fix(discord): transcribe inbound audio attachments

[theonlyhennygod]

Summary

• add Discord channel transcription config wiring via .with_transcription(config.transcription.clone())
• extend inbound Discord attachment processing to detect audio attachments and transcribe them with the shared Whisper-compatible transcription module
• enforce configured duration limits when Discord exposes duration_secs, while preserving existing image/text attachment behavior

Root Cause

Discord inbound attachments only handled images and text; audio attachments were skipped, so no transcription path was ever invoked.

Validation

• cargo fmt --all -- --check
• cargo test --lib discord::tests::process_attachments_ -- --nocapture
• cargo test --lib discord::tests::is_audio_attachment -- --nocapture
• cargo test --lib discord::tests::infer_audio_filename_ -- --nocapture
• cargo test --lib discord::tests::with_transcription_ -- --nocapture
• cargo check --package zeroclaw --lib

Notes

• process_attachments_transcribes_audio_when_enabled is included as an ignored test because this sandbox disallows loopback TCP binds; it can run in unrestricted CI/dev environments.

Closes #2686

Summary by CodeRabbit

• New Features

  • Added voice transcription for Discord audio attachments. Audio files are now automatically transcribed to text and included in message content when enabled per channel. Supports configurable maximum duration limits to control transcription processing.

• Tests

  • Extended test coverage for voice transcription functionality, including configuration options and various enabled/disabled scenarios.

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📥 Commits

Reviewing files that changed from the base of the PR and between ae41b17 and c7b58b5.

📒 Files selected for processing (2)

• src/channels/discord.rs
• src/channels/mod.rs

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Validation error: Unrecognized key(s) in object: 'tools', 'path_filters', 'review_instructions'

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📝 Walkthrough

Walkthrough

This PR implements voice transcription support for Discord channels by introducing a TranscriptionConfig field to DiscordChannel, extending the attachment processing logic to detect, fetch, and transcribe audio files when enabled, and wiring the configuration through the Discord channel initialization.

Changes

Cohort / File(s)	Summary
Discord Voice Transcription src/channels/discord.rs	Added transcription: Option<TranscriptionConfig> field and with_transcription() method to DiscordChannel. Extended process_attachments() to accept optional transcription config, classify audio attachments, apply duration limits, fetch audio data, invoke transcription service, and inject [Voice:<filename>] markers into output. Introduced helper functions for audio detection, content-type normalization, filename inference, and audio extension mapping. Updated call-sites and added tests for transcription flows.
Channel Configuration src/channels/mod.rs	Chained .with_transcription(config.transcription.clone()) to the Discord channel construction in collect_configured_channels to apply transcription settings from config.

Sequence Diagram(s)

sequenceDiagram
    participant Discord as Discord Channel Handler
    participant Fetch as HTTP Client
    participant Transcribe as Transcription Service
    participant Output as Message Output

    rect rgba(100, 150, 200, 0.5)
    Note over Discord,Output: Audio Transcription Flow
    Discord->>Discord: Detect audio attachment
    Discord->>Discord: Check duration limits
    Discord->>Fetch: Fetch audio file
    Fetch-->>Discord: Audio data
    Discord->>Transcribe: transcribe_audio(data, config)
    Transcribe-->>Discord: Transcript text
    Discord->>Output: Inject [Voice:filename] transcript
    end

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• [Bug]: The transcription on the Discord channel isn't working. #2686: This PR directly addresses the bug where Discord channel transcription was not functioning; implements the missing transcription feature with audio detection, duration filtering, and transcript injection.
• [Feature]: Support voice transcription in Matrix channel #2668: Proposes per-channel voice transcription for Matrix channels using the same TranscriptionConfig and shared transcribe_audio utility pattern.

Possibly related PRs

• feat: support config-level api_key for transcription #2112: Modifies transcription code paths and updates the transcribe_audio function signature to accept &TranscriptionConfig and handle API key configuration, directly integrating with the transcription calls introduced here.
• fix(channel:discord): robust inbound image marker detection #2237: Modifies src/channels/discord.rs attachment processing logic, including helper functions for attachment classification and fetching that overlap with audio detection utilities added in this PR.
• fix(discord): recover text attachments when content type is missing #1871: Updates process_attachments() logic in Discord channel to handle attachment classification and fetching, with overlapping concerns around audio detection and content-type inference.

Suggested labels

size: M, risk: medium, channel, channel: transcription

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description is incomplete. While it covers the problem, solution, and validation steps, it lacks required metadata sections including risk level, size label, scope labels, module labels, change type, security impact, privacy status, backward compatibility, and rollback plan.	Complete all required sections in the description template: Label Snapshot, Change Metadata, Security Impact, Privacy/Data Hygiene, Compatibility, and Rollback Plan.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix(discord): transcribe inbound audio attachments' clearly and concisely describes the main change—adding transcription support for audio attachments in Discord channels.
Linked Issues check	✅ Passed	The PR fully addresses issue #2686: it detects audio attachments in Discord, integrates transcription via the shared Whisper module, respects duration limits, and provides functional parity with other channels like Telegram.
Out of Scope Changes check	✅ Passed	All changes are narrowly scoped to fixing Discord audio transcription: adding transcription config wiring, audio detection, transcription integration, and supporting tests. No unrelated refactoring or scope creep detected.
Docstring Coverage	✅ Passed	Docstring coverage is 86.49% which is sufficient. The required threshold is 80.00%.

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• Create PR with unit tests
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• Commit unit tests in branch issue-2686-discord-transcription

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[github-actions]

PR intake checks found warnings (non-blocking)

Fast safe checks found advisory issues. CI lint/test/build gates still enforce merge quality.

• Missing required PR template sections: ## Validation Evidence (required), ## Security Impact (required), ## Privacy and Data Hygiene (required), ## Rollback Plan (required)
• Incomplete required PR template fields: summary problem, summary why it matters, summary what changed, validation commands, security risk/mitigation, privacy status, rollback plan
• Missing Linear issue key reference (RMN-<id>, CDV-<id>, or COM-<id>) in PR title/body (recommended for traceability, non-blocking).

Action items:

1. Complete required PR template sections/fields.
2. (Recommended) Link this PR to one active Linear issue key (RMN-xxx/CDV-xxx/COM-xxx) for traceability.
3. Remove tabs, trailing whitespace, and merge conflict markers from added lines.
4. Re-run local checks before pushing:
   • ./scripts/ci/rust_quality_gate.sh
   • ./scripts/ci/rust_strict_delta_gate.sh
   • ./scripts/ci/docs_quality_gate.sh

Detected Linear keys: none

Run logs: https://github.com/zeroclaw-labs/zeroclaw/actions/runs/22666032846

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