fix(continuity): wire scratch-commit-before-release and rewrite bootstrap prompt (Phase 4 items 3, 5, 6)

Release now re-verifies every handoff Anchor.Dirty file hash (previously
unchecked after the top-level anchor SHA compare), snapshots dirty state
onto a per-task scratch branch before uploading, and rewrites the anchor
to the new commit so successor pickup collapses to a single HEAD compare.
ScratchCommit made idempotent for repeated rotations of the same task.

Bootstrap's prompt now points the agent at the scratch-branch commit
history instead of vague "read the handoff" prose, and does not claim a
GET /v1/artifacts/<ref> endpoint that doesn't exist.

MarkdownChanges had zero callers and zero tests; deleted per AUDIT.md's
explicit deletion option rather than half-wiring an undesigned feature.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1rkJ2hBMybnJctPbcy4tT

AUDIT.md

@@ -573,6 +573,56 @@ just a method-name swap):
   — killing or releasing a real running agent from an audit session without
   the user present is exactly the kind of action that warrants asking first.
 
+## B5 — closed, 2026-07-27 (later same day)
+
+`CLIAdapter.Release` now does something real instead of refusing. Design
+mirrors the `.orchestra-report.md` marker convention B3 already established
+for completion, since the same problem applies to handoffs: the plane must
+never invent a handoff, only validate and forward the one the agent wrote
+(§6.1). Concretely:
+
+1. The agent is expected to write `.orchestra-handoff.json`
+   (`herdr.HandoffFile`) at the worktree root before its stop hook lets
+   rotation proceed — a §6.1 handoff schema, not free prose.
+2. `Release` reads that file, decodes it with `continuity.Decode` (schema +
+   required-field validation, same as pickup), and cross-checks
+   `Anchor.GitSHA` against `herdr.HeadSHA(session.Worktree)` — the anchor is
+   re-verified against the real checkout, not trusted from the agent's
+   self-report, closing the same class of gap as B3's receipt-from-transcript
+   choice.
+3. Only if both checks pass does it upload the handoff via `continuity.Save`
+   (`CLIAdapter.CAS`, wired to the same `*store.Store` used everywhere else)
+   and return the resulting ref — this is what `Coordinator.rotate` puts in
+   `TaskReleased.handoff_ref`.
+4. Only *then* does it call the real `pane.release_agent({pane_id, source:
+   "herdr:"+harness, agent: harness})` to drop herdr's claim — sequenced last
+   so a herdr-side failure can't strand an already-uploaded handoff with no
+   way to retry the release call (retrying `Release` re-reads the same file
+   and is idempotent).
+
+A missing or invalid handoff file, an anchor mismatch, or a `pane.release_agent`
+error are all refused (non-nil error, no event emitted) — `Coordinator.rotate`
+already treats an errored `Release` as "leave the lease intact, retry next
+tick," so this gives the agent room to finish writing the handoff rather than
+stranding the task.
+
+`herdr.Claude`/`Codex`/`OpenCode` constructors now take a `continuity.CAS`
+parameter; `cmd/orchestra/main.go` passes the existing `*store.Store` (which
+already implements `PutArtifact`/`Artifact`).
+
+New tests in `internal/herdr/adapter_test.go` drive `Release` against a real
+git worktree and a fake in-process herdr TCP listener (`fakeHerdr`) responding
+to `pane.release_agent`: upload-and-release on a valid handoff, refusal with
+no handoff file, refusal on anchor mismatch, refusal with no CAS configured.
+
+**Still not done** (unchanged, separate from B5 itself): nothing yet makes
+the *agent* actually write `.orchestra-handoff.json` — that's Phase 4 item 2's
+other half (a stop-hook-side convention, analogous to
+`.orchestra-report.md`/`deploy/hooks/orchestra-stop.sh` for completion) and
+Phase 4 items 3/5/6 (`ScratchCommit` before release, the §6.2 bootstrap-prompt
+rewrite, `MarkdownChanges` wiring). `go build ./...`, `go vet ./...`, and
+`go test ./...` all still pass.
+
 ## B6 — partial fix, 2026-07-27 (Phase 4 items 1 and 4)
 
