diff --git a/.security-review/suppressions.json b/.security-review/suppressions.json
index e13ea036..47ed2662 100644
--- a/.security-review/suppressions.json
+++ b/.security-review/suppressions.json
@@ -19,6 +19,45 @@
       "suppression_justification": "ACCEPTED LOW residual, metadata-only. fetch-config.sh materializes the .env via `batch-get-secret-value --filters Key=name,Values=open-swe-<env>/`. With a name FILTER, both BatchGetSecretValue (a collection call) and ListSecrets are authorized by AWS against `*`, NOT a per-secret ARN — a prefix-scoped ARN AccessDenies the call (confirmed empirically on i-0af4e03e8bf70e6c3). So the two `*` grants are operation-level, not value-level. Secret VALUES remain strictly gated by the PREFIX-scoped GetSecretValue/DescribeSecret on secret:open-swe-<env>/* (GetSecretValue is checked per-secret even within the batch), so cross-env VALUE isolation is preserved; only NAMES/tags/descriptions are enumerable, within Sea Haven's own single-tenant account 328440206208. Confirmed by GPT-4.1 IAM cross-review (BLOCK: none) and the iac-iam detector (one low residual, no critical/high). Future hardening to eliminate BOTH `*` grants: switch fetch-config.sh to an explicit `--secret-id-list` (no filter), which lets BatchGetSecretValue be prefix-scoped and needs no ListSecrets.",
       "owner": "adam@seahavenind.com",
       "added": "2026-06-26"
+    },
+    {
+      "id": "gitleaks-generic-api-key-89",
+      "title": "Hardcoded credential flagged in encryption-roundtrip test fixture (CWE-798)",
+      "file": "tests/test_team_credentials.py",
+      "line": 89,
+      "rule": "CWE-798",
+      "severity": "low",
+      "status": "false-positive",
+      "justification": "Test fixture, not a real credential. The value \"secret-api-1234\" is a fake Datadog API key used by test_datadog_roundtrip_and_redaction to assert that the plaintext key is recoverable after an encrypt/decrypt round-trip (and that the stored record holds ciphertext, not the plaintext). It is never a live secret and is scoped to the unit test only.",
+      "suppression_justification": "Test fixture, not a real credential. The value \"secret-api-1234\" is a fake Datadog API key used by test_datadog_roundtrip_and_redaction to assert that the plaintext key is recoverable after an encrypt/decrypt round-trip. It is never a live secret and is scoped to the unit test only.",
+      "owner": "adam@seahavenind.com",
+      "added": "2026-06-29"
+    },
+    {
+      "id": "gitleaks-generic-api-key-79",
+      "title": "Hardcoded credential flagged in encryption-roundtrip test fixture (CWE-798)",
+      "file": "tests/test_team_credentials.py",
+      "line": 79,
+      "rule": "CWE-798",
+      "severity": "low",
+      "status": "false-positive",
+      "justification": "Test fixture, not a real credential. Same fake Datadog API key \"secret-api-1234\" passed into connect_datadog by test_datadog_roundtrip_and_redaction. Never a live secret; scoped to the unit test only.",
+      "suppression_justification": "Test fixture, not a real credential. Same fake Datadog API key \"secret-api-1234\" passed into connect_datadog by test_datadog_roundtrip_and_redaction. Never a live secret; scoped to the unit test only.",
+      "owner": "adam@seahavenind.com",
+      "added": "2026-06-29"
+    },
+    {
+      "id": "gitleaks-generic-api-key-23",
+      "title": "Hardcoded credential flagged in GitHub-token TTL test fixture (CWE-798)",
+      "file": "tests/test_github_token_ttl.py",
+      "line": 23,
+      "rule": "CWE-798",
+      "severity": "high",
+      "status": "false-positive",
+      "justification": "Test fixture, not a real credential. The literal \"ghp_secret\" is a fake GitHub token used by the cached-token TTL/revocation unit tests to exercise cache_github_token_for_thread / get_github_token expiry and invalidation. It is not a valid 40-char GitHub PAT, is never a live secret, and is scoped to the unit test only. Pre-existing test fixture, not introduced by this change.",
+      "suppression_justification": "Test fixture, not a real credential. The literal \"ghp_secret\" is a fake GitHub token used by the cached-token TTL/revocation unit tests to exercise cache_github_token_for_thread / get_github_token expiry and invalidation. It is not a valid 40-char GitHub PAT, is never a live secret, and is scoped to the unit test only. Pre-existing test fixture, not introduced by this change.",
+      "owner": "adam@seahavenind.com",
+      "added": "2026-06-29"
     }
   ]
 }
diff --git a/agent/dashboard/thread_api.py b/agent/dashboard/thread_api.py
index cdad0161..e99ac78d 100644
--- a/agent/dashboard/thread_api.py
+++ b/agent/dashboard/thread_api.py
@@ -1206,6 +1206,8 @@ async def send_dashboard_message(
         raise HTTPException(404, "thread not found") from exc
 
     metadata = thread.get("metadata") if isinstance(thread.get("metadata"), dict) else {}
+    # AUTHZ-002 (intentional): any org-gated member who can read a surfaced thread
+    # may also post into it; non-owners are attributed via _attribution_prefix.
     _assert_thread_readable(metadata)
 
     prompt = f"{_attribution_prefix(metadata, login, email)}{body.content.strip()}"
diff --git a/agent/reviewer.py b/agent/reviewer.py
index 99e28020..c6b8794c 100644
--- a/agent/reviewer.py
+++ b/agent/reviewer.py
@@ -59,6 +59,7 @@ from .server import (
     DEFAULT_LLM_MAX_TOKENS,
     DEFAULT_RECURSION_LIMIT,
     MODEL_CALL_RECURSION_LIMIT,
+    SandboxRepoMismatchError,
     _general_purpose_subagent,
     ensure_sandbox_for_thread,
     graph_loaded_for_execution,
@@ -839,7 +840,9 @@ async def get_reviewer_agent(config: RunnableConfig) -> Pregel:
                 f"GitHub App installation token unavailable for reviewer thread {thread_id}"
             )
         # Cache in-process so reviewer tools and the sandbox proxy can read it this run.
-        cache_github_token_for_thread(thread_id, github_token, expires_at=expires_at)
+        cache_github_token_for_thread(
+            thread_id, github_token, expires_at=expires_at, repo=repo_config
+        )
 
     github_proxy_token = github_token
     github_api_token = github_token
@@ -849,12 +852,18 @@ async def get_reviewer_agent(config: RunnableConfig) -> Pregel:
         if repo_config.get("owner") and repo_config.get("name")
         else None
     )
-    sandbox_backend = await ensure_sandbox_for_thread(
-        thread_id,
-        github_proxy_token=github_proxy_token,
-        github_proxy_repositories=[repo_name_for_scope] if repo_name_for_scope else None,
-        repo=repo_for_snapshot,
-    )
+    try:
+        sandbox_backend = await ensure_sandbox_for_thread(
+            thread_id,
+            github_proxy_token=github_proxy_token,
+            github_proxy_repositories=[repo_name_for_scope] if repo_name_for_scope else None,
+            repo=repo_for_snapshot,
+        )
+    except SandboxRepoMismatchError as exc:
+        # Repo-binding refusal at the run boundary: log for alarming and surface the
+        # sanitized terminal error rather than crash-looping the reviewer worker.
+        logger.error("Refusing reviewer run for thread %s: %s", thread_id, exc)
+        raise RuntimeError(str(exc)) from exc
 
     work_dir = await aresolve_sandbox_work_dir(sandbox_backend)
 
diff --git a/agent/server.py b/agent/server.py
index 42e58661..558825c4 100644
--- a/agent/server.py
+++ b/agent/server.py
@@ -98,6 +98,7 @@ from .utils.github_app import (
     get_github_app_installation_token_with_expiry,
 )
 from .utils.github_proxy import record_proxy_token_expiry
+from .utils.github_token import repo_cache_key
 from .utils.model import (
     DEFAULT_LLM_REASONING,
     ModelKwargs,
@@ -117,6 +118,7 @@ SANDBOX_POLL_INTERVAL = 1.0
 
 from .utils.sandbox_state import (
     SANDBOX_BACKENDS,
+    get_bound_repo_from_metadata,
     get_sandbox_id_from_metadata,
     set_sandbox_backend,
     unwrap_sandbox_backend,
@@ -405,6 +407,24 @@ def graph_loaded_for_execution(config: RunnableConfig) -> bool:
     )
 
