diff --git a/.github/workflows/python.yml b/.github/workflows/python.yml
new file mode 100644
index 0000000..da35008
--- /dev/null
+++ b/.github/workflows/python.yml
@@ -0,0 +1,28 @@
+name: python
+
+on:
+  push:
+    paths:
+      - "scimesh/**"
+      - "tests/**"
+      - "pyproject.toml"
+      - ".github/workflows/python.yml"
+  pull_request:
+    paths:
+      - "scimesh/**"
+      - "tests/**"
+      - "pyproject.toml"
+      - ".github/workflows/python.yml"
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+          cache: pip
+      - run: python -m pip install --upgrade pip
+      - run: python -m pip install -e '.[dev]'
+      - run: pytest -q
diff --git a/.gitignore b/.gitignore
index c7419b5..93ddbb4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,7 @@ results/
 *_similarities.csv
 test_results.csv
 test_structures/
+
+# Local coordinator-worker execution state
+worker-data*/
+scimesh-worker-data/
diff --git a/README.md b/README.md
index be03abe..b51582f 100644
--- a/README.md
+++ b/README.md
@@ -1,11 +1,12 @@
 # SciMesh
 
 SciMesh is a scientific-workload framework for molecular datasets. Its public CLI
-currently runs exact similarity search and sparse similarity-graph construction
-locally in one Python process; it creates no dense similarity matrix. A Python
-Worker client and the planned Go/PostgreSQL coordinator contract are tracked in
-the repository, but distributed execution is not available yet; see
-[`STATUS.md`](STATUS.md).
+runs exact similarity search and sparse similarity-graph construction locally in
+one Python process; it creates no dense similarity matrix. The Go/PostgreSQL
+coordinator and Python worker can run a diagnostic, shard-based
+`similarity-search` pipeline locally. Its CSV artifacts are not a global result
+until CTX-07--09 add planning and reduction; use the local CLI for scientific
+results today. See [`STATUS.md`](STATUS.md).
 
 The ChEMBL TSV database is intentionally not included in this repository. Download it separately and pass its path to the commands below. The expected columns are `chembl_id` and `canonical_smiles`.
 
diff --git a/STATUS.md b/STATUS.md
index f6a7a23..b3b842d 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -36,7 +36,7 @@ Docker PostgreSQL stack on 2026-07-23.
 | CTX-08 Distributed similarity-search | Not started | Local reference exists. |
 | CTX-09 Reducer and final-result API | Not started | Depends on CTX-07 and CTX-08. |
 | CTX-10 Distributed similarity-graph | Not started | Local reference exists. |
-| CTX-11 Dashboard/operator view | In progress | `feat/web-interface` adds a protected local view: job/task/worker status, dataset upload, diagnostic partial-artifact download, and polling. Final-result reduction remains CTX-09. |
+| CTX-11 Dashboard/operator view | Implemented (diagnostic scope) | Protected local view: job/task/worker status, validated similarity-search upload, diagnostic partial-artifact download, and bounded polling. Final-result reduction remains CTX-09. |
 | CTX-12 Reliability, security, CI | In progress | Unit, race, PostgreSQL integration, and smoke checks exist; CI hardening remains. |
 
 ## Next recommended assignment
@@ -53,6 +53,9 @@ reduction boundaries before implementing distributed search or graph execution.
   names and hyphenated CLI names while the contract is consolidated.
 - A real-stack worker test uses a small `query_smiles` shard. Resolving a
   `query_id` once and sharing it across shards belongs to CTX-07.
+- The coordinator accepts uploaded distributed jobs only for
+  `similarity-search` with `query_smiles`. It rejects `similarity-graph` until
+  CTX-10 supplies cross-shard pair planning.
 
 ## Update rule
 
diff --git a/coordinator/cmd/coordinator/main.go b/coordinator/cmd/coordinator/main.go
index 1134257..8447414 100644
--- a/coordinator/cmd/coordinator/main.go
+++ b/coordinator/cmd/coordinator/main.go
@@ -71,14 +71,14 @@ func run() error {
 	useCases := httptransport.UseCases{
 		RegisterWorker:   usecase.NewRegisterWorker(workerRepo, clk),
 		CreateJob:        usecase.NewCreateJob(jobRepo, taskRepo, tx, clk),
-		SubmitDataset:    usecase.NewSubmitDataset(blobStore, artifactRepo, jobRepo, taskRepo, tx, clk),
-		ClaimTask:        usecase.NewClaimTask(taskRepo, clk, cfg.LeaseDuration),
+		SubmitDataset:    usecase.NewSubmitDataset(blobStore, artifactRepo, jobRepo, taskRepo, tx, clk, cfg.DefaultMaxAttempts),
+		ClaimTask:        usecase.NewClaimTask(taskRepo, jobRepo, workerRepo, tx, clk, cfg.LeaseDuration),
 		RenewLease:       usecase.NewRenewLease(taskRepo, workerRepo, tx, clk, cfg.LeaseDuration),
 		CompleteTask:     usecase.NewCompleteTask(taskRepo, jobRepo, artifactRepo, tx, clk),
 		FailTask:         usecase.NewFailTask(taskRepo, jobRepo, tx, clk),
 		GetJobStatus:     usecase.NewGetJobStatus(jobRepo, taskRepo),
 		CancelJob:        usecase.NewCancelJob(jobRepo, taskRepo, tx, clk),
-		UploadArtifact:   usecase.NewUploadArtifact(taskRepo, artifactRepo, blobStore, clk),
+		UploadArtifact:   usecase.NewUploadArtifact(taskRepo, artifactRepo, blobStore, tx, clk),
 		DownloadArtifact: usecase.NewDownloadArtifact(artifactRepo, blobStore),
 		GetTaskInput:     usecase.NewGetTaskInput(taskRepo, artifactRepo, blobStore),
 		Dashboard:        usecase.NewDashboard(uiReadRepo),
@@ -87,7 +87,7 @@ func run() error {
 	// Background reapers are tracked so shutdown can wait for them. Without this
 	// the process would exit mid-UPDATE, and the deferred pool.Close() would pull
 	// connections out from under them.
-	expireLeases := usecase.NewExpireLeases(taskRepo, clk)
+	expireLeases := usecase.NewExpireLeases(taskRepo, jobRepo, tx, clk)
 	markOffline := usecase.NewMarkWorkersOffline(workerRepo, clk, cfg.WorkerOfflineAfter)
 
 	var wg sync.WaitGroup
diff --git a/coordinator/internal/chunk/tsv.go b/coordinator/internal/chunk/tsv.go
index f020810..b62e8b5 100644
--- a/coordinator/internal/chunk/tsv.go
+++ b/coordinator/internal/chunk/tsv.go
@@ -7,12 +7,19 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"strings"
 )
 
 // ErrNoRows is returned when the input has a header but no data rows: a job with
 // zero tasks could never complete, so it is rejected at the source.
 var ErrNoRows = fmt.Errorf("input has no data rows")
 
+// maxShardBytes bounds the coordinator memory used by one in-progress shard.
+// The uploaded file may be much larger: it is first stored on disk, then split
+// in small bounded pieces. Operators can lower rowsPerShard when this limit is
+// reached rather than exhausting the coordinator process.
+const maxShardBytes = 64 << 20 // 64 MiB
+
 // SplitTSV reads a header-plus-rows text stream and cuts it into shards of at
 // most rowsPerShard data rows. Every shard repeats the header, so a worker can
 // parse its shard in isolation. emit is called once per shard, in order, with a
@@ -26,13 +33,25 @@ var ErrNoRows = fmt.Errorf("input has no data rows")
 // Only one shard is buffered at a time, so memory is bounded by shard size (a
 // worker-sized slice of the data), not by the size of the whole dataset.
 func SplitTSV(r io.Reader, rowsPerShard int, emit func(index int, shard io.Reader) error) error {
-	return SplitTSVLimit(r, rowsPerShard, 0, emit)
+	return splitTSVLimit(r, rowsPerShard, 0, nil, emit)
 }
 
 // SplitTSVLimit behaves like SplitTSV but emits no more than maxRows data rows.
 // A maxRows value of zero means unlimited. This lets an operator make a small,
 // representative pipeline check without materialising a second dataset file.
 func SplitTSVLimit(r io.Reader, rowsPerShard, maxRows int, emit func(index int, shard io.Reader) error) error {
+	return splitTSVLimit(r, rowsPerShard, maxRows, nil, emit)
+}
+
+// SplitChEMBLTSVLimit is the coordinator's scientific-upload splitter. It
+// validates the two columns every local SciMesh workload requires before any
+// shard task is persisted, while generic SplitTSV remains reusable for future
+// non-chemistry workloads.
+func SplitChEMBLTSVLimit(r io.Reader, rowsPerShard, maxRows int, emit func(index int, shard io.Reader) error) error {
+	return splitTSVLimit(r, rowsPerShard, maxRows, validateChEMBLHeader, emit)
+}
+
+func splitTSVLimit(r io.Reader, rowsPerShard, maxRows int, validateHeader func([]byte) error, emit func(index int, shard io.Reader) error) error {
 	if rowsPerShard <= 0 {
 		return fmt.Errorf("rowsPerShard must be positive, got %d", rowsPerShard)
 	}
@@ -51,6 +70,11 @@ func SplitTSVLimit(r io.Reader, rowsPerShard, maxRows int, emit func(index int,
 		return ErrNoRows // completely empty input
 	}
 	header := append([]byte(nil), sc.Bytes()...)
+	if validateHeader != nil {
+		if err := validateHeader(header); err != nil {
+			return err
+		}
+	}
 
 	var (
 		buf   bytes.Buffer
@@ -71,9 +95,15 @@ func SplitTSVLimit(r io.Reader, rowsPerShard, maxRows int, emit func(index int,
 
 	for sc.Scan() {
 		if rows == 0 {
+			if len(header)+1 > maxShardBytes {
+				return fmt.Errorf("TSV header exceeds maximum shard size of %d bytes", maxShardBytes)
+			}
 			buf.Write(header)
 			buf.WriteByte('\n')
 		}
+		if buf.Len()+len(sc.Bytes())+1 > maxShardBytes {
+			return fmt.Errorf("shard exceeds maximum size of %d bytes; lower rowsPerShard", maxShardBytes)
+		}
 		buf.Write(sc.Bytes())
 		buf.WriteByte('\n')
 		rows++
@@ -103,3 +133,17 @@ func SplitTSVLimit(r io.Reader, rowsPerShard, maxRows int, emit func(index int,
 	}
 	return nil
 }
+
+func validateChEMBLHeader(header []byte) error {
+	seen := make(map[string]struct{})
+	for _, field := range strings.Split(strings.TrimPrefix(string(header), "\ufeff"), "\t") {
+		seen[field] = struct{}{}
+	}
+	if _, ok := seen["chembl_id"]; !ok {
+		return fmt.Errorf("TSV is missing required column chembl_id")
+	}
+	if _, ok := seen["canonical_smiles"]; !ok {
+		return fmt.Errorf("TSV is missing required column canonical_smiles")
+	}
+	return nil
+}
diff --git a/coordinator/internal/chunk/tsv_test.go b/coordinator/internal/chunk/tsv_test.go
index 585b35a..ea3dc04 100644
--- a/coordinator/internal/chunk/tsv_test.go
+++ b/coordinator/internal/chunk/tsv_test.go
@@ -119,6 +119,14 @@ func TestSplitLimitUsesOnlyLeadingDataRows(t *testing.T) {
 	}
 }
 
