# CloudRunner not persisting returned variables between Function and Display blocks **URL:** \ **Category:** Bug Reports\ **Created:** [October 23, 2025, 11:35pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782 "2025-10-23T23:35:22Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![rdearmas](https://avatars.discourse-cdn.com/v4/letter/r/ac8455/32.png) [@rdearmas](https://community.mindstudio.ai/u/rdearmas)\ **Post date:** [October 23, 2025, 11:35pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/1 "2025-10-23T23:35:22Z")
### **Description of the issue** When using CloudRunner in a MindStudio project, return values from a Function block (Run Function) are not being persisted into the workflow, resulting in `"undefined"` or `"empty message"` in subsequent Display Content blocks. The function executes successfully — console logs confirm all logic completes normally — but the values returned (e.g., `configSummary` or `configSummaryVar`) never appear in the workflow state or downstream blocks. This persists across all variable-name configurations (`configSummary`, `configSummaryVar`, `output.configSummary`, etc.), and even after: - Re-creating the Function block, - Removing all Reference Data fields, - Embedding static tables directly in code, - Using simplified string returns and single-object returns, - Confirming that console output shows the data being returned. **In the run logs:** - Function completes normally (`✅ Product selection complete.`). - “Resolved function configuration object” shows correct schema. - The Display Content block then logs: * * * ### **Intended behavior** CloudRunner should persist all values explicitly returned by a Function block (whose keys match the block’s Output Variable names) so that subsequent blocks (e.g., Display Content) can access them via `{{variableName}}`. * * * ### **AI Agent link** * * * ### **Attachments** - Run log JSON (`mindstudio-run-be0f5c99…`, `mindstudio-run-ec666120…`, etc.) > **[Dropbox](https://www.dropbox.com/scl/fi/kfm4gvevmbsipo9fzndxb/Run-Logs.zip?rlkey=pz9z9i2ndhyr1uhlcrx235oz4&dl=0)** | # | Filename (as uploaded) | What it demonstrates | | --- | --- | --- | | 1️⃣ | **mindstudio-run-26eabdc6-4f8c-4ffd-a80e-4aff05d9f288.log.json** | Early `undefined` — before table parsing fix; proves function executed but variables dropped. | | 2️⃣ | **mindstudio-run-c7921420-4de5-485e-8b6c-4cbd6716d343.log.json** | Shows CloudRunner flattening `[object Object]` in Reference Data inputs. | | 3️⃣ | **mindstudio-run-648b72a2-6d8c-42ef-ba77-32e184c2c6e4.log.json** | Demonstrates schema still injecting empty tables (`burnerTable:""` etc.). | | 4️⃣ | **mindstudio-run-7ce39e13-7441-416e-ba9b-df0f44123c0e.log.json** | Confirms successful internal logic but empty outputs returned. | | 5️⃣ | **mindstudio-run-00d926ec-46b3-4c47-ba60-69471000ae8d.log.json** | Valid data inside function; `undefined` output downstream. | | 6️⃣ | **mindstudio-run-abb7234d-8283-4f9f-baf4-d745724c9c76.log.json** | Shows return object exists yet still lost when passed to Display Content. | | 7️⃣ | **mindstudio-run-f0ab77b2-233f-4dbb-a734-3d73afe42570.log.json** | Logs “Empty message” while function clearly returns data. | | 8️⃣ | **mindstudio-run-e86fdd58-b77f-44fe-a69a-3c7221312a8c.log.json** | Confirms CloudRunner executes correctly but loses output serialization. | | 9️⃣ | **mindstudio-run-a357955e-b0e6-4eab-857e-7e56a857fefe.log.json** | First trace showing schema mismatch between expected vs returned variables. | | 🔟 | **mindstudio-run-135664c1-0226-4803-8938-7ba14346c1f4.log.json** | “Empty message” variant; function completes cleanly but returns vanish. | | 11️⃣ | **mindstudio-run-2f4eac12-db2d-44dc-8509-2404538f3871.log.json** | Confirms inline tables ignored because CloudRunner injects empty schema keys. | | 12️⃣ | **mindstudio-run-ec666120-2367-4f90-aa15-775e258eb61f.log.json** | Definitive proof: runtime executes successfully; return object dropped. | | 13️⃣ | **mindstudio-run-be0f5c99-aab6-41d2-81aa-322435efffb8.log.json** | Most recent run — shows proper console logs but `{{configSummary}}` → `undefined`. | * * * ### **Notes** - Runtime: CloudRunner - Behavior confirmed across multiple function schema resets and variable mappings. - Same logic works in Sandbox or local execution, so this appears to be a CloudRunner serialization or variable-binding issue. ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 24, 2025, 10:58am UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/2 "2025-10-24T10:58:45Z")
Hello @rdearmas, Thanks for the post. Could you Publish the Agent and share the remix link so we can take a closer look? Also, could you clarify your use case and what you’d like the Agent to do? ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex008/uploads/mindstudio/original/1X/b8a61c98533a48e975398396421002dcae1678e8.jpeg) [@system](https://community.mindstudio.ai/u/system)\ **Post date:** [October 24, 2025, 4:32pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/3 "2025-10-24T16:32:16Z")
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**Author:** ![system](https://canada1.discourse-cdn.com/flex008/uploads/mindstudio/original/1X/b8a61c98533a48e975398396421002dcae1678e8.jpeg) [@system](https://community.mindstudio.ai/u/system)\ **Post date:** [October 24, 2025, 4:39pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/4 "2025-10-24T16:39:58Z")
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**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 27, 2025, 2:14pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/5 "2025-10-27T14:14:26Z")
Hello @rdearmas, Thanks for sharing the remix link! You are correct, data doesn’t persist across different Custom Functions in a MindStudio Agent unless you write it to ai.vars. _ **Here’s what’s happening in your Agent:** _ CloudRunner executes your function and you see logs, but the object you return doesn’t automatically turn into {{variables}} the next block can use. Display Content expects {{configSummary}} to be present in ai.vars.configSummary. Since it isn’t set, it shows undefined. **1. Persist values with ai.vars** Replace your current return in “initializeReferenceTables” with: ```auto const burnerTableJson = JSON.stringify(burnerTable); const controlTableJson = JSON.stringify(controlTable); const mediaTableJson = JSON.stringify(mediaTable); if (typeof ai !== 'undefined' && ai && ai.vars) { ai.vars.burnerTable = burnerTableJson; ai.vars.controlTable = controlTableJson; ai.vars.mediaTable = mediaTableJson; } return { burnerTable: burnerTableJson, controlTable: controlTableJson, mediaTable: mediaTableJson }; } ``` And do the same in the “selectProducts” function: ```auto if (typeof ai !== 'undefined' && ai && ai.vars) { ai.vars.configResult = JSON.stringify(configResult); ai.vars.configSummary = configSummary; } return { configResult: JSON.stringify(configResult), configSummary }; ``` **2. Reference variables in the Process Selection block configuration** Make sure the block config references the outputs from the first function: ![image](https://canada1.discourse-cdn.com/flex008/uploads/mindstudio/original/2X/3/364f0235dafdfdbc8c9b722047e6fbeb1ec1246d.png) ---
**Author:** ![rdearmas](https://avatars.discourse-cdn.com/v4/letter/r/ac8455/32.png) [@rdearmas](https://community.mindstudio.ai/u/rdearmas)\ **Post date:** [October 27, 2025, 4:26pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/6 "2025-10-27T16:26:45Z")
Hi Alex, Thanks for the detailed explanation — we actually tried this exact approach multiple times. Here’s what happens in practice: 1. When we use `ai.vars` inside **CloudRunner / Virtual Machine mode** , the values don’t persist or propagate downstream. 2. When we switch to **Sandbox** , the same code and logic work correctly — but Sandbox doesn’t support external HTTP calls or production execution, so it’s not viable for deployment. 