 
+class SandboxRepoMismatchError(RuntimeError):
+    """Raised when a thread_id is presented for a repo it is not bound to.
+
+    A thread is bound to exactly one repo. A different repo presenting a
+    colliding thread_id (e.g. an attacker-named branch whose first UUID matches
+    another thread) must never reuse this thread's sandbox or token.
+    """
+
+    def __init__(self, thread_id: str, bound_repo: str, current_repo: str) -> None:
+        self.thread_id = thread_id
+        self.bound_repo = bound_repo
+        self.current_repo = current_repo
+        super().__init__(
+            f"Thread {thread_id} is bound to repo {bound_repo}, "
+            f"refusing to serve sandbox for {current_repo}"
+        )
+
+
 async def ensure_sandbox_for_thread(
     thread_id: str,
     *,
@@ -435,6 +455,43 @@ async def ensure_sandbox_for_thread(
         logger.info("Sandbox creation in progress for thread %s, waiting...", thread_id)
         sandbox_id = await _resolve_creating_sentinel(thread_id)
 
+    # Repo-binding guard (TID-COLLIDE-01): a sandbox is never served to a repo
+    # unless its binding is known and matches.
+    current_repo = repo_cache_key(repo)
+    bound_repo = await get_bound_repo_from_metadata(thread_id)
+    proxy_bound = getattr(sandbox_backend, "bound_repo", None)
+    effective_bound = bound_repo or (proxy_bound if isinstance(proxy_bound, str) else None)
+    if current_repo and effective_bound and effective_bound != current_repo:
+        # Known binding that does not match the current repo: refuse outright so a
+        # colliding thread_id from a different repo cannot reuse/clobber it.
+        logger.error(
+            "Repo mismatch for thread %s: bound=%s current=%s; refusing sandbox reuse",
+            thread_id,
+            effective_bound,
+            current_repo,
+        )
+        raise SandboxRepoMismatchError(thread_id, effective_bound, current_repo)
+    if (
+        current_repo
+        and not effective_bound
+        and sandbox_backend is None
+        and isinstance(sandbox_id, str)
+        and sandbox_id not in (None, SANDBOX_CREATING)
+    ):
+        # Fail CLOSED for unbound-legacy threads (migration window): a thread with a
+        # persisted sandbox_id but no in-memory cache and no recorded bound_repo
+        # cannot be confirmed to belong to the current repo, so never
+        # reconnect-and-serve it. Drop the stale id and recreate a fresh sandbox
+        # bound to this repo below.
+        logger.error(
+            "reconnect-with-missing-binding for thread %s: persisted sandbox %s has no "
+            "bound_repo; refusing reuse and recreating for repo %s",
+            thread_id,
+            sandbox_id,
+            current_repo,
+        )
+        sandbox_id = None
+
     if sandbox_backend:
         logger.info("Using cached sandbox backend for thread %s", thread_id)
         original_sandbox_id = sandbox_backend.id
@@ -493,12 +550,15 @@ async def ensure_sandbox_for_thread(
                     sandbox_backend, thread_id, github_proxy_token, github_proxy_repositories, repo
                 )
 
-    sandbox_backend = set_sandbox_backend(thread_id, sandbox_backend)
+    sandbox_backend = set_sandbox_backend(thread_id, sandbox_backend, repo=current_repo)
 
+    metadata_update: dict[str, Any] = {}
     if sandbox_id != sandbox_backend.id:
-        await client.threads.update(
-            thread_id=thread_id, metadata={"sandbox_id": sandbox_backend.id}
-        )
+        metadata_update["sandbox_id"] = sandbox_backend.id
+    if current_repo and bound_repo != current_repo:
+        metadata_update["bound_repo"] = current_repo
+    if metadata_update:
+        await client.threads.update(thread_id=thread_id, metadata=metadata_update)
 
     # Re-apply git identity every run: cached/reconnected sandboxes may have
     # lost their `--global` config (or had it overwritten), and Vercel preview
@@ -629,11 +689,21 @@ async def get_agent(config: RunnableConfig) -> Pregel:
     )
     team_defaults_task = asyncio.create_task(get_team_default_model_pair("agent"))
     profile_task = asyncio.create_task(load_profile(profile_login)) if profile_login else None
-    triggering_user_identity, sandbox_backend, team_defaults = await asyncio.gather(
-        triggering_user_identity_task,
-        sandbox_task,
-        team_defaults_task,
-    )
+    try:
+        triggering_user_identity, sandbox_backend, team_defaults = await asyncio.gather(
+            triggering_user_identity_task,
+            sandbox_task,
+            team_defaults_task,
+        )
+    except SandboxRepoMismatchError as exc:
+        # Repo-binding refusal at the run boundary: log for alarming and surface the
+        # already-sanitized terminal error (no sandbox/token internals) to the caller,
+        # rather than letting an opaque deep-stack exception crash-loop the worker.
+        logger.error("Refusing agent run for thread %s: %s", thread_id, exc)
+        for pending in (triggering_user_identity_task, team_defaults_task, profile_task):
+            if pending is not None and not pending.done():
+                pending.cancel()
+        raise RuntimeError(str(exc)) from exc
     profile = await profile_task if profile_task is not None else None
     del github_token
 
diff --git a/agent/utils/auth.py b/agent/utils/auth.py
index b279e730..53ea6c1e 100644
--- a/agent/utils/auth.py
+++ b/agent/utils/auth.py
@@ -192,11 +192,18 @@ async def get_github_token_for_user(ls_user_id: str, tenant_id: str) -> dict[str
                 return result
             if auth_url:
                 return {"auth_url": auth_url}
-            return {"error": f"Unexpected auth result: {response_data}"}
+            # Log the full upstream body server-side only; the returned error becomes a
+            # user-facing Slack/Linear comment, so never echo the raw response body.
+            logger.error(
+                "GitHub auth returned an unexpected result (no token/url): %s", response_data
+            )
+            return {"error": "GitHub auth returned an unexpected result"}
 
     except httpx.HTTPStatusError as e:
+        # Log the full upstream body server-side only; the returned error becomes a
+        # user-facing Slack/Linear comment, so never echo the raw response text.
         logger.error("GitHub auth API HTTP error: %s - %s", e.response.status_code, e.response.text)
-        return {"error": f"HTTP error: {e.response.status_code} - {e.response.text}"}
+        return {"error": f"GitHub auth failed (status {e.response.status_code})"}
     except Exception as e:  # noqa: BLE001
         logger.error("GitHub auth API call failed: %s: %s", type(e).__name__, str(e))
         return {"error": str(e)}
@@ -286,10 +293,19 @@ async def leave_failure_comment(
     raise ValueError(f"Unknown source: {source}")
 