+func TestChEMBLSplitRejectsMissingRequiredColumns(t *testing.T) {
+	err := SplitChEMBLTSVLimit(strings.NewReader("id\tsmiles\nA\tCC\n"), 1, 0,
+		func(int, io.Reader) error { return nil })
+	if err == nil || !strings.Contains(err.Error(), "chembl_id") {
+		t.Errorf("err = %v, want missing-column error", err)
+	}
+}
+
 // The scanned bytes are reused by bufio; the shard buffer must copy them, or a
 // later row would corrupt an earlier one. This guards that copy.
 func TestSplitDoesNotAliasScannerBuffer(t *testing.T) {
diff --git a/coordinator/internal/infra/config.go b/coordinator/internal/infra/config.go
index 5414866..7d6db0e 100644
--- a/coordinator/internal/infra/config.go
+++ b/coordinator/internal/infra/config.go
@@ -129,6 +129,9 @@ func LoadConfig() (Config, error) {
 	if cfg.DefaultMaxAttempts, err = getEnvInt("DEFAULT_MAX_ATTEMPTS", cfg.DefaultMaxAttempts); err != nil {
 		return Config{}, err
 	}
+	if cfg.DefaultMaxAttempts < 1 {
+		return Config{}, fmt.Errorf("DEFAULT_MAX_ATTEMPTS must be positive")
+	}
 
 	return cfg, nil
 }
diff --git a/coordinator/internal/infra/config_test.go b/coordinator/internal/infra/config_test.go
index f9c0945..953887c 100644
--- a/coordinator/internal/infra/config_test.go
+++ b/coordinator/internal/infra/config_test.go
@@ -32,3 +32,14 @@ func TestLoadConfigAllowsDistinctUIAndWorkerTokens(t *testing.T) {
 		t.Fatalf("unexpected tokens: %+v", cfg)
 	}
 }
+
+func TestLoadConfigRejectsNonPositiveDefaultMaxAttempts(t *testing.T) {
+	t.Setenv("ENV_FILE", filepath.Join(t.TempDir(), "missing.env"))
+	t.Setenv("DATABASE_URL", "postgres://test")
+	t.Setenv("DEFAULT_MAX_ATTEMPTS", "0")
+
+	_, err := LoadConfig()
+	if err == nil || !strings.Contains(err.Error(), "DEFAULT_MAX_ATTEMPTS") {
+		t.Fatalf("LoadConfig error = %v, want default-attempt validation", err)
+	}
+}
diff --git a/coordinator/internal/memstore/memstore.go b/coordinator/internal/memstore/memstore.go
index 44db68e..c7f1076 100644
--- a/coordinator/internal/memstore/memstore.go
+++ b/coordinator/internal/memstore/memstore.go
@@ -160,17 +160,18 @@ func (r *TaskRepo) CancelByJob(_ context.Context, jobID uuid.UUID, now time.Time
 	return cancelled, nil
 }
 
-func (r *TaskRepo) ExpireLeases(ctx context.Context, now time.Time) (int64, error) {
+func (r *TaskRepo) ExpireLeases(ctx context.Context, now time.Time) ([]uuid.UUID, error) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
-	var n int64
+	affected := make([]uuid.UUID, 0)
 	for _, t := range r.tasks {
-		if t.Status == domain.TaskLeased && t.LeaseExpiresAt != nil && t.LeaseExpiresAt.Before(now) {
+		if (t.Status == domain.TaskLeased || t.Status == domain.TaskRunning) &&
+			t.LeaseExpiresAt != nil && t.LeaseExpiresAt.Before(now) {
 			t.ExpireLease(now)
-			n++
+			affected = append(affected, t.JobID)
 		}
 	}
-	return n, nil
+	return affected, nil
 }
 
 // --- JobRepo -------------------------------------------------------------
@@ -298,6 +299,23 @@ func (r *ArtifactRepo) Get(ctx context.Context, id uuid.UUID) (*domain.Artifact,
 	return &cp, nil
 }
 
+func (r *ArtifactRepo) FindPartialResult(_ context.Context, taskID uuid.UUID, attempt int) (*domain.Artifact, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	for _, a := range r.arts {
+		if a.TaskID != nil && *a.TaskID == taskID && a.Kind == domain.ArtifactPartialResult &&
+			a.Attempt != nil && *a.Attempt == attempt {
+			return cloneArtifact(a), nil
+		}
+	}
+	return nil, nil
+}
+
+func cloneArtifact(a *domain.Artifact) *domain.Artifact {
+	cp := *a
+	return &cp
+}
+
 // --- BlobStore -----------------------------------------------------------
 
 type BlobStore struct {
diff --git a/coordinator/internal/memstore/ui_read.go b/coordinator/internal/memstore/ui_read.go
index ce36e5c..23bff9d 100644
--- a/coordinator/internal/memstore/ui_read.go
+++ b/coordinator/internal/memstore/ui_read.go
@@ -60,6 +60,18 @@ func (r *UIReadRepo) ListTasksByJob(_ context.Context, jobID uuid.UUID) ([]domai
 	sort.Slice(out, func(i, j int) bool { return out[i].ChunkIndex < out[j].ChunkIndex })
 	return out, nil
 }
+
+func (r *UIReadRepo) ListTasksByJobs(ctx context.Context, jobIDs []uuid.UUID) (map[uuid.UUID][]domain.Task, error) {
+	out := make(map[uuid.UUID][]domain.Task, len(jobIDs))
+	for _, id := range jobIDs {
+		tasks, err := r.ListTasksByJob(ctx, id)
+		if err != nil {
+			return nil, err
+		}
+		out[id] = tasks
+	}
+	return out, nil
+}
 func (r *UIReadRepo) ListWorkers(_ context.Context, limit int) ([]domain.Worker, error) {
 	if limit < 1 || limit > 100 {
 		return nil, domain.ErrInvalidInput
diff --git a/coordinator/internal/storage/postgres/artifact_repo.go b/coordinator/internal/storage/postgres/artifact_repo.go
index f42abac..8f807f8 100644
--- a/coordinator/internal/storage/postgres/artifact_repo.go
+++ b/coordinator/internal/storage/postgres/artifact_repo.go
@@ -70,3 +70,33 @@ func (r *ArtifactRepo) Get(ctx context.Context, id uuid.UUID) (*domain.Artifact,
 	a.Kind = domain.ArtifactKind(kind)
 	return &a, nil
 }
+
+func (r *ArtifactRepo) FindPartialResult(ctx context.Context, taskID uuid.UUID, attempt int) (*domain.Artifact, error) {
+	sql, args, err := psql.Select(artifactColumns...).
+		From("artifacts").
+		Where(sq.Eq{
+			"task_id": taskID,
+			"attempt": attempt,
+			"kind":    string(domain.ArtifactPartialResult),
+		}).
+		ToSql()
+	if err != nil {
+		return nil, err
+	}
+
+	var (
+		a    domain.Artifact
+		kind string
+	)
+	err = conn(ctx, r.pool).QueryRow(ctx, sql, args...).Scan(
+		&a.ID, &a.JobID, &a.TaskID, &a.Attempt, &kind, &a.Filename, &a.StorageKey,
+		&a.ContentType, &a.SizeBytes, &a.SHA256, &a.CreatedAt)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("find partial result: %w", err)
+	}
+	a.Kind = domain.ArtifactKind(kind)
+	return &a, nil
+}
diff --git a/coordinator/internal/storage/postgres/integration_test.go b/coordinator/internal/storage/postgres/integration_test.go
index 6b3395a..b4b18ac 100644
--- a/coordinator/internal/storage/postgres/integration_test.go
+++ b/coordinator/internal/storage/postgres/integration_test.go
@@ -360,12 +360,23 @@ func TestCompleteTaskReplayIsIdempotent(t *testing.T) {
 		t.Errorf("replay must be idempotent, got %v", err)
 	}
 
-	// A different result artifact for the same task is a genuine conflict.
-	art2 := seedArtifact(t, pool, job.ID, &claimed.ID, domain.ArtifactPartialResult)
-	other := in
-	other.ResultArtifactID = art2.ID
-	if _, err := uc.Execute(ctx, other); !errors.Is(err, domain.ErrResultConflict) {
-		t.Errorf("err = %v, want ErrResultConflict", err)
+}
+
+func TestPartialResultIsUniquePerTaskAttempt(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	job, tasks := seedJob(t, pool, 1)
+	taskID := tasks[0].ID
+	first := seedArtifact(t, pool, job.ID, &taskID, domain.ArtifactPartialResult)
+	second, err := domain.NewArtifact(job.ID, &taskID, domain.ArtifactPartialResult, "retry.csv", "text/csv", time.Now().UTC())
+	if err != nil {
+		t.Fatal(err)
+	}
+	attempt := 1
+	second.Attempt = &attempt
+	second.SetContent("other-sha", 5)
+	if err := NewArtifactRepo(pool).Insert(ctx, second); err == nil {
+		t.Fatalf("second partial artifact for %s/%d was accepted after %s", taskID, attempt, first.ID)
 	}
 }
 
diff --git a/coordinator/internal/storage/postgres/task_repo.go b/coordinator/internal/storage/postgres/task_repo.go
index 18b2646..11b0616 100644
--- a/coordinator/internal/storage/postgres/task_repo.go
+++ b/coordinator/internal/storage/postgres/task_repo.go
@@ -337,17 +337,26 @@ SET status           = CASE WHEN attempt < max_attempts THEN 'pending'::task_sta
                             ELSE error_message END,
     completed_at     = CASE WHEN attempt >= max_attempts THEN $1 ELSE completed_at END,
     version          = version + 1
-WHERE status IN ('leased','running') AND lease_expires_at < $1`
+WHERE status IN ('leased','running') AND lease_expires_at < $1
+RETURNING job_id`
 
-func (r *TaskRepo) ExpireLeases(ctx context.Context, now time.Time) (int64, error) {
-	var affected int64
+func (r *TaskRepo) ExpireLeases(ctx context.Context, now time.Time) ([]uuid.UUID, error) {
+	var affected []uuid.UUID
 	err := withRetry(ctx, func(ctx context.Context) error {
-		tag, err := conn(ctx, r.pool).Exec(ctx, expireLeasesSQL, now, domain.ErrCodeLeaseExpired)
+		rows, err := conn(ctx, r.pool).Query(ctx, expireLeasesSQL, now, domain.ErrCodeLeaseExpired)
 		if err != nil {
 			return err
 		}
-		affected = tag.RowsAffected()
-		return nil
+		defer rows.Close()
+		affected = affected[:0]
+		for rows.Next() {
+			var jobID uuid.UUID
+			if err := rows.Scan(&jobID); err != nil {
+				return err
+			}
+			affected = append(affected, jobID)
+		}
+		return rows.Err()
 	})
 	return affected, err
 }
diff --git a/coordinator/internal/storage/postgres/ui_read_repo.go b/coordinator/internal/storage/postgres/ui_read_repo.go
index 4a24ed2..81270b1 100644
--- a/coordinator/internal/storage/postgres/ui_read_repo.go
+++ b/coordinator/internal/storage/postgres/ui_read_repo.go
@@ -75,6 +75,31 @@ func (r *UIReadRepo) ListTasksByJob(ctx context.Context, jobID uuid.UUID) ([]dom
 	return tasks, rows.Err()
 }
 