 Two of Phase 4's six items landed; the rest are unchanged (still open, listed
@@ -619,9 +669,55 @@ cooperation):
   handoff and a stop-hook path uploading it via `POST /v1/artifacts` before
   `Coordinator.rotate` calls `Adapter.Release`. `Release` still just refuses
   (see B5 above) — there is nothing yet to validate-and-mint a ref from.
-- Item 3: `ScratchCommit` before release — not wired into `rotate` at all.
-- Item 5: `CLIAdapter.Bootstrap`'s prompt is still ad hoc prose, not the
-  §6.2 ~200-token procedure (read handoff → validate-handoff → re-read
-  TASK.md → proceed).
-- Item 6: `MarkdownChanges` (§6.3 adjacent-task notice) still uncalled from
-  anything but its own test.
+
+## Phase 4 items 3, 5, 6 — landed 2026-07-27
+
+1. **`ScratchCommit` wired into `Release`, not into `rotate`.** Rather than
+   calling it from `Coordinator.rotate` (which only has a `herdr.Session`,
+   not the handoff), `CLIAdapter.Release` now runs it itself, after
+   validating the agent-authored handoff's `Anchor.GitSHA` against the
+   worktree's real HEAD and re-verifying every `Anchor.Dirty` file's hash
+   still matches what the agent recorded (previously untested — a file
+   edited *after* the handoff was written but before release would have
+   silently sailed through). If the handoff has dirty entries, `Release`
+   commits them atomically onto `orchestra/scratch/<handoff-meta-id>` via
+   `continuity.ScratchCommit`, then **rewrites the handoff's anchor** to the
+   new scratch commit SHA with `Dirty` cleared, before uploading to CAS —
+   this is what "collapses §6.2 step 3 to one sha compare" means in
+   practice: the successor's `ValidatePickup` now only needs
+   `git rev-parse HEAD == handoff.anchor.git_sha`, no per-file rehashing,
+   because everything was committed before the ref was minted.
+   `ScratchCommit` itself was changed to be idempotent — reuse an existing
+   scratch branch (`git switch` before falling back to `git switch -c`) and
+   skip the commit if there's nothing to snapshot — since a task can rotate,
+   and therefore hit this path, more than once.
+   Covered by `TestReleaseScratchCommitsDirtyFilesBeforeUpload` (asserts the
+   anchor advances to the new commit, dirty is cleared, and the worktree
+   ends up on the scratch branch) and `TestReleaseRefusesOnStaleDirtyFile`
+   (internal/herdr/adapter_test.go).
+2. **Item 5 — Bootstrap prompt rewritten.** `CLIAdapter.Bootstrap` no longer
+   sends the one-line "read handoff, validate anchor, continue" prose. It
+   now tells the agent the plane has *already* validated anchor/TASK.md
+   (true, per B6's `ValidatePickup` gate in `Coordinator.Start` — no need to
+   ask the agent to redundantly re-verify trust), and points it at
+   `git log --stat -5` / `git branch --show-current` in the worktree as the
+   actual source of "what the prior agent did and what's left," since that's
+   now a real, inspectable scratch-branch commit rather than an opaque ref.
+   Deliberately does **not** claim a `GET /v1/artifacts/<ref>` fetch path —
+   no such HTTP route exists (`/v1/artifacts` is POST-only, upload only,
+   confirmed by reading `cmd/orchestra/main.go`); an earlier draft of this
+   prompt invented that endpoint and was corrected before landing, which is
+   exactly the class of bug this audit exists to catch.
+3. **Item 6 — `MarkdownChanges` deleted, not wired.** Confirmed zero
+   callers anywhere (including its own tests — there were none, despite
+   being listed as "believed accurate" in a prior progress.md snapshot).
+   Wiring it for real needs a design for what "adjacent task" means and
+   where the notice surfaces (brief? a new event type?), which is a real
+   feature, not a wiring fix — AUDIT.md explicitly allows "delete it and
+   record the deviation" as the alternative to half-implementing that. Taking
+   that option rather than bolting on an undesigned notification path.
+
+**Still open from Phase 4**: item 2 (handoff production / stop-hook write of
+`.orchestra-handoff.json` for non-Claude harnesses is untouched; Claude's
+own stop-hook convention exists per B3/B5 but nothing yet drives Codex/
+opencode to write one).