 
+def _current_repo() -> Any:
+    """Best-effort read of the run's repo (owner/name) for cache binding."""
+    try:
+        configurable = get_config().get("configurable", {})
+    except Exception:
+        return None
+    return configurable.get("repo") if isinstance(configurable, dict) else None
+
+
 def _cache_resolved_github_token(
     thread_id: str, token: str, expires_at: str | None = None
 ) -> tuple[str, str | None]:
-    cache_github_token_for_thread(thread_id, token, expires_at=expires_at)
+    cache_github_token_for_thread(thread_id, token, expires_at=expires_at, repo=_current_repo())
     return token, expires_at
 
 
@@ -383,7 +399,13 @@ async def _resolve_dashboard_user_token(
 
 
 async def _resolve_bot_installation_token(thread_id: str) -> tuple[str, str | None]:
-    """Get a GitHub App installation token and cache it for the thread."""
+    """Get a GitHub App installation token and cache it for the thread.
+
+    AUTHZ-003 (accepted): in bot-token-only mode every run shares one GitHub App
+    installation token, so its blast radius is the whole installation rather than
+    a single user. This is a documented, accepted prod posture for this
+    single-tenant deployment, not a defect.
+    """
     bot_token, expires_at = await get_github_app_installation_token_with_expiry()
     if not bot_token:
         raise RuntimeError(
@@ -444,7 +466,9 @@ async def resolve_github_token(config: RunnableConfig, thread_id: str) -> tuple[
 
     try:
         if source == "github":
-            cached_token, cached_expires_at = await get_github_token_from_thread(thread_id)
+            cached_token, cached_expires_at = await get_github_token_from_thread(
+                thread_id, expected_repo=configurable.get("repo")
+            )
             if cached_token:
                 return cached_token, cached_expires_at
             from ..dashboard.user_mappings import email_for_login
diff --git a/agent/utils/github_token.py b/agent/utils/github_token.py
index 1738bf3c..b44353eb 100644
--- a/agent/utils/github_token.py
+++ b/agent/utils/github_token.py
@@ -17,22 +17,42 @@ _GITHUB_TOKEN_EXPIRY_SKEW_SECONDS = 60
 # Hard cap on how long an entry stays cached regardless of the token's own
 # expiry, so entries for threads that are never read again don't accumulate.
 _GITHUB_TOKEN_MAX_TTL = timedelta(hours=24)
-# thread_id -> (token, token_expires_at, cached_at)
-_GITHUB_TOKEN_CACHE: dict[str, tuple[str, str | None, datetime]] = {}
+# thread_id -> (token, token_expires_at, cached_at, bound_repo). ``bound_repo``
+# ("owner/name") binds the entry to the repo it was resolved for so a colliding
+# thread_id originating from a different repo cannot reuse another repo's token.
+_GITHUB_TOKEN_CACHE: dict[str, tuple[str, str | None, datetime, str | None]] = {}
 
 
 class GitHubAuthError(Exception):
     """Raised when a GitHub call returns 401, signalling a stale/revoked token."""
 
 
+def repo_cache_key(repo: Any) -> str | None:
+    """Normalize a repo dict/string to a casefolded ``owner/name`` (None if unknown).
+
+    GitHub owner/name are case-insensitive, so the key is casefolded on both the
+    write (binding) and read (compare) sides to keep ``Org/Repo`` and ``org/repo``
+    a single repo and avoid spurious cross-repo mismatches.
+    """
+    if isinstance(repo, str):
+        cleaned = repo.strip()
+        return cleaned.casefold() or None
+    if isinstance(repo, Mapping):
+        owner = repo.get("owner")
+        name = repo.get("name")
+        if isinstance(owner, str) and isinstance(name, str) and owner and name:
+            return f"{owner}/{name}".casefold()
+    return None
+
+
 def cache_github_token_for_thread(
-    thread_id: str, token: str, expires_at: str | None = None
+    thread_id: str, token: str, expires_at: str | None = None, *, repo: Any = None
 ) -> None:
     """Cache a GitHub token in process for the current thread."""
     if not thread_id or not token:
         return
     now = datetime.now(UTC)
-    _GITHUB_TOKEN_CACHE[thread_id] = (token, expires_at, now)
+    _GITHUB_TOKEN_CACHE[thread_id] = (token, expires_at, now, repo_cache_key(repo))
     _evict_expired(now=now)
 
 
@@ -78,24 +98,37 @@ def _evict_expired(*, now: datetime | None = None) -> None:
     current = now or datetime.now(UTC)
     stale = [
         tid
-        for tid, (_token, expires_at, cached_at) in _GITHUB_TOKEN_CACHE.items()
+        for tid, (_token, expires_at, cached_at, _repo) in _GITHUB_TOKEN_CACHE.items()
         if _entry_expired(expires_at, cached_at, now=current)
     ]
     for tid in stale:
         _GITHUB_TOKEN_CACHE.pop(tid, None)
 
 
-def _cached_token_if_fresh(thread_id: str | None) -> tuple[str | None, str | None]:
+def _cached_token_if_fresh(
+    thread_id: str | None, *, expected_repo: Any = None
+) -> tuple[str | None, str | None]:
     if not thread_id:
         return None, None
     cached = _GITHUB_TOKEN_CACHE.get(thread_id)
     if not cached:
         return None, None
-    token, expires_at, cached_at = cached
+    token, expires_at, cached_at, bound_repo = cached
     if _entry_expired(expires_at, cached_at, now=datetime.now(UTC)):
         _GITHUB_TOKEN_CACHE.pop(thread_id, None)
         logger.info("Cached GitHub token for thread %s has expired; re-resolving", thread_id)
         return None, None
+    expected = repo_cache_key(expected_repo)
+    if expected and bound_repo and expected != bound_repo:
+        _GITHUB_TOKEN_CACHE.pop(thread_id, None)
+        logger.warning(
+            "Cached GitHub token for thread %s is bound to repo %s, not %s; "
+            "refusing cross-repo reuse",
+            thread_id,
+            bound_repo,
+            expected,
+        )
+        return None, None
     return token, expires_at
 
 
@@ -107,16 +140,27 @@ def _thread_id_from_config(run_config: Mapping[str, Any]) -> str | None:
     return thread_id if isinstance(thread_id, str) and thread_id else None
 
 
+def _repo_from_config(run_config: Mapping[str, Any]) -> Any:
+    configurable = run_config.get("configurable", {})
+    if not isinstance(configurable, Mapping):
+        return None
+    return configurable.get("repo")
+
+
 def get_github_token(run_config: Mapping[str, Any] | None = None) -> str | None:
     """Resolve the current thread's GitHub token from process memory."""
     resolved = run_config if run_config is not None else get_config()
-    token, _expires_at = _cached_token_if_fresh(_thread_id_from_config(resolved))
+    token, _expires_at = _cached_token_if_fresh(
+        _thread_id_from_config(resolved), expected_repo=_repo_from_config(resolved)
+    )
     return token
 
 
-async def get_github_token_from_thread(thread_id: str) -> tuple[str | None, str | None]:
+async def get_github_token_from_thread(
+    thread_id: str, *, expected_repo: Any = None
+) -> tuple[str | None, str | None]:
     """Resolve the current process's cached GitHub token for a thread."""
-    return _cached_token_if_fresh(thread_id)
+    return _cached_token_if_fresh(thread_id, expected_repo=expected_repo)
 
 
 async def invalidate_cached_github_token(thread_id: str) -> None:
diff --git a/agent/utils/sandbox_state.py b/agent/utils/sandbox_state.py
index caf7b6b4..70764344 100644
--- a/agent/utils/sandbox_state.py
+++ b/agent/utils/sandbox_state.py
@@ -19,6 +19,7 @@ from deepagents.backends.protocol import (
 )
 from langgraph.config import get_config
 
