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description: Fix a corrupted or truncated FIT file so Garmin Connect and Strava accept it: chiptime repair salvages, synthesizes, and self-checks.

Repair crash files

The most common FIT tragedy: a device crashes four hours into a ride. The file holds every sample up to the crash, but its header says "0 bytes", the CRC is wrong, and the final session/activity messages were never written. Platforms reject it; the ride is "lost".

One call

chiptime repair crashed.fit -o fixed.fit
chiptime validate fixed.fit --platform garmin-connect   # verify before upload

fixed = chiptime.repair("crashed.fit")
fixed.data                 # complete, valid .fit bytes
fixed.output_strict_ok     # self-check: the output parses in strict mode
fixed.provenance           # exactly what was salvaged and synthesized
open("fixed.fit", "wb").write(fixed.data)

What repair actually does

  1. Salvage — parse the input in recovery mode: fix the header, resync past damage, keep every readable message.
  2. Synthesize — rebuild what platforms require but the crash destroyed: session and activity messages recomputed from the records, correct sizes and CRCs. Implausible fields that would make platforms reject the file (like a 1989 local_timestamp some trainers write) are dropped — and logged.
  3. Self-check — re-parse the output in strict mode. output_strict_ok is that verdict; repair never hands you a file it can't read back flawlessly itself.

Everything synthesized is marked in provenance — a repaired file never pretends data was recorded when it was reconstructed.

Honesty boundary

Repair reconstructs containers (headers, totals, CRCs, required messages) from data that exists. It never fabricates samples: if the last hour wasn't written, the repaired file is an honest shorter ride, not an imagined full one.

Validate against platforms

from chiptime.validate import validate

findings = validate("fixed.fit", platform="garmin-connect")   # or "strava", "strict-spec"
for f in findings:
    print(f.severity, f.code, f.detail)

The platform profiles encode the observed acceptance rules of each service — the checks that actually make uploads fail.