3 docs tagged with "tracing"

A breakpoint stops time. On bare metal that is a fair trade, because the interesting question is usually "what is in this variable", and a halted core answers it perfectly. Under an RTOS the interesting questions have changed shape: why did the control loop run 4 ms late, which task was holding that mutex, what ran between the interrupt and the response. Every one of those is a statement about a sequence in time, and the instant you halt, the sequence you wanted to observe is gone.

There is a category of bug that a breakpoint destroys by looking at it, and a log line destroys almost as thoroughly. A race between two interrupts, an occasional priority inversion, a state machine that takes a wrong branch once in ten thousand iterations — halting the core to inspect any of these changes exactly the timing that produced them, and a printf line inserted to catch them costs enough cycles to close the window it was supposed to observe. The Debug Toolbox's perturbation table already ranks every instrument in this folder by how much it disturbs the thing it is measuring; trace is the answer at the bottom of that table, the one built specifically to be close to zero.

LangSmith tracing records every step a LangChain/LangGraph run takes — each model call, tool call, and retriever lookup — as a nested tree you can inspect after the fact. It's the fastest way to find which step in a multi-step chain produced a bad answer.