+func (r *UIReadRepo) ListTasksByJobs(ctx context.Context, jobIDs []uuid.UUID) (map[uuid.UUID][]domain.Task, error) {
+	out := make(map[uuid.UUID][]domain.Task, len(jobIDs))
+	if len(jobIDs) == 0 {
+		return out, nil
+	}
+	sql, args, err := psql.Select(taskColumns...).From("tasks").
+		Where(sq.Eq{"job_id": jobIDs}).OrderBy("job_id ASC", "chunk_index ASC").ToSql()
+	if err != nil {
+		return nil, err
+	}
+	rows, err := conn(ctx, r.pool).Query(ctx, sql, args...)
+	if err != nil {
+		return nil, fmt.Errorf("list tasks by jobs: %w", err)
+	}
+	defer rows.Close()
+	for rows.Next() {
+		task, err := scanTask(rows)
+		if err != nil {
+			return nil, err
+		}
+		out[task.JobID] = append(out[task.JobID], *task)
+	}
+	return out, rows.Err()
+}
+
 func (r *UIReadRepo) ListWorkers(ctx context.Context, limit int) ([]domain.Worker, error) {
 	if limit < 1 || limit > 100 {
 		return nil, domain.ErrInvalidInput
diff --git a/coordinator/internal/transport/http/handlers.go b/coordinator/internal/transport/http/handlers.go
index 4bbf5c8..33ad06b 100644
--- a/coordinator/internal/transport/http/handlers.go
+++ b/coordinator/internal/transport/http/handlers.go
@@ -79,6 +79,10 @@ func (s *Server) handleClaim(w http.ResponseWriter, r *http.Request) {
 		s.writeError(w, r, domain.ErrInvalidInput)
 		return
 	}
+	if _, err := uuid.Parse(req.WorkerID); err != nil {
+		s.writeError(w, r, domain.ErrInvalidInput)
+		return
+	}
 
 	claimed, err := s.uc.ClaimTask.Execute(ctx, usecase.ClaimTaskInput{
 		WorkerID:  req.WorkerID,
diff --git a/coordinator/internal/transport/http/server_test.go b/coordinator/internal/transport/http/server_test.go
index 261197c..52c453f 100644
--- a/coordinator/internal/transport/http/server_test.go
+++ b/coordinator/internal/transport/http/server_test.go
@@ -23,8 +23,9 @@ const token = "secret"
 const uiToken = "ui-secret"
 
 type env struct {
-	ts    *httptest.Server
-	blobs *memstore.BlobStore
+	ts       *httptest.Server
+	blobs    *memstore.BlobStore
+	workerID string
 }
 
 func newEnv(t *testing.T, ready func(context.Context) error) *env {
@@ -45,22 +46,28 @@ func newEnvWithUIToken(t *testing.T, ready func(context.Context) error, configur
 	uc := coordhttp.UseCases{
 		RegisterWorker:   usecase.NewRegisterWorker(work, clk),
 		CreateJob:        usecase.NewCreateJob(jobs, tasks, tx, clk),
-		SubmitDataset:    usecase.NewSubmitDataset(blobs, arts, jobs, tasks, tx, clk),
-		ClaimTask:        usecase.NewClaimTask(tasks, clk, lease),
+		SubmitDataset:    usecase.NewSubmitDataset(blobs, arts, jobs, tasks, tx, clk, 3),
+		ClaimTask:        usecase.NewClaimTask(tasks, jobs, work, tx, clk, lease),
 		RenewLease:       usecase.NewRenewLease(tasks, work, tx, clk, lease),
 		CompleteTask:     usecase.NewCompleteTask(tasks, jobs, arts, tx, clk),
 		FailTask:         usecase.NewFailTask(tasks, jobs, tx, clk),
 		GetJobStatus:     usecase.NewGetJobStatus(jobs, tasks),
 		CancelJob:        usecase.NewCancelJob(jobs, tasks, tx, clk),
-		UploadArtifact:   usecase.NewUploadArtifact(tasks, arts, blobs, clk),
+		UploadArtifact:   usecase.NewUploadArtifact(tasks, arts, blobs, tx, clk),
 		DownloadArtifact: usecase.NewDownloadArtifact(arts, blobs),
 		GetTaskInput:     usecase.NewGetTaskInput(tasks, arts, blobs),
 		Dashboard:        usecase.NewDashboard(memstore.NewUIReadRepo(jobs, tasks, work, arts)),
 	}
+	worker, err := uc.RegisterWorker.Execute(context.Background(), usecase.RegisterWorkerInput{
+		Name: "test-worker", Capabilities: []string{"w", "similarity-search"},
+	})
+	if err != nil {
+		t.Fatalf("register test worker: %v", err)
+	}
 	srv := coordhttp.NewServer(uc, slog.New(slog.NewTextHandler(io.Discard, nil)), 5*time.Second, 15*time.Second, 1<<30, ready)
 	ts := httptest.NewServer(srv.Handler(token, configuredUIToken))
 	t.Cleanup(ts.Close)
-	return &env{ts: ts, blobs: blobs}
+	return &env{ts: ts, blobs: blobs, workerID: worker.ID.String()}
 }
 
 func healthy(context.Context) error { return nil }
@@ -68,6 +75,7 @@ func healthy(context.Context) error { return nil }
 // do sends an authenticated JSON request and returns status + decoded body.
 func (e *env) do(t *testing.T, method, path, body string) (int, map[string]any) {
 	t.Helper()
+	body = strings.ReplaceAll(body, `"worker_id":"w1"`, `"worker_id":"`+e.workerID+`"`)
 	req, _ := http.NewRequestWithContext(context.Background(), method, e.ts.URL+path, strings.NewReader(body))
 	req.Header.Set("Authorization", "Bearer "+token)
 	if body != "" {
@@ -330,6 +338,26 @@ func TestRegisterRejectsNoCapabilities(t *testing.T) {
 	}
 }
 
+func TestClaimRequiresRegisteredWorkerAndUsesStoredCapabilities(t *testing.T) {
+	e := newEnv(t, healthy)
+	if code, _ := e.do(t, "POST", "/tasks/claim", `{"worker_id":"not-a-uuid"}`); code != http.StatusBadRequest {
+		t.Fatalf("invalid worker id claim = %d, want 400", code)
+	}
+	if code, _ := e.do(t, "POST", "/tasks/claim", `{"worker_id":"11111111-1111-4111-8111-111111111111"}`); code != http.StatusNotFound {
+		t.Fatalf("unregistered worker claim = %d, want 404", code)
+	}
+	if code, _ := e.do(t, "POST", "/jobs", `{"workload":"w","input_uri":"s3://in","chunks":[{"chunk_index":0,"input_uri":"s3://c","input_sha256":"sha"}]}`); code != http.StatusCreated {
+		t.Fatalf("create job = %d", code)
+	}
+	code, worker := e.do(t, "POST", "/workers/register", `{"name":"search-only","capabilities":["similarity-search"]}`)
+	if code != http.StatusCreated {
+		t.Fatalf("register = %d", code)
+	}
+	if code, _ := e.do(t, "POST", "/tasks/claim", `{"worker_id":"`+worker["worker_id"].(string)+`","capabilities":["w"]}`); code != http.StatusNoContent {
+		t.Fatalf("forged capability claim = %d, want 204", code)
+	}
+}
+
 func TestFullLifecycle(t *testing.T) {
 	e := newEnv(t, healthy)
 
@@ -393,9 +421,9 @@ func TestForeignArtifactResultConflict(t *testing.T) {
 
 func TestUploadDatasetChunksAndServesInput(t *testing.T) {
 	e := newEnv(t, healthy)
-	tsv := "id\tsmiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\nE\tCCCCCC\n"
+	tsv := "chembl_id\tcanonical_smiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\nE\tCCCCCC\n"
 
-	code, body := e.uploadDataset(t, "w", 2, tsv)
+	code, body := e.uploadDataset(t, "similarity-search", 2, tsv)
 	if code != 201 {
 		t.Fatalf("upload: status = %d", code)
 	}
@@ -421,7 +449,7 @@ func TestUploadDatasetChunksAndServesInput(t *testing.T) {
 		t.Fatalf("get input: status = %d", resp.StatusCode)
 	}
 	shard, _ := io.ReadAll(resp.Body)
-	if !strings.HasPrefix(string(shard), "id\tsmiles\n") {
+	if !strings.HasPrefix(string(shard), "chembl_id\tcanonical_smiles\n") {
 		t.Errorf("shard missing header: %q", shard)
 	}
 }
@@ -430,11 +458,12 @@ func TestUploadDatasetLimitsRows(t *testing.T) {
 	e := newEnv(t, healthy)
 	var buf bytes.Buffer
 	mw := multipart.NewWriter(&buf)
-	_ = mw.WriteField("workload", "w")
+	_ = mw.WriteField("workload", "similarity-search")
+	_ = mw.WriteField("parameters", `{"query_smiles":"CCO"}`)
 	_ = mw.WriteField("chunk_rows", "2")
 	_ = mw.WriteField("max_rows", "3")
 	fw, _ := mw.CreateFormFile("file", "chembl.tsv")
-	_, _ = io.Copy(fw, strings.NewReader("id\tsmiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\n"))
+	_, _ = io.Copy(fw, strings.NewReader("chembl_id\tcanonical_smiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\n"))
 	_ = mw.Close()
 	req, _ := http.NewRequestWithContext(context.Background(), "POST", e.ts.URL+"/jobs/upload", &buf)
 	req.Header.Set("Authorization", "Bearer "+token)
@@ -451,6 +480,29 @@ func TestUploadDatasetLimitsRows(t *testing.T) {
 	}
 }
 
+func TestUploadDatasetRejectsMissingChEMBLColumns(t *testing.T) {
+	e := newEnv(t, healthy)
+	var buf bytes.Buffer
+	mw := multipart.NewWriter(&buf)
+	_ = mw.WriteField("workload", "similarity-search")
+	_ = mw.WriteField("parameters", `{"query_smiles":"CCO"}`)
+	_ = mw.WriteField("chunk_rows", "2")
+	fw, _ := mw.CreateFormFile("file", "not-chembl.tsv")
+	_, _ = io.Copy(fw, strings.NewReader("id\tsmiles\nA\tCC\n"))
+	_ = mw.Close()
+	req, _ := http.NewRequestWithContext(context.Background(), "POST", e.ts.URL+"/jobs/upload", &buf)
+	req.Header.Set("Authorization", "Bearer "+token)
+	req.Header.Set("Content-Type", mw.FormDataContentType())
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusBadRequest {
+		t.Errorf("missing ChEMBL columns = %d, want 400", resp.StatusCode)
+	}
+}
+
 func TestErrorMappings(t *testing.T) {
 	e := newEnv(t, healthy)
 	zero := "00000000-0000-0000-0000-000000000000"
@@ -478,10 +530,11 @@ func TestUploadDatasetRejectsAmbiguousMultipartInput(t *testing.T) {
 	e := newEnv(t, healthy)
 	var buf bytes.Buffer
 	mw := multipart.NewWriter(&buf)
-	_ = mw.WriteField("workload", "w")
+	_ = mw.WriteField("workload", "similarity-search")
+	_ = mw.WriteField("parameters", `{"query_smiles":"CCO"}`)
 	_ = mw.WriteField("chunk_rows", "not-a-number")
 	fw, _ := mw.CreateFormFile("file", "chembl.tsv")
-	_, _ = io.Copy(fw, strings.NewReader("id\tsmiles\nA\tCC\n"))
+	_, _ = io.Copy(fw, strings.NewReader("chembl_id\tcanonical_smiles\nA\tCC\n"))
 	_ = mw.Close()
 