cmd/orchestra/main.go

@@ -95,11 +95,11 @@ func main() {
 				}
 				switch h.Harness {
 				case "claude":
-					adapters[h.ID] = herdr.Claude(client, 200000)
+					adapters[h.ID] = herdr.Claude(client, 200000, s)
 				case "opencode":
-					adapters[h.ID] = herdr.OpenCode(client, 200000)
+					adapters[h.ID] = herdr.OpenCode(client, 200000, s)
 				case "codex", "":
-					adapters[h.ID] = herdr.Codex(client, 200000)
+					adapters[h.ID] = herdr.Codex(client, 200000, s)
 				default:
 					log.Printf("herdr %s has unsupported harness %q", h.ID, h.Harness)
 				}

internal/continuity/continuity.go

@@ -200,28 +200,6 @@ func Load(ref string, cas CAS) (Handoff, error) {
 	return Decode(b)
 }
 
-type Notice struct {
-	Path   string
-	SHA256 string
-	At     time.Time
-}
-
-func MarkdownChanges(root string, paths []string) ([]Notice, error) {
-	out := []Notice{}
-	for _, p := range paths {
-		if !strings.HasSuffix(strings.ToLower(p), ".md") {
-			continue
-		}
-		b, e := os.ReadFile(filepath.Join(root, p))
-		if e != nil {
-			return nil, e
-		}
-		s := sha256.Sum256(b)
-		out = append(out, Notice{p, hex.EncodeToString(s[:]), time.Now().UTC()})
-	}
-	return out, nil
-}
-
 // ScratchCommit records WIP atomically on a dedicated branch before rotation.
 func ScratchCommit(root, branch, message string) error {
 	if branch == "" || strings.ContainsAny(branch, " \t\n") {
@@ -237,15 +215,24 @@ func ScratchCommit(root, branch, message string) error {
 	if len(status) != 0 {
 		return errors.New("TASK.md is immutable")
 	}
-	if strings.TrimSpace(message) == "" {
-		return errors.New("scratch commit message required")
-	}
-	for _, args := range [][]string{{"switch", "-c", branch}, {"add", "-A"}, {"commit", "-m", message}} {
-		if err := exec.Command("git", append([]string{"-C", root}, args...)...).Run(); err != nil {
+	// Reuse the branch across rotations of the same task rather than failing
+	// on "branch already exists" — a task can rotate more than once.
+	if err := exec.Command("git", "-C", root, "switch", branch).Run(); err != nil {
+		if err := exec.Command("git", "-C", root, "switch", "-c", branch).Run(); err != nil {
 			return err
 		}
 	}
-	return nil
+	if err := exec.Command("git", "-C", root, "add", "-A").Run(); err != nil {
+		return err
+	}
+	full, err := exec.Command("git", "-C", root, "status", "--porcelain").Output()
+	if err != nil {
+		return err
+	}
+	if len(full) == 0 {
+		return nil // nothing to snapshot; branch already reflects the worktree
+	}
+	return exec.Command("git", "-C", root, "commit", "-m", message).Run()
 }
 
 func ScratchPush(root, branch, remote string) error {

internal/herdr/adapter.go

@@ -2,13 +2,29 @@ package herdr
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"orchestra/internal/continuity"
+	"os"
 	"path/filepath"
 	"strings"
 	"time"
 )
 
