Harden BTW isolation lifecycle

Preserve drafts when Ctrl+C is pressed during an active BTW run and cover returning to the parent through the documented /btw toggle.

internal/agent/compaction.go

@@ -56,10 +56,6 @@ type CompactionOptions struct {
 	// injected so Compact stays pure and testable; the agent loop wires it to a
 	// real provider call.
 	Summarize func(toSummarize []zeroruntime.Message) (string, error)
-	// taskState is a snapshot supplied by the running agent. Its immutable
-	// objective is always preserved; mutable fields are admitted only when its
-	// plan projection still matches the transcript.
-	taskState *taskStateSnapshot
 }
 
 // CompactionResult is the metadata-bearing result returned by CompactMessages.
@@ -224,7 +220,7 @@ func CompactMessages(messages []zeroruntime.Message, opts CompactionOptions) (Co
 
 	// Preserve structured state (active plan + loaded skills) from the elided
 	// middle verbatim, so it is not lost or paraphrased away by the prose summary.
-	content := appendPreservedState(summaryLabel+"\n"+summary, middle, opts.taskState)
+	content := appendPreservedState(summaryLabel+"\n"+summary, middle)
 
 	compacted := make([]zeroruntime.Message, 0, systemEnd+1+(len(messages)-boundary))
 	compacted = append(compacted, messages[:systemEnd]...)
@@ -330,7 +326,6 @@ type compactionState struct {
 	// OnText is deliberately NOT forwarded (compaction stays invisible to the user),
 	// but its token COST must still be counted so usage reports and budgets include it.
 	onUsage func(Usage)
-	task    *taskState
 
 	// calibrationRatio scales the raw byte/4 token estimate toward the provider's
 	// real prompt-token count. ApproxTextTokens over-counts code-heavy content by
@@ -370,15 +365,13 @@ func (state *compactionState) calibratedTokens(raw int) int {
 	return int(float64(raw) * state.calibrationRatio)
 }
 
-func newCompactionState(options Options, task *taskState) *compactionState {
-	state := &compactionState{
+func newCompactionState(options Options) *compactionState {
+	return &compactionState{
 		enabled:      options.ContextWindow > 0,
 		threshold:    compactionThreshold(options.ContextWindow),
 		preserveLast: options.CompactionPreserveLast,
 		onUsage:      options.OnUsage,
-		task:         task,
 	}
-	return state
 }
 
 // maybeCompact runs proactive compaction at the top of a turn. It returns the
@@ -425,7 +418,6 @@ func (state *compactionState) maybeCompact(
 	compacted, err := Compact(messages, CompactionOptions{
 		PreserveLast: state.preserveLast,
 		Summarize:    summarizeClosure(ctx, provider, state.onUsage),
-		taskState:    state.task.snapshotForCompaction(messages),
 	})
 	if err != nil {
 		// Summarizer failed: keep the original history. The reactive path (or a
@@ -476,7 +468,6 @@ func (state *compactionState) recover(
 	result, compactErr := Compact(messages, CompactionOptions{
 		PreserveLast: state.preserveLast,
 		Summarize:    summarizeClosure(ctx, provider, state.onUsage),
-		taskState:    state.task.snapshotForCompaction(messages),
 	})
 	if compactErr != nil {
 		// A genuine compaction attempt was made (and failed): the budget is spent

internal/agent/compaction_preserve.go

@@ -30,10 +30,6 @@ const (
 const (
 	maxRecentEdits   = 20
 	maxEditNoteBytes = 160
-	// maxTaskObjectiveBytes keeps the original objective recognizable after
-	// compaction without allowing an unusually large prompt to recreate the
-	// context pressure the compaction just removed.
-	maxTaskObjectiveBytes = 512
 )
 
 const (
@@ -80,14 +76,32 @@ func extractLatestPlan(messages []zeroruntime.Message) string {
 // ({"plan":[{content,status,...}]}) as terse status-tagged bullet lines. Returns
 // "" on malformed arguments or an empty plan.
 func formatPlanArguments(arguments string) string {
-	plan, ok := parseTaskPlan(arguments)
-	if !ok {
+	var parsed struct {
+		Plan []struct {
+			Content string `json:"content"`
+			Step    string `json:"step"`
+			Status  string `json:"status"`
+			Notes   string `json:"notes"`
+		} `json:"plan"`
+	}
+	if err := json.Unmarshal([]byte(strings.TrimSpace(arguments)), &parsed); err != nil {
 		return ""
 	}
-	lines := make([]string, 0, len(plan))
-	for _, item := range plan {
-		line := "- [" + item.Status + "] " + item.Content
-		if notes := item.Notes; notes != "" {
+	lines := make([]string, 0, len(parsed.Plan))
+	for _, item := range parsed.Plan {
+		content := strings.TrimSpace(item.Content)
+		if content == "" {
+			content = strings.TrimSpace(item.Step)
+		}
+		if content == "" {
+			continue
+		}
+		status := strings.TrimSpace(item.Status)
+		if status == "" {
+			status = "pending"
+		}
+		line := "- [" + status + "] " + content
+		if notes := strings.TrimSpace(item.Notes); notes != "" {
 			line += "\n  Notes: " + notes
 		}
 		lines = append(lines, line)
@@ -417,25 +431,12 @@ func capBody(body string) string {
 // preservedState is the JSON shape of the carried-across-compaction block.
 type preservedState struct {
 	Plan                string                 `json:"plan,omitempty"`
-	Task                *preservedTaskState    `json:"task,omitempty"`
 	RecentEdits         []preservedEdit        `json:"recent_edits,omitempty"`
 	Tools               []preservedTool        `json:"tools,omitempty"`
 	Skills              []preservedSkill       `json:"skills,omitempty"`
 	ProjectInstructions []preservedInstruction `json:"project_instructions,omitempty"`
 }
 
-type preservedTaskState struct {
-	Objective           string     `json:"objective"`
-	Status              taskStatus `json:"status,omitempty"`
-	Pending             int        `json:"pending,omitempty"`
-	InProgress          int        `json:"in_progress,omitempty"`
-	Completed           int        `json:"completed,omitempty"`
-	Failed              int        `json:"failed,omitempty"`
-	VerificationPassed  int        `json:"verification_passed,omitempty"`
-	VerificationFailed  int        `json:"verification_failed,omitempty"`
-	VerificationOutcome Outcome    `json:"verification_outcome,omitempty"`
-}
-
 type preservedEdit struct {
 	Path string `json:"path"`
 	Note string `json:"note,omitempty"`
@@ -463,27 +464,8 @@ type preservedInstruction struct {
 // may live only inside the injected summary message, which on a later compaction
 // lands in middle with no real tool calls left to extract. Fresh tool calls and
 // instruction blocks override the carried-forward copy by name/source.
-func appendPreservedState(summary string, middle []zeroruntime.Message, taskSnapshot *taskStateSnapshot) string {
+func appendPreservedState(summary string, middle []zeroruntime.Message) string {
 	priorState := parsePreservedStateBlock(latestSummaryContent(middle))
-	task := priorState.Task
-	if taskSnapshot != nil {
-		task = &preservedTaskState{
-			Objective: capTaskObjective(taskSnapshot.Objective),
-		}
-		// Plan parity corroborates only the mutable task projection. The objective
-		// comes directly from the run prompt and is immutable, so it must survive
-		// even after compaction removes the plan tool call needed for comparison.
-		if taskSnapshot.PlanParity == taskPlanParityMatch {
-			task.Status = taskSnapshot.Status
-			task.Pending = taskSnapshot.Plan.Pending
-			task.InProgress = taskSnapshot.Plan.InProgress
-			task.Completed = taskSnapshot.Plan.Completed
-			task.Failed = taskSnapshot.Plan.Failed
-			task.VerificationPassed = taskSnapshot.Verification.Passed
-			task.VerificationFailed = taskSnapshot.Verification.Failed
-			task.VerificationOutcome = taskSnapshot.Verification.LastOutcome
-		}
-	}
 
 	// Plan: a fresh update_plan in middle is authoritative; otherwise carry the
 	// plan preserved by an earlier compaction.
@@ -511,25 +493,12 @@ func appendPreservedState(summary string, middle []zeroruntime.Message, taskSnap
 		projectInstructionEntries(middle),
 	)
 
-	if block := formatPreservedState(plan, task, edits, tools, skills, instructions); block != "" {
+	if block := formatPreservedState(plan, edits, tools, skills, instructions); block != "" {
 		summary += "\n\n" + block
 	}
 	return summary
 }
 
-func capTaskObjective(objective string) string {
-	objective = strings.TrimSpace(objective)
-	if len(objective) <= maxTaskObjectiveBytes {
-		return objective
-	}
-	const suffix = "…"
-	limit := maxTaskObjectiveBytes - len(suffix)
-	for limit > 0 && !utf8.RuneStart(objective[limit]) {
-		limit--
-	}
-	return strings.TrimSpace(objective[:limit]) + suffix
-}
-
 // mergeRecentEdits overlays fresh edits onto edits preserved by an earlier
 // compaction. Unlike mergeSkillEntries (which keeps refreshed entries in their
 // original slot), a path touched again by a fresh edit MOVES to the newest
@@ -586,11 +555,11 @@ func preservedEditsToEntries(edits []preservedEdit) []skillEntry {
 
 // formatPreservedState renders state as the labelled, single-line
 // JSON block. Returns "" when there is nothing to preserve.
-func formatPreservedState(plan string, task *preservedTaskState, edits, tools, skills, instructions []skillEntry) string {
-	if plan == "" && task == nil && len(edits) == 0 && len(tools) == 0 && len(skills) == 0 && len(instructions) == 0 {
+func formatPreservedState(plan string, edits, tools, skills, instructions []skillEntry) string {
+	if plan == "" && len(edits) == 0 && len(tools) == 0 && len(skills) == 0 && len(instructions) == 0 {
 		return ""
 	}
-	state := preservedState{Plan: plan, Task: task}
+	state := preservedState{Plan: plan}
 	for _, e := range edits {
 		state.RecentEdits = append(state.RecentEdits, preservedEdit{Path: e.name, Note: e.body})
 	}

internal/agent/compaction_preserve_test.go

@@ -1,7 +1,6 @@
 package agent
 
 import (
-	"encoding/json"
 	"strings"
 	"testing"
 	"unicode/utf8"
@@ -60,103 +59,6 @@ func TestCompactPreservesActivePlan(t *testing.T) {
 	}
 }
 
