diff --git a/internal/handlers/helpers.go b/internal/handlers/helpers.go
index d88e7cb..04cd2bb 100644
--- a/internal/handlers/helpers.go
+++ b/internal/handlers/helpers.go
@@ -343,7 +343,14 @@ var codeToAgentAction = map[string]errorCodeMeta{
 	// StatusNotFound / StatusMethodNotAllowed / StatusRequestEntityTooLarge
 	// / StatusUnsupportedMediaType.
 	"not_found": {
-		AgentAction: "Tell the user the URL is wrong or the resource no longer exists. Have them check the path against https://instanode.dev/docs — anon resources also auto-expire after 24h, so re-provision if needed.",
+		// BUG-API-105 (QA 2026-05-29): the agent_action used to tack on
+		// "anon resources also auto-expire after 24h" — irrelevant when
+		// the 404 is a typo'd internal path or unknown route, and
+		// actively misleading on authenticated misroutes. Hint kept
+		// behind a "see /docs" pointer; the auto-expire footnote now
+		// only fires when the surface-specific 404 (resource_not_found
+		// / webhook_not_found / etc.) emits it.
+		AgentAction: "Tell the user the URL is wrong or the resource no longer exists. Have them check the path against https://instanode.dev/docs — if they were calling a token-keyed URL the token may have expired or been mistyped.",
 	},
 	"method_not_allowed": {
 		AgentAction: "Tell the user the HTTP method is wrong for this URL. Have them check the Allow response header (or https://instanode.dev/docs) for the supported methods.",
diff --git a/internal/handlers/openapi.go b/internal/handlers/openapi.go
index 0974a73..ed94413 100644
--- a/internal/handlers/openapi.go
+++ b/internal/handlers/openapi.go
@@ -2909,12 +2909,12 @@ const openAPISpec = `{
       },
       "StackRequest": {
         "type": "object",
-        "description": "Multipart form. The 'manifest' field is the YAML instant.yaml text; each service declared under services: must have a matching multipart field named after the service whose content is a gzipped tar archive of that service's build context.",
+        "description": "Multipart form. The 'manifest' field is the YAML instant.yaml text; each service declared under services: must have a matching multipart field named after the service whose content is a gzipped tar archive of that service's build context. Codegen note: the dynamic per-service field is expressed via additionalProperties (OpenAPI cannot model literal-named fields whose names come from another field at runtime). Treat additionalProperties as: 'for every service S in manifest.services, send a multipart field named S whose value is the gzipped tar of S's build context.' DOG-30 (QA 2026-05-29).",
         "properties": {
           "manifest": { "type": "string", "description": "instant.yaml contents. Example: services:\\n  api:\\n    build: ./api\\n    port: 8080\\n  web:\\n    build: ./web\\n    port: 8080\\n    expose: true\\n    env: { API_URL: service://api }" },
-          "name": { "type": "string", "minLength": 1, "maxLength": 64, "pattern": "^[A-Za-z0-9][A-Za-z0-9 _-]*$", "description": "REQUIRED. Short human-readable label for this stack (1-64 chars after trimming; must start with a letter or digit, then letters/digits/spaces/underscores/hyphens). Missing/empty → 400 name_required. Bad format/length → 400 invalid_name." },
-          "<service-name>": { "type": "string", "format": "binary", "description": "One field per service declared in the manifest, named after the service. Value is a gzipped tar archive containing that service's Dockerfile + source. Total request body cap is 200 MB." }
+          "name": { "type": "string", "minLength": 1, "maxLength": 64, "pattern": "^[A-Za-z0-9][A-Za-z0-9 _-]*$", "description": "REQUIRED. Short human-readable label for this stack (1-64 chars after trimming; must start with a letter or digit, then letters/digits/spaces/underscores/hyphens). Missing/empty → 400 name_required. Bad format/length → 400 invalid_name." }
         },
+        "additionalProperties": { "type": "string", "format": "binary", "description": "One multipart field per service declared in the manifest, with the field NAME equal to the real service name (e.g. 'api' or 'web', NOT the literal placeholder '<service-name>') and the VALUE a gzipped tar archive (≤50 MiB) containing that service's Dockerfile + source. Codegen clients should emit one upload field per manifest entry." },
         "required": ["manifest", "name"]
       },
       "StackResponse": {
diff --git a/internal/handlers/openapi_test.go b/internal/handlers/openapi_test.go
index a377e0e..2d8e583 100644
--- a/internal/handlers/openapi_test.go
+++ b/internal/handlers/openapi_test.go
@@ -138,6 +138,50 @@ func TestOpenAPI_StacksEndpointsDocumented(t *testing.T) {
 	}
 }
 
+// TestOpenAPI_StackRequestUsesAdditionalProperties pins DOG-30 (QA 2026-05-29):
+// the dynamic per-service multipart field used to be modeled with a literal
+// "<service-name>" property in the StackRequest schema, which codegen clients
+// (Postman, OpenAPI-generator, etc.) would interpret as "a property literally
+// named <service-name>", emitting broken upload code. The contract is now
+// expressed with additionalProperties — the OpenAPI-3 idiom for "any
+// additional field with this shape".
+func TestOpenAPI_StackRequestUsesAdditionalProperties(t *testing.T) {
+	var v map[string]any
+	if err := json.Unmarshal([]byte(openAPISpec), &v); err != nil {
+		t.Fatalf("openAPISpec parse: %v", err)
+	}
+	schema, ok := digMap(v, "components", "schemas", "StackRequest")
+	if !ok {
+		t.Fatal("DOG-30: StackRequest schema missing entirely")
+	}
+
+	// The literal placeholder must NOT appear as a property — it's the
+	// regression marker for the original bug. Codegen clients emitted a
+	// real field literally named "<service-name>" when this was present.
+	props, _ := schema["properties"].(map[string]any)
+	if _, has := props["<service-name>"]; has {
+		t.Error("DOG-30: StackRequest.properties still contains the literal '<service-name>' placeholder — codegen clients will emit a broken field with that literal name. Use additionalProperties to express the dynamic per-service shape instead.")
+	}
+
+	// additionalProperties must be present with the binary-upload shape so
+	// codegen clients understand "for every service in manifest.services,
+	// emit one upload field named after the service".
+	ap, has := schema["additionalProperties"]
+	if !has {
+		t.Fatal("DOG-30: StackRequest schema missing additionalProperties — the dynamic per-service multipart field has no machine-readable contract")
+	}
+	apMap, ok := ap.(map[string]any)
+	if !ok {
+		t.Fatalf("DOG-30: StackRequest.additionalProperties must be an object schema, got %T", ap)
+	}
+	if apMap["type"] != "string" {
+		t.Errorf("DOG-30: StackRequest.additionalProperties.type must be 'string' (multipart upload), got %v", apMap["type"])
+	}
+	if apMap["format"] != "binary" {
+		t.Errorf("DOG-30: StackRequest.additionalProperties.format must be 'binary' (multipart binary upload), got %v", apMap["format"])
+	}
+}
+
 // TestOpenAPI_MultiEnvEndpointsDocumented guards RETRO-2026-05-12 §10.17:
 // the env-promotion endpoints (POST /api/v1/stacks/:slug/promote and
 // POST /api/v1/vault/copy) must be discoverable in the spec, and both must