fix(agent): guard against non-positive context_length poisoning the cache - #85507
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Reapply the non-positive context-length guards onto the post-history-replacement mainline without carrying any stale branch history. save_context_length() now refuses to persist length <= 0 (keeping upstream's normalized _context_cache_key), and get_model_context_length() drops non-positive cache hits at the head of the invalidation chain (Codex/Kimi/MiniMax/Grok branches become elif) so a poisoned entry re-resolves instead of short-circuiting to 0. Refresh of PR #25812; original head d62ed5eb92f057d8c707ba937b44f168f2df0677.
Follow-up to the salvaged #25812 — the original PR shipped without tests.
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૮ >ﻌ< ა ci reviewran on 064d23f — test: regression coverage for the non-positive context-cache
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alt-glitch
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type/bug
This was referenced Aug 13, 2026
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Summary
A cached
context_lengthof 0 (corrupted cache, failed probe, manual edit) poisoned the whole resolution chain:0 is not Noneshort-circuits step 1, so the compressor and every downstream display got context_length=0 forever. This refuses to persist non-positive values and drops any pre-existing non-positive entry so it re-resolves.Salvages #25812 by @OmarB97 (cherry-picked, authorship preserved). The original shipped without tests; we added sabotage-verified regression coverage on top.
Changes
agent/model_metadata.py(@OmarB97):save_context_length()refuseslength <= 0; step-1 dropscached <= 0entries and re-resolves.tests/agent/test_model_metadata.py(ours): never-persisted + dropped-and-re-resolved regression tests.Validation
test_model_metadata.pyInfographic