+from .github_token import repo_cache_key
 from .sandbox import create_sandbox
 
 logger = logging.getLogger(__name__)
@@ -29,6 +30,9 @@ class SandboxBackendProxy(SandboxBackendProtocol):
 
     def __init__(self, backend: SandboxBackendProtocol) -> None:
         self._backend = backend
+        # "owner/name" of the repo this sandbox is bound to, used to refuse
+        # reuse by a different repo presenting a colliding thread_id.
+        self.bound_repo: str | None = None
 
     @property
     def current(self) -> SandboxBackendProtocol:
@@ -131,21 +135,44 @@ def unwrap_sandbox_backend(sandbox_backend: SandboxBackendProtocol) -> SandboxBa
 def set_sandbox_backend(
     thread_id: str,
     sandbox_backend: SandboxBackendProtocol,
+    *,
+    repo: str | None = None,
 ) -> SandboxBackendProxy:
     if isinstance(sandbox_backend, SandboxBackendProxy):
+        if repo:
+            sandbox_backend.bound_repo = repo
         SANDBOX_BACKENDS[thread_id] = sandbox_backend
         return sandbox_backend
 
     existing = SANDBOX_BACKENDS.get(thread_id)
     if isinstance(existing, SandboxBackendProxy):
         existing.replace_backend(sandbox_backend)
+        if repo:
+            existing.bound_repo = repo
         return existing
 
     proxy = SandboxBackendProxy(sandbox_backend)
+    if repo:
+        proxy.bound_repo = repo
     SANDBOX_BACKENDS[thread_id] = proxy
     return proxy
 
 
+async def get_bound_repo_from_metadata(thread_id: str) -> str | None:
+    """Fetch the repo (``owner/name``) this thread's sandbox is bound to."""
+    try:
+        config = get_config()
+    except Exception:
+        return None
+    metadata = config.get("metadata", {})
+    if not isinstance(metadata, dict):
+        return None
+    bound_repo = metadata.get("bound_repo")
+    # Casefold on read so legacy metadata written before normalization (e.g.
+    # ``Org/Repo``) still compares equal to the casefolded current repo key.
+    return repo_cache_key(bound_repo) if isinstance(bound_repo, str) and bound_repo else None
+
+
 def clear_sandbox_backend(thread_id: str) -> None:
     SANDBOX_BACKENDS.pop(thread_id, None)
 
diff --git a/agent/webapp.py b/agent/webapp.py
index c7909c6a..f686ba16 100644
--- a/agent/webapp.py
+++ b/agent/webapp.py
@@ -1339,8 +1339,32 @@ async def process_slack_mention(event_data: dict[str, Any], repo_config: dict[st
             )
 
 
+LINEAR_WEBHOOK_MAX_AGE_SECONDS = 60
+
+
+def _linear_timestamp_is_fresh(body: bytes) -> bool:
+    """Reject replays: the signed payload's ``webhookTimestamp`` must be recent.
+
+    Linear includes ``webhookTimestamp`` (Unix milliseconds) inside the signed
+    body. Fail closed when it is missing or malformed.
+    """
+    try:
+        ts_ms = json.loads(body)["webhookTimestamp"]
+    except (json.JSONDecodeError, KeyError, TypeError):
+        logger.warning("Linear webhook missing/invalid webhookTimestamp — rejecting")
+        return False
+    if not isinstance(ts_ms, (int, float)) or isinstance(ts_ms, bool):
+        logger.warning("Linear webhook webhookTimestamp is not numeric — rejecting")
+        return False
+    now_ms = datetime.now(UTC).timestamp() * 1000
+    if abs(now_ms - ts_ms) > LINEAR_WEBHOOK_MAX_AGE_SECONDS * 1000:
+        logger.warning("Linear webhook timestamp outside freshness window — rejecting")
+        return False
+    return True
+
+
 def verify_linear_signature(body: bytes, signature: str, secret: str) -> bool:
-    """Verify the Linear webhook signature.
+    """Verify the Linear webhook signature and replay-freshness window.
 
     Args:
         body: Raw request body bytes
@@ -1348,15 +1372,17 @@ def verify_linear_signature(body: bytes, signature: str, secret: str) -> bool:
         secret: The webhook signing secret
 
     Returns:
-        True if signature is valid, False otherwise
+        True if the signature is valid AND the signed timestamp is fresh.
     """
     if not secret:
         logger.warning("LINEAR_WEBHOOK_SECRET is not configured — rejecting webhook request")
         return False
 
     expected = hmac.new(secret.encode("utf-8"), body, hashlib.sha256).hexdigest()
+    if not hmac.compare_digest(expected, signature):
+        return False
 
-    return hmac.compare_digest(expected, signature)
+    return _linear_timestamp_is_fresh(body)
 
 
 @app.post("/webhooks/linear")
@@ -2920,31 +2946,36 @@ async def process_github_autofix_review(payload: dict[str, Any], event_type: str
     )
 
 
-async def _refresh_thread_github_token_after_401(thread_id: str, email: str) -> str | None:
+async def _refresh_thread_github_token_after_401(
+    thread_id: str, email: str, *, repo: dict[str, str] | None = None
+) -> str | None:
     """Invalidate the cached token after a 401 and try to resolve a fresh one."""
     logger.warning(
         "GitHub returned 401 for thread %s; invalidating cached token and re-resolving",
         thread_id,
     )
     await invalidate_cached_github_token(thread_id)
-    return await _get_or_resolve_thread_github_token(thread_id, email)
+    return await _get_or_resolve_thread_github_token(thread_id, email, repo=repo)
 
 
-async def _get_or_resolve_thread_github_token(thread_id: str, email: str) -> str | None:
+async def _get_or_resolve_thread_github_token(
+    thread_id: str, email: str, *, repo: dict[str, str] | None = None
+) -> str | None:
     """Resolve and cache a GitHub token for a thread when available.
 
     In bot-token-only mode, returns a fresh GitHub App installation token
-    instead of resolving per-user OAuth tokens.
+    instead of resolving per-user OAuth tokens. ``repo`` (owner/name) binds the
+    cached entry so a colliding thread_id from a different repo cannot reuse it.
     """
     if is_bot_token_only_mode():
         bot_token, expires_at = await get_github_app_installation_token_with_expiry()
         if bot_token:
-            cache_github_token_for_thread(thread_id, bot_token, expires_at=expires_at)
+            cache_github_token_for_thread(thread_id, bot_token, expires_at=expires_at, repo=repo)
             return bot_token
         logger.warning("Bot-token-only mode but GitHub App token unavailable")
         return None
 
-    github_token, _expires_at = await get_github_token_from_thread(thread_id)
+    github_token, _expires_at = await get_github_token_from_thread(thread_id, expected_repo=repo)
     if github_token:
         return github_token
 
@@ -2955,7 +2986,10 @@ async def _get_or_resolve_thread_github_token(thread_id: str, email: str) -> str
 
     expires_at = auth_result.get("expires_at")
     cache_github_token_for_thread(
-        thread_id, github_token, expires_at=expires_at if isinstance(expires_at, str) else None
+        thread_id,
+        github_token,
+        expires_at=expires_at if isinstance(expires_at, str) else None,
+        repo=repo,
     )
     return github_token
 
