GCP service account JSON overwritten with placeholder on start() after stop

[jwm4]

Description

When a local instance with Vertex AI (GCP service account) is stopped and then started, the GCP service account JSON file in the volume (/home/node/.openclaw/gcp/sa.json) is overwritten with the literal string (on-volume) instead of the actual credentials.

This causes LiteLLM to fail with:

Vertex_aiException InternalServerError - ('File /home/node/.openclaw/gcp/sa.json is not a valid json file.',
JSONDecodeError('Expecting value: line 1 column 1 (char 0)'))

Root Cause

In src/server/routes/status-instances.ts:127, the config parser sets gcpServiceAccountJson to a placeholder string when it detects the credential path was set:

gcpServiceAccountJson: savedVars.GOOGLE_APPLICATION_CREDENTIALS ? "(on-volume)" : undefined,

This is intended as a sentinel value to indicate credentials exist on the volume. However, the start() method in local.ts treats any truthy gcpServiceAccountJson as real content and writes it to the volume (lines 1819-1830), overwriting the valid SA JSON with (on-volume).

Expected Behavior

The start() method should skip writing the GCP SA file when the value is a placeholder, or parseSavedLocalInstanceConfig() should not set gcpServiceAccountJson at all since the real file already exists on the volume.

Steps to Reproduce

1. Deploy a local instance with Vertex AI and a GCP service account JSON
2. Verify the agent works (LiteLLM authenticates successfully)
3. Stop the instance
4. Start the instance
5. Agent fails — LiteLLM cannot parse sa.json

Workaround

Teardown and do a fresh deploy instead of stop/start.

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This issue was filed by Claude Code under the supervision of Bill Murdock.