+// sha256sum returns the sha256 of a file, or nil if it can't be read — the
+// caller compares against a known-good hex digest, so a nil/short mismatch
+// naturally fails that comparison rather than needing its own error path.
+func sha256sum(path string) []byte {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil
+	}
+	sum := sha256.Sum256(b)
+	return sum[:]
+}
+
 type Adapter interface {
 	Lease(context.Context, string, string) (Session, error)
 	Bootstrap(context.Context, Session, string) error
@@ -46,8 +62,18 @@ type CLIAdapter struct {
 	Harness string
 	Window  int64
 	Usage   func(string) (Usage, error)
+	// CAS is where the agent-authored §6.1 handoff artifact is uploaded on
+	// release. Nil disables Release (adapters built without one refuse
+	// loudly rather than skip validation).
+	CAS continuity.CAS
 }
 
+// HandoffFile is the convention the agent writes its §6.1 handoff to before
+// stopping, mirroring the .orchestra-report.md convention B3 established for
+// completion: the plane never invents a handoff, it only validates and
+// uploads the one the agent wrote (herdr does not write handoffs, §6.1).
+const HandoffFile = ".orchestra-handoff.json"
+
 func (a CLIAdapter) CreateWorktree(ctx context.Context, repo, root, taskID string) (string, error) {
 	path, err := a.Client.Worktree(ctx, repo, filepath.Join(root, taskID), "orchestra/"+taskID)
 	if err != nil {
@@ -72,21 +98,85 @@ func (a CLIAdapter) Lease(ctx context.Context, task, worktree string) (Session,
 	}
 	return s, nil
 }
+// bootstrapPrompt implements the §6.2 pickup procedure: the plane has already
+// run ValidatePickup before this is ever sent (Coordinator.Start blocks the
+// task and never bootstraps on failure), so this prompt does not ask the
+// agent to re-derive trust in the handoff — it orients the agent inside a
+// checkout the plane has already certified, and tells it what NOT to touch.
+const bootstrapPrompt = `You are picking up an in-progress Orchestra task (handoff ref %s).
+This worktree's anchor and TASK.md have already been verified by the plane before you were started — you do not need to re-derive trust in them.
+1. Re-read TASK.md at the worktree root. It is immutable; never edit it.
+2. Run 'git log --stat -5' and 'git branch --show-current' in this worktree — the prior agent's uncommitted work was snapshotted onto a scratch branch with a descriptive commit message before rotation; that commit is the record of what it did and what's left.
+3. Do not repeat work already recorded as done or as a dead end in that commit history.
+4. Continue the task from there.`
+
 func (a CLIAdapter) Bootstrap(ctx context.Context, s Session, ref string) error {
-	return a.Client.Prompt(ctx, s.PaneID, fmt.Sprintf("Read handoff %s, validate the anchor and TASK.md, then continue.", ref), time.Minute)
+	return a.Client.Prompt(ctx, s.PaneID, fmt.Sprintf(bootstrapPrompt, ref), time.Minute)
 }
-// Release previously called the invented "pane.release" method expecting a
-// handoff_ref back. Neither exists in the real protocol (confirmed against a
-// live herdr instance, AUDIT.md Phase 0): the real method is
-// pane.release_agent(pane_id, source, agent), which only releases herdr's
-// claim on the agent session — it cannot return a handoff_ref, because herdr
-// does not write handoffs, the agent does (§6.1). Wiring this correctly needs
-// the Phase 4 handoff-production path (agent writes handoff, stop hook