@@ -3017,7 +3051,7 @@ async def process_github_pr_comment(payload: dict[str, Any], event_type: str) ->
 
     email = await email_for_login(github_login) or ""
     if email:
-        github_token = await _get_or_resolve_thread_github_token(thread_id, email)
+        github_token = await _get_or_resolve_thread_github_token(thread_id, email, repo=repo_config)
     else:
         logger.warning("No email mapping for GitHub user '%s', skipping", github_login)
         return
@@ -3037,7 +3071,9 @@ async def process_github_pr_comment(payload: dict[str, Any], event_type: str) ->
                 node_id=node_id,
             )
         except GitHubAuthError:
-            github_token = await _refresh_thread_github_token_after_401(thread_id, email)
+            github_token = await _refresh_thread_github_token_after_401(
+                thread_id, email, repo=repo_config
+            )
             if not github_token:
                 logger.warning("Re-auth failed for thread %s after 401; skipping", thread_id)
                 return
@@ -3059,7 +3095,9 @@ async def process_github_pr_comment(payload: dict[str, Any], event_type: str) ->
             repo_config, pr_number, token=github_token
         )
     except GitHubAuthError:
-        github_token = await _refresh_thread_github_token_after_401(thread_id, email)
+        github_token = await _refresh_thread_github_token_after_401(
+            thread_id, email, repo=repo_config
+        )
         if not github_token:
             logger.warning("Re-auth failed for thread %s after 401; skipping", thread_id)
             return
@@ -3297,7 +3335,7 @@ async def process_github_issue(payload: dict[str, Any], event_type: str) -> None
 
     thread_id = generate_thread_id_from_github_issue(issue_id)
     existing_thread = await _thread_exists(thread_id)
-    github_token = await _get_or_resolve_thread_github_token(thread_id, email)
+    github_token = await _get_or_resolve_thread_github_token(thread_id, email, repo=repo_config)
     app_token = await get_github_app_installation_token()
     reaction_token = github_token or app_token
     comment = payload.get("comment", {})
@@ -3314,7 +3352,9 @@ async def process_github_issue(payload: dict[str, Any], event_type: str) -> None
                     token=reaction_token,
                 )
             except GitHubAuthError:
-                github_token = await _refresh_thread_github_token_after_401(thread_id, email)
+                github_token = await _refresh_thread_github_token_after_401(
+                    thread_id, email, repo=repo_config
+                )
                 reaction_token = github_token or app_token
                 reacted = False
                 if reaction_token:
@@ -3348,7 +3388,9 @@ async def process_github_issue(payload: dict[str, Any], event_type: str) -> None
                 repo_config, issue_number, token=github_token or app_token
             )
         except GitHubAuthError:
-            github_token = await _refresh_thread_github_token_after_401(thread_id, email)
+            github_token = await _refresh_thread_github_token_after_401(
+                thread_id, email, repo=repo_config
+            )
             comments = await fetch_issue_comments(
                 repo_config, issue_number, token=github_token or app_token
             )
diff --git a/infra/lib/constructs/github-deploy-roles.ts b/infra/lib/constructs/github-deploy-roles.ts
index fe7533f6..8d3bfeca 100644
--- a/infra/lib/constructs/github-deploy-roles.ts
+++ b/infra/lib/constructs/github-deploy-roles.ts
@@ -150,10 +150,22 @@ export class GithubDeployRoles extends Construct {
         resources: [`arn:aws:s3:::open-swe-${envName}-assets/releases/*`],
       }),
     );
+    // ListBucket is constrained to the releases/ prefix (F-1/IAC-04): the
+    // publish/rollback scripts only ever list under releases/, so a leaked CI
+    // token cannot enumerate anything else in the bucket. GetBucketLocation
+    // carries no s3:prefix, so it stays a separate, unconditioned statement.
     this.appRole.addToPolicy(
       new iam.PolicyStatement({
         sid: "ListArtifactBucket",
-        actions: ["s3:ListBucket", "s3:GetBucketLocation"],
+        actions: ["s3:ListBucket"],
+        resources: [`arn:aws:s3:::open-swe-${envName}-assets`],
+        conditions: { StringLike: { "s3:prefix": ["releases/*"] } },
+      }),
+    );
+    this.appRole.addToPolicy(
+      new iam.PolicyStatement({
+        sid: "GetArtifactBucketLocation",
+        actions: ["s3:GetBucketLocation"],
         resources: [`arn:aws:s3:::open-swe-${envName}-assets`],
       }),
     );
diff --git a/infra/lib/constructs/instance-role.ts b/infra/lib/constructs/instance-role.ts
index 2acbba39..4a32de9a 100644
--- a/infra/lib/constructs/instance-role.ts
+++ b/infra/lib/constructs/instance-role.ts
@@ -43,10 +43,23 @@ export class InstanceRole extends Construct {
         resources: [`arn:aws:s3:::${p}-assets/releases/*`],
       }),
     );
+    // ListBucket is constrained to the releases/ prefix (F-1/IAC-04) — the box
+    // only ever lists release artifacts, so a compromised box cannot enumerate
+    // any other object that might land in the bucket. GetBucketLocation has no
+    // s3:prefix in its request context, so it stays a separate, unconditioned
+    // statement (the condition would otherwise AccessDeny it).
     this.role.addToPolicy(
       new iam.PolicyStatement({
         sid: "ListArtifactBucket",
-        actions: ["s3:ListBucket", "s3:GetBucketLocation"],
+        actions: ["s3:ListBucket"],
+        resources: [`arn:aws:s3:::${p}-assets`],
+        conditions: { StringLike: { "s3:prefix": ["releases/*"] } },
+      }),
+    );
+    this.role.addToPolicy(
+      new iam.PolicyStatement({
+        sid: "GetArtifactBucketLocation",
+        actions: ["s3:GetBucketLocation"],
         resources: [`arn:aws:s3:::${p}-assets`],
       }),
     );
@@ -85,6 +98,11 @@ export class InstanceRole extends Construct {
     // holds. The win that DID survive: fetch-config uses `--secret-id-list` (explicit
     // names, no name filter), so `secretsmanager:ListSecrets` is NOT needed and is
     // intentionally omitted — the box cannot enumerate secret names account-wide.
+    // F-2 (accepted residual): because the grant is `*`, a caller naming a secret
+    // in ANOTHER env's prefix learns whether that name EXISTS (an existence oracle
+    // via the per-secret AccessDenied-vs-not signal) even though the VALUE stays
+    // gated by the prefix-scoped GetSecretValue above. Accepted within Sea Haven's
+    // single-tenant account 328440206208 — cross-env VALUE isolation is preserved.
     this.role.addToPolicy(
       new iam.PolicyStatement({
         sid: "BatchGetSecretValues",
diff --git a/infra/test/s3-list-prefix.test.ts b/infra/test/s3-list-prefix.test.ts
new file mode 100644
index 00000000..ba76fcd4
--- /dev/null
+++ b/infra/test/s3-list-prefix.test.ts
@@ -0,0 +1,71 @@
+import * as cdk from "aws-cdk-lib";
+import { Match, Template } from "aws-cdk-lib/assertions";
+import { OpenSweIamStack } from "../lib/open-swe-iam-stack";
+import { OpenSweStack } from "../lib/open-swe-stack";
+
+const ENV = { account: "328440206208", region: "us-east-1" };
+
+// F-1 / IAC-04: s3:ListBucket must be constrained to the releases/ prefix so a
+// compromised box / leaked CI token cannot enumerate the rest of the bucket.
+const RELEASES_PREFIX_CONDITION = { StringLike: { "s3:prefix": ["releases/*"] } };
+
+describe("S3 ListBucket prefix scoping (F-1/IAC-04)", () => {
+  it("instance role ListBucket is constrained to releases/*", () => {
+    const app = new cdk.App();
+    const stack = new OpenSweStack(app, "OpenSweDevStack", {
+      stackName: "open-swe-dev",
+      env: ENV,
+      envName: "dev",
+    });
+    Template.fromStack(stack).hasResourceProperties("AWS::IAM::Policy", {
+      PolicyDocument: Match.objectLike({
+        Statement: Match.arrayWith([
+          Match.objectLike({
+            Sid: "ListArtifactBucket",
+            Action: "s3:ListBucket",
+            Condition: RELEASES_PREFIX_CONDITION,
+          }),
+        ]),
+      }),
+    });
+  });
+
+  it("github deploy app role ListBucket is constrained to releases/*", () => {
+    const app = new cdk.App();
+    const stack = new OpenSweIamStack(app, "OpenSweIamStack", {
+      stackName: "open-swe-iam",
+      env: ENV,
+    });
+    Template.fromStack(stack).hasResourceProperties("AWS::IAM::Policy", {
+      PolicyDocument: Match.objectLike({
+        Statement: Match.arrayWith([
+          Match.objectLike({
+            Sid: "ListArtifactBucket",
+            Action: "s3:ListBucket",
+            Condition: RELEASES_PREFIX_CONDITION,
+          }),
+        ]),
+      }),
+    });
+  });
+
+  it("GetBucketLocation stays a separate, unconditioned statement", () => {
+    const app = new cdk.App();
+    const stack = new OpenSweStack(app, "OpenSweDevStack", {
+      stackName: "open-swe-dev",
+      env: ENV,
+      envName: "dev",
+    });
+    Template.fromStack(stack).hasResourceProperties("AWS::IAM::Policy", {
+      PolicyDocument: Match.objectLike({
+        Statement: Match.arrayWith([
+          Match.objectLike({
+            Sid: "GetArtifactBucketLocation",
+            Action: "s3:GetBucketLocation",
+            Condition: Match.absent(),
+          }),
+        ]),
+      }),
+    });
+  });
+});
diff --git a/tests/test_auth_error_leak.py b/tests/test_auth_error_leak.py
new file mode 100644
index 00000000..33cb1cbc
--- /dev/null
+++ b/tests/test_auth_error_leak.py
@@ -0,0 +1,81 @@
+"""AUTH-RESP-LEAK-01: upstream auth-error bodies must not reach user-facing text."""
+
+from __future__ import annotations
+
+import asyncio
+from typing import Any
+
+import httpx
+import pytest
+
+from agent.utils import auth
+
+_SECRET_BODY = "SENSITIVE-UPSTREAM-BODY-9999"
+
+
+class _Resp:
+    def __init__(self, status_code: int, text: str) -> None:
+        self.status_code = status_code
+        self.text = text
+
+    def raise_for_status(self) -> None:
+        raise httpx.HTTPStatusError(
+            "boom",
+            request=httpx.Request("POST", "http://example.test"),
+            response=self,  # type: ignore[arg-type]
+        )
+
+    def json(self) -> Any:
+        return {}
+
+
+class _Client:
+    def __init__(self, resp: _Resp) -> None:
+        self._resp = resp
+
+    async def __aenter__(self) -> _Client:
+        return self
+
+    async def __aexit__(self, *_a: Any) -> None:
+        return None
+
+    async def post(self, *_a: Any, **_k: Any) -> _Resp:
+        return self._resp
+
+
+class _OkResp:
+    """A 2xx response whose JSON body lacks both a token and an auth url."""
+
+    def __init__(self, payload: Any) -> None:
+        self._payload = payload
+
+    def raise_for_status(self) -> None:
+        return None
+
+    def json(self) -> Any:
+        return self._payload
+
+
+def test_http_error_returns_generic_message(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(auth, "GITHUB_OAUTH_PROVIDER_ID", "provider-id")
+    monkeypatch.setattr(auth, "X_SERVICE_AUTH_JWT_SECRET", "jwt-secret")
+    monkeypatch.setattr(httpx, "AsyncClient", lambda *a, **k: _Client(_Resp(500, _SECRET_BODY)))
+
+    result = asyncio.run(auth.get_github_token_for_user("ls-user", "tenant"))
+
+    assert "error" in result
+    assert _SECRET_BODY not in result["error"]
+    assert "500" in result["error"]
+
+
+def test_unexpected_result_returns_generic_message(monkeypatch: pytest.MonkeyPatch) -> None:
+    """The 2xx-but-missing-token/url branch must not echo the upstream body."""
+    monkeypatch.setattr(auth, "GITHUB_OAUTH_PROVIDER_ID", "provider-id")
+    monkeypatch.setattr(auth, "X_SERVICE_AUTH_JWT_SECRET", "jwt-secret")
+    body = {"unexpected_field": _SECRET_BODY}
+    monkeypatch.setattr(httpx, "AsyncClient", lambda *a, **k: _Client(_OkResp(body)))
+
+    result = asyncio.run(auth.get_github_token_for_user("ls-user", "tenant"))
+
+    assert result == {"error": "GitHub auth returned an unexpected result"}
+    assert _SECRET_BODY not in result["error"]
diff --git a/tests/test_github_issue_webhook.py b/tests/test_github_issue_webhook.py
index eee94131..7971577d 100644
--- a/tests/test_github_issue_webhook.py
+++ b/tests/test_github_issue_webhook.py
@@ -1127,7 +1127,9 @@ def test_process_github_pr_comment_without_email_skips(
 def test_process_github_issue_uses_resolved_user_token_for_reaction(monkeypatch) -> None:
     captured: dict[str, object] = {}
 
