fix: prevent MCP startup failure on missing 'type' field #7417

linuxmetel · 2025-12-01T01:35:25Z

Fix the issue #7416 that the codex-cli produce an error "MCP startup failure on missing 'type' field" in the startup.

Cause: serde in convert_to_rmcp (codex-rs/rmcp-client/src/utils.rs) failed because no r#type value was provided
Fix: set a default r#type value in the corresponding structs

github-actions · 2025-12-01T01:35:36Z

All contributors have signed the CLA ✍️ ✅
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chatgpt-codex-connector · 2025-12-01T01:38:54Z

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codex/codex-rs/mcp-types/src/lib.rs

Lines 553 to 557 in b486736

    
           pub annotations: Option<Annotations>, 
        
           pub data: String, 
        
           #[serde(rename = "mimeType")] 
        
           pub mime_type: String, 
        
           #[serde(default = "image_str")]

Audio blocks without type now deserialize as images

Because ContentBlock is untagged and tries variants in order (image comes before audio), adding #[serde(default = "image_str")] to ImageContent.r#type means any payload from the Rust SDK that omits the type field but has data/mimeType will now match the image variant first; serde will fill type: "image" and never attempt the audio variant. The intended fix for missing type therefore misclassifies audio content rather than returning an error, so audio responses passed through convert_to_mcp will surface as images and be rendered/handled incorrectly.

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linuxmetel · 2025-12-01T01:39:34Z

I have read the CLA Document and I hereby sign the CLA

linuxmetel · 2025-12-01T01:59:23Z

Thank you. I believe the structs that require default values for r#type are ToolOutputSchema and ToolInputSchema, and the issue seems to occur in calls such as RmcpClient::list_tools(). I will update the implementation so that only these two structs define default values for r#type.

linuxmetel · 2025-12-01T02:00:07Z

@codex review

chatgpt-codex-connector · 2025-12-01T02:02:13Z

Codex Review: Didn't find any major issues. Can't wait for the next one!

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etraut-openai · 2025-12-01T02:50:58Z

Thanks for the contribution. Before I assign this for review by one of the codex team members, please fix the CI failures. Looks like a simple format issue, so it should be straightforward.

linuxmetel · 2025-12-01T04:18:35Z

@codex review

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chatgpt-codex-connector · 2025-12-01T04:21:14Z

codex-rs/mcp-types/generate_mcp_types.py

+    # apply patch
+    subprocess.run(["patch", "src/lib.py", "-i", "lib.py.patch"], check=True)


Correct mcp type generator patch command

Running generate_mcp_types.py without --check now fails because the new patch step calls patch src/lib.py -i lib.py.patch, but the generated file and the checked-in patch are src/lib.rs/lib.rs.patch. With check=True on subprocess.run, this raises immediately when the files aren’t found, preventing the mcp types from being regenerated or having the defaults re-applied when the schema changes.

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linuxmetel · 2025-12-01T04:34:38Z

@codex review

chatgpt-codex-connector · 2025-12-01T04:38:59Z

Codex Review: Didn't find any major issues. Another round soon, please!

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linuxmetel · 2025-12-01T04:46:02Z

@etraut-openai Thank you for your review. The CI error occurred because mcp-types/src/lib.rs differed from the auto-generated file after my fix. I’ve updated generate_mcp_types.py so that it applies the corresponding patch to the Rust source file. It might be a bit ad hoc, but it’s simple and appropriate for this case.

etraut-openai · 2025-12-01T04:54:32Z

That's a pretty bad hack. It's unlikely that change will be accepted.

linuxmetel · 2025-12-01T04:59:19Z

I see. I will rewrite the script.

Cause: - serde in `convert_to_rmcp` (`codex-rs/rmcp-client/src/utils.rs`) failed for `ToolInputSchema` and `ToolOutputSchema` because no `r#type` value was provided. Fix: - set a default `r#type` value for these two structs so a missing `type` no longer breaks MCP startup.

linuxmetel · 2025-12-01T05:33:41Z

@codex review

chatgpt-codex-connector · 2025-12-01T05:36:30Z

Codex Review: Didn't find any major issues. Nice work!

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linuxmetel · 2025-12-01T05:41:37Z

I’ve reworked the generate_mcp_types.py script to use a more proper approach.

linuxmetel · 2025-12-01T07:49:04Z

@etraut-openai Is this now ok?

linuxmetel · 2025-12-01T09:57:25Z

it's my mistake

gpeal

Thanks!

linuxmetel force-pushed the linuxmetel-patch-1 branch from b486736 to 75342ef Compare December 1, 2025 01:37

github-actions bot added a commit that referenced this pull request Dec 1, 2025

@linuxmetel has signed the CLA in #7417

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linuxmetel force-pushed the linuxmetel-patch-1 branch from 75342ef to 9ac39d2 Compare December 1, 2025 01:59

etraut-openai added the needs-response Additional information is requested label Dec 1, 2025

linuxmetel force-pushed the linuxmetel-patch-1 branch from 9ac39d2 to c7ad4bc Compare December 1, 2025 04:17

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linuxmetel force-pushed the linuxmetel-patch-1 branch from c7ad4bc to 2458694 Compare December 1, 2025 04:34

linuxmetel force-pushed the linuxmetel-patch-1 branch from 2458694 to 7ffc9ff Compare December 1, 2025 05:33

etraut-openai removed the needs-response Additional information is requested label Dec 1, 2025

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gpeal merged commit c936c68 into openai:main Dec 1, 2025
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		# apply patch
		subprocess.run(["patch", "src/lib.py", "-i", "lib.py.patch"], check=True)

fix: prevent MCP startup failure on missing 'type' field #7417

fix: prevent MCP startup failure on missing 'type' field #7417

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