-func TestCompactPreservesBoundedTaskContext(t *testing.T) {
-	objective := strings.Repeat("世", maxTaskObjectiveBytes)
-	task := newTaskState(objective, nil)
-	task.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"write code","status":"in_progress"},{"content":"add tests","status":"pending"}]}`})
-	messages := stateConversation()
-	compacted, err := Compact(messages, CompactionOptions{
-		PreserveLast: 2,
-		Summarize:    func([]zeroruntime.Message) (string, error) { return "SUMMARY", nil },
-		taskState:    task.snapshotForCompaction(messages),
-	})
-	if err != nil {
-		t.Fatalf("Compact: %v", err)
-	}
-	state := parsePreservedStateBlock(compacted[1].Content)
-	if state.Task == nil || state.Task.Status != taskStatusActive || state.Task.InProgress != 1 || state.Task.Pending != 1 {
-		t.Fatalf("unexpected compact task state: %#v", state.Task)
-	}
-	if len(state.Task.Objective) > maxTaskObjectiveBytes || !utf8.ValidString(state.Task.Objective) {
-		t.Fatalf("objective was not safely bounded: %d bytes %q", len(state.Task.Objective), state.Task.Objective)
-	}
-}
-
-func TestCompactPreservesObjectiveAfterPlanParityMismatch(t *testing.T) {
-	prior := preservedState{Task: &preservedTaskState{Objective: "stale objective", Status: taskStatusActive, Pending: 1}}
-	encoded, err := json.Marshal(prior)
-	if err != nil {
-		t.Fatal(err)
-	}
-	messages := []zeroruntime.Message{
-		{Role: zeroruntime.MessageRoleSystem, Content: "system"},
-		{Role: zeroruntime.MessageRoleUser, Content: summaryLabel + "\nold\n\n" + preservedStateLabel + "\n" + string(encoded)},
-		{Role: zeroruntime.MessageRoleAssistant, Content: "continuing"},
-		{Role: zeroruntime.MessageRoleUser, Content: "more"},
-		{Role: zeroruntime.MessageRoleAssistant, Content: "working"},
-		{Role: zeroruntime.MessageRoleUser, Content: "again"},
-		{Role: zeroruntime.MessageRoleAssistant, Content: "done"},
-	}
-	compacted, err := Compact(messages, CompactionOptions{
-		PreserveLast: 2,
-		Summarize:    func([]zeroruntime.Message) (string, error) { return "SUMMARY", nil },
-		taskState: &taskStateSnapshot{
-			Objective:  "current objective",
-			PlanParity: taskPlanParityMismatch,
-		},
-	})
-	if err != nil {
-		t.Fatalf("Compact: %v", err)
-	}
-	state := parsePreservedStateBlock(compacted[1].Content)
-	if state.Task == nil || state.Task.Objective != "current objective" {
-		t.Fatalf("immutable objective was lost on plan mismatch: %#v", state.Task)
-	}
-	if state.Task.Status != "" || state.Task.Pending != 0 {
-		t.Fatalf("uncorroborated mutable task fields survived plan mismatch: %#v", state.Task)
-	}
-}
-
-func TestTaskObjectiveSurvivesRepeatedCompactionWithoutPlanRefresh(t *testing.T) {
-	task := newTaskState("keep this objective", nil)
-	task.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"write code","status":"in_progress"},{"content":"add tests","status":"pending"}]}`})
-	messages := stateConversation()
-
-	first, err := Compact(messages, CompactionOptions{
-		PreserveLast: 2,
-		Summarize:    func([]zeroruntime.Message) (string, error) { return "FIRST", nil },
-		taskState:    task.snapshotForCompaction(messages),
-	})
-	if err != nil {
-		t.Fatalf("first Compact: %v", err)
-	}
-	secondInput := append(append([]zeroruntime.Message{}, first...),
-		zeroruntime.Message{Role: zeroruntime.MessageRoleUser, Content: "more"},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, Content: "working"},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleUser, Content: "again"},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, Content: "done"},
-	)
-	snapshot := task.snapshotForCompaction(secondInput)
-	if snapshot.PlanParity != taskPlanParityMismatch {
-		t.Fatalf("plan call should be absent after first compaction, parity=%q", snapshot.PlanParity)
-	}
-	second, err := Compact(secondInput, CompactionOptions{
-		PreserveLast: 2,
-		Summarize:    func([]zeroruntime.Message) (string, error) { return "SECOND", nil },
-		taskState:    snapshot,
-	})
-	if err != nil {
-		t.Fatalf("second Compact: %v", err)
-	}
-	state := parsePreservedStateBlock(second[1].Content)
-	if state.Task == nil || state.Task.Objective != "keep this objective" {
-		t.Fatalf("objective lost after second compaction: %#v", state.Task)
-	}
-	if state.Task.Status != "" || state.Task.InProgress != 0 {
-		t.Fatalf("uncorroborated mutable fields survived second compaction: %#v", state.Task)
-	}
-}
-
 func TestCompactPreservesLoadedSkills(t *testing.T) {
 	summary := compactStateConversation(t, stateConversation())
 	if !strings.Contains(summary, preservedStateLabel) {
@@ -381,10 +283,12 @@ func TestExtractLatestPlanReturnsMostRecent(t *testing.T) {
 	}
 }
 
-func TestFormatPlanArgumentsRejectsUnsupportedStepAlias(t *testing.T) {
+func TestFormatPlanArgumentsAcceptsStepAlias(t *testing.T) {
 	got := formatPlanArguments(`{"plan":[{"step":"write failing test","status":"in_progress"},{"content":"keep existing shape","status":"pending"}]}`)
-	if got != "" {
-		t.Fatalf("unsupported alias should reject the whole plan like update_plan, got %q", got)
+	for _, want := range []string{"- [in_progress] write failing test", "- [pending] keep existing shape"} {
+		if !strings.Contains(got, want) {
+			t.Fatalf("expected %q in formatted plan, got %q", want, got)
+		}
 	}
 }
 

internal/agent/compaction_test.go

@@ -581,7 +581,7 @@ func TestCompactNeverProducesConsecutiveUserMessages(t *testing.T) {
 }
 
 func TestRecoverNoopDoesNotConsumeReactiveBudget(t *testing.T) {
-	st := newCompactionState(Options{ContextWindow: 1000, CompactionPreserveLast: 2}, nil)
+	st := newCompactionState(Options{ContextWindow: 1000, CompactionPreserveLast: 2})
 	provider := &mockProvider{turns: [][]zeroruntime.StreamEvent{{
 		{Type: zeroruntime.StreamEventText, Content: "SUMMARY"}, {Type: zeroruntime.StreamEventDone},
 	}}}
@@ -628,7 +628,7 @@ func TestRecoverNoopDoesNotConsumeReactiveBudget(t *testing.T) {
 }
 
 func TestRecoverDisabledIsNoop(t *testing.T) {
-	st := newCompactionState(Options{ContextWindow: 0}, nil)
+	st := newCompactionState(Options{ContextWindow: 0})
 	msgs := []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "x"}}
 	called := false
 	// recover must not invoke the provider/summarize when disabled, even on a

internal/agent/completion_policy.go

@@ -39,7 +39,7 @@ func newCompletionPolicy(requireSemanticCheck bool) *completionPolicy {
 	return &completionPolicy{requireSemanticCheck: requireSemanticCheck}
 }
 
-func (policy *completionPolicy) evaluate(text string, context completionContext) completionEvaluation {
+func (policy *completionPolicy) evaluate(text string, planPending bool) completionEvaluation {
 	// A direct admission is strong local evidence and takes precedence over all
 	// weaker signals, avoiding both continuation nudges and semantic checks.
 	if reason := selfReportedIncompletion(text); reason != "" {
@@ -50,7 +50,7 @@ func (policy *completionPolicy) evaluate(text string, context completionContext)
 	// weak evidence because bookkeeping can be stale. Both get a bounded chance
 	// to continue, but only a persisted cue is ultimately incomplete.
 	cue := endsWithContinuationCue(text)
-	if cue || context.PlanPending {
+	if cue || planPending {
 		if policy.continueNudges < maxContinueNudges {
 			policy.continueNudges++
 			reason := "your message ended mid-step"

internal/agent/completion_policy_test.go

@@ -1,19 +1,16 @@
 package agent
 
-import (
-	"strings"
-	"testing"
-)
+import "testing"
 
 func TestCompletionPolicyLocalEvidenceDecidesWithoutSemanticCheck(t *testing.T) {
 	policy := newCompletionPolicy(false)
 
-	complete := policy.evaluate("Done. All required checks pass.", completionContext{})
+	complete := policy.evaluate("Done. All required checks pass.", false)
 	if complete.Decision != CompletionComplete {
 		t.Fatalf("confident completion decision = %q, want %q", complete.Decision, CompletionComplete)
 	}
 
-	incomplete := policy.evaluate("I couldn't verify the result, so this is my best guess.", completionContext{})
+	incomplete := policy.evaluate("I couldn't verify the result, so this is my best guess.", false)
 	if incomplete.Decision != CompletionIncomplete {
 		t.Fatalf("admitted failure decision = %q, want %q", incomplete.Decision, CompletionIncomplete)
 	}
@@ -22,13 +19,13 @@ func TestCompletionPolicyLocalEvidenceDecidesWithoutSemanticCheck(t *testing.T)
 func TestCompletionPolicyPreservesBoundedPlanStallProtection(t *testing.T) {
 	policy := newCompletionPolicy(false)
 	for attempt := 0; attempt < maxContinueNudges; attempt++ {
-		got := policy.evaluate("Let me inspect the remaining configuration:", completionContext{PlanPending: true})
+		got := policy.evaluate("Let me inspect the remaining configuration:", true)
 		if got.Decision != CompletionUncertain || got.Action != completionActionContinue {
 			t.Fatalf("attempt %d = (%q, %q), want uncertain continue", attempt+1, got.Decision, got.Action)
 		}
 	}
 
-	got := policy.evaluate("Let me inspect the remaining configuration:", completionContext{PlanPending: true})
+	got := policy.evaluate("Let me inspect the remaining configuration:", true)
 	if got.Decision != CompletionIncomplete {
 		t.Fatalf("decision after nudge budget = %q, want %q", got.Decision, CompletionIncomplete)
 	}
@@ -37,13 +34,13 @@ func TestCompletionPolicyPreservesBoundedPlanStallProtection(t *testing.T) {
 func TestCompletionPolicyTreatsPendingPlanAsWeakEvidence(t *testing.T) {
 	policy := newCompletionPolicy(false)
 	for attempt := 0; attempt < maxContinueNudges; attempt++ {
-		got := policy.evaluate("All set.", completionContext{PlanPending: true})
+		got := policy.evaluate("All set.", true)
 		if got.Decision != CompletionUncertain || got.Action != completionActionContinue {
 			t.Fatalf("attempt %d = (%q, %q), want uncertain continue", attempt+1, got.Decision, got.Action)
 		}
 	}
 
-	got := policy.evaluate("All set.", completionContext{PlanPending: true})
+	got := policy.evaluate("All set.", true)
 	if got.Decision != CompletionComplete {
 		t.Fatalf("stale plan decision after nudge budget = %q, want %q", got.Decision, CompletionComplete)
 	}
@@ -52,12 +49,12 @@ func TestCompletionPolicyTreatsPendingPlanAsWeakEvidence(t *testing.T) {
 func TestCompletionPolicyAllowsExactlyOneRequiredSemanticCheck(t *testing.T) {
 	policy := newCompletionPolicy(true)
 
-	first := policy.evaluate("Implemented and tested.", completionContext{})
+	first := policy.evaluate("Implemented and tested.", false)
 	if first.Decision != CompletionUncertain || first.Action != completionActionSemanticCheck {
 		t.Fatalf("first decision = (%q, %q), want uncertain semantic check", first.Decision, first.Action)
 	}
 
-	second := policy.evaluate("PASS. The result meets the task criterion.", completionContext{})
+	second := policy.evaluate("PASS. The result meets the task criterion.", false)
 	if second.Decision != CompletionComplete {
 		t.Fatalf("post-check decision = %q, want %q", second.Decision, CompletionComplete)
 	}
@@ -65,11 +62,3 @@ func TestCompletionPolicyAllowsExactlyOneRequiredSemanticCheck(t *testing.T) {
 		t.Fatal("semantic check was requested more than once")
 	}
 }
-
-func TestAcceptanceVerificationNudgeIncludesBoundedObjective(t *testing.T) {
-	objective := "make the requested behavior observable"
-	nudge := acceptanceVerificationNudge(objective)
-	if !strings.Contains(nudge, "Task objective: "+objective) {
-		t.Fatalf("semantic check was not grounded in the objective: %q", nudge)
-	}
-}

internal/agent/guardrails.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"encoding/json"
 	"strconv"
 	"strings"
 
@@ -126,8 +127,9 @@ func endsWithContinuationCue(text string) bool {
 // which the update_plan tool coerces to "pending") counts as remaining, matching
 // that tool's own status normalization.
 func planStatusRemaining(status string) bool {
-	switch normalizeTaskPlanStatus(status) {
-	case "completed", "failed":
+	switch strings.ToLower(strings.TrimSpace(status)) {
+	case "completed", "complete", "done", "finished", "resolved", "✓", "x", "[x]",
+		"failed", "fail", "error", "errored", "blocked", "cancelled", "canceled", "abandoned", "skipped":
 		return false
 	default:
 		return true
@@ -305,8 +307,8 @@ func hasAnyPrefix(s string, prefixes []string) bool {
 // the bug-hunt surfaced: well-formed output treated as correct; pre-existing tests
 // passing treated as the objective being met; and a result that merely matches a
 // baseline the task asked to beat or improve. General — no task-specific content.
-func acceptanceVerificationNudge(objective string) string {
-	nudge := "Before this task can be marked complete, " + acceptanceNudgeMarker + " — " +
+func acceptanceVerificationNudge() string {
+	return "Before this task can be marked complete, " + acceptanceNudgeMarker + " — " +
 		"NOT the shape or format of your output, NOT that pre-existing tests pass, and NOT that your " +
 		"result merely matches a baseline you were asked to beat or improve. " +
 		"Re-read the original task, then run a concrete check that exercises the actual requirement: " +
@@ -314,10 +316,6 @@ func acceptanceVerificationNudge(objective string) string {
 		"thing the task asked you to produce, recover, fix, or optimize. " +
 		"If that check passes, reply PASS and cite the evidence. " +
 		"If it does not pass — or you cannot run such a check — say so plainly and keep working; do not claim success."
-	if objective = capTaskObjective(objective); objective != "" {
-		nudge += "\n\nTask objective: " + objective
-	}
-	return nudge
 }
 
