Retention Promise vs New Offer

Need unbiased advice.

7 yoe (Cloud), 3+ years in the current org. No promotion yet despite leading deliveries.

Current CTC around 15. offer in hand is mid 20. Org countered slightly lower stating band limit without promotion.

GM verbally promised promotion in a few months & possible AI team exposure (not documented).

New role aligns more with multi-cloud DevOps and European client.

Both service-based. Current: remote + good manager but indian client New: HCL, Hybrid mode

Stay for the promise or move for better hope?