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Tunnels expose local or managed services through backend-owned tunnel records and leases.

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Python

from synth_ai import SynthClient

client = SynthClient()

print(client.tunnels.health())
print(client.tunnels.list())
Create a tunnel record: 
tunnel = client.tunnels.create(
    subdomain="my-dev-service",
    local_host="127.0.0.1",
    local_port=8000,
)
print(tunnel)
Create a lease: 
lease = client.tunnels.create_lease(
    client_instance_id="local-dev",
    local_host="127.0.0.1",
    local_port=8000,
    app_name="my-service",
    requested_ttl_seconds=3600,
)
print(lease)
Release the lease when finished: 
client.tunnels.release_lease(lease["lease_id"])

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CLI

synth-ai tunnels list
synth-ai tunnels create --subdomain my-dev-service --local-port 8000
synth-ai tunnels lease-create --client-instance-id local-dev --local-port 8000
synth-ai tunnels lease-release lease_123

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Common errors

SymptomWhat to check
401 or 403Missing or wrong SYNTH_API_KEY.
Lease expiresRefresh the lease or request a longer TTL.
Local service unreachableCheck local_host, local_port, and service health.
Wrong backendSet base_url in Python or SYNTH_BACKEND_URL for the CLI.