := strings.IndexByte(content, '\n')
-	if firstLineEnd < 0 {
+	before, _, ok := strings.Cut(content, "\n")
+	if !ok {
 		return "", ""
 	}
-	heading := strings.TrimSpace(content[:firstLineEnd])
+	heading := strings.TrimSpace(before)
 	if !strings.Contains(heading, projectInstructionsHeadingMarker) {
 		return "", ""
 	}
@@ -417,10 +417,7 @@
 	if len(body) <= maxPreservedSkillBytes {
 		return body
 	}
-	limit := maxPreservedSkillBytes - len(truncationNote)
-	if limit < 0 {
-		limit = 0
-	}
+	limit := max(maxPreservedSkillBytes-len(truncationNote), 0)
 	// Walk back to the start of a rune so a multibyte sequence is never split.
 	for limit > 0 && !utf8.RuneStart(body[limit]) {
 		limit--
@@ -583,7 +580,7 @@
 // block. JSON escaping makes this lossless even when a skill body contains
 // markdown headings, code fences, or quotes. Returns ("", nil) when absent or
 // malformed.
 func parsePreservedState(summaryContent string) (string, []skillEntry) {
 	state := parsePreservedStateBlock(summaryContent)
 	return state.Plan, preservedSkillsToEntries(state.Skills)
 }

internal/agent/compaction_recent_edits_test.go

@@ -91,7 +91,7 @@ func TestRecentEditsMergeNewerWins(t *testing.T) {
 func TestRecentEditsCapKeepsReeditedFile(t *testing.T) {
 	// Earlier compaction preserved exactly maxRecentEdits files, f0 the oldest.
 	older := make([]skillEntry, 0, maxRecentEdits)
-	for i := 0; i < maxRecentEdits; i++ {
+	for i := range maxRecentEdits {
 		older = append(older, skillEntry{name: fmt.Sprintf("f%d.go", i), body: "old"})
 	}
 	// Fresh window re-edits the OLDEST file (f0) and adds a brand-new file, so the

internal/agent/compaction_summarizer_test.go

@@ -109,7 +109,7 @@ func TestSummarizeWithFallbackChunksOnContextLimit(t *testing.T) {
 	if err != nil {
 		t.Fatalf("summarizeWithFallback failed: %v", err)
 	}
-	for i := 0; i < n; i++ {
+	for i := range n {
 		if !strings.Contains(summary, fmt.Sprintf("msg-%d", i)) {
 			t.Fatalf("combined summary missing msg-%d: %q", i, summary)
 		}

internal/agent/defer_savings_test.go

@@ -50,7 +50,7 @@ func (t richMCPTool) Deferred() bool { return true }
 func TestDeferralTokenSavingsMeasurement(t *testing.T) {
 	const mcpToolCount = 6
 	registry := tools.NewRegistry()
-	for i := 0; i < mcpToolCount; i++ {
+	for i := range mcpToolCount {
 		registry.Register(richMCPTool{name: fmt.Sprintf("mcp__websearch__search_v%d", i)})
 	}
 	registry.Register(fakeToolSearchTool{})

internal/agent/guardrails.go

@@ -315,18 +315,18 @@ func IsNoProgressStop(content string) bool {
 	}
 	rest := trimmed[len(noOutputStopPrefix):]
 	const turnsSep = " turns "
-	sep := strings.Index(rest, turnsSep)
-	if sep < 0 {
+	before, after, ok := strings.Cut(rest, turnsSep)
+	if !ok {
 		return false
 	}
 	// The text between the prefix and " turns " must be exactly the bare integer
 	// count; anything else means this isn't the guard's own answer.
-	if _, err := strconv.Atoi(rest[:sep]); err != nil {
+	if _, err := strconv.Atoi(before); err != nil {
 		return false
 	}
 	// The marker must be immediately followed (one space) by the suffix and then
 	// end — no arbitrary text wedged in between.
-	return rest[sep+len(turnsSep):] == noOutputStopMarker+" "+noOutputStopSuffix
+	return after == noOutputStopMarker+" "+noOutputStopSuffix
 }
 
