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style(router): trim repeated explanatory comments in tag routing prefix scoping

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Greptile flagged the comments in tag_based_routing.py and its tests as duplicating
the same rationale across multiple functions and tests. Consolidates each
explanation to a single place and shortens the rest to what is distinct per site.
This commit is contained in:
Deepanshu 2026-09-05 09:05:56 -04:00
parent 4a18a022e2
commit 893f2cab1f
2 changed files with 26 additions and 66 deletions
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35
litellm/router_strategy/tag_based_routing.py
View file

@ -435,16 +435,10 @@ def _inherited_constraint_sets(
def _inherited_full_tags(inherited_tags: object, routing_prefix: str) -> frozenset[str]:
# Every policy-contributed tag's exact, marker-preserving rewritten form --
# used to exempt inherited tags from the request-tag noop filter below, since
# key/team/project policy is not caller-controlled and merges its tags into
# the same "tags" list a caller's own tags land in (see
# litellm_pre_call_utils.py). Matching on the full tag (not just its bare
# value, as an earlier version of this helper did) matters: bare-value-only
# matching would let a caller smuggle an unprefixed tag past the filter just
# by sharing its bare value with a policy tag under a different "&"/"!"
# marker (e.g. policy requires "&region:eu"; caller separately, unprefixed,
# sends "!region:eu" -- bare-value matching would wrongly exempt it too).
# Policy tags exempt request-tag scoping regardless of prefix (see
# _scope_to_confirmed_and_inherited_tags); matched by exact rewritten form,
# not bare value, so a caller can't exempt an unrelated tag by reusing a
# policy tag's bare value under a different "&"/"!" marker.
if not isinstance(inherited_tags, (list, tuple)):
return frozenset()
return frozenset(_strip_routing_prefix(inherited_tags, routing_prefix)[0])
@ -456,20 +450,13 @@ def _scope_to_confirmed_and_inherited_tags(
inherited_tags: object,
routing_prefix: str,
) -> tuple[str, ...]:
# Once a routing prefix is configured, an unprefixed request tag (e.g. an
# unrelated attribution tag like "user_id:234") must never be treated as a
# routing signal at all -- not matched, not required, not excluded, and
# never a cause of no_deployments_with_tag_routing. Only tags the caller
# explicitly marked with the prefix participate in tag-based routing.
# Exemption is keyed on each tag's exact, marker-preserving rewritten form
# (not _strip_routing_prefix's own `confirmed` return, which is bare values
# only, used by _chain_allows_fail_open's "known required tag" check for a
# different purpose): bare-value matching would let a caller smuggle an
# unprefixed tag past this filter just by sharing its bare value with a
# genuinely confirmed or inherited tag under a different "&"/"!" marker.
# _inherited_full_tags exempts key/team/project policy's own tags
# unconditionally: policy isn't caller-controlled and was never expected to
# carry the prefix, so it must keep applying regardless.
# Once a prefix is configured, an unprefixed request tag is noise, not a
# routing signal -- except a tag the caller explicitly prefixed, or one
# policy already contributed via inherited_tags (not caller-controlled, so
# exempt regardless of prefix). Matching the full rewritten tag rather than
# _strip_routing_prefix's bare-value `confirmed` return (used elsewhere for
# the "known required tag" fail-open check) avoids exempting an unrelated
# tag that happens to share a bare value under a different marker.
confirmed_full_tags: Final = frozenset(
rewritten for rewritten, original in zip(rewritten_tags, original_tags) if original.startswith(routing_prefix)
)

