diff --git a/.superpowers/sdd/evidence-task-5c-report.md b/.superpowers/sdd/evidence-task-5c-report.md
index 9bcd4282..dc17bc57 100644
--- a/.superpowers/sdd/evidence-task-5c-report.md
+++ b/.superpowers/sdd/evidence-task-5c-report.md
@@ -122,3 +122,16 @@ and the final full harness plus scoped Ruff/diff invocation completed with exit
 Final focused verification: `89 passed` across corpus/CLI JSON, direct/HTTP parity, migrations, and
 real Docker pgvector lifecycle; scoped Ruff and `git diff --check` clean. A contemporaneous full-suite
 run reached unrelated Task 6 immutable-file tamper tests; those files were deliberately not changed.
+
+## Immutable corpus/workspace binding
+
+- A corpus root becomes bound to the workspace id persisted in its ACTIVE manifest. Job, non-job,
+  explicit GC, and ACTIVE search entry points compare the configured namespace before discovery,
+  vector access, staging, deletion, or ACTIVE mutation.
+- Reusing the same paths after renaming a workspace now fails closed with a typed/sanitized message:
+  use a new corpus root or perform an intentional explicit rebuild. Unscoped legacy manifests also
+  fail this ownership check.
+- Tests prove unchanged-document reuse cannot silently mix workspace A vectors into a workspace B
+  manifest, and that mismatched job, GC, and search paths perform no vector/filesystem mutations.
+
+Focused workspace-binding, search-pack, preprocess JSON, and scoped Ruff/diff tests pass.
diff --git a/harness/tests/test_corpus_pipeline.py b/harness/tests/test_corpus_pipeline.py
index e4d067bb..23da70ef 100644
--- a/harness/tests/test_corpus_pipeline.py
+++ b/harness/tests/test_corpus_pipeline.py
@@ -329,6 +329,66 @@ def test_pipeline_result_dump_does_not_deepcopy_frozen_metadata():
     assert payload["manifest"]["metadata"] == {"nested": {"value": ["safe"]}}
 