 // toolFailureHintMarker is a stable substring for tests.
@@ -555,12 +553,16 @@ func (state *guardState) pendingPlanItems() bool {
 // many items are still remaining. Malformed arguments leave the prior count
 // unchanged (best-effort — the plan panel itself tolerates the same).
 func (state *guardState) observePlanUpdate(arguments string) {
-	plan, ok := parseTaskPlan(arguments)
-	if !ok {
+	var parsed struct {
+		Plan []struct {
+			Status string `json:"status"`
+		} `json:"plan"`
+	}
+	if json.Unmarshal([]byte(arguments), &parsed) != nil {
 		return
 	}
 	pending := 0
-	for _, item := range plan {
+	for _, item := range parsed.Plan {
 		if planStatusRemaining(item.Status) {
 			pending++
 		}

internal/agent/loop.go

@@ -181,20 +181,10 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 	options.runPermissions = runPermissions
 	defer runPermissions.cleanup()
 
-	promptParts := buildSystemPromptParts(options)
-	messages := zeroruntime.SeedMessagesWithImages(promptParts.prompt, prompt, options.Images)
+	messages := zeroruntime.SeedMessagesWithImages(buildSystemPrompt(options), prompt, options.Images)
 
 	guards := newGuardState()
-	task := newTaskState(prompt, options.Trace)
-	compactor := newCompactionState(options, task)
-	defer func() {
-		// A final transcript comparison is observational. It records drift but
-		// never rewrites the result or changes execution after the fact.
-		task.observePlanParity(result.Messages)
-		// Tool-result observations are intentionally coalesced; this final event
-		// guarantees their aggregate counts are present even on an early return.
-		task.emit()
-	}()
+	compactor := newCompactionState(options)
 	// The execution-profile posture controller. nil Options.Profile (every
 	// existing caller) makes every observe/decide call a no-op, keeping the
 	// loop byte-identical for unprofiled runs.
@@ -278,14 +268,16 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 		exposed, _ := partitionToolsCached(registry, permissionMode, options, loaded, toolDefCache)
 		toolPartitionSpan.End()
 
-		// Fingerprint the exact system prompt built at run start plus this turn's
-		// provider-visible tool definitions in their emitted order. Reusing the
-		// retained prompt parts avoids rebuilding workspace context while ensuring
-		// the trace describes the same bytes carried by the request.
+		// Prompt-prefix fingerprint: hash the seven cacheable sub-components
+		// of this turn's request (system prompt sections, project context,
+		// skills, partitioned tool list, tool schemas) and emit one trace
+		// event. Stable across turns => cacheable. Drift in any sub-hash
+		// names the sub-component that broke the cache for this turn. The
+		// computation is pure and cheap (seven SHA-256s of small strings)
+		// and is a no-op when tracing is off.
 		if options.Trace != nil {
-			fp := computePrefixFingerprint(buildPromptSubstringsFromParts(promptParts, exposed))
+			fp := ComputePrefixFingerprint(options, exposed)
 			options.Trace.EmitPrefixHash(trace.PrefixHash{
-				SystemPromptHash:       fp.SystemPromptHash,
 				BaseInstructionsHash:   fp.BaseInstructionsHash,
 				ConfirmationPolicyHash: fp.ConfirmationPolicyHash,
 				ProjectContextHash:     fp.ProjectContextHash,
@@ -579,9 +571,7 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 			// model's final answer ONLY when the work is actually done. Default off
 			// (RequireCompletionSignal), so interactive runs stay byte-identical.
 			if options.RequireCompletionSignal {
-				completionContext := task.completionContext(messages, guards.pendingPlanItems())
-				evaluation := completionPolicy.evaluate(collected.Text, completionContext)
-				task.observe(taskStateEvent{kind: taskStateEventCompletion, completion: evaluation})
+				evaluation := completionPolicy.evaluate(collected.Text, guards.pendingPlanItems())
 				switch evaluation.Decision {
 				case CompletionIncomplete:
 					result.Incomplete = true
@@ -606,15 +596,13 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 						options.Trace.Counter(trace.CounterAcceptanceChecks, 1)
 						messages = append(messages, zeroruntime.Message{
 							Role:    zeroruntime.MessageRoleUser,
-							Content: acceptanceVerificationNudge(completionContext.Objective),
+							Content: acceptanceVerificationNudge(),
 						})
 					}
 					continue
 				case CompletionComplete:
 					// Local evidence is sufficient; proceed to final diagnostics.
 				}
-			} else {
-				task.observe(taskStateEvent{kind: taskStateEventCompletion, completion: completionEvaluation{Decision: CompletionComplete}})
 			}
 			// Finalization diagnostics gate: edits from this run may still have
 			// checks in flight — the per-turn drain waits only briefly and defers
@@ -638,11 +626,6 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 		// executing so the empty-turn counter resets and plan-tracking signals
 		// stay current.
 		guards.observeTurn(collected)
-		for _, call := range collected.ToolCalls {
-			if call.Name == planToolName {
-				task.observe(taskStateEvent{kind: taskStateEventPlan, arguments: call.Arguments})
-			}
-		}
 
 		failureHint := ""
 		// turnRequestedModel records the FIRST mid-run escalation target requested
@@ -694,7 +677,6 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 			}
 			options.Trace.Counter(trace.CounterToolCalls, 1)
 			recordOutputBudgetTrace(options.Trace, toolResult)
-			task.observe(taskStateEvent{kind: taskStateEventToolResult, toolResult: toolResult})
 			if options.OnToolResult != nil {
 				options.OnToolResult(toolResult)
 			}
@@ -776,7 +758,6 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 		if options.SelfCorrect != nil && len(changedFilesThisBatch) > 0 {
 			feedback, selfCorrectOutcome := options.SelfCorrect.AfterEdit(ctx, dedupeStrings(changedFilesThisBatch))
 			posture.observeSelfCorrect(selfCorrectOutcome)
-			task.observe(taskStateEvent{kind: taskStateEventVerification, verification: selfCorrectOutcome})
 			if feedback != "" {
 				messages = append(messages, zeroruntime.Message{
 					Role:    zeroruntime.MessageRoleUser,

internal/agent/loop_test.go

@@ -8,7 +8,6 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"reflect"
 	"runtime"
 	"strings"
 	"testing"
@@ -1259,46 +1258,6 @@ func TestRunExecutesToolCallThroughRegistry(t *testing.T) {
 	}
 }
 
-func TestRunPreservesRequestPrefixAcrossTurns(t *testing.T) {
-	root := t.TempDir()
-	writeAgentTestFile(t, filepath.Join(root, "notes.txt"), "alpha\n")
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewReadFileTool(root))
-	provider := &mockProvider{turns: [][]zeroruntime.StreamEvent{
-		{
-			{Type: zeroruntime.StreamEventToolCallStart, ToolCallID: "call-1", ToolName: "read_file"},
-			{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "call-1", ArgumentsFragment: `{"path":"notes.txt"}`},
-			{Type: zeroruntime.StreamEventToolCallEnd, ToolCallID: "call-1"},
-			{Type: zeroruntime.StreamEventDone},
-		},
-		{
-			{Type: zeroruntime.StreamEventText, Content: "done"},
-			{Type: zeroruntime.StreamEventDone},
-		},
-	}}
-
-	if _, err := Run(context.Background(), "read notes", provider, Options{
-		Cwd:       root,
-		Registry:  registry,
-		SessionID: "session-stable-prefix",
-	}); err != nil {
-		t.Fatal(err)
-	}
-	if len(provider.requests) != 2 {
-		t.Fatalf("provider requests = %d, want 2", len(provider.requests))
-	}
-	first, second := provider.requests[0], provider.requests[1]
-	if len(second.Messages) < len(first.Messages) || !reflect.DeepEqual(second.Messages[:len(first.Messages)], first.Messages) {
-		t.Fatalf("first request messages must be an exact prefix of the second:\nfirst=%#v\nsecond=%#v", first.Messages, second.Messages)
-	}
-	if !reflect.DeepEqual(first.Tools, second.Tools) {
-		t.Fatalf("tool definitions drifted between turns:\nfirst=%#v\nsecond=%#v", first.Tools, second.Tools)
-	}
-	if first.PromptCacheKey != "session-stable-prefix" || second.PromptCacheKey != first.PromptCacheKey {
-		t.Fatalf("prompt cache key must remain stable: first=%q second=%q", first.PromptCacheKey, second.PromptCacheKey)
-	}
-}
-
 func TestRunSanitizesMalformedToolCallArgumentsBeforeRetry(t *testing.T) {
 	root := t.TempDir()
 	registry := tools.NewRegistry()

internal/agent/prompt_fingerprint.go

@@ -11,11 +11,12 @@ import (
 	"github.com/Gitlawb/zero/internal/zeroruntime"
 )
 
-// promptSubstrings are the cacheable components of the prompt a run sends to a
-// model. systemPrompt is the exact joined system-message content. The remaining
-// fields retain useful diagnostic boundaries within that prompt and tool list.
+// promptSubstrings are the seven cacheable sub-components of the prompt a run
+// sends to a model. Each is the literal content the sub-component would emit
+// into the system prompt or tool list, hashed so a downstream observer can
+// detect drift turn-over-turn. The substrings are produced by
+// buildPromptSubstrings and consumed by ComputePrefixFingerprint.
 type promptSubstrings struct {
-	systemPrompt       string
 	baseInstructions   string
 	confirmationPolicy string
 	projectContext     string
@@ -24,55 +25,92 @@ type promptSubstrings struct {
 	schema             string
 }
 
-// buildPromptSubstrings builds the prompt and retains both its exact joined
-// form and narrower diagnostic components. Callers that already built the
-// prompt should use buildPromptSubstringsFromParts to avoid repeating workspace
-// reads.
+// buildPromptSubstrings assembles the seven cacheable sub-components of the
+// prompt without joining them. The system prompt sections are produced by the
+// same private builders that buildSystemPrompt uses, so the substrings are
+// byte-identical to what would have appeared in the joined prompt. The tools
+// and schema substrings are derived from the partitioned tool list (caller-
+// provided) so this helper does not need to re-run the partition.
+//
+// This is the seam ComputePrefixFingerprint reads from. It exists as a
+// separate function (rather than returning both prompt and substrings from
+// buildSystemPrompt) so existing callers of buildSystemPrompt are unaffected
+// and the substrings helper is independently testable.
 func buildPromptSubstrings(options Options, exposed []zeroruntime.ToolDefinition) promptSubstrings {
-	return buildPromptSubstringsFromParts(buildSystemPromptParts(options), exposed)
-}
+	core := strings.TrimSpace(options.SystemPrompt)
+	if core == "" {
+		core = strings.TrimSpace(coreSystemPrompt)
+	}
+	if core == "" {
+		core = fallbackSystemPrompt
+	}
 
