diff --git a/.github/workflows/gemini-invoke.yml b/.github/workflows/gemini-invoke.yml
index 5bec70a52..a308ae184 100644
--- a/.github/workflows/gemini-invoke.yml
+++ b/.github/workflows/gemini-invoke.yml
@@ -42,7 +42,7 @@ jobs:
 
       - name: 'Run Gemini CLI'
         id: 'run_gemini'
-        uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude
+        uses: './' # ratchet:exclude
         env:
           TITLE: '${{ github.event.pull_request.title || github.event.issue.title }}'
           DESCRIPTION: '${{ github.event.pull_request.body || github.event.issue.body }}'
diff --git a/.github/workflows/gemini-issue-fixer.yml b/.github/workflows/gemini-issue-fixer.yml
index a19804418..1a72ebedb 100644
--- a/.github/workflows/gemini-issue-fixer.yml
+++ b/.github/workflows/gemini-issue-fixer.yml
@@ -39,7 +39,7 @@ jobs:
         uses: 'actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8' # ratchet:actions/checkout@v6
 
       - name: 'Run Gemini PR Create'
-        uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude
+        uses: './' # ratchet:exclude
         id: 'gemini_pr_create'
         env:
           GITHUB_TOKEN: '${{ steps.mint_identity_token.outputs.token || secrets.GITHUB_TOKEN }}'
diff --git a/.github/workflows/gemini-plan-execute.yml b/.github/workflows/gemini-plan-execute.yml
index 9dfe61a21..56ce7dd86 100644
--- a/.github/workflows/gemini-plan-execute.yml
+++ b/.github/workflows/gemini-plan-execute.yml
@@ -44,7 +44,7 @@ jobs:
 
       - name: 'Run Gemini CLI'
         id: 'run_gemini'
-        uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude
+        uses: './' # ratchet:exclude
         env:
           TITLE: '${{ github.event.pull_request.title || github.event.issue.title }}'
           DESCRIPTION: '${{ github.event.pull_request.body || github.event.issue.body }}'
diff --git a/.github/workflows/gemini-review.yml b/.github/workflows/gemini-review.yml
index dc525cd74..6d17d5d02 100644
--- a/.github/workflows/gemini-review.yml
+++ b/.github/workflows/gemini-review.yml
@@ -42,7 +42,7 @@ jobs:
         uses: 'actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8' # ratchet:actions/checkout@v6
 
       - name: 'Run Gemini pull request review'
-        uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude
+        uses: './' # ratchet:exclude
         id: 'gemini_pr_review'
         env:
           GITHUB_TOKEN: '${{ steps.mint_identity_token.outputs.token || secrets.GITHUB_TOKEN || github.token }}'
diff --git a/.github/workflows/gemini-scheduled-triage.yml b/.github/workflows/gemini-scheduled-triage.yml
index 962164576..c21789488 100644
--- a/.github/workflows/gemini-scheduled-triage.yml
+++ b/.github/workflows/gemini-scheduled-triage.yml
@@ -89,7 +89,7 @@ jobs:
         id: 'gemini_issue_analysis'
         if: |-
           ${{ steps.find_issues.outputs.issues_to_triage != '[]' }}
-        uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude
+        uses: './' # ratchet:exclude
         env:
           GITHUB_TOKEN: '' # Do not pass any auth token here since this runs on untrusted inputs
           ISSUES_TO_TRIAGE: '${{ steps.find_issues.outputs.issues_to_triage }}'
diff --git a/.github/workflows/gemini-triage.yml b/.github/workflows/gemini-triage.yml
index 22b1413c2..a298164b8 100644
--- a/.github/workflows/gemini-triage.yml
+++ b/.github/workflows/gemini-triage.yml
@@ -59,7 +59,7 @@ jobs:
         id: 'gemini_analysis'
         if: |-
           ${{ steps.get_labels.outputs.available_labels != '' }}
-        uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude
+        uses: './' # ratchet:exclude
         env:
           GITHUB_TOKEN: '' # Do NOT pass any auth tokens here since this runs on untrusted inputs
           ISSUE_TITLE: '${{ github.event.issue.title }}'
diff --git a/.github/workflows/test-minimal.yml b/.github/workflows/test-minimal.yml
new file mode 100644
index 000000000..f5a47ada5
--- /dev/null
+++ b/.github/workflows/test-minimal.yml
@@ -0,0 +1,21 @@
+name: '🧪 Test Minimal'
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - 'fix/auth-priority-and-hang'
+    paths:
+      - '.github/workflows/test-minimal.yml'
+
+jobs:
+  test:
+    runs-on: 'ubuntu-latest'
+    steps:
+      - name: 'Checkout'
+        uses: 'actions/checkout@v4'
+
+      - name: 'Run Gemini Version'
+        uses: './'
+        with:
+          prompt: '--version'
+          gemini_debug: true
diff --git a/action.yml b/action.yml
index 54acd0f94..d6dd630ab 100644
--- a/action.yml
+++ b/action.yml
@@ -107,7 +107,7 @@ runs:
       id: 'validate_inputs'
       shell: 'bash'
       run: |-
-        set -exuo pipefail
+        set -euo pipefail
 
