dify - 💡(How to fix) Fix [Bug] Authorization header prefix ("Bearer "/"Basic ") accumulates on repeated Custom Tool calls due to credentials mutation

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Dify version

1.13.13

Cloud or Self Hosted

Self Hosted (Docker)

Steps to reproduce

When a Custom Tool is configured with API Key Header authentication and prefix Bearer (or Basic), the Authorization header value gets a new Bearer (or Basic ) prefix prepended on every invocation, because runtime.credentials["api_key_value"] is mutated in-place and the runtime object is shared across calls.

As a result, repeated calls (Agent multi-step, parallel calls, retries) send increasingly malformed headers and fail with 401/403.

Reproduce

1. Create a Custom Tool with the following authentication settings:
   • Auth type: API Key
   • Header name: Authorization
   • Prefix: Bearer
   • Value: <my_token> (e.g. a 64-char string)
2. Build a simple Agent / Workflow that calls this tool 3 times in a row (e.g. with different query parameters).
3. Inspect the Authorization header received by the upstream API.

Observed headers

Each subsequent call adds another Bearer (7 chars) to the header.

Real log from upstream API

[WARNING] 403 token-mismatch  got=Bearer...ae(len=71)  expected_len=64
[WARNING] 403 token-mismatch  got=Bearer...ae(len=78)  expected_len=64
[WARNING] 403 token-mismatch  got=Bearer...ae(len=85)  expected_len=64

71 - 64 = 7 → 1× "Bearer " 78 - 64 = 14 → 2× "Bearer " 85 - 64 = 21 → 3× "Bearer "

✔️ Expected Behavior

Every call should send exactly:

Authorization: Bearer <token>

regardless of how many times the tool is invoked.

❌ Actual Behavior

The Bearer (or Basic ) prefix is prepended cumulatively on every invocation, because the credential dictionary held by self.runtime is mutated in-place.