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[GH-ISSUE #1678] [langchain]: SSL_ERROR_NO_CYPHER_OVERLAP when attempting to access https://api.python.langchain.com #227

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opened 2026-02-17 17:19:27 -05:00 by yindo · 1 comment
yindo commented 2026-02-17 17:19:27 -05:00
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Originally created by @Looking4OffSwitch on GitHub (Dec 1, 2025).
Original GitHub issue: https://github.com/langchain-ai/docs/issues/1678

Type of issue

issue / bug

Language

Python

Description

Description

The LangChain Python API documentation site at https://api.python.langchain.com is inaccessible due to an SSL/TLS cipher negotiation failure. Browsers return SSL_ERROR_NO_CYPHER_OVERLAP, indicating that the server and client cannot agree on a common encryption algorithm.

Affected URL(s)

  • https://api.python.langchain.com/en/latest/prompts/langchain_core.prompts.few_shot.FewShotPromptTemplate.html
  • https://api.python.langchain.com/en/latest/ (entire subdomain)

Error Message

Secure Connection Failed

An error occurred during a connection to api.python.langchain.com.
Cannot communicate securely with peer: no common encryption algorithm(s).

Error code: SSL_ERROR_NO_CYPHER_OVERLAP

Environment

Item Details
Browsers tested Firefox (latest), Chrome (latest), Edge (latest)
Operating systems tested Windows 11, macOS (multiple versions)
Network Multiple networks tested (home, mobile hotspot)
Date first observed December 1, 2025

Steps to Reproduce

  1. Open any browser (Firefox, Chrome, Edge)
  2. Navigate to https://api.python.langchain.com/en/latest/
  3. Observe the SSL connection failure

Expected Behavior

The API documentation pages should load normally over HTTPS.

Actual Behavior

All browsers fail to establish a secure connection, returning SSL_ERROR_NO_CYPHER_OVERLAP.

Troubleshooting Already Attempted

  • Tested on multiple browsers (Firefox, Chrome, Edge)
  • Tested on multiple operating systems (Windows, macOS)
  • Verified system clock is accurate
  • Cleared browser cache and SSL state
  • Tested on multiple networks
  • Checked Firefox about:config TLS settings (all defaults)

Additional Context

  • The main documentation site at https://python.langchain.com/ works correctly.
  • This appears to be a server-side SSL certificate or TLS configuration issue on the api.python.langchain.com subdomain.
  • The error suggests the server may be configured with cipher suites that are incompatible with modern browsers, or there is a certificate chain/configuration problem.

Suggested Investigation

  • Verify SSL certificate validity and chain for api.python.langchain.com
  • Check TLS cipher suite configuration on the server/CDN
  • Confirm the certificate is correctly bound to the api.python.langchain.com subdomain
  • Consider testing with SSL Labs Server Test to identify configuration issues
Originally created by @Looking4OffSwitch on GitHub (Dec 1, 2025). Original GitHub issue: https://github.com/langchain-ai/docs/issues/1678 ### Type of issue issue / bug ### Language Python ### Description ## Description The LangChain Python API documentation site at `https://api.python.langchain.com` is inaccessible due to an SSL/TLS cipher negotiation failure. Browsers return `SSL_ERROR_NO_CYPHER_OVERLAP`, indicating that the server and client cannot agree on a common encryption algorithm. ### Affected URL(s) - `https://api.python.langchain.com/en/latest/prompts/langchain_core.prompts.few_shot.FewShotPromptTemplate.html` - `https://api.python.langchain.com/en/latest/` (entire subdomain) ### Error Message ``` Secure Connection Failed An error occurred during a connection to api.python.langchain.com. Cannot communicate securely with peer: no common encryption algorithm(s). Error code: SSL_ERROR_NO_CYPHER_OVERLAP ``` ### Environment | Item | Details | |------|---------| | **Browsers tested** | Firefox (latest), Chrome (latest), Edge (latest) | | **Operating systems tested** | Windows 11, macOS (multiple versions) | | **Network** | Multiple networks tested (home, mobile hotspot) | | **Date first observed** | December 1, 2025 | ### Steps to Reproduce 1. Open any browser (Firefox, Chrome, Edge) 2. Navigate to `https://api.python.langchain.com/en/latest/` 3. Observe the SSL connection failure ### Expected Behavior The API documentation pages should load normally over HTTPS. ### Actual Behavior All browsers fail to establish a secure connection, returning `SSL_ERROR_NO_CYPHER_OVERLAP`. ### Troubleshooting Already Attempted - [x] Tested on multiple browsers (Firefox, Chrome, Edge) - [x] Tested on multiple operating systems (Windows, macOS) - [x] Verified system clock is accurate - [x] Cleared browser cache and SSL state - [x] Tested on multiple networks - [x] Checked Firefox `about:config` TLS settings (all defaults) ### Additional Context - The main documentation site at `https://python.langchain.com/` works correctly. - This appears to be a server-side SSL certificate or TLS configuration issue on the `api.python.langchain.com` subdomain. - The error suggests the server may be configured with cipher suites that are incompatible with modern browsers, or there is a certificate chain/configuration problem. ### Suggested Investigation - Verify SSL certificate validity and chain for `api.python.langchain.com` - Check TLS cipher suite configuration on the server/CDN - Confirm the certificate is correctly bound to the `api.python.langchain.com` subdomain - Consider testing with [SSL Labs Server Test](https://www.ssllabs.com/ssltest/) to identify configuration issues
yindo added the langchainexternal labels 2026-02-17 17:19:27 -05:00
yindo closed this issue 2026-02-17 17:19:27 -05:00
yindo commented 2026-02-17 17:19:27 -05:00
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@mdrxy commented on GitHub (Jan 23, 2026):

https://api.python.langchain.com is an old link, would ask where you're finding it used?

@mdrxy commented on GitHub (Jan 23, 2026): `https://api.python.langchain.com` is an old link, would ask where you're finding it used?
yindo changed title from [langchain]: SSL_ERROR_NO_CYPHER_OVERLAP when attempting to access https://api.python.langchain.com to [GH-ISSUE #1678] [langchain]: SSL_ERROR_NO_CYPHER_OVERLAP when attempting to access https://api.python.langchain.com 2026-06-05 17:25:44 -04:00
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Reference: langchain-ai/docs#227
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