The base URL shape checklist: /v1, trailing slashes, and double paths

Disclosure and availability: DaoXE is a multi-model multi-protocol API gateway we operate. Public base: https://daoxe.com/v1. Not available in mainland China. This article is for developers in regions allowed by the service terms.

Most gateway failures I see are not model quality.

They are path join bugs.

The host is reachable. The key works in curl. The client still hits 404.

This post is the base URL checklist I run before blaming the API.

Series

1. Smoke test
2. Multiprotocol
3. Client setup
4. curl OK, IDE fails
5. Claude protocol
6. models.dev + /models
7. Agent pre-flight
8. Env var names
9. This post: base URL shape

What “OpenAI-compatible base” usually means

Many clients expect a root like:

https://daoxe.com/v1

They then append:

/chat/completions
/models
/embeddings

So the final path becomes:

https://daoxe.com/v1/chat/completions

If you already put /chat/completions in the base, or you omit /v1 when the client does not add it, you get nonsense paths.

Failure table

Verify with curl to the exact joined URL

Do not only test “the host is up.”

Test the same path the client will call:

export DAOXE_API_KEY="your_api_key"
export DAOXE_BASE_URL="https://daoxe.com/v1"
export DAOXE_MODEL="paste_exact_id_from_models"

curl --fail-with-body --show-error --silent \
  -H "Authorization: Bearer $DAOXE_API_KEY" \
  -H "Content-Type: application/json" \
  -d "{
    \"model\": \"$DAOXE_MODEL\",
    \"max_tokens\": 8,
    \"messages\": [{\"role\":\"user\",\"content\":\"OK\"}]
  }" \
  "$DAOXE_BASE_URL/chat/completions"

If that is green and the client is red, log the client’s request URL. Compare character-for-character.

Client-specific mental model

Read the client’s one line of docs. Do not assume every “OpenAI-compatible” UI joins paths the same way.

Soft CTA

Product side:

https://daoxe.com/?utm_source=devto&utm_medium=organic&utm_campaign=global_launch_baseurl

Public notes: CLIENT_SETUP.md

Comment with client name + the exact request URL from its logs (redact the key).