 	req, _ := http.NewRequestWithContext(context.Background(), "POST", e.ts.URL+"/jobs/upload", &buf)
@@ -505,6 +558,9 @@ func (e *env) putArtifact(t *testing.T, taskID, worker string, attempt int, data
 		e.ts.URL+"/tasks/"+taskID+"/artifacts/r.csv", strings.NewReader(data))
 	req.Header.Set("Authorization", "Bearer "+token)
 	req.Header.Set("Content-Type", "text/csv")
+	if worker == "w1" {
+		worker = e.workerID
+	}
 	req.Header.Set("X-Worker-ID", worker)
 	req.Header.Set("X-Task-Attempt", itoa(attempt))
 	resp, err := http.DefaultClient.Do(req)
@@ -526,6 +582,7 @@ func (e *env) uploadDataset(t *testing.T, workload string, rows int, tsv string)
 	var buf bytes.Buffer
 	mw := multipart.NewWriter(&buf)
 	_ = mw.WriteField("workload", workload)
+	_ = mw.WriteField("parameters", `{"query_smiles":"CCO"}`)
 	_ = mw.WriteField("chunk_rows", itoa(rows))
 	fw, _ := mw.CreateFormFile("file", "chembl.tsv")
 	_, _ = io.Copy(fw, strings.NewReader(tsv))
diff --git a/coordinator/internal/transport/http/templates/job.html b/coordinator/internal/transport/http/templates/job.html
index f983e2d..b985a2e 100644
--- a/coordinator/internal/transport/http/templates/job.html
+++ b/coordinator/internal/transport/http/templates/job.html
@@ -22,7 +22,7 @@
   <script>
     const id={{printf "%q" .ID}},state={pending:['Waiting for a worker','waiting','Waiting for an available worker with the required capability.'],leased:['Assigned to a worker','active','A worker has claimed the task and should begin processing shortly.'],running:['Running','active','A worker is reading a shard, calculating fingerprints, and uploading its result through the coordinator.'],completed:['Tasks complete','success','Every shard task is complete. Files below are still partial results.'],failed:['Needs attention','danger','One or more shard tasks failed. Open the task list below for details.'],cancelled:['Stopped','waiting','The operator stopped this job. No new shards can be claimed.']};
     const stop=document.querySelector('#stop-job');if(stop)stop.addEventListener('click',async()=>{if(!confirm('Stop this job? Unfinished shards will be cancelled.'))return;stop.disabled=true;const response=await fetch('/ui/api/jobs/'+id+'/cancel',{method:'POST'});if(!response.ok){stop.disabled=false;alert('Unable to stop this job.');return}location.reload()});
-    setInterval(async()=>{try{const response=await fetch('/ui/api/jobs/'+id);if(!response.ok)return;const job=await response.json(),info=state[job.status]||[job.status,'waiting','Status reported by the coordinator.'],done=job.completed+job.failed+job.cancelled,percent=job.total?Math.min(100,Math.floor(done*100/job.total)):0,badge=document.querySelector('#status');badge.textContent=info[0];badge.className='status status-'+info[1];document.querySelector('#hint').textContent=info[2];document.querySelector('#progress').textContent=job.completed+' of '+job.total+' tasks complete'+(job.failed?' · failed: '+job.failed:'')+(job.cancelled?' · stopped: '+job.cancelled:'');document.querySelector('#progress-bar').style.width=percent+'%';for(const key of ['total','completed','pending','failed','cancelled'])document.querySelector('#'+key).textContent=job[key];document.querySelector('#active').textContent=job.leased+job.running}catch(_){}} ,2000);
+    const terminal=new Set(['completed','failed','cancelled']);let timer;const poll=async()=>{try{const response=await fetch('/ui/api/jobs/'+id);if(!response.ok)return;const job=await response.json(),info=state[job.status]||[job.status,'waiting','Status reported by the coordinator.'],done=job.completed+job.failed+job.cancelled,percent=job.total?Math.min(100,Math.floor(done*100/job.total)):0,badge=document.querySelector('#status');badge.textContent=info[0];badge.className='status status-'+info[1];document.querySelector('#hint').textContent=info[2];document.querySelector('#progress').textContent=job.completed+' of '+job.total+' tasks complete'+(job.failed?' · failed: '+job.failed:'')+(job.cancelled?' · stopped: '+job.cancelled:'');document.querySelector('#progress-bar').style.width=percent+'%';for(const key of ['total','completed','pending','failed','cancelled'])document.querySelector('#'+key).textContent=job[key];document.querySelector('#active').textContent=job.leased+job.running;if(terminal.has(job.status)&&timer){clearInterval(timer);timer=undefined}}catch(_){}};const start=()=>{if(!timer&&!document.hidden&&!terminal.has(document.querySelector('#status').textContent.toLowerCase()))timer=setInterval(poll,2000)};document.addEventListener('visibilitychange',()=>{if(document.hidden&&timer){clearInterval(timer);timer=undefined}else start()});start();
   </script>
 </body>
 </html>
diff --git a/coordinator/internal/usecase/artifact.go b/coordinator/internal/usecase/artifact.go
index 5cb8b8b..7a0187f 100644
--- a/coordinator/internal/usecase/artifact.go
+++ b/coordinator/internal/usecase/artifact.go
@@ -14,12 +14,13 @@ type UploadArtifact struct {
 	tasks     TaskRepository
 	artifacts ArtifactRepository
 	blobs     BlobStore
+	tx        TxManager
 	clk       Clock
 }
 
 func NewUploadArtifact(tasks TaskRepository, artifacts ArtifactRepository,
-	blobs BlobStore, clk Clock) *UploadArtifact {
-	return &UploadArtifact{tasks: tasks, artifacts: artifacts, blobs: blobs, clk: clk}
+	blobs BlobStore, tx TxManager, clk Clock) *UploadArtifact {
+	return &UploadArtifact{tasks: tasks, artifacts: artifacts, blobs: blobs, tx: tx, clk: clk}
 }
 
 func (uc *UploadArtifact) Execute(ctx context.Context, in UploadArtifactInput) (*domain.Artifact, error) {
@@ -32,6 +33,15 @@ func (uc *UploadArtifact) Execute(ctx context.Context, in UploadArtifactInput) (
 	if !task.IsLeaseHeldBy(in.WorkerID, in.Attempt, uc.clk.Now()) {
 		return nil, domain.ErrLeaseConflict
 	}
+	// A client can retry a PUT after losing the response. Return the one durable
+	// result for this lease attempt instead of storing duplicate artifacts.
+	existing, err := uc.artifacts.FindPartialResult(ctx, in.TaskID, in.Attempt)
+	if err != nil {
+		return nil, err
+	}
+	if existing != nil {
+		return existing, nil
+	}
 
 	taskID := task.ID
 	art, err := domain.NewArtifact(task.JobID, &taskID, domain.ArtifactPartialResult,
@@ -50,25 +60,41 @@ func (uc *UploadArtifact) Execute(ctx context.Context, in UploadArtifactInput) (
 	}
 	art.SetContent(sum, size)
 
-	// The stream may take longer than the lease. Re-check after it finishes so
-	// an expired worker cannot leave a durable result record behind. Completion
-	// performs the same ownership check under its transaction.
-	current, err := uc.tasks.Get(ctx, in.TaskID)
+	// The stream may take longer than the lease. Lock the task while re-checking
+	// ownership and inserting metadata: completion or another upload cannot race
+	// this final decision. The database unique index is a second line of defence.
+	var durable *domain.Artifact
+	err = uc.tx.WithinTx(ctx, func(ctx context.Context) error {
+		current, err := uc.tasks.GetForUpdate(ctx, in.TaskID)
+		if err != nil {
+			return err
+		}
+		if !current.IsLeaseHeldBy(in.WorkerID, in.Attempt, uc.clk.Now()) {
+			return domain.ErrLeaseConflict
+		}
+		existing, err := uc.artifacts.FindPartialResult(ctx, in.TaskID, in.Attempt)
+		if err != nil {
+			return err
+		}
+		if existing != nil {
+			durable = existing
+			return nil
+		}
+		if err := uc.artifacts.Insert(ctx, art); err != nil {
+			return err
+		}
+		durable = art
+		return nil
+	})
 	if err != nil {
 		_ = uc.blobs.Delete(ctx, art.StorageKey)
 		return nil, err
 	}
-	if !current.IsLeaseHeldBy(in.WorkerID, in.Attempt, uc.clk.Now()) {
+	if durable != art {
+		// Another request won the race while this stream was being written.
 		_ = uc.blobs.Delete(ctx, art.StorageKey)
-		return nil, domain.ErrLeaseConflict
 	}
-
-	// Persist the record. If that fails the blob would be an orphan, so remove it.
-	if err := uc.artifacts.Insert(ctx, art); err != nil {
-		_ = uc.blobs.Delete(ctx, art.StorageKey)
-		return nil, err
-	}
-	return art, nil
+	return durable, nil
 }
 
 // DownloadArtifact returns an artifact's metadata together with a reader over
diff --git a/coordinator/internal/usecase/job.go b/coordinator/internal/usecase/job.go
index 748f021..f6e0497 100644
--- a/coordinator/internal/usecase/job.go
+++ b/coordinator/internal/usecase/job.go
@@ -33,6 +33,17 @@ func NewCreateJob(jobs JobRepository, tasks TaskRepository, tx TxManager, clock
 // The all-or-none guarantee comes from TxManager: a half-created job would
 // leave chunks no worker could ever complete.
 func (uc *CreateJob) Execute(ctx context.Context, in CreateJobInput) (*domain.Job, error) {
+	if in.Workload == "similarity-graph" || in.Workload == "similarity_graph" {
+		// CTX-10 must plan triangular block pairs; ordinary independent input
+		// chunks would silently omit every cross-chunk molecular pair.
+		return nil, domain.ErrInvalidInput
+	}
+	if (in.Workload == "similarity-search" || in.Workload == "similarity_search") &&
+		len(in.Chunks) > 1 && in.Parameters["query_id"] != nil {
+		// Resolving once against the source dataset belongs to CTX-07. Letting
+		// each shard resolve it would make most tasks fail or use inconsistent data.
+		return nil, domain.ErrInvalidInput
+	}
 	chunks := make([]domain.ChunkSpec, 0, len(in.Chunks))
 	for _, c := range in.Chunks {
 		chunks = append(chunks, domain.ChunkSpec(c))
@@ -92,6 +103,17 @@ func (uc *CancelJob) Execute(ctx context.Context, jobID uuid.UUID) (int64, error
 		if job.Status == domain.JobCompleted || job.Status == domain.JobFailed {
 			return domain.ErrJobNotCancellable
 		}
+		// The lease reaper can be the transition that exhausted the final task.
+		// Check the authoritative task histogram as well as the cached job status,
+		// so a stale status can never turn a failed/completed job into cancelled.
+		counts, err := uc.tasks.CountByStatus(ctx, jobID)
+		if err != nil {
+			return err
+		}
+		derived := progressFrom(*job, counts).DeriveStatus()
+		if derived == domain.JobCompleted || derived == domain.JobFailed {
+			return domain.ErrJobNotCancellable
+		}
 		cancelled, err = uc.tasks.CancelByJob(ctx, jobID, now)
 		if err != nil {
 			return err
@@ -212,3 +234,18 @@ func syncJobStatus(ctx context.Context, jobs JobRepository, tasks TaskRepository
 	}
 	return jobs.UpdateStatus(ctx, jobID, status, completedAt)
 }
+
+func syncExpiredJobStatuses(ctx context.Context, jobs JobRepository, tasks TaskRepository,
+	jobIDs []uuid.UUID, now time.Time) error {
+	seen := make(map[uuid.UUID]struct{}, len(jobIDs))
+	for _, jobID := range jobIDs {
+		if _, duplicate := seen[jobID]; duplicate {
+			continue
+		}
+		seen[jobID] = struct{}{}
+		if err := syncJobStatus(ctx, jobs, tasks, jobID, now); err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/coordinator/internal/usecase/ports.go b/coordinator/internal/usecase/ports.go
index 7b56211..119a0c9 100644
--- a/coordinator/internal/usecase/ports.go
+++ b/coordinator/internal/usecase/ports.go
@@ -60,9 +60,9 @@ type TaskRepository interface {
 	// lease. It returns how many tasks changed.
 	CancelByJob(ctx context.Context, jobID uuid.UUID, now time.Time) (int64, error)
 
-	// ExpireLeases applies the lease-expiry rule to every elapsed task and
-	// reports how many were affected.
-	ExpireLeases(ctx context.Context, now time.Time) (int64, error)
+	// ExpireLeases applies the lease-expiry rule to every elapsed task and returns
+	// the distinct jobs whose aggregate status may have changed.
+	ExpireLeases(ctx context.Context, now time.Time) ([]uuid.UUID, error)
 }
 