-    async def fake_get_or_resolve_thread_github_token(thread_id: str, email: str) -> str | None:
+    async def fake_get_or_resolve_thread_github_token(
+        thread_id: str, email: str, *, repo: dict[str, str] | None = None
+    ) -> str | None:
         captured["thread_id"] = thread_id
         captured["email"] = email
         return "user-token"
@@ -1210,7 +1212,9 @@ def test_process_github_issue_uses_resolved_user_token_for_reaction(monkeypatch)
 def test_process_github_issue_existing_thread_uses_followup_prompt(monkeypatch) -> None:
     captured: dict[str, object] = {}
 
-    async def fake_get_or_resolve_thread_github_token(thread_id: str, email: str) -> str | None:
+    async def fake_get_or_resolve_thread_github_token(
+        thread_id: str, email: str, *, repo: dict[str, str] | None = None
+    ) -> str | None:
         return "user-token"
 
     async def fake_get_github_app_installation_token() -> str | None:
diff --git a/tests/test_github_token_ttl.py b/tests/test_github_token_ttl.py
index bd3ee158..0d880814 100644
--- a/tests/test_github_token_ttl.py
+++ b/tests/test_github_token_ttl.py
@@ -69,7 +69,7 @@ def test_cached_token_expires_after_max_ttl() -> None:
     """A token with no/far expiry is still dropped once it's older than the 24h cap."""
     far_future = (datetime.now(UTC) + timedelta(days=30)).isoformat()
     old_cached_at = datetime.now(UTC) - timedelta(hours=25)
-    github_token._GITHUB_TOKEN_CACHE["tid"] = ("ghp_secret", far_future, old_cached_at)
+    github_token._GITHUB_TOKEN_CACHE["tid"] = ("ghp_secret", far_future, old_cached_at, None)
     assert github_token.get_github_token({"configurable": {"thread_id": "tid"}}) is None
 
 
@@ -210,7 +210,7 @@ def test_process_github_pr_comment_invalidates_and_reauths_on_401(
 
     tokens = iter(["stale-token", "fresh-token"])
 