 
+def test_reused_corpus_root_rejects_workspace_rename_before_any_mutation(tmp_path):
+    vectors = Vectors()
+    first = pipeline(tmp_path, Source([(item("one", "a"), "stable")]), vectors=vectors)
+    first.run_as_job(
+        workspace_id="workspace-a", workspace_root=tmp_path,
+        config_fingerprint="sha256:" + "1" * 64,
+        input_fingerprint="sha256:" + "2" * 64,
+    )
+    active = first.store.active_generation()
+    records = list(vectors.records)
+    renamed_source = Source([(item("one", "a"), "stable")])
+    renamed = pipeline(tmp_path, renamed_source, vectors=vectors)
+    with pytest.raises(PipelineError, match="different workspace"):
+        renamed.run_as_job(
+            workspace_id="workspace-b", workspace_root=tmp_path,
+            config_fingerprint="sha256:" + "1" * 64,
+            input_fingerprint="sha256:" + "2" * 64,
+        )
+    assert renamed_source.acquire_calls == []
+    assert renamed.store.active_generation() == active
+    assert vectors.records == records
+
+
+def test_gc_rejects_workspace_mismatch_without_deleting(tmp_path):
+    vectors = Vectors()
+    owner = pipeline(tmp_path, Source([(item("one", "a"), "stable")]), vectors=vectors)
+    owner.run_as_job(
+        workspace_id="workspace-a", workspace_root=tmp_path,
+        config_fingerprint="sha256:" + "1" * 64,
+        input_fingerprint="sha256:" + "2" * 64,
+    )
+    generations = owner.store.list_generations()
+    wrong = pipeline(tmp_path, Source([]), vectors=vectors)
+    wrong.workspace_id = "workspace-b"
+    with pytest.raises(PipelineError, match="different workspace"):
+        wrong.gc(workspace_root=tmp_path)
+    assert wrong.store.list_generations() == generations
+
+
+def test_active_search_rejects_workspace_mismatch_before_delegate(tmp_path):
+    from tht.search.evidence import ActiveEvidenceSearcher, CorpusWorkspaceMismatchError
+
+    vectors = Vectors()
+    owner = pipeline(tmp_path, Source([(item("one", "a"), "stable")]), vectors=vectors)
+    owner.run_as_job(
+        workspace_id="workspace-a", workspace_root=tmp_path,
+        config_fingerprint="sha256:" + "1" * 64,
+        input_fingerprint="sha256:" + "2" * 64,
+    )
+
+    class Delegate:
+        def search(self, *args, **kwargs):
+            raise AssertionError("workspace mismatch reached vector delegate")
+
+    with pytest.raises(CorpusWorkspaceMismatchError, match="different workspace"):
+        ActiveEvidenceSearcher(
+            owner.store, Delegate(), expected_workspace_id="workspace-b",
+        ).search([1.0], kinds=["evidence"])
+
+
 def test_unchanged_documents_skip_acquire_normalize_chunk_and_embed(tmp_path):
     one = item("one", "a")
     first_source = Source([(one, "hello")])
diff --git a/harness/tht/cli/preprocess_cmd.py b/harness/tht/cli/preprocess_cmd.py
index 5b102a98..92676154 100644
--- a/harness/tht/cli/preprocess_cmd.py
+++ b/harness/tht/cli/preprocess_cmd.py
@@ -113,6 +113,7 @@ def gc_from_config(config: Path, *, dry_run: bool = False):
         pipeline_version="evidence-v1",
         retain_published_generations=cfg.vector.retain_published_generations,
     )
+    pipeline.workspace_id = config.stem.lower().replace(".", "-").replace("_", "-")
     with pipeline.store.writer_lock():
         return pipeline.gc(workspace_root=corpus_root.parent, dry_run=dry_run)
 
diff --git a/harness/tht/cli/search_cmd.py b/harness/tht/cli/search_cmd.py
index f065fd26..ed6d79bf 100644
--- a/harness/tht/cli/search_cmd.py
+++ b/harness/tht/cli/search_cmd.py
@@ -53,7 +53,10 @@ def search_cmd(
     require_vector_cfg(cfg)
     from tht.search.evidence import active_searcher
 
-    runtime_searcher = active_searcher(cfg, open_searcher(cfg))
+    runtime_searcher = active_searcher(
+        cfg, open_searcher(cfg),
+        workspace_id=config.stem.lower().replace(".", "-").replace("_", "-"),
+    )
     if kind is not None and kind not in KIND_MAP:
         typer.secho(
             f"ERRORE: --kind sconosciuto: {kind} (validi: {', '.join(KIND_MAP)})",
@@ -260,7 +263,10 @@ def pack_cmd(
     try:
         from tht.search.evidence import active_searcher
 
-        searcher = active_searcher(cfg, open_searcher(cfg))
+        searcher = active_searcher(
+            cfg, open_searcher(cfg),
+            workspace_id=config.stem.lower().replace(".", "-").replace("_", "-"),
+        )
         embedder = make_embedder(cfg.embeddings)
         vec = embedder.embed_query(question)
     except degrade as e:
diff --git a/harness/tht/corpus/pipeline.py b/harness/tht/corpus/pipeline.py
index 0a516889..a51027d9 100644
--- a/harness/tht/corpus/pipeline.py
+++ b/harness/tht/corpus/pipeline.py
@@ -85,6 +85,16 @@ class CorpusPipeline:
         self.retain_published_generations = retain_published_generations
         self.workspace_id = workspace_id
 