 // JobRepository persists jobs.
@@ -89,6 +89,9 @@ type WorkerRepository interface {
 type ArtifactRepository interface {
 	Insert(ctx context.Context, a *domain.Artifact) error
 	Get(ctx context.Context, id uuid.UUID) (*domain.Artifact, error)
+	// FindPartialResult returns the durable result already uploaded for one task
+	// attempt. A nil artifact means the attempt has not uploaded one yet.
+	FindPartialResult(ctx context.Context, taskID uuid.UUID, attempt int) (*domain.Artifact, error)
 }
 
 // BlobStore holds artifact bytes, addressed by an opaque storage key. It streams
diff --git a/coordinator/internal/usecase/task.go b/coordinator/internal/usecase/task.go
index 131cffe..1af5bf8 100644
--- a/coordinator/internal/usecase/task.go
+++ b/coordinator/internal/usecase/task.go
@@ -21,12 +21,15 @@ import (
 
 type ClaimTask struct {
 	tasks         TaskRepository
+	jobs          JobRepository
+	workers       WorkerRepository
+	tx            TxManager
 	clock         Clock
 	leaseDuration time.Duration
 }
 
-func NewClaimTask(tasks TaskRepository, clock Clock, leaseDuration time.Duration) *ClaimTask {
-	return &ClaimTask{tasks: tasks, clock: clock, leaseDuration: leaseDuration}
+func NewClaimTask(tasks TaskRepository, jobs JobRepository, workers WorkerRepository, tx TxManager, clock Clock, leaseDuration time.Duration) *ClaimTask {
+	return &ClaimTask{tasks: tasks, jobs: jobs, workers: workers, tx: tx, clock: clock, leaseDuration: leaseDuration}
 }
 
 // Execute reclaims elapsed leases first, then hands out one task.
@@ -42,27 +45,46 @@ func (uc *ClaimTask) Execute(ctx context.Context, in ClaimTaskInput) (*domain.Cl
 	if in.WorkerID == "" {
 		return nil, domain.ErrInvalidInput
 	}
-	now := uc.clock.Now()
-
-	if _, err := uc.tasks.ExpireLeases(ctx, now); err != nil {
-		return nil, err
+	workloads := in.Workloads
+	if workerID, err := uuid.Parse(in.WorkerID); err == nil {
+		worker, err := uc.workers.Get(ctx, workerID)
+		if err != nil {
+			return nil, err
+		}
+		// Never trust caller-supplied capabilities: registration is the durable
+		// worker identity and its allowlist.
+		workloads = worker.Capabilities
 	}
+	var claimed *domain.ClaimedTask
+	err := uc.tx.WithinTx(ctx, func(ctx context.Context) error {
+		now := uc.clock.Now()
+		affectedJobs, err := uc.tasks.ExpireLeases(ctx, now)
+		if err != nil {
+			return err
+		}
+		if err := syncExpiredJobStatuses(ctx, uc.jobs, uc.tasks, affectedJobs, now); err != nil {
+			return err
+		}
 
-	task, err := uc.tasks.ClaimNext(ctx, ClaimFilter{
-		Workloads:  in.Workloads,
-		Owner:      in.WorkerID,
-		Now:        now,
-		LeaseUntil: now.Add(uc.leaseDuration),
+		task, err := uc.tasks.ClaimNext(ctx, ClaimFilter{
+			Workloads:  workloads,
+			Owner:      in.WorkerID,
+			Now:        now,
+			LeaseUntil: now.Add(uc.leaseDuration),
+		})
+		if err != nil {
+			return err
+		}
+		if task != nil {
+			value := task.AsClaimed()
+			claimed = &value
+		}
+		return nil
 	})
 	if err != nil {
 		return nil, err
 	}
-	if task == nil {
-		return nil, nil // empty queue is a normal state, not an error
-	}
-
-	claimed := task.AsClaimed()
-	return &claimed, nil
+	return claimed, nil // nil means an empty queue
 }
 
 // --- RenewLease ----------------------------------------------------------
@@ -230,18 +252,30 @@ func (uc *FailTask) Execute(ctx context.Context, in FailTaskInput) (*domain.Task
 
 type ExpireLeases struct {
 	tasks TaskRepository
+	jobs  JobRepository
+	tx    TxManager
 	clock Clock
 }
 
-func NewExpireLeases(tasks TaskRepository, clock Clock) *ExpireLeases {
-	return &ExpireLeases{tasks: tasks, clock: clock}
+func NewExpireLeases(tasks TaskRepository, jobs JobRepository, tx TxManager, clock Clock) *ExpireLeases {
+	return &ExpireLeases{tasks: tasks, jobs: jobs, tx: tx, clock: clock}
 }
 
-// Execute reports how many tasks were reclaimed.
+// Execute reclaims elapsed tasks and persists the state of every affected job.
 //
 // The sweep is one set-based statement rather than a load-decide-save loop:
 // several coordinators run it concurrently, and a single atomic UPDATE makes
 // the duplicate work harmless — the loser simply updates 0 rows.
 func (uc *ExpireLeases) Execute(ctx context.Context) (int64, error) {
-	return uc.tasks.ExpireLeases(ctx, uc.clock.Now())
+	var affected []uuid.UUID
+	err := uc.tx.WithinTx(ctx, func(ctx context.Context) error {
+		now := uc.clock.Now()
+		var err error
+		affected, err = uc.tasks.ExpireLeases(ctx, now)
+		if err != nil {
+			return err
+		}
+		return syncExpiredJobStatuses(ctx, uc.jobs, uc.tasks, affected, now)
+	})
+	return int64(len(affected)), err
 }
diff --git a/coordinator/internal/usecase/ui.go b/coordinator/internal/usecase/ui.go
index c7283c3..dac5fe0 100644
--- a/coordinator/internal/usecase/ui.go
+++ b/coordinator/internal/usecase/ui.go
@@ -15,6 +15,7 @@ type UIReadRepository interface {
 	GetJob(ctx context.Context, jobID uuid.UUID) (*domain.Job, error)
 	ListJobs(ctx context.Context, limit int) ([]domain.Job, error)
 	ListTasksByJob(ctx context.Context, jobID uuid.UUID) ([]domain.Task, error)
+	ListTasksByJobs(ctx context.Context, jobIDs []uuid.UUID) (map[uuid.UUID][]domain.Task, error)
 	ListWorkers(ctx context.Context, limit int) ([]domain.Worker, error)
 	ListArtifactsByJob(ctx context.Context, jobID uuid.UUID) ([]domain.Artifact, error)
 }
@@ -88,12 +89,16 @@ func (d *Dashboard) Overview(ctx context.Context, limit int) (DashboardView, err
 		return DashboardView{}, err
 	}
 	out := DashboardView{Jobs: make([]JobCard, 0, len(jobs)), Workers: make([]WorkerCard, 0, len(workers))}
+	jobIDs := make([]uuid.UUID, 0, len(jobs))
 	for _, job := range jobs {
-		tasks, err := d.read.ListTasksByJob(ctx, job.ID)
-		if err != nil {
-			return DashboardView{}, err
-		}
-		out.Jobs = append(out.Jobs, jobCard(job, tasks))
+		jobIDs = append(jobIDs, job.ID)
+	}
+	tasksByJob, err := d.read.ListTasksByJobs(ctx, jobIDs)
+	if err != nil {
+		return DashboardView{}, err
+	}
+	for _, job := range jobs {
+		out.Jobs = append(out.Jobs, jobCard(job, tasksByJob[job.ID]))
 	}
 	for _, worker := range workers {
 		out.Workers = append(out.Workers, WorkerCard{ID: worker.ID.String(), Name: worker.Name, Status: string(worker.Status), Capabilities: worker.Capabilities, LastHeartbeatAt: worker.LastHeartbeatAt})
diff --git a/coordinator/internal/usecase/upload.go b/coordinator/internal/usecase/upload.go
index 20fb899..ad394db 100644
--- a/coordinator/internal/usecase/upload.go
+++ b/coordinator/internal/usecase/upload.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"math"
 
 	"github.com/google/uuid"
 
@@ -15,20 +16,27 @@ import (
 // creates the job with one task per shard — the coordinator-side counterpart of
 // a client submitting pre-chunked URIs.
 type SubmitDataset struct {
-	blobs     BlobStore
-	artifacts ArtifactRepository
-	jobs      JobRepository
-	tasks     TaskRepository
-	tx        TxManager
-	clk       Clock
+	blobs       BlobStore
+	artifacts   ArtifactRepository
+	jobs        JobRepository
+	tasks       TaskRepository
+	tx          TxManager
+	clk         Clock
+	maxAttempts int
 }
 
 func NewSubmitDataset(blobs BlobStore, artifacts ArtifactRepository, jobs JobRepository,
-	tasks TaskRepository, tx TxManager, clk Clock) *SubmitDataset {
-	return &SubmitDataset{blobs: blobs, artifacts: artifacts, jobs: jobs, tasks: tasks, tx: tx, clk: clk}
+	tasks TaskRepository, tx TxManager, clk Clock, maxAttempts int) *SubmitDataset {
+	return &SubmitDataset{blobs: blobs, artifacts: artifacts, jobs: jobs, tasks: tasks, tx: tx, clk: clk, maxAttempts: maxAttempts}
 }
 
 func (uc *SubmitDataset) Execute(ctx context.Context, in SubmitDatasetInput) (SubmitDatasetResult, error) {
+	if err := validateUploadedWorkload(in.Workload, in.Parameters); err != nil {
+		return SubmitDatasetResult{}, err
+	}
+	if uc.maxAttempts < 1 {
+		return SubmitDatasetResult{}, domain.ErrInvalidInput
+	}
 	now := uc.clk.Now()
 
 	job, err := domain.NewUploadedJob(in.Workload, in.Parameters, now)
@@ -64,7 +72,7 @@ func (uc *SubmitDataset) Execute(ctx context.Context, in SubmitDatasetInput) (Su
 		cleanup()
 		return SubmitDatasetResult{}, err
 	}
-	splitErr := chunk.SplitTSVLimit(rc, in.RowsPerShard, in.MaxRows, func(index int, shard io.Reader) error {
+	splitErr := chunk.SplitChEMBLTSVLimit(rc, in.RowsPerShard, in.MaxRows, func(index int, shard io.Reader) error {
 		art, err := domain.NewArtifact(job.ID, nil, domain.ArtifactShard,
 			fmt.Sprintf("shard-%d.tsv", index), in.ContentType, now)
 		if err != nil {
@@ -77,7 +85,7 @@ func (uc *SubmitDataset) Execute(ctx context.Context, in SubmitDatasetInput) (Su
 		putKeys = append(putKeys, art.StorageKey)
 		art.SetContent(ssum, ssize)
 
-		task, err := domain.NewShardTask(job.ID, index, in.Workload, art.ID, ssum, in.Parameters, 0, now)
+		task, err := domain.NewShardTask(job.ID, index, in.Workload, art.ID, ssum, in.Parameters, uc.maxAttempts, now)
 		if err != nil {
 			return err
 		}
@@ -88,7 +96,8 @@ func (uc *SubmitDataset) Execute(ctx context.Context, in SubmitDatasetInput) (Su
 	_ = rc.Close()
 	if splitErr != nil {
 		cleanup()
-		return SubmitDatasetResult{}, splitErr
+		// Dataset shape is caller input, not an internal coordinator failure.
+		return SubmitDatasetResult{}, domain.ErrInvalidInput
 	}
 
 	// 3. Persist job + all artifacts + all tasks atomically.
@@ -118,6 +127,76 @@ func (uc *SubmitDataset) Execute(ctx context.Context, in SubmitDatasetInput) (Su
 	}, nil
 }
 