-// uploads it to CAS, plane validates and mints the ref) before Release has
-// anything real to return. Refusing loudly until then rather than calling a
-// method that doesn't exist.
+// Release reads the §6.1 handoff the agent wrote to HandoffFile at the
+// worktree root, validates its schema and anchor against the worktree's real
+// HEAD, uploads it to CAS, and only then releases herdr's claim on the pane
+// via the real pane.release_agent(pane_id, source, agent) method (confirmed
+// live against herdr, AUDIT.md Phase 0 — the invented "pane.release" never
+// existed and could never have returned a handoff_ref regardless, since
+// herdr does not write handoffs, the agent does). A missing or invalid
+// handoff is refused rather than guessed at: the caller (Coordinator.rotate)
+// leaves the lease intact and retries next tick, giving the agent time to
+// finish writing it.
 func (a CLIAdapter) Release(ctx context.Context, s Session) (string, error) {
-	return "", fmt.Errorf("adapter: Release not implemented — pane.release is not a real herdr method and handoff production (AUDIT.md Phase 4) is not wired yet")
+	if a.CAS == nil {
+		return "", fmt.Errorf("adapter: CAS store required to upload handoff")
+	}
+	path := filepath.Join(s.Worktree, HandoffFile)
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return "", fmt.Errorf("adapter: handoff not written yet (%s): %w", path, err)
+	}
+	h, err := continuity.Decode(b)
+	if err != nil {
+		return "", fmt.Errorf("adapter: invalid handoff: %w", err)
+	}
+	sha, err := HeadSHA(s.Worktree)
+	if err != nil {
+		return "", fmt.Errorf("adapter: read worktree HEAD: %w", err)
+	}
+	if h.Anchor.GitSHA != sha {
+		return "", fmt.Errorf("adapter: handoff anchor %s does not match worktree HEAD %s", h.Anchor.GitSHA, sha)
+	}
+	for _, d := range h.Anchor.Dirty {
+		if hex.EncodeToString(sha256sum(filepath.Join(s.Worktree, d.Path))) != d.SHA256 {
+			return "", fmt.Errorf("adapter: handoff dirty file changed since it was written: %s", d.Path)
+		}
+	}
+	// Atomically commit whatever the handoff described as dirty onto a
+	// per-task scratch branch (§6.2 step 3) *before* uploading, so the
+	// successor's pickup validation collapses to a single HEAD compare
+	// instead of re-hashing every dirty file individually.
+	if len(h.Anchor.Dirty) > 0 {
+		branch := "orchestra/scratch/" + h.Meta.ID
+		if err := continuity.ScratchCommit(s.Worktree, branch, "orchestra: pre-release WIP snapshot ("+h.Meta.ID+")"); err != nil {
+			return "", fmt.Errorf("adapter: scratch commit: %w", err)
+		}
+		newSHA, err := HeadSHA(s.Worktree)
+		if err != nil {
+			return "", fmt.Errorf("adapter: read scratch HEAD: %w", err)
+		}
+		h.Anchor.GitSHA = newSHA
+		h.Anchor.Branch = branch
+		h.Anchor.Dirty = nil
+	}
+	ref, err := continuity.Save(h, a.CAS)
+	if err != nil {
+		return "", fmt.Errorf("adapter: upload handoff: %w", err)
+	}
+	if err := a.Client.Call(ctx, "pane.release_agent", map[string]any{
+		"pane_id": s.PaneID,
+		"source":  "herdr:" + a.Harness,
+		"agent":   a.Harness,
+	}, nil); err != nil {
+		return "", fmt.Errorf("adapter: pane.release_agent: %w", err)
+	}
+	return ref, nil
 }
 func (a CLIAdapter) Kill(ctx context.Context, s Session) error {
 	return a.Client.Call(ctx, "pane.close", map[string]any{"pane_id": s.PaneID}, nil)
@@ -224,12 +314,12 @@ func (a CLIAdapter) resolveSessionFile(s Session) (string, error) {
 	}
 }
 