-func buildPromptSubstringsFromParts(parts systemPromptParts, exposed []zeroruntime.ToolDefinition) promptSubstrings {
+	// The confirmation policy is appended unconditionally in buildSystemPrompt;
+	// the substring here is the same constant.
+	policy := strings.TrimSpace(confirmationPolicy)
+
+	// projectContext is the joined output of workspaceContext, which itself
+	// walks the AGENTS.md / ZERO.md / .zero/AGENTS.md chain. Hashing the
+	// joined string captures every guideline file's contribution and the
+	// ordering between them.
+	project := workspaceContext(options.Cwd)
+
+	// skills is the joined output of skillsContext, with each skill on its own
+	// line. The substring is the literal text the model would see.
+	skills := skillsContext(options)
+
+	// tools and schema are derived from the partitioned tool list. The list
+	// passed in is already in stable order (partitionToolsCached is the
+	// canonical stable partitioner) so concatenating in slice order is
+	// sufficient — we sort names again defensively in case a future caller
+	// hands us a list from a different partitioner.
 	toolsSubstr, schemaSubstr := toolSubstrings(exposed)
 
 	return promptSubstrings{
-		systemPrompt:       parts.prompt,
-		baseInstructions:   parts.baseInstructions,
-		confirmationPolicy: parts.confirmationPolicy,
-		projectContext:     parts.projectContext,
-		skills:             parts.skills,
+		baseInstructions:   core,
+		confirmationPolicy: policy,
+		projectContext:     project,
+		skills:             skills,
 		tools:              toolsSubstr,
 		schema:             schemaSubstr,
 	}
 }
 
-// toolSubstrings preserves the emitted tool order. Names and descriptions are
-// fingerprinted separately from schemas so either kind of drift is identifiable.
-// Order is part of request identity: silently sorting here would hide a provider-
-// visible reordering and could report a false cache hit.
+// toolSubstrings extracts a stable, name-sorted digest of the partitioned tool
+// list. The tools substring is "name1\nname2\n..." (sorted) so a reordering of
+// the partition produces a different hash. The schema substring is the
+// concatenation of each tool's JSON schema in name order, so a schema change
+// is detected independently of the tool ordering.
 func toolSubstrings(exposed []zeroruntime.ToolDefinition) (toolsSubstr, schemaSubstr string) {
 	if len(exposed) == 0 {
 		return "", ""
 	}
-	var toolsSB, schemaSB strings.Builder
+	names := make([]string, 0, len(exposed))
+	byName := make(map[string]zeroruntime.ToolDefinition, len(exposed))
 	for _, def := range exposed {
-		writeLengthPrefixed(&toolsSB, def.Name)
-		writeLengthPrefixed(&toolsSB, def.Description)
+		names = append(names, def.Name)
+		byName[def.Name] = def
+	}
+	sort.Strings(names)
+	var toolsSB, schemaSB strings.Builder
+	for i, name := range names {
+		if i > 0 {
+			toolsSB.WriteByte('\n')
+		}
+		toolsSB.WriteString(name)
+		def := byName[name]
 		// Parameters is rendered to a canonical JSON string per tool. The
 		// schema-render cache in internal/agent (used by partitionToolsCached)
 		// guarantees the same render is byte-identical across turns for the
 		// same tool, so this substring is a stable hash input.
-		writeLengthPrefixed(&schemaSB, def.Name)
-		writeLengthPrefixed(&schemaSB, canonicalSchemaString(def.Parameters))
+		schemaSB.WriteString(name)
+		schemaSB.WriteByte('\n')
+		schemaSB.WriteString(canonicalSchemaString(def.Parameters))
+		schemaSB.WriteByte('\n')
 	}
 	return toolsSB.String(), schemaSB.String()
 }
 
-func writeLengthPrefixed(sb *strings.Builder, value string) {
-	fmt.Fprintf(sb, "%d:", len(value))
-	sb.WriteString(value)
-}
-
 // canonicalSchemaString renders a tool's parameter schema to a stable string.
 // tools.ToolDef.Parameters is a map[string]any in the common case; Go's
 // fmt.Sprintf("%v", m) iterates a map in random order, which would produce
@@ -189,16 +227,36 @@ func writeStable(sb *strings.Builder, v any) {
 	}
 }
 
-// ComputePrefixFingerprint builds and fingerprints a prompt for callers that do
-// not already have one. The agent loop uses computePrefixFingerprint with the
-// prompt parts it built once at run start, ensuring tracing observes the exact
-// request content without repeating workspace I/O.
-func ComputePrefixFingerprint(options Options, exposed []zeroruntime.ToolDefinition) prefixFingerprint {
-	return computePrefixFingerprint(buildPromptSubstrings(options, exposed))
-}
+// ComputePrefixFingerprint returns a trace.PrefixHash (a 7-field fingerprint
+// of the prompt prefix) for one turn of a run. The seven sub-hashes are
+// independent SHA-256s of the corresponding sub-component; the complete-prefix
+// hash is a SHA-256 of the canonical concatenation of the other six, so any
+// sub-component drift is observable both individually and in aggregate.
+//
+// I/O side effects: buildPromptSubstrings calls workspaceContext, which runs
+// git (gitBranchForPrompt, FindProjectGitRoot) and reads the AGENTS.md /
+// ZERO.md / .zero/AGENTS.md chain plus the repo map. The same workspace-
+// context work is performed separately by buildSystemPrompt a few lines
+// later in the request-build path, so on every traced turn the file and
+// git reads happen twice. The duplication is intentional for this PR (a
+// follow-up will pass substrings through) and is a known perf cost only on
+// the opt-in trace path.
+//
+// A stable CompletePrefixHash across turns means the four captured
+// sub-components (baseInstructions, confirmationPolicy, projectContext,
+// skills) are byte-identical. It does NOT rule out drift in the seven
+// uncaptured sections of buildSystemPrompt (modelPromptAddendum,
+// sessionRuntimeContext, approvedCommandPrefixContext, workspaceSeedContext,
+// userGuidelines, specialistDelegationContext, responseStyleContext). For
+// default Options the four captured substrings are the full prompt; for
+// non-default Options the seven uncaptured sections may contribute, and a
+// consumer correlating CompletePrefix stability with cached_input_tokens
+// must cross-check the model_switches counter (modelPromptAddendum changes
+// on a model switch) to disambiguate "no drift" from "drift in an
+// uncaptured section."
 
-func computePrefixFingerprint(subs promptSubstrings) prefixFingerprint {
-	systemPrompt := sha256hex(subs.systemPrompt)
+func ComputePrefixFingerprint(options Options, exposed []zeroruntime.ToolDefinition) prefixFingerprint {
+	subs := buildPromptSubstrings(options, exposed)
 	base := sha256hex(subs.baseInstructions)
 	policy := sha256hex(subs.confirmationPolicy)
 	project := sha256hex(subs.projectContext)
@@ -206,10 +264,9 @@ func computePrefixFingerprint(subs promptSubstrings) prefixFingerprint {
 	toolsH := sha256hex(subs.tools)
 	schema := sha256hex(subs.schema)
 	complete := sha256hex(strings.Join([]string{
-		systemPrompt, toolsH, schema,
+		base, policy, project, skills, toolsH, schema,
 	}, "|"))
 	return prefixFingerprint{
-		SystemPromptHash:       systemPrompt,
 		BaseInstructionsHash:   base,
 		ConfirmationPolicyHash: policy,
 		ProjectContextHash:     project,
@@ -225,7 +282,6 @@ func computePrefixFingerprint(subs promptSubstrings) prefixFingerprint {
 // in loop.go) so the trace package does not need to import this one. The field
 // names match the trace.PrefixHash JSON tags 1:1.
 type prefixFingerprint struct {
-	SystemPromptHash       string
 	BaseInstructionsHash   string
 	ConfirmationPolicyHash string
 	ProjectContextHash     string

internal/agent/prompt_fingerprint_test.go

@@ -28,28 +28,38 @@ func TestComputePrefixFingerprintStableAcrossCalls(t *testing.T) {
 	}
 }
 
-// Tool order and descriptions are provider-visible and therefore part of the
-// cacheable prefix identity.
-func TestComputePrefixFingerprintToolsHashMatchesEmittedOrderAndDescriptions(t *testing.T) {
+// TestComputePrefixFingerprintToolsHashIsNameSetSensitive asserts the
+// name-set sensitivity of the ToolsHash. The test name used to read as
+// "reorder changes hash" but the assertion is the opposite: the hash is
+// name-set sensitive, not name-order sensitive (toolSubstrings sorts
+// names before hashing). The partitioner is expected to produce a stable
+// order, so a name-order change is not a hash signal — a name-set change
+// is. The test asserts both: permutation of the same tools produces the
+// same hash, and adding a tool produces a different hash.
+func TestComputePrefixFingerprintToolsHashIsNameSetSensitive(t *testing.T) {
 	opts := Options{Cwd: t.TempDir(), SystemPrompt: "core"}
 	a := []zeroruntime.ToolDefinition{
-		{Name: "read_file", Description: "read", Parameters: map[string]any{"schema": "schema-read"}},
-		{Name: "grep", Description: "search", Parameters: map[string]any{"schema": "schema-grep"}},
+		{Name: "read_file", Parameters: map[string]any{"schema": "schema-read"}},
+		{Name: "grep", Parameters: map[string]any{"schema": "schema-grep"}},
 	}
 	b := []zeroruntime.ToolDefinition{
-		{Name: "grep", Description: "search", Parameters: map[string]any{"schema": "schema-grep"}},
-		{Name: "read_file", Description: "read", Parameters: map[string]any{"schema": "schema-read"}},
+		{Name: "grep", Parameters: map[string]any{"schema": "schema-grep"}},
+		{Name: "read_file", Parameters: map[string]any{"schema": "schema-read"}},
 	}
+	// toolSubstrings sorts names internally, so the ToolsHash is identical
+	// for a permutation of the same tools. We assert that here to document
+	// the contract: name-order independence, name-set sensitivity.
 	fpA := ComputePrefixFingerprint(opts, a)
 	fpB := ComputePrefixFingerprint(opts, b)
-	if fpA.ToolsHash == fpB.ToolsHash {
-		t.Fatalf("ToolsHash must change when emitted order changes: a=%s b=%s", fpA.ToolsHash, fpB.ToolsHash)
+	if fpA.ToolsHash != fpB.ToolsHash {
+		t.Fatalf("ToolsHash must be name-set sensitive, not name-order sensitive: a=%s b=%s", fpA.ToolsHash, fpB.ToolsHash)
 	}
-	c := append([]zeroruntime.ToolDefinition(nil), a...)
-	c[0].Description = "read a file"
+	// A different tool set must produce a different ToolsHash.
+	c := append([]zeroruntime.ToolDefinition{}, a...)
+	c = append(c, zeroruntime.ToolDefinition{Name: "bash", Parameters: map[string]any{"schema": "schema-bash"}})
 	fpC := ComputePrefixFingerprint(opts, c)
 	if fpA.ToolsHash == fpC.ToolsHash {
-		t.Fatalf("ToolsHash must change when a description changes: a=%s c=%s", fpA.ToolsHash, fpC.ToolsHash)
+		t.Fatalf("ToolsHash must change when the tool set changes: a=%s c=%s", fpA.ToolsHash, fpC.ToolsHash)
 	}
 }
 
@@ -91,35 +101,25 @@ func TestComputePrefixFingerprintSystemPromptChangeChangesBaseHash(t *testing.T)
 	}
 }
 
-// CompletePrefixHash represents the exact joined system prompt and the ordered
-// tool definitions. Narrower system-section hashes remain diagnostic only.
+// TestComputePrefixFingerprintCompleteIsAggregateOfSubHashes asserts the
+// canonical-join property: CompletePrefixHash must depend on every sub-hash.
+// This is the regression catch for "did anyone reorder or drop a sub-hash
+// from the canonical join without updating CompletePrefixHash."
 func TestComputePrefixFingerprintCompleteIsAggregateOfSubHashes(t *testing.T) {
 	opts := Options{Cwd: t.TempDir(), SystemPrompt: "core"}
 	exposed := []zeroruntime.ToolDefinition{{Name: "read_file", Parameters: map[string]any{"k": "v"}}}
 	fp := ComputePrefixFingerprint(opts, exposed)
 	// Manually compute what the canonical join should be.
 	expected := sha256hex(strings.Join([]string{
-		fp.SystemPromptHash,
+		fp.BaseInstructionsHash,
+		fp.ConfirmationPolicyHash,
+		fp.ProjectContextHash,
+		fp.SkillsHash,
 		fp.ToolsHash,
 		fp.SchemaHash,
 	}, "|"))
 	if fp.CompletePrefixHash != expected {
-		t.Fatalf("CompletePrefixHash must equal sha256hex of the exact system, tools, and schema hashes:\n  got:      %s\n  expected: %s", fp.CompletePrefixHash, expected)
-	}
-}
-
-func TestComputePrefixFingerprintCoversEverySystemPromptSection(t *testing.T) {
-	base := Options{Cwd: t.TempDir(), SystemPrompt: "core", Model: "gpt-5"}
-	changed := base
-	changed.ResponseStyle = "concise"
-
-	fpBase := ComputePrefixFingerprint(base, nil)
-	fpChanged := ComputePrefixFingerprint(changed, nil)
-	if fpBase.SystemPromptHash == fpChanged.SystemPromptHash {
-		t.Fatal("SystemPromptHash must change when any rendered system section changes")
-	}
-	if fpBase.CompletePrefixHash == fpChanged.CompletePrefixHash {
-		t.Fatal("CompletePrefixHash must include the exact full system prompt")
+		t.Fatalf("CompletePrefixHash must equal sha256hex of the canonical join of the other six:\n  got:      %s\n  expected: %s", fp.CompletePrefixHash, expected)
 	}
 }
 