+// validateUploadedWorkload is deliberately narrow until CTX-07/08/10 adds a
+// typed distributed-workload registry. In particular, running similarity-graph
+// independently per TSV shard is scientifically wrong: cross-shard pairs would
+// be absent from the apparent graph.
+func validateUploadedWorkload(workload string, parameters map[string]any) error {
+	if workload != "similarity-search" {
+		return domain.ErrInvalidInput
+	}
+	allowed := map[string]struct{}{
+		"query_smiles": {}, "top_k": {}, "threshold": {},
+		"threshold_direction": {}, "progress_every": {},
+	}
+	for key := range parameters {
+		if _, ok := allowed[key]; !ok {
+			return domain.ErrInvalidInput
+		}
+	}
+	query, ok := parameters["query_smiles"].(string)
+	if !ok || query == "" || len(query) > 200 {
+		return domain.ErrInvalidInput
+	}
+	if value, ok := parameters["top_k"]; ok && !isPositiveJSONInteger(value) {
+		return domain.ErrInvalidInput
+	}
+	if value, ok := parameters["progress_every"]; ok && !isNonNegativeJSONInteger(value) {
+		return domain.ErrInvalidInput
+	}
+	if value, ok := parameters["threshold"]; ok && !isUnitIntervalNumber(value) {
+		return domain.ErrInvalidInput
+	}
+	if value, ok := parameters["threshold_direction"]; ok && value != "greater" && value != "less" {
+		return domain.ErrInvalidInput
+	}
+	return nil
+}
+
+func isPositiveJSONInteger(value any) bool    { return isJSONInteger(value, false) }
+func isNonNegativeJSONInteger(value any) bool { return isJSONInteger(value, true) }
+
+func isJSONInteger(value any, allowZero bool) bool {
+	var n int64
+	switch v := value.(type) {
+	case int:
+		n = int64(v)
+	case int64:
+		n = v
+	case float64:
+		if math.Trunc(v) != v || v > math.MaxInt64 || v < math.MinInt64 {
+			return false
+		}
+		n = int64(v)
+	default:
+		return false
+	}
+	return n >= 0 && (allowZero || n > 0)
+}
+
+func isUnitIntervalNumber(value any) bool {
+	switch v := value.(type) {
+	case float64:
+		return !math.IsNaN(v) && !math.IsInf(v, 0) && v >= 0 && v <= 1
+	case int:
+		return v >= 0 && v <= 1
+	case int64:
+		return v >= 0 && v <= 1
+	default:
+		return false
+	}
+}
+
 // GetTaskInput resolves a task's input shard and opens it for streaming. The
 // caller closes the reader.
 type GetTaskInput struct {
diff --git a/coordinator/internal/usecase/usecase_test.go b/coordinator/internal/usecase/usecase_test.go
index 68b94ac..2083c5c 100644
--- a/coordinator/internal/usecase/usecase_test.go
+++ b/coordinator/internal/usecase/usecase_test.go
@@ -68,18 +68,18 @@ func newHarness() *harness {
 	}
 	tx := memstore.Tx{}
 	h.createJob = usecase.NewCreateJob(h.jobs, h.tasks, tx, h.clk)
-	h.submit = usecase.NewSubmitDataset(h.blobs, h.arts, h.jobs, h.tasks, tx, h.clk)
-	h.claim = usecase.NewClaimTask(h.tasks, h.clk, lease)
+	h.submit = usecase.NewSubmitDataset(h.blobs, h.arts, h.jobs, h.tasks, tx, h.clk, 3)
+	h.claim = usecase.NewClaimTask(h.tasks, h.jobs, h.work, tx, h.clk, lease)
 	h.renew = usecase.NewRenewLease(h.tasks, h.work, tx, h.clk, lease)
 	h.complete = usecase.NewCompleteTask(h.tasks, h.jobs, h.arts, tx, h.clk)
 	h.fail = usecase.NewFailTask(h.tasks, h.jobs, tx, h.clk)
 	h.status = usecase.NewGetJobStatus(h.jobs, h.tasks)
 	h.results = usecase.NewListResults(h.tasks)
 	h.register = usecase.NewRegisterWorker(h.work, h.clk)
-	h.uploadArt = usecase.NewUploadArtifact(h.tasks, h.arts, h.blobs, h.clk)
+	h.uploadArt = usecase.NewUploadArtifact(h.tasks, h.arts, h.blobs, tx, h.clk)
 	h.downloadArt = usecase.NewDownloadArtifact(h.arts, h.blobs)
 	h.getInput = usecase.NewGetTaskInput(h.tasks, h.arts, h.blobs)
-	h.expire = usecase.NewExpireLeases(h.tasks, h.clk)
+	h.expire = usecase.NewExpireLeases(h.tasks, h.jobs, tx, h.clk)
 	h.cancel = usecase.NewCancelJob(h.jobs, h.tasks, tx, h.clk)
 	return h
 }
@@ -138,6 +138,44 @@ func TestClaimLeasesAndAdvancesAttempt(t *testing.T) {
 	}
 }
 
+func TestRegisteredWorkerCannotBroadenItsCapabilitiesAtClaim(t *testing.T) {
+	h := newHarness()
+	h.seedJob(t, "restricted", 1)
+	worker, err := h.register.Execute(ctx, usecase.RegisterWorkerInput{
+		Name: "search-only", Capabilities: []string{"similarity-search"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	claimed, err := h.claim.Execute(ctx, usecase.ClaimTaskInput{
+		WorkerID: worker.ID.String(), Workloads: []string{"restricted"},
+	})
+	if err != nil || claimed != nil {
+		t.Fatalf("claim = (%v, %v), want no compatible task", claimed, err)
+	}
+}
+
+func TestCreateJobRejectsUnsafeDistributedScientificPlans(t *testing.T) {
+	h := newHarness()
+	_, err := h.createJob.Execute(ctx, usecase.CreateJobInput{
+		Workload: "similarity-graph", InputURI: "s3://input",
+		Chunks: []usecase.ChunkInput{{ChunkIndex: 0, InputURI: "s3://chunk", InputSHA256: "sha"}},
+	})
+	if !errors.Is(err, domain.ErrInvalidInput) {
+		t.Errorf("graph job err = %v, want ErrInvalidInput", err)
+	}
+	_, err = h.createJob.Execute(ctx, usecase.CreateJobInput{
+		Workload: "similarity-search", InputURI: "s3://input", Parameters: map[string]any{"query_id": "CHEMBL1"},
+		Chunks: []usecase.ChunkInput{
+			{ChunkIndex: 0, InputURI: "s3://chunk0", InputSHA256: "sha"},
+			{ChunkIndex: 1, InputURI: "s3://chunk1", InputSHA256: "sha"},
+		},
+	})
+	if !errors.Is(err, domain.ErrInvalidInput) {
+		t.Errorf("sharded query_id job err = %v, want ErrInvalidInput", err)
+	}
+}
+
 func TestClaimEmptyQueueReturnsNil(t *testing.T) {
 	h := newHarness()
 	c, err := h.claim.Execute(ctx, usecase.ClaimTaskInput{WorkerID: "w1", Workloads: []string{"w"}})
@@ -281,7 +319,7 @@ func TestUploadRejectsLeaseThatExpiresDuringStreaming(t *testing.T) {
 	h.seedJob(t, "w", 1)
 	taskID, attempt := h.leaseOne(t, "w1", "w")
 	h.uploadArt = usecase.NewUploadArtifact(
-		h.tasks, h.arts, expiringBlobStore{BlobStore: h.blobs, clock: h.clk}, h.clk,
+		h.tasks, h.arts, expiringBlobStore{BlobStore: h.blobs, clock: h.clk}, memstore.Tx{}, h.clk,
 	)
 
 	_, err := h.uploadArt.Execute(ctx, usecase.UploadArtifactInput{
@@ -414,6 +452,23 @@ func TestUploadArtifactRejectsForeignWorker(t *testing.T) {
 	}
 }
 
+func TestUploadArtifactIsIdempotentPerTaskAttempt(t *testing.T) {
+	h := newHarness()
+	h.seedJob(t, "w", 1)
+	taskID, attempt := h.leaseOne(t, "w1", "w")
+	first := h.uploadResult(t, taskID, "w1", attempt)
+	second, err := h.uploadArt.Execute(ctx, usecase.UploadArtifactInput{
+		TaskID: taskID, WorkerID: "w1", Attempt: attempt,
+		Filename: "retry.csv", ContentType: "text/csv", Body: strings.NewReader("different bytes"),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if second.ID != first {
+		t.Errorf("retry artifact = %s, want existing %s", second.ID, first)
+	}
+}
+
 func TestDownloadArtifactRoundTrips(t *testing.T) {
 	h := newHarness()
 	h.seedJob(t, "w", 1)
@@ -434,10 +489,10 @@ func TestDownloadArtifactRoundTrips(t *testing.T) {
 
 func TestSubmitDatasetChunksAndServesInput(t *testing.T) {
 	h := newHarness()
-	tsv := "id\tsmiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\nE\tCCCCCC\n"
+	tsv := "chembl_id\tcanonical_smiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\nE\tCCCCCC\n"
 
 	res, err := h.submit.Execute(ctx, usecase.SubmitDatasetInput{
-		Workload: "w", RowsPerShard: 2, Filename: "chembl.tsv",
+		Workload: "similarity-search", Parameters: map[string]any{"query_smiles": "CCO"}, RowsPerShard: 2, Filename: "chembl.tsv",
 		ContentType: "text/tab-separated-values", Body: strings.NewReader(tsv),
 	})
 	if err != nil {
@@ -453,7 +508,7 @@ func TestSubmitDatasetChunksAndServesInput(t *testing.T) {
 		t.Errorf("job total = %d, want 3", prog.Total)
 	}
 
-	c, err := h.claim.Execute(ctx, usecase.ClaimTaskInput{WorkerID: "w1", Workloads: []string{"w"}})
+	c, err := h.claim.Execute(ctx, usecase.ClaimTaskInput{WorkerID: "w1", Workloads: []string{"similarity-search"}})
 	if err != nil || c == nil {
 		t.Fatalf("claim shard: %v", err)
 	}
@@ -472,9 +527,9 @@ func TestSubmitDatasetChunksAndServesInput(t *testing.T) {
 
 func TestSubmitDatasetLimitsRowsBeforeCreatingShards(t *testing.T) {
 	h := newHarness()
-	tsv := "id\tsmiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\nE\tCCCCCC\n"
+	tsv := "chembl_id\tcanonical_smiles\nA\tCC\nB\tCCC\nC\tCCCC\nD\tCCCCC\nE\tCCCCCC\n"
 	res, err := h.submit.Execute(ctx, usecase.SubmitDatasetInput{
-		Workload: "w", RowsPerShard: 2, MaxRows: 3, Filename: "chembl.tsv",
+		Workload: "similarity-search", Parameters: map[string]any{"query_smiles": "CCO"}, RowsPerShard: 2, MaxRows: 3, Filename: "chembl.tsv",
 		ContentType: "text/tab-separated-values", Body: strings.NewReader(tsv),
 	})
 	if err != nil {
@@ -485,6 +540,26 @@ func TestSubmitDatasetLimitsRowsBeforeCreatingShards(t *testing.T) {
 	}
 }
 
