diff --git a/src/sentry/seer/endpoints/group_ai_autofix.py b/src/sentry/seer/endpoints/group_ai_autofix.py
index 2d7d5a502221..58f69081b32d 100644
--- a/src/sentry/seer/endpoints/group_ai_autofix.py
+++ b/src/sentry/seer/endpoints/group_ai_autofix.py
@@ -3,7 +3,7 @@
 import logging
 import uuid
 from collections.abc import Collection
-from typing import Any
+from typing import Annotated, Any, Final, Literal, NotRequired, TypedDict
 
 from drf_spectacular.utils import OpenApiParameter, extend_schema
 from rest_framework import serializers, status
@@ -24,6 +24,7 @@
     RESPONSE_NOT_FOUND,
     RESPONSE_UNAUTHORIZED,
 )
+from sentry.apidocs.descriptions import ApiDescription
 from sentry.apidocs.examples.autofix_examples import AutofixExamples
 from sentry.apidocs.parameters import GlobalParams, IssueParams
 from sentry.apidocs.response_types import (
@@ -92,6 +93,7 @@
     SEER_OUT_OF_CREDITS_CODE,
     SEER_OUT_OF_QUOTA_CODE,
     SEER_PERMISSION_DENIED,
+    SeerPaymentRequiredCode,
     get_seer_run,
     resolve_seer_run,
 )
@@ -109,9 +111,13 @@
 
 # Marks the one 409 from this endpoint that a caller can recover from on its own:
 # the run named in the body is alive, so polling it is the whole remedy.
-RUN_IN_FLIGHT_CODE = "run_in_flight"
+RunInFlightCode = Literal["run_in_flight"]
+RUN_IN_FLIGHT_CODE: Final[RunInFlightCode] = "run_in_flight"
 
-AUTOFIX_SETUP_REQUIRED_DETAIL = {
+# The API schema documents these codes as an enum, so a new code has to be added here.
+AutofixSetupCode = Literal["scm_integration_required", "repos_not_linked"]
+
+AUTOFIX_SETUP_REQUIRED_DETAIL: dict[AutofixSetupCode, str] = {
     "scm_integration_required": (
         "Seer Autofix requires a supported SCM integration (GitHub or GitLab) "
         "to be installed for your organization before a new run can be started."
@@ -123,6 +129,43 @@
 }
 
 
+class AutofixConflictResponse(TypedDict):
+    detail: Annotated[str, ApiDescription("Why the step can't run")]
+    code: NotRequired[
+        Annotated[
+            Literal[AutofixSetupCode, RunInFlightCode],
+            ApiDescription(
+                "Set when a client can act on the conflict. `scm_integration_required` and "
+                "`repos_not_linked` mean the organization or project must finish Seer setup "
+                "before a new run can start. `run_in_flight` means a step is already running "
+                "for the run in `run_id`, so poll it instead of retrying"
+            ),
+        ]
+    ]
+    run_id: NotRequired[
+        Annotated[int, ApiDescription("ID of the run in Seer. Set with `run_in_flight`")]
+    ]
+    sentry_run_id: NotRequired[
+        Annotated[
+            str | None,
+            ApiDescription(
+                "ID of the run in Sentry. Set with `run_in_flight`, null for legacy runs"
+            ),
+        ]
+    ]
+
+
+class AutofixPaymentRequiredResponse(TypedDict):
+    detail: Annotated[str, ApiDescription("Why the organization can't run Seer")]
+    code: Annotated[
+        SeerPaymentRequiredCode,
+        ApiDescription(
+            "`seer_out_of_credits` when the organization has no Seer credits left, "
+            "`seer_out_of_quota` when it has no Seer budget"
+        ),
+    ]
+
+
 class GroupAutofixPermission(GroupAiPermission):
     # `seer:write` covers the analysis steps only; see _require_publish_scope.
     scope_map = {
@@ -200,7 +243,7 @@ def _record_user_context_length(request_data: Any) -> None:
     )
 
 
-def _check_autofix_setup(organization: Organization, project: Project) -> str | None:
+def _check_autofix_setup(organization: Organization, project: Project) -> AutofixSetupCode | None:
     """Return the setup code blocking a new autofix run, or None if it can start.
 
     Mirrors the frontend gate in AutofixContent: legacy usage-based Seer plans
@@ -330,8 +373,14 @@ class GroupAutofixEndpoint(ConditionalGetResponseMixin, FormattableResponseMixin
             202: inline_sentry_response_serializer("AutofixPostResponse", AutofixPostResponse),
             400: RESPONSE_BAD_REQUEST,
             401: RESPONSE_UNAUTHORIZED,
+            402: inline_sentry_response_serializer(
+                "AutofixPaymentRequiredResponse", AutofixPaymentRequiredResponse
+            ),
             403: RESPONSE_FORBIDDEN,
             404: RESPONSE_NOT_FOUND,
+            409: inline_sentry_response_serializer(
+                "AutofixConflictResponse", AutofixConflictResponse
+            ),
         },
         examples=AutofixExamples.AUTOFIX_POST_RESPONSE,
     )
@@ -342,6 +391,8 @@ def post(
         | Response[AutofixHandoffResponse]
         | Response[None]
         | Response[DetailResponse]
+        | Response[AutofixConflictResponse]
+        | Response[AutofixPaymentRequiredResponse]
         | Response[ValidationErrorResponse]
         | Response[str]
     ):
diff --git a/src/sentry/seer/endpoints/utils.py b/src/sentry/seer/endpoints/utils.py
index 3414c3bd2aba..e306540c8e97 100644
--- a/src/sentry/seer/endpoints/utils.py
+++ b/src/sentry/seer/endpoints/utils.py
@@ -2,7 +2,7 @@
 
 import uuid as uuid_module
 from collections.abc import Callable
-from typing import TYPE_CHECKING, Any, NamedTuple, TypeVar
+from typing import TYPE_CHECKING, Any, Final, Literal, NamedTuple, TypeVar
 
 from rest_framework import status
 from rest_framework.response import Response
@@ -18,8 +18,10 @@
 SEER_PERMISSION_DENIED = "You are not authorized to perform this action"
 
 # Let API clients like the CLI and MCP tell billing 402s apart without parsing detail text.
-SEER_OUT_OF_CREDITS_CODE = "seer_out_of_credits"
-SEER_OUT_OF_QUOTA_CODE = "seer_out_of_quota"
+# The API schema documents these codes as an enum, so a new code has to be added here.
+SeerPaymentRequiredCode = Literal["seer_out_of_credits", "seer_out_of_quota"]
+SEER_OUT_OF_CREDITS_CODE: Final[SeerPaymentRequiredCode] = "seer_out_of_credits"
+SEER_OUT_OF_QUOTA_CODE: Final[SeerPaymentRequiredCode] = "seer_out_of_quota"
 
 SEER_AUTOFIX_START_OUT_OF_CREDITS_DETAIL = (
     "Your organization does not have enough credits to start an Autofix run."