3. We also tested returning values explicitly (without relying on `ai.vars`), for example: So effectively, **CloudRunner ignores both `ai.vars` persistence and direct `return {}` outputs** , breaking the chain between Custom Functions. That’s why our Agent consistently fails at runtime, even though the functions themselves execute successfully and log expected data. Our expectation is that **explicit return values** should be usable as inputs for downstream blocks — the same way they are in Sandbox or MindStudio’s LLM output blocks. Could you please confirm whether this is a **known CloudRunner limitation or bug** , and whether there’s a roadmap fix for it? Attached is the full Run Log (`mindstudio-run-160efa1b-aa9a-4d11-b968-11804cf32f08.log.json`) that clearly show the returned data and missing variable propagation. Thanks for your help with this. (Attachment mindstudio-run-160efa1b-aa9a-4d11-b968-11804cf32f08.log.json is missing) ---
**Author:** ![rdearmas](https://avatars.discourse-cdn.com/v4/letter/r/ac8455/32.png) [@rdearmas](https://community.mindstudio.ai/u/rdearmas)\ **Post date:** [October 27, 2025, 4:37pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/7 "2025-10-27T16:37:16Z")
I don’t know if my email response went through, so I will paste it here again. Hi Alex, Thanks for the detailed explanation — we actually tried this exact approach multiple times. Here’s what happens in practice: 1. When we use `ai.vars` inside **CloudRunner / Virtual Machine mode** , the values don’t persist or propagate downstream. 2. When we switch to **Sandbox** , the same code and logic work correctly — but Sandbox doesn’t support external HTTP calls or production execution, so it’s not viable for deployment. 3. We also tested returning values explicitly (without relying on `ai.vars`), for example: So effectively, **CloudRunner ignores both `ai.vars` persistence and direct `return {}` outputs** , breaking the chain between Custom Functions. That’s why our Agent consistently fails at runtime, even though the functions themselves execute successfully and log expected data. Our expectation is that **explicit return values** should be usable as inputs for downstream blocks — the same way they are in Sandbox or MindStudio’s LLM output blocks. Could you please confirm whether this is a **known CloudRunner limitation or bug** , and whether there’s a roadmap fix for it? Here’s a link to a Dropbox Folder that contains error logs: > **[Dropbox](https://www.dropbox.com/scl/fo/25621kc69qm5l4ea7isji/ADR8NNffjXuWIfdp5BB6NHs?rlkey=kfyagno4axzcmurktriizbdj9&dl=0)** | Date | Log File Name | Key Evidence | | --- | --- | --- | | **Oct 23, 2025** | **`mindstudio-run-abb7234d-8283-4f9f-baf4-d745724c9c76.log.json`** | Explicitly implemented `ai.vars.burnerTable`, `ai.vars.controlTable`, and `ai.vars.mediaTable` in `initializeReferenceTables`. Despite this, the next block (`selectProducts`) received empty data and output “Empty Message.” | | **Oct 23, 2025** | **`mindstudio-run-f0ab77b2-233f-4dbb-a734-3d73afe42570.log.json`** | `ai.vars.configResult` and `ai.vars.configSummary` were written successfully within `selectProducts`, confirmed in logs, but Display Content still rendered as “Empty Message.” | | **Oct 23, 2025** | **`mindstudio-run-e86fdd58-b77f-44fe-a69a-3c7221312a8c.log.json`** | Re-test after confirming correct syntax for both initialize and select functions. Log shows `ai.vars` objects exist and store JSON strings, yet output remains undefined. | | **Oct 23, 2025** | **`mindstudio-run-a357955e-b0e6-4eab-857e-7e56a857fefe.log.json`** | Final “ai.vars version” test — both functions return objects and write to `ai.vars`; CloudRunner accepts execution but downstream block still cannot read any `ai.vars` variables. | ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 28, 2025, 12:37pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/8 "2025-10-28T12:37:26Z")
