Prompt cache misses and re-writes

“Interactive sessions get only 5m prompt-cache TTL while claude -p on same login gets 1h”

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Still happening. 7 reports and thumbs-up in the last 7 days and 6 the week before, down from 15 a week at the late-October peak. Not fixed, and no vendor reply yet.

11 bugs in this theme

Interactive sessions get 5m cache TTLHas a workaround18 people
Background agent summary requestsNo workaround yet12 people
Sleep re-sends full agent contextNo workaround yet4 people
Context after prompt breaks cache4 people
Subagent resume cache miss4 people
Resume re-writes prompt cacheNo workaround yet3 people
CLAUDE.md cache not sharedHas a workaround3 people
Prompt cache misses after system messageHas a workaround3 people
Warm prompt cache fully missedNo workaround yet2 people
Cross-session prompt cache missesNo workaround yet2 people

Show all 11Show only the largest 10

Subagent prompt cache expiresNo workaround yet2 people

What's included

Mid-session, cache reads drop to the system-prompt floor or to zero and the whole conversation is re-written, sometimes for dozens of consecutive calls
Headless -p runs and --resume re-write the full history every turn on some models, linked in reports to trailing role:system messages or turns without thinking
New sessions never share cached CLAUDE.md, memory or skills context because a per-session scratchpad or job path, or the first prompt, sits in the same prefix
Interactive sessions write 5-minute cache entries while claude -p on the same account writes 1-hour entries

Not included

Usage limits or billing totals reported without cache read/write measurements
Context compaction behavior unrelated to cache hits

Original reports27, newest first

Nov 2, 2026Background subagent progress summary misses prompt cache, rewriting full context about every 35s#106863
Oct 29, 2026agent_summary re-sends each background agent's full transcript every ~30 s, with no way to turn it off#105981
Oct 21, 2026Prompt cache: CLAUDE.md context is rewritten on every session start because it shares messages[0] with the first prompt#104051
Oct 20, 2026Interactive sessions request 5-minute prompt cache on enterprise org, headless uses 1-hour TTL#103753
Oct 20, 2026Interactive CLI uses 5m prompt cache TTL instead of 1h since v2.1.301#103673
Oct 19, 2026Interactive sessions default to 5m prompt-cache TTL while claude -p gets 1h#103392
Oct 18, 2026Max 20x: subagents waiting on long Bash commands lose their 5-minute prompt cache and re-write full context — 54% of weekly limit in <24 h, invisible to the user#103309
Oct 18, 2026Failure loop during sleep consumes weekly usage with no output (subagent suspected)#103233
Oct 16, 2026Sleep-mid-response cut-offs trigger an unbounded, uncached full-context regeneration loop#102780
Oct 15, 2026macOS: background agents re-send full context on every DarkWake after lid close (81 requests sent, 29 completed overnight; usage consumed while asleep)#102597

Show all 27Show only the newest 10

Oct 15, 2026Overnight sleep re-writes agent cache per wake-up, drains weekly limit; ambiguous "стоять" stops agents#102269
Oct 14, 2026Prompt cache: CLAUDE.md context is never shared across sessions because it shares a cache segment with the first user prompt#102042
Oct 13, 2026Interactive sessions write the 5-minute prompt cache from session start, while claude -p on the same account writes 1-hour (2.1.296, Team seat, survives /login)#101685
Oct 6, 2026claude -p misses the prompt cache after a turn without thinking (Opus 5.5, Fable 5.1, Sonnet 5.5)#100065
Oct 5, 2026v2.1.290: --resume on opus-5-5/sonnet-5-5 re-writes the whole history to the prompt cache every time (haiku unaffected)#99833
Oct 3, 2026Subagents use the 5-minute prompt cache while the main session uses 1-hour; slow responses cause repeated full-context cache rewrites#99360
Oct 2, 2026Warm 1h prompt cache fully missed (cache_read_input_tokens = 0, 634k tokens re-written) 1.6 min after the previous request, mid tool loop — v2.1.288, Opus 5.5#99096
Sep 30, 2026Prompt cache falls to 7,085-token system floor for 43–58 consecutive calls#98574
Sep 30, 2026Prompt cache drops to 7,085-token system floor across runs of 43–58 calls#98557
Sep 30, 2026Session-invariant context (skill/agent listings, deferred tools, CLAUDE.md) is sent after the first user prompt, so every new session and subagent rewrites it to the prompt cache#98513
Sep 25, 2026Session-specific scratchpad path early in the context stops cache reuse across sessions#97262
Sep 25, 2026Prompt cache never hits after a mid-conversation role:"system" message (resume and hook output), Opus 5.x / Fable#96998
Sep 22, 2026Opus 5.5 / Fable 5.1 in -p mode re-write the whole conversation cache every turn (Sonnet caches fine; totalTokensReminder: off does not help)#96163
Sep 22, 2026Cache entry written with its breakpoint on a trailing role: system message is never reused — with the per-user-turn <total_tokens> reminder on, every tool-less turn re-writes the whole conversation (likely also the root cause of #93490)#96101
Sep 16, 2026Prompt cache misses on every background session: per-session job-dir path contaminates the cacheScope:"org" system-prompt block#94815
Sep 16, 2026Resuming a background subagent misses its prompt cache: messages_changed, no thinking blocks#94728
Sep 14, 2026CLAUDE.md / auto-memory block is never shared across sessions: it sits in messages[0] after the system breakpoint, with no cache_control of its own#94417