 // Reminder markers are stable substrings used both to build the reminder text

internal/agent/guardrails_test.go

@@ -326,7 +326,7 @@ func TestRunInjectsStalePlanReminderAfterManyToolCalls(t *testing.T) {
 	turns := [][]zeroruntime.StreamEvent{
 		toolTurn("plan-1", "update_plan", `{"plan":[{"content":"step one"}]}`),
 	}
-	for i := 0; i < staleToolCallThreshold+2; i++ {
+	for range staleToolCallThreshold + 2 {
 		turns = append(turns, toolTurn("call", "read_file", `{"path":"notes.txt"}`))
 	}
 	turns = append(turns, textTurn("done"))
@@ -360,7 +360,7 @@ func TestRunStalePlanReminderIsOneShotPerInterval(t *testing.T) {
 	}
 	// Enough tool calls to exceed the threshold by a wide margin; the reminder
 	// must fire once for the interval, not on every subsequent turn.
-	for i := 0; i < staleToolCallThreshold*2; i++ {
+	for range staleToolCallThreshold * 2 {
 		turns = append(turns, toolTurn("call", "read_file", `{"path":"notes.txt"}`))
 	}
 	turns = append(turns, textTurn("done"))
@@ -390,7 +390,7 @@ func TestRunInjectsToolOnlyProgressReminder(t *testing.T) {
 	registry.Register(tools.NewReadFileTool(root))
 
 	turns := make([][]zeroruntime.StreamEvent, 0, toolOnlyProgressReminderAt+1)
-	for i := 0; i < toolOnlyProgressReminderAt; i++ {
+	for range toolOnlyProgressReminderAt {
 		turns = append(turns, toolTurn("call", "read_file", `{"path":"notes.txt"}`))
 	}
 	turns = append(turns, textTurn("done"))
@@ -441,7 +441,7 @@ func repeatedFlakyTurns(n int) [][]zeroruntime.StreamEvent {
 		{Type: zeroruntime.StreamEventDone},
 	}
 	turns := make([][]zeroruntime.StreamEvent, 0, n)
-	for i := 0; i < n; i++ {
+	for range n {
 		turns = append(turns, turn)
 	}
 	return turns

internal/agent/loop.go

@@ -6,6 +6,8 @@
 	"errors"
 	"fmt"
 	"io"
+	"maps"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
@@ -2481,9 +2483,7 @@
 		return nil
 	}
 	copied := make(map[string]any, len(args))
-	for key, value := range args {
-		copied[key] = value
-	}
+	maps.Copy(copied, args)
 	return copied
 }
 
@@ -2512,7 +2512,7 @@
 }
 
 // partitionToolsCached is partitionTools with an optional per-tool definition
 // cache. The partitioning itself (visibility, deferral, ordering) is recomputed
 // every call — it must be, because a tool's deferred state can flip mid-run (e.g.
 // swarm tools un-defer once a swarm is active). Only the expensive part —
 // rendering each tool's JSON-schema parameters — is memoized by tool name, since a
@@ -2679,12 +2679,7 @@
 }
 
 func containsToolName(names []string, name string) bool {
-	for _, candidate := range names {
-		if candidate == name {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(names, name)
 }
 
 func schemaToRuntimeMap(schema tools.Schema) map[string]any {
@@ -2803,7 +2798,7 @@
 		return nil
 	}
 	var names []string
-	for _, part := range strings.Split(raw, ",") {
+	for part := range strings.SplitSeq(raw, ",") {
 		if trimmed := strings.TrimSpace(part); trimmed != "" {
 			names = append(names, trimmed)
 		}

internal/agent/loop_test.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"slices"
 	"strings"
 	"testing"
 
@@ -2393,12 +2394,7 @@ func TestRunAlwaysAllowWithoutSandboxStillAllowsCall(t *testing.T) {
 }
 
 func containsPermissionDecision(decisions []PermissionDecisionAction, want PermissionDecisionAction) bool {
-	for _, decision := range decisions {
-		if decision == want {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(decisions, want)
 }
 
 // cancelMidStreamProvider cancels the run while the provider stream is open and

internal/agent/reconnect_test.go

@@ -134,7 +134,7 @@ func TestJitteredBackoffStaysInBounds(t *testing.T) {
 	// so backoff still grows attempt over attempt while decorrelating retries.
 	for attempt := 1; attempt <= 5; attempt++ {
 		base := backoffFor(attempt)
-		for i := 0; i < 200; i++ {
+		for range 200 {
 			got := jitteredBackoff(attempt)
 			if got < base || got > base+base/2 {
 				t.Fatalf("attempt %d jittered backoff %v out of [%v, %v]", attempt, got, base, base+base/2)

internal/agent/skills_context_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestSkillsContextCapsLongList(t *testing.T) {
 	skills := make([]SkillInfo, 0, 40)
-	for i := 0; i < 40; i++ {
+	for i := range 40 {
 		n := strconv.Itoa(i)
 		skills = append(skills, SkillInfo{Name: "skill-" + n, Description: "does something useful, number " + n})
 	}