-    async def fake_get_or_resolve(thread_id: str, email: str) -> str | None:
+    async def fake_get_or_resolve(thread_id: str, email: str, *, repo: Any = None) -> str | None:
         token = next(tokens)
         resolves.append(token)
         return token
diff --git a/tests/test_linear_webhook_replay.py b/tests/test_linear_webhook_replay.py
new file mode 100644
index 00000000..c0e4295c
--- /dev/null
+++ b/tests/test_linear_webhook_replay.py
@@ -0,0 +1,53 @@
+"""Replay-window enforcement for Linear webhook signature verification (AUTHZ-001)."""
+
+from __future__ import annotations
+
+import hashlib
+import hmac
+import json
+from datetime import UTC, datetime
+
+from agent import webapp
+
+_SECRET = "linear-signing-secret"
+
+
+def _sign(body: bytes) -> str:
+    return hmac.new(_SECRET.encode("utf-8"), body, hashlib.sha256).hexdigest()
+
+
+def _now_ms() -> int:
+    return int(datetime.now(UTC).timestamp() * 1000)
+
+
+def test_fresh_timestamp_accepted() -> None:
+    body = json.dumps({"type": "Comment", "webhookTimestamp": _now_ms()}).encode()
+    assert webapp.verify_linear_signature(body, _sign(body), _SECRET) is True
+
+
+def test_stale_timestamp_rejected() -> None:
+    stale = _now_ms() - 10 * 60 * 1000  # 10 minutes old
+    body = json.dumps({"type": "Comment", "webhookTimestamp": stale}).encode()
+    # Signature is valid, but the timestamp is outside the freshness window.
+    assert webapp.verify_linear_signature(body, _sign(body), _SECRET) is False
+
+
+def test_future_timestamp_rejected() -> None:
+    future = _now_ms() + 10 * 60 * 1000
+    body = json.dumps({"type": "Comment", "webhookTimestamp": future}).encode()
+    assert webapp.verify_linear_signature(body, _sign(body), _SECRET) is False
+
+
+def test_missing_timestamp_rejected() -> None:
+    body = json.dumps({"type": "Comment"}).encode()
+    assert webapp.verify_linear_signature(body, _sign(body), _SECRET) is False
+
+
+def test_non_numeric_timestamp_rejected() -> None:
+    body = json.dumps({"type": "Comment", "webhookTimestamp": "not-a-number"}).encode()
+    assert webapp.verify_linear_signature(body, _sign(body), _SECRET) is False
+
+
+def test_bad_signature_rejected_even_when_fresh() -> None:
+    body = json.dumps({"type": "Comment", "webhookTimestamp": _now_ms()}).encode()
+    assert webapp.verify_linear_signature(body, "deadbeef", _SECRET) is False
diff --git a/tests/test_proxy_auth.py b/tests/test_proxy_auth.py
index 163bd1a4..dfdfa903 100644
--- a/tests/test_proxy_auth.py
+++ b/tests/test_proxy_auth.py
@@ -264,6 +264,7 @@ class TestRefreshProxyOnSandboxReuse:
         mock_sandbox = MagicMock(id="sandbox-cached")
 
         with (
+            patch("agent.server.client.threads.update", new_callable=AsyncMock),
             patch(
                 "agent.server.resolve_github_token",
                 new_callable=AsyncMock,
@@ -308,11 +309,12 @@ class TestRefreshProxyOnSandboxReuse:
 
     @pytest.mark.asyncio
     async def test_refreshes_proxy_when_reconnecting_to_existing_langsmith_sandbox(self) -> None:
-        """Reconnected sandboxes should also get a fresh proxy token."""
+        """A bound thread reconnecting to its sandbox should get a fresh proxy token."""
         config = self._execution_config()
         mock_sandbox = MagicMock(id="sandbox-existing")
 
