Handle FatalError in DurableAgent tool execution - #376

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Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.

Changes

  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.

Example

constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});

The LLM receives the error as a tool result and can retry with different parameters or inform the user.

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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI changed the title [WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI requested a review from pranaygpNovember 20, 2025 20:59
VaguelySerious
VaguelySerious reviewed Nov 20, 2025
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Comment threadpackages/ai/src/agent/durable-agent.ts Outdated
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pranaygp
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pranaygp merged commit 154670a into mainNov 20, 2025
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pranaygp deleted the copilot/handle-tool-call-errors branch November 20, 2025 22:17
@mpaicoding-byte

mpaicoding-byte commented Jan 20, 2026

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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?

@VaguelySerious

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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow

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the thinking here was (we can revisit this) -

  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)

this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM

@VaguelySerious

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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive

@mpaicoding-byte

mpaicoding-byte commented Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO

@VaguelySeriousVaguelySerious mentioned this pull request Feb 27, 2026
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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Handle FatalError in DurableAgent tool execution - #376
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Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
Warning
Firewall rules blocked me from connecting to one or more addresses (expand for details)
I tried to connect to the following addresses, but was blocked by firewall rules:
  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
If you need me to access, download, or install something from one of these locations, you can either:
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🦋 Changeset detected
Latest commit: 6e61ab9
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 1 package
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
VaguelySerious
reviewed
Nov 20, 2025
View reviewed changes
Comment threadpackages/ai/src/agent/durable-agent.ts
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November 20, 2025 21:01
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merged commit 154670a
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@mpaicoding-byte
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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
@VaguelySerious
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Jan 21, 2026

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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
@pranaygp
pranaygp
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Jan 21, 2026

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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
VaguelySerious
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Jan 21, 2026

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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
mpaicoding-byte
commented
Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
@VaguelySeriousVaguelySerious
mentioned this pull request
Feb 27, 2026
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Handle FatalError in DurableAgent tool execution - #376
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Merged
Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
Warning
Firewall rules blocked me from connecting to one or more addresses (expand for details)
I tried to connect to the following addresses, but was blocked by firewall rules:
  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
If you need me to access, download, or install something from one of these locations, you can either:
View original Slack conversation
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Latest commit: 6e61ab9
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This PR includes changesets to release 1 package
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
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@mpaicoding-byte
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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
@VaguelySerious
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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
@pranaygp
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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
mpaicoding-byte
commented
Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
@VaguelySeriousVaguelySerious
mentioned this pull request
Feb 27, 2026
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, 'i');
if (__m === '*' || __re.test(location.href)) {
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}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Handle FatalError in DurableAgent tool execution - #376
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Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
Warning
Firewall rules blocked me from connecting to one or more addresses (expand for details)
I tried to connect to the following addresses, but was blocked by firewall rules:
  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
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Latest commit: 6e61ab9
The changes in this PR will be included in the next version bump.
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
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@mpaicoding-byte
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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
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Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
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Feb 27, 2026
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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Handle FatalError in DurableAgent tool execution - #376
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copilot/handle-tool-call-errors
Nov 20, 2025
Merged
Handle FatalError in DurableAgent tool execution#376
pranaygp merged 5 commits into
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CopilotAI
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
Warning
Firewall rules blocked me from connecting to one or more addresses (expand for details)
I tried to connect to the following addresses, but was blocked by firewall rules:
  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
If you need me to access, download, or install something from one of these locations, you can either:
View original Slack conversation
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🦋 Changeset detected
Latest commit: 6e61ab9
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 1 package
NameType
@workflow/aiPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
VaguelySerious
reviewed
Nov 20, 2025
View reviewed changes
Comment threadpackages/ai/src/agent/durable-agent.ts
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merged commit 154670a
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deleted the

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November 20, 2025 22:17
@mpaicoding-byte
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Jan 20, 2026

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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
@VaguelySerious
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Jan 21, 2026

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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
@pranaygp
pranaygp
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Jan 21, 2026

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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
VaguelySerious
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Jan 21, 2026

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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
mpaicoding-byte
commented
Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
@VaguelySeriousVaguelySerious
mentioned this pull request
Feb 27, 2026
 Merged

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Handle FatalError in DurableAgent tool execution - #376
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pranaygp merged 5 commits into
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copilot/handle-tool-call-errors
Nov 20, 2025
Merged
Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
Warning
Firewall rules blocked me from connecting to one or more addresses (expand for details)
I tried to connect to the following addresses, but was blocked by firewall rules:
  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
If you need me to access, download, or install something from one of these locations, you can either:
View original Slack conversation
💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.
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🦋 Changeset detected
Latest commit: 6e61ab9
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 1 package
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
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reviewed
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Comment threadpackages/ai/src/agent/durable-agent.ts
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merged commit 154670a
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@mpaicoding-byte
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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
@VaguelySerious
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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
@pranaygp
pranaygp
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Jan 21, 2026

