When would you reach for an oscilloscope versus a logic analyzer?

Use an oscilloscope when the question is about the analog nature of a signal, its actual shape and electrical quality, and a logic analyzer when the question is about digital behavior across many lines. A scope shows voltage versus time at high fidelity on a few channels, so it reveals whether an edge is clean or ringing, whether a "logic high" is actually reaching a valid voltage or sitting at a marginal level, the rise/fall time, noise, overshoot, and glitches too brief to be valid bits, anything where the signal's waveform matters, including genuinely analog signals like a sensor output. A logic analyzer treats each line as a 0 or 1 against a threshold and captures many channels at once (8, 16, 32+), and crucially decodes protocols, turning SPI, I²C, UART, or CAN waveforms into the actual bytes and frames, so it's the tool for verifying multi-line digital timing and bus transactions. The practical decision: if a bus or set of digital signals is doing the wrong thing logically (wrong byte, missing ACK, wrong order, timing relationships across lines), reach for the logic analyzer; if a digital signal is intermittently wrong or you suspect an electrical problem (slow edge, marginal level, ringing, noise), reach for the scope, because only it shows that the "digital" signal isn't a clean level. They complement each other, LA to see what happened, scope to see why.