@@ -141,9 +141,6 @@ func TestBuildPromptSubstringsDefaultOptions(t *testing.T) {
 	if subs.baseInstructions != "test core" {
 		t.Fatalf("baseInstructions substring must equal the core system prompt: got %q want %q", subs.baseInstructions, "test core")
 	}
-	if subs.systemPrompt != buildSystemPrompt(opts) {
-		t.Fatal("systemPrompt substring must equal the exact joined system prompt")
-	}
 	if subs.confirmationPolicy == "" {
 		t.Fatalf("confirmationPolicy substring must be non-empty (the embedded policy is always present)")
 	}
@@ -154,9 +151,6 @@ func TestBuildPromptSubstringsDefaultOptions(t *testing.T) {
 	// sha256hex of the substrings, with no truncation or reformatting
 	// between the two layers.
 	fp := ComputePrefixFingerprint(opts, nil)
-	if fp.SystemPromptHash != sha256hex(subs.systemPrompt) {
-		t.Fatalf("SystemPromptHash in fingerprint must equal sha256hex of the joined prompt")
-	}
 	if fp.BaseInstructionsHash != sha256hex(subs.baseInstructions) {
 		t.Fatalf("BaseInstructionsHash in fingerprint must equal sha256hex of the substring")
 	}

internal/agent/system_prompt.go

@@ -70,22 +70,6 @@ const (
 // guidelines), and the safety confirmation policy. It is built once per run so
 // every turn shares one (cacheable) system turn.
 func buildSystemPrompt(options Options) string {
-	return buildSystemPromptParts(options).prompt
-}
-
-// systemPromptParts retains both the exact joined prompt and the diagnostic
-// sections used by prompt-prefix tracing. Building these together prevents the
-// tracing path from re-reading workspace state and guarantees that the hash is
-// computed from the same prompt bytes placed in the request.
-type systemPromptParts struct {
-	prompt             string
-	baseInstructions   string
-	confirmationPolicy string
-	projectContext     string
-	skills             string
-}
-
-func buildSystemPromptParts(options Options) systemPromptParts {
 	core := strings.TrimSpace(options.SystemPrompt)
 	if core == "" {
 		core = strings.TrimSpace(coreSystemPrompt)
@@ -113,31 +97,22 @@ func buildSystemPromptParts(options Options) systemPromptParts {
 	if user := userGuidelines(); user != "" {
 		sections = append(sections, user)
 	}
-	project := workspaceContext(options.Cwd)
-	if project != "" {
-		sections = append(sections, project)
+	if ws := workspaceContext(options.Cwd); ws != "" {
+		sections = append(sections, ws)
 	}
 	if delegation := specialistDelegationContext(options); delegation != "" {
 		sections = append(sections, delegation)
 	}
-	skillsBlock := skillsContext(options)
-	if skillsBlock != "" {
+	if skillsBlock := skillsContext(options); skillsBlock != "" {
 		sections = append(sections, skillsBlock)
 	}
 	if style := responseStyleContext(options); style != "" {
 		sections = append(sections, style)
 	}
-	policy := strings.TrimSpace(confirmationPolicy)
-	if policy != "" {
+	if policy := strings.TrimSpace(confirmationPolicy); policy != "" {
 		sections = append(sections, policy)
 	}
-	return systemPromptParts{
-		prompt:             strings.Join(sections, "\n\n"),
-		baseInstructions:   core,
-		confirmationPolicy: policy,
-		projectContext:     project,
-		skills:             skillsBlock,
-	}
+	return strings.Join(sections, "\n\n")
 }
 
 // responseStyleContext renders the operator-selected reply style (TUI /style) as

internal/agent/task_state.go

@@ -1,359 +0,0 @@
-package agent
-
-import (
-	"encoding/json"
-	"reflect"
-	"sort"
-	"strings"
-
-	"github.com/Gitlawb/zero/internal/tools"
-	"github.com/Gitlawb/zero/internal/trace"
-	"github.com/Gitlawb/zero/internal/zeroruntime"
-)
-
-type taskStatus string
-
-const (
-	taskStatusActive     taskStatus = "active"
-	taskStatusComplete   taskStatus = "complete"
-	taskStatusIncomplete taskStatus = "incomplete"
-)
-
-type taskPlanParity string
-
-const (
-	taskPlanParityUnknown  taskPlanParity = "unknown"
-	taskPlanParityMatch    taskPlanParity = "match"
-	taskPlanParityMismatch taskPlanParity = "mismatch"
-)
-
-type taskPlanItem struct {
-	Content string `json:"content"`
-	Status  string `json:"status"`
-	Notes   string `json:"notes,omitempty"`
-}
-
-type taskPlanState struct {
-	Items      []taskPlanItem `json:"items,omitempty"`
-	Pending    int            `json:"pending"`
-	InProgress int            `json:"in_progress"`
-	Completed  int            `json:"completed"`
-	Failed     int            `json:"failed"`
-}
-
-type taskToolState struct {
-	Succeeded int `json:"succeeded"`
-	Failed    int `json:"failed"`
-}
-
-type taskVerificationState struct {
-	Passed      int     `json:"passed"`
-	Failed      int     `json:"failed"`
-	LastOutcome Outcome `json:"last_outcome,omitempty"`
-}
-
-type taskStateSnapshot struct {
-	Revision           int                   `json:"revision"`
-	Objective          string                `json:"objective"`
-	Status             taskStatus            `json:"status"`
-	Plan               taskPlanState         `json:"plan"`
-	Tools              taskToolState         `json:"tools"`
-	Verification       taskVerificationState `json:"verification"`
-	ChangedFiles       []string              `json:"changed_files,omitempty"`
-	CompletionDecision CompletionDecision    `json:"completion_decision,omitempty"`
-	CompletionReason   string                `json:"completion_reason,omitempty"`
-	PlanParity         taskPlanParity        `json:"plan_parity"`
-}
-
-type taskStateEventKind int
-
-const (
-	taskStateEventPlan taskStateEventKind = iota + 1
-	taskStateEventToolResult
-	taskStateEventVerification
-	taskStateEventCompletion
-)
-
-type taskStateEvent struct {
-	kind         taskStateEventKind
-	arguments    string
-	toolResult   ToolResult
-	verification Outcome
-	completion   completionEvaluation
-}
-
-// taskState is a deterministic projection of facts the loop already observes.
-// It does not initiate work or replace the transcript; consumers must check
-// transcript parity before using its compact representation.
-type taskState struct {
-	snapshotValue taskStateSnapshot
-	changedFiles  map[string]struct{}
-	recorder      *trace.Recorder
-	planObserved  bool
-}
-
-func newTaskState(objective string, recorder *trace.Recorder) *taskState {
-	state := &taskState{
-		snapshotValue: taskStateSnapshot{
-			Objective:  strings.TrimSpace(objective),
-			Status:     taskStatusActive,
-			PlanParity: taskPlanParityUnknown,
-		},
-		changedFiles: map[string]struct{}{},
-	}
-	state.recorder = recorder
-	return state
-}
-
-func (state *taskState) observe(event taskStateEvent) bool {
-	if state == nil {
-		return false
-	}
-	changed := false
-	switch event.kind {
-	case taskStateEventPlan:
-		plan, ok := parseTaskPlan(event.arguments)
-		if !ok {
-			return false
-		}
-		state.snapshotValue.Plan = summarizeTaskPlan(plan)
-		state.planObserved = true
-		state.markActive()
-		changed = true
-	case taskStateEventToolResult:
-		state.markActive()
-		if event.toolResult.Status == tools.StatusOK {
-			state.snapshotValue.Tools.Succeeded++
-		} else {
-			state.snapshotValue.Tools.Failed++
-		}
-		for _, path := range event.toolResult.ChangedFiles {
-			path = strings.TrimSpace(path)
-			if path != "" {
-				state.changedFiles[path] = struct{}{}
-			}
-		}
-		state.snapshotValue.ChangedFiles = sortedKeys(state.changedFiles)
-		changed = true
-	case taskStateEventVerification:
-		if event.verification == OutcomeDisabled {
-			return false
-		}
-		state.markActive()
-		state.snapshotValue.Verification.LastOutcome = event.verification
-		switch event.verification {
-		case OutcomePassed:
-			state.snapshotValue.Verification.Passed++
-		case OutcomeCorrecting, OutcomeReported, OutcomeAborted:
-			state.snapshotValue.Verification.Failed++
-		}
-		changed = true
-	case taskStateEventCompletion:
-		state.snapshotValue.CompletionDecision = event.completion.Decision
-		state.snapshotValue.CompletionReason = event.completion.Reason
-		switch event.completion.Decision {
-		case CompletionComplete:
-			state.snapshotValue.Status = taskStatusComplete
-		case CompletionIncomplete:
-			state.snapshotValue.Status = taskStatusIncomplete
-		default:
-			state.snapshotValue.Status = taskStatusActive
-		}
-		changed = true
-	}
-	if changed {
-		state.snapshotValue.Revision++
-		if event.kind != taskStateEventToolResult {
-			state.emit()
-		}
-	}
-	return changed
-}
-
-func (state *taskState) markActive() {
-	state.snapshotValue.Status = taskStatusActive
-	state.snapshotValue.CompletionDecision = ""
-	state.snapshotValue.CompletionReason = ""
-}
-
-func (state *taskState) snapshot() taskStateSnapshot {
-	if state == nil {
-		return taskStateSnapshot{}
-	}
-	snapshot := state.snapshotValue
-	snapshot.Plan.Items = append([]taskPlanItem(nil), state.snapshotValue.Plan.Items...)
-	snapshot.ChangedFiles = append([]string(nil), state.snapshotValue.ChangedFiles...)
-	return snapshot
-}
-
-// observePlanParity compares only the latest plan projection with the plan tool
-// calls still present in messages. It mutates the snapshot and emits when the
-// parity value changes; objective, tool, and verification fields are not part of
-// this comparison.
-func (state *taskState) observePlanParity(messages []zeroruntime.Message) taskPlanParity {
-	if state == nil {
-		return taskPlanParityUnknown
-	}
-	transcriptPlan, found, valid := latestTaskPlan(messages)
-	tracked := state.snapshotValue.Plan.Items
-	parity := taskPlanParityMatch
-	if !valid || found != state.planObserved || (found && !reflect.DeepEqual(transcriptPlan, tracked)) {
-		parity = taskPlanParityMismatch
-	}
-	if state.snapshotValue.PlanParity != parity {
-		state.snapshotValue.PlanParity = parity
-		state.snapshotValue.Revision++
-		state.emit()
-	}
-	return parity
-}
-
-type completionContext struct {
-	Objective             string
-	PlanPending           bool
-	PlanMatchesTranscript bool
-}
-
-func (state *taskState) completionContext(messages []zeroruntime.Message, transcriptPlanPending bool) completionContext {
-	context := completionContext{PlanPending: transcriptPlanPending}
-	if state == nil {
-		return context
-	}
-	context.Objective = state.snapshotValue.Objective
-	context.PlanMatchesTranscript = state.observePlanParity(messages) == taskPlanParityMatch
-	if context.PlanMatchesTranscript {
-		context.PlanPending = state.snapshotValue.Plan.Pending+state.snapshotValue.Plan.InProgress > 0
-	}
-	return context
-}
-
-func (state *taskState) snapshotForCompaction(messages []zeroruntime.Message) *taskStateSnapshot {
-	if state == nil {
-		return nil
-	}
-	state.observePlanParity(messages)
-	snapshot := state.snapshot()
-	return &snapshot
-}
-
-func (state *taskState) emit() {
-	if state == nil || state.recorder == nil {
-		return
-	}
-	snapshot := state.snapshotValue
-	state.recorder.EmitTaskState(trace.TaskStateEvent{
-		Revision:            snapshot.Revision,
-		Status:              string(snapshot.Status),
-		PlanPending:         snapshot.Plan.Pending,
-		PlanInProgress:      snapshot.Plan.InProgress,
-		PlanCompleted:       snapshot.Plan.Completed,
-		PlanFailed:          snapshot.Plan.Failed,
-		ToolsSucceeded:      snapshot.Tools.Succeeded,
-		ToolsFailed:         snapshot.Tools.Failed,
-		VerificationPassed:  snapshot.Verification.Passed,
-		VerificationFailed:  snapshot.Verification.Failed,
-		VerificationOutcome: string(snapshot.Verification.LastOutcome),
-		ChangedFileCount:    len(snapshot.ChangedFiles),
-		CompletionDecision:  string(snapshot.CompletionDecision),
-		PlanParity:          string(snapshot.PlanParity),
-	})
-}
-
-func parseTaskPlan(arguments string) ([]taskPlanItem, bool) {
-	var object map[string]json.RawMessage
-	if json.Unmarshal([]byte(strings.TrimSpace(arguments)), &object) != nil {
-		return nil, false
-	}
-	rawPlan, ok := object["plan"]
-	if !ok || string(rawPlan) == "null" {
-		return nil, false
-	}
-	var parsed []struct {
-		ID      *string `json:"id"`
-		Content string  `json:"content"`
-		Status  string  `json:"status"`
-		Notes   string  `json:"notes"`
-	}
-	if json.Unmarshal(rawPlan, &parsed) != nil {
-		return nil, false
-	}
-	plan := make([]taskPlanItem, 0, len(parsed))
-	for _, raw := range parsed {
-		if raw.Content == "" {
-			return nil, false
-		}
-		plan = append(plan, taskPlanItem{
-			Content: raw.Content,
-			Status:  normalizeTaskPlanStatus(raw.Status),
-			Notes:   raw.Notes,
-		})
-	}
-	lastInProgress := -1
-	for index := range plan {
-		if plan[index].Status == "in_progress" {
-			if lastInProgress >= 0 {
-				plan[lastInProgress].Status = "completed"
-			}
-			lastInProgress = index
-		}
-	}
-	if len(plan) == 0 {
-		return nil, true
-	}
-	return plan, true
-}
-
-func normalizeTaskPlanStatus(status string) string {
-	switch strings.ToLower(strings.TrimSpace(status)) {
-	case "completed", "complete", "done", "finished", "resolved", "✓", "x", "[x]":
-		return "completed"
-	case "in_progress", "in-progress", "inprogress", "in progress", "active", "doing", "started", "current", "wip", "ongoing", "running":
-		return "in_progress"
-	case "failed", "fail", "error", "errored", "blocked", "cancelled", "canceled", "abandoned", "skipped":
-		return "failed"
-	default:
-		return "pending"
-	}
-}
-
-func summarizeTaskPlan(items []taskPlanItem) taskPlanState {
-	plan := taskPlanState{Items: append([]taskPlanItem(nil), items...)}
-	for _, item := range items {
-		switch item.Status {
-		case "completed":
-			plan.Completed++
-		case "in_progress":
-			plan.InProgress++
-		case "failed":
-			plan.Failed++
-		default:
-			plan.Pending++
-		}
-	}
-	return plan
-}
-
-func latestTaskPlan(messages []zeroruntime.Message) ([]taskPlanItem, bool, bool) {
-	for i := len(messages) - 1; i >= 0; i-- {
-		for j := len(messages[i].ToolCalls) - 1; j >= 0; j-- {
-			call := messages[i].ToolCalls[j]
-			if call.Name != planToolName {
-				continue
-			}
-			plan, ok := parseTaskPlan(call.Arguments)
-			return plan, true, ok
-		}
-	}
-	return nil, false, true
-}
-
-func sortedKeys(values map[string]struct{}) []string {
-	keys := make([]string, 0, len(values))
-	for value := range values {
-		keys = append(keys, value)
-	}
-	// Paths are evidence, not chronology. Stable ordering makes replay snapshots
-	// deterministic even if events originate from parallel read batches later.
-	sort.Strings(keys)
-	return keys
-}