Hi @rdearmas, Thanks for the quick reply! Here’s a remix link to a sample Agent that uses two Custom Functions in a VM environment: [https://app.mindstudio.ai/agents/rdearmas–sample-agent-with-two-custom-functions-102f3d3e/remix](https://app.mindstudio.ai/agents/rdearmas--sample-agent-with-two-custom-functions-102f3d3e/remix) Here’s the setup: 1. Display Content block saves a story to a variable 2. The first function trims it to 100 characters 3. The trimmed version is displayed 4. The second function turns it into a .txt file 5. The link to the file is displayed Hope this helps! ---
**Author:** ![rdearmas](https://avatars.discourse-cdn.com/v4/letter/r/ac8455/32.png) [@rdearmas](https://community.mindstudio.ai/u/rdearmas)\ **Post date:** [October 28, 2025, 4:42pm UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/9 "2025-10-28T16:42:23Z")
Hi Alex, Thanks for sending the sample Agent — I reviewed it, and it does help illustrate how `ai.vars` works **within a single execution context**. However, my use case is slightly different and reproduces a distinct issue: our Agent uses **two Custom Functions in separate blocks** (`initializeReferenceTables` and `selectProducts`) running in **CloudRunner / VM** mode. When `ai.vars` values are set in the first function, they’re not available in the second — even though the log confirms they were written successfully. The difference is that each Custom Function in CloudRunner appears to run inside its own containerized VM, resetting `ai.vars` to an empty object each time. That means `ai.vars` persistence only works _within_ one block chain, not _across_ multiple Custom Functions — unlike the behavior in Sandbox. In short: - ✅ The sample works because both functions run in the same context. - ❌ Our workflow fails because each Custom Function block gets a fresh `ai.vars` object in CloudRunner. Could you confirm whether CloudRunner is designed to isolate `ai.vars` per function instance? If so, is there any supported method to pass data objects between Custom Functions in CloudRunner (for example, through explicit return objects or serialized JSON variables)? We’ve verified this behavior in multiple run logs (e.g. `mindstudio-run-abb7234d-8283-4f9f-baf4-d745724c9c76.log.json`, `mindstudio-run-a357955e-b0e6-4eab-857e-7e56a857fefe.log.json`). If this is not possible in Mindstudio, please just let me know. Thanks ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 29, 2025, 10:55am UTC](https://community.mindstudio.ai/t/cloudrunner-not-persisting-returned-variables-between-function-and-display-blocks/1782/10 "2025-10-29T10:55:43Z")
Hi @rdearmas, > [@rdearmas](#): > > I reviewed it, and it does help illustrate how `ai.vars` works **within a single execution context**. > [@rdearmas](#): > > The sample works because both functions run in the same context. When you mention both functions running “in the same context”, could you clarify what you mean by that? The sample Agent also uses two separate Custom Function blocks running in the VM environment, so I’d like to understand what makes the context different in your case. To answer your questions: > [@rdearmas](#): > > Could you confirm whether CloudRunner is designed to isolate `ai.vars` per function instance? Yes, that’s correct. > [@rdearmas](#): > > If so, is there any supported method to pass data objects between Custom Functions in CloudRunner (for example, through explicit return objects or serialized JSON variables)? You can assign values to variables defined in the block configurations using ai.vars. In your case, you can replace the return function with the snippet below to make sure the values are assigned and accessible in the following blocks with {{burnerTable}} and other defined variables: ```auto ai.vars[ai.config.burnerTableVar] = JSON.stringify(burnerTable); ai.vars[ai.config.controlTableVar] = JSON.stringify(controlTable); ai.vars[ai.config.mediaTableVar] = JSON.stringify(mediaTable); ```