+    def _assert_workspace_binding(self) -> None:
+        manifest = self.store.active_manifest()
+        if manifest is None:
+            return
+        persisted = manifest.metadata.get("workspace_id")
+        if persisted != self.workspace_id:
+            raise PipelineError(
+                "corpus belongs to a different workspace; use a new corpus root or explicit rebuild"
+            )
+
     def _protected_generations(self, workspace_root: Path) -> set[str]:
         protected = {value for value in (self.store.active_generation(),) if value}
         runs = workspace_root / ".tht-jobs" / "evidence" / "runs"
@@ -102,11 +112,7 @@ class CorpusPipeline:
         return protected
 
     def gc(self, *, workspace_root: Path, dry_run: bool = False) -> dict:
-        active_manifest = self.store.active_manifest()
-        if active_manifest is not None:
-            persisted_workspace = active_manifest.metadata.get("workspace_id")
-            if isinstance(persisted_workspace, str):
-                self.workspace_id = persisted_workspace
+        self._assert_workspace_binding()
         published = self.store.published_generations()
         list_vectors = getattr(self.vector_store, "list_evidence_generations", None)
         vector_generations = set(list_vectors("evidence", self.workspace_id)) if list_vectors else set()
@@ -166,11 +172,13 @@ class CorpusPipeline:
 
     def run(self, *, dry_run: bool = False, resume: str | None = None) -> PipelineResult:
         with self.store.writer_lock():
+            self._assert_workspace_binding()
             return self._run(dry_run=dry_run, resume=resume)
 
     def run_as_job(self, **kwargs) -> PipelineResult:
         self.workspace_id = kwargs["workspace_id"]
         with self.store.writer_lock():
+            self._assert_workspace_binding()
             return self._run_as_job(**kwargs)
 
     def _run_as_job(
diff --git a/harness/tht/search/evidence.py b/harness/tht/search/evidence.py
index 47ff2718..1b41417e 100644
--- a/harness/tht/search/evidence.py
+++ b/harness/tht/search/evidence.py
@@ -3,12 +3,17 @@
 from tht.corpus.store import CorpusStore
 
 
+class CorpusWorkspaceMismatchError(RuntimeError):
+    """The configured workspace does not own the persisted corpus."""
+
+
 class ActiveEvidenceSearcher:
     """Searcher facade that enforces ACTIVE generation predicates before LIMIT."""
 
-    def __init__(self, corpus: CorpusStore, delegate):
+    def __init__(self, corpus: CorpusStore, delegate, expected_workspace_id: str | None = None):
         self.corpus = corpus
         self.delegate = delegate
+        self.expected_workspace_id = expected_workspace_id
 
     def search(self, embedding, top_n=10, kinds=None, metadata_filter=None):
         requested = set(kinds) if kinds is not None else {
@@ -31,6 +36,12 @@ class ActiveEvidenceSearcher:
             if include_evidence:
                 manifest = self.corpus.active_manifest()
                 workspace_id = manifest.metadata.get("workspace_id") if manifest else None
+                if manifest is not None and self.expected_workspace_id is not None and (
+                    workspace_id != self.expected_workspace_id
+                ):
+                    raise CorpusWorkspaceMismatchError(
+                        "corpus belongs to a different workspace; use a new corpus root or rebuild"
+                    )
                 if manifest is not None and isinstance(workspace_id, str):
                     by_generation: dict[str, list[str]] = {}
                     mapping = dict(manifest.metadata.get("document_generations", {}))
@@ -50,9 +61,9 @@ class ActiveEvidenceSearcher:
         return sorted(hits, key=lambda hit: (-hit.similarity, hit.id))[:top_n]
 
 
-def active_searcher(cfg, delegate):
+def active_searcher(cfg, delegate, *, workspace_id: str | None = None):
     corpus_root = cfg.paths.artifacts.parent / "corpus"
-    return ActiveEvidenceSearcher(CorpusStore(corpus_root), delegate)
+    return ActiveEvidenceSearcher(CorpusStore(corpus_root), delegate, workspace_id)
 
 
 def resolve_evidence_file(