         # Emit a clear warning in three places without failing the step
         warn() {
@@ -134,7 +134,7 @@ runs:
         fi
 
         if [[ ${auth_methods} -gt 1 ]]; then
-          warn "Multiple authentication methods provided. Please use only one of 'gemini_api_key', 'google_api_key', or 'gcp_workload_identity_provider'."
+          echo "::notice title=Authentication priority::Multiple authentication methods provided. The action will prioritize them in the following order: 1. Workload Identity Federation, 2. Vertex AI API Key, 3. Gemini API Key. Conflicting environment variables will be unset for the CLI."
         fi
 
         # Validate Workload Identity Federation inputs
@@ -231,9 +231,14 @@ runs:
         GEMINI_CLI_VERSION: '${{ inputs.gemini_cli_version }}'
         EXTENSIONS: '${{ inputs.extensions }}'
         USE_PNPM: '${{ inputs.use_pnpm }}'
+        GOOGLE_CLOUD_ACCESS_TOKEN: '${{ steps.auth.outputs.access_token }}'
+        GOOGLE_GENAI_USE_VERTEXAI: '${{ inputs.use_vertex_ai }}'
+        GEMINI_API_KEY: '${{ inputs.gemini_api_key }}'
+        GOOGLE_API_KEY: '${{ inputs.google_api_key }}'
       shell: 'bash'
       run: |-
         set -euo pipefail
+        mkdir -p ~/.gemini
 
         VERSION_INPUT="${GEMINI_CLI_VERSION:-latest}"
 
@@ -260,6 +265,21 @@ runs:
           echo "Error: Gemini CLI not found in PATH"
           exit 1
         fi
+
+        # Sanitize authentication environment variables to avoid conflicts when installing extensions.
+        if [[ -n "${GOOGLE_CLOUD_ACCESS_TOKEN:-}" ]]; then
+          unset GEMINI_API_KEY
+          unset GOOGLE_API_KEY
+          unset GOOGLE_APPLICATION_CREDENTIALS
+        elif [[ "${GOOGLE_GENAI_USE_VERTEXAI:-false}" == "true" && -n "${GOOGLE_API_KEY:-}" ]]; then
+          unset GEMINI_API_KEY
+        elif [[ -n "${GEMINI_API_KEY:-}" ]]; then
+          export GOOGLE_GENAI_USE_VERTEXAI="false"
+          export GOOGLE_GENAI_USE_GCA="false"
+          unset GOOGLE_API_KEY
+          unset GOOGLE_CLOUD_ACCESS_TOKEN
+        fi
+
         if [[ -n "${EXTENSIONS}" ]]; then
           echo "Installing Gemini CLI extensions:"
           echo "${EXTENSIONS}" | jq -r '.[]' | while IFS= read -r extension; do
@@ -289,6 +309,31 @@ runs:
         # Keep track of whether we've failed
         FAILED=false
 