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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
mpaicoding-byte
commented
Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
@VaguelySeriousVaguelySerious
mentioned this pull request
Feb 27, 2026
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Handle FatalError in DurableAgent tool execution - #376
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Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
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  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
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@mpaicoding-byte
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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
@VaguelySerious
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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
@pranaygp
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Jan 21, 2026

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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
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Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
@VaguelySeriousVaguelySerious
mentioned this pull request
Feb 27, 2026
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Handle FatalError in DurableAgent tool execution - #376
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Handle FatalError in DurableAgent tool execution#376
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FatalError thrown in DurableAgent tool execution currently kills the workflow. It should convert to a tool error result sent back to the LLM, matching AI SDK behavior.
Changes
  • packages/ai/src/agent/durable-agent.ts: Wrap tool execution in try-catch. Convert FatalError to error-text tool result. Re-throw other errors for retry.
  • packages/ai/src/agent/durable-agent.test.ts: Add tests for error handling scenarios.
Example
constagent=newDurableAgent({model: 'anthropic/claude-opus',tools: {getTool: {description: 'Get data',inputSchema: z.object({id: z.string()}),execute: async({ id })=>{// Previously: kills workflow// Now: error sent to LLM as tool resultthrownewFatalError('Invalid ID');},},},});
The LLM receives the error as a tool result and can retry with different parameters or inform the user.
Warning
Firewall rules blocked me from connecting to one or more addresses (expand for details)
I tried to connect to the following addresses, but was blocked by firewall rules:
  • fonts.googleapis.com
    • Triggering command: /usr/local/bin/node /usr/local/bin/node /home/REDACTED/work/workflow/workflow/node_modules/.pnpm/next@15.5.4_@opentelemetry&#43;api@1.9.0_react-dom@19.1.0_react@19.1.0__react@19.1.0/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)
If you need me to access, download, or install something from one of these locations, you can either:
View original Slack conversation
💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.
@changeset-bot
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commented
Nov 20, 2025•

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🦋 Changeset detected
Latest commit: 6e61ab9
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 1 package
NameType
@workflow/aiPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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@pranaygp
Fix DurableAgent to handle FatalError in tool calls
5ba6355
Convert FatalError exceptions in tool execution to tool-result errors that get
propagated back to the LLM, mimicking AI SDK behavior. Non-fatal errors are
re-thrown to allow workflow retry mechanisms to handle them.
- Updated executeTool to catch FatalError and convert to error-text tool result
- Added comprehensive tests for error handling scenarios
- All tests passing
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
@pranaygp
Address code review feedback and add changeset
8f1485d
Remove unnecessary type assertion and add changeset for the DurableAgent fix
Co-authored-by: pranaygp <1797812+pranaygp@users.noreply.github.com>
CopilotAI
changed the title
[WIP] Fix tool call error handling in DurableAgentHandle FatalError in DurableAgent tool executionNov 20, 2025
CopilotAI
requested a review
from pranaygpNovember 20, 2025 20:59
VaguelySerious
VaguelySerious
reviewed
Nov 20, 2025
View reviewed changes
Comment threadpackages/ai/src/agent/durable-agent.ts
Outdated

@VaguelySerious
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marked this pull request as ready for review
November 20, 2025 21:01
pranaygp
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Comment thread.changeset/handle-tool-errors.md
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merged commit 154670a
into
mainNov 20, 2025

17 of 25 checks passed

@pranaygp
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November 20, 2025 22:17
@mpaicoding-byte
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Jan 20, 2026

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Ideally it should stop the workflow right? It could be an issue with an api call in that step or some code logic in that step. So when that is fixed, then it should resume from that step completion. Wondering what was the intent behind this logic or is there any another way to achieve this?
@VaguelySerious
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commented
Jan 21, 2026

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@pranaygp Good point from @mpaicoding-byte, FatalError is a user-thrown error and should intentionally kill the workflow
@pranaygp
pranaygp
commented
Jan 21, 2026

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the thinking here was (we can revisit this) -
  • RetryableError (or any error) allows the workflow system to deterministically retry
  • FatalError bubbles into the LLM since the LLM was the invokeR of the function and the LLM needs to know the status of the tool call (success/failed state)
this maps to throwing errors in tools in AI sdk. when a tool throws an error it doesn't kill the entire generateText/streamText loop - it returns the failed tool call as an error response back to the LLM
@VaguelySerious
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Jan 21, 2026

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Ah, I remember. That too makes sense, though I can see how from the user's perspective, not being able to intentionally throw any error in a step (tool) that terminates the agent is counterintuitive
@mpaicoding-byte
mpaicoding-byte
commented
Jan 25, 2026

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Thanks @VaguelySerious@pranaygp for looking at this. It could also be unintentional, maybe there is no try catch implemented properly and there was some fatal error from an api or some function, that ideally should be considered as a system error and the step should be retried and eventually the error should be propogated to workflow IMO
@VaguelySeriousVaguelySerious
mentioned this pull request
Feb 27, 2026
 Merged

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