-var Claude = func(c *Client, w int64) CLIAdapter {
-	return CLIAdapter{Client: c, Harness: "claude", Window: w, Usage: ClaudeUsage}
+var Claude = func(c *Client, w int64, cas continuity.CAS) CLIAdapter {
+	return CLIAdapter{Client: c, Harness: "claude", Window: w, Usage: ClaudeUsage, CAS: cas}
 }
-var Codex = func(c *Client, w int64) CLIAdapter {
-	return CLIAdapter{Client: c, Harness: "codex", Window: w, Usage: CodexUsage}
+var Codex = func(c *Client, w int64, cas continuity.CAS) CLIAdapter {
+	return CLIAdapter{Client: c, Harness: "codex", Window: w, Usage: CodexUsage, CAS: cas}
 }
-var OpenCode = func(c *Client, w int64) CLIAdapter {
-	return CLIAdapter{Client: c, Harness: "opencode", Window: w, Usage: OpenCodeUsage}
+var OpenCode = func(c *Client, w int64, cas continuity.CAS) CLIAdapter {
+	return CLIAdapter{Client: c, Harness: "opencode", Window: w, Usage: OpenCodeUsage, CAS: cas}
 }

internal/herdr/adapter_test.go

@@ -0,0 +1,235 @@
+package herdr
+
+import (
+	"bufio"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"net"
+	"orchestra/internal/continuity"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+type memCAS struct{ m map[string][]byte }
+
+func (c *memCAS) PutArtifact(b []byte) (string, error) {
+	if c.m == nil {
+		c.m = map[string][]byte{}
+	}
+	id := string(rune(len(c.m) + 'a'))
+	c.m[id] = b
+	return id, nil
+}
+func (c *memCAS) Artifact(ref string) ([]byte, error) { return c.m[ref], nil }
+
+func runGit(t *testing.T, dir string, args ...string) {
+	t.Helper()
+	cmd := exec.Command("git", append([]string{"-C", dir}, args...)...)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("git %v: %v: %s", args, err, out)
+	}
+}
+
+// fakeHerdr accepts one JSON-RPC connection and replies with an empty result
+// to every request — enough to exercise CLIAdapter.Release's pane.release_agent
+// call without a live herdr instance.
+func fakeHerdr(t *testing.T) *Client {
+	t.Helper()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { ln.Close() })
+	go func() {
+		conn, err := ln.Accept()
+		if err != nil {
+			return
+		}
+		defer conn.Close()
+		var req Request
+		if err := json.NewDecoder(bufio.NewReader(conn)).Decode(&req); err != nil {
+			return
+		}
+		json.NewEncoder(conn).Encode(Response{ID: req.ID, Result: json.RawMessage(`{}`)})
+	}()
+	return &Client{Path: ln.Addr().String(), dial: func() (net.Conn, error) { return net.Dial("tcp", ln.Addr().String()) }}
+}
+
+func validHandoff(anchorSHA string) continuity.Handoff {
+	return continuity.Handoff{
+		Meta:     continuity.Meta{ID: "t1", Reason: "threshold", RotationIndex: 1},
+		Anchor:   continuity.Anchor{GitSHA: anchorSHA, Branch: "main"},
+		Goal:     "finish the thing",
+		DoneWhen: []string{"tests pass"},
+		Action:   "continue",
+		Command:  "go test ./...",
+	}
+}
+
+func TestReleaseUploadsHandoffAndReleasesAgent(t *testing.T) {
+	repo := t.TempDir()
+	runGit(t, repo, "init")
+	runGit(t, repo, "config", "user.email", "t@t")
+	runGit(t, repo, "config", "user.name", "t")
+	runGit(t, repo, "commit", "--allow-empty", "-m", "init")
+	head, err := HeadSHA(repo)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := continuity.Encode(validHandoff(head))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(repo, HandoffFile), b, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	cas := &memCAS{}
+	a := CLIAdapter{Client: fakeHerdr(t), Harness: "claude", CAS: cas}
+	ref, err := a.Release(context.Background(), Session{PaneID: "p1", Worktree: repo})
+	if err != nil {
+		t.Fatalf("Release: %v", err)
+	}
+	if ref == "" {
+		t.Fatal("expected non-empty handoff ref")
+	}
+	if _, ok := cas.m[ref]; !ok {
+		t.Fatal("handoff was not uploaded to CAS")
+	}
+	got, err := continuity.Load(ref, cas)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Anchor.GitSHA != head {
+		t.Fatalf("stored handoff anchor=%s want=%s", got.Anchor.GitSHA, head)
+	}
+}
+
+func TestReleaseRefusesWithoutHandoffFile(t *testing.T) {
+	repo := t.TempDir()
+	runGit(t, repo, "init")
+	a := CLIAdapter{Client: fakeHerdr(t), Harness: "claude", CAS: &memCAS{}}
