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JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191

Open
#6204
Open
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
#6204
Labels
component: jumpstarttype: bug

Description

@laura-zambrano
laura-zambrano
opened on Aug 19, 2026

PySDK Version

  • PySDK V2 (2.x)
  • PySDK V3 (3.x)

Describe the bug
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.

As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.

To reproduce

fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])

The environment variables will already show up as corrupted when executing this method.

Expected behavior
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.

Screenshots or logs
Example of the corrupted environment block showing duplicated values:

SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

System information

  • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)

  • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart

  • Framework version: N/A

  • Python version: Python 3

  • CPU or GPU: Any

  • Custom Docker image (Y/N): N

Additional context
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.

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    component: jumpstarttype: bug

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      , 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
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(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
      Skip to content
      JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
      Open
      #6204
      Open
      JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
      #6204
      Labels
      component: jumpstarttype: bug
      Description
      @laura-zambrano
      laura-zambrano
      opened on Aug 19, 2026
      PySDK Version
      •  PySDK V2 (2.x)
      •  PySDK V3 (3.x)
      Describe the bug
      
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
      As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
      To reproduce
      fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
      The environment variables will already show up as corrupted when executing this method.
      Expected behavior
      
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
      Screenshots or logs
      
Example of the corrupted environment block showing duplicated values:
      SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

      System information
      • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
      • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
      • Framework version: N/A
      • Python version: Python 3
      • CPU or GPU: Any
      • Custom Docker image (Y/N): N
      Additional context
      
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
      Metadata
      Metadata
      Assignees
      No one assigned
        Labels
        component: jumpstarttype: bug
        Type
        No type
        Projects
        No projects
          Milestone
          No milestone
          Relationships
          None yet
          Development
          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
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var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
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})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
          Skip to content
          JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
          Open
          #6204
          Open
          JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
          #6204
          Labels
          component: jumpstarttype: bug
          Description
          @laura-zambrano
          laura-zambrano
          opened on Aug 19, 2026
          PySDK Version
          •  PySDK V2 (2.x)
          •  PySDK V3 (3.x)
          Describe the bug
          
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
          As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
          To reproduce
          fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
          The environment variables will already show up as corrupted when executing this method.
          Expected behavior
          
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
          Screenshots or logs
          
Example of the corrupted environment block showing duplicated values:
          SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

          System information
          • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
          • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
          • Framework version: N/A
          • Python version: Python 3
          • CPU or GPU: Any
          • Custom Docker image (Y/N): N
          Additional context
          
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            component: jumpstarttype: bug
            Type
            No type
            Projects
            No projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
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terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
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var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
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span.className = 'userscript-highlight';
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var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
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highlight(document.body);
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mutations.forEach(function(m) {
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if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
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observer.observe(document.body, { childList: true, subtree: true });
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}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
              Skip to content
              JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
              Open
              #6204
              Open
              JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
              #6204
              Labels
              component: jumpstarttype: bug
              Description
              @laura-zambrano
              laura-zambrano
              opened on Aug 19, 2026
              PySDK Version
              •  PySDK V2 (2.x)
              •  PySDK V3 (3.x)
              Describe the bug
              
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
              As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
              To reproduce
              fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
              The environment variables will already show up as corrupted when executing this method.
              Expected behavior
              
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
              Screenshots or logs
              
Example of the corrupted environment block showing duplicated values:
              SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

              System information
              • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
              • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
              • Framework version: N/A
              • Python version: Python 3
              • CPU or GPU: Any
              • Custom Docker image (Y/N): N
              Additional context
              
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
              Metadata
              Metadata
              Assignees
              No one assigned
                Labels
                component: jumpstarttype: bug
                Type
                No type
                Projects
                No projects
                  Milestone
                  No milestone
                  Relationships
                  None yet
                  Development
                  No branches or pull requests
                  Issue actions
                  
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
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var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
                  Skip to content
                  JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
                  Open
                  #6204
                  Open
                  JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
                  #6204
                  Labels
                  component: jumpstarttype: bug
                  Description
                  @laura-zambrano
                  laura-zambrano
                  opened on Aug 19, 2026
                  PySDK Version
                  •  PySDK V2 (2.x)
                  •  PySDK V3 (3.x)
                  Describe the bug
                  
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
                  As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
                  To reproduce
                  fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
                  The environment variables will already show up as corrupted when executing this method.
                  Expected behavior
                  
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
                  Screenshots or logs
                  
Example of the corrupted environment block showing duplicated values:
                  SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

                  System information
                  • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
                  • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
                  • Framework version: N/A
                  • Python version: Python 3
                  • CPU or GPU: Any
                  • Custom Docker image (Y/N): N
                  Additional context
                  
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
                  Metadata
                  Metadata
                  Assignees
                  No one assigned
                    Labels
                    component: jumpstarttype: bug
                    Type
                    No type
                    Projects
                    No projects
                      Milestone
                      No milestone
                      Relationships
                      None yet
                      Development
                      No branches or pull requests
                      Issue actions
                      
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
                      Skip to content
                      JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
                      Open
                      #6204
                      Open
                      JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
                      #6204
                      Labels
                      component: jumpstarttype: bug
                      Description
                      @laura-zambrano
                      laura-zambrano
                      opened on Aug 19, 2026
                      PySDK Version
                      •  PySDK V2 (2.x)
                      •  PySDK V3 (3.x)
                      Describe the bug
                      
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
                      As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
                      To reproduce
                      fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
                      The environment variables will already show up as corrupted when executing this method.
                      Expected behavior
                      