+func TestSubmitDatasetRejectsUnsupportedDistributedWorkloads(t *testing.T) {
+	h := newHarness()
+	_, err := h.submit.Execute(ctx, usecase.SubmitDatasetInput{
+		Workload: "similarity-graph", Parameters: map[string]any{"threshold": 0.7}, RowsPerShard: 2,
+		Filename: "chembl.tsv", ContentType: "text/tab-separated-values",
+		Body: strings.NewReader("chembl_id\tcanonical_smiles\nA\tCC\n"),
+	})
+	if !errors.Is(err, domain.ErrInvalidInput) {
+		t.Errorf("graph submission err = %v, want ErrInvalidInput", err)
+	}
+	_, err = h.submit.Execute(ctx, usecase.SubmitDatasetInput{
+		Workload: "similarity-search", Parameters: map[string]any{"query_id": "CHEMBL1"}, RowsPerShard: 2,
+		Filename: "chembl.tsv", ContentType: "text/tab-separated-values",
+		Body: strings.NewReader("chembl_id\tcanonical_smiles\nA\tCC\n"),
+	})
+	if !errors.Is(err, domain.ErrInvalidInput) {
+		t.Errorf("query_id submission err = %v, want ErrInvalidInput", err)
+	}
+}
+
 func TestCancelJobInvalidatesClaimedAndPendingTasks(t *testing.T) {
 	h := newHarness()
 	jobID := h.seedJob(t, "w", 3)
@@ -531,3 +606,22 @@ func TestExpireLeasesReclaims(t *testing.T) {
 		t.Errorf("expire = (%d, %v), want (1, nil)", n, err)
 	}
 }
+
+func TestFinalLeaseExpiryPersistsFailedJobAndCannotBeCancelled(t *testing.T) {
+	h := newHarness()
+	jobID := h.seedJob(t, "w", 1)
+	for attempt := 1; attempt <= domain.DefaultMaxAttempts; attempt++ {
+		h.leaseOne(t, "w1", "w")
+		h.clk.Advance(lease + time.Second)
+		if _, err := h.expire.Execute(ctx); err != nil {
+			t.Fatalf("expire attempt %d: %v", attempt, err)
+		}
+	}
+	progress, err := h.status.Execute(ctx, jobID)
+	if err != nil || progress.Job.Status != domain.JobFailed || progress.DeriveStatus() != domain.JobFailed {
+		t.Fatalf("progress = %+v, err = %v; want persisted failed job", progress, err)
+	}
+	if _, err := h.cancel.Execute(ctx, jobID); !errors.Is(err, domain.ErrJobNotCancellable) {
+		t.Errorf("cancel terminal lease failure = %v, want ErrJobNotCancellable", err)
+	}
+}
diff --git a/coordinator/migrations/0009_unique_partial_result_attempt.down.sql b/coordinator/migrations/0009_unique_partial_result_attempt.down.sql
new file mode 100644
index 0000000..a724fb8
--- /dev/null
+++ b/coordinator/migrations/0009_unique_partial_result_attempt.down.sql
@@ -0,0 +1,5 @@
+BEGIN;
+
+DROP INDEX IF EXISTS uq_partial_result_task_attempt;
+
+COMMIT;
diff --git a/coordinator/migrations/0009_unique_partial_result_attempt.up.sql b/coordinator/migrations/0009_unique_partial_result_attempt.up.sql
new file mode 100644
index 0000000..e6ce5e0
--- /dev/null
+++ b/coordinator/migrations/0009_unique_partial_result_attempt.up.sql
@@ -0,0 +1,26 @@
+BEGIN;
+
+-- Old deployments can contain more than one partial result because earlier
+-- versions accepted repeated PUTs. Preserve the one referenced by a completed
+-- task and discard stale rows; unfinished tasks must upload again after a
+-- deploy, just as they do after a lost lease.
+DELETE FROM artifacts AS a
+USING tasks AS t
+WHERE a.task_id = t.id
+  AND a.kind = 'partial_result'::artifact_kind
+  AND t.status <> 'completed'::task_status;
+
+DELETE FROM artifacts AS a
+USING tasks AS t
+WHERE a.task_id = t.id
+  AND a.kind = 'partial_result'::artifact_kind
+  AND t.status = 'completed'::task_status
+  AND a.id <> t.result_artifact_id;
+
+-- One lease attempt has one durable partial result. This makes an upload retry
+-- idempotent and prevents repeated uploads from accumulating orphan artifacts.
+CREATE UNIQUE INDEX uq_partial_result_task_attempt
+    ON artifacts (task_id, attempt)
+    WHERE kind = 'partial_result'::artifact_kind;
+
+COMMIT;
diff --git a/coordinator/scripts/smoke.sh b/coordinator/scripts/smoke.sh
index 2d9a1f2..ac018d6 100755
--- a/coordinator/scripts/smoke.sh
+++ b/coordinator/scripts/smoke.sh
@@ -51,6 +51,13 @@ check "register worker"                 201 -X POST "${HOST}/workers/register" "
 	-d '{"name":"smoke-worker","capabilities":["similarity_search"],"cpu_count":4,"memory_mb":8192}'
 check "register without capabilities → 400" 400 -X POST "${HOST}/workers/register" "${auth[@]}" \
 	-d '{"name":"bad"}'
+registration=$(curl -sS "${auth[@]}" -X POST "${HOST}/workers/register" \
+	-d '{"name":"smoke-worker-active","capabilities":["similarity_search","similarity-search"],"cpu_count":4}')
+worker_id=$(printf '%s' "$registration" | python3 -c 'import json,sys;print(json.load(sys.stdin)["worker_id"])' 2>/dev/null)
+if [[ -z "${worker_id:-}" ]]; then
+	echo "  ✗ could not register active worker: $registration"
+	exit 1
+fi
 
 echo
 echo "job lifecycle"
@@ -75,7 +82,7 @@ declare -A our_chunks
 task_id=""
 attempt=""
 for _ in $(seq 1 40); do
-	claim=$(curl -sS "${auth[@]}" -X POST "${HOST}/tasks/claim" -d '{"worker_id":"w1"}')
+	claim=$(curl -sS "${auth[@]}" -X POST "${HOST}/tasks/claim" -d "{\"worker_id\":\"${worker_id}\"}")
 	[[ -z "$claim" ]] && break # 204: queue drained
 
 	read -r c_job c_task c_chunk c_attempt < <(printf '%s' "$claim" |
@@ -100,7 +107,7 @@ else
 fi
 
 check "heartbeat"                          200 -X POST "${HOST}/tasks/${task_id}/heartbeat" "${auth[@]}" \
-	-d "{\"worker_id\":\"w1\",\"attempt\":${attempt}}"
+	-d "{\"worker_id\":\"${worker_id}\",\"attempt\":${attempt}}"
 
 # --- artifacts + result (uploads happen while the task is still leased) ---
 bearer=(-H "Authorization: Bearer ${TOKEN}")
@@ -108,43 +115,47 @@ bearer=(-H "Authorization: Bearer ${TOKEN}")
 # upload <filename> -> prints the artifact_id
 upload() {
 	curl -sS -X PUT "${HOST}/tasks/${task_id}/artifacts/$1" "${bearer[@]}" \
-		-H 'Content-Type: text/csv' -H 'X-Worker-ID: w1' -H "X-Task-Attempt: ${attempt}" \
+		-H 'Content-Type: text/csv' -H "X-Worker-ID: ${worker_id}" -H "X-Task-Attempt: ${attempt}" \
 		--data-binary $'query,match,score\nA,B,0.9\n' |
 		python3 -c 'import json,sys;print(json.load(sys.stdin)["artifact_id"])' 2>/dev/null
 }
 
 check "upload artifact"                    200 -X PUT "${HOST}/tasks/${task_id}/artifacts/result.csv" "${bearer[@]}" \
-	-H 'Content-Type: text/csv' -H 'X-Worker-ID: w1' -H "X-Task-Attempt: ${attempt}" \
+	-H 'Content-Type: text/csv' -H "X-Worker-ID: ${worker_id}" -H "X-Task-Attempt: ${attempt}" \
 	--data-binary $'query,match,score\nA,B,0.9\n'
 check "foreign worker upload → 409"        409 -X PUT "${HOST}/tasks/${task_id}/artifacts/x.csv" "${bearer[@]}" \
 	-H 'Content-Type: text/csv' -H 'X-Worker-ID: impostor' -H "X-Task-Attempt: ${attempt}" \
 	--data-binary 'x'
 
-# Two result artifacts, uploaded now while the lease is held: one to complete
-# with, a second to prove a different manifest is rejected after completion.
+# A retry of a PUT returns the same durable artifact for the task attempt.
 art_id=$(upload primary.csv)
 art_id2=$(upload secondary.csv)
+if [[ "$art_id" == "$art_id2" ]]; then
+	printf '  \033[32m✓\033[0m %-46s %s\n' "duplicate upload is idempotent" "$art_id"
+	pass=$((pass + 1))
+else
+	printf '  \033[31m✗\033[0m %-46s got %s and %s\n' "duplicate upload is idempotent" "$art_id" "$art_id2"
+	fail=$((fail + 1))
+fi
 check "download artifact"                  200 "${HOST}/artifacts/${art_id}/download" "${bearer[@]}"
 
 check "foreign worker submits → 409"       409 -X POST "${HOST}/tasks/${task_id}/result" "${auth[@]}" \
 	-d "{\"worker_id\":\"impostor\",\"attempt\":${attempt},\"result\":{\"artifact_id\":\"${art_id}\"}}"
 check "submit result"                      200 -X POST "${HOST}/tasks/${task_id}/result" "${auth[@]}" \
-	-d "{\"worker_id\":\"w1\",\"attempt\":${attempt},\"result\":{\"artifact_id\":\"${art_id}\"}}"
+	-d "{\"worker_id\":\"${worker_id}\",\"attempt\":${attempt},\"result\":{\"artifact_id\":\"${art_id}\"}}"
 check "replay same result → idempotent"    200 -X POST "${HOST}/tasks/${task_id}/result" "${auth[@]}" \
-	-d "{\"worker_id\":\"w1\",\"attempt\":${attempt},\"result\":{\"artifact_id\":\"${art_id}\"}}"
-check "different result → 409"             409 -X POST "${HOST}/tasks/${task_id}/result" "${auth[@]}" \
-	-d "{\"worker_id\":\"w1\",\"attempt\":${attempt},\"result\":{\"artifact_id\":\"${art_id2}\"}}"
+	-d "{\"worker_id\":\"${worker_id}\",\"attempt\":${attempt},\"result\":{\"artifact_id\":\"${art_id}\"}}"
 check "GET /jobs/{id}"                     200 "${HOST}/jobs/${job_id}" "${auth[@]}"
 
 echo
 echo "input validation"
 check "malformed uuid → 400"               400 -X POST "${HOST}/tasks/not-a-uuid/result" "${auth[@]}" \
-	-d '{"worker_id":"w1","attempt":1,"result":{"artifact_id":"00000000-0000-0000-0000-000000000000"}}'
+	-d "{\"worker_id\":\"${worker_id}\",\"attempt\":1,\"result\":{\"artifact_id\":\"00000000-0000-0000-0000-000000000000\"}}"
 # Note: Go's encoding/json matches field names case-insensitively, so
 # "worker_ID" would be accepted as "worker_id". Only a genuinely unknown key
 # trips DisallowUnknownFields.
 check "unknown json field → 400"           400 -X POST "${HOST}/tasks/claim" "${auth[@]}" \
-	-d '{"worker_id":"w1","totally_unknown":1}'
+	-d "{\"worker_id\":\"${worker_id}\",\"totally_unknown\":1}"
 check "unknown job → 404"                  404 "${HOST}/jobs/00000000-0000-0000-0000-000000000000" "${auth[@]}"
 
 echo
@@ -152,11 +163,11 @@ echo "dataset upload → chunking"
 # Upload a 5-row TSV split at 2 rows/shard → expect 3 shard tasks. The text
 # fields precede the file part, which the coordinator streams.
 up=$(curl -sS "${bearer[@]}" -X POST "${HOST}/jobs/upload" \
-	-F 'workload=similarity_search' \
-	-F 'parameters={"top_k":10}' \
+	-F 'workload=similarity-search' \
+	-F 'parameters={"query_smiles":"CCO","top_k":10}' \
 	-F 'chunk_rows=2' \
 	-F 'file=@-;filename=chembl.tsv;type=text/tab-separated-values' <<'TSV'
-id	smiles
+chembl_id	canonical_smiles
 A	CC
 B	CCC
 C	CCCC
@@ -180,7 +191,7 @@ fi
 up_input=""
 for _ in $(seq 1 30); do
 	c=$(curl -sS "${bearer[@]}" -H 'Content-Type: application/json' -X POST "${HOST}/tasks/claim" \
-		-d '{"worker_id":"up-w","capabilities":["similarity_search"]}')
+		-d "{\"worker_id\":\"${worker_id}\"}")
 	[[ -z "$c" ]] && break
 	cj=$(printf '%s' "$c" | python3 -c 'import json,sys;print(json.load(sys.stdin)["job_id"])' 2>/dev/null)
 	[[ "$cj" != "$up_job" ]] && continue
diff --git a/docs/api-contract.md b/docs/api-contract.md
index 50abf4d..103b2d1 100644
--- a/docs/api-contract.md
+++ b/docs/api-contract.md
@@ -107,7 +107,8 @@ Content-Type: application/json
 ```
 
 `cpu_count`/`memory_mb` are accepted for forward compatibility and not yet
-persisted. `capabilities` must be non-empty (an allowlisted workload set).
+persisted. `capabilities` must be non-empty. A claim uses the capabilities
+stored at registration; the request cannot broaden them.
 
 ## Claim task
 
@@ -120,7 +121,8 @@ Content-Type: application/json
 ```
 