internal/agent/task_state_test.go

@@ -1,204 +0,0 @@
-package agent
-
-import (
-	"context"
-	"reflect"
-	"testing"
-
-	"github.com/Gitlawb/zero/internal/tools"
-	"github.com/Gitlawb/zero/internal/trace"
-	"github.com/Gitlawb/zero/internal/zeroruntime"
-)
-
-func TestTaskStateReplayIsDeterministic(t *testing.T) {
-	events := []taskStateEvent{
-		{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"inspect","status":"done"},{"content":"implement","status":"in progress"},{"content":"verify"}]}`},
-		{kind: taskStateEventToolResult, toolResult: ToolResult{Name: "apply_patch", Status: tools.StatusOK, ChangedFiles: []string{"a.go", "a.go", "b.go"}}},
-		{kind: taskStateEventToolResult, toolResult: ToolResult{Name: "go test", Status: tools.StatusError}},
-		{kind: taskStateEventVerification, verification: OutcomePassed},
-		{kind: taskStateEventCompletion, completion: completionEvaluation{Decision: CompletionUncertain, Reason: "pending work"}},
-	}
-
-	first := newTaskState("ship the change", nil)
-	second := newTaskState("ship the change", nil)
-	for _, event := range events {
-		first.observe(event)
-		second.observe(event)
-	}
-
-	if !reflect.DeepEqual(first.snapshot(), second.snapshot()) {
-		t.Fatalf("replaying the same events produced different snapshots:\nfirst:  %#v\nsecond: %#v", first.snapshot(), second.snapshot())
-	}
-	got := first.snapshot()
-	if got.Status != taskStatusActive || got.Plan.Pending != 1 || got.Plan.InProgress != 1 || got.Plan.Completed != 1 {
-		t.Fatalf("unexpected plan snapshot: %#v", got)
-	}
-	if got.Tools.Succeeded != 1 || got.Tools.Failed != 1 || len(got.ChangedFiles) != 2 {
-		t.Fatalf("unexpected evidence snapshot: %#v", got)
-	}
-	if got.Verification.Passed != 1 || got.Verification.Failed != 0 || got.Verification.LastOutcome != OutcomePassed {
-		t.Fatalf("unexpected verification snapshot: %#v", got.Verification)
-	}
-}
-
-func TestTaskStateCoalescesToolResultsIntoNextTraceEvent(t *testing.T) {
-	recorder := trace.NewRecorder("session", "run", "")
-	state := newTaskState("objective", recorder)
-	for range 20 {
-		state.observe(taskStateEvent{kind: taskStateEventToolResult, toolResult: ToolResult{Status: tools.StatusOK}})
-	}
-	if events := recorder.Finish().TaskStates; len(events) != 0 {
-		t.Fatalf("tool results should be coalesced, got %d trace events", len(events))
-	}
-
-	recorder = trace.NewRecorder("session", "run-2", "")
-	state = newTaskState("objective", recorder)
-	for range 20 {
-		state.observe(taskStateEvent{kind: taskStateEventToolResult, toolResult: ToolResult{Status: tools.StatusOK}})
-	}
-	state.observe(taskStateEvent{kind: taskStateEventCompletion, completion: completionEvaluation{Decision: CompletionComplete}})
-	events := recorder.Finish().TaskStates
-	if len(events) != 1 || events[0].ToolsSucceeded != 20 {
-		t.Fatalf("coalesced tool total missing from completion snapshot: %#v", events)
-	}
-}
-
-func TestRunEmitsTaskStateFromExistingLoopEvents(t *testing.T) {
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewUpdatePlanTool())
-	provider := &mockProvider{turns: [][]zeroruntime.StreamEvent{
-		{
-			{Type: zeroruntime.StreamEventToolCallStart, ToolCallID: "plan-1", ToolName: planToolName},
-			{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "plan-1", ArgumentsFragment: `{"plan":[{"content":"implement","status":"completed"}]}`},
-			{Type: zeroruntime.StreamEventToolCallEnd, ToolCallID: "plan-1"},
-			{Type: zeroruntime.StreamEventDone},
-		},
-		{
-			{Type: zeroruntime.StreamEventText, Content: "done"},
-			{Type: zeroruntime.StreamEventDone},
-		},
-	}}
-	recorder := trace.NewRecorder("session", "run", "")
-
-	result, err := Run(context.Background(), "implement the change", provider, Options{
-		Registry: registry,
-		Trace:    recorder,
-	})
-	if err != nil {
-		t.Fatalf("Run: %v", err)
-	}
-	if result.FinalAnswer != "done" {
-		t.Fatalf("final answer = %q, want done", result.FinalAnswer)
-	}
-	events := recorder.Finish().TaskStates
-	if len(events) < 3 {
-		t.Fatalf("expected plan, tool, completion, and parity snapshots, got %#v", events)
-	}
-	last := events[len(events)-1]
-	if last.Status != string(taskStatusComplete) || last.PlanCompleted != 1 || last.ToolsSucceeded != 1 || last.PlanParity != string(taskPlanParityMatch) {
-		t.Fatalf("unexpected final task snapshot: %#v", last)
-	}
-}
-
-func TestTaskStateSnapshotIsImmutable(t *testing.T) {
-	state := newTaskState("objective", nil)
-	state.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"one","status":"pending"}]}`})
-	state.observe(taskStateEvent{kind: taskStateEventToolResult, toolResult: ToolResult{Status: tools.StatusOK, ChangedFiles: []string{"one.go"}}})
-
-	snapshot := state.snapshot()
-	snapshot.Plan.Items[0].Content = "mutated"
-	snapshot.ChangedFiles[0] = "mutated.go"
-
-	fresh := state.snapshot()
-	if fresh.Plan.Items[0].Content != "one" || fresh.ChangedFiles[0] != "one.go" {
-		t.Fatalf("snapshot mutation leaked into task state: %#v", fresh)
-	}
-}
-
-func TestTaskStatePlanParityUsesLatestPlan(t *testing.T) {
-	state := newTaskState("objective", nil)
-	state.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"old","status":"completed"}]}`})
-	state.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"new","status":"in_progress"}]}`})
-
-	messages := []zeroruntime.Message{{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{
-		{Name: planToolName, Arguments: `{"plan":[{"content":"new","status":"in_progress"}]}`},
-	}}}
-	if parity := state.observePlanParity(messages); parity != taskPlanParityMatch {
-		t.Fatalf("parity = %q, want match", parity)
-	}
-
-	messages[0].ToolCalls[0].Arguments = `{"plan":[{"content":"different","status":"pending"}]}`
-	if parity := state.observePlanParity(messages); parity != taskPlanParityMismatch {
-		t.Fatalf("parity = %q, want mismatch", parity)
-	}
-}
-
-func TestTaskStateMatchesPlanToolNormalization(t *testing.T) {
-	state := newTaskState("objective", nil)
-	arguments := `{"plan":[{"content":"first","status":"in_progress"},{"content":"second","status":"in_progress"}]}`
-	state.observe(taskStateEvent{kind: taskStateEventPlan, arguments: arguments})
-
-	snapshot := state.snapshot()
-	if snapshot.Plan.Completed != 1 || snapshot.Plan.InProgress != 1 {
-		t.Fatalf("multiple active items were not normalized like the plan tool: %#v", snapshot.Plan)
-	}
-	messages := []zeroruntime.Message{{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{Name: planToolName, Arguments: arguments}}}}
-	if parity := state.observePlanParity(messages); parity != taskPlanParityMatch {
-		t.Fatalf("normalized state should still match its transcript event, got %q", parity)
-	}
-
-	empty := newTaskState("objective", nil)
-	empty.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[]}`})
-	emptyMessages := []zeroruntime.Message{{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{Name: planToolName, Arguments: `{"plan":[]}`}}}}
-	if parity := empty.observePlanParity(emptyMessages); parity != taskPlanParityMatch {
-		t.Fatalf("explicit empty plan should match transcript, got %q", parity)
-	}
-}
-
-func TestTaskStateContextFallsBackWhenTranscriptDiffers(t *testing.T) {
-	state := newTaskState("objective", nil)
-	state.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"tracked","status":"completed"}]}`})
-	messages := []zeroruntime.Message{{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{
-		{Name: planToolName, Arguments: `{"plan":[{"content":"transcript","status":"pending"}]}`},
-	}}}
-
-	context := state.completionContext(messages, true)
-	if !context.PlanPending || context.PlanMatchesTranscript {
-		t.Fatalf("completion context must retain transcript truth on mismatch: %#v", context)
-	}
-	if context.Objective != "objective" {
-		t.Fatalf("objective lost from completion context: %#v", context)
-	}
-}
-
-func TestTaskStateCompactionSnapshotRetainsObjectiveOnPlanMismatch(t *testing.T) {
-	state := newTaskState("objective", nil)
-	state.observe(taskStateEvent{kind: taskStateEventPlan, arguments: `{"plan":[{"content":"verify","status":"pending"}]}`})
-	matching := []zeroruntime.Message{{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{
-		{Name: planToolName, Arguments: `{"plan":[{"content":"verify","status":"pending"}]}`},
-	}}}
-	if snapshot := state.snapshotForCompaction(matching); snapshot == nil || snapshot.Objective != "objective" {
-		t.Fatalf("matching transcript should produce compact state, got %#v", snapshot)
-	}
-
-	mismatching := append([]zeroruntime.Message(nil), matching...)
-	mismatching[0].ToolCalls = []zeroruntime.ToolCall{{Name: planToolName, Arguments: `{"plan":[{"content":"other","status":"pending"}]}`}}
-	if snapshot := state.snapshotForCompaction(mismatching); snapshot == nil || snapshot.Objective != "objective" || snapshot.PlanParity != taskPlanParityMismatch {
-		t.Fatalf("plan mismatch must retain immutable objective and mark mutable state uncorroborated, got %#v", snapshot)
-	}
-}
-
-func TestParseTaskPlanRejectsArgumentsTheToolWouldReject(t *testing.T) {
-	for _, arguments := range []string{
-		`{}`,
-		`{"plan":null}`,
-		`{"plan":[{"step":"alias is not accepted"}]}`,
-		`{"plan":[{"content":""}]}`,
-		`{"plan":[{"content":"valid"},{"content":""}]}`,
-		`{"plan":[{"id":4,"content":"valid"}]}`,
-	} {
-		if plan, ok := parseTaskPlan(arguments); ok {
-			t.Fatalf("parseTaskPlan(%s) = %#v, true; want rejected", arguments, plan)
-		}
-	}
-}