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
                      Screenshots or logs
                      
Example of the corrupted environment block showing duplicated values:
                      SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

                      System information
                      • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
                      • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
                      • Framework version: N/A
                      • Python version: Python 3
                      • CPU or GPU: Any
                      • Custom Docker image (Y/N): N
                      Additional context
                      
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
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var __re = new RegExp('^' + ".*" + '
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
                          Skip to content
                          JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
                          Open
                          #6204
                          Open
                          JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
                          #6204
                          Labels
                          component: jumpstarttype: bug
                          Description
                          @laura-zambrano
                          laura-zambrano
                          opened on Aug 19, 2026
                          PySDK Version
                          •  PySDK V2 (2.x)
                          •  PySDK V3 (3.x)
                          Describe the bug
                          
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
                          As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
                          To reproduce
                          fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
                          The environment variables will already show up as corrupted when executing this method.
                          Expected behavior
                          
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
                          Screenshots or logs
                          
Example of the corrupted environment block showing duplicated values:
                          SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

                          System information
                          • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
                          • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
                          • Framework version: N/A
                          • Python version: Python 3
                          • CPU or GPU: Any
                          • Custom Docker image (Y/N): N
                          Additional context
                          
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
                          Metadata
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                          No one assigned
                            Labels
                            component: jumpstarttype: bug
                            Type
                            No type
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                            No projects
                              Milestone
                              No milestone
                              Relationships
                              None yet
                              Development
                              No branches or pull requests
                              Issue actions
                              
, 'i');
if (__m === '*' || __re.test(location.href)) {
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function applyDarkMode() {
if (!enabled) return;
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if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
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style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
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filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
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filter: invert(1) hue-rotate(180deg) !important;
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border-color: #444 !important;
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::-webkit-scrollbar-thumb { background: #444 !important; }
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/* Selection */
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::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
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var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
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if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
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console.log('[Universal Dark Mode] Disabled');
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var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub · Issue #6191 · aws/sagemaker-python-sdk · GitHub
                              Skip to content
                              JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub #6191
                              Open
                              #6204
                              Open
                              JumpStartModel corrupts environment variables (incorrect snake_case conversion) when using a private hub#6191
                              #6204
                              Labels
                              component: jumpstarttype: bug
                              Description
                              @laura-zambrano
                              laura-zambrano
                              opened on Aug 19, 2026
                              PySDK Version
                              •  PySDK V2 (2.x)
                              •  PySDK V3 (3.x)
                              Describe the bug
                              
When using the JumpStartModel class to deploy a model reference hosted on a private hub (by passing the hub_name parameter), a subset of the container environment variable names arrive corrupted. The variable names from the instance-specific overrides are recursively converted from UpperCamelCase to snake_case. The SDK uses a regular expression that inserts an underscore before every capital letter and then lowercases the result.
                              As a result, a variable like SM_VLLM_MAX_MODEL_LEN becomes s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n. This causes the instance-specific override to silently fail and not merge over the base defaults, as the spelling collision is broken. The defect is located in the hub deserialization path (JumpStartInstanceTypeVariants.from_describe_hub_content_response), which applies a walk_and_apply_json(response, camel_to_snake) function across the entire document structure.
                              To reproduce
                              fromsagemaker.jumpstart.modelimportJumpStartModel# Note: Requires a private hub setup with a ModelReference to a JumpStart modelmodel=JumpStartModel(
model_id="huggingface-vlm-gemma-4-e4b-it", model_version="*",
config_name="generate_lowest_cost",
hub_name="mi-hub-jumpstart-2", # Replace with your private hub nameregion="eu-south-2", )
# Inspect the container definition before creating the modelcontainer_def=model.prepare_container_def(
accept_eula=True
)
# Check the environment variablesprint(container_def["Environment"])
                              The environment variables will already show up as corrupted when executing this method.
                              Expected behavior
                              
The environment variables from instance-specific overrides (located under HostingInstanceTypeVariants) should retain their original names (e.g., SM_VLLM_MAX_MODEL_LEN). The values from these instance-specific overrides should properly override the base defaults without having their keys modified into snake_case with underscores during JSON parsing.
                              Screenshots or logs
                              
Example of the corrupted environment block showing duplicated values:
                              SM_VLLM_MAX_MODEL_LEN = 4096
s_m__v_l_l_m__m_a_x__m_o_d_e_l__l_e_n = 131072
h_f__h_u_b__o_f_f_l_i_n_e = 1

                              System information
                              • SageMaker Python SDK version: 2.245.0 (Defect confirmed by AWS Support to also be present in recent versions 2.257.6 and 3.20.0)
                              • Framework name (eg. PyTorch) or algorithm (eg. KMeans): JumpStart
                              • Framework version: N/A
                              • Python version: Python 3
                              • CPU or GPU: Any
                              • Custom Docker image (Y/N): N
                              Additional context
                              
AWS Premium Support investigated this under Case ID 178704468000307. They confirmed that the equivalent public-hub function, from_json, performs no key conversion at all, which is why the exact same model deploys correctly when taken from the public catalog. The issue occurs specifically because the names in HostingInstanceTypeVariants are defined as keys in a map, and are thus incorrectly caught by the camel_to_snake recursive rewrite during hub deserialization.
                              Metadata
                              Metadata
                              Assignees
                              No one assigned
                                Labels
                                component: jumpstarttype: bug
                                Type
                                No type
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                                No projects
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                                  No milestone
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                                  None yet
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                                  Issue actions