+	if _, err := a.Release(context.Background(), Session{PaneID: "p1", Worktree: repo}); err == nil {
+		t.Fatal("expected error when no handoff file is present")
+	}
+}
+
+func TestReleaseRefusesOnAnchorMismatch(t *testing.T) {
+	repo := t.TempDir()
+	runGit(t, repo, "init")
+	runGit(t, repo, "config", "user.email", "t@t")
+	runGit(t, repo, "config", "user.name", "t")
+	runGit(t, repo, "commit", "--allow-empty", "-m", "init")
+
+	b, err := continuity.Encode(validHandoff("deaddeaddeaddeaddeaddeaddeaddeaddeaddead"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(repo, HandoffFile), b, 0644); err != nil {
+		t.Fatal(err)
+	}
+	a := CLIAdapter{Client: fakeHerdr(t), Harness: "claude", CAS: &memCAS{}}
+	if _, err := a.Release(context.Background(), Session{PaneID: "p1", Worktree: repo}); err == nil {
+		t.Fatal("expected error on anchor mismatch")
+	}
+}
+
+func TestReleaseScratchCommitsDirtyFilesBeforeUpload(t *testing.T) {
+	repo := t.TempDir()
+	runGit(t, repo, "init")
+	runGit(t, repo, "config", "user.email", "t@t")
+	runGit(t, repo, "config", "user.name", "t")
+	runGit(t, repo, "commit", "--allow-empty", "-m", "init")
+	head, err := HeadSHA(repo)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	wipPath := filepath.Join(repo, "wip.txt")
+	if err := os.WriteFile(wipPath, []byte("in progress"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	sum := sha256.Sum256([]byte("in progress"))
+	h := validHandoff(head)
+	h.Anchor.Dirty = []continuity.Dirty{{Path: "wip.txt", SHA256: hex.EncodeToString(sum[:])}}
+	b, err := continuity.Encode(h)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(repo, HandoffFile), b, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	cas := &memCAS{}
+	a := CLIAdapter{Client: fakeHerdr(t), Harness: "claude", CAS: cas}
+	ref, err := a.Release(context.Background(), Session{PaneID: "p1", Worktree: repo})
+	if err != nil {
+		t.Fatalf("Release: %v", err)
+	}
+	got, err := continuity.Load(ref, cas)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Anchor.GitSHA == head {
+		t.Fatal("expected anchor to advance to the new scratch commit")
+	}
+	if len(got.Anchor.Dirty) != 0 {
+		t.Fatal("expected dirty entries to be cleared after scratch commit")
+	}
+	newHead, err := HeadSHA(repo)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Anchor.GitSHA != newHead {
+		t.Fatalf("stored anchor=%s does not match worktree HEAD=%s", got.Anchor.GitSHA, newHead)
+	}
+	branch, err := exec.Command("git", "-C", repo, "branch", "--show-current").Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Anchor.Branch != "orchestra/scratch/t1" || string(branch) != got.Anchor.Branch+"\n" {
+		t.Fatalf("expected worktree on scratch branch, got %q (handoff says %q)", branch, got.Anchor.Branch)
+	}
+}
+
+func TestReleaseRefusesOnStaleDirtyFile(t *testing.T) {
+	repo := t.TempDir()
+	runGit(t, repo, "init")
+	runGit(t, repo, "config", "user.email", "t@t")
+	runGit(t, repo, "config", "user.name", "t")
+	runGit(t, repo, "commit", "--allow-empty", "-m", "init")
+	head, err := HeadSHA(repo)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := os.WriteFile(filepath.Join(repo, "wip.txt"), []byte("changed after handoff written"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	stale := sha256.Sum256([]byte("original content"))
+	h := validHandoff(head)
+	h.Anchor.Dirty = []continuity.Dirty{{Path: "wip.txt", SHA256: hex.EncodeToString(stale[:])}}
+	b, err := continuity.Encode(h)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(repo, HandoffFile), b, 0644); err != nil {
+		t.Fatal(err)
+	}
+	a := CLIAdapter{Client: fakeHerdr(t), Harness: "claude", CAS: &memCAS{}}
+	if _, err := a.Release(context.Background(), Session{PaneID: "p1", Worktree: repo}); err == nil {
+		t.Fatal("expected refusal when a dirty file no longer matches the handoff's recorded hash")
+	}
+}
+
+func TestReleaseRequiresCAS(t *testing.T) {
+	a := CLIAdapter{Client: fakeHerdr(t), Harness: "claude"}
+	if _, err := a.Release(context.Background(), Session{PaneID: "p1", Worktree: t.TempDir()}); err == nil {
+		t.Fatal("expected error when CAS is nil")
+	}
+}

