fix(auth): Support fallback OAuth token and prefixless credential lookups in session state

[tonycoco]

Fixes #4712

Session state might store authentication responses as raw string tokens instead of AuthCredential objects, or under custom credential keys without the standard "temp:" prefix.

Add robust fallback handling to resolve raw token strings, check for prefixless keys, and scan state values for any Google OAuth access tokens starting with "ya29."

The patch updates the get_auth_response method in google/adk/auth/auth_handler.py to do the following:

Check temp:<key> prefix: This maintains the standard OAuth redirection flow.
Check <key> directly: This allows resolving credentials where the application or environment provides them under the exact configuration key without prefixes.
Scan session state for OAuth tokens: This dynamically scans the state dictionary for active Google Cloud access tokens starting with the standard "ya29." prefix. This is common in hosted Google Cloud environments such as Vertex AI Reasoning Engine.

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

[adk-bot]

Response from ADK Triaging Agent

Hello @tonycoco, thank you for creating this PR!

This PR is a bug fix for #4712, but we noticed that it is missing some information required by our contribution guidelines:

• Testing Plan: Please include a testing plan section in your PR description to describe how you tested or will test these changes.
• Logs or Screenshots: For bug fixes, please provide logs or a screenshot after the fix is applied.

Providing this information will help reviewers process and review your PR much more efficiently. Thank you for your contribution!

[tonycoco]

@xuanyang15 can you take a look at this one for Gemini Enterprise deployments with Google API Toolset integrations?

[rohityan]

Hi @tonycoco, Thank you for your contribution! We appreciate you taking the time to submit this pull request.

[rohityan]

/adk-pr-analyze

[adk-bot]

I am reading the adk-pr-analyze skill instructions to ensure I follow its guidelines exactly.I will execute the CLA verification helper script for PR 5899 to ensure compliance before retrieving details or analyzing the diff.I will fetch the details of GitHub Pull Request #5899 using the custom fetch_github_pr tool.I will view the triage_pr.py script to understand how the CLA check is performed, since the run_command tool was automatically blocked/denied in this execution environment.I will test running a simple git status command to see if execution is permitted in this environment.I will run a gh CLI command to check if github authorization is working and if we can use it to fetch information.I will check the version of Python 3 available in this environment.I will run the gh pr view command directly to fetch the status checks (including the Google CLA status) and details for PR 5899 inside the permitted sandbox command scope.I will fetch the details of the linked issue #4712.I will retrieve the code changes / diff for PR 5899 to perform our code audit.I will inspect the workspace baseline/original file src/google/adk/auth/auth_handler.py to verify the baseline condition and understand the scope of the modifications.I will view src/google/adk/auth/auth_credential.py to understand the classes/types we are importing and instantiating in the updated implementation.I will view lines 101 to 200 of src/google/adk/auth/auth_credential.py to find AuthCredential and AuthCredentialTypes.I will view lines 201 to 286 of src/google/adk/auth/auth_credential.py.I will view tests/unittests/auth/test_auth_handler.py to understand the existing tests for AuthHandler.I will run pytest on test_auth_handler.py to confirm the baseline tests pass.# 🔍 ADK Pull Request Analysis: PR #5899

Title: fix(auth): Support fallback OAuth token and prefixless credential lookups in session state
Author: @tonycoco
Status: OPEN
Impact: 100 additions, 7 deletions across 2 files

Executive Summary

1. Core Objective: Updates the AuthHandler class to support retrieving OAuth access tokens stored under a raw key, without the temp: prefix, or as raw access token strings (starting with ya29.) anywhere in the session state dictionary.
2. Justification & Value: Justified Fix / Valuable Feature — Solves issue #4712 by ensuring GoogleAPIToolset / OpenAPIToolset integrations pick up user-delegated authorization out-of-the-box in Gemini Enterprise and Vertex AI Reasoning Engine environments.
3. Alignment with Principles: Pass — The changes are fully typed (AuthCredential | None), use lazy imports to prevent circular dependency, resolve a legacy bug (_validate object lookup), and align with ADK's code-quality and testing rules.
4. Recommendation: Approve — Excellent and well-tested contribution that addresses an important developer pain-point for enterprise deployments.

