Document strict minimum duration mode for session replay

[Copilot]

Changes

Added documentation for strictMinimumDuration config option introduced in posthog-js 1.291.0 (PostHog/posthog-js#2557). This mode changes how minimum duration is enforced for session recordings.

Updated section: "Minimum duration" in how-to-control-which-sessions-you-record.mdx

Key documentation changes:

• Legacy mode (default): Checks against session age. Starts sending after session is X seconds old, even if buffer cleared by page refresh. Can miss early session data.

• Strict mode (1.291.0+): Checks against actual buffered data timestamps. Only sends after X seconds of continuous recording on a single page. More accurate for filtering short sessions.

Example with 12s minimum:

• Legacy: User on page A (6s) → navigates to page B → after 6s more, sends recording (captures only page B)
• Strict: User on page A (6s) → navigates to page B → must stay 12s on page B before sending (captures full page B session)

Configuration:

posthog.init('<ph_project_api_key>', {
  session_recording: {
    strictMinimumDuration: true
  }
})

Added guidance on choosing between modes and noted strict mode will become default in future releases.

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Original prompt

in PR PostHog/posthog-js#2557 we have added a new mode to the replay minimum duration config. i want to update the documentation on the how to control reply page to explain the new mode and the difference between that and the old one. in the new mode you must be on a single page without navigation or refresh for minium duration or we won't start sending the recording, in the old mode we would start sending the recording to the backend after the session was min dur seconds old even if the buffer had been cleared by navigation or page refresh. the new config is available in 1.291.0 and will soon be the default

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Project	Deployment	Preview	Updated (UTC)
posthog	Ready	Preview	Nov 12, 2025 6:04pm

[greptile-apps]

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[gewenyu99]

😆 nice, let me give copilot a bit of help, but generally looks fine