+        # Always unset GOOGLE_APPLICATION_CREDENTIALS to prevent the CLI from hanging on credential discovery
+        # in environments where multiple auth methods might be present (like GHA).
+        unset GOOGLE_APPLICATION_CREDENTIALS
+
+        # Sanitize authentication environment variables to avoid conflicts.
+        # Priority:
+        # 1. Workload Identity Federation (use_vertex_ai or use_gemini_code_assist with access token)
+        # 2. Vertex AI API Key (use_vertex_ai with google_api_key)
+        # 3. Gemini API Key (gemini_api_key)
+        if [[ -n "${GOOGLE_CLOUD_ACCESS_TOKEN:-}" ]]; then
+          unset GEMINI_API_KEY
+          unset GOOGLE_API_KEY
+          # Unset credential file pointers that might cause conflicts with the access token and hang.
+          unset GOOGLE_APPLICATION_CREDENTIALS
+          unset CLOUDSDK_AUTH_CREDENTIAL_FILE_OVERRIDE
+          unset GOOGLE_GHA_CREDS_PATH
+        elif [[ "${GOOGLE_GENAI_USE_VERTEXAI:-false}" == "true" && -n "${GOOGLE_API_KEY:-}" ]]; then
+          unset GEMINI_API_KEY
+        elif [[ -n "${GEMINI_API_KEY:-}" ]]; then
+          export GOOGLE_GENAI_USE_VERTEXAI="false"
+          export GOOGLE_GENAI_USE_GCA="false"
+          unset GOOGLE_API_KEY
+          unset GOOGLE_CLOUD_ACCESS_TOKEN
+        fi
+
         # Run Gemini CLI with the provided prompt, using JSON output format
         # We capture stdout (JSON) to TEMP_STDOUT and stderr to TEMP_STDERR
         if [[ "${GEMINI_DEBUG}" = true ]]; then
@@ -324,12 +369,18 @@ runs:
         if jq -e . "${TEMP_STDOUT}" >/dev/null 2>&1; then
            RESPONSE=$(jq -r '.response // ""' "${TEMP_STDOUT}")
         fi
-        if jq -e . "${TEMP_STDERR}" >/dev/null 2>&1; then
-           ERROR_JSON=$(jq -c '.error // empty' "${TEMP_STDERR}")
+
+        # Stderr might contain non-JSON (like stack traces), so we try to extract the last valid JSON object
+        if grep -q "{" "${TEMP_STDERR}"; then
+           # Extract the last curly-braced block from stderr
+           ERROR_CANDIDATE=$(tac "${TEMP_STDERR}" | awk '/^}/{p=1} p; /^{/{if(p)exit}' | tac)
+           if [[ -n "${ERROR_CANDIDATE}" ]] && jq -e . <<< "${ERROR_CANDIDATE}" >/dev/null 2>&1; then
+              ERROR_JSON=$(jq -c '.error // empty' <<< "${ERROR_CANDIDATE}")
+           fi
         fi
 
-        if { [[ -s "${TEMP_STDERR}" ]] && ! jq -e . "${TEMP_STDERR}" >/dev/null 2>&1; }; then
-          echo "::warning::Gemini CLI stderr was not valid JSON"
+        if { [[ -s "${TEMP_STDERR}" ]] && [[ -z "${ERROR_JSON}" ]]; }; then
+          echo "::warning::Gemini CLI stderr contains data but no valid JSON error object was extracted"
         fi
 
         if { [[ -s "${TEMP_STDOUT}" ]] && ! jq -e . "${TEMP_STDOUT}" >/dev/null 2>&1; }; then
@@ -338,22 +389,25 @@ runs:
 
 
         # Set the captured response as a step output, supporting multiline
-        echo "gemini_response<<EOF" >> "${GITHUB_OUTPUT}"
+        # Use a unique delimiter to avoid collisions
+        EOF_DELIMITER="gh_gemini_out_$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 8 | head -n 1)"
+
+        echo "gemini_response<<${EOF_DELIMITER}" >> "${GITHUB_OUTPUT}"
         if [[ -n "${RESPONSE}" ]]; then
           echo "${RESPONSE}" >> "${GITHUB_OUTPUT}"
         else
           cat "${TEMP_STDOUT}" >> "${GITHUB_OUTPUT}"
         fi
-        echo "EOF" >> "${GITHUB_OUTPUT}"
+        echo "${EOF_DELIMITER}" >> "${GITHUB_OUTPUT}"
 
         # Set the captured errors as a step output, supporting multiline
-        echo "gemini_errors<<EOF" >> "${GITHUB_OUTPUT}"
+        echo "gemini_errors<<${EOF_DELIMITER}" >> "${GITHUB_OUTPUT}"
         if [[ -n "${ERROR_JSON}" ]]; then
           echo "${ERROR_JSON}" >> "${GITHUB_OUTPUT}"
         else
           cat "${TEMP_STDERR}" >> "${GITHUB_OUTPUT}"
         fi
-        echo "EOF" >> "${GITHUB_OUTPUT}"
+        echo "${EOF_DELIMITER}" >> "${GITHUB_OUTPUT}"
 
         # Generate Job Summary
         if [[ -n "${GITHUB_STEP_SUMMARY:-}" ]]; then