 - `204 No Content`: no compatible task.
-- `200 OK`: a task is leased atomically.
+- `200 OK`: a task is leased atomically. `worker_id` must be a registered UUID;
+  its persisted capabilities, rather than this request field, decide eligibility.
 
 ```json
 {
diff --git a/docs/building-workers.md b/docs/building-workers.md
index 8e23884..08f8d6a 100644
--- a/docs/building-workers.md
+++ b/docs/building-workers.md
@@ -46,24 +46,25 @@ coordinator was started with. Never log it, never send it in an error body.
 
 ```http
 POST /workers/register
-{ "name": "lab-worker-01", "capabilities": ["similarity_search"] }
+{ "name": "lab-worker-01", "capabilities": ["similarity-search"] }
 ```
 
 Response: `{ "worker_id": "<uuid>", "heartbeat_interval_seconds": 15 }`.
 
-- `capabilities` are the workload names you can run — the coordinator only hands
-  you matching tasks.
+- `capabilities` are fixed at registration — the coordinator only hands you
+  matching tasks and a later claim cannot broaden that set.
 - **Keep `worker_id`**. Use it as your identity in every later call. Using the
   registered UUID is what lets the coordinator track your liveness (it marks
   workers offline after they go silent).
-- Current coordinator jobs use `similarity_search` / `similarity_graph`; the
-  reference Python worker also accepts the public CLI spellings with hyphens.
+- Current diagnostic uploads use `similarity-search` with `query_smiles`. The
+  reference worker accepts the legacy `similarity_search` spelling too. Do not
+  advertise `similarity-graph` until CTX-10 implements cross-shard pair planning.
 
 ## 2. Claim a task
 
 ```http
 POST /tasks/claim
-{ "worker_id": "<uuid>", "capabilities": ["similarity_search"] }
+{ "worker_id": "<uuid>", "capabilities": ["similarity-search"] }
 ```
 
 - `200` → a leased task (below).
@@ -74,9 +75,9 @@ POST /tasks/claim
   "task_id": "<uuid>",
   "attempt": 1,
   "lease_expires_at": "2026-07-22T12:05:00Z",
-  "workload": "similarity_search",
+  "workload": "similarity-search",
   "input": { "uri": "/tasks/<uuid>/input", "sha256": "<hex>" },
-  "parameters": { "query_id": "CHEMBL939", "top_k": 20 }
+  "parameters": { "query_smiles": "CCO", "top_k": 20 }
 }
 ```
 
diff --git a/docs/openapi.yaml b/docs/openapi.yaml
index 7117a78..4e574df 100644
--- a/docs/openapi.yaml
+++ b/docs/openapi.yaml
@@ -96,7 +96,9 @@ paths:
       description: >
         multipart/form-data. The text fields (`workload`, `parameters`,
         `chunk_rows`, `max_rows`) MUST precede the `file` part: the file is streamed, not
-        buffered, so the fields have to be parsed before it arrives.
+        buffered, so the fields have to be parsed before it arrives. Currently
+        only diagnostic `similarity-search` with `parameters.query_smiles` is
+        accepted; distributed graph planning is not implemented.
       requestBody:
         required: true
         content:
@@ -388,7 +390,7 @@ components:
           type: array
           minItems: 1
           items: { type: string }
-          example: [similarity_search, similarity_graph]
+          example: [similarity-search]
         cpu_count:
           type: integer
           description: Accepted for forward compatibility; not yet persisted.
@@ -419,7 +421,7 @@ components:
       type: object
       required: [workload, input_uri, chunks]
       properties:
-        workload: { type: string, example: similarity_search }
+        workload: { type: string, example: similarity-search }
         input_uri: { type: string }
         parameters: { type: object, additionalProperties: true }
         chunks:
@@ -437,11 +439,11 @@ components:
       type: object
       required: [workload, file]
       properties:
-        workload: { type: string, example: similarity_search }
+        workload: { type: string, enum: [similarity-search], example: similarity-search }
         parameters:
           type: string
           description: JSON object, sent as a string form field.
-          example: '{"top_k":10}'
+          example: '{"query_smiles":"CCO","top_k":10}'
         chunk_rows:
           type: integer
           description: Data rows per shard. Default 1000.
@@ -486,11 +488,11 @@ components:
       type: object
       required: [worker_id]
       properties:
-        worker_id: { type: string }
+        worker_id: { type: string, format: uuid, description: Registered worker identity. }
         capabilities:
           type: array
           items: { type: string }
-          description: Workloads this worker can run. Empty means "any".
+          description: Accepted for compatibility only; registration capabilities decide eligibility.
         max_concurrency:
           type: integer
           description: Accepted; the coordinator leases one task per call.
diff --git a/docs/worker-daemon-task.md b/docs/worker-daemon-task.md
index c5e7445..e4d2f07 100644
--- a/docs/worker-daemon-task.md
+++ b/docs/worker-daemon-task.md
@@ -59,7 +59,7 @@ Content-Type: application/json
 
 {
   "name": "lab-worker-01",
-  "capabilities": ["similarity-search", "similarity-graph"],
+  "capabilities": ["similarity-search"],
   "cpu_count": 8,
   "memory_mb": 16384
 }
@@ -74,8 +74,8 @@ POST /tasks/claim
 Content-Type: application/json
 
 {
-  "worker_id": "worker-01",
-  "capabilities": ["similarity-search", "similarity-graph"],
+  "worker_id": "<registered-uuid>",
+  "capabilities": ["similarity-search"],
   "max_concurrency": 1
 }
 ```
@@ -95,7 +95,7 @@ When a task is available, it returns `200 OK`:
     "sha256": "..."
   },
   "parameters": {
-    "query_id": "CHEMBL939",
+    "query_smiles": "CCO",
     "top_k": 20
   }
 }
diff --git a/scimesh/worker/config.py b/scimesh/worker/config.py
index c0d5c9a..84a1157 100644
--- a/scimesh/worker/config.py
+++ b/scimesh/worker/config.py
@@ -38,13 +38,14 @@ class WorkerConfig:
     cleanup_after_seconds: float | None = None
     max_tasks: int | None = None
     exit_when_idle: bool = False
+    # Distributed similarity-graph requires triangular block-pair planning and
+    # is deliberately not advertised until CTX-10. A normal worker must never
+    # make a multi-shard graph job appear scientifically complete.
     # The local CLI uses hyphens; the first coordinator contract used
-    # underscores. Advertise both stable spellings while jobs are migrated.
+    # underscores, so retain the search alias during migration.
     capabilities: tuple[str, ...] = (
         "similarity-search",
-        "similarity-graph",
         "similarity_search",
-        "similarity_graph",
     )
 
     def __post_init__(self) -> None:
diff --git a/scimesh/worker/daemon.py b/scimesh/worker/daemon.py
index 3ecb742..f8e51a7 100644
--- a/scimesh/worker/daemon.py
+++ b/scimesh/worker/daemon.py
@@ -7,6 +7,7 @@ from dataclasses import replace
 from dataclasses import dataclass
 from pathlib import Path
 import random
+import re
 import shutil
 import threading
 import time
@@ -199,7 +200,7 @@ class WorkerDaemon:
         return RunOnceOutcome(claimed=True, completed=completed)
 
     def _report_failure(self, task: ClaimedTask, error: Exception) -> None:
-        message = str(error).replace(str(self.config.work_dir), "<worker-dir>")[:300]
+        message = self._sanitize_error_message(error)
         try:
             self.coordinator.fail(task, {"worker_id": self._worker_id(), "attempt": task.attempt, "error_code": type(error).__name__, "error_message": message})
         except CoordinatorTransientError:
@@ -207,6 +208,16 @@ class WorkerDaemon:
         except Exception:
             self._log("failed", task, error_type="FailureReportError")
 
+    def _sanitize_error_message(self, error: Exception) -> str:
+        """Keep coordinator-visible failures useful without exposing local paths."""
+        message = str(error).replace(str(self.config.work_dir), "<worker-dir>")
+        # CalledProcessError includes the complete argv, including sys.executable
+        # outside work_dir. Replace POSIX and Windows absolute paths before the
+        # message reaches the coordinator database or operator UI.
+        message = re.sub(r"(?<![\w:])[A-Za-z]:\\[^\s'\"\],)]+", "<path>", message)
+        message = re.sub(r"(?<![\w:])/(?:[^\s'\"\],)]+)", "<path>", message)
+        return message[:300]
+
     def _register_worker(self) -> None:
         registered = self.coordinator.register(
             self.config.worker_name,
diff --git a/tests/test_worker_daemon.py b/tests/test_worker_daemon.py
index 031098b..7bf6f65 100644
--- a/tests/test_worker_daemon.py
+++ b/tests/test_worker_daemon.py
@@ -3,6 +3,7 @@ from __future__ import annotations
 import hashlib
 import logging
 from pathlib import Path
+import subprocess
 import time
 from datetime import datetime, timedelta, timezone
 from urllib.request import Request
@@ -236,6 +237,19 @@ def test_bad_checksum_reports_failure_without_running(tmp_path: Path) -> None:
     assert not coordinator.submissions
 
 
+def test_failure_reporting_removes_paths_outside_the_worker_directory(tmp_path: Path) -> None:
+    worker, coordinator, _, _, _ = daemon(tmp_path, make_task(b"input"), b"input")
+    error = subprocess.CalledProcessError(
+        1,
+        ["/home/alice/.venv/bin/python", "-m", "scimesh.cli", "/private/input.tsv"],
+    )
+    worker._report_failure(make_task(b"input"), error)
+    message = coordinator.failures[0]["error_message"]
+    assert "/home/alice" not in message
+    assert "/private/input.tsv" not in message
+    assert "<path>" in message
+
+
 def test_directory_creation_failure_is_reported(tmp_path: Path) -> None:
     content = b"input fixture"
     worker, coordinator, _, _, config = daemon(tmp_path, make_task(content), content)
@@ -431,6 +445,7 @@ def test_environment_overrides_allow_cli_only_configuration(monkeypatch: pytest.
     assert config.worker_id is None
     assert "similarity-search" in config.capabilities
     assert "similarity_search" in config.capabilities
+    assert "similarity-graph" not in config.capabilities
 
 
 def test_relative_work_dir_is_normalized_for_runner_subprocesses(