internal/providers/openai/provider_test.go

@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
-	"reflect"
 	"strings"
 	"testing"
 	"time"
@@ -1376,61 +1375,3 @@ func TestOpenAIRequestPromptCacheKey(t *testing.T) {
 		}
 	}
 }
-
-func TestOpenAIRequestPreservesCacheablePrefixAcrossTurns(t *testing.T) {
-	provider, err := New(Options{Model: "gpt-test"})
-	if err != nil {
-		t.Fatalf("New returned error: %v", err)
-	}
-	tools := []zeroruntime.ToolDefinition{{
-		Name:        "read_file",
-		Description: "Read a file.",
-		Parameters: map[string]any{
-			"type": "object",
-			"properties": map[string]any{
-				"path": map[string]any{"type": "string"},
-			},
-		},
-	}}
-	firstMessages := []zeroruntime.Message{
-		{Role: zeroruntime.MessageRoleSystem, Content: "stable system prompt"},
-		{Role: zeroruntime.MessageRoleUser, Content: "first turn"},
-	}
-	secondMessages := append([]zeroruntime.Message(nil), firstMessages...)
-	secondMessages = append(secondMessages,
-		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, Content: "first response"},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleUser, Content: "second turn"},
-	)
-
-	marshalBody := func(messages []zeroruntime.Message) map[string]any {
-		t.Helper()
-		mapped := provider.openAIRequest(zeroruntime.CompletionRequest{
-			Messages:       messages,
-			Tools:          tools,
-			PromptCacheKey: "session-stable-prefix",
-		})
-		data, marshalErr := json.Marshal(mapped)
-		if marshalErr != nil {
-			t.Fatalf("marshal request: %v", marshalErr)
-		}
-		var body map[string]any
-		if unmarshalErr := json.Unmarshal(data, &body); unmarshalErr != nil {
-			t.Fatalf("unmarshal request: %v", unmarshalErr)
-		}
-		return body
-	}
-
-	first := marshalBody(firstMessages)
-	second := marshalBody(secondMessages)
-	firstWireMessages := first["messages"].([]any)
-	secondWireMessages := second["messages"].([]any)
-	if !reflect.DeepEqual(secondWireMessages[:len(firstWireMessages)], firstWireMessages) {
-		t.Fatalf("first wire messages must be an exact prefix of the second:\nfirst=%#v\nsecond=%#v", firstWireMessages, secondWireMessages)
-	}
-	if !reflect.DeepEqual(first["tools"], second["tools"]) {
-		t.Fatalf("wire tool definitions drifted:\nfirst=%#v\nsecond=%#v", first["tools"], second["tools"])
-	}
-	if first["prompt_cache_key"] != second["prompt_cache_key"] || first["prompt_cache_key"] != "session-stable-prefix" {
-		t.Fatalf("wire prompt cache key must remain stable: first=%#v second=%#v", first["prompt_cache_key"], second["prompt_cache_key"])
-	}
-}

internal/tools/registry.go

@@ -2,7 +2,6 @@ package tools
 
 import (
 	"context"
-	"sort"
 
 	"github.com/Gitlawb/zero/internal/redaction"
 	"github.com/Gitlawb/zero/internal/sandbox"
@@ -114,9 +113,6 @@ func (registry *Registry) All() []Tool {
 	for _, tool := range registry.tools {
 		tools = append(tools, tool)
 	}
-	sort.Slice(tools, func(left, right int) bool {
-		return tools[left].Name() < tools[right].Name()
-	})
 	return tools
 }
 

internal/tools/registry_test.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"os"
 	"path/filepath"
-	"slices"
 	"strings"
 	"testing"
 
@@ -73,23 +72,6 @@ func TestCoreReadOnlyToolsExposeSafeMetadata(t *testing.T) {
 	}
 }
 
-func TestRegistryAllReturnsToolsSortedByName(t *testing.T) {
-	registry := NewRegistry()
-	for _, name := range []string{"write_file", "bash", "read_file"} {
-		registry.Register(fakePlainTool{baseTool: baseTool{name: name, description: name}})
-	}
-
-	all := registry.All()
-	got := make([]string, 0, len(all))
-	for _, tool := range all {
-		got = append(got, tool.Name())
-	}
-	want := []string{"bash", "read_file", "write_file"}
-	if !slices.Equal(got, want) {
-		t.Fatalf("Registry.All() order = %v, want %v", got, want)
-	}
-}
-
 func TestCoreNetworkToolsExposeSafetyMetadata(t *testing.T) {
 	// web_search is only registered when a backend is configured.
 	t.Setenv("ZERO_WEBSEARCH_BASE_URL", "https://search.example/api")

internal/trace/emit.go

@@ -106,7 +106,6 @@ func WriteNDJSON(w io.Writer, t *TurnTrace) error {
 	for _, p := range t.PrefixHashes {
 		if err := enc.Encode(map[string]any{
 			"type":                "prefix_hash",
-			"system_prompt":       p.SystemPromptHash,
 			"base_instructions":   p.BaseInstructionsHash,
 			"confirmation_policy": p.ConfirmationPolicyHash,
 			"project_context":     p.ProjectContextHash,
@@ -137,27 +136,6 @@ func WriteNDJSON(w io.Writer, t *TurnTrace) error {
 			return err
 		}
 	}
-	for _, event := range t.TaskStates {
-		if err := enc.Encode(map[string]any{
-			"type":                 "task_state",
-			"revision":             event.Revision,
-			"status":               event.Status,
-			"plan_pending":         event.PlanPending,
-			"plan_in_progress":     event.PlanInProgress,
-			"plan_completed":       event.PlanCompleted,
-			"plan_failed":          event.PlanFailed,
-			"tools_succeeded":      event.ToolsSucceeded,
-			"tools_failed":         event.ToolsFailed,
-			"verification_passed":  event.VerificationPassed,
-			"verification_failed":  event.VerificationFailed,
-			"verification_outcome": event.VerificationOutcome,
-			"changed_file_count":   event.ChangedFileCount,
-			"completion_decision":  event.CompletionDecision,
-			"plan_parity":          event.PlanParity,
-		}); err != nil {
-			return err
-		}
-	}
 	return nil
 }
 
@@ -227,15 +205,6 @@ func WriteText(w io.Writer, t *TurnTrace) error {
 				event.Truncated, event.Reason, event.SpillCreated)
 		}
 	}
-	if len(t.TaskStates) > 0 {
-		latest := t.TaskStates[len(t.TaskStates)-1]
-		write("task state: revision=%d status=%s plan=%d/%d/%d/%d tools=%d/%d verification=%d/%d(%s) files=%d plan_parity=%s completion=%s\n",
-			latest.Revision, latest.Status, latest.PlanPending, latest.PlanInProgress,
-			latest.PlanCompleted, latest.PlanFailed, latest.ToolsSucceeded,
-			latest.ToolsFailed, latest.VerificationPassed, latest.VerificationFailed,
-			latest.VerificationOutcome, latest.ChangedFileCount, latest.PlanParity,
-			latest.CompletionDecision)
-	}
 	return firstErr
 }
 

internal/trace/parse.go

@@ -101,14 +101,13 @@ func ReadNDJSON(r io.Reader) (*TurnTrace, error) {
 			if !sawTraceHeader {
 				return nil, errors.New("parse trace: not a valid NDJSON trace (no type:trace header)")
 			}
-			// Round-trip the prefix-hash fields. Missing fields are
+			// Round-trip the seven prefix-hash fields. Missing fields are
 			// accepted as empty strings (a partially-written trace from a
 			// crashed emitter must not fatal a parse). The decoder tolerates
-			// any shape the encoder produced and the keys are the
+			// any shape the encoder produced and the seven keys are the
 			// contract — adding a new field is non-breaking; renaming one
 			// requires a schema version bump.
 			t.PrefixHashes = append(t.PrefixHashes, PrefixHash{
-				SystemPromptHash:       stringField(obj, "system_prompt"),
 				BaseInstructionsHash:   stringField(obj, "base_instructions"),
 				ConfirmationPolicyHash: stringField(obj, "confirmation_policy"),
 				ProjectContextHash:     stringField(obj, "project_context"),
@@ -132,26 +131,6 @@ func ReadNDJSON(r io.Reader) (*TurnTrace, error) {
 				Reason:                  stringField(obj, "reason"),
 				SpillCreated:            boolField(obj, "spill_created"),
 			})
-		case "task_state":
-			if !sawTraceHeader {
-				return nil, errors.New("parse trace: not a valid NDJSON trace (no type:trace header)")
-			}
-			t.TaskStates = append(t.TaskStates, TaskStateEvent{
-				Revision:            int(parseInt64(obj["revision"])),
-				Status:              stringField(obj, "status"),
-				PlanPending:         int(parseInt64(obj["plan_pending"])),
-				PlanInProgress:      int(parseInt64(obj["plan_in_progress"])),
-				PlanCompleted:       int(parseInt64(obj["plan_completed"])),
-				PlanFailed:          int(parseInt64(obj["plan_failed"])),
-				ToolsSucceeded:      int(parseInt64(obj["tools_succeeded"])),
-				ToolsFailed:         int(parseInt64(obj["tools_failed"])),
-				VerificationPassed:  int(parseInt64(obj["verification_passed"])),
-				VerificationFailed:  int(parseInt64(obj["verification_failed"])),
-				VerificationOutcome: stringField(obj, "verification_outcome"),
-				ChangedFileCount:    int(parseInt64(obj["changed_file_count"])),
-				CompletionDecision:  stringField(obj, "completion_decision"),
-				PlanParity:          stringField(obj, "plan_parity"),
-			})
 		default:
 			// Unknown event type: tolerate (forward-compat) but only after a
 			// header has been seen.
@@ -172,8 +151,8 @@ func ReadNDJSON(r io.Reader) (*TurnTrace, error) {
 	if !sawTraceHeader {
 		return nil, errors.New("parse trace: non-empty input had no type:trace header")
 	}
-	if len(t.Spans) == 0 && len(t.Counters) == 0 && len(t.PrefixHashes) == 0 && len(t.OutputBudgets) == 0 && len(t.TaskStates) == 0 {
-		return nil, errors.New("parse trace: header present but no events recovered (corrupt or truncated)")
+	if len(t.Spans) == 0 && len(t.Counters) == 0 && len(t.PrefixHashes) == 0 && len(t.OutputBudgets) == 0 {
+		return nil, errors.New("parse trace: header present but no spans, counters, or prefix hashes recovered (corrupt or truncated)")
 	}
 	return t, nil
 }

internal/trace/recorder.go

@@ -29,10 +29,6 @@ type Recorder struct {
 	firstActionStamped  bool
 }
 
-// maxTaskStateEvents bounds trace growth in pathological long runs. Once full,
-// the latest aggregate replaces the tail so final state is never lost.
-const maxTaskStateEvents = 128
-
 // NewRecorder returns a ready recorder. sessionID correlates with the agent
 // session (Options.SessionID); runID is a per-Run sequence; profile is an
 // optional label (e.g. "cold", "warm") for benchmark runs.
@@ -207,24 +203,6 @@ func (r *Recorder) EmitOutputBudget(event OutputBudgetEvent) {
 	r.tr.OutputBudgets = append(r.tr.OutputBudgets, event)
 }
 