57
tests/test_litellm/router_strategy/test_router_tag_routing.py
View file

@ -3162,11 +3162,8 @@ async def test_chat_request_carrying_litellm_metadata_still_routes_on_proxy_merg
assert deployment["model_info"]["id"] == "team-a-deployment"
# --- unprefixed request tags must be a no-op once tag_routing_prefix is configured
# (GitHub issue #39901): an unrelated attribution tag (e.g. "user_id:234") the
# caller happens to send must never be treated as a routing signal the moment an
# operator opts into tag_routing_prefix, since the prefix's entire point is to
# scope which tags carry routing intent. ---
# --- unprefixed request tags must be a no-op once tag_routing_prefix is
# configured (GitHub issue #39901) ---
def _untagged_single_deployment_router(tag_routing_prefix: str = "route:"):
@ -3188,10 +3185,7 @@ def _untagged_single_deployment_router(tag_routing_prefix: str = "route:"):
@pytest.mark.asyncio()
async def test_unprefixed_request_tag_is_noop_when_prefix_configured():
# No deployment in the group carries any tags at all -- a perfectly normal,
# unadopted state. An unrelated tag the caller happens to send must not be
# treated as a routing signal, matched, or cause no_deployments_with_tag_routing,
# once tag_routing_prefix is configured.
# Zero deployment tags in the group; an unrelated tag must not raise.
router = _untagged_single_deployment_router()
response = await router.acompletion(
@ -3206,8 +3200,7 @@ async def test_unprefixed_request_tag_is_noop_when_prefix_configured():
@pytest.mark.asyncio()
async def test_no_tags_still_noop_when_prefix_configured():
# Baseline regression guard: a request with no tags at all already worked
# before this fix and must keep working identically after it.
# Baseline: no tags at all must keep working identically.
router = _untagged_single_deployment_router()
response = await router.acompletion(
@ -3222,9 +3215,7 @@ async def test_no_tags_still_noop_when_prefix_configured():
@pytest.mark.asyncio()
async def test_prefixed_tag_still_raises_when_unresolvable():
# A genuinely prefixed tag remains a real, trusted routing directive: if it
# can't be resolved against any deployment, this must still raise. Proves the
# fix scopes out unprefixed noise without disabling tag routing entirely.
# A genuinely prefixed, unresolvable tag must still raise.
router = _untagged_single_deployment_router()
with pytest.raises(Exception, match='Not allowed to access model due to tags configuration\\.') as exc_info:
@ -3242,9 +3233,7 @@ async def test_prefixed_tag_still_raises_when_unresolvable():
@pytest.mark.asyncio()
async def test_unprefixed_tag_still_raises_when_no_prefix_configured():
# Backward-compat guard: with tag_routing_prefix left at its default empty
# string, an unprefixed tag must behave exactly as it did before this fix --
# the new filtering only activates once a prefix is actually configured.
# Backward compat: no prefix configured, so the old behavior is unchanged.
router = _untagged_single_deployment_router(tag_routing_prefix="")
with pytest.raises(Exception, match='Not allowed to access model due to tags configuration\\.') as exc_info:
@ -3262,11 +3251,7 @@ async def test_unprefixed_tag_still_raises_when_no_prefix_configured():
@pytest.mark.asyncio()
async def test_inherited_required_tag_unaffected_by_prefix_scoping():
# An unprefixed admin/team-policy "&" requirement (merged into "tags" by
# litellm_pre_call_utils.py and snapshotted into inherited_tags) is not
# caller-controlled and must keep constraining deployment choice even once
# tag_routing_prefix is configured -- the new scoping applies only to what the
# caller themselves declared, not to what policy already contributed.
# An unprefixed policy "&" requirement in inherited_tags must still apply.
router = _eu_region_router()
router.update_settings(tag_routing_prefix="route:")
@ -3282,10 +3267,8 @@ async def test_inherited_required_tag_unaffected_by_prefix_scoping():
@pytest.mark.asyncio()
async def test_inherited_excluded_tag_unaffected_by_prefix_scoping():
# Same guarantee for an unprefixed admin/team-policy "!" exclusion, exercised
# without exhausting the pool (no fail-open floor involved) -- this proves the
# primary (non-fail-open) candidate computation itself still honors it, not
# just the trusted-only fail-open fallback.
# Same, for a "!" exclusion, without exhausting the pool -- proves the
# primary candidate computation honors it, not just the fail-open floor.
router = _eu_region_router()
router.update_settings(tag_routing_prefix="route:")
@ -3301,15 +3284,9 @@ async def test_inherited_excluded_tag_unaffected_by_prefix_scoping():
@pytest.mark.asyncio()
async def test_foreign_tag_ignored_alongside_inherited_constraint_when_prefix_configured():
# Realistic combined scenario: the caller's own unrelated attribution tag
# rides alongside an inherited policy requirement in the same request. The
# foreign tag must be ignored while the inherited requirement still routes
# correctly. Deliberately not using _eu_region_router() here: both of its
# deployments set allow_fail_open=True, so a leaked "user_id:234" positive
# tag would still resolve to "eu-1" via the fail-open floor's own
# inherited-tags intersection, masking a regression in the filter itself.
# No allow_fail_open here means a leaked foreign tag has no safety net to
# hide behind -- it must show up as an outright raise, not a lucky match.
# A foreign tag and an inherited requirement in the same request: the
# foreign tag must be ignored. No allow_fail_open (unlike _eu_region_router)
# so a leaked foreign tag can't self-heal via the fail-open floor.
router = litellm.Router(
model_list=[
{
@ -3347,13 +3324,9 @@ async def test_foreign_tag_ignored_alongside_inherited_constraint_when_prefix_co
@pytest.mark.asyncio()
async def test_unprefixed_tag_cannot_piggyback_via_bare_value_collision_with_confirmed_tag():
# Regression: exemption from the noop filter must be keyed on a tag's exact,
# marker-preserving form, not just its bare value. A caller sending both a
# genuinely confirmed positive tag ("route:region:eu") and an unrelated,
# unprefixed exclusion sharing the same bare value ("!region:eu") must not
# have that exclusion smuggled through just because "region:eu" happens to
# be confirmed under a different marker -- the exclusion is caller noise and
# must stay inert, same as any other unprefixed tag.
# Exemption is keyed on the exact tag, not its bare value: a confirmed
# "route:region:eu" must not exempt an unrelated "!region:eu" sharing the
# same bare value under a different marker.
router = litellm.Router(
model_list=[
{