         with (
+            patch("agent.server.client.threads.update", new_callable=AsyncMock),
             patch(
                 "agent.server.resolve_github_token",
                 new_callable=AsyncMock,
@@ -323,6 +325,13 @@ class TestRefreshProxyOnSandboxReuse:
                 new_callable=AsyncMock,
                 return_value="sandbox-existing",
             ),
+            # Thread is bound to the current repo, so reconnect proceeds (an unbound
+            # legacy thread would instead fail closed and recreate).
+            patch(
+                "agent.server.get_bound_repo_from_metadata",
+                new_callable=AsyncMock,
+                return_value="langchain-ai/open-swe",
+            ),
             patch("agent.server.create_sandbox", return_value=mock_sandbox) as mock_create,
             patch(
                 "agent.server.get_github_app_installation_token_with_expiry",
diff --git a/tests/test_repo_binding_isolation.py b/tests/test_repo_binding_isolation.py
new file mode 100644
index 00000000..6e9c94bd
--- /dev/null
+++ b/tests/test_repo_binding_isolation.py
@@ -0,0 +1,225 @@
+"""Repo-binding isolation for the sandbox and GitHub-token caches.
+
+Covers TID-COLLIDE-01: a second repo presenting a colliding thread_id must not
+reuse the first repo's in-process sandbox or cached GitHub token.
+"""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime, timedelta
+from typing import Any
+
+import pytest
+
+from agent import server
+from agent.utils import github_token
+
+
+@pytest.fixture(autouse=True)
+def _clear_caches() -> None:
+    github_token._GITHUB_TOKEN_CACHE.clear()
+    server.SANDBOX_BACKENDS.clear()
+
+
+# --- token cache repo binding ------------------------------------------------
+
+
+def test_cached_token_not_reused_across_repos() -> None:
+    """A token bound to repo A is refused for a colliding thread_id from repo B."""
+    future = (datetime.now(UTC) + timedelta(hours=1)).isoformat()
+    github_token.cache_github_token_for_thread(
+        "tid", "ghp_repoA", expires_at=future, repo={"owner": "acme", "name": "alpha"}
+    )
+
+    # Same thread_id, different repo → must NOT serve repo A's token.
+    cfg_b = {"configurable": {"thread_id": "tid", "repo": {"owner": "evil", "name": "beta"}}}
+    assert github_token.get_github_token(cfg_b) is None
+    # And the poisoned entry is evicted.
+    assert "tid" not in github_token._GITHUB_TOKEN_CACHE
+
+
+def test_cached_token_reused_for_same_repo() -> None:
+    future = (datetime.now(UTC) + timedelta(hours=1)).isoformat()
+    github_token.cache_github_token_for_thread(
+        "tid", "ghp_repoA", expires_at=future, repo={"owner": "acme", "name": "alpha"}
+    )
+    cfg_a = {"configurable": {"thread_id": "tid", "repo": {"owner": "acme", "name": "alpha"}}}
+    assert github_token.get_github_token(cfg_a) == "ghp_repoA"
+
+
+def test_unbound_token_served_when_repo_unknown() -> None:
+    """Legacy entries with no bound repo still resolve when no repo is supplied."""
+    github_token.cache_github_token_for_thread("tid", "ghp_legacy")
+    assert github_token.get_github_token({"configurable": {"thread_id": "tid"}}) == "ghp_legacy"
+
+
+def test_cached_token_reused_for_same_repo_case_insensitive() -> None:
+    """``Org/Repo`` and ``org/repo`` are the same repo: no spurious refusal."""
+    future = (datetime.now(UTC) + timedelta(hours=1)).isoformat()
+    github_token.cache_github_token_for_thread(
+        "tid", "ghp_repoA", expires_at=future, repo={"owner": "Acme", "name": "Alpha"}
+    )
+    cfg = {"configurable": {"thread_id": "tid", "repo": {"owner": "acme", "name": "alpha"}}}
+    assert github_token.get_github_token(cfg) == "ghp_repoA"
+
+
+def test_repo_cache_key_normalizes() -> None:
+    assert github_token.repo_cache_key({"owner": "o", "name": "r"}) == "o/r"
+    assert github_token.repo_cache_key("o/r") == "o/r"
+    assert github_token.repo_cache_key({"owner": "o"}) is None
+    assert github_token.repo_cache_key(None) is None
+    # Casefolded so different casing of the same repo collapses to one key.
+    assert github_token.repo_cache_key({"owner": "Org", "name": "Repo"}) == "org/repo"
+    assert github_token.repo_cache_key("Org/Repo") == "org/repo"
+
+
+# --- sandbox repo binding ----------------------------------------------------
+
+
+class _FakeBackend:
+    def __init__(self, sandbox_id: str) -> None:
+        self.id = sandbox_id
+        self.bound_repo: str | None = None
+
+    def execute(self, *_a: Any, **_k: Any) -> Any:  # pragma: no cover - must not run
+        raise AssertionError("colliding-repo sandbox must not be pinged/reused")
+
+
+@pytest.mark.asyncio
+async def test_ensure_sandbox_refuses_colliding_repo(monkeypatch: pytest.MonkeyPatch) -> None:
+    async def fake_sandbox_id(_tid: str) -> str:
+        return "sb-A"
+
+    async def fake_bound_repo(_tid: str) -> str:
+        return "acme/alpha"
+
+    monkeypatch.setattr(server, "get_sandbox_id_from_metadata", fake_sandbox_id)
+    monkeypatch.setattr(server, "get_bound_repo_from_metadata", fake_bound_repo)
+    backend = _FakeBackend("sb-A")
+    backend.bound_repo = "acme/alpha"
+    server.SANDBOX_BACKENDS["tid"] = backend  # type: ignore[assignment]
+
+    with pytest.raises(server.SandboxRepoMismatchError):
+        await server.ensure_sandbox_for_thread("tid", repo={"owner": "evil", "name": "beta"})
+
+
+@pytest.mark.asyncio
+async def test_ensure_sandbox_allows_matching_repo(monkeypatch: pytest.MonkeyPatch) -> None:
+    async def fake_sandbox_id(_tid: str) -> str:
+        return "sb-A"
+
+    async def fake_bound_repo(_tid: str) -> str:
+        return "acme/alpha"
+
+    calls: dict[str, int] = {"git": 0}
+    backend = _FakeBackend("sb-A")
+    backend.bound_repo = "acme/alpha"
+
+    async def fake_check(b: Any, *_a: Any, **_k: Any) -> Any:
+        return b
+
+    async def fake_refresh(b: Any, *_a: Any, **_k: Any) -> Any:
+        return b
+
+    async def fake_git(_b: Any) -> None:
+        calls["git"] += 1
+
+    monkeypatch.setattr(server, "get_sandbox_id_from_metadata", fake_sandbox_id)
+    monkeypatch.setattr(server, "get_bound_repo_from_metadata", fake_bound_repo)
+    monkeypatch.setattr(server, "check_or_recreate_sandbox", fake_check)
+    monkeypatch.setattr(server, "_refresh_github_proxy_or_recreate", fake_refresh)
+    monkeypatch.setattr(server, "set_sandbox_backend", lambda _tid, b, **_k: b)
+    monkeypatch.setattr(server, "_configure_git_identity", fake_git)
+    server.SANDBOX_BACKENDS["tid"] = backend  # type: ignore[assignment]
+
+    result = await server.ensure_sandbox_for_thread("tid", repo={"owner": "acme", "name": "alpha"})
+    assert result is backend
+    assert calls["git"] == 1
+
+
+@pytest.mark.asyncio
+async def test_ensure_sandbox_reuses_same_repo_case_insensitive(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A bound sandbox is reused when the current repo differs only by casing."""
+
+    async def fake_sandbox_id(_tid: str) -> str:
+        return "sb-A"
+
+    async def fake_bound_repo(_tid: str) -> str:
+        return "acme/alpha"
+
+    backend = _FakeBackend("sb-A")
+    backend.bound_repo = "acme/alpha"
+
+    async def fake_check(b: Any, *_a: Any, **_k: Any) -> Any:
+        return b
+
+    async def fake_refresh(b: Any, *_a: Any, **_k: Any) -> Any:
+        return b
+
+    async def fake_git(_b: Any) -> None:
+        return None
+
+    monkeypatch.setattr(server, "get_sandbox_id_from_metadata", fake_sandbox_id)
+    monkeypatch.setattr(server, "get_bound_repo_from_metadata", fake_bound_repo)
+    monkeypatch.setattr(server, "check_or_recreate_sandbox", fake_check)
+    monkeypatch.setattr(server, "_refresh_github_proxy_or_recreate", fake_refresh)
+    monkeypatch.setattr(server, "set_sandbox_backend", lambda _tid, b, **_k: b)
+    monkeypatch.setattr(server, "_configure_git_identity", fake_git)
+    server.SANDBOX_BACKENDS["tid"] = backend  # type: ignore[assignment]
+
+    # Different casing of the same repo must not raise and must reuse the sandbox.
+    result = await server.ensure_sandbox_for_thread("tid", repo={"owner": "ACME", "name": "Alpha"})
+    assert result is backend
+
+
+@pytest.mark.asyncio
+async def test_legacy_unbound_sandbox_recreated_not_reused(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A legacy thread (sandbox_id present, bound_repo absent) must fail closed.
+
+    With no recorded binding, the existing sandbox cannot be confirmed to belong
+    to the current repo, so it is never reconnected-and-served: a fresh sandbox is
+    created and bound to the requesting repo instead.
+    """
+
+    async def fake_sandbox_id(_tid: str) -> str:
+        return "sb-legacy"
+
+    async def fake_bound_repo(_tid: str) -> None:
+        return None
+
+    def fake_reconnect(*_a: Any, **_k: Any) -> Any:  # pragma: no cover - must not run
+        raise AssertionError("must not reconnect to a legacy unbound sandbox")
+
+    fresh = _FakeBackend("sb-fresh")
+
+    async def fake_create_with_proxy(*_a: Any, **_k: Any) -> Any:
+        return fresh
+
+    async def fake_git(_b: Any) -> None:
+        return None
+
+    class _Threads:
+        async def update(self, **_k: Any) -> None:
+            return None
+
+        async def get(self, *_a: Any, **_k: Any) -> dict[str, Any]:
+            return {}
+
+    class _Client:
+        threads = _Threads()
+
+    monkeypatch.setattr(server, "get_sandbox_id_from_metadata", fake_sandbox_id)
+    monkeypatch.setattr(server, "get_bound_repo_from_metadata", fake_bound_repo)
+    monkeypatch.setattr(server, "create_sandbox", fake_reconnect)
+    monkeypatch.setattr(server, "_create_sandbox_with_proxy", fake_create_with_proxy)
+    monkeypatch.setattr(server, "_configure_git_identity", fake_git)
+    monkeypatch.setattr(server, "client", _Client())
+
+    result = await server.ensure_sandbox_for_thread("tid", repo={"owner": "evil", "name": "beta"})
+
+    assert result.id == "sb-fresh"
+    assert server.SANDBOX_BACKENDS["tid"].bound_repo == "evil/beta"
diff --git a/tests/test_reviewer.py b/tests/test_reviewer.py
index 109fc90c..a381a0ce 100644
--- a/tests/test_reviewer.py
+++ b/tests/test_reviewer.py
@@ -221,7 +221,9 @@ async def test_reviewer_resolves_app_installation_token_at_run_start() -> None:
     # Token is resolved in this process at run start (scoped to the repo), not read
     # from a cache the webhook handler populated in a different process.
     mock_app_token.assert_awaited_once_with(repositories=["repo"])
-    mock_cache_token.assert_called_once_with("reviewer-thread-id", "app-token", expires_at=None)
+    mock_cache_token.assert_called_once_with(
+        "reviewer-thread-id", "app-token", expires_at=None, repo={"owner": "acme", "name": "repo"}
+    )
     middleware = create_agent.call_args.kwargs["middleware"]
     assert reviewer.check_message_queue_before_model in middleware