-// EmitTaskState records one content-free structured task snapshot. Calls retain
-// event order so revisions can be replayed alongside the tool and turn stream.
-func (r *Recorder) EmitTaskState(event TaskStateEvent) {
-	if r == nil {
-		return
-	}
-	r.mu.Lock()
-	defer r.mu.Unlock()
-	if r.finished {
-		return
-	}
-	if len(r.tr.TaskStates) < maxTaskStateEvents {
-		r.tr.TaskStates = append(r.tr.TaskStates, event)
-		return
-	}
-	r.tr.TaskStates[len(r.tr.TaskStates)-1] = event
-}
-
 // Finish stamps CompletedAt, derives each span's parent (by interval
 // containment) and exclusive time, and returns a snapshot of the trace. Calling
 // Finish more than once returns the same snapshot.
@@ -245,7 +223,6 @@ func (r *Recorder) Finish() *TurnTrace {
 	snap.Counters = append([]Counter(nil), r.tr.Counters...)
 	snap.PrefixHashes = append([]PrefixHash(nil), r.tr.PrefixHashes...)
 	snap.OutputBudgets = append([]OutputBudgetEvent(nil), r.tr.OutputBudgets...)
-	snap.TaskStates = append([]TaskStateEvent(nil), r.tr.TaskStates...)
 	return &snap
 }
 

internal/trace/task_state_test.go

@@ -1,66 +0,0 @@
-package trace
-
-import (
-	"bytes"
-	"strings"
-	"testing"
-)
-
-func TestTaskStateTraceRoundTripContainsNoTaskContent(t *testing.T) {
-	recorder := NewRecorder("session", "run", "")
-	recorder.Start()
-	event := TaskStateEvent{
-		Revision:            4,
-		Status:              "active",
-		PlanPending:         2,
-		PlanCompleted:       1,
-		ToolsSucceeded:      3,
-		ToolsFailed:         1,
-		VerificationPassed:  1,
-		VerificationOutcome: "passed",
-		ChangedFileCount:    2,
-		PlanParity:          "match",
-	}
-	recorder.EmitTaskState(event)
-
-	var output bytes.Buffer
-	if err := WriteNDJSON(&output, recorder.Finish()); err != nil {
-		t.Fatalf("WriteNDJSON: %v", err)
-	}
-	if strings.Contains(output.String(), "secret objective") || strings.Contains(output.String(), "private.go") {
-		t.Fatalf("task content leaked into trace: %s", output.String())
-	}
-	if strings.Contains(output.String(), "objective_hash") {
-		t.Fatalf("trace contains a confirmable objective fingerprint: %s", output.String())
-	}
-	parsed, err := ReadNDJSON(strings.NewReader(output.String()))
-	if err != nil {
-		t.Fatalf("ReadNDJSON: %v", err)
-	}
-	if len(parsed.TaskStates) != 1 || parsed.TaskStates[0] != event {
-		t.Fatalf("unexpected round trip: %#v", parsed.TaskStates)
-	}
-}
-
-func TestTaskStateIsDocumentedAsOptionalTraceEvent(t *testing.T) {
-	for _, key := range OptionalEventKeys() {
-		if key == "task_state" {
-			return
-		}
-	}
-	t.Fatal("task_state missing from OptionalEventKeys")
-}
-
-func TestTaskStateTraceIsBoundedAndRetainsLatestSnapshot(t *testing.T) {
-	recorder := NewRecorder("session", "run", "")
-	for revision := 1; revision <= maxTaskStateEvents+20; revision++ {
-		recorder.EmitTaskState(TaskStateEvent{Revision: revision})
-	}
-	events := recorder.Finish().TaskStates
-	if len(events) != maxTaskStateEvents {
-		t.Fatalf("task state events = %d, want cap %d", len(events), maxTaskStateEvents)
-	}
-	if got := events[len(events)-1].Revision; got != maxTaskStateEvents+20 {
-		t.Fatalf("latest revision = %d, want %d", got, maxTaskStateEvents+20)
-	}
-}

internal/trace/trace.go

@@ -103,27 +103,6 @@ type OutputBudgetEvent struct {
 	SpillCreated            bool   `json:"spill_created"`
 }
 
-// TaskStateEvent is a content-free snapshot of the run's structured task
-// projection. Objective text, plan content, tool output, file paths, and
-// confirmable content fingerprints are deliberately excluded so tracing cannot
-// become a secret-bearing side channel.
-type TaskStateEvent struct {
-	Revision            int    `json:"revision"`
-	Status              string `json:"status"`
-	PlanPending         int    `json:"plan_pending"`
-	PlanInProgress      int    `json:"plan_in_progress"`
-	PlanCompleted       int    `json:"plan_completed"`
-	PlanFailed          int    `json:"plan_failed"`
-	ToolsSucceeded      int    `json:"tools_succeeded"`
-	ToolsFailed         int    `json:"tools_failed"`
-	VerificationPassed  int    `json:"verification_passed"`
-	VerificationFailed  int    `json:"verification_failed"`
-	VerificationOutcome string `json:"verification_outcome,omitempty"`
-	ChangedFileCount    int    `json:"changed_file_count"`
-	CompletionDecision  string `json:"completion_decision,omitempty"`
-	PlanParity          string `json:"plan_parity"`
-}
-
 // TurnTrace is the finished record for one agent.Run. It is the value
 // emitters serialize; it is not mutated after Finish returns a snapshot.
 type TurnTrace struct {
@@ -139,19 +118,34 @@ type TurnTrace struct {
 	Counters            []Counter           `json:"counters"`
 	PrefixHashes        []PrefixHash        `json:"prefix_hashes,omitempty"`
 	OutputBudgets       []OutputBudgetEvent `json:"output_budgets,omitempty"`
-	TaskStates          []TaskStateEvent    `json:"task_states,omitempty"`
 }
 
 // PrefixHash is one fingerprint of the prompt prefix emitted by an agent run.
-// SystemPromptHash covers the exact joined system-message content, including
-// every dynamic section. ToolsHash covers tool names and descriptions in their
-// emitted order; SchemaHash covers their canonical parameter schemas in that
-// same order. CompletePrefixHash combines those three provider-visible parts.
-// The remaining hashes retain narrower diagnostic boundaries so a trace can
-// identify common sources of system-prompt drift. All hashes are hex-encoded
-// SHA-256 and emitted as a "prefix_hash" NDJSON event.
+// The seven fields decompose the cacheable part of the request so a downstream
+// observer can detect which sub-component drifted turn-over-turn:
+// base_instructions (the embedded core system prompt), confirmation_policy,
+// project_context (AGENTS.md / ZERO.md chain), skills, tools, schema (tool
+// JSON schemas), and complete_prefix (SHA-256 of the canonical concatenation
+// of the other six). All hashes are hex-encoded SHA-256.
+//
+// Scope: the fingerprint covers 4 of 11 sections of buildSystemPrompt. The
+// seven sections NOT covered — modelPromptAddendum, sessionRuntimeContext,
+// approvedCommandPrefixContext, workspaceSeedContext, userGuidelines,
+// specialistDelegationContext, responseStyleContext — fire only for
+// non-default Options. For default Options (the common case), the four
+// captured substrings are the full prompt and the fingerprint is accurate.
+//
+// A run with a stable CompletePrefix across turns means the four captured
+// sub-components are byte-identical. A run where CompletePrefix changes
+// names the captured sub-component that drifted, but does NOT rule out
+// drift in the seven uncaptured sections. modelPromptAddendum in particular
+// changes on a model switch (a model_switches counter the trace already
+// emits), so a consumer correlating CompletePrefix stability with
+// cached_input_tokens must cross-check the model_switches counter to
+// disambiguate "no drift" from "drift in an uncaptured section." The fields
+// are emitted as a "prefix_hash" event in the NDJSON trace (see
+// WriteNDJSON).
 type PrefixHash struct {
-	SystemPromptHash       string `json:"system_prompt"`
 	BaseInstructionsHash   string `json:"base_instructions"`
 	ConfirmationPolicyHash string `json:"confirmation_policy"`
 	ProjectContextHash     string `json:"project_context"`
@@ -302,6 +296,5 @@ func OptionalEventKeys() []string {
 		"counter:" + CounterPrefixDrift,
 		"counter:" + CounterPostureEscalations,
 		"event:prefix_hash",
-		"task_state",
 	}
 }

internal/trace/trace_test.go

@@ -374,7 +374,6 @@ func TestReadNDJSONRoundTrip(t *testing.T) {
 	// event type. Insertion order is preserved by the parser (no sort
 	// is applied on read or write).
 	r.EmitPrefixHash(PrefixHash{
-		SystemPromptHash:       "system1",
 		BaseInstructionsHash:   "b1",
 		ConfirmationPolicyHash: "c1",
 		ProjectContextHash:     "p1",
@@ -384,7 +383,6 @@ func TestReadNDJSONRoundTrip(t *testing.T) {
 		CompletePrefixHash:     "complete1",
 	})
 	r.EmitPrefixHash(PrefixHash{
-		SystemPromptHash:       "system2",
 		BaseInstructionsHash:   "b2",
 		ConfirmationPolicyHash: "c2",
 		ProjectContextHash:     "p2",
@@ -429,10 +427,10 @@ func TestReadNDJSONRoundTrip(t *testing.T) {
 	if parsed.PrefixHashes[0].CompletePrefixHash != "complete1" || parsed.PrefixHashes[1].CompletePrefixHash != "complete2" {
 		t.Fatalf("prefix_hash insertion order lost: got %+v want [complete1, complete2]", parsed.PrefixHashes)
 	}
-	if parsed.PrefixHashes[0].SystemPromptHash != "system1" || parsed.PrefixHashes[0].BaseInstructionsHash != "b1" || parsed.PrefixHashes[0].SchemaHash != "x1" {
+	if parsed.PrefixHashes[0].BaseInstructionsHash != "b1" || parsed.PrefixHashes[0].SchemaHash != "x1" {
 		t.Fatalf("prefix_hash sub-hashes lost on first event: got %+v", parsed.PrefixHashes[0])
 	}
-	if parsed.PrefixHashes[1].SystemPromptHash != "system2" || parsed.PrefixHashes[1].BaseInstructionsHash != "b2" || parsed.PrefixHashes[1].SchemaHash != "x2" {
+	if parsed.PrefixHashes[1].BaseInstructionsHash != "b2" || parsed.PrefixHashes[1].SchemaHash != "x2" {
 		t.Fatalf("prefix_hash sub-hashes lost on second event: got %+v", parsed.PrefixHashes[1])
 	}
 }