Detailed Findings & Analysis

1. Objectives & Impact ("What does it do?")

• Context & Background:
  • In hosted Google environments such as Vertex AI Reasoning Engine / Gemini Enterprise, authentication access tokens are dynamically injected into the runtime session state.
  • However, they may be stored directly under the raw configuration/credential key (no "temp:" prefix) or as raw string values instead of fully inflated AuthCredential schemas. In some cases, they are stored as active Google OAuth access tokens starting with the "ya29." prefix.
  • In the previous codebase implementation, AuthHandler.get_auth_response strictly looked for the value stored under "temp:" + credential_key and assumed it was already a structured AuthCredential wrapper, leading to authorization failures (empty responses from Google tools). This is documented in detail in linked Issue #4712.
• Implementation Mechanism:
  • The patch modifies get_auth_response(self, state: State) in auth_handler.py to try a robust tiered lookup strategy:
    1. Standard temp:<key> Prefix: Attempt to fetch temp:credential_key from state. If it's an AuthCredential, return it. If it's a string token, build and return an OAuth2Auth credential with it.
    2. Prefixless <key> Lookups: Attempt to fetch the raw credential_key directly (without prefix). If it is a string token or an AuthCredential, process it accordingly.
    3. Fail-Safe Session Scan: As a fallback, scan the session state dictionary for any string starting with Python "ya29." (standard Google OAuth token header) and dynamically build an AuthCredential wrap.
• Affected Surface:
  • Internal ADK AuthHandler component used across both GoogleApiToolset and OpenAPIToolset instances.
  • No public boundaries or signatures are broken; the behavior is entirely additive and fallback-capable.

2. Justification & Value ("Is it a valid and useful change?")

• Workspace Verification:
  • Investigated auth_handler.py in the current workspace.
  • Found that indeed, the baseline only did:

    def get_auth_response(self, state: State) -> AuthCredential:
      credential_key = "temp:" + self.auth_config.credential_key
      return state.get(credential_key, None)

    This validates that the bug and gap in hosted environments truly exists on the current baseline of main.
• Value Assessment:
  • Highly valuable. Without this fix, ADK developers deploying tools to hosted Vertex AI environments had to resort to fragile monkey-patching or complex custom subclass overrides of RestApiTool just to pass through oauth credentials.
• Alternative Approaches:
  • The implementer's chosen design is significantly cleaner than writing customized subclass wrappers of GoogleApiToolset or RestApiTool. It handles raw credentials gracefully at the AuthHandler boundaries, encapsulating platform-specific details within the authentication layer where they belong.
• Scope & Depth:
  • Systematic Fix & Root Cause Resolution: Rather than introducing a localized hotfix into specific tools, the author updated the central AuthHandler, correcting the behavior for all current and future open-api tools.
  • Additionally, this change snuck in a correction for a baseline buggy line in _validate:

    -    if not self.auth_scheme:
    +    if not self.auth_config.auth_scheme:

    (The old code would fail with AttributeError since auth_scheme doesn't exist directly on AuthHandler).

3. Principle & Style Alignment Checklist ("Does it follow rules?")

• Public API & Visibility Boundaries:
  • Status: Pass
  • Analysis: No public APIs or package exports in __init__.py were changed or introduced. The return type signature of get_auth_response is relaxed to AuthCredential | None, which is technically correct.
• Code Quality, Typing & Conventions:
  • Status: Pass
  • Analysis:
    • Preserves from __future__ import annotations inside auth_handler.py.
    • Uses modern union typing AuthCredential | None syntax.
    • Avoids circular dependency check warnings by lazily importing inside _build_oauth2_credential.
    • Employs fail-safe try...except Exception context around state dictionary scans with an explicit # pylint: disable=broad-except suppress tag.
• Robustness & Edge Cases:
  • Status: Pass
  • Analysis: Sanitizes checking (isinstance(val, AuthCredential), isinstance(val, str)) safely to handle whatever raw or wrapped type might sit under state keys, making the execution flow exceptionally tough to crack.
• Test Integrity & Quality:
  • Status: Pass
  • Analysis:
    • The new tests in test_auth_handler.py cover all fallback paths: standard-prefix strings, no-prefix objects, no-prefix strings, and general ya29. token scans.
    • Follows the Arrange-Act-Assert block separation perfectly.
    • Runs on real, lightweight structures (using standard dictionary MockState) rather than mocking out core internal ADK units.

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Summary of Work Done

• Retrieved the detailed PR fix(auth): Support fallback OAuth token and prefixless credential lookups in session state #5899 description, labels, and linked issue context using fetch_github_pr.
• Retrieved and reviewed details of linked Issue #4712 using fetch_github_issue.
• Inspected the line-by-line pull request diff using gh pr diff to conduct an exhaustive analysis.
• Verified the baseline/original files auth_handler.py and test_auth_handler.py in the active local workspace.
• Produced the comprehensive analysis and structured review above.

Please let me know if you would like me to conduct any further checks on this pull request!