Adding an LLM to a legacy app: four boundaries in 30 seconds
Silent video: no voiceover, music or sound effects. This transcript repeats every on-screen word and describes each scene.
The film includes the topic label "LLM in a legacy app", the note "Illustrative diagram", the TecnoStack logo and progress numbers 1, 2, 3, 4, 5, 6. Elements enter and leave during transitions; in portrait, the closing sign-off replaces the footer.

[0:00–0:05] Beat 1 of 6 (intro)
Kicker: LLM integration
Headline: Add AI beside the core
Support: Keep business rules in charge
Diagram (decision paths): Legacy app; Inside the core; Beside the core
Connections: Legacy app → Inside the core; Legacy app → Beside the core
Highlighted: Beside the core
Scene: Branching diagram: Legacy app, Inside the core, Beside the core. Connections: Legacy app to Inside the core; Legacy app to Beside the core. Emphasis: Beside the core.

[0:05–0:10] Beat 2 of 6 (step1)
Kicker: 01
Headline: One narrow adapter
Support: Typed requests; checked results
Diagram (flow): Legacy screen; Adapter service; Language model; Schema check
Connections: Legacy screen → Adapter service; Adapter service → Language model; Language model → Schema check
Highlighted: Adapter service
Scene: Flow: Legacy screen, Adapter service, Language model, Schema check. Connections: Legacy screen to Adapter service; Adapter service to Language model; Language model to Schema check. Emphasis: Adapter service.

[0:10–0:15] Beat 3 of 6 (step2)
Kicker: 02
Headline: Use the signed-in user's permissions
Support: Identity comes from the server
Diagram (flow): Signed-in user; Short-lived token; Adapter service; Data API
Connections: Signed-in user → Short-lived token; Short-lived token → Adapter service; Adapter service → Data API
Highlighted: Short-lived token
Scene: Flow: Signed-in user, Short-lived token, Adapter service, Data API. Connections: Signed-in user to Short-lived token; Short-lived token to Adapter service; Adapter service to Data API. Emphasis: Short-lived token.

[0:15–0:20] Beat 4 of 6 (step3)
Kicker: 03
Headline: Expose small, typed tools
Support: Reads by default; writes become proposals
Diagram (hub and spokes): Adapter tools; Look up order; Read refund policy; Draft refund
Connections: Adapter tools → Look up order; Adapter tools → Read refund policy; Adapter tools → Draft refund
Highlighted: Draft refund
Scene: Network: Adapter tools, Look up order, Read refund policy, Draft refund. Connections: Adapter tools to Look up order; Adapter tools to Read refund policy; Adapter tools to Draft refund. Emphasis: Draft refund.

[0:20–0:25] Beat 5 of 6 (step4)
Kicker: 04
Headline: Writes wait for confirmation
Support: Existing rules still validate the request
Diagram (decision paths): Assistant request; Read path; Write path; User confirms
Connections: Assistant request → Read path; Assistant request → Write path; Write path → User confirms
Highlighted: Write path; User confirms
Scene: Branching diagram: Assistant request, Read path, Write path, User confirms. Connections: Assistant request to Read path; Assistant request to Write path; Write path to User confirms. Emphasis: Write path, User confirms.

[0:25–0:30] Beat 6 of 6 (close)
Kicker: TECNOSTACK
Headline: Boundaries first, then the model
Support: Read the full TecnoStack guide
Diagram (evidence checklist): Adapter seam; User identity; Typed tools; Separate reads and writes
Highlighted: Adapter seam; User identity; Typed tools; Separate reads and writes
Sign-off: TecnoStack logo and tecnostack.com
Scene: Comparison without scores: Adapter seam, User identity, Typed tools, Separate reads and writes. Emphasis: Adapter seam, User identity, Typed tools, Separate reads and writes.