progress.md

@@ -99,6 +99,47 @@ Fixed so far:
   named caveat: TASK.md hashing is best-effort and untested for the
   herdr-hosted (`WorktreeCreator`) worktree path.
 
+- **B5 (closed)** — `CLIAdapter.Release` previously just refused (no real
+  herdr method existed to call and there was nothing to validate against).
+  Now: reads the agent-authored `.orchestra-handoff.json` from the worktree
+  root, validates it with `continuity.Decode`, cross-checks its anchor SHA
+  against the worktree's real `HeadSHA` (never trusts the agent's self-report
+  outright), uploads it to CAS via `continuity.Save` to mint the
+  `handoff_ref`, and only then calls the real `pane.release_agent({pane_id,
+  source, agent})` to drop herdr's claim — sequenced last so a herdr-side
+  error can't strand an uploaded handoff. Any failure (missing file, invalid
+  schema, anchor mismatch, herdr error) is a refusal, which `rotate` already
+  treats as "retry next tick" rather than stranding the task. `herdr.Claude/
+  Codex/OpenCode` now take a `continuity.CAS` (main.go passes the existing
+  `*store.Store`). New tests in `internal/herdr/adapter_test.go` cover all
+  four paths against a real git worktree and a fake in-process herdr
+  listener. **Not done:** nothing yet makes the agent actually *write*
+  `.orchestra-handoff.json` (needs a stop-hook convention analogous to
+  `.orchestra-report.md`) — that and the rest of Phase 4 (ScratchCommit
+  before release, §6.2 bootstrap-prompt rewrite, `MarkdownChanges`) remain
+  open.
+
+- **Phase 4 items 3, 5, 6** — `CLIAdapter.Release` now re-verifies every
+  `Anchor.Dirty` file hash (previously only the top-level `Anchor.GitSHA`
+  was checked; a file edited after the handoff was written but before
+  release would have gone through unnoticed), then, if there were dirty
+  entries, snapshots them atomically onto a per-task scratch branch
+  (`continuity.ScratchCommit`, made idempotent so a task can rotate more
+  than once) and rewrites the handoff's anchor to that new commit with
+  `Dirty` cleared before uploading — so the successor's pickup check is a
+  single HEAD compare, not N file rehashes. `CLIAdapter.Bootstrap`'s prompt
+  was rewritten to point the agent at `git log`/the scratch branch instead
+  of a vague "read the handoff" instruction, and deliberately avoids
+  claiming a `GET /v1/artifacts/<ref>` endpoint, since no such route exists
+  (`/v1/artifacts` is POST-only). `continuity.MarkdownChanges` (§6.3
+  adjacent-task notice) had zero callers and zero tests despite being
+  listed as implemented in an earlier snapshot — deleted rather than
+  half-wired, per AUDIT.md's explicit "delete and record the deviation"
+  option. New tests: `TestReleaseScratchCommitsDirtyFilesBeforeUpload`,
+  `TestReleaseRefusesOnStaleDirtyFile` (internal/herdr/adapter_test.go).
+  **Not done:** Phase 4 item 2 (handoff production for Codex/opencode —
+  nothing yet drives those harnesses to write `.orchestra-handoff.json`).
+
 Not yet started: B7 (quota projection has no producer),
 Codex/opencode completion producers, the turn-decision endpoint, S2–S4,
 S7–S11. See `AUDIT.md` for the full plan.