internal/agent/system_prompt.go

@@ -388,10 +388,7 @@ func truncateGuidelineContent(content string, limit int) string {
 	if limit <= 0 {
 		return ""
 	}
-	cut := limit - len(truncationMarker)
-	if cut < 0 {
-		cut = 0
-	}
+	cut := max(limit-len(truncationMarker), 0)
 	for cut > 0 && !utf8.RuneStart(content[cut]) {
 		cut--
 	}
@@ -443,7 +440,7 @@ func projectGuidelineDirs(cwd, gitRoot string) []string {
 	}
 	dirs := []string{gitRoot}
 	cur := gitRoot
-	for _, seg := range strings.Split(rel, string(filepath.Separator)) {
+	for seg := range strings.SplitSeq(rel, string(filepath.Separator)) {
 		if seg == "" || seg == "." {
 			continue
 		}
@@ -636,8 +633,8 @@ func gitBranchForPrompt(cwd string) string {
 		return ""
 	}
 	ref := strings.TrimSpace(string(data))
-	if strings.HasPrefix(ref, "ref: ") {
-		return strings.TrimPrefix(strings.TrimPrefix(ref, "ref: "), "refs/heads/")
+	if after, ok := strings.CutPrefix(ref, "ref: "); ok {
+		return strings.TrimPrefix(after, "refs/heads/")
 	}
 	if len(ref) >= 7 {
 		return ref[:7]

internal/agenteval/suite.go

@@ -30,7 +30,7 @@ type Task struct {
 	ExpectedChangedFiles  []string      `json:"expectedChangedFiles"`
 	ForbiddenChangedFiles []string      `json:"forbiddenChangedFiles,omitempty"`
 	RequiredTraceEvents   []string      `json:"requiredTraceEvents,omitempty"`
-	ContextChecks         ContextChecks `json:"contextChecks,omitempty"`
+	ContextChecks         ContextChecks `json:"contextChecks"`
 }
 
 type Command struct {

internal/agenteval/trace.go

@@ -8,7 +8,7 @@ import (
 
 func ParseTraceEventKeys(stdout string) []string {
 	seen := map[string]bool{}
-	for _, line := range strings.Split(stdout, "\n") {
+	for line := range strings.SplitSeq(stdout, "\n") {
 		line = strings.TrimSpace(line)
 		if line == "" {
 			continue

internal/background/manager.go

@@ -33,7 +33,7 @@ type Task struct {
 	Status         Status    `json:"status"`
 	OutputFile     string    `json:"outputFile"`
 	StartedAt      time.Time `json:"startedAt"`
-	CompletedAt    time.Time `json:"completedAt,omitempty"`
+	CompletedAt    time.Time `json:"completedAt"`
 	ExitCode       int       `json:"exitCode,omitempty"`
 }
 

internal/cli/agent_eval.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"slices"
 	"strings"
 	"time"
 
@@ -316,16 +317,14 @@ func appendAgentEvalModel(models []string, value string) []string {
 	if value == "" {
 		return models
 	}
-	for _, model := range models {
-		if model == value {
-			return models
-		}
+	if slices.Contains(models, value) {
+		return models
 	}
 	return append(models, value)
 }
 
 func appendAgentEvalModels(models []string, value string) []string {
-	for _, model := range strings.Split(value, ",") {
+	for model := range strings.SplitSeq(value, ",") {
 		models = appendAgentEvalModel(models, model)
 	}
 	return models

internal/cli/app_test.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"slices"
 	"strings"
 	"testing"
 	"time"
@@ -812,13 +813,7 @@ func TestRunSkipPermissionsUnsafeMergesAddDirGrants(t *testing.T) {
 				t.Fatal("AgentOptions.Sandbox = nil, want sandbox engine")
 			}
 			roots := launchedOptions.AgentOptions.Sandbox.Scope().Roots()
-			found := false
-			for _, root := range roots {
-				if root == resolvedExtra {
-					found = true
-					break
-				}
-			}
+			found := slices.Contains(roots, resolvedExtra)
 			if !found {
 				t.Fatalf("scope roots = %v, want extra root %q", roots, resolvedExtra)
 			}

internal/cli/cron_claim_test.go

@@ -19,14 +19,12 @@ func TestFireJobClaimPreventsDoubleFire(t *testing.T) {
 	// Two schedulers fire the same due job concurrently; the atomic claim must let
 	// exactly one through, so the job never double-fires (M9).
 	var wg sync.WaitGroup
-	for i := 0; i < 2; i++ {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
+	for range 2 {
+		wg.Go(func() {
 			job, _ := store.Get(due.ID)
 			var out, errb bytes.Buffer
 			fireJob(store, nowFn, job, &out, &errb, fx.run)
-